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Biomedical subjects

M Jobin

Publications and source records attributed to M Jobin.

35 records · Page 2Linked to original sources
PubMed1979

Plasma catecholamines and cardiovascular responses to cold and mental activity.

Plasma epinephrine (E) and norepinephrine (NE) as well as blood pressure and heart rate variations were measured in 12 male subjects before, during, and after a cold hand test (5 degrees C for 2 min), a mental arithmetic test, and a combination of both these tests. Although the cold and mental tests had comparable effects on blood pressure, the heart rate response was greater than the mental test. The mental test produced a greater increase of E than the cold test, but the effect of the cold test was greater on NE than on E. Changes in heart rate were significantly correlated with E variations but not with NE, whereas changes in blood pressure were correlated with NE. Resting NE was correlated with resting blood pressure and resting E with resting heart rate. Finally the levels of basal E were positively correlated with the increase in E during the test. Cardiovascular changes were shown to be differently modified by a mental and a cold test. Evidence was given indicating that these changes are related to differences in E and NE responses in the presence of these tests.

Adrenal Medulla↗
PubMed1977

Metabolic and cardiovascular responses to norepinephrine in trained and nontrained human subjects.

Forty young male adults, aged 18-30 yr, with maximal oxygen intake (VO2 max) varying between 35 and 76 ml-kg-1-min-1 were studied. The fasting subjects were perfused for 15 min with saline and thereafter for 30 min with norepinephrine (0.1 mug/kg per min). Blood variables were determined at the end of slaine perfusion, at 15 and 30 min during norepinephrine perfusion and 15 min after the end of NE perfusion. Trained subjects are characterized by lower basal plasma glucose and insulin concentration. NE perfusion produced a larger increase in plasma glucose in the trained subjects. Levels of insulin in the postperfusion period were smaller in the trained group. Serum free fatty acids (FFA) and glycerol increased less in the trained subjects during NE perfusion and this difference persisted in the post-perfusion period. During NE perfusion, blood lactate increased only in the nontrained subjects. Initial heart rate and blood pressure were lower in trained subjects but, during NE perfusion, elevated levels of blood pressure and decreased levels of heart rate were comparable in both groups. Because of similarities in responses to exercise and to NE in trained subjects, the results of the present study suggest a possible role for NE in exercise training.

Adolescent↗
PubMed1976

Effect of pharmacological blockade of ACTH and TSH secretion on the acute stimulation of prolactin release by exposure to cold and ether stress.

Acute exposure of male rats to cold (5C)leads to a rapid increase of plasma levels of thyrotropin (TSH), prolactin (PRL), corticosterone, and L-thyroxine. Exposure to ether is similarly followed by a rapid increase of plasma levels of PRL and corticosterone, while TSH release is inhibited. Acute treatment with dexamethasone (500 mug) inhibits almost completely the PRL response to both exposure to cold and ether stress, while the plasma TSH response to cold is only delayed and the decrease of plasma TSH observed after ether stress is unchanged. Basal plasma levels of both TSH and PRL are lowered after treatment with the steroid. Thyroxine treatment lowers the plasma TSH concentration to undetectable levels without affecting the plasma PRL response to cold or ether exposure. The present data suggest that the rise of plasma PRL observed after cold exposure is not related to TRH and may suggest that common mechanisms control ACTH and PRL secretion during acute stress exposure.

Adrenocorticotropic Hormone↗
PubMed1975

Effect of exposure to cold on hypothalamic TRH activity and plasma levels of TSH and prolactin in the rat.

No significant change in hypothalamic TRH content was found in rats during acute (5-240 min) exposure to cold (5 degrees C), in spite of rapid and sustained elevations in plasma TSH and thyroxine. Plasma PRL rose markedly in the first 15 min, but returned to normal thereafter. Chronic exposure to cold (32 days) was characterized by elevated plasma and pituitary levels of both TSH and PRL in the presence of an unaltered hypothalamic TRH content. If increased TRH release from the hypothalamus occurs during exposure to cold, as suggested by the pituitary-thyroid stimulation, either it is compensated for by an equal rise in synthesis, or the extra amount released is negligible in comparison with the hypothalamic content of TRH. The acute PRL response to exposure to cold may be related to an acute TRH release but could also result from the accompanying stress response acting by a mechanism independent of TRH.

Animals↗
PubMed1975

Interactions between the pituitary, thyroid and adrenal cortex during acute exposure to cold or to electric shocks in the rat.

In intact rats acclimated to 25 +/- 1 degrees C, acute exposure to cold resulted in simultaneous stimulation of TSH and ACTH secretion. The plasma TSH response to cold was identical at temperatures varying from +14 to -10 degrees C, whereas the adrenocortical response increased proportionally to the severity of cold. Acute stimulation of ACTH secretion by exposure to a stressful situation (electrical shocks) did not alter the TSH response to cold. Conversely, acute blockade of the pituitary-adrenocortical response by dexamethasone treatment did not enhance the TSH response to cold. Chronic stimulation of ACTH secretion resulting from adrenalectomy did not interfere with the TSH response during subsequent exposure to cold. However, a reduced adrenocortical response to cold was observed during chronic hypersecretion of TSH resulting from previous thyroidectomy. These findings do not support the hypothesis of an inverse relationship between TSH and ACTH secretions during acute cold exposure, but rather suggest that these secretions are independent.

Adrenal Cortex↗
PubMedDate not supplied

Imaging of DNA by scanning force microscopy.

The scanning probe microscopies applied to the sequencing of DNA is a challenging goal attempted by several groups. But one limitant parameter has been the sample preparation of DNA molecules. Here we report how to hold DNA molecules fixed on mica substrate and we show the three-dimensional configuration of double-stranded DNA obtained with our scanning force microscope. We can image DNA under negative supercoiling, a feature of general importance controlling the activities of DNA. We compared the electron micrographs of a carbon replica of the same DNA specimen with scanning force images which demonstrates well the feasibility and accuracy of our scanning probe measurements.

DNA↗