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Biomedical subjects

R Solomon

Publications and source records attributed to R Solomon.

At least 19 recordsLinked to original sources
PubMed1992

The effect of tributyltin chloride on vascular responses to atrial natriuretic peptide.

The effects of tributylin chloride (TBT) on vascular smooth muscle responses to norepinephrine, nitroprusside (SNP) and atrial natriuretic peptide (ANP) were studied in isolated aortic rings of rats. TBT did not interfere with norepinephrine-induced contraction or SNP-induced vasorelaxation. However, TBT produced a dose-dependent inhibition of ANP-induced vasorelaxation. Inhibition was not observed with inorganic tin chloride, SnCl2. The inhibition of vasorelaxation was accompanied by a parallel inhibition of ANP-induced cGMP generation. SNP-induced generation of cGMP was not affected by TBT. TBT did not interfere with binding of ANP to its receptor in bovine adrenal glands suggesting that the effects of TBT were mediated by direct interaction with membrane-bound guanylate cyclase.

Animals↗
PubMed1992

Mechanisms of early death despite thrombolytic therapy: experience from the Thrombolysis in Myocardial Infarction Phase II (TIMI II) study.

Mechanisms of death among patients who died within 18 h of enrollment in the Thrombolysis in Myocardial Infarction Phase II (TIMI II) study were analyzed. Of 3,339 patients enrolled, 32 died within the 1st 4 h and 31 died within the subsequent 14 h. Thirteen of the 63 patients had shock at enrollment; 22 had advanced hemodynamic compromise without shock and 28 initially had minimal to no compromise. Prior infarction was present in 16 patients (25%). Pump failure was responsible for 39 early deaths (62%), ventricular rupture for 10 (16%), arrhythmia for 8 (13%) and complications of therapy for 6 (10%). Nine of 720 patients randomized to immediate intravenous beta-adrenergic blocking agent therapy had an early death compared with 6 of 714 assigned to deferred beta-blocker therapy. Thus, mortality is highest in the early hours after myocardial infarction, even in patients treated with thrombolytic therapy and is most frequently due to pump failure. These results imply that efforts to reduce mortality during this critical time period should be directed at prevention, limitation or palliation of early pump failure.

Adrenergic beta-Antagonists↗
PubMed1992

Diltiazem enhances potassium disposal in subjects with end-stage renal disease.

Seven subjects with end-stage renal disease (ESRD) who were anuric and dialysis-dependent were studied during a 28-hour interdialytic period to assess changes in plasma potassium. Plasma potassium, glucose, magnesium, aldosterone, and cortisol were measured every 4 hours. Eight normal subjects were similarly treated. Subjects with ESRD had a progressive increase in plasma potassium, in contrast to normal subjects who exhibited a characteristic diurnal variation. In ESRD, diltiazem significantly reduced the rate of increase in plasma potassium compared with placebo and resulted in a significantly lower net increase in potassium over the entire 28-hour period. Diltiazem did not affect plasma potassium in normal subjects. Diltiazem did not affect plasma aldosterone, cortisol, glucose, or magnesium. In conclusion, diltiazem reduced the rate of increase of plasma potassium during a 28-hour interdialytic period.

Adolescent↗
PubMed1992

C-type natriuretic peptides stimulate chloride secretion in the rectal gland of Squalus acanthias.

Homologous shark C-type natriuretic peptide (sCNP) was infused as a bolus and as a constant infusion in the isolated perfused rectal gland of the same species, Squalus acanthias. sCNP was a potent stimulator of chloride secretion similar in its dose-response curve to vasoactive intestinal peptide. sCNP was equipotent with killifish CNP but more potent than human CNP (hCNP). Truncated and substituted, forms of hCNP were also capable of stimulation of chloride secretion in the order hCNP greater than hCNP (6-22) = [Gly9]hCNP greater than hCNP-(7-21). sCNP was more potent than human atrial natriuretic peptide (hANP), which was more potent than porcine brain natriuretic peptide. hANP-(31-67) was without effect. These studies suggest that sCNP may be the physiological regulator of rectal gland function. The receptor in the rectal gland is unknown but based on the order of potencies, position 4 in the NH2-terminal end and the ring itself are important for ligand effects.

Amino Acid Sequence↗
PubMed1991

Downregulation of specific protein carboxylmethyltransferase immunoreactivity in human endometrial carcinoma.

Protein carboxylmethyltransferases (PCMT), enzymes that methylate free carboxyl groups of proteins, are involved in functional modification of various proteins including those of age-damaged proteins and the oncogenic ras proteins. Several species of PCMT are associated with these modifications. By using western blot analysis and specific antibodies raised against one type of PCMT, a 30-kilodalton (KD) cytosolic enzyme from Torpedo electric organ was identified in human erythrocytes and endometrium. The high specificity of the antibodies made it possible to compare levels of immunoreactive 30-KD PCMT protein in normal human endometria and endometrial carcinomas. Assays done on samples from 23 patients indicated the average levels of immunoreactive 30-KD PCMT in endometrial carcinomas was one fifth that of normal endometrium. The sensitivity of the assay was 83%, and its specificity was 90%. These results suggest that levels and activity of the 30-KD PCMT may be downregulated to maintain the phenotypic expression of the endometrial carcinoma. These assays may be used to assist in the detection of endometrial carcinomas.

Adult↗
PubMed1991

The diurnal rhythm of plasma potassium: relationship to diuretic therapy.

Plasma potassium levels have been implicated in the genesis of cardiac arrhythmias, particularly in patients receiving diuretic therapy. The present study was undertaken to evaluate the stability of plasma potassium levels throughout a 28-h period. Normal volunteers (n = 8) and subjects with essential hypertension (n = 10) were studied in a clinical research center while receiving controlled dietary intakes. Plasma potassium followed a diurnal rhythm in both groups, with a peak level at 12 h and a trough level at 24 h. The average peak-to-trough difference was 0.62 +/- 0.05 mmol/L. Urinary potassium excretion also followed a diurnal rhythm, with the lowest excretory rate during the evening hours, when plasma potassium reached its nadir. Subjects with essential hypertension were restudied after 4 weeks of hydrochlorothiazide (50 mg/day) and then after an additional 4 weeks of hydrochlorothiazide (50 mg/day) and amiloride (5 mg/day). Hydrochlorothiazide alone reduced plasma potassium at all times of measurement without altering the diurnal rhythm. The combination of hydrochlorothiazide and amiloride resulted in higher plasma potassium levels in the morning, but did not significantly affect evening plasma potassium levels. The frequency of hypokalemia (K less than or equal to 3.0 mmol/L) was related to the time at which the plasma potassium was measured. We conclude that plasma potassium undergoes a diurnal rhythm and that diuretics shift this rhythm to uniformly lower values. This rhythm must be considered when defining the frequency of hypokalemia.

Adult↗
PubMed1989

The effect of organotin compounds on chloride secretion by the in vitro perfused rectal gland of Squalus acanthias.

The effects of various organotins on membrane function and electrolyte transport were studied in the marine elasmobranch, Squalus acanthias. The isolated perfused rectal gland was used as a model of electrolyte transport. This gland can be stimulated to secrete chloride by atrial natriuretic peptide, veratrine, and vasoactive intestinal polypeptide although the mechanism of action of each secretagogue is different. By analysis of the inhibitory effect of an organotin in the presence of each secretagogue, the mechanism of inhibition can be inferred. Tributyltin (TBT) produced a reversible inhibition of epithelial transport at 10(-8) to 10(-7) M which resulted from inhibition of stimulus-secretion coupling in VIP-containing neurons within the gland. The transporting epithelial cells were unaffected at these concentrations. Trimethytin (TMT) produced inhibition at 10(-7) M which was not reversible and which affected primarily the transporting epithelial cells. Triethyltin and triphenyltin were without effect. The inhibitory effect of TBT and TMT was not affected by simultaneous administration of dithiothreitol. TBT also produced inhibition of oxygen consumption, Na+,K-ATPase, and proton ATPase in dispersed rectal gland cells. These results indicate that organotins are toxic to cell membrane functions which are intimately involved in the movement of electrolytes. This is the first evidence of toxicity to membrane transport functions in a marine species which is at risk from environmental exposure.

Animals↗
PubMed1989

Quantitation of HIV-1 RNA in blood cells of ARC and AIDS patients.

Peripheral blood mononuclear cells from HIV-1-infected persons were mixed with 5 M guanidine thiocyanate, and HIV-1-specific probes were hybridized with target RNA directly in the lysate. No RNA purification was needed. Hybrids were purified by repeated capture on superparamagnetic beads coated with oligo(dT) in a device-assisted format, a procedure termed "reversible target capture." Blood mononuclear cells from 70 ARC and AIDS patients were examined and found to have an average of 1.8 x 10(5) molecules of HIV-1 RNA per 2 x 10(6) cells.

AIDS-Related Complex↗
PubMed1989

A noise-free molecular hybridization procedure for measuring RNA in cell lysates.

A solution hybridization technique was designed to measure RNA abundance in crude cell lysates and at the same time to maximize confidence that signals resulted from true molecular hybridization. Cell lysates were prepared in 5 M guanidine thiocyanate, then RNA molecules in the lysates were hybridized with two probes, a 32P-labeled RNA "label probe" which provided signal and an oligodeoxyribonucleotide "capture probe" containing a poly(dA) tail which provided a mechanism for selective purification. Ternary hybrids were "captured" on oligo(dT)-coated superparamagnetic beads through a readily reversible interaction with the poly(dA) of the capture probe. RNA did not bind to dT beads through poly(A) under the capture conditions used. Hybrids were purified through cycles of capture on and release from dT beads, with each cycle yielding a 100- to 1000-fold reduction in noise (unhybridized label probe) and a 50-90% recovery of signal (hybridized label probe). Noise was driven below detectable limits after three cycles of capture, thereby improving the sensitivity of measuring target RNA. As few as 15,000 target molecules, 15 fg of a 3-kb RNA, was detectable in the equivalent of 2 x 10(6) cells in concentrated cell lysates (10(8) cells/ml). Since hybridization with both probes was required in order to yield a signal, hybridization specificity could be adjusted with either or both probes. The greater specificity and lack of noise increased confidence that the signal was proportional to the amount of RNA of interest.

Guanidines↗
PubMed1989

Probes for quantitating subpicogram amounts of HIV-1 RNA by molecular hybridization.

A set of probes was designed for the quantitation of HIV-1 RNA in infected cells by a molecular hybridization procedure called reversible target capture. Reversible target capture is analogous to sandwich hybridization, except that the link between hybrid complexes and the affinity support was reversible, allowing for repeated capture of hybrids on, and release from, fresh affinity support. Repeated cycles of capture resulted in a high degree of purification of hybrids from unreacted probe, thereby greatly reducing assay noise and increasing assay sensitivity. Probes against the HIV-1 pol gene were chosen because their target sequences were highly conserved among HIV-1 isolates, while being divergent enough to provide discrimination from other human T cell tropic viruses. Subpicogram quantities of HIV-1 pol gene RNA were measured with signal:noise ratios of over 10. Hybridization signal increased with increasing target RNA with a proportionality constant of 1.

Cells, Cultured↗
PubMed1989

Low background scintillation counting.

Counting radioactive samples with Beckman Instrument's Ready Caps, using a restricted energy window, LL-UL = 400-1000, resulted in machine backgrounds of under 2 cpm and efficiencies of counting relative to liquid scintillation cocktails (LSC) of 51%, 65%, 57%, 62%, and 1% for 32P, 125I, 14C, 35S and 3H, respectively. Signal-to-noise ratios from a quantitative molecular hybridization technique were increased 8-10 fold. There may be a general application for this product in experiments yielding low amounts of radioactivity in liquid samples.

Animals↗
PubMed1988

Identification of two distinct protein carboxyl methyltransferases in eucaryotic cells.

Two distinct protein carboxyl methyltransferases (PCM) were identified in the electric organ of Torpedo ocellata. They were separated from each other in the active form by means of nondenaturing gel electrophoresis and by p-(chloromercuri)benzoate-agarose chromatography, and were individually identified by specific polyclonal antibodies. The existence of at least two distinct PCMs in eucaryotic cells raises the possibility that these enzymes are involved in distinct transmethylation reactions.

Animals↗