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Biomedical subjects

Y Nakano

Publications and source records attributed to Y Nakano.

At least 19 recordsLinked to original sources
PubMed1992

Molecular genetic analysis of the catalytic site of Streptococcus mutans glucosyltransferases.

In the present communication molecular genetic approaches have been utilized to confirm the nature of the catalytic site of Streptococcus mutans glucosyltransferases (GTF)s. Site-directed mutagenesis was used to convert the putative sucrose binding Asp-451 of the GTF-I enzyme from S. mutans GS5 to Glu, Asn, and Thr. All three of the resulting mutated enzymes displayed no detectable sucrase or GTF activities. By contrast, mutation of nearby Asp residues did not markedly reduce enzymatic activity. The inactive enzymes also appear to bind acceptor dextrans as well as the parental enzyme. These results confirm the essential role of Asp-451 of the GTF-I from strain GS5 and analogous Asp residues in other related GTFs in enzymatic activity.

Amino Acid Sequence↗
PubMed1992

Isolation and properties of gamma-tocopherol methyltransferase in Euglena gracilis.

Gamma-Tocopherol methyltransferase (EC2.1.1.-), which catalyzes the conversion of gamma-tocopherol into alpha-tocopherol, was present in a cell homogenate of Euglena gracilis. The enzyme was loosely bonded to the outer membrane of chloroplasts and solubilized from chloroplast membranes by a detergent, followed by partial purification in a three-step procedure. The methyltransferase showed a pH optimum of 7.5 and a temperature optimum of 35 degrees C and had an M(r) of 150,000. The activity was about 1.4-fold higher with gamma-tocopherol than with beta-tocopherol as substrate. The enzyme was specific for S-adenosylmethionine as a methyl donor, with a Km value of 50 microM. The addition of homogentisate, L-tyrosine and L-phenylalanine into a suspension of Euglena cells increased the relative pool sizes of alpha- and gamma-tocopherol, but not those of beta- and delta-tocopherol. The contents of alpha- and gamma-tocopherol in a chloroplast fraction of Euglena were always higher than those of any other fraction after any period of incubation with homogentisate. Based on the results of the present experiments, we propose a biosynthetic pathway of alpha-tocopherol in Euglena gracilis.

Animals↗
PubMed1992

Sex difference for tolerance of 5-HT1A receptor-mediated temperature and corticosterone responses in mice.

Repeated treatment with 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) resulted in significant attenuation of 8-OH-DPAT-induced hypothermia and adrenocorticol effect in mice of both sexes, while it did not affect the 8-OH-DPAT-induced decrease in 5-hydroxyindoleacetic acid in the hypothalamus in either sex. The attenuated responses developed more rapidly in female than in male mice, indicating sex differences in the adaptive regulation of the 5-HT1A receptor-mediated responses.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Complete determination of disulfide bonds localized within the short consensus repeat units of decay accelerating factor (CD55 antigen).

Decay accelerating factor (DAF) has 4 SCR (short consensus repeat) units. Each SCR unit consists of approx. 60 amino acids characterized by having four conserved cysteine residues and several other highly conserved residues which include proline, tryptophan, tyrosine/phenylalanine and glycine. To determine the disulfide-bonding pattern, we used the urine form of DAF. After thermolysin and trypsin digestion, we isolated seven disulfide-linked peptides by HPLC purification. Because all of the cysteine residues are disulfide-bonded, DAF should contain eight disulfide bonds. After subtilisin and trypsin digestion, we isolated the eighth disulfide-bonded peptides by HPLC purification. From sequence analyses of these peptides, we could identify all disulfide bonds in the 4 SCR units of DAF as being between the first and the third and between the second and the fourth half-cystines within each SCR unit.

Amino Acid Sequence↗
PubMed1992

The role of corticotropin-releasing factor and vasopressin in hypoglycemia-induced proopiomelanocortin gene expression in the rat anterior pituitary gland.

In this study, we examined the effect of passive immunization of endogenous corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) on hypoglycemia-induced adrenocorticotropic hormone (ACTH) secretion and determined proopiomelanocortin messenger RNA (POMC mRNA) levels in the anterior pituitary as well as hypothalamic CRF mRNA levels in pentobarbital anesthetized rats. The response of plasma ACTH to hypoglycemia was partially inhibited by the administration of CRF-antiserum (CRF-As) or AVP-antiserum (AVP-As) alone, but was found to be completely abolished by the administration of CRF-As + AVP-As as compared to the response in normal rabbit serum-treated rats. The hypoglycemia-induced POMC mRNA level in the anterior pituitary was completely inhibited by the administration of CRF-As alone and CRF-As + AVP-As, but was not inhibited by AVP-As alone as compared to the response in normal rabbit serum-treated rats. The administration of CRF-As and/or AVP-As did not affect hypoglycemia-induced CRF mRNA levels in the hypothalamus. These results indicate that the synergistic effect of CRF and AVP is important for hypoglycemia-induced ACTH secretion, but CRF is essential and indispensable for hypoglycemia-induced POMC gene expression in the anterior pituitary (AP).

Animals↗
PubMed1992

Effect of L-glutamate on 2-oxoglutarate decarboxylase in Euglena gracilis.

The effect of tricarboxylic acid-cycle intermediates and related compounds on 2-oxoglutarate decarboxylase activity was investigated. The addition of L-glutamate to Euglena cells grown on glucose/(NH4)2SO4 medium resulted in an increase in 2-oxoglutarate decarboxylase activity, which was abolished by the simultaneous addition of cycloheximide. Immunochemical titration, immunoblot analysis and labelling in vivo with antibody raised against 2-oxoglutarate decarboxylase showed that the increase in 2-oxoglutarate decarboxylase activity was due to synthesis of new protein and not to activation of pre-existing protein. The experimental results reported here demonstrate that L-glutamate is assimilated by the pathway, via 2-oxoglutarate, that consists of L-glutamate-oxaloacetate aminotransferase, 2-oxoglutarate decarboxylase and succinate semialdehyde dehydrogenase, rather than by the gamma-aminobutyrate shunt, consisting of L-glutamate decarboxylase and gamma-aminobutyrate aminotransferase.

Animals↗
PubMed1992

NADPH-cytochrome c (P-450) reductase has the activity of NADPH-linked aquacobalamin reductase in rat liver microsomes.

To elucidate the mammalian system for synthesis of cobalamin coenzymes, microsomal NADPH-linked aquacobalamin reductase was purified and characterized. The enzyme was purified about 534-fold over rat liver microsomal fraction in a yield of about 32%. The purified enzyme was homogeneous in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and had a monomeric molecular weight of 79,000. The purified aquacobalamin reductase showed a high specific activity (about 55 mumol/min per mg protein) of NADPH-cytochrome c (P-450) reductase. About 33% of the NADPH-cytochrome c reductase activity found in the microsomal fraction was recovered in the final purified preparation. The activity ratio of NADPH-cytochrome c reductase/NADPH-linked aquacobalamin reductase was about 5.0 through the purification steps, indicating that the rat liver microsomal NADPH-linked aquacobalamin reductase is the NADPH-cytochrome c reductase.

Animals↗
PubMed1992

A re-evaluation of the classification of olfactory epithelia in patients with olfactory disorders.

We have previously demonstrated that human olfactory epithelia can be classified into five grades according to the degree of degeneration present in patients with various kinds of olfactory disorders. In practice, however, the occurrence of additional types of cell changes in other kinds of olfactory disorders and findings with immunohistochemical techniques have led us to re-evaluate our previous classification. In the present study, changes in olfactory epithelia from ten patients with various kinds of olfactory disorders are discussed and a revised classification is proposed. Microvillar and differentiating cells were also evaluated in the epithelium studied.

Adult↗
PubMed1992

SP-40,40 is a constituent of Alzheimer's amyloid.

Cerebrospinal fluid (CSF), serum and seminal plasma contain a small amount of SP-40,40, a modulatory protein of the human complement system. The SP-40,40 in each body fluid was different in molecular size on SDS-PAGE, and glioblastoma cells, hepatoma cells and testicular tumor cells produced SP-40,40, while neuroblastoma cells did not. Therefore, it was estimated that CSF SP-40,40 originated in glia cells, serum SP-40,40 in liver cells and seminal plasma SP-40,40 in testicular cells. SP-40,40 concentrations in CSF of the patients with Alzheimer's disease and the patients with cerebral tumor were higher than those of normal donors. beta-Amyloid deposits in the brains of the patients with Alzheimer's disease were stained with an anti-SP-40,40 monoclonal antibody (mAb) but not with an anti-S-protein mAb, while cellular processes around beta-amyloid were stained with an anti-S-protein mAb but not with an anti-SP-40,40 mAb. Therefore, beta-amyloid contained SP-40,40 in a form different from that in the soluble membrane attack complex (SMAC, SC5b-9) of the complement, which contains S-protein as well as SP-40,40.

Alzheimer Disease↗
PubMed1992

Elevated levels of serum aldolase A in patients with renal cell carcinoma.

To clarify whether serum aldolase A is a useful biomarker for renal cell carcinoma (RCC), we determined serum levels of the aldolase A isozyme by an enzyme immunoassay in patients suffering from RCC, other urological tumors, and benign urological diseases. Forty-six of 126 patients with RCC (37%) had elevated serum aldolase A. The positive rates were 23% in stage I, 40% in stage II, 63% in stage III, and 46% in stage IV. In 10 (83%) of 12 patients whose serum levels had been elevated preoperatively, these were reduced to within the normal range after nephrectomy. Four of 7 patients (57%) with progressive disease had elevated levels of aldolase A. In contrast, the positive rates were only 9.9% in 71 patients with other urological tumors and 5.8% in 52 cases of benign urological diseases. High concentrations of aldolase A isozyme in RCC tissues might be reflected in elevated serum levels. The present findings indicate that serum aldolase A is a useful biomarker for monitoring the clinical course of patients with RCC.

Biomarkers, Tumor↗
PubMed1992

Superficial bladder cancer treated by total cystectomy: tumour characteristics and patient survival.

Of 113 patients with bladder cancer who underwent total cystectomy from January 1980 to December 1990, 30 (27%) had superficial tumours (pTa, pTis, and pT1). Nineteen of these 30 patients (63%) were primarily treated by total cystectomy and the remaining 11 (37%) had a past history of treatment for bladder cancer. Major reasons for choice of total cystectomy were multifocal tumours, frequent recurrence, and diffuse carcinoma in situ. Histologically stage pT1, grade 3 tumours were frequently accompanied by carcinoma in situ and often by lymphatic invasion. None of the 24 patients undergoing pelvic lymphadenectomy had lymph node metastasis. Of 25 male patients 15 (60%) underwent simultaneous prophylactic urethrectomy. Two of the remaining 10 males (20%) not undergoing this additional operation died of subsequent urethral recurrence. The 5-year actuarial survival rate was 80% for the 30 patients when all causes of death were considered. It was concluded that patients with superficial bladder cancer who undergo total cystectomy without prophylactic urethrectomy require close follow-up with urethral washings for cytology to detect early urethral recurrence, an important determinant for survival.

Adult↗
PubMed1992

Relationship between pathologic prognostic factors and abnormal levels of des-gamma-carboxy prothrombin and alpha-fetoprotein in hepatocellular carcinoma.

The relationship between pathologic prognostic factors and abnormal levels of des-gamma-carboxy prothrombin and alpha-fetoprotein was investigated in 42 patients with resectable hepatocellular carcinoma. The frequencies of macroscopic massive type, intrahepatic metastasis, and portal vein tumor thrombus were significantly higher in patients with positive des-gamma-carboxy prothrombin (p less than 0.05) but not with alpha-fetoprotein. Other histologic factors in tumorous and nontumorous tissues were not significantly different irrespective of the positivity of these markers. In patients with tumors not more than 6 cm in diameter, the frequency of intrahepatic metastasis was positively correlated with the positivity of des-gamma-carboxy prothrombin (p less than 0.05) and inversely with that of alpha-fetoprotein (p less than 0.05). Furthermore, intrahepatic metastasis was most frequently observed in patients with positive des-gamma-carboxy prothrombin and negative alpha-fetoprotein (eight of nine) and least frequently in cases with negative des-gamma-carboxy prothrombin and positive alpha-fetoprotein (one of eight). These findings indicated that both des-gamma-carboxy prothrombin and alpha-fetoprotein might be useful markers for the prediction of intrahepatic spread of hepatocellular carcinoma.

Biomarkers↗
PubMed1992

Nonspecific regulatory mechanism of contact sensitivity: nonspecific suppressor factor (NSF)-treated intermediate cells produce a second nonspecific suppressor factor (NSFint).

Nonspecific suppressor factor (NSF), which inhibits the passive transfer of contact sensitivity (CS), is produced spontaneously from macrophage-like suppressor cells induced by intravenous administration of oxazolone (Ox)-conjugated spleen cells. NSF binds selectively to Ia-positive, cyclophosphamide (CY)-sensitive, and plastic-adherent cells (named intermediate cells) present in the normal spleen. NSF-treated intermediate cells acquire the ability to suppress the passive transfer of CS nonspecifically. In this study, NSF-treated intermediate cells were found to release a second nonspecific suppressor factor (NSFint) during a 2-hr culture, while retaining their suppressor activity. Investigation of the relationship between these two factors showed that both NSF and NSFint were trypsin-sensitive, nondialyzable proteins. However, gel chromatography revealed that NSF was about 43 kDa, while NSFint was about 20 kDa. NSF was released from macrophage-like suppressor cells after RNA-dependent protein synthesis. In contrast, production of NSFint was energy dependent but did not require protein synthesis. Intermediate cells pretreated with lysosomotropic agents, such as ammonium chloride or chloroquine, did not acquire suppressor activity nor release suppressor factors due to NSF treatment. These observations suggest that NSFint is an altered form of NSF released by the intermediate after having undergone some modification; the biochemical mechanism is not known. This study showed that the intermediate cells play an active role in the suppressor cascade of NSF.

Animals↗
PubMed1992

Color fusion and flicker fusion frequencies using tritanopic pairs.

We determined color fusion and flicker fusion frequencies for tritanopic color pairs, so that only short wavelength sensitive cones were modulated. The minimally distinct border (MDB) technique was used to determine tritanopic pairs for each observer. If S-cones do not contribute to the luminance channel, color fusion and flicker fusion frequencies should be equal, because the achromatic flicker perceived beyond color fusion frequency is supposed to be elicited just by the luminance channel. The results show a significant difference between color fusion and flicker fusion frequencies for all pairs and for all subjects, which suggests a contribution of S-cones to the luminance channel. However, the results also showed that the residual achromatic flicker can not be eliminated by adjusting relative luminance of two colors flickering in counter-phase. The relative luminance stayed the same as the MDB setting when residual flicker was minimized. This means that minimum flicker was obtained when L- and M-cones are temporally silenced, and suggests little or no contribution of S-cones to luminance channel. These conflicting results might be explained by phase shift between responses of S-cones and other longer-wavelength-sensitive cones.

Adult↗
PubMed1992

Islet amyloid polypeptide (IAPP) secretion from islet cells and its plasma concentration in patients with non-insulin-dependent diabetes mellitus.

Islet amyloid polypeptide (IAPP/Amylin) is a novel peptide which was extracted from islet amyloid deposits in patients with non-insulin-dependent diabetes mellitus (NIDDM). However, its pattern of secretions and plasma concentrations under various conditions has not yet been made clear enough. In this study, we examined IAPP secretion from islet beta-cells in vitro using cultured islet cells of neonatal rat pancreas and plasma IAPP responses under various conditions in vivo in normal control subjects and patients with glucose intolerance. Our data revealed that (1) IAPP is co-secreted with insulin from islet cells of the rat pancreas by glucose and non-glucose stimuli; (2) fasting plasma IAPP levels in normal control subjects are 24.9 +/- 2.0 pg/ml and the molar ratio of IAPP/insulin is approximately 1/7; (3) fasting IAPP levels are high in obese patients and low in insulin-dependent diabetic patients, and the molar ratio of IAPP/C-peptide in NIDDM patients is lower than that in normal control subjects, suggesting the basal hyposecretion of IAPP relative to insulin in NIDDM; and (4) the obese patients who had a hyperresponsiveness of insulin relative to C-peptide had the hyperresponsiveness of IAPP relative to C-peptide during an oral glucose load, suggesting that IAPP may have some physiological effect in glucose metabolism.

Adult↗
PubMed1992

Differing effects of delta-9-tetrahydrocannabinol (THC) on murine spleen cell populations dependent upon stimulators.

Delta-9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, can suppress the immune response, both in vitro and in vivo. In the present study, THC was found to either up-regulate or down-regulate lymphocytes depending on the method of stimulation. When the mitogens concanavalin A (Con A) or phytohemagglutinin (PHA) were used to stimulate THC-treated splenocytes, a down-regulation of lymphocyte proliferation occurred, which reflected lower T-cell numbers in general and Ly2 positive cells specifically. When splenocytes were stimulated directly by using anti-CD3 antibody it was found that low concentrations of THC enhanced lymphocyte proliferation, T-cell numbers in general, and Ly2 cells specifically. These results emphasize that THC can either enhance or suppress aspects of the immune response, depending on the specific immune stimulants used and the specific parameter of immunity measured.

Adjuvants, Immunologic↗