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Biomedical subjects

S Maeda

Publications and source records attributed to S Maeda.

At least 325 records · Page 18Linked to original sources
PubMed1997

Effects of K+ channel blockers and K+ ionophore on isoprenaline-induced secretion of amylase from rat parotid acini.

The involvement of K+ channels in regulating secretion of amylase from isolated rat parotid acini was studied in conjunction with beta-adrenoceptor function. It was observed that increasing the concentration of extracellular K- or adding K+ channel blockers enhanced the secretion of amylase. Among several K+ channel blockers, tetraethylammonium, apamin and charybdotoxin were effective to enhance secretion by 48, 69 and 84%, respectively. Glibenclamide was without effect. A low concentration of isoprenaline (10(-7) M) enhanced secretion by 154% and its simultaneous application with tetraethylammonium gave a synergistic effect, producing 371% stimulation. Combination of tetraethylammonium and a low concentration of carbachol (10(-6) M) did not give the synergistic effect. Isoprenaline at the concentration of 10(-6) M enhanced secretion by 313% and this was reduced to 116% by 10(-5) M valinomycin, a K+ ionophore. Valinomycin was without effect on carbachol (10(-5) M)-induced secretion. Somatostatin (10(-5) M) and morphine (10(-4) M) also reduced isoprenaline-induced secretion of amylase. These results suggested the regulation of Ca(2+)-activated K+ channels by isoprenaline in amylase secretory processes in parotid acini.

Adrenergic beta-Agonists↗
PubMed1997

Substrate-binding lipoprotein of the cyanobacterium Synechococcus sp. strain PCC 7942 involved in the transport of nitrate and nitrite.

Of the four genes (nrtABCD) required for active transport of nitrate in the cyanobacterium Synechococcus sp. strain PCC 7942, nrtBCD encode membrane components of an ATP-binding cassette transporter involved in the transport of nitrite as well as of nitrate, whereas nrtA encodes a 45-kDa cytoplasmic membrane protein, the biochemical function of which remains unclear. Characterization of the nrtA deletional mutants showed that the 45-kDa protein is essential for the functioning of the nitrate/nitrite transporter. A truncated NrtA protein lacking the N-terminal 81 amino acids, expressed in Escherichia coli cells as a histidine-tagged soluble protein, was shown to bind nitrate and nitrite with high affinity (Kd = 0.3 microM). Immunoblotting analysis using the antibody against the 45-kDa protein revealed a 48-kDa precursor of the protein, which accumulated in the cyanobacterial cells treated with globomycin, an antibiotic that specifically inhibits cleavage of the signal peptide of lipoprotein precursors. These findings indicated that the nrtA gene product is a nitrate- and nitrite-binding lipoprotein. The N-terminal sequences of putative cyanobacterial substrate-binding proteins suggested that lipoprotein modification of substrate-binding proteins of ATP-binding cassette transporters is common in cyanobacteria.

Amino Acid Sequence↗
PubMed1997

Alternative splicing of the erythropoietin receptor gene correlates with erythroid differentiation in rat hematopoietic and leukemic cells.

An alternative splicing of the rat erythropoietin receptor (EpoR) gene was identified in normal and erythroleukemia cells. A 105 bp insert was found at a region corresponding to the extracellular domain of EpoR. The alternative transcript was translated to a soluble EpoR (EpoR-S) expressed in spleen, bone marrow, and cultured erythroleukemia cells in addition to the full-length EpoR (EpoR-F). One of the rat erythroleukemia sublines, K4DT, which partially lost erythroid phenotypes and manifested monocyte/macrophage characteristics also lacked EpoR-S expression. Thus, expression of EpoR-S may play an important role in differentiation of rat erythroid cells.

Alternative Splicing↗
PubMed1997

Marked increases in concentrations of apolipoprotein in the cerebrospinal fluid of poliovirus-infected macaques: relations between apolipoprotein concentrations and severity of brain injury.

Apolipoproteins in cerebrospinal fluid (CSF) might have important functional roles in the pathophysiology of brain and lipid metabolism in the vascular component. The present study examined apolipoprotein A-I (apo-A-I) and apolipoprotein E (apo-E) levels in CSF and serum from poliovirus-infected macaques. Poliovirus-infected macaques developed motor deficits and were classified into three groups: (1) muscle weakness in one or both legs; (2) partial paralysis in one or both legs; (3) complete paralysis in one or both legs. No motor deficits were evident in the control or sham-treated macaques. Apo-A-I concentrations in CSF were markedly elevated in poliovirus-infected macaques with weakness, partial or complete paralysis, in comparison with either control or sham-treated animals, and were proportional to the severity of motor impairment. Apo-E concentrations in CSF were also significantly elevated in poliovirus-infected macaques with complete paralysis. The magnitude of increase in CSF apo-A-I or apo-E concentrations was also closely associated with the degree of histologic neurological damage and inflammation (lesion scores). However, no changes in serum apo-A-I and apo-E concentrations were observed in the poliovirus-infected macaques compared with control macaques. Furthermore there were no significant correlations apo-A-I or apo-E concentrations between serum and CSF. We hypothesize that the elevation of apo-A-I and apo-E concentrations after poliovirus infection is caused by immune stimulation within the central nervous system (CNS). Measures of CSF apo-A-I and apo-E levels might serve as a useful marker for the severity and/or the range of CNS injury.

Animals↗
PubMed1997

Cardiac-like musculature of the intrapulmonary venous wall of the long-clawed shrew (Sorex unguiculatus), common tree shrew (Tupaia glis) and common marmoset (Callithrix jacchus).

BACKGROUND: The cardiac-like musculature is distributed not only in the heart wall but also in the intrapulmonary venous wall in a few species of insectivores. It has been suggested that the evolutionary origin of venous cardiac-like musculature may be traceable to a basic stock of certain mammalian lines of descent. So, it is important to clarify whether the musculature may be a common structure in lower mammals from insectivores to primates and to examine the functional significance of the structure. METHODS: The distribution of cardiac-like musculature in the intrapulmonary venous wall of the long-clawed shrew (Sorex unguiculatus), common tree shrew (Tupaia glis), and common marmoset (Callithrix jacchus) was observed by light and electron microscopy. The presence of atrial natriuretic polypeptide (ANP) was examined in the musculature by immunohistochemistry. RESULTS: All three species contained cardiac-like myocytes in the tunica media of intrapulmonary venous wall. In the common tree shrew and the common marmoset, cardiac-like musculature was found in the small intrapulmonary vein of 150-200 microns in diameter, while, in the long-clawed shrew, it was distributed even in the intrapulmonary vein of 30 microns in diameter. Ultrastructure of myocytes was fundamentally similar to that of atrial myocytes in the long-clawed shrew and the common tree shrew. The presence of atrial natriuretic polypeptide (ANP) was also demonstrated by immunohistochemistry in the intrapulmonary venous walls of common tree shrews. CONCLUSIONS: The results indicate that the pulmonary venous cardiac-like musculature occurs in the lower eutherian mammals from insectivores to primitive primates. The musculature is thought to act as a regulatory pump in pulmonary circulation and as an endocrine apparatus of ANP.

Animals↗
PubMed1997

Coronary disease-prone behavior among Japanese men: job-centered lifestyle and social dominance. Type A Behavior Pattern Conference.

In Japan the type A behavior pattern, particularly its component of hostility, is known to have less value as a risk for coronary artery disease (CAD) than in the United States. We developed a questionnaire (Japanese Coronary-prone Behavior Scale [JCBS]) to investigate the behavioral correlates with CAD among contemporary Japanese persons. The JCBS was administered to 419 Japanese men undergoing coronary angiography; 310 of them had angiographic or clinical evidence or both of CAD, and 109 had no evidence of CAD. The group with CAD had more coronary risk factors than the group without CAD, but the two groups did not differ in type A behavior pattern as assessed with the Jenkins Activity Survey. Stepwise discriminant analysis, in which standard coronary risk factors were forced into the model, revealed that inclusion of nine JCBS items (scale C) in the model resulted in the best discrimination between the two groups. Cross-validation results showed that the error-rate estimates for the discriminant models that consisted only of standard coronary risk factors, only of scale C items, and of their combination were 34.7, 32.4, and 27.0%, respectively. The scale C items represented a job-centered lifestyle, social dominance, and suppressed overt type A behaviors. These results indicate that an independent behavior pattern prone to CAD is discernible among Japanese men and suggest that the behavior pattern may contain characteristics that can be differentiated from those that constitute the type A behavior pattern.

Aged↗
PubMed1997

Differences in the change in the time course of plasma endothelin-1 and endothelin-3 levels after exercise in humans. The response to exercise of endothelin-3 is more rapid than that of endothelin-1.

Several studies have indicated that endothelin-1 (ET-1) and endothelin-3 (ET-3) are produced by different cells. Although ET-1 is produced by vascular endothelial cells, these cells do not produce ET-3. The presence of ET-3 in the brain of several species suggests that ET-3 is a novel neuropeptide. It is unclear whether there are differences in the release of ET-1 and ET-3 under various physiological conditions in humans. In the present study, we measured the plasma concentrations of both ET-1 and ET-3 before and after endurance exercise on a cycle ergometer. Male athletes exercised on a cycle ergometer for 30 min at intensity of 130% of their individual ventilatory threshold (VT), which is intense exercise. Plasma ET-1 and ET-3 were greatly elevated by exercise, but there was a marked difference in the time-course of the change in plasma concentration between the two peptides. The level of ET-1 peaked 30 min after exercise, whereas that of ET-3 peaked immediately after exercise. Thus, plasma ET-3 increased faster than plasma ET-1 after exercise. The exercise-induced change in the time course in plasma ET-3, but not in ET-1, is similar to that in plasma norepinephrine which is a neurotransmitter, suggesting that the rapid elevation in plasma ET-3 is partly attributable to the neuronal response to exercise. The observed difference in the change in the time course of plasma ET-1 and ET-3 levels suggests that the mechanisms by which exercise alters the release and/or synthesis of these two peptides differ.

Adolescent↗
PubMed1997

In situ detection of parathyroid hormone-related protein in ovarian clear cell carcinoma.

A case of ovarian clear cell carcinoma associated with hypercalcemia is reported. A 67-year-old woman developed the lung metastasis 8 months after primary surgery. The patient manifested symptoms of humoral hypercalcemia of malignancy (HHM) during the last 3 months of her clinical course. Serum and urinary C-terminus parathyroid hormone-related protein (PTHrP) levels were remarkably high. No increase in interleukin (IL) 1beta, tumor necrosis factor (TNF) alpha, vitamin D3 metabolites or intact PTH was detected. Pamidronate disodium treatment was transiently suppressed her serum calcium level. The patient died despite seven courses of chemotherapy. Autopsy showed multiorgan metastases and accelerated osteoclastic bone resorption; skeletal metastasis was not detected. Immunohistochemical analysis clearly showed the localization of PTHrP at both the primary and metastatic sites. The transcripts of PTHrP at pulmonary metastatic sites were revealed by in situ hybridization and the reverse transcription polymerase chain reaction (RT-PCR) method. PTHrP was the causative factor for HHM in this case. It is therefore suggested that hypercalcemia may have occurred after PTHrP production had overcome the homeostatic level during the terminal stage, although PTHrP production continued irrespective of the patient's serum calcium level.

Adenocarcinoma, Clear Cell↗
PubMed1997

Expression and localization of bone morphogenetic proteins (BMPs) and BMP receptors in ossification of the ligamentum flavum.

To clarify the pathogenesis of ossification of the ligamentum flavum (OLF), we examined the expression and localization of bone morphogenetic proteins (BMPs) and their receptors (BMPRs) in the ligamentum flavum of the patients with OLF by immunohistochemical staining and compared them with staining patterns in control patients. The BMPRs appeared extensively in mature and immature chondrocytes around the calcified zone and in spindle-shaped cells and round cells in the remote part from ossified foci in examined tissue of OLF. The ligands for BMPRs, BMP-2/-4 and osteogenic protein-1 (OP-1)/BMP-7, colocalized in OLF patients. In the control cases, expression of BMPs and BMPRs was observed around the calcified zone at the insertion of the ligamentum flavum to the bone, and limited expression was found in the smaller range. Thus, the expression profile of BMPs and BMPRs in OLF patients was entirely different from the control patients, suggesting that BMPs may be involved in promoting endochondral ossification at ectopic ossification sites in OLF, and that ossification activity is continuous in these patients.

Activin Receptors↗
PubMed1997

Comparison of amyloid deposition in two lines of transgenic mouse that model familial amyloidotic polyneuropathy, type I.

We previously produced a transgenic mouse line designated MT-hMet30 by introducing the human mutant transthyretin (TTR) gene carrying the mouse metallothionein promoter, and showed that the presence of human variant TTR is sufficient for amyloid deposition in various tissues of these transgenic mice. However, the expression pattern of human mutant transthyretin gene in the mouse was different from that in man. To analyse pathologic processes, it is essential to establish a transgenic mouse line in which the development and tissue-specific expression of the human mutant TTR gene is the same as in man. Thus, we produced two additional transgenic mouse lines carrying the human mutant TTR gene containing either 0.6 kb (0.6-hMet30) or 6.0 kb (6.0- hMet30) of the upstream region. The expression levels of 6.0-hMet 30 gene in the liver and serum were the same as in man and about 10 times higher than those of 0.6-hMet30 gene in the liver and serum were the same as similar tissues to human patients except for the peripheral and autonomic nervous tissues. The amyloid deposition started earlier and was more extensive in 6.0-hMet30 than 0.6-hMet30 mice, suggesting that the serum levels of human mutant TTR are correlated with the occurrence and degree of amyloid deposition, to some extent. Neither amyloid deposition nor degenerative changes were observed in the peripheral and autonomic nervous systems despite the transgene expression in the choroid plexus of the 6.0-hMet30 mice. In the 6.0-hMet30 mice, amyloid deposition started at 9 months of age, although the serum level of human mutant TTR reached the adult level at 1 month. These results suggest that intrinsic environmental factors other than the mutant gene are involved in the late-onset deposition of amyloid fibrils. Transgenic mice described here should be useful for analysing such factors.

Age Factors↗
PubMed1997

Codon 201Arg/Gly polymorphism of DCC (deleted in colorectal carcinoma) gene in flat- and polypoid-type colorectal tumors.

Recent studies have identified the distinct existence of flat-type colorectal tumors. The low incidence of ras gene mutations in these tumors suggests that their genetic pathways of tumor progression may be different from those of the polypoid type. To elucidate further genetic alterations in flat-type colorectal tumors, codon 201Arg/Gly polymorphism in the DCC (deleted in colorectal carcinoma) gene was analyzed in normal tissue (normal colonic mucosa or peripheral lymphocytes) and in tumor tissue from 191 patients with colorectal tumors (36 patients with flat-type colorectal tumors, 81 patients with polypoid-type colorectal tumors, and 74 patients with advanced carcinomas). For normal controls, 30 samples obtained from patients who had neither colorectal tumors (confirmed by total colonoscopy) nor a family history of colorectal carcinoma were analyzed. DCC gene codon 201Arg/Gly polymorphism was investigated by polymerase chain reaction-based restriction fragment length polymorphism analysis, fluorescence-based dideoxy sequencing, or both. For the flat type, the frequency of codon 201Gly of the DCC gene was 64% and 54% in the normal tissue of patients with adenoma with high-grade dysplasia and submucosal carcinoma, respectively. It was 49%, 52%, and 49% in the normal tissue of patients with polypoid-type adenoma with high-grade dysplasia, submucosal carcinoma, and advanced carcinoma, respectively. In the normal tissue, codon 201Gly of the DCC gene was more frequently observed in patients with flat-type adenoma with low-grade dysplasia (67%) than in those with polypoid-type adenoma with low-grade dysplasia (18%) or in normal controls (17%, P < 0.05, chi2 test). Codon 201Arg/Gly polymorphism in tumor tissues did not differ from that in the corresponding normal tissues, except for 10 cases of carcinoma with loss of heterozygosity (LOH). In carcinomas with LOH, preferential loss of the codon 201Arg allele was noted (9/10 cases). These results suggest that codon 201Gly of the DCC gene is not only associated with flat-type colorectal tumors, but that it may serve as a useful genetic marker for identifying groups at higher risk for colorectal cancer.

Carcinoma↗
PubMed1997

High seropositivity of anti-CagA antibody in Helicobacter pylori-infected patients irrelevant to peptic ulcers and normal mucosa in Japan.

CagA-positive H. pylori is reported to be associated with gastroduodenal disease in Western countries. To evaluate the relationship between CagA and disease, cloning of the entire cagA gene (3771 bp), insertion of a partial fragment (1272 bp) into an expression vector, purification of the recombinant protein, production of an antibody against the recombinant CagA protein through rabbits, and use of the recombinant CagA protein as an antigen, detection of the anti-CagA antibody by western blotting were all performed. Sera of 132 H. pylori-infected patients undergoing endoscopy were studied. Anti-CagA antibodies were detected in 90%, 87%, 90%, 94%, and 93% of patients with gastric ulcer (N = 34), duodenal ulcer (N = 27), chronic gastritis (N = 31), gastric cancer (N = 17), and normal mucosa (N = 15), respectively. High seropositivity of anti-CagA antibody even in individuals with normal mucosa indicated that CagA may not be a unique marker for disease by H. pylori infection in Japan.

Amino Acid Sequence↗
PubMed1997

Identification and nitrogen regulation of the cyanase gene from the cyanobacteria Synechocystis sp. strain PCC 6803 and Synechococcus sp. strain PCC 7942.

An open reading frame (slr0899) on the genome of Synechocystis sp. strain PCC 6803 encodes a polypeptide of 149 amino acid residues, the sequence of which is 40% identical to that of cyanase from Escherichia coli. Introduction into a cyanase-deficient E. coli strain of a plasmid-borne slr0899 resulted in expression of low but significant activity of cyanase. Targeted interruption of a homolog of slr0899 from Synechococcus sp. strain PCC 7942, encoding a protein 77% identical to that encoded by slr0899, resulted in loss of cellular cyanase activity. These results indicated that slr0899 and its homolog in the strain PCC 7942 represent the cyanobacterial cyanase gene (designated cynS). While cynS of strain PCC 6803 is tightly clustered with the four putative molybdenum cofactor biosynthesis genes located downstream, cynS of strain PCC 7942 was found to be tightly clustered with the two genes located upstream, which encode proteins similar to the subunits of the cyanobacterial nitrate-nitrite transporter. In both strains, cynS was transcribed as a part of a large transcription unit and the transcription was negatively regulated by ammonium. Cyanase activity was low in ammonium-grown cells and was induced 7- to 13-fold by inhibition of ammonium fixation or by transfer of the cells to ammonium-free media. These findings indicated that cyanase is an ammonium-repressible enzyme in cyanobacteria, the expression of which is regulated at the level of transcription. Similar to other ammonium-repressible genes in cyanobacteria, expression of cynS required NtcA, a global nitrogen regulator of cyanobacteria.

Amino Acid Sequence↗
PubMed1997

Rapid screening of point mutations of the Neisseria gonorrhoeae parC gene associated with resistance to quinolones.

To detect quinolone resistance-associated mutations within the Asp-86, Ser-87, Ser-88, and Glu-91 codons of the Neisseria gonorrhoeae parC gene, we developed a rapid and simple assay based on amplification of the regions of the parC gene containing the mutations sites by PCR and digestion of the PCR products with restriction enzymes. By using the method of primer-specified restriction site modification, artificial SalI, PstI, EcoRI, and HinfI restriction sites were created in the regions containing the Asp-86, Ser-87, Ser-88, and Glu-91 codons, respectively. The mutations generating alterations at Asp-86, Ser-87, Ser-88, and Glu-91 were detected as failures of SalI, PstI, EcoRI, and HinfI to digest the respective PCR products. Fifty-five clinical strains of N. gonorrhoeae were examined for mutations in the parC gene by this assay. Appropriate mutations at either the Asp-86, Ser-87, Ser-88, or Glu-91 codon were detected in each of 11 strains in which a mutation had previously been observed by DNA sequencing. This rapid and simple assay could be a useful device for screening genetic alterations in the parC gene associated with resistance to quinolones in N. gonorrhoeae.

DNA Topoisomerase IV↗
PubMed1997

High prevalence of cytotoxin positive Helicobacter pylori in patients unrelated to the presence of peptic ulcers in Japan.

BACKGROUND: It has been reported that infection with vacuolating cytotoxin positive Helicobacter pylori strains is associated with gastroduodenal disease in Western countries. AIMS: To evaluate the prevalence of cytotoxin producing strains among patients with H pylori infection in relation to gastrointestinal diseases in Japan. PATIENTS: Ninety seven patients undergoing endoscopy. METHODS: A Western blot assay was conducted to detect serum antibodies against the cytotoxin using recombinant cytotoxin (VacA protein) as an antigen. To obtain a purified recombinant cytotoxin, the vacA gene (2233 nucleotides) was cloned into an expression vector to produce the protein (744 amino acids), which was expressed in Escherichia coli. RESULTS: Serum IgG antibodies to the cytotoxin were present in 85%, 95%, 95%, and 100% of infected patients with gastric ulcer (n = 26), duodenal ulcer (n = 21), chronic gastritis (n = 19), and endoscopically normal mucosa (n = 14), respectively. CONCLUSION: The western blot method using recombinant VacA protein is simple and useful for detecting antibody to vacuolating cytotoxin. This method showed antibodies against cytotoxin were highly prevalent, even in subjects with endoscopically normal mucosa in Japan, indicating that the cytotoxin may not be an independent cause of gastrointestinal diseases induced by H pylori infection.

Amino Acid Sequence↗