Search PubMed⌕ Search

Biomedical subjects

K Muramatsu

Publications and source records attributed to K Muramatsu.

At least 91 records · Page 5Linked to original sources
PubMed1994

Effects of N-nitro-L-arginine on coronary artery tone and reactive hyperemia after brief coronary occlusion in conscious dogs.

AIM: To determine the role of an endothelium-derived relaxing factor (nitric oxide) in controlling basal coronary tone and coronary vasomotion after brief coronary occlusion (reactive hyperemia). METHODS: In 10 chronically instrumented conscious dogs, we studied the diameter changes of the large epicardial coronary artery and coronary blood flow in response to intracoronary administration of acetylcholine (0.1 and 1 microgram) and brief coronary occlusion for 5 and 20 s before and after intracoronary infusion of N-nitro-L-arginine (LNNA). RESULTS: Intracoronary infusion of LNNA (1, 3, and 10 mg) decreased the diameter of the large epicardial coronary artery and coronary blood flow in a dose-dependent manner without altering arterial pressure and heart rate. LNNA (10 mg) significantly attenuated the increase in artery diameter and coronary blood flow by acetylcholine. The ratio of artery dilation to the blood flow response after acetylcholine was not affected by LNNA. LNNA (10 mg) significantly decreased the ratio of repayment to debt flow volume of reactive hyperemia, but did not affect the ratio of peak to resting flow; it also significantly attenuated the reactive dilation of the large epicardial coronary artery after reactive hyperemia. The ratio of artery dilation to repayment flow volume (micron/ml) during reactive hyperemia was attenuated significantly by LNNA. CONCLUSION: These findings suggest that endothelium-derived nitric oxide may contribute to basal coronary tone and that reactive dilation of the large epicardial coronary artery during reactive hyperemia was caused by flow-mediated nitric oxide release, whereas coronary artery dilation after acetylcholine was caused largely by the direct receptor-mediated release of nitric oxide.

Acetylcholine↗
PubMed1993

Results of vascularized joint allograft under immunosuppression with cyclosporine.

The effects of cyclosporine (CsA), a strong immunosuppressive drug, on vascularized allogeneic joint transplantations were examined. An orthotopical transplant model of a vascularized knee joint allograft was developed using inbred DA and Lewis rats to investigate the fate of grafts following withdrawal of short-term immunosuppression compared to continuous immunosuppression with CsA. Five isograft controls acquired solid bone union at both femur and tibia sites within 4 weeks, and joint function as skeletal support was maintained until 25 weeks. Without immunosuppression, ten allografts were severely rejected within the first week, and joint destruction occurred immediately. Twenty-five short-term immunosuppressed rats acquired solid union, but, after withdrawal of immunosuppression, grafted joints showed gradual rejection and were destroyed due to pathological fractures or joint instability, although partial revascularization from the recipient occurred. Ten allografts under continuous immunosuppression at a dose of 10 mg/kg/day showed no rejection and remained viable for 12 weeks postoperatively, but thereafter all rats died. Death was considered to be a side effect of CsA. Fifteen animals, under continuous immunosuppression at a dose of 5 mg/kg/day, showed no rejection except in the bone marrow; the grafted joint function was not effected until 25 weeks. Continuous treatment with low and nontoxic doses (5 mg/kg/day) of CsA was necessary to maintain the functions of the grafted joint.

Animals↗
PubMed1993

Meiotic mutations from natural populations of Drosophila melanogaster.

Two meiotic genes from natural populations are described. A female meiotic mutation, mei(1)g13, mapped to 17.4 on the X chromosome, causes nondisjunction of all homologs except for the fourth chromosomes. In addition, it reduces recombination by 10% in the homozygotes and causes 18% increased recombination in the heterozygotes. A male meiotic mutation, mei-1223m144, is located on the third chromosome. Although this mutation causes nondisjunction of all chromosomes, each chromosome pair exhibits a different nondisjunction frequency. Large variations in the sizes of the premature sperm heads observed in the homozygotes may reflect irregular meiotic pairing and the subsequent abnormal segregation, resulting in aneuploid chromosome complements.

Animals↗
PubMed1993

Lymphokine production by mesenteric lymph node cells from BALB/C mice during Hymenolepis nana infection.

Mesenteric lymph node cells (MLNC) prepared from BALB/c mice during infection with Hymenolepis nana proliferated extensively when cultured in the presence of soluble egg antigen, as assessed by measuring 3H-thymidine incorporation. Analysis of Hymenolepis-specific proliferative cells in MLNC by using monoclonal antibody specific for mouse T lymphocyte surface antigens revealed that the proliferative response of MLNC was mediated by Thy-1.2+, L3T4+ cells, that is, helper T cells. Supernatant of MLNC cultured with egg antigen contained large amounts of interleukin-2 and interferon-gamma, but only low levels of interleukin-5. The titer of these cytokines did not correlate with the interval between oral infection and collection of MLNC. These results strongly indicate that the Th1 subtype of helper T lymphocytes respond well to stimulation of H. nana egg antigen and suggest that acute inflammatory responses are involved in host-protective immunity to H. nana.

Animals↗
PubMed1993

Diaschisis.

Following acute, localized lesions of the central nervous system, arising from any cause, there are immediate depressions of neuronal synaptic functions in other areas of the central nervous system remote from the lesion. These remote effects result from deafferentation, a phenomenon known as "diaschisis". After an interval of time, which will vary directly with the severity of the lesion, functional recovery occurs due to synaptic reactivation of neurones. This is favourably influenced by rehabilitation. Diaschisis most commonly manifests itself by such neurological signs as impaired consciousness or cognitive impairments including dementia, dyspraxias, dystaxias, dysphasias, incoordination and sensory neglect. The nature of diaschisis has been demonstrated by widespread depressions of local cerebral blood flow and metabolism extending far beyond the anatomical lesion. Recovery of function is associated with recovery of local perfusion and metabolism.

Afferent Pathways↗
PubMed1992

Variability of respiratory system compliance in mechanically ventilated infants.

We measured respiratory flow, volume by integrated flow, and airway pressure in four mechanically ventilated infants. Compliance of the respiratory system (Crs) was measured by the multiple occlusion method. Airway occlusion and release were achieved by a balloon in an occlusion valve between the endotracheal tube and a pneumotachometer, all connected in series with the respirator circuit. Values of Crs varied greatly due to changes in mean airway pressure (MAP). The Crs increased with the elevation of MAP on some occasions and decreased on others. Values of Crs also varied corresponding to different occlusion pressures for individual levels of MAP. Thus Crs changed continuously, even within a single respiratory cycle. The observed variability in Crs was explained by the following mechanism: a pressure-volume (P-V) loop of tidal ventilation moves its position within the pressure-volume diagram and changes shape due to variations of the ventilator settings. In some infants the lungs were ventilated in the range of the linear portion of the P-V diagram while in others they may have been ventilated on the flattened portion. Some patients had convex expiratory P-V curves even with low pressure swings during tidal ventilation.

Airway Resistance↗
PubMed1992

Macrophages in protective immunity to Hymenolepis nana in mice.

When mice were treated with carrageenan just before infection with eggs of Hymenolepis nana, they failed to exhibit sterile immunity to the egg challenge, with evidence of a decrease in the number of peripheral macrophages (Mø) and the rate of carbon clearance. Although there were high levels of interleukin-1 (IL-1) released into the intestinal tracts of the parasitized mice at challenge infection, there was almost no release of IL-1 in those treated with carrageenan just before challenge. These results strongly suggest that Mø have an important role in protective immunity to H. nana in mice.

Animals↗
PubMed1992

[An outbreak of municipal water-associated food poisoning caused by Salmonella enteritidis].

An outbreak of municipal water-associated food poisoning by Salmonella Enteritidis occurred in Takatoh Town. Nagano prefecture during September 4 to 19, 1989. The major symptoms observed in the 680 patients consisted of diarrhea (70.9%), abdominal pain (51.2%), fever (44.6%), headache (27.9%), nausea (5.9%) and vomiting (5.7%). In the outbreak, S. Enteritidis was the only suspected etiological agent isolated from both patients and municipal water supply. All of the 21 isolates were lysine decarboxylase activity negative. In other respects, the isolates conformed to the general characteristics of Salmonella. All of them were further characterized by phagovar 8 type, uniform drug susceptibilities and carrying 2.7 kb plasmid. Inspite of the evidence that the infection caused by a peculiar strain linked to the strain in municipal water supply used by the patients, it was impossible to determine the exact source of contamination in the water. The outbreak above seems to be the most large-scale among those of Salmonella found poisoning associated with drinking water in Japan.

Adolescent↗
PubMed1992

[Experimental studies on vascularized allogeneic joint transplantation in rats].

Examination was made on the effects of Cyclosporine A, an immunosuppressive drug, on vascularized joint allografts. Genetically inbred DA and Lewis rats were used and a model of knee joint orthotopical transplantation across the major histocompatibility barrier was developed. Nine non-immunosuppressive allografts failed to acquire bony union. Twenty-seven short term immunosuppressive rats acquired solid union, but following withdrawal of immunosuppression, the grafts were soon rejected and joint function was lost due to pathological fractures of the grafted bone or joint instability. Thirteen allografts of continuous immunosuppression at a dose of 5 mg/kg/day showed no rejection, though the bone marrow did, and there was no impairment of function. The continuous administration of low and non-toxic dose of Cyclosporine A was necessary for maintaining grafted joint functions.

Animals↗
PubMed1991

Effects of endothelin-1 on epicardial coronary tone, coronary blood flow, ECG-ST change and regional wall motion in anesthetized dogs.

The effects of intracoronary-administrated endothelin-1 on coronary hemodynamics and regional myocardial function were studied in anesthetized open-chest dogs. Epicardial coronary diameter (CoD) and coronary blood flow (CBF) were measured by a sonomicrometer of 10 MHz piezoelectric crystals and an electro-magnetic flow probe on the left circumflex coronary artery (LCX). Regional wall motion was sonomicrometrically measured at regions supplied by the LCX and left anterior descending artery (LAD) and electrocardiograms were recorded. Endothelin-1, administered as a bolus injections into the LCX via an intracoronary cannula, in a dose-dependent manner reduced COD and CBF. The extent of the reduction of COD and CBF at a dose-dependent manner reduced COD and CBF. The extent of the reduction of COD and CBF at a dose of 300 pmol was 12.3 +/- 1.5% (P less than 0.01) and 86 +/- 5% (P less than 0.01), respectively, of the control. The extent of CBF reduction and deterioration of systolic wall motion were linearly related with the dosage of endothelin-1. ST-elevation (lead II) and fatal ECG abnormalities, including complete atrioventricular block or ventricular fibrillation, were observed with doses above 60 and 100 pmol, respectively. Coronary angiography revealed that filling defects of dye were propagated from the third or distal branches to those of more proximal arteries when the doses of endothelin-1 were cumulatively infused into the LCX. Accordingly, lethal myocardial ischemia induced by endothelin-1 is produced by critical obstruction of rather small coronary vessels.

Animals↗
PubMed1991

Hymenolepis nana: adoptive transfer of protective immunity and delayed type hypersensitivity response with mesenteric lymph node cells in mice.

A marked degree of footpad swelling was observed in BALB/c mice infected with Hymenolepis nana eggs, when soluble egg antigen was injected into their footpads 4 to 21 days after the egg infection, indicating delayed type hypersensitivity responses in infected mice. Adoptive transfer with mesenteric lymph node cells from donor mice (BALB/c strain; +/+) infected with eggs 4 days before cell collection could confer this hypersensitivity to recipient nude mice (BALB/c strain; nu/nu). These mesenteric lymph node cells were then divided into two fractions, blast-enriched and blast-depleted cells, by density gradient centrifugation with Percoll. The recipients intravenously injected with the blast-depleted cell fraction showed a marked increase in footpad thickness, whereas the intravenous transfer of the blast-enriched cell fraction resulted in an insignificant increase in footpad thickness. The transfer of the blast-enriched cell fraction, but not of the blast-depleted cell fraction, conferred a strong adoptive immunity on syngeneic recipient nude mice, when the immunity transferred was assessed by examining cysticercoids developed in the intestinal villi on Day 4 of challenge infection. The lack of delayed type hypersensitivity response in mice that received the blast-enriched cell population was not due to a lack of the capacity of the cells to induce the response, because the cells were capable of inducing a significant increase in thickness of footpads of normal mice when these cells were locally injected into the footpad together with soluble egg antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Two generalized transducing phages in Vibrio parahaemolyticus and Vibrio alginolyticus.

Two bacteriophages named phi VP253 and phi VP143 isolated after ultraviolet induction from lysogenic strains of Vibrio parahaemolyticus have been shown to be generalized transducing phages. So far, seven different auxotrophic markers of a V. parahaemolyticus strain could be transduced at the frequencies ranging from 2.2 x 10(-7) to 7.5 x 10(-5) per infected cell at the m.o.i. of approximately 1.0. The phage phi VP143, but not phi VP253, lysed 20 of the 28 strains of V. alginolyticus and the occurrence of generalized transduction by this phage in this Vibrio species has been confirmed. Molecular size of the genomes of both phages were estimated to be approximately 48 kb as judged from electrophoretic mobilities of the DNAs digested with HindIII endonuclease. The results and similarity of the two phages in morphology and other properties suggest very close relatedness of the phages.

Animals↗
PubMed1991

Clinical characteristics of patients with dilated cardiomyopathy and bradyarrhythmias.

The clinical characteristics of patients with dilated cardiomyopathy and bradyarrhythmias were studied. Among 50 patients with dilated cardiomyopathy, 6 had bradyarrhythmias. Among these patients were one with sinus bradycardia, one with atrial fibrillation and slow ventricular responses and sick sinus syndrome (SSS), one with SSS with advanced AV block, and 3 with advanced AV block. The average age at the onset of their cardiac symptoms (60.3 +/- 12.1 years (mean +/- SD)) was significantly (p less than 0.01) higher than that of 43 patients without bradyarrhythmias (40.0 +/- 17.6). The left ventricular diastolic dimension and ejection fraction were similar among patients with and without bradyarrhythmias. In 31 follow-up patients without bradyarrhythmias, 8 (25.8%) died of cardiac causes; whereas, in 5 patients with bradyarrhythmias, 4 had been implanted with pacemakers and 3 (60.0%) died of cardiac causes. Furthermore, the age at the onset of cardiac symptoms in patients with any kind of conduction disturbance, except tachyarrhythmia, was 50.4 +/- 16.5 years (n = 25), which was significantly higher (p less than 0.02) than that of patients without conduction disturbances (37.7 +/- 19.3 years, n = 23). We concluded that bradyarrhythmias are not rare complications in patients with dilated cardiomyopathy, and the mortality rate tends to be higher in patients with bradyarrhythmias than in those without them. Furthermore, the risks of conduction disturbances and bradyarrhythmias were higher in the elderly patients.

Adult↗
PubMed1990

[O5-antigenic classification of Salmonella typhimurium isolated from outbreaks of Salmonella enteritis].

S. typhimurium (STM) were isolated from outbreaks of Salmonella enteritis and were studied for their reactivity to monoclonal antibody TMY1 specific for Salmonella O5-antigen with the following results; By using the bacterial agglutination test with TMY1, STM were classified into O5-antigenic molecule positive and negative (copenhagen type) strains, suggesting the usefulness of TMY1 as an exquisite epidemiologic tool for Salmonella enteritis.

Antigens, Bacterial↗
PubMed1990

Significance of the amino acid composition of dietary protein in the regulation of plasma cholesterol.

Three approaches were employed to identify the amino acid residue(s) that is responsible for the different effects of dietary proteins on the plasma cholesterol level in rats fed cholesterol-enriched diets. 1) Experiments on the effects of individual amino acids added to a 25% casein diet showed that sulfur-containing amino acids have the most potent effects on the plasma cholesterol level. Under the dietary conditions used, methionine significantly increased the level of plasma cholesterol while cystine decreased it. It was found that glycine can prevent the methionine-induced enhancement of plasma cholesterol. 2) There was a significant negative correlation between cystine content of dietary proteins and plasma cholesterol levels when animals were fed 7 kinds of animal and plant proteins. 3) Experiments with amino acid mixtures varying in methionine, cystine, and glycine content showed that diets high in methionine and low in cystine and glycine content tend to increase the plasma cholesterol level and diets of opposite amino acid content tend to decrease the plasma cholesterol level. From these results, it was suggested that sulfur-containing amino acids and glycine in dietary proteins are responsible, at least in part, for the alteration of plasma cholesterol level by dietary proteins.

Amino Acids↗
PubMed1989

Effects of a selective inhibitor of cyclic AMP phosphodiesterase on the pial microcirculation in feline cerebral ischemia.

We evaluated the effects of cilostazol, a selective inhibitor of cyclic adenosine monophosphate phosphodiesterase, on the pial vessels of adult cats subjected to endothelial damage followed by middle cerebral artery occlusion. Six cats were treated with cilostazol and four with 30% N,N-dimethylformamide in 70% saline (solvent). The brain surface was irradiated with ultraviolet rays through a cranial window for 3 minutes to selectively damage the endothelium of the pial vessels in both groups. Beginning 32 minutes after termination of the irradiation, the middle cerebral artery was occluded for 30 minutes. Thirty minutes before occlusion, intravenous infusion of 30 micrograms/kg/min cilostazol or 0.1 ml/kg/min solvent was begun and continued until the end of the study. Before occlusion, the infusion of cilostazol induced a significant (p less than 0.05) dilatation while the infusion of solvent produced no significant changes in the diameter of the pial arteries. The pial veins of solvent-treated cats showed significant (p less than 0.05) constriction during occlusion, whereas cilostazol-treated cats exhibited only mild constriction of the pial veins. The formation of platelet thrombi after occlusion was significantly (p less than 0.05) inhibited in the pial veins of cilostazol-treated compared with solvent-treated cats. Similarly, the microcirculation of the pial veins was effectively restored after reopening of the middle cerebral artery in cilostazol-treated compared with solvent-treated cats. Our data suggest that cilostazol is an effective antithrombotic agent as well as a potent vasodilator acting on vascular smooth muscle.

Animals↗