PubMed Health⌕ Search

Biomedical subjects

S Shimada

Publications and source records attributed to S Shimada.

At least 19 recordsLinked to original sources
PubMed1992

Leukotriene A4 hydrolase, a bifunctional enzyme. Distinction of leukotriene A4 hydrolase and aminopeptidase activities by site-directed mutagenesis at Glu-297.

We previously obtained evidence for intrinsic aminopeptidase activity for leukotriene (LT)A4 hydrolase, an enzyme characterized to specifically catalyse the hydrolysis of LTA4 to LTB4, a chemotactic compound. From a sequence homology search between LTA4 hydrolase and several aminopeptidases, it became clear that they share a putative active site for known aminopeptidases and a zinc binding domain. Thus, Glu-297 of LTA4 hydrolase is a candidate for the active site of its aminopeptidase activity, while His-296, His-300 and Glu-319 appear to constitute a zinc binding site. To determine whether or not this putative active site is also essential to LTA4 hydrolase activity, site-directed mutagenesis experiments were carried out. Glu-297 was mutated into 4 different amino acids. The mutant E297Q (Glu changed to Gln) conserved LTA4 hydrolase activity but showed little aminopeptidase activity. Other mutants at Glu-297 (E297A, E297D and E297K) showed markedly reduced amounts of both activities. It is thus proposed that either a glutamic or glutamine moiety at 297 is required for full LTA4 hydrolase activity, while the free carboxylic acid of glutamic acid is essential for aminopeptidase.

Amino Acid Sequence↗
PubMed1992

Dopamine transporter site-directed mutations differentially alter substrate transport and cocaine binding.

Polar amino acids lying within three hydrophobic regions of the dopamine transporter (DAT) are analogous to those important for ligand recognition by catecholamine receptors. Possible functional significance of these amino acids was examined by expressing DAT cDNAs mutated in these polar residues. Replacement of aspartate at position 79 with alanine, glycine, or glutamate dramatically reduced uptake of [3H]dopamine and the tritium-labeled Parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium (MPP+) and reduced the mutants' affinity for the tritium-labeled cocaine analog (-)-2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (CFT) without affecting Bmax. Replacement of the serine residues at positions 356 and 359 in the seventh hydrophobic region by alanine or glycine caused reductions in [3H]dopamine and [3H]MPP+ uptake, whereas [3H]CFT binding was less affected. Substitution of two serines in the eighth hydrophobic region yielded wild-type values for [3H]dopamine and [3H]MPP+ uptake and [3H]CFT binding. These results demonstrate that aspartate and serine residues lying within the first and seventh hydrophobic putative transmembrane regions are crucial for DAT function and provide identification of residues differentially important for cocaine binding and for dopamine uptake.

1-Methyl-4-phenylpyridinium↗
PubMed1992

Synaptic contacts between CGRP-immunoreactive terminals and enkephalin-immunoreactive neurons in the central amygdaloid nucleus of the rat.

An immunoelectron microscopic method combined with immunofluorescence double staining was carried out to examine the relationship between calcitonin gene-related peptide (CGRP)-like immunoreactive (LI) axon terminals and enkephalin (ENK)-LI neurons in the central amygdaloid nucleus (Ce) of the rat. The latter method showed that many ENK-LI cell bodies are densely surrounded by CGRP-LI axons in the lateral subdivision of the Ce (CeL). After taking fluorescence micrographs, the immunoperoxidase technique was used to examine the CGRP-LI axonal profiles under an electron microscope. CGRP-LI terminals were frequently found to form axo-somatic synaptic contacts with ENK-LI neurons in the CeL.

Amygdala↗
PubMed1992

Parkinsonism-inducing neurotoxin MPP+: uptake and toxicity in nonneuronal COS cells expressing dopamine transporter cDNA.

Expression of a cloned dopamine transporter complementary DNA in COS cells allows these primate kidney cells to accumulate the parkinsonism-inducing neurotoxin metabolite MPP+ (1-methyl-4-phenylpyridinium) avidly, and MPP+ toxicity results. By documenting that the dopamine transporter can confer MPP+ sensitivity to nonneural cells, these results highlight the key role that this transporter could play in mechanisms underlying parkinsonism.

1-Methyl-4-phenylpyridinium↗
PubMed1992

Extrathymic origin of V gamma 1/V delta 6 T cells in the skin.

The dendritic epidermal cells (dEC) from young (8-week-old) athymic mice were found to express mRNA for gamma/delta T cell receptors (TcR). The mRNA found in the dEC from athymic mice was expressed only for V gamma 1-J gamma 4-C gamma 4 and V delta 6-J delta 1-C delta with both chains having productive rearrangements and junctional diversity. On the other hand, the dEC from euthymic mice carried V gamma 5-J gamma 1-C gamma 1 and V delta 1-J delta 2-C delta in addition to the V gamma 1/V delta 6 subset found in athymic mice. Therefore, this V gamma 1/V delta 6 subset, which has been implicated in the murine gamma/delta T cell responses to mycobacterial antigens and self heat-shock proteins, is the product of extrathymic maturation in the dEC from both athymic and euthymic mice.

Animals↗
PubMed1992

Direct induction of tetraploids or homozygous diploids in the industrial yeast Saccharomyces cerevisiae by hydrostatic pressure.

Hydrostatic pressure and a dye plate method were used to investigate the direct induction of tetraploids or homozygous diploids from the industrial diploid or haploid yeast Saccharomyces cerevisiae. Above 200 MPa, hydrostatic pressure greatly inactivated the strains HF399s1 (alpha haploid), P-540 (a/alpha diploid), and P-544 (a/alpha diploid). At the same time, when pressure-treated cells of these strains were spread on a dye plate, some of the visible colonies were stained red/blue or dark blue (variant colonies); the rest stained violet, similar to colonies originating from diploid cells or haploid cells that were not pressure-treated. In addition, above 100 MPa, the formation of variant colonies increased with increasing pressure, and maximized (1 x 10(-1)) at 200 and 250 MPa, respectively. The size of almost all variant cells from P-544, P-540, and HF399s1 was visibly increased compared with that of untreated cells and the measured cellular DNA content of P-540 and HF399s1 was double that of untreated cells. Furthermore, based on random spore analysis and mass-matings, induced variants in the diploid strains were found to be tetraploid with an a/a/alpha/alpha genotype at the mating-type locus or, in the haploid strains, homozygous diploid with an alpha/alpha genotype. From these results we conclude that pressure treatment in combination with a dye plate is a useful method for strain improvement by direct induction of tetraploids or homozygous diploids from industrial strains whether diploid or haploid.

Crosses, Genetic↗
PubMed1992

Induction of T-cell-mediated immunity against MethA fibrosarcoma by intratumoral injections of a bacillus Calmette-Guérin nucleic acid fraction.

MY-1, which consists of DNA and RNA extracted and purified from bacillus Calmette-Guérin (BCG), has been shown to have strong antitumor activity against various experimental tumors. To examine the role of T cells in the antitumor mechanism of MY-1, the effect of MY-1 injection on the development of tumor-specific immunity against MethA fibrosarcoma was investigated. MY-1 injections inhibited tumor growth less effectively in T-cell-deficient nude mice than in normal BALB/c mice. MethA tumor growth was suppressed after inoculation with L3T4-positive lymphocytes from tumor-bearing mice treated with MY-1. MethA-specific delayed-type hypersensitivity was also detected in tumor-bearing mice treated with MY-1. Immunohistochemical analyses showed that many L3T4-positive and a few Lyt2-positive cells infiltrated the regressing tumors. These results indicate that intratumoral MY-1 injections induce a MethA-specific, L3T4-positive cell-mediated, delayed-type hypersensitivity, which is necessary for the tumor regression.

Animals↗
PubMed1992

Structure-activity relationships of synthetic diosgenyl diglycosides.

The haemolytic and antifungal activities of six synthetic diosgenyl diglycosides and diosgenyl maltotrioside were compared with each other and with those of the parent glucoside. In general, the haemolytic activity of each of these glycosides was higher than, and the antifungal activity as strong as, that of the glucoside. However, both activities of the lactoside were much lower than those of the others.

Antifungal Agents↗
PubMed1992

Dopamine transporter mRNA: dense expression in ventral midbrain neurons.

Oligonucleotides and a full-length cDNA encoding a functional dopamine transporter (DAT1) hybridize to a 3.7 kb mRNA that is concentrated in mRNA prepared from midbrain and absent in specimens from cerebellum or cerebral cortex. In situ hybridization reveals substantial hybridization densities overlying neurons of the substantia nigra, pars compacta, and the parabrachialis pigmentosus region of the ventral tegmental area (VTA). Neurons in the linear and paranigral VTA regions display lower levels of expression. Preliminary studies in arcuate neurons suggest modest hybridization. Different dopaminergic cell groups display different levels of DAT1 dopamine transporter expression.

Animals↗
PubMed1992

Relationship between steatocystoma multiplex and eruptive vellus hair cysts.

Steatocystoma multiplex (SM) and eruptive vellus hair cysts (EVHC) share a clinical resemblance, but have distinctive histologic features. We describe a patient who had both SM and EVHC lesions and discuss the relationship between the two diseases. We believe that SM and EVHC are within the spectrum of the same disease process and could both be termed multiple pilosebaceous cysts.

Abdomen↗
PubMed1992

Changes of host cell infiltration into Meth A fibrosarcoma tumor during the course of regression induced by injections of a BCG nucleic acid fraction.

MY-1, which consists of DNA and RNA extracted and purified from Mycobacterium bovis strain BCG, causes the regression of various experimental syngeneic tumors when injected intratumorally. In order to identify the host cells involved in the antitumor mechanism(s) of MY-1, we examined Meth A tumors inoculated intradermally to BALB/c mice, which were given multiple injections of MY-1 following tumor inoculation. Histological and immunohistochemical examinations were performed at several time points. On day 4 after inoculation, the MY-1-treated tumors were heavily infiltrated with a heterogeneous population of mononuclear cells with low density nuclei. The MY-1-injected tumors contained asialo-GM1-positive cells and Mac-1-positive cells, which indicated that the infiltrating mononuclear cells were natural killer cells and macrophages. On day 14 after inoculation, the tumors were infiltrated with a large number of L3T4-positive cells and fewer Lyt-2-positive cells, both of which were more abundant in the MY-1-treated tumors than in the control tumors. The observed sequence of host cell infiltration corresponded well with our previous studies which have indicated that the antitumor mechanism of MY-1 is divided into two phases, i.e. the early phase when natural killer cells and macrophages inhibit tumor growth, and the late phase when L3T4-positive cells act to induce tumor regression via a delayed-type hypersensitivity against tumor cells.

Animals↗
PubMed1992

Identification of an equivalent to murine Thy-1+ dendritic epidermal cells in the rat epidermis.

In the murine epidermis, there exist Thy-1+ dendritic epidermal cells (Thy-1+DEC). These cells are Thy-1+, CD45+, CD3+ and asialo GM1+ but CD5-, CD4-, CD8-, or Ia-1-, and express T cell receptor (TCR) gamma delta. Recently, most of these TCR gamma delta of Thy-1 DEC are shown to consist of a V gamma 3-V delta 1 combination. There has been no evidence that the same type of cell population exists in other species except mice. In this study, we investigated the existence of a Thy-1+DEC equivalent in the rat epidermis. The epidermal sheets obtained from rats were stained with various monoclonal antibodies to rat lymphocytes. We developed a monoclonal antibody (1F4) to rat CD3 complex. 1F4 stained thymocytes and peripheral T cells and also immunoprecipitated T cell receptor with CD3 complex. Using 1F4 and a recently developed monoclonal antibody to rat TCR alpha beta, we could identify dendritic CD4-, CD8-, CD5-, CD3+, TCR alpha beta- cells in the rat epidermis. These CD3+, TCR alpha beta- cells are strong candidates as an equivalent to TCR gamma delta + murine Thy-1+ DEC.

Animals↗
PubMed1992

Clinical events in association with timing of intraventricular hemorrhage in preterm infants.

To ascertain whether any routine practices or clinical manipulations in a neonatal intensive care unit could induce intraventricular hemorrhage (IVH) in preterm infants, we performed ultrasonic monitoring of the germinal layer continuously for 48 hours in 33 extremely premature infants with respiratory distress. Intraventricular hemorrhage developed in 16 of these infants. In four infants the timing of the germinal layer hemorrhage was confirmed with ultrasonic monitoring. Three of the four cases were apparently associated with clinical events occurring at the moment of IVH: manual ventilation for improvement of hypercapnia associated with primary pulmonary hypertension of the newborn; correction of hyperkalemia, which was causing an arrhythmia, with administration of calcium gluconate and sodium bicarbonate; and administration of surfactant-TA to improve respiratory failure caused by pulmonary hemorrhage. In these three infants it appeared that one of the basic factors inducing IVH might be an increase in blood pressure with or without hypercapnia, causing cerebral reperfusion after ischemic damage of the germinal layer.

Blood Pressure↗
PubMed1992

Time course and inhibition of saponin-induced hemolysis.

Hemolytic activities of 3 steroid saponins reached plateaus within 5 min, whereas those of 4 triterpenoid saponins did not within 60 min. Erythrocytes pretreated with a low concentration of tigogenin were resistant to hemolysis of some of these saponins, but those pretreated with hecogenin or tomatidine were as sensitive as non-treated erythrocytes. Therefore, the ketone group of hecogenin or the amino group of tomatidine would weaken the interactions between the erythrocytes and these sapogenins. Furthermore, incubations of these saponins with a small amount of cholesterol diminished the hemolytic activities.

Animals↗
PubMed1992

Role of asparagine-linked carbohydrates in pulmonary metastasis of B16-F10 murine melanoma cells: implication through glycosylation inhibition by nojirimycin.

N-linked oligosaccharide moieties of cell surface glycoconjugates may be involved in the metastatic potential of tumour cells. Many studies have examined the anti-metastatic properties of inhibitors of carbohydrate synthesis or processing in vitro. However, there has so far been little evidence of such inhibitory factors on metastasis in vivo because of the general high toxicity of the inhibitors. In this study, we found nojirimycin (NM) to be a substantially non-toxic carbohydrate synthesis inhibitor that inhibited the experimental metastasis of B16-F10 melanoma cells not only in vitro but also in vivo. When NM was administered intraperitoneally to syngeneic C57BL/6 mice, the inhibition was dose-dependent, with 40-75% suppression of pulmonary colonization observed after 5 days exposure to NM (at 0.4 or 4 mg/day). An in vitro lectin sensitivity assay showed that NM-treated B16-F10 cells were less susceptible to the lectin concanavalin-A, suggesting alteration or decrease of high mannose-type carbohydrate moieties on the cell surface. Further in vitro analysis of adhesiveness between B16-F10 cells and endothelial cells demonstrated that NM treatment causes reduced binding of B16-F10 cells to endothelial cells. We have also studied the effect of NM on natural killer (NK) cells in mice. NM treatment elicited no substantial increase in the cytotoxic activity of splenic NK cells against YAC-1 target cells. These results indicate that NM acts on the process of adhesion and that specific structures of the cell surface carbohydrate moieties may be involved in the colonization phase of metastasis in vivo.

1-Deoxynojirimycin↗
PubMed1992

DNA from bacteria, but not from vertebrates, induces interferons, activates natural killer cells and inhibits tumor growth.

The nucleic acid fraction from cells of 6 species of bacterium and 2 kinds of vertebrate, calf and salmon, was extracted and purified by the same procedures as described previously. When the spleen cells from BALB/c mice were incubated with the nucleic acid fraction from either of the bacteria, natural killer (NK) activity of the cells was remarkably elevated and the cells produced factors to activate macrophages and to inhibit viral growth. It was shown that the factor to activate macrophages was interferon (IFN)-gamma and that to inhibit viral growth was IFN-alpha/beta. On the other hand, the nucleic acid fraction from either of the vertebrate cells did not show such activities. Pretreatment of the bacterial nucleic acid fraction with DNase, but not with RNase, abrogated completely the biological activities. The activities of the bacterial nucleic acid were not influenced by the presence of polymyxin B, an inhibitor of lipopolysaccharide (LPS), and the spleen cells from not only BALB/c mice but also LPS-insensitive C3H/HeJ mice were activated, indicating that the activities of the fraction were not ascribed to LPS contaminated possibly into the fraction, but to DNA itself. Intralesional injection with the bacterial DNA fraction caused regression of mouse IMC tumors, but the injection with the vertebrate DNA fraction did not. These findings prompted us to examine the biological activities of DNA samples from a variety of animals and plants, which were provided from other laboratories or purchased from manufacturers. All of the DNA samples from cells of 5 kinds of bacterium, 2 of virus and 4 of invertebrate augmented NK activity and induced IFN, more or less, in mouse spleen calls, while the DNA from 10 kinds of vertebrate, including 3 of fish and 5 of mammal, showed no such activities. The DNA from 2 species of plants, were also inactive. Possible mechanisms to explain the different biological activities of DNA from different cell sources were discussed based on our previous finding that the particular palindromic sequences with a G-C motif(s) are required for induction of IFNs and activation of NK cells with synthetic 30-mer oligonucleotides.

Adjuvants, Immunologic↗