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Biomedical subjects

R Bloch

Publications and source records attributed to R Bloch.

At least 55 records · Page 3Linked to original sources
PubMed1984

Effects of theophylline and isoproterenol on the activity on the isolated guinea pig ureter.

To determine the role of the autonomic nervous system and of cyclic AMP in the control of ureteral peristalsis, isolated guinea pig ureters were placed in a 20-ml organ bath containing modified Krebs solution. Theophylline induced significant dose-dependent reduction in frequency and amplitude of contractions of the ureter hypertonified with barium chloride. No change in frequency or amplitude of contractions was observed with isoproterenol. Besides, our data explain why beta-agonist drugs are of very little value in the treatment of renal colic due to spasms of the pelviureteral tract.

Animals↗
PubMed1983

The effects of rapid saline infusion on sodium excretion, renal function, and blood pressure at different sodium intakes in man.

To examine the effects of increasing dietary sodium intake on natriuresis, filtration rate, and renal blood flow following rapid volume expansion, we infused 2-liter normal saline over 2 hr into normal men in balance at 10, 300, 600, and 800 mEq/day sodium intake. Natriuresis and kaliuresis were related to prior sodium intake. Fractional excretion of sodium (6%-7%) was maximal at the 600 mEq/day sodium intake and increased no further at the 800 mEq/day sodium intake. Although blood pressure increased with rapid saline infusion, natriuresis and blood pressure were not associated. Creatinine clearance decreased or remained constant, while PAH clearance decreased during saline infusion at each level. The data suggest that although natriuresis following rapid saline infusion is dependent upon prior sodium intake, under given circumstances it may be independent of glomerular filtration rate, renal blood flow, or blood pressure.

Adolescent↗
PubMed1982

[Morphine antagonizes the central hypotensive effect of clonidine in the anesthetized cat].

A dose of 1 microgram/kg of clonidine injected intracerebroventricularly (I.C.V.) in the normotensive anaesthetized Cat elicits a significant and long lasting drop in the mean arterial blood pressure (23 +/- 5 mmHg) and the heart rate (34 +/- 5 beats/min.). A pretreatment with morphine (100 micrograms/kg, I.C.V.) completely prevents the central hypotensive effect of clonidine, whereas the bradycardia is only weakly influenced. Administered after clonidine, morphine reverses the hypotensive effect of clonidine whereas morphine does not affect its bradycardic action. These data demonstrate that morphine antagonizes the central hypotensive effect of clonidine.

Anesthesia, General↗
PubMed1982

Evidence for a neuromodulatory role of GABA at the first synapse of the baroreceptor reflex pathway. Effects of GABA derivatives injected into the NTS.

Microinjections of GABA and of the specific agonist of GABA receptors, muscimol, in the intermediate nucleus tractus solitarii (NTS) of pentobarbitone anaesthetized cats produced hypertension and tachycardia. The GABA receptor antagonist, bicuculline, had opposite effects and prevented those of muscimol. Therefore, a GABAergic system appears to modulate the cardiovascular regulation within the NTS. d,l-Baclofen also increased blood pressure and heart rate when injected into the same region, but this effect was not antagonized by bicuculline. The mechanism of this action of baclofen is discussed.

Animals↗
PubMed1982

The blood pressure-raising effects of high dietary sodium intake: racial differences and the role of potassium.

Fourteen normotensive men (7 black, 7 white) were studied following equilibration during dietary sodium intake of 10, 300, 600, 800, 1200, and 1500 mEq sodium per day. Significant (p less than 0.05) increases in mean arterial blood pressure were seen after sodium intake of 800 mEq/d. Blood pressure increased at lower levels of sodium intake (800 mEq/d) and to a greater magnitude (21 mm Hg) in blacks than in whites (1200 mEq/d; 13 mm Hg). Sodium loading was associated with marked suppression of plasma renin activity, aldosterone and norepinephrine, and increases in cardiac index. At higher levels of sodium intake urinary potassium loss was seen. A subsequent experiment replacing urinary potassium losses as they occurred in six subjects demonstrated attenuation of the blood pressure increases seen in response to dietary sodium loading. These studies demonstrate a potential role for sodium and potassium in blood pressure regulation in normotensive man, and suggest that heterogeneity of response may be involved in the development of hypertension in individuals predisposed to avid sodium conservation.

Adolescent↗
PubMed1981

The central hypotensive action of baclofen in the anaesthetized cat.

In the pentobarbital-anaesthetized cat, the intracerebroventricular administration of 20 microgram/kg d,1-baclofen led to marked hypotension and bradycardia, whereas the same dose of d-baclofen (i.c.v.) had no cardiovascular effect. When the drug was prevented from reaching the brain stem structures by collecting perfusate through a catheter lodged in the Aqueduct of Sylvius, the efficacy of d,1-baclofen was increased. Bicuculline did not antagonize the central cardiovascular effects of d,1-baclofen at doses which inhibit the cardiovascular effects of GABA agonists. However, both glutamic acid and kainic acid prevented and reversed the central hypotension and bradycardia produced by d,1-baclofen. These effects of baclofen may therefore be mediated by a selective inhibition of the release of the excitatory neurotransmitter, glutamate, within forebrain structures involved in central cardiovascular regulation.

Anesthesia↗
PubMed1981

The nucleus reticularis lateralis: a region highly sensitive to clonidine.

Slow bilateral microinjections of a low dose of clonidine (75 ng/kg) in the cat's nucleus reticularis lateralis (NRL) lead to significant hypotension and bradycardia. This finding confirms the existence of a ventromedullary highly sensitive site of action of clonidine. It is suggested that clonidine inhibits some vasopressive and cardioacceleratory structures within the NRL region.

Animals↗
PubMed1981

Cephalosporin-aminoglycoside synergistic nephrotoxicity: fact or fiction?

A review of synergistic nephrotoxicity associated with the concomitant administration of aminoglycoside and cephalosporin antibiotics is presented. A combination of these antibiotics is frequently administered in clinical practice as initial therapy in the treatment of gram-negative bacillary infection. The nephrotoxicity associated with cephalosporin/aminoglycoside administration in humans has been characterized as an acute tubular necrosis. Attempts to investigate this type of toxicity in animals using the rat as the model have revealed that the rat kidney is not affected by the aminoglycoside/cephalosporin combination in the same manner as the human kidney. The results from studies using the rat were not predictive of the nephrotoxicity encountered in humans, and cephalosporins actually appear to protect the rat from aminoglycoside-induced renal damage. The mechanism of the protective effect in rats and the toxic effects in man remain unknown. A species differentiation clearly exists between man and rats with respect to the nephrotoxic effects of aminoglycoside/cephalosporin combinations. The weight of present evidence indicates that, in man, an aminoglycoside/cephalosporin combination is synergistically nephrotoxic.

Aminoglycosides↗
PubMed1981

The ventromedullary hypotensive effect of muscimol in the anaesthetized cat.

Muscimol, a rigid analogue of GABA, was injected into the CNS of urethane-anaesthetized, normotensive cats. Bilateral microinjections of a small dose of muscimol (100 ng/kg, 0.5 microliter on each side) in the nucleus reticularis lateralis (NRL) induced hypotension. The marked fall in blood pressure obtained by injecting 1 microgram/kg of muscimol unilaterally into the NRL is completely reversed by subsequent local administration of bicuculline (5 microgram/kg, 0.5 microliter), a specific GABA antagonist. These data confirm that a GABAergic inhibitory system modulates the pressor tonic structures localized in the region of the NRL and that the anteroventral part of the medulla oblongata includes a trigger zone for the hypotensive action of muscimol.

Anesthesia↗
PubMed1981

[Intramural diverticulosis of the esophagus (author's transl)].

The first case report of a patient with intramural diverticulosis was given in 1960 by Mendl et al. Since then at least 32 cases have been described. In this paper another case report is given, whose clinical symptomatology differs from most other cases described. The etiology and the pathogenetic significance of candidiasis in this disorder still remains unclear. Differential diagnosis and etiology are discussed.

Diagnosis, Differential↗
PubMed1981

[Effect of propranolol on diuretic activity of furosemide hypertensive patients (author's transl)].

The effect of propranolol on water and sodium depletion provoked by frusemide was studied. Nine hypertensive patients were treated at 2-day intervals with a single dose of 40 mg of frusemide associated with a placebo or propranolol (320 mg given in 8 doses over a period of 24 hours). The association frusemide-propranolol is more hypotensive than frusemide alone. Propranolol reduced the rise in plasma renin activity and aldosteronuria provoked by the diuretic; total sodium output/24 h remained stable but sodium elimination was increased in the later samples. This prolongation of the natriuretic action is correlated with the inhibition of hyperaldosteronuria. Propranolol depresses urinary osmolality for a longer period than frusemide alone and water elimination tends to be higher. This action of the beta-blocker on urine concentration is independent of its effects on aldosteronuria but is correlated with the inhibition of the rise in plasma renin activity.

Aldosterone↗
PubMed1981

[The role of acid in ulcer pain (author's transl)].

In 33 patients (duodenal ulcer 11, gastric ulcer 10, nonulcerous bulbar lesions 7, anastomotic ulcer 4, antral erosions 1), approximately 4 ml HCL 0,1 N were instilled under endoscopic view directly onto the lesion, with the purpose of eliciting patients-specific pain. Five (5) patients were test-positive; their pain was reproduced (duodenal ulcer 1, gastric ulcer 2, other bulbar lesions 2), the rest was negative. Twenty-three of the 33 patients were studied during a period of spontaneous pain, 4 exhibiting a positive test; 9 were asymptomatic, and 2 of these had a positive test. The role of acid in ulcer pain remains unclear. The pertinent literature is discussed.

Female↗