Biomedical subjects

T Shibata

Publications and source records attributed to T Shibata.

At least 451 records · Page 25Linked to original sources

PubMed1995

A heterogeneous electrophysiological profile of bone marrow-derived mast cells.

Electrophysiological properties of mouse bone marrow-derived mast cells (BMMC) were studied under the whole-cell clamp configuration. About one third of the cells were quiescent, but others expressed either inward or outward currents. Inwardly rectifying (IR) currents were predominant in 14% of the cells, and outwardly rectifying (OR) currents in 24%. The rest (22%) of the cells exhibited both inward and outward currents. The IR currents were eliminated by 1 mM Ba2+, and were partially inhibited by 100 microM quinidine. The reversal potential was dependent on extracellular K+, thereby indicating that K+ mediated the IR currents. The negative conductance region was seen at potentials positive to EK. The OR currents did not apparently depend on the extracellular K+ concentration, but were reduced by lowering the extracellular Cl- concentration. The OR currents were partially blocked by 1 mM Ba2+, and were further blocked by a Cl- channel blocker, 4,4'-diisothiocyano-2,2'-stilbenedisulfonate (DIDS). In addition, the reversal potential of the OR currents was positively shifted by decreasing the ratio of external and internal Cl- concentrations, suggesting that Cl- was a major ion carrier. In cells exhibiting IR currents, the membrane potential varied among cells and tended to depolarize by elevating the external K+ concentration. In cells with OR currents, the resting potential was hyperpolarized in association with an increase in conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

A possible mechanism for the hypoxia-hypoglycemia-induced release of excitatory amino acids from cultured hippocampal astrocytes.

In order to elucidate the mechanism of release of excitatory amino acid (EAA) induced by hypoxia-hypoglycemia (in vitro ischemia) from cultured hippocampal astrocytes, we compared the EAA release by in vitro ischemia with those by other treatments. The EAA release induced by in vitro ischemia treatment was rapid and reversible. The amount of released aspartate was comparable to that of glutamate, although the endogenous content of aspartate was one sixth that of glutamate. High-K (100 mM) treatment and the addition of 5 mM NaCN induced a rapid EAA release and the glutamate release was much greater than aspartate. Addition of 5 mM iodoacetate, a glycolysis inhibitor, induced a slow EAA release, and the amount of released aspartate was much higher than that of glutamate. On the other hand, the in vitro ischemia treatment and the addition of 5 mM NaCN induced only 20% reduction in ATP content for initial 5 min, whereas the addition of 5 mM iodoacetate induced a marked reduction. Our data suggest that ischemia-induced EAA release from astrocytes is a complex process in which local energy failure, inhibition of glycolysis, and depolarization of the cell membrane are involved.

Adenosine Triphosphate↗

PubMed1995

Acute and subacute inhalation toxicity of diborane in male ICR mice.

To clarify the toxicity of diborane, we conducted acute (15 ppm for 1, 2, 4 or 8 h) and subacute (5 ppm for 2 or 4 weeks) inhalation studies on ICR mice. The concentration resulting in a 50% kill after 4 h exposure was 31.5 ppm. Body weight gain was suppressed and the lung weight was increased in diborane-exposed mice in both acute and subacute studies. In the acute study, diffuse pan bronchiolitis-like lesions developed in the lung in various degrees depending on exposure time, which can be pathologically characterized as infiltration of inflammatory cells into the terminal bronchioles and surrounding alveoli, pulmonary congestion and bleeding and/or edema. In the subacute study, we observed lymphoid hyperplasia in the perivascular and peribronchial areas, and infiltration of macrophage and plasma cells into the alveoli. In the mice exposed for 4 weeks, the lesions were more severe than in those exposed for 2 weeks, consisting of hyperplasia and desquamation of Clara cells. In the nasal cavity, we saw mucous exudate and inflammatory cells, suggesting irritation caused by diborane. The histopathological findings, except for the respiratory organs, did not reveal any exposure-related changes. No significant changes were seen in hematological and serum biochemical examinations either. In conclusion, the target organ of diborane inhalation is the respiratory organs, particularly the lung. Further inhalation experiments are essential to investigate the safety exposure levels of diborane.

Administration, Inhalation↗

PubMed1995

Multi-site-specific endonucleases and the initiation of homologous genetic recombination in yeast.

The notion that homologous recombination is a regulated biological process is not a familiar one. In yeasts, homologous recombination and most site-specific ones are initiated by site-specific double-stranded breaks that are introduced within cis-acting elements for the recombination. On the other hand, yeasts have a group of site-specific endonucleases (multi-site-specific endonucleases) that have a number of cleavage sites on each DNA. One of them, Endo.SceI of S. cerevisiae, was shown to introduce double-stranded breaks at a number of well-defined sites on the mitochondrial DNA in vivo. An Endo.SceI-induced double-stranded break was demonstrated to induce homologous recombination in mitochondria. Like the case of homologous recombination of nuclear chromosomes, the double-stranded break induces gene conversion of both genetic markers flanking and in the proximity of the cleavage site, and the cleaved DNA acts as a recipient of genetic information from the uncleaved partner DNA. The 70 kDa-heat-shock protein (HSP70)-subunit of Endo.SceI and a general role of the HSP70 in the regulation of protein-folding suggest the regulation of nucleolytic activity of Endo.SceI.

Base Sequence↗

PubMed1995

Assessment of micronucleus induction in SCCVII cells treated with bioreductive agents, WIN 59075 (SR 4233) and mitomycin C, under aerobic and hypoxic conditions.

WIN 59075 (SR4233, tirapazamine) is a promising bioreductive antitumor agent preferentially more toxic to hypoxic cells and presently undergoing phase I clinical trials. In this investigation, we have examined the applicability of the cytokinesis-block micronucleus assay to assess the effects of bioreductive agents. SCCVII tumor cells were treated with WIN 59075 or mitomycin C at various concentrations under aerobic and hypoxic conditions. Significant induction of micronuclei in binucleate cells was demonstrated in a dose-dependent fashion and it appeared to be strongly correlated with the loss of clonogenicity in the colony assay. Both agents showed selectively higher toxicity to hypoxic cells than to aerobic cells and the ratios of the concentrations required to obtain the equivalent effects under aerobic and hypoxic conditions could be also estimated by this method as follows: the hypoxic toxicity ratios were 120-130 for WIN 59075 and 3.0-3.3 for mitomycin C. For several favorable characteristics, the cytokinesis-block micronucleus assay can provide an alternative, rapid, and reproducible means for evaluation of antitumor activities from chromosomal breakage caused by the bioreductive agents.

Dose-Response Relationship, Drug↗

PubMed1995

Neurotoxicity of acromelic acid in cultured neurons from rat spinal cord.

Acromelic acid A, which contains the kainic acid structure in its molecule, is known to cause selective damage of interneurons in the rat lower spinal cord. In the present study, the potent neurotoxicity of acromelic acid A was demonstrated in cultured rat spinal neurons in terms of the activity of lactate dehydrogenase that was released from degenerated neurons into the culture medium. Acromelic acid A increased the lactate dehydrogenase activity in time- and concentration-dependent manners, and its EC50 was about 2.5 microM, which was much lower than that of kainic acid (70 microM) and (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (EC50; 11 microM). The maximum level of lactate dehydrogenase released by acromelic acid A was quite similar to that by kainic acid, but was about twice the level produced by (RS)-alpha-3-hydroxy-5-methyl-4-isoxazolepropionic acid. Exposure to acromelic acid A caused release of L-glutamate from the cells into the medium; however, the concentration of L-glutamate released was far below the level for inducing the neurotoxic effects. The neurotoxicity of 10 microM acromelic acid A was almost completely inhibited by 30 microM 6-nitro-7-sulphamoylbenzo(F)quinoxaline-2,3-dione and 6-cyano-7-nitroquinoxaline-2,3-dione, potent antagonists for non-N-methyl-D-aspartate receptors, but was partly (35%) reduced by 30 microM dizocilpine maleate. In cultured hippocampal neurons, the toxicity of acromelic acid A was significantly less effective (EC50: 18 microM) than that in spinal neurons, whereas the toxicity of kainic acid was almost the same in both neurons. These results suggest that acromelic acid A directly activates non-N-methyl-D-aspartate receptors on the cultured spinal neurons to induce neuronal death. A new type of non-N-methyl-D-aspartate receptors which is specific to acromelic acid A is suggested to be present at least in spinal neurons.

Amino Acids↗

PubMed1995

Diagnostic usefulness of activation-recovery interval for reciprocal ECG changes. Effects of regional myocardial cooling, warming, or coronary occlusion on epicardial electrograms in dogs.

The proximal left circumflex coronary artery (LCx) was cannulated and perfused with blood from the carotid artery in nine open-chest dogs. Perfused blood temperature was modulated by immersing a bypass tube in a temperature-controlled water tank. Two epicardial electrodes were placed, one at the LCx area and one at the left anterior descending coronary artery (LAD) area. The temperature of the autoperfused blood was set at 23 degrees C and was gradually elevated to 42 degrees C during 30 minutes. The QRS, ST-T, and QRST areas, and the activation-recovery interval of the electrode at the LCx area, changed unidirectionally in relation to elevation of the blood temperature. Although the QRS, ST-T, and QRST areas of the electrode at the LAD area changed in proportion to changes in the electrode at the LCx area, the activation-recovery interval of the electrode at the LAD area remained constant in all dogs. During 2-minute occlusion of the proximal LCx (n = 7), the activation-recovery interval of the electrode at the LAD area also remained constant despite the presence of reciprocal electrocardiographic changes. The activation-recovery interval is a useful index for defining whether a change in ST-T in a unipolar electrogram is due to a local electrophysiologic effect or a reciprocal effect.

Action Potentials↗

PubMed1995

Clinical evaluation of the efficacy of EDTA solution as an endodontic irrigant.

The effect of eliminating the smear layer by means of 15% EDTA solution as a root canal irrigant was studied in 189 single-rooted infected teeth. Each tooth was treated at two appointments, and the root canal bacteriological examination was studied on the first (pretreatment, and after enlargement and irrigation) and second (pretreatment) visits. The root canals were irrigated with 15% EDTA solution with ultrasonics agitation. No antibacterial intracanal medications were used between the appointment. When 15% EDTA solution was used, no bacteria could be recovered from 93 of 129 root canals at the sampling stage on second visit. No bacteria were found in 21 of 60 root canals when saline solution was used as an irrigant. These results suggest that 15% EDTA solution is more effective than saline solution as a root canal irrigant.

Anti-Infective Agents, Local↗

PubMed1995

Limited TCR V beta usage of infiltrating T cells in synovial tissues from patients with HTLV-I associated arthropathy.

Human T cell lymphotropic virus type-I (HTLV-I) is the etiologic agent of adult T cell leukemia/lymphoma and recently has also been suggested to be involved in chronic arthritis. The synovia of patients with rheumatoid arthritis (RA) contains activated T lymphocytes, with a restricted expression of T cell receptor (TCR) variable (V) beta gene segments. To characterize the T-cell populations of RA among HTLV-I carriers and noncarriers, we performed the immunohistochemical staining of CD4 and CDB, as well as a reverse transcription polymerase chain reaction (RT-PCR) to estimate the proportion of TCR beta RNA containing any particular V elements on the synovial specimens. In all but one HTLV-I carrier, the proviral DNA and/or RNA expression of HTLV-I was detected in the synovium. The CD4-positive cells proliferated markedly in the HTLV-I carriers compared with the noncarriers. In contrast to mononuclear cells in the peripheral blood, synovial T cells expressed only a few V beta transcripts, and no definite difference was observed between the carriers and the noncarriers. These results suggest that a common major antigen associated with the pathogenesis of RA may thus selectively interact with the V beta component of the TCR. Using RT-PCR, we studied the expression of the recombination-activating gene-1 (RAG-1), which was used in the V(D)J recombination of immunoglobulin and TCR genes. In all cases, RAG-1 was transcripted. The results supported the possibility that the extrathymic development of the selected TCR V beta T cells occurred in the synovia.

Adult↗

PubMed1995

Spontaneous generation of human CD8+ TCR alpha beta+ cells derived from precursors within the double negative compartment.

Flow cytometric analysis demonstrated that fresh human thymocytes contain only a low level of mature CD8+ TCR alpha beta + or CD8+ TCR gamma delta + cells and they consist consist of approximately 70% double positive (DP) and approximately 10% double negative (DN) cells. These unfractionated thymocytes could be selectively expanded in vitro by stimulation with 12-O-tetradecanoylphorbol 13-acetate (TPA) and PHA in the presence of IL-2. The majority of the cells expanded from unfractionated thymocytes expressed CD3, TCR alpha beta and CD8 molecules after long-term culture (18 days). When highly purified DN thymocytes were expanded over a period of 18 days in the presence of DP cells, they also co-expressed CD3, TCR alpha beta and CD8 molecules on their surface. However, when purified DN thymocytes were expanded alone, that is, in the absence of DP cells for 18 days, they expressed CD3-associated TCR gamma delta, but not CD8 or TCR alpha beta. Despite the expression of measurable levels of IL-2 alpha and beta receptors, as well as a significant level of TCR alpha beta, purified DP cells failed to proliferate. These findings provide the first evidence, in humans, that the progression of precursor cells in the DN compartment to a later stage of differentiation can be induced outside the thymus and that DP cells can affect the development of TCR expression in proliferating DN thymocytes.

CD8-Positive T-Lymphocytes↗

PubMed1995

Aggravation of rat nephrotoxic serum nephritis by anti-myeloperoxidase antibodies.

To investigate a possible role of anti-neutrophil cytoplasmic antibodies directed against myeloperoxidase (MPO-ANCA) in glomerulonephritis, we prepared anti-rat MPO antiserum by immunization of rat MPO into a rabbit. Then we administered anti-rat MPO antiserum (group 1) or normal rabbit serum (NRS) (group 2) into rats before injection of nephrotoxic serum (NTS), which induced nephrotoxic serum nephritis (NTN). Other groups of rats received either anti-rat MPO anti-serum (group 3) or NRS (group 4) before injection of NRS but not NTS. Rats in group 1 and group 2 were sacrificed at either 3 hours, 15 hours, or 14 days after NTS injection. Rats in group 3 and group 4 were sacrificed at 15 hours after the last NRS injection. By light microscopy, in rats with NTN sacrificed at 3 hours, counts of polymorphonuclear leukocytes (PMN) per glomerulus were 21.6 +/- 3.5 in group 1 and 8.4 +/- 1.7 in group 2 (P < 0.01). At 15 hours, massive glomerular fibrin deposits were observed in group 1 rats (fibrin score, 131 +/- 8), but not in group 2 rats (fibrin score, 27 +/- 21; P < 0.01). By direct immunofluorescence microscopy, rat MPO was found along glomerular capillary walls more intensely in group 1 rats than in group 2 rats. No pathological alterations were found in group 3 and group 4 rats. Further, renal elution studies revealed that eluted rabbit IgG contained anti-rat MPO antibodies in group 1 rats but not in group 3 rats. These results suggest that the anti-MPO antibodies are directly involved in the more severe glomerular lesions in group 1 rats via interactions with MPO itself or activation of PMN, which release various kinds of mediators including MPO.

Animals↗

PubMed1995

Analysis of the nucleotide sequence of chromosome VI from Saccharomyces cerevisiae.

The complete nucleotide sequence of Saccharomyces cerevisiae chromosome VI (270 kb) has revealed that it contains 129 predicted or known genes (300 bp or longer). Thirty-seven (28%) of which have been identified previously. Among the 92 novel genes, 39 are highly homologous to previously identified genes. Local sequence motifs were compared to active ARS regions and inactive loci with perfect ARS core sequences to examine the relationship between these motifs and ARS activity. Additional ARS sequences were predominantly observed in 3' flanking sequences of active ARS loci.

Base Composition↗

PubMed1995

Transient increase of cyclic AMP induced by glutamate in cultured neurons from rat spinal cord.

We demonstrated that glutamate increased the cyclic AMP level in cultured neurons from rat spinal cord. A bath application of glutamate (300 microM) elicited a rapid increase of the cyclic AMP concentration reaching a level three times as high as the basal level in approximately 3 min, and its content then decreased to the control level in 15 min. The increase was not observed in a Ca(2+)-free medium and was inhibited by an antagonist of NMDA receptors or a voltage-sensitive Ca2+ channel blocker. Preincubation with W7 also inhibited the glutamate-evoked cyclic AMP increase. NMDA, aspartate, and high-K+ conditions also induced a cyclic AMP increase; however, a decreasing phase did not follow. The decreasing phase was observed when (2S,1'S,2'S)-2-(carboxycyclopropyl)-glycine, a potent agonist for metabotropic glutamate receptors, was combined with NMDA. These results suggest that the cyclic AMP increase is mediated by a Ca2+ influx via both NMDA receptors and voltage-sensitive Ca2+ channels followed by an activation of the Ca2+/calmodulin system, and the decreasing phase observed in the case of glutamate exposure is due to the activation of the metabotropic glutamate receptors.

Animals↗

PubMed1995

Fascial sling for the management of urinary incontinence due to sphincter incompetence.

The surgical management of urinary incontinence due to sphincter incompetence is still a challenging issue for urologists to date. We reviewed our experience with the fascial sling performed in 10 male and 3 female patients 3 to 72 years old (median age 13 years) with sphincter incompetence, including 11 with a neurogenic bladder (8 with myelodysplasia, 2 after pelvic operation and 1 after spinal cord injury), 1 after transurethral resection of the prostate and 1 after surgical injury to the bladder neck. Patient selection for a sling procedure was based on cystography (an open bladder neck) and urodynamic findings (underactive external urethral sphincter on electromyography and low maximum urethral closure pressure). A free graft of fascia was harvested from the rectus fascia in 8 patients and from the fascia lata in 5, and the fascial sling was placed around the bladder neck in 11 and the bulbous urethra in 2. Augmentation cystoplasty was performed concomitantly in 9 patients with poor bladder compliance (8 ileocystoplasty and 1 gastrocystoplasty). Postoperative followup ranged from 4 to 63 months (mean 36). Nine patients became continent and 3 improved significantly but remain damp. Of these 12 patients 10 with a neurogenic bladder were placed on intermittent catheterization, while the 2 without a neurogenic bladder are able to void normally. The remaining patient with surgical failure due to inadvertent wound infection received an indwelling urethral catheter. In all but this patient preoperative and postoperative maximum urethral closure pressures were 34.3 +/- 5.7 and 37.2 +/- 3.8 cm. water, respectively, without a significant increase. However, postoperative simultaneous measurements of intravesical and intraurethral pressure demonstrated a dramatic increase in intraurethral pressure during coughing or straining because of the action of the sling. Postoperative upper urinary tract deterioration has not been documented to date. Although various surgical options have been available, the fascial sling seems to be promising in the management of refractory urinary incontinence due to sphincter incompetence.

Adolescent↗

PubMed1995

Small cytoplasmic RNA (scRNA) gene from Clostridium perfringens can replace the gene for the Bacillus subtilis scRNA in both growth and sporulation.

Small cytoplasmic RNA (scRNA) is a member of an evolutionarily conserved signal-recognition-particle-like RNA family. Using a DNA fragment of Bacillus subtilis scRNA gene as a probe, we cloned and characterized a Clostridium perfringens gene encoding the scRNA. Mapping the 5' and 3' ends of scRNA revealed that C. perfringens scRNA consists of 269 nucleotides: the sequence has about 70% primary sequence homology with B. subtilis scRNA. The predicted secondary structure appeared to be similar to that of B. subtilis scRNA, indicating that there are domains I and II in C. perfringens scRNA, in addition to domain IV. Functional analysis showed that C. perfringens scRNA could compensate for vegetative growth and allow the formation of heat-resistant spores in an scRNA-depleted B. subtilis strain, whereas Escherichia coli 4.5S RNA could not maintain sporulation. Since both E. coli 4.5S RNA and C. perfringens scRNA have the same binding specificity to B. subtilis Ffh protein, the difference in complementation activity reflects the function of domains I and II.

Amino Acid Sequence↗

PubMed1995

Genetic polymorphism of the sixth component of complement (C6) in dogs.

Using agarose gel isoelectric focusing and immunoblotting with rabbit anti-rabbit C6, a genetic polymorphism was found in the sixth component of complement (C6) in 18 Asian native breeds or populations and three European breeds of dog. The C6 locus was highly polymorphic. The phenotype distribution data indicated that dog C6 phenotypes were controlled by seven codominant alleles, C6A,C6B,C6C,C6D,C6E,C6F and C6G, at a single autosomal locus. Breed differences were observed among the gene frequencies, especially between Asian and European breeds. Two gene flows from the adjacent areas into Japanese native dogs were postulated.

Animals↗

PubMed1995

Continence mechanism of the orthotopic neobladder: urodynamic analysis of ileocolic neobladder and external urethral sphincter functions.

BACKGROUND: The main objectives of bladder substitution are the preservation of the upper urinary tract and maintenance of urinary continence. Orthotopic bladder substitution makes it possible to achieve urinary continence as well as normal passage of urine through the urethra. Creation of a low pressure reservoir and careful preservation of the distal sphincter mechanism are considered to be of utmost importance for the maintenance of urinary continence after orthotopic bladder substitution. However, sphincter behavior after orthotopic bladder substitution has not been fully elucidated. The purpose of this study was to evaluate the vesicourethral continence mechanism after orthotopic bladder substitution in male patients. METHODS: Urodynamic evaluation was performed in 14 male patients after cystoprostatectomy for bladder cancer and an ileocolic neobladder using a cecourethral anastomosis. RESULTS: Good continence was achieved in 86% (12/14) of the patients during the day and in 79% (11/14) at night. On cystometry, maximum capacity of the neobladders was 434 +/- 21 ml (mean +/- SEM), and basal pressure at maximum capacity was 15.6 +/- 0.9 cm water. Phasic neobladder contraction with amplitudes ranging from 14 to 40 (26.6 +/- 2.7) cm water were noted in 11 of 14 patients. Sphincter electromyography demonstrated an increase in the frequency of action potentials of the external urethral sphincter during neobladder filling from empty to 80% of capacity (from 8.9 +/- 1.6 to 14.6 +/- 2.1 spikes per second; mean percentage increase, 64%, in patients with daytime continence). Maximum urethral closure pressure on urethral pressure profile was 49.9 +/- 3.5 (range, 30 to 64) cm water in patients with daytime continence, while in two patients who were incontinent during the day and at night maximum urethral closure pressure was lower (16 and 24 cm water) and the recruitment of action potentials of the external urethral sphincter during neobladder filling was impaired (percentage increase, 15% and 20%). CONCLUSIONS: An ileocolic neobladder has characteristics of a low pressure reservoir with a satisfactory continence rate. The vesicourethral continence reflex is well preserved in patients with continence after orthotopic bladder substitution.

Cecum↗

PubMed1995

Pharmacokinetics of wood creosote: glucuronic acid and sulfate conjugation of phenolic compounds.

Wood creosote, principally a mixture of non-, alkyl- and/or alkoxy-substituted phenolic compounds, was orally administered to adult male volunteers to determine its metabolites and pharmacokinetic parameters. After a 133-mg single dose, its major constituents (i.e. phenol 15 mg, guaiacol 32 mg, p-cresol 18 mg and creosol 24 mg) were found in peripheral venous blood and urine, mostly as glucuronic acid and, except for creosol, as sulfate conjugates. Low concentrations of unconjugated phenols were also detected. The metabolites in the serum started to increase 15 min after the dose, and they reached their maximum concentrations 30 min after administration. The maximum concentrations of glucuronides were 0.18 +/- 0.07, 0.91 +/- 0.38, 0.33 +/- 0.18 and 0.47 +/- 0.23 mg/l; those of sulfates were 0.16 +/- 0.06, 0.22 +/- 0.09, 0.17 +/- 0.07 and < 0.04 mg/l for phenol, guaiacol, p-cresol and creosol, respectively. The 24-hour urinary recoveries of the sum of each compound and its metabolites were 75 +/- 35, 45 +/- 36, 103 +/- 51 and 74 +/- 36%, in the above order. The presence of guaiacol glucuronide in blood and urine was directly verified by its isolation and structure analyses.

Adult↗