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M Shibata

Publications and source records attributed to M Shibata.

At least 343 records · Page 19Linked to original sources
PubMed1995

Modeling of a possible conformational change associated with the catalytic mechanism in the hammerhead ribozyme.

Here we describe a possible model of the cleavage mechanism in the hammerhead ribozyme. In this model, the 2' hydroxyl of C17 is moved into an appropriate orientation for an in-line attack on the G1.1 phosphate through a change in its sugar pucker from C3' endo to C2' endo. This conformational change in the active site is caused by a change in the uridine turn placing the N2 and N3 atoms of G5 of the conserved core in hydrogen bonding geometry with the N3 and N2 atoms on the conserved G16.2 residue. The observed conformational change in the uridine turn suggests an explanation for the conservation of G5. In the crystal structure of H.M. Pley et al., Nature 372, 68-74 (1994), G5 is situated 5.3A away from G16.2. However, the uridine turn is sufficiently flexible to allow this conformational change with relatively modest changes in the backbone torsion angles (average change of 14.2 degrees). Two magnesium ions were modeled into the active site with positions analogous to those described in the functionally similar Klenow fragment 3'-5' exonuclease (L.S. Beese and T.A. Steitz, EMBO J. 10, 25-33 (1991)), the Group I intron (T.A. Steitz and J.A. Steitz, P.N.A.S. U.S.A. 90, 6498-6502 (1993); R.F. Setlik et al., J. Biomol. Str. Dyn. 10, 945-972 (1993)) and other phosphotransferases. Comparison of this model with one in which the uridine turn conformation was not changed showed that although the changes in the C17 sugar pucker could be modeled, insufficient space existed for the magnesium ions in the active site.

Base Sequence↗
PubMed1995

Differences in cell proliferation and apoptosis between reversible and irreversible mucosal lesions associated with uracil-induced urolithiasis in N-butyl-N-(4-hydroxybutyl)nitrosamine-pretreated.

Differences between the reversible papillomatosis and preneoplastic lesions of the urinary bladder of rats were investigated in terms of cell proliferation and apoptosis after cessation of uracil administration. Animals were given N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) for 4 weeks and then uracil for 8 weeks in order to induce urinary bladder lesions. During this period and after cessation of treatment until week 20, subgroups of animals were killed to allow sequential assessment of cell kinetics and apoptosis. Labeling indices (LI) in papillomatosis showed a marked elevation after 2 weeks of uracil treatment with a rapid decline thereafter. In contrast, LI in dysplasias, papillomas and carcinomas gradually elevated during the uracil treatment. Cessation of the uracil stimulation resulted in a complete disappearance of labeled cells in areas of papillomatosis accompanied by significant appearance of apoptotic bodies in the epithelial cells and shrinkage of the lesions. In the focal dysplasias and papillomas, however, any reduction in LI was temporary and followed by a rapid reelevation. The number of apoptotic bodies were relatively few in neoplastic lesions. Thus, removal of growth-stimulating uracil-calculi resulted in return of hyperplastic epithelium to normal by a homeostatically controlled apoptotic mechanism. In contrast, preneoplasias and neoplasias demonstrated an autonomous growth ability.

Animals↗
PubMed1995

Finding the global minimum: a fuzzy end elimination implementation.

The 'fuzzy end elimination theorem' (FEE) is a mathematically proven theorem that identifies rotameric states in proteins which are incompatible with the global minimum energy conformation. While implementing the FEE we noticed two different aspects that directly affected the final results at convergence. First, the identification of a single dead-ending rotameric state can trigger a 'domino effect' that initiates the identification of additional rotameric states which become dead-ending. A recursive check for dead-ending rotameric states is therefore necessary every time a dead-ending rotameric state is identified. It is shown that, if the recursive check is omitted, it is possible to miss the identification of some dead-ending rotameric states causing a premature termination of the elimination process. Second, we examined the effects of removing dead-ending rotameric states from further considerations at different moments of time. Two different methods of rotameric state removal were examined for an order dependence. In one case, each rotamer found to be incompatible with the global minimum energy conformation was removed immediately following its identification. In the other, dead-ending rotamers were marked for deletion but retained during the search, so that they influenced the evaluation of other rotameric states. When the search was completed, all marked rotamers were removed simultaneously. In addition, to expand further the usefulness of the FEE, a novel method is presented that allows for further reduction in the remaining set of conformations at the FEE convergence. In this method, called a tree-based search, each dead-ending pair of rotamers which does not lead to the direct removal of either rotameric state is used to reduce significantly the number of remaining conformations. In the future this method can also be expanded to triplet and quadruplet sets of rotameric states. We tested our implementation of the FEE by exhaustively searching ten protein segments and found that the FEE identified the global minimum every time. For each segment, the global minimum was exhaustively searched in two different environments: (i) the segments were extracted from the protein and exhaustively searched in the absence of the surrounding residues; (ii) the segments were exhaustively searched in the presence of the remaining residues fixed at crystal structure conformations. We also evaluated the performance of the method for accurately predicting side chain conformations. We examined the influence of factors such as type and accuracy of backbone template used, and the restrictions imposed by the choice of potential function, parameterization and rotamer database. Conclusions are drawn on these results and future prospects are given.

Algorithms↗
PubMed1995

Combined dorsal forearm and lateral arm flap.

The free latissimus dorsi musculocutaneous flap and the free groin flap have been used for the coverage of medium- to large-sized soft-tissue defects in the hand. However, these are often too bulky for the hand, requiring secondary operation for thinning. We have used the dorsal forearm flap combined with the lateral arm flap for the coverage of large soft-tissue defects in the hand. This flap is based on the reversed vascular pedicle of the posterior interosseous artery. The posterior radial collateral branch of the profunda brachii artery is then anastomosed to the recipient vessel to augment the vascular supply to the lateral arm flap. We have used this combination flap in two clinical cases and achieved one-stage soft-tissue reconstruction of the hand.

Adult↗
PubMed1995

Low humoral responses to hepatitis C virus among pediatric renal transplant recipients.

Immunosuppressed patients infected with hepatitis C virus (HCV) are known to have a low prevalence of antibodies to the virus. We examined 12 HCV-infected renal transplant recipients and 18 immunocompetent patients in terms of viral markers. The renal patients had a lower prevalence of anti-C100-3 antibodies and lower titers of anti-p22 than the immunocompetents. Low titers of the antibodies seemed to be characteristic of HCV, because titers of anti-mumps and anti-cytomegalovirus antibodies were the same or even increased. Quantitation of HCV RNA showed approximately 200-fold more copies of mean HCV RNA in the sera of the kidney patients than in the immunocompetents. This indicates that the low humoral responsiveness to HCV is not due to the lower concentration of the virus. Immunosuppressive conditions seemed to suppress anti-HCV production with greater magnitude than other viral antibodies.

Adolescent↗
PubMed1995

[Isolation of verotoxin-producing Escherichia coli from pediatric patients suffering from enteritis with bloody stool and intussusception].

We tried to isolate verotoxin-producing Escherichia coli (VTEC) on sorbitol-MacConkey (SMAC) agar and in part by the polymerase chain reaction (PCR) method from sporadic enteritis patients with bloody stools and intussusception patients who came to three pediatric clinics in the Fukuoka area from October 1990 to September 1994. VTEC O157:H7 strains were isolated from 6 (10.5%) of 57 patients with bloody stools, Campylobacter spp. 15 (26.3%), Salmonella spp. 14 (24.6%) and Yersinia enterocolitica 2. We were not able to detect VT genes by PCR from 11 of 20 patients from whose stools no causative bacteria were isolated. Massive fresh bloody stools following frequent watery diarrhea were typical of the VTEC enteritis patients. Only 1 patient had fever and 2 had leukocytosis, but the C-reactive protein in all of them was below 1+. The VTEC strains were isolated during the summer season, 1 in June, 2 in July, and 3 in September. Since in the area O157:H7 appeared to be the most prevalent VTEC serotype, SMAC is very useful for screening VTEC in bloody stools. VTEC seems to be a rare pathogen of intussusception because the organisms were detected from none of the 30 patients.

Adolescent↗
PubMed1995

Detection and quantification of virus DNA in plasma of patients with Epstein-Barr virus-associated diseases.

Epstein-Barr virus (EBV) causes various diseases, such as infectious mononucleosis (IM), fatal IM, EBV-associated hemophagocytic syndrome (EBVAHS), and chronic active EBV infection (CAEBV). In the present study, cell-free EBV DNA was detected in the plasma of patients with EBV-associated diseases by PCR assay. The patients included 20 patients with IM, 2 patients with fatal IM, 4 patients with EBVAHS, 4 patients with CAEBV, and 38 healthy children (20 EBV seropositive and 18 EBV seronegative). In patients with IM, plasma samples were positive for EBV DNA in all patients (100%) in the acute phase and in 44% of the patients in the convalescent phase, but plasma samples from the 38 healthy control children were negative (0%) for EBV DNA. Quantitative PCR assay revealed that plasma from patients with IM contained the highest amount of virus DNA within 7 days following the onset of disease (mean, 6 x 10(4) copies per ml). The EBV DNA concentration decreased thereafter as the patients recovered. Plasma from patients with fatal IM contained more than 100 times more copies of EBV DNA (3 x 10(7) copies per ml) than plasma from patients with IM. Plasma from patients with the acute phase of EBVAHS contained 10 times more copies of EBV DNA (5 x 10(5) copies per ml) than plasma from IM, and then patients with the number of copies decreased similarly in both groups of patients in the convalescent phase (2 x 10(4) copies per ml). The amount of virus DNA in patients with CAEBV (6 x 10(4) copies per ml) was similar to that noted in patients with IM; however, it became higher (1 x 10(6) copies per ml) when the patients' clinical status deteriorated. These data suggest that the presence of cell-free EBV DNA in plasma is a common phenomenon in patients with EBV-associated diseases. The concentration of EBV DNA in plasma seems to be higher in patients with the more severe clinical categories of EBV diseases.

Acute Disease↗
PubMed1995

Lysophosphatidic acid alters cerebrovascular reactivity in piglets.

Effects of the lipid mediator lysophosphatidic acid (LPA) were studied on the cerebral circulation of newborn pigs using closed cranial windows. Topical application of synthetic LPA caused dose-dependent vasoconstriction and inhibited vasodilation to hypercapnia and isoproterenol. These vasodilators elicited a rise in the adenosine 3',5'-cyclic monophosphate (cAMP) content of the cerebrospinal fluid, which was inhibited dose dependently by LPA. Pertussis toxin (1 microgram/ml) completely abolished LPA-induced vasoconstriction and the altered vascular reactivity, and LPA no longer decreased cAMP. Electrophysiological recording of currents evoked by LPA-like lipids in Xenopus oocytes showed that cerebrospinal fluid is normally devoid of LPA-like factors. In contrast, the amount of LPA-like factors generated 4 days after intrathecal injection of autologous blood was in the range of 1-10 microM LPA equivalents. The data indicate that LPA-like bioactive mediators were generated in an intracranial hematoma model and that these phospholipids might play a role in the pathophysiology of altered vascular reactivity often found in posthemorrhagic conditions and could also contribute to the development of posthemorrhagic vasoconstriction.

Animals↗
PubMed1995

Prostacyclin receptor activation and pial arteriolar dilation after endothelial injury in piglets.

BACKGROUND AND PURPOSE: Both light/dye endothelial injury and indomethacin treatment inhibit hypercapnia-induced cerebral prostacyclin synthesis and pial arteriolar dilation in newborn pigs. Topical iloprost can allow hypercapnia-induced dilation of pial arterioles to occur in piglets treated with indomethacin. We addressed the hypothesis that prostacyclin receptor activation with iloprost can return the ability of pial arterioles with endothelial injury to respond to hypercapnia. We also examined whether the endothelial dependence and the permissive role of prostacyclin extended to histamine-induced dilation or are specific for hypercapnia. METHODS: Experiments used chloralose-anesthetized piglets equipped with closed cranial windows. Hypercapnia (PaCO2 approximately 80 mm Hg) and topically applied histamine (10(-6) and 10(-5) mol/L) dilated pial arterioles. Dilations in response to both stimuli were abolished by light/dye treatment. RESULTS: Simultaneous topical treatment with iloprost (10(-12) mol/L, which caused no residual dilation, returned dilation of pial arterioles to both hypercapnia and histamine. On removal of iloprost, responses were again absent and returned with readdition of iloprost to the cortical cerebrospinal fluid. Neither isoproterenol nor sodium nitroprusside returned responses to hypercapnia after light/dye treatment. CONCLUSIONS: These data add further support to the hypothesis that prostacyclin represents an important endothelial-derived signal in the newborn pig cerebral circulation that can permit appropriate responses by adjacent smooth muscle in response to specific stimuli.

Animals↗
PubMed1995

Hematoma-induced enhanced cerebral vasoconstrictions to leukotriene C4 and endothelin-1 in piglets: role of prostanoids.

Cerebral hematoma enhances vasoconstriction induced by topical application of the vasoconstrictor agents endothelin-1 (ET-1) and leukotriene C4 (LTC4). We investigated the influence of dilator prostanoids on vasoconstrictions induced by ET-1 and LTC4 in piglets. Newborn pigs anesthetized with alpha-chloralose were fitted with closed cranial windows 4 d after cortical subarachnoid injections of artificial cerebrospinal fluid (aCSF) (control) or blood (hematoma). The responsiveness of pial arterioles to topical application of the vasoconstrictors ET-1 and LTC4 was examined in the control and hematoma groups before and after treatment with indomethacin (5 mg/kg, i.v.). Vasoconstriction to topical application of LTC4 and ET-1 was enhanced by hematoma compared with the control (28 +/- 2% versus 21 +/- 2% for 10(-8) M LTC4 and by 25 +/- 2% versus 15 +/- 1% for 10(-8) M ET-1, respectively). The lower dose of ET-1 (10(-12) M) dilated pial arterioles in the control group by 6 +/- 2%, hematoma blocked this dilation and it was converted to constriction (10 +/- 1%). Indomethacin treatment enhanced vasoconstriction to LTC4 in the control group to a similar constriction to that observed in the hematoma group. Indomethacin treatment also enhanced vasoconstriction to ET-1 in the control group (25 +/- 1% for 10(-8) M) to similar constrictions to those observed in the hematoma group (25 +/- 2% for 10(-8) M). Dilation to the lower dose of ET-1 was blocked and converted to constriction (17 +/- 2% for 10(-12) M) by indomethacin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Studies on histamine H2-receptor antagonistic property of FRG-8813, a novel anti-ulcer drug].

The present study was conducted to investigate the histamine H2-receptor antagonistic property of FRG-8813 by using isolated guinea pig right atria, gastric cells and cerebral cortex preparations. FRG-8813 inhibited the histamine-induced positive chronotropic response of the right atria and shifted the concentration-response curve of histamine to the right with suppression of the maximal response. Although the inhibitory effect of FRG-8813 was enhanced in a time-dependent manner and long-lasting, the antagonism was reversible. The potency of FRG-8813 was 2 times and 50 times greater than those of famotidine and cimetidine, respectively. FRG-8813 decreased the histamine-induced [14C]aminopyrine accumulation in gastric cells. Schild plot analysis showed that the slopes of FRG-8813, famotidine and cimetidine were 1.56, 1.40 and 1.07, respectively, suggesting that the mode of the antagonism of FRG-8813 is also unsurmountable in gastric cells. The lack of effect on dbcAMP- and bethanechol-induced [14C]aminopyrine accumulations indicated the selectivity of FRG-8813 for histamine H2-receptor. As in the right atria, the potency of H2-antagonism was 1.5 times and 40 times greater than those of famotidine and cimetidine, respectively. In the [3H]tiotidine binding study of the cerebral cortex preparation, the Ki values showed that the affinity of FRG-8813 was 2 times and 80 times more potent than those of famotidine and cimetidine, respectively. In conclusion, FRG-8813 is an unsurmountable and selective histamine H2-receptor antagonist with 2 times greater potency than famotidine. The antagonistic activity is reversible in spite of the time-dependent increase of the antagonism.

Acetamides↗
PubMed1995

Gastroprotective activity of FRG-8813, a novel histamine H2-receptor antagonist, in rats.

FRG-8813 ((+/-)-2-(furfurylsulfinyl)-N-[4-[4-(piperidinomethyl)-2- pyridyl]oxy-(Z)-2-butenyl]acetamide) is a novel histamine H2-receptor antagonist with gastric antisecretory and gastroprotective activities. The present study was designed to investigate the property of gastroprotective action. The oral ED50 values for inhibition of mucosal lesions against 1% NH3-, 60% ethanol in 0.15 N HCl-, 100% ethanol-, 0.6 N HCl- and sodium taurocholate in 0.4 N HCl-induced damage were 3.3, 11.1, 14.9, 23.3 and 23.1 mg/kg, respectively. FRG-8813 was gastroprotective despite pretreatment with omeprazole, suggesting that the protective effect is independent of its antisecretory activity. It is unlikely that FRG-8813 works as a mild irritant because it showed a gastroprotective effect after intraperitoneal injection, but oral administration itself did not influence the rat gastric mucosa. Although pretreatment with indomethacin or N-ethylmaleimide did not affect the gastroprotection of FRG-8813, chemical deafferentation induced by capsaicin abolished the gastroprotection. Furthermore, prior administration of tetrodotoxin, the calcitonin gene-related peptide (CGRP) antagonist hCGRP or NG-nitro-L-arginine attenuated the gastroprotection of FRG-8813 as well as that of capsaicin. In contrast to capsaicin, repeated administration of FRG-8813 neither enhanced the susceptibility of the mucosa to damage nor affected the gastroprotective action of short-term treatment. In conclusion, these results suggest that FRG-8813 has gastroprotective activity independently of acid antisecretory activity and that capsaicin-sensitive nerves may be partially or fully involved in the gastroprotective mechanisms of FRG-8813.

Acetamides↗
PubMed1995

In vitro assessment of teratogenic potential of cis-1-[4-(p-menthane-8-yloxy) phenyl]piperidine [corrected].

Teratogenic potential of cis-1-[4-(p-menthane-8-yloxy) phenyl] piperidine [corrected] (YM9429) was assessed by in vitro culture method using fetal palatal tissues of CD rats. YM9429 induced fetal cleft palate in vivo in CD rats when dams were orally treated during days 11-14 of pregnancy at dose of 500 mg/kg/day, but no abnormalities were detected when treated on days 15-16 (Shibata, 1993). After 4 successive days oral treatment during days 11-14 of pregnancy, the maternal plasma levels of the drug were less than 5 micrograms/ml on day 15 and less than 1 microgram/ml on day 16. After a single oral dosing on day 14, the fetal levels were approximately 0.3 microgram/g-fetus at 2 hours post dosing. When the fetal maxillary regions removed from the normal fetuses on day 15 of pregnancy were cultured with YM9429 at the concentrations of 5 and 1 micrograms/ml-medium for 48 or 72 hours, normal and full contact of the palatal shelves was observed. These results supported the previous findings that YM9429 demonstrated no teratogenic effects in vivo by maternal treatment on days 15-16 of pregnancy, and suggested other mechanisms than the direct influences on the fetal palatal shelves in the latter phases of morphogenesis including reorientation, horizontal extension and adhesion.

Animals↗
PubMed1995

New glycosidases inhibitors, panosialins D and wD produced by Streptomyces sp. OH-5186.

New panosialin analog, panosialins D and wD have been isolated from the culture broth of Streptomyces sp. OH-5186. Their structures were elucidated as 5-(13-methylpentadecyl)-1,3-benzenediol bis(sodium sulfate) and 5-(13-methylpentadecyl)-1,3-benzenediol 1-(sodium sulfate), respectively. They showed strong inhibitory activity against alpha-mannosidase, alpha-glucosidase, and beta-glucosidase. Panosialins wA-wD mixture also showed weak mitogenic activity but suppressed the mitogen induced activity.

Animals↗
PubMed1995

[Static palatography and image processing system by computer.].

In this study the artificial palates made of black vinyl seat covering the palate and occlusal surfaces of maxillary teeth were coated with white alginate powder and inserted into the mouth of the subjects.After pronunciation of the test sounds,the tongue contact areas on artificial palate were demonstrated by wetting of powder and changing in color from white to black.Thus,photographnys of palatograms were taken.After taking 5 palatogram of each sound,the samples were averaged by an image processor.The averaged outline of each subject's palatogram was converted into a standarized dental arch form,with the gray scale of each image reversed and reduced,and then added to every pattern of the same sound produced by all subjects.Thus,palatograms were based on the frequency of over lapping.From this compiling, contact areas that were common in more than four out of six subjects were extracted.

English Abstract↗
PubMed1995

Reduced muscle uptake of oxygen during exercise in patients with systemic lupus erythematosus.

OBJECTIVE: To assess the factors limiting aerobic exercise capacity in patients with systemic lupus erythematosus (SLE). METHODS: The anaerobic threshold (AT) and O2 pulse, i.e., VO2/heart rate (HR), were measured in 21 patients with SLE without cardiopulmonary complications by the analysis of expired gas during incremental work load in exercise testing. The relationships between work rate (WR) and VO2, HR and VO2/weight (Wt), and lupus activity index (LAI) and AT were analyzed. RESULTS: The AT of the patients with SLE was significantly lower than for a control group. Little increase in O2 pulse and very low delta VO2/delta WR and delta VO2/Wt@delta HR were found during work load in some patients with SLE, especially those with a low AT and high LAI. Patients with SLE with a high LAI tended to show a low AT. CONCLUSION: The low aerobic exercise capacity of patients with SLE appeared to be mainly due to a small increase in O2 pulse. This may have resulted from impaired oxygen diffusion in the inflamed peripheral muscles in patients with active SLE. Low AT may explain in part why patients with SLE become easily fatigued.

Adult↗