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M Taira

Publications and source records attributed to M Taira.

At least 217 records · Page 12Linked to original sources
PubMed1987

Replacement of lysine residue 1030 in the putative ATP-binding region of the insulin receptor abolishes insulin- and antibody-stimulated glucose uptake and receptor kinase activity.

To test whether the tyrosine kinase activity of the insulin receptor is crucial for insulin action, we have constructed mutations of the human insulin receptor at Lys-1030, which is in the presumed ATP-binding region. By using oligonucleotide-directed mutagenesis, this lysine residue was replaced with either methionine, arginine, or alanine. Chinese hamster ovary cells were transfected by mutant cDNAs and the expressed insulin receptors were characterized. We show here that none of these mutants exhibited insulin-activated autophosphorylation and kinase activity in vitro. They also do not mediate insulin- and antibody-stimulated uptake of 2-deoxyglucose. The tyrosine kinase activity is thus required for a key physiological response of insulin.

Adenosine Triphosphate↗
PubMed1987

cDNA sequence of human transforming gene hst and identification of the coding sequence required for transforming activity.

The hst gene was originally identified as a transforming gene in DNAs from human stomach cancers and from a noncancerous portion of stomach mucosa by DNA-mediated transfection assay using NIH3T3 cells. cDNA clones of hst were isolated from the cDNA library constructed from poly(A)+ RNA of a secondary transformant induced by the DNA from a stomach cancer. The sequence analysis of the hst cDNA revealed the presence of two open reading frames. When this cDNA was inserted into an expression vector containing the simian virus 40 promoter, it efficiently induced the transformation of NIH3T3 cells upon transfection. It was found that one of the reading frames, which coded for 206 amino acids, was responsible for the transforming activity.

Amino Acid Sequence↗
PubMed1986

Transforming gene from human stomach cancers and a noncancerous portion of stomach mucosa.

DNAs from 21 human stomach cancers, 16 metastatic stomach cancers to lymph nodes, and 21 apparently noncancerous specimens of stomach mucosae from a total of 26 patients with stomach cancer were tested for their ability to induce neoplastic transformation of NIH 3T3 cells on transfection by the calcium phosphate precipitation technique. Three samples of DNA were shown to have transforming activity; one was from a primary stomach cancer of one patient, the second was from a noncancerous portion of stomach mucosa of the same patient, and the third was from a lymph node metastasis of stomach cancer from another patient. These transformants were tumorigenic in nude mice, and DNAs from the cells could induce secondary transformants. A portion of the transforming gene from the stomach cancer of one patient, which contained the sequences expressed in the NIH 3T3 transformants, was cloned. The transforming gene did not have any homology with the transforming sequences reported previously. We have applied the term hst to this novel human transforming gene. The transforming gene, hst, was found to be present in all the primary and secondary transformants induced by the other two samples of DNA.

Adenocarcinoma↗
PubMed1986

Amplifications of both c-Ki-ras with a point mutation and c-myc in a primary pancreatic cancer and its metastatic tumors in lymph nodes.

Activated c-Ki-ras with a point mutation (GGT to CGT) at codon 12, resulting in the substitution of arginine for glycine, was found in DNA from metastatic pancreatic adenocarcinoma in a lymph node. By means of restriction endonuclease length polymorphism with SacI digestion, we were able to demonstrate that the same point mutation of c-Ki-ras was present in the primary tumor and in metastases in lymph nodes. DNA from the normal spleen of the patient did not have this type of point mutation. Moreover, amplifications of 3- to 6-fold of the activated c-Ki-ras and 50-fold of c-myc were found in the primary tumor and the metastases in the two lymph nodes, indicating that point mutation had occurred at a relatively early stage of the tumor development, before amplification of the gene. This is the first clear demonstration of amplification of activated c-Ki-ras accompanied by amplification of c-myc in both primary and metastatic human tumors in vivo.

Base Sequence↗
PubMed1985

Inversely repeating integrated hepatitis B virus DNA and cellular flanking sequences in the human hepatoma-derived cell line huSP.

Among recombinant phages carrying integrated hepatitis B virus (HBV) DNA sequences cloned from the human hepatoma-derived cell line huSP, one clone, lambda hu-489, revealed some unusual features. The 2.25-kilobase Eco D fragment from the insert of this clone hybridized to the HBV DNA probe only and its nucleotide sequence was determined. The viral sequence, as well as a cellular flanking sequence, showed extensive rearrangement accompanied by inverted repetition. The Eco D fragment contained HBV DNA from the 5'-end region of gene S to the middle of gene X, followed by a long cellular flanking sequence. Moreover, a part of gene X was found inversely repeated at the head of the same gene S in a head-to-head configuration truncated by the same cellular sequence. Therefore, the same junction sequence of viral DNA and the cellular sequence was found at two different sites in the Eco D fragment in opposite polarities.

Base Sequence↗
PubMed1985

[Long-term toxicological studies with mizoribine (Bredinin) in beagle dogs (the first report). Blood chemistries, pharmacokinetics of mizoribine and fertility studies of the male dogs].

For long-term toxicological studies, mizoribine at the dose of 2.5 mg/kg body weight was administered orally to two male and two female Beagle dogs for 36 consecutive months, once a day, 6 days a week, with a day-off on the 7th of each week. As a control group, 2 male and 2 female dogs were kept under the same conditions as the treated group. The above experiment resulted in no abnormal general symptoms being found in either group. In addition, body weight gain instead of weight loss was observed in both groups. Moreover, hematological and biological parameters were in the normal range, and no statistical difference was obtained between the two groups. An additional 10 mg/kg of mizoribine was administered once to both groups at the months of 6, 12, 18, 24, or 36 after the onset of this toxicological study so as to determine the pharmacokinetic behavior of serum mizoribine. This resulted in no significant difference being observed between the two groups. Therefore, it can be inferred that accumulation of mizoribine is not induced by its long-term repeated administration. In fertility study, the analysis of the sperm and the mating ability of a male dog with an appropriate healthy female dog revealed that mizoribine at this dose did not provoke any abnormalities in male gonadal functions.

Animals↗
PubMed1984

Activity during active sleep of bulbar reticular neurons firing rhythmically during mastication in cats.

Unitary activity was recorded from 17 bulbar reticular neurons, which fired rhythmically during mastication, in unanesthetized, spontaneously respiring cats during sleep and wakefulness. All these neurons showed the highest mean firing rate during food ingestion, and none of them showed any tonic discharge during active sleep. The results are discussed in terms of a functional differentiation of bulbar reticular inhibitory neurons projecting to jaw-closer motoneurons in relation to phasic inhibition during mastication and tonic inhibition during active sleep of jaw-closer motoneurons.

Animals↗
PubMed1984

Role of medullary reticular neurons in the inhibition of trigeminal motoneurons during active sleep.

We sought to identify those cells involved in the generation of atonia of the masseter muscles during active sleep. A neuronal population was examined in the medullary reticular formation which has been shown to project monosynaptically to trigeminal motoneurons and provide inhibitory input to them. These neurons exhibited a pattern of state-dependent discharge which was characterized by a tonic increase in firing frequency which paralleled the tonic decrease in somatomotor reflex activity (within the trigeminal system) in the continuum of wakefulness to quiet (NREM) sleep to active sleep. This population of cells discharged at extremely high rates during active sleep, especially during periods of rapid eye movements, when postsynaptic inhibitory control of motoneurons is most prominent. We therefore suggest that these medullary units are the inhibitory neurons which are responsible for the postsynaptic inhibition of trigeminal motoneurons during active sleep.

Animals↗
PubMed1983

Rearrangement of the surface antigen gene of hepatitis B virus integrated in the human hepatoma cell lines.

The rearrangement of integrated HBV DNA sequences in three different hepatoma cell lines, huH-1, huH-2, KG-55-T from Japanese patients, were studied by blot hybridization using whole HBV genome or a HBsAg or HBcAg DNA as a probe. The characteristic existence of multiple integration sites of HBV DNA sequences in each HindIII-restricted hepatoma cell DNA was revealed by the HBV genome probe. Detection of the isolated HBsAg gene in the HindIII fragment indicates that the integration of HBV DNA was not always related to the maintenance of the whole viral genome, and that movement of the HBsAg gene to another location occurred by rearrangement. On the other hand, the presence of the HBV DNA sequence without the intact HBcAg gene was shown in some of the HindIII fragments, when the HBcAg gene, probe was used, but a HindIII fragment, containing only the HBcAg gene, was not detected so far. The absence of the intact HBcAg gene suggests that the viral genome may lose a part of the HBcAg gene in the process of integration. This is consistent with recent findings of Ogston et al. (1982) that in Woodchuck hepatocellular carcinoma viral sequences are extensively rearranged.

Base Sequence↗
PubMed1983

Tumor-associated mutations of rat mitochondrial transfer RNA genes.

Mitochondrial DNA is a sensitive target of chemical carcinogens (Backer and Weinstein (1980) Science 209, 297-299), suggesting that mutations of the mitochondrial genome occur in tumor cells. We examined this point by comparing mitochondrial DNA sequences in four rat tumors with those of normal rat liver. Some novel mutations found in the tRNA genes of tumor mitochondria were as follows: nucleotides deletions in the aminoacyl-acceptor stem of the tRNATyr gene or in the anticodon stem of the tRNATrp gene and insertions in the "YpsiC" loop of the tRNACys gene. These structures are extraordinary compared with those of the tRNA genes of other mammals, indicating that these mutations are each associated with a corresponding tumor.

Animals↗
PubMed1983

Phase-linked variations in the amplitude of the digastric nerve jaw-opening reflex response during fictive mastication in the rabbit.

The diagastric nerve reflex response to stimulation of the upper lip was studied in urethan-anesthetized rabbits paralysed with pancuronium bromide. Rhythmic bursts of masticatory activity were evoked in the nerve by repetitive electrical stimulation of the motor cortex. The amplitude and latency of the reflex responses during fictive mastication were compared with preceding control values. When stimuli close to threshold were given, the largest and earliest responses occurred during the digastric burst. When intense stimuli were employed, the largest responses were out of phase with the burst, although the latency was still shortest when the motoneurons were rhythmically active. Since the pattern is essentially the same as that seen during normal mastication, we conclude that the cyclical modulation of reflex amplitude and latency is not the result of sensory feedback generated by the movements themselves but is instead governed by the central motor program.

Animals↗
PubMed1982

A new RNA polymerase and in vitro transcription of the origin of replication from rat mitochondrial DNA.

A new RNA polymerase was found in a rat mitochondrial extract. This enzyme showed strong template preference in vitro for the supercoiled recombinant plasmid consisting of pBR322 and the D-loop region of rat mtDNA carrying the origin of heavy-strand replication. The main products synthesized by the D-loop region were two RNAs of different sizes. Both of these products were light-strand products transcribed from the region upstream from the origin of replication. This specific transcription is discussed in relation to initiation of primer RNA synthesis for heavy-strand replication of rat mtDNA.

Animals↗