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Biomedical subjects

M Ohta

Publications and source records attributed to M Ohta.

At least 127 records · Page 7Linked to original sources
PubMed2000

Production of shiga toxin by Escherichia coli measured with reference to the membrane vesicle-associated toxins.

Production of Shiga toxin (Stx) 1 and 2 from Stx-producing Escherichia coli (STEC) was measured with reference to the membrane vesicle (MV)-associated toxins. An immunoblot analysis method using specific antibodies for Stx1 and Stx2 was developed for the detection of the extracellular toxins. All 46 STEC isolates, studied including 30 O157 and 16 other O-antigenic isolates, released Stx1 and Stx2 as MV-associated and MV-removed fractions under aerobic and anaerobic conditions. Treatment of vesicles with polymyxin B that disrupted MVs increased the release of Stx1 and Stx2. Therefore, delivery of Stx1 and Stx2 by MVs is a general mechanism in STEC. Stx1 remained within MVs rather than in the MV-removed fraction under an aerobic culture condition. On the other hand, a larger proportion of Stx2 was detected in the MV-removed fraction. The kinetic patterns of the release of the toxins from STEC strains showed that both Stx1 and Stx2 were released into the growth medium during the exponential growth phase. An rpoS-deficient mutation did not have altered levels of extracellular Stx1 and Stx2, supporting the idea that Stx1 and Stx2 are produced during exponential growth phase.

Aerobiosis↗
PubMed2000

Application of liquid chromatography/mass spectrometry and liquid chromatography with tandem mass spectrometry to the analysis of the site-specific carbohydrate heterogeneity in erythropoietin.

High-performance liquid chromatography with electrospray ionization mass spectrometry (LC/MS) and liquid chromatography with tandem mass spectrometry (LC/MS/MS) were applied to the analysis of the site-specific carbohydrate heterogeneity in erythropoietin (EPO) used as a model of the sialylated glycoprotein. N-linked oligosaccharides were released from recombinant human EPO expressed in Chinese hamster ovary cells enzymatically and reduced with NaBH(4). Many different sialylated oligosaccharides of EPO were separated and characterized by LC/MS equipped with a graphitized carbon column (GCC). Glycosylation sites and the preliminary glycosylation pattern at each glycosylation site were determined by LC/MS of endoproteinase Glu-C-digested EPO. The detailed site-specific carbohydrate heterogeneity caused by the differences in the molecular weight, branch, linkage, and sequence was elucidated by GCC-LC/MS of the N-linked oligosaccharides released from the isolated glycopeptides. Structural details of the isomers were analyzed by LC/MS/MS, and it was indicated that di- and trisialylated tetraantennary oligosaccharides are attached to Asn24, 38, and 83, whereas their isomers, di- and trisialylated triantennary oligosaccharides containing N-acetyllactosamines, are combined with Asn24. Our method is useful for the determination of glycosylation sites, the site-specific carbohydrate heterogeneity of glycoproteins, and the carbohydrate structure.

Animals↗
PubMed2000

Rapid isolation and identification of staphylococcal exoproteins by reverse phase capillary high performance liquid chromatography-electrospray ionization mass spectrometry.

The isolation of staphylococcal extracellular toxins and enzymes (exoproteins) usually requires time-consuming purification steps such as repeated chromatographic separations and isoelectric focusing. We performed rapid isolation, quantification and identification of staphylococcal exoproteins by reverse phase capillary high performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS) followed by the determination of N-terminal amino acid sequences of separated peaks. We identified two novel exoproteins as well as previously reported antigens ORF-1 and ORF-2, glutamyl endopeptidase in Staphylococcus aureus NCTC8325 and protein A, staphylococcal enterotoxin C3 (SEC3), toxic shock syndrome toxin-1 (TSST-1) and alpha-toxin in a clinical isolate methicillin-resistant S. aureus (MRSA) 3543. MRSA3543 secreted 5.33 and 1.45 microg of SEC3 and TSST-1 per 20 microg total exoproteins ml(-1), respectively. The capillary LC treatment of the exoprotein fraction separated at least 12 peaks, indicating its high-resolution power. We found that when a protein was once determined by its N-terminal sequence, its mass spectrum and the obtained molecular mass was applicable for the assignment of the protein.

Amino Acid Sequence↗
PubMed2000

Metabolism of vitamin D(3) by human CYP27A1.

Human vitamin D(3) 25-hydroxylase (CYP27A1) cDNA was expressed in Escherichia coli, and its enzymatic properties were revealed. The reconstituted system containing the membrane fraction prepared from the recombinant E. coli cells was examined for the metabolism of vitamin D(3). Surprisingly, at least eight forms of metabolites including the major product 25(OH)D(3) were observed. HPLC analysis and mass spectrometric analysis suggested that those metabolites were 25(OH)D(3), 26(OH)D(3), 27(OH)D(3), 24R,25(OH)(2)D(3), 1alpha, 25(OH)(2)D(3, )25,26(OH)(2)D(3) (25,27(OH)(2)D(3)), 27-oxo-D(3) and a dehydrogenated form of vitamin D(3). These results suggest that human CYP27A1 catalyzes multiple reactions and multiple-step metabolism toward vitamin D(3). The K(m) and V(max) values for vitamin D(3) 25-hydroxylation and 25(OH)D(3) 1alpha-hydroxylation were estimated to be 3.2 microM and 0.27 (mol/min/mol P450), and 3.5 microM and 0.021 (mol/min/mol P450), respectively. These kinetic studies have made it possible to evaluate a physiological meaning of each reaction catalyzed by CYP27A1.

Base Sequence↗
PubMed2000

Induction of aldose reductase in cultured human microvascular endothelial cells by advanced glycation end products.

Accelerated formation and accumulation of advanced glycation end products, as well as increased flux of glucose through polyol pathway, have been implicated in the pathogenesis of diabetic vascular complications. We investigated effects of advanced glycation end products on the levels of aldose reductase mRNA, protein, and activity in human microvascular endothelial cells. When endothelial cells were cultured with highly glycated bovine serum albumin, aldose reductase mRNA in endothelial cells demonstrated concentration-dependent elevation. The increase in aldose reductase mRNA was accompanied by elevated protein expression and enzyme activity. Significant increase in the enzyme expression was also observed when endothelial cells were cultured with serum obtained from diabetic patients with end-stage renal disease. Pretreatment of the endothelial cells with probucol or vitamin E prevented the advanced glycation end products-induced increases in aldose reductase mRNA and protein. Electrophoretic mobility shift assays using the nuclear extracts of the endothelial cells treated with advanced glycation end products showed enhancement of specific DNA binding activity for AP-1 consensus sequence. These results indicate that accelerated formation of advanced glycation end products in vivo may elicit activation of the polyol pathway, possibly via augmented oxidative stress, and amplify endothelial cell damage leading to diabetic microvascular dysfunction.

Aldehyde Reductase↗
PubMed2000

Possible role of hepatocyte growth factor/scatter factor and activin A produced by the target organ in liver metastasis.

The molecular mechanism of organ-specific metastasis to the liver remains largely unknown. However, it is conceivable that paracrine growth factors produced by a target organ induce migration and proliferation of malignant cells to that organ, and this is the cause of organ-specific metastasis. In this study, we investigated the effect of hepatocyte growth factor/scatter factor (HGF/SF) and activin A, which are known to be produced by the liver, on the motility and growth of liver-metastatic cell line FBJ-LL. HGF/SF and activin A induced motility synergistically, but they did not affect the proliferation of FBJ-LL cells. Expression of the HGF/SF receptor, the c-met gene, and the activin-receptor type IA, type IB, and type IIA genes in FBJ-LL cells was detected by reverse transcription polymerase chain reaction. These findings suggest that both HGF/SF and activin A promote organ-specific metastasis to the liver by induction of migration through their specific receptors on liver-metastatic cells.

Activin Receptors, Type I↗
PubMed2000

Apomorphine up-regulates NGF and GDNF synthesis in cultured mouse astrocytes.

Apomorphine, a D1/D2 dopamine agonist, is an anti-parkinsonian drug. We examined the effects of apomorphine on synthesis of neurotrophic factors in cultured mouse astrocytes. After 24 h incubation with apomorphine, NGF and GDNF contents in the culture medium increased to 122-fold and 1.8-fold of the control, respectively; whereas the BDNF content did not change significantly. In Northern blot analysis, expression of NGF mRNA in astrocytes reached the maximum level at 6 h after addition of the drug. By semiquantitative RT-PCR analysis, the GDNF transcript level was found to reach 2.9-fold of the control level at 15 h. These results suggest that apomorphine may exert neuroprotective effects by stimulation of NGF and GDNF synthesis in astrocytes.

Animals↗
PubMed2000

Molecular cloning of globotriaosylceramide/CD77 synthase, a glycosyltransferase that initiates the synthesis of globo series glycosphingolipids.

The expression cloning of a cDNA for globotriaosylceramide (Gb3)/CD77 synthase (alpha1,4-galactosyltransferase) was achieved using an anti-Gb3 antibody and mouse L cells as a recipient cell line for the transfection. The isolated cDNA clone designated pVTR1 predicted a type II membrane protein with 19 amino acids of cytoplasmic domain, 26 amino acids of transmembrane region, and a catalytic domain with 308 amino acids. Introduction of the cDNA clone into L cells resulted in the neosynthesis of Gb3/CD77, and the extracts of the transfectant cells showed alpha1, 4-galactosyltransferase activity only on lactosylceramide and galactosylceramide. In Northern blotting, a 2.3-kilobase mRNA was strongly expressed in heart, kidney, spleen, and placenta and weakly in colon, small intestine, and brain. Transfection of the cDNA into L cells resulted in the constitution of sensitivity to the apoptosis with Shiga-like toxins (verotoxins). Since Gb3/CD77 synthase initiates the synthesis of globo series glycolipids, the isolation of this cDNA will make possible further investigations into the function of its important series of glycolipids.

Amino Acid Sequence↗
PubMed2000

Influence of interleukin-1beta gene polymorphisms on age-at-onset of sporadic Parkinson's disease.

We studied genetic polymorphisms in the promoter region (position -511) and exon 5 (position +3953) of the interleukin (IL)-1beta gene in 122 Japanese patients with Parkinson's disease (PD) and 112 controls. We also examined polymorphisms in the IL-1alpha and the IL-1 receptor antagonist genes. No significant difference was found in these genetic markers between PD patients and controls. However, PD patients with homozygotes for allele 1 at position -511 of the IL-1beta gene (IL-1B-511*1), a low producer of IL-1beta, were significantly earlier in the disease onset than those with the IL-1B-511*2 homozygotes, a high producer of IL-1beta. This suggests that IL-1beta might play a role, possibly a protective effect for dopaminergic neurons, in PD. Further population and functional studies are necessary to clarify the role of IL-1beta in PD patients.

Age Factors↗
PubMed2000

High incorporation of L-amino acids to cereulide, an emetic toxin from Bacillus cereus.

Cereulide is a principal toxin causing emetic syndrome produced by Bacillus cereus. This paper deals with biosynthetic studies on this unusual cyclic depsipeptide toxin from 13C labeled L-amino acid precursors (Val, Leu, Ala) upon cultivation in synthetic media. The analyses were made at atomic level of the constituent amino- or oxy-acids through NMR and ESI-MS/MS spectroscopic methods on cereulide and its hydrolysate dipeptides. The incorporation of the 13C atom was 95% in each O-Val, O-Leu and L-Val, while 40% in D-Ala of cereulide.

Amino Acids↗
PubMed2000

The staphylokinase gene is located in the structural gene encoding N-acetylmuramyl-L-alanine amidase in methicillin-resistant Staphylococcus aureus.

The nucleotide sequence of a 15600-bp DNA fragment containing the staphylokinase gene (sakNU3-1) of methicillin-resistant Staphylococcus aureus (MRSA) NU3-1 was determined. The sak gene was found within the ply gene encoding N-acetylmuramyl-L-alanine amidase and thus the ply gene should be inactivated. In the flanking region of the sak gene, the tandem repeat sequences (GAAGTGTT and GAATGGTT) were present as possible junction points between the sak and ply genes. No sequences characteristic of the presence of an IS-like element were found. Upstream from the ply gene, the kdpA, kdpB and kdpC homologues were present. Downstream from the ply gene, the tagA, tagH and tagG homologues were present. The sak gene was inserted into the same position of ply in 5/6 of sak(+) MRSA isolates with different genotypes. In all of these sak(+) isolates, Sak was detected in the culture supernatant.

Cloning, Molecular↗
PubMed2000

Growth suppression of Escherichia coli by induction of expression of mammalian genes with transmembrane or ATPase domains.

Growth inhibition of Escherichia coli host cells is frequently observed when some mammalian genes are induced to express exogenously. To find common features of these mammalian genes, an assay was designed for the isolation of these genes which show growth-inhibitory effect on E. coli by induction of expression. Of 38,000 clones derived from a mouse brain cDNA library, 64 cDNA clones were systematically selected out by this method, of which 45 clones had putative open reading frames encoding proteins with putative membrane-associated regions or ATP-binding/ATPase activities. These results show that a fraction of membrane-associated proteins or ATP-binding/ATPase genes can be isolated from cDNA libraries by our simple method.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Lymphatic lipid transport is not impaired in ageing rat intestine.

Lymphatic lipid transport in the intestine of adult and ageing rats was compared. Adult (8-10 months old) and old (24-26 months old) male Wistar rats were cannulated into the mesenteric lymph under ethrane anesthesia. On the following day, lipid emulsion containing 35.4 mg/h of olive oil was infused intraduodenally for 7 h and lymph collected hourly was assayed for triglyceride and apolipoprotein A-IV (apo A-IV). The results showed there was no difference in lymphatic lipid and apo A-IV transport between adult and old rats. Since apo A-IV synthesis in the enterocytes is linked to the intracellular assembly of lipoprotein, it is likely that in addition to lymphatic transport, production of chylomicrons is not impaired in ageing rats.

Aging↗
PubMed2000

Comparative efficacy of positron emission tomography and ultrasonography in preoperative evaluation of axillary lymph node metastases in breast cancer.

PURPOSE: In primary breast cancer, axillary nodal status is the most powerful predictive factor of recurrence. However, axillary lymph node dissection may cause surgical complications. If preoperative evaluation of axillary lymph node metastases is possible, unnecessary axillary lymph node dissections can be avoided. The purpose of this study was to evaluate the efficacy of positron emission tomography (PET) on detection of axillary lymph node metastases in breast cancer. METHODS: PET scans of the axilla were obtained in 32 patients with primary breast cancer. All patients fasted for at least 4 hours before the examination. After transmission scans for attenuation correction were performed, emission scans after intravenous injection of 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) were obtained. RESULTS: Overall accuracy of PET alone, ultrasonography alone, and in combination in the detection of axillary metastases were 82%, 79%, and 85% respectively. CONCLUSION: There were no significant differences between PET, ultrasonography, and PET in combination with ultrasonography regarding sensitivity, specificity and accuracy in the detection of axillary metastases.

Adult↗
PubMed2000

Clinical and pathologic factors predicting axillary lymph node involvement in breast cancer.

The diagnosis of axillary disease remains a challenge in the management of breast cancer and is a subject of controversy. In 1998, the Japanese Breast Cancer Society conducted a study assessing axillary lymph node involvement in breast cancer. The study included (a) clinical assessment by pre-operative imaging modalities, (b) histologic assessment for peritumoral lymphatic invasion, (c) biologic assessment by gelatinolytic activity using film in situ zymography, and (d) sentinel lymph node (SLN) biopsy. Clinical assessments by CT, PET, and US as well as biologic assessment were limited in their ability to detect axillary lymph node disease, although these imaging techniques may be useful to exclude node-positive patients from the need for SLN biopsy. Histologic assessment for peritumoral lymphatic invasion was useful, particularly for detecting false-negative cases by SLN biopsy. Nevertheless, the utility of SLN biopsy in assessing axillary nodal status was confirmed. Axillary lymph node dissection (ALND) can be avoided in patients with a small tumor and a negative SLN. However, further studies will be required to investigate the value of SLN biopsy for predicting regional control and survival before it can replace routine ALND as the optimal staging procedure for operable breast cancer.

Axilla↗
PubMed2000

Nerve distribution to the human knee joint: anatomical and immunohistochemical study.

The nerve distribution to the knee joints was analyzed in 5 cadavers and 10 joint capsules specimens were resected during total knee arthroplasty. We found nerve fibers immunoreactive for anti-substance P antibody in the articular capsule. By confocal laser scanning microscopy, we evaluated the three-dimensional structures of the Ruffini's corpuscles and the free nerve endings, both of which were immunoreactive for anti-protein gene product 9.5.

Arthroplasty, Replacement, Knee↗