Mechanisms of the renal vasodilation caused by insulin in anesthetized pigs

The present study was planned to determine the mechanisms involved in the renal vasodilation caused by insulin. Changes in flow caused by the intravenous infusion of 0.004 IU/kg/min of insulin at constant heart rate, aortic blood pressure, left ventricular contractility and blood levels of glucose and potassium in the left renal artery were assessed using an electromagnetic flowmeter. In ten pigs, infusion of insulin caused an increase in renal blood flow which averaged 12.8% of the control values. After hemodynamic variables had returned to control values, insulin infusion was repeated in five pigs following blockade of alpha-adrenergic receptors with injection of phentolamine into the renal artery and in the other five pigs following blockade of nitric oxide formation with injection in the same artery of Nomega-nitro-L-arginine methyl ester (L-NAME). After blockade of alpha-adrenergic receptors, insulin infusion caused an increase in renal blood flow which averaged 18.1% of the control values, being significantly enhanced with respect to the increase previously obtained in the same pigs. On the contrary, after blockade of nitric oxide formation insulin infusion caused a decrease in renal blood flow which averaged 6.5% of the control values. These responses were respectively abolished by the subsequent injection into the renal artery of L-NAME and phentolamine. The present study showed that the renal vasodilation caused by insulin in the anesthetized pig was the result of two opposite effects which involved a predominant vasodilation mediated by the release of nitric oxide from the endothelium and a sympathetic vasoconstrictor mechanism mediated by alpha-adrenergic receptors.

Trends in psychiatric inpatient rates from 1991-1995 in the State of Washington: the effect of insurance type on utilization

This study examined whether there have been changes in inpatient psychiatric use among publicly and privately insured patients by analyzing trends in adult psychiatric hospitalizations from 1991 through 1995 in the State of Washington. A state-wide Comprehensive Hospital Abstract Reporting System (CHARS) was used to track psychiatric hospital utilization patterns. The results show a significant growth in psychiatric hospitalizations among the publicly insured patients due to their high proportion of severe and persistent mental illness. There was a flat trend in psychiatric hospitalizations suggesting that private insurers aggressively monitor the costly use of hospitalizations for mentally ill patients.

Impact of HMO ownership on management processes and utilization outcomes

OBJECTIVE

To examine the effects of health maintenance organization (HMO) ownership characteristics on selected utilization outcomes and management processes affecting utilization.

STUDY DESIGN

We used 1995 HMO data from the American Association of Health Plans.

PATIENTS AND METHODS

Using regression analysis, we examined the relation between HMO utilization (hospital discharges, days, and average length of stay; cardiac catheterization procedures; and average cost of outpatient prescriptions) and the structural characteristics of HMOs: ownership type (insurance company, hospital, physician, independent, and national managed care company), HMO size, for-profit status, model type, geographic region, and payer mix.

RESULTS

HMO ownership type is significantly associated with medical management processes, including risk sharing by providers, risk sharing by consumers, and other management strategies. Relative to hospital-owned HMOs, insurance company-owned HMOs have fewer hospital discharges, fewer hospital days, and longer lengths of stay. National managed care organization-owned HMOs have fewer cardiac catheterizations and lower average outpatient prescription costs. Independently owned HMOs have more cardiac catheterizations. For-profit HMOs have lower prescription costs. Relative to hospital-owned HMOs, insurance company-owned HMOs are more likely to use hospital risk sharing and provider capitation and less likely to use out-of-pocket payments for hospital use and a closed formulary. National managed care organization-owned HMOs are less likely to use provider capitation, out-of-pocket payments for hospital use, catastrophic case management, and hospital risk sharing. Physician-hospital-owned HMOs are less likely to use catastrophic case management. For-profit HMOs are more likely to use hospital risk sharing and catastrophic case management.

CONCLUSION

HMO ownership type affects utilization outcomes and management strategies.

The effect of progesterone on coronary blood flow in anaesthesized pigs

The present study was designed to investigate the effect of progesterone on the coronary circulation and to determine the mechanisms involved. In pigs anaesthetized with sodium pentobarbitone, changes in left circumflex or anterior descending coronary blood flow caused by intravenous infusion of progesterone at constant heart rate and arterial blood pressure were assessed using an electromagnetic flowmeter. In 14 pigs, infusion of 1 mg h(-1) of progesterone caused an increase in coronary blood flow without affecting left ventricular dP/dtmax (rate of change of left ventricular systolic pressure) and filling pressures of the heart. In a further four pigs, this vasodilatory coronary effect was enhanced by graded increases in the dose of the hormone of between 1, 2 and 3 mg h(-1). The mechanisms of the above response were studied in the 14 pigs by repeating the experiment after haemodynamic variables had returned to the control values observed before infusion. In six pigs, blockade of muscarinic cholinoceptors and adrenoceptors with atropine, propranolol and phentolamine did not affect the coronary vasodilatation caused by progesterone. In the remaining eight pigs, this response was abolished by intracoronary injection of N(omega)-nitro-L-arginine methyl ester (L-NAME) even when performed after reversing the increase in arterial blood pressure and coronary vascular resistance caused by L-NAME with continuous intravenous infusion of papaverine. The present study showed that intravenous infusion of progesterone primarily caused coronary vasodilatation. The mechanism of this response was shown to involve the endothelial release of nitric oxide.

Effect of distension of the gallbladder on plasma renin activity in anesthetized pigs

BACKGROUND

Gallbladder pathology has been associated with cardiovascular disease. Recently, we showed that gallbladder distension in anesthetized pigs reflexly increased heart rate, arterial pressure, and coronary and renal vascular resistance through efferent sympathetic mechanisms. Renin release is affected by sympathetic output, and angiotensin liberation may result in vasoconstriction. This study was undertaken to determine whether gallbladder distension primarily causes a reflex change in plasma renin activity (PRA) and to assess its influence on observed pressor and coronary responses as well as on regional vascular resistance.

METHODS AND RESULTS

In 34 alpha-chloralose-anesthetized pigs, balloons positioned within the gallbladder were distended for 30 minutes with volumes of Ringer's solution equal to those of withdrawn bile. In 19 pigs, gallbladder distension at constant heart rate, arterial pressure, and renal flow increased PRA in the absence of changes in urinary sodium excretion. This increase was abolished by cervical vagotomy, section of renal nerves, or blockade of beta-adrenergic receptors. In another 15 pigs, blockade of angiotensin II receptors significantly attenuated the pressor and coronary, mesenteric, and iliac vasoconstriction responses to gallbladder distension.

CONCLUSIONS

The present study showed that innocuous gallbladder distension primarily caused a reflex increase in PRA. This increase, which involved afferent vagal pathways and efferent sympathetic mechanisms related to beta-adrenergic receptors, contributed significantly to the pressor and coronary, mesenteric, and iliac vasoconstriction responses to gallbladder distension.

The role of nitric oxide in the coronary vasoconstriction caused by growth hormone in anaesthetized pigs

Intravenous injection of growth hormone in anaesthetized pigs has been shown to cause coronary vasoconstriction by antagonizing the vasodilatory effects of 2-adrenergic receptors. Because nitric oxide is believed to modulate or mediate 2-adrenergic effects, the present study was undertaken in the same experimental model to determine the role of nitric oxide in the above response to growth hormone. In fourteen pigs anaesthetized with sodium pentobarbitone, changes in left circumflex or anterior descending coronary blood flow caused by intravenous injection of 0.05 i.u. kg-1 of growth hormone at constant heart rate and arterial blood pressure were assessed using electromagnetic flowmeters. In a first control group of six pigs, growth hormone caused a decrease in coronary blood flow which averaged 13.1 % of the baseline values. In a second group of eight pigs, intravenous administration of N-nitro-L-arginine methyl ester (L-NAME) was used to block the endothelial release of nitric oxide. In these pigs, the subsequent injection of growth hormone did not cause any significant changes in coronary blood flow, even when performed after reversing the increase in arterial blood pressure and coronary vascular resistance caused by L-NAME with continuous intravenous infusion of papaverine. These results indicated that the coronary vasoconstricting effect of growth hormone, known to involve antagonism of 2-adrenergic vasodilatory effect, was mediated by inhibition of nitric oxide release.

Role of nitric oxide in the control of the heart rate within the nucleus ambiguus of rats

The aim of this study was to determine whether NO plays a role in the control of heart rate (HR) within the nucleus ambiguus (NA). Experiments were performed in 29 male Wistar rats anaesthetized with urethane. Microinjections of the NO-donor sodium nitroprusside (SNP; 5 mmol) as well as of L-arginine (L-arg; 50 mmol) into functionally identified cardioinhibitory sites within the NA significantly decreased HR (-57.7 +/- 8.4 and -53.8 +/- 3.2 bpm, respectively), whereas the NO-synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) significantly increased HR (+40 +/- 2.7 bpm). Bilateral vagotomy and i.v. injection of atropine (0.5mg/kg) always abolished the HR decrease induced by SNP and L-arg, whereas propranolol did not affect the HR responses. These results demonstrated that NO mechanisms within the NA play a role in the parasympathetic control of the HR.

The role of beta 2-adrenergic vascular receptors in the peripheral vasodilation caused by 17 beta-estradiol in anesthetized pigs

It has been previously shown in anesthetized pigs that intravenous infusion of 2 microg/h of 17beta-estradiol primarily dilated renal, iliac and coronary circulations, while higher doses of the hormone were required to cause vasodilation also in the mesenteric vascular bed. In the same experimental model, a tonic beta2-adrenoceptor mediated vasodilation, which could be argued to attenuate the vasodilator effect of 17beta-estradiol, has been described. The present study was planned to investigate the role of beta2-adrenergic receptors in the hemodynamic responses of renal and mesenteric vascular beds to 17beta-estradiol. Changes in flow caused by intravenous infusion of 2 microg/h of the hormone at constant heart rate and aortic blood pressure in the left renal and superior mesenteric arteries were assessed using electromagnetic flowmeters. In six pigs, infusion of 17beta-estradiol caused an increase in renal blood flow, which averaged 12.1% of the control values, without affecting mesenteric blood flow. In the same pigs, after hemodynamic variables had returned to the baseline values, blockade of beta2-adrenergic receptors with butoxamine caused an increase in aortic blood pressure and an increase in renal and mesenteric resistance. The subsequent infusion of 17beta-estradiol elicited increases in renal and mesenteric blood flow which respectively averaged 19.6% and 12.8%. Therefore, the present study in anesthetized pigs have shown that the vasodilator responses of the renal and mesenteric circulations to 17beta-estradiol were attenuated and even masked by a tonic beta2-adrenoceptor mediated vasodilation. This indicates that some vasodilator effects elicited by normally used replacement doses of the hormone may not be apparent.

Coronary effects of cyclovirobuxine D in anesthetized pigs and in isolated porcine coronary arteries

The present study was undertaken in anesthetized pigs and in isolated porcine coronary arteries to determine the primary coronary effects of cyclovirobuxine D. In six pigs, the intravenous administration of 1.5 mg/kg of cyclovirobuxine D whilst preventing changes in heart rate and aortic blood pressure caused increases in left ventricular dP/dtmax and coronary blood flow which respectively averaged 10% and 23.9%. These responses were progressively augmented by graded increases in the dose of the drug (four pigs) and were not affected by blockade of cholinergic and adrenergic receptors (five pigs). Intravenous blockade of nitric oxide synthase (L-NAME, five pigs) abolished both responses, while intracoronary injection of L-NAME (five pigs) abolished only the coronary vasodilatation. In ten isolated coronary segments, cyclovirobuxine D significantly reduced the degree of potassium chloride-induced contraction. This reduction was not affected by inhibition of cyclooxygenase with indomethacin (five segments) or potassium channels blockade with glibenclamide (five segments), but it was abolished by L-NAME (five segments) or removal of endothelium (five segments). The present study showed that cyclovirobuxine D caused a primary effect of coronary vasodilatation, which involved mechanisms related to the endothelial release of nitric oxide.

The effect of 17beta-oestradiol on regional blood flow in anaesthetized pigs

1. The present study was designed to investigate the effects of 17beta-oestradiol on the mesenteric, renal, iliac and coronary circulations and to determine the mechanisms involved. 2. In pigs anaesthetized with sodium pentobarbitone, changes in blood flow in the superior mesenteric, left renal, left external iliac and left circumflex coronary arteries caused by intravenous infusion of 17beta-oestradiol at constant heart rate and arterial pressure were assessed using electromagnetic flowmeters. 3. In eight pigs, infusion of 2 microg h-1 of the hormone caused an increase in renal, iliac and coronary blood flow without affecting mesenteric blood flow, left ventricular dP/dtmax (rate of change of left ventricular systolic pressure) and filling pressures of the heart. In four pigs, these vasodilator effects were enhanced by graded increases in the dose of the hormone between 1, 2 and 3 microg h-1; the highest dose also caused an increase in mesenteric blood flow. 4. In five pigs, blockade of muscarinic cholinoceptors and adrenoceptors with the intravenous administration of atropine, propranolol and phentolamine did not affect the vasodilator responses caused by infusion of 2 microg h-1 of 17beta-oestradiol. 5. The increases in renal, iliac and coronary blood flow caused by infusion of 2 microg h-1 of 17beta-oestradiol were prevented, respectively, by the injection of Nomega-nitro-L-arginine methyl ester (L-NAME) into the renal artery (five pigs), the iliac artery (five pigs) or the coronary artery (five pigs). In five pigs, all responses were prevented by injection of L-NAME into all three arteries. In two pigs, injection of L-NAME into the mesenteric, renal, iliac and coronary arteries abolished the vasodilator responses to the infusion of 3 microg h-1 of 17beta-oestradiol. 6. The present study shows that intravenous infusion of 2 microg h-1 of 17beta-oestradiol primarily dilated renal, iliac and coronary circulations and that a higher dose of the hormone also caused vasodilatation in the mesenteric vascular bed. The mechanism of these responses was shown to be nitric oxide dependent.

The effect of distension of the uterus on plasma renin activity (PRA) in anaesthetized pigs

It has recently been shown that distension of the uterus in anaesthetized pigs causes reflex haemodynamic responses through efferent sympathetic mechanisms. The present study was undertaken to determine whether these mechanisms include activation of the renin-angiotensin system. The same methods were used in 14 pigs which were anaesthetized with alpha-chloralose and artificially ventilated. Balloons positioned within the uterus were distended for periods of 30 min by injecting 20 ml of warm Ringer solution. The responses of arterial blood pressure and heart rate were respectively prevented by blockade of alpha-adrenergic receptors with phentolamine and atrial pacing. Changes in plasma renin activity (PRA) were assessed during the last minute of distension by radioimmunoassay of angiotensin I. In each of 10 pigs, distension of the uterus (mean uterine transmural pressure of 17 mmHg) caused an increase in PRA in the absence of changes of interfering haemodynamic variables. In the remaining four pigs, this response was graded by step increments of the distension. The increase in PRA caused by uterine distension was abolished by bilateral section of the renal nerves (five pigs) or by blockade of beta-adrenergic receptors with propranolol. The present study showed that distension of the uterus in anaesthetized pigs primarily caused a reflex increase in PRA. This reflex response was mediated by renal nerves and involved beta-adrenergic receptors.

Gains from public-private collaborations to improve community health

In several disciplines there exists theoretical and empirical evidence to show that community affects health and behaviors; but to date such evidence has remained largely outside the health services field. In this article, the authors introduce and contribute to this evidence and then discuss how those in the healthcare sector can work to increase public-private collaborations. Telephone survey data collected in 1995 from 1,826 randomly selected residents of a Northwest urban county were used in multivariate analysis to assess the relationship between community quality and health status. Community quality was measured by residents' perceptions of community problems. Findings indicate that individual ratings of community problems predicted mental health functioning. This effect was found overall and for men and women separately. These results suggest that health is dependent on how people perceive the quality of their community. Leadership and vision can make an enormous difference in the quality of a community health system and in the cost-effectiveness of the care provided. Healthcare leaders can develop their understanding of their community and the impact of community characteristics on health through consultation with experts, input from community leaders, and visits to the neighborhoods that surround the delivery services. Community networks can be developed with the common focus of improving the community's health. Collaborative efforts between the private health sector, the public health sector, and community members can enhance social relationships and thus promote the health of residents.

The relationship of community quality to the health of women and men

Using a 1996 community survey of behavioral risk factors, this cross-sectional study of 804 residents in a rural community examines the relationship of community quality to the health status of women and men. We use two categories of community factors to assess community quality: measures of the social quality of community life, and measures of community quality that focus on the physical environment. Health status is assessed by four measures that examine perceived health status and functioning. Regression results indicate that there is a significant relationship between the quality of the community and health status for both women and men. Specifically, women's perceptions about the social quality of their community are positively associated with their perceived health status and functioning; furthermore, these relationships are significantly different from those of men. Men's perceptions of their physical environment are significantly related to their reported functioning and health, to a limited extent these relationships are different from women. These relationships support our hypothesis that gender differentially affects the relationship between community quality and health.

Haemodynamic effects of the intravenous administration of growth hormone in anaesthetized pigs

Administration of growth hormone in humans has been reported variably to affect arterial blood pressure and ventricular contractility. The present study was undertaken in anaesthetized pigs to establish whether increases in the blood levels of growth hormone primarily affect haemodynamic variables and to determine the mechanisms involved. In pigs anaesthetized with pentobarbitone sodium, left circumflex or anterior descending coronary blood flow was measured with an electromagnetic flowmeter. In a first group of 23 pigs, growth hormone administration (0.05 IU kg-1 i.v.) increased aortic blood pressure and reduced coronary blood flow when heart rate and aortic blood pressure were held constant. These responses were augmented by graded increases in plasma levels of growth hormone. The mechanisms of the above responses were studied in a second group of 29 pigs and involved beta2-adrenergic receptors since they were abolished by propranolol or butoxamine but not by atropine, phentolamine or atenolol. The present study showed that administration of growth hormone in anaesthetized pigs primarily increased aortic blood pressure and vasoconstricted the coronary circulation. The mechanisms of these responses involved beta2-adrenoceptor effects.

[Twelve years of ureterorenoscopy: evolution of the technique]

In the last ten years the diagnostic and therapeutical approach to ureteral neoplasms and stones changed their feature, due to improvement of the ureteroscopy. The passage through flexible to rigid and finally semirigid ureteroscopes permitted reduction of invasiveness with higher results. The positive changes to the energy sources, in regard to cost-benefit, it was versus ballistic energy. Ureteroscopy should now be considered as a simple and safe technique, with minimal morbidity and invasiveness and also short operative times.

The effects of combined distension of the stomach and the descending colon on coronary blood flow in anaesthetized pigs

The effects of the combined distension of the stomach and the descending colon on coronary blood flow were examined in seven alpha-chloralose anaesthetized pigs whilst preventing changes in heart rate and aortic blood pressure. Changes in coronary blood flow in the left circumflex or anterior descending coronary artery were assessed using electromagnetic flowmeters during distension with Ringer solution of balloons positioned in the viscera. In a first set of studies, graded distension of the stomach with distending volumes of 0.8, 1.1 and 1.4 l always caused graded decreases in coronary blood flow. The additional distension of the descending colon at a distending volume of 0.25 l augmented the response of decrease in coronary blood flow caused by the first two levels of gastric distension, but it did not have any further effect when added to the higher level of gastric distension. Similar results were obtained in a second set of studies in which distension of the stomach at a volume of 0.8 l was additionally performed during graded distension of the descending colon with distending volumes of 0.25, 0.35 and 0.45 l. These effects elicited by combined distension of the two viscera were not affected by the administration of propranolol, but they were abolished by subsequent administration of phentolamine. The results showed that combined distension of the stomach and the descending colon in anaesthetized pigs augmented the reflex response of coronary vasoconstriction and that the response to distension of one viscus was attenuated during increased levels of distension of the other viscus. These combined responses to distension of the two viscera involved efferent sympathetic mechanisms related to alpha-adrenoceptors.

Hemodynamic effects of the intravenous administration of cyclovirobuxine D [correction of cyclorirobuxine D] in anesthetized pigs

The present study was undertaken in anesthetized pigs to determine the primary effects of cyclovirobuxine D [corrected] given intravenously on hemodynamic variables. In eight pigs, the administration of 1.5 mg/kg of cyclovirobuxine D [corrected] caused a small increase in aortic blood pressure. When this response was prevented, a decrease in heart rate was obtained in each of the eight pigs. When this response was also prevented, an increase in the maximum rate of change of left ventricular systolic pressure (left ventricular dP/dtmax) was observed. In four pigs, the decrease in heart rate and the increase in left ventricular dP/dtmax were progressively augmented by graded increases in the dose of cyclovirobuxine D [corrected]. In six pigs, the responses of hemodynamic variables to cyclovirobuxine D [corrected] were not affected by blockade of cholinergic and adrenergic receptors. In a further six pigs, blockade of nitric oxide synthase with N omega-nitro-L-arginine methyl ester did not affect the decrease in heart rate caused by the drug, but abolished the increases in left ventricular dP/dtmax and aortic blood pressure. The present study showed that intravenous administration of cyclovirobuxine D [corrected] primarily caused a decrease in heart rate and an increase in left ventricular inotropic state, which secondarily determined an increase in aortic blood pressure, and suggested that the response of heart rate involved a direct effect of the drug on the heart, while the response of left ventricular contractility was related to mechanisms dependent on the release of nitric oxide.

Changes in regional blood flow in response to distension of the uterus in anaesthetised pigs

The present study was undertaken in anaesthetised pigs to determine the primary reflex effects of distension of the uterus on the peripheral circulation. Experiments were performed in seven pigs anaesthetised with alpha-chloralose and artificially ventilated. Blood flow in the superior mesenteric, left renal and left external iliac arteries was assessed using electromagnetic flowmeters. Distension of the uterus was performed whilst preventing changes in heart rate and aortic blood pressure by injecting 20 ml of warm Ringer solution in a balloon positioned within the viscus (mean transmural pressure of about 18 mmHg). In each pig, distension of the uterus caused decreases in all measured blood flows. In four pigs, these decreases were graded by step increments of distension. In the seven pigs, the responses of decrease in mesenteric, renal and iliac blood flows were not affected by blockade of beta-adrenergic receptors with propranolol, but were abolished by the subsequent blockade of alpha-adrenergic receptors with phentolamine. The present study showed that distension of the uterus in anaesthetised pigs primarily caused reflex vasoconstriction in the mesenteric, renal and iliac vascular beds. This reflex response was mediated by sympathetic mechanisms which involved alpha vascular adrenergic receptors.

The effects of CEO-board relations on hospital performance

This article assesses the relationship between CEO-board relations and hospital financial performance. A study of 90 acute care California hospitals examined changes in the relations between the CEO and governing board over two time periods in 1985 and 1989. The results show that CEO-board participation is an effective governance mechanism that significantly enhances hospital performance.

Reflex haemodynamic responses caused by distension of the uterus in anaesthetized pigs

The present study was undertaken in anaesthetized pigs to determine whether distension of the uterus reflexly affects the aortic blood pressure, heart rate, left ventricular inotropic state and the coronary circulation. Experiments were performed in 17 pigs anaesthetized with alpha-chloralose and artificially ventilated. Coronary blood flow was measured with an electromagnetic flowmeter positioned around the origin of the left circumflex coronary artery. The uterus was distended by injecting 20 ml warm Ringer solution into a balloon positioned within the uterus (mean transmural pressure of about 17 mmHg). Distension of the uterus without controlling any haemodynamic variable caused an increase in aortic blood pressure. When this response was prevented, an increase in heart rate was obtained in each animal. When the heart rate and blood pressure responses were prevented, the distension did not cause significant changes in the maximum rate of change of left ventricular pressure, but always caused a decrease in mean coronary blood flow. In five pigs, the increase in heart rate and the decrease in mean coronary blood flow were graded by step increments of distension. In six pigs, the haemodynamic responses to distension of the uterus were not affected by the administration of atropine. In 12 pigs, which included the six given atropine, the increase in heart rate was abolished by the administration of propranolol and the increase in aortic blood pressure and the decrease in mean coronary blood flow were abolished by the subsequent administration of phentolamine. In the remaining five pigs, the haemodynamic responses caused by uterine distension were abolished by the administration of bretylium tosylate. The present study showed that distension of the uterus in anaesthetized pigs primarily caused reflex increases in heart rate and aortic blood pressure and coronary vasoconstriction. These reflex responses were mediated by efferent sympathetic mechanisms.

Reflex coronary vasoconstriction caused by gallbladder distension in anesthetized pigs

BACKGROUND

Gallbladder distension in anesthetized pigs reflexly increases heart rate and arterial pressure by means of afferent vagal pathways and efferent sympathetic mechanisms. The effect of such distension on the coronary circulation is unknown. The present study was undertaken to determine whether gallbladder distension primarily causes reflex changes in left circumflex blood flow.

METHODS AND RESULTS

In 21 pigs anesthetized with sodium pentobarbitone (16) or alpha-chloralose (5), left circumflex blood flow was measured with an electromagnetic flowmeter. A balloon positioned within the gallbladder was distended with volumes of Ringer's solution equal to the volumes of bile previously withdrawn (mean vol: 62 mL; mean gallbladder pressure: 12 mm Hg). Heart rate and arterial pressure were kept constant by atrial pacing and by a pressurized reservoir connected to the left femoral artery. Gallbladder distension always caused a decrease in circumflex blood flow. In 6 of the 16 sodium pentobarbitone-anesthetized pigs, this decrease was graded by step increments of distension. In 5 of these 16 pigs, the decrease in circumflex blood flow was not affected by atropine. In 10 of these 16 pigs, including those given atropine, the response was not affected by propranolol but was abolished by subsequently giving phentolamine. Cervical vagotomy abolished the coronary vasoconstriction in the remaining 6 pigs. In the 5 alpha-chloralose-anesthetized pigs, the response was not significantly affected by cutting the splanchnic nerves but was abolished by subsequent cervical vagotomy.

CONCLUSIONS

The present study showed that innocuous distension of the gallbladder in anesthetized pigs caused a reflex coronary vasoconstriction that involved efferent sympathetic mechanisms related to alpha-adrenoceptors and afferent vagal pathways.

Influence of GABAergic mechanisms on baroreceptor inputs to nucleus tractus solitarii of rats

The firing frequency of baroreceptive neurons in the nucleus tractus solitarii (NTS) during microiontophoretic application of muscimol, a gamma-aminobutyric acid (GABA)A agonist, or baclofen, a GABAB agonist, was monitored in anesthetized rats. Muscimol decreased the spontaneous discharge of 69 of 73 (94.5%) NTS baroreceptive neurons without affecting the remaining four neurons (5.5%). The statistical comparison on a bin-by-bin basis of the peri-R wave interval histograms of the discharge of each NTS neuron showed that the inhibitory action of muscimol was always exerted on the whole neuronal discharge independently of its correlation to the cardiac cycle. Baclofen inhibited 60 of 73 (82.2%) NTS neurons without affecting the remaining 13 neurons (17.8%). In 31 of 60 (51.7%) neurons inhibited by baclofen, this substance significantly affected only pulse-synchronous peaks of neuronal discharge without significant inhibition of the neuronal firing between cardiac cycle-related peaks. Fifty-eight of 73 (79.5%) NTS neurons studied were inhibited by both muscimol and baclofen, 11 neurons (15%) only by muscimol, 2 neurons (2.7%) only by baclofen, and 2 neurons (2.7%) were unaffected by both substances. These results demonstrate that both GABAA and GABAB receptors mediate inhibition of the spontaneous discharge in the great majority of the NTS baroreceptive neurons studied and suggest different functions of the two types of GABA receptors in influencing baroreceptor inputs to the NTS.

The effect of distension of the stomach on peripheral blood flow in anaesthetized pigs

The present study was undertaken in anaesthetized pigs to determine the primary reflex effects of gastric distension on the peripheral circulation. Changes in blood flow in the splenic, superior mesenteric, left renal and left external iliac arteries were assessed using electromagnetic flowmeters during distension of a balloon in the stomach, performed at constant aortic blood pressure and heart rate, with 0.6 l of Ringer solution (mean gastric transmural pressure of about 12 mmHg). In fourteen pigs, a decrease in splenic, renal and iliac flows and variable changes in mesenteric flow were obtained. A decrease in mesenteric flow and more marked decreases in the other flows occurred in response to the distension after the administration of propranolol or butoxamine. In five pigs, the vasoconstrictive responses were graded by step increments in gastric distending volume from 0.4 to 0.8 l. The above responses were abolished by the administration of phentolamine (eight pigs) and by bilateral cervical vagotomy (six pigs). The results showed that innocuous distension of the stomach in anaesthetized pigs reflexly caused vasoconstriction in the splenic, renal and iliac vascular beds; vasoconstriction also occurred in the mesenteric vascular bed but only after beta-blockade. These reflex responses were mediated by sympathetic mechanisms which involved both alpha and beta vascular adrenoceptors and their afferent limb was in the vagal nerves.

Ontogeny of CD40L [corrected] expression by activated peripheral blood lymphocytes in humans

The CD40 ligand (CD40L) is a molecule expressed by activated T cells which plays a critical role in the regulation of B-cell responses, including differentiation into Ig-producing cells. Using the specific monoclonal antibody TRAP1 we have evaluated the ontogeny of CD40L expression in 97 normal individuals between birth and 50 years of age. The expression of CD40L is a function of age; it is severely reduced at birth, progressively increases during the first months of life, and reaches a plateau in the second decade. This progressive attainment of the ability to express CD40L is due to a process of maturation of the CD4 + subset, being significantly correlated with the expression of the CD45RO antigen.

Role of ventrolateral medulla in reflex cardiovascular responses to activation of skin and muscle nerves

Central neuronal circuits mediating reflex cardiovascular responses to skin and muscle nerve stimulation were studied in rats under urethan anesthesia. Responses of right rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM) cardiovascular neurons to stimulation of contralateral skin and muscle afferent fibers were investigated. Stimulation of the tibial (muscle) nerve excited 19 (86%) of 22 CVLM neurons and inhibited 18 (82%) of 22 RVLM neurons. Stimulation of the sural (skin) nerve excited 20 (91%) of the 22 RVLM neurons but did not affect the firing rate of any of the 22 CVLM neurons. Electrolytic lesions of the CVLM abolished the depressor responses induced by stimulation of the tibial nerve without affecting the pressor response caused by sural nerve stimulation. Similarly, reversible blockade of the CVLM by microinjection of gamma-amino-butyric acid or CoCl2 abolished the depressor response to stimulation of the tibial nerve without affecting the pressor response induced by sural nerve stimulation. These results suggest that vasodepressor responses to muscle nerve activation are mediated by a neuronal inhibitory pathway to the RVLM relayed through the CVLM.

Changing pattern of pathogens causing broviac catheter-related bacteraemias in children with cancer

The incidence of pathogens causing catheter-related bacteraemias in children undergoing antineoplastic chemotherapy with or without bone marrow transplantation at G. Gaslini Children's Hospital, Genoa, Italy, was analysed by comparing data from a retrospective study (1985-1988) with that obtained from a prospective one (1989-1992). In both periods catheter-related bacteraemias one (1989-1992). In both periods catheter-related bacteraemias were more frequent in non-neutropenic than in neutropenic patients. Among catheter-unrelated bacteraemias the pattern of infecting pathogens remained unchanged between the study periods, with Gram-positive bacteria remaining the predominant pathogens. Conversely, among catheter-related bacteraemias, the incidence of Gram-negative bacilli increased significantly from 3 to 38%, and that of Gram-positive bacteria fell from 63 to 32% (P = 0.001, chi 2 test for heterogeneity.

Does the hospital board need a doctor? The influence of physician board participation on hospital financial performance

In this study, the authors attempted to determine if physician board participation enhances or impairs the operational performance of a hospital. Two theories--managerialism and agency theory--are compared to determine if participation on the hospital board by inside (i.e., medical staff) and outside physicians provides informational advantages (managerialism) or poses the threat for opportunism (agency theory). Using hospital operating margin to measure hospital performance for a 4-year period (1985-1988), the findings indicate that boards with inside physician (medical staff) participation had significantly better performance than those without such physician participation. Supportive of the managerialist perspective, the findings strongly suggest that medical staff board participation can enhance operational performance. Implications of physician-hospital relations for future hospital strategies as well as health care reform issues are discussed.

Hospital board effectiveness: relationships between governing board composition and hospital financial viability

OBJECTIVE

Two theories--agency and managerialism--are compared with respect to their usefulness in explaining the role of insiders on the hospital board: whether their participation enhances or impairs board financial decision making.

DATA SOURCES/STUDY SETTING

The study used 1985 hospital financial and governing board data for a representative sample of acute care California hospitals.

STUDY DESIGN

Relationships were examined cross-sectionally between the presence or absence of insiders on the board and measures of hospital financial viability while controlling for the organizational factors of system affiliation, ownership, size, region, and corporate restructuring.

PRINCIPAL FINDINGS

Multiple regression analysis found significant relationships between insider (CEO, medical staff) participation and hospital viability.

CONCLUSIONS

These results support the managerial theory of governance by suggesting that the CEO and medical staff provide informational advantages to the hospital governing board. However, the cross-sectional design points to the need for future longitudinal studies in order to sequence these relationships between insider participation and improved hospital viability.

Somatic and visceral inputs to neurons of the rostral ventrolateral medulla

Sympathoexcitatory neurons in the rostral ventrolateral medulla (RVLM) play an essential role in the generation of basal sympathetic tone and in the reflex regulation of blood pressure. In this study responses of RVLM "cardiovascular" neurons to somatic and visceral afferent stimulation were investigated. The activity of 34 RVLM neurons was recorded in urethan-anesthetized paralyzed and artificially ventilated rats. These neurons were identified as cardiovascular based on their baroreceptor sensitivity and their pulse-synchronous discharge. Electrical stimulation of the sciatic nerve excited 31 of the 34 RVLM units (91%). Renal nerve stimulation inhibited firing of 14 of 22 RVLM neurons tested (64%), not affecting the remaining 8 units. Stimulation of splenic nerves inhibited the discharge of 7 of 12 RVLM neurons tested (58%), whereas the remaining 5 units were not affected. All RVLM units responsive to visceral afferent stimulation were also responsive to sciatic nerve stimulation. These results indicate that RVLM cardiovascular neurons receive somatic and visceral inputs, suggesting an involvement of these units in the integration of homeostatic responses to changes in the internal and external environment.

Hospital board effectiveness: relationships between board training and hospital financial viability

This study examined whether hospital governing boards that invest in board education and training are more informed and effective decision-making bodies. Measures of hospital financial viability (i.e., selected financial ratios and outcomes) are used as indicators of hospital board effectiveness. Board participation in educational programs was significantly associated with improved profitability, liquidity, and occupancy levels, suggesting that investment in the education of directors is likely to enhance hospital viability and thus increase board effectiveness.

Neuronal and cardiovascular responses to ANF microinjected into nucleus ambiguous

Effects of microinjection of atrial natriuretic factor (ANF) into cardioinhibitory sites in the nucleus ambiguous (NA) or on single vagal cardioinhibitory neurons (VCN) were investigated in urethan-anesthetized rats. Sites containing cardioinhibitory neurons were identified by observing a marked and reproducible bradycardia in response to microiontophoretically applied (20-40 nA) or microinjected (20 nl) 0.1 M L-glutamate. In 35 of the 40 (87.5%) cardioinhibitory sites identified by microinjection of glutamate, ANF (20 nl of 10(-7) M) decreased heart rate (HR; -47.1 +/- 2.5 beats/min). No responses were elicited in the other five sites. In animals paralyzed and artificially ventilated, the HR effects of ANF were not significantly different before and after muscle paralysis. Microinjections of 10 nl of 10(-7) M ANF caused excitation of 19 of 21 VCN (90%), which was followed by a decrease in HR (-20.8 +/- 2.3 beats/min); no neuronal or cardiovascular responses were elicited by ANF in the remaining two VCN. Bilateral vagotomy or atropine sulfate (1 mg/kg iv) abolished cardiac slowing without affecting neuronal activation, whereas propranolol (2 mg/kg iv) did not affect either response to ANF. These results suggest that ANF is a neuromediator involved in the excitation of cardioinhibitory neurons in the NA.

Actions of 3 alpha,5 alpha-tetrahydrodeoxycorticosterone on single neurones of the mesencephalic reticular formation in the rat

The effects of microinjections of 3 alpha,5 alpha-tetrahydrodeoxycorticosterone (3 alpha-THDOC) on single neurones of the mesencephalic reticular formation (MRF) were investigated in rats anaesthetized with urethan. Microinjections of approximately 100 nl of 0.5-2 microM 3 alpha-THDOC inhibited firing of 105 of 112 neurones (94%). Microinjections of approximately 100 nl of 100-250 nM of 3 alpha-THDOC did not alter neuronal activity, but in 52 of 68 cases (76%) it potentiated the inhibitory action of microiontophoretically applied gamma-aminobutyric acid (GABA). The 3 beta-isomer of tetrahydrodeoxycorticosterone did not elicit any changes in neuronal firing. The effects of 3 alpha-THDOC were reversibly antagonized by microiontophoretically applied bicuculline. This 'in vivo' study supports the hypothesis that 3 alpha-THDOC may function as endogenous modulator of GABAA-mediated inhibition in various physiopathological conditions.

Neuronal and cardiovascular responses to ANF microinjected into the solitary nucleus

The effect on single-unit activity, arterial pressure, and heart rate of a microinjection of atrial natriuretic factor (ANF) into 78 histologically verified sites in the nucleus tractus solitarii (NTS) was investigated in rats. Injections of 50 nl of 10(-7) M ANF excited 34 neurons (44%), mainly localized at the level of the obex, inhibited 15 (19%), and had no effect on the remaining 29 (37%). The increase in firing frequency of the 34 excited neurons was always followed by a decline in mean arterial pressure [MAP, -10.6 +/- 1.8 (SE) mmHg; P less than 0.01] and heart rate [HR, -9.6 +/- 3.1 (SE) beats/min; P less than 0.05]. When injections of ANF caused either no effect or inhibition of single-unit activity, no changes in either MAP or HR were observed. Single units excited by injections of ANF were also excited by activation of arterial baroreceptors and inhibited by baroreceptor unloading. Control injections of an inactive peptide analogue of ANF or of vehicle never produced any effects on neuronal firing frequency or on MAP and HR. Similar results were obtained from animals paralyzed and artificially ventilated. These results support the hypothesis that ANF plays a role in the chemical transmission of baroreceptor information within the NTS.

Effects of corticosterone on neurones of the locus coeruleus, in the rat

The effects of microelectrophoretic application of corticosterone (CS) on single neurones of the locus coeruleus (LC) were investigated in rats under urethane anaesthesia. Ejecting currents generally ranged from 10 to 60 nA. CS produced an excitatory effect in 73% of the neurones and no effect in 27%. The prevailingly excitatory effects induced by CS on LC neurones may be related to the regulation of those complex events, which constitute the 'stress response'.