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Biomedical subjects

C A van der Merwe

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

At least 37 records · Page 2Linked to original sources
PubMed1989

[The incidence of ischemic heart disease in white South Africans cremated in Pretoria, 1978-1985].

The prevalence of ischaemic heart disease was studied in a population selected on the basis of an application for cremation by the next of kin. In the age group 35-44 years 15.2% of the deaths were ascribed to ischaemic heart disease (IHD), while the corresponding figure in the general population was 27.2%. In females in the age group 45-54 years IHD was responsible for 9.3% of the deaths; the corresponding prevalence in the general population was 18.3%. The figures for all age groups and both sexes were 22% for the cremation group and 24.5% for the general population. In the economically active group (20-65) years, the figures were 20.0% for the cremation group and 30% for the general population. There was no significant difference in the IHD deaths between Afrikaans-speakers and other language groups. These findings are not necessarily applicable to the general population, as the cremation group is not truly representative, but the consistently lower prevalence of IHD suggests that there is over-reporting of this disease in unmonitored death certification.

Cause of Death↗
PubMed1989

Causes of death at Tshepong, a rural hospital, 1986-1987.

A prospective study was undertaken to determine causes of death at Tshepong Hospital in the western Transvaal over 1 year. Specific attention was paid to the accurate coding of causes of death; this entailed discussions with the attending doctor as well as 38 autopsies. Only 2.4% of deaths were coded under 'symptoms, signs and ill-defined conditions'. The 1046 deaths followed a typical Third-World pattern when classified according to the International Classification of Diseases (1979). Deaths during the perinatal period were additionally classified according to the recommendations of the Third Conference on Priorities in Perinatal Care in South Africa. The commonest cause of death was conditions originating in the perinatal period (19.2%), followed by infections and parasitic diseases (15.9%), diseases of the circulatory system (14.8%), endocrine, nutritional and metabolic diseases and immune-disorders (12.1%), and neoplasms (8.8%). The other main groups accounted for under 8% each. The commonest cause of death in all age groups above 35 years was diseases of the cardiovascular system, and the commonest cause of death among females aged 15 - 35 years was complications of pregnancy, childbirth and the puerperium. The hospital maternal mortality rate was 4.7/1,000 deliveries and the hospital perinatal mortality rate was 53/1,000 deliveries.

Adolescent↗
PubMed1989

[The ultrasonic demonstration of gas in the endometrial cavity--an aid for the diagnosis of puerperal endometritis].

A pilot study was undertaken to determine the prevalence of gas in the puerperal endometrial cavity and to determine whether this finding has any relationship to the mode of delivery or to the development of puerperal endometritis. On the first day after delivery 192 patients were examinee ultrasonographically and gas was demonstrated in 26 (13.54%). Gas was found significantly more often in relation to caesarean section and intra-uterine manipulation than in normal vaginal deliveries (P less than 0.0001). On the third puerperal day the gas disappeared in 12 patients but persisted in 14, of whom 7 had signs of endometritis. Endometritis was diagnosed in a total of 8 patients and only 1 did not have signs of gas in the endometrial cavity. Although the figures are small it is concluded that ultrasonography of the puerperal uterus might assist in the diagnosis of puerperal endometritis.

Adolescent↗
PubMed1989

Consecutive melatonin circadian rhythms in normal volunteers.

Circadian plasma melatonin secretion patterns were determined in 12 healthy men over 3 consecutive 24-hour periods. The rhythms showed marked intra-individual stability, but pronounced interindividual variation. Plasma melatonin may serve as a reliable biological marker. Plasma melatonin assayed between 23h00 and 01h00 gave a reliable indication of an individual's circadian melatonin rhythm.

Adult↗
PubMed1989

The relationship between total urinary testosterone and renal calculi.

It is generally known that age and sex are risk factors of urolithiasis. Therefore the total urinary testosterone concentrations of persons with and without renal stones were investigated by means of radioimmunoassay. The total testosterone level of the first morning midstream urine was comparable with 24 urine samples of 16 healthy persons (rs = 0.9618). Investigation of the total urinary testosterone confirmed that the concentration is age dependent. A distinct decrease in total testosterone was observed in elderly persons. Therefore the total testosterone concentrations of the two groups, with and without stones, were studied within the same age interval (P = 0.8292). The the testosterone level differed significantly for these two groups (P = 0.0006). In general, the testosterone level of the kidney stone patients was lower than that of their healthy counterparts. In order to determine whether this variation in testosterone concentration would affect the urinary urokinase activity, a correlation study was undertaken. A positive correlation was found between the total urinary testosterone concentrations and the activity of urokinase (rs = 0.7305). It therefore seems that the total urinary testosterone concentrations may play a role in the pathogenesis of the multifactorial disease, urolithiasis.

Age Factors↗
PubMed1989

Investigation of the relationships between plasma levels of ascorbate, vitamin E and beta-carotene and the frequency of sister-chromatid exchanges and release of reactive oxidants by blood leucocytes from cigarette smokers.

In this study the frequencies of sister-chromatid exchanges (SCEs) were correlated with measurements of the release of reactive oxidants by phagocytes, as determined by luminol-enhanced chemiluminescence (LECL), and levels of the anti-oxidants ascorbate, beta-carotene and vitamin E in blood specimens taken from 65 young asymptomatic cigarette smokers. Increased SCE frequencies correlated with LECL responses (p less than 0.0075) of activated blood phagocytes. Anti-oxidant levels did not correlate with either LECL or SCEs. These findings indicate that increased generation of reactive oxidants by circulating phagocytes from cigarette smokers are associated with cytogenetic changes.

Adult↗
PubMed1989

Random variation in tuberculin sensitivity in schoolchildren. Serial skin testing before and after preventive treatment for tuberculosis.

Schoolchildren were Mantoux-tested with 2 TU freeze-dried PPD RT23, and the strong reactors with indurations of 14.0 mm or more were selected for treatment with one of three different fixed drug combinations containing isoniazid or with placebo for 2 to 6 months. The initial tuberculin test was repeated after 8, 14, and 27 months. Of the 8,934 black schoolchildren initially tested, 5,165 did not react to the skin test, 2,898 had indurations up to 14.0 mm, and 871 reacted strongly. Of these strong reactors, 808 were allocated to four preventive treatment groups. On completion of treatment, the mean tuberculin reaction for all groups was significantly decreased. Because the placebo group showed changes similar to those seen in the other treatment groups, the tuberculin skin test is probably not suitable for monitoring the success of preventive therapy. Differences between skin test results before and after treatment when retesting only strong reactors are caused by a combination of effects that are difficult to distinguish. Assuming random variation in tuberculin sensitivity, the decrease can be explained as a combined effect of regression to the mean and some boosting. The increased reaction sizes in the subsequent Mantoux tests are explained by the booster phenomenon and possibly by reinfection. When using a cutting point for deriving a positive reactor, the chance of being selected for preventive treatment may depend primarily on the moment in time when the test is done. Thus, all reactors with no recent BCG vaccination should equally be considered for treatment.

Adolescent↗
PubMed1989

[Semi-microanalytical method of fluoride determination in enamel biopsies].

When making use of potentiometric micro-analytical methods in fluoride determination, only a portion of the lantanium fluoride (LaF) crystal of the fluoride electrode is employed. Although there is no difference in sensitivity when using either the total surface or a part of the surface of the LaF crystal, there are advantages in using the total surface of the crystal. For the purpose of utilizing these advantages to a maximum, a semi-micro-analytical method of fluoride determination was developed. A perspex electrode container with a specimen capacity of 50 microliters was designed and constructed in order to bring the total surface of the LaF crystal into contact with the testing solution. Due to the inexpensive and simple design of the containers there are practically no restrictions on the number that could be employed. The solution obtained from a single enamel biopsy could be used for at least two or three analyses. The results obtained by employing the technique described, showed that the method is precise and accurate. The semi-microanalytical method offers an alternative to the micro-analytical method of fluoride determination in enamel biopsies.

Dental Enamel↗
PubMed1989

[Attitude of South African dentists and final year dental students to advertising].

Advertising or promotion comprises two aspects: the advertising message and the advertising medium. Since both aspects are viewed differently by various professions, including the dental profession, the current investigation was carried out to ascertain the attitude of South African dental practitioners. Although it was found that the majority of dentists were against the advertising of new practices and re-advertising of existing practices, the majority of the final year dental students of 1986 were in favour. Both groups, however, were against unlimited advertising and also preferred professional cards to press, radio and television as the medium of communication.

Adult↗
PubMed1988

Quality of semen obtained by electroejaculation from chacma baboons (Papio ursinus).

Fifty-four baboons (Papio ursinus) were subjected to an electro-ejaculation procedure that yielded 683 usable ejaculates in 705 attempts. Quality evaluations by usual human spermiogram methods were applicable with only minor modifications to the procedures. By human criteria these wild baboons remained fertile after capture, and their use as a fertility model in pharmacological studies appeared to be appropriate.

Animals↗
PubMed1987

Neonatal maintenance solution--is neonatalyte safe?

Newborns in the neonatal unit at Ga-Rankuwa Hospital who required intravenous fluids were randomly allocated, after 24 hours of life, to receive either Neonatalyte (Sabax) or a control solution. Biochemical monitoring was performed every 12 hours for a period of 5 days. Neonatalyte does not cause hyperkalaemia or hypocalcaemia in the early neonatal period.

Calcium↗
PubMed1987

Prevalence of otitis media in a Venda village.

During mid-winter in 1985, 263 children and 217 adults from a remote rural community in Venda, were examined for the presence of middle ear lesions by: pneumatic otoscopic examination; tympanometry; and contralateral acoustic reflex. A diagnostic algorithm was applied to assess the findings. The prevalence of otitis media (OM) in children (less than or equal to 15 years) was 8.4% and in adults (greater than 15 years) 2.3%, with the highest figure in the 0-23 months age group. OM with effusion was found in 3.6% of the children. Our data suggest the existence of considerable differences in the prevalence of OM between comparable black rural communities.

Adolescent↗