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Biomedical subjects

D Thomas

Publications and source records attributed to D Thomas.

At least 973 records · Page 54Linked to original sources
PubMed1978

The pharmacokinetics and metabolism of the anilide local anaesthetics in neonates. I. Lignocaine.

The pharmacokinetics and metabolism of lignocaine in premature neonates was studied after subcutaneous administration. The collection of serial urine together with a limited number of blood samples from neonates enabled simultaneous computer fitting of data to a pharmacokinetic model. The disposition kinetics of lignocaine in four neonates were compared with similar data reported for adults. Neonates had prolonged t1/2 (neonate mean: 3.16 h; adult mean: 1.80 h), and an increased total volume of distribution (neonate mean: 2.75 l/kg; adult mean: 1.11 l/kg) compared with adults. Total plasma clearance (Cltp) normalised on body weight showed no significant difference between neonates (mean: 0.610 l/h/kg) and adults (mean: 0.550 l/h/kg). The urinary excretion of lignocaine and several of its metabolites was studied in 8 neonates and 11 adults. Neonates were shown to excrete much more unchanged lignocaine (mean: 19.67%) compared with adults (mean: 4.27%) and the proportion of the dose excreted as 4-hydroxyxylidine is considerably reduced in neonates (neonate mean: 8.89%; adult mean: 63.78%). The use of the two pharmacokinetic parameters, t1/2 and Cltp, as indices of drug elimination ability are discussed.

Adult↗
PubMed1978

A new method for cell immobilization.

A new method for producing particles and membranes containing immobilized bacteria is presented. These immobilized bacteria display good stability over time making them well suited for use in a packed-bed reactor. Such a reactor is tested as a function of the different parameters of the system. The results are qualitatively similar to those obtained with purified enzyme reactors, but some discrepancies with the plug-flow model are noted. It is necessary to use a more sophisticated model in order to fit the experimental data.

Bacteriological Techniques↗
PubMed1978

Stocking rate and the productivity of Rhodes grass pastures on the Lilongwe Plain, Malawi.

An experiment was undertaken over three wet (summer) seasons to investigate the effects of different set stocking rates on animal performance from fertilised Rhodes grass pastures. The three set stocking rates were 2.5, 5 and 7.5 livestock-units/ha (1 livestock unit=342 kg liveweight). Pasture productivity was related to stocking intensity. Animal gain per hectare was directly related to stocking rate. Gain per animal, gain per livestock unit and number of grazing days were all inversely proportional to stocking rate. Animals on the low stocking rate were carried through almost to the end of the dry (winter) season with only small changes in liveweight. The practical significance of the results is discussed.

Animal Feed↗
PubMed1978

Low density lipoprotein. A metabolic pathway for return of cholesterol to the splanchnic bed.

The mechanism(s) by which cholesterol returns to the splanchnic bed from peripheral tissues are not well understood. To study this phenomenon in fasting man, lipoproteins were isolated from plasma obtained from hepatic vein and aorta. Cholesterol content of each lipoprotein class was determined and arteriovenous (AV) differences could be calculated for each patient. The results in the first 24 patients indicated splanchnic secretion of very low density lipoprotein cholesterol (mean AV difference - 3 mg/100 ml, P < 0.01), but not significant AV difference for total cholesterol, high density lipoprotein cholesterol, or low density lipoprotein (LDL) B protein. In contrast, for LDL (d 1.006-1.063 g/ml), there was significant uptake of cholesterol across the AV bed +8 mg/100 ml, P < 0.0002). In a further 15 patients, similar samples were obtained and intermediate density lipoprotein isolated at d 1.006-1.019 g/ml and LDL at 1.019-1.063 g/ml. The AV difference previously noted could now be localized to the 1.019-1.063 cholesterol ester moiety (+8 mg/100 ml, P < 0.0005). In the final 14 patients, the LDL cholesterol AV difference was again confirmed and shown to be unrelated to heparin. As well, there was secretion of triglyceride in the hepatic vein LDL. These quantitative data obtained in man raise the possibility that LDL rather than high density lipoprotein transports cholesterol ester to the splanchnic bed.

Apolipoproteins↗
PubMed1977

[Current indications of coronary arteriography in coronary artery disease (with the exception of acute myocardial infarction) (author's transl)].

The indications of coronary arteriography have multiplied in recent years. Therapeutic indications have followed knowledge of the good results of revascularisation surgery. Initially limited to severe stable angina improved little or not at all by major anti-angina agents, they have been extended, in the view of many, to include various types of unstable angina where, in addition to the symptomatic improvement obtained, an attempt is made to decrease the incidence of myocardial infarction and of long term mortality. Indications relative to determination of the extent of disease may be preventive: the fear of severe coronary lesions on the basis of effort test results, the fear of a second infarction immediately following a primary lesion, or as a virtually routine examination in young individuals in order to better assess the degree of disease and to guide treatment. Diagnostic indication should be rare.

Angina Pectoris, Variant↗
PubMed1977

Paraquat poisoning is not necessarily fatal.

This paper describes a case of deliberate ingestion of paraquat successfully managed with gastric lavage, forced diuresis, haemodialysis, gastrointestinal purgation and the adminstration of specific adsorbents.

Adult↗
PubMed1977

Jaw wiring in treatment of obesity.

17 patients with severe (median percentage above ideal weight 100%) and resistant obesity underwent jaw wiring. There were no major complications and patients tolerated the procedure and subsequent minor inconveniences. All patients lost weight at a rate (median 25-3 kg in six months) comparable with that of intestinal bypass surgery and one achieved and maintained her ideal weight. Two-thirds of the patients, however, regained some weight after the wires were removed. Jaw wiring is a simple effective procedure which can be carried out in most hospitals, and has a place in an integrated approach to obesity.

Adolescent↗
PubMed1977

Kinetic studies dealing with immobilized reversible enzyme system. Experimental evidence for shift of apparent equilibrium constant within bienzyme system.

Two chemostat methods for studying the immobilized enzyme kinetics are presented. The methods are applied to glucose-6-phosphate isomerase immobilized within a proteic membrane. The first method is based on the steady state behavior of a Continuously Stirred Tank Reactor (C.S.T.R.) and the second one on a diffusion-reaction process. The apparent equilibrium ratio between glucose 6-phosphate and fructose 6-phosphate is measured for the immobilized enzyme system. No modification is observed with a monoenzyme membrane. In the presence of a glucose-6-phosphate dehydrogenase activity the product of the first reaction is trapped by the second one and due to the local intramembrane concentrations an apparent modification of the equilibrium ratio is observed. The apparent modification is studied with the bienzyme membrane as a function of the concentration of NADP co-substrate of the second enzyme. A "Michaelian" relationship is observed.

Animals↗
PubMed1977

Influence of human skin surface lipids on protection time of topical mosquito repellent.

Skin surface lipids were extracted from volunteers who had been ranked according to the duration of protection from mosquitoes by diethyltoluamide. These lipids were analyzed by GLC-mass spectrometry for their fatty acid contents. Correlations were found between total skin lipid content and protection time of diethyltoluamide and between certain fatty acid concentrations in the skin lipids and the protection time of diethyltoluamide.

Administration, Topical↗
PubMed1977

Intensive fattening of beef cattle on Rhodes grass pastures on the Lilongwe Plain, Malawi.

Beef fattening experiments were conducted in two wet seasons with Malawi zebu (Mz) and Friesian X Malawi zebu (F X Mz) steers grazing nitrogen-fertilised Rhodes grass pastures. The effects of stocking rate (5,7-5 or 10 steers/ha) and level of supplement (maize: madeya (maize bran) fed to steers at either 0-6 or 1-5 per cent of liveweight) were investigated over a 100 day period. Neither stocking rate nor supplement had an effect on daily liveweight gain but gain per hectare increased significantly with stocking rate. Comparative performance of the two breed types showed that the superior absolute gains of the F X Mz steers were not reflected in the efficiency parameters of supplement conversion or gain and carcass yield per unit liveweight. Hindquarter percentage was higher and subcutaneous fat was better distributed in the F X Mz. The practical significance of the results is discussed.

Animal Feed↗
PubMed1977

Intensive fattening of beef cattle by stall feeding on the Lilongwe Plain, Malawi. I. Type of forage and level and type of supplementation.

Experiments were undertaken with Malawi zebu steers over three wet seasons to investigate the effects of feeding improved forages (zero grazed) and supplements on animal performance. The forages fed were Guinea grass and pearl millet and the supplements maize: madeya (maize bran) or maize: madeya: cottonweed cake. The daily allowance of supplement was, on a DM basis, liveweight equivalent to 0-6, 1-1 or 1-5 per cent of cattle (1973, 1974). In 1975 the supplementation treatments were nil, maize: madeya or leucaena fed at 0-6 per cent liveweight. Daily gains of steers were similar with both forages except in 1975 when those fed on pearl millet grew 19 per cent faster than those on Guinea grass. The performance of steers was increased with supplementation only where forage quality declined. The significance of the results are discussed.

Animal Feed↗
PubMed1977

Intensive fattening of beef cattle by stall feeding on the Lilongwe Plain, Malawi. II. Utilisation of crop residues, crop by-products and leucaena.

Experiments were conducted over three dry seasons to investigate the value for fattening beef cattle, of crop residues (maize stover, groundnut haulm) and madeya (maize bran) with varying levels of dried leucaena leaf or cottonseed cake. The inclusion of groundnut haulm in the roughage increased animal performance when madeya was restricted. Increasing the protein content of the madeya supplement but restricting the quantity of madeya fed did not influence liveweight gain although the efficiency of concentrate conversion was enhanced. Restricting the amount of maize stover and feeding madeya to appetite had no significant effect on liveweight gain, but the inclusion of leucaena up to a level of 12 per cent crude protein improved animal performance. There were no differences between cottonseed cake or leucaena when fed with madeya at the same levels of crude protein.

Animal Feed↗
PubMed1977

Intensive fattening of beef cattle by stall feeding on the Lilongwe Plain, Malawi. III. Comparative productivity of Malawi zebu and Friesian X Malawi zebu steers.

Beef fattening experiments were undertaken on the Lilonge Plain with Malawi zebu (Mz) and Friesian X Malawi zebu (F X Mz) steers. Animals were fattened under various dietary regimes based on either green forage crops or crop residues supplemented with concentrate rations of local origin. Mz steers consumed less feed and liveweight gain was approximately 75 per cent that of the F X Mz. Measurement of the efficiency parameters of feed conversion, gain and carcass yield per unit of liveweight revealed no significant differences between the two breed types. Slaughter observations indicated better fat distribution in the F X Mz and a significantly higher proportion of hindquarter. The significance of the results is discussed.

Animal Feed↗