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Biomedical subjects

R Soma

Publications and source records attributed to R Soma.

14 recordsLinked to original sources
PubMed1992

Effect of DCA administration or endurance training on lactate metabolism in mice during and after exercise.

The purpose of this study was to investigate the effect of the activation of tissue oxidative capacity by dichloroacetate (DCA) administration or endurance training on oxidative removal of lactate, which is the major pathway of lactate metabolism, in mice during prolonged exercise and after supramaximal exercise. DCA administration significantly decreased the blood lactate concentration and activated the oxidative removal of lactate during prolonged exercise. DCA administration did not change lactate metabolism in mice after supramaximal exercise. Endurance training significantly decreased the blood lactate concentration during prolonged exercise and also activated the oxidative removal of lactate. Endurance training significantly increased the recovery of the blood lactate concentration after supramaximal exercise, while it did not activate the oxidative removal of lactate. These results suggest that the activation of the tissue oxidative capacity decreases the blood lactate concentration and also can activate the oxidative removal of lactate during prolonged exercise, while it does not activate the oxidative removal of lactate after supramaximal exercise.

Animals↗
PubMed1991

Effect of dichloroacetate on oxidative removal of lactate in mice after supramaximal exercise.

1. The effect of dichloroacetate (DCA), which activates substrate oxidation on oxidative removal of lactate in mice after supramaximal exercise was investigated. 2. DCA significantly decreased the blood lactate concentration and increased the oxidative removal of lactate during prolonged exercise. 3. No significant differences were found in the removal of the blood lactate concentration, in oxidative removal of lactate after supramaximal exercise. 4. It is concluded that DCA administration which activates lactate oxidation during exercise does not activate lactate oxidation in mice after supramaximal exercise.

Animals↗
PubMed1990

Evaluation of clonidine suppression and various provocation tests in the diagnosis of pheochromocytoma.

Recent investigations have shown that the widely used clonidine suppression test is sometimes fallible for the diagnosis of pheochromocytoma. A comparative assessment was made of the following suppression and provocation tests, the clonidine suppression test, and the glucagon, metoclopramide, and naloxone provocation tests. The assessment was performed in 6 patients with pheochromocytoma and in 19 patients without pheochromocytoma who were initially suspected of harboring a tumor. BP response did not predict the presence of pheochromocytoma in any test. Plasma norepinephrine (NE) concentrations determined at 120 and 180 min after oral 150 micrograms of clonidine gave false negative results in 2 of the 5 patients with pheochromocytoma tested. Both plasma NE and epinephrine (E) concentrations were measured before and sequentially after each provocative agent. Neither NE nor E responded to 1 mg of glucagon iv in 2 of the 4 patients with pheochromocytoma tested. Determination of the peak level, peak increment, and % peak increment of NE and E following 10 mg of naloxone iv did not distinguish the two groups. The % peak increments of both NE and E in all 4 patients with pheochromocytoma given 5 mg of metoclopramide iv exceeded the mean + 3 SD values of the patients without pheochromocytoma (25 + 28% for NE, and 25 + 42% for E). These results suggested that, when performed with judicious patient selection (ambiguous plasma or urinary catecholamine levels), the measurement of plasma catecholamines in response to metoclopramide can be a useful adjunctive tool in the diagnosis of pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMed1990

Pituitary peptides other than ACTH may not be aldosterone secretagogue in primary aldosteronism.

In order to elucidate whether pituitary peptides other than ACTH which are derived from the proopiomelanocortin (POMC) are involved for aldosterone secretion in primary aldosteronism, we administered ovine corticotropin releasing factor (CRF), beta-endorphin and naloxone to seven patients with aldosterone producing adenoma. One hundred micrograms of CRF produced an augmented aldosterone response in patients with aldosteronism, while 500 micrograms of beta-endorphin infusion failed to cause any significant changes in neither normal subjects nor patients. An opioid antagonist, naloxone (10 mg, iv) produced no noticeable change in plasma aldosterone in normal subjects, while it caused a slight increase in patients with primary aldosteronism. Plasma cortisol increased to a similar degree in response to CRF and naloxone in normal subjects and patients. In three patients with isolated ACTH deficiency, neither aldosterone nor cortisol responded to these stimuli. The present results indicate that POMC-derived pituitary peptides other than ACTH are unlikely to participate in the aldosterone secretion in normal subjects or in patients with primary aldosteronism.

Adenoma↗
PubMed1990

Mineralocorticoid and renal receptor binding activity of 21-deoxyaldosterone.

Since several aldosterone metabolites are known to be active, we have assessed the mineralocorticoid biological and renal receptor binding activities of the aldosterone metabolites, 21-deoxyaldosterone (21-deoxy-Aldo), 21-deoxytetrahydroaldosterone (21-deoxy-THAldo), and 3 alpha, 5 beta-tetrahydroaldosterone (THAldo). We synthesized these steroids by bioreduction of aldosterone with intestinal bacteria. Mineralocorticoid agonist activity of 21-deoxy-Aldo, 21-deoxy-THAldo and THAldo, determined by bioassay using adrenalectomized rats, was 1-5%, less than 0.01%, and 0.1-0.5% that of aldosterone, respectively. 21-Deoxy-Aldo showed no antagonist activity. The relative affinity in competing with [3H]aldosterone for binding to mineralocorticoid receptors in adrenalectomized rat kidney cytosols was 94%, less than 0.01%, and less than 0.01% that of aldosterone. The relative binding affinity for rat renal glucocorticoid receptors was 23%, less than 0.01%, and less than 0.01% that of dexamethasone, and for corticosteroid-binding globulin 17%, less than 0.01%, and less than 0.01% that of cortisol. These results show that the naturally occurring steroid, 21-deoxy-Aldo, possesses mineralocorticoid agonist activity which is equivalent to that of 11-deoxycorticosterone, and has substantial affinity for rat renal mineralocorticoid and glucocorticoid receptors. The results also implicate the pathophysiological role of 21-deoxy-Aldo as a potential mineralocorticoid in 21-hydroxylase deficiency, where urinary excretion of this steroid is invariably elevated.

Adrenalectomy↗
PubMed1990

Angiotensin II generation in mesenteric arteries in rats: effects of nephrectomy, deoxycorticosterone and dexamethasone.

Angiotensin II (ANG II) generation in the mesenteric arteries was studied in four groups of rats: deoxycorticosterone (DOCA)/salt treated, glucocorticoid treated, nephrectomized and control rats. Basal plasma renin activity (PRA) was undetectable in the nephrectomized group and suppressed in the DOCA/salt treated rats, but was increased in the rats treated with glucocorticoid. The Basal plasma ANG II concentration changed comparably with PRA in all four groups of rats. In the control rats, ANG II was released from the mesenteric arteries at a rate of 43.0 +/- 12.0 pg/h, and it was not decreased by nephrectomy. In DOCA/salt rats and glucocorticoid rats, ANG II release significantly decreased to 12.8 +/- 7.1 and 6.9 +/- 1.5 pg/h, respectively. Captopril treatment significantly reduced ANG II release from the mesenteric arteries in both controls and nephrectomized rats, but did not influence ANG II output in DOCA/salt rats or in glucocorticoid treated rats. In nephrectomized rats, captopril lowered blood pressure in association with a significant reduction in the mesenteric ANG II formation. These results indicate that the renal and vascular renin-angiotensin system (RAS) may be independently regulated, and in nephrectomized animals the vascular RAS contributes in part to the maintenance of blood pressure. The present results also suggest that volume expansion per se and/or pharmacological intervention by DOCA and glucocorticoid could modulate vascular ANG II generation.

Analysis of Variance↗
PubMed1989

Possible association of aldosterone producing adenoma and non-functioning adrenal tumor.

A 37-year-old woman presented with hyperaldosteronism, suppressed renin levels, and a left adrenal mass on CT scanning. Selective adrenal venous sampling indicated a marked rise of the aldosterone level in the right adrenal vein, while the level in the left vein was low. On laparotomy, an aldosterone producing adenoma (APA) of 12x10x5 mm in size was found in the right adrenal gland and was resected, while the left mass was left in situ. The post-operative course showed normalization of both the clinical and biochemical features of primary aldosteronism, with no sign of recurrence or of enlargement of the remaining adrenal mass in 2.5 years of follow up, suggesting the possible coexistence of a "non-functioning" tumor. This case demonstrates the importance of adrenal venous sampling for the localization of APA particularly since the presence of the APA may be masked by a visualized but unrelated adrenal mass.

18-Hydroxycorticosterone↗
PubMed1987

Glycyrrhizic acid and its hydrolysate as mineralocorticoid agonist.

Mineralocorticoid activity of glycyrrhetinic acid (GR) was studied in vivo (electrical potential difference in rat rectum) and in vitro (brush border Mg2+-HCO3- ATPase in rat small intestine, kidney cytosol binding of GR with and without RU-28362, anti-glucocorticoid compound) in order to clarify the mechanism of mineralocorticoid-like activity of GR. Scatchard analysis of [3H]aldosterone showed that Kd of higher affinity site (type I) 6.0 X 10(-9) M, Bmax 1.0 X 10(-14) mol/mg protein, and Kd of lower affinity site (type II) 1.6 X 10(-7) M, Bmax 7.5 X 10(-14) mol/mg protein. GR competed for [3H]aldosterone binding sites in kidney cytosol at the concentration of 10(4) times as that of unlabeled aldosterone. RU-28362 displaced aldosterone binding curve, whereas GR binding kinetic was not affected by this compound. Adrenalectomy caused a significant fall in brush border Mg2+-HCO3- ATPase activity (75% reduction compared with the initial level) which was not restored by GR administration. Electrical potential differences in the adrenalecomized rats were significantly lower than those in the control rats, which did not increase after GR administration.

Adrenalectomy↗
PubMed1977

[Comparison of limited weight values and the sensitivity of analytical methods used for the detection of toxic atmospheric agents in working places].

This research has been carried out in order to estimate minimum sampling periods for the substances detailed in the VLP table given by the Italian Occupational Medicine Service and the Industrial Hygiene Group. These data take the following points into consideration: 1) sensitivity of the analytical method; 2) value and condition of sample at fulfilment of sampling periods; 3) sampling speed; 4) VLP, with special reference to ceiling value for very short exposure. As to dust the minimum period required is about 1 minute for numeric sampling, and 35 minutes for gravimetric sampling. 85% from the above-mentioned substances can be sampled at minimum periods which range from 1 to 5 minutes.

Air Pollutants↗