United Albany Brethren Benefit Society
- Authors: Berning, J M
- Date: 1984
- Language: English
- Type: Article
- Identifier: vital:6991 , http://hdl.handle.net/10962/d1012416
- Description: The United Albany Brethren Benefit Society (Albany Brethren) was a Grahamstown example of the friendly society movement which reached a peak in Britain during the last century.
- Full Text:
- Date Issued: 1984
- Authors: Berning, J M
- Date: 1984
- Language: English
- Type: Article
- Identifier: vital:6991 , http://hdl.handle.net/10962/d1012416
- Description: The United Albany Brethren Benefit Society (Albany Brethren) was a Grahamstown example of the friendly society movement which reached a peak in Britain during the last century.
- Full Text:
- Date Issued: 1984
Curiosity first, applications later
- Berold, Robert, Limson, Janice L
- Authors: Berold, Robert , Limson, Janice L
- Date: 2009
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7188 , http://hdl.handle.net/10962/d1006281 , http://www.sajs.co.za/sites/default/files/publications/pdf/1-4-1-PB.pdf , Nyokong, Tebello
- Description: Tebello Nyokong speaks to Robert Berold and Janice Limson about her career as a chemist. Tebello Nyokong, who holds a research chair in medicinal chemistry and nanotechnology at Rhodes University, has become the first South African scientist to win the L’Oreal-UNESCO award for women in science, in the physical sciences. Only one laureate is selected from each of five world regions, and Nyokong is the 2009 laureate for Africa and the Arab states. She and the winners from the other four regions travel to Paris in March to each accept the award and a generous prize of close to R1 million. Nyokong now heads the new Nanotechnology Innovation Centre for medical sensors: the biggest single research investment in the history of Rhodes. Linked to other nanotechnology centres in the country, it is designed to bridge the gap between research and the market.
- Full Text:
- Date Issued: 2009
- Authors: Berold, Robert , Limson, Janice L
- Date: 2009
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7188 , http://hdl.handle.net/10962/d1006281 , http://www.sajs.co.za/sites/default/files/publications/pdf/1-4-1-PB.pdf , Nyokong, Tebello
- Description: Tebello Nyokong speaks to Robert Berold and Janice Limson about her career as a chemist. Tebello Nyokong, who holds a research chair in medicinal chemistry and nanotechnology at Rhodes University, has become the first South African scientist to win the L’Oreal-UNESCO award for women in science, in the physical sciences. Only one laureate is selected from each of five world regions, and Nyokong is the 2009 laureate for Africa and the Arab states. She and the winners from the other four regions travel to Paris in March to each accept the award and a generous prize of close to R1 million. Nyokong now heads the new Nanotechnology Innovation Centre for medical sensors: the biggest single research investment in the history of Rhodes. Linked to other nanotechnology centres in the country, it is designed to bridge the gap between research and the market.
- Full Text:
- Date Issued: 2009
Chris McGregor/Archie Shepp.
- Authors: Bethune, Christian
- Subjects: McGregor, Chris--1936-1990 , Shepp, Archie , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Language: French
- Type: Article
- Identifier: vital:13501 , http://hdl.handle.net/10962/d1005748 , McGregor, Chris--1936-1990 , Shepp, Archie , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Description: Photocopied article from the French magazine Jazz Magazine about Chris McGregor's Brotherhood of Breath sharing the stage with Archie Shepp at a concert at La Courneuve, France, the 18th of March 1989. The author of this article criticizes the length of the concert, which was, according to him, too long (2:30 without any break).
- Full Text:
- Authors: Bethune, Christian
- Subjects: McGregor, Chris--1936-1990 , Shepp, Archie , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Language: French
- Type: Article
- Identifier: vital:13501 , http://hdl.handle.net/10962/d1005748 , McGregor, Chris--1936-1990 , Shepp, Archie , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Description: Photocopied article from the French magazine Jazz Magazine about Chris McGregor's Brotherhood of Breath sharing the stage with Archie Shepp at a concert at La Courneuve, France, the 18th of March 1989. The author of this article criticizes the length of the concert, which was, according to him, too long (2:30 without any break).
- Full Text:
Learning from the people : participatory rural appraisal, geography and rural development in the 'new' South Africa
- Binns, Tony, Hill, Trevor R, Nel, Etienne L
- Authors: Binns, Tony , Hill, Trevor R , Nel, Etienne L
- Date: 1997
- Language: English
- Type: Article
- Identifier: vital:6675 , http://hdl.handle.net/10962/d1006649
- Description: Top-down rural development strategies in Africa have generally not succeeded in raising living standards among the rural poor. It is argued that inappropriate development strategies have stemmed from methodologies that fail to appreciate the whole picture in rural communities, and in particular ignore local people's perceptions, needs and understanding. Participatory Rural Appraisal (PRA) represents a significant step forward in the design of methodologies and a selection of these techniques is evaluated. Many PRA methods have much in common with the field research methods that have been used by geographers over many years to interpret people-environment relationships. A research investigation in Eastern Cape Province, South Africa, suggests that geographers could have an important role to play in this area of applied research and, in particular, in the context of post-apartheid South Africa there is an urgent challenge to be met in promoting rural development in poor, former black Homeland areas.
- Full Text:
- Date Issued: 1997
- Authors: Binns, Tony , Hill, Trevor R , Nel, Etienne L
- Date: 1997
- Language: English
- Type: Article
- Identifier: vital:6675 , http://hdl.handle.net/10962/d1006649
- Description: Top-down rural development strategies in Africa have generally not succeeded in raising living standards among the rural poor. It is argued that inappropriate development strategies have stemmed from methodologies that fail to appreciate the whole picture in rural communities, and in particular ignore local people's perceptions, needs and understanding. Participatory Rural Appraisal (PRA) represents a significant step forward in the design of methodologies and a selection of these techniques is evaluated. Many PRA methods have much in common with the field research methods that have been used by geographers over many years to interpret people-environment relationships. A research investigation in Eastern Cape Province, South Africa, suggests that geographers could have an important role to play in this area of applied research and, in particular, in the context of post-apartheid South Africa there is an urgent challenge to be met in promoting rural development in poor, former black Homeland areas.
- Full Text:
- Date Issued: 1997
Beyond the development impasse : the role of local economic development and community self-reliance in rural South Africa
- Authors: Binns, Tony , Nel, Etienne L
- Date: 1999
- Language: English
- Type: Article
- Identifier: vital:6673 , http://hdl.handle.net/10962/d1006647
- Description: The failure of successive generations of imported, Western development strategies and projects to deliver meaningful reductions in poverty and achieve basic needs in Africa, has provoked a deep questioning of Western concepts and methodologies of development. Non-governmental organisations and development practitioners are increasingly focusing their attention on strategies which build upon local knowledge, skills and resources. The concepts of ‘self- reliance’ and local economic development are examined in the context of development challenges which face Africa. This is followed by a detailed case study of local economic development in the rural Mpofu District of the former Ciskei Homeland, which was incorporated into the Eastern Cape province of South Africa with the demise of apartheid in 1994.
- Full Text:
- Date Issued: 1999
- Authors: Binns, Tony , Nel, Etienne L
- Date: 1999
- Language: English
- Type: Article
- Identifier: vital:6673 , http://hdl.handle.net/10962/d1006647
- Description: The failure of successive generations of imported, Western development strategies and projects to deliver meaningful reductions in poverty and achieve basic needs in Africa, has provoked a deep questioning of Western concepts and methodologies of development. Non-governmental organisations and development practitioners are increasingly focusing their attention on strategies which build upon local knowledge, skills and resources. The concepts of ‘self- reliance’ and local economic development are examined in the context of development challenges which face Africa. This is followed by a detailed case study of local economic development in the rural Mpofu District of the former Ciskei Homeland, which was incorporated into the Eastern Cape province of South Africa with the demise of apartheid in 1994.
- Full Text:
- Date Issued: 1999
The effect of prolonged cold storage of eland (Taurotragus oryx) cauda epididymides on the spermatozoa: possible implications for the conservation of biodiversity
- Bissett, Charlene, Bernard, Ric T F
- Authors: Bissett, Charlene , Bernard, Ric T F
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6947 , http://hdl.handle.net/10962/d1011976
- Description: The objectives of this study were to investigate the effects of prolonged storage of cauda epididymides at 4 °C on spermatozoa, and to determine the practicality of utilising epididymal sperm, harvested from testes collected during routine culling of game animals, in assisted reproductive technologies. Testes from eland (Taurotragus oryx) were collected and epididymides removed and maintained at 4 °C. Sperm motility, viability, morphology and membrane integrity were examined at 12 h intervals for 108 h. Sperm motility and viability were significantly lower at the end of the experiment than at the start (P < 0.05) and there was individual variation in the rate at which motility and viability declined. The total number of normal sperm decreased significantly with prolonged storage at 4 °C. Midpiece defects were the most common and head and tail abnormalities were rare. A significant decrease in acrosomal and nuclear membrane integrity was observed with prolonged cold storage but there was no significant change in cell membrane integrity. However, about 30% of epididymal sperm survived for 3 days at 4 °C and more than 10% survived for 4 days, and it should be possible to use sperm from culled animals in some assisted reproductive technologies.
- Full Text:
- Date Issued: 2005
- Authors: Bissett, Charlene , Bernard, Ric T F
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6947 , http://hdl.handle.net/10962/d1011976
- Description: The objectives of this study were to investigate the effects of prolonged storage of cauda epididymides at 4 °C on spermatozoa, and to determine the practicality of utilising epididymal sperm, harvested from testes collected during routine culling of game animals, in assisted reproductive technologies. Testes from eland (Taurotragus oryx) were collected and epididymides removed and maintained at 4 °C. Sperm motility, viability, morphology and membrane integrity were examined at 12 h intervals for 108 h. Sperm motility and viability were significantly lower at the end of the experiment than at the start (P < 0.05) and there was individual variation in the rate at which motility and viability declined. The total number of normal sperm decreased significantly with prolonged storage at 4 °C. Midpiece defects were the most common and head and tail abnormalities were rare. A significant decrease in acrosomal and nuclear membrane integrity was observed with prolonged cold storage but there was no significant change in cell membrane integrity. However, about 30% of epididymal sperm survived for 3 days at 4 °C and more than 10% survived for 4 days, and it should be possible to use sperm from culled animals in some assisted reproductive technologies.
- Full Text:
- Date Issued: 2005
Disabling myth or writing for the world: the secondary schools language project in the Eastern Province, South Africa
- Authors: Bleach, Jean
- Date: 1998
- Language: English
- Type: Article
- Identifier: vital:7016 , http://hdl.handle.net/10962/d1007170
- Description: The majority of learners in South African schools are black, and they learn through English as a second language (L2). This contrasts with white students who learn through their first language (L1), English or Afrikaans. Most black students in South Africa are multilingual, and new developments in the curriculum promise to value this achievement. Even now, young black students display considerable competence in their written English when they use electronic links to communicate with fellow students and adults worldwide. Computers motivate students as writers and language learners. One of the many disabling myths that threatens to impede progress towards equity in educational outcomes in South Africa is the myth that teachers of writing in historically black schools will wait a very long time for the technologies of word processing and e-mail to be available to them. In the Eastern Province many schools have no telephones or electricity. The ANC Government is struggling to meet basic needs quickly and computers could then be used to promote equity among learners. In this study, students had only limited access to keyboard and e-mail facilities, yet the enthusiasm and concentration computers generated meant that they could leapfrog many hours of classroom instruction.
- Full Text:
- Date Issued: 1998
- Authors: Bleach, Jean
- Date: 1998
- Language: English
- Type: Article
- Identifier: vital:7016 , http://hdl.handle.net/10962/d1007170
- Description: The majority of learners in South African schools are black, and they learn through English as a second language (L2). This contrasts with white students who learn through their first language (L1), English or Afrikaans. Most black students in South Africa are multilingual, and new developments in the curriculum promise to value this achievement. Even now, young black students display considerable competence in their written English when they use electronic links to communicate with fellow students and adults worldwide. Computers motivate students as writers and language learners. One of the many disabling myths that threatens to impede progress towards equity in educational outcomes in South Africa is the myth that teachers of writing in historically black schools will wait a very long time for the technologies of word processing and e-mail to be available to them. In the Eastern Province many schools have no telephones or electricity. The ANC Government is struggling to meet basic needs quickly and computers could then be used to promote equity among learners. In this study, students had only limited access to keyboard and e-mail facilities, yet the enthusiasm and concentration computers generated meant that they could leapfrog many hours of classroom instruction.
- Full Text:
- Date Issued: 1998
Identification of Cadherin 2 (CDH2) Mutations in Arrhythmogenic Right Ventricular Cardiomyopathy
- Authors: Bongani M. Mayosi
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5666 , vital:44622
- Full Text:
- Authors: Bongani M. Mayosi
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5666 , vital:44622
- Full Text:
Maximum likelihood and Bayesian approaches to stock assessment when data are questionable
- Booth, Anthony J, Quinn II, T J
- Authors: Booth, Anthony J , Quinn II, T J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6764 , http://hdl.handle.net/10962/d1007962
- Description: This study examines the use of age-structured maximum likelihood and Bayesian approaches for stock assessment of the Namibian monkfish, Lophius vomerinus, resource with questionable data, in which time series are short, abundance indices are variable, and research data conflict with commercial data. Bayesian approaches with both noninformative and informative priors are investigated to determine if they enhance estimation stability. Three data scenarios are assessed: commercial and research survey data, research survey data only, and commercial data only. Both statistical approaches show that resource abundance has decreased with exploitable biomass estimated at approximately 44% of pristine levels. The maximum likelihood and the Bayesian approach with noninformative priors result in similar estimates. As the abundance data contained little information pertaining to possible density dependence within the stock–recruit relationship, only a Bayesian approach with informative priors reduces uncertainty in the steepness parameter h. Estimated management quantities are sensitive both to the set of data sources and whether prior information was informative or not. The strengths of the Bayesian approach include the integration of prior information with uncertain data, the exploration of data conflicts, and the ability to show the uncertainty in estimates of management parameters. Its weakness is that estimation stability is dependent on the choice of priors, which alters some posterior distributions of management quantities.
- Full Text:
- Date Issued: 2006
- Authors: Booth, Anthony J , Quinn II, T J
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6764 , http://hdl.handle.net/10962/d1007962
- Description: This study examines the use of age-structured maximum likelihood and Bayesian approaches for stock assessment of the Namibian monkfish, Lophius vomerinus, resource with questionable data, in which time series are short, abundance indices are variable, and research data conflict with commercial data. Bayesian approaches with both noninformative and informative priors are investigated to determine if they enhance estimation stability. Three data scenarios are assessed: commercial and research survey data, research survey data only, and commercial data only. Both statistical approaches show that resource abundance has decreased with exploitable biomass estimated at approximately 44% of pristine levels. The maximum likelihood and the Bayesian approach with noninformative priors result in similar estimates. As the abundance data contained little information pertaining to possible density dependence within the stock–recruit relationship, only a Bayesian approach with informative priors reduces uncertainty in the steepness parameter h. Estimated management quantities are sensitive both to the set of data sources and whether prior information was informative or not. The strengths of the Bayesian approach include the integration of prior information with uncertain data, the exploration of data conflicts, and the ability to show the uncertainty in estimates of management parameters. Its weakness is that estimation stability is dependent on the choice of priors, which alters some posterior distributions of management quantities.
- Full Text:
- Date Issued: 2006
Possible trace fossils of putative termite origin in the Lower Jurassic (Karoo Supergroup) of South Africa and Lesotho
- Bordy, Emese M, Bumby, A J, Catuneanu, O, Eriksson, P G
- Authors: Bordy, Emese M , Bumby, A J , Catuneanu, O , Eriksson, P G
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6732 , http://hdl.handle.net/10962/d1007541
- Description: Complex structures in the sandstones of the Lower Jurassic aeolian Clarens Formation (Karoo Supergroup) are found at numerous localities throughout southern Africa, and can be assigned to five distinct architectural groups: (1) up to 3.3-m high, free-standing, slab-shaped forms of bioturbated sandstones with elliptical bases, orientated buttresses and an interconnecting large burrow system; (2) up to 1.2-m high, free-standing, irregular forms of bioturbated sandstones with 2-cm to 4-cm thick, massive walls, empty chambers and vertical shafts; (3) about 0.15-m to 0.25-m high, mainly bulbous, multiple forms with thin walls (<2 cm), hollow chambers with internal pillars and bridges; (4) about 0.15-m to 0.2-m (maximum 1-m) high, free-standing forms of aggregated solitary spheres associated with massive horizontal, orientated capsules or tubes, and meniscate tubes; and (5) about 5 cmin diameter, ovoid forms with weak internal shelving in a close-fitting cavity. Based on size, wall thickness, orientation and the presence of internal chambers, these complex structures are tentatively interpreted as ichnofossils of an Early Jurassic social organism; the different architectures are reflective of the different behaviours of more than one species, the history of structural change in architectural forms (ontogenetic series) or an architectural adaptation to local palaeoclimatic variability. While exact modern equivalents are unknown, some of these ichnofossils are comparable to nests (or parts of nests) constructed by extant termites, and thus these Jurassic structures are very tentatively interpreted here as having been made by a soil-dwelling social organism, probably of termite origin. This southern African discovery, along with reported Triassic and Jurassic termite ichnofossils from North America, supports previous hypotheses that sociality in insects, particularity in termites, likely evolved prior to the Pangea breakup in the Early Mesozoic.
- Full Text:
- Date Issued: 2009
- Authors: Bordy, Emese M , Bumby, A J , Catuneanu, O , Eriksson, P G
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6732 , http://hdl.handle.net/10962/d1007541
- Description: Complex structures in the sandstones of the Lower Jurassic aeolian Clarens Formation (Karoo Supergroup) are found at numerous localities throughout southern Africa, and can be assigned to five distinct architectural groups: (1) up to 3.3-m high, free-standing, slab-shaped forms of bioturbated sandstones with elliptical bases, orientated buttresses and an interconnecting large burrow system; (2) up to 1.2-m high, free-standing, irregular forms of bioturbated sandstones with 2-cm to 4-cm thick, massive walls, empty chambers and vertical shafts; (3) about 0.15-m to 0.25-m high, mainly bulbous, multiple forms with thin walls (<2 cm), hollow chambers with internal pillars and bridges; (4) about 0.15-m to 0.2-m (maximum 1-m) high, free-standing forms of aggregated solitary spheres associated with massive horizontal, orientated capsules or tubes, and meniscate tubes; and (5) about 5 cmin diameter, ovoid forms with weak internal shelving in a close-fitting cavity. Based on size, wall thickness, orientation and the presence of internal chambers, these complex structures are tentatively interpreted as ichnofossils of an Early Jurassic social organism; the different architectures are reflective of the different behaviours of more than one species, the history of structural change in architectural forms (ontogenetic series) or an architectural adaptation to local palaeoclimatic variability. While exact modern equivalents are unknown, some of these ichnofossils are comparable to nests (or parts of nests) constructed by extant termites, and thus these Jurassic structures are very tentatively interpreted here as having been made by a soil-dwelling social organism, probably of termite origin. This southern African discovery, along with reported Triassic and Jurassic termite ichnofossils from North America, supports previous hypotheses that sociality in insects, particularity in termites, likely evolved prior to the Pangea breakup in the Early Mesozoic.
- Full Text:
- Date Issued: 2009
Enigmatic trace fossils from the Aeolian lower Jurassic Clarens formation, Southern Africa
- Authors: Bordy, Emese M
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6730 , http://hdl.handle.net/10962/d1007538
- Description: The Lower Jurassic aeolienites of the Clarens Formation in southern Africa contain unique sedimentary structures that are unlikely to be non-biogenic. They are also unlike any known modern or ancient trace fossils. Here, some nigmatic, horizontal,regularly-oriented sedimentary structures are described, which occur in association with other trace fossils as well as features that were previously nterpreted as nests of termites or termite-like ancient social nsects. These spectacular structures are exposed in enormous profusion as straight, ~5 mm cylinders with strong compass orientation, in parallel alignment with one another and to ancient horizontal bedding planes. Their fill is identical to that of the host rock: clean, well-sorted, very fine- to finegrained quartz-arenite. In cross-section, each structure is defined by a subtle, ~0.1 mm thin, concentric gap. Without comparable modern biogenic structures, the biological origin of the structures is uncertain. Their strong compass orientations are, however, also inconsistent with an inorganic origin, even though they may resemble pipey concretions generated by flowing groundwater. Nonetheless, this paper, based on spatiotemporal distribution patterns of the oriented structures, their locally high abundance and association with obvious trace fossils, as well as other sedimentological and palaeontological lines of evidence, argues that the compass structures may be products of ancient social invertebrates living in a resource-limited, semi-arid to arid environment. Furthermore, the compass structures as well as the accompanying structures of the predominantly aeolian Clarens Formation collectively imply the recurrence of favourable ecological parameters (e.g., moist ubstrates) related to episodic climate fluctuations in the Early Jurassic of southern Pangaea (i.e., southern Gondwana).
- Full Text:
- Date Issued: 2008
- Authors: Bordy, Emese M
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6730 , http://hdl.handle.net/10962/d1007538
- Description: The Lower Jurassic aeolienites of the Clarens Formation in southern Africa contain unique sedimentary structures that are unlikely to be non-biogenic. They are also unlike any known modern or ancient trace fossils. Here, some nigmatic, horizontal,regularly-oriented sedimentary structures are described, which occur in association with other trace fossils as well as features that were previously nterpreted as nests of termites or termite-like ancient social nsects. These spectacular structures are exposed in enormous profusion as straight, ~5 mm cylinders with strong compass orientation, in parallel alignment with one another and to ancient horizontal bedding planes. Their fill is identical to that of the host rock: clean, well-sorted, very fine- to finegrained quartz-arenite. In cross-section, each structure is defined by a subtle, ~0.1 mm thin, concentric gap. Without comparable modern biogenic structures, the biological origin of the structures is uncertain. Their strong compass orientations are, however, also inconsistent with an inorganic origin, even though they may resemble pipey concretions generated by flowing groundwater. Nonetheless, this paper, based on spatiotemporal distribution patterns of the oriented structures, their locally high abundance and association with obvious trace fossils, as well as other sedimentological and palaeontological lines of evidence, argues that the compass structures may be products of ancient social invertebrates living in a resource-limited, semi-arid to arid environment. Furthermore, the compass structures as well as the accompanying structures of the predominantly aeolian Clarens Formation collectively imply the recurrence of favourable ecological parameters (e.g., moist ubstrates) related to episodic climate fluctuations in the Early Jurassic of southern Pangaea (i.e., southern Gondwana).
- Full Text:
- Date Issued: 2008
Sedimentology of the upper Karoo fluvial strata in the Tuli Basin, South Africa
- Bordy, Emese M, Catuneanu, O
- Authors: Bordy, Emese M , Catuneanu, O
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6731 , http://hdl.handle.net/10962/d1007540
- Description: The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) may be grouped in four stratigraphic units: the basal, middle and upper units, and the Clarens Formation. This paper presents the findings of the sedimentological investigation of the fluvial terrigenous clastic and chemical deposits of the upper unit. Evidence provided by primary sedimentary structures, palaeontological record, borehole data, palaeo-flow measurements and stratigraphic relations resulted in the palaeo-environmental reconstruction of the upper unit. The dominant facies assemblages are represented by sandstones and finer-grained sediments, which both can be interbedded with subordinate intraformational coarser facies. The facies assemblages of the upper unit are interpreted as deposits of a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the upper unit, the climate was semi-arid with sparse precipitation resulting in high-magnitude, low-frequency devastating flash floods. The current indicators of the palaeo-drainage system suggest flow direction from northwest to southeast, in a dominantly extensional tectonic setting. Based on sedimentologic and biostratigraphic evidence, the upper unit of the Tuli Basin correlates to the Elliot Formation in the main Karoo Basin to the south.
- Full Text:
- Date Issued: 2001
- Authors: Bordy, Emese M , Catuneanu, O
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6731 , http://hdl.handle.net/10962/d1007540
- Description: The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) may be grouped in four stratigraphic units: the basal, middle and upper units, and the Clarens Formation. This paper presents the findings of the sedimentological investigation of the fluvial terrigenous clastic and chemical deposits of the upper unit. Evidence provided by primary sedimentary structures, palaeontological record, borehole data, palaeo-flow measurements and stratigraphic relations resulted in the palaeo-environmental reconstruction of the upper unit. The dominant facies assemblages are represented by sandstones and finer-grained sediments, which both can be interbedded with subordinate intraformational coarser facies. The facies assemblages of the upper unit are interpreted as deposits of a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the upper unit, the climate was semi-arid with sparse precipitation resulting in high-magnitude, low-frequency devastating flash floods. The current indicators of the palaeo-drainage system suggest flow direction from northwest to southeast, in a dominantly extensional tectonic setting. Based on sedimentologic and biostratigraphic evidence, the upper unit of the Tuli Basin correlates to the Elliot Formation in the main Karoo Basin to the south.
- Full Text:
- Date Issued: 2001
Molecular chaperones in biology, medicine and protein biotechnology
- Boshoff, Aileen, Nicoll, William S, Hennessy, Fritha, Ludewig, M H, Daniel, Sheril, Modisakeng, Keoagile W, Shonhai, Addmore, McNamara, Caryn, Bradley, Graeme, Blatch, Gregory L
- Authors: Boshoff, Aileen , Nicoll, William S , Hennessy, Fritha , Ludewig, M H , Daniel, Sheril , Modisakeng, Keoagile W , Shonhai, Addmore , McNamara, Caryn , Bradley, Graeme , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6457 , http://hdl.handle.net/10962/d1004479
- Description: Molecular chaperones consist of several highly conserved families of proteins, many of which consist of heat shock proteins. The primary function of molecular chaperones is to facilitate the folding or refolding of proteins, and therefore they play an important role in diverse cellular processes including protein synthesis, protein translocation, and the refolding or degradation of proteins after cell stress. Cells are often exposed to different stressors, resulting in protein misfolding and aggregation. It is now well established that the levels of certain molecular chaperones are elevated during stress to provide protection to the cell. The focus of this review is on the impact of molecular chaperones in biology, medicine and protein biotechnology, and thus covers both fundamental and applied aspects of chaperone biology. Attention is paid to the functions and applications of molecular chaperones from bacterial and eukaryotic cells, focusing on the heat shock proteins 90 (Hsp90), 70 (Hsp70) and 40 (Hsp40) classes of chaperones, respectively. The role of these classes of chaperones in human diseases is discussed, as well as the parts played by chaperones produced by the causative agents of malaria and trypanosomiasis. Recent advances have seen the application of chaperones in improving the yields of a particular target protein in recombinant protein production. The prospects for the targeted use of molecular chaperones for the over-production of recombinant proteins is critically reviewed, and current research on these chaperones at Rhodes University is also discussed.
- Full Text:
- Date Issued: 2004
- Authors: Boshoff, Aileen , Nicoll, William S , Hennessy, Fritha , Ludewig, M H , Daniel, Sheril , Modisakeng, Keoagile W , Shonhai, Addmore , McNamara, Caryn , Bradley, Graeme , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6457 , http://hdl.handle.net/10962/d1004479
- Description: Molecular chaperones consist of several highly conserved families of proteins, many of which consist of heat shock proteins. The primary function of molecular chaperones is to facilitate the folding or refolding of proteins, and therefore they play an important role in diverse cellular processes including protein synthesis, protein translocation, and the refolding or degradation of proteins after cell stress. Cells are often exposed to different stressors, resulting in protein misfolding and aggregation. It is now well established that the levels of certain molecular chaperones are elevated during stress to provide protection to the cell. The focus of this review is on the impact of molecular chaperones in biology, medicine and protein biotechnology, and thus covers both fundamental and applied aspects of chaperone biology. Attention is paid to the functions and applications of molecular chaperones from bacterial and eukaryotic cells, focusing on the heat shock proteins 90 (Hsp90), 70 (Hsp70) and 40 (Hsp40) classes of chaperones, respectively. The role of these classes of chaperones in human diseases is discussed, as well as the parts played by chaperones produced by the causative agents of malaria and trypanosomiasis. Recent advances have seen the application of chaperones in improving the yields of a particular target protein in recombinant protein production. The prospects for the targeted use of molecular chaperones for the over-production of recombinant proteins is critically reviewed, and current research on these chaperones at Rhodes University is also discussed.
- Full Text:
- Date Issued: 2004
Reduction in transport in wheat (Triticum aestivum) is caused by sustained phloem feeding by the Russian wheat aphid (Diuraphis noxia)
- Botha, Christiaan E J, Matsiliza, Babalwa
- Authors: Botha, Christiaan E J , Matsiliza, Babalwa
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6498 , http://hdl.handle.net/10962/d1004498
- Description: The Russian wheat aphid (Diuraphis noxia) feeds preferentially from the phloem of longitudinal veins of nonresistant wheat leaves. The xenobiotic, 5,6-CFDA was applied to exposed leaf blade mesophyll cells in control and aphid-infested plants. In control plants, the fluorophore moved approximately 5–6cm from the point of application of 5,6-CFDA within 3h of application. The fluorochrome was transported in the sieve tube companion cell complex, including those in the numerous interconnecting transverse veins. Leaf blades on which the Russian wheat aphid had been feeding demonstrated a marked decrease in 5,6-CF transport. Aphids feeding on the leaves formed local sinks and redirected the fluorophore (and presumably associated assimilate) to the aphids’ gut, with little longitudinal translocation of 5,6-CF below inserted stylets or aphid feeding areas. Aniline blue staining revealed massive deposits of wound and reaction callose caused by the aphids, with callose associated with the sieve plates, pore-plasmodesma between the companion cells and their associated sieve tubes, as well as with plasmodesmal aggregates in parenchymatous elements within the vascular bundles. Leaves that had been colonised by aphids but from which the aphids were removed, showed extensive wound callose deposits, which persisted for up to 48h after removal of aphid colonies, suggesting that the damage caused by aphid feeding is a long-term, non-transient event in non-resistant plants.
- Full Text:
- Date Issued: 2004
- Authors: Botha, Christiaan E J , Matsiliza, Babalwa
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6498 , http://hdl.handle.net/10962/d1004498
- Description: The Russian wheat aphid (Diuraphis noxia) feeds preferentially from the phloem of longitudinal veins of nonresistant wheat leaves. The xenobiotic, 5,6-CFDA was applied to exposed leaf blade mesophyll cells in control and aphid-infested plants. In control plants, the fluorophore moved approximately 5–6cm from the point of application of 5,6-CFDA within 3h of application. The fluorochrome was transported in the sieve tube companion cell complex, including those in the numerous interconnecting transverse veins. Leaf blades on which the Russian wheat aphid had been feeding demonstrated a marked decrease in 5,6-CF transport. Aphids feeding on the leaves formed local sinks and redirected the fluorophore (and presumably associated assimilate) to the aphids’ gut, with little longitudinal translocation of 5,6-CF below inserted stylets or aphid feeding areas. Aniline blue staining revealed massive deposits of wound and reaction callose caused by the aphids, with callose associated with the sieve plates, pore-plasmodesma between the companion cells and their associated sieve tubes, as well as with plasmodesmal aggregates in parenchymatous elements within the vascular bundles. Leaves that had been colonised by aphids but from which the aphids were removed, showed extensive wound callose deposits, which persisted for up to 48h after removal of aphid colonies, suggesting that the damage caused by aphid feeding is a long-term, non-transient event in non-resistant plants.
- Full Text:
- Date Issued: 2004
A xylem retrieval pathway in rice leaf blades – evidence of a role for endocytosis?
- Botha, Christiaan E J, Aoki, N, Scofield, G N, Liu, Lin, Furbank, R T, White, R G
- Authors: Botha, Christiaan E J , Aoki, N , Scofield, G N , Liu, Lin , Furbank, R T , White, R G
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6505 , http://hdl.handle.net/10962/d1005930 , http://dx.doi.org/10.1093/jxb/ern150
- Description: The structure and transport properties of pit membranes at the interface between the metaxylem and xylem parenchyma cells and the possible role of these pit membranes in solute transfer to the phloem was investigated. Electron microscopy revealed a fibrillar, almost tubular matrix within the pit membrane structure between the xylem vessels and xylem parenchyma of leaf blade bundles in rice (Oryza sativa). These pits are involved primarily with regulating water flux to the surrounding xylem parenchyma cells. Vascular parenchyma cells contain large mitochondrial populations, numerous dictyosomes, endomembrane complexes and vesicles in close proximity to the pit membrane. Taken collectively this suggests that endocytosis may occur at this interface. A weak solution of 5,6-carboxyfluorescein diacetate (5,6-CFDA) was applied to cut ends of leaves and after a minimum of 45 minutes, the distribution of the fluorescent cleavage product, 5,6-carboxyfluorescein (5,6-CF) was observed using confocal microscopy. Cleavage of 5,6-CFDA occurred within the xylem parenchyma cells and the non-polar 5,6-CF was then symplasmically transported to other parenchyma elements and ultimately, via numerous pore plasmodesmata, to adjacent thick-walled sieve tubes. Application of Lucifer Yellow, and, separately, Texas Red labelled dextran (10 kDa) to the transpiration stream, confirmed that these membrane-impermeant probes could only have been offloaded from the xylem via the xylem vessel-xylem parenchyma pit membranes, suggesting endocytotic transmembrane transfer of these membrane-impermeant fluorophores. Accumulation within the thick-walled sieve tubes, but not in thin-walled sieve tubes, confirms the presence of a symplasmic phloem loading pathway, via pore plasmodesmata between xylem parenchyma and thick-walled sieve tubes, but not thin-walled sieve tubes.
- Full Text:
- Date Issued: 2008
- Authors: Botha, Christiaan E J , Aoki, N , Scofield, G N , Liu, Lin , Furbank, R T , White, R G
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6505 , http://hdl.handle.net/10962/d1005930 , http://dx.doi.org/10.1093/jxb/ern150
- Description: The structure and transport properties of pit membranes at the interface between the metaxylem and xylem parenchyma cells and the possible role of these pit membranes in solute transfer to the phloem was investigated. Electron microscopy revealed a fibrillar, almost tubular matrix within the pit membrane structure between the xylem vessels and xylem parenchyma of leaf blade bundles in rice (Oryza sativa). These pits are involved primarily with regulating water flux to the surrounding xylem parenchyma cells. Vascular parenchyma cells contain large mitochondrial populations, numerous dictyosomes, endomembrane complexes and vesicles in close proximity to the pit membrane. Taken collectively this suggests that endocytosis may occur at this interface. A weak solution of 5,6-carboxyfluorescein diacetate (5,6-CFDA) was applied to cut ends of leaves and after a minimum of 45 minutes, the distribution of the fluorescent cleavage product, 5,6-carboxyfluorescein (5,6-CF) was observed using confocal microscopy. Cleavage of 5,6-CFDA occurred within the xylem parenchyma cells and the non-polar 5,6-CF was then symplasmically transported to other parenchyma elements and ultimately, via numerous pore plasmodesmata, to adjacent thick-walled sieve tubes. Application of Lucifer Yellow, and, separately, Texas Red labelled dextran (10 kDa) to the transpiration stream, confirmed that these membrane-impermeant probes could only have been offloaded from the xylem via the xylem vessel-xylem parenchyma pit membranes, suggesting endocytotic transmembrane transfer of these membrane-impermeant fluorophores. Accumulation within the thick-walled sieve tubes, but not in thin-walled sieve tubes, confirms the presence of a symplasmic phloem loading pathway, via pore plasmodesmata between xylem parenchyma and thick-walled sieve tubes, but not thin-walled sieve tubes.
- Full Text:
- Date Issued: 2008
Phloem loading in the sucrose-export-defective (SXD-1) mutant maize is limited by callose deposition at plasmodesmata in bundle sheath-vascular parenchyma interface
- Botha, Christiaan E J, Cross, Robin H M, Van Bel, A J E, Peter, Craig I
- Authors: Botha, Christiaan E J , Cross, Robin H M , Van Bel, A J E , Peter, Craig I
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6503 , http://hdl.handle.net/10962/d1005926
- Description: Using Lucifer Yellow we have demonstrated that the phloem-loading pathway from the mesophyll to the bundle sheath-vascular parenchyma interface in Zea mays source leaves follows a symplasmic route in small and intermediate vascular bundles in control as well as in the green sections of mutant sucrose-export-defective (SXD-1) plants. In the anthocyanin-rich mutant leaf sections, Lucifer Yellow transport was prohibited along the same path, at the bundle sheath-vascular parenchyma interface in particular. Plasmodesmata at the latter interface in SXD-1 anthocyanin-rich leaf sections appear to be structurally altered through callose deposition at the plasmodesmal orifices. We suggest that a transport bottleneck at the bundle sheath-vascular parenchyma interface is thus orchestrated and regulated through callose formation, preventing symplasmic transport across this important loading interface.
- Full Text:
- Date Issued: 2000
- Authors: Botha, Christiaan E J , Cross, Robin H M , Van Bel, A J E , Peter, Craig I
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6503 , http://hdl.handle.net/10962/d1005926
- Description: Using Lucifer Yellow we have demonstrated that the phloem-loading pathway from the mesophyll to the bundle sheath-vascular parenchyma interface in Zea mays source leaves follows a symplasmic route in small and intermediate vascular bundles in control as well as in the green sections of mutant sucrose-export-defective (SXD-1) plants. In the anthocyanin-rich mutant leaf sections, Lucifer Yellow transport was prohibited along the same path, at the bundle sheath-vascular parenchyma interface in particular. Plasmodesmata at the latter interface in SXD-1 anthocyanin-rich leaf sections appear to be structurally altered through callose deposition at the plasmodesmal orifices. We suggest that a transport bottleneck at the bundle sheath-vascular parenchyma interface is thus orchestrated and regulated through callose formation, preventing symplasmic transport across this important loading interface.
- Full Text:
- Date Issued: 2000
A tale of two neglected systems-structure and function of the thin- and thick-walled sieve tubes in monocotyledonous leaves
- Authors: Botha, Christiaan E J
- Date: 2013
- Language: English
- Type: Article , text
- Identifier: vital:6499 , http://hdl.handle.net/10962/d1004514 , http://dx.doi.org/10.3389/fpls.2013.00297
- Description: There is a large body of information relating to the ontogeny, development and the vasculature of eudicotyledonous leaves. However, there is less information available concerning the vascular anatomy of monocotyledonous leaves. This is surprising, given that there are two uniquely different phloem systems present in large groups such as grasses and sedges. Monocotyledonous leaves contain marginal, large, intermediate, and small longitudinal veins that are interconnected by numerous transverse veins. The longitudinal veins contain two metaphloem sieve tube types, which, based upon their ontogeny and position within the phloem, are termed early (thin-walled) and late (thick-walled) sieve tubes. Early metaphloem comprises sieve tubes, companion cells and vascular parenchyma (VP) cells, whilst the late metaphloem, contains thick-walled sieve tubes (TSTs) that lack companion cells. TSTs are generally adjacent to, or no more than one cell removed from the metaxylem. Unlike thin-walled sieve tube (ST) -companion cell complexes, TSTs are connected to parenchyma by pore-plasmodesma units and are generally symplasmically isolated from the STs. This paper addresses key structural and functional differences between thin- and thick-walled sieve tubes and explores the unique advantages of alternate transport strategies that this 5–7 million years old dual system may offer. It would seem that these two systems may enhance, add to, or play a significant role in increasing the efficiency of solute retrieval as well as of assimilate transfer.
- Full Text:
- Date Issued: 2013
- Authors: Botha, Christiaan E J
- Date: 2013
- Language: English
- Type: Article , text
- Identifier: vital:6499 , http://hdl.handle.net/10962/d1004514 , http://dx.doi.org/10.3389/fpls.2013.00297
- Description: There is a large body of information relating to the ontogeny, development and the vasculature of eudicotyledonous leaves. However, there is less information available concerning the vascular anatomy of monocotyledonous leaves. This is surprising, given that there are two uniquely different phloem systems present in large groups such as grasses and sedges. Monocotyledonous leaves contain marginal, large, intermediate, and small longitudinal veins that are interconnected by numerous transverse veins. The longitudinal veins contain two metaphloem sieve tube types, which, based upon their ontogeny and position within the phloem, are termed early (thin-walled) and late (thick-walled) sieve tubes. Early metaphloem comprises sieve tubes, companion cells and vascular parenchyma (VP) cells, whilst the late metaphloem, contains thick-walled sieve tubes (TSTs) that lack companion cells. TSTs are generally adjacent to, or no more than one cell removed from the metaxylem. Unlike thin-walled sieve tube (ST) -companion cell complexes, TSTs are connected to parenchyma by pore-plasmodesma units and are generally symplasmically isolated from the STs. This paper addresses key structural and functional differences between thin- and thick-walled sieve tubes and explores the unique advantages of alternate transport strategies that this 5–7 million years old dual system may offer. It would seem that these two systems may enhance, add to, or play a significant role in increasing the efficiency of solute retrieval as well as of assimilate transfer.
- Full Text:
- Date Issued: 2013
Plasmodesmatal frequency in relation to short-distance transport and phloem loading in leaves of barley (Hordeum vulgare). Phloem is not loaded directly from the symplast
- Botha, Christiaan E J, Cross, Robin H M
- Authors: Botha, Christiaan E J , Cross, Robin H M
- Date: 1997
- Language: English
- Type: Article
- Identifier: vital:6504 , http://hdl.handle.net/10962/d1005928
- Description: We investigated the phloem loading pathway in barley, by determining plasmodesmatal frequencies at the electron microscope level for both intermediate and small blade bundles of mature barley leaves. Lucifer yellow was injected intercellularly into bundle sheath, vascular parenchyma, and thin-walled sieve tubes. Passage of this symplastically transported dye was monitored with an epifluorescence microscope under blue light. Low plasmodesmatal frequencies endarch to the bundle sheath cells are relatively low for most interfaces terminating at the thin- and thick-walled sieve tubes within this C3 species. Lack of connections between vascular parenchyma and sieve tubes, and low frequencies (0.5% plasmodesmata per μm cell wall interface) of connections between vascular parenchyma and companion cells, as well as the very low frequency of pore-plasmodesmatal connections between companion cells and sieve tubes in small bundles (0.2% plasmodesmata per μm cell wall interface), suggest that the companion cell-sieve tube complex is symplastically isolated from other vascular parenchyma cells in small bundles. The degree of cellular connectivity and the potential isolation of the companion cell-sieve tube complex was determined electrophysiologically, using an electrometer coupled to microcapillary electrodes. The less negative cell potential {average -52 mV) from mesophyll to the vascular parenchyma cells contrasted sharply with the more negative potential (-122.5 mV) recorded for the companion cell-thin-walled sieve tube complex. Although intercellular injection of lucifer yellow clearly demonstrated rapid (0.75 μm s-1) longitudinal and radial transport in the bundle sheath-vascular parenchyma complex, as well as from the bundle sheath through transverse veins to adjacent longitudinal veins, we were neither able to detect nor present unequivocal evidence in support of the symplastic connectivity of the sieve tubes to the vascular parenchyma. Injection of the companion cell-sieve tube complex, did not demonstrate backward connectivity to the bundle sheath. We conclude that the low plasmodesmatal frequencies, coupled with a two-domain electropotential zonation configuration, and the negative transport experiments using lucifer yellow, precludes symplastic phloem loading in barley leaves.
- Full Text:
- Date Issued: 1997
- Authors: Botha, Christiaan E J , Cross, Robin H M
- Date: 1997
- Language: English
- Type: Article
- Identifier: vital:6504 , http://hdl.handle.net/10962/d1005928
- Description: We investigated the phloem loading pathway in barley, by determining plasmodesmatal frequencies at the electron microscope level for both intermediate and small blade bundles of mature barley leaves. Lucifer yellow was injected intercellularly into bundle sheath, vascular parenchyma, and thin-walled sieve tubes. Passage of this symplastically transported dye was monitored with an epifluorescence microscope under blue light. Low plasmodesmatal frequencies endarch to the bundle sheath cells are relatively low for most interfaces terminating at the thin- and thick-walled sieve tubes within this C3 species. Lack of connections between vascular parenchyma and sieve tubes, and low frequencies (0.5% plasmodesmata per μm cell wall interface) of connections between vascular parenchyma and companion cells, as well as the very low frequency of pore-plasmodesmatal connections between companion cells and sieve tubes in small bundles (0.2% plasmodesmata per μm cell wall interface), suggest that the companion cell-sieve tube complex is symplastically isolated from other vascular parenchyma cells in small bundles. The degree of cellular connectivity and the potential isolation of the companion cell-sieve tube complex was determined electrophysiologically, using an electrometer coupled to microcapillary electrodes. The less negative cell potential {average -52 mV) from mesophyll to the vascular parenchyma cells contrasted sharply with the more negative potential (-122.5 mV) recorded for the companion cell-thin-walled sieve tube complex. Although intercellular injection of lucifer yellow clearly demonstrated rapid (0.75 μm s-1) longitudinal and radial transport in the bundle sheath-vascular parenchyma complex, as well as from the bundle sheath through transverse veins to adjacent longitudinal veins, we were neither able to detect nor present unequivocal evidence in support of the symplastic connectivity of the sieve tubes to the vascular parenchyma. Injection of the companion cell-sieve tube complex, did not demonstrate backward connectivity to the bundle sheath. We conclude that the low plasmodesmatal frequencies, coupled with a two-domain electropotential zonation configuration, and the negative transport experiments using lucifer yellow, precludes symplastic phloem loading in barley leaves.
- Full Text:
- Date Issued: 1997
Regulation within the supracellular highway - plasmodesma are the key
- Botha, Christiaan E J, Cross, Robin H M
- Authors: Botha, Christiaan E J , Cross, Robin H M
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6500 , http://hdl.handle.net/10962/d1005918
- Description: Plasmodesmal connections are unique, highly dynamic intercellular structures that are lined by the plasmamembrane. They are believed to be a vital intercellular communication channel between living cells, linking numbers of living cells into interconnected, highly specialised cellular domains, thus enabling the plant to act as an integrated organism. Their evolution in the higher plant was inevitable. It is accepted that cell heterogeneity rather than cell divergence pressurised developing plant systems along a route that led to the development of intercellular passages and connections. With time these connections have evolved to allow some degree of regulation and traffic control. This paper explores some of the structure/function relationships in plasmodesmata. Attention is focused on the potential role of the neck region of these remarkable structures and discusses models which may explain the processes involved in regulating the movement of substances from cell to cell.
- Full Text: false
- Date Issued: 2001
- Authors: Botha, Christiaan E J , Cross, Robin H M
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6500 , http://hdl.handle.net/10962/d1005918
- Description: Plasmodesmal connections are unique, highly dynamic intercellular structures that are lined by the plasmamembrane. They are believed to be a vital intercellular communication channel between living cells, linking numbers of living cells into interconnected, highly specialised cellular domains, thus enabling the plant to act as an integrated organism. Their evolution in the higher plant was inevitable. It is accepted that cell heterogeneity rather than cell divergence pressurised developing plant systems along a route that led to the development of intercellular passages and connections. With time these connections have evolved to allow some degree of regulation and traffic control. This paper explores some of the structure/function relationships in plasmodesmata. Attention is focused on the potential role of the neck region of these remarkable structures and discusses models which may explain the processes involved in regulating the movement of substances from cell to cell.
- Full Text: false
- Date Issued: 2001
The ultrastructure and computer-enhanced digital image analysis of plasmodesmata at the Kranz mesophyll-bundle sheath interface of Themeda triandra var. imberbis (Retz) A. Camus in conventionally-fixed leaf blades
- Botha, Christiaan E J, Hartley, B J, Cross, Robin H M
- Authors: Botha, Christiaan E J , Hartley, B J , Cross, Robin H M
- Date: 1993
- Language: English
- Type: Article
- Identifier: vital:6502 , http://hdl.handle.net/10962/d1005925
- Description: The ultrastructure of the plasmodesmata at the Kranz mesophyll-bundle sheath (KMS-BS) interface in Themeda triandra, and the substructures within the plasmodesmata were investigated, using conventionally fixed leaf-blade material, enhanced by the addition of 0.1% tannic acid to the primary fixative. Examination of high-resolution electronmicrographs, and computer-enhanced digital images suggests that these plasmodesmata are complex structures, comprised of helically-arranged particulate material. The electron-dense particles are between 2.5 and 3.0nm in diameter. These particles are specifically associated with the inner face of the inner plasmalemma membrane leaflet, and the outer region of the desmotubule wall. The electron-dense particles are presumably proteinaceous and embedded in a lipid matrix. In the constricted median portion of the KMS-BS plasmodesmata, the space between the desmotubule and the inner plasmalemma membrane leaflet and areas surrounding the proteinaceous particles thereof (the cytoplasmic sleeve) is about 3nm in cross-section, and constitutes what we believe to be the space through which intercellular transport takes place.
- Full Text: false
- Date Issued: 1993
- Authors: Botha, Christiaan E J , Hartley, B J , Cross, Robin H M
- Date: 1993
- Language: English
- Type: Article
- Identifier: vital:6502 , http://hdl.handle.net/10962/d1005925
- Description: The ultrastructure of the plasmodesmata at the Kranz mesophyll-bundle sheath (KMS-BS) interface in Themeda triandra, and the substructures within the plasmodesmata were investigated, using conventionally fixed leaf-blade material, enhanced by the addition of 0.1% tannic acid to the primary fixative. Examination of high-resolution electronmicrographs, and computer-enhanced digital images suggests that these plasmodesmata are complex structures, comprised of helically-arranged particulate material. The electron-dense particles are between 2.5 and 3.0nm in diameter. These particles are specifically associated with the inner face of the inner plasmalemma membrane leaflet, and the outer region of the desmotubule wall. The electron-dense particles are presumably proteinaceous and embedded in a lipid matrix. In the constricted median portion of the KMS-BS plasmodesmata, the space between the desmotubule and the inner plasmalemma membrane leaflet and areas surrounding the proteinaceous particles thereof (the cytoplasmic sleeve) is about 3nm in cross-section, and constitutes what we believe to be the space through which intercellular transport takes place.
- Full Text: false
- Date Issued: 1993