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Biomedical subjects

N Hirai

Publications and source records attributed to N Hirai.

At least 55 records · Page 3Linked to original sources
PubMed1998

Reaction times of head movements occurring in association with express saccades during human gaze shifts.

During lateral gaze shifts to a visual target of 10 degrees eccentricity, the gap paradigm (presence of a 200 ms gap between offset of fixation lamp and onset of target lamp) produced a significant decrease in the reaction times (RTs) of head movements (54 ms) and saccades (82 ms) when compared with those obtained under the overlap paradigm across five subjects. Correlation coefficients between the RTs of saccades and head movements were significantly lower under the gap paradigm than those under the overlap paradigm. Particularly, the RTs of head movements occurring in association with express saccades were independent of the saccade RTs. These results indicate that the head and eye motor systems are controlled by the separate neural mechanisms in the conditions which produce express saccades.

Electromyography↗
PubMed1998

Morphology of single primary spindle afferents of the intercostal muscles in the cat.

A reconstruction was made of the trajectory of primary spindle afferents from the intercostal muscles in the spinal cord of the cat. Intraaxonal recordings were performed from the primary spindle afferents that were identified by their response to lung inflation and stimulus threshold to activate the action potentials. The afferents were stained by using intraaxonal injection of horseradish peroxidase (HRP). Results were obtained mainly from internal intercostal Ia fibers, which entered the spinal cord and bifurcated into ascending and descending branches. The ascending branches could be traced up to 10.7 mm, and the descending branches could be traced up to 7.3 mm. The ascending branches extended to the next segment. Collaterals ranging from one to six were given off from these branches. The distances between adjacent collaterals ranged from 0.9 mm to 4.7 mm. Each collateral had similar morphological characteristics. The collaterals entered the dorsal horn and ran toward lamina IX through the medial half of the gray matter. Fine branches and boutons were given off in laminae V, VII, VIII, and IX. The aggregations of these branches were found in lamina VII, mainly in the region of Clarke's column and in the ventral and ventrolateral regions thereof and in lamina IX, mainly in the nucleus lateromedialis. Most terminals did not contact the somata of target neurons in all laminae in which terminals were found. However, a few terminals were found to contact large neurons in lamina IX. In addition to these aggregates, there were some terminals scattered throughout the ventral horn. Thus, it was concluded that single intercostal Ia afferents project to the region of Clarke's column, to the intercostal motor nucleus, and to the intermediate regions.

Afferent Pathways↗
PubMed1998

Serial changes in plasma levels of soluble P-selectin in patients with acute myocardial infarction.

The present study examines whether an acute inflammatory response occurs during acute myocardial infarction (AMI) by measuring soluble P-selectin levels. We examined plasma soluble P-selectin levels in 16 consecutive patients with AMI, in 15 patients with angina, and in 13 control subjects with chest pain but normal coronary arteries and no coronary spasm. In patients with AMI, blood samples were obtained immediately after admission and at 1, 4, 24, and 48 hours, and 1 week after initiation of reperfusion therapy. The plasma soluble P-selectin levels were significantly higher in the AMI group on admission than in the other 2 groups (83 +/- 13 ng/ml, p < 0.01). The plasma soluble P-selectin levels at baseline were not significantly different between the angina and control groups (28 +/- 4 vs 24 +/- 5 ng/ml, p = NS). Plasma soluble P-selectin levels reached their peak significantly at 4 hours after initiation of the reperfusion therapy in patients with AMI. The peak level was significantly higher than the level on admission (115 +/- 17 vs 83 +/- 13 ng/ml, p < 0.05). The plasma soluble P-selectin levels were higher in the AMI group than in the angina and control groups over the time course (p < 0.01). Our data indicate that the plasma soluble P-selectin levels are increased in patients with AMI, and that the levels are increases after reperfusion therapy more than before reperfusion. We suggest that the increase in the plasma soluble P-selectin levels may be caused by the activation of endothelial cells and platelets after myocardial ischemia and reperfusion during AMI.

Aged↗
PubMed1998

Involvement of liver-associated immunity in hepatic metastasis formation.

AIMS: Hepatic metastasis formation and prevention were studied from the viewpoint of liver-associated immunity. METHODS: RCN-9, a colonic cancer cell line derived from Fischer rats, and its subclone RCN-H4, in which the cancer is highly metastatic to the liver, were used. Fischer rats that were inoculated with parent RCN-9 colonic cancer cells (5 x 10(6)) via the portal vein showed liver metastasis in less than 60% of the animals. In contrast, all rats (100%) that received RCN-H4 produced multiple liver metastases. To investigate the difference of hepatic metastasis formation, we assessed the susceptibility of both cell lines against hepatic sinusoidal lymphocytes (HSL) by 51Cr-release assay, and the expression of MHC class I and class II of both cell lines by flow cytometry. In addition, we examined whether activation of HSL by interleukin-12 (IL-12) can prevent liver metastasis of highly metastatic clone RCN-H4. RESULTS: The RCN-H4 clone showed decreased susceptibility to lysis by natural cytotoxic cells in HSL. This decrease in cell susceptibility was attributable to an increase in cell surface expression of MHC class I antigen. Administration of IL-12, a potent NK/CTL stimulatory cytokine, augmented the cytotoxic activity against the RCN-H4 clone and prevented liver metastasis of RCN-H4 inoculated into the portal vein. CONCLUSIONS: Liver metastasis formation is positively correlated with the strength of the hepatic immune system which mainly consists of ontogenetically primitive T cells. As these effectors exert their cytotoxicity in a MHC-nonrestricted fashion, tumor cells that highly express MHC class I antigen can readily avoid hepatic surveillance and apt to cause liver metastasis. Augmentation of the hepatic immune system, for instance, with IL-12 administration, can prevent liver metastasis even in tumor cells with a high potential for liver metastasis.

Adenocarcinoma↗
PubMed1998

Superiority of hepatic arterial infusion in preventing catabolism of 5-FU compared with portal vein infusion revealed by an in vivo 19F NMR study.

PURPOSE: The aim of this study was to identify the route of administration of 5-FU with the greatest pharmacological advantage in a rat model using non-invasive in vivo 19F nuclear magnetic resonance (NMR) spectroscopy. METHODS: 5-FU (50 mg/kg) was administered to anesthetized Wistar rats cannulated into the hepatic artery, portal vein or tail vein and 11 NMR spectra were acquired from the liver region to 60.5 min every 5.5 min. RESULTS: With systemic i.v. (tail vein) infusion, the 19F-NMR signal for 5-FU from the liver region peaked in the first spectrum (0-5.5 min), and then gradually decreased. The signal for the 5-FU catabolite alpha-fluoro-beta-alanine (FBAL) gradually increased to the sixth spectrum (0-33.0 min) and then plateaued. Following portal vein infusion the intensity of the first 5-FU spectrum was twice as high as that following i.v. infusion, but the intensity decreased and the FBAL signal increased gradually in the sixth spectrum as systemic i.v. infusion. In contrast, the intensity of the 5-FU signal following hepatic artery infusion was the same as that following portal vein infusion in the first spectrum, and maintained a strong intensity to the final spectrum (60.5 min). The FBAL signal was detected from the second spectrum following hepatic artery infusion, but its intensity was significantly weaker than that following i.v. or portal vein infusion. CONCLUSIONS: Hepatic arterial infusion resulted in the active form of 5-FU being present for a longer time and its degradation in the liver being suppressed compared with the results following portal vein infusion. This catabolic advantage of hepatic arterial infusion could lead to a more potent anti-tumor activity against liver metastases, but could also lead to significant host toxicity including biliary toxicity. We recommend that the dose/schedule of 5-FU administered via the hepatic artery should be adjusted carefully.

Animals↗
PubMed1998

Effects of (+)-8',8',8'-trifluoroabscisic acid on alpha-amylase expression and sugar accumulation in rice cells.

The effects of (+)-8',8',8'-trifluoroabscisic acid (trifluoro-ABA) on alpha-amylase expression were studied in rice embryoless half-seeds, scutella, and suspension-cultured cells derived from the embryo, and the effects of the analog on sugar accumulation were also studied in scutella and suspension-cultured cells. Treatment with (+)-trifluoro-ABA strongly inhibited the gibberellic acid-inducible expression of alpha-amylase I-1 encoded by RAmy1A in the aleurone layers of embryoless half-seeds at the levels of transcription, protein synthesis, and enzyme activity. It was also found that (+)-trifluoro-ABA stimulated (i) the uptake of glucose from the incubation medium and (ii) the synthesis of sucrose in scutellar tissues and suspension-cultured cells of rice. The biological activity of (+)-trifluoro-ABA was found to be more potent and persistent than that of natural ABA. We further examined the effects of trifluoro-ABA on the expression of alpha-amylase I-1 in scutellar tissues and suspension-cultured cells. It was found that (+)-trifluoro-ABA did not inhibit the formation of alpha-amylase I-1 in the absence of external glucose. However, glucose and (+)-trifluoro-ABA cooperatively suppressed the formation of alpha-amylase I-1. Judging from these results, we conclude that the regulatory mechanism for the expression of alpha-amylase I-1 in the scutellar epithelium is distinguishable from that operating in the aleurone layer.

Abscisic Acid↗
PubMed1998

A metastasis to the nasal tip from a cervical carcinoma--a case report.

Metastases to the nasal tip from gynecological malignancies are extremely rare. We present a case of a tumor metastatic to the nasal tip from a carcinoma of the uterine cervix. We administered high-dose focal irradiation to the site of the tumor. The literature on metastases to the nose, maxillary sinuses, and paranasal sinuses from gynecologic malignancies is reviewed.

Aged↗
PubMed1998

Problems with assays based on fibrin clot formation principle: analysis of multilaboratory data.

In order to investigate the inter-laboratory differences of coagulation assays, three different control plasmas were distributed for coagulation assays to 162 institutes. Three types of coagulation tests, that is, prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen (Fbg) assay were carried out by routine methods in each institute. In our laboratory, the Fbg concentrations were measured in two different plasmas using one instrument and nine reagents, and the Fbg concentrations were measured in ten control plasmas using three instruments and one reagent. Results were obtained as follows: (1) The coefficient of variance (CV) for control plasma with the highest value was significant in the PT assay and APTT assay. (2) Inter and intra-institute differences in PT and APTT assays were observed when the reagent or the instrument used was changed. (3) Inter and intra-institute differences in PT and APTT assays were also observed when both the reagent and the instrument were changed. (4) Inter and intra-institute differences in the PT and APTT assays were observed between the manual and the mechanical methods. (5) The CVs for the Fbg assays were the largest in the plasma at the lowest concentration of the three plasmas. (6) When control plasmas of three different Fbg concentrations were assayed, the number of the institutes which obtained a value greater than 3 standard deviations (SDs) was highest for the control plasma with the lowest concentrations of Fbg, and some of the instruments were not able to measure such a low Fbg concentration. (7) When the fibrinogen concentration was measured in various kinds of commercially-available control plasmas with a calibrated instrument, the values determined were different from the assigned ones and varied significantly from instrument to instrument. From the results, we concluded that standardization of the quality of control plasma, and its value assignment to the plasma should be established as soon as possible, and that a reliable standard fibrinogen assay should be developed.

Blood Coagulation↗
PubMed1998

Relationship between serum angiotensin-converting enzyme activity and plasma plasminogen activator inhibitor activity in patients with recent myocardial infarction.

BACKGROUND: An elevated level of angiotensin-converting enzyme (ACE) has been demonstrated to increase the risk of myocardial infarction. Plasminogen activator inhibitor (PAI) is the most important physiological inhibitor of tissue plasminogen activator in plasma. An elevated level of PAI has been reported to be associated with decreased fibrinolytic capacity and to constitute a marker of the risk for recurrent coronary thrombosis. METHODS: We measured the serum ACE activity and plasma PAI activity in 34 patients with recent myocardial infarction, and evaluated the correlation between these two values by linear regression analysis. We also administered captopril (37.5 mg/day) to 17 of these patients and placebo to the other 17 patients at random, and compared the changes in PAI activity and ACE activity in these two groups over a 1-month period. RESULTS: There was a significant correlation between the serum ACE activity and the plasma PAI activity at baseline in the patients (r = 0.498, P < 0.01). The captopril-treated patients showed significantly reduced PAI activity (P < 0.01), and a concomitant decrease in ACE activity. CONCLUSION: These results suggest that elevated ACE activity is associated with impaired fibrinolysis and that treatment with an ACE inhibitor improves the fibrinolytic function in patients with recent myocardial infarction. The results also suggest that the renin-angiotensin system plays a role in the increased risk of ischemic cardiovascular events when it is activated, and in the reduction of risk of recurrent myocardial infarction by ACE inhibition.

Adult↗
PubMed1997

Effects of fructose-induced hypertriglyceridemia on hepatorenal toxicity of acetaminophen in rats: role of pharmacokinetics and metabolism of acetaminophen.

Fructose-induced hypertriglyceridemic rats become resistant to hepatotoxicity and susceptible to nephrotoxicity of acetaminophen (APAP), as compared with normal ones. The present study was designed to test the hypothesis that alterations in the distribution of APAP and in the intrinsic susceptibility to toxicants are responsible for the alteration in hepatorenal toxicity of APAP in fructose-induced hypertriglyceridemic rats. Following APAP-administration (750 mg/kg, i.p.), fructose-pretreated rats (25% fructose in drinking water for 5 weeks) showed nephrotoxicity of APAP more promptly and more severely than normal ones. Renal APAP-concentrations at the early phase (15 and 30 min. after APAP-administration) were significantly greater in fructose-pretreated rats than those in normal ones. Plasma and hepatic APAP concentrations in fructose-pretreated rats were greater than those in normal ones only at the later phase (plasma; 6 hr, liver; 6 and 12 hr after APAP-administration). There were no significant differences in the APAP-induced depletion of hepatic and renal glutathione and in the basal hepatic and renal cytochrome P-450 contents between these rats. Fructose-pretreated rats were also more susceptible to p-aminophenol (PAP), a nephrotoxic metabolite of APAP, than normal rats. Therefore, enhanced susceptibility to APAP-nephrotoxicity in fructose-pretreated rats may be due, at least in part, to increased renal APAP concentration and increased intrinsic susceptibility to the metabolic nephrotoxicant.

Acetaminophen↗
PubMed1997

Effects of fructose-induced hypertriglyceridemia on hepatorenal toxicity of acetaminophen in rats. II. Role of enhancement of fructose metabolism and overproduction of triglyceride in the liver and kidney on hepatorenal toxicity of acetaminophen.

Fructose-induced hypertriglyceridemic rats are resistant to hepatoxicity and susceptible to nephrotoxicity of acetaminophen (APAP) as compared with normal ones. The present studied were designed to evaluate how fructose-treatment affects the developmental mode of hepatorenal toxicity of APAP. First, following fructose-pretreatment for various durations (1 day, 1 week or 3 weeks), 1-day-fructose-pretreatment induced hypertriglyceridemia and enhancement of APAP-nephrectoxicity simultaneously. However, it took at least 3 weeks for fructose-pretreatment to reduce APAP-hepatotoxicity. Second, following fructose, sucrose or glucose-pretreatment for 3 weeks, fructose-pretreated rats showed marked hypertriglyceridemia and modification of APAP-hepatorenal toxicity. Sucrose-pretreated rats showed less effects than fructose-pretreated rats. Glucose-pretreated rats showed no changes in plasma triglyceride and APAP-hepatorenal toxicity. Third, rats with hypertriglyceridemia induced by olive oil or Triton WR-1339 which did not produce enhanced metabolism and triglyceride-overproduction in the liver and kidney showed no modification of APAP-hepatorenal toxicity. Pretreatment of glycerol which was metabolized in liver and kidney and induced an overproduction of triglyceride resulted in an enhancement of APAP-nephrotoxicity. These results indicate that an enhancement of fructose metabolism and an overproduction of triglyceride in liver and kidney are responsible for the modification of APAP-hepatorenal toxicity in fructose-induced hypertriglyceridemic rats.

Acetaminophen↗
PubMed1997

Cardiotonic activity of the rhizome of Polygonatum sibiricum in rats.

The cardiotonic effect of the rhizome of Polygonatum sibiricum was investigated in the left atria of rats. The methanol extract of the rhizome of Polygonatum sibiricum (OM) (1-7 mg/ml) concentration-dependently increased the developed tension of the left atrium. It also strongly inhibited cAMP phosphodiesterase. The increase cAMP level correlated the increase in left atrial contraction. On the other hand, OM did not inhibit Na+, K+-ATPase. The cardiotonic effect of OM was strongly inhibited by reserpine, a sympatholytic agent. Furthermore, OM-treated left atria inhibited the tension produced by propranolol, a beta adrenocepter antagonist. These findings suggested that the cardiotonic effect is due to stimulating beta adrenoceptors through activation of sympathetic nerves.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Posterior communicating artery section during surgery for basilar tip aneurysm.

Although dividing the posterior communicating artery (PComA) during surgery has been criticized for increasing the risk of ischaemia, this procedure increase working space improving visibility and the ability to manipulate during treatment of basilar tip aneurysms via the pterional approach. We divided a hypoplastic PComA in 4 of our cases of basilar tip aneurysm. This was necessary because either (1) the length of the PComA and intracranial internal carotid artery (ICA) limited medial retraction of the ICA and access to the basilar bifurcation region, or (2) the PComA and its perforators ran just in front of the aneurysm, interfering with its exposure. We were able to clip the aneurysm neck in all four patients, three of whom had complications including temporary impairment of consciousness, ocular movement disorders and altered sensation in the extremities. Patients with complications showed transient hypersomnolence immediately after surgery; computed tomography showed small thalamic infarctions. However, in two of three patients the ischaemic events occurred contralateral to the side of PComA section. All patients regained consciousness within a week and were discharged with mild ocular movement palsies. In our cases except one with ischaemic complications, thalamic infarction probably resulted from thalamo-perforating artery injury when the aneurysm neck was clipped, rather than tuberothalamic artery injury due to section of the PComA. Taking previous reports and our results into consideration, we believe that division of a hypoplastic PComA is a safe procedure in particular cases when the grade of subarachnoid haemorrhage is not poor and there are no cerebrovascular risk factors, although we realize it is desirable to preserve normal blood flow.

Aged↗
PubMed1996

Activity of the intercostal muscle spindle afferents in the lower thoracic segments during spontaneous breathing in the cat.

Intraaxonal recordings of 33 spindle afferents from the inspiratory (n = 8) and expiratory (n = 25) intercostal muscles in the lower thoracic segment (T9-11), were made during spontaneous breathing in the anesthetized cat. All of them showed respiration-related activity. However, only three spindle afferents (one from the inspiratory and two from the expiratory intercostal muscles) showed higher firing frequency during the active contraction phase of the receptor-bearing muscle. The remaining 30 spindle afferents (seven from the inspiratory and 23 from the expiratory muscles) showed the maximum firing discharge during the passive stretch phase of the parent muscles. On the other hand, in the middle thoracic segments (T6-7), five of six spindle afferents from the inspiratory muscles and four of nine spindle afferents from the expiratory muscles showed maximum firing rate during parent muscle contraction in agreement with previous study. These results suggest that the spindle activity in the lower thoracic segments is dominated by muscle length changes, whereas that in the middle thoracic segments is largely via the fusimotor pathway.

Animals↗
PubMed1996

Detection of antibodies against bovine immunodeficiency-like virus in daily cattle in Hokkaido.

Serological survey of bovine immunodeficiency-like virus (BIV) infection was performed in cattle of 3 different farms in Hokkaido, where a relatively high seroprevalence was recorded for bovine leukemia virus (BLV). About a half of 120 cattle tested were seropositive for BLV, while 7.5% of the cattle were seropositive for BIV. Though increased numbers of leukocytes were frequently observed in BLV-seropositive cows, no such changes were observed in BIV-positive but BLV-negative cows. No correlation was demonstrated between BIV- and BLV-seroprevalence of the cattle.

Animals↗
PubMed1996

Demonstration of serum-neutralising antibody to turkey rhinotracheitis virus in serum from chicken flocks in Japan.

Since between 1989 and 1991, broiler, broiler breeder and layer chickens reared in three different prefectures of Japan, Hyogo, Ibaraki, and Miyazaki, were diagnosed clinically as having swollen head syndrome (SHS) these flocks were survey for antibody to turkey rhinotracheitis (TRT) virus using a serum neutralisation (SN) test. TRT-specific SN antibody was found in flocks of chickens in 2 out of the 3 prefectures. Thereafter, particular in the summers of both 1993 and 1994 outbreaks of SHS occurred in almost all areas of major chicken production in Japan. Almost chicken flocks affected by SHS possessed TRT SN antibody. No chicken sera collected between 1972 and 1988 possessed any SN antibody to TRT virus. It is suggested that in Japan, TRT virus is widely prevalent in areas of major poultry production.

Animals↗
PubMed1996

Immunomodulative effects of bovine immunodeficiency-like virus (BIV)-infection and mixed infection of BIV and bovine leukemia virus on sheep.

Experimental bovine immunodeficiency-like virus (BIV)-infection and mixed infection of BIV and bovine leukemia virus (BLV) were performed on sheep. BIV proviral DNA and anti-BIV antibodies were persistently detected in all BIV-inoculated sheep. A slight increase in lymphocyte counts was observed in BIV-infected sheep, but the percentages of CD4+ and CD8+ cells in sheep peripheral blood mononuclear cells (PBMCs) were not significantly changed. A transient decrease in lymphocyte blastogenic response to concanavalin. A was observed in two of three BIV-infected sheep at 3-6 months after inoculation. From 6 months after BLV-inoculation to sheep which were previously infected with BIV, the numbers of lymphocytes expressing a tumor-associated antigen (TAA) of bovine leukosis were increased compared to those of a sheep inoculated with BLV alone. The BLV titers in PBMCs and the antibody titers against BLV from sheep infected with both BIV and BLV were higher than those of a sheep inoculated with BLV alone.

Adjuvants, Immunologic↗