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Biomedical subjects

S Koga

Publications and source records attributed to S Koga.

At least 91 records · Page 5Linked to original sources
PubMed1997

Dynamics of respiratory response to sinusoidal work load in humans.

The present study was undertaken to investigate possible distortion in responses of respiratory variables including O2 uptake (VO2), CO2 output (VCO2), and ventilation (VE) to sinusoidal work load, and to find out whether the conventional transfer models were applicable to analyze the dynamics of these variables. Six healthy subjects performed exercise for 32 min on a bicycle ergometer with electro-magnetic braking. The work load was varied sinusoidally between 30 W and 60% of maximum O2 uptake (VO2max) during periods from 1 to 16 min. The respiratory variables were measured on a breath-by-breath basis with a mass spectrometer and a computer system. The responses of VO2, VCO2, and VE to sinusoidal work load were not completely sinusoidal in form but were somewhat distorted, forming saw-tooth waves with steeper down-slopes during periods of 4-16 min, but this distortion was not observed at 1 min or 2 min periods. However, the results could be approximately described by a first-order model without or with time delay. Time constants of the first-order model without time delay were 46 sec for VO2, 62 sec for VCO2, and 73 sec for VE, respectively. We also found a close relationship between the time constants of VO2 and VCO2 and VO2max. These results suggested that exponential functions may be applied and are expected to yield valid results in assessing physical fitness, although the control of ventilatory and gas exchange in exercise does show non-linear characteristics.

Adult↗
PubMed1997

Primary renal angiosarcoma: a case report and review of the literature.

Primary renal angiosarcoma is very rare. To our knowledge, only 15 cases have been reported to date. A 77-year-old Japanese man with a unilateral kidney presented with massive hematuria followed by renal failure. A renal tumor was suspected and a left nephrectomy was performed. The histopathological diagnosis was angiosarcoma of the kidney. A hemorrhagic tumor measuring 10 x 5 cm and clotted blood was found in the medullary area. The atypical tumor cells had a sinusoidal and solid appearance, and showed immunohistochemically positive reactions for some of the endothelial markers. The patient died about 21 months after the nephrectomy and the autopsy revealed massive metastases to the liver and retroperitoneum. One of the differential diagnoses of the case was angiomyolipoma, because the tumor cells were relatively bland in their histological appearance with entrapped fat cells in the pelvic area. Fifteen case reports with titles that included the term 'hemangiosarcoma/angiosarcoma', 'hemangioendothelioma/endothelioma' or 'vascular sarcoma' of the kidney were reviewed and compared to the present case.

Aged↗
PubMed1997

Nucleoside Oxidase, a Hydrogen Peroxide-Forming Oxidase, from Flavobacterium meningosepticum.

A novel enzyme which catalyzes the oxidation of nucleosides to nucleoside-5(prm1)-carboxylic acids, forming hydrogen peroxide, was purified to homogeneity from Flavobacterium meningosepticum T-2799. The enzyme has a molecular weight of about 500,000, and four nonidentical subunits (molecular weights of 81,000, 69,000, 33,000, and 16,000) were detected on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On the basis of visible absorption spectra of the purified enzyme, the enzyme is concluded to be a hemoprotein. It also contains covalently bound flavin adenine dinucleotide. The various nucleosides, such as adenosine (K(infm) = 48 (mu)M), inosine (K(infm) = 66 (mu)M), guanosine (K(infm) = 21 (mu)M), thymidine (K(infm) = 50 (mu)M), uridine (K(infm) = 80 (mu)M), and cytidine (K(infm) = 50 (mu)M), were oxidized by the enzyme, but nucleotides, bases, and ribose were not.

Journal Article↗
PubMed1997

Effect of increased muscle temperature on oxygen uptake kinetics during exercise.

To test whether increased muscle temperature (Tm) would improve O2 uptake (VO2) kinetics, seven men performed transitions from rest to a moderate work rate [below the estimated lactate threshold (LTest)] and a heavy work rate (VO2 = 50% of the difference between LTest and peak VO2) under conditions of normal Tm (N) and increased Tm (H), produced by wearing hot water-perfused pants before exercise. Quadriceps Tm was significantly higher in H, but rectal temperature was similar for the two conditions. There were no significant differences in the amplitudes of the fast component of VO2 or in the time constants of the on and off transients for moderate and heavy exercise between the two conditions. The increment in VO2 between the 3rd and 6th min of heavy exercise was slightly but significantly smaller for H than for N. These data suggest that elevated Tm before exercise onset, which would have been expected to increase O2 delivery and off-loading to the muscle, had no appreciable effect on the fast exponential component of VO2 kinetics (invariant time constant). These data further suggest that elevated Tm does not contribute to the slow component of VO2 during heavy exercise.

Adult↗
PubMed1997

[Disseminated intravascular coagulation in a case of adult onset Still's disease].

We report a 82-year-old woman with adult onset Still's disease (AOSD), who presented with high fever, skin rash, swollen axillary lymph nodes, accelerated erythrocyte sedimentation rate, leukocytosis, abnormal liver function tests, hypoalbuminemia, negative antinuclear antibody and rheumatoid factor, and lack of renal involvement. Disseminated intravascular coagulation (DIC) was also diagnosed on admission. An antipyretic relieved high fever and DIC soon improved. Three years later, AOSD relapsed accompanied by hypercoagulation and hyperfibrinolysis. The patient developed subdural hematoma and DIC due to a brain contusion. High titers of serum soluble adhesion molecules and soluble thrombomodulin were noted on the first episode of DIC. These findings indicated that endothelial cells were damaged in AOSD complicated by DIC.

Aged↗
PubMed1996

Kinetics of oxygen uptake and cardiac output at onset of arm exercise.

Pulmonary oxygen uptake (V O2) kinetics at onset of exercise is reported to be slower for arm than for leg exercise. This could be attributed to reduced cardiac output (Q) or reduced arteriovenous O2 content difference or both. To test this, V O2 mean tissue oxygen consumption (V O2T) and Q kinetics in arm cranking were compared with corresponding values found in leg cycling. The increase in V O2 during phase 1 (abrupt increase after onset of exercise) was less in arm than in leg exercise, suggesting that immediate Q adjustments to arm exercise were less pronounced. Mean response times (MRT, the relative rates at which a steady state was attained) for V O2, V O2T, and Q were prolonged during arm exercise. The MRT of VO 2 in arm exercise at a given blood lactate increase was higher than in leg exercise. The delayed V O2 kinetics in arm exercise might be due to delayed Q kinetics and higher anaerobic glycolysis occurring early during arm exercise.

Adult↗
PubMed1996

A multicenter validation of regional cerebral blood flow quantitation using [123I]iodoamphetamine and single photon emission computed tomography.

Recently, two methods have been proposed for regional cerebral blood flow (rCBF) quantitation using [123I]iodoamphetamine (IMP) and single-photon emission computed tomography (SPECT). The table look-up (TLU) method has been shown to provide both rCBF and volume of distribution, Vd, images from two SPECT scans, while a single-scan autoradiographic (ARG) technique provided rCBF using a fixed and assumed Vd. In both methods, a single blood sample was referred to calibrate the previously determined standard input function. The present multicenter project was designed to evaluate the accuracy of both methods for use as clinical investigative tools. Ten independent institutions performed [123I]IMP-SPECT studies according to both methods in 76 subjects (10 normal volunteers, 32 patients with cerebrovascular disease, and 34 patients with other diseases). Calculated rCBF values were compared with those obtained by the following reference methods available in the participating institutions; [15O] H2O positron emission tomography (PET) (five institutions), [133Xe]SPECT (four institutions), and the [123I]IMP microsphere method (three institutions). Both ARG and TLU methods provided rCBF values that were significantly correlated with those measured by the [15O] H2O PET technique (p < 0.001 for all subjects; overall regression equation, y = 15.14 + 0.54x) and those measured by the [123I]IMP-microsphere method (p < 0.001 for all subjects: y = 2.0 + 0.80x). Significant correlation (p < 0.05) was observed in 18 of 24 subjects studied with the [133Xe] SPECT reference technique (overall regression equation, y = 15.0 + 0.55x). Mean cortical gray matter rCBF in a group of normal subject was 43.9 +/- 3.3 and 43.4 +/- 2.0 ml/min/100 g for the ARG and TLU methods, respectively. Regional Vd of [123I]IMP estimated by the TLU method was 45 ml/ml +/- 20% in the normal cortical region. Close agreement between ARG and TLU rCBF values was observed (y = -3.21 + 1.07x, r = 0.97), confirming the validity of assuming a fixed Vd in the ARG method. Results of this study demonstrate that both the ARG and TLU methods accurately and reliably estimate rCBF in a variety of clinical settings.

Adolescent↗
PubMed1996

Guidance with real-time CT fluoroscopy: early clinical experience.

A recently developed real-time computed tomography (CT) fluoroscopy system, which provides effective real-time reconstruction and display of CT images, was used to monitor nonvascular interventional procedures performed in 57 patients. Biopsy of thoracic lesions (n = 38), biopsy or drainage of pelvic lesions (n = 6), drainage or aspiration of intracranial hematomas (n = 9), and other procedures (n = 4) were performed. CT fluoroscopy successfully depicted the entire procedure in all patients. In thoracic lesions, a mean 1.3 passes was necessary to gain access to the lesion. Sufficient cytologic samples were obtained in 32 of 33 pulmonary lesions with a mean diameter of 26 mm.

Adult↗
PubMed1996

Radiation dosimetry at CT fluoroscopy: physician's hand dose and development of needle holders.

The radiation dose to physicians' hands without and with use of needle holders was determined at 10 computed tomography (CT) fluoroscopy-guided transthoracic needle biopsies. As measured with ionization chambers (tube voltage, 80 kVp; tube current, 30 mA), the mean absorbed dose rate without and with holders was 1.14 mGy/sec +/- 0.02 (standard deviation) and 0.019 mGy/sec +/- 0.001, respectively. The mean duration of CT fluoroscopy was 59 seconds in 10 biopsies performed with a holder and 82 seconds in 10 biopsies performed without a holder (difference not statistically significant). The needle holders did not cause any artifacts that interfered with the biopsy procedure.

Biopsy, Needle↗
PubMed1996

Pulmonary oxygen uptake kinetics in nonsteady state.

The body does not always achieve a steady state and is more often kept in a nonsteady state. It is important not only in terms of physiological anthropology but also in its application to rehabilitation and training to clarify whether oxygen transport or utilization is the limiting factor in oxygen uptake in the nonsteady state. Hypotheses concerning the limiting factor in oxygen uptake have their own rationales, and it is still controversial as to which is actually responsible. The limiting factor in oxygen uptake may vary according to exercise conditions. Under certain conditions, oxygen transport would be responsible for limiting the oxygen uptake, and under others, oxygen utilization or both oxygen transport and utilization would be responsible. These conditions differ according to the type of exercise (e.g. step exercise vs. cycling, leg vs. arm exercise, and dynamic vs. static exercise), posture, recruited muscle fibers, and other experimental conditions. Considering that oxygen uptake is regulated by coupling among respiration, circulation, and metabolism, it may be possible that interactions among these functions vary in a complicated manner according to exercise conditions, which may require a different limiting factor in regulating oxygen uptake.

Biological Transport↗