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E Kubota

Publications and source records attributed to E Kubota.

At least 73 records · Page 4Linked to original sources
PubMed1988

Characterization of hepatic microsomal metabolism as an in vivo detoxication pathway of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a selective neurotoxin to the nigrostriatal dopaminergic neurons, has been shown to be metabolized by microsomal flavin-containing monooxygenase (FMO) to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine N-oxide and by cytochrome (cyt.) P-450 to 4-phenyl-1,2,3,6-tetrahydropyridine in the liver. The present study was conducted to determine whether and to what extent each of these metabolic processes would function as the detoxication pathway(s) of MPTP. Administration of either MPTP metabolites, MPTP N-oxide or 4-phenyl-1,2,3,6-tetrahydropyridine, to mice resulted in no significant reductions in striatal dopamine and its metabolites. Pretreatment of mice with alternate substrate of FMO, N-methylmercaptoimidazole or thiobenzamide significantly (P less than .001 to .05) enhanced MPTP-induced reductions in striatal dopamine and its metabolites. In contrast, neither pretreatments with cyt. P-450 inhibitors, SKF-525A (2-diethylaminoethyl-2,2-diphenyl-valerate), quinidine and cimetidine nor with the inducers, phenobarbital and 3-methyl-cholanthrene altered the neurotoxic effects of MPTP. The rate of clearance (Vmax/Km) of N-oxygenation by hepatic microsomes from intact mice was 32 times greater than that of N-demethylation. Although phenobarbital treatment increased Vmax/Km of N-demethylation by 100%, it was still 10 times lower than that of N-oxygenation. Thus, the different responsivenesses of MPTP-treated mice to alternate substrates of FMO and cyt. P-450 modulators appear to come from the difference in the rate of metabolism between N-oxygenation and N-demethylation of MPTP.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1987

High affinity peptide histidine isoleucine-preferring receptors in rat liver.

Peptide Histidine Isoleucine (PHI) is generally considered a low affinity agonist for Vasoactive Intestinal Peptide (VIP) receptors. In this study, we investigated the presence and characteristics of [125I]PHI binding sites on rat liver membranes. Detergents at nonsolubilizing concentrations (1 mM CHAPS or 0.01% Tween-20) were included in the assay buffer to reduce adsorptive loss of PHI to acceptable levels and permit measurement of PHI-binding to receptors. Under these conditions, binding of PHI to liver membranes was time- and temperature-dependent, reversible and saturable. Unlabeled PHI was 9.7-fold more potent than VIP, and 357-fold more potent than secretin in displacing [125I]-PHI binding. Scatchard analysis suggested the presence of two classes of PHI receptors, with Kd 27 pM and 512 pM. The data from [125I]-PHI and [125I]-VIP binding studies suggested that one class of receptors was PHI-preferring, and the other, equally reactive with PHI and VIP. The concentration of immunoreactive PHI, measured by radioimmunoassay, in blood from the hepatic portal vein of anesthetized rats was 2-fold higher than that from the hepatic vein, suggesting uptake of circulating PHI by the liver.

Animals↗
PubMed1986

Vasoactive intestinal polypeptide relaxes pulmonary artery by an endothelium-independent mechanism.

Vasoactive intestinal polypeptide (VIP) is a potent endogenous vasodilator. VIP-induced vasodilation is independent of adrenergic or cholinergic receptors and, for the most part, of arachidonate metabolites, but its mechanism is still unknown. In view of the recently demonstrated essential role of endothelium in the relaxant effect of numerous vasodilators, we have investigated the importance of endothelium in the vascular relaxation induced by VIP. Vascular smooth muscle preparations were circular strips of the pulmonary artery of guinea pig, rat and rabbit, and rat thoracic aorta, previously contracted by a synthetic prostaglandin endoperoxide analog. VIP relaxed pulmonary artery of all species by an endothelium-independent mechanism, but relaxed rat thoracic aorta only in the presence of intact endothelium.

Animals↗
PubMed1985

The target minor H antigen for F1 cytotoxic T lymphocytes induced by Igh-congenic parental spleen cells is coded for by gene linked to H-2.

Graft-vs-host reaction (GvHR) induced in (B10.BR X CWB)F1 (BWF1; H-2k/b, Ighb/b) by i.v. injection with CWB (H-2b, Ighb) spleen cells resulted in complete suppression of cytotoxic T lymphocyte (CTL) responsiveness of the F1 host spleen cells (GvHR-associated immunosuppression). In contrast, GvHR induced in BWF1 mice with CSW (H-2b, Ighj; Igh-congenic to CWB) spleen cells did not affect CTL responsiveness of the F1 host spleen cells at all. The BWF1 hosts undergoing the CSW-induced GvHR generated anti-CSW CTL in their spleens, and the subsequent culture of such BWF1 spleen cells with CSW stimulator cells, augmented the CTL activity. The BWF1 anti-CSW CTL lysed both Con A- and LPS-induced splenic blasts from mouse strains carrying the Ighj allele in the context of self H-2Kb. However, determination of the Igh haplotype in the serum IgG and of the susceptibility of the splenic lymphocytes to the BWF1 anti-CSW CTL on backcross mice, which carry either Ighb/j or Ighb/b in the context of H-2b/b or H-2b/k, showed clearly that Ighj and the gene coding for the target antigen for the BWF1 anti-CSW CTL segregated at ratios close to 1:1. The study in which linkage between the gene(s) coding for the target antigen for the BWF1 anti-CSW CTL and H-2 was examined on CWB X (C3H X CWB)F1 backcross mice and (B10.BR X CSW)F1 X B10 mice demonstrated that the gene, most likely a single gene, coding for the target antigen for the BWF1 anti-CSW CTL is located at 8.5 +/- 4.3 cross-over units to the right or left of the H-2 complex. We designated the minor H antigen to be recognized by the BWF1 anti-CSW CTL as H-X+, and we discuss the distinction between the H-X+ locus and the other minor H loci on chromosome 17.

Animals↗
PubMed1985

Vasoactive intestinal peptide as a possible transmitter of nonadrenergic, noncholinergic relaxation of pulmonary artery.

Electrical field stimulation of isolated guinea pig pulmonary artery induced a brief initial contraction followed by a more prolonged relaxation. alpha-Adrenergic blockade prevented the contraction and enhanced the relaxation. beta-Adrenergic and cholinergic muscarinic blockade partially reduced the relaxation, but 44.4% of the relaxation persisted after adrenergic and cholinergic blockade. The PA relaxation was associated with the release of immunoreactive VIP, both before and after this blockade. Tetrodotoxin abolished the nonadrenergic, noncholinergic relaxation and markedly reduced the release of VIP. This relaxation was similarly attenuated by a monoclonal antibody against VIP.

Acetylcholine↗
PubMed1985

In vivo priming of mouse CTL precursors directed to product of a newly defined minor H-42 locus is under a novel control of class II MHC gene.

In a previous study, we discovered a new mouse minor histocompatibility antigen encoded by a locus at 8.5 cM apart from the H-2 complex, and we have since named the locus H-42. One allele of H-42, which is named H-42a, had been elucidated, but the other alleles, which we tentatively named H-42b, have not been elucidated. In the present study, we explored MHC control on the anti-H-42a cytotoxic T lymphocyte (CTL) responsiveness in H-42b mice. In vivo immunization (i.v. injection) of H-42b mice with 5 to 30 X 10(6) spleen cells (SC) bearing allogeneic H-42a antigen but carrying H-2 complex (mouse MHC) matched with the H-42b mice failed to prime anti-H-42a CTL but induced stable and specific anti-H-42a CTL unresponsiveness, i.e., tolerance, in the H-42b recipient mice. In contrast, H-2 heterozygous H-42b F1 mice injected with SC bearing H-42a alloantigen on either of the parental H-2 haplotypes were effectively primed to generate anti-H-42a CTL. Exploration of the region or subregion in the H-2 complex of H-42a donor SC that should be compatible with H-42b recipient mice for the induction of their anti-H-42a CTL tolerance demonstrated that the compatibility at I region, most probably I-A subregion, but not at K, S, or D region, determined the induction of the tolerance. MHC class II compatible H-42a skin graft (SG) to H-42b mice, however, consistently primed the anti-H-42a CTL in the H-42b recipients. These results were discussed in several aspects, including uniqueness of MHC class II control on the CTL response to minor H-42a antigen, possibility of inactivation of responding anti-H-42a precursor CTL or helper T cells in H-42b mice by encountering the veto cells present in MHC class II-matched H-42a SC population, and significance of the present observations as a mechanism of CTL tolerance to self-components.

Animals↗
PubMed1984

Modulation of F1 cytotoxic potentials by GvHR: role and mode of action of non-MHC genes that determine the hybrid resistance to GvHR-associated suppression of F1 cytotoxic potential.

The resistance of unirradiated F1 mice against graft-vs-host reaction (GvHR) induced by lymphocytes from certain parental strains is apparently a violation of the basic law in classical transplantation immunity. To explore genetic mechanisms of this peculiar phenomenon, GvHR-associated immunosuppression was examined on various kinds of F1 mice undergoing GvHR induced by parental lymphocytes. In F1 mice raised by crossing DBA/2 mice with various H-2-congeneic B10-series strains, parental lymphocytes having non-H-2 genetic background of DBA (DBA/2 and DBA/1) invariably could not induce GvHR-associated immunosuppression, irrespective of the H-2 haplotype incompatibility involved, whereas lymphocytes of the partner parental strain induced the immunosuppression. The number of the relevant loci in the DBA non-H-2 was assessed to be three recessive loci by examination of the capability to induce the GvHR-associated immunosuppression on lymphocytes from individual (B 10.D2 X DBA/2)F1 X DBA/2 backcross mice. On the other hand, in F1 mice raised by crossing C3H/He or AKR/J mice with various H-2-congeneic B10-series strains, parental lymphocytes of H-2k haplotype, irrespective of their non-H-2 haplotype, invariably could not induce the GvHR-associated immunosuppression. Furthermore, it was revealed that non-H-2 genes of parental C3H or AKR incorporated in the F1 mice determine the resistance of the F1 mice against the H-2k-induced GvHR. The results of examination of the resistance on individual (B10 X [B10.BR X C3H/He]F1) and (B10 X [B10.BR X AKR/J]F1) mice suggested that three non-H-2 loci of C3H/He or two non-2 loci of AKR/J incorporated in F1 hybrids could determine the resistance of the respective F1 mice.

Animals↗
PubMed1983

Further improvement of dye-exclusion microcytotoxicity assay by introducing low melting point agarose into the medium.

We developed an improved method for the dye-exclusion microcytotoxicity test by introducing low melting point agarose (LMP-Aga) into the assay medium. The procedures in our method are made very feasible by such noble characteristics of LMP-Aga that once solubilized, the sol state is retained at 37 degrees C, while once gelated, the gelated state is retained even at 37 degrees C. The most important advantage of our method is that even distribution, without any accumulation, of the target cells on the bottom surface of the test wells and no dislodgement of the target cells from the wells by mechanical force inflicted during the assay, enable us to observe the target cells precisely and to obtain an accurate percentage of dead target cells. Another advantage of the present method is that in complement-mediated cytotoxicity tests, it is possible to use unabsorbed normal serum as complement source because naturally occurring cytotoxicity in normal serum is completely removed during the diffusion into the LMP-Aga medium. Thus it should be concluded that our method is excellent in all respects, e.g., accuracy and reproducibility in the results of the test, and feasibility of the procedures.

Animals↗
PubMed1983

Fetal calf serum-injected F1 mice spontaneously generate specific anti-parental cytotoxic T lymphocytes in in vitro culture.

Spleen cells from adult (BALB/c x AKR/J)F1 mice primed in vivo with fetal calf serum (FCS) can spontaneously generate anti-parental AKR/J cytotoxic T cells (CTL) in a 5-day in vitro culture containing 5% FCS. This response is distinguished by the following features: (i) it is anti-parental but not anti-self, and (ii) it has specificity for the Kk parental determinant as shown by mapping studies on a variety of targets and antiserum-blocking experiments. Although specifically elicited by FCS and mediated by FCS-induced T-helper cells, it is ascertained that this cytotoxicity is not directed against Kk components modified by absorbed FCS as shown by cold-target competition studies. Further experiments involved a comparative investigation of the patterns of lysis of allogenically induced CTL, FCS-induced CTL, and natural killer (NK) cytotoxic activities on tumor cell targets. The resistance of BW 5147 tumor targets to NK- and FCS-induced lysis was found to be dramatically overcome by treatment with mitomycin C, and provides circumstantial evidence for a functional relationship between the FCS-induced anti-parental CTL effectors and NK cells based on the observed similarity in lytic patterns of these two effector types. With reference to the work of other authors, the possibility that hybrid resistance and its possible in vitro counterpart, F1 anti-parental CTL cytotoxicity, and NK activity are mediated by similar or common effector mechanisms is discussed.

Animals↗
PubMed1983

Modulation of F1 cytotoxic potentials by GvHR. Host- and donor-derived cytotoxic lymphocytes arise in the unirradiated F1 host spleens under the condition of GvHR-associated immunosuppression.

As an approach to dissect complex cellular events that lead to GvHR-associated immune disorders, we followed cytotoxic activities, including NK cytotoxicity, in the spleens of unirradiated F1 hosts undergoing GvHR induced by parental spleen cells. Spleen cells of (B10 X DBA/2)F1 or (B10 X AKR/J)F1 hosts undergoing GvHR induced by parental B10 spleen cells displayed a prompt and marked increase in NK cell activity within 36 hr, and the heightened activity lasted until day 8. The activity then declined abruptly and disappeared on day 12 of GvHR. Inversely, donor B10-derived CTL specifically directed to the opposite parental alloantigens of the F1 hosts emerged in these F1 host spleens on day 8, and the CTL activity reached a peak on day 12 when the host NK cell activity disappeared. During the period that the donor-derived anti-host CTL were present, these F1 host spleen cells lost not only NK cell activity but also the ability to mount in vitro CTL responses. In contrast, the respective F1 strain mice undergoing GvHR induced by the parental DBA/2 or AKR/J spleen cells showed only transient but marked increases in NK cell activity during the initial 36 hr, and then the activity decreased gradually to return to the normal level on day 10. In such GvHR F1 host spleens, donor-derived CTL could never be detected, and the spleen cells showed normal in vitro CTL responsiveness during the entire observation period of 16 days. These results are discussed from the viewpoint of genetically defined cellular events that lead to the GvHR-associated immune disorders.

Animals↗
PubMed1980

Congenital tracheoesophageal fistula without esophageal atresia. A 22 year experience.

Experience in managing the patients with congenital tracheoesophageal fistula without esophageal atresia led to the following conclusions: (1) The pulmonary and gastrointestinal manifestations of this lesion may be subtle and similar to those of other disorders. A high index of suspicion is required to recognize the fistula. (2) Skillful and persistent efforts should be made to establish the diagnosis and localize the fistula before any surgical attempt at correction. (3) Adequate preoperative preparation, cannulation of the fistula and careful surgical dissection will minimize surgical complications.

Child, Preschool↗