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Nifedipine-cyclodextrin binary systems : solid-state photostability and dissolution behaviour

  • Authors: Worthington, Matthew Stanley
  • Date: 1998
  • Subjects: Nifedipine Calcium -- Antagonists Cyclodextrins Cyclodextrins in pharmaceutical technology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3830 , http://hdl.handle.net/10962/d1007233
  • Description: Nifedipine is a photolabile calcium channel antagonist which undergoes rapid photodegradation in solution and in solid-state with an accompanying loss of pharmacological potency and clinical efficacy. Nifedipine photostabilization which has received considerable attention has principally been achieved by physical obscuration and through the use of colourants or ultraviolet light absorbers incorporated into liquid preparations, translucent packaging materials, gelatin capsules and/or their fillings and tablet coatings or cores. This study was initiated by a South African pharmaceutical manufacturer in response to increasing evidence that cyclodextrin (CD) inclusion complexation may improve drug photostability. The brief was to evaluate the potential of selected cyclodextrins as photoprotecting agents for nifedipine in the solid-state. Areas of investigation included i) quantitative method development and validation for selective determination of nifedipine, ii) phase solubility studies to establish the solubilizing potential and complexing tendencies of selected cyclodextrins, iii) preparation of solid-state nifedipine - cyclodextrin binary systems using an industrially applicable method, iv) pre-formulation photostability studies to determine the effects of the cyclodextrins on solid-state nifedipine photostability and v) comparative in vitro dissolution assessments of nifedipine, the nifedipine - cyclodextrin binary systems and their respective physical mixtures. Phase solubility studies demonstrated that soluble nifedipine - cyclodextrin complexes were formed in aqueous solution, but the magnitude of the interactions were generally low as reflected by the calculated stability constants which decreased in the rank order, heptakis (2,6-dimethyI)-β-CD (DM-β-CD) > randomly methylated-β-CD (RM-β-CD) > β-CD ≈ 2-hydroxypropyl-β-CD (2HP-β- CD) > γ-CD ≥ 2-hydroxypropyl-γ-CD (2HP-γ-CD). An industrially applicable kneading method yielded binary systems with spectral and thermal characteristics similar to the respective physical mixtures, implying weak solid-state inclusion complexation. Preparation of an amorphous nifedipine - RM-β-CD product using a heating method is reported. A 1.7- and 1.9-fold improvement in solid-state nifedipine photostability was observed for I : 1 molar ratio β-CD and γ-CD kneaded products, respectively, when exposed to window-filtered daylight and could be attributed to changes in opacity of the crystalline kneaded products. The remaining cyclodextrins produced negligible nifedipine photostabilization. Nifedipine in vitro dissolution was improved considerably from γ-CD and RM-β-CD .kneaded products as a result of increased nifedipine wettability, solubility and reduced particle size. iii
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  • Date Issued: 1998

Nomaweza

Nomkangayo

Northen entrance to Grahamstown Botanical Gardens

Northen entrance to Grahamstown Botanical Gardens

Novasum' Tsholo

Nten Nko File

NUM - Induction course participants manual

  • Authors: NUM
  • Date: 1998
  • Subjects: NUM
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/149554 , vital:38863
  • Description: This Induction Course is the most important education programme in the National Union of Mineworkers. It is the beginning of a development programme for shaft/shop stewards as cadres of the labour movement and cadres of the working class movement. The Induction Course is part of a programme to organise, deepen organisational understanding, raise class-consciousness and develop working class leadership. Once a shaft/shop steward has completed the course, he/she must demand progression through the intermediate course to the leadership school. Development and desire for selfgrowth should be in the hands of stewards themselves. We train shaft/shop stewards because we are committed to ensuring that Mine and Energy workers themselves determine their destiny. They must lead and control their own union. This can only become reality if it translates into these workers taking over all strategic positions in the union. The Induction Course must instill ambition and make our members develop dreams about the union.
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  • Date Issued: 1998

Paris 95

  • Authors: TP Audiorama Orchestra (performers) , Showbiz
  • Date: 1998
  • Subjects: Popular music , Popular music--Africa, West , Africa Cote d'Ivoire Abidjan f-iv
  • Language: French
  • Type: sound recordings , field recordings , sound recording-musical
  • Identifier: http://hdl.handle.net/10962/129596 , vital:36310 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC30-05
  • Description: Ako music from Cote d'Ivoire performed by the TP Audiorama Orchestra, the first orchestra to develp this genre of Ivorian music
  • Full Text: false
  • Date Issued: 1998

Patterns of marine harvest effort in southwestern New Georgia, Solomon Islands: resource management or optimal foraging?

  • Authors: Shankar, Aswani
  • Date: 1998
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/439971 , vital:73724 , xlink:href="https://doi.org/10.1016/S0964-5691(98)00047-7"
  • Description: Numerous researchers in the field of maritime anthropology have accepted the notion that marine tenure institutions are cultural systems designed to conserve marine resources. This idea has attained wide acceptance without the development of an ecological model to account for the occurrence of conservation and/or depletion of resources. In this study, foraging theory is offered as an alternative theoretical framework to examine the diversity of human resource exploitation strategies in coastal ecosystems. The results generated by the foraging models are considered here in relation to their significance in linking ecological evolutionary approaches in anthropology with coastal resource management.
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  • Date Issued: 1998

Pension payouts, periodic marketing and the continuance of urban dependence in rural South Africa

  • Authors: Fox, Roddy C , Nel, Etienne L
  • Date: 1998
  • Language: English
  • Type: Article
  • Identifier: vital:6681 , http://hdl.handle.net/10962/d1006675
  • Description: The former homeland areas of South Africa are characterised by extreme poverty, high levels of urban dependence, a reliance on pensions and low levels of agricultural production. This paper is based on a case-study of the Eastern Cape province and details rural realities, the importance of pensions and the constraints which face current plans to develop and expand the periodic marketing network.
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  • Date Issued: 1998

Photoassisted reduction of thionyl chloride by neodymium, europium, thulium and lutetium diphthalocyanines

  • Authors: Nensala, Ngudiankama , Nyokong, Tebello
  • Date: 1998
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/293590 , vital:57101 , xlink:href="https://doi.org/10.1016/S0277-5387(98)00133-8"
  • Description: Diphthalocyanine complexes of Nd III, EuIII, TmIII and LuIII ( [Pc (−2) Nd IIIPc (−2) ] −, [Pc (−2) EuIIIPc (−2) ] −, [Pc (−2) TmIIIPc (−2) ] − and [Pc (−2) LuIIIPc (−2) ] −, respectively) , undergo one or two-electron oxidation in the presence of thionyl chloride. The oxidation products depend on the concentration of the thionyl chloride. At low concentrations of SOCl2 (larger than 10−4 mol dm−3) one-electron oxidation occurs only upon photolysis, giving the neutral lanthanide diphthalocyanine, Pc (−2) LnPc (−1) , complexes. The Pc (−2) LnPc (−1) species undergo one-electron photooxidation to the [Pc (−1) LnPc (−1) ] + in dichloromethane and in the presence of SOCl2. At large concentrations of SOCl2 (>10−2 mol dm−3) , two electron oxidation of the [Pc (−2) LnPc (−2) ] − species directly to [Pc (−1) LnPc (−1) ] + occurs.
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  • Date Issued: 1998

Photograph of SABC Board Members

  • Date: 1998 , 2022-09-23
  • Subjects: Bam, Brigalia
  • Language: English
  • Type: Photographs , realia
  • Identifier: http://hdl.handle.net/10948/56625 , vital:56872
  • Description: Dr. Brigalia Bam served on the Board of the South African Broadcasting Corporation (SABC) from 1997-1998. This is a photograph of the Board Members. , Donated/gifted to Nelson Mandela University Archives , Forms part of: Brigalia Bam collection
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  • Date Issued: 1998

Pictograms in pharmacy:

  • Authors: Dowse, Roslind , Ehlers, Martina S
  • Date: 1998
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/157048 , vital:40082 , https://0-doi.org.wam.seals.ac.za/10.1111/j.2042-7174.1998.tb00924.x
  • Description: This review examines the use of pictograms in health care. Well designed pictograms are simple, clear, graphic symbols able to convey their intended meaning to all patients, including those who are illiterate, elderly or visually impaired. Although some research on the effectiveness of pictograms has not supported the hypothesis that pictograms are beneficial for the acquisition and comprehension of information, most studies investigating health‐related applications of pictograms have shown them to be of benefit in the comprehension and recall of instructions on prescription and over‐the‐counter medicines. However, the success of pictograms as a communication aid in pharmacy depends first on a rigorous design process, followed by well‐designed, randomised, controlled trials using an appropriate method of evaluation. The final stage is to investigate the optimal way of using pictograms in practice and to assess their effect on behavioural outcomes, such as compliance.
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  • Date Issued: 1998

Port Elizabeth History: A Select Annotated Bibliography

  • Authors: Baines, Gary F
  • Date: 1998
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/125742 , vital:35813 , https://doi.10.1080/02582479808671323
  • Description: When I commenced my work on aspects of Port Elizabeth’s history in the late 1980s, there was no body of scholarly literature on which to draw. Since thena number of significant publications, both periodical articles and books, as well as theses have appeared, and something of a corpus of works on the city now exists. It seems appropriate to take stock of the current state of Port Elizabeth’s historiography by compiling a bibliography.
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  • Date Issued: 1998

Precision of tristimulus chromameter results from corticosteroid-induced skin blanching

  • Authors: Smith, Eric W , Haigh, John M
  • Date: 1998
  • Language: English
  • Type: Conference paper
  • Identifier: vital:6342 , http://hdl.handle.net/10962/d1006609
  • Description: The human skin blanching (vasoconstriction) assay has been in use for 3 decades as a tool for the assessment of the release of corticosteroids from topical dosage forms. Application of corticosteroids produces a whitening (blanching) of the skin, the intensity of which is directly related to the clinical efficacyof the formulation. Assessment of the intensity of the induced blanching has classically been, and continues to be, pe1fonned by visual grading, a method which has been criticised because of the subjectivenature of the assessment Recently there has been considerablediscussion in the literature regarding the use of the chromameter as an objective instrumental method of monitoring corticosteroid induced skin blanching for bioequivalence assessment purposes. The FDA has released a Guidance document recommending the use of the chromameter for this purpose. The chromameter measures colour in teims of three indices: the L-scale (light-dark), the a-scale (red-green) and the b-scale (yellow-blue).Any colour can be expressedabsolutelyin terms of these three values.The Guidance protocol suggests the use of only the a-scale values in quantifying the blanching response after correction of the data which includes subtraction of baseline and unmedicated site values. One of the unresolved issues in the FDA Guidance document is this method of data manipulation suggested since the instrument should be capable of assigning an absolute colour value to each site during the vasoconstriction period. The purpose of this study was to manipulate the instrumental data from a typical blanching study in a number of ways to investigate the appropriatenessof these suggested procedures.
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  • Date Issued: 1998

Preliminary investigation of the molecular pathogenicity determinants of Xanthomonas campestris pv. zeae

  • Authors: Downing, T G
  • Date: 1998
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4066 , http://hdl.handle.net/10962/d1004922
  • Description: Xanthomonas campestris pv. zeae was shown to posses a vast range of potential plant cell wall degrading enzymes including at least one protease, a carboxymethylcellulase, pectin lyase, polygalacturonase and a B-endoglucanase. Replicon stability and transfer system efficiencies were determined for a range of oriC, and oriT -tra combinations, and suitable vectors were constructed and identified for insertional inactivation by homologous recombination. Ideal suicide replicons were found to be pACYC184 and p15A, while P, Wand Q group replicons were supported by X campestris pv. zeae. Group P and group N transfer systems were shown to be highly efficient in intra-genus matings between Escherichia coli and X campestris pv. zeae, with the exception of P-tra systems in trans for the delivery of Tn5. Various cloning vectors were tested for stability and mobility. Tn5 was shown to transpose at high frequencies into the genome of the bacterial plant pathogen, and insertion was relatively random. Suitable screening assays were established to allow rapid isolation of mutants with potential virulence or pathogenic deviations, after mutagenesis. Two non-pathogenic mutants were identified, one of which was a putative hrp·, while the other was a leaky virulence. A single mutant showing 40% reduced protease activity was also shown to exhibit reduced virulence indicating a minor role for the protease in pathogenicity. The majority of virulence mutants showed altered growth in different levels of nutritional availability and complexity. Nutritional viability (the ability to acquire and use nutrients at a sufficient rate to grow fast enough to overcome host defences) was shown to be essential for virulence and possibly pathogenicity. Wild-type in-planta behaviour was analysed and growth and spread patterns typical for pathogenic response identified. Chief amongst these was the requirement for a threshold level of cells per leaf area or length, before symptoms could develop. Occlusion of vascular bundles was shown not to be the primary factor in the pathogenicity of X campestris pv. zeae. Threshold levels for lesion development indicate the absence of a diffusable lesion forming element, and possibly the requirement of cell density for induction of certain functions. , KMBT_363
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  • Date Issued: 1998

Prince Edward Islands' offshore oceanographic study: report of research cruise April-May 1997

  • Authors: Pakhomov, Evgeny A , Froneman, P William , Ansorge, Isabelle J
  • Date: 1998
  • Language: English
  • Type: text , article
  • Identifier: vital:6939 , http://hdl.handle.net/10520/AJA00382353_9017 , https://journals.co.za/content/sajsci/94/4/AJA00382353_9017 , http://hdl.handle.net/10962/d1011962
  • Description: preprint , Focuses on the preliminary results of the second cruise of the Marion Island Oceanographic Study designed to provide oceanological observations off Prince Edward Islands from April 25 to May 28, 1997. Physical and chemical oceanographic results; Surface seawater temperature; Total chlorophyll-a distribution.
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  • Date Issued: 1998

Problems in rural transformation in South Africa specifically in the land reform arena:

  • Authors: Antrobus, Geoffrey G , Fraser, Gavin C G , Tapson, D R
  • Date: 1998
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/143035 , vital:38195 , https://www.infona.pl/resource/bwmeta1.element.agro-article-dc77672d-7269-4641-bf99-605eaa5fe369
  • Description: Problems in rural transformation in South Africa specifically in the land reform arena
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  • Date Issued: 1998

Profile on POTWA

  • Authors: Post and Telecommunications Workers Association (Potwa)
  • Date: 1998
  • Subjects: POTWA
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/250717 , vital:52042
  • Description: POTWA was formed in August 1986 in Soweto after workers’ rejection of the liaison committees and workers’ councils tailored by management for black workers in the Department of Post and Telecommunications. Racist salaries also helped to mobilise workers into the union. At the launching congress, Potwa had already signed-up 10 000 members year, the union settled wage claims in nine regions.
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  • Date Issued: 1998
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