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Biomedical subjects

M Taniguchi

Publications and source records attributed to M Taniguchi.

At least 487 records · Page 27Linked to original sources
PubMed1993

Melatonin release from pineal cells of diurnal and nocturnal birds.

Melatonin release from the pineal cells of chicks, pigeons and crows (diurnal birds) in vitro was compared with that from owls (a nocturnal bird). The pineal cells of diurnal birds secreted large amounts of melatonin during the dark period, whereas owl pineal cells released virtually no melatonin over 24 h and did not respond to exogenous stimulant agents. Histological examination revealed that the owl pineal gland is very small and has a poor vascular network. These results suggest that the pineal gland of owls may have degenerated and is not involved in the circadian clock mechanism in this species.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Cloning and chromosome mapping of the human Mel-18 gene which encodes a DNA-binding protein with a new 'RING-finger' motif.

It has recently been reported that there exists a new 'RING-finger' protein family among the zinc-finger (Zf) proteins. Previously, we had isolated the mouse Mel-18 cDNA (mMel-18) encoding the nuclear RING-finger protein that exhibits an ability to bind to a nonspecific DNA column. Here, we have isolated and characterized the human Mel-18 cDNA (hMel-18) using the mMel-18 cDNA as a probe. The deduced hMel-18 protein contains 344 amino acids (38 kDa) with a RING-finger motif, a helix-loop-helix (HLH)-like structure and a Pro/Ser-rich region. The hMel-18 gene is conserved among vertebrates. Its mRNA is highly expressed in placenta, lung and kidney, but the level is low in liver, pancreas and skeletal muscle. Using in situ hybridization, we mapped hMel-18 to band q22 of chromosome 12. It is possible that the Mel-18/bmi-1 gene family represents a mammalian homologue of the Drosophila polycomb gene group.

Amino Acid Sequence↗
PubMed1993

Tyrosine kinase activity of the ret proto-oncogene products in vitro.

We investigated tyrosine kinase activity of the ret proto-oncogene products (proto-Ret proteins), using a cell lysate of NB-39-nu neuroblastoma cells. The 150 kDa and 170 kDa proto-Ret proteins immunoprecipitated with antibodies against their carboxy-terminal 20 amino acids were shown to be phosphorylated predominantly on tyrosine residues in immunocomplex kinase assay. The level of tyrosine phosphorylation of the 150 kDa proto-Ret protein was approximately 10-fold higher than that of the 170 kDa proto-Ret protein, although both proteins were expressed at similar levels in neuroblastoma cells. This result was confirmed by using a lysate of SK-N-MC human primitive neuroectodermal tumor cells transfected with the ret proto-oncogene. The kinase activity of proto-Ret proteins was significantly inhibited by antibodies against their kinase domain, indicating that these antibodies recognize crucial epitopes for the enzymatic activity. On the other hand, the proto-Ret proteins were not phosphorylated in vivo in NB-39-nu cells and SK-N-MC transfectants.

Amino Acids↗
PubMed1993

Extrathymic development of V alpha 14-positive T cells.

It is known that rearrangement of the T cell antigen receptor (TCR) gene occurs in the thymus during T cell development and consequently results both in the deletion of DNA between the variable (V) and diversity/joining segments and in the formation of a circular DNA with recombination signal sequences. Here, we provide evidence that V alpha 14+ TCR gene rearrangements take place in extrathymic sites, such as bone marrow, liver, and intestine, but not in spleen, because we were able to detect frequent productive and nonproductive V alpha 14+ coding and signal sequences as a result of TCR rearrangements in extrathymic sites. Similar findings were also detected in athymic mice. Quantitative analysis shows that the relative amounts of V alpha 14 gene-mediated signal sequences in extrathymic tissues are higher than those in thymus. On the contrary, TCR rearrangements of V alpha 1.1 T cells, which are known to develop in the thymus, were mainly detected in the thymus, Peyer's patch, and spleen, but not in other extrathymic tissues, showing patterns distinct from V alpha 14 TCR rearrangements. These findings are evidence of extrathymic development of V alpha 14+ T cells. Differential characteristic TCR rearrangement patterns also indicate that distinct TCR repertoires are generated in different lymphoid tissues.

Animals↗
PubMed1993

Na+/H+ exchanger and reperfusion-induced ventricular arrhythmias in isolated perfused heart: possible role of amiloride.

The roles of the Na+/H+ exchange system in the development and cessation of reperfusion induced ventricular arrhythmias were studied in the isolated perfused rat heart. The hearts were perfused in the working heart mode with modified Krebs Henseleit bicarbonate (KHB) buffer and whole heart ischemia was induced by a one-way ball valve with 330 beat/min pacing. Ischemia was continued for 15 min followed by 20 min of aerobic reperfusion (control). Amiloride (1.0 mM), an inhibitor of the Na+/H+ exchange system, was added to the KHB buffer only during reperfusion (group B) or only during ischemic periods (group C). Electrocardiographic and hemodynamic parameters were monitored throughout the perfusion. Coronary effluent was collected through pulmonary artery cannulation and PO2, PCO2, HCO3- and pH were measured by blood-gas analyzer. The incidence of reperfusion induced ventricular arrhythmias was 100%, 100% and 0% in control, group B and group C, respectively. The mean onset time of termination of reperfusion arrhythmias was significantly shorter in group B than in control. PCO2 increased from 39.0 +/- 0.9 to 89.3 +/- 6.0 mmHg at the end of ischemia in control and from 40.6 +/- 0.4 to 60.5 +/- 5.8 in group C, the difference between groups was statistically significant. HCO3- level decreased from 21.8 +/- 0.1 to 18.3 +/- 0.5 mmol/l in control, however, this decrease was significantly inhibited in group C (from 22.0 +/- 0.5 to 20.3 +/- 0.2). The increase in PCO2 and the decrease in HCO3- in group B were similar over time to those observed in control.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1993

Comparison of acceptor protein specificities on the formation of ADP-ribose.acceptor adducts by arginine-specific ADP-ribosyltransferase from rabbit skeletal muscle sarcoplasmic reticulum with those of the enzyme from chicken peripheral polymorphonuclear cells.

We compared acceptor-protein specificities on the formation of ADP-ribose.acceptor adducts by arginine-specific ADP-ribosyltransferase (EC 2.4.2.31) purified from rabbit skeletal muscle sarcoplasmic reticulum (SR) with those of the enzyme purified from chicken peripheral polymorphonuclear cells (heterophils). Major differences are as follows: (1), p33 and beta/gamma-actin, preferential endogenous acceptor proteins for the modification by the heterophil enzyme (Mishima, K., Terashima, M., Obara, S., Yamada, K., Imai, K and Shimoyama, M. (1991) J. Biochem. 110, 388-394 and Terashima, M., Mishima, K., Yamada, K., Tsuchiya, M., Wakutani, T. and Shimoyama, M. (1992) Eur. J. Biochem. 204, 305-311) were not modified by the SR enzyme. (2), The modification of p33 by the heterophil enzyme was enhanced by addition of polyanions such as DNA while the protein did not function as acceptor for modification by the SR enzyme even in the presence of DNA. (3), To ADP-ribosylate endogenous substrate Ca(2+)-transporting ATPase (EC 3.6.1.38) of rabbit skeletal muscle SR, the SR ADP-ribosyltransferase required polycations such as poly(L-lysine), whereas the heterophil enzyme modified the ATPase in the absence of poly(L-lysine). These results suggest that vertebrate arginine-specific ADP-ribosyltransferase prefers its own acceptor protein for the modification. Some other properties of the SR and the heterophil ADP-ribosyltransferases were also compared.

Adenosine Diphosphate Ribose↗
PubMed1993

ATP-dependent protein synthesis in isolated pea chloroplasts. Evidence for accumulation of a translation intermediate of the D1 protein.

In the presence of externally added ATP, in the dark, isolated pea chloroplasts accumulate two proteins of molecular masses of about 22 and 24 kDa which precipitate with specific antibodies raised against the D1 protein. By chasing in the light, these proteins disappeared on the fluorogram concomitant with the appearance of the precursor- and mature-sized D1 proteins. Polysome analysis indicated that the 22-kDa component is associated with membrane-bound ribosomes and is thus ascribed to a translation intermediate of the D1 protein. On the other hand, the 24-kDa component could not be found in the polysome fraction under the experimental condition used, suggesting the possibility that this component is a degradation product of the D1 protein. The conclusion from this analysis is that the synthesis and/or stable accumulation of the D1 protein requires factor(s) caused by illumination, in addition to ATP, in isolated pea chloroplasts.

Adenosine Triphosphate↗
PubMed1993

Effects of four intravenous anesthetic agents on motor evoked potentials elicited by magnetic transcranial stimulation.

The influence of four intravenous anesthetic agents on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (magnetic MEP) was examined in 77 subjects. The patients were anesthetized by a continuous intravenous infusion of one of the following anesthetic agents: propofol, etomidate, methohexital, or thiopental. Comparable anesthetic effects among the four agents were achieved by computing an infusion scheme for each drug. Infusion rates were increased slowly in a step-wise manner in order to reach minimal anesthetic blood concentrations within 15 minutes. During anesthesia induction, magnetic MEPs were recorded every 2 minutes from the abductor pollicis brevis muscle. The patient's level of consciousness was assessed and documented in the alternating minutes. A dose-related reduction of the MEP amplitudes was seen in all drug groups, while the latencies remained constant. Reduction of the amplitude was occasionally so prominent that the MEP was completely abolished before adequate anesthesia was achieved. MEPs were obtainable at the end of anesthesia induction in 14% of the propofol group (n = 22), 57% of the etomidate group (n = 21), 53% of the methohexital group (n = 19), and 20% of the thiopental group (n = 15). Propofol and thiopental showed significantly stronger suppression of MEP, when compared to etomidate (both P < 0.01) and to methohexital (P = 0.01 and 0.05, respectively). Etomidate was the least detrimental anesthetic agent for intraoperative monitoring of magnetic MEP. Nonetheless, the low incidence of 57% of preserved MEP in subjects without motor deficits indicated the inadequacy of this technique for intraoperative monitoring. More effective transcranial stimulation techniques are required for successful intraoperative MEP monitoring.

Adult↗
PubMed1993

A new Pax gene, Pax-9, maps to mouse chromosome 12.

Members of the Pax gene family have recently been shown to play important roles in mouse embryogenesis. Of eight so far characterized Pax genes, three have been associated with mouse developmental mutants. Here we report the cloning of a new Pax gene, Pax-9. Most of the DNA sequence encoding the highly conserved paired domain has been determined and compared with previously known paired domains. This comparison classifies Pax-9 as a member of the same subgroup as Pax-1/undulated. By analysis of the segregation of a Pax-9 restriction fragment length polymorphism and a large number of simple sequence length polymorphisms in an interspecific C57BL/6 x Mus musculus mollosinus backcross, Pax-9 was mapped close to the D12Nds1 locus on the proximal part of Chromosome (Chr) 12.

Amino Acid Sequence↗
PubMed1993

Liver sarcoidosis showing low-density intrahepatic septa on postcontrast computed tomography.

The authors present a patient with massive liver sarcoidosis, showing only slight hepatomegaly on precontrast computed tomogram and multiple low-density intrahepatic septa on postcontrast computed tomogram. Sarcoidosis frequently involves the liver, but rarely shows abnormal findings other than hepatomegaly on computed tomograms. Only a few cases have demonstrated a low density intrahepatic area on computed tomograms. In this report, we present a patient with massive liver and pulmonary sarcoidosis, showing low density intrahepatic septa and pulmonary fibrosis on computed tomograms.

Humans↗
PubMed1993

A case of chronic pancreatitis complicated by massive pericardial and right pleural effusion.

A 42-year-old man was admitted complaining of dyspnea. Chest X-ray showed an increase in cardiac size, and echocardiography revealed a large volume of pericardial effusion. Pancreatic enzyme levels were elevated in both serum and pericardial effusion. Computed tomography and endoscopic retrograde pancreatography demonstrated a fistula connecting a pancreatic pseudocyst with the pericardium and the right pleural cavity. Massive pericardial and right pleural effusion is an extremely rare complication of chronic pancreatitis. In this case, computed tomography and endoscopic retrograde pancreatography were useful for diagnosing the fistula.

Adult↗
PubMed1993

Neuroblastoma in a transgenic mouse carrying a metallothionein/ret fusion gene.

We have recently succeeded in producing transgenic mice carrying a hybrid gene consisting of mouse metallothionein promoter-enhancer and the ret oncogene (MT/ret). (Iwamoto et al., 1991b). A retroperitoneal tumour developed in one of 17 MT/ret transgenic founder mice. Histological analysis revealed that the tumour consisted of undifferentiated neuroblasts and differentiated ganglion cells, the latter of which were strongly positive for neuron specific enolase. Expression of the ret transgene was observed at high levels in RNA from the tumour, but not in those of other normal tissues. In addition, a 100kDa ret protein was detected in the cell lysate of the tumour. Taken together with our previous data, these results suggest a possible role for the ret oncogene in the proliferation of neural crest cells.

Animals↗
PubMed1993

The fetal thymus stores immature hemopoietic cells capable of differentiating into non-T lineage cells constituting the thymus stromal element.

Immature hemopoietic cell lines were established by transforming fetal thymocytes in vitro with a ts mutant of Abelson murine leukemia virus. They are positive for c-kit and IL-2R alpha but negative for lineage specific markers. Their TCR and Ig heavy chain genes are in germline configuration, and are expressed as germline gene transcripts. When these cell lines were stimulated in vitro with IL-1 their morphology changed into that of typical macrophages (M phi). Subsequent analysis of a particular clone, which displayed the morphological change at the highest efficiency among established cell lines, indicated that the clone possesses the capacity to differentiate into I-A-M phi capable of secreting several cytokines, and supporting the proliferation of fetal and adult thymocytes in vitro. If their surface markers are considered, their normal counterparts would be present in a minor subset of CD4-CD8- double-negative cells in the thymus in early development. The results raise the possibility that the thymic organ at an early stage of development stores immature hemopoietic cells capable of differentiating into a non-T lineage constituting the thymic stromal elements.

Abelson murine leukemia virus↗
PubMed1993

Intestinal intraepithelial lymphocytes preferentially repopulate the intestinal epithelium.

We have used C.B-17 severe combined immune deficiency (SCID) mice to study the repopulation of intestinal intraepithelial cells in these mice. We have found that intestinal intraepithelial lymphocytes (IELs) injected into SCID mice preferentially repopulate the intestinal epithelium. About 5 weeks after injection we can detect significant numbers of IEL in repopulated SCID mice. Repopulation occurs in approximately 70% of the injected mice and the amount of recovered cells per mouse is variable. The recovered cells are of donor-type origin and exhibit a typical IEL phenotype. The donor-type T lymphocytes that can sometimes be found in other organs of IEL-repopulated SCID mice are generally of low number. They are not stained with antibodies against IEL-specific markers and their phenotypes appear to be more typical for T cells normally found in these sites. In contrast, the intestinal epithelium of SCID mice cannot be efficiently repopulated with lymphocytes using cells of other organs including thymocytes, Peyer's patch lymphocytes, and bone marrow cells. From our data we conclude that intestinal IELs are confined to the intestinal epithelium and possibly contain a precursor-type cell that preferentially regenerates cells of its own population.

Animals↗