Allosteric Modulation of Human Hsp90α Conformational Dynamics:
- Authors: Penkler, David L , Atilgan, Canan , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162936 , vital:40998 , https://doi.org/10.1021/acs.jcim.7b00630
- Description: Central to Hsp90’s biological function is its ability to interconvert between various conformational states. Drug targeting of Hsp90’s regulatory mechanisms, including its modulation by cochaperone association, presents as an attractive therapeutic strategy for Hsp90 associated pathologies. In this study, we utilized homology modeling techniques to calculate full-length structures of human Hsp90α in closed and partially open conformations and used these structures as a basis for several molecular dynamics based analyses aimed at elucidating allosteric mechanisms and modulation sites in human Hsp90α.
- Full Text:
- Date Issued: 2018
Aminoacyl tRNA synthetases as malarial drug targets: a comparative bioinformatics study
- Authors: Nyamai, Dorothy Wavinya , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148368 , vital:38733 , DOI: 10.1101/440891
- Description: Treatment of parasitic diseases has been challenging due to evolution of drug resistant parasites, and thus there is need to identify new class of drugs and drug targets. Protein translation is important for survival of malarial parasite, Plasmodium, and the pathway is present in all of its life cycle stages. Aminoacyl tRNA synthetases are primary enzymes in protein translation as they catalyse amino acid addition to the cognate tRNA. This study sought to understand differences between Plasmodium and human aminoacyl tRNA synthetases through bioinformatics analysis.
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- Date Issued: 2018
An ecosystem service value chain analysis framework: a conceptual paper
- Authors: Rawlins, Jonathan M , De Lange, Willem J , Fraser, Gavin C G
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69321 , vital:29499 , https://doi.org/10.1016/j.ecolecon.2017.12.023
- Description: Modern day societies and economies are becoming increasingly vulnerable to the continued erosion of the stocks and flows of essential ecosystem services. Thus, the management of complex socio-economic systems to effectively provide these essential services has become a global priority policy and academic research area. Understanding how underlying processes and functions contribute towards the provision of final ecosystem services can facilitate improved dissemination of credible, legitimate and salient information to decision-makers. This paper presents an ecosystem service value chain analysis framework that applies basic system dynamics modelling in the form of causal loop diagrams to facilitate an alternative analysis of ecosystem service value chains. A scoping application of the framework is applied to a case study for flood attenuation services in the Baviaanskloof catchment in South Africa. The framework enables the identification of forward linkages and ripple effects in individual value chains of final ecosystem services as well as the identification and assessment of challenges and opportunities within individual causal pathways. Ultimately, providing the potential to advance strategies for improving the efficiency and effectiveness of final ecosystem service provision.
- Full Text: false
- Date Issued: 2018
An endangered seahorse selectively chooses an artificial structure
- Authors: Claassens, Louw , Booth, Anthony J , Hodgson, Alan N
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123718 , vital:35486 , https://doi.10.1007/s10641-018-0732-4
- Description: The development of a residential marina estate within the Knysna estuary, South Africa, introduced Reno mattresses (horizontal wire cages filled with rocks) as a novel habitat for the endangered Knysna seahorse Hippocampus capensis. Consistently high seahorse densities on these artificial structures, despite the availability of seagrass habitat, begged the question of whether this habitat was chosen by the seahorse in preference to natural vegetation. An in situ habitat choice experiment was conducted which focused on the choice made by adult H. capensis between natural vegetation (Zostera capensis) and artificial (Reno mattress) habitat within a choice chamber. Seahorses were significantly more likely to move away from Z. capensis onto a Reno mattress structure or remain on this structure. This study concludes that higher H. capensis densities on Reno mattresses within Thesen Islands Marina are owing to some positive feature of this habitat and the underlying processes responsible for the choice made by this species (additional food, holdfasts, protection) can now be investigated.
- Full Text:
- Date Issued: 2018
An exploratory study of Heads of Departments' responses to student calls for decolonised higher education
- Authors: Grant, Carolyn , Quinn, Lynn , Vorster, Jo-Anne E
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123420 , vital:35436 , https://doi.org/10.17159/2520-9868/i72a05
- Description: Central to the tumultuous student protests of 2015 and 2016 was an urgent call for the decolonisation of South African universities. Existing curricula, including teaching and assessment practices, as well as institutional cultures and structures were challenged. Against this backdrop, in this article we focus on the academic leadership role of Heads of Departments (HoDs) at Rhodes University. In this small-scale project we interrogate how HoDs conceptualised their roles in this uncertain and complex context. From the data analysis a number of tensions emerged in the ways in which they articulated and enacted their roles. The findings indicate that the protests have contributed to the increasing complexity of the role of an HoD. Issues raised during the protests catalysed HoDs at Rhodes University, some for the first time, into considering the implications of the decolonising call from students and into exercising stronger transformative leadership roles.
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- Date Issued: 2018
An illustrated booklet for reinforcing community health worker knowledge of tuberculosis and facilitating patient counselling:
- Authors: Okeyo, Ida L A , Dowse, Roslind
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/156629 , vital:40032 , https://phcfm.org/index.php/phcfm/article/view/1687/2559
- Description: Community health workers (CHWs) have facilitated the move to decentralize tuberculosis (TB) management, but lack access to information appropriate both for personal use and in patient interaction and education. To explore the impact of a pictorial-based TB booklet on reinforcing CHW knowledge and facilitating patient counselling.
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- Date Issued: 2018
An Immersive Audio Control System Using Mobile Devices and Ethernet AVB-Capable Speakers:
- Authors: Foss, Richard , Devonport, Sean
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426745 , vital:72388 , https://www.aes.org/e-lib/browse.cfm?elib=19714
- Description: Immersive Sound is commonly used to create the localization of sound sources above, below, and around listeners. To achieve this immersive goal, sound systems are employing an ever-increasing number of speakers. Given that immersive sound systems have large speaker configurations such as in cinemas, theaters, museums, and home theater installations, there is a need to provide control for these various contexts and also to provide a means of automating this control. An immersive sound system has been created that allows for the real-time control over sound source localization. It is a multi-user client/server system where the client devices are mobile devices, thereby allowing remote control over sound source localization. Touch and orientation capabilities of mobile devices are used for the generation of three-dimensional coordinates. The server receives localization control messages from the client and uses an Ethernet AVB (audio video bridging) network to distribute appropriate mix levels to speakers with built-in signal processing. These localization messages can be recorded by users for later playback.
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- Date Issued: 2018
An integrated framework for assessing coastal community vulnerability across cultures, oceans and scales
- Authors: Aswani, Shankar , Howard, J A E , Gasalla, Maria A , Jennings, Sarah , Malherbe, W , Martins, I M , Salim, Shyam S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123063 , vital:35402 , https://doi.10.1080/17565529.2018.1442795
- Description: Across the globe, many coastal communities rely on marine resources for their food security (FS), income and livelihoods and with predicted trends in human populations, the number of people reliant on these resources is likely to increase (FAO, 2012). However, the effects of climate change including increased variability are already being experienced by coastal communities and appear to be accelerating (Doney et al., 2012). Depending on a range of factors, including location, these changes are having mild to severe impacts on communities both in direct and indirect ways (Miller et al., 2010). Communities in coastal areas, for instance, are particularly at risk due to sea level rise but also through their dependence on marine resources that are impacted by multiple climate change pressures. A change in the availability and condition of marine resources has consequences on the livelihoods of fishing populations or those who depend directly on fishing as a source of food (Badjeck, Allison, Halls, & Dulvy, 2010).
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- Date Issued: 2018
Antibiotic-Resistant Pathogenic Escherichia Coli Isolated from Rooftop Rainwater-Harvesting Tanks in the Eastern Cape, South Africa
- Authors: Malema, Mokaba Shirley , Abia, Akebe Luther King , Tandlich, Roman , Zuma, Bonga , Kahinda, Jean-Marc Mwenge , Ubomba-Jaswa, Eunice
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71729 , vital:29931 , https://doi.org/10.3390/ijerph15050892
- Description: Although many developing countries use harvested rainwater (HRW) for drinking and other household purposes, its quality is seldom monitored. Continuous assessment of the microbial quality of HRW would ensure the safety of users of such water. The current study investigated the prevalence of pathogenic Escherichia coli strains and their antimicrobial resistance patterns in HRW tanks in the Eastern Cape, South Africa. Rainwater samples were collected weekly between June and September 2016 from 11 tanks in various areas of the province. Enumeration of E. coli was performed using the Colilert®18/Quanti-Tray® 2000 method. E. coli isolates were obtained and screened for their virulence potentials using polymerase chain reaction (PCR), and subsequently tested for antibiotic resistance using the disc-diffusion method against 11 antibiotics. The pathotype most detected was the neonatal meningitis E. coli (NMEC) (ibeA 28%) while pathotype enteroaggregative E. coli (EAEC) was not detected. The highest resistance of the E. coli isolates was observed against Cephalothin (76%). All tested pathotypes were susceptible to Gentamicin, and 52% demonstrated multiple-antibiotic resistance (MAR). The results of the current study are of public health concern since the use of untreated harvested rainwater for potable purposes may pose a risk of transmission of pathogenic and antimicrobial-resistant E. coli.
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- Date Issued: 2018
Arbuscular mycorrhizal fungi persist in dying Euphorbia ingens trees
- Authors: Vivas, M , Crous, C J , Dames, Joanna F , van der Linde, J A , Coetzee, M P A , Roux, J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440465 , vital:73784 , https://doi.org/10.1016/j.sajb.2017.12.009
- Description: Forest declines have been reported with increasing regularity during the last decade and are expected to increase due to the ongoing environmental changes. During adverse environmental conditions, plant symbioses with mycorrhizas can help to reduce plant stress. Mycorrhizas are symbiotic associations between fungi and roots of living plants. Plants offer carbohydrates to the fungus and the fungus improves the acquisition of nutrients and water to the plant. Specifically, arbuscular mycorrhizal (AM) fungi are the most abundant mycorrhizas. In South Africa, there are increasing reports describing the decline of native Euphorbia ingens trees. This study analysed the presence and abundance of AM fungal colonisation in the roots of E. ingens trees, and the number of AM fungal spores in the surrounding soil, with the aim to improve the understanding of the rapid decline of these trees. AM fungal colonisation and spores in relation to the soil properties were also analysed. Soil and root samples were collected from different rates of declining E. ingens trees at three sites in South Africa. AM fungal colonisation of the roots was assessed and fungal spores in the surrounding soil were enumerated. Soil phosphorus, mineral nitrogen and pH were analysed from the soil samples. The results showed that AM fungi are associated with E. ingens trees. AM abundance was influenced by site specific properties and not by E. ingens health. Moreover, the level of soil NO3− and soil texture significantly influenced AM colonisation in roots and the number of spores enumerated. These preliminary findings provide background information for further research into the large-scale decline of E. ingens populations in South Africa.
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- Date Issued: 2018
Art topples monuments: artistic practice and colonial/postcolonial relations in the public space of Luanda
- Authors: Siegert, Nadine
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147014 , vital:38585
- Description: Even though there have been very few modern and contemporary artworks in the urban space of Luanda in the years after independence in 1975—and especially after the end of the civil war in 2002—there are two works by Angolan artists that are of particular interest: the sculpture Mitologias II (1984) by António Ole (b. 1951) and the photographic series Redefining the Power (2011) by Kiluanji Kia Henda (b. 1978). Both works address the possibility of using contemporary art as a symbolic form of the replacement of power, since both are built on pedestals that had previously supported monuments of Portuguese colonial power. They might, therefore, be read as a form of substitution for monuments that would commemorate and celebrate independence or the end of colonialism. This article also discusses whether these two artworks can also be regarded as counter-monuments and this contributes to the discourse on the visual and material culture of Lusophone Africa.
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- Date Issued: 2018
Assessment of the likely sensitivity to climate change for the key marine species in the southern Benguela system
- Authors: Ortega-Cisneros, Kelly , Yokwana, Sibusiso , Sauer, Warwick H H , Cochrane, Kevern L , James, Nicola C , Potts, Warren M , Singh, L , Smale, Malcolm J , Wood, A , Pecl, Gretta T
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123211 , vital:35415 , https://doi.10.2989/1814232X.2018.1512526
- Description: Climate change is altering many environmental parameters of coastal waters and open oceans, leading to substantial present-day and projected changes in the distribution, abundance and phenology of marine species. Attempts to assess how each species might respond to climate change can be data-, resource- and time-intensive. Moreover, in many regions of the world, including South Africa, species may be of vital socioeconomic or ecological importance though critical gaps may exist in our basic biological or ecological knowledge of the species. Here, we adapt and apply a trait-based sensitivity assessment for the key marine species in the southern Benguela system to estimate their potential relative sensitivity to the impacts of climate change. For our analysis, 40 priority species were selected based on their socioeconomic, ecological and/or recreational importance in the system. An extensive literature review and consultation with experts was undertaken concerning each species to gather information on their life history, habitat use and potential stressors. Fourteen attributes were used to estimate the selected species’ sensitivity and capacity to respond to climate change. A score ranging from low to high sensitivity was given for each attribute, based on the available information. Similarly, a score was assigned to the type and quality of information used to score each particular attribute, allowing an assessment of data-quality inputs for each species. The analysis identified the white steenbras Lithognathus lithognathus, soupfin shark Galeorhinus galeus, St Joseph Callorhinchus capensis and abalone Haliotis midae as potentially the most sensitive species to climate-change impacts in the southern Benguela system. There were data gaps for larval dispersal and settlement and metamorphosis cues for most of the evaluated species. Our results can be used by resource managers to determine the type of monitoring, intervention and planning that may be required to best respond to climate change, given the limited resources and significant knowledge gaps in many cases.
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- Date Issued: 2018
Avian thermoregulation in the heat: is evaporative cooling more economical in nocturnal birds?
- Authors: O'Connor, Ryan S , Smit, Ben , Talbot, William A , Gerson, Alexander R , Brigham, R Mark , Wolf, Blair O , McKechnie, Andrew E
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441518 , vital:73895 , https://journals.biologists.com/jeb/article/221/17/jeb181420/19595/Avian-thermoregulation-in-the-heat-is-evaporative
- Description: Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta. We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass.
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- Date Issued: 2018
Avian thermoregulation in the heat: phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance
- Authors: Smit, Ben , Whitfield, Maxine C , Talbot, William A , Gerson, Alexander R , McKechnie, Andrew E , Wolf, Blair O
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440517 , vital:73789 , https://doi.org/10.1242/jeb.174870
- Description: Little is known about the phylogenetic variation of avian evaporative cooling efficiency and heat tolerance in hot environments. We quantified thermoregulatory responses to high air temperature (Ta) in ∼100-g representatives of three orders, namely, the African cuckoo (Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias caudatus, Coraciiformes) and Burchell's starling (Lamprotornis australis, Passeriformes). All three species initiated respiratory mechanisms to increase evaporative heat dissipation when body temperature (Tb) approached 41.5°C in response to increasing Ta, with gular flutter observed in cuckoos and panting in rollers and starlings. Resting metabolic rate and evaporative water loss increased by quantitatively similar magnitudes in all three species, although maximum rates of evaporative water loss were proportionately lower in starlings. Evaporative cooling efficiency [defined as the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP)] generally remained below 2.0 in cuckoos and starlings, but reached a maximum of ∼3.5 in rollers. The high value for rollers reveals a very efficient evaporative cooling mechanism, and is similar to EHL/MHP maxima for similarly sized columbids which very effectively dissipate heat via cutaneous evaporation. This unexpected phylogenetic variation among the orders tested in the physiological mechanisms of heat dissipation is an important step toward determining the evolution of heat tolerance traits in desert birds.
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- Date Issued: 2018
Baseline isotopic data for Wolffia spp.: another option for tracing N-loading in freshwater systems?
- Authors: Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68721 , vital:29308 , https://0-doi.org.wam.seals.ac.za/10.1086/696126
- Description: δ15N values of aquatic plants can reflect anthropogenic N loading. Recent work suggests the duckweed Spirodela spp. effectively maps N loading in freshwater ecosystems, but its use may be complicated by a cyanobacterium–duckweed symbiosis that could reduce its utility in low-nutrient environments. I aimed to evaluate the potential of a 2nd duckweed species Wolffia spp., which lacks a cyanobacterial symbiosis, for use in pollution monitoring in freshwater ecosystems. I used a series of laboratory experiments to investigate δ15N equilibration rates and concentration-level effects of single-source N solutions in plant tissue over 16 d to provide baseline data for sewage-plume mapping with Wolffia spp. I also tested concentration-level effects in multisource solutions to investigate the effects of mixed-source inputs. Wolffia reflected environmental N sources with a 12- to 16-d isotopic equilibration time and showed enriched and depleted δ15N ratios for manure and KNO3 solutions, respectively, but distinguished poorly between lower concentrations of manure. Fractionations at isotopic equilibrium were opposite to expectations and decreased with increasing [N]. Wolffia showed a consistent preference for NH3 in mixed-source treatments, regardless of the proportion or concentration of NH3 or NO3– available, and a capacity for N storage, which may complicate mapping of N-loading in natural environments. Wolffia is likely to be a less useful bioindicator than the previously tested Spirodela. Future research should focus on field applications of Spirodela spp. to test its capacity for sewage-plume mapping of freshwater ecosystems in a natural environment.
- Full Text: false
- Date Issued: 2018
Before you arrive We Are Here: Shuma Sopotela’s ‘Indlulamthi’
- Authors: Makandula, Sikhumbuzo
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147248 , vital:38608 , https://artthrob.co.za/2018/08/03/before-you-arrive-we-were-here-shuma-sopotelas-indlulamthi/
- Description: Chuma Sopotela’s multimedia performance ‘Indlulamthi’ at the National Arts Festival proposes a healing of the ‘Settler Frontier’ through a sonicscape. This production was realized with Lulamil Nikani, the Palestinian actor Ahmad Tobasi and Makhanda-based children from Ntsika High School and several other children groups she invited.
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- Date Issued: 2018
Beneficial effects of medicinal plants in fish diseases
- Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier S , Krause, Rui W M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126177 , vital:35856 , https://doi.org/10.1007/s10499-017-0219-x
- Description: Fish are constantly in contact with pathogens inhabiting water. High populationdensity as well as poor hydrodynamic conditions and feeding lead to an increased sensitivitytowards infections. In order to prevent major economic losses due to diseases, variousmedications are used for treatment and prevention of infections. The use of antimicrobialdrugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms.Alternatives are being sought over the last few years to replace antibiotics, and medicinalplants are one of available options for this purpose. These plants are rich in secondarymetabolites and phytochemical compounds, which have an effect against viral, bacterial, andparasitic diseases in fish. Their main advantage is their natural origin and most of these plantsdo not represent threat for human health, the fish, and the environment. The goal of this reviewis to present information on the treatment of viral, bacterial, and parasitic diseases in fishthrough medicinal plants, with focus on the mechanisms of action of the identified secondarymetabolites, fractions, or plant extracts.
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- Date Issued: 2018
Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: an antimalarial, antitrypanosomal and cytotoxity evaluation
- Authors: Meyer, Franck , Isaacs, Michelle , Noundou, Xavier S , Krause, Rui W M , Teinkela, J E M , Hoppe, Heinrich C , Mpondo, Albert E M , Azebaze, Anatole G B , Nguemfo, Edwige L , Wintjens, Rene
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126142 , vital:35853 , https://doi.org/10.1016/j.sjbs.2017.07.002
- Description: The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC50 value 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC50 of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC50 value of 9.5 μg/mL) and trypanocidal (IC50 value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.
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- Date Issued: 2018
Biological activity of plant extracts and isolated compounds from Alchornea laxiflora: Anti-HIV, antibacterial and cytotoxicity evaluation
- Authors: Ndinteh, Derek T , Olivier, Denise K , Noundou, Xavier S , Krause, Rui W M , Mnkandhla, D , Isaacs, Michelle , Hoppe, Heinrich C , Muganza, F M , Mbafor, J T , Van Vuuren, S F , Patnala, S
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126634 , vital:35907 , https://doi.org/10.1016/j.sajb.2018.08.010
- Description: This study was designed to assess the cytotoxicity, anti-HIV and antibacterial efficacy of various solvent extracts of roots, stem and leaves of Alchornea laxiflora, as well as five compounds isolated from its methanolic stem extract viz.; ellagic acid (1); 3-O-methyl-ellagic acid (2), 3-O-β-d-glucopyranosyl-β-sitosterol (3), 3-O-acetyl-oleanolic acid (4) and 3-O-acetyl-ursolic acid (5). The tested crude extracts were prepared from several solvent polarities including: hexane (Hex), chloroform (CHCl3), ethyl acetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O). The anti-HIV properties were assessed on HIV-1 subtype C integrase while the cytotoxicity was tested against Hela cells. The antibacterial activity was studied on a panel of pathogens including gastrointestinal, skin, respiratory and urinary-tract infection causing Gram positive bacteria viz.; Bacillus cereus (ATCC 11778), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25923) and Staphylococcus saprophyticus (ATCC 15305)] and Gram-negative bacteria, i.e., Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Moraxella catarrhalis (ATCC 23246). All the tested samples were determined to be non-toxic due to the low inhibitions observed. The most potent anti-HIV activity was observed for the methanolic extract of A. laxiflora root (ALR4) with an IC50 value of 0.21 ng/ml, which was more active than chicoric acid used as reference drug (6.82 nM). Roots, stem and leaves of A. laxiflora extracts exhibited antibacterial activities against most of the Gram-positive bacteria with the minimum inhibitory concentrations (MIC) ranging between 50 and 63 μg/ml. Compounds 1–5 displayed antibacterial activities against S. saprophyticus with MIC values as low as 4 μg/ml. The results inferred from this study demonstrate the potential of A. laxiflora root as a source for new anti-HIV drugs and scientifically validate the traditional use of A. laxiflora in the treatment of gastrointestinal, skin, respiratory and urinary tract related infections. These results reaffirm the ethnopharmacological significance of African traditional medicines.
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- Date Issued: 2018
Biological control of Salvinia molesta in South Africa revisited
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
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- Date Issued: 2018