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S Seino

Publications and source records attributed to S Seino.

At least 127 records · Page 7Linked to original sources
PubMed1993

Expression of calcium channel mRNAs in rat pancreatic islets and downregulation after glucose infusion.

Recent studies have shown that two different voltage-dependent Ca2+ channels are expressed in pancreatic islets, the beta-cell/neuroendocrine-brain and the cardiac subtypes. The effects of chronic hyperglycemia on the levels in pancreatic islets of the mRNAs encoding the alpha 1-subunits of the beta-cell and cardiac subtype Ca2+ channels were studied in rats made hyperglycemic by infusion of glucose for 48 h. A competitive reverse transcriptase-polymerase chain reaction procedure was used to obtain quantitative data on the levels of these two transcripts in islets obtained from individual rats. The quantitative polymerase chain reaction data indicate that the levels of mRNA encoding the alpha 1-subunit of the beta-cell Ca2+ channel are 2.5-fold greater than those for the cardiac subtype. The levels of beta-cell Ca2+ channel mRNA were 72.9% lower in the glucose-infused animals when compared with the saline-infused animals (P < 0.005) and those of the cardiac channel were 72.1% lower in the animals infused with glucose (P < 0.02). In contrast, glucose infusion resulted in a twofold increase in insulin mRNA levels and did not significantly alter levels of beta-actin mRNA. In situ hybridization studies revealed that the mRNAs for these two Ca2+ channels are expressed at higher levels in normal rat islets than in the surrounding acinar tissue, which suggests that the observed changes in mRNA levels occur within cells of the pancreatic islet. To assess the possible functional consequences of this reduction in expression of mRNA for the Ca2+ channels, the insulin secretory responses of perfused pancreases to the Ca2+ channel agonist Bay K8644 were studied.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1993

A variant form of laminin is responsible for the neurite outgrowth-promoting activity in conditioned medium from a squamous carcinoma cell line.

We examined the effects of conditioned medium (CM) obtained from a squamous carcinoma cell line, termed SAS, on chick sympathetic neuritic outgrowth. Neurons grown on a substratum coated with CM extended their neurites. Antisera raised against human laminin and mouse EHS laminin immunoprecipitated the neurite outgrowth-promoting factor in CM. The most purified fraction of CM contained a 740-kDa protein which reacted with the anti-laminin sera and was composed of three polypeptides of 330 kDa, 215 kDa and 195 kDa. The 215-kDa and 195-kDa polypeptides, but not the 330-kDa polypeptide were shown to be antigenically related to mouse laminin and human laminin by immunoblotting. The presence of merosin M chain in SAS cells was ruled out by using the method of reverse transcription polymerase chain reaction (RT-PCR). These results suggest that the 740-kDa protein is a laminin variant having a novel heavy chain of 330 kDa and is responsible for neurite outgrowth-promoting activity in CM.

Animals↗
PubMed1993

[Combined use of chest X-rays and body mass index to predict pulmonary hemodynamics in patients with chronic obstructive pulmonary disease].

A study was undertaken to determine whether measurements of radiological indices from chest X-rays and body mass index (BMI) were useful in predicting pulmonary artery hypertension. Measurements of the cardiothoracic ratio (CTR) as well as right descending pulmonary artery diameter (RDPA) and BMI were made in 27 patients with chronic obstructive pulmonary disease (COPD). Mean pulmonary arterial pressure (mPA) correlated with CTR, RDPA and BMI. Multiple regression analysis gave the useful equation: predicted mPA = -3.523 + 0.196xBMI + 0.110xCTR + 0.786xRDPA (r = 0.704, p < 0.002). Fifteen patients were found to have pulmonary hypertension, defined as mPA > or = 20 mmHg. The sensitivity of CTR and BMI were 86.7%. The specificity of BMI was 83.3%. These results suggest that the measurements CTR, RDPA and BMI may be useful in screening for pulmonary hypertension in patients with COPD.

Aged↗
PubMed1992

Human Oct3 gene family: cDNA sequences, alternative splicing, gene organization, chromosomal location, and expression at low levels in adult tissues.

Transcription factors containing the POU-domain have been shown to be important regulators of tissue-specific gene expression in the pituitary and lymphoid cells. Using a polymerase chain reaction (PCR)-based strategy, we have searched for similar factors that may be expressed in adult human pancreatic islets. This approach resulted in the amplification of sequences encoding the octamer binding proteins Oct1 and Oct3 (also called Oct4). The isolation of cDNAs encoding Oct3 revealed the expression of two isoforms of this transcription factor termed Oct3A and Oct3B that are generated by alternative splicing. Human Oct3A and Oct3B are composed of 360 and 265 amino acids, respectively, of which the 225 amino acids at the COOH-termini are identical. The sequence of human Oct3A shows 87% amino acid identity with mouse Oct3. Reverse-transcriptase PCR showed low levels of expression of both Oct3A and Oct3B mRNA in all adult human tissues examined. We also isolated and characterized the human Oct3 gene (OTF3) and a related gene, OTF3C. The human Oct3 gene, localized to human chromosome 6 in the region of the MHC complex, spans about 7 kb and consists of five exons. The Oct3-related gene, OTF3C, is a retroposon and has been localized to human chromosome 8. Southern blotting and PCR amplification of human DNA indicated the presence of other OTF3-related genes as has been previously noted in the mouse. Two polymorphisms which can be typed using PCR were identified in OTF3 which will facilitate genetic studies of this gene.

Amino Acid Sequence↗
PubMed1992

Cloning of the alpha 1 subunit of a voltage-dependent calcium channel expressed in pancreatic beta cells.

The isoforms of the alpha 1 subunits of voltage-dependent Ca2+ channels expressed in human pancreatic islets were identified by using a pair of degenerate oligonucleotide primers and the polymerase chain reaction (PCR) to amplify mRNAs encoding alpha 1 subunit-like sequences. The sequences of the PCR products indicate that islets express the heart-type alpha 1 subunit as well as a second isoform whose complete sequence has not been previously reported. The sequences of cloned cDNAs encoding the human beta-cell, or neuroendocrine-type, alpha 1 subunit indicate that it is composed of 2181 amino acids. It shares 68%, 64%, and 41% identity with the sequences of the alpha 1 subunits of rabbit heart, skeletal muscle, and brain, respectively, and is predicted to have a similar structure including four homologous domains composed of six membrane-spanning segments each. RNA blotting studies indicate that the beta-cell-type alpha 1 subunit is also expressed in brain as well as in the insulin-producing cell lines RINm5F and beta TC-3; however, it could not be detected by RNA blotting in a third cell line, HIT-T15. In situ hybridization studies revealed expression of beta-cell-type alpha 1 subunit mRNA in beta cells of rat pancreatic islets, implying that this protein may play a role in the regulation of insulin secretion.

Amino Acid Sequence↗
PubMed1992

Glucose transporter expression in brain. cDNA sequence of mouse GLUT3, the brain facilitative glucose transporter isoform, and identification of sites of expression by in situ hybridization.

Complementary DNAs encoding the mouse GLUT3/brain facilitative glucose transporter have been isolated and sequenced. The predicted amino acid sequence indicates that mouse GLUT3 is composed of 493 amino acids and has 83 and 89% identity and similarity, respectively, to the sequence of human GLUT3. In contrast to human GLUT3 mRNA, which can be readily detected by RNA blotting in all human tissues that have been examined, mouse GLUT3 mRNA was only present at significant levels in brain. In situ hybridization showed differential expression of GLUT3 mRNA in several regions of adult mouse brain. Specific expression was observed in the hippocampus, with GLUT3 mRNA levels being higher in areas CA1 to CA3 than in the dentate gyrus. It was also detected in the Purkinje cell layer of the cerebellum and in the cerebral cortex, with higher expression in the piriform cortex than in other regions of the cortex. Antisera to mouse GLUT3 immunoblotted a series of proteins of 45-50 kDa in mouse brain plasma membranes. These results are consistent with GLUT3 being a neuronal glucose transporter.

Amino Acid Sequence↗
PubMed1992

Cloning and functional characterization of a family of human and mouse somatostatin receptors expressed in brain, gastrointestinal tract, and kidney.

Somatostatin is a tetradecapeptide that is widely distributed in the body. It acts on multiple organs including brain, pituitary, gut, exocrine and endocrine pancreas, adrenals, thyroid, and kidneys to inhibit release of many hormones and other secretory proteins. In addition, it functions as a neuropeptide affecting the electrical activity of neurons. Somatostatin exerts its biological effects by binding to specific high-affinity receptors, which appear in many cases to be coupled to GTP-binding proteins. Here we report the cloning, functional expression, and tissue distribution of two different somatostatin receptors (SSTRs). SSTR1 and SSTR2 contain 391 and 369 amino acids, respectively, and are members of the superfamily of receptors having seven transmembrane segments. There is 46% identity and 70% similarity between the amino acid sequences of SSTR1 and SSTR2. Stably transfected Chinese hamster ovary cells expressing SSTR1 or SSTR2 exhibit specific somatostatin binding, with an apparently higher affinity for somatostatin-14 than somatostatin-28, and NH2-terminally extended form of somatostatin-14. RNA blotting studies show that SSTR1 and SSTR2 are expressed at highest levels in jejunum and stomach and in cerebrum and kidney, respectively. A SSTR1 probe hybridized to multiple DNA fragments in EcoRI digests of human and mouse DNA, indicating that SSTR1 and SSTR2 are members of a larger family of somatostatin receptors. Thus, the biological effects of somatostatin are mediated by a family of receptors that are expressed in a tissue-specific manner.

Amino Acid Sequence↗
PubMed1992

Sequences of primate insulin genes support the hypothesis of a slower rate of molecular evolution in humans and apes than in monkeys.

The chimpanzee and African green monkey insulin genes have been cloned and sequenced. These two sequences together with the previously reported sequences for the human and owl monkey insulin genes provide additional support for the hominoid-rate-slowdown hypothesis, i.e., a slower rate of nucleotide substitution in humans and apes than in monkeys. When these sequences and other primate sequences available for the relative-rate test were considered together, the substitution rate in the Old World monkey lineage was shown to be significantly higher than the rates in the human and chimpanzee lineages. This was true regardless of whether the eta-globin pseudogene was included in the analysis. Therefore, in contrast to the claim by Easteal, the hominoid-rate-slowdown is not unique to the eta-globin pseudogene but appears to be a rather general phenomenon. On average, the substitution rate at silent sites is about 1.5 times higher in the Old World monkey lineage than in the human and chimpanzee lineages.

Amino Acid Sequence↗
PubMed1992

Somatostatin receptors, an expanding gene family: cloning and functional characterization of human SSTR3, a protein coupled to adenylyl cyclase.

We previously reported the cloning of two distinct somatostatin receptor (SSTR) subtypes, SSTR1 and SSTR2. Although both SSTR1 and SSTR2 bound somatostatin specifically and with high affinity, neither was coupled to adenylyl cyclase, a major cellular effector of somatostatin's actions. Here we report the cloning and functional characterization of a third member of the SSTR family. Human SSTR3 is a protein of 418 amino acids and has 45% and 46% identity with human SSTR1 and SSTR2, respectively. RNA blotting studies showed that SSTR3 mRNA could be readily detected in brain and pancreatic islets. The pharmacological properties of human SSTR3 were characterized by transiently expressing the human SSTR3 gene in COS-1 cells. Membranes from cells expressing human SSTR3 bound the somatostatin agonist [125I]CGP 23996 specifically and with high affinity, with a rank order of potency of somatostatin-28 = CGP 23996 > somatostatin-14 > SMS-201-995. Studies using cells transiently coexpressing the human dopamine D1 receptor and human SSTR3 showed that somatostatin was able to inhibit dopamine-stimulated cAMP formation in a dose-dependent manner, indicating that SSTR3 was functionally coupled to adenylyl cyclase. These results indicate that the diverse biological effects of somatostatin are mediated by a family of receptor with distinct, but overlapping, tissue distributions, unique pharmacological properties, and potentially different functions.

Adenylyl Cyclases↗
PubMed1992

Expression of GLUT1 and GLUT2 glucose transporter isoforms in rat islets of Langerhans and their regulation by glucose.

Previous studies revealed that rat islets express the GLUT2-liver facilitative glucose transporter isoform, a glucose carrier with a low affinity for glucose but a high capacity for glucose transport. These studies indicated the presence of a second glucose transporter in rat islets; however, they did not indicate to which of the five known facilitative glucose transporters it corresponded. In this study, we isolated RNA from rat islets of Langerhans and confirmed the presence of GLUT2 mRNA. In addition, we present data indicating that the second isoform expressed in islets is the GLUT1-erythrocyte isoform. The effect of culturing islets in 5.5, 8.3, or 11.1 mM glucose on the levels of GLUT1 and GLUT2 mRNA also was examined. The levels of GLUT1 and GLUT2 mRNA were two- and threefold higher, respectively, in islets cultured for 24 h in 11.1 mM glucose compared with those incubated in the presence of 5.5 mM glucose. Therefore, the previously observed increase in GLUT2 mRNA levels in the islets of rats made hyperglycemic by chronic infusion of glucose can be mimicked in vitro, implying that glucose regulates GLUT2 mRNA expression.

Animals↗
PubMed1992

Human GLUT4/muscle-fat glucose-transporter gene. Characterization and genetic variation.

Four overlapping DNA fragments spanning 32 kb containing the human GLUT4 facilitative glucose-transporter gene were isolated and characterized. The sequence of the GLUT4 gene (approximately 6.3 kb) and 2.0 kb of the promoter region was determined. The sequence of the promoter revealed potential binding sites for transcription factors known to regulate gene expression in muscle cells and adipocytes. However, transfection of constructs including 2 kb of the GLUT4 promoter fused to the bacterial CAT gene into 3T3-L1 adipocytes displayed only weak promoter activity. Because insulin resistance plays a prominent role in the development of NIDDM, genetic variation in the sequence of GLUT4 also was evaluated. Oligonucleotide primer pairs were selected that allowed the protein-coding region of the human GLUT4 gene to be amplified by PCR. The sequence of the protein-coding region of the GLUT4 gene and all intron-exon junctions was determined for a single diabetic Pima Indian and was identical to that of the cloned gene and cDNA. SSCP analysis was used to screen patients with diabetes mellitus and normal, healthy nondiabetic individuals for mutations at the GLUT4 locus. In addition to the silent substitution in the codon for Asn130 (AAC or AAT) and a Val383 (GTC)-->Ile(ATC) replacement described previously, two new variants were identified. One was a T-->A substitution in intron 1 that was found in 1 of 36 NIDDM patients who were typed for this variant. The second was a Ile385(ATT)-->Thr(ACT) replacement that occurred in 1 normal individual and was not found in any of 676 other normal and diabetic subjects. A large and racially diverse group of normal and diabetic individuals also was screened for the Ile383 polymorphism. It occurred in both diabetic and nondiabetic subjects. There is no indication from our data that these polymorphisms are associated with NIDDM.

3T3 Cells↗
PubMed1992

Pharmacological properties of two cloned somatostatin receptors.

Previous studies have shown that at least two subtypes of somatostatin (SRIF) receptors (SRIF1 and SRIF2) are expressed in mammalian cells. SRIF1 receptors have high affinity for MK 678, whereas SRIF2 receptors have no affinity for MK 678 but selectively bind peptides with structures similar to that of CGP 23996. Recently, two SRIF receptor genes have been cloned from human and mouse genomic libraries. In the present study, the pharmacological properties of these two cloned SRIF receptors, expressed in Chinese hamster ovary (CHO) cells, were investigated, to determine whether they have any similarity to the previously described SRIF1 and SRIF2 receptor subtypes. Both cloned receptors could be labeled with 125I-Tyr11-SRIF and exhibited high affinity for SRIF. The SSTR1 receptor could also bind CGP 23996-like compounds but not MK 678. In contrast, the SSTR2 receptor was insensitive to CGP 23996-like compounds but bound MK 678 with high affinity. These findings indicate that the peptide specificities of the cloned SSTR1 and SSTR2 receptors differ from each other. Pretreatment of CHO cells expressing the two cloned SRIF receptors with SRIF abolished high affinity agonist binding to the cloned SSTR2 receptor but not the cloned SSTR1 receptor. Agonist binding to SSTR1 receptors was not significantly affected by guanosine-5'-)-(3-thiotriphosphate) or pertussis toxin pretreatment, whereas agonist binding to SSTR2 receptors was inhibited by both treatments. These findings suggest that SSTR2 receptors can be regulated and they associate with pertussis toxin-sensitive guanine nucleotide-binding proteins, whereas SSTR1 receptors do not. SRIF is a potent inhibitor of adenylyl cyclase activity in mammalian cells. However, neither the cloned SSTR2 nor SSTR1 receptor mediated SRIF inhibition of adenylyl cyclase activity in stably transformed CHO cells or COS-1 cells transiently expressing the cloned receptors, suggesting that neither cloned receptor couples to adenylyl cyclase. The results of these studies indicate that the two cloned SRIF receptors have different pharmacological properties. The characteristics of the cloned SSTR2 receptor are similar to those of the previously described SRIF1 receptor, and the characteristics of the cloned SSTR1 receptor are similar to those of the previously described SRIF2 receptor.

Adenylate Cyclase Toxin↗
PubMed1992

Differential expression of somatostatin receptor subtypes in brain.

The tetradecapeptide somatostatin has been implicated as an important regulator of neuronal and neuroendocrine function in the CNS. The cellular actions of somatostatin are mediated by specific receptors. The genes encoding two different somatostatin receptors (SSTRs) have been isolated and characterized, and RNA blotting studies have shown that both SSTR1 and SSTR2 are expressed in the brain. In order to gain a better understanding of the functions of somatostatin in the CNS, the distribution of SSTR1 and SSTR2 mRNAs was determined using the technique of in situ hybridization. SSTR1 mRNA was present throughout the mouse brain, particularly in the supra- and infragranular layers of the cortex, the amygdala, hippocampus, bed nucleus of the stria terminalis, substantia innominata, hypothalamus, pretectum, substantia nigra, parabrachial nucleus, and nucleus of the solitary tract. SSTR2 mRNA was primarily observed in the infragranular layers of the cortex, the amygdala, claustrum, endopiriform nucleus, arcuate and paraventricular nuclei of the hypothalamus, and medial habenular nucleus. Several regions of the brain reported to contain dense somatostatin-like immunoreactive terminal fields and receptor binding sites were devoid of both SSTR1 and SSTR2 mRNA, suggesting the existence of additional SSTR subtypes.

Animals↗
PubMed1992

Study on anti-IgA antibody in patients with IgA nephropathy.

Serum IgG antibodies to polyclonal IgA, IgA1 and IgA2 were evaluated by enzyme-linked immunosorbent assay in 50 patients with IgA nephropathy and 30 healthy controls to elucidate the relationship between IgA and IgG in IgA nephropathy. Anti-IgA antibody was considered positive if the titer exceeded the mean value in normal controls by greater than 2 SD. In patients with IgA nephropathy, 18 cases (36%) demonstrated anti-IgA antibody, 19 cases (38%) anti-IgA1 antibody and 7 cases (14%) anti-IgA2 antibody. Western blots confirmed the existence of anti-IgA antibody in these patients. There were no significant differences in serum IgA concentration, serum creatinine concentration, degree of hematuria, amount of urinary protein, and rate of glomerular IgG deposition between the "positive" group and "negative" group. Although the mechanism of production and the role of this antibody remain unknown, it may represent one of the diverse immune abnormalities of IgA nephropathy and may be involved in the pathogenesis of IgA nephropathy.

Adolescent↗