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Biomedical subjects

S Usui

Publications and source records attributed to S Usui.

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

A CMOS integrated circuit for multichannel multiple-subject biotelemetry using bidirectional optical transmissions.

A CMOS integrated circuit for a noninvasive biological-signal telemetry system specified for use in medical and physiological studies of the influence of weightlessness in space is presented. The system can monitor multichannel (4 channels maximum) biological signals from multiple subjects (4 subjects maximum) in real time by using time multiplexing. A key technique, so-called synchronized multiple-subject telemetry, to achieve multiple-subject telemetry has been proposed. This technique utilizes bidirectional optical transmissions with direct and scattered infrared lights between an observer and each of the subjects. An experimental CMOS IC to give a small light-weight low-power, and smart telemetry instrument for use on animals has been developed. This IC is for evaluating circuit blocks of the implantable monolithic telemetry instrument. The major circuit blocks include CMOS digital circuits for synchronization, subject selection and time multiplexing, analog circuits for pulse interval modulation (PIM), and other blocks such as a CMOS optical pulse receiver and an LED driver. A preliminary experimental multichannel telemetry from two subjects has been performed with the implemented IC chips, and the principal operation of the multiple-subject optical biotelemetry has been demonstrated.

Aerospace Medicine↗
PubMed1994

Inhomogeneity of cellular activation time and Vmax in normal myocardial tissue under electrical field stimulation.

To clarify the mechanism underlying the ectopic excitation after countershock, the cellular activation processes of cardiac tissue with a low-potential-gradient electric field (LPEF) were investigated in experiments using guinea pig papillary muscles and in computer simulation. Action potential upstrokes in papillary muscles during longitudinal propagation (LP) or transverse propagation (TP) were different from those of nonpropagating ones in single ventricular cells in terms of lower maximum upstroke velocity (Vmax) (LP, 231 V/s; TP, 309 V/s) and the presence of a linear ascending segment in the phase-plane plot. High Vmax (409 V/s) close to the single cell (512 V/s) was obtained in the muscle at the collision of LP (LC). Field stimulation of the muscles with LPEF < 5 V/cm caused inhomogeneous excitation suggesting multiple wave fronts, which collide with each other, and a wide spatial dispersion of Vmax (132-388 V/s). Phase-plane plots of action potential with lower Vmax were similar to LP or TP, whereas those with higher Vmax were similar to LC. In the two-dimensional discrete sheet composed of 51 x 51 elements of modified Beeler-Reuter model, the inhomogeneous excitation induced by LPEF is mimicked by setting a random variation of stimulus onset in each element. LPEF may induce inhomogeneous excitation with multiple wave fronts through a complex electrotonic interaction. This would provide a basis for the genesis of ectopic focal excitation.

Action Potentials↗
PubMed1994

Preparation and antitumor activities of mitomycin C beta-(1-->6)-branched (1-->3)-beta-D-glucan conjugate.

The conjugate of mitomycin C (MMC) with carboxymethylated schizophyllan (CMSPG) which was prepared from monochloroacetic acid and schizophyllan (SPG), a beta-(1-->6)-branched (1-->3)-beta-D-glucan from Schizophyllum commune Fries, was synthesized by using 1-ethyl-3-(3-dimethylaminopropyl)- carbodiimide. The degree of the substitution of carboxymethyl groups in CMSPG was estimated as approximately 0.87, and locations of carboxymethyl groups in CMSPG were predominantly determined at O-4, O-6, and O-4, 6 positions in glucose residues. The contents of MMC in the conjugate were estimated to be between 8 and 12% (w/w). The conjugate showed successive monoexponential liberation, with a half-life of 7.2 h. Although the in vitro cytotoxicity of the conjugate against L1210 leukemia cells was similar to that of MMC when the cells were exposed for 24 and 48 h, the 50% growth-inhibitory concentration of the conjugate for L1210 was two times higher than that of MMC with exposure for 12 h. The antitumor activity of the conjugate against subcutaneously implanted sarcoma 180 solid tumor in mice by intraperitoneal (i.p.) administration was similar to that of MMC at a dose of 1.5 mg eq MMC per kg per d for both 7 times of continuous administration and 4 times of intermittent administration. However, the reduction in the number of leukocytes in the peripheral blood, which was the side effect of MMC, was suppressed by the intermittent administration of the conjugate. The conjugate maintained the ability to induce the tumor regressing factor and the neutrophil chemotactic factor in the serum.

Animals↗
PubMed1994

Polysaccharides in Fungi. XXXIV. A polysaccharide from the fruiting bodies of Amanita muscaria and the antitumor activity of its carboxymethylated product.

A water-insoluble, alkali-soluble, glucan (AM-APP), [alpha]D +160 degrees in 0.4 M NaOH, was isolated from the alkaline extract of the fruiting bodies of Amanita muscaria. The results of chemical and spectroscopic investigations indicate that AM-APP is a linear (1 --> 3)-alpha-D-glucan with a molecular weigh estimated by gel chromatography of about 42000. Its carboxymethylated product (AM-APP-CM) showed potent antitumor activity against sarcoma 180 in mice, although the native polysaccharide (AM-APP) had little effect. The distribution of carboxymethyl groups in the molecule was analyzed by gas chromatography and mass spectrometry. The degree of substitution of carboxymethyl groups was 0.95 and the substituents were located at O-2, at O-4, at O-6, at O-2 and O-6, and at O-4 and O-6 on glucose.

Acetates↗
PubMed1994

[Polysaccharides in fungi. XXXIII. Hypoglycemic activity of an acidic polysaccharide (AC) from Tremella fuciformis].

Glucuronoxylomannan (AC) from the fruiting bodies of Tremella fuciformis exhibited a significant dose-dependent hypoglycemic activity in normal mice and also showed a significant activity in streptozotocin-induced diabetic mice, by intraperitoneal (i.p.) administration. The activities of AC-derivatives such as a product of AC which side chains had been removed were lower than that of native AC. AC raised the plasma insulin level in normal mice. Administration of AC to normal mice significantly increased the activities of hepatic hexokinase and glucose-6-phosphatase dehydrogenase, but it decreased that of hepatic glucose-6-phosphatase. Furthermore, AC reduced the glycogen content in the liver, increased the total lipid in epididymal adipose tissue, and lowered the plasma cholesterol level. The foregoing results indicated that the hypoglycemic activity of AC in normal mice was at least responsible for the increase of insulin secretion and for the acceleration of glucose metabolism. Single oral administration at a dose of 50-300 mg/kg of AC did not affect the plasma glucose level in normal mice, but continuous oral administrations of the AC solution (0.75 g/l) instead of water for a long time was found to be effective on the plasma glucose level in both experiments of the mice injected once i.p. with streptozotocin (170 mg/kg) at 0 d of AC administration and streptozotocin-induced diabetic mice.

Animals↗
PubMed1994

Parabolic flight experiments on physiological data acquisition and processing technologies using small jet aircraft (MU300).

The parabolic aircraft flight provides a short low gravity environment for approximately 20 seconds, which may not be sufficient for a research on the physiological phenomenon induced by actual weightlessness in space. However, the method is still useful to reveal essential and characteristic feature of physiological signs, and is available for testing hardware and also training of crew member during altered gravity. This paper reports the summary of parabolic flight experiments recently conducted as a NASDA program (1990-1992). The program is providing opportunities in low gravity research with small jet aircraft for researchers and agencies. The flight experiments in the life science area have been conducted mostly focused on a physiological changes and basic methodology which may be effective under the altered gravity condition. In this study, the following research team, NASDA, Research Institute of Environmental Medicine, Nagoya University, Toyohashi University of Technology, Tokyo Metropolitan Hospital, Torey Research Center and JSUP were involved and coordinated for the research.

Aircraft↗
PubMed1994

Reproducibility of VO2-VCO2 relationship during incremental exercise protocol.

We examined the effect of two different slope protocols to the reproducibility of the VO2-VCO2 relationship and the lactic acidosis threshold (LAT) during incremental exercise. Two adult male subjects performed a cycle ergometer exercise 2 to 4 times repeatedly in which the increase of work rate was 25 W every 1 or 2 min according to experimental design method. Gas exchange parameters during each exercise was measured every 10 s. The V-slope method was applied to the data which remained after the deletion of the data during the transient phase with the onset of exercise and above respiratory compensation of metabolic acidosis (RCMA), for detecting LAT and summarizing the VO2-VCO2 relationship below and above LAT. LAT had a high reproducibility whichever slope protocol was used. The confidential limit of LAT estimated by a statistical method was about +/- 0.1 l/min in terms of VO2. There were stable and reasonable responses of VO2-VCO2 during incremental exercise in which the work rate increased 25 W every 1 min.

Acidosis, Lactic↗
PubMed1993

Reconstruction of ionic currents in a molluscan photoreceptor.

Two-microelectrode voltage-clamp measurements were made to determine the kinetics and voltage dependence of ionic currents across the soma membrane of the Hermissenda type B photoreceptor. The voltage-dependent outward potassium currents, IA and ICa(2+)-K+, the inward voltage-dependent calcium current, ICa2+ and the light-induced current, IIgt, were then described with Hodgkin-Huxley-type equations. The fast-activating and inactivating potassium current, IA, was described by the equation; IA(t) = gA(max)(ma infinity[1-exp(-t/tau ma)])3 x (ha infinity [1-exp(-t/tau ha)] + exp(-t/tau ha)) (Vm-EK), where the parameters ma infinity, ha infinity, tau ma, and tau ha are functions of membrane potential, Vm, and ma infinity and ha infinity are steady-state activation and inactivation parameters. Similarly, the calcium-dependent outward potassium current, ICa(2+)-K+, was described by the equation, ICa(2+)-K+ (t) = gc(max)(mc infinity(VC)(1-exp[-t/tau mc (VC)]))pc (hc infinity(VC) [1-exp(-t/tau hc)] + exp(-t/tau hc(VC)])pc(VC-EK). In high external potassium, ICa(2+)-K+ could be measured in approximate isolation from other currents as a voltage-dependent inward tail current following a depolarizing command pulse from a holding potential of -60 mV. A voltage-dependent inward calcium current across the type B soma membrane, ICa2+, activated rapidly, showed little inactivation, and was described by the equation: ICa2+ = gCa(max) [1 + exp](-Vm-5)/7]-1 (Vm-ECa), where gCa(max) was 0.5 microS. The light-induced current with both fast and slow phases was described by: IIgt(t) = IIgt1 + IIgt2 + IIgt3, IIgti = gIgti [1-exp(- ton/tau mi)] exp(-ton/tau hi)(Vm-EIgti) (i = 1, 2). For i = 3, /Igt(t) = gigt3m33h3(Vm - Eigt3)exp(-ton/Ton) x exp(-tfoff/t Off). Based on these reconstructions of ionic currents, learning-induced enhancement of the long lasting depolarization (LLD) of the photoreceptor'slight response was shown to arise from progressive inactivation of /A, lca2+ -K+, and lCa2+.

Animals↗
PubMed1992

Cytochrome b560 (QPs1) of mitochondrial succinate-ubiquinone reductase. Immunochemistry, cloning, and nucleotide sequencing.

Mitochondrial succinate-ubiquinone reductase is composed of two parts, a water-soluble succinate dehydrogenase and a two-polypeptide membrane-anchoring protein fraction (QPs). The larger polypeptide of QPs is believed to be associated with cytochrome b560 (QPs1). The structure of QPs1 was studied by immunochemistry and molecular cloning and sequencing. Antibodies against QPs1 were raised in rabbits, purified, and characterized by enzyme-linked immunosorbent assay and Western blotting. The purified antibodies inhibited 75% of the reconstitutive activity of QPs and reacted with both submitochondrial particles (SMP) and mitoplasts. The binding of these antibodies to SMP was greatly increased when succinate dehydrogenase was removed from SMP by alkaline treatment, indicating that QPs1 is a transmembranous protein and that some of its specific epitopes are covered by succinate dehydrogenase. Anti-QPs1 antibodies were used to screen one cDNA clone encoding QPs1 from a bovine heart cDNA lambda gt11 expression library. The cDNA insert is 946 base pairs with an open reading frame of 396 base pairs that encodes for 132 amino acid residues. The molecular weight of QPs1, calculated from the deduced amino acid sequence, is 14,320. Although the apparent molecular weight of QPs1, estimated by high resolution SDS-polyacrylamide gel electrophoresis, is approximately 11,000, the existence of a presequence was ruled out by mass spectrometric analysis of protein fragments. QPs1 is a very hydrophobic protein. Three probable membrane-spanning segments were revealed by a hydropathy plot of the sequence. QPs1 has a higher sequence similarity to the sdhC peptide of Escherichia coli than to the sdhC peptide (cytochrome b558) of Bacillus subtilis. Like the bacterial proteins, QPs1 has 2 conserved histidines at positions 34 and 90. The conserved nature and similar location of these 2 histidines, on the matrix-side surface of the membrane, suggest that they are involved in heme ligation of cytochrome b560.

Amino Acid Sequence↗
PubMed1992

Rat circadian rhythms entrain to a descending saw-tooth light intensity cycle.

We reexamined whether rat circadian rhythms entrained to the light intensity cycle of a descending saw-tooth (ST-d) form, in which illuminance decreased rectilinearly from 300 lx to 0 lx in 24 h, and abruptly returned to 300 lx (lights-on time). Ambulation, drinking and subcutaneous body temperature were simultaneously monitored in 5 intact, 5 pinealectomized and 5 orchiectomized rats. Additionally, sleep was monitored in the intact rats. In all the rats, entrainment was confirmed during 65 days' exposure to the ST-d cycle. The waveforms of the entrained rhythms were much modified compared with those during LD 12:12. The estimated activity periods of the entrained rhythms straddled the lights-on time of the ST-d cycle. In all the groups of rats, administration of a single ST-d cycle in constant dim red light produced only delay shifts irrespective of its circadian phase, and there was no significant circadian variation in the magnitude of phase shifts. The results indicate that rat circadian rhythms entrain to the ST-d cycle with an unexpected phase position, which cannot be explained by the phase-response curve.

Animals↗
PubMed1992

Continuous measurement of Na concentration in CSF during gastric water infusion in dehydrated rats.

To assess the differential stimulus to central and intravascular osmoreceptors during recovery from thermal dehydration, we measured Na concentrations in cerebrospinal fluid ([Na]CSF) and plasma ([Na]p) continuously and compared these during simulated drinking by gastric water infusion (INF) in euhydrated and thermally dehydrated rats under anesthesia. Continuous measurement of [Na]CSF was obtained with a double-barreled Na electrode placed in the lateral ventricle. Continuous measurement of [Na]p was obtained from a flow cell Na electrode in an extracorporeal shunt. Measurements were made during 10 min of INF (2.5 ml/100 g body wt) into the stomach and during 20 min of recovery. Changes in [Na]CSF always lagged behind those in [Na]p and were quantitatively smaller after INF. The decrease in [Na]CSF occurred sooner in dehydrated than in euhydrated rats in response to the decrease in [Na]p (P < 0.01). These results suggest that water and/or Na movement between blood and CSF is accelerated during restitution from thermal dehydration, acting to prevent overhydration during the early phase of rehydration.

Animals↗
PubMed1992

Effects of anticipation, prior-exercise, and breathing frequency to ventilatory response during step exercise: a preliminary study.

We examined the effects of anticipation, prior-exercise, and restricted breathing frequency on the ventilatory transient response to bicycle step exercise (75 W, 4 min, 50 rpm), i.e., 1) whether the increase of work rate was anticipated by the subject or not, 2) whether the exercise was preceded by light exercise (25 W), or rest, and 3) whether the exercise entrained the breathing frequency (f: 12.5/min, or 25/min) or not (voluntary). The corresponding step-on exercise was randomly performed at least two to five times by one adult male subject. As a result, a) the initial rapid ventilatory component, phase 1, was not observed when initiated from light exercise, whereas the overshot phase 1 was observed from rest in anticipation and voluntary breathing frequency condition due to the rapid increase of tidal volume; b) compared with the anticipation condition, the phase 1 response of VE in the non-anticipation condition was slower with prior-rest, and not with prior-light exercise; and c) the restriction of the breathing frequency for entraining the exercise rhythm did not affect the initial rapid response, but decreased the fluctuation of VE in the steady state, compared to the condition of voluntary breathing frequency.

Adult↗
PubMed1991

Subunit IV (Mr = 14,384) of the cytochrome b-c1 complex from Rhodobacter sphaeroides. Cloning, DNA sequencing, and ubiquinone binding domain.

The Rhodobacter sphaeroides gene encoding subunit IV of the cytochrome b-c1 complex (fbcQ) was cloned and sequenced. The fbcQ cistron is 372 base pairs long and encodes 124 amino acid residues. The molecular mass of subunit IV, deduced from the nucleotide sequence, is 14,384 Da. A hydropathy plot of the predicted amino acid sequence revealed only one transmembrane helix; it is near the C-terminal end. The 3-azido-2-methyl-5-methoxy-6-(3,7-dimethyl[3H]octyl)-1,4-benzoquinone ([3H]azido-Q)-labeled subunit IV was isolated from the [3H]-azido-Q-treated cytochrome b-c1 complex. A ubiquinone-binding peptide was obtained by digesting the labeled subunit IV with V8 protease followed by high performance liquid chromatography separation. Amino acid analysis and partial N-terminal sequencing of this ubiquinone-binding peptide revealed that it corresponded to residues 77-124 of subunit IV. Based on the hydropathy profile and predicted tendency to form alpha-helices and beta-sheets, we propose a structural model for subunit IV. In this model the ubiquinone-binding domain is located near the surface of the membrane.

Affinity Labels↗