Biomedical subjects

H Asai

Publications and source records attributed to H Asai.

At least 19 recordsLinked to original sources

PubMed1999

Rubber-like elasticity and volume changes in the isolated spasmoneme of giant Zoothamnium sp. under Ca2+-induced contraction.

Using glycerinated spasmoneme of giant Zoothamnium sp., the physical properties of spasmoneme before and after Ca2+-induced contraction (pCa 4.5) were investigated. The volume change of spasmoneme contraction was measured under zero tension. The length and diameter decreased by about 50% of their initial value as a result of contraction, which means that contraction is nearly isotropic. Thus the volume of spasmoneme decreased drastically by 86% of its original value. The swollen ratio of extended and contracted spasmoneme were 0.07 and 0.37, respectively. Tension-extension relationships of extended and contracted spasmonemes were measured. By applying the theory of rubber elasticity, the number of segments of a chain in originally extended spasmoneme was only 3.3, i.e., the chain was almost a straight one. On the other hand, the number of segments of a chain in contracted spasmoneme was more than 100, i.e., the chain was essentially a random one. Furthermore, the total number of chains in single spasmoneme was the same in extended and contracted spasmoneme. This means that the interchain cross-links of chains were not influenced by addition or removal of Ca2+. Moreover, the molecular weight of a chain is estimated to be at most about 50 kd. By considering all these results, it is concluded that the contractile mechanism of spasmoneme originates in the intramolecular folding and unfolding induced by Ca2+ binding and detaching.

Animals↗

PubMed1998

The optical activity of lysozyme crystals.

The components of the gyration tensor of the enzyme lysozyme were measured by using the HAUP method: g11 = -0.90 x 10(-5) and g33 = 1.05 x 10(-5) at 303.4 K and a wavelength of 4880 A. The optical rotatory powers along the a and c axes in the same conditions were calculated: rho a = -21.3 and rho c = -24.8 degrees cm-1. The optically active property of lysozyme is strange in that, although it contains a considerable quantity of alpha-helices (about 30%), the rotatory powers are unexpectedly small in magnitude, one order of magnitude less than those of quartz and with very large anisotropy. A conceptual consideration of this phenomenon is given. In order to assess the difference between the structures in both crystalline and solution states, the chirality index r was calculated to be 0.16. This value indicates that the structural change of lysozyme from the solution into the crystalline state is expressed by an increase of 19% in optical activity. From the NMR results [Smith et al. (1993), J. Mol. Biol. 229, 930-944], it is anticipated that the r value reflects the increased constraint in atomic motion in the side chains of exposed amino acid residues in the crystalline state.

Animals↗

PubMed1998

Increased expression of 3-hydroxyanthranilate 3,4-dioxygenase gene in brain of epilepsy-prone El mice.

The El mouse is an established animal model for human epilepsy. We previously reported that the level of quinolinic acid (QUIN), an excitotoxin, was high in the brain of epilepsy-prone El mice and that the increased production of QUIN was secondary to an increased activity of 3-hydroxyanthranilate 3,4-dioxygenase (3-HAO, EC 1.13.11. 6) in the brains of these mice. In this study, we cloned and sequenced the cDNA for 3-HAO and showed that its expression in the brain of El mice was higher than that of control ddY mice. These results suggest that a genetic defect leading to derepression of the 3-HAO gene expression in the brain may be involved in the pathogenesis for the epileptic diseases of El mice.

3-Hydroxyanthranilate 3,4-Dioxygenase↗

PubMed1998

Delayed onset of hemolytic anemia in CBA-Pk-1slc/Pk-1slc mice with a point mutation of the gene encoding red blood cell type pyruvate kinase.

The Pk-1slc gene encodes a mutant red blood cell (RBC) type pyruvate kinase (PK), and adult CBA-Pk-1slc/Pk-1slc mice show a severe nonspherocytic hemolytic anemia. However, the number of RBCs and the proportion of reticulocytes were comparable between neonatal CBA-Pk-1slc/Pk-1slc mice and control -+/+ mice. Since the age-dependent increase of RBCs was much greater in CBA-+/+ mice than in CBA-Pk-1slc/Pk-1slc mice, significant anemia was observed in the latter mice on day 14 after birth. The increase of RBCs in CBA-+/+ mice was due to the prolongation of their survival time. The half life of RBCs increased in CBA-+/+ mice with ages, but it decreased in CBA-Pk-1slc/Pk-1slc mice. The relatively longer half life of RBCs in neonatal CBA-Pk-1slc/Pk-1slc mice appeared to be due to the delayed switching from M2-type PK that are expressed by undifferentiated erythroid precursor cells to RBC-type PK that are expressed by mature RBCs.

Age of Onset↗

PubMed1998

High-speed video cinematographic demonstration of stalk and zooid contraction of Vorticella convallaria.

Stalk contraction and zooid contraction of living Vorticella convallaria were studied by high-speed video cinematography. Contraction was monitored at a speed of 9000 frames per second to study the contractile process in detail. Complete stalk contraction required approximately 9 ms. The maximal contraction velocity, 8.8 cm/s, was observed 2 ms after the start of contraction. We found that a twist appeared in the zooid during contraction. As this twist unwound, the zooid began to rotate like a right-handed screw. The subsequent stalk contraction steps, the behavior of which was similar to that of a damped harmonic oscillator, were analyzed by means of the equation of motion. From the beginning of stalk contraction, the Hookean force constant increased, and reached an upper limit of 2.23 x 10(-4) N/m 2-3 ms after the start of contraction. Thus, within 2 ms, the contraction signal spread to the entire stalk, allowing the stalk to generate the full force of contraction. The tension of an extended stalk was estimated to be 5.58 x 10(-8) N from the Hookean force constant of a stalk. This value coincides with that of the isometric tension of a glycerol-treated V. convallaria, confirming that the contractile system of V. convallaria is well preserved despite glycerol treatment.

Animals↗

PubMed1998

Upregulation of retinal vascular endothelial growth factor mRNAs in spontaneously diabetic rats without ophthalmoscopic retinopathy. A possible participation of advanced glycation end products in the development of the early phase of diabetic retinopathy.

Vascular endothelial growth factor (VEGF) has recently been shown to be involved in the pathogenesis of proliferative diabetic retinopathy. However, its involvement in the development of the early phase of diabetic retinopathy is not fully understood. In this study we investigated the retinal VEGF mRNA level in spontaneously diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats, a model of non-insulin-dependent diabetes, without overt retinopathy, using quantitative reverse-transcription polymerase chain reaction. The retinal VEGF mRNA level was 2.2 times higher (p < 0.0005) in OLETF rats than in control rats at the age of 60 weeks. Moreover, their retinal mRNA level was positively correlated with serum concentration of advanced glycation end products (AGEs) but not to serum glucose concentration. Furthermore, the peak latency of the oscillatory potentials in the electroretinogram, one of the most sensitive markers for the early phase of diabetic retinopathy, was significantly prolonged in OLETF rats (p < 0.05), being also correlated with the serum AGE concentration. The results thus suggest that AGEs, which are formed acceleratedly in diabetic conditions, are involved in the development of the early phase of diabetic retinopathy probably through the induction of retinal VEGF mRNAs.

Animals↗

PubMed1997

Chemical modification of amino acid residues in glycerinated Vorticella stalk and Ca(2+)-induced contractility.

The glycerinated stalk of the peritrich ciliate Vorticella, was treated with various reagents to chemically modify the amino acid residues. The influences of these modifcations on spasmoneme contractility were investigated. First, it was confirmed that the spasmoneme contraction is not inhibited by alteration of SH groups. It was also demonstrated that chemical modification of methionine and tryptophan residues abolishes spasmoneme contractility. The reagents used for chemical modification were N-bromosuccinimide (NBS), chloramine T, and 2-hydroxy-5-nitrobenzyl bromide (HNBB), which abolished spasmoneme contractility at concentrations of 40-50 microM, 200-300 microM, and 4 mM, respectively. These results suggest that, along with Ca2+ binding proteins, there are other as yet to be identified proteins involved in contractility.

2-Hydroxy-5-nitrobenzyl Bromide↗

PubMed1997

Possible therapeutic effect of T-794, a novel reversible inhibitor of monoamine oxidase-A, on post-stroke emotional disturbances, assessed in animal models of depression.

Emotional disturbances, such as lack of motivation or depression, are common after stroke. The drugs mainly used to treat these syndromes in Japan are the cerebral metabolic enhancers whose biochemical and pharmacological profiles are similar to those of antidepressant drugs. In order to examine the possible therapeutic effect of T-794 [(5R)-3-(6-(cyclopropylmethoxy) 2-naphthalenyl)-5-(methoxymethyl) 2-oxazolidone], a new reversible inhibitor of monoamine oxidase (MAO) type A, on those emotional disturbances, its antidepressant activity was compared with those of major cerebral metabolic enhancers in rodents with or without treatment of cerebral ischemia. Oral administration of T-794 potently prevented reserpine-induced ptosis (ED50 = 4.41 mg/kg), akinesia (ED50 = 3.29 mg/kg), and hypothermia (minimum effective dose = 3 mg/kg) in mice. It was at least 3.7, 13.0, and 3.3 times more potent than cerebral metabolic enhancers tested (indeloxazine, bifemelane, amantadine and idebenone) in antagonism of the ptosis, the akinesia, and the hypothermia, respectively. Effect of T-794 was also examined in the behavioral despair test in rats subjected to forebrain ischemia. The ischemia was induced by a combination of bilateral common carotid artery occlusion (15 min) and systemic hypotension (sodium nitroprusside 5 mg/kg, s.c). From 13 d after the surgery, drugs were orally administered twice daily 7 times, and following the last administration rats were assessed for their behavior. T-794 reduced the duration of immobility in the behavioral despair test at 30 mg/kg without affecting spontaneous motor activity, whereas indeloxazine showed no significant effect. Antidepressant-like activity of T-794 was suggested in rodents with as well as those without cerebral ischemia. The results suggest that T-794 may make an important contribution to the treatment of emotional disturbances following stroke.

Animals↗

PubMed1996

Genomic structure and transcription of a murine odorant receptor gene: differential initiation of transcription in the olfactory and testicular cells.

We have characterized genomic structure and transcription of a murine odorant receptor (OR) gene, MOR23. This gene has two distinct transcriptional initiation regions, which are differentially utilized in the olfactory and testicular cells. We have found that the MOR23 gene has an intron within the 5'-untranslated region upstream of the coding sequence. In olfactory cells, transcription of the gene is initiated in the region upstream of this intron, while in testicular cells, transcription starts within the intron. Differential initiation of transcription is discussed in the context of tissue-specific expression of the OR genes.

Animals↗

PubMed1996

Improved preparation and swimming behavior of Triton-extracted models of Didinium nasutum.

An improved method for the preparation of Triton X-100 extracted models of Didinium nasutum was established. Didinium models prepared by treatment with a Triton X-100 solution, containing specific proteolysis inhibitors and dimethyl sulfoxide, maintained an intact shape at 25 degrees C for a longer time than models prepared by treatment with a Triton X-100 solution not containing the proteolysis inhibitors and dimethyl sulfoxide. The improved Didinium models were reactivated so as to swim forward in the presence of Mg2+ and ATP or ADP. They did not swim backward in response to Ca2+, in contrast to well-known Paramecium models. However, the improved Didinium models showed circular swimming and spinning in response to 10(-6) M or higher concentrations of Ca2+. This observation suggests that the quick directional change as well as the spinning, which are characteristic of live Didinium, are due to an increase in the endoplasmic Ca2+ concentration around the ciliary system. The response of the Didinium ciliary system to Ca2+ may differ from the response of the Paramecium ciliary system to Ca2+.

Adenosine Triphosphate↗

PubMed1996

Ca(2+)-induced tension development in the stalks of glycerinated Vorticella convallaria.

We have developed a method of measuring the isometric tension in glycerinated stalks of Vorticella convallaria. Using this method, we measured tension vs. pCa relations in glycerinated V. convallaria stalks. The maximum isometric tension was 4 x 10(-8) N on average. The Hill's parameter, n, which is the number of calcium ions bound simultaneously and cooperatively to a contractile element (a force generating element), is approximately 3.2 when the Ca2+ concentration is increased and 2.5 when it is decreased. In order to estimate the efficiency of the energy conversion of Ca2+ binding to mechanical work, we measured the Ca(2+)-induced Carnot cycle in the Vorticella stalk. The energy efficiency was tentatively estimated to be about 7%. With this method, we have also succeeded in measuring the isometric tension of isolated spasmoneme, the rubber-like contractile fibrous organelle in the stalk. The maximum tension of spasmoneme was approximately one tenth that of the glycerinated stalk. We speculate that the isolated spasmoneme was only partially functional due to damage sustained when it was pulled out of the stalk.

Animals↗

PubMed1996

Force development of dynamic and static contractions in children and adults.

There are still unclarified points remaining in regard to the characteristics of force development in children who are immature in their basic activities in daily living. Moreover, there are morphological, histological, and biochemical differences between immature and mature muscles. In the present study, dynamic elbow flexion and static contractions which were performed by elbow flexors with maximum effort were examined by force-velocity and force-time relationships and electromyograms (EMG) in six-year-old children and in adults. In dynamic contractions with various loads, the force-velocity relationship for children was (P + 5.65) (v + 1.48) = 19.51, and (P + 14.65) (v + 2.26) = 96.21 for adults. The maximum power in children and adults was 22.8 watts and 160.8 watts, respectively. The contraction delay in children was greater than that in adults for every relative load. In static contractions, the maximum rate of force development for children was significantly lower than that for adults at each pre-tension. With an increase in pre-tension, the adult rate showed a tendency to decrease, whereas the rate for children showed no change. The electromechanical delay observed in children was significantly greater than that in adults. For dynamic and static contractions, the contractile speed in children was lower than that in adults.

Adult↗

PubMed1996

Cortisol response to exercise and post-exercise suppression of blood lymphocyte subset counts.

This study examined a temporal relationship between exercise-induced changes in blood cortisol levels and circulating leukocyte and lymphocyte subset counts during and after exercise. Twenty-one young male, sedentary subjects [mean age, 20.8 +/- 2.4 (SD) yr; mean VO2max, 48.0 +/- 7.9 (SD) ml/kg/min] underwent a cycle ergometer exercise for 60 min at 60% VO2max. Peripheral blood samples, collected every 30 min during exercise and at 30, 60 min, 2.5 and 6 h of recovery, were used for the determination of serum cortisol and plasma catecholamines; lymphocyte subsets were analyzed by flow-cytometry. Based on the analysis of serum cortisol levels in response to exercise, the subjects can be identified as two groups: cortisol-responder (n = 13) and non-responder (n = 8) groups. Other than the cortisol response, the two groups showed no significant differences in terms of age, physical build, aerobic fitness, maximal heart rate, and pre-exercise blood leukocyte and lymphocyte subset counts. The two groups also did not differ significantly in their relative work rate and catecholamine response to the exercise. Both cortisol responder and non-responder groups displayed a granulocytosis, lymphocytosis and monocytosis during exercise, and a further granulocytosis after exercise. Changes in lymphocyte count and distribution during recovery, however, differed significantly between the two groups. In the circulation of the cortisol non-responder group, total lymphocyte counts returned to the baseline level shortly after exercise, whereas a significant lymphopenia occurred at 2.5 h of recovery in the cortisol responder group: the CD4+ cells showed the greatest decrease in cell count, followed by the CD8+ cells. In both groups, the CD16+ cell-counts tended to decline below the pre-exercise values at 30 and 60 min of recovery and returned to the baseline values by 2.5 h of recovery. The CD19+ cell-count was not suppressed in both groups after exercise. These results suggest that exercise-induced secretion of blood cortisol may contribute to post-exercise suppression of the helper- and cytotoxic-T cell counts, but does not seem to be involved in post-exercise changes in the NK-cell and B-cell counts as well as in post-exercise granulocytosis.

Adult↗

PubMed1996

Metabolism of acetaldehyde to acetate by rat hepatic P-450s: presence of different metabolic pathway from acetaldehyde dehydrogenase system.

NADPH-dependent activity of acetaldehyde oxidation was investigated in microsomes by assaying [14C]acetic acid produced from [14C]acetaldehyde with ion-exchange column. Rat hepatic microsomes exhibited acetaldehyde oxidation activity in the presence of NADPH. This activity was induced 2-fold by the treatment of rats with ethanol. We designated this NADPH-dependent oxidation system as microsomal acetaldehyde-oxidizing system (MAOS), to distinguish from the NAD-dependent acetaldehyde oxidation system by acetaldehyde in mitochondria and cytsol. We further investigated essential enzymes contributing to MAOS activity. Acetaldehyde oxidation activity was investigated in eight forms of purified P-450 in a reconstituted system. Cytochrome P-450 (CYP) 2E1 had the highest oxidation activity and CYP1A2 and CYP4A2 had the next highest activity. Other forms had low activity. To assess the contribution of these forms to MAOS activity, immunoblot was done. CYP2E1 was induced 2-fold by ethanol treatment, but CYP1A2 and CYP4A2 were not reflecting the MAOS activity increased by ethanol treatment. These results suggest that CYP2E1 is the essential enzyme in the MAOS of rats.

Acetaldehyde↗

PubMed1996

Effect of vitamin E deficiency on inhibition of liver regeneration by long-term administration of alcohol.

The effects of vitamin E (VE) deficiency on liver regeneration suppressed by long-term administration of alcohol were studied. Male rats were divided into two groups: the alcohol group and the control group. In addition, each group was subdivided into two groups according to the presence or not of VE. Altogether, four groups were provided: a group maintained on the VE-deficient alcohol diet (group EA), a group maintained on the VE-deficient control diet (group EC), a group maintained on the ordinary alcohol diet (group A), and a group maintained on the ordinary control diet (group C). After pair-feeding for 6 weeks, partial hepatectomy was performed to determine the omithine decarboxylase (ODC) activity, polyamine levels, lipid peroxide levels, and DNA synthesis, DNA synthesis at 24 hr after partial hepatectomy was suppressed significantly in the alcohol administration group, regardless of the presence or not of VE DNA synthesis at 48 hr after partial hepatectomy tended to show low values in group EA, compared with group A. As for the hepatic ODC activity, group EA showed the lowest value at 4 hr after partial hepatectomy. Of polyamines, the putrescine level in group EA at 4 hr after partial hepatectomy was significantly low, compared with the other three groups. The levels of spermidine and spermine decreased by long-term administration of alcohol, but the effect of VE deficiency was not found. The lipid peroxide level increased significantly in the VE-deficient diet administration group, but the effect of alcohol administration was not found. These results suggested that the decrease in putrescine after ODC suppression by VE deficiency in addition to the decrease in spermidine and spermine caused by long-term alcohol administration were concerned with suppression of DNA synthesis later.

Animals↗

PubMed1996

Fetal circulatory responses during maternal bleeding.

The purpose of this study was to investigate the fetal circulatory responses during maternal hemorrhage. Five pregnant goats with fetuses with a mean gestational age of 132 +/- 2 days were used. The maternal blood was withdrawn at 350 ml/h for 2 hours (e.g. 700 ml, 11.9 ml/kg maternal weight) and reinfused at the same speed. During maternal bleeding, maternal arterial pressure (MAP) gradually decreased. As a result of this maternal hypotension, fetal arterial pO2 and pH decreased, and PCO2 increased. After the reinfusion, fetal pO2 recovered but pH and PCO2 did not recover. Fetal arterial pressure (FAP) increased and heart rate (FHR) decreased during maternal bleeding and returned to the control level, after the reinfusion. Fetal arginine vasopressin (AVP) concentration increased to 401.2 +/- 318.5 pg/ml at the maximum bleeding. There were significant positive correlation between AVP concentration and FAP, and negative correlation between AVP and FHR during maternal bleeding. Therefore, we concluded that 700 ml maternal bleeding for 2 hours resulted the decrease in fetal pH, pO2, and FHR, and increase in PCO2, FAP, and AVP concentration. Fetal pH, PCO2, and AVP did not return to the control level in spite of reinfusion.

Animals↗

PubMed1996

[Comparison of fetal circulatory responses during maternal bleeding and fetal bleeding].

The purpose of this study was to compare the fetal circulatory responses during maternal hemorrhage and fetal hemorrhage. Four pregnant goats, gestational age 131 +/- 7 days for the fetal hemorrhage and 5 goats, 132 +/- 2 days (term 145 days) for the maternal hemorrhage were used. The amounts of hemorrhage were 700ml per 2 hours for the maternal hemorrhage and 40ml per 2 hours for the fetal hemorrhage. Although fetal arterial pH decreased during both hemorrhages, fetal arterial pO2 increased during the fetal hemorrhage and decreased in the maternal hemorrhage. The fetal arginine vasopressin concentration and plasma renin activity increased during both hemorrhages, but the rates of change in the hormone concentrations were higher during the fetal hemorrhage. The fetal aldosterone concentration decreased during maternal hemorrhage but increased during fetal hemorrhage. FAP increased and FHR decreased during maternal hemorrhage. FAP and FHR were significantly correlated to the AVP concentration. These relationships were not found during fetal hemorrhage. We therefore concluded that fetal responses were completely different in pO2, FAP and FHR during the maternal and fetal hemorrhages.

Aldosterone↗

PubMed1996

Microsomal ethanol oxidizing system activity by human hepatic cytochrome P450s.

To assess the contribution of cytochrome P450 (P450) to the microsomal ethanol oxidation system (MEOS) in humans, we examined ethanol oxidization activity in human hepatic microsomes and multiple forms of human hepatic P450s expressed in B-lymphoblastoid cells. Acetaldehyde produced by the MEOS was converted into a fluorescent derivate with cyclohexane-1,3-dione and analyzed by high-performance liquid chromatography using a fluorescence detector. The ethanol oxidation activity of seven forms of human P450s was investigated. P450s 2E1 and 1A2 formed acetaldehyde at high rates. In immunoinhibition studies, anti-P450 2E1 antibody inhibited the ethanol oxidation activity of human hepatic microsomes by 54%, and anti-P450 1A2 antibody inhibited ethanol oxidation activity by 21%. 7,8-Benzoflavone, an inhibitor of P450 1A forms, also inhibited this activity by 38%. The correlation of ethanol oxidation activity with the levels of immunoreactive P450 2E1 in individual human microsomes was highly significant (r = 0.91, P < .001), and the correlation of ethanol oxidation activity with the levels of P450 1A2 was also highly significant (r = 0.87, P < .001). The Km values of P450s 2E1 and 1A2 for ethanol oxidation were 16.5 and 23.6 mM, respectively. These results indicated that P450 2E1 was a major contributor to the MEOS in humans; however, P450 1A2 was considered to play an important role in the MEOS.

Adolescent↗