Biomedical subjects

H Hosomi

Publications and source records attributed to H Hosomi.

At least 19 recordsLinked to original sources

PubMed1992

Renojejunal reflex controlling jejunal absorption of fluid and NaCl.

The aim of this study was to elucidate renojejunal reflex controlling the net jejunal fluid, Na+, and Cl- absorption in response to an increased ureteropelvic pressure (UPP) in anesthetized dogs. Unilateral UPP was increased under hydrostatic pressure from 0 to 80 mmHg by a step of 20 mmHg in random order, while the contralateral UPP was maintained at around 0 mmHg. The net absorption of fluid, Na+, and Cl- decreased in proportion to increased UPP. At a UPP of 0 mmHg, the net jejunal fluid, Na+, and Cl- absorption were 11.1 +/- 0.4 ml, 2.48 +/- 0.07, and 1.98 +/- 0.05 mEq, and significantly decreased to 7.38 +/- 0.6 ml, 2.11 +/- 0.15, and 1.68 +/- 0.13 mEq by an increase of UPP to 40 mmHg, respectively. An increase of bilateral UPP up to 40 mmHg or more occlusively depressed the absorption. These responses were blocked by renal denervation and by administration of atropine but not by yohimbine. These results indicate that the increase of UPP decreases jejunal fluid, Na+, and Cl- absorption (renojejunal reflex), and that the afferent and efferent limbs of this reflex are the renal nerves and cholinergic fibers. This renojejunal reflex might play an important role in body fluid homeostasis under the pathological condition.

Animals↗

PubMed1992

Effects of atherosclerosis on mean and daily variation of arterial pressure in conscious WHHL rabbits.

Effects of atherosclerosis on the mean value and daily variation of arterial pressure were studied in 12 Watanabe-heritable hyperlipidemic (WHHL) rabbits aged 12 to 35 months and 25 normal Japanese white rabbits aged 6 to 30 months. A pressure catheter was inserted through the left subclavian artery under pentobarbital anesthesia. A few days after the catheterization, the mean arterial pressure (MAP) of the rabbits, which were active and in a good state of appetite, was recorded by an analogue-to-digital converter every second for about 6 hrs and stored in a computer. The mean (M) and standard deviation (SD) in the WHHL rabbit, calculated from each successive MAP record, ranged widely from 85.8 to 131.4 mmHg and 5.6 to 12.6 mmHg, respectively. There was no significant correlation between M and SD in the WHHL rabbit. M and variance (V) of MAP in the WHHL rabbit were significantly higher than those in the normal rabbit. M did not show any significant change with increasing ages, whereas SD increased significantly with aging in the WHHL rabbit. Concentrations of serum total cholesterol and triglyceride in the WHHL rabbit were 475 and 328 mg/dl, which were about nine and seven times as high as those in the normal rabbit, respectively. Macroscopic and histopathological examinations of the aorta revealed development and spread of sclerotic lesions with aging in the WHHL rabbit. We can conclude that development of atherosclerosis with aging in the WHHL rabbit causes malfunction of the baroreceptors, which contributes to hypertension and lability of arterial pressure.

Aging↗

PubMed1992

Impaired baroreflex control of arterial pressure in WHHL rabbits.

The present study was designed to investigate baroreflex control capacity of arterial pressure (AP) in the conscious Watanabe heritable hyperlipidemic (WHHL) rabbit. The control capacity of the baroreflex system was assessed with overall open-loop gain (G). Seven WHHL and 14 normal Japanese white rabbits were chronically implanted two catheters in the aortic arch through the left subclavian and common carotid arteries. A small amount of blood (2 ml/kg, body weight) was rapidly extracted into a syringe via the left common carotid artery in the conscious state. Mean arterial pressure (MAP) was monitored with a catheter-transducer system through the left subclavian artery. The MAP responses to the rapid hemorrhage were averaged 8 times by a computer. G was calculated as G = delta API/delta APS-1, where delta API was an immediate MAP fall after the hemorrhage and delta APS was a steady-state error 1-2 min after the hemorrhage. The values of G in the conscious normal and WHHL rabbits were 7.35 +/- 0.24 and 1.91 +/- 0.29 (mean +/- SE, p < 0.01), respectively. To investigate effects of pentobarbital anesthesia on baroreflex system, the hemorrhage experiment was repeated several times under pentobarbital anesthesia (20 mg/kg, i.v.). The values of G in the anesthetized normal and WHHL rabbits were 6.69 +/- 0.23 and 1.68 +/- 0.34 (mean +/- SE, p < 0.01), respectively. G in the normal and WHHL rabbits did not show any significant change in the presence and absence of pentobarbital anesthesia (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗

PubMed1992

Neural, humoral, and metabolic control of coronary vascular resistance during exercise.

Neural, humoral, and metabolic effects on coronary vascular resistance were examined during exercise in conscious dogs, chronically instrumented for the measurement of aortic pressure, heart rate, and left circumflex coronary blood flow. Exercise significantly decreased coronary vascular resistance (CVR) in intact (INT) group, in which CVR was controlled by neural, humoral, and metabolic factors. In cardiac denervated (CD) group with pretreatment of alpha blocker (phentolamine, 2 mg/kg), in which CVR was controlled only by metabolic factor, exercise significantly decreased CVR. To eliminate metabolic effect on CVR, CVR was normalized by the product of CVR and double product (DP = mean aortic pressure x heart rate). CVR.DP did not change throughout the exercise in dogs with CD with alpha blocker. Thus, metabolic effect on CVR during exercise can be excluded by the product of CVR and DP. This calculation was applied to INT group with alpha blocker and CD group without blockers. The 12 km/h exercise significantly increased CVR.DP from 4.1 +/- 0.3 x 10(4) to 6.4 +/- 0.9 x 10(4) in INT group with alpha blocker, in which CVR was controlled only by neural factor, and from 2.8 +/- 0.2 x 10(4) to 4.5 +/- 0.5 x 10(4) in CD group, in which CVR was controlled only by humoral factor. These data suggest that 1) neural and humoral coronary vasoconstriction occurs during exercise, 2) neural and humoral vasoconstriction is overwhelmed by metabolic vasodilation, and 3) CVR.DP is a beneficial calculation for excluding metabolic effect on CVR during exercise.

Animals↗

PubMed1992

Effects of increased ureteropelvic pressure on fluid and NaCl absorption across the jejunum.

The aim of the present study was to elucidate the effects of an increased ureteropelvic pressure (UPP) on the net jejunal fluid, Na+, and Cl- absorption in anesthetized dogs. UPP was changed under hydrostatic pressure with warmed Ringer's solution. At a UPP of 0 mmHg, the net jejunal fluid, Na+, and Cl- absorption were 10.1 +/- 0.5 ml, 2.4 +/- 0.1, and 2.0 +/- 0.1 mEq, and were significantly reduced to 5.9 +/- 0.4 ml, 2.0 +/- 0.1, and 1.6 +/- 0.1 mEq, respectively, by an increase in UPP to 60 mmHg. After lowering the UPP to 0 mmHg, the net absorption recovered to the control values. The same experiments were performed after ipsilateral renal denervation. Ipsilateral renal denervation completely abolished this response. This result suggests that the afferent pathway of this response is the renal nerves. We also assessed the validity of the method using a jejunal loop by examining the effects of repetition of the absorption experiment on the net absorption. The net absorption was not altered by 6 times repetition of the absorption experiment. To determine the collection ratio, phenol red was used in the first and sixth absorption experiments. The collection ratios were 92.2 +/- 1.1 and 90.3 +/- 0.9%, respectively. There was no significant difference in collection ratio between the first and sixth values. This is the first report in which an increased UPP was found to inhibit the net jejunal fluid, Na+, and Cl- absorption.

Animals↗

PubMed1992

Systems analysis of the carotid sinus baroreflex system using a sum-of-sinusoidal input.

The purpose of the present study was to determine the dynamic characteristics of the carotid sinus baroreflex system (CS) employing systems analysis. In 28 anesthetized and mechanically ventilated dogs with vagotomy, intracarotid sinus pressure (ICSP) was changed artificially. In protocol 1 (n = 7), we estimated the transfer function of the CS by means of a single sinusoidal input (SIN), the Gaussian white-noise input (GWN), and a sum-of-sinusoidal input (SUM). The transfer function of ICSP to systemic arterial pressure (SAP) was second-order delay with an identical corner frequency of 0.025 Hz and damping ratio of 0.7. The steady-state gain estimated using GWN (1.12 +/- 0.13) or SUM (1.13 +/- 0.08) was significantly smaller than SIN (1.69 +/- 0.25). In protocol 2, to find the reason why there was a difference among the estimated steady-state gains, we investigated the effect of ICSP pulsation on the open-loop gain of the CS. The maximum gain of the gain curve was decreased and the operating range was increased significantly with the 2-Hz pulsation. We could simulate the above phenomena by using a model with a nonlinear sigmoidal relationship between ICSP and SAP. The dynamic characteristics of the CS appeared to be changed by pulsation, but this phenomenon was attributable to the sigmoidal nature of the relationship between ICSP and SAP. Pulsation decreases the maximum gain and increases the operating range, which may contribute to stability of the CS and homeostasis of SAP.

Animals↗

PubMed1992

ANP decreases arterial oxygen partial pressure by increasing shunt flow in pulmonary circulation.

This study was designed to clarify the decreased arterial oxygen partial pressure (PaO2) mechanism induced by atrial natriuretic peptide (ANP) infusion. In order to examine the effects of ANP on gas exchange across the normal lungs, ANP was infused to eight anesthetized dogs, ventilated with mixed gases of oxygen and nitrogen. PaO2 and venous oxygen partial pressure (PvO2), ventilation-perfusion ratio (VA/Q), shunt-total blood flow ratio (QS/QT) were measured before and during ANP infusion under ventilation with 10, 20, 30% oxygen. In this study ANP decreased PaO2 from 89.0 +/- 4.2 to 85.4 +/- 5.4 mmHg during 20% oxygen ventilation, and from 138.1 +/- 3.6 to 132.5 +/- 4.1 mmHg during 30% oxygen ventilation. ANP increased VA/Q and QS/QT. We conclude that the decrease in PaO2 caused by ANP infusion was mainly due to the increased venous admixture.

Animals↗

PubMed1992

Effects of brain natriuretic peptide and C-type natriuretic peptide infusion on urine flow and jejunal absorption in anesthetized dogs.

Effects of brain natriuretic peptide (BNP) or C-type natriuretic peptide (CNP) on urinary excretion and jejunal absorption of fluid and electrolytes were examined in anesthetized dogs. Intravenous infusion of BNP increased urinary fluid and electrolyte excretion and decreased jejunal fluid and electrolyte absorption. CNP had a similar effect on jejunal absorption as BNP. However, CNP had no significant effect on renal fluid or electrolyte excretion. These results indicate that: 1) BNP is a powerful natriuretic peptide comparable to ANP and; 2) CNP may also contribute to the regulation of body fluid homeostasis by way of inhibiting net jejunal fluid and electrolyte absorption.

Animals↗

PubMed1992

[Conservative treatment of Hunt syndrome].

Based on the pathophysiology of Bell's palsy that edema as well as ischemia lead to both compression and hypoxia, Stennert employed high doses of cortisone and dextran and reported a high recovery rate. In the past 5 years, we have been treating patients with Bell's palsy and Hunt syndrome with a high dose of steroids or low-molecular dextran (SD therapy). SD therapy was administrated in 71 cases of Hunt syndrome, and the results were compared with those of a group of 36 patients who had been treated with orally administrated low-dose steroids. All patients with incomplete palsies recovered completely, regardless of the mode of treatment. In cases of complete palsy, 62% of patients recovered completely when treated with SD therapy. In contrast, 29% of the patients treated with orally administrated steroids recovered completely. These results indicate that for patients with complete palsy SD therapy is more effective than oral steroid therapy, while patients with incomplete palsy recover completely with oral steroids. On the basis of this study, oral steroids are best used in cases of incomplete palsy unless complete palsy develops. In these latter cases, we now believe that SD therapy should be started immediately.

Administration, Oral↗

PubMed1991

Neural control of urinary sodium excretion during hypertonic NaCl load in conscious rabbits: role of renal and hepatic nerves and baroreceptors.

We examined responses of renal nerve activity, urine flow, and urinary Na+ excretion to a hypertonic NaCl infusion in chronically instrumented conscious rabbits with unilateral renal denervation. The intravenous infusion of 20% NaCl, at 0.2 ml/min for 30 min, increased plasma osmolality by 27 +/- 5 mOsm/kg, and plasma Na+ by 16 +/- 3 mEq/l, and decreased hematocrit by 5 +/- 1%. These changes were accompanied by a marked decrease in renal nerve activity by 82 + 7%. Urine flow and urinary Na+ excretion increased gradually and peaked at the end of infusion. The innervated kidney excreted 23.3 +/- 3.3 ml urine and 5.5 +/- 0.7 mEq Na+ for the subsequent 60 min. However, the contralateral denervated kidney excreted only 9.5 +/- 2.0 ml urine and 2.2 +/- 0.6 mEq Na+; these values were significantly less than those of the innervated kidney. To examine the role of the sinoaortic and cardiopulmonary baroreceptors and the hepatic nerves in the response of renal nerve activity to the hypertonic NaCl infusion, renal nerve activity was examined in conscious rabbits with sinoaortic baroreceptor denervation (SAD) plus vagotomy and/or section of the anterior and posterior hepatic nerves (SAPH). In rabbits with SAD plus vagotomy or SAPH, the NaCl infusion also decreased renal nerve activity. After combining SAPH and SAD plus vagotomy, the decrease in renal nerve activity was completely blocked. These results indicate that hypertonic NaCl infusion elicits a marked decrease in renal nerve activity which is mediated predominantly by sinoaortic and cardiopulmonary baroreflexes and the hepatic nerves, and that the decrease in renal nerve activity plays an important role in the augmentation of renal function.

Afferent Pathways↗

PubMed1991

Effects of hepatic NaCl receptor stimulation on renal nerve activity in conscious rabbits.

The effects of intrahepatic NaCl or osmo-receptor stimulation on renal nerve activity were examined in chronically instrumented conscious rabbits. Combined infusions of 9% NaCl via the portal vein and distilled water via the inferior vena cava did not alter plasma osmolality or plasma Na concentration of the systemic circulation but decreased renal nerve activity. Combined infusion of 6.5% LiCl and distilled water did not have any effects on renal nerve activity. The decrease in renal nerve activity induced by portal 9% NaCl infusions was completely abolished after section of the anterior and posterior hepatic nerves. These results indicate that stimulation of the intrahepatic NaCl receptors, not of the osmoreceptors, elicits a reflex decrease in renal nerve activity, which is mainly mediated by the anterior and posterior hepatic nerves.

Animals↗

PubMed1991

Conservative treatment of Bell's palsy with steroids and dextran-pentoxiphylline combined therapy.

In 1980, Stennert proposed for the treatment of Bell's palsy an infusion therapy consisting of initially high dosages of steroids in combination with low-molecular dextran and pentoxiphylline. Excellent results were reported as a consequence of administering this treatment scheme. This "steroid-dextran" medication was modified (SD therapy) and administered in 172 cases of Bell's palsy. The results were compared with those of a group of 59 patients who had been treated with orally administered low-dose steroids in combination with vasodilators, adenosine triphosphate and vitamins. All patients with incomplete palsies recovered completely, regardless of the mode of treatment. In cases of complete palsy, 87% of patients recovered completely when treated with SD therapy. In contrast, 68% of the patients treated with orally administered steroids recovered completely.

Dextrans↗

PubMed1991

Reflex control of renal nerve activity originating from the osmoreceptors in the hepato-portal region.

The reflex effects of hepatic osmoreceptors on the renal sympathetic nerve activity (RNA) were studied in 30 pentobarbital anesthetized, vagotomized and sino-aortic baroreceptor denervated (SAD + VD) rabbits. The changes in mean arterial pressure (MAP), heart rate (HR), and RNA were examined when 9% NaCl, 6.5% LiCl or 50% glucose solution was infused into the hepatic portal vein at a rate of 0.15 ml/kg/min for 10 min. Infusion of 9% NaCl solution into the hepatic portal vein increased the plasma osmolality by 10.8 +/- 1.0 mOsmol/kg from the control level in the blood of the hepatic portal vein and by 2.8 +/- 2.0 mOsmol/kg from the control level in the systemic blood. MAP was significantly elevated by 10.2 +/- 5.0 mmHg but HR did not change with hepatic portal infusion of 9% NaCl solution. Intraportal infusion of 9% NaCl solution significantly decreased the RNA by 28.6-34.2% from the control level, 6.5% LiCl solution by 28.6 +/- 4.7%, and 50% glucose solution by 26.2 +/- 3.0%. Femoral arterial infusion of hypertonic NaCl solution, however, did not evoke any significant change in RNA in SAD + VD rabbits. These findings suggest that increases in osmolality and NaCl concentration in the systemic circulation do not result in a decrease of RNA. Furthermore, after section of the anterior and posterior plexus of the hepatic nerve, hepatic portal infusion of hypertonic NaCl solution elicited no change in RNA. The present data indicate that an increase in osmolality in the hepatic portal venous blood results in a reflex decrease of RNA. This reflex may be important for restoration of a postprandial increase in osmolality.

Animals↗

PubMed1991

Effects of atrial natriuretic peptide on water and NaCl absorption across the intestine.

Previous studies have demonstrated that atrial natriuretic peptide (ANP) causes natriuresis and diuresis. However, it is not established whether ANP also alters fluid and electrolyte balance via actions on intestinal absorption of water and sodium chloride. Therefore, the purpose of the present study was to investigate the effects of ANP on water and NaCl absorption across the intestine. First, we determined that ANP was taken up from the intestinal circulation in conscious dogs. During the intravenous infusion of ANP (0.3 microgram.kg-1.min-1), 27.4% of the ANP delivered to the intestinal vascular bed were removed from the circulation at that vascular bed, whereas only 1% of the ANP delivered to the hepatic circulation was removed at the hepatic vascular bed. Second, we determined the effects of the ANP infusion on splanchnic circulation in conscious dogs. ANP decreased hepatic arterial blood flow by 14%, portal venous blood flow by 16%, total hepatic blood flow by 15%, and cardiac output by 14%. Finally, we studied the effects of ANP on intestinal absorption of water and NaCl. ANP suppressed net absorption of water by 61%, Na+ by 43%, and Cl- by 42% across the jejunum but not the ileum. These results suggest that ANP modulates water and NaCl homeostasis across the jejunum but not across the ileum.

Animals↗

PubMed1991

Atrial natriuretic peptide attenuates an increase in pulmonary vascular incremental resistance due to high pulmonary venous pressure.

The aim of this study was to determine whether an elevation of pulmonary venous pressure (PVP) and atrial natriuretic peptide (ANP) affects pulmonary vascular resistance (PVR) and pulmonary vascular incremental resistance (iPVR). We vascularly isolated the left lower lobe of the lung and perfused it with blood using a pulsatile pump. Blood flow (PBF) to the isolated lobe was decreased in 6 to 7 steps from about 8 to 1 ml/(kg.min). PVR was calculated from measurements of PBF and the pressure difference between pulmonary arterial pressure and PVP at four different levels of fixed PVP. iPVR was estimated from a slope of the pressure-flow relationships between effective pulmonary driving pressure and PBF at four different levels of fixed PVP. iPVR was 2.2 +/- 0.2, 2.2 +/- 0.1, 2.4 +/- 0.1, and 2.6 +/- 0.2 mmHg.min.kg/ml, when PVP was 0, 5, 10, and 15 mmHg, respectively. To test whether or not the response of the pulmonary vascular bed to the elevated PVP is modulated by ANP, iPVR was estimated before and after an administration of ANP in the perfusion circuit. Increased iPVR from 2.1 +/- 0.2 to 2.5 +/- 0.2 mmHg.min.kg/ml in response to the elevation of PVP from 0 to 15 mmHg decreased to the control level after the administration of ANP. ANP, however, did not change the control iPVR. PVR decreased with increasing PVP. ANP decreased PVR when PVP was 0 mmHg, but did not change it when PVP was 15 mmHg. These results suggest that ANP decreases PVR and restores the decreased pulmonary vascular compliance.

Animals↗

PubMed1991

Effect of exercise on fractional extraction of catecholamines by the denervated heart in conscious dogs.

To examine the applicability of Halter's assumption to the denervated heart during exercise, we measured the concentrations of norepinephrine (NE) and epinephrine (E) in arterial and coronary sinus plasma in cardiac denervated dogs. As the level of exercise was increased from 0 (at rest) to 3, 6, and 12 km/h, fractional extraction (FE) of NE significantly decreased from 51 +/- 7 to 39 +/- 5, 34 +/- 6, and 30 +/- 5%, respectively. FE of E did not decrease at exercise (at rest, 57 +/- 10; 3 km/h, 60 +/- 9; 6 km/h, 60 +/- 5; and 12 km/h, 66 +/- 6%). There was no significant difference between FE of NE and E at rest and at 3 km/h, but FE of NE was significantly less than that of E with 6 and 12 km/h exercise. We conclude that FE of NE by the denervated heart decreases during exercise, and that FE of NE and E are approximately equal at rest and at mild exercise, but not at strenuous exercise.

Animals↗

PubMed1991

Non invasive analysis of hemodynamic changes in dogs with acute pancreatitis.

To elucidate the hemodynamic changes in the course of acute pancreatitis in dogs, various parameters were monitored non-invasively and real-timely by the ultrasonic flow probes which had been placed in advance. The dogs were divided into two groups, i.e., control group (CG) and infusion group (IG). In the infusion group, lactated Ringer solution was infused intravenously for 12 hours in order to maintain LAP or CVP at the mean +/- 1 mmHg of its control value before inducing pancreatitis. In the control group, lactated Ringer solution was not infused. Cardiac output (CO) and LV dp/dt abruptly decreased in a few hours and remained low levels in a control group (CG), but not in an infusion group (IG). It shows that the decreased CO was caused by a decrease in preload but not by a depression of contractility. Gastroduodenal arterial flow (GDAF) and GDAF/CO decreased in a few hours and kept low level in CG, but not in IG. Therefore, a decrease in GDAF is mainly caused by an increase in vascular resistance due to an increase in Hematocrit. Superior pancreatico-duodenal venous flow (SPDVF) and SPDVF/CO decreased immediately in both groups, revealing that there is severely depressive outflow from pancreas because of hemorrhage and destruction of pancreatic parenchyma immediately after the onset of pancreatitis. In CG, Total hepatic flow (THF) and Portal vein flow (PVF) gradually decreased in a few hours and kept low levels, but Common hepatic arterial flow (CHAF) did not decrease. This suggests that decrease of THF is due to decrease of PVF. THF/CO increased in CG. PVF/CO decreased in CG, while CHAF/CO increased in both groups. The increased CHAF compensated for the decreased PVF, which may play an important role in protecting the liver.

Acute Disease↗

PubMed1990

Effects of portal infusion of hypertonic solution on jejunal electrolyte transport in anesthetized dogs.

Jejunal electrolyte absorption was measured in the jejunal loops of anesthetized dogs during infusions of hypertonic solutions via the portal vein. The net Na absorption was not influenced by the 9% NaCl infusion into the inferior vena cava, although it was significantly attenuated by the portal 9% NaCl infusion. This effect may not be due to the osmotic stimulus, since the portal 50% glucose or 6.5% LiCl infusion had no significant influence on the net Na absorption. To determine the mechanism of the decrease in the net Na absorption during the portal hypertonic NaCl infusion, the net Na absorption was measured after the section of anterior and posterior hepatic nerves (SAPH) or intravenous atropine injection. Both SAPH and the intravenous atropine injection completely blocked the effect of the portal 9% NaCl infusion on the net Na absorption. These results indicate that 1) net Na absorption in dog jejunum is depressed by the hypertonic NaCl infusion via the portal vein; 2) the effect is NaCl specific and may not be due to the osmotic stimulus; and 3) the afferent limbs of this effect are the anterior and posterior hepatic nerves, and the efferent limb of this effect is the vagus nerve. Thus the hepatojejunal reflex may play an important role in the regulation of body fluid homeostasis.

Absorption↗