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Biomedical subjects

M Saito

Publications and source records attributed to M Saito.

At least 19 recordsLinked to original sources
PubMed1992

Total metabolic flow of glycosphingolipid biosynthesis is regulated by UDP-GlcNAc:lactosylceramide beta 1-->3N-acetylglucosaminyltransferase and CMP-NeuAc:lactosylceramide alpha 2-->3 sialyltransferase in human hematopoietic cell line HL-60 during differentiation.

We have previously reported that ganglioside GM3 was remarkably increased during monocytoid differentiation of human myelogenous leukemia cell line HL-60 cells and that neolacto series gangliosides (NeuAc-nLc) were enriched during granulocytoid differentiation. In addition, HL-60 was differentiated into monocytic lineage by exogenous GM3 and into granulocytoid by NeuAc-nLc. In the present report, the enzymatic bases of glycosphingolipid biosynthesis in HL-60 during differentiation induced by 12-O-tetradecanoylphorbol-13-acetate and all-trans-retinoic acid were investigated. The following results were of particular interest. (i) Lactosylceramide alpha 2-->3 sialyltransferase (GM3 synthase) was remarkably up-regulated during monocyte differentiation, while the GM3 synthase level did not change in granulocytic differentiation. (ii) By contrast, lactosylceramide beta 1-->3N-acetylglucosaminyltransferase (Lc3Cer synthase) was down-regulated during monocytic differentiation, while the activity of Lc3Cer synthase was found to increase in granulocytic differentiation. (iii) The activities of four downstream glycosyltransferases (for synthesis of NeuAc-nLc) were found to increase or to remain unchanged during monocytic and granulocytic differentiation. These results strongly suggested the following. The dramatic GM3 increase and the decrease of NeuAc-nLc during monocytic differentiation are the consequences of the up-regulation of GM3 synthase and the down-regulation of Lc3Cer synthase, although the downstream enzymes are ready to catalyze their enzyme reactions. The notable increase of NeuAc-nLc and the relative decrease of GM3 during granulocytic differentiation are the results of the unchanged level of GM3 synthase and the up-regulation of Lc3Cer synthase together with the activation of the downstream glycosyltransferases. These results suggest that these two key upstream glycosyltransferases, GM3 synthase and Lc3Cer synthase, play critical roles in regulating the glycosphingolipid biosynthesis in HL-60 cells during differentiation. This switching mechanism of these two glycosyltransferases, together with our previous findings, might be one of the most important parts of the determining system of differentiation direction in human myeloid cells into monocytic or granulocytic lineages.

Antibodies, Monoclonal↗
PubMed1992

An immunohistologic evaluation of C-erbB-2 gene product in patients with urinary bladder carcinoma.

BACKGROUND: Amplification or overexpression of the c-erbB-2 gene have been reported to correlate with poor patient prognosis in human breast, gastric, and ovarian cancer. Recently, the c-erbB-2 gene product was found to be expressed frequently in the urinary bladder carcinoma. In the current study, the presence of the c-erbB-2 gene product in urinary bladder carcinomas was compared with patient outcome to evaluate whether c-erbB-2 gene product could identify a subset of patients who are destined to have a poor prognosis. METHODS: Immunohistologic study of the c-erbB-2 gene product was done in formaldehyde-fixed paraffin-embedded tissue specimens obtained from 88 transitional cell carcinomas of the human urinary bladder. Eighty-three patients who underwent complete tumor resection by total cystoprostatectomy (30 patients) or by bladder-preserving operations such as transurethral surgery (50 patients) or partial cystectomy (3 patients) entered a follow-up study. The other five patients did not enter the follow-up study because of lost follow-up (2 patients) or distant metastasis at the time of surgery. RESULTS: The c-erbB-2 gene product was expressed in 23 of 88 patients (26%), showing an increase in the expression rate corresponding to the advancement of tumor grade (P < 0.05) and tumor stage (P < 0.2). The 5-year disease-free survival rate was 48.5% for patients with c-erbB-2 negative tumors versus 9.7% for those with c-erbB-2 positive tumors (P < 0.01). The 5-year actuarial survival rate was 65.5% for patients with c-erbB-2 negative tumors versus 41.8% for those with c-erbB-2 positive tumors (P < 0.05). Multivariate analysis using Cox regression model showed that the c-erbB-2 gene product tissue status was a significant prognostic factor independent of grade and stage of the tumor. CONCLUSIONS: The results suggest that the c-erbB-2 gene product could be a tumor marker to identify a malignant subgroup in bladder carcinomas.

Adult↗
PubMed1992

Prothrombin Himi: a compound heterozygote for two dysfunctional prothrombin molecules (Met-337-->Thr and Arg-388-->His).

A congenitally dysfunctional form of prothrombin, Prothrombin Himi, shows reduced fibrinogen clotting activity, although it retains full hydrolytic activity toward synthetic substrates. To elucidate the structural abnormality of the variant prothrombin, we first performed genetic analysis of dysprothrombin. Polymerase chain reaction amplification of the exons 8 through 14 of the proband and her family members' prothrombin genes, which code the thrombin moiety, followed by single-strand conformation polymorphism analysis, identified two variant conformers in exon 10 specific to this family. One variant allele detected in the father was inherited by the proband and one of her sisters, and the other detected in the mother was also inherited by them. This result indicates that the proband has two different base pair changes in the gene. Sequencing showed two novel point mutations in the proband's gene. One is a T to C transition at position 8751, resulting in the substitution of threonine for methionine at codon 337 (Thrombin Himi I). The other is a G to A transition at 8904, resulting in the substitution of histidine for arginine at codon 388 (Thrombin Himi II). By sequencing analysis of her parents, it was determined that Thrombin Himi I was inherited from the father and Thrombin Himi II from the mother. These results confirm that Prothrombin Himi is compound heterozygous for two dysfunctional prothrombin molecules.

Amino Acid Sequence↗
PubMed1992

Transforming growth factor-beta inhibits phosphorylation of the retinoblastoma susceptibility gene product in human monocytic leukemia cell line JOSK-I.

Proliferation of the human monocytic leukemia cell line JOSK-I is inhibited by transforming growth factor-beta (TGF-beta). Growth inhibition by TGF-beta was not due to either a toxic effect or to induction of differentiation. TGF-beta induced a cell cycle arrest at late G1 phase and was not found to be inhibitory to JOSK-I cells in S phase or G2/M. This G1 cell cycle arrest was associated with an accumulation of the unphosphorylated form of the retinoblastoma susceptibility gene product (Rb) in good correlation with inhibition of DNA synthesis. In contrast to the effects of TGF-beta, two other agents which induced a G1 arrest of JOSK-I cells had a different effect on Rb. Aphidicolin blocked cells at G1/S but could not reduce Rb phosphorylation as great as that seen with TGF-beta. 12-O-Tetradecanoylphorbol-13-acetate, an inducer of differentiation, did reduce Rb phosphorylation, but not until 72 h, when differentiation had already occurred. The identities of the Rb kinases are unknown, but recent evidence suggests that the cdc2 gene product could participate in Rb phosphorylation. Although cdc2 mRNA and total protein levels were not affected, TGF-beta inhibited the rate of translation and kinase activity of cdc2 in JOSK-I cells. These results suggest that growth inhibition of hematopoietic cells by TGF-beta is linked to suppression of Rb phosphorylation to retain Rb in an unphosphorylated, growth-inhibitory state. The suppression of Rb phosphorylation is suggested to be mediated through inhibition of cdc2 kinase activity by TGF-beta.

Aphidicolin↗
PubMed1992

Cold exposure increases glucose utilization and glucose transporter expression in brown adipose tissue.

When rats were exposed to a cold environment (4 degrees C) for 10 days, tissue glucose utilization was increased in brown adipose tissue (BAT), a tissue specified for non-shivering thermogenesis, but not in skeletal muscle. Cold exposure also caused an increase in the amount of GLUT4, an isoform of glucose transporters expressed in insulin-sensitive tissues, in parallel with an increased cellular level of GLUT4 mRNA. In contrast to BAT, no significant effect of cold exposure was found in skeletal muscle. The results suggest the cold-induced increase in glucose utilization by BAT is attributable, at least in part, to the increased expression of GLUT4.

Acclimatization↗
PubMed1992

Effect of L-threo-3,4-dihydroxyphenylserine on muscle sympathetic nerve activity in humans.

To clarify the effect of L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS), a precursor of norepinephrine (NE), the effect of this drug on microneurographically recorded muscle sympathetic nerve activity (MSA) from the tibial nerve was analyzed in ten healthy male volunteers. A single dose of 600 mg of L-threo-DOPS was orally administered and the effect of this norepinephrine precursor on MSA at resting and at upright standing positions, as well as the MSA responsiveness to head-up tilting was examined by comparing the data obtained after administration of the drug with those obtained under control conditions. The plasma NE levels were determined in two subjects. The results were as follows: (1) resting MSA increased significantly 80 min after administration of L-threo-DOPS and was accompanied by an increase in plasma NE levels; (2) standing MSA when treated with the drug was not significantly different from values obtained under control conditions; and (3) MSA responsiveness to orthostasis was reduced after L-threo-DOPS. We conclude from the activation of MSA by L-threo-DOPS that this drug raised blood pressure not only through an increase in metabolized plasma NE levels, but also through the enhancement of MSA by activation of descending noradrenergic or adrenergic pathways proximal to the recording site of the sympathetic discharge.

Adult↗
PubMed1992

Molecular cloning of a murine IL-6 receptor-associated signal transducer, gp130, and its regulated expression in vivo.

The IL-6R system comprises two functionally different chains: a ligand binding-chain (IL-6R) and a non-ligand-binding but signal-transducing chain (gp130). gp130 associates with the IL-6-IL-6R complex, resulting in the formation of high-affinity IL-6 binding sites, and transduces the signal. A cDNA for murine gp130 has been cloned from the cDNA library of murine macrophages by using a human gp130 cDNA as a probe. The overall homology with human gp130 was 76.8% at the protein level. The extracellular region of murine gp130, as observed in human gp130, comprises 6 U of a fibronectin type III module and part of this region of approximately 200 amino acids has typical features of a cytokine receptor family. Cloned murine gp130 could transduce the growth signal in a murine IL-3-dependent cell line in response to a complex of IL-6 and soluble IL-6R. Two species of murine gp130 mRNA (7 and 10 kb) were expressed in almost all the cell lines. These transcripts were also ubiquitously expressed in murine tissues, embryonic stem cells, and embryos as early as day 6 of gestation. Administration of IL-6 in mouse caused up-regulation of the gp130 mRNA levels in several tissues. Both gp130 and IL-6R mRNA in liver were up-regulated in vivo by IL-6.

Amino Acid Sequence↗
PubMed1992

Rapid priming of human monocytes by human hematopoietic growth factors: granulocyte-macrophage colony-stimulating factor (CSF), macrophage-CSF, and interleukin-3 selectively enhance superoxide release triggered by receptor-mediated agonists.

The effects of hematopoietic growth factors on human monocyte superoxide (O2-) release were investigated by using purified human monocytes in suspension. Among growth factors studied, granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage-CSF (M-CSF), and interleukin-3 (IL-3) primed human monocytes and enhanced O2- release stimulated by the receptor-mediated agonists, N-formyl-methionyl-leucyl-phenylalanine (FMLP) and concanavalin A (Con A), but not by phorbol myristate acetate, which bypasses the receptors to stimulate the cells. The optimal priming was obtained by pretreatment of cells with 1 to 5 ng/mL (0.07 to 0.34 nmol/L) GM-CSF, 50 to 100 ng/mL (0.5 to 1.1 nmol/L) M-CSF, or 10 to 20 ng/mL (0.6 to 1.3 nmol/L) IL-3 for 10 minutes at 37 degrees C. Potency of the maximal priming effects on FMLP- or Con A-induced O2- release was GM-CSF greater than M-CSF = IL-3. The combination of the optimal concentrations of any two CSFs resulted in the effect of more potent priming agent alone. Enhancement of O2- release by GM-CSF was observed over the complete range of effective concentrations of FMLP (10(-8) to 10(-6) mol/L). The pretreatment of monocytes with granulocyte-CSF (50 ng/mL), interferon-gamma (1,000 U/mL), or IL-4 (20 ng/mL) for 10 minutes at 37 degrees C had no effect on O2- release stimulated by FMLP or Con A. These findings show that GM-CSF, M-CSF, and IL-3 selectively enhance O2- release in human monocytes triggered by receptor-mediated agonists after short-term preincubation.

Adult↗
PubMed1992

The molecular biology of interleukin 6 and its receptor.

Functional pleiotropy and redundancy are characteristic features of cytokines. Interleukin 6 (IL-6) is a typical example: IL-6 induces cellular differentiation or expression of tissue-specific genes; it is involved in processes such as antibody production in B cells, acute-phase protein synthesis in hepatocytes, megakaryocyte maturation, cytotoxic T cell differentiation, and neural differentiation of PC12 (pheochromocytoma) cells. It promotes growth of myeloma/plasmacytoma cells, T cells, keratinocytes and renal mesangial cells, and it inhibits growth of myeloid leukaemic cell lines and certain carcinoma cell lines. The IL-6 receptor consists of two polypeptide chains, a ligand-binding chain (IL-6R) and a non-ligand-binding, signal-transducing chain (gp130). Interaction of IL-6 with IL-6R triggers the association of gp130 and IL-6R, and the signal can be transduced through gp130. Association of gp130 with IL-6R is involved in the formation of high affinity binding sites. This two-chain model has been shown to be applicable to receptor systems for several other cytokines, such as granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-3, IL-5 and nerve growth factor (NGF). The pleiotropy and redundancy of cytokines may be explained on the basis of this unique receptor system.

Animals↗
PubMed1992

Increased levels of plasma thrombomodulin in chronic myelogenous leukemia.

Circulating blood plasma contains proteinase-degraded forms of thrombomodulin that are soluble. We quantitatively assayed the plasma levels of thrombomodulin in 15 patients with chronic myelogenous leukemia (CML) in chronic phase by method of an enzyme-linked immunosorbent assay using a monoclonal antibody to protease-degraded products of thrombomodulin. Plasma levels of thrombomodulin in patients with CML at diagnosis were significantly increased (19.5 +/- 6.2 ng/ml: means +/- SD) compared with the levels in normal controls (8.0 +/- 1.9 ng/ml, n = 20) (P less than 0.001). Fibrin degradation products (D-dimer), thrombin-antithrombin III complex, and plasmin alpha 2-antiplasmin complex were almost normal, suggesting that intravascular coagulation or plasmin-mediated fibrinolysis little occurred in these patients. On the other hand, the plasma levels of elastase-alpha 1-proteinase inhibitor (E-alpha 1PI) complex, which was the indicator of released leukocyte elastase, were significantly increased in CML (P less than 0.0001). The plasma levels of thrombomodulin and E-alpha 1PI complex were decreased in parallel with decline of leukocyte counts in 10 patients with CML following anti-leukemic therapy. Furthermore, a statistically significant correlation was observed between the plasma levels of thrombomodulin and E-alpha 1PI complex obtained at 39 time points in 15 patients with CML (r = 0.81, P less than 0.001). These results suggest that the increased plasma levels of thrombomodulin in CML may be partly caused by leukocyte elastase, which may split the surface thrombomodulin and release protease-degraded fragments of it into the circulation.

Antineoplastic Agents↗
PubMed1992

Role of endothelin in disseminated intravascular coagulation.

We examined the changes in plasma levels of endothelin-1 (ET-1), a potent vasoconstrictor peptide, in 47 cases of disseminated intravascular coagulation (DIC) to investigate the role of ET-1 in DIC and its relation to multiple organ failure (MOF). A significant elevation of plasma levels of ET-1 was observed in some cases of DIC, especially in patients with sepsis, blastic crisis of chronic myelogenous leukemia, and cancer. However, no such significant elevation was observed in patients with acute promyelocytic leukemia (APL), acute leukemias except for APL, or non-Hodgkin lymphoma. Plasma levels of ET-1 were higher in patients with DIC with MOF than in those without MOF. Although the levels of ET-1 were decreased or remained low with clinical improvement in most DIC patients, the levels were further increased or remained high in patients who showed no improvement in DIC. It is suggested that ET-1 must play an important role in further progression of MOF with the vasoconstriction and microcirculatory disorders.

Disseminated Intravascular Coagulation↗
PubMed1992

Treatment of myeloid leukemic cells with the phosphatase inhibitor okadaic acid induces cell cycle arrest at either G1/S or G2/M depending on dose.

The phosphatase inhibitor okadaic acid was found to induce cell cycle arrest of human myeloid leukemic cell lines HL-60 and U937 in a concentration- and time-dependent manner. Exposure to low concentrations of okadaic acid (2-8nM) for 24-48 hr caused greater than 70% of cells to arrest at G2/M, with up to 40% of the cells arrested in early mitosis. Cell viability decreased rapidly after 48 hr of treatment, and morphological and DNA structure analysis indicated that this was primarily due to the induction of apoptosis. The cells arrested in mitosis by 8 nM okadaic acid could be highly enriched by density gradient centrifugation and underwent apoptosis when further cultured either with or without okadaic acid, indicating that the effects of okadaic acid were irreversible. In contrast to the effects of low concentrations of okadaic acid, high concentrations (500 nM), inhibited proliferation in less than 3 hr. Remarkably, the majority of cells also entered a mitosis-like state characterized by dissolution of the nuclear membrane and condensation and partial separation of chromosomes. However, these cells had a diploid content of DNA, indicating that the cell cycle arrest occurred at G1/S with premature chromosome condensation (PCC), rather than at G2/M. If cells were first blocked at G1/S with hydroxyurea and then treated with okadaic acid, greater than 90% developed PCC in less than 3 hr without replicating their DNA. Caffeine was not able to induce PCC in these cells, either with or without prior inhibition of DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Cycle↗
PubMed1992

Transformation of vitamin D3 to 1 alpha,25-dihydroxyvitamin D3 via 25-hydroxyvitamin D3 using Amycolata sp. strains.

To enzymatically synthesize active metabolites of vitamin D3, we screened about 500 bacterial strains and 450 fungal strains, of which 12 strains were able to convert vitamin D3 to 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] via 25-hydroxyvitamin D3 [25(OH)D3]. The conversion activity was only detected in strains belonging to the genus Amycolata among all the organisms tested. A preparative-scale conversion of vitamin D3 to 25(OH)D3 and 1 alpha,25(OH)2D3 in a 200-1 tank fermentor using A. autotrophica FERM BP-1573 was accomplished, yielding 8.3 mg 25(OH)D3/l culture and 0.17 mg 1 alpha,25(OH)2D3/l culture. A related compound, vitamin D2, could be also converted to 25-hydroxyvitamin D2 and 1 alpha,25-dihydroxyvitamin D2 using the same strain. The cytochrome P-450 of FERM BP-1573 was detected by reduced CO difference spectra in whole-cell suspensions. Vitamin D3 in the culture induced cytochrome P-450 and the conversion activity simultaneously, suggesting that the hydroxylation at C-25 of vitamin D3 and at C-1 of 25(OH)D3 originates from cytochrome P-450.

Actinomycetales↗
PubMed1992

Unusual rapidly growing gastric myxoid neurofibroma: a case report.

A 62-year-old man was first found to have a gastric tumor in the fornix during a routine health examination 16 months previously. The case was not associated with von Recklinghausen's disease. Initially, the tumor was approximately 4 mm in diameter, but grew very rapidly to 20 mm in 13 months, and to 30 mm in the following month, without manifesting clinical symptoms. Malignancy was suspected because of the rapid growth and the endoscopic findings: a rough-granular elevated lesion with a wide stalk, and with erosions and mucus on its surface. Although endoscopic biopsy was done several times, the routine histological examinations were inconclusive. Endoscopic resection was therefore carried out. Examination of the resected specimen showed that the main elements consisted of wavy, long-spindled cells, which crossed irregularly, and whose interstitium was myxomatous. Immunohistochemically the specimen showed strongly positive reaction for S-100 protein and positive reaction for neuron specific enolase (NSE). Based on these immunohistochemical findings, a final diagnosis of gastric myxoid neurofibroma was made, which showed rapid growth due to myxomatous change. The patient showed a good postoperative course and no recurrence has been recognized by follow-up endoscopy.

Humans↗
PubMed1992

Alpha 2-adrenergic modulation of pancreatic glucagon secretion in rats.

The present study was designed to clarify the mechanism of adrenergic modulation of pancreatic glucagon secretion in rats under physiological conditions by 1) epinephrine infusion alone or together with adrenergic blockers and 2) administration of adrenergic agonists. Intravenous infusion of epinephrine alone (1 microgram/kg/min, equal to 0.7 nmol/kg/min) caused a significant increase in glucagon secretion. Phentolamine (an alpha blocker) or yohimbine (an alpha 2 blocker) administration completely inhibited the increase of glucagon secretion caused by epinephrine infusion, but neither the administration of bunazosin (an alpha 1 blocker) nor beta blockers inhibited it. Infusion of clonidine (an alpha 2 agonist) caused significant increase of glucagon secretion even at a low dose of 0.5 nmol/kg/min, although infusion of neither an alpha 1 nor a beta 2 agonist caused it even at the high dose of 40.0 nmol/kg/min. It is concluded that the alpha 2 receptor mechanism plays the most important role in the adrenergic modulation of glucagon secretion in rats under physiological conditions.

Adrenergic alpha-Agonists↗
PubMed1992

Effect of scopolamine on the electrical resistance of the paw pads of mice.

We examined the electrical resistance of the paw pads of mice under the same conditions as used previously in studies of the passive avoidance response. Administration of scopolamine (0.05-1 mg/kg, SC) 10 or 30 min prior to placement of animals in an experimental box resulted in a profound increase in electrical resistance. In contrast, subcutaneous injection of butylscopolamine (1-20 mg/kg), diazepam (1 or 2 mg/kg), or pentobarbital (10 or 20 mg/kg) did not substantially alter subject resistance. Scopolamine may act on the CNS to induce increased paw skin resistance.

Animals↗