Search PubMed⌕ Search

Biomedical subjects

S Nagata

Publications and source records attributed to S Nagata.

At least 199 records · Page 11Linked to original sources
PubMed1998

Alanine dehydrogenase from Enterobacter aerogenes: purification, characterization, and primary structure.

Alanine dehydrogenase [EC 1. 4. 1. 1] was purified to homogeneity from a crude extract of Enterobacter aerogenes ICR 0220. The enzyme had a molecular mass of about 245 kDa and consisted of six identical subunits. The enzyme showed maximal activity at about pH 10.9 for the deamination of L-alanine and at about pH 8.7 for the amination of pyruvate. The enzyme required NAD+ as a coenzyme. Analogs of NAD+, deamino-NAD+ and nicotinamide guanine dinucleotide served as coenzymes. Initial-velocity and product inhibition studies suggested that the deamination of L-alanine proceeded through a sequential ordered binary-ternary mechanism. NAD+ bound first to the enzyme, followed by L-alanine, and the products were released in the order of ammonia, pyruvate, and NADH. The Km were 0.47 mM for L-alanine, 0.16 mM for NAD+, 0.22 mM for pyruvate, 0.067 mM for NADH, and 66.7 mM for ammonia. The Km for L-alanine was the smallest in the alanine dehydrogenases studied so far. The enzyme gene was cloned into Escherichia coli JM109 cells and the nucleotides were sequenced. The deduced amino acid sequence was very similar to that of the alanine dehydrogenase from Bacillus subtilis. However, the Enterobacter enzyme has no cysteine residue. In this respect, the Enterobacter enzyme is different from other alanine dehydrogenases.

Alanine Dehydrogenase↗
PubMed1998

Expression of inhibin alpha-subunit in horse testis.

Inhibin is believed to play roles in the pituitary secretion of FSH and in the paracrine regulation of testicular function. Although it has been generally accepted that inhibin is produced in Sertoli cells, there was a recent evidence for the localization of inhibin in Leydig cells of primates, rat and sheep. However, there is no report on the expression of inhibin in the adult horse testis. Therefore, using immunohistochemistry, western blotting and in situ hybridization techniques, the present study examined inhibin alpha-subunit (Ih-alpha) expression in the adult horse testis. For the detection of Ih-alpha protein, we used anti-porcine Ih-alpha antibody in immunohistochemistry and western blotting. Furthermore, digoxigenin-labeled complementary RNA probes were prepared to detect intracellular messenger RNA (mRNA) of Ih-alpha. Immunostainings for Ih-alpha were found not only in Leydig cells but also in Sertoli cells. The intensity in Leydig cells was stronger than in Sertoli cells. Immunoreactivities for Ih-alpha were found at approximately 46 kDa, 56 kDa and 90 kDa in the homogenates from testicular interstitial tissues. The bands at 56 kDa and 90 kDa agree with previous report, but not at 46 kDa. Signals for mRNA of Ih-alpha by in situ hybridization were detected in Leydig cells and in the basal region of seminiferous epithelium including Sertoli cells. These results suggest that Ih-alpha is expressed in Leydig cells and Sertoli cells of horse testis, and the expression level should be higher in Leydig cells than Sertoli cells.

Animals↗
PubMed1998

[Psychosocial evaluation on the correct recollection of periodic medical checkups of workers. 2. Long-term change in the recalled results of medical checkups].

A self-administered questionnaire study of 333 workers (male 253, female 80) in a manufacturing company was carried out one month after informing the workers of the results of their medical checkups in 1993. The questionnaire included several items such as recalled abnormal findings of health examination and ways of overcoming the abnormal findings, recalled results of their medical checkups in 1992, self-confidence in their recollection of the results, and the usefulness of medical checkups. The following were investigated: the relationship between actual as well as recalled results of medical checkups in 1992 and the recollection of them after one year, the effects of examinations after medical checkups in 1992 on their recollection of the checkup results after one year, the effects of actual as well as recalled 1992 checkup results on the recollection of the results one month after informing the workers of the results of their medical checkups in 1993, assurance of correct recollection of the results, the relationship between the usefulness of medical checkups, explanation of abnormal findings and the percentage of correct answers to the results of medical checkups in 1993 one month after informing the workers of their results. It was found that the percentage of correct answers to the results after one year was significantly lower than that after one month in 1992. The rate decreased with the increase in the number of abnormal items in medical checkups. Moreover, the rate also decreased when the results were abnormal. Further examinations in addition to the medical checkups influenced their recollection somewhat after one year. The results that the workers still remembered in 1992 had a stronger effect on their recalling the results one month after informing them in 1993 than the actual results in 1992. The workers' confidence in their recollection of the results was untrustworthy in the same way as their recollection of the results, and they were not able to maintain the recollection of the correct results, although many of the workers realized the usefulness of the medical checkups. Our results suggest that explanation of abnormal medical findings in 1993 was effective because the percentage of partial concordance between actual and recalled results was much higher in the workers who received the explanation than in the workers who did not receive it.

Adult↗
PubMed1998

[Effect of walking during all weekdays, holidays, and at work on mental and physical health in workers].

In order to clarify the effects of walking under various psychosocial and occupational conditions on psychophysiological health, we examined the relationship between the number of steps walked in several situations, such as on all weekdays, at work, and over the weekend, and the results of medical checkups, psychological tests, Breslow's 7 health practices, and other attitudes toward walking as well as health by using a pedometer in a certain manufacturing company. Most of the workers estimated their usual number of steps walked as being less than actual levels on both weekdays and holidays. Generally, the increased number of steps walked was significantly correlated with increased HDL-cholesterol levels, and decreased Triglyceride levels. Contrary to such physical effects, there were more variations with respect to the relationship between walking and psychological health. Moreover, the development of a walking habit at work resulted in some factors becoming worse, such as relaxation, trait anxiety, and serum AST levels when compared to those on all weekdays and over the weekend. In conclusion, it is necessary to consider several situations in which workers usually walk and we must also practice counseling and education for health promotion, to promote walking for health care in the workplace.

Adult↗
PubMed1998

Embolization of cerebral aneurysms using Guglielmi detachable coils--problems and treatment plans in the acute stage after subarachnoid hemorrhage and long-term efficiency.

This study investigated the problems in treating ruptured aneurysms using Guglielmi detachable coils (GDCs) in the acute stage and evaluated the long-term efficacy in a series of 25 patients with 29 aneurysms. Eight patients with ruptured aneurysm treated within 2 weeks of the onset of subarachnoid hemorrhage (SAH) suffered no mortality or morbidity related to the procedure. Five patients achieved good outcomes despite severe SAH and returned to their previous lives. Three patients had poor clinical outcomes, two related to vasospasm and one related to pulmonary complication. More than 9 months follow-up was completed in 14 patients with 16 aneurysms. All six small aneurysms with small necks were completely obliterated and no recanalization was seen, and two of the eight large or giant aneurysms were completely obliterated. Recanalization was seen in four large or giant aneurysms and one small aneurysm due to coil compaction within 13 months. One patient died of rupture of a large aneurysm 18 months after complete obliteration of the aneurysm. Embolization using GDCs in the acute stage after SAH can prevent rerupture of cerebral aneurysms. However, recanalization due to coil compaction was the major problem in the chronic stage. Intensive follow-up and additional embolization, if necessary, is important.

Aged↗
PubMed1998

Mechanism of impaired left ventricular wall motion in the diabetic heart without coronary artery disease.

OBJECTIVE: To elucidate whether impairment of the myocardial free fatty acid (FFA) metabolism and small vessel abnormalities in the myocardium are etiologic or contributory factors of myocardial dysfunction in patients with NIDDM without any significant coronary artery disease. RESEARCH DESIGN AND METHODS: We performed myocardial imaging with 123I-labeled beta-methyl-p-iodophenyl pentadecanoic acid (BMIPP), a branched analog of FFA, and dipyridamole-infusion 201thallium scintigraphy (Dip) in nine patients who demonstrated left ventricular wall motion abnormalities without any significant coronary artery disease and in fifteen control cases. As an index of myocardial FFA metabolism, the heart-to-mediastinum count ratio (H/M) of BMIPP was calculated from the mean count in the regions of interest at the heart and the upper mediastinum. RESULTS: Nine patients with reduced wall motion documented by left ventriculography (LVG), (hypokinetic group) demonstrated significantly lower BMIPP uptake (2.1 +/- 0.2, mean +/- SD) than fifteen patients with normal wall motion (normokinetic group) (2.3 +/- 0.2, P < 0.05). Regional ventricular wall motion observed by LVG, regional BMIPP uptake, and regional redistribution phenomenon (RD) were evaluated for five regions of the left ventricle: anterior, septal, apical, lateral, and inferoposterior regions. Wall motion was abnormal in 24 out of 120 regions. Regional BMIPP uptake was reduced in 47 regions. RD in Dip was observed in 23 regions. In regional analysis, the existence of defect in the BMIPP image showed significant correlation with wall motion abnormality (P < 0.01), but there was no significant relationship between the RD in Dip and regional wall motion abnormality (P = 0.16). Myocardial biopsy specimens obtained from the right ventricle of 20 patients showed no pathologic changes, with the exception of two patients. CONCLUSIONS: Our findings suggest that impairment of myocardial FFA metabolism rather than small vessel abnormalities in the myocardium is responsible for modest left ventricular dysfunction in patients with diabetes.

Adult↗
PubMed1998

The virtual retinal display: a new technology for virtual reality and augmented vision in medicine.

INTRODUCTION: The Virtual Retinal Display (VRD) is a new technology for creating visual images. It was developed at the Human Interface Technology Laboratory (HIT Lab) by Dr. Thomas A. Furness III. The VRD creates images by scanning low power laser light directly onto the retina. This special method results in images that are bright, high contrast and high resolution. In this paper, we describe how the VRD functions, the special consequences of its mechanism of action and potential medical applications of the VRD, including surgical displays and displays for people with low vision. A description of its safety analysis will also be included. In one set of tests we had a number of patients with partial loss of vision view images with the VRD. There were two groups of subjects: patients with macular degeneration, a degenerative disease of the retina and patients with keratoconus. Typical VRD images are on the order of 300 nanowatts. VRD images are also readily viewed superimposed on ambient room light. In our low vision test subjects, 5 out of 8 subjects with macular degeneration felt the VRD images were better and brighter than the CRT or paper images and they were able to reach the same or better level of resolution. All patients with Keratoconus were able to resolve lines of test several lines smaller with the VRD than with their own correction. Further, they all felt that the VRD images were sharper and easier to view. The VRD is a safe new display technology. The power levels recorded from the system are several orders below the power levels prescribed by the American National Standard. The VRD readily creates images that can be easily seen in ambient roomlight and it can create images that can be seen in ambient daylight. The combination of high brightness and contrast and high resolution make the VRD an ideal candidate for use in a surgical display. Further, tests show strong potential for the VRD to be a display technology for patients with low vision.

Equipment Design↗
PubMed1998

Trigeminal neuralgia caused by the metastasis of malignant lymphoma to the trigeminal nerve: a case report.

The authors cared for a patient suffering from left trigeminal neuralgia who had systemic malignant lymphoma which had been treated with chemotherapy. The lesion of the left trigeminal nerve was not detected by brain CT scans or by the magnetic resonance images made at the onset of trigeminal neuralgia. However, metastasis to the left trigeminal nerve root was disclosed 6 months after the onset of the systemic lymphoma. Open biopsy confirmed lymphomatous involvement of the left trigeminal nerve root. In this case the site of the metastasis was mainly the trigeminal nerve root entry zone in the cerebellopontine cistern, and the lesion caused left trigeminal neuralgia and sensory impairment.

Aged↗
PubMed1997

Membrane Fas ligand kills human peripheral blood T lymphocytes, and soluble Fas ligand blocks the killing.

It has been believed that the Fas expressed on human peripheral blood T cells (PBT) is nonfunctional, because these cells are insensitive to agonistic anti-Fas/Apo-1 mAbs that efficiently kill in vitro-activated T cells and many Fas-expressing cell lines. Here, we demonstrate that membrane-bound Fas ligand (FasL) kills both fresh and in vitro-activated PBT, indicating that the Fas expressed on fresh PBT is functional. In contrast, soluble FasL kills only the latter. Naive T cells in umbilical cord blood do not express Fas, but can be induced to express Fas by IFN-gamma or by a combination of IL-2 and anti-CD28 mAb, after which they acquire sensitivity to membrane but not to soluble FasL. Soluble FasL inhibited the killing of fresh PBT by membrane FasL. These results indicate that the shedding of FasL from the membrane is a mechanism for downregulating at least part of its killing activity.

Adult↗
PubMed1997

No evidence for involvement of mouse protein-tyrosine phosphatase-BAS-like Fas-associated phosphatase-1 in Fas-mediated apoptosis.

Recently, one of the PDZ domains in the cytosolic protein-tyrosine phosphatase Fas-associated phosphatase-1 (FAP-1)/protein-tyrosine phosphatase-BAS (PTP-BAS) was shown to interact with the carboxyl-terminal tS-L-V peptide of the human Fas receptor (Sato, T., Irie, S., Kitada, S., and Reed, J. C. (1995) Science 268, 411-415), suggesting a role for protein (de)phosphorylation in Fas signaling. To investigate whether this interaction is conserved in mouse, we performed yeast two-hybrid interaction experiments and transfection studies in mouse T cell lines. For the corresponding PDZ motif in the mouse homologue of FAP-1/PTP-BAS, protein-tyrosine phosphatase-BAS-like (PTP-BL), only an interaction with human but not with mouse Fas could be detected. Presence of the tS-L-V motif proper, which is unique for human Fas, rather than the structural context of its carboxyl terminus, apparently explains the initially observed binding. To test for functional conservation of any indirect involvement of PTP-BL in Fas-mediated signaling, we generated T lymphoma cell lines stably expressing mouse or human Fas receptor with and without PTP-BL. No inhibitory effect of PTP-BL was observed upon triggering apoptosis using mouse or human Fas-activating antibodies. Together with the markedly different tissue expression patterns for PTP-BL and Fas receptor, our findings suggest that protein-tyrosine phosphatase PTP-BL does not play a key role in the Fas-mediated death pathway.

Animals↗
PubMed1997

Requirement for the CD95 receptor-ligand pathway in c-Myc-induced apoptosis.

Induction of apoptosis by oncogenes like c-myc may be important in restraining the emergence of neoplasia. However, the mechanism by which c-myc induces apoptosis is unknown. CD95 (also termed Fas or APO-1) is a cell surface transmembrane receptor of the tumor necrosis factor receptor family that activates an intrinsic apoptotic suicide program in cells upon binding either its ligand CD95L or antibody. c-myc-induced apoptosis was shown to require interaction on the cell surface between CD95 and its ligand. c-Myc acts downstream of the CD95 receptor by sensitizing cells to the CD95 death signal. Moreover, IGF-I signaling and Bcl-2 suppress c-myc-induced apoptosis by also acting downstream of CD95. These findings link two apoptotic pathways previously thought to be independent and establish the dependency of Myc on CD95 signaling for its killing activity.

3T3 Cells↗
PubMed1997

ERM (ezrin/radixin/moesin)-based molecular mechanism of microvillar breakdown at an early stage of apoptosis.

Breakdown of microvilli is a common early event in various types of apoptosis, but its molecular mechanism and implications remain unclear. ERM (ezrin/radixin/moesin) proteins are ubiquitously expressed microvillar proteins that are activated in the cytoplasm, translocate to the plasma membrane, and function as general actin filament/plasma membrane cross-linkers to form microvilli. Immunofluorescence microscopic and biochemical analyses revealed that, at the early phase of Fas ligand (FasL)-induced apoptosis in L cells expressing Fas (LHF), ERM proteins translocate from the plasma membranes of microvilli to the cytoplasm concomitant with dephosphorylation. When the FasL-induced dephosphorylation of ERM proteins was suppressed by calyculin A, a serine/threonine protein phosphatase inhibitor, the cytoplasmic translocation of ERM proteins was blocked. The interleukin-1beta-converting enzyme (ICE) protease inhibitors suppressed the dephosphorylation as well as the cytoplasmic translocation of ERM proteins. These findings indicate that during FasL-induced apoptosis, the ICE protease cascade was first activated, and then ERM proteins were dephosphorylated followed by their cytoplasmic translocation, i.e., microvillar breakdown. Next, to examine the subsequent events in microvillar breakdown, we prepared DiO-labeled single-layered plasma membranes with the cytoplasmic surface freely exposed from FasL-treated or nontreated LHF cells. On single-layered plasma membranes from nontreated cells, ERM proteins and actin filaments were densely detected, whereas those from FasL-treated cells were free from ERM proteins or actin filaments. We thus concluded that the cytoplasmic translocation of ERM proteins is responsible for the microvillar breakdown at an early phase of apoptosis and that the depletion of ERM proteins from plasma membranes results in the gross dissociation of actin-based cytoskeleton from plasma membranes. The physiological relevance of this ERM protein-based microvillar breakdown in apoptosis will be discussed.

Animals↗
PubMed1997

Transforming growth factor-beta1 abrogates Fas-induced growth suppression and apoptosis of murine bone marrow progenitor cells.

Fas, a member of the tumor necrosis factor (TNF ) receptor superfamily is a critical downregulator of cellular immune responses. Proinflammatory cytokines like interferon-gamma (IFN-gamma) and TNF-alpha can induce Fas expression and render hematopoietic progenitor cells susceptible to Fas-induced growth suppression and apoptosis. Transforming growth factor-beta1 (TGF-beta1 ) is an essential anti-inflammatory cytokine, thought to play a key role in regulating hematopoiesis. In the present studies we investigated whether TGF-beta1 might regulate growth suppression and apoptosis of murine hematopoietic progenitor cells signaled through Fas. In the presence of TNF, activation of Fas almost completely blocked clonogenic growth of lineage-depleted (Lin-) bone marrow (BM) progenitor cells in response to granulocyte-macrophage colony-stimulating factor (GM-CSF ), CSF-1, or a combination of multiple cytokines. Whereas TGF-beta1 alone had no effect or stimulated growth in response to these cytokines, it abrogated Fas-induced growth suppression. Single-cell studies and delayed addition of TGF-beta1 showed that the ability of TGF-beta1 to inhibit Fas-induced growth suppression was directly mediated on the progenitor cells and not indirect through potentially contaminating accessory cells. Furthermore, TGF-beta1 blocked Fas-induced apoptosis of Lin- BM cells, but did not affect Fas-induced apoptosis of thymocytes. TGF-beta1 also downregulated the expression of Fas on Lin- BM cells. Thus, TGF-beta1 potently and directly inhibits activation-dependent and Fas-mediated growth suppression and apoptosis of murine BM progenitor cells, an effect that appears to be distinct from its ability to induce progenitor cell-cycle arrest. Consequently, TGF-beta1 might act to protect hematopoietic progenitor cells from enhanced Fas expression and function associated with proinflammatory responses.

Animals↗
PubMed1997

Activation of distinct caspase-like proteases by Fas and reaper in Drosophila cells.

The cytoplasmic region of Fas, a mammalian death factor receptor, shares a limited homology with reaper, an apoptosis-inducing protein in Drosophila. Expression of either the Fas cytoplasmic region (FasC) or of reaper in Drosophila cells caused cell death. The death process induced by FasC or reaper was inhibited by crmA or p35, suggesting that its death process is mediated by caspase-like proteases. Both Ac-YVAD aldehyde and Ac-DEVD aldehyde, specific inhibitors of caspase 1- and caspase 3-like proteases, respectively, inhibited the FasC-induced death of Drosophila cells. However, the cell death induced by reaper was inhibited by Ac-DEVD aldehyde, but not by Ac-YVAD aldehyde. A caspase 1-like protease activity that preferentially recognizes the YVAD sequence gradually increased in the cytosolic fraction of the FasC-activated cells, whereas the caspase 3-like protease activity recognizing the DEVD sequence was observed in the reaper-activated cells. Partial purification and biochemical characterization of the proteases indicated that there are at least three distinct caspase-like proteases in Drosophila cells, which are differentially activated by FasC and reaper. The conservation of the Fas-death signaling pathway in Drosophila cells, which is distinct from that for reaper, may indicate that cell death in Drosophila is controlled not only by the reaper suicide gene, but also by a Fas-like killer gene.

Animals↗
PubMed1997

Involvement of STAT3 in the granulocyte colony-stimulating factor-induced differentiation of myeloid cells.

Granulocyte colony-stimulating factor (G-CSF) stimulates proliferation and differentiation of the progenitor cells of neutrophilic granulocytes. The binding of G-CSF to its receptor specifically activates JAK1 and JAK2 kinases, as well as STAT3, a signal transducer and activator of transcription (STAT). To examine the role of STAT3 in G-CSF receptor-mediated signal transduction, two different forms of the dominant negative STAT3 were introduced into a mouse myeloid cell line that exogenously expresses the mouse G-CSF receptor. In response to G-CSF, the parental myeloid cells grew for about 4 days, and then they stopped dividing and differentiated into cells with lobulated nuclei. During this period, the expression of the myeloperoxidase (MPO) gene was induced, while c-myc gene expression was down-regulated. In contrast, in the cells expressing the dominant negative STAT3, G-CSF could induce neither growth arrest nor morphological change. However, the induction of the MPO gene by G-CSF was not affected by the dominant negative STAT3. These results indicate that STAT3 activation is responsible for part of the G-CSF-induced differentiation of neutrophils but that another pathway, involving the expression of the MPO gene, that does not utilize the activated STAT3, is also required to fully differentiate the cells.

Acute-Phase Proteins↗
PubMed1997

Binding of NF-Y transcription factor to one of the cis-elements in the myeloperoxidase gene promoter that responds to granulocyte colony-stimulating factor.

The expression of the myeloperoxidase (MPO) gene is restricted to cells of the myeloid cell lineage and is induced by granulocyte colony-stimulating factor (G-CSF). In this study, a series of deletion mutations was introduced in the promoter of the human MPO gene, which was then fused to the chloramphenicol acetyltransferase gene. The G-CSF-induced promoter activity was examined in mouse myeloid precursor FDC-P1 transformants that constitutively express the G-CSF receptor. A G-CSF-responsive element (GRE) in the MPO gene was found approximately 800 base pairs upstream from the transcription initiation site. When the 5'-flanking region of the human MPO gene contained this element, it yielded promoter activity in cells cultured with G-CSF but not in cells cultured with interleukin 3. Gel shift assays with the element showed that a specific nuclear factor(s) (NF/G-CSF) binds to the element. The NF/G-CSF was purified by affinity chromatography using an oligonucleotide of GRE. Protein sequence analysis of the purified NF/G-CSF indicated that NF/G-CSF is a ubiquitous transcription factor, NF-Y, which is composed of three subunits. The recombinant NF-Y was then shown to bind to GRE in a combination of the three subunits.

Animals↗