Biomedical subjects

T Ohmori

Publications and source records attributed to T Ohmori.

At least 145 records · Page 8Linked to original sources

PubMed1993

Endopeptidase activity of cathepsin C, dipeptidyl aminopeptidase I, from bovine spleen.

By employing various synthetic substrates, as well as soluble denatured protein substrate (TAP-lysozyme) and its derivatives, endopeptidase activity of cathepsin C, dipeptidyl aminopeptidase I [EC 3.4.14.1], from bovine spleen was investigated. Cathepsin C efficiently degraded Z-Phe-Arg-MCA, Pro-Phe-Arg-MCA, and Suc-Leu-Leu-Val-Tyr-MCA. This endopeptidase activity required sulfhydryl reagents and halide ions, as in the case of the dipeptidyl aminopeptidase (DAP) activity. We confirmed that this endopeptidase activity is due to cathepsin C itself based on the results on gel-filtration and anion-exchange chromatographies, comparative studies of the inhibitory effects of leupeptin and E-64 on this activity and those of cathepsins B and L, and further the competitive inhibitions by mutual substrates for the DAP and endopeptidase activities of cathepsin C. We also found that cathepsin C endopeptidase activity towards TAP-lysozyme and its N-alpha-acetylated tryptic peptides showed marked dependence on sulfhydryl reagents and chloride ion. Thus, we concluded that cathepsin C has endopeptidase activity as well as DAP activity. The binding energy between the enzyme and the amino acid side chains of the substrate may be as important for the endopeptidase activity as is the electrostatic interaction between the enzyme and the free alpha-amino group of the substrate for the DAP activity.

Animals↗

PubMed1993

The mechanism of the difference in cellular uptake of platinum derivatives in non-small cell lung cancer cell line (PC-14) and its cisplatin-resistant subline (PC-14/CDDP).

A cisplatin-resistant non-small cell lung cancer cell line, PC-14/CDDP, was established from PC-14 by stepwise escalation of CDDP concentrations in vitro. PC-14/CDDP cells were 11.4-fold more resistant to CDDP compared with PC-14 cells. This resistant cell line was cross-resistant to platinum analogues, such as carboplatin (CBDCA) (x 3.5), cis-diammine(glycolate-O,O')platinum(II) (254-S) (x 5.6) and cis-dichloro(ethylenediammine)platinum(II) (cis-DEP) (x 4.2). On the other hand, relative resistance value to ormaplatin was only 1.4-fold. To elucidate the mechanism(s) of CDDP resistance and of its circumvention by ormaplatin, we investigated the characteristics of this cell line. Total sulfhydryl content was slightly elevated in PC-14/CDDP cells compared with PC-14 cells. There was no significant difference in the DNA repair ability between the two cell lines. Cellular accumulations of CDDP, CBDCA, 254-S, and cis-DEP in PC-14/CDDP cells were markedly decreased to 23%, 27%, 29%, and 32% of those in PC-14 cells, respectively. However, the accumulation of ormaplatin in PC-14/CDDP was almost the same as that in PC-14. To elucidate the mechanisms of uptake of these platinum analogs in the cells, we studied the effects of ouabain, an Na+,K(+)-ATPase inhibitor, on cellular drug uptake in both cell lines. Preincubation with 300 nM ouabain for 1 h inhibited approximately 60% of CDDP accumulation in PC-14. However ouabain preincubation at any concentration up to 300 nM did not affect CDDP accumulation in PC-14/CDDP. The accumulation of ormaplatin was not inhibited by ouabain in either of the cell lines. These data suggest that the mechanism of the uptake of ormaplatin is different from that of CDDP, and that ormaplatin exerts a cytotoxic effect in CDDP-resistant cells which have defective cisplatin accumulation.

Antineoplastic Agents↗

PubMed1993

Adenoendocrine cell carcinoma of the gallbladder: a histochemical and immunohistochemical study.

A case of adenoendocrine cell carcinoma of the gallbladder with adenomucous cells and neuroendocrine cells is reported. A histochemical and immunohistochemical study revealed that the primary tumor in the gallbladder was composed of mucus-secreting and/or argyrophil cells. Furthermore, the tumor showed a positive reaction to carcinoembryonic antigen (CEA) in all tumor cells, to chromogranin A and cytokeratin in many tumor cells, to endocrine granule constituent (EGC) in some tumor cells, and to serotonin and somatostatin in a few tumor cells. In addition, a few mucous cells showed argyrophilia and EGC-positivity in their cytoplasms. This case suggests that the adenoendocrine cell tumor is derived from endodermal stem cells as a result of bidirectional (exocrine and endocrine) differentiation.

Adenocarcinoma↗

PubMed1993

Immunohistochemical study of superoxide dismutase in the olfactory mucosa.

We used an anti-copper, zinc-superoxide dismutase (Cu,Zn-SOD) antibody in an immunohistochemical investigation of the distribution of SOD in the mouse olfactory mucosa. We also investigated differential staining with this antibody in comparison with an antibody specific to carnosine, a marker of mature olfactory cells. Mouse olfactory mucosa were immunostained with the ABC method with anti-SOD and anti-carnosine antibodies. When anti-SOD antibody was used, the sustentacular cells were positive in the olfactory region, whereas the olfactory cells were negative. In the respiratory region, the columnar epithelial cells were positive, whereas goblet cells were negative. The olfactory cells, olfactory vesicles and axons showed positive staining with anti-carnosine antibody, whereas the sustentacular and basal cells were negative.

Animals↗

PubMed1993

Novel water-soluble derivatives of docosahexaenoic acid increase diacylglycerol production mediated by phosphatidylcholine-specific phospholipase C.

The effect of ascorbic acid 6-docosahexaenoate (DHA-VC) on the phospholipase-C-mediated hydrolysis of phosphatidylcholine was investigated. In human non-small cell lung cancer cells (PC-14) exposed to DHA-VC for 24 hr, a dose-dependent increase in phosphatidylcholine-specific phospholipase C (PC-PLC) activity was seen. PC-PLC activity in whole-cell homogenate of PC-14 cells was increased about 2.5-fold by 2 hr of treatment with DHA-VC (20 micrograms/ml). Treatment with DHA-VC also augmented PC-PLC activity in the crude membrane extract. On the other hand, DHA-VC inhibited the activity of phospholipase A2 (ID50 = 800 micrograms/ml). Another water-soluble analog, choline docosahexaenoate, also stimulated PC-PLC activity. To explore the effect of DHA-VC on phosphatidylcholine turnover, we analyzed phospholipids labeled with [14C] choline or [3H]myristate by thin-layer chromatography, and found that the amount of [14C]- and [3H]-labeled phosphatidylcholine was constant in the presence of DHA-VC. These results suggest that phosphatidylcholine turnover was not influenced by DHA-VC. DHA-VC treatment increased protein kinase C activity of the cells in the late phase (120 min), suggesting that DHA-VC-induced diacylglycerol production mediated by PC-PLC causes protein kinase C activation. Considering that significant inhibition of DNA synthesis occurred 12 hr after 2 hr of treatment with DHA-VC (20 micrograms/ml), DHA-VC-induced PC-PLC activation seems to be an early event in DHA-VC-induced cytotoxicity, which suggests that the effects of DHA-VC on signal transduction pathways may play an important role in the cytotoxicity of DHA-VC.

Ascorbic Acid↗

PubMed1993

[A study on the pharmacological action of phencyclidine].

Phencyclidine (PCP) produces schizophreniform psychoses in drug abusers and exacerbates symptoms in chronic schizophrenics. Although the exact mechanisms of psychotomimetic effects are unknown, the drug is known to act as an indirect dopamine (DA) agonist by inhibiting neuronal reuptake of DA. The drug is also known to work as a N-methyl-D-aspartate (NMDA) antagonist. Aiming to investigate characteristics of these two properties of PCP in the same experimental system, the effects of PCP on spontaneous and NMDA-induced DA efflux from superfused slices of rat striatum were examined. DA and 3,4-dihydroxyphenylacetic acid (DOPAC) in the superfusate samples were extracted via alumina extraction and measured by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). PCP, at concentrations greater than 1 microM, produced a concentration-dependent increase of the spontaneous efflux of DA. DOPAC efflux was also concentration-dependently increased by PCP. However, PCP inhibited DA efflux induced by NMDA even at a low concentration (0.1 microM), which did not alter the spontaneous efflux of the transmitter. The mode of the inhibition of PCP was shown to be noncompetitive with an estimated IC 50 value of 280 nM. These results indicate that PCP acts simultaneously as a weak indirect DA agonist and as a potent noncompetitive NMDA antagonist. Since psychological change in normal subjects or exacerbation of schizophrenic symptoms has been reported to occur with a small dose of PCP, the psychotomimetic effects of the drug are more likely to be mediated by its interaction with NMDA receptor. The clinical significance of the present study is discussed in relation with the qlutamatergic hypothesis of schizophrenia.

Animals↗

PubMed1992

Detection of topoisomerase I gene point mutation in CPT-11 resistant lung cancer cell line.

CPT-11, a recently developed topoisomerase I (Topo I) inhibitor, attracts the attention not only of basic researchers but also of clinicians because of its high antitumor activity. The CPT-11 resistant human lung cancer cell line, PC-7/CPT, showed 10-fold resistance compared to parental cell line, PC-7. The total activity of Topo I in the resistant cell line was one fourth that of the parental sensitive cell line. The Topo I from the resistant cells was also 5-fold more resistant to the inhibitory effect of CPT-11 than that of the parental cells. We speculated that the alteration of the Topo I gene may be responsible for the change in topoisomerase activity of the CPT-11 resistant cell line. Therefore, we analyzed the mutation of Topo I gene using the method of single strand conformation polymorphism of polymerase chain reaction and the reverse transcriptase. We divided Topo I cDNA into ten fragments which overlapped each other and covered whole coding sequences of the Topo I cDNA. We observed mobility shift of two fragments in the PC-7/CPT, suggesting the presence of some mutations in these fragments. We performed the direct-sequencing of these portions by the dideoxy chain termination method and observed an altered sequence having a G to A base change in PC-7/CPT. This base substitution results in replacement of the conserved threonine at 729 position with alanine. These results suggest that the point mutation of Topo I gene is related to the decreases of Topo I activity and the sensitivity to Topo I inhibitor in PC-7/CPT cells.

Antineoplastic Agents, Phytogenic↗

PubMed1992

Age-dependent increase of extrathymic T cells in the liver and their appearance in the periphery of older mice.

The liver is a major site of generation of extrathymic T cells with unique properties (e.g., expressing intermediate TCR and containing self-reactive clones). We investigated herein whether the levels of extrathymic alpha beta T cells varied in various organs as a function of age. A systematic examination of the number of mononuclear cells in various organs of BALB/c mice revealed that the number of hepatic MNC increased with age whereas the number of thymocytes decreased. These changes were more striking in mice fed under conventional conditions than under specific pathogen-free condition. The age-dependent changes in the number of mononuclear cells in the spleen and lymph nodes were minimal. Although the total proportion of alpha beta T cells in each organ remained constant, the staining patterns of TCR-alpha beta as shown by immunofluorescence profiles varied. The most prominent change was that intermediate TCR-alpha beta cells, which constituted a small population in the liver of young mice, expanded in the liver of older mice. Intermediate TCR cells appeared even in the periphery of older mice. These findings were confirmed by the appearance of extrathymic T cells with other unique properties, e.g., double-negative CD4-8- phenotype and CD44 expression. In athymic nude mice, only intermediate TCR cells were present in the liver and periphery. An age-dependent increase of intermediate TCR cells was also seen in these mice. Taken together with the result of bromodeoxyuridine-injection experiment, which showed an intensive in vivo proliferation of cells in the hepatic sinusoids, extrathymic T cells may differentiate predominantly in the liver and appeared even to the periphery in older mice.

Age Factors↗

PubMed1992

Amygdala kindling does not alter the N-methyl-D-aspartate receptor-channel complex which modulates dopamine release in the rat striatum and amygdala.

Kindling is suggested to be critically associated with enhancement of N-methyl-D-aspartate (NMDA) type excitatory amino acid synaptic transmission. The present study examined effects of kindling on NMDA-induced dopamine (DA) efflux from slices of the rat striatum and amygdala. When assayed 5-7 days after the last evoked seizure, no difference was observed between kindled and non-kindled striatum in the ability of NMDA to induce DA release, or in the effect of MK-801 or 7-chlorokynurenic acid to inhibit the amino acid-induced transmitter release. The present study revealed that NMDA receptors are also involved in the modulation of DA release in the amygdala. However, no difference was observed between kindled and non-kindled amygdala in the ability of NMDA to induce DA release. These results suggest that amygdala kindling does not alter activity of the NMDA receptor-channel complex modulating DA release in the striatum and amygdala.

Amygdala↗

PubMed1992

Serotonergic measures in suicide brain: the concentration of 5-HIAA, HVA, and tryptophan in frontal cortex of suicide victims.

Concentrations of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and tryptophan (TRP) were determined in the frontal cortex of individuals who died by suicide, homicide, accident, or the result of physical diseases. Females had significantly higher tryptophan concentrations than males. There was a significant correlation HVA and the interval between death to refrigeration of the body. Mean HVA levels were higher from noon to 5 PM. Suicide and homicide victims had significantly higher cortical HVA concentrations than those who died of physical disease but not accident victims. This was not accounted for by gender, age, postmortem interval from death to refrigeration of the body or to autopsy, specimen storage time, or drug effects. The ratio of HVA/5-HIAA was also significantly higher in suicides compared with those who died of physical disease. No differences in cortical 5-HIAA or tryptophan concentrations between the four groups were found. There were no differences in the levels of the three substances in violent and nonviolent suicides. There were no significant correlations between 5-HIAA, HVA and TRP concentrations in all subjects or any of the four subgroups. The implications of these findings for the role of serotonin and dopamine in suicide and violence are discussed.

Accidents↗

PubMed1992

MK-801, a non-competitive antagonist of NMDA receptor, prevents methamphetamine-induced decrease of striatal dopamine uptake sites in the rat striatum.

We investigated the effects of MK-801, a non-competitive antagonist of NMDA receptor, on methamphetamine-induced decrease in dopamine (DA) uptake sites in the rat striatum. Repeated administrations of an escalating dose of methamphetamine (2.5, 5, 7.5, 10 mg/kg s.c. x2, every other day for a week) produced decreased DA uptake sites assayed by binding with [3H]GBR 12935 in the striatum. Co-administration of MK-801 and methamphetamine significantly prevented the methamphetamine-induced decrease in striatal [3H]GBR 12935 binding. Administration of MK-801 alone did not affect [3H]GBR 12935 binding. These results suggest that some neurochemical effects of methamphetamine may be mediated via mechanism involving excitatory amino acids.

Animals↗

PubMed1992

The structure of glutaraldehyde in aqueous solution determined by ultraviolet absorption and light scattering.

The structure of glutaraldehyde (GA) in aqueous solutions has been the subject of much debate. Since there were fundamental problems in the experiments in the preceding studies, in this article, the structure of GA was investigated with uv absorption and light scattering to avoid those problems. It was discovered that 70% glutaraldehyde solution contains a large quantity of polymeric species with cyclic hemiacetal structure. On dilution, the polymerized glutaraldehyde slowly converted to monomers. In dilute solution, glutaraldehyde is almost monomeric at pH 3-8, the major portion taking the cyclic hemiacetal structure. The structure of GA in 20% solution is similar to that in more dilute solution. alpha, beta-Unsaturated structure does not exist in aqueous solution regardless of the concentration of glutaraldehyde.

Glutaral↗

PubMed1992

Day-to-day changes in oxygen uptake kinetics at the onset of exercise during strenuous endurance training.

The aim of this study was to assess the effect of strenuous endurance training on day-to-day changes in oxygen uptake (VO2) on-kinetics (time constant) at the onset of exercise. Four healthy men participated in strenuous training for 30 min.day-1, 6 days.week-1 for 3 weeks. The VO2 was measured breath-by-breath every day except Sunday at exercise intensities corresponding to the lactate threshold (LT) and the onset of blood lactate accumulation (OBLA) which were obtained before training. Furthermore, an incremental exercise test was performed to determine LT, OBLA and maximal oxygen uptake (VO2max) before and after the training period and every weekend. The 30-min heavy endurance training was performed on a cycle ergometer 5 days.week-1 for 3 weeks. Another six men served as the control group. After training, significant reductions of the VO2 time constant for exercise at the pretraining LT exercise intensity (P less than 0.05) and at OBLA exercise intensity (P less than 0.01) were observed, whereas the VO2 time constants in the control group did not change significantly. A high correlation between the decrease in the VO2 time constant and training day was observed in exercise at the pretraining LT exercise intensity (r = -0.76; P less than 0.001) as well as in the OBLA exercise intensity (r = -0.91; P less than 0.001). A significant reduction in the blood lactate concentration during submaximal exercise and in the heart rate on-kinetics was observed in the training group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

In vitro enhancement of fluoropyrimidine-induced cytotoxicity by leucovorin in colorectal and gastric carcinoma cell lines but not in non-small-cell lung carcinoma cell lines.

Leucovorin (LV) increases the cytotoxic effect of fluorouracil (FUra) and 5-fluoro-2'-deoxyuridine (FdUrd) by enhancing the formation of the fluorodeoxyuridine monophosphate (FdUMP) thymidylate synthase (TS) 5,10-methylenetetrahydrofolate (mTHF) ternary complex. To study the difference in the efficacy of this combination against different tumors, we compared the effect of LV (20 microM) on the cytotoxicity of FUra, FdUrd, and 5-fluorouridine (FUrd) in vitro against cell lines of five colorectal carcinomas (CC), five gastric carcinomas (GC), and four non-small-cell lung carcinomas (NSCLC) using the colony-forming assay. At the concentration used in the experiments, LV alone failed to inhibit colony formation in any of the cell lines tested. The NSCLC cell lines were more resistant to FdUrd than were the CC and GC lines. LV modulated the cytotoxicity of FdUrd in all five CC lines and in three of the five GC lines but failed to do so in any of the NSCLC lines. In addition, following 20 h treatment with 1 microM [3H]-FdUrd, formation of the FdUMP/TS/mTHF ternary complex was enhanced by LV in the LV-sensitized CC and GC cell lines but not in the LV-refractory NSCLC lines. These in vitro data corresponded well to the results of clinical trials. Therefore, the colony-forming assay may be useful for the identification of the sensitivity of tumors according to phenotype.

Adenocarcinoma↗

PubMed1992

Effect of phencyclidine on spontaneous and N-methyl-D-aspartate (NMDA)-induced efflux of dopamine from superfused slices of rat striatum.

Phencyclidine (PCP) acts as an indirect dopamine (DA) agonist by inhibiting the neuronal reuptake of DA, while it also works as a N-methyl-D-aspartate (NMDA) antagonist. Aiming to investigate characteristics of these two properties of PCP in the same experimental system, the effects of PCP on spontaneous and NMDA-induced efflux of DA from superfused slices of the striatum of the rat were examined. Dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) in the samples of superfusate were extracted by alumina extraction and measured by high-performance liquid chromatography with electrochemical detection (HPLC-EC). Phencyclidine at concentrations greater than 1 microM, produced a concentration-dependent increase of the spontaneous efflux of DA. The efflux of DOPAC was also concentration-dependently increased by PCP. However, PCP inhibited the efflux of DA induced by NMDA, even at a small concentration (0.1 microM), which did not alter the spontaneous efflux of the transmitter. The mode of the inhibition by PCP was shown to be noncompetitive, with an estimated IC50 value of 280 nM. These results suggest that PCP, at small concentrations, reduces the synaptic levels of DA by blocking the facilitating effect of endogenous glutamate on the release of DA and, at slightly greater concentrations, the drug also works as an indirect DA agonist, to increase the levels of the transmitter in the synaptic clefts. The clinical significance of the dual effects of PCP is discussed in relation with the unique schizophrenomimetic property of PCP.

Animals↗

PubMed1992

Inactivation of herpes viruses by high hydrostatic pressure.

The effects of high hydrostatic pressure on herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV) were examined. Pressure at more than 300 MPa for 10 min at 25 degrees C inactivated these virions and drastically inhibited their infection to cultured cells, and at greater than 400 MPa, reduced infective titers of HSV-1 and HCMV by more than 7 and 4 logs, respectively. Electron microscopic examination illustrated coincidentally that high pressure at 300 MPa damaged the virus envelope and prevented the virus particles from binding to the cells. The findings suggest that treatment at high hydrostatic pressure is promising as a means of inactivating HSV-1, HCMV and other enveloped viruses.

Animals↗

PubMed1992

Mechanisms of collateral sensitivity to fluorouracil of a cis-diamminedichloroplatinum(II)-resistant human non-small lung cancer cell line.

A cisplatin(CDDP)-resistant subline of a human lung cancer cell line, PC-7/CDDP, was 4.7-fold more resistant to CDDP than the parent line in a colony-forming assay. The sensitivity of this cell line to anthracyclines, vinca-alkaloid, etoposide, mitomycin C, and bleomycin was similar to that of the parental line, PC-7. However, PC-7/CDDP exhibited 4-fold higher sensitivity to fluorouracil (FUra). Possible mechanisms associated with the collateral sensitivity to FUra were studied in PC-7/CDDP cells. The sensitivity of both cell lines to FUra did not correlate with the effect of FUra on RNA. On the other hand, FUra induced a greater reduction in dTTP pools and more single strand breaks in PC-7/CDDP than in PC-7 cells. These results suggest that the pathway for de novo deoxyribonucleotide synthesis may be a target for FUra in PC-7/CDDP cells. However, inhibition of thymidylate synthase after FUra treatment did not correlate with the DNA-directed activity of FUra. Based on the above findings, the decreased salvage synthesis of dTTP was considered a possible mechanism of the greater reduction of dTTP pools in PC-7/CDDP cells. However, the activity of dThd kinase was the same in both cell lines. In the presence of physiological concentrations of exogenous dThd in the serum, uptake of dThd was less in PC-7/CDDP cells than that in PC-7 cells. Our data suggest that FUra-induced cytotoxicity in PC-7/CDDP cells is associated with the inhibition of dTTP synthesis and that the decreased uptake of dThd is a possible mechanism of the collateral sensitivity to FUra in PC-7/CDDP cells.

Adenocarcinoma↗

PubMed1992

Alteration of type II regulatory subunit of cAMP-dependent protein kinase in human cisplatin-resistant cells as a basis of collateral sensitivity to 8-chloro-cAMP.

A cyclic adenosine 3',5'-monophosphate (cAMP) analogue, 8-chloro-cAMP (8-Cl-cAMP), had a collateral growth-inhibitory effect on a cis-diamminedichloroplatinum(II) (CDDP)-resistant human cancer cell lines (PC-14/CDDP). The non-selective analogues dibutyryl-cAMP, 8-bromo-cAMP and forskolin, which are cAMP agonists, showed far less cytotoxicity than 8-Cl-cAMP in both cell lines. There was no significant difference in cAMP content between PC-14 and PC-14/CDDP. Because 8-Cl-cAMP has been shown to bind selectively to the site I receptor of the type II regulatory subunit (RII) of cAMP-dependent protein kinase, we determined the level of expression of regulatory subunits in PC-14 and PC-14/CDDP cells by photoaffinity labeling. PC-14/CDDP cells had a higher RII level, low site I receptor of type I regulatory subunit (RI) level, and a lower RI/RII ratio than the parental PC-14 cells. Exposure to 8-Cl-cAMP increased the RI and RII level in PC-14/CDDP cells in dose- and time-dependent manners. On the other hand, in parental PC-14 cells, RII was not detected and the levels of RI and RII were not increased by exposure to 8-Cl-cAMP. These results suggested that the change in RI and/or RII levels caused by 8-Cl-cAMP was correlated with 8-Cl-cAMP-induced growth inhibition and that the collateral sensitivity to 8-Cl-cAMP in CDDP-resistant cells was due to the increased RII level. Our results suggest that 8-Cl-cAMP can be used in combination with CDDP and that measurement of RI and RII levels and/or the RI/RII ratio is a useful tool to predict CDDP sensitivity.

8-Bromo Cyclic Adenosine Monophosphate↗