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Biomedical subjects

Y Ohyabu

Publications and source records attributed to Y Ohyabu.

At least 19 recordsLinked to original sources
PubMed2001

Lack of positive interaction between CO2 and hypoxic stimulation for P(CO2)-VAS response slope in humans.

To compare the effect of hypoxia on ventilatory responses and respiratory sensation to carbon dioxide, 29 young adults were examined using a modified Read's rebreathing method with four experimental conditions. We used varying gas mixtures and kept PET(O2) constant at >300, 100, 80 and 60 mmHg for each four rebreathing tests. Respiratory sensation was measured by visual analog scale (VAS). The slope of the CO2-ventilation response curve increased significantly with hypoxia, confirming a positive ventilatory interaction between hypoxia and hypercapnia. However, the slope of the CO2-VAS response curve remained unchanged. The V(E)-VAS relation slope tended to become depressed with advancing hypoxia, i.e. the magnitude of VAS elicited by a given ventilation decreased with hypoxia, signifying that dyspneic sensation was effectively mitigated during hypoxic hyperventilation. We suggest that this relief of dyspneic sensation might be due to the inhibitory respiratory effect from augmented pulmonary stretch receptor (PSR) activity.

Adult↗
PubMed2001

Cellular characterization of an in-vitro cell culture model of seal-induced cardiac ischaemia.

The lack of a well-characterized in-vitro cell culture model of load-induced cardiac ischaemia has hampered investigations into the mechanism of ischemic injury. We therefore developed a new in-vitro model of cardiac ischaemia that mimics distinct features of ischaemic injury. Neonatal rat heart cells were cultured in a sealed flask for 24-72 h. In this environment, the cells were exposed to stresses of hypoxia, acidosis and stagnant incubation medium. The pO2 and pH of the medium gradually decreased during the ischaemic insult and ultimately fell to a level of 14 mmHg and pH 6.8, respectively. The model triggered severe cell injury, including morphological degeneration, CPK release, beating impairment and ATP depletion. Apoptosis occurred in some cardiomyocytes as early as 24 h after onset of seal-induced ischaemia. This was evidenced by positive nuclear staining using Hoechst 33258 and by the induction of caspase-3 mRNA. By 72 h, internucleosomal DNA fragmentation was observed in 45% of the myocytes; however, a non-myocyte preparation subjected to the same ischaemic insult exhibited no evidence of DNA fragmentation. These results demonstrate that neonatal cardiomyocytes subjected to the new simulated ischaemia model exhibit several similarities to cardiac ischaemia, including the simultaneous appearance of necrosis, breakdown of cellular ATP, beating cessation and apoptosis. The new model should prove useful in unravelling the molecular alterations underlying ischaemic injury and myocardial apoptosis.

Adenosine Triphosphate↗
PubMed2000

Taurine attenuates hypertrophy induced by angiotensin II in cultured neonatal rat cardiac myocytes.

The effect of taurine on angiotensin II-induced changes in cell morphology and biochemistry of the cultured neonatal cardiomyocyte was examined. Angiotensin II (1-100 nM) alone caused a slow increase in the surface area of the myocyte accompanied by an induction of the expression of atrial natriuretic peptide (ANP) and an upregulation of transforming growth factor beta(1) gene (TGF-beta(1)). The signaling pathway of angiotensin II (1-100 nM) was found to proceed through protein kinase C and the rapid activation of mitogen-activated protein (MAP) kinases. Pretreatment of the myocyte with taurine (20 mM) in the absence of angiotensin II had no visible effect on cell size or growth rate. However, the cells that were pretreated with taurine (20 mM) for 24 h exhibited reduced responsiveness to angiotensin II (100 nM) relative to surface cell area enlargement and the upregulation of the late and growth factor genes(ANP, TGF-beta(1)). Angiotensin II-mediated activation of the MAP kinases (extracellular signal-regulated protein kinase 1/2: ERK1/2) was not blocked by taurine. Taurine reduced the phosphorylation of a 29-kDa protein, a reaction which was enhanced by angiotensin II and appears to involve protein kinase C step. The results indicate that taurine is an effective inhibitor of certain aspects of angiotensin II action.

Angiotensin II↗
PubMed1991

Survival of patients with bladder cancer--analysis of prognostic factors.

A recognition of prognostic factors in the treatment of patients with bladder cancer is important. Using a variety of clinical and histological parameters, we have performed monovariable and multivariable analyses on the survival rates of patients. Eighty three patients with bladder cancer who underwent total cystectomy were studied. Eleven factors were evaluated, i.e. age, sex, tumor form, number and size of the tumors, histological stage and grade, intramural infiltration pattern, presence of intramural lymphatic and venous invasion, and the use of adjuvant chemotherapy. Monovariable analysis of survival curves indicated that histological stage and grade, intramural lymphatic invasion, venous invasion, and infiltration pattern are important as prognostic factors. Multivariable analysis, which is more relevant than monovariable analysis, showed that histological stage, followed by age, histological grade, intramural lymphatic invasion and infiltration pattern, in order of decreasing value, were most important as prognostic factors.

Female↗
PubMed1990

Ventilatory and heart rate chemosensitivity in track-and-field athletes.

Fifty-four male track-and-field athletes and 18 male non-athletes were examined by isocapnic progressive hypoxia and CO2 rebreathing tests. Ventilatory and heart rate (HR) responses to hypoxia were analysed by a hyperbolic relationship and the ventilatory response to hypercapnia by a linear regression. The results showed that ventilatory sensitivity during hypoxia was significantly attenuated in the long-distance runners and sprinters compared to the non-athletes. Although heart rate sensitivity during hypoxia in none of the athletes showed a significant difference compared to that of the non-athletes, baseline HR in the long-distance runners was significantly lower than that of the non-athletes. None of the athletes showed significant differences in ventilatory sensitivity during hypercapnia compared to the non-athletes.

Adolescent↗
PubMed1990

Exercise and ventilatory chemosensitivities.

Although physical training does not affect CO2 chemosensitivity at rest, different kinds of physical training affect hypoxic ventilatory chemosensitivity at rest in different ways. On the other hand, a number of studies indicated that the mechanism of exercise hyperpnea is related to hypoxic chemosensitivity.

Exercise↗
PubMed1990

[Mucin-producing cystadenoma (borderline malignancy) of the renal pelvis and ureter. A case report].

The patient was a 63-year-old women who visited our hospital with the chief complaints of swelling, chills, fever and right lumbago. Fifteen years ago, she received surgical exploration for right renal stones at another department of urology. A large, soft and round kidney was palpable from the right upper quadrant of abdomen to the right lower abdomen. The parenchyma of the right kidney was thinned and inside the kidney there was a huge amount of yellowish mucin. The histological diagnosis was mucin-producing cyst-adenoma (borderline malignancy) of the renal pelvis and ureter. Mucin-producing cystadenoma of the renal pelvis and ureter origin was very rare, and only 4 similar cases to our patient were so far reported.

Cystadenoma↗
PubMed1989

Comparison of ventilatory and heart rate responses to hypoxia at rest and during light exercise in high school judo athletes.

Ventilatory and heart rate responses to hypoxia at rest and during light exercise (30W) were compared in 21 high school judo athletes. The results of ventilatory and heart rate responses to hypoxia were analyzed by the hyperbolic equations, VE = VO + AVE/(PETO2-CVE) and HR = HRO + AHR/(PETO2-CHR), respectively, where VE and HR are the observed ventilation and heart rate, VO and HRO the horizontal asymptote in ventilation and heart rate for infinite endtidal PO2 (PETO2), AVE and AHR the slope constants indicating the magnitude of hypoxic sensitivity, and CVE and CHR the vertical asymptote in PETO2 for infinite ventilation and heart rate. AVE was further recalculated after VE was normalized for a 70 kg body mass, using an allometric coefficient, and was defined as AVEN. The absolute magnitudes of hypoxic response in ventilation and heart rate at PETO2 40 mmHg were also determined as delta V40 = AVE/(40-CVE) and delta HR40 = AHR/(40-CHR), respectively. (1) The enhanced hypoxic ventilatory chemosensitivity previously found in heavy-weight judo athletes at rest was confirmed. However this characteristic disappeared with exercise. (2) It was also confirmed that there was no significant correlation between hypoxic heart rate sensitivity and body weight at rest. With exercise, this was found also to be the case. (3) On the other hand, when the hypoxic responses at rest were compared to those of the exercise studies, significant positive correlations were illustrated in both ventilatory and heart rate responsiveness. These results demonstrated that although ventilatory and heart rate responses did not quantitatively exhibit parallel change, the two activities did demonstrate a certain synergism between rest and exercise.

Adolescent↗
PubMed1989

[Milk of calcium renal stone: a case report].

A case of milk of calcium renal stone is presented. A 29-year-old woman complained of fever up and left lateral abdominal pain was diagnosis of milk of calcium renal stone. Ultrasonography showed hemispheric hypoechoic area and horizontal high echoic line with acoustic shadow. So-called "milk of calcium renal stone" is relatively uncommon and reports of ultrasonographic features are rare.

Acute Disease↗
PubMed1989

[The retroperitoneal liposarcoma: a case report].

A 62-year-old woman was admitted to our hospital because of a mass in the right abdomen. Ultrasonography, aortography and computed tomographic (CT) scanning revealed the right kidney displaced by a huge and avascular mass containing fatty tissue. Also magnetic resonance imaging (MRI) indicated that it was contained of lipomatous tissue and demonstrated the mass occupying the entire right abdominal cavity. The tumor including the right kidney was resected, following diagnosis of the retroperitoneal tumor. The exercised tumor measured 28 X 22 X 18 cm and weighed 2,010g. The histological diagnosis was well-differentiated liposarcoma. She has been healthy for three months following postoperative chemotherapy. Many reports have been made on the ultrasonographic and CT appearance of retroperitoneal liposarcoma, but few have been made on the MRI appearance. According to our case, imaging diagnosis by MRI also seems to be useful in making a histological diagnosis of liposarcoma.

Combined Modality Therapy↗
PubMed1987

Differences in ventilatory responses to hypoxia and hypercapnia between normal and judo athletes with moderate obesity.

Hypercapnic and hypoxic ventilatory sensitivities were compared in twenty-one judoists and 24 control subjects with similar degrees of moderate obesity. Data from ten non-obese control subjects were also included as a reference. Mean body weight (BW) and % of ideal body weight in the judoists and the obese and non-obese controls were 100 +/- 14.8, 94.4 +/- 5.3 and 63.4 +/- 6.1 (mean +/- SD) kg, and 142.3 +/- 16.7, 142.2 +/- 12.9 and 98.4 +/- 10.7%, respectively. Mean body fat in the judoists was 16.2 +/- 13.9%, being 25.3 +/- 7.7% in the obese control group, the difference being significant (p less than 0.01). Hypercapnic sensitivities in terms of the CO2 ventilatory response slope (S) and its normalized value for 70 kg BW (SN) of the obese controls were higher than the judoists. These findings were also verified by the CO2-occlusion pressure responses. S and SN in the obese controls were significantly correlated with BW and % body fat. However, no positive correlation was found between BW and S or SN in the judoists as well as between lean body mass and S or SN in the obese control. Hypoxic sensitivity in terms of the PETO2-ventilation hyperbola slope (A) and its normalized value (AN) in the obese control was significantly higher than the non-obese control, but the difference from the judoists was not significant. A and AN were found to increase with increasing % body fat in both judoists and obese controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1986

Hypercapnic and hypoxic ventilatory responses during growth.

Cross-sectional studies on hypercapnic and hypoxic ventilatory chemosensitivities were performed in 71 children ranging in age from 7 to 18 yrs. The subjects were classified into 6 successive 2-year age groups. CO2 ventilatory response was measured by rebreathing 5% CO2 in O2, a slight modification of the method originally proposed by Read. The results were evaluated when the CO2-ventilation feedback control system was supposed to have attained the open-loop condition. Hypoxic ventilatory response was measured by the isocapnic progressive hypoxia test. To obtain good reproducibility in the ventilatory response, end-tidal PCO2 was maintained at 5 mmHg higher than the resting condition throughout the test. Normalized ventilatory responses to CO2 by body surface area (S/BSA) progressively decreased from the 7-8 through the 11-12 yr groups, and then tended to decrease further in a more gradual manner with increasing age. This trend was very similar to the normalized CO2 output (VCO2/BSA), but did not parallel so closely the normalized O2 intake (VO2/BSA). When ventilatory and metabolic parameters were normalized by body weight (BW), or the lean body mass (LBM), qualitatively similar relationships between CO2 sensitivities and metabolic parameters were also obtained. Contrary to the hypercapnic response, hypoxic ventilatory chemosensitivities were not significantly different among the 6 different age groups. We concluded that normalized hypercapnic chemosensitivity decreased during growth and corresponded well with decreased CO2 output per unit body mass.

Adolescent↗
PubMed1984

Ventilatory and heart rate responses to hypoxia in well-trained judo athletes.

Twenty-four active judo athletes were examined by an isocapnic progressive hypoxia test. The results of ventilatory and heart rate responses to hypoxia were analyzed by the hyperbolic equations, VE = VO + AVE/(PETO2 - CVE) and HR = HRO + AHR/(PETO2 - CHR), respectively, where VE and HR are observed ventilation and heart rate, VO and HRO the horizontal asymptote in ventilation and heart rate for infinite end-tidal PO2 (PETO2), AVE and AHR the slope constant indicating the magnitude of hypoxic sensitivity, and CVE and CHR the vertical asymptote in PETO2 for infinite ventilation and heart rate. AVE was further re-calculated after VE was normalized for a 70 kg body mass, using an allometric coefficient, and was defined as AVEN. 1) AVE and AVEN significantly increased with increasing body weight (BW) as has been reported previously, but no such correlation was found between AHR and BW. 2) VO2 at rest was found to be positively correlated with AVE and AVEN but not with AHR. 3) The relationship between AVE and AHR was not significant. Thus, the characteristic feature seen in hypoxic ventilatory activity was not accompanied by a similar trend in heart rate response.

Adolescent↗