M. De Villiers

Phosphatidylcholine biosynthesis in myocardial ischaemia

In this study the effect of myocardial ischaemia was evaluated on two aspects of phospholipid metabolism: (i) the de novo synthesis of myocardial phospholipids, as indicated by the incorporation of (methyl-3H) choline and (ii) the incorporation of radiolabelled long chain fatty acids into tissue phospholipids. Two models of ischaemia were used namely normothermic ischaemic arrest and hypoxic, low-flow perfusion of the isolated rat heart. The results showed that within 10 min, hypoxic low-flow perfusion significantly inhibited the incorporation rate of (methyl-3H) choline into tissue phospholipids. Since the tissue choline content remained unaltered under these conditions, the results suggested that the de novo synthesis of phosphatidylcholine is very susceptible to ischaemic damage. Inhibition of (methyl-3H) choline incorporation into tissue phospholipids appeared to be due to both a reduction in choline uptake and specific inhibition of the CDP pathway. Perfusion with glucose (10 mM) as substrate completely abolished the ischaemia-induced reduction in (methyl-3H) choline incorporation, indicating that glycolytically produced ATP played an important role in phosphatidylcholine biosynthesis. In contrast to these results, myocardial ischaemia stimulated the incorporation of long-chain saturated and unsaturated fatty acids into tissue phospholipids. In summary, the results obtained showed that myocardial ischaemia profoundly affected phospholipid metabolism which, in turn, might contribute to membrane damage.

Seasonal occurrence of vine pests in commercially treated vineyards in the Hex River Valley in the Western Cape Province, South Africa

The population fluctuations of arthropods attacking table grapes were studied in 12 commercially treated vineyards in the Hex River Valley in South Africa for three years. Sampling was conducted by inspecting different plant parts and using a variety of traps. Planococcus ficus (Signoret) males in the pheromone traps started increasing during December, to reach a peak at the end of February. Cordon infestation preceded bunch infestation by three to five months, the latter occurring from about January or February. Thrips, mainly Frankliniella occidentalis (Pergande), caught on blue sticky traps were active during spring and early summer. Damage to the berries occurred about four weeks after thrips were recorded on the sticky traps. Phlyctinus callosus Boh. was recorded under fluted cardboard bands tied around the stems of vines from early October, with the first bunch damage recorded towards the end of October. More Epichoristodes acerbella (Walker) moths were caught in pheromone traps during the cool winter months than during the hotter summer months. Damage to the bunches started during November and declined during January and February, only to increase again towards the end of February and March. Although Helicoverpa armigera (Hübner) moths were caught in pheromone traps, no damage ascribed to this insect was recorded. The only phytophagous mite was Tetranychus urticae Koch, which was active throughout the fruiting season. The most common predatory mite was Euseius addoensis (Van der Merwe & Reyke).

The potential distribution of Bactrocera dorsalis: considering phenology and irrigation patterns.

A species in the Bactrocera dorsalis (Hendel) complex was detected in Kenya during 2003 and classified as Bactrocera invadens Drew, Tsuruta & White. Having spread rapidly throughout Africa, it threatens agriculture due to crop damage and loss of market access. In a recent revision of the B. dorsalis complex, B. invadens was incorporated into the species B. dorsalis. The potential distribution of B. dorsalis has been previously modelled. However, previous models were based on presence data and did not incorporate information on the seasonal phenology of B. dorsalis, nor on the possible influence that irrigation may have on its distribution. Methyl eugenol-baited traps were used to collect B. dorsalis in Africa. Seasonal phenology data, measured as fly abundance throughout the year, was related to each locations climate to infer climatic growth response parameters. These functions were used along with African distribution records and development studies to fit the niche model for B. dorsalis, using independent global distribution records outside Africa for model validation. Areas at greatest risk of invasion by B. dorsalis are South and Central America, Mexico, southernmost USA, parts of the Mediterranean coast, parts of Southern and Eastern Australia and New Zealands North Island. Under irrigation, most of Africa and Australia appear climatically suitable.

The role of educational strategies to reverse the inverse performance spiral in academically-isolated rural hospitals

Abstract The importance of continuous professional development for health care workers is widely acknowledged, but the identification of optimal implementation strategies remains a challenge, particularly in academically isolated rural areas. We report the results of a qualitative study that evaluated the effect of an educational intervention aimed at rural doctors in the Western Cape Province, South Africa. We also present a conceptual framework for developing best practice educational strategies to reverse the inverse performance spiral in academically isolated rural hospitals. Doctors felt that participation in relevant learning activities improved their competence, increased the levels of job satisfaction they experienced, increased their willingness to stay in a rural environment, and impacted positively on the quality of services provided. However, the success of educational strategies is heavily dependant on the local environment (context), as well as the practical applicability and clinical relevance of the activities (process). Successful educational strategies may help to reverse the inverse performance spiral previously described in academically isolated rural hospitals, however, this requires effective local leadership that creates a positive learning environment and supports clinically relevant learning activities. The study findings also indicate the need for health care providers and institutions of higher education to join forces to improve the quality of rural health care.

Mitochondrial Ca2+ fluxes: role of free fatty acids, acyl-CoA and acylcarnitine

It has been suggested that accumulation of lipid metabolites, such as fatty acids, fatty acyl-CoA and acylcarnitine, in the ischaemic myocardium, may be responsible for disturbances in mitochondrial Ca2+ fluxes. In view of the presence of an intracellular fatty acid binding protein, the question arose whether these intermediates affect mitochondrial Ca2+ uptake and release similarly in vivo. In this study the effects of linoleic acid, palmitic acid, palmitoyl-CoA and palmitoylcarnitine were studied on mitochondrial Ca2+ fluxes in the absence and presence of albumin, an avid binder of fatty acid derivatives. Albumin reversed the effects of the above compounds on mitochondrial Ca2+ uptake and release, suggesting that the presence of an intracellular fatty acid binding protein may protect the ischaemic myocardial cell against the deleterious effects of accumulated fatty acid derivatives.

Mitochondrial Ca2+ fluxes and levels during ischaemia and reperfusion: Possible mechanisms

It has been shown that myocardial ischaemia depresses the uptake and enhances the release of Ca2+ by mitochondria. Reperfusion of the ischaemic areas may result in a further deterioration of the above processes. Despite these marked changes in Ca2+ fluxes, reperfusion has been shown always to be associated with a marked increase in mitochondrial Ca2+ content. To explain the latter observation, it has been proposed that reperfusion promotes respiration-supported mitochondrial Ca2+ uptake in preference to ADP phosphorylation. To evaluate this hypothesis, the effect of exogenous ADP on mitochondrial respiration-linked Ca2+ uptake was investigated in control, ischaemic and ischaemic-reperfused hearts. The results show that ADP significantly depresses mitochondrial Ca2+ uptake in all three preparations, indicating that Ca2+ is not taken up preferentially to ADP phosphorylation in reperfused tissue. It is suggested that reperfusion-induced increased mitochondrial Ca2+ levels are probably not due to increased respiration-linked Ca2+ uptake, but rather to augmented conversion of ionized Ca2+ to calcium phosphate which does not participate in ionic fluxes.

Developing an educational research framework for evaluating rural training of health professionals: A case for innovation

Background: World-wide, rural clinical training of undergraduate medical students is looking to transform learning experiences, calling for the adoption of innovative approaches that create spaces for curriculum renewal and new ways of thinking. In order for these teaching models to gain acceptance and credibility among the relevant academic communities, it is critical that they be studied and evaluated. Aim: This article describes an innovative rural education intervention and a concomitant, intentional process that was adopted to establish a research framework within which the intervention will be evaluated. Methods: Key role-players participated in a one-day workshop aimed at developing the framework. A collaborative, structured process that moved through three phases of deliberation and reflection was followed. Results: The documentation and raw data generated during the workshop was used to generate the framework that will serve as a blueprint for ensuring the study and evaluation of the educational innovation. Conclusion: Establishing an educational research framework, by adopting a consultative and collaborative process, provides a vehicle for encouraging a culture of critical accountability that seeks to discern evidence of good practice in the training of health care workers in a rural context.

A radioimmunoassay for metoclopramide

A radioimmunoassay for the anti-emetic drug, metoclopramide, in the pmol range was developed. The immunogen was prepared by photolytic coupling of metoclopramide to bovine serum albumin. A crosslinking reagent, N-hydroxy-succinimidyl-4-azidobenzoate, was first reacted with serum albumin through nucleophilic substitution. Ultraviolet irradiation (lambda greater than 300 nm) of the photoactive serum albumin conjugate in the presence of metoclopramide resulted in covalent attachment of the drug to the protein. An 125I-labelled metoclopramide derivative was prepared by diazotisation of the aromatic amine group and substitution of the resultant diazo group with 125I-. Binding data of the antibody with radioiodinated metoclopramide gave a linear Scatchard plot indicative of a homogeneous antibody population. A dissociation constant of 3 X 10(-11) mol/l was calculated for the antigen-antibody interaction. The antibodies showed negligible cross-reactivity with lignocaine which is structurally closely related to metoclopramide.

From ‘TO POLY’ to generalized poly‐figures and their classification: a learning experience

A heuristic description of a personal learning experience in a LOGO micro‐world is given. The figures produced by the familiar POLY procedure are generalized, and an attempt is made to develop a workable definition and a useful classification. It depicts the gradual evolution of relevant mathematical concepts, and the part intuition played in this process. Moreover, it shows mathematics both as a process of discovery and creative work, illustrating the difference between the final product and the untidy processes used to arrive there.

Phytosanitary host status of apples as a host for false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) : short communication

Recent publications suggest that apples, Malus domestica Borkh., and pears Pyrus communis L., are hosts for false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Timm 2005; Timm et al. 2007; Timm et al. 2010). In these publications Blomefield (1989) and Newton (1998) are cited. However, these last two authors did not actually mention apples or pears as hosts for T. leucotreta. This error has also been alluded to in a recent T. leucotreta pest risk analysis (EPPO 2013). In addition, a personal communication with A.E. Timm(a.timm@ru.ac.za) confirmed that she had only caught T. leucotreta in pheromone traps in apple and pear orchards, and had not obtained material directly from infested fruit.