Biomedical subjects

H Hosomi

Publications and source records attributed to H Hosomi.

At least 55 records · Page 3Linked to original sources

PubMed1994

The effects of feeding and secretin administration on the pancreaticoduodenal papilla of conscious dogs.

The aim of this study was to define the functional role of the pancreaticoduodenal papilla (PDP) in the regulation of pancreatic outflow into the duodenum in response to feeding and secretin administration in conscious dogs. The canine model we developed allowed for measurement of the pancreatic ductal pressure and pancreatic outflow simultaneously in a physiological state without interfering with the flow of pancreatic juice via the intact sphincter of the duodenal papilla. Feeding increased the pancreatic outflow from 2.8 +/- 0.2 to 13.4 +/- 1.3 ml/15 min with a slight increase in the pancreatic ductal pressure from 8.5 +/- 0.6 to 13.7 +/- 1.4 cmH2O. The administration of secretin increased the pancreatic outflow from 2.8 +/- 0.2 to 12.7 +/- 1.0 ml/15 min without increasing the pancreatic ductal pressure. The viscosity of the pancreatic juice increased during exposure to food, but decreased following food intake and secretin administration, after which the PDP seemed to dilate by about 40% of the fasting value. The results suggest that PDP changes its opening to maintain the pancreatic ductal pressure below a certain level, even if pancreatic secretion into the pancreatic duct increases due to food intake and secretin administration.

Ampulla of Vater↗

PubMed1994

Effects of microinjection of kainic acid into the nucleus tractus solitarius on fluid and NaCl absorption across the jejunum.

Effects of bilateral chemical inactivation of the nucleus tractus solitarius (NTS) by microinjection of kainic acid (KA) on fluid and NaCl absorption across the jejunum were examined in anesthetized Sprague-Dawley rats. Jejunal fluid and NaCl absorption was measured in a jejunal loop before and after the microinjection of artificial cerebrospinal fluid (aCSF) or KA into the NTS. Net fluid and NaCl absorption was not altered by a microinjection of aCSF. However, net fluid (from 1.12 +/- 0.07 to 1.66 +/- 0.06 ml/30 min) and NaCl (Na+ from 164.5 +/- 10.1 to 243.3 +/- 7.1 muEq/30 min; and Cl- from 175.9 +/- 7.5 to 260.8 +/- 6.5 muEq/30 min) absorption was significantly increased by the chemical inactivation of the NTS. To examine the efferent mechanism of the increased net absorption induced by the NTS inactivation, mesenteric nerve activity (MNA) was measured before and after the inactivation of the NTS. MNA was significantly increased by 165.9 +/- 74.2% after the bilateral inactivation of the NTS. Furthermore, absorption experiments were conducted in rats with pretreatment of atropine (acetylcholine-antagonist) or yohimbine (specific alpha 2-antagonist). In atropine treated rats, net jejunal absorption was significantly increased by the inactivation of the NTS. However, the increase in net absorption induced by the inactivation of the NTS was completely abolished by pretreatment with yohimbine. These results suggest that the NTS has a tonic suppression on jejunal absorption through alpha 2-adrenergic mechanism.

Animals↗

PubMed1994

Chemical inactivation of the nucleus tractus solitarius abolished hepatojejunal reflex in the rat.

Jejunal electrolyte absorption was measured in the jejunal loop of anesthetized rats during an infusion of 9% NaCl solution via the portal vein. Net absorption of Na and Cl, and osmolality were significantly depressed by the portal 9% NaCl infusion. The decrease in net absorption was completely abolished by hepatic denervation. In addition, bilateral chemical inactivation of the nucleus tractus solitarius (NTS) by microinjection of kainic acid abolished the depressing effect of the portal venous infusion of 9% NaCl. These findings indicate that NTS is involved in the central pathway of the hepatojejunal reflex.

Animals↗

PubMed1994

High-rate sequential sampling of auditory brain-stem and somatosensory evoked responses in hypoxia.

We developed a high-rate sequential recording technique that allowed simultaneous measurements of both auditory brain-stem response (ABR) and somatosensory evoked potential (SEP) every 10 sec. Using this method, a transient increase in amplitude of all the ABR and SEP components in response to hypoxia in dogs could be detected. The increase in amplitude preceded the prolongation of latency. Our study showed that there were successive changes of evoked potentials in response to hypoxia. A transient increase in amplitude is the first to occur, followed by a latency prolongation and an amplitude decrease for both ABRs and SEPs.

Animals↗

PubMed1994

Relationship between the suppressive actions on intestinal absorption and on cGMP production for the natriuretic peptide family in dogs.

1. The aim of this study was to investigate whether the suppressive effects of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) on net intestinal absorption were related to guanosine 3',5'-cyclic monophosphate (cGMP) production in the intestine. 2. We measured the plasma cGMP concentration of the arterial, jejunal and ileal venous blood after intravenous infusions of natriuretic peptides (97 pmol/kg per min for 30 min) in anaesthetized dogs. 3. The infusion of ANP increased cGMP concentration of the aortic blood by 49.9 +/- 9.0 (pmol/mL), BNP by 71.8 +/- 12.3 and CNP by 5.5 +/- 1.3. The increases in cGMP after ANP and BNP were larger than after CNP. The infusion of ANP increased jejunal arteriovenous differences in cGMP concentration by 69.9 +/- 3.5 (pmol/mL) and ileal arteriovenous differences by 8.7 +/- 3.2. In BNP infusion, the jejunal and ileal arteriovenous differences in cGMP concentration tended to increase by 15.6 +/- 5.8 (pmol/mL) and by 14.8 +/- 6.6 but neither were significant. CNP infusion did not change the jejunal and ileal arteriovenous differences in cGMP concentration. 4. These results suggest that, while the actions of ANP on intestinal absorption may be mediated by cGMP, those of BNP and CNP are not.

Animals↗

PubMed1993

Sulfite suppresses transducer function of the carotid sinus baroreceptor.

The purpose of this study was to examine the effect of sodium metabisulfite (MBS) solution on the transducer function of the carotid sinus baroreceptor. In anesthetized dogs with vagotomy, we vascularly isolated the carotid bifurcation to load a pressure on the carotid sinus baroreceptor. As the pressure load, we used a slow ramp increase (0.7 mmHg/s) in intracarotid sinus pressure (ICSP). The response of carotid sinus nerve activity (CSNA) to the slow ramp increase in ICSP was suppressed when the isolated carotid sinus was filled with the MBS solution of 10(-2) M. This suppressive effect of MBS solution on the response of CSNA was reversible. The MBS solution had no effect on the pressure-volume relationship of the arterial wall of the isolated carotid sinus and on the impulse conduction of carotid sinus nerve. This suppressive effect of the MBS solution of 10(-2) M was weakened by introducing oxygen gas into the solution to lose the total sulfite anions in the solution. These results suggest that: (1) the MBS solution reversibly suppresses the transducer function of the carotid sinus baroreceptor; (2) the target construction of the carotid sinus region that was affected by the MBS solution might be the carotid sinus baroreceptor nerve terminal where ICSP was transduced into carotid sinus nerve firing; and (3) the suppressive effect might be provoked by the sulfite anions in the MBS solution.

Animals↗

PubMed1993

Effects of endothelin on fluid and NaCl absorption across the jejunum in anesthetized dogs.

The aim of the present study was to investigate the effects of endothelin (ET) on fluid and NaCl absorption across the jejunum. Dogs were anesthetized with pentobarbital sodium (30 mg/kg i.v.). Polyethylene catheters were placed in the superior mesenteric arteries and portal vein for infusions and to measure arterial and portal venous pressure. Superior mesenteric arterial blood flow was continuously measured with an ultrasonic flow probe. A 30-cm-long jejunal loop was made at 10 cm from the duodenal fossa. Infusion of saline, ET-1, ET-3, or phenylephrine (PE) was initiated 10 min before pouring the test solution into the jejunal loop and continued for 25 min. The net fluid (7.2 +/- 0.9 ml, mean +/- SE, n = 8), Na+ (1.1 +/- 0.1 mEq), and Cl- (1.1 +/- 0.2 mEq) absorption during saline infusion was not significantly different from those (7.0 +/- 1.0 ml, 1.1 +/- 0.1 mEq, and 1.1 +/- 0.2 mEq) during ET-1 infusion but was significantly decreased to 4.8 +/- 0.6 ml, 0.7 +/- 0.1 mEq, and 0.7 +/- 0.1 mEq by ET-3 infusion. ET-1 increased the mesenteric vascular resistance by 84.7 +/- 23.4% and ET-3 by 64.3 +/- 7.5%. To study the underlying mechanisms, the absorption experiment was performed after the increase in vascular resistance and administration of nitric oxide (NO) synthase inhibitor. We increased the resistance by 127.8 +/- 12.6% with PE and found no effect. Pretreatment with NO synthase inhibitor did not influence the decreased absorption induced by ET-3. In conclusion, ET-3 suppresses jejunal absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗

PubMed1993

Hepatorenal reflex plays an important role in natriuresis after high-NaCl food intake in conscious dogs.

Responses of renal nerve activity and urinary Na+ and Cl- excretion were examined in chronically instrumented conscious dogs through feedings of boiled rice with or without NaCl. The boiled rice (20 g/kg body wt) without NaCl did not influence plasma Na+ and Cl- concentrations, renal nerve activity, or urinary Na+ excretion but decreased urinary Cl- excretion. On the other hand, boiled rice containing NaCl (0.4 g/kg body wt) increased plasma Na+ (+3.8 +/- 0.7 meq/l) and Cl- (+3.0 +/- 1.5 meq/l) concentrations, then decreased renal nerve activity by 61 +/- 4%, and increased urinary Na+ and Cl- excretions. In dogs with hepatic denervation, a decrease in renal nerve activity, which was observed in intact dogs in response to the high-NaCl food intake, was completely abolished along with significant attenuation of postprandial natriuresis. That is, only 9 +/- 5% of the loaded Na+ and 7 +/- 3% of the loaded Cl- were excreted during 4 consecutive hours in hepatic-denervated dogs, whereas 36 +/- 5% of the loaded Na+ and 36 +/- 4% of the loaded Cl- were excreted in intact dogs. In dogs with renal denervation, postprandial natriuresis was also attenuated. These results indicate that the high-NaCl food intake elicits a decrease in renal nerve activity, the decrease is predominantly mediated by the hepatic nerves, and the decrease in renal nerve activity plays an important role in augmentation of urinary Na+ and Cl- excretion. Thus, the hepatorenal reflex may play an important role in controlling extracellular fluid homeostasis during food intake.

Animals↗

PubMed1993

Effects of endothelins on fluid and NaCl absorption across the jejunum anesthetized dogs.

The aim of this study was to investigate the effects of endothelins on fluid the NaCl absorption across the jejunum, the jejunal fluid and NaCl absorption and mesenteric hemodynamics in jejunal loops in anesthetized dogs during infusion of saline, endothelin-1 or endothelin-3 into the superior mesenteric artery. Infusion of endothelin-3 decreased the net fluid, Na+, and Cl- absorption; however, saline and endothelin-1 had no effect. To investigate the role of nitric oxide and soluble guanylate cyclase activation in the mechanisms underlying endothelin-3-induced decrease in fluid and electrolyte absorption, measurements were obtained in the presence of the nitric oxide synthesis inhibitor, nitro-L-arginine methyl ester (L-NAME) or the soluble guanylate cyclase inhibitor, methylene blue. The endothelin-3-induced decrease in absorption was not influenced by the pretreatment with inhibitors. These results suggest that the endothelin-3 response was not mediated by nitric oxide or soluble guanylate cyclase.

Amino Acid Oxidoreductases↗

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↗