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Biomedical subjects

S Hata

Publications and source records attributed to S Hata.

At least 127 records · Page 7Linked to original sources
PubMed1994

Stretching releases Ca2+ from intracellular storage sites in canine cerebral arteries.

Mechanical stretch applied to canine cerebral artery produced myogenic contraction. The contraction of the artery in response to quick stretch was dependent on not only the transmembrane influx of Ca2+ through 1,4-dihydropyridine-sensitive Ca2+ channels but also the release of Ca2+ from intracellular storage sites: the stretch-produced contractile component that was resistant to 0.1 microM nicardipine, a Ca(2+)-channel antagonist, was inhibited by about 50% after treatment with ryanodine, and was almost completely suppressed by 0.1 mM 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate, a putative phospholipase C inhibitor, or by lowering the temperature from 35 to 20 degrees C. The results suggest that in addition to transmembrane influx of Ca2+ through L-type Ca2+ channels, the release of Ca2+ from both ryanodine-sensitive and -insensitive intracellular storage sites, which increases intracellular Ca2+, accounts for the stretch-induced contraction of canine basilar artery. It seems also possible that inositol 1,4,5-trisphosphate is a common mediator for the release of Ca2+ from both types of intracellular storage sites.

Animals↗
PubMed1994

The pulmonary vascular response to acute hypoxia in chronic pulmonary disease: morphological assessment with magnified pulmonary wedge angiography.

To detect hypoxic pulmonary vasoconstriction (HPV) morphologically, we investigated the pulmonary vascular response to acute hypoxia in 27 patients with chronic pulmonary disease (CPD) and 8 healthy subjects. Pulmonary hemodynamic measurements and magnified pulmonary wedge angiography (MPWA) were carried out before and after inhalation of 13% oxygen in nitrogen for 15 min. The diameters of central arteries (A) and muscular arteries (B) were measured using a densitometric method. Vasoconstriction was detected in the muscular arteries than in the central arteries by MPWA. There was a significant correlation between delta P (changes of mean PA pressure) and delta B/A (changes in diameters of B/A) in the CPD group. A significant correlation was found between delta SvO2 and delta B/A in the control group. We conclude that MPWA was a very useful method for the simple detection of HPV in patients with CPDs and we detected one site of HPV on the ninth generation of the pulmonary arterial tree by MPWA.

Adult↗
PubMed1994

Effect of food on propranolol oral clearance and a possible mechanism of this food effect.

To better define the mechanism of the increased plasma concentration of propranolol (PL) after meals, the effect of the dietary constitution of a meal on the kinetics of PL and beta-naphthoxylactic acid (NLA), a main metabolite, after administration of the drug, was investigated in rats. Additionally, the hepatic uptake of PL and cytochrome P-450 (P-450) content and uridine 5'-diphosphoglucuronyltransferase (UDPGT) activity in liver were measured after glucose intake. As a result, protein (skim milk) intake slightly, but not significantly, increased the area under the plasma concentration-time curve (AUC) and bioavailability of PL, with a slight increase (16%) in hepatic blood flow, and enhanced PL metabolism to NLA. Soybean oil and fatty acid intake significantly decreased the bioavailability of PL, while glucose intake dramatically decreased the hepatic uptake of PL and P-450 content at high glucose levels, resulting in a decrease in the plasma PL concentration at the initial time period and in the inhibition of a metabolic conversion to NLA. Thus, a possible mechanism involved in the effect of food on PL bioavailability could have been due largely to the decreased microsomal P-450 content and hepatic uptake of PL after glucose intake, but only partly to the increased hepatic blood flow after protein intake.

Administration, Oral↗
PubMed1994

Metabolism of finasteride in rat hepatic microsomes: age and sex differences and effects of P450 inducers.

1. The age- and sex-related metabolism of finasteride and the effects of P450 inducers and inhibitors were investigated using rat hepatic microsomes. 2. No marked age difference (3-13 weeks) in the rates of finasteride disappearance and the formation of 1 (omega-hydroxyfinasteride) and 4 (6 alpha-OH finasteride) was observed in the male rat. Whereas the rate of 1 formation remained about the same in male rat aged 1 year as compared with rat aged 7 weeks, a 21 and 45% decrease in the rate of finasteride disappearance and 4 formation, respectively, were observed. 3. The rates of finasteride disappearance and metabolite formation 1 and 4 in the female rat decreased with an increase in age (3-7 weeks). Metabolite 4 was hardly formed by the hepatic microsomes from the female rat at 7 weeks of age. 4. Hepatic microsomes from the male rat treated with phenobarbital (PB) and dexamethasone (Dex) increased the rate of the finasteride disappearance (PB, 5.5-fold; Dex, 11.6-fold), whereas no increase in this activity was observed after administration of beta-naphthoflavone (BNF). Similarly, pretreatment of the female rat with PB and Dex resulted in increases of 26.6 and 8.4-fold in the rate of finasteride disappearance, respectively, whereas no inductive effect on this activity was observed in the BNF-treated female rat. 5. These observations suggest that finasteride is metabolized by P4502B, P4502C, and P4503A subfamilies in the male rat and by P4502B and P4502C subfamilies in the female rat.

Aging↗
PubMed1993

Chicken ovalbumin upstream promoter-transcription factor (COUP-TF) represses transcription from the promoter of the gene for ornithine transcarbamylase in a manner antagonistic to hepatocyte nuclear factor-4 (HNF-4).

Chicken ovalbumin upstream promoter-transcription factor (COUP-TF) and hepatocyte nuclear factor-4 (HNF-4) are orphan members of the steroid/thyroid receptor superfamily and exhibit ubiquitous and liver-enriched tissue distribution, respectively. The gene for rat ornithine transcarbamylase (OTC), an ornithine cycle enzyme, is mainly expressed in the liver and is under the control of the promoter and the 11-kilobase upstream enhancer, both of which are liver-selective. Two sites of the promoter region and two sites of the enhancer region of the OTC gene, as well as the ovalbumin promoter site, were recognized by both HNF-4 and COUP-TF, showing that these two factors have closely related binding specificities. Since HNF-4 activated expression from the OTC promoter in cotransfection analysis, this factor appears to participate in liver-selective activation of the OTC gene. On the other hand, COUP-TF repressed the expression from the OTC promoter, whereas it activated expression from several other promoters. Therefore, COUP-TF plays a dual regulatory role depending on the promoter context. Repression of a tissue-specific promoter by a ubiquitous transactivator and derepression by a related tissue-enriched transactivator is potentially an important mechanism for tissue-specific activation of a gene.

Animals↗
PubMed1993

Characterization of Geotrichum candidum lipase III with some preference for the inside ester bond of triglyceride.

A new form of Geotrichum candidum lipase with a unique positional specificity was found to exist in the culture broth as a minor component together with the well-documented major form. Unlike the major form, which cleaves both the inside and outside ester bonds of triglyceride indiscriminately, the newly isolated form showed some preference for the inside (2-position) ester bond. The new enzyme was also characterized by its own fatty acid specificity, i.e., an outstandingly high activity towards triolein and methyl oleate among the simple triglycerides and fatty acid methyl esters tested. Moreover, the enzyme possessed a specific activity three times as high as the major form. Notable difference in circular dichroism spectra were observed between the two forms, indicating distinct conformational differences. Edman degradation revealed that the N-terminal sequence of the new form differed from that of the major form, thus demonstrating the existence of a novel lipase gene on the chromosome.

Amino Acid Sequence↗
PubMed1993

Isolation and characterization of novel nodulin cDNAs representing genes expressed at early stages of soybean nodule development.

We took advantage of a subtractive hybridization procedure to isolate a set of cDNA clones of nodule-specific genes (nodulin genes) from developing soybean root nodules. Single-stranded 32P-labelled cDNA synthesized from nodule poly(A)+ RNA was hybridized with a large excess of uninfected root poly(A)+ RNA. Unhybridized cDNA was selected and used to screen nodule cDNA libraries. By this procedure we isolated several novel nodulin cDNA clones together with most of the nodulin cDNAs previously described. Four novel nodulin genes, which were expressed long before the onset of nitrogen fixation, were further characterized. GmN#36 and GmN#93 transcripts appeared in the roots less than 3 days after sowing and inoculation with Bradyrhizobium, but GmN#36 transcripts were also detected at very low levels in the stems of uninfected plants. Transcripts of GmN#315 and GmN#70 first appeared at 6-7 days, just before nodule emergence. Amino acid sequences of the predicted products of GmN#36, GmN#93 and GmN#70 exhibited no significant homology to proteins identified so far. The GmN#315 encoded protein has a limited but significant homology to some plant cyanins, suggesting that it is a metal-binding glycoprotein. In situ hybridization studies revealed that GmN#36 transcripts first appeared in the pericycle cells of the root stele near the infected site. During nodule emergence they were found in a few cell layers surrounding the vascular strands connecting the nodule meristem with the root stele, and in mature nodules they were present specifically in the pericycle cells in vascular bundles. These observations led us to hypothesize that GmN#36 gene products play a role in the transport and/or degradation of photosynthate. On the other hand, GmN#93 transcripts first appeared in the primary nodule meristem just below the root epidermis. In mature nodules they were only present in the infected cells.

Amino Acid Sequence↗
PubMed1993

Corneal endothelial cell loss induced by air bags.

BACKGROUND: Although the automobile air bag is a safety device used to protect drivers from death and moderate-to-severe injury, recently it also has been reported to be associated with some ophthalmic injuries. The authors have encountered a case in which a normal air bag may have caused a driver's corneal endothelial cell loss. In this study, the authors evaluate corneal endothelial cell loss caused by several types of air bags in the hope that air bag technology may be improved. METHODS: The authors performed impact tests with whole pig eyes fixed in a crash test dummy, using five different types of air bags. The area of damaged corneal endothelial cell was analyzed quantitatively. RESULTS: The authors found that corneal endothelial cell loss was correlated with the inflator power of the air bag but not with its weight. CONCLUSION: Although greater inflator power is needed for rapid air bag expansion, the effect on the eye should be considered in further refining this device. There may be greater latitude in the selection of air bag material. The authors believe their technique is applicable to the assessment of many air bag or passenger variables.

Accidents, Traffic↗
PubMed1993

[Corneal endothelium damage by air bag system].

We have reported in the past a car crash in which the air bag system might have caused driver's corneal endothelial cell loss. To evaluate the corneal endothelial cell loss caused by air bag systems, we performed several air bag impact tests. We found that the corneal endothelial cell loss was greater at a distance of 240 mm than other distances. We also found that the corneal endothelial cell loss caused by the air bag which has bigger inflater and heavier material was significantly greater than that caused by other systems. This study offers basic data to improve the safety of air bag systems.

Air Bags↗
PubMed1993

[A case of obstructive sleep apnea syndrome with increased lung water during sleep].

A 22-year-old man was admitted to the department of plastic surgery in our university with diagnosis of ankylosis and microgeniea. His complaints were snoring and somnolence in the daytime, so we performed a Respigraph (Chest) that showed obstructive apnea during sleep. We diagnosed obstructive sleep apnea syndrome. So we observed pulmonary circulation and measured lung water using the double indicator dilution method (Nihon Koden, MTV-1100) during sleep. During the period of apnea, arterial oxygen pressure and mixed venous saturation decreased, reversely, mean pulmonary arterial pressure rose, lung water (ETV) and central blood volume increased. We considered that the increase of lung water during sleep apnea is caused by hemodynamic change due to hypoxia and increase of venous return. After operation, the value of blood gas assay and apnea index were improved.

Adult↗
PubMed1992

Signal peptide for peroxisomal targeting: replacement of an essential histidine residue by certain amino acids converts the amino-terminal presequence of peroxisomal 3-ketoacyl-CoA thiolase to a mitochondrial signal peptide.

The role of the histidine residue at position -17 of the amino-terminal signal peptide of rat peroxisomal 3-ketoacyl-CoA thiolase was studied in vivo, employing site-directed mutagenesis. Among the nine amino acids tested, only glutamine could partially substitute for the histidine. Mutants carrying basic amino acids, arginine and lysine, and hydrophobic residues, leucine and valine, in place of histidine were all translocated to mitochondria, but not to peroxisomes. These results indicate that the signal peptide of the thiolase is recognized by a mechanism totally different from that for the SKL motif, a known peroxisomal targeting signal. Relationship of the thiolase signal peptide to those of mitochondrial proteins is discussed.

Acetyl-CoA C-Acyltransferase↗
PubMed1992

A novel isoform of rat hepatocyte nuclear factor 4 (HNF-4).

Based on the published nucleotide sequence for rat hepatocyte nuclear factor 4 (HNF-4; Sladek, F.M., Zhong, W., Lai, E. and Darnell, J.E., Jr. (1990) Genes Dev. 4, 2353-2365), we have cloned a cDNA by means of polymerase chain reaction amplification of reverse-transcribed RNA (RT-PCR). Our clone contained an extra segment of 30 bp, which was not found in the previously reported clone, in the coding region near the C-terminus. Further RT-PCR analysis demonstrated that both isoforms of HNF-4 mRNA, i.e., with or without the 30 nucleotide segment, occur in rat liver and kidney, presumably by differential splicing.

Amino Acid Sequence↗
PubMed1992

Analysis of carrot genes for proliferating cell nuclear antigen homologs with the aid of the polymerase chain reaction.

We designed a polymerase chain reaction-based strategy to obtain information about the origin and distribution of a newly discovered proliferating cell nuclear antigen (PCNA) homolog. Carrot genomic segments were amplified using degenerate primers for two conserved regions of known PCNA homologs. The genes encoding the larger PCNA as well as typical PCNA contained introns. Thus, unlike processed PCNA pseudogenes in mammals, the larger homolog is not generated through reverse transcription of a typical PCNA mRNA. Moreover, introns of the larger PCNA homolog were positioned at the characteristic sites in plant PCNA genes. Attempts to amplify cDNA for an additional PCNA homolog from mammalian cells have been unsuccessful. These results suggest that the larger PCNA homolog was generated, presumably through gene duplication, after the divergence of the Planta and Animalia.

Amino Acid Sequence↗
PubMed1992

Identification of carrot cDNA clones encoding a second putative proliferating cell-nuclear antigen, DNA polymerase delta auxiliary protein.

The proliferating cell-nuclear antigen (PCNA) plays a key role in the control of eukaryotic DNA replication. We have isolated two cross-hybridizing groups of cDNA encoding carrot homologs of PCNA. Sequence analysis and Southern-blot experiments showed that the cDNA were derived from two distinct genes. One corresponded to the typical PCNA, which is known to be highly conserved in eukaryotes from yeast to man; its mRNA is 1.2 kb in size and the calculated molecular mass of the protein is 29 kDa. The other encoded a larger PCNA homolog which has not previously been reported; the mRNA is 1.5 kb in size, the N-terminal three quarters (calculated molecular mass, 29 kDa) of the protein product is 88% identical at the amino acid level to the typical PCNA, but the protein has an extra C-terminal domain of 11 kDa. Both PCNA homologs were apparently coexpressed concomitant with somatic embryogenesis. The mRNA level of the novel homolog is 10-20% that of the typical PCNA in the embryos. The presence of the second putative PCNA may provide new insight into studies on the mechanism of DNA replication in eukaryotes.

Amino Acid Sequence↗
PubMed1992

Isolation and characterization of cDNA clones encoding cdc2 homologues from Oryza sativa: a functional homologue and cognate variants.

Using probes obtained by PCR amplification, we have isolated two cognate rice cDNAs (cdc2Os-1 and cdc2Os-2) encoding structural homologues of the cdc2+/CDC28 (cdc2) protein kinase from a cDNA library prepared from cultured rice cells. Comparison of the deduced amino acid sequences of cdc2Os-1 and cdc2Os-2 showed that they are 83% identical. They are 62% identical to CDC28 of Saccharomyces cerevisiae and much more similar to the yeast and mammalian p34cdc2 kinases than to rice R2, a cdc2-related kinase isolated previously by screening the same rice cDNA library with a different oligonucleotide probe. Southern blot analysis indicated that the three rice clones (cdc2Os-1, cdc2Os-2 and R2) are derived from distinct genes and are each found in a single copy per rice haploid genome. RNA blot analysis revealed that these genes are expressed in proliferating rice cells and in young rice seedlings. cdc2Os-1 could complement a temperature-sensitive yeast mutant of cdc28. However, despite the similarity in structure, both cdc2Os-2 and R2 were unable to complement the same mutant. Thus, the present results demonstrate the presence of structurally related, but functionally distinct cognates of the cdc2 cell cycle kinase in rice.

Amino Acid Sequence↗