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Biomedical subjects

M Sakurada

Publications and source records attributed to M Sakurada.

At least 19 recordsLinked to original sources

The Tokyo subway sarin attack--lessons learned.

The sarin gas attack in the Tokyo subway system is reviewed from a clinical toxicology perspective. Based on the lessons learned from this attack, the following areas should be addressed on a global scale. First, an adequate supply of protective equipment is required, including level B protective equipment with a pressure demand breathing apparatus. In addition, a system should be established that enables a possible cause to be determined based on symptoms, physical findings, general laboratory tests, and a simple qualitative analysis for poisonous substances. If an antidote is needed, the system should enable it to be administered to the victims as quickly as possible. Preparation for a large-scale chemical attack by terrorists requires the prior establishment of a detailed decontamination plan that utilizes not only mass decontamination facilities but also public facilities in the area. A system should be established for summarizing, evaluating, and disseminating information on poisonous substances. Finally, a large-scale scientific investigation of the Tokyo sarin attack should be conducted to examine its long-term and subclinical effects and the effects of exposure to asymptomatic low levels of sarin.

Antidotes↗

Superiority of minipool nucleic acid amplification technology for hepatitis B virus over chemiluminescence immunoassay for hepatitis B surface antigen screening.

BACKGROUND AND OBJECTIVES: The Japanese Red Cross (JRC) have developed a fully automated multiplex (MPX) nucleic acid amplification technology (NAT) system for hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus 1 (HIV-1). This is used to test serologically negative blood units from volunteer, non-remunerated donors. The system utilizes a 50-sample pool for NAT screening with an input volume of each pool. This results in a significantly higher sensitivity for hepatitis B than that seen with highly sensitive hepatitis B surface antigen (HBsAg) testing. MATERIALS AND METHODS: From 1 February 2000 to 15 October 2001, over 11 million donations, which were serologically negative, were tested using the MPX NAT system. Donations found to be HBV DNA positive were further tested by using the chemiluminescence immunoassay (CLIA). RESULTS: Out of 181 HBV DNA-positive donations, 96 (53%) and 76 (42%) were negative by individual enzyme immunoassay (EIA) and CLIA testing, respectively. CONCLUSIONS: The sensitivity of the 50-sample pool MPX NAT system was higher than that of individual HBsAg screening by CLIA. By adopting this NAT-screening system, the JRC has improved the safety of the blood supply and maintained supply across Japan.

Blood Donors↗

Effects of aflastatin A, an inhibitor of aflatoxin production, on aflatoxin biosynthetic pathway and glucose metabolism in Aspergillus parasiticus.

Aflastatin A inhibits aflatoxin production by Aspergillus parasiticus via an unknown mechanism. We found that aflastatin A clearly inhibited production of norsolorinic acid, an early biosynthetic intermediate of aflatoxin, at a concentration of 0.25 microg/ml. Reverse-transcriptase polymerase chain reaction (RT-PCR), and real-time quantitative PCR (TaqMan PCR) experiments indicated that the transcription of genes encoding aflatoxin biosynthetic enzymes (pksA, ver-1, and omtA) and a gene encoding a regulatory protein for expression of the biosynthetic enzymes (aflR) were significantly reduced by the addition of aflastatin A. We also found that aflastatin A elevated the glucose consumption and ethanol accumulation by A. parasiticus, and repressed transcription of genes involved in ethanol utilization. These results suggest that aflastatin A inhibits a very early step in aflatoxin biosynthesis prior to the transcription of aflR and can influence glucose metabolism in the fungus.

Aflatoxins↗

Intraperitoneal PACAP administration decreases blood glucose in GK rats, and in normal and high fat diet mice.

PACAP is an islet peptide that serves as an endogenous amplifier of glucose induced insulin secretion. Furthermore, we has recently found that PACAP also potentiates insulin stimulated glucose uptake in adipocytes. Therefore, an antidiabetic action of PACAP is possible. In the present study, we examined the effect of PACAP treatment of the hyperglycemia in GK rats, an animal model of type 2 diabetes, and in high fat fed C47BL/6J mice, an animal model for glucose intolerance. GK rats housed with normal diet exhibited a normal level of blood glucose until three weeks old but significant hyperglycemia at eight weeks. When GK rats were treated with daily PACAP38 (i.p. injection, 6 pmol/kg) from age three weeks, development of hyperglycemia was prevented. In high fat fed mice, i.p. administration of PACAP27 for five (25 nmol/kg twice daily) reduced plasma glucose levels to 6.9 +/- 0.2 mmol/l compared to 8.1 +/- 0.2 mmol/l in saline injected animals (p < 0.001) without altering baseline insulin levels. We conclude that PACAP reduces circulating glucose in animal models of type 2 diabetes and glucose intolerance. The mechanism of this action needs to be established.

Animals↗

Blasticidin A derivatives with highly specific inhibitory activity toward aflatoxin production in Aspergillus parasiticus.

Blasticidin A (1), an antibiotic, has strong inhibitory activity toward aflatoxin production by Aspergillus parasiticus. We prepared some derivatives of 1 and examined their biological activities. Among them, derivatives 3 and 4 without the tetramic acid moiety of 1 maintained inhibitory activity toward aflatoxin production, but did not show antifungal activity or toxicity. RT-PCR experiments indicated that derivatives 3 and 4 as well as 1 significantly reduced the expression of genes encoding aflatoxin biosynthetic enzymes (pksA, ver-1 and omtA) and a regulatory gene (aflR) in A. parasiticus. These results suggested that derivatives 3 and 4 can inhibit aflatoxin production more specifically than 1 by inhibiting an early step prior to the expression of aflR in the pathway of aflatoxin biosynthesis.

Aflatoxins↗

Preparation of biotinylated allosamidins with strong chitinase inhibitory activities.

NaIO4 oxidation of allosamidin (1), a strong inhibitor of family 18 chitinases, followed by a coupling with Biotin Hydrazide afforded its mono- and dibiotinylated derivatives, 4 and 6. Reduction of 4 by NaBH4 afforded its reduced form 5. Each of these three biotinylated derivatives maintained strong chitinase inhibitory activity. Especially, 6 inhibited a Trichoderma chitinase as strongly as 1.

Acetylglucosamine↗

Purification and characteristics of membrane-bound chitinase of anaerobic ruminal fungus Piromyces communis OTS1.

A membrane-bound chitinase from cell wall fractions of the anaerobic ruminal fungus, Piromyces communis OTS1, was purified by affinity chromatography, gel filtration, and chromatofocusing. The molecular size of the chitinase was estimated by gel filtration to be 42.4 kDa and by SDS-PAGE to be 44.8 kDa, and its pI was 4.4. Activity was inhibited by Hg2+ and allosamidin. The activity at 39 degrees C was greatest at pH 6.0. It had an 'endo' type action. Solubilization tests indicated that plasmalemma-bound chitinase was held in place by an electrostatic type interaction. Characterization of the membrane-bound chitinase was more similar to that of extracellular chitinase than cytosolic chitinase. This suggested that membrane-bound chitinase was the origin of extracellular chitinase.

Anaerobiosis↗

Insulin secretion from isolated rat islets induced by the novel hypoglycemic agent A-4166, a derivative of D-phenylalanine.

A derivative of D-phenylalanine, A-4166, reportedly evokes a more rapid and short-lived hypoglycemic action in vivo than any of the currently available sulfonylureas. This novel oral hypoglycemic agent is structurally different from sulfonylureas. Therefore, studies were designed to elucidate the mechanisms by which A-4166 stimulates insulin secretion. Insulin release from incubated or perifused rat islets was dose-dependently stimulated by 10 to 200 mumol/l A-4166, in the presence of 2.8 mmol/l glucose. Both A-4166 and tolbutamide evoke a prompt rise in insulin secretion followed by a sustained gradually decreasing release from perfused islets in the presence of low glucose, although A-4166 appeared to be more sensitive than tolbutamide to subthreshold glucose concentration. Diazoxide abolished the initial release and blunted sustained release. Removing calcium from the perifusate abolished insulin release within 15 minutes. A-4166 inhibited [3H]-glibenclamide binding to HIT cell membranes and 86Rb efflux from ATP-depleted or diazoxide-treated cells. These results suggest that the insulin release induced by A-4166 is relevant to this agent occupying the tolbutamide binding sites. Therefore, one possible mechanism accounting for the more rapid and short-lived hypoglycemic action of A-4166 in vivo, as compared with tolbutamide, may involve the reported differences in the bioavailability of A-4166.

ATP-Binding Cassette Transporters↗

[A case of progressive right coronary ostial stenosis after Carrel patch method using gelatin-resorcin-formalin glue].

A 31-year-old man with type A chronic aortic dissection associated with annuloaortic ectasia underwent the concomitant graft replacement of the total aortic root and the transverse aortic arch. The two coronary arteries were reconstructed using the Carrel patch method. The false lumen of right coronary artery was closed by injection of GRF glue into the dissected space and compressing the dissected layers. Postoperative course was uneventful, and the patient has returned to normal daily life 2 months after surgery. Remarkable progression of the right coronary artery ostial stenosis was observed by coronary angiography 6 months after surgery. The remarkable progression of stenosis may occur in association with injection of GRF glue into the dissected space, although the exact etiology of the progressive stenosis remains obscure.

Adult↗

Comparison of a hypervariable segment in the human dopamine D4 receptor (DRD4) gene between the Japanese and Mongolian populations.

Amplifiable length polymorphism (AmpFLP) genotyping and direct sequencing of a hypervariable segment in the human dopamine D4 receptor (DRD4) gene were performed from genomic DNA of 100 unrelated Japanese and Mongolian individuals. The 4-repeat allele (314 bp) was the most prevalent and appeared at 0.88 and 0.82 in the Japanese and Mongolian populations, respectively. Homogeneity test of distribution showed no significant deviation from the observed frequencies of genotypes between the Japanese and Mongolian populations, but sequence analysis of the 4-repeat allele indicated that there could be ethnic differences between the two populations at the nucleotide level. The DRD4 allele and genotype frequencies in 10 patients with Parkinson's disease did not differ from those in the control Japanese population. In one Parkinsonian patient, however, a nucleotide change in one of the 4-repeat alleles was discovered. These results suggest that there could be ethnic and/or individual differences in the specific nucleotide changes within the repeat sequence because some alleles with the same number of repeat units had sequence variations. Thus, the DRD4 polymorphism exists at two levels and therefore could be a useful marker for forensic identification and anthropological studies.

Alleles↗

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an islet substance serving as an intra-islet amplifier of glucose-induced insulin secretion in rats.

1. We examined whether pituitary adenylate cyclase-activating polypeptide with 38 or 27 residues (PACAP-38 or PACAP-27) serves as an intra-islet regulator of glucose-induced insulin secretion in rats. PACAP antiserum specific for PACAP-38 and PACAP-27 was used to neutralize the effect of endogenous PACAP in islets. PACAP release from islets was bioassayed using the response of cytosolic Ca2+ concentration ([Ca2+]i) in single beta-cells, monitored by dual-wavelength fura-2 microfluorometry. Expression of PACAP mRNA was studied by reverse transcription-polymerase chain reaction (RT-PCR), while expression of PACAP was studied by metabolic labelling and immunoblotting. Localization of PACAP receptors was studied immunohistochemically. 2. High glucose-stimulated insulin release from isolated islets was attenuated by PACAP antiserum but not by non-immune sera. 3. The islet incubation medium with high glucose (Med) possessed a capacity, which was neutralized by PACAP antiserum, to increase [Ca2+]i in beta-cells. PACAP antiserum also neutralized the [Ca2+]i-increasing action of synthetic PACAP-38 and PACAP-27, but not that of vasoactive intestinal polypeptide (VIP) and glucagon. 4. Both Med and synthetic PACAP increased [Ca2+]i in beta-cells only in the presence of stimulatory, but not basal, glucose concentrations. In contrast, ATP, a substance that is known to be released from beta-cells, increased [Ca2+]i in beta-cells at both and stimulatory glucose concentrations. 5. Expression of PACAP mRNA and biosynthesis of PACAP-38 were detected in islets and a beta-cell line, MIN6. 6. Immunoreactivity for PACAP-selective type-I receptor was observed in islets. 7. [Ca2+]i measurements combined with immunocytochemistry with insulin antiserum revealed a substantial population of glucose-unresponsive beta-cells, many of which were recruited by PACAP-38 into [Ca2+]i responses. 8. These results indicate that PACAP-38 is a novel islet substance that is synthesized and released by islet cells and then, in an autocrine and/or paracrine manner, potentiates and arouses beta-cell responses to glucose, thereby amplifying glucose-induced insulin secretion in islets.

Adenosine Triphosphate↗

Purification and characteristics of an autolytic chitinase of Piromyces communis OTS1 from culture medium.

An autolysis chitinase was purified from the cultural medium of the anaerobic fungus Piromyces communis OTS1 by ammonium sulfate precipitation, affinity chromatography with regenerated chitin, chromato-focusing, gel filtration, and chromato-focusing again. The optimal pH and temperature were 6.0 and 50 degrees C, respectively, for a 20-min assay. The chitinase was stable from pH 6.0 to 8.0, but was unstable at 70 degrees C for 20 min. The molecular mass of chitinase was estimated by SDS-PAGE to be 44.9 kDa, and its pI was 4.4. The enzyme activity, which was of the 'endo' type, was inhibited by Hg2+ and allosamidin. The chitinase hydrolyzes chitin powder and fungal cell walls at a higher rate than an artificial chitin substrate. It can be concluded that extracellular chitinase is similar to cytosolic chitinase, but they are not the same protein.

Chitinases↗

The columnar and layer-specific response properties of neurons in the primary auditory cortex of Mongolian gerbils.

The columnar and layer-specific response properties of neurons in the primary auditory cortex (AI) of Mongolian gerbils were studied using single-unit recordings of responses to tone-burst stimuli presented to the ear contralateral to the recording side. During near-radial microelectrode penetrations of the AI in 100-microm steps, the best frequency (BF), best threshold (BT), best amplitude (BA), latency, tuning curve and Q10dB were recorded. Neurons encountered during single penetrations showed similar BFs, indicating a columnar frequency organization, but their latencies and Q10dBs differed. The BAs and BTs recorded within single penetrations often showed a similar value in the middle cortical layers. The latencies and Q10dBs of these neurons exhibited a tendency toward a layer-specific distribution. The latencies of neurons located in layers I-V were longer than those located in layer VI. The Q10dBs of neurons located in layers III and IV were higher than those located in layers I and VI. These results are almost consistent with those of previous studies on frequency representation, and indicated the existence of an integrative mechanism of frequency processing in the AI. This is the first study in which a layer-specific, partially columnar organization for stimulus amplitude is described.

Acoustic Stimulation↗

Current status of PACAP as a regulator of insulin secretion in pancreatic islets.

PACAP-27 and PACAP-38 as low as 10(-13) M stimulate insulin release from rat islets in a glucose-dependent manner. PACAP also glucose dependently increases cAMP and [Ca2+]i in rat islet beta cells. The [Ca2+]i and insulin secretory responses to PACAP exhibit a similar concentration-response relationship, exhibiting a peak at 10(-13) M. When the [Ca2+]i response is abolished by nitrendipine, a blocker of L-type Ca2+ channels, the insulin response is also inhibited. Insulinotropic peptides glucagon, GLP-1, and VIP also increase [Ca2+]i in beta cells, but only in the nanomolar concentration range. PACAP is 4 logs more potent that VIP, a peptide that exhibits 68% amino acid homology and shares the type II PACAP receptor with PACAP. Immunoreactivity for the type I PACAP receptor is demonstrated in rat islets. Furthermore, PACAP immunoreactivity is demonstrated in nerve fibers and islets in rat pancreas. Based on these findings, we can draw the following conclusions: (1) PACAP is localized in pancreatic nerve fibers and islets; (2) PACAP in the subpicomolar range stimulates insulin release from islets; (3) the stimulation of insulin release is mediated by the cAMP-dependent increase in [Ca2+]i in beta cells; (4) all the PACAP effects are glucose-dependent; (5) PACAP is the most potent insulinotropic hormone known, and (6) the type I PACAP receptor appears to mediate the action of PACAP in the subpicomolar range. Finally, we hypothesize that PACAP is a pancreatic peptide of both neural and islet origin and functions as an intrinsic potentiator of glucose-induced insulin secretion in pancreatic islets (FIG 6).

Animals↗