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Biomedical subjects

J Yamamoto

Publications and source records attributed to J Yamamoto.

At least 343 records · Page 19Linked to original sources
PubMed1986

The meiotic segregation of human sperm chromosomes in two men with accessory marker chromosomes.

Accessory marker chromosomes are occasionally discovered in normal individuals and they are presumed "clinically inert" since they do not appear to have any phenotypic effect. However, they do pose a theoretical risk at meiosis since they could disrupt the normal pairing and disjunction of homologous chromosomes. Sperm chromosome complements have been studied in two normal males, each of whom carry a small bisatellited accessory marker chromosome 47,XY, + mar (psps), to determine if these marker chromosomes are associated with an increased frequency of aneuploid gametes. Pronuclear chromosomes were visualized after in vitro fertilization of golden hamster eggs with human sperm. The frequency of sperm complements containing a marker chromosome was not significantly different from 50% as theoretically expected, in either male (17/43 and 13/31 with marker chromosomes). One male had 2/43 (4.7%) aneuploid sperm, which is very close to the average frequency of aneuploid sperm seen in control donors (5%). The other male had 6/31 complements with chromosomal abnormalities. One set of sperm chromosomes had structural abnormalities, and five (16.1%) had numerical abnormalities. This frequency of aneuploidy is significantly elevated over the frequency seen in control donors (P = .0002). It is particularly interesting that all the abnormalities involved small chromosomes, as would be expected if the marker chromosome participated in distributive pairing and thereby disrupted normal disjunction of chromosomes of similar size. These preliminary results suggest that accessory marker chromosomes may increase the risk of aneuploid gametes in some individuals.

Adult↗
PubMed1986

Effects of immunostimulation with OK432, coenzyme Q10, or levamisole on dimethylhydrazine-induced colonic carcinogenesis in rats.

Effects of immunostimulation with OK432, Coenzyme Q10 (Co-Q10), or levamisole on dimethylhydrazine (DMH)-induced colonic carcinogenesis were investigated in 45 Donryu-rats. The manipulation with one of these immunopotentiators did not prevent DMH-induced colonic carcinogenesis in these rats. However, the number of tumors was significantly reduced and the incidence of invasive carcinomas decreased by immunostimulation. The treatment also reduced the number of lesions with epithelial dysplasia within the flat colonic mucosa.

1,2-Dimethylhydrazine↗
PubMed1986

An increased frequency of human sperm chromosomal abnormalities after radiotherapy.

13 cancer patients were studied before radiotherapy (RT) and at regular intervals after RT to determine the effect of RT on chromosomal abnormalities in sperm. The men were 19-47 years old and received testicular radiation doses of 0.4-5.0 Gray. Human pronuclear sperm chromosomes were analysed after penetration of zona-pellucida-free hamster eggs. Unfortunately the hamster egg penetration rates were exceedingly low, both before and after RT and this limited the number of sperm chromosome complements which could be analysed. Before RT, the frequency of abnormal sperm chromosome complements was 0% (0/9). After RT, the majority of men were azoospermic for 24 months but complements could be analysed from 4 men. In the first 12 months the frequency of abnormalities was 13% (1/8) and at 24 months it was 13% (7/55). By 36 months after RT, most men had recovered sperm production and the frequency of abnormalities in 8 men was 21% (18/86), which is significantly higher than the rate in control donors (8.5%). For individual men the range was 6-67%, and there was a significant correlation between testicular radiation dose and the frequency of sperm chromosomal abnormalities. The frequencies of both numerical and structural abnormalities were significantly increased after RT. This is the first evidence that radiation may increase the frequency of chromosomal abnormalities in human gametes.

Adult↗
PubMed1986

Chromosomal analysis of unfertilized human oocytes.

Unfertilized human oocytes were obtained from women in an in-vitro fertilization programme. The women had a mean age of 29.4 years (range 24-35 years). Chromosomal complements could be analysed in 50 oocytes. Q-banding of the chromosomes facilitated identification of individual chromosomes: 34 oocytes (68%) had the normal haploid chromosomal complement, 14 complements were hypohaploid (28%), 1 complement was hyperhaploid (2%) and 2 had structural abnormalities (4%). (One oocyte had numerical and structural abnormalities). The 16 abnormal oocytes were obtained from 15 different women. A conservative estimate of aneuploidy in this sample is 4%; however, the frequency of aneuploidy may be higher if there is a predisposition to chromosome loss during oogenesis. This study provides information on the largest series of karyotyped unfertilized human oocytes published to date.

Adult↗
PubMed1986

Enhanced vasopressin release upon activation of the central neural mechanism in spontaneously hypertensive rats.

Monopolar electrical stimulation of the intermediate portion of the solitary nucleus in spontaneously hypertensive rats (SHRs) with cervical cordotomy and vagotomy resulted in a 1.68 times greater increase in plasma vasopressin concentration than in Wistar rats. The result implies that such an enhanced function of the central neural mechanism to release vasopressin in SHR backs up the functionally aberrant cardiovascular receptors.

Animals↗
PubMed1986

Acute systemic and regional hemodynamic effects of alpha 1-adrenoceptor blockade in conscious spontaneously hypertensive rats.

The acute hemodynamic effect of the selective alpha1-antagonist, 2-[4-(n-butyryl)-homopiperazine-1-y1]-4-amino-6,7-dimethoxy-quinazoline (bunazosin; E-643), was studied by the microsphere technique in 62 conscious spontaneously hypertensive rats. We found that a large fall in total peripheral resistance with a moderate increase in cardiac output accounted for the moderate decrease in arterial pressure; the heart rate did not change; the skeletal muscle, brain, heart, and gastrointestinal tract sensitively dilated, and kidney less sensitively dilated, their resistance vessels, with little change in their blood flow.

Adrenergic alpha-Antagonists↗
PubMed1986

Morphological study on the relationship between the muscular architecture of the ventricles and cardiac hypertrophy in the M strain of stroke-prone spontaneously hypertensive rats.

The relationships between blood pressure and hypertrophy in cardiac muscle cells and their nuclei were histometrically and microphotometrically examined in the M strain of stroke-prone spontaneously hypertensive rats (M-SHRSP). In 60-day-old M-SHRSP, hypertrophy of the cardiac muscle nuclei preceded increases in cardiac muscle cell diameters (MCD) and lengths (MCL). Increases in MCD started in the middle and deep layers of the lateral wall of the left ventricle. At 90 days of age, hypertrophy of cardiac muscle cells and nuclei occurred equally in the middle and deep layers of the left ventricle. Right ventricular hypertrophy began to appear after 90 days of age. In the middle and deep layers of the left ventricle and in the septum in 150-day-old M-SHRSP the MCL were 1.4 times those in 30-day-old M-SHRSP and the MCD were 1.8 times those in 30-day-old M-SHRSP.

Animals↗
PubMed1986

[A case of retroperitoneal alveolar soft part sarcoma].

We present the first case of retroperitoneal alveolar soft part sarcoma (ASPS) to be reported in Japan. The patient was a 27-years-old woman. After the retroperitoneal (tumors were) removed, bilateral lung metastasis was found and removed. Shortly thereafter, a recurrent retroperitoneal tumor arose, but because removal of the tumor was impossible, injection of 100 mg of cisplatin and 100 mg of adriamycin into the feeding artery was performed, and radiotherapy was also undertaken. However, the treatments were not effective, and the patient is now being followed on an outpatient basis.

Adult↗
PubMed1986

Systemic and regional hemodynamic effects of E614 (tripamide) as studied in conscious SHR.

Experiments were conducted on 53 conscious young male spontaneously hypertensive rats utilizing radiolabeled microspheres to analyze the acute and chronic hemodynamic effects of a newly synthesized antihypertensive drug, E614. The hemodynamic variables were observed on the 1st and 6th days of E614 treatment (p.o., once daily) in separate groups of rats. When the drug was given at a smaller dose (10 mg/kg body weight) over 6 days, the hypotensive action of E614 was found to be due mainly to a reduction of the total peripheral vascular resistance with no significant change in the cardiac output (CO). A supra-pharmacological dose (100 mg/kg), however, lowered the mean arterial pressure (AP) due mainly to a significant reduction of the CO in both the acute and chronic treatments. We found little influence of the drug on heart rate, and the coronary and renal vascular beds in any of the present experimental settings. The cerebral blood flow appeared not to change significantly unless the AP fell to such an extent that a fall in cerebral blood flow took place despite the autoregulatory mechanism of the brain blood vessels. The tissue perfusion was also well preserved in the gastrointestinal tract.

Animals↗
PubMed1985

Variation in activities of non-plasmin fibrinolytic proteinase and plasminogen-activator in the lung and spleen induced by bacterial endotoxin in rats with special reference to the effects of MD-805.

The behavior of direct fibrinolytic (non-plasmin) proteinase activity and plasminogen-activator activity in the lung and spleen was investigated in rats after a single intravenous injection of bacterial endotoxin, and the influence of thrombin inhibitors on the effects of the endotoxin was assessed. The non-plasmin fibrinolytic activity was markedly increased following a decrease of plasminogen-activator in the lung. In addition, variations in hematological parameters, i.e. a decrease of platelet count, fibrinogen level and antithrombin III, and an increase of blood urea nitrogen and euglobulin fibrinolytic activity, were induced by the injection, indicating the occurrence of disseminated intravascular coagulation. In comparative studies on the effects of the endotoxin injection and thrombin infusion, in the lung and spleen an increase of fibrinolytic proteinase activity was induced in a similar manner; the plasminogen-activator activity in the lung was decreased by the endotoxin injection but not decreased by the thrombin infusion. In prevention studies with heparin and MD-805, the latter was found to prevent the decrease of either fibrinogen or platelet count. However, the former failed to prevent the decrease of platelet count although that of the fibrinogen level was prevented. Heparin and MD-805 exerted no preventive effect on the endotoxin-induced variations of proteinase activity and plasminogen-activator activity in the lung.

Animals↗
PubMed1985

Effects of right ventricular ischemia on left ventricular geometry and the end-diastolic pressure-volume relationship in the dog.

We studied the effects of right ventricular ischemia on left ventricular three-dimensional geometry and the end-diastolic pressure-volume relationship in 16 open-chest dogs before and after pericardiectomy. Left ventricular volume was calculated from three internal dimensions measured with ultrasonic crystals. In one group of eight dogs, right coronary artery (RCA) occlusion for 2 min with the pericardium intact reduced aortic flow by 24 +/- 9% (p less than .001) and septal-lateral dimension by 8 +/- 5% (p less than .01), without changing anterior-posterior and apical-basal dimensions. However, parameters of left ventricular systolic function (aortic flow, left ventricular systolic pressure, peak dP/dt, and mean percent systolic shortening) were similar to those observed at a comparable level of left ventricular end-diastolic volume during inferior vena caval occlusion. In the other group of eight dogs, during RCA occlusion before pericardiectomy the left ventricular end-diastolic pressure-volume relationship determined during rapid blood transfusion shifted leftward and upward significantly from the preocclusion relationship. After pericardiectomy, RCA occlusion caused less significant changes in aortic flow and septal-lateral dimension as well as in the left ventricular end-diastolic pressure-volume relationship. We concluded that right ventricular ischemia causes a leftward shift of the interventricular septum in end-diastole and an alteration of the left ventricular end-diastolic pressure-volume relationship without changing left ventricular myocardial performance. These changes are enhanced by the intact pericardium.

Animals↗
PubMed1985

Are American psychiatric outpatients more depressed than Chinese outpatients?

It has often been suggested that Americans tend to seek psychiatric help for depression, whereas Chinese patients are more likely to have somatic symptoms of emotional disturbance. When the authors tested this assumption by studying 99 Taiwanese and 97 American psychiatric outpatients given computerized diagnoses based on information obtained in a standard psychiatric interview schedule, they found that the Chinese patients scored higher on the measures of somatization but also on the measures of depression.

Adolescent↗
PubMed1985

Characteristics of the cortical and hippocampal EEG power spectra of rabbits during normal behavioral states and after administration of CNS acting drugs.

The EEG power spectra of the motor cortex (MC) and hippocampus (HPC) in rabbits were characterized, and the effects of CNS acting drugs on the spectra were investigated. The EEGs of rabbits with chronically implanted electrodes were recorded with bipolar leads and simultaneously analyzed for 15 min with a computer to obtain their power spectra. MC spectra had one peak of delta wave, and HPC spectra had two peaks of delta and theta waves, whose peak powers and frequencies were changed in correspondence to the level of consciousness. Pentobarbital (20 mg/kg, i.v.) produced the peaks at 11 and 4 Hz in MC and HPC spectra, respectively. Morphine (5 mg/kg, i.v.) produced the peak at 7 Hz in MC spectra and shifted the theta wave peak of HPC to lower frequencies. Diazepam (4 mg/kg, i.v.) produced the peak at 14 Hz in MC spectra and decreased the two peak powers in HPC spectra. Chlorpromazine (4 mg/kg, i.v.) shifted the theta wave peak of HPC to lower frequencies. Amitriptyline (5 mg/kg, i.v.) increased the peak powers of the delta waves in MC and HPC spectra. These results suggest that each of the five CNS acting drugs produces the characteristic spectra, and they are different from the spectra obtained during normal behavioral states.

Amitriptyline↗
PubMed1985

Production of the modified form of human plasminogen by alpha 2-macroglobulin-plasmin complexes.

It has been speculated that the modified form of plasminogen, a precursor of proteolytic enzyme plasmin in plasma, plays an important role in fibrinolysis in the blood. The present study was undertaken to examine the production by alpha 2-macroglobulin-plasmin complexes. alpha 2-Macroglobulin-plasmin complexes were purified from urokinase-activated plasma by affinity chromatography on lysine-Sepharose and gel filtration on Ultrogel AcA 22. The plasmin complex converted native plasminogen into the modified form more easily in the presence of epsilon-aminocaproic acid. The modification of native plasminogen by alpha 2-macroglobulin-bound plasmin was completely inhibited by aprotinin, and partly by soybean trypsin inhibitor. alpha 2-macroglobulin-bound plasmin produced modified plasminogen in human plasma where potent plasmin inhibitors exist, though the degree of production was small. The present results support the speculation of the important role of the modified form in vivo.

Animals↗
PubMed1985

Approach for quantifying the overall function of the ascending central neural integration to release vasopressin in rats.

Electrical stimulation of the intermediate portion of the solitary nucleus (SOL) is known to consistently elicit a pressor response and increase in the release of vasopressin (VP) in rats, when the cervical spinal cord and vago-sympathetic trunks are cut. The aim of the present study was to provide a methodological assessment for this technique, in order to quantify the central neuroendocrine function to release VP. Experiments were conducted on rats with cervical cordotomy and vagotomy, under 60% N2O anesthesia and artificial ventilation. The animals were maintained at their normal arterial blood pressure by infusing phenylephrine, which itself exerted little influence on the arterial plasma VP concentration (pVP) during SOL stimulation. In order to prevent blood loss, cross circulation with a donor rat was utilized in the blood sampling for pVP determination. We confirmed that this technique itself did not significantly affect the pVP level. A monopolar stimulus at a frequency of 50 Hz was found to produce the pressor response most effectively. The current spread of the stimulation (0.5 ms duration; 1 s on/1 s off; up to at least 120 microA) did not induce a false-positive pressor response mediated by other structures adjacent to the SOL. We suggest that electrical stimulation of the SOL in rats with cervical cordotomy and vagotomy, for observing the pressor response and/or increase of pVP, represents a rapid approach for screening the overall function of the ascending efferent part of the reflex mechanisms to release VP.

Animals↗