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Biomedical subjects

N Sato

Publications and source records attributed to N Sato.

At least 19 recordsLinked to original sources
PubMed1995

Elevated calcium level induces calcium-dependent proteolysis of A-CAM (N-cadherin) in heart--analysis by detergent-treated model.

Calcium overload induces cardiac muscle cell dysfunction in cardiovascular diseases. We investigated the effects of elevated calcium level on adherens-junction-specific cell adhesion molecule (A-CAM). Incubation of Triton X-100-treated canine heart homogenate in the presence of Ca2+ reduced the content of A-CAM. Reduction in A-CAM requires milli-molar Ca2+ and was inhibited by protease inhibitors, leupeptin and calpeptin. Immunohistochemical observation revealed that m-calcium-activated neutral protease (m-CANP) was colocalized with A-CAM in intercalated disks. These data suggested that m-CANP proteolyzes A-CAM in response to calcium overload in cardiac muscle.

Animals↗
PubMed1995

Cloning, subcellular localization and expression of CHL1, a subunit of magnesium-chelatase in soybean.

Mg-insertion is the first committed step in chlorophyll synthesis and is catalyzed by Mg-chelatase. In photosynthetic bacteria, bchI gene product was suggested to be a subunit of Mg-chelatase. We isolated a bchI homolog from a soybean cDNA library and designated it as chlI. CHLI consisted of 421 amino acid residues and the sequence exhibited a high similarity to other BchI homologs. CHLI contained an ATP-binding motif found in other BchI homologs. CHLI was localized in the soluble fraction in soybean chloroplasts, suggesting that it was a stromal subunit of Mg-chelatase. chlI mRNA in cell culture (SB-P) of soybean was reversibly induced by light.

Adenosine Triphosphate↗
PubMed1995

70-kDa heat shock cognate protein interacts directly with the N-terminal region of the retinoblastoma gene product pRb. Identification of a novel region of pRb-mediating protein interaction.

Retinoblastoma protein (pRb) functions as a tumor suppressor, and certain proteins are known to bind to pRb in the C-terminal region. Although the N-terminal region of pRb may also mediate interaction with some proteins, no such protein has been identified yet. We demonstrated previously the in vivo protein association between pRb and 73-kDa heat shock cognate protein (hsc73) in certain human tumor cell lines. In this report we analyzed the interaction between these two proteins in vitro. Our data showed that hsc73 interacts with the novel N-terminal region of pRb; that is, pRb binds directly to hsc73 and dissociates from hsc73 in an ATP-dependent manner. By using deletion mutants of cDNA encoding pRb, the hsc73 binding site of pRb was determined to be located in the region (residues 301-372) outside the so-called A pocket (residues 373-579) of this tumor suppressor protein. This finding was compatible with the fact that the adenovirus E1A oncoprotein, which is known to bind to the E2F binding pocket region of pRb, could not compete with hsc73 for the binding. Furthermore, phosphorylation of pRb by cyclin-dependent kinase inhibited the binding of pRb to hsc73. These data suggest that hsc73 may act exclusively as the molecular chaperone for nonphosphorylated pRb. As a result, hsc73 may function as a molecular stabilizer of nonphosphorylated pRb.

Adenosine Triphosphate↗
PubMed1995

Hepatocyte growth factor inhibits intercellular communication via gap junctions in rat hepatocytes.

We demonstrated that HGF reduces gap junctional intercellular communication of rat hepatocyte doublets and increases cell spreading. Intercellular communication via gap junctions was markedly reduced in hepatocyte doublets with HGF (20 ng/ml) 3-12 hr after inoculation. Immunocytochemistry revealed spotty localization of connexin 32 on the plasma membrane of 3-hr cultured control hepatocyte doublets, whereas HGF-treated doublets showed significantly less connexin 32 staining. Genistein maintained intercellular communication in the presence of HGF, indicating that HGF reduces intercellular communication by down regulation of connexin 32 through the c-met/HGF receptor-tyrosine-kinase-mediated pathway. Furthermore, TGF-beta 1 maintained intercellular communication in the presence of HGF. Regulation of intercellular communication in hepatocytes by HGF and TGF-beta 1 might play an important role during liver regeneration.

Analysis of Variance↗
PubMed1995

Pituitary PRL secretion induced by tetraethylammonium is inhibited by dopamine through D2 receptors.

We have evaluated the inhibitory effect of dopamine on PRL secretion induced by blocking K+ channels. Tumor-derived GH4C1 cells and collagenase-dispersed normal anterior pituitary (AP) cells from young adult male rats were perifused with Krebs-Ringer Hepes medium. In both cell types blocking K+ channels with tetraethylammonium (TEA) induced PRL secretion but did not stimulate cyclic AMP generation. Blocking Na+ channels with 1 microM tetrodotoxin had no effect on basal or TEA-induced PRL secretion. Dopamine inhibited the TEA-induced rise in [Ca2+]i in GH4C1 cells expressing dopamine D2 short receptors. In normal AP cells, 1-100 nM dopamine blocked PRL secretion induced by 20 mM TEA in a log-linear concentration-dependent fashion, with a plateau at > 100 nM dopamine (IC50 30 nM). The D2 dopaminergic receptor agonist, quinpirole, at 100 nM completely blocked PRL secretion induced by 20 mM TEA. The D2 dopaminergic receptor antagonist, sulpiride, at 10 microM reversed the inhibitory effect of 10 microM dopamine on PRL secretion induced by 20 mM TEA. Pretreatment of cells with 100 ng/ml pertussis toxin (PTX) for 24 h prevented 100 nM dopamine inhibition of PRL secretion induced by 20 mM TEA. The data indicate that in both normal lactotroph cells and in tumor-derived cells expressing D2 receptors, PRL secretion stimulated by blocking K+ channels is inhibited by dopamine binding to D2 receptors on the plasma membrane. This inhibition involves interaction with PTX-sensitive Gi protein.

Adenylyl Cyclases↗
PubMed1995

[Changes of specific and non-specific immunological functions before and after transsphenoidal tumor excision--a case of Cushing disease].

The interrelationship between the hypothalamic-pituitary-adrenal axis and the immune system has been becoming clear. However, most research about this interrelationship has been performed by in vitro experiments and by using animal models. To know the effect of hypercortisolism on human immune systems in vivo, we report at 32-year-old man with typical Cushing disease whose specific and non-specific immunological functions were estimated before and after successful transsphenoidal surgery. We made a diagnosis of Cushing disease with dexamethasone suppression test, CRF stimulation test, venous sampling, and MRI scan. Before transsphenoidal surgery, both plasma ACTH (100pg/ml) and urinary free cortisol (567 micrograms/day) were higher than the normal range, and the parameters of specific (CD4/CD8 ratio, serum Ig A, PHA/Con-A induced T cell blast formation, and NK cell activity) and non-specific (neutrophil phagocytosis and bactericidal function) immunological functions were clearly impaired. However, at 6 weeks and 6 months after the tumor excision when hormonal abnormalities were changed to normal, every impaired immunological function was improved to the normal range. These data suggest that impaired specific and non-specific immunological functions were induced by hyercortisolism not only in vitro but also in vivo (a state of Cushing disease).

Adrenocortical Hyperfunction↗
PubMed1995

A family of cold-regulated RNA-binding protein genes in the cyanobacterium Anabaena variabilis M3.

I previously found a cold-regulated RNA-binding protein gene rbpA (now named rbpA1) in Anabaena variabilis M3 [Sato, N. (1994) Plant Mol. Biol. 24, 819-823]. I show here that this gene is a member of a gene family containing at least eight members as evidenced by Southern blot and immunoblot analyses. I have isolated three additional genes (rbpB, rbpC and rbpD) in this family. Of these, rbpB was 100% identical to the rbpB gene of Anabaena 7120 reported previously. Another gene named rbpA in Anabaena 7120 was also found to exist in A.variabilis M3 with identical sequence and named rbpA2. The amino acid sequences of these gene products were highly conserved, except that the RbpD protein lacked glycine-rich C-terminal domain present in all other known members of the gene family. RNA blot and immunoblot analyses showed that the expression of rbpA1, rbpA2, rbpB, rbpC and rbpD, as well as uncloned rbp genes was regulated by cold, though the exact time-course and extent of response to cold were different among these genes. Gel-filtration assay showed that all of the Rbp proteins have higher affinities to poly(G) and poly(U) than to poly(A) and poly(C).

Amino Acid Sequence↗
PubMed1995

Isolation and characterization of mutants affected in lipid metabolism of Chlamydomonas reinhardtii.

Two mutants affected in lipid metabolism of Chlamydomonas reinhardtii were isolated by treating cells with ultraviolet light. Both mutants showed high chlorophyll fluorescent yields, as compared with parents, and were designated as hf-2 and hf-9 (for high fluorescence). hf-2 was shown to be defective in the synthesis of a chloroplast-specific lipid, sulfoquinovosyl diacylglycerol. hf-9 was shown to be defective in desaturation at the omega 6 position of fatty acids of monogalactosyl diacylglycerol, digalactosyl diacylglycerol, sulfoquinovosyl diacylglycerol and phosphatidylglycerol. The mutants exhibited alterations in photosynthetic activity and chloroplast ultrastructure.

Animals↗
PubMed1995

Proliferation and differentiation of myelodysplastic CD34+ cells: phenotypic subpopulations of marrow CD34+ cells.

In a search for a mechanism to explain the impaired growth of progenitor cells in patients with myelodysplastic syndromes (MDS), marrow CD34+ cells were purified up to 94.9% +/- 4.2% for normal individuals and 88.1% +/- 17.6% for MDS patients, using monoclonal antibodies and immunomagnetic microspheres (MDS CD34+ cells). Phenotypic subpopulations of these CD34+ cells were analyzed for CD38, HLA-DR, CD33, CD13, CD14, CD41 and CD3 plus CD19, in association with proliferative and differentiative capacities. The 15 studies performed included 12 MDS patients. Coexpression rate of CD13 significantly increased in the MDS CD34+ cell population with a value of 91.4% +/- 11.6% and ranging from 60.3% to 100%, and exceeded 99% in four studies, whereas that of normal CD34+ cells was 49.9% +/- 15.8%, ranging from 28.2% to 70.1% (P < .001). Coexpression rate of CD38, HLA-DR, CD33, CD14, and CD3 plus CD19 in MDS CD34+ cells did not significantly differ from that of normal CD34+ cells. The total number of colonies and clusters grown from 100 normal marrow CD34+ cells was 40.4 +/- 8.6, the range being from 27.2 to 50.3; this varied in MDS marrow CD34+ cells with a value of 34.0 +/- 28.7, the range being 0 to 95.9. The lineage of colonies and clusters promoted by MDS marrow CD34+ cells was predominantly committed to nonerythroid with impaired differentiation in 13 of 15 studies (87%). CD13 is first expressed during hematopoiesis by colony-forming unit granulocyte-macrophage and is absent in erythroid progenitors. Therefore, this study provides direct evidence for the lineage commitment of MDS CD34+ cells to nonerythroid with impaired differentiation and explains the mechanism of nil or low colony expression of MDS progenitor cells to erythroid lineage.

Aged↗
PubMed1995

Monoethylglycinexylidide formation as an independent measure of warm hepatic ischemia and reperfusion injury.

An accurate serologic measure of hepatic function would be clinically useful in selecting donors for liver transplantation. An experimental model that incorporates varying lengths of total hepatic warm ischemia with reperfusion injury was utilized to compare serologic parameters and mitochondrial performance of oxidative phosphorylation in predicting hepatocellular injury. Monoethylglycinexylidide (MEGX) formation following bolus intravenous lidocaine injection was found to be significantly decreased (P < 0.0001) at all periods of ischemia when compared to that in nonischemic controls. A serum MEGX level of < 50 micrograms/liter suggested severe hepatic damage. No correlation was found between MEGX level and liver viability as measured by animal survival. Serum transaminase (AST and ALT) levels demonstrated progressive, nonsignificant elevations with increasing length of ischemia (P = 0.0779 at the maximum ischemic time). Polarographic measurements of mitochondrial oxidative phosphorylation did not reveal a significant alteration in subcellular metabolism with prolonged ischemic time. These data highlight the comparative sensitivity of MEGX formation as an early quantitative measurement of hepatocellular injury during warm ischemia, although it was not predictive of organ viability.

Adenosine Triphosphate↗
PubMed1995

Colonic mucosal hemodynamics and tissue oxygenation in patients with ulcerative colitis: investigation by organ reflectance spectrophotometry.

Colonic mucosal hemodynamics were investigated at the rectosigmoidal region of the colon in 46 patients with ulcerative colitis and in 18 normal subjects by organ reflectance spectrophotometry under colonoscopy. The value for the index of mucosal hemoglobin concentration (IHb) was significantly higher, and value for the index of mucosal hemoglobin oxygen saturation (ISO2) was significantly lower in patients with active ulcerative colitis than values in the normal controls or in patients with inactive ulcerative colitis. The results indicate mucosal congestion and hypoxemia in patients with active ulcerative colitis. The changes in IHb and ISO2 correlated well with the severity of ulcerative colitis scored by endoscopic findings and with the number of infiltrating inflammatory cells in the mucosa analyzed histologically in biopsy samples. In conclusion, the colonic mucosal microcirculation in patients with active ulcerative colitis was disturbed and showed congestion and hypoxemia. The analysis of hemodynamic changes may be helpful for assessing the activity of ulcerative colitis.

Adult↗
PubMed1995

Effect of cocaine on the contracture response to 1% halothane in patients undergoing diagnostic muscle biopsy for malignant hyperthermia.

Two case reports have cited the recreational use of cocaine as possible trigger of a malignant hyperthermia (MH) crisis. We evaluated whether toxic concentrations of cocaine altered the in vitro muscle response to halothane during contracture tests for MH. Twenty-two patients were studied. Muscle biopsies were obtained and first tested for MH susceptibility with 3% halothane and caffeine contracture testing. Ten patients were diagnosed as MH-susceptible and 12 as MH non-susceptible, in accordance with the North American Malignant Hyperthermia Group protocol. Then, muscle strips were exposed to 1% halothane in the presence and absence of 0.1 mmol.L-1 cocaine. Cocaine alone did not affect baseline muscle tension in either group. With 1% halothane, MH non-susceptible muscle showed no contracture with or without cocaine. In contrast, in the presence of 1% halothane, MH-susceptible muscle showed either no change in contracture (six patients), an increase (two patients), or a decrease (two patients) when exposed to cocaine. However, the overall effect of cocaine on muscle contracture in the presence of 1% halothane was insignificant in both groups. We conclude that cocaine, even at toxic levels, does not have a direct effect on skeletal muscle contractility and thus is safe for MH-susceptible patients.

Adult↗
PubMed1995

A novel intracellular antigen in HL-60 cells that changes in molecular weight after granulocytic and monocytic differentiation.

The present study reports the identification and partial characterization of a novel antigen with M(r) 100,000 by a monoclonal antibody (D29A8) that was obtained by immunizing BALB/c mice with nuclei of HL-60 cells. D29A8 detected mainly a nucleolar macromolecule with M(r) 100,000 (p100). On the other hand, when HL-60 cells were induced to differentiate either into a granulocytic or monocytic pathway, the antibody detected mainly a cytoplasmic macromolecule with M(r) 95,000 (p95). Since two subtypes of the antigen (p100 and p95) appear to be present in the same cells that differ in the stage of cell differentiation, the antigen may play an important role in cellular differentiation.

Animals↗