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Biomedical subjects

P H Joubert

Publications and source records attributed to P H Joubert.

At least 19 recordsLinked to original sources
PubMed1998

A new mixed micellar preparation for oral vitamin K prophylaxis: randomised controlled comparison with an intramuscular formulation in breast fed infants.

OBJECTIVE: To compare a new oral preparation of vitamin K1 (Konakion MM) containing lecithin and glycocholic acid with a standard intramuscular (IM) preparation during the first 8 weeks of life in exclusively breast fed infants. METHODS: Infants were randomised at birth to the IM group (1 mg vitamin K) or the oral group (2 mg given at birth and repeated at 7 and 30 days of life). Prothrombin time (INR), plasma vitamin K1, and PIVKA II (undercarboxylated prothrombin) were monitored at 14, 30, and 56 days of age. RESULTS: Seventy nine infants were randomised to the oral group and 77 to the IM group. Sixty seven infants in each group completed eight weeks of the study. Prothrombin times did not differ between the two groups. Mean (SD) plasma vitamin K1 values (in ng/ml) decreased in both groups over time, but were higher in the oral group at 14 and 56 days: 2.0 (1.6) v 1.3 (1.1) at 14 days; 0.5 (0.3) v 0.5 (0.7) at 30 days; and 0.5 (0.8) v 0.2 (0.2) at 56 days of life. PIVKA II was raised (> or = 0.1 AU/ml) in cord blood in 47% of the infants. By 14 days, only one infant in each group had a raised PIVKA II value and both of these initially had high concentrations of PIVKA II in cord blood. At 30 days, there were no raised PIVKA II values. At 56 days, there were no raised PIVKA II values in the oral group, although three infants in the IM group had raised values. CONCLUSIONS: Plasma vitamin K concentrations were at least equal or significantly higher in babies given oral vitamin K supplements compared with IM treated babies at the time points measured. Through the first 8 weeks of life, multiple doses of the new oral preparation maintain haemostasis and vitamin K status in breast fed infants at least equal to that of the intramuscular preparation.

Administration, Oral↗
PubMed1995

Epidemiology and control of schistosomiasis mansoni in communities living on the Cuando River floodplain of East Caprivi, Namibia.

The Cuando River area of eastern Caprivi, Namibia, is highly endemic for Schistosoma mansoni whereas S. haematobium transmission, due to the scarcity of its intermediate host snail, Bulinus africanus, does not occur. Chemotherapy (6-monthly blanket treatments with praziquantel) combined with focal mollusciciding (monthly application of niclosamide) was used in a project in the area to control the disease. Although as many adults and pre-school children as possible were tested and treated, the project concentrated largely on school-age children. It took 3 years for prevalence to decline from > 80% to 20% because of a lack of proper sanitary facilities and piped water supplies and high rates of absenteeism and re-infection. However, intensity of infection decreased more rapidly, from an arithmetic mean of > 200 to < 5 eggs/g faeces. Hepatomegaly was common among school children when the project started but could be seen in only a small percentage of them after 3 years of control. Neither the bovine schistosome, S. mattheei, nor the lechwe schistosomes, S. margrebowiei and S. leiperi, were observed in the excreta of humans living in the area.

Adolescent↗
PubMed1992

Cardiac glycoside poisoning involved in deaths from traditional medicines.

Autopsy cases (from all areas of South Africa except the Cape Province) are referred for chemical investigation to the Johannesburg Forensic Chemistry Laboratory of the State Health Department. Over a 1-year period in 41 autopsies where death was presumed to have been caused by a herbal medicine, the presence of cardiac glycosides was sought and was found in 44%. Most of the cases were from the Transvaal, followed by Natal. Clinical histories of the patients revealed that gastrointestinal irritation was the most common syndrome experienced after traditional medicine administration (54%). It is concluded that in patients presenting with gastro-intestinal symptoms, presumably due to poisoning by traditional medicines, cardiac glycoside poisoning should be suspected.

Adolescent↗
PubMed1991

Compliance in black patients with non-insulin-dependent diabetes mellitus receiving oral hypoglycaemic therapy.

Poor compliance with drug therapy is an important cause of therapeutic failure. Sixty-eight black patients with non-insulin-dependent diabetes mellitus receiving oral hypoglycaemic agents were interviewed and various factors, such as age, sex, degree of control and type of therapy, were recorded by means of a questionnaire. Compliance was determined by qualitatively assessing urine for the presence of the drugs. An alarmingly high incidence of non-compliance of 65% was found, which could still be an under-estimation because of the long half-life of one of the drugs involved--chlorpropamide. Although interesting trends were noted, no statistically significant differences between compliant and non-compliant patients were found. In the light of the high incidence of non-compliance, a larger and more detailed study seems to be warranted to identify problem areas and to plan appropriate interventions.

Black or African American↗
PubMed1991

A comparison of the effects of digoxin and digitoxin on systolic time intervals and colour vision.

Animal studies suggest that for the same inotropism hydrophilic cardiac glycosides produce greater depression of atrioventricular (AV) conduction than lipophilic ones. This has been explained on the basis of a greater vagomimetic effect with hydrophilic agents and a greater sympathomimetic effect with lipophilic agents. In this randomized, cross-over study we investigated the effects of placebo, digoxin (relatively hydrophilic), and digitoxin (relatively lipophilic) in twelve healthy volunteers. For both drugs steady-state serum concentrations in the mid-therapeutic range were achieved. Both drugs produced the same positive inotropic effect as measured by systolic time intervals (QS2c). There was a trend for digoxin to have a greater effect on AV conduction than digitoxin. After atropine or propranolol there was no difference between the effect of the two cardiac glycosides on AV conduction. No significant effects on colour vision were seen. We conclude that, there do not seem to be pharmacodynamic differences between digoxin and digitoxin at mid-therapeutic serum concentrations.

Adult↗
PubMed1991

Further studies on the susceptibility of Bulinus africanus to infection with Schistosoma haematobium.

Genetic manipulation of the intermediate host snails of schistosomiasis has been proposed as a possible method of reducing the rate at which the parasite is transmitted to the final host. This technique is based on the finding that snail-schistosome compatibility is variable, and that refractory snails could be introduced into natural habitats in an attempt to change existing highly-susceptible populations into non-susceptible ones. In our search for such a refractory snail population, offspring from eight different Bulinus africanus populations were infected with Schistosoma haematobium, isolated from school children in the Nelspruit district. A great variation in minimum prepatent period was recorded (33-55 days), while the infected snails surviving that period ranged from 22-89%. A significant difference was found between the infection rates of B. africanus from Newlands in Natal and those of the other seven populations from the Eastern Transvaal Lowveld. The former population could be regarded as partially refractory, and none of the other populations proved to be completely refractory, to infection.

Animals↗
PubMed1991

Laboratory evaluation of B-2 as a molluscicide in the control of the snail intermediate hosts of schistosomiasis in South Africa.

There is a continuous need for the development and evaluation of new, inexpensive but highly effective molluscides for the control of freshwater snails acting as intermediate hosts of schistomiasis. For this reason B-2 (Hokko Chemical Industry Co. Ltd, Japan), also called Phebrol (sodium 2,5-dichloro-4-bromophenol), was evaluated in our laboratory as a candidate molluscicide for the control of freshwater snails in South Africa. Bulinus africanus and Biomphalaria pfeifferi, intermediate hosts of Schistosoma haematobium and Schistosoma mansoni respectively, were exposed to different B-2 concentrations for 24 and 48 hours. An indigenous fish species, Oreochromis mossambicus, which is common in local schistosomiasis endemic areas, was also exposed to the molluscicide. The calculated values obtained from a probit analysis (LC50, 24 hours: B. africanus = 2.6 mg 1(-1) and B. pfeifferi = 2.9 mg 1(-1), indicated that these species from southern Africa are less sensitive to B-2 than are B. truncatus and B. pfeifferi from northern Africa, which in turn are less sensitive than the Oncomelania spp. from Japan, China and the Philippines. It is expected that molluscicidal levels of B-2 would be harmful to O. mossambicus populations. Although B-2 has a marked potential for snail control in South Africa, niclosamide (Bayluscide) remains the molluscicide of choice.

Animals↗
PubMed1991

The molluscicidal properties of Apodytes dimidiata subsp. dimidiata (Icacinaceae).

The molluscicidal and piscicidal activity of extracts from the leaves, berries and bark of the tree Apodytes dimidiata were evaluated experimentally. The leaves were highly toxic to both Bulinus africanus and Biomphalaria pfeifferi, the intermediate host snails of Schistosoma spp. B. pfeifferi profusely exuded mucus which appeared to render some protection against the toxic substance(s) of the plant but did not prevent their eventual demise. The LC10 after one-hour exposures of fish (Oreochromis mossambicus) was within molluscicidal levels.

Animals↗
PubMed1990

Penbutolol in the treatment of mild to moderate essential hypertension in black South Africans.

The antihypertensive effects of penbutolol, a nonselective beta-adrenoceptor antagonist with intrinsic sympathomimetic activity, was assessed in nonobese black South Africans aged 25 to 65 years with uncomplicated mild to moderate essential hypertension. After a 4-week placebo run-in period 50 patients entered a randomized placebo-controlled study with a crossover design. For 8 weeks they received a once daily dose of 40 mg penbutolol (or placebo) which was increased to 80 mg per day for the next 4 weeks in poor responders. This was followed by a 4-week placebo washout period after which a crossover of treatment was achieved and a second 12-week period of treatment initiated. Thirty-five patients completed the whole study and in 15 patients diastolic blood pressure was reduced below 95 mm Hg. The mean systolic pressures of these patients decreased by 21 mm Hg and their mean diastolic pressure decreased by 11 mm Hg during treatment with penbutolol. These results suggest that penbutolol monotherapy is an alternative therapeutic approach to hypertension in black South Africans.

Adult↗
PubMed1990

Apparent racial difference in response to angiotensin I infusion.

Angiotensin I was infused into 16 healthy volunteers, 8 blacks and 8 whites with diastolic blood pressures below 75 mm Hg and the infusion rate increased at 3 min intervals until a diastolic blood pressure of equal to or greater than 95 mm Hg was achieved. Blacks exhibited a significantly greater angiotensin I sensitivity needing 1.8 micrograms/min as opposed to 3.9 micrograms/min in whites to achieve the target blood pressure. Plasma renin activities were similar in the two groups, but blacks had significantly higher urinary sodium values than whites, 223 mmol per 24 h as compared to 121 mmol per 24 h. It is concluded that the differences in response could be largely due to differences in dietary sodium intake. These factors need to be carefully considered when using angiotensin I infusion as a pharmacodynamic model for studying the effects of ACE inhibitors.

Adult↗
PubMed1990

Scanning electron microscopical observations on the shedding of the tegument of adult Schistosoma mattheei.

In search of indications of membrane turnover the teguments of male Schistosoma mattheei from cattle and laboratory rodents were studied by means of scanning electron microscopy. A number of slightly elevated circular patches of tegument which appeared to peel off on the edges were seen on the outer membrane of a limited number of specimens from both rodents and cattle. It is suggested that this phenomenon may represent limited rapid turnover of the outer layer in response to host immunological action.

Animals↗
PubMed1990

Adherence of blood platelets and leucocytes to hybrid schistosomes.

The bovine parasite, Schistosoma mattheei was crossed with the human schistosome, S. haematobium. The F1 hybrids resulting from this cross were viable in both snails and rodents. However, F1 x F1 (F2) crosses were less viable in snails and a proportion of them seemed to be changed structurally when viewed by scanning electron microscopy. Certain of the schistosomes were covered with a dense mass of interconnected blood platelets resembling a temporary haemostatic plug but not a blood clot. Interspersed between the platelets were a small number of leucocytes. We suggest that the platelets may have responded to the presence of an antigen which is masked in normal schistosomes but which is exposed in certain F2 hybrids.

Animals↗
PubMed1990

Interaction in the laboratory between Helisoma duryi, a possible competitor snail, and Biomphalaria pfeifferi, snail intermediate host of Schistosoma mansoni.

The planorbid snail, Helisoma duryi, has been proposed as a possible biocontrol agent against the intermediate host snails of schistosomiasis. In an attempt to evaluate the possible effect of interference between H. duryi and Biomphalaria pfeifferi, life-tables were compiled for these two snail species maintained both in the presence of each other and separately. The calculated population parameters indicated that H. duryi had a higher innate capacity of increase, net reproduction rate and finite rate of increase as well as a longer lifespan than the target species. However, the biological potential of B. pfeifferi was not influenced by the presence of H. duryi, and the latter appears to be unable to act as competitor against B. pfeifferi under similar prevailing conditions. It is possible that the situation might change under conditions of crowding and starvation.

Animals↗