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Biomedical subjects

A Ishida

Publications and source records attributed to A Ishida.

At least 127 records · Page 7Linked to original sources
PubMed1997

Changes in right ventricular volume in early human neonates.

To evaluate changes in the right ventricular volume in early human neonates, twenty fullterm infants were examined at 2, 24 and 120 h of age by two-dimensional echocardiography. End-diastolic and end-systolic right ventricular volumes (RVEDV and RVESV, respectively) were calculated with a computer system based on the bi-plane Simpson's rule using the apical four chamber and parasternal short axis views. Then right ventricular stroke volume (RVSV), ejection fraction (RVEF), and the mean normalized systolic ejection rate were obtained. The inner diameter of the ductus arteriosus was also measured simultaneously. RVEDV increased significantly by 24 h of age, but remained constant thereafter. RVESV remained virtually unchanged from 2 to 120 h, resulting in a significant increase (36%) of RVSV at 24 h compared with that at 2 h. The mean normalized systolic ejection rate remained unchanged. There was a good correlation between RVEDV and RVSV (r = 0.83). All ductus arteriosus except three narrow ones was closed by 24 h of age. In conclusion, at 24 h of age, the significantly increased RVEDV was closely related to the increased RVSV, which might be induced by increased volume load to the right ventricle because of the closure of the ductus arteriosus.

Ductus Arteriosus↗
PubMed1997

Induction of the cyclin-dependent kinase inhibitor p21(Sdi1/Cip1/Waf1) by nitric oxide-generating vasodilator in vascular smooth muscle cells.

Nitric oxide-generating vasodilators inhibit vascular smooth muscle cell proliferation. To elucidate the mechanism underlying this process, we investigated the effect of S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide-releasing agent, on the smooth muscle cell cycle. When G0 cells were stimulated with fetal bovine serum and basic fibroblast growth factor, DNA synthesis assessed by [3H]thymidine incorporation started about 15 h later. SNAP dose-dependently inhibited this incorporation, and this effect was maximal at 100 microM. This inhibition was attenuated when SNAP was added after 9-12 h. SNAP inhibited the activity of cyclin-dependent kinase 2 (Cdk2) and phosphorylation of the retinoblastoma protein, both of which usually increased from about 9 h, whereas it did not inhibit the activities of cyclin D-associated kinase(s), Cdk4, and Cdk6, which normally increased from 0-3 h. Although SNAP reduced the mRNA levels of cyclins E and A, it neither reduced their protein levels nor impaired their association with Cdk2. SNAP did not reduce the mRNA levels of cyclins G, C, and D1, Cdk2, Cdk4, and Cdk5, which were normally elevated from 0-3 h. The mRNA and protein levels of the Cdk inhibitor p21 were high in the early G1 phase, peaking at 3 h and then rapidly decreasing after 6 h. In the presence of SNAP, however, p21 expression was enhanced, and moreover, the later decrease disappeared. SNAP also increased the amount of Cdk2-associated p21. These results suggested that nitric oxide inhibits the G1/S transition by inhibiting Cdk2-mediated phosphorylation of the retinoblastoma protein and that p21 induction is involved in the Cdk2 inhibition.

Animals↗
PubMed1997

Detection of protein phosphatase activities in sodium dodecyl sulfate-polyacrylamide gel using peptide substrates.

A method for detection of protein phosphatase activity toward phosphorylated oligopeptides in SDS-polyacrylamide gel was developed. A synthetic peptide (MHRQETVDC) corresponding to the autophosphorylation site of calmodulin-dependent protein kinase II (residue 281-289) was conjugated to poly-L-lysine and phosphorylated with [gamma-32P]ATP by the action of calmodulin-dependent protein kinase II, and the [32P]-phosphopeptide-polymer conjugate was included as a substrate for protein phosphatases in gels. When a crude extract from rat brain was electrophoresed on polyacrylamide gel containing the [32P]phosphopeptide conjugate, followed by treatment for in situ renaturation and autoradiography, three transparent bands corresponding to apparent molecular weights of 52,000, 58,000 and 74,000, resulting from the removal of the [32P]phosphate from the phosphopeptide conjugate included in the gel were observed, indicating the existence of at least three different phosphoprotein phosphatases catalyzing dephosphorylation of the phosphopeptide in the brain. Among the three, two bands corresponding to molecular weights of 52,000 and 58,000 were not clearly observed when other phosphopeptide-polymer conjugates such as C-syntide-2 and CAMKAKS peptide were included in gels, suggesting that site-specific protein phosphatases can be detected in crude tissue extracts by this in-gel protein phosphatase assay.

Amino Acid Sequence↗
PubMed1997

Glomerular proliferating cell kinetics in acute post-streptococcal glomerulonephritis (APSGN).

To investigate the time sequence of glomerular cell proliferation in acute human glomerulonephritis, renal biopsy tissues were examined from 15 acute post-streptococcal glomerulonephritis (APSGN) patients (who were biopsied 1-31 days after onset), using an immunoperoxidase technique with monoclonal antibodies against proliferating cell nuclear antigen (PCNA) and various cell surface markers. Few, if any, PCNA+ cells were observed in normal glomeruli, but many cells were positive for PCNA in the acute phase of APSGN. Glomerular PCNA+ cells were observed either within glomerular tufts, or lining Bowman's capsule (parietal epithelial cells); the number of positive cells tended to decrease exponentially as the disease duration increased (r = -0.91, P < 0.0001). PCNA+ cells within glomerular tufts were further identified by double immunostaining. PCNA was not found in PMN or T cells, but a small proportion of macrophages were PCNA+. Most of the remaining PCNA+ cells were resident glomerular cells; the proportion of PCNA+ endothelial cells (CD31+) was over 80 per cent in the early phase, but as the disease continued the proportion of mesangial cells (alpha-smooth muscle actin+) increased to about half of the total PCNA+ cells within the tuft. These data indicate that the hypercellular glomeruli in APSGN are due not only to immune cell infiltration, but also to resident glomerular cell proliferation, probably induced by locally produced growth factors.

Acute Disease↗
PubMed1997

Chronological and immunohistochemical observations of cerebellar dysplasia and vermis defect in the hereditary cerebellar vermis defect (CVD) rat.

Hereditary cerebellar vermis defect (CVD) rats, a new neurological mutant, developed both cerebellar vermis defect and cerebellar dysplasia. Developmental alterations in the cerebellum of the CVD rats were studied chronologically and immunohistochemically. The earliest architectural abnormality was a maldevelopment of the inferior cerebellar peduncle from embryonic day 17 (E17), leading to an indistinct separation between the cerebellum and the pons. From E19, the CVD rats lacked vermis development and, therefore, the cerebellar hemispheres were fused. After birth, Purkinje cells and external granule cells (EGCs) penetrated into the pontine tissue, but retained their normal position until postnatal day 10. Cerebellar lamination began to be disturbed due to abnormal perivascular aggregations of the EGCs, resulting in convoluted and occasionally perivascular lamination. There were no Bergmann glia in the heterotopic cerebellum of the pons, and abnormally arranged Bergmann glia were observed in the mildly disorganized cerebellar hemispheres. Immunohistochemistry for calbindin revealed that abnormal orientation of the Purkinje cells might be related to the perivascular EGCs. Parvalbumin-immunopositive microneurons were seen only in the disarranged molecular layers, and synaptophysin-immunopositive cerebellar glomeruli were present in the afflicted internal granular layers. These findings suggest that perivascular EGCs may play an important role in cerebellar dysplasia and the developmental plasticity in the altered cerebellogenesis.

Animals↗
PubMed1997

Calcium- and calmodulin-dependent phosphorylation of AMPA type glutamate receptor subunits by endogenous protein kinases in the post-synaptic density.

We have detected immunoreactivities of AMPA receptor subunits GluR1-4 in post-synaptic density (PSD) fraction and tested whether they can be phosphorylated by endogenous kinases. Incubation of PSD with Ca2+ and calmodulin increased phosphorylation of GluR1 and GluR2/3. The phosphorylation of GluR1 was largely blocked by a Ca2+/calmodulin-dependent protein kinase type II inhibitor. Thus Ca2+/calmodulin-dependent phosphorylation of glutamate receptor may be a mechanism underlying enhanced post-synaptic receptor responsiveness in LTP.

Animals↗
PubMed1997

Cranial computed tomography scans of premature babies predict their eventual learning disabilities.

It remains difficult to predict, early enough to intervene effectively, the risk of the development of learning disabilities among extremely low birth weight (ELBW) infants (birth weights less than 1,000 g). We prospectively studied the relationship between dilatations of lateral ventricles of the cranial computed tomography (CT) scan taken at the postconceptional age of 40 weeks and learning disabilities in their school age. Using a computer digitizer, we measured the areas of ventricles on cranial CT scans. The mean area of lateral ventricles of the learning disabilities-suspected group was significantly larger than that of the control group (392.9 and 277.4 mm2, respectively; P < .01). There were no significant differences between the two groups in gestation, birth weight, physical measurements, and developmental quotients at early school age. The dilatation of the lateral ventricles assessed by cranial CT at the corrected term may be one of the first predictors of learning disabilities recognizable at early school age.

Brain↗
PubMed1997

Experimental acute glomerulonephritis induced in the rabbit with a specific streptococcal antigen.

FITC-labelled IgG obtained from patients convalescing from acute poststreptococcal glomerulonephritis (APSGN) stains glomeruli of patients with early APSGN. We previously reported a streptococcal antigen (preabsorbing antigen (PA-Ag)) that preabsorbed the stain out of sera from the convalescent patients and thus prevented glomerular staining. To confirm the nephritogenicity of PA-Ag, we administered up to 40 mg of this antigen to rabbits for 8 days and observed them for up to 9 weeks. Immunohistological analysis showed diffuse and global glomerular staining for C3 without notable staining for gamma-globulin. Light microscopic examinations revealed slight to moderate proliferative glomerulonephritis with exudative change. Control rabbits, which received similar doses of bovine serum albumin, did not show significant staining for C3. A transient and significant decrease in CH50 was observed from weeks 3 to 7 (9.7 +/- 0.3 U/ml at week 3; normal range 12.9 +/- 0.6 U/ml). This experimental model showed a resemblance to immunological and immunohistological features of APSGN in humans. Although the precise mechanisms are yet to be determined, complement activation by PA-Ag seems to hold a key position in this model and in the human disease.

Acute Disease↗
PubMed1997

A case of neonatal choriocarcinoma.

Choriocarcinoma occurring in a placenta and metastasizing to the fetus is quite rare. We describe here a case of such infantile choriocarcinoma, initially appeared as refractory anemia and rapidly metastasized to the liver, lungs, and brain. The placenta looked normal and was not submitted to histological examinations. Neither noninvasive nor invasive diagnostic methods (ultrasonography, computed tomography, magnetic resonance image, scintigraphy, and hepatic arteriography) gave any diagnostic information on the tumor. Liver biopsy was considered too risky due to a possible bleeding. Correct diagnosis was established only after the postmortem examination. Two months after the infant's death, we were informed that the mother was found having hepatic and pulmonary tumors. The importance of the maternal history and measurement of urinary human chorionic gonadotropin is emphasized for a rapid and correct diagnosis of infantile choriocarcinoma.

Anemia, Refractory↗
PubMed1997

Nitric oxide-induced ciliary muscle relaxation during contraction with endothelin-1 is mediated through elevation of cyclic GMP.

PURPOSE: Nitric oxide (NO) relaxes ciliary smooth muscle, and endothelin-1 (ET-1) is reported to regulate ciliary muscle tone. Despite the physiological significance of nitric oxide and ET-1, very few studies have attempted to characterize the mutual modes of action of these mediators in this tissue. Thus, the present experiments were designed to investigate a possible relaxation mechanism of nitric oxide in bovine ciliary muscle that has been contracted by ET-1. METHODS: The effects of sodium nitroprusside (SNP), as a nitric oxide donor, methylene blue, as an inhibitor of guanylate cyclase, and 8-bromo-cyclic GMP on the bovine ciliary muscle contracted with ET-1 were examined. The changes in cyclic GMP level and relaxation, in response to SNP alone or in combination with 3-isobutyl-1-methylxanthine (IBMX) as a nonselective inhibitor of phosphodiesterases, were also determined. RESULTS: Sodium nitroprusside (SNP) produced a concentration-dependent relaxation, which was significantly (p < 0.005) augmented by 10(-5) M 3-isobutyl-1-methylxanthine (IBMX) and significantly (p < 0.005) attenuated by 3 x 10(-5) M methylene blue as an inhibitor of guanylate cyclase. The relaxation in response to SNP was accompanied by an increase in the cyclic 3':5' guanosine monophosphate (cyclic GMP) level, which was again significantly (p < 0.05) augmented by 10(-5) M IBMX and significantly (p < 0.005) attenuated by 3 x 10(-5) M methylene blue. The exogenously applied 8-bromo-cyclic GMP relaxed the ciliary muscle strips during the contraction caused by ET-1. CONCLUSIONS: These results lead us to assume that NO generated from SNP is closely related to cyclic GMP production via the activation of guanylate cyclase and, in turn, causes a relaxation response in the bovine ciliary muscle contracted with ET-1.

1-Methyl-3-isobutylxanthine↗
PubMed1997

A new peptide conjugate as a highly specific substrate for MAP kinase.

A synthetic peptide (APRTPGGRC) cross-linked to poly-L-lysine through a carboxy-terminal cysteinyl residue was found to be a highly specific substrate for mitogen-activated protein (MAP) kinases. This peptide conjugate exhibited a much lower Km value (74 microM) than the free peptide substrate (APRTPGGRR, Km > 1 mM) previously used as a specific substrate for MAP kinases. Unlike myelin basic protein, which has been often used as a substrate for MAP kinases, this conjugate did not serve as substrate for cAMP-dependent protein kinase, protein kinase C, or multifunctional calmodulin-dependent protein kinases. Using the peptide conjugate as a substrate, MAP kinase activities in crude cell extracts were directly determined by in vitro assay and specifically detected by in-gel assay.

Animals↗
PubMed1997

Analysis of the posture control system under fixed and sway-referenced support conditions.

To delineate the relative roles of each of the feedback sensors in the posture control system such as the visual, vestibular, and proprioceptive sensors, an identification technique was applied to measurements of antero-posterior sway angeles of the body and ankle moments under the following conditions: standing on a fixed support with eyes open (ox), standing on a fixed support with eyes closed (cx), standing on a sway-referenced support with eyes open (os), and standing on a sway-referenced support with eyes closed (cs). Frequency response functions from the sway angle to the ankle moment were calculated. Gain and phase characteristics for conditions (os) and (cs) were similar to those of Nashner's vestibular model in the high-frequency range, which shows that the vestibular system may be dominant. The gain was higher under condition (cx) than under (ox). Judging from the phase characteristics, this was probably due to increased weighting of the proprioceptive sensor over the vestibular sensor. There was a tendency for gain to increase as balance tasks became more demanding.

Adult↗
PubMed1997

Characteristics of neurons with high-frequency discharge in the central nervous system and their relationship to chronic pain. Experimental and clinical investigations.

High-frequency extracellular unitary activity was recorded mainly in the ventral caudal nucleus of the thalamus in chronic-pain patients. These high-frequency discharge (hyperactive) neurons shows three types of discharge pattern with different interval histograms. Some of these hyperactive neurons were suppressed by the administration of a calcium antagonist (nicardipine). In an experimental study, chronic-pain models were made in rats according to the method of Lombard et al. (1979). From these animals, hyperactive neurons were recorded from the contralateral thalamic nuclei, lemniscus medialis. Hyperactive neurons were examined via electrical stimulation of and/or iontophoretic application. The results suggest that there is some relationship to the glutamatergic and GABAergic (probably GABAA) fibers or receptors.

Animals↗
PubMed1997

Magnesium attenuates a striatal dopamine increase induced by anoxia in the neonatal rat brain: an in vivo microdialysis study.

We evaluated the effects of magnesium on extracellular dopamine (DA) and its metabolites in the striatum of 5-d-old rats submitted to 16 min of anoxia using microdialysis and HPLC. Rat pups were divided into three groups and received either 1) intrastriatal perfusion (IS) of MgSO4, 2) intraperitoneal injection (IP) of MgSO4, and 3) NaCl and Ringer's solution, respectively in place of MgSO4. After stabilization, Mg2+, saline, and Ringer's solution were administered; then, 114 animals were exposed to 100% nitrogen for 16 min. Anoxia induced a DA surge, an acutely marked increase of DA, in both the control and the IP group. In contrast, the DA surge was significantly suppressed in the IS group (p < 0.01, analysis of variance). During anoxia, the plasma Mg2+ in the IP group, but not in the IS group, maintained a significantly higher level compared with the basal level. On the other hand, Mg2+ in the perfusates in the IS group, but not in the IP group, maintained a significantly high level during anoxia. Alterations induced by anoxia in other metabolites, 3,4-dihydroxyphenylacetic acid, homovanillic acid, norepinephrine, and 5-hydroxyindole-3-acetic acid, did not significantly differ among the three groups. We propose that elevated levels of Mg2+ in the striatum had inhibitory effects on the DA surge during anoxia.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

Efficient synthesis and gastric (H+/K+)-ATPase-inhibitory activity of 2-aryl-4,5-dihydro-1H-thieno[3,2-e]benzimidazoles.

A series of 2-aryl-4,5-dihydro-1H-thieno[3,2-e]benzimidazoles (1, 2) was prepared by condensation of 5-acylamino-4,5,6,7-tetrahydrobenzo[b]thiophen-4-ones (9, 10) with ammonium acetate under azeotropic reaction conditions. Various congeners, N-methyl and N-phenyl analogues (3-5), 4,5-dihydro-1H-thieno[2,3-e]benzimidazoles (6), 4,5-dihydro-1H-thieno[2,3-g]benzoxazoles (7), and 4,5-dihydro-1H-thieno[2,3-g]benzothiazoles (8), were also prepared. Several compounds in this series were shown to be K(+)-competitive inhibitors of the gastric (H+/K+)-ATPase and more potent inhibitors than SK&F-96067, 3-butyryl-8-methoxy-4-(2-tolylamino)quinoline, on pentagastrin-stimulated acid secretion in chronic gastric fistula rats after intraduodenal administration.

Animals↗
PubMed1997

Symptomatic aortic regurgitation after Blalock-Taussig shunt in tetralogy of Fallot with bicuspid aortic valve.

We report here a case of a premature baby with tetralogy of Fallot and bicuspid aortic valve. After the successful completion of the Blalock-Taussig (BT) shunt, severe aortic valve regurgitation (AR) appeared, although it was trivial preoperatively. Severe postoperative heart failure was induced by progression of the AR. Postoperative echocardiography revealed that the progression of the AR was provoked by appearance of prolapse of the cusp as the result of rapid increase of blood flow through the aortic valve after the BT shunt. We propose that, in planning the BT shunt for patients with tetralogy of Fallot, preoperative examinations for a possible bicuspid aortic valve should be done and postoperative precaution considering possible appearances of severe AR and congestive heart failure will be necessary.

Anastomosis, Surgical↗
PubMed1997

Changes in left ventricular diastolic filling patterns before and after the closure of the ductus arteriosus in very-low-birth weight infants.

To evaluate serial changes in left ventricular diastolic filling patterns in preterm infants, we performed echocardiographic examinations in 18 very-low-birth weight infants and 20 fullterm infants before and after the closure of the ductus arteriosus. In the fullterm infants, the ductal closure induced significant decreases in the peak velocity and flow velocity integral of early diastole, first third filling fraction, and mitral stroke volume. In the preterm infants, by contrast, there were significant increases in the flow velocity integral of early diastole, first third filling fraction, and mitral stroke volume after the ductal closure. No differences following the ductal closure were found in the atrial phase of filling and peak filling rate normalized to stroke volume in either group. When the ductus arteriosus was open, essentially the same left-to-right shunting of the ductus arteriosus was detected in both preterm and fullterm infants, but the Doppler flow patterns of the patent foramen ovale were different: the fullterm infants had a single flow peak mainly during ventricular late systole and early diastole, but the preterm infants had two or three flow peaks with nearly equal amplitudes lasting from ventricular systole to diastole, which resembled the Doppler flow pattern of atrial septal defect. Only a faint Doppler flow signal of the foramen ovale was observed after the ductus arteriosus closed. Our results obtained from the preterms suggest that the left-to-right shunt through the foramen ovale may be one important factor to alter the Doppler transmitral filling patterns during the fetal to neonatal cardiovascular changes.

Ductus Arteriosus↗