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Biomedical subjects

M Yamashita

Publications and source records attributed to M Yamashita.

At least 19 recordsLinked to original sources
PubMed1995

A Klebsiella aerogenes moaEF operon is controlled by the positive MoaR regulator of the monoamine regulon.

A 30-kDa protein accumulated upon induction by a high concentration of tyramine or dopamine in cells of Klebsiella aerogenes (Ka). These cells carried a plasmid (pAS123) that included the arylsulfatase operon (atsBA). Deletion analysis showed that the region essential for induction of the 30-kDa protein was located within a 2.0-kb cloned segment downstream of the atsBA operon. The nucleotide (nt) sequence of the 2.0-kb fragment revealed two open reading frames (ORFs), moaE and moaF. Transcription from a putative promoter of moaE was induced by the addition of tyramine, and the moaF gene was co-transcribed from this monoamine-inducible Ka promoter. The deduced Ka MoaE protein was homologous to insect-type alcohol dehydrogenase. The sequence of the 18 amino acids from the N-terminus of the purified 30-kDa protein agreed with that deduced from the nt sequence of moaF. Using a Ka strain with a mutant moaR gene, we found that MoaR, that acts as the positive regulator of the monoamine regulon, also acts as the positive regulator of the moaEF operon.

Alcohol Dehydrogenase↗
PubMed1995

The warm temperature acclimation-related 65-kDa protein, Wap65, in goldfish and its gene expression.

cDNAs encoding a warm temperature acclimation-related protein (Wap65) were cloned from the muscle and hepatopancreas cDNA libraries of the warm temperature-acclimated goldfish Carassius auratus, and their nucleotide sequences containing 5'- and 3'-noncoding regions together with their polyadenylation signal were determined. The deduced amino acid sequence of Wap65 was 31% homologous to rat hemopexin. However, goldfish Wap65 lacked a few possible glycosylation sites and presumed functional histidine residues, implying that it may have different functions from hemopexin. Wap65 contained a leader peptide of 30 amino acids and a mature protein region of 415 amino acids. Southern blot analysis demonstrated that the protein is expressed by a single copy gene in the goldfish haploid genome. In RNA blot analysis using isolated cDNA clones, a single transcript of about 2.0 kilobases was detected in the hepatopancreas but not in brain, muscle, or hemocytes. The abundancy of this transcript markedly increased in the hepatopancreas as a result of warm temperature acclimation. Electrophoretic analysis of plasma proteins revealed a good correlation of plasma Wap65 levels to those of the corresponding transcript in the hepatopancreas, suggesting that serum Wap65 concentrations are regulated mainly by transcript levels in the hepatopancreas via the secretion process.

Acclimatization↗
PubMed1995

Specific deficit of the ON response in visual transmission by targeted disruption of the mGluR6 gene.

Taking advantage of the restricted expression of metabotropic glutamate receptor subtype 6 (mGluR6) in retinal ON bipolar cells, we generated knockout mice lacking mGluR6 expression. The homozygous mutant mice showed a loss of ON responses but unchanged OFF responses to light. The mutant mice displayed no obvious changes in retinal cell organization nor in the projection of optic fibers to the brain. Furthermore, the mGluR6-deficient mice showed visual behavioral responses to light stimulation as examined by shuttle box avoidance behavior experiments using light exposure as a conditioned stimulus. The results demonstrate that mGluR6 is essential in synaptic transmission to the ON bipolar cell and that the OFF response provides an important means for transmitting visual information.

Animals↗
PubMed1995

Molecular mechanisms of the activation of maturation-promoting factor during goldfish oocyte maturation.

Oocyte maturation is triggered by the activation in the oocyte cytoplasm of maturation-promoting factor (MPF), which consists of cdc2 (a catalytic subunit) and cyclin B (a regulatory subunit). Immature goldfish oocytes contain only inactive monomeric 35-kDa cdc2 and do not stockpile cyclin B. In maturing oocytes, activation of cdc2 is associated with its Thr161 phosphorylation and mobility shift on SDS-PAGE from 35 to 34 kDa after binding to cyclin B. Using mutant cdc2, we show that Thr161 phosphorylation is required for both the downward shift and the kinase activation. Since cdc2 Tyr15 is not phosphorylated after binding to cyclin B, it does not require dephosphorylation. This situation is obviously different from that in immature Xenopus oocytes, in which the cdc2-cyclin B complex preexists with cdc2 phosphorylated on both Tyr15 and Thr161, thereby requiring Tyr15 dephosphorylation catalyzed by cdc25 phosphatase for MPF activation. These results indicate that these species employ different mechanisms of MPF activation during oocyte maturation, although the final molecular structure of the active MPF (cdc2 bound to cyclin B and phosphorylated on Thr161) is identical.

Amino Acid Sequence↗
PubMed1995

Association of p34cdc2 and cyclin B1 during meiotic maturation in porcine oocytes.

The relative levels and association of p34cdc2 and cyclin B1 have been determined in pig oocytes during meiotic progression from G2 to metaphase II (MII). Fully grown G2-arrested porcine oocytes contained large amounts of free p34cdc2 and extremely small amounts of p34cdc2-cyclin B1 complex which did not increase in amount during the GV stage. Cyclin B1 is not synthesized in measurable quantities until 23 hr after the start of maturation. During the first metaphase (MI) the amount of both cyclin B1 and the p34cdc2-cyclin B1 complex increased sharply until 35 hr. Thereafter the amount of the p34cdc2-cyclin B1 complex increased again to 45 hr, resulting in higher levels of the complex in MII than in MI. Moreover, three distinct migration forms of p34cdc2 were detected in pig oocytes by immunoblotting with anti-PSTAIRE antibody, and most of the cyclin B1-associated p34cdc2 was detected in the lower band in MI oocytes but migrated in the second band during MII. These results suggest that cyclin B1 levels in porcine oocytes differ from those in starfish, clam, and Xenopus oocytes in which considerably higher concentrations of cyclin B1 appear to be present during the GV stage and that the nature of the association between p34cdc2 and cyclin B1 changes between the first and the second metaphase.

Animals↗
PubMed1995

Molecular cloning and immunological analysis of goldfish cyclin A during oocyte maturation.

Cyclin A belongs to a family of proteins involved in the regulation of the eukaryotic cell cycle. Although cyclin A is thought to be involved in the regulation of both S and M phase, its exact role in the cell cycle, especially in the meiotic cycle (oocyte maturation), is uncertain. We isolated cyclin A cDNA clones from a goldfish oocyte cDNA library. Monoclonal antibody raised against bacterially produced goldfish cyclin A recognized a 47-kDa protein that disappeared after egg activation. Unlike goldfish cyclin B, which is absent in immature oocytes, cyclin A was already present in immature oocytes and its protein level did not change remarkably during oocyte maturation. These results differ from the finding in Xenopus, in which cyclin A is absent, but cyclin B is present, in immature oocytes. Goldfish cyclin A was associated with cdc2 kinase in mature oocytes, but not with cdk2. Recombinant cyclin A bound to and activated cdc2 in a cell-free system, but cyclin A and cdk2 binding was not observed. The kinase activity of cyclin A-cdc2 was undetectable in immature oocytes and first appeared at about the time of germinal vesicle breakdown (GVBD). In contrast to the cyclin B-cdc2 activity that corresponded to the occurrence of GVBD, cyclin A-cdc2 activity increased only slightly until GVBD was completed and increased drastically after the completion of the first meiotic division. Furthermore, microinjection of cyclin A mRNA into immature oocytes did not cause GVBD; however, microinjection of cyclin B mRNA did. These results suggest that cyclin A-cdc2 kinase and cyclin B-cdc2 kinase play different roles in controlling oocyte maturation. The roles of cyclin A in the rapid activation of cyclin B-cdc2 kinase at meiosis I and II transition and in the maintenance of high maturation-promoting factor activity in mature unfertilized eggs are discussed.

Amino Acid Sequence↗
PubMed1995

Ca2+ channel activities in the limb bud of early embryonic chick.

Ca2+ channel activities were recorded in the limb bud of embryonic day 4 chick with Ca2+ sensitive fluorescence (Fura-2) measurements and patch clamp techniques. Rises in intracellular Ca2+ concentrations were evoked by depolarization with the application of 100 mM K+ and this Ca2+ response was abolished by removing extracellular Ca2+. The Ca2+ response was blocked by 10 microM nifedipine and enhanced by 5 microM Bay K 8644. Long-lasting inward currents were revealed by whole-cell patch clamp recordings from dissociated cells of the limb bud. The inward current was also blocked by 10 microM nifedipine. Our study suggested the presence of L-type Ca2+ channels in the limb bud cells.

Animals↗
PubMed1995

HTLV-I from Iranian Mashhadi Jews in Israel is phylogenetically related to that of Japan, India, and South America rather than to that of Africa and Melanesia.

A new endemic focus of human T-lymphotropic virus type I (HTLV-I) was recently reported among Mashhadi Jews, a group of immigrants from northeastern Iran to Israel. We extracted DNAs from fresh peripheral blood mononuclear cells (PBMCs) and/or gargle mouthwash from 10 HTLV-I carriers, who consisted of members of one family, and HTLV-I-associated myelopathy (HAM) and adult T-cell leukemia (ATL) patients. Long terminal repeat (LTR) regions of proviral DNAs were sequenced and analyzed phylogenetically. In a phylogenetic tree, all the Mashhadi HTLV-I isolates belonged to subtype A, one of the three subtypes of the cosmopolitan type of HTLV-I, and made a tight cluster distinct from the other isolates of subtype A from Japan, India, the Caribbean Basin, and South America. Although a few nucleotide substitutions were observed among the clones sequenced, no characteristic sequence variation was found in different disease manifestations, even in one family or different sources of DNA preparation.

Adult↗
PubMed1995

Cervical approach for the repair of esophageal atresia.

Repair of esophageal atresia is usually performed by a thoracic approach. In cases associated with a tracheoesophageal fistula (TEF) located in a high position, however, the cervical approach is a reasonable alternative. In the literature, the authors found only three patients repaired by this approach. This report describes three additional cases of esophageal atresia successfully repaired by the cervical approach. Three neonates with esophageal atresia and TEF were confirmed as having an unusually high position of the distal TEF by the preoperative bronchoscopy and contrast study. The transcervical approach for repair was chosen. The skin was incised transversely at the right supraclavicular region, and the sternocleidomastoid muscle and the carotid sheath were retracted posterolaterally. After the division of the TEF, the suture site of the tracheal fistula was covered by a flap of the sternothyroid muscle that was inserted between the trachea and the esophagus, thus avoiding opposing suture lines. These cases emphasize that pediatric surgeons should be aware of the presence of cervical esophageal atresia in which distal TEF is located above the clavicle, and suggest that cervical repair is feasible for the patient whose distal TEF moves up above the first rib on inspiration. The most reliable methods for detecting the location of the distal TEF are telescopic bronchoscopy and contrast study.

Bronchoscopy↗
PubMed1995

Predeposited autologous blood transfusion for surgery in infants and children.

Homologous blood transfusions have associated infectious and immunological risks. Since 1989 the authors have conducted predeposited autologous blood transfusions (PABT) for infants and children in whom transfusions were expected to be required during an elective operation. Autologous blood was deposited in 13 patients ranging in age from 9 months to 10 years (median, 21 months) with weight from 7.3 kg to 33.6 kg (median, 10.5 kg). They included eight patients with Hirschsprung's disease, three patients with benign tumors, and two others. The volume of predeposition was calculated to maintain the patients' hematocrit at 30% after collection. Blood was deposited once or twice, 1 to 2 weeks before the operation. The actual volume of predeposited blood was 19.1 +/- 2.4 mL/kg in infants with Hirschsprung's disease, 21.8 +/- 10.0 mL/kg in children with Hirschsprung's disease, and 12.6 +/- 2.2 mL/kg in children with other diseases. Nine patients were operated on using only PABT, 2 patients required homologous blood transfusions in addition to PABT, and 2 patients did not require any blood transfusions. No complications occurred as a result of PABT except preoperative anemia. PABT is a safe and effective means of procuring blood for intraoperative transfusions in infants and children undergoing major elective general pediatric surgical procedures.

Blood Transfusion, Autologous↗
PubMed1995

A case of pituitary apoplexy in a child.

A case of pituitary apoplexy is reported in a 14-year-old girl who presented with headaches and progressive visual disturbance. Magnetic resonance imaging demonstrated subacute hemorrhage into a pituitary adenoma. Transsphenoidal removal of the tumor was performed successfully. Pituitary apoplexy in children is rare. Thus we will discuss the clinical features and neuroradiological findings.

Adolescent↗
PubMed1995

Development of the otolith organs and semicircular canals in the Japanese red-bellied newt, Cynops pyrrhogaster.

The sequence in which the otoliths and semicircular canals and their associated sensory epithelia appear and develop in the newt are described. Three-dimensional reconstruction of serial sections through the otic vesicle of newt embryos from stages 31 through 58 demonstrate the first appearance, relative position and growth of the otoliths. A single otolith is first seen in stage 33 embryos (approximately 9 days old); this splits into separate utricular and saccular otoliths at stage 40 (13 days). The lateral semicircular canal is the first to appear, at stage 41 (14 days). The anterior and posterior canals appear approximately one week later and the vestibular apparatus is essentially fully formed at stage 58 (approximately 5 weeks). The data reported here will serve as ground-based controls for fertilized newt eggs flown on the International Microgravity Laboratory-2 Space Shuttle flight, to investigate the influence of microgravity on the development of the gravity-sensing organs.

Animals↗
PubMed1995

Regulation of oocyte growth and maturation in fish.

This chapter has briefly reviewed the current status of investigations on the hormonal regulation of oocyte growth and maturation in fish (see Figs. 4 and 9). Pituitary gonadotropins are of primary importance in triggering these processes in fish oocytes. In both cases, however, the actions of gonadotropins are not direct, but are mediated by the follicular production of steroidal mediators, estradiol-17 beta (oocyte growth) and 17 alpha,20 beta-DP or 20 beta-S (oocyte maturation). Investigators have established that both estradiol-17 beta and 17 alpha,20 beta-DP are biosynthesized by salmonid ovarian follicles via an interaction of two cell layers, the thecal and granulosa cell layers (two-cell-type model). The granulosa cell layers are the site of production of these two steroidal mediators, but their production depends on the provision of precursor steroids by the thecal cell layers. A distinct steroidogenic shift from estradiol-17 beta to 17 alpha,20 beta-DP, occurring in salmonid ovarian follicles immediately prior to oocyte maturation, is a prerequisite for the growing oocytes to enter the maturation stage, and requires a complex and integrated network of gene regulation involving cell specificity, hormonal regulation, and developmental patterning. The cDNAs for most of the steroidogenic enzymes responsible for estradiol-17 beta and 17 alpha,20 beta-DP biosynthesis have been cloned from rainbow trout ovaries. Our next task is to determine how gonadotropin and other factors act on ovarian follicle cells to turn the expression of these specific genes on and off at specific times during oocyte growth and maturation. Increasing evidence now suggests that a variety of neuromodulatory, autocrine, and paracrine factors may also be involved in the regulation of steroidogenesis in fish ovarian follicles. Molecular biological technologies should be applied to identify these substances. Of considerable interest is the finding that MIH, unlike most steroid hormones, acts on its receptors at the surface of oocytes. Further studies of the association of the MIH-MIH receptor complex with a Gi protein, probably resulting in the inactivation of adenylate cyclase, should lead to a discovery of a new mechanism of steroid hormone action. The early steps following MIH action involve the formation of the major cytoplasmic mediator of MIH, MPF. Fish MPF, like that of Xenopus and starfish, consists of two components: cdc2 kinase and cyclin B. Nevertheless, the mechanism of MIH-induced MPF activation in fish oocytes differs from that in Xenopus and starfish because the appearance of cyclin B protein is a crucial step for 17 alpha,20 beta-DP-induced oocyte maturation in fish.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1995

Job satisfaction in Japanese nurses.

This study investigated job satisfaction among nurses in Japan. The instrument for measuring occupational satisfaction of hospital nurses developed by Stamps and her associates was used. Initial items were reviewed by content experts who were familiar with measurement of work satisfaction among health professionals and nursing practice in Japan. Based on the item analysis in the cultural context, several items were reworded or eliminated from the original version. Twenty-five items were retained and translated into English by bilingual professionals. The questionnaire was administered to 613 nurses practising in a large, acute-care hospital in a southern part of Japan. The results from testing psychometric properties of the translated version of the instrument were satisfactory. It may be concluded that nurses in the study were not satisfied but not dissatisfied either. On all items, they showed relatively strong commitment to their work. However, extrinsic factors such as having little opportunities for promotion or less favourable working conditions appeared to negatively influence job satisfaction in the study. The findings support the dual factor theory of Herzberg and also Maslow's theory. Considering the lowest scored item, little opportunities for promotion, which reflects the employment system in Japan, administrators, who are usually male medical practitioners, should be made aware of a need for creating clinical ladder opportunities for nurses who would be promoted based on a merit system, instead of the current practice of a seniority system.

Adult↗
PubMed1995

Molecular cloning, expression in Streptomyces lividans, and analysis of a gene cluster from Arthrobacter simplex encoding 3-ketosteroid-delta 1-dehydrogenase, 3-ketosteroid-delta 5-isomerase and a hypothetical regulatory protein.

The Arthrobacter simplex gene coding for 3-ketosteroid-delta 1-dehydrogenase, a key enzyme in the degradation of the steroid nucleus, was cloned in Streptomyces lividans. Nucleotide sequence analysis revealed that the gene for 3-ketosteroid-delta 1-dehydrogenase (ksdD) is clustered with at least two more genes possibly involved in steroid metabolism. Upstream of ksdD, we found a gene, ksdR, encoding a hypothetical regulatory protein that shows homologies to KdgR, the negative regulator of pectin biodegradation in Erwinia, and GyIR, the activator for glycerol metabolism in Steptomyces. A helix-turn-helix DNA-binding domain can be predicted at similar positions near the N-terminal of KsdR, KdgR and GyIR. ksdl adjoining downstream to ksdD codes for a protein that has strong similarities to 3-ketosteroid-delta 5-isomerases. The highly conserved Tyr and Asp residues are present in the active-centre motif of the enzyme. The translated ksdD gene product was found to be similar to the 3-ketosteroid-delta 1-dehydrogenase of Pseudomonas testosteroni and to the fumarate reductase of Shewanella putrefaciens. A region highly conserved between the two steroid dehydrogenases can be aligned to the active-centre motif of the fumarate reductase. S. lividans strains carrying the ksdD gene overexpressed 3-ketosteroid-delta 1-dehydrogenase. The expression of 3-ketosteroid-delta 5-isomerase, however, was barely detectable in recombinant S. lividans strains carrying the ksdl gene, or in the parental Arthrobacter strain.

Amino Acid Sequence↗
PubMed1995

Sinus node recovery function is relatively well preserved under halothane anaesthesia in children.

The purpose of this study was to evaluate the effect of halothane on sinus node recovery time (SNRT). Nine children with congenital heart disease scheduled for cardiac catherization were studied. After the routine procedure, the sinus node was paced at rates of 120, 150 and 180 beats per minute. SNRTs were measured with control conditions and under 1 MAC halothane anaesthesia. The absolute SNRT was standardized and expressed as '%SNRT' and 'Corrected SNRT (CSNRT)'. CSNRT was slightly prolonged by halothane (P = 0.042), while the %SNRT was not significantly prolonged. We conclude that the recovery function of the sinus node is relatively well preserved under 1 MAC halothane in children.

Anesthesia, Inhalation↗
PubMed1995

Thalamo-olivary degeneration in a patient with laryngopharyngeal dystonia.

A 67 year old woman with a two year history of laryngopharyngeal dystonia, spasmodic dysphonia, and parkinsonism succumbed to Wernicke's encephalopathy and died six months later. Necropsy showed, besides Wernicke's encephalopathy, degenerative changes in selected thalamic nuclei (dorsomedial, pulvinar, and the medial geniculate bodies) and the inferior olives and numerous cerebellar torpedoes. The substantia nigra and basal ganglia were spared. Immunostaining for prion protein was negative. This patient indicated a new type of presentation of so-called pure thalamic degeneration, or more precisely thalamo-olivary degeneration.

Aged↗