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Biomedical subjects

M Thomson

Publications and source records attributed to M Thomson.

At least 127 records · Page 7Linked to original sources
PubMed1989

Comparative biochemical and pharmacological properties of epidermal secretions from Ariid catfish of the Arabian Gulf.

1. Comparative biochemical and pharmacological studies on epidermal secretions from three species of Ariid catfish were carried out to determine whether they share common properties. 2. Protein compositions are generally similar, but show some differences in size and numbers of proteins. 3. Lipids also differ. However, seasonal and dietary changes in lipid compositions exceed the differences among species. 4. Enzymes in the secretions appear common to each fish species, though some differences are noted in relative activities. 5. Toxicity responses of rabbits to injections with secretions from each of the catfish species indicated that two were lethal, with similar lethal dose levels when injected intravenously. 6. Secretions from all three catfish induced changes in plasma enzyme levels indicative of heart and liver damage, and also induced changes in blood glucose and cholesterol levels.

Animals↗
PubMed1989

Pressor effects of the alpha 2-adrenoceptor agonist B-HT 933 in anaesthetized and haemorrhagic rats: comparison with the haemodynamic effects of amidephrine.

1. Blood pressure responses to single and multiple bolus doses of the alpha 2-adrenoceptor agonist B-HT 933 were analysed in intact anaesthetized rats which were either normotensive or hypotensive as a result of haemorrhage. Single bolus doses of B-HT 933 in normotensive rats induced a fall in blood pressure, whilst further doses induced dose-dependent pressor responses which were inhibited by the alpha 2-adrenoceptor antagonist yohimbine and unaffected by the alpha 1-adrenoceptor agonist prazosin. In the haemorrhagic, hypotensive animals, single bolus doses of B-HT 933 induced immediate dose-dependent pressor responses; the maximum pressor responses to the bolus of B-HT 933 and its ED50 values were the same in both the normotensive and hypotensive, haemorrhagic animals. 2. Cardiac output, its distribution and tissue blood flows were determined with tracer microspheres in intact anaesthetized normotensive and haemorrhagic, hypotensive rats during depressor (normotensive) and pressor (normotensive and hypotensive) responses to B-HT 933. Haemodynamics were also determined during pressor responses to the alpha 1-adrenoceptor agonist amidephrine. 3. In control normotensive rats, a single dose of B-HT 933 (1 mg kg-1) reduced blood pressure by reducing cardiac output (through a decrease in heart rate). It increased the fractional distribution of cardiac output to the spleen and stomach, reduced it to the heart and liver and reduced cardiac and hepatic blood flow. A further dose of B-HT 933 (1 mg kg-1 bolus followed by 100 micrograms min-1 infusion) increased blood pressure by increasing total peripheral resistance, which was accompanied by decreased proportions of cardiac output passing to the heart, liver and testes. There was also increased fractional distribution of cardiac output to the lungs, spleen, kidneys and stomach but blood flows through the liver and testes were reduced. Amidephrine (6 micrograms kg-1 bolus followed by 0.5 micrograms min-1 infusion) increased blood pressure by increasing cardiac output through an increased stroke volume. It increased cardiac output distribution to the kidneys and brain, increasing blood flow through the heart, lungs, brain, testes, epididimides, skin and large intestine. 4. Haemorrhage caused a fall in blood pressure which resulted from decreased total peripheral resistance and cardiac output (the latter due to decreases in both heart rate and stroke volume). It reduced the proportion of cardiac output distributed to the lungs, spleen, kidneys, testes and pancreas/mesentery and decreased blood flow through these organs as well as through the heart, liver, brain, epididimides, skin and the gastrointestinal tract.4

Adrenergic alpha-Agonists↗
PubMed1989

The effects of enalapril on hypertension and quality of life. A large multicenter study in Belgium.

Belgian general practitioners studied the effect of enalapril over a period of 6 months on hypertension and quality of life in 4988 patients, whose hypertensive condition remained uncontrolled by previous treatments and/or in whom this previous drug regimen was not tolerated. Blood pressure was reduced from an average of 170/101 mm Hg at the onset of the trial to 145/85.5 mm Hg after 24 weeks. The treatment with enalapril was well tolerated and tolerance improved remarkably in the patients, whose previous treatment had caused intolerance. Quality of life, determined by means of the Nottingham Health Profile questionnaire, was favourably influenced in the patients participating in this study.

Adult↗
PubMed1989

Linoleic acid and coronary heart disease.

Low tissue concentrations of the essential fatty acid, linoleic acid, occur in communities with high rates of coronary disease and in patients with angina and myocardial infarction. This relationship is independent of lipids and blood pressure, but in smokers linoleic acid is particularly low because they eat less linoleic acid-containing foods.

Coronary Disease↗
PubMed1988

Oestrogen receptors, lactate dehydrogenase and cellularity in human breast cancer.

Oestrogen receptor (ER) concentrations in breast tissues are almost universally expressed in relation to total soluble protein, though the latter does not fully correct for gross variations in receptor concentration due to variations in tissue cellularity. It was considered possible that the concentration of a specific glycolytic enzyme might be a better index and reflection of tumour cellularity. Measurements of the concentrations of lactate dehydrogenase (LDH), oestrogen receptor and total soluble protein and estimates of tumour cellularity were therefore performed on 98 breast tissues (80 breast cancers, 18 benign tissues). Cellularity and the concentrations of oestrogen receptor, lactate dehydrogenase and total soluble protein were significantly higher in breast cancers than in the benign tissues. The concentration of oestrogen receptors (positives only) was, as expected, related to tissue cellularity (correlation coefficient, r = 0.35). The concentrations of both LDH and total soluble protein were also both strongly related to tissue cellularity (correlation coefficients r = 0.67 and 0.75, respectively), and to each other (r = 0.78). These results suggest that (1) total soluble protein concentration is a good index of cellularity and (2) there is unlikely to be any additional value in expressing receptor concentrations relative to LDH since the latter appears to be a 'typical' soluble protein.

Biomarkers, Tumor↗
PubMed1988

Differential processing of corticotrophin-releasing hormone by the human placenta and hypothalamus.

The molecular forms of corticotrophin-releasing hormone (CRH) in human placentae and hypothalami were investigated by gel permeation chromatography of water extracts. Hypothalamic extracts produced one peak of immunoreactivity which coeluted with human CRH at Kd = 0.53. Placental extracts, however, had in addition to that peak, two other peaks eluting earlier at the void and at Kd = 0.35-0.38. Tryptic digestion of the middle peak produced immunoreactivity which coeluted with the standard. Larger forms were also found in plasma of women in the third trimester of pregnancy and during labour but not in eluates from superfused placental fragments which had only CRH41-sized material. These data indicate that tissue-specific post-translational processing occurs for CRH, and suggests that the link between synthesis and secretion is more immediate in the placenta than hypothalamus.

Chromatography, Gel↗
PubMed1988

Antibacterial activity of some alpha-substituted 2-methyl-5-nitrofurans.

The minimum inhibitory concentration values against Gram-negative and Gram-positive bacteria were determined and compared for a selected group of synthesized alpha-substituted 2-methyl-5-nitrofuran derivatives. In vitro oxidation of thiols to disulfides by 2-(iodomethyl)-5-nitrofuran indicated that oxidation of enzyme-thiol groups to disulfide bonds was a possible mode of action; but was discounted by noninhibition of thiol enzymes by these compounds. Electron-microscopic studies of the morphology of bacteria after treatment with these derivatives showed the formation of unusual elongation, branching and atypical rod shapes in E. coli, while S. aureus manifested multibud formation with some cytoplasmic protrusions. The possible mode of action of these compounds is discussed.

Anti-Bacterial Agents↗
PubMed1988

Factors predisposing to difficult labor in primiparas.

Why do some women have difficult labor whereas other women have relatively easy labor? A study of possible predisposing factors was conducted in 398 and 383 primiparas admitted for uncomplicated spontaneous labor at two hospitals. Psychosocial factors, notably anxiety about childbirth, and physical factors, especially maternal height and body mass index, were measured before the onset of labor. Difficult labor was defined in primiparas admitted to the hospital for spontaneous uncomplicated labor as (1) prolonged labor that was longer than 15 hours from admission until full dilation with vaginal delivery or (2) cesarean section. Anxiety about childbirth as self-reported before the onset of labor did not predispose to difficult labor at either hospital. Short height and heavy body mass index predisposed to difficult labor. Further work is needed to elucidate psychosocial factors predisposing to difficult labor.

Anxiety↗
PubMed1988

Isolation of transketolase from human erythrocytes.

Transketolase was isolated from human red blood cells with over 6,200 fold purification by a new method. The stepwise procedure for the isolation of the enzyme from erythrocyte hemolysate included the use of ethanol/chloroform precipitation, chromatography on hydroxyapatite and finally, affinity adsorption on carboxymethyl-cellulose. The molecular weight of erythrocyte transketolase, as determined by polyacrylamide gel electrophoresis, appeared to be about 140,000. The pH optimum for activity was between 7.6 and 7.8 and the optimum temperature for activity was 50 degrees C. The Km values for xylulose-5-phosphate, ribose-5-phosphate and fructose-6-phosphate were 2.0 x 10(-4) M, 3.2 x 10(-4) M and 2.0 x 10(-3) M, respectively.

Chromatography, Ion Exchange↗
PubMed1988

Alcohol consumption and nutrient intake in middle-aged Scottish men.

The relation between alcohol consumption and dietary intake was examined in 164 middle-aged Scottish men taking part in a study of risk factors for coronary heart disease (CHD). A 7-d weighed dietary record was used to assess alcohol and nutrient intake. The mean daily intake of alcohol was 26 g (SD 31 g). Energy derived from alcohol tended to replace energy derived from other nutrients and increasing intake of alcohol was associated with a decrease in the amounts of carbohydrate, total fat, and saturated and monounsaturated fatty acids in the diet. Those with a low alcohol intake (0.1-9 g alcohol/d) had a higher intake of total fiber, cereal fiber, polyunsaturated fatty acids, and linoleic acid and a smaller proportion smoked cigarettes. The differences are small but may contribute to the lower mortality from CHD reported by other studies in those with a low alcohol intake.

Alcohol Drinking↗
PubMed1988

Secretion of beta-endorphin into the maternal circulation by uteroplacental tissues in response to hypoglycaemic stress.

The placenta has been shown to contain ACTH and beta-endorphin but the roles of these peptides are unknown. To investigate whether they are released into the maternal circulation from the placenta in response to physiological stimuli the effects of hypoglycaemic stress were investigated. Plasma samples were collected from the femoral artery (FA) and uterovarian (UV) vein of nine pregnant sheep before and during hypoglycaemia induced by intravenous insulin (100U). Plasma concentrations of ovine beta-endorphin (o beta-EP) were measured by radioimmunoassay. Concentrations of o beta-EP rose in both vessels by 60 min after insulin. The peak concentrations of o beta-EP (pmol/l) were 122 +/- 29 (mean +/- SEM, n = 8) in the UV and 96 +/- 24 (n = 9) fmol/ml in the FA 60 min after insulin injection. There was no difference between the concentrations of o beta-EP in the vessels before insulin injection but at 60 and 120 min after insulin the concentrations of o beta-EP were significantly higher in the UV than FA (P less than 0.02, analysis of variance). This indicates that the pregnant uterus or placenta can respond to hypoglycaemia by secreting beta-EP into the maternal circulation. It is therefore possible that placental pro-opiomelanocortin (POMC) peptides may have a role in maternal endocrinology and metabolism.

Animals↗
PubMed1988

Secretion of corticotropin-releasing hormone by superfused human placental fragments.

Corticotropin-releasing hormone (CRH) immunoreactivity (IR) is present in the blood of women in the 3rd trimester of pregnancy and in placental extracts. We have used a placental fragment superfusion system to investigate the release of CRH from fresh placental tissue. Fragments of normal term placenta were mixed with Biogel P2, packed into minicolumns and superfused with carbogen-gassed Earles buffer at 37 degrees C. The rheology of the superfusion system was determined and the oxygen consumption of the superfused placental fragments indicated viability of the tissue preparation over a 5-hour time span. CRH IR in the eluate was measured by radioimmunoassay (RIA) using the 41 residue synthetic peptide human, rat CRH-41 (h, r CRH-41) as the standard, 125I labelled Tyr- h, r CRH as the tracer and rabbit anti-ovine CRH as the antibody. The sensitivity of the assay is 2 pM. Size exclusion chromatography on Sephadex G-50 of the placental column eluate displayed one major peak of CRH IR which co-eluted with that of h, r CRH. Placental fragment superfusate displayed potent CRH bioactivity as assessed by beta-endorphin secretion from ovine pituitary cells. Replacing the superfusing medium of the placental fragments with 45 mM KCl resulted in a prompt increase in the release of CRH IR. These results indicate that placental cells in vitro secrete a molecule of similar molecular weight, immunoreactivity and bioactivity to h, r CRH and that the rate of secretion may be regulated.

Animals↗
PubMed1988

Cigarette smoking, social class and nutrient intake: relevance to coronary heart disease.

The association of cigarette smoking habits and social class with nutrient intake was investigated in 162 men aged 45-54 using a 7-d weighed dietary record. Cigarette smokers had a significantly lower intake of fibre and polyunsaturated fatty acids and a lower P:S ratio than non-smokers. Fibre intake was lower in men in the manual compared to the non-manual group but smoking was a more powerful influence than social class. The differences in nutrient intake were accompanied by differences in the consumption of polyunsaturated margarines and cereal-containing foods. These results should be considered in the explanation of the increased incidence of coronary heart disease in smokers.

Anthropometry↗