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Biomedical subjects

J Dupont

Publications and source records attributed to J Dupont.

At least 145 records · Page 8Linked to original sources
PubMed1978

Thyroid function and blood pressure in two new strains of spontaneously hypertensive and normotensive rats.

1. The influence of thryoid function on the development of hypertension was studied in strains of spontaneously hypertensive (SH) and normotensive rats. 2. Surgical thyroidectomy decreased systolic blood pressure more markedly in SH rats than in normotensive rats. The effects of oral administration of 5 and 100 micrograms of thyroxine 24 h-1 100 g-1 were studied in the thyroidectomized animals. In the two strains the blood pressure returned to control levels only after administration of the larger dose. 3. The evolution of body weight, total plasma tri-iodothyronine (T3) and tetraiodothyronine (T4) concentrations were followed as a function of age in SH rats and normotensive rats from 5 to 21 weeks. At each age, SH rats showed significantly larger body weight and decreased T4 concentrations. Plasma T3 in SH rats was lower than in normotensive rats until 15 weeks of age, after which the difference was not significant. At 11 weeks, plasms free T3 and T4 concentrations were slightly lower in SH rats than in normotensive rats. 4. The more marked hypotensive effects of surgical thyroidectomy in SH rats cannot be related to increased thyroid function.

Aging↗
PubMed1976

Fatty acid and prostaglandin composition of left ventricular myocardium from dexamethasone-treated dogs with severe low output syndrome (LOS).

The effects of dexamethasone (DEX) administration on the left ventricular myocardial content of fatty acids and prostaglandins E1, E2 and F2alpha were studied. Following a complete right and left cardiac catheterization, either DEX (8 mg/kg) or an equivalent volume of its vehicle was given intravenously 30 minutes prior to low output syndrome (LOS induction, and supplemental doses of DEX (4 mg/kg) or vehicle administered at 15 and 75 minutes post-LOS induction. Low output syndrome was induced by intravenous administration of a myocardial depressor protein (MDP) which has been isolated from the venom of the Western diamondback rattlesnake, Crotalus atrox. Neither DEX nor its vehicle had a significant effect during the entire experiment, that is, in the normal or low cardiac output state in most of the hemodynamic parameters investigated. The three hour mortality rate for the DEX-treated animals was 22% (n=10) while that of the control group was 41% (n=26) indicating that the beneficial effects of this corticosteroid are not really apparent from hemodynamic evaluation alone. Since DEX only had a significant post-LOS induction effect in maintaining a lower left ventricular end-diastolic and pulmonary capillary wedge pressures, a higher arterio-venous oxygen saturation difference, and a more efficient contractile state of myocardial fibers (Vmax), an indirect correlation to coronary arterial blood flow at the subcellular level was sought. To this effect, prostaglandins and specific lipid classes of left ventricular myocardium (LVM) from control and LOS animals receiving either vehicle or DEX were analyzed. Low output state induction alone raised myocardial PG levels above those of sham-catheterized animals; on the other hand, dexamethasone induced a significant decrease in the three prostaglandins studied when administered to control (no LOS) animals. In the presence of LOS, however, dexamethasone overrode in part the increase in PGE1 and PGE2 brought about by LOS while in the case of PGF2alpha the LOS effect was totally prevented and its concentration was not significantly higher than in control animals receiving dexamathasone. LOS induction led to an increase in myristic and arachidonic acids and a decrease in palmitic and linolenic acids. Dexamethasone administration to control animals increased the concentration of stearic acid above all the other groups but decreased the concentration of linolenic acid when compared to DEX-treated animals with LOS or sham-catheterized animals. There were no significant differences in the total myocardial lipid among the four groups of animals studied. It is suggested that the potentially beneficial effects of corticosteroid administration to animals with low output syndrome are related to their effects on fatty acid and prostaglandin content of myocardium.

Animals↗
PubMed1976

Radioimmunoassay of prostaglandins E1, E2, and F2alpha in unextracted plasma, serum and myocardium.

A radioimmunoassay procedure for the determination of PGE1, PGE2, and PGF2alpha is presented. The procedure involves the pre-precipitation of each prostaglandin specific antiserum with the precipitating antisera (ARGG), and the use of these antisera mixtures in assaying for PGE1, PGE2, and PGF2alpha. Applicability of the methods to unextracted plasma, serum and myocardial homogenate has been demonstrated through tests of specificity, recovery, reproducability and parallelism. A mathematical correction for cross-reactivity between PGE1 and PGE2, and their opposing antisera is given. To demonstrate the utility of the methodology in differentiation of experimental variables, prostaglandin concentrations in unincubated serum, incubated serum, and the rate of prostaglandin production in serum of dogs are given.

Animals↗
PubMed1976

Kinetic analysis of cholesterol turnover in rat tissues.

A number of studies have been conducted on serum cholesterol disappearance following a single injection of tracer. They have shown 2 or 3 component curves depending on the length of time of observation. They have been interpreted to indicate pools of cholesterol in fast or slow equilibrium with serum and generally depicted as representing groups of tissues. A cholesterol kinetic study was conducted using rats so that each tissue could be analyzed for appearance-disappearance of cholesterol from 30 minutes to 75 days. Serum and liver appeared to die-away for 30 days in a 2 component configuration, then exhibited a repetition of the same curve in the next 30 days. Skeletal muscle and kidney had a slow buildup for 2 weeks, then a plateau for 2 weeks then a 2 component die-away. Adipose showed a high plateau from 30 minutes to 30 days then a 2 component die-away, with specific activity higher than serum at all times. The data are interpreted to indicate that adipose tissue sequestered part of the tracer dose and all tissues reached equilibrium at about 30 days. After that time all tissues had a statistically significant 2 component die-away curve. The mathematical models tested suggest that in the steady state, cholesterol enters and exits the slow pool of serum, kidney, muscle and adipose and in liver enters both pools. Interpretation of the complete die-away is that the tracer dose first equilibrates with membrane free cholesterol, then with the intracellular cholesterol, and finally dies-away at the rate of release by the slow intercellular pool.

Adipose Tissue↗
PubMed1976

Plasma renin activity as a function of age in two new strains of spontaneously hypertensive and normotensive rats.

1. Strains of spontaneously hypertensive and normotensive rats were selected by repeated inbreeding. 2. Brief ether anesthesia was shown to produce a two- to three-fold increase in plasma renin activity in both strains. 3. Plasma renin activity was significantly higher in young spontaneously hypertensive than in normotensive rats of the same age (5-7 weeks). After the ninth week plasma renin activity decreased and, at week 45, became significantly lower in hypertensive than in normotensive rats. 4. When hypertension was established a significant inverse relationship was found between plasma renin activity and systolic blood pressure in spontaneously hypertensive and in normotensive rats. 5. It seems unlikely that the renin-angiotensin system plays a major role in the maintenance of the established spontaneous hypertension in this strain. However, renin hypersecretion may be important in the early pre-hypertensive stage of genetic hypertension in rats.

Aging↗
PubMed1975

Electron transport in the membrane of lutoids from the latex of Hevea brasiliensis.

1. An antimycin-insensitive NADH-cytochrome c oxidoreductase (E.C. 1.6.99.3) activity can be demonstrated in the membrane of lutoids isolated from the latex of Hevea brasiliensis. This electron transport system can also use ferricyanide as an electron acceptor, but is unable to oxidize NADPH. 2. Two beta-type cytochromes are present in the membranes. Cytochrome beta563 is partially reduced by NADH and ascorbate, but is not reducible by NADPH. It shows a double peak at 555 and 561 nm at 77 degrees K. A second cytochrome, cytochrome beta561, seems to be reducible by hydrosulfite only. 3. In the reduced state, these cytochromes do not combine with CO. The occurrence of cytochrome P-450 could not be demonstrated. 4. The role of the NADH oxidation system is considered in relation to the biosynthesis of polyisoprene compounds in the latex.

Antimycin A↗
PubMed1975

[Circadian rhythms in the urinary excretion of salicylate (chronopharmacokinetics) in healthy adults].

Six healthy adults volunteered to ingest a 1 g solution/24 h of sodium salicylate in a study consisting of 4 standardized tests. The difference between tests was the timing of drug absorption: 07(00), 11(00), 19(00) and 23(00) respectively. The 4 separate tests were performed at least 1 week apart. Subjects; synchronization : diurnal routine activity with light-on at 07(00) and light-off at 23(00) Urine was collected at four-hour intervals, for 48 hours following drug ingestion. By the mean cosinor summary of least squares fits of a 24-hour cosine curve, or by other testing, a within-day difference is established for several chronopharmacokinetic parameters characterizing urinary salicylate excretion. By criteria including the height of the peak excretion, the span necessary to reach the peak, etc., it is shown that, as compared to drug administration at other times, salicylate is excreted faster into the urine, reaches higher values sooner and falls off faster when the drug is ingested between 19(00) and 23(00).

Adult↗
PubMed1975

Identification and quantitation of cholanoic acids in hepatic and extra-hepatic tissues of rat.

Tissues of rats were examined for the presence of cholanoic acids. Quantitation of extraction, deconjugation, and isolation were verified by use of radioactive standards. Identification was made by thin layer and gas liquid chromatographic comparison to standards and mass spectrometry. All tissues examined were found to contain several conjugated cholanoic acids. Liver contained primarily cholic acid and peripheral tissues primarily dihydroxy compounds, mainly hyodeoxycholic acid.

Adipose Tissue↗
PubMed1975

Linoleate enrichment of diet and prostaglandin metabolism in rats.

Evidence that biosynthesis of prostaglandins (PG) in tissues of animals deficient in essential fatty acids is dependent on the availability of their precursors has been demonstrated. The purpose of this study was to determine the following: (1) effects of dietary linoleate enrichment on PG biosynthesis in rats; (2) effects of exogenous PGE2 and dietary linoleate on plasma free fatty acids and serum cholesterol in fed and fasted rats. Rats were fed three different concentrations of dietary linoleate as beef tallow, hydrogenated vegetable fat, or corn oil. The concentrations of PGE1 and PGF2a measured by radioimmunoassay were higher in rats fed the fed the beef tallow diet independent of energy status. A decrease in the concentration of PG between fasted and fed rats receiving hydrogenated vegetable fat is discussed in respect to the possible influence of trans isomers of unsaturated fatty acids on the biosynthesis of PG. There were significant effects of fasting on serum cholesterol concentration regardless of diet and significant interactions among effects of PGE2, fasting, and diet, suggesting regulatory effects of PGE2 on serum cholesterol concentration. The increase in plasma free fatty acids associated with fasting was prevented by PGE2 for all diets, but had the most marked effect on rats fed hydrogenated vegetable fat.

Animal Nutritional Physiological Phenomena↗
PubMed1975

A tool for individualized management of fat-controlled diets.

Presently recommended fat-controlled dietary plans are rigid in pattern and require omission of some foods and substitution of others with little regard for the individual's food preferences. A tool for individualized management of fat-controlled diets has been developed. Commonly eaten foods have been grouped according to their fat content. After the patient's habitual dietary intake is analyzed by computer or food composition table, changes in the diet are recommended, using the food groups, so that the guidelines of a fat-controlled diet may be met with a minimum deviation from individual food preferences.

Adult↗
PubMed1975

[Circadian variations of the effects of ethanol and of blood ethanol values in the healthy adult man. Chronopharmacological study].

Six healthy young men (22 to 26 years) who had fasted for 12 hours volunteered for this study (subject synchronization: diurnal activity from 07(00) to midnight and nocturnal rest). A set dose of ethanol (0.67 g/kg body weight) was ingested at the fixed (and random) hours of 07(00), 11(00), 19(00) and 23(00), with a week between tests. A set of physiological variables: psychological tests (selft-rating of mood, of physical vigor and of ebriety, tempo, random number addition test); physical variables (heart rate, systolic and diastolic blood pressure, peak expiratory flow, oral temperature and grip strength); blood variables (plasma ethanol, cortisol, lactic acid, pyruvic acid, glucose and erythrocyte K+) and urinary variables (volume, epinephrine, nor-epinephrine and 5-HIAA) were documented at least at 4 hourly intervals and set times. The cosinor method was used for chronobiological statistical analyses. The parameters characterizing the ethanol pharmacokinetics (chronopharmacokinetics) demonstrated a circadian rhythm (p less than 0.05): e. g. the peak height of ethanolemia is greater when ethanol is ingested at 07(00) than at other times. Also a circadian rhythm in biosystems susceptibility can be demonstrated (p less than 0.05) (chronesthesy) with a peak time not necessarily corresponding either to that of ethanolemia or to that of other variables. The overall circadian changes in ethanol effects (chronergy) can be viewed as a combination of both ethanol chronesthesy and chronokinetics.

Adult↗