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Biomedical subjects

R G Carroll

Publications and source records attributed to R G Carroll.

At least 73 records · Page 4Linked to original sources
PubMed1988

Disparity between renal venous norepinephrine and renin responses to sodium depletion.

To evaluate the hypothesis that sodium depletion produces a chronic increase in renal nerve activity, arterial and renal venous plasma norepinephrine (NE) concentrations were measured in conscious dogs subjected to various degrees of sodium depletion. After 9 days of sodium depletion (LS), there was a net loss of 69 +/- 10 meq sodium, and mean arterial pressure (MAP) was reduced from 94 +/- 5 to 88 +/- 4 mmHg. At this time plasma renin activity (PRA) was increased from a control level (sodium intake = 45 meq/day) of 0.34 +/- 0.08 to 1.47 +/- 0.26 ng angiotensin I (ANG I).ml-1.h-1 in association with an approximately sixfold increase in the PRA gradient across the kidneys. Subsequently, when captopril was infused during an additional 7 days of sodium deprivation [(LS + converting enzyme inhibitor CEI)], there was further sodium depletion (31 +/- 11 meq) and hypotension (MAP = 65 +/- 6 mmHg) and PRA and the renal PRA gradient increased even further. In marked contrast, there were no significant changes in either arterial plasma NE concentration (control = 102 +/- 5 pg/ml) or the renal arteriovenous gradient of plasma NE concentration during either LS or LS + CEI. These experiments show a distinct disparity between changes in the PRA and the plasma NE concentration gradient across the kidneys during LS and fail to support the contention that increased renal nerve activity is an important long-term adaptive response to sodium depletion.

Animals↗
PubMed1987

Prevention of "irreversible" hemorrhagic shock by the preservation of cellular integrity.

The clinically encountered state of hypovolemic shock results from a series of metabolic and cardiovascular responses to tissue hypoperfusion. Recent advances have increased our understanding of the consequences of tissue hypoxia, and identified at the cellular level those changes which cause the damage to be "irreversible", or refractory to treatment. To be successful, therapeutic interventions should be designed to 1) limit, if not reverse, the subcellular alterations in membrane stability and mitochondrial function which herald the transition from compensated to decompensated shock, and 2) re-hydrate the individual to restore normal circulatory dynamics and to prevent further cellular damage. It is proposed that calcium channel blocking agents and/or high energy phosphate compounds may delay the positive feedbacks which cause irreversible tissue damage, and thus may be useful initial interventions in the treatment of hypovolemic shock.

Adenosine Triphosphate↗
PubMed1987

SPECT gallium scanning for lymphoma and infection.

Thirty gallium scans, using currently acceptable dosage levels (5-6 mCi) and a conventional rotating gamma camera, were performed on 20 patients with lymphoma or infection. Compared to planar scans, SPECT increased sensitivity and lesion detection from 48% to 89% in lymphoma, and from 50% to 80% in infection. The predictive value of a negative site was 81% in lymphoma and 67% in infection. Gallium utility is markedly increased by SPECT imaging. A normal gallium SPECT scan is highly accurate in ruling out disease.

Adult↗
PubMed1986

Cardiovascular and renal responses to chronic vasopressin infusion.

Arginine vasopressin (AVP) was infused into the renal artery of seven uninephrectomized conscious dogs at successive rates of 0.09, 0.36, and 1.46 ng X kg-1 X min-1 for 18, 9, and 5 days, respectively; subsequently, the nonpressor analogue of AVP, 1-desamino-8-D-arginine vasopressin (DDAVP), was infused intrarenally for 7 additional days. The lowest infusion rate of AVP produced a high concentration of AVP in the renal circulation (maximal antidiuresis) with only a relatively moderate increase in peripheral plasma AVP concentration. For comparison, the effects of a comparable increase in peripheral plasma AVP concentration during intravenous infusion at this same rate were observed in an additional group of dogs. Acutely, when this low dose of AVP was infused either intrarenally or intravenously, there was marked antidiuresis, but there were no significant changes in mean arterial pressure (MAP), renal hemodynamics, or urinary electrolyte excretion. Chronically, in both groups of animals, cumulative water balance was positive, and glomerular filtration rate, effective renal plasma flow, and MAP (16-18 mmHg) all increased; plasma renin activity decreased. Similar changes were observed during DDAVP infusion. When elevated peripheral plasma levels of AVP were achieved during the higher infusion rates of AVP, natriuresis and diuresis occurred, but, otherwise there was little change in the above variables, including MAP. Thus the hydrosmotic effects of AVP appear to account for its moderate hypertensive activity. Further, the failure of AVP to produce prominent hypertension, even when pronounced systemic vasoconstrictor effects are manifested, may be a result of its inability to promote significant renal vasoconstriction and antinatriuresis.

Aldosterone↗
PubMed1986

Effects of graded changes in reflex renal nerve activity on renal function.

The effects of reflexly produced graded increases in renal nerve activity on excretion of sodium and potassium, urinary flow, glomerular filtration rate (GFR), renal plasma flow (RPF), renin release, and renal venous norepinephrine (NE) overflow were examined in anesthetized dogs. Renal nerve activity was increased by carotid artery occlusion while renal perfusion pressure was held constant. Linear correlation was determined by plotting the percent change from control for each dependent variable vs. the percent change in mean renal nerve activity (MRNA). The percent changes from control for sodium excretion and urinary flow were negatively correlated with percent change from control in MRNA (P less than 0.01), and the percent change from control for renin release was positively correlated with percent change from control in MRNA (P less than 0.05). NE overflow was observed to increase as renal nerve activity increased. These results indicate that physiologically elicited increases in MRNA from 10 to greater than 100% are significantly correlated with changes in sodium excretion, urine flow, and renin release with little or no measurable change in GFR, RPF, or potassium excretion.

Animals↗
PubMed1984

Vascular recovery following hemorrhage in the dogfish shark Squalus acanthias.

Cardiovascular regulatory systems were examined in the dogfish shark after hemorrhage of 1% of body weight. An immediate 45% decrease in mean dorsal aortic pressure and delayed increases in plasma epinephrine concentration and plasma norepinephrine concentration were noted. During the recovery period following hemorrhage, the catecholamine levels peaked (epinephrine 203% of control, norepinephrine 148% of control) and then returned toward control values. Hematocrit, however, continued to decline as blood pressure recovered. Phentolamine pretreatment, which in itself caused a 55% decrease in dorsal aortic pressure, did not prevent the recovery of blood pressure after hemorrhage. This study indicates that 1) hemorrhage causes an increase in circulatory catecholamine concentration, possibly by a baroreceptor reflex; 2) volume recruitment, as indicated by the drop in hematocrit, is a major mechanism contributing to the recovery of dorsal aortic pressure after hypotension; and 3) alpha-adrenergic receptors are not necessary for the recovery of dorsal aortic pressure after hemorrhage.

Animals↗
PubMed1983

Utility of the routine left lateral view in gated blood pool studies.

One hundred twenty-four sequential gated blood pool studies were examined by four observers in order to determine the impact on overall interpretation created by the addition of a routine left lateral view to supplement the standard LAO and RAO projections. Of these 124 studies, 114 studies in 87 patients were considered technically adequate. Forty-one of the 114 studies revealed differences in the perception of apex motion in the LAO as compared with the left lateral view. In seven of these 41 cases, the overall diagnostic impression was altered by the left lateral view. A 15-minute increase in technician time at an incremental cost of $3.00 is attributed to the added view. Approximately 6% of overall diagnostic impressions were altered because of this additional routine view.

Coronary Disease↗
PubMed1982

Dogfish pressor response to potassium blocked by magnesium and phentolamine.

In vivo infusion of MgCl2 blocks the dogfish pressor response to K+. This action of Mg2+ was contrasted to phentolamine in in vivo and in vitro experiments. Mg2+ blocks the spontaneous release of catecholamines from dogfish chromaffin tissue but does not alter the norepinephrine-induced contraction of the isolated dogfish artery. In vivo infusion of Mg2+ causes a significant decrease in resting catecholamine levels and diminishes the catecholamine release caused by K+ challenge. Both Mg2+ and phentolamine block the pressor action of K+, Mg2+ by preventing the K+-induced release of catecholamines and phentolamine by preventing the circulating catecholamines from interacting with alpha-adrenergic receptor sites.

Animals↗
PubMed1982

Catecholamine release and blood pressure changes induced by exercise in dogfish.

Plasma norepinephrine (NE), epinephrine (E), and potassium (K+) were measured before, during a 3-min bout of exercise, and at intervals after exercise in Squalus acanthias. The dorsal aortic pressure response following 1 min of exercise was observed in another series of experiments. Plasma E, NE, and K+ increased significantly and progressively during the exercise period and for 2 min after exercise. Plasma E increased significantly during the 1st min; NE during the 2nd min; but K+ did not increase significantly until the 3rd min of exercise. Blood pressure decreased significantly during 1 min of exercise but increased over control level within 4 min after the end of exercise coincident with the peak of plasma E and NE concentrations. Plasma NE, E, and blood pressure decreased slowly in parallel fashion during the 37-min postexercise period of observation. Increased plasma K+ from skeletal muscle is probably not the primary stimulus for early catecholamine release in exercising dogfish, but increased plasma K+ does contribute to releasing and maintaining plasma NE and E levels in the postexercise period. This results in a sustained pressor effect that promotes blood flow and aids in metabolic recovery.

Animals↗
PubMed1982

Evolution of angiotensin II-induced catecholamine release.

The interaction between angiotensin II (ANG II) and catecholamines was examined in nonmammalian vertebrates. ANG II challenge caused a significant pressor response in representatives of the seven vertebrate classes. Additionally, plasma levels of both epinephrine and norepinephrine increased following intravascular ANG II injection in the conscious lumpfish, bullfrog, and turtle, and the anesthetized chicken. Phentolamine pretreatment totally abolished ANG II pressor action in the hagfish and chicken and diminished the ANG II pressor response in other classes of vertebrates. The ability of ANG II to release catecholamines appears to be a phylogenetically ancient interaction and indicates that catecholamines may play an important role in the physiological expression of ANG II action in lower vertebrates.

Angiotensin II↗
PubMed1981

Vascular response of the dogfish and sculpin to angiotensin II.

The mechanism by which angiotensin II (AII) exerts its pressor effect was examined in a saltwater teleost and elasmobranch. In vivo application of AII failed to elicit any changes in dogfish (Squalus acanthias) mesenteric microcirculatory blood flow, but the sculpin (Myoxocephalus octodecimspinosus) mesentery bed showed consistent reversible decreases in blood flow following AII application. Topical treatment with 0.5 mg phentolamine did not attenuate the AII response. In vitro addition of AII did not alter the mean resting tension of the dogfish celiac artery or intestinal vein, but significantly contracted the sculpin aorta. Addition of chromaffin tissue to the dogfish arterial muscle bath imparted significant vasoaction to AII when compared to saline. Both in vivo and in vitro experiments demonstrate the absence of functional AII vascular receptors in dogfish and their presence in the sculpin. Additional evidence for the mediation of AII vascular action in the dogfish by catecholamine release has been demonstrated.

Angiotensin II↗
PubMed1981

Systemic arterial pressor responses induced by potassium in dogfish, Squalus acanthias.

Intravascular injection of small doses of potassium (0.025-0.5 meq) into dogfish results in dose-related dorsal aortic pressor responses. The responses are blocked by phentolamine, an alpha-adrenergic blocking agent. Assays of plasma catecholamines before and after injection of potassium (K+) showed that plasma levels of epinephrine (E) and norepinephrine (NE) had increased significantly (E, 314%; NE, 233%) 1 min after injection. The pressor responses were initiated 40-90 s after K+ injection at which time plasma E and NE levels were already significantly elevated. Experiments on isolated dogfish arterial strips showed that phentolamine cannot block the increase in vascular smooth muscle tension that occurs after direct exposure to small increases (0.003 meq/ml) in K+ concentration. Because phentolamine effectively blocks the pressor response to even higher doses of K+ in vivo, it is thought that, in addition to any direct vasoconstrictor effect or K+, the adrenergic stimulation provided by catecholamine release is required to produce the observed pressor response.

Animals↗
PubMed1979

Selected lobar injury after infusion of oleic acid.

A model of respiratory distress has been developed using sheep in which an isolated lobar injury is induced by infusion of oleic acid into a selected lobar artery. The directed insult permits acute and chronic phase study without the requirement of intensive pulmonary support. One hour after selective lobar injury the affected pulmonary venous oxygenation (Ppvo2) was reduced from greater than 310 to 66-90 Torr. Ppvo2 was most impaired at 48 h (40-55 Torr), but showed improvement by 96 h postinjury. Radionuclide estimates of lobar ventilation and perfusion demonstrated an initial fall in ventilation by 51% and corresponding 41% reduction in perfusion. By 24 h the depression of perfusion matched that of ventilation. Sequential light and scanning electron microscopy demonstrated the presence of a nonhomogeneous injury with areas of both complete parenchymal replacement by fibrous tissue and those with minimal architectural distortion. The selective injury model offers a useful methodology for the evaluation of the effects of various agents on the acute and chronic response of the lung to injury.

Acute Disease↗
PubMed1979

Radiation-associated disease: disease incidence and cost effectiveness of follow-up.

The organization, costs and outcome of a metropolitan area-wide recall campaign for patients irradiated for benign disease is documented. The campaing resulted in an increase in the number of thyroid malignancies discovered in both the irradiated and the nonirradiated population. The organization of the campaign cost $100,000. An estimated excess of 100 thyroid carcinomas were found in the 17 months following the campaign compared to the 17 months prior to the campaign in the Pittsburgh Standard Metropolitan Statistical Area. Of 150 patients who were radium exposed as infants and remained in the Pittsburgh area, 60% knew of their exposure only by direct hospital contact and were not reached by media public education. Seven of those 150 patients had thyroid carcinoma on 35 year follow-up, and 30% had some benign or malignant tumor.

Cost-Benefit Analysis↗
PubMed1978

Experimental retained antrum. Diagnostic technics and histopathologic correlations.

Retained gastric antrum was evaluated in six dogs, and diagnostic methods correlated with histopathology. Secretin and calcium infusion did not significantly alter circulating gastrin levels. 99 mTc scanning was uniformly positive and did not depend on the presence of parietal cells. The failure to consistently develop hypergastrinemia and the absence of gastrin cell hyperplasia suggest that factors other than gastrin may be implicated in the recurrent ulceration seen with retained antrum.

Animals↗
PubMed1977

Pulmonary perfusion defect and bronchial artery collateral blood flow.

A five-year-old child with severe congestive heart failure following repair of tetralogy of Fallot was examined for correction of a suspected left-to-right shunt. Lung scan and selective bronchial angiographs demonstrated greatly diminished perfusion to the right upper lobe, which was supplied by a large bronchial artery. Technetium microspheres were injected into the artery for quantification. Subsequently, the artery was occluded by injection of the tissue-adhesive bucrylate. During the following year, radionuclide scans showed improvement in the uniformity and percentage distribution of pulmonary perfusion by way of the pulmonary artery. The child has become asymptomatic following closure of the bronchial vessel.

Bronchi↗