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Biomedical subjects

C Chapman

Publications and source records attributed to C Chapman.

At least 199 records · Page 11Linked to original sources
PubMed1976

Thyroid-pituitary response to cardiopulmonary bypass.

The effects of open heart surgery on various parameters of thyroid-pituitary function were studied in 11 patients. The pattern of hormonal changes was variable. T4 concentration increased during anaesthesia and bypass, following which it returned to normal once haemodynamic stability had been regained. The pattern of change in T3 concentration did not follow consistently that of T4 and the proportional increase in concentration was not as great. There was a significant reduction in T3 concentration with the onset of haemodynamic stability. For individual patients there was no obvious correlation between changes in the concentrations of TSH, T3 and T4. The increases may be explained by release of T3 or T4 from extrathyroid tissue.

Adult↗
PubMed1975

Studies of lipid class and fatty acid profiles of rat mammary tumors induced by 7, 12-dimethylbenz(a)anthracene.

The lipid class and fatty acid composition profiles of mammary glands of female rats fed a nutritionally adequate diet are compared to those of tumors induced in the mammary glands by intravenous injection of dimethylbenz(a)anthracene of animals fed the same diet. Ca. 95% of the lipids of the mammary glands of the control group of animals consisted of triglycerides; glycolipids and phospholipids were present in only minor amounts. In contrast, the lipids of the mammary tumors contained much lower amounts of neutral lipids and higher concentrations of phospholipids. The glycolipid fraction was a minor component of both tissues but differed greatly in composition. The composition of the phospholipid and neutral lipid fractions, particulary the latter, of the mammary tumors also differed from that of the mammary glands of the control animals. The neutral lipids of the tumor tissues contained elevated levels of free fatty acids and cholesterol and much lower concentrations of triglyceride compared to the mammary gland lipids. Differences also were observed in the fatty acid composition of tumor and mammary gland lipid. The greatest differences occurred in the concentrations of polyunsaturated fatty acids which were generally much higher in the tumor lipids.

Animals↗
PubMed1974

Anti-litter procedures in an urban high-density area.

In urban high-density areas, litter has become an increasingly obvious and pervasive problem. In the present study, repeated measures of the amount of litter on randomly selected yards in an urban low-income housing project were used to evaluate the effectiveness of a series of anti-litter procedures directed at the children residing in the project. Paying children for volume of trash collected resulted in only a small decrease in the number of litter pieces present. Paying them for cleaning assigned yards markedly decreased the level of litter in all sampled yards. Thus, children can be employed to maintain a clean neighborhood in spite of the rapid accumulation of new litter in urban yards.

Journal Article↗
PubMed1970

Measurement of plasma digoxin concentration by radioimmunoassay.

A rapid, sensitive, and precise method for measuring the plasma digoxin concentration has been developed with the radioimmunoassay technique. Seventy patients receiving digoxin were shown to have plasma digoxin concentrations between 0.4 and 5 ng./ml. Preliminary studies show that though there is a positive correlation between total daily dose and the plasma digoxin concentration, the relationship is not close, and a relatively wide range of plasma digoxin concentrations appear to be consistent with effective digitalization.

Animals↗
PubMed1969

Adenosine phosphates and the control of glycolysis and gluconeogenesis in yeast.

1. Changes in dry weight, protein, RNA and DNA were measured in yeast during adaptation to glycolytic metabolism. 2. Only RNA increased significantly during the lag phase, but during the exponential phase all these cellular components increased in parallel. 3. The concentrations of ATP, ADP, AMP and glucose 6-phosphate were measured in respiring yeast and during the transition to glycolytic metabolism. 4. In respiring cells the concentration of AMP was at its highest and that of ATP was at its lowest; this relationship was reversed in glycolysing cells. 5. ADP concentration was similar in respiring and glycolysing cells, but glucose 6-phosphate concentration was much higher in the glycolysing cells. 6. A possible reason for mitochondrial repression is suggested. 7. It is concluded that adenosine phosphates do not control the direction of glycolytic flux in yeast and an alternative control of glycolysis and gluconeogenesis by enzyme activation and inactivation is suggested.

Adenine Nucleotides↗
PubMed1968

The kinetics of enzyme changes in yeast under conditions that cause the loss of mitochondria.

1. Aerobically grown yeast having a high activity of glyoxylate-cycle, citric acid-cycle and electron-transport enzymes was transferred to a medium containing 10% glucose. After a lag phase of 30min. the yeast grew exponentially with a mean generation time of 94min. 2. The enzymes malate dehydrogenase, isocitrate lyase, succinate-cytochrome c oxidoreductase and NADH-cytochrome c oxidoreductase lost 45%, 17%, 27% and 46% of their activity respectively during the lag phase. 3. When growth commenced pyruvate kinase, pyruvate decarboxylase, alcohol dehydrogenase, glutamate dehydrogenase (NADP(+)-linked) and NADPH-cytochrome c oxidoreductase increased in activity, whereas aconitase, isocitrate dehydrogenase (NAD(+)- and NADP(+)-linked), alpha-oxoglutarate dehydrogenase, fumarase, malate dehydrogenase, succinate-cytochrome c oxidoreductase, NADH-cytochrome c oxidoreductase, NADH oxidase, NADPH oxidase, cytochrome c oxidase, glutamate dehydrogenase (NAD(+)-linked), glutamate-oxaloacetate transaminase, isocitrate lyase and glucose 6-phosphate dehydrogenase decreased. 4. During the early stages of growth the loss of activity of aconitase, alpha-oxoglutarate dehydrogenase, fumarase and glucose 6-phosphate dehydrogenase could be accounted for by dilution by cell division. The lower rate of loss of activity of isocitrate dehydrogenase (NAD(+)- and NADP(+)-linked), glutamate dehydrogenase (NAD(+)-linked), glutamate-oxaloacetate transaminase, NADPH oxidase and cytochrome c oxidase implies their continued synthesis, whereas the higher rate of loss of activity of malate dehydrogenase, isocitrate lyase, succinate-cytochrome c oxidoreductase, NADH-cytochrome c oxidoreductase and NADH oxidase means that these enzymes were actively removed. 5. The mechanisms of selective removal of enzyme activity and the control of the residual metabolic pathways are discussed.

Alcohol Oxidoreductases↗
PubMedDate not supplied

A new syndrome with mental retardation, short stature and an Xq duplication.

We describe a new X-linked syndrome of marked short stature, severe intellectual handicap and an unusual facial appearance. High resolution prometaphase banding showed affected males to have an X chromosome tandem duplication; their karyotypes were designated 46,dup(X) (q13.1-q21.1)Y. In carrier females the abnormal X chromosome was late replicating. To verify the duplication, gene dosage studies were performed using an enzyme assay and DNA techniques. Prenatal diagnosis is available for carrier females using chromosome analysis of amniocytes or chorionic villi.

Child↗
PubMedDate not supplied

Comparison of the plasma concentrations and efficacy of mexiletine and of a slow-release preparation of mexiletine in patients admitted to a coronary care unit.

We determined if therapeutic plasma concentrations of mexiletine (0.75-2.0 microgram/ml) could be maintained in patients admitted to a coronary care unit by twice daily dosing of a new slow-release (S.R.) formulation of mexiletine. Twenty patients, 14 with acute myocardial infarction, entered the first study and received either 250 mg conventional mexiletine at 0.8, and 14 h or 360 mg S.R. mexiletine at 0 and 12 h each day for 7 days. Blood samples were taken daily for measurement of plasma mexiletine concentrations. A continuous 24 -h ECG recording was obtained in all patients between days 3 and 6. The mean plasma concentration was greater on all days in the group that received conventional mexiletine; these differences were most marked during the first 15 h on day 1. The mean trough values on days 2-7 were in the range 0.73-1.22 microgram/ml after mexiletine and 0.63-1.17 microgram/ml after S.R. mexiletine. The incidence of ventricular arrhythmias was the same in the two groups; side effects were less common in the group receiving S.R mexiletine. Since the plasma concentration increased slowly during day 1 with S.R. mexiletine, a second study was carried out in 19 similar patients who received 360 mg S.R. mexiletine, 720 mg S.R. mexiletine, or 360 mg S.R. mexiletine and 250 mg conventional mexiletine and 12 h later 360 mg S.R. mexiletine. The plasma concentration increased most rapidly after the third regime, reaching 0.97 +/- 0.09 microgram/ml at 3 hours. These results show that therapeutic plasma concentrations of mexiletine can be maintained by the 12-hourly administration of 360 mg S.R. mexiletine, but that an additional loading dose of 250 mg mexiletine increases the plasma concentration more rapidly.

Aged↗
PubMedDate not supplied

Urinary transferrin excretion in type 1 (insulin-dependent) diabetes mellitus.

Urinary excretion of transferrin and albumin was studied by radioimmunoassay in 47 adult patients with Type 1 diabetes and 28 control subjects. Median (range) urinary transferrin excretion rate was significantly elevated in the diabetic group 0.58 (0.02-2663.3) micrograms min-1 compared with the control group 0.04 (0.01-0.28) micrograms min-1, p less than 0.001. Urinary transferrin:creatinine ratios (x 10(2)) were different in diabetic 47 (0.6-958.0) micrograms mmol-1 and control groups 0.7 (0.06-2.3) micrograms mmol-1, p less than 0.001). There were correlations between urinary transferrin and albumin excretion rates in diabetic (r = 0.78, p less than 0.001) and control groups (r = 0.81, p less than 0.05). Forty (85%) diabetic patients had elevated transferrin excretion rates, 18 (38.3%) had elevated albumin excretion rates. All diabetic patients with elevated albumin excretion rates had elevated transferrin excretion rates. Twenty-one (77.8%) of the patients with normal albumin excretion rates had elevated transferrin excretion rates. Urinary excretion of N-acetyl-beta-D-glucosaminidase was greater in diabetic patients than control subjects (142 vs 58 mumol h-1 l-1, p less than 0.001). There were correlation between transferrin and N-acetyl-beta-D-glucosaminidase excretion (r = 0.67, p less than 0.01) and albumin and N-acetyl-beta-D-glucosaminidase excretion (r = 0.63, p less than 0.01) in the diabetic group. Elevated urinary transferrin excretion rate may be a marker for renal dysfunction in diabetes mellitus.

Acetylglucosaminidase↗
PubMedDate not supplied

The relationship between plasminogen activator inhibitor-1 and insulin resistance in newly diagnosed type 2 diabetes mellitus.

It is not clear whether elevated levels of the fibrinolytic inhibitor, plasminogen activator inhibitor-1 (PAl-1) in Type 2 diabetes mellitus are the result of obesity or coexistent atherosclerosis. Therefore the relationship between PAl-1 and insulin resistance, determined by the homeostasis model assessment (HOMA) was investigated in a group of 26 insulin-resistant, normotensive newly diagnosed Type 2 diabetic patients with a low probability of atherosclerosis. Compared with a normal control group, closely matched for body mass index (BMI), fibrinolytic activity was depressed in the diabetic patients due to elevated levels of the inhibitor PAl-1, 17.6 (11.1-28) vs 8.4 (4.9-14.1) IU ml-1, p < 0.001. PAl-1 was related to BMI, r = 0.59, p < 0.001 plasma insulin, r = 0.66, p < 0.001; insulin resistance, r = 0.54, p < 0.005 and urinary albumin excretion, r = 0.48, p < 0.01, but not HbA1c or fasting glucose. PAl-1 was not related to blood pressure or plasma triglyceride levels. This study suggests that at the time of diagnosis of Type 2 diabetes mellitus, elevated PAl-1 levels are already linked to other risk factors for vascular disease including hyperinsulinaemia, insulin resistance, and urinary albumin excretion, and this is not the result of obesity or coexistent atherosclerosis.

Blood Glucose↗