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Biomedical subjects

K Sakamoto

Publications and source records attributed to K Sakamoto.

At least 379 records · Page 21Linked to original sources
PubMed1996

Seasonal variation of mood and behaviour in a healthy middle-aged population in Japan.

A population survey of seasonality in six representative cities in Japan was conducted using the Japanese version of the Seasonal Pattern Assessment Questionnaire (SPAQ). The questionnaires were given to 951 parents (male: female ratio 1:1 age range 34-59 years) of high-school students. Significant regional differences in seasonal variations of mood, length of sleep, and weight were observed; the proportion of individuals reporting high seasonality in the two northern cities was significantly higher than that in the other areas. These results provide evidence for a northern predominance in the prevalence of seasonal affective disorder in Japan.

Adult↗
PubMed1996

Nitric oxide: a modulator for the epidermal growth factor receptor expression in developing ovarian granulosa cells.

the present study was designed to assess the involvement of nitric oxide (NO) in the regulation of the epidermal growth factor (EGF) receptor during development of rat granulosa cells, which were prepared by puncturing ovaries of diethylstilbestrol-treated rats. The immature cells were cultured for 48 h with follicle-stimulating hormone (FSH) to be transformed into mature cells. A marked accumulation of guanosine 3',5' -cyclic monophosphate (cGMP) was observed during development. The accumulation of cGMP, but not of adenosine 3',5'-cyclic monophosphate (cAMP), was suppressed by specific inhibitors of NO synthase, L-NG-monomethyl-L-arginine (L-NMMA) and L-N(G)-nitro-L-arginine, and a selective inhibitor of the inducible NO synthase, aminoguanidine. The L-NMMA-induced suppression was partially reversed by addition of L-arginine to cultures but not D-arginine, indicating that NO formation is inhibited by competing with analogues of L-arginine for NO synthase. Treatment with 2-(4-carboxyphenyl)-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide , an antagonist of NO, caused suppression in the increase of EGF binding sites, whereas exposure of the cells to sodium nitroprusside (SNP), an NO donor, caused elevation in EGF binding sites, with increasing extra- and intracellular cGMP levels. Analysis of the EGF receptor by affinity labeling with 125I-labeled EGF revealed that the intensity of the cross-linked receptor molecular with a molecular mass of 180 kDa was increased by exposure to SNP. The facilitatory effect of SNP on the EGF receptor was observed when the cAMP-dependent pathway was fully activated by FSH. However, the NO effect may be mediated by a cGMP-independent pathway, as 8-bromo-cGMP did not mimic the action of SNP. These results indicate that the L-arginine-NO system may contribute to the regulation of EGF receptor expression in developing granulosa cells stimulated by FSH.

Animals↗
PubMed1996

Hormonal regulation of prostaglandin F2 alpha receptor gene expression in mouse ovary.

In this study we examined regulation by pituitary gonadotropins of the prostaglandin F2 alpha (PGF2 alpha) receptor gene expression in the mouse ovary. Administration of pregnant mare serum gonadotropin (PMSG) to 35-day-old mice in the diestrus phase stimulated the ovary and enhanced the production of progesterone at 1 h PMSG also increased the ovarian PGF2 alpha receptor mRNA level in a time-dependent manner, reaching a sixfold maximum at 1 h. These actions of PMSG were mimicked by human chorionic gonadotropin (hCG), follicle-stimulating hormone (FSH), and cholera toxin, all of which elevate intracellular adenosine 3',5'-cyclic monophosphate (cAMP). In situ hybridization revealed that PGF2 alpha receptor mRNA was localized to the corpus luteum, but the intensity of staining varied among corpora lutea in the same ovary. Exogenous PGF2 alpha inhibited the PMSG-stimulated progesterone production. These results demonstrate that gonadotropins may induce the expression of the PGF2 alpha receptor gene in luteal cells of the corpus luteum, probably by acting through a cAMP-mediated pathway, and that expression of the PGF2 alpha receptor may be functionally associated with the decrease in serum progesterone level.

Animals↗
PubMed1996

Two opsins from the compound eye of the crab Hemigrapsus sanguineus

The primary structures of two opsins from the brachyuran crab Hemigrapsus sanguineus were deduced from the cDNA nucleotide sequences. Both deduced proteins were composed of 377 amino acid residues and included residues highly conserved in visual pigments of other species, and the proteins were 75 % identical to each other. The distribution of opsin transcripts in the compound eye, determined by in situ hybridization, suggested that the mRNAs of the two opsins were expressed simultaneously in all of the seven retinular cells (R1-R7) forming the main rhabdom in each ommatidium. Two different visual pigments may be present in one photoreceptor cell in this brachyuran crab. The spectral sensitivity of the compound eye was also determined by recording the electroretinogram. The compound eye was maximally sensitive at about 480 nm. These and previous findings suggest that both opsins of this brachyuran crab produce visual pigments with maximal absorption in the blue-green region of the spectrum. Evidence is presented that crustaceans possess multiple pigment systems for vision.

Journal Article↗
PubMed1996

S-methylmethionine sulfonium in fruits of citrus hybrids.

The S-methylmethionine sulfonium (MMS) concentrations in fruits of citrus hybrids were measured, and found to increase during ripening of the fruit. However, there of eleven hybrids of 'Seto unshiu' crossed with 'Morita ponkan' and four of 9 hybrids of 'Murcott' tangor crossed with 'Seto unshiu' had low MMS concentrations even at late harvest stage. Crossbreeding is useful in producing new citrus fruits that have juices with the desirable characteristics of their parents without formation of dimethyl sulfide which is an off-flavor.

Citrus↗
PubMed1996

Effect of warming of exercising legs on exercise capacity in patients with impaired exercise tolerance.

OBJECTIVE: The purpose of this study was to determine whether warming of exercising legs improves exercise capacity in patients with cardiac disease and low exercise tolerance. BACKGROUND: Exercising muscle temperature reflects both muscle metabolic rate and muscle blood flow. Increase in muscle temperature in exercising legs is impaired in patients with chronic heart failure. We hypothesized that the mechanisms responsible for impairment of temperature increase in exercising muscle might be related to those responsible for low exercise tolerance. METHODS: We studied 17 patients with cardiac disease whose anaerobic threshold (AT) ranged from 6.6 to 14.8 ml/kg/min (mean 11.2 +/- 1.9 SD). Subjects performed symptom-limited sitting cycle ergometer exercise with or without warming of the thighs. Both thighs were warmed by use of hot packs fixed by supporters. To determine the effect of the supporters themselves on AT and peak VO2, the same ergometer exercise was performed by 7 patients with or without supporters. Peak VO2 and AT were determined by concomitant respiratory gas monitoring. RESULTS: 1) Warming of the thighs increased deep temperature in the thighs (1.0 approximately 2.8 degrees C). 2) AT and peak VO2 were significantly improved in the warming exercise compared with the non-warming exercise (p < 0.01, p < 0.01). 3) There was no significant difference in AT or peak VO2 between the exercise with and without supporters. CONCLUSION: The findings of this study indicate that warming of exercising legs improves exercise capacity in patients with cardiac disease and low exercise tolerance.

Aged↗
PubMed1996

The influence of location of electrode on muscle fiber conduction velocity and EMG power spectrum during voluntary isometric contraction measured with surface array electrodes.

A surface array electrode was used to investigate muscle fiber conduction velocity (MFCV) and EMG power spectrum during voluntary isometric contraction of m. biceps brachii. The mean power frequency (MPF) and the total power (TP) at various locations of the muscle were obtained from the power spectrum. MFCVs at various locations of the muscle were measured directly using the averaging method. The values of MPF, TP and MFCV were identified with respect to the electrode locations on the m. biceps brachii. MPF was shown as high near the end-plate and low near the tendon of the muscle during contraction of 40% of isometric maximum voluntary contraction (MVC). TP showed low value near the end-plate and the tendon of the muscle fiber and different values at different location setting electrode during voluntary isometric contraction. TP at each location on the muscle surface increased when the contraction levels increased in the contractions range of 20 to 60% MVC. MFCVs showed a high value near the end-plate and the tendon of the muscle during the contraction of 40% MVC. These results indicated that MPF, TP and MFCV at different locations on the muscle were different along the length of the muscle fiber.

Adult↗
PubMed1996

Discrimination of forearm's motions by surface EMG signals using neural network.

We tried to discriminate different forearm's motions by surface EMG signals using neural network. In order to get a higher discrimination rate, the positions of electrodes were improved. We also tried to discriminate similar motions in order to clarify the limitation of the discrimination by surface EMG signals. Two experiments were carried out. One was to discriminate five different motions: grasp, wrist flexion, wrist extension, forearm pronation, and forearm supination (Experiment 1). The other was to discriminate four similar motions which have different quantitative definitions at grasp, wrist flexion/ extension, or forearm pronation/supination (Experiment 2). Four surface electrodes were placed on the skin above the main active muscles: short radial extensor m. of wrist, supinator m., long radial extensor m. of wrist, and ulnar flexor m. of wrist, considering anatomical functions of the forearm's muscles. EMG signals were recorded during 2 sec while the subjects kept the motions. Recorded EMG signals were sampled at 200 msec intervals after full-wave rectifying and low-pass filtering. Therefore, the number of sampling data patterns of EMG signals was 10 for every motion. Three layers of neural network was used for discrimination. The number of units in the input layer is 4, and the number of units in the output layer is 5 or 4. In order to get the best discrimination rate of the motions, we changed the number of units in the hidden layer from 3 to 12. The neural network was trained by the back-propagation algorithm. In Experiment 1, the best average values of discrimination rates under three patterns of EMG signals for each subject were 96.0%, 98.0%, and 87.2% when the numbers of units in the hidden layer were 10, 11, and 3 respectively. In Experiment 2 using original EMG patterns, the best average values of discrimination rates at grasp, extension/flexion, and pronation/supination were 59.5%, 76.0%, and 25.0% respectively. By using normalized EMG patterns, these were 40.0%, 84.8%, and 55.5% respectively.

Adult↗
PubMed1996

Distribution of muscle fiber conduction velocity of M. biceps brachii during voluntary isometric contraction with use of surface array electrodes.

Surface electromyogram (EMG) was recorded in m. biceps brachii during the contractions of 20, 40 and 60% of maximum voluntary isometric contraction (MVC) in twelve healthy male subjects, using surface array electrodes. The distribution of muscle fiber conduction velocity (MFCV) was found directly using the averaging technique and the cross-correlation function technique. MFCVs in the region of 20-40 mm measured from end-plate denoted constant value of about 4 m/s in 20% MVC, while MFCVs in the region around end-plate and tendons showed about 10 m/s in 20% MVC. The values of MFCV depended on the contraction levels of muscle. The model for the generation of MFCV which considered the ensemble of muscle fibers with the shape of a cone was proposed. The theoretical values of MFCV by the muscle fiber ensemble model (MFE model) proposed in the paper showed in good agreement with the experimental results.

Action Potentials↗
PubMed1996

Localized fibrous mesothelioma with bronchogenic carcinoma.

We report a case of localized fibrous mesothelioma (LFM) of the pleura with bronchogenic carcinoma. LFM arose in the visceral pleura of the upper lobe in the left lung, and lung adenocarcinoma was located in the ipsilateral lower lobe. LFM is a rare mesenchymal tumor of the pleura. Concomitant occurrence with bronchogenic carcinoma has not been previously reported in the English literature.

Biopsy, Needle↗
PubMed1996

A case of hypertensive-diabetic cardiomyopathy demonstrating left ventricular wall motion abnormality.

We report a case of hypertensive-diabetic cardiomyopathy demonstrating left ventricular regional wall motion abnormality, with a normal coronary artery documented on coronary arteriography. Dipyridamole-infusion 201Tl scintigraphy demonstrated transient perfusion defects in the infero-posterior wall of the left ventricle, where reduced wall motion was demonstrated on contrast left ventriculography. Myocardial SPECT (single photon emission tomography) imaging with [123I] beta-methyliodophenylpentadecanoic acid (BMIPP) and 201Tl demonstrated reduced [123I]BMIPP uptake compared with 201Tl uptake in the infero-posterior wall of left ventricle. These results suggest that the impairment of myocardial free fatty acid metabolism is an etiologic or contributory factor for regional wall motion abnormality, together with small-vessel coronary artery disease, in this patient.

Cardiomyopathies↗
PubMed1996

Structure-activity relationships of cephalosporins having a (dimethylisoxazolidinio)vinyl moiety at their 3-position.

A series of cephalosporins having a (dimethylisoxazolidinio)vinyl group at their 3-position were synthesized to investigate their structure-activity relationships. With regard to the olefin geometry, the (E)-vinyl compound exhibited higher in vitro activity than the (Z)-compound. Regarding the C-7 substituents, the replacement of 2-aminothiazole with 5-amino-1,2,4-thiadiazole increased the anti-pseudomonal activity. Determination of the absolute configuration of the C-3 substituent is also presented. Among the compounds synthesized, we selected 7 beta-[(Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(fluoromethoxyimi no)acetamido]-3-[(E)-2-((S)-2,2-dimethyl-5-isoxazolidinio)vinyl ]-3-cephem-4-carboxylate (YM-40220), which showed well-balanced in vitro activity and an excellent in vivo efficacy against Staphylococcus aureus Smith, as a candidate for further development.

Animals↗
PubMed1996

FR901483, a novel immunosuppressant isolated from Cladobotryum sp. No. 11231. Taxonomy of the producing organism, fermentation, isolation, physico-chemical properties and biological activities.

FR901483, a novel immunosuppressant, has been isolated from the fermentation broth of Cladobotryum sp. No. 11231. The molecular formula of FR901483 has been determined as C20H31N2O6P. FR901483 exerts a potent immunosuppressive activity in vitro and significantly prolongs graft survival time in the rat skin allograft model. This compound has an intriguing tricyclic structure possessing a phosphate ester in its molecule. The ester residue may play an important role in exerting immunosuppressive activity because the desphosphoryl compound is devoid of activity. It is thought that the primary target of immunosuppression by this compound is inhibition of purine nucleotide biosynthesis.

Animals↗