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Biomedical subjects

S H Nelson

Publications and source records attributed to S H Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1988

Cell polarity in sea urchin embryos: reorientation of cells occurs quickly in aggregates.

Four apical components were used as markers for the apical end of the cell in studies centering on cell polarity in the early blastula stage of sea urchin embryos and in aggregates of cleavage stage cells. Cells were observed to maintain their polarity for several hours if dissociated and cultured in suspension. Orientation of cells in aggregates initially is random; however, within 3 hr the cells have reoriented so that their apical-basal axis corresponds to the correct inside-outside position in the aggregate. This reorientation occurs before formation of a basal lamina or a new hyalin layer in the aggregate, and appears to take place by a rotation or other movement of individual cells. The polarity within each cell is maintained during reorientation. An apical surface antigen is colocalized with concentrations of filamentous actin. Treatment of isolated cells with cytochalasin B causes the antigen to lose its apical position and eventually become distributed around the outside of the cell. Microtubules are visible radiating from two foci closely associated with the nucleus in untreated cells. Treatment of isolated cells with nocodazole leaves the apical cell surface marker and its associated actin undisturbed, but causes the nucleus to lose its apical position. Cytochalasin B and colchicine both prevent reorientation of cells in aggregates. Thus polarity appears to be a constant for the cells, and their reorientation in aggregates occurs prior to the polarized release of extraembryonic matrix and basal lamina.

Actin Cytoskeleton↗
PubMed1988

Comparison of nitroprusside and hydralazine in isolated uterine arteries from pregnant and nonpregnant patients.

The purpose of the present study was to determine the relative potency of nitroprusside and hydralazine with respect to inhibition of norepinephrine-induced contraction of isolated, uterine arteries from pregnant and nonpregnant patients. The arteries, obtained after hysterectomy, were dissected free from surrounding tissue, and arterial rings were prepared and mounted in tissue chambers filled with Kreb's-bicarbonate solution. Isometric tension was recorded. At concentrations of 10(-9) M to 10(-5) M, both nitroprusside and hydralazine produced concentration-dependent inhibition of the contractile response to norepinephrine. Nitroprusside and hydralazine were more potent in relaxing arteries contracted by a lower concentration (3 X 10(-6) M) of norepinephrine than by a higher concentration (10(-5) M) of norepinephrine. Regardless of the concentration of norepinephrine, nitroprusside was considerably more potent than hydralazine. The concentrations of nitroprusside that produced 50% inhibition (IC50) of the contractile response to norepinephrine (3 X 10(-6) M) in uterine arteries from pregnant and nonpregnant patients were 3.2 +/- 0.5 X 10(-9) M (n = 5) and 1.2 +/- 0.1 X 10(-9) M (n = 6), respectively. The IC50 values for hydralazine acting against norepinephrine (3 X 10(-6) M) in the uterine arteries from pregnant and nonpregnant patients were 5.1 +/- 0.5 X 10(-7) M (n = 5) and 4.0 +/- 0.5 X 10(-7) M (n = 6), respectively. Nitroprusside (10(-6) M), compared to hydralazine (10(-5) M), produced the greater maximal inhibition of norepinephrine-induced contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed1988

Current issues in state mental health forensic programs.

The major current issues facing state and local forensic mental health programs are presented in this paper. Debates over forensic patients' rights and the insanity defense are discussed, together with many administrative problems such as the pros and cons of correctional versus mental health system program control and payment incentives for treatment. The authors cite the differing goals of correctional and mental health systems, i.e., security and treatment, as reasons for difficulties in developing needed collaboration. Guidelines are suggested to address such important issues as mixing civil with criminal patients, developing units for special populations, defining patients who can respond to treatment, and follow-up after discharge.

Adolescent↗
PubMed1985

Pregnancy: increased effect of verapamil in human uterine arteries.

The effect of verapamil on the contractile response to norepinephrine in isolated, suffused uterine arteries from pregnant and nonpregnant humans was investigated. The arteries, obtained after hysterectomy, were dissected free from surrounding tissue and arterial rings were prepared and mounted in tissue chambers filled with Krebs-bicarbonate solution. Isometric tension was recorded. There was no significant difference between arteries from pregnant patients and arteries from nonpregnant patients when maximal contractile response and sensitivity to norepinephrine were compared. At concentrations of 0.3 and 3 microM, verapamil attenuated the response to norepinephrine in uterine arteries from both pregnant and nonpregnant patients. However, verapamil was significantly more potent in blocking the response to norepinephrine in arteries from pregnant patients.

Adolescent↗
PubMed1985

Dopamine receptors: structure-activity relationship of d-tubocurarine analogues.

d-Tubocurarine (dTC) and d-tubocurine acted as antagonists of the dopamine-induced inhibition of adrenergic neurotransmission in the isolated, perfused rabbit ear artery. N-Methyl-dTC and O,O,N-trimethyl-dTC (metocurine) did not exhibit dopaminergic antagonist activity. dTC contains one tertiary (3 degrees) nitrogen and one quaternary (4 degrees) nitrogen and d-tubocurine contains two 3 degrees nitrogens; whereas, both N-methyl-dTC and O,O,N-trimethyl-dTC have two 4 degrees nitrogens. The results suggest that a dTC analogue (e.g., metocurine) which lacks a 3 degrees nitrogen should be considered for use in patients treated with dopamine.

Animals↗
PubMed1985

Neuronal dopamine receptors of the rabbit ear artery: pharmacological characterization of the receptor.

Dopamine and apomorphine were examined in the rabbit isolated perfused ear artery for both direct effects on vascular smooth muscle and effects on the response to field stimulation of sympathetic nerve terminals. The neuroinhibitory effect of both dopamine (EC50 = 37 nM) and apomorphine (EC50 = 44 nM) occurred at concentrations which did not produce vasoconstriction. The neuroinhibitory effect of dopamine was shown to be due to inhibition of noradrenaline release by measurement of 3H-overflow from prelabelled tissues. At relatively high concentrations dopamine produced vasoconstriction. In a superfused segment of ear artery, dopamine was found to be a full agonist at the alpha 1-adrenoreceptor, with an EC50 (15 microM) about 75 fold higher than the EC50 for noradrenaline. At concentrations up to 3 microM, apomorphine had no vasoconstrictor activity in the perfused ear artery. Representative examples of several classes of dopamine antagonists, including the phenothiazines, butyrophenones, diphenylbutylpiperidines and benzamides produced competitive antagonism of dopamine or apomorphine-induced inhibition, with nearly identical Kb values against these two agonists. The pharmacological characteristics of the neuronal dopamine receptor on the rabbit ear artery would indicate this receptor to be typical of the D2 subclass, and this tissue to be a useful model for quantitative studies on dopamine receptor agonists and antagonists.

Animals↗
PubMed1983

d-Tubocurarine as a dopaminergic antagonist in the rabbit ear artery.

d-Tubocurarine has been reported to inhibit the action of dopamine on mollusc neurons. The purpose of the present study was to determine whether or not d-tubocurarine acts as an antagonist on mammalian dopamine receptors. The isolated, perfused rabbit ear artery was the experimental preparation used. In this preparation dopamine and apomorphine produced concentration-dependent inhibition of the response to electrical field stimulation of the periarterial sympathetic nerves. d-Tubocurarine antagonized the inhibitory effect of dopamine and apomorphine in a competitive manner. The calculated dissociation constants for d-tubocurarine acting against dopamine and apomorphine were 1.9 +/- 0.6 microM and 1.7 +/- 0.5 microM, respectively. d-Tubocurarine (1-100 microM), by itself, did not affect the response of the artery to sympathetic nerve stimulation. Other nicotinic antagonists hexamethonium, pancuronium and mecamylamine did not affect the dopamine action. These results suggest that d-tubocurarine could attenuate the therapeutic benefit of dopamine if both of these drugs are administered concomitantly.

Animals↗
PubMed1983

Interactions of salsolinol and its mono-O-methylated analogs with adrenergic and dopaminergic receptors in the rabbit ear artery.

We have examined the action of the tetrahydroisoquinoline derivatives salsolinol, 6-O-methyl salsolinol (6-O-Me-Sal) and 7-O-methyl salsolinol (7-O-Me-Sal) on adrenergic and dopaminergic receptors in the isolated and perfused rabbit ear artery. The racemic form of the three compounds and the S-(--)-isomer of 6-O-Me-Sal were used. Salsolinol (0.3-10 micrometers) produced concentration-dependent inhibition of the vasoconstrictor response to electrical stimulation of the periarterial sympathetic nerves but did not inhibit the vasoconstrictor response to exogenous norepinephrine. The inhibitory effect of salsolinol on neurotransmission was antagonized by yohimbine, but not by sulpiride or propranolol. The dissociation constant (KB) for yohimbine acting as an antagonist of salsolinol was 98 +/- 8 nM. 6-O-Me-Sal and 7-O-Me-Sal did not affect the response to nerve stimulation or norepinephrine administration; however, these mono-O-methylated analogs of salsolinol antagonized the inhibition of neurotransmission produced by dopamine. The KB values for 6-O-Me-Sal and 7-O-Me-Sal acting as antagonists of dopamine were 1.3 +/- 0.2 and 6.4 +/- 0.31 microM, respectively. S-(--)-6-O-Me-Sal, with a KB value of 0.64 +/- 0.06 microM, was about twice as potent as racemic 6-O-Me-Sal. We conclude that salsolinol acts as an agonist on prejunctional alpha adrenergic receptors and that 6-O-Me-Sal and 7-O-Me-Sal act as antagonists on dopaminergic receptors.

Animals↗
PubMed1979

Standards affecting mental health care: a review and commentary.

The author describes the increasing focus on regulation and the standards applied to the field of mental health. He discusses four distinct but overlapping types of standards: 1) clinical, 2) practitioner, 3) program and facility, and 4) payment. He emphasizes the increasing influence of legislation and judicial decisions and points out several trends in standard setting affecting mental health care. Psychiatrists and other mental health practitioners are called on to take a larger role in shaping these standards to ensure that the quality of patient care is not compromised.

Accreditation↗
PubMed1976

Current issues in national insurance for mental health services.

The current economic crisis has again placed in jeopardy the inclusion of mental health benefits under national health insurance. The author notes that progress has been made in establishing effective peer review systems and in demonstrating that costs of mental health services are reasonable. Yet the lack of agreement on diagnosis and appropriate treatment, the inadequacy of utilization, cost, and treatment outcome data, and the absence of professional self-regulation remain causes for concern in the effort toward eventual comprehensive coverage for mental disorders.

Costs and Cost Analysis↗