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Biomedical subjects

R A Yeates

Publications and source records attributed to R A Yeates.

43 records · Page 3Linked to original sources
PubMed1979

In vitro damage of cultured ookinetes of Plasmodium gallinaceum by digestive proteinases from susceptible Aedes aegypti.

After exposure to extracts from blood fed A. aegupti cultured ookinetes of P. gallinaceum were damaged to various, defined extents. Immature ookinetes were found to be more sensitive to damage than mature ones. The damage was dependent on the digestion time after which the Aedes extracts had been prepared and could be correlated with the proteolytic activity in the extracts. Control experiments demonstrated that the factors responsible for damage were neither present in unfed mosquitoes nor in blood alone and that the damage was not a result of osmotic stress. After the treatment of the Aedes extracts with lima bean trypsin inhibitor the ookinete damage was much less, indicating that the Aedes trypsin was the major agent of damage. These results were supported by experiments in which the tryptic activity of the extracts was eliminated by thermal denaturation. It is concluded that in the mosquito midgut most of the ookinetes are damaged by digestive enzymes and that this is one factor leading to the discrepancy between the number of ingested macrogametocytes and the number of oocysts which is usually found in nature. It seems that the only ookinetes which have a chance of surviving are those which develop in the centre of the blood clot, away from the site of enzyme action.

Aedes↗
PubMed1978

Effects of therapy on plasma-high-density-lipoprotein-cholesterol concentration in diabetes mellitus.

In 122 diabetic patients there was a signnificant inverse correlation between plasma-high-density-lipoprotein (H.D.L.)-Cholesterol concentrations and glycosylated haemoglobin concentrations. In an insulin-treated subgroup improvement in diabetic control, confirmed by a decrease in glycosylated haemoglobin concentrations, was accompanied by a significant rise in plasma-H.D.L.-cholesterol concentration. This result suggests that improved diabetic control may diminish the risk of premature ischaemic heart-disease. When three groups of patients on different treatments were matched for age, sex, weight, and diabetic control, diabetic patients receiving sulphonylureas had significantly lower plasma-H.D.L.-cholesterol concentrations than those receiving insulin or on diet alone, or non-diabetic controls. This association suggests that sulphonyl-urea administration may constitute a positive risk factor for ischaemic heart-disease in diabetic patients.

Adolescent↗
PubMed1978

Antibody responses in self-infections with Necator americanus.

Antibody responses were measured in a volunteer infected four times with Necator americanus over a 27-month period. The main source of antigen was culture fluid in which living adult N. americanus had been maintained for several days. Antibodies to worm acetylcholinesterase and IgE antibodies were detected only with this material, but antibodies were identified by the enzyme-linked immunosorbent (ELISA) assay, with either adult worm secretions or extracts of third-stage infective larvae. The total serum IgE level fell after the first infection, but although it then increased during subsequent infections, it never rose above 600 U per ml. None of the antibody responses suppressed the rat of worm development to maturity, or reduced the fecundity of the parasites. However, it is suggested that the development of the immune response may be associated with the waning of the severe gastro-intestinal symptoms which were experienced in this infection, and which are frequently characteristic of hookworm infections.

Acetylcholinesterase↗
PubMed1976

Measurement of anti-enzyme antibodies using an active-site directed radiolabel.

A new technique is described for measuring antibodies to an enzyme which is not available in pure form. The secretions of the rat parasitic nematode, Nippostrongylus brasiliensis, were treated with tritiated diisopropylfluorophosphate. Only one component, an acetylcholinesterase, was radiolabelled. Antibodies to this enzyme in rat antisera were estimated by the Farr technique using the labelled enzyme as antigen. The acetylcholinesterase secreted by Necator americanus, the human hookworm, was similarly specifically labelled.

Acetylcholinesterase↗
PubMedDate not supplied

Fluconazole concentrations in pulmonary tissue and pericardial fluid.

In order to investigate the clinical efficacy of the triazole antifungal agent fluconazole (FCA) in the treatment of pulmonary mycosis, in the present study the concentrations of fluconazole in human pulmonary tissue, pericardial fluid and serum were determined at 1, 2, 12 and 13 h after intravenous administration of fluconazole 200 mg. The mean FCA concentrations in the serum were 4.04 mg/l (1 h), 3.82 mg/l (2 h), 2.35 mg/l (12 h) and 2.13 mg/l (13 h). The respective FCA levels in the pulmonary tissue were 4.64 mg/kg, 4.54 mg/kg; 3.50 mg/kg and 3.40 mg/kg and the concentrations in the pericardial fluid were 3.86 mg/l, 3.57 mg/l, 2.35 mg/l and 2.13 mg/l. The FCA concentrations in the pulmonary tissue that were statistically significant higher than the serum concentrations were found at 2 h, 12 h and 13 h after intravenous administration (p < 0.05).

Animals↗
PubMedDate not supplied

A new pharmaceutical concept for the treatment of oropharyngeal and oesophageal candidosis with fluconazole.

Administration of fluconazole in capsule form has proved effective in the prophylaxis and treatment of mucosal candidosis, particularly in immunosuppressed patients. An additional topical effect in oropharyngeal and oesophageal candidosis might be expected with a fluconazole suspension. This hypothesis was therefore tested in a crossover study in 12 healthy volunteers in whom the concentrations of the antimycotic were measured in saliva and plasma after oral administration of 100 mg fluconazole as either a capsule or a suspension. The time courses of the fluconazole concentrations were very similar with the two formulations in plasma, but significantly different in saliva. Thus, the mean Cmax for fluconazole in saliva of 551 micrograms ml-1 was reached 5 min after ingestion of the suspension, compared with a value of 3 micrograms ml-1 some 4 h after taking the capsule. The mean concentration of the antimycotic in saliva over the observation period (0-96 h) was more than 80% higher with the suspension than with the capsule.

Administration, Oral↗