Biomedical subjects

T Tamura

Publications and source records attributed to T Tamura.

At least 811 records · Page 45Linked to original sources

PubMed1992

Comparison of laser Doppler fluxmetry and the thermal diffusion method of measuring skin blood flow with hydrogen clearance.

Laser Doppler fluxmetry (LDF) and the thermal diffusion method (TDF) were compared with the hydrogen clearance method in ten rabbit ears. The LDF signal followed the rapid change in blood flow caused by aortic occlusion and the signal obtained by TDF showed a time delay and the response was less steep compared with the LDF signal. Simultaneous recording showed both methods correlated well with the hydrogen clearance method, but the relationship varied among the studies (the slope 0.0189-0.0967 for LDF, the slope 0.052-0.682 for TDF). Both methods appear to provide a good indicator of the response pattern of blood flow in the region tested. However, variability among the subjects indicates that the quantitative application of both techniques is difficult.

Animals↗

PubMed1992

Serum folate and fetal growth retardation: a matter of compliance?

Serum folate levels were measured at 30 weeks' gestational age in 289 pregnant women, each of whom had been provided with folate supplementation at enrollment in prenatal care. There was a significant association between low serum folate levels and fetal growth retardation. High folate levels were most likely explained by recent folic acid intake. Therefore, we were concerned that the decreased fetal growth associated with low folate levels may have been related to a combination of psychological and behavioral characteristics for which low serum folate levels were only a surrogate measure. A profile of maternal psychosocial status was created, which included measures of depression, anxiety, self-esteem, mastery, stress, and social support. Poorer psychological scores were significantly related to lower serum folate levels. However, in women with both good and poor psychosocial scores, high folate levels were significantly associated with increased birth weight, a relationship that persisted even after adjusting for maternal race, body mass index, smoking, history of a low birth weight infant, and infant gender. Our findings suggest that women with good psychosocial scores are more likely to take folate, but that the use of folate itself is related to a lower risk of fetal growth retardation and increased birth weight.

Affective Symptoms↗

PubMed1992

Proteasomes: protein and gene structures.

Proteasomes are ring- or cylinder-shaped particles that have a sedimentation coefficient of 20S and are composed of a characteristic set of small polypeptides. These particles have a latent multicatalytic proteinase activity. Recently, proteasomes were found to combine reversibly with multiple protein components to form 26S proteolytic complexes that catalyze ATP-dependent, selective breakdown of proteins ligated with ubiquitin. This suggests that the 26S complexes are a new type of ATP-requiring protease in eukaryotic cells. We have studied the structures of various eukaryotic proteasomes at the molecular level by physicochemical and recombinant DNA techniques and have proposed that the gross structures of proteasomes, such as their size and shape, have been highly conserved during evolution. Proteasome subunits appear to be encoded by a family of homologous genes named the "proteasome gene family," which may have evolved from a common ancestral gene. Evidence obtained by genetic analyses in yeast and studies on the levels of proteasome expression in various eukaryotic cells indicates that proteasomes have essential roles in the cell. In this review, we summarize available information on the protein and gene structures of proteasomes and discuss the biological functions of proteasomes.

Amino Acid Sequence↗

PubMed1992

[An infantile case of cerebral infarction associated with thrombocytosis].

Cerebral infarction in children is often caused by intracranial vascular disorder, cardiac disease, head injury, or infection, and is rarely induced by blood disease. In this paper, we describe an infantile case of cerebral infarction associated with thrombocytosis. A female infant of eight months of age developed left hemiparesis after a slight head injury. Her CT and MRI demonstrated a cerebral infarction located from the right internal capsule to the right corona radiata. Laboratory findings revealed iron-deficiency anemia and thrombocytosis with a platelet count 107.5 x 10(4)/mm3. Although she had no disorder that had caused iron deficiency, serum Fe value of the patient was low with a count of 18 micrograms/dl. Her bone marrow was normal except for a slight increase in the number of megakaryocytes. One month later, her anemia was improved by means of oral iron replacement. However, her platelet count remained at more than 100 x 10(4)/mm3 as it had been before. Her condition of left-sided hemiparesis gradually improved by a program of rehabilitation, and did not recur after aspirin administration. Although the main cause of her thrombocytosis that led to a transient cerebrovascular accident is obscure, it is postulated that her iron deficiency anemia induced secondary thrombocytosis, or else the patient had essential thrombocytosis.

Anemia, Hypochromic↗

PubMed1992

[Myelodysplastic syndrome associated with marked eosinophilia and basophilia].

Myelodysplastic syndrome (refractory anemia with excess of blasts; RAEB) with marked basophilia and eosinophilia is described. An 82-year-old male was admitted to our hospital because of severe normocytic normochromic anemia (Hb 5.6 g/dl). The white cell count was 9,200/microliters with marked basophilia (34.5%) and eosinophilia (19.5%). The bone marrow aspiration also revealed both basophilia and eosinophilia, with blast contents of 9%. Diagnosis of RAEB was established. Although the treatment with red cell transfusion and ubenimex (Bastatin) was started, anemia was not improved. A karyotype of the bone marrow cells from this patient showed 47, XY, +8, i (17q), which has been observed as additional chromosomal abnormalities in blastic crisis of chronic myelogenous leukemia. The diagnosis of CML was not compatible with this case, because Ph1 chromosome and bcr gene rearrangement were negative. It is concluded that eosinophilia and basophilia might be derived from clonal abnormalities associated with MDS.

Aged↗

PubMed1992

Physiological monitoring techniques for home health care.

Practical techniques of nonconstrained physiological monitoring which are acceptable in daily life have been attempted, and obtained preliminary results: Successive records of temperature profile on a bed provide information such as body movement, and sleep hours. ECG can be recorded automatically in a bathtub with electrodes on the inside wall of the tub. Heart rate can be measured by ECG taken at a toilet seat. Proposed techniques do not require any effort of measurement procedure to the subject, and thus it is expected that physiological data can be accumulated automatically even though subjects never aware the monitoring procedure.

Activities of Daily Living↗

PubMed1991

Inhibition of rapid potassium flux during cerebral ischemia in vivo with an excitatory amino acid antagonist.

Previous studies have demonstrated that microdialysis is capable of detecting an abrupt and massive increase in extracellular K+ concentration ([K+]e) and a concomitant increase in extracellular concentration of excitatory amino acids (EAAs) during cerebral ischemia in the rat hippocampus in vivo. Following in situ administration of kynurenic acid (KYN), a broad-spectrum antagonist of EAAs, through the dialysis probe (5-10 mM), a delay in reaching the maximum level of increased [K+]e was observed in a dose-dependent manner. The initial component of the rapid increase in [K+]e appears to be mediated by EAAs released from nerve terminals.

Amino Acids↗

PubMed1991

Calcium-dependent component of massive increase in extracellular potassium during cerebral ischemia as demonstrated by microdialysis in vivo.

This study characterizes the physiological features and limitations of K(+)-free dialysis to detect changes in extracellular concentration of K+ ([K+]e) in the rat hippocampus in vivo. It also demonstrates the effects of Ca(2+)-free perfusate containing Co2+ or Mg2+, which blocks Ca2+ entry into the presynaptic nerve terminal, on the abrupt increase in [K+]e detected by this technique during cerebral ischemia. K(+)-free dialysis for 40 min caused no significant changes in the baseline [K+]e. In contrast, Ca(2+)-free dialysis for 40 min significantly reduced the extracellular Ca2+ concentration. Under this condition, together with addition of Co2+ or Mg2+ to the perfusate, the increase in [K+]e was delayed, and a delay in reaching the maximum level was observed in a dose-dependent manner. These results are consistent with the hypothesis that the initial increase in [K+]e during cerebral ischemia is related to the Ca(2+)-dependent exocytotic release of neurotransmitters from depolarized nerve terminals.

Animals↗

PubMed1991

Sequences involved in brain-specific in vitro transcription from the core promoter of the mouse myelin basic protein gene.

In the previous study, we have shown that a short DNA stretch from -35 to -17 in the core promoter of the mouse myelin basic protein (MBP) gene is mainly responsible for brain-specificity in in vitro transcription. In this study, we found from intensive mutation analysis that the TATA-box sequence at -34 is not critical, but sequences downstream from the TATA-box especially around -20 were important for brain-specificity. The existence of a tissue-specific factor for the MBP core promoter different from the TATA-box-binding factor TFIID is implicated.

Animals↗

PubMed1991

Improved method for preparation of ubiquitin-ligated lysozyme as substrate of ATP-dependent proteolysis.

A simple method was developed for preparation of proteins conjugated with ubiquitin. Heat-denatured 125I-labeled lysozyme was highly ubiquitinated by incubation at pH 9.0 with a ubiquitin-protein ligase system consisting of E1, E2 and E3 that had been partially purified from rabbit reticulocytes by affinity chromatography with ubiquitin as a ligand. The resulting conjugates were separated from free lysozyme and other proteins by successive chromatographies on anion and cation ion-exchange resins. The ubiquitinated 125I-lysozymes recovered in the fraction not adsorbed to either resin served as an efficient substrate for ATP-dependent proteolysis in a reticulocyte lysate or with a purified 26 S protease complex. By the present method, 125I-lysozyme-Ub conjugates can be prepared in 3 h with a high yield of 15-20%.

Adenosine Triphosphate↗

PubMed1991

PCR detection of distal Yp sequences in an XX true hermaphrodite.

An XX true hermaphrodite was examined for the presence of Y-specific sequences using Southern-blotting and polymerase chain reaction (PCR) techniques. Of 25 loci examined, only two, the proximal border of the pseudoautosomal region (PABY) and the sex determining region of the Y chromosome (SRY), were detected. A crossing over event in paternal meiosis, proximal to the SRY locus but distal to the zinc finger protein (ZFY) locus, presumably transferred to two loci to the X chromosome.

Adolescent↗

PubMed1991

Calcium-dependent glutamate release concomitant with massive potassium flux during cerebral ischemia in vivo.

The changes in extracellular glutamate ([Glu]e) and potassium ([K+]e) in the rat hippocampus during cerebral ischemia were determined simultaneously by microdialysis in vivo. Biphasic increases in [Glu]e, i.e. an earlier rapid increase concomitant with an abrupt increase in [K+]e followed by a later slow increase, were observed. Dialysis with Ca(2+)-free perfusate containing Co2+ blocked the earlier rapid increase completely but the later slow increase only partially. These findings suggest that Ca(2+)-dependent exocytotic release from the presynaptic nerve terminals is involved predominantly in the earlier rapid increase in [Glu]d. The later slow increase in [Glu]d may be due in part to a breakdown of membrane function resulting from several causes, including a loss of the electrogenic component of the glutamate gradients across the plasma membrane, and a loss of function of the glutamate uptake system.

Animals↗

PubMed1991

Striking homology of the 'variable' N-terminal as well as the 'conserved core' domains of the mouse and human TATA-factors (TFIID).

A complementary DNA (cDNA) encoding a mouse TFIID (mIID) was isolated from mouse brain cDNA libraries. The 316 amino acid sequence deduced from cDNA sequences revealed the presence of an amino-terminal region enriched in serine, threonine, and proline (STP-cluster), an uninterrupted stretch of 13 glutamine residues (Q-run), a second STP-cluster, and a conserved carboxy-terminal region. Amino acid sequences of the first STP-cluster and the conserved carboxy-terminal region were identical to those of the human TFIID (hIID). However, the Q-run was considerably shorter than that in hIID and sequences in the second STP-cluster diverged from those of the hIID. The murine TFIID transcript is expressed as a 2 kilobase poly(A)+ RNA in the mouse brain. Southern blot analysis identified a single gene copy per haploid mouse genome.

Amino Acid Sequence↗

PubMed1991

Transcription inhibition of the somatic-type phosphoglycerate kinase 1 gene in vitro by a testis-specific factor that recognizes a sequence similar to the binding site for Ets oncoproteins.

To elucidate the mechanism by which transcription of the somatic-type phosphoglycerate kinase 1 gene is inactivated during mammalian spermatogenesis, we examined the presence of specific transcription inhibitor(s) in the testis by a cell-free transcription system. Transcription of the mouse phosphoglycerate kinase 1 gene using nuclear extracts of the rat liver was significantly inhibited by the addition of testis extracts, whereas brain extracts had little effect. Transcription inhibition required the binding of a testis-specific factor, designated TIN-1, to the region between positions -268 and -259 relative to transcription initiation site at +1. This region had the sequence 5'-AGGAAGTTCC-3' that includes an inverted repeat of the binding motif, 5'-GGAA-3', for the oncoprotein Ets. A UV-crosslinking experiment revealed that 43- and 45-kDa polypeptides present in testis extracts bind to that sequence. These results suggest that a testis-specific transcription inhibitor TIN-1 inactivates the phosphoglycerate kinase 1 gene in the mammalian spermatogenic pathway.

Animals↗

PubMed1991

ATP-dependent reversible association of proteasomes with multiple protein components to form 26S complexes that degrade ubiquitinated proteins in human HL-60 cells.

The role of proteasomes in ubiquitin (Ub)-dependent protein degradation was studied by analyzing lysates of human promyelocytic leukemia HL-60 cells by glycerol density gradient centrifugation. High succinyl-Leu-Leu-Val-Tyr-4-methylcoumaryl-7-amide hydrolyzing activity was found in the 26S fraction, whereas the 20S fraction containing proteaomes had no activity. Addition of 0.05% sodium dodecylsulfate to the latter fraction, however, induced marked activity. The 26S, but not the 20S fraction catalyzed ATP-dependent degradation of [125I]lysozyme-Ub conjugate. Depletion from the lysate of ATP caused complete shift of the active 26S complex to the latent 20S form, whereas in the lysate prepared from ATP-depleted cells, ATP converted 20S proteasomes to 26S complexes. The immunoprecipitated 26S complexes were found to consist of proteasomes and 13-15 other proteins ranging in size from 35 to 110 kDa. We conclude that in the lysate, latent proteasomes undergo reversible, ATP-dependent association with multiple protein components to form 26S complexes that catalyze ATP-dependent degradation of Ub-protein conjugates.

Adenosine Triphosphate↗

PubMed1991

Randomized trial of cyclophosphamide, doxorubicin, and vincristine versus cisplatin and etoposide versus alternation of these regimens in small-cell lung cancer.

Between April 1985 and May 1988, we conducted a randomized study comparing two standard chemotherapy regimens with the same regimens given on an alternating basis in patients with small-cell lung cancer. The patients were randomly assigned to receive cyclophosphamide at a dose of 800 mg/m2 intravenously (IV) on day 1, doxorubicin at 50 mg/m2 IV on day 1, and vincristine at 1.4 mg/m2 IV on day 1 (CAV); cisplatin at 80 mg/m2 IV on day 1 and etoposide at 100 mg/m2 IV on days 1, 3, and 5 (PE); or CAV alternating with PE (CAV/PE). Each regimen was repeated every 3-4 weeks. Three hundred patients were entered in the study, and 288 of them were eligible for analysis (97 for CAV, 97 for PE, and 94 for CAV/PE). The response rates for PE (78%) and CAV/PE (76%) were significantly higher than the rate for CAV (55%), while the complete response rates were similar (14%, 16%, and 15%, respectively). Nine (23%) of 39 patients who failed to respond to the initial CAV regimen responded to PE when they were crossed over. In contrast, only one (8%) of 13 patients responded to CAV after failing to respond to the PE regimen, suggesting that these two regimens were partially non-cross-resistant. The response duration on CAV/PE was significantly longer than that with CAV (P = .004). The survival time with CAV/PE (11.8 months) was superior to that with CAV (9.9 months) (P = .027) or that with PE (9.9 months) (P = .056). In patients with limited disease, the survival in the alternating arm was significantly superior to the survival in the CAV arm (P = .014) or the survival in the PE arm (P = .023). The toxic effects were acceptable in all three chemotherapy regimens. These results favor the alternating chemotherapy over either standard chemotherapy, such as CAV and PE, although the differences are not dramatic.

Adult↗

PubMed1991

Desensitization of the epidermal adenylate cyclase system: agonists and phorbol esters desensitize by independent mechanisms.

Exposure of pig epidermis to adenylate cyclase stimulators results in receptor-specific desensitization. We investigated the nature of the agonist-induced desensitization, which was compared with the phorbol ester-induced, receptor-nonspecific desensitization. Both phorbol ester-induced desensitization and the agonist-induced desensitization were accompanied by an increase in forskolin- and cholera toxin-induced cyclic AMP accumulations. The magnitude of the increase in the agonist-induced desensitization was parallel to the degree of the initial cyclic AMP accumulation; histamine and adenosine, which increase more cyclic AMP than epinephrine, resulted in a more marked increase in forskolin- and cholera toxin-induced cyclic AMP accumulations. Similarly, epidermis desensitized to multiple receptors revealed more marked forskolin- and cholera toxin-induced cyclic AMP accumulations than epidermis desensitized to a single receptor. In contrast to the phorbol ester-induced desensitization, agonist-induced desensitization was not affected by the protein kinase C inhibitors H-7 and staurosporin. Further, agonist-induced desensitization was still inducible in phorbol ester-desensitized epidermis and vice versa. In contrast to the agonist-induced desensitization, which is accompanied by the preceding adenylate cyclase stimulation, no evidence for the stimulation of the adenylate cyclase during phorbol ester treatment was obtained. Neither agonist-induced desensitization nor phorbol ester-induced desensitization affected the content of inhibitory guanine nucleotide binding protein of the epidermis, which was monitored by the pertussis toxin (IAP)-catalyzed ADP ribosylation reaction. Our results indicate that agonist-induced desensitization and the phorbol ester-induced desensitization are independent of each other. Although both processes are characterized by increased forskolin- and toxin-induced cyclic AMP accumulations, the former is accompanied by initial cyclic AMP accumulation; the latter is not.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1991

Molecular cloning and sequence analysis of cDNAs for five major subunits of human proteasomes (multi-catalytic proteinase complexes).

Proteasomes are multicatalytic proteinase complexes consisting of a set of non-identical polypeptide components. Of these multiple components, the nucleotide sequences of five major subunits (named HC2, HC3, HC5, HC8 and HC9) of human proteasomes have been determined from recombinant cDNA clones by screening a human HepG2 hepatoblastoma cell cDNA library with rat proteasome cDNAs isolated previously as probes. The polypeptides deduced from their nucleotide sequences consisted of 263, 234, 241, 255 and 261 amino acid residues with calculated molecular weights of 29,554, 25,897, 26,487, 28,431 and 29,482, respectively, which are encoded by single independent genes. The primary structures of these subunits of human proteasomes closely resemble those of their rat counterparts and show considerably high inter-subunit homology, although the homology of HC5 is relatively low. These findings, together with the structural similarities of other eukaryotic proteasomes including those of Drosophila and yeast (Saccharomyces cerevisiae) support and extend the previously proposed concept that eukaryotic proteasome genes form a multi-gene family with the same evolutionary origin.

Amino Acid Sequence↗