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Biomedical subjects

M McCleary

Publications and source records attributed to M McCleary.

17 recordsLinked to original sources
PubMed1982

Sinusal afferents supplying superior cervical ganglion.

Sinusal distension can evoke activity in nerves supplying the superior cervical ganglion. These nerves, which have been shown to have little depressor influence, may carry an inhibitory input from the carotid sinus to the superior cervical ganglion (SCG). They have the morphological characteristics of the nerve of Hering and show cardiac pulse-related activity that may reach a maximum of 50 impulses/s during distension of the sinus. Electrical stimulation of the ascending preganglionic sympathetic trunk supplying the SCG may evoke discreet bursts of activity in these fibers, which do not summate with continued stimulation.

Animals↗
PubMed1982

Paradoxical relationship between the superior cervical ganglia and the antihypertensive action of propranolol in the spontaneous hypertensive rat.

The effect of dl-propranolol (1.0 mg/kg/day i.p.) on heart rate and blood pressure in young and old normo- and hypertensive rats was studied before and after bilateral sympathectomy of the superior cervical ganglia. Denervation alone produced no significant changes in blood pressure or heart rate in the normo- or hypertensive rat of either age. Thirty-five consecutive days of propranolol treatment significantly lowered blood pressure in the older established spontaneous hypertensive rat and prevented the increases from occurring in the younger, developing hypertensive rat. Blood pressure was not modified in the normotensive Wistar-Kyoto rat by propranolol. Denervation of the superior cervical ganglia at the beginning of the propranolol treatment or midway through the protocol abolished the antihypertensive effects in the young and old spontaneous hypertensive rat. A close temporal association of denervation with the loss of the antihypertensive effect was demonstrated. Although propranolol administration continued after denervation, the antihypertensive effects of the drug did not reappear.

Animals↗
PubMed1981

Carotid sinus distension and superior cervical ganglion transmission.

The functional relationship between sinusal distension and the sympathetic innervation of the feline carotid sinus was investigated by neurophysiological techniques. A balloon catheter was used to distend the sinus region while recording evoked postganglionic activity from the superior cervical ganglion. When the SCG was stimulated at 1.0 or 10.0/s, balloon inflation reduced postganglionic action potential height by 25-50% and increased ganglionic negativity. These effects were subsequently abolished by section of one of the remaining intact postganglionic trunks. This evidence suggests that a pressure-modulated reflex arc, similar to the intestinointestinal reflex, might exist between the carotid sinus and superior and cervical ganglion.

Action Potentials↗
PubMed1980

Inferior cardiac nerve activity in the cat during superfusion of the vascularly isolated carotid sinus with propranolol.

1 Inferior cardiac nerve activity in 9 cats was in inverse relationship to the pressure maintained in the systemically isolated and perfused carotid sinus. 2 Perfusion with propranolol produced no change in this relationship at a concentration of 5.0 microgram/ml, but abolished it at 50.0 microgram/ml. 3 The results suggest that concentrations of propranolol which have been reported to enhance the sensitivity of the carotid sinus to pressure do not enhance one neurophysiological component of the reflex depressor response.

Animals↗
PubMed1979

Inferior cardiac nerve activity in the cat during occlusion of the mesenteric artery.

A number of studies in this and other laboratories using hemodynamic and pharmacologic evidence have suggested that occlusion of the mesenteric artery evokes a pressor reflex initiated by mesenteric baroreceptors. To provide additional evidence in support of this hypothesis, neurophysiological recordings were made of inferior cardiac nerve activity during mesenteric artery occlusion (MAO). The results indicate that MAO enhances inferior cardiac nerve activity in the cat, providing that the carotid sinus nerves have been cut. Cutting of the mesenteric nerves further facilitates cardiac nerve activity and abolishes the response to mesenteric artery occlusion. The evidence suggests that MAO evokes a reflex sympathetic discharge which is subject to override by the carotid sinus depressor reflex. The afferent limb of the reflex is characterized by a tonic depressor outflow from the mesenteric pressure receptors.

Animals↗
PubMed1978

A mechanism to explain the antihypertensive action of propranolol.

The present experiments were designed to measure the direct effects of propranolol on carotid sinus pressoreceptor nerve activity in the semi-isolated, superfused sinus of the cat. Propranolol (5 microgram/ml) significantly enhanced carotid sinus nerve activity at perfusion pressures of 100, 150 and 250 mm Hg. The enhancement was due primarily to the recruitment of new fibers. In similar preparations, perfused at constant flow, propranolol increased sinus resistance in parallel with the increase in sinus discharge. These effects were rapidly dissipated by rinsing with drug-free perfusion solution. The evidence suggests that propranolol may produce a change in either the elastic or autoregulatory modalities of sinus smooth muscle. This may produce a functional "resetting" of the sinus and provide a mechanism to explain the antihypertensive effect of propranolol.

Action Potentials↗
PubMed1977

Pharmacology of the hemodynamic and myocardial response to occlusion of the mesenteric artery in the cat.

Occlusion of the superior mesenteric artery in the cat produces increases in heart rate, systemic pressure, cardiac output and muscle blood flow. Total peripheral resistance is reduced and regional resistance in skin increased. Blockade of the right and left cardiac nerves with xylocaine lowered basal heart rate and reduced cardiac output. The increase in heart rate produced by occlusion of the artery (MAO) was prevented by blockade of the stellate ganglia and cardiac nerves. Propranolol lowered basal heart rate and cardiac output and subsequently blocked the increase in both parameters during MAO. The increase in muscle blood flow was also blocked resulting in an increase in total resistance. We conclude that, in the cat, MAO reflexly increases myocardial tone and enhances venous return from muscle, the latter by a reflex beta adrenergic vasodilation. Both factors provide for the increase in cardiac output. A reflex beta adrenergic vasodilation in muscle, evoked by vasoconstriction in the mesenteric bed, may contribute to survival in the hemorrhaged animals, since capillary exchange in muscle may be increased by this reflex and fluid shifted from the extra--to the intravascular compartment.

Animals↗
PubMed1977

Hemodynamic reflex in muscle in response to brief occlusion of the mesenteric artery.

Brief occlusion of the superior mesenteric artery in the cat produces increases in systemic pressure and in muscle blood flow. Capillary filtration in muscle, measured during occlusion of the superior mesenteric artery, exceeds that of the controls. Propranolol, which blocks the evoked increase in muscle blood flow, reduces capillary filtration during occlusion to less than the control. Cutting the mesenteric nerve returns capillary filtration to the control level. Passive redistribution of blood, such as might follow occlusion of a large vascular region, is not the basis for the evoked changes in muscle hemodynamics. They are abolished by cutting the mesenteric nerve and by propranolol, and are demonstrable during constant pressure perfusion of muscle. The evidence suggests that occlusion of the mesenteric artery produces an increase in capillary filtration by balancing a reflex sympathetic beta-adrenergic vasodilation in pre-capillary resistance vessels with an increase in resistance in the precapillary sphincters.

Animals↗
PubMed1975

Mesenteric baroreceptors.

Occlusion of the mesenteric vessels in the cat and injection of catecholamines produced significant changes in skin and muscle blood flows. These were abolished by cutting the mesenteric nerves. The occurrence of systemic pressure and peripheral resistance changes in cross-perfused mesenteric preparations indicates that hemodynamic factors alone, such as might result from occlusion of a large vascular region, were not initiating the reflex. This also excludes extramesenteric receptors within the heart and large vessels from the reflex. Since both intravascular pressure and catecholamines have been shown to modify Pacinian receptor discharge in vivo, the evidence suggests that the mesenteric Pacinian corpuscle is the baroreceptor probably initiating the vasomotor reflexes in skin and muscle. The net effect of mesenteric receptor activity appears to be an inhibition of vasomotor neurons supplying skin and muscle.

Animals↗
PubMedDate not supplied

Drug abuse in pregnancy. Detection and intervention.

Drug abuse in the obstetric population of a large urban HMO is discussed. Marijuana metabolites were detected in 9.1% of urines submitted for routine pregnancy testing, while cocaine use was detected in 1.3%. A separate group of urines submitted for urine culture at the time of the first obstetric visit were tested and showed levels of 5.0% and 0.2%, respectively. Cocaine use was associated in an estimated 1-2% of all live births. The unexpected magnitude of this problem led to the creation of an outreach clinic and a process of care. The preliminary experience of our program forms the basis of this report.

Cocaine↗