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Biomedical subjects

C A van der Merwe

Publications and source records attributed to C A van der Merwe.

At least 19 recordsLinked to original sources
PubMed1999

Dysfunction of sensory nerves during attacks of hypokalemic periodic paralysis.

Reversible electrophysiologic abnormalities of sensory nerve function were found by chance in three patients with hypokalemic periodic paralysis, a disorder previously considered to affect the function of muscle membranes only. A formal, prospective study was therefore conducted. Serial nerve conduction studies were done in ten additional patients. Amplitude of sensory action potentials was significantly smaller during paralytic attacks, but did not differ from controls after normalization of serum potassium concentration. These apparently novel findings might be explained by previous electrodiagnostic studies either not involving the testing of sensory nerves at all, or not being repeated after recovery from an attack. Involvement of sensory nerves in hypokalemic periodic paralysis is suggested to arise through dorsal root ganglia having an incomplete blood-nerve barrier and sensory neurons being particularly vulnerable to derangements affecting nerve cell metabolism. Neuronal inexcitability is postulated to occur consequent upon possible inactivation of the sodium-potassium pump by the low concentration of extracellular potassium. In patients with acute areflexic limb weakness, the diagnosis of hypokalemic periodic paralysis should not be excluded by abnormal results of sensory nerve conduction studies.

Adult↗
PubMed1996

Health effects of passive smoking in adolescent children.

OBJECTIVE AND DESIGN: To study the effects of passive smoking on health in adolescent schoolchildren by questionnaire, spirometry and laboratory investigations. SETTING: Two schools in the Vanderbijlpark area. PARTICIPANTS: Seven hundred and twenty-six high-school children of average age 16 years. OUTCOME MEASURES: Lung function, serological abnormality or historical (i.e. questionnaire) evidence of ill health. RESULTS: The prevalence of respiratory illness before and after 2 years, respiratory symptoms, earache over the past year, low birth weight and learning difficulties were found to be significantly increased in the children exposed to parenteral smoke in the home, especially those exposed to maternal smoking. Spirometric and laboratory parameters, however, were not affected by passive smoking.

Adolescent↗
PubMed1996

Cardiovascular and respiratory effects of detomidine in isoflurane-anaesthetised horses.

Anaesthesia was induced in horses (n = 6) with a mixture of thiopentone and guaiphenesin and maintained by mechanical ventilation with a mixture of oxygen, air and isoflurane. Inspiratory and end-expiratory concentrations of oxygen, carbon dioxide and isoflurane were measured. Electrocardiography was used to evaluate heart rate and rhythm. Mean systemic arterial pressure (SAPm), pulmonary artery pressure (PAPm), right atrial pressure (RAPm) and pulmonary capillary wedge pressure (PCWP) were measured directly. Cardiac output was determined using the thermodilution method. Microcirculation in the upper triceps brachii muscle was estimated using laser Doppler flowmetry. Blood gas values, pH and haemoglobin concentration (Hb) were determined in arterial and mixed venous blood. Baseline values were taken after stabilisation of anaesthesia and were statistically compared to values obtained after an intravenous bolus of detomidine (10 micrograms/kg) had been injected at Time 0. Samples were then collected at 2, 10, 20, 30, 40 and 50 min. End-expiratory concentration of isoflurane was maintained at 1.8% during the experimental period described above. Thereafter, the isoflurane concentration was reduced to 1.3% and samples were collected at 60, 70 and 80 min. Detomidine caused a significant reduction of heart rate (HR), cardiac index (CI), oxygen transport (O2TR) and a significant elevation of the SAPm, systemic vascular resistance (SVR) and coefficient of utilisation of oxygen (O2CU) at 2 min. A significant reduction in HR, CI, SAPm, Hb, content of oxygen in arterial blood (CaO2) and O2TR and a significant elevation of O2CU were observed 10-50 min after the injection of detomidine. Reduction of the isoflurane end-expiratory concentration to 1.3% was followed by a progressive improvement of the SAPm, CI and muscle perfusion towards the baseline values. Further reduction of Hb and CaO2 as compared to the baseline values was observed during the period. The data suggest that detomidine potentiates some of the cardiovascular effects of isoflurane in horses.

Adrenergic alpha-Agonists↗
PubMed1995

Vitamin E, pulmonary functions, and phagocyte-mediated oxidative stress in smokers and nonsmokers.

Relationships among the plasma levels of vitamin E (VE), the numbers and prooxidative activities of circulating phagocytes, serum alpha-1-protease inhibitor (API), and pulmonary functions were investigated in 83 asymptomatic male cigarette smokers and 65 nonsmoking controls. Plasma levels of VE, of cholesterol, and of API were measured using high performance liquid chromatography, spectrophotometry, and nephelometry, respectively, whereas reactive oxidant (ROS) generation by activated blood phagocytes was measured using a whole blood luciginen-enhanced chemiluminescence method. Smoking was associated with significantly increased circulating neutrophil counts (p 0.0001), serum API (p 0.0001) and phagocyte-derived ROS-generation (p 0.0001), and decreased spirometric values (FEV1: p 0.0138 and FEF25-75: p 0.0654). Plasma VE and cholesterol levels were not significantly different between smokers and nonsmokers. However, in smokers both plasma VE and cholesterol correlated significantly and positively with serum API (r 0.24, p 0.03 and r 0.30, p 0.005, respectively), neutrophil counts (r 0.24, p 0.03 and r 0.25, p 0.03, respectively), and phagocyte-derived ROS-generation (r 0.32, p 0.003 and r 0.32, p 0.003, respectively), and significantly and inversely with FEV1 (r -0.23, p 0.03 and r -0.22, p 0.04, respectively) and FEF25-75 (r -0.32, p 0.003 and r -0.26, p 0.02, respectively). In nonsmokers plasma VE, but not cholesterol, was positively correlated with FEV1 (r 0.34, p 0.007) and FEF25-75 (r 0.40, p 0.001). The results suggest that VE protects the lungs of both smokers and nonsmokers and may act as a mobilizable antioxidant in response to smoking-induced oxidative stress.

Adult↗
PubMed1995

Water fluoridation in South Africa: will it be effective?

The National Oral Health Survey showed that differences in the prevalence and experience of dental caries occurred between racial groups and between geographical areas according to fluoride levels in the domestic water supply that varied from <0.05 ppm in the coastal areas to 0.35 ppm in the Bloemfontein area. The Orange Free State (OFS) Goldfields were not included in the survey. The fluoride content of the water supply to this community varies from 0.2 to 0.9 ppm, with a long term average of 0.54 ppm. A survey was conducted in this area to determine the effect of the raised fluoride level on the caries levels in Black and White children. The results show that caries levels in Black children in the OFS Goldfields are >50 per cent and >80 per cent lower than that found in the Bloemfontein and coastal areas respectively. In the OFS Goldfields 39 per cent of White and 16 per cent of Black 12 year old children presented with dental fluorosis on the maxillary central incisors. The results of this study seem to indicate that Black children will benefit more from water fluoridation than White children.

Adolescent↗
PubMed1994

Investigation of the relative contributions of cigarette smoking and mineral dust exposure to activation of circulating phagocytes, alterations in plasma concentrations of vitamin C, vitamin E, and beta carotene, and pulmonary dysfunction in South African gold miners.

OBJECTIVES: To determine the relative effects of cigarette smoking and mineral dust exposure on numbers and activity of circulating phagocytes, plasma nutritional antioxidant state, and pulmonary function in South African gold miners. METHODS: Pulmonary function was assessed spirometrically, whereas reactive oxidant generation by circulating phagocytes, and plasma concentrations of the nutritional antioxidative nutrients vitamin C and vitamin E and beta carotene were measured with chemiluminescence, spectrophotometry, or high performance liquid chromatography respectively. RESULTS: Cigarette smoking, but not mineral dust exposure, was associated with increased numbers and pro-oxidative activity of circulating neutrophils and monocytes, decreased plasma concentrations of vitamin C, and pulmonary dysfunction. DISCUSSION: In this study group occupational exposure to mineral dust has not been found to promote increases in the numbers or reactivity of circulating phagocytes or to be a significant cause of pulmonary dysfunction, the changes found being due primarily to cigarette smoking.

Adult↗
PubMed1993

The effect of a long-term exercise programme on the rheumatoid hand.

Forty-four female patients with sero-positive active RA participated in a 48-month trial to assess the effect of simple hand exercises. Twenty-two patients in the test group were given a daily exercise regime of six exercises. The control group were not given any exercises. At the end of 48 months there was a statistically significant improvement in grip strength (P < 0.0001) and pincer grip strength (P < 0.0005) in the test group. There was a significant deterioration in the control group (P < 0.0000). A simple exercise programme is beneficial for the rheumatoid hand as far as grip and pincer grip strength are concerned.

Adult↗
PubMed1992

Enhanced release of elastase and oxidative inactivation of alpha-1-protease inhibitor by stimulated human neutrophils exposed to Pseudomonas aeruginosa pigment 1-hydroxyphenazine.

The in vitro effects of the Pseudomonas aeruginosa-derived phenazine pigments pyocyanin and 1-hydroxyphenazine (1-hp) on neutrophil elastase release and myeloperoxidase-induced inactivation of alpha-1-protease inhibitor (alpha 1-PI) were investigated. 1-hp (6-25 microM), but not pyocyanin, caused a dose-dependent enhancement of elastase release by FMLP:cytochalasin B (CB)-activated human neutrophils. 1-hp (0.78-6.25 microM) also increased the oxidative inactivation of the elastase inhibitory capacity of alpha 1-PI exposed to FMLP:CB-activated neutrophils. Methionine, a scavenger of hypochlorous acid, completely protected alpha 1-PI from inactivation by stimulated neutrophils in the presence or absence of 1-hp. Similar protective effects were observed with sodium azide, an inhibitor of myeloperoxidase. P. aeruginosa-derived 1-hp may promote an elastase-antielastase imbalance in vivo by increasing the release of neutrophil elastase and by enhancing the oxidative inactivation of alpha 1-PI, thereby contributing to the development of tissue destruction in P. aeruginosa-infected patients.

Humans↗
PubMed1992

A quantitative study of the attitudes of members of a black developing community towards their dogs and veterinary services.

To further the study of human-companion animal interactions in black developing communities, the clients (n = 94) of a university-based animal hospital, serving primarily a developing community, were interviewed. The interviews covered demographics, socio-economic aspects, perceptions, values and attitudes of clients towards their dogs. Regular and new clients were compared. A profile of the hospital's black clientele was also constructed. The study showed that the majority of black clients value their dogs for the sake of security and protection. Attitudes towards pets parallelled improvements in socio-economic status. Most clients felt positive towards existing veterinary services. The results of this study support and highlight the value of a previous observational study and could prove to be invaluable in designing, implementing and planning socially relevant animal health services.

Black or African American↗
PubMed1992

The fluoride content of enamel as a diagnostic aid in fluorosis.

This study was undertaken to compare the fluoride content ([F]) of sound and hypoplastic enamel of dogs' teeth for use as a diagnostic aid for fluorosis. Enamel biopsies (0.5N HClO4; 15 seconds; 3.143 mm2) were conducted on macroscopically sound areas of the middle buccal surfaces of the right upper canine teeth. The [F], and the calcium concentrations of the etching solutions were determined using the potentiometric analytical method and the flame spectrophotometer respectively. Depth of etch (DOE) was calculated. The results of the study showed that the higher [F] in the hypoplastic enamel when compared to that of sound enamel (p > 0.05), was more a result than a cause of the hypoplasia. In this study, the [F] of the enamel was used successfully to exclude the possibility of fluorosis.

Animals↗
PubMed1991

[Attitude of a group of South Africans toward advertising by dentists in private practice].

The advertising of dental services in South Africa is controlled by rules and regulations of the South African Medical and Dental Council. According to these, advertising is not permissible with the exception of specified professional information which may be made known only by means of a nameplate and an entry in a telephone directory. Questionnaires were sent to a randomised sample of 2,100 persons in order to determine the attitude of South Africans towards advertising by private practitioners. According to information obtained from this study there is a strong indication that consumers of dental services prefer a freer form of advertising by dentists in the private practice.

Adult↗
PubMed1991

[Fluoride status of a community and fluoride concentration in its drinking water].

Despite the low fluoride (F) content of the drinking water (less than 0.05 mg/l), an optimum to above optimum daily F intake was shown for the community in Tshikundamalema (Republic of Venda, Southern Africa). In order to evaluate the biological availability of fluoride in the diet, the assimilation of the fluoride ion in enamel was tested. Six age groups (selected according to WHO criteria) consisting of 10 individuals each were used in the study. Enamel biopsies (2N HCl0(4); 3,143 mm2; 8 seconds) were conducted on the mid-labial surfaces of the central maxillary incisors. The fluoride concentrations of the etching solutions were analyzed according to the potentiometric analytical method. The calcium concentrations were determined by means of a flame spectrophotometer. The F content of the outer 10 microns in the enamel of the community was examined in relation to the total daily intake of fluoride for the community. The results obtained from the study showed that, the F content of the enamel of the community (x = 1,133 pg/micrograms; 10 microns depth of etch) correlated with the F intake of the community (x = 3.15 mg F/day). Thus the F content of the diet was biologically available to the body. However, between age groups and sexes, no correlation could be found between the fluoride status and the fluoride intake.

Adolescent↗
PubMed1991

Caries experience and treatment needs of five-year-old caucasian nursery school children in Pretoria.

The caries experience of five-year-old caucasian children at various sites in the world at the present time could be termed moderate to low, and a declining tendency has been noted in the past decade. The aim of this study was to determine the current status and trends of caries experience of 5-year-old caucasian nursery school children in Pretoria. The results from this study, conducted in 1987, showed that 50.9 per cent of 5-year-olds were free of caries experience (dmft = 0) and that the mean dmft was low, viz. 1.97. A comparison of these results with figures published in 1979 indicates that a notable reduction in caries experience has taken place during a period of eight years, the proportion of 5-year-olds free of caries experience having been 40 per cent in 1979, with a mean dmft of 2.9. The most significant change during this period was the decrease in the decayed component of the dmft.

Child, Preschool↗
PubMed1990

Sialic acid concentrations in the urine of men with and without renal stones.

It has been suggested that urinary sialidase may play a role in the formation of renal stones. The present study was therefore undertaken to compare spectrophotometrically the different types of sialic acid concentrations and sialidase activities in fresh first morning urine specimens of men (21-65 years) with (13) and without (9) calcium oxalate renal stones. Although the free urinary sialic acid concentrations of the two groups of men were statistically about the same (P = 0.0614), the total (P = 0.003) and bound (P = 0.0012) urinary sialic acid concentrations differed significantly. Both the total and bound sialic acid concentrations were lower in the urine specimens of the stone patients than in their healthy counterparts. This decrease in urinary sialic acid concentrations was firstly thought to be the result of elevated breakdown enzymes of sialic acid, which would favour the production of pyruvate. However, spectrophotometric determinations of the endogenous pyruvate concentrations of the two types of urine specimens did not differ significantly (P = 0.0708). Secondly, the decrease in total urinary total sialic acid concentration of stone patients, could be attributed to less sialic acid synthesis or less renal excretion. Therefore, the same experiments were repeated using serum of 13 patients and 9 healthy men. Conversely, the total (P = 0.4425) and bound (P = 0.2850) serum sialic acid concentrations were found to be similar in the two types of subjects. However, the free serum sialic acid concentration of stone patients was significantly lower than in the healthy subjects (P = 0.0062).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

The effect of gamma-linolenic acid, an in vitro cytostatic substance contained in evening primrose oil, on primary liver cancer. A double-blind placebo controlled trial.

The cytostatic effects of essential fatty acid metabolic intermediates and of some prostaglandins and leukotrienes in vitro have been extensively documented. The essential fatty acids (EFAs) exhibit no side-effects when taken as a dietary supplement, even in large doses. Primary Liver Cancer (PLC) is a fatal disease in our area as it is always multifocal in nature. In vitro studies have shown a cytostatic effect of gamma-linolenic acid (GLA) on primary liver cancer cells. In a double-blind placebo controlled trial, using Evening Primrose Oil (as a source of GLA) as a dietary supplement in PLC patients, no statistically significant effect was observed on survival time or liver size. There was however a statistical significant beneficial effect on Gamma Glutamyl transferase values as a measure of liver function. No side-effects were observed. The large size of tumour and the low doses of GLA used in this trial probably explain the lack of significant effect on survival times.

Antineoplastic Agents↗
PubMed1990

Correlation between the macromolecular effects of estradiol and catecholestradiols and the total prostatic catecholestrogen concentration.

Various authors have demonstrated that estrogens stimulate both protein and DNA synthesis, as well as cell proliferation. This study was therefore undertaken to investigate the correlation between these physiological effects of estrogens and the total prostatic catecholestrogens. Either 17 beta-estradiol (5 ng), 2-hydroxyestradiol (40 ng), 4-hydroxyestradiol (17 ng), propane-1,2-diol or a saline solution was injected intraperitoneally to 22-day-old Sprague-Dawley rats daily. Regardless of the treatment, the prostate mass, the rate of DNA or protein synthesis correlates positively with the total prostatic catecholestrogen concentration. We therefore conclude that the effect of each estrogen per se should be regarded in terms of the total prostatic catecholestrogen concentration.

Animals↗
PubMed1990

Triiodothyronine treatment for Raynaud's phenomenon: a controlled trial.

The effects of 80 micrograms triiodothyronine (T3) daily were compared with placebo in a double blind controlled crossover trial in 18 patients with Raynaud's phenomenon. Reductions in the frequency, duration and severity of attacks while taking T3 were gradual but highly significant. Four of 6 subjects had skin ulcer healing. Skin temperatures in the hands increased significantly. The skin temperature recovery times after cold exposure were significantly shorter during T3 therapy compared with placebo. Although large dosages of T3 were well tolerated, 6 patients experienced episodic palpitations, and slight but significant increases in heart rate and pulse pressure were observed. Evaluation of the use of physiological doses of T3 (60 micrograms daily or less) in the treatment of Raynaud's phenomenon is suggested.

Adolescent↗