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Biomedical subjects

T Baba

Publications and source records attributed to T Baba.

At least 307 records · Page 17Linked to original sources
PubMed1993

Recruitment of epidermal growth factor and transferrin receptors into coated pits in vitro: differing biochemical requirements.

The biochemical requirements for epidermal growth factor (EGF) and transferrin receptor-mediated endocytosis were compared using perforated human A431 cells. Morphological studies showed that horseradish peroxidase (HRP)-conjugated EGF and gold-labeled antitransferrin (Tfn) receptor antibodies were colocalized during endocytosis in vitro. The sequestration of both ligands into deeply invaginated coated pits required ATP hydrolysis and cytosolic factors and was inhibited by GTP gamma S, indicating mechanistic similarities. Importantly, several differences in the biochemical requirements for sequestration of EGF and Tfn were also detected. These included differing requirements for soluble AP (clathrin assembly protein) complexes, differing cytosolic requirements, and differing sensitivities to the tyrosine kinase inhibitor, genistein. The biochemical differences detected between EGF and Tfn sequestration most likely reflect specific requirements for the recruitment of EGF-receptors (R) into coated pits. This assay provides a novel means to identify the molecular bases for these biochemical distinctions and to elucidate the mechanisms involved in ligand-induced recruitment of EGF-R into coated pits.

Adenosine Triphosphate↗
PubMed1993

Identification, cDNA cloning, and gene expression of soluble starch synthase in rice (Oryza sativa L.) immature seeds.

Three forms of soluble starch synthase were resolved by anion-exchange chromatography of soluble extracts from immature rice (Oryza sativa L.) seeds, and each of these forms was further purified by affinity chromatograph. The 55-, 57-, and 57-kD proteins in the three preparations were identified as candidates for soluble starch synthase by western blot analysis using an antiserum against rice granule-bound starch synthase. It is interesting that the amino-terminal amino acid sequence was identical among the three proteins, except that the 55-kD protein lacked eight amino acids at the amino terminus. Thus, these three proteins are products of the same gene. The cDNA clones coding for this protein have been isolated from an immature rice seed library in lambda gt11 using synthetic oligonucleotides as probes. The deduced amino acid sequence of this protein contains a lysine-X-glycine-glycine consensus sequence for the ADP-glucose-binding site of starch and glycogen synthases. Therefore, we conclude that this protein corresponds to a form of soluble starch synthase in immature rice seeds. The precursor of the enzyme contains 626 amino acids, including a 113-residue transit peptide at the amino terminus. The mature form of soluble starch synthase shares a significant but low sequence identity with rice granule-bound starch synthase and Escherichia coli glycogen synthase. However, several regions, including the substrate-binding site, are highly conserved among these three enzymes. Blot hybridization analysis demonstrates that the gene encoding soluble starch synthase is a single-copy gene in the rice genome and is expressed in both leaves and immature seeds. These results suggest that soluble and granule-bound starch synthases play distinct roles in starch biosynthesis of plant.

Amino Acid Sequence↗
PubMed1993

Determinants of the quantity of the stable SecY complex in the Escherichia coli cell.

While SecY in wild-type Escherichia coli cells is stable and is complexed with other proteins within the membrane, moderately overexpressed and presumably uncomplexed SecY was degraded with a half-life of 2 min. The fact that the amount of stable SecY is strictly regulated by the degradation of excess SecY was demonstrated by competitive entry of the SecY+ protein and a SecY-LacZ alpha fusion protein into the stable pool. Simultaneous overexpression of SecE led to complete stabilization of excess SecY. Overproduced SecD and SecF did not affect the stability of SecY, but plasmids carrying ORF12 located within the secD-secF operon partially stabilized this protein. In contrast, mutational reduction of the SecE content (but not the ORF12 content) led to the appearance of two populations of newly synthesized SecY molecules, one that was immediately degraded and one that was completely stable. Thus, the E. coli cell is equipped with a system that eliminates SecY unless it is complexed with SecE, a limiting partner of SecY. Our observations implied that in wild-type cells, SecY and SecE rapidly associate with each other and remain complexed.

Bacterial Proteins↗
PubMed1993

Demonstration of antidiarrheal and antimotility effects of wood creosote.

Wood creosote administered to rats prevented castor-oil-induced diarrhea with an ED50 of 53 mg/kg p.o. This antidiarrheal effect was apparently produced by acceleration of net fluid absorption from the intestine, as shown by a 52% decrease (p < 0.001) of residual fluid volume in an intestinal loop, and partly by suppression of intestinal motility. Wood creosote also inhibited spontaneous longitudinal contractions of isolated ileal segments in rats (IC50 = 28 mg/l) and guinea pigs (IC50 = 17 mg/l). Contractions of the guinea pig ileum induced by electrical stimulation, bradykinin and acetylcholine were also inhibited dose-dependently. We conclude that wood creosote has an antidiarrheal activity and that this effect is exerted by inhibition of intestinal motility and by augmentation of net fluid absorption from the intestine.

Acetylcholine↗
PubMed1993

Comparative studies on the inhibitory effects of calcium antagonists on cytosolic Ca2+ levels increased by high-potassium or glutamate in cultured rat cerebellar granule cells.

The inhibitory effects of calcium antagonists on high-potassium or glutamate (Glu) enhanced intracellular calcium ion ([Ca2+]i) levels were studied in cultured cerebellar granule cells. Dosages between 0.5 and 10 microM of flunarizine, nicardipine, SM6586 and SM12565 reduced the rise in [Ca2+]i induced by 50 mM KCl in a dose-dependent manner, although diltiazem, verapamil and nifedipine showed less effects on such [Ca2+]i increases. SM6586, SM12565 and flunarizine at dosages below 10 microM each reduced the magnitude of the [Ca2+]i increase induced by 25 microM Glu, but the other examined calcium antagonists were less effective. These results suggest the dissimilar efficacy of calcium antagonists on the inhibition of [Ca2+]i levels increased by high-potassium and Glu.

Animals↗
PubMed1993

[Anesthetic management of a patient undergoing hemodialysis for coronary artery bypass surgery without extracorporeal circulation].

A 58-year-old female with renal failure underwent anastomosis of the left internal mammary artery to the left anterior descending branch of coronary artery without extracorporeal circulation (ECC) and cardiac arrest. Anesthesia was maintained smoothly with modified NLA under normothermia. Without use of ECC, which often disturbs water and electrolyte metabolism, the patient's physical status remained quite stable. Though the left anterior descending artery was clamped for 20 minutes during the anastomosis, there was no complication, including perioperative myocardial infarction. For high risk patients with ECC such as patients with renal failure, respiratory failure and cerebrovascular diseases, this method is useful for the coronary artery bypass surgery.

Coronary Artery Bypass↗
PubMed1993

[A critical patient relieved from status asthmaticus with isoflurane inhalation therapy].

In cases of life-threatening status asthmaticus which are refractory to drug therapy, the administration of inhalation anesthetics can be life-saving as they help alleviate bronchial spasm. We had an 11-year-old female patient suffering from status asthmaticus who was moribund from severe CO2 narcosis and was not responding to any of the conventional therapies. She finally fell into ventricular fibrillation. After cardiopulmonary resuscitation, we administered 2.0% isoflurane in oxygen. Within half an hour, her high inspiratory pressure was dramatically decreased, and then the isoflurane concentration was maintained at 1.0%. After 14 hours of isoflurane anesthesia, PaCO2 decreased to the normal level and the isoflurane treatment was discontinued. The endotracheal tube was removed 4 hours later. She had an uneventful recovery and was discharged from the hospital 11 days later. With its low metabolic rate and therefore low organ toxicity, as well as its low arrhythmogenicity with remarkable bronchodilating activity, we feel isoflurane may well be superior to other inhalation anesthetics in the treatment of status asthmaticus.

Administration, Inhalation↗
PubMed1992

Calreticulin is present in the acrosome of spermatids of rat testis.

We have already succeeded in purifying a calcium-binding protein (CalBP) from rat spermatogenic cells [Nakamura et al., Biochem. Biophys. Res. Commun., 176 (1991) 1358]. In this study, the location of this protein within rat testis was examined, using a rabbit antisera for this protein. The antigen was localized on the developing acrosomes during spermiogenesis. The NH2-terminal amino acid sequence obtained for rat CalBP was identical to that of calreticulin obtained for the skeletal muscle of mice and closely resembled that for rabbit calreticulin. On the immunoblot analysis, the purified rat CalBP reacted with an antibody raised against rabbit skeletal muscle calreticulin. The results indicate that calreticulin is present in the acrosome of spermatids of rat testes.

Acrosome↗
PubMed1992

Identification of the fourth member of the mammalian endoprotease family homologous to the yeast Kex2 protease. Its testis-specific expression.

We used the polymerase chain reaction to identify a mouse testis cDNA that represented another member of a growing class of mammalian endoproteases involved in the processing of precursor proteins. This cDNA encoded a 655-residue protein, designated PC4, containing a bacterial subtilisin-like catalytic domain closely related to those of the recently characterized precursor-processing endoproteases, furin, PC1/PC3, PC2, and Kex2. Within this domain, the amino acid sequence of PC4 was 70, 58, 55, and 45% identical with those of mouse furin, mouse PC1/PC3, mouse PC2, and yeast Kex2, respectively. Northern blot analysis indicated that the PC4 mRNA was detectable only in the testes after the 20th day of postnatal development. Moreover, this message was mainly expressed in the round spermatids. These data suggest that PC4 represents a prime candidate for a precursor-processing endoprotease in the testicular germ cells and that its gene expression is regulated during spermatogenesis.

Amino Acid Sequence↗
PubMed1992

Response of microglial cells to experimental rat glioma.

The response of indigenous CNS microglia to an experimentally induced glioma has been studied in rat brain using lectin histochemistry with the Griffonia simplicifolia B4-isolectin. The study was undertaken 2 weeks after tumor cell injection when tumor size was near maximal. Reactive microglial cells formed a dense band that surrounded most of the well-circumscribed tumor mass, and extended along the corpus callosum into the contralateral cerebral hemisphere. From the periphery inward, reactive microglia extended into the tumor tissue, where large numbers of them were found to be present as microglia-derived macrophages. The lectin stain, which also labels endothelial cells, revealed a highly vascularized tumor with ongoing neovascularization apparent as vascular sprouts. Moderate numbers of lectin-stained blood monocytes were localized primarily inside the vessel lumina. Our results show that microglial cells react to brain tumors; however, it remains to be determined whether the microglial response represents an active antitumor defense mechanism that could be manipulated during immunotherapeutic approaches.

Animals↗
PubMed1992

Genetics of neurofibromatosis 1 in Japan: mutation rate and paternal age effect.

We have performed formal genetic studies on 26 patients (14 males, 12 females) with neurofibromatosis 1 (von Recklinghausen's disease, NF1) in Japan. Family studies of 74 members of 18 kindreds revealed that 50% of the cases were caused by a new mutation; the mutation rate was assumed to be 7.3-10.5 x 10(-5). A tendency of paternal age effect, which was not accounted for by the maternal age effect, was observed, but live-birth order had no significant effect. Genetic linkage of neurofibromatosis 1 to the NF1 gene or the genetic marker in the pericentric region of chromosome 17 was established in 3 informative families.

Age Factors↗
PubMed1992

Immunophenotypic analysis of infiltrating leukocytes and microglia in an experimental rat glioma.

The appearance and cellular distribution of major histocompatibility complex (MHC), as well as lymphocytic and macrophage antigens has been studied in a fully developed experimental rat forebrain glioma. Activated microglial cells and microglia-derived macrophages expressing CR3 complement receptor molecules and MHC class II (Ia) antigen were found throughout the tumor, and with increased density along the tumor's periphery. MHC class I antigen expression was entirely absent from tumor cells, and found only occasionally on microglia. The expression of leukocyte common antigen, and CD4 and CD8 antigens was conspicuous throughout the tumor, and associated with lymphocytes, perivascular cells, and microglia. Cells expressing the ED2 macrophage epitope were almost exclusively of the perivascular type and revealed a distribution dissimilar to that of cells positive for Ia antigen. The ED2 epitope was found sporadically on ramified microglial cells. The results show that despite heavy infiltration with blood mononuclear and CNS microglial cells, the tumor showed no evidence of destruction caused by inflammatory cells. Possible mechanisms of tumor immunosuppressive activity preventing the full immunological activation of microglia and blood mononuclear cells are discussed.

Animals↗