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Biomedical subjects

G M Walsh

Publications and source records attributed to G M Walsh.

At least 109 records · Page 6Linked to original sources
PubMed1980

Altered cardiovascular responses to glossopharyngeal nerve stimulation in the spontaneously hypertensive rat.

Alterations in arterial blood pressure and heart rate in response to electrical stimulation of glossopharyngeal nerve (GPN) were examined in 6-10 months old, male spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) normotensive rats. GPN stimulation resulted in frequency-dependent decreases in arterial blood pressure in both SHR and WKY rats. SHR were more sensitive to GPN stimulation than WKY controls. Vasodepressor responses to GPN stimulation were greater in SHR than in WKY rats over a wide range of stimulus frequencies. At the frequency which produced the maximum response (50 Hz) the vasodepressor response was 68% greater in SHR than in WKY control. The results, indicate that neurogenically-induced vasodepression is enhanced in SHR, suggesting that decreased vasodepressor capacity mediated through the central nervous system is not involved in the maintenance of elevated blood pressure in SHR. In contrast to increased vasodepressor responses in SHR, GPN stimulation produced less bradycardia in SHR than it did in WKY rats. This difference may be central in origin because peripheral vagal stimulation produced essentially equal bradycardia in SHR and WKY normotensives.

Animals↗
PubMed1979

Ether-induced vasodilation in the rat.

The hypotensive effect of ether in rats was investigated by the direct Fick technique to determine whether hypotension was produced by reduced cardiac output or decreased total peripheral resistance. Relative to the conscious state, ether anesthesia decreased mean arterial pressure 9%, total peripheral resistance 47%, oxygen extraction 37%, and heart rate 7%; changes were qualitatively similar to those produced by hydralazine (0.5 mg/kg, i.v.) except that hydralazine did not decrease heart rate. These effects were no longer present two hours after withdrawal of ether. This study demonstrated that ether anesthesia in rats has a potent systemic arterial vasodilating action which is offset by increased cardiac output, resulting in mild hypotension.

Anesthesia↗
PubMed1978

Altered hemodynamic responses to acute hypoxemia in spontaneously hypertensive rats.

Conscious spontaneously hypertensive rats (SHR), 5--7 wk old, were studied hemodynamically by the direct Fick procedure to determine whether high total peripheral resistance (TPR) coexisted with increased oxygen consumption (QO2) at an early stage of hypertension development. Since under resting conditions cardiac output in SHR was not significantly different from normotensive controls, the elevated arterial pressure and QO2 were associated with increased TPR. Arterial hypoxemia was induced to reduce oxygen availability and to assess whether increased TPR in SHR could be reversed by this procedure. During hypoxemia, normotensive controls (WKY) responded with increased cardiac output and decreased arterial pressure and TPR. In contrast, arterial pressure and cardiac output fell in SHR; and the increased TPR persisted. QO2 fell in hypoxemic SHR demonstrating that the relationship between total body oxygen consumption and cardiac output was abnormal in young SHR, and that increased TPR in SHR was not dependent on resting levels of QO2 or oxygen availability. Although QO2 was elevated in SHR compared to age-matched WKY, this condition was not essential for maintained elevated vascular resistance.

Aging↗
PubMed1978

Fluid volumes during onset of spontaneous hypertension in rats.

Body fluid volumes were examined in young spontaneously hypertensive rats (SHR) and in two strains of age-matched normotensive controls to ascertain whether expanded plasma volume (PV) or extracellular fluid volume (ECFV) was associated with onset of spontaneous hypertension. Mean arterial pressure (MAP) was measured in conscious male SHR, Wistar-Kyoto normotensive (WKY), and American Wistar normotensive (NR) rats 3 h after arterial cannulation. At age 10-14 days no differences in MAP or PV (determine with 125I-albumin) were found between SHR and WKY. At age 18-43 days, SHR had elevated MAP and a small but significant elevation in total body water volume (TBWV; wet weight minus dry weight) compared to WKY and NR; no differences among the three groups were found in PV or ECFV (estimated with inulin). These results provide no evidence that expanded PV or ECFV plays a role in the pathogenic mechanisms of spontaneous hypertension, but do not exclude the possibility of altered vascular compliance. The slightly elevated TBWV in SHR may be related to reduced body fat in SHR.

Aging↗
PubMed1978

Regional blood flows measured in conscious rats by combined Fick and microsphere methods.

Regional blood flow measurements made by the radioactive microsphere technique were studied in conscious rats. A femoral arterial reference sample blood flow was measured directly, and at the same time indirectly by the combined use of direct Fick cardiac output and microsphere techniques. A significant correlation (r = .81, P less than .01) was obtained between direct and indirect blood flow values when 200--400 microspheres were trapped in the reference sample. When 100--200 microspheres were trapped, regional blood flow was 32% below true flow (P less than .01); and cardiac output, calculated by the reference sample method, was 57% greater than Fick cardiac output (P less than .01). When three consecutive Fick determinations and microsphere injections (20,000 per injection, 15 micrometer diam) were made in conscious rats, significant correlations were obtained among the first, second, and third regional blood flow measurements (r = .95, P less than .01). The results have demonstrated that cardiac output and reference blood flow can be measured with accuracy and precision in the conscious rat by the radioactive microsphere procedure.

Animals↗
PubMed1978

Hemodynamic changes induced by prolonged NaCl and DOCA administration in spontaneously hypertensive rats.

The results of this study demonstrate that the spontaneously hypertensive rat is sensitive to salt excess. The hypertensinogenic effect of salt was mediated through elevation of peripheral vascular resistance. The addition of DOCA aggravated the hypertension, mainly be elevating the cardiac output without appreciably decreasing peripheral vascular resistance. SHR'S EXPOSED TO 1% NaCl consumed more fluids and excreted more sodium and urine than control rats. Those exposed to 1% NaCl and DOCA had higher fluid consumptions and excreted more sodium than the other two groups. These effects of sodium in a neurogenic strain of hypertensive rats suggest a possible interplay between the neurogenic and salt-dependent components in the development and maintenance of hypertension. They also suggest that SHRs, like other hypertensive rat models, are salt sensitive.

Animals↗
PubMed1977

Systemic hemodynamic effects of microspheres in conscious rats.

The effect of increasing quantities of carbonized microspheres (15 +/- 5 micrometer diam) on systemic hemodynamics was evaluated in 21 Sprague-Dawley, 6 normotensive Wistar-Kyoto (WKY), and 8 spontaneously hypertensive (SHR) male rats. Total cumulative injections of more than 100,000 microspheres produced significant systemic hemodynamic alterations manifested by decreased oxygen consumption, cardiac output, and mean arterial pressure; and by increased heart rate, total peripheral resistance, and arterial-venous blood oxygen content difference. There were no hemodynamic alterations characteristic of any rat species, and reproducibility of three separate injections of 20,000 microspheres in each rat was excellent.

Animals↗
PubMed1976

Direct Fick application for measurement of cardiac output in rat.

The direct Fick procedure for cardiac output determination in rat was validated by simultaneous comparison with electromagnetic flowmeter techniques. Significant coefficients of correlation were obtained between absolute cardiac output values (r = 0.789, P less than 0.001), increases (r = 0.768, P less than 0.001) and decreases (r = 0.672, P less than 0.01) in cardiac output detected by the two methods. As demonstrated in other species, cardiac output values of the Fick procedure in the rat were between 40 and 58% greater than respective electromagnetic flow probe values; however, percent changes in cardiac output obtained by the two methods were similar. The larger values of cardiac output obtained by the direct Fick method may be related, to a great extent, to the distribution of blood flow to the coronary and bronchial circulations. Fick cardiac output measurements were reproducible within rats, and the degree of variation in values among rats was similar to that obtained with the flowmeter procedure. The result indicate that the Fick meth od provides a valid estimation of cardiac output in the rat, with the ability to detect moderate changes (22-36%) in cardiac output.

Animals↗