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Biomedical subjects

S Yoshida

Publications and source records attributed to S Yoshida.

At least 109 records · Page 6Linked to original sources
PubMed2001

Characterization and identification of exflagellation-inducing factor in the salivary gland of Anopheles stephensi (Diptera: Culicidae).

Gamete activation factor (GAF) induces exflagellation of Plasmodium microgametes. We found GAF in the salivary glands of female mosquitoes, Anopheles stephensi. The exflagellation was induced in a concentration-dependent manner in the supernatant of salivary gland's crude homogenate. The exflagellation-inducing activity in the salivary gland was higher than that in the midgut and the head. GAF in the salivary glands was found to be heat stable and low molecular weight (<3000 molecular weight). Analysis of the supernatant by capillary electrophoresis and UV absorbance profile showed that the salivary glands contained xanthurenic acid, which was previously identified as GAF in the head of A. stephensi. The exflagellation-inducing activity in the salivary gland declined immediately after a blood meal, implying that GAF was in the saliva, and was delivered into the midgut together with the blood and induced exflagellation in the midgut.

Animals↗
PubMed2001

L-isoform but not S-isoform of myelin associated glycoprotein promotes neurite outgrowth of mouse cerebellar neurons.

Myelin associated glycoprotein (MAG) has growth promoting effect on mouse cerebellar neurons. In the present study, we examined which isoform of MAG has the effect. cDNA for L-MAG and S-MAG was stably transfected into BALB/c 3T3 cells, on which cerebellar neurons were cultured. The neurons were stained with antibody against microtubule-associated protein-2. Neurites of the neurons cultured on cells expressing L-MAG extended significantly further than those cultured on cells expressing S-MAG or on control cells. Therefore, intracellular domain of MAG may have the potential to affect MAG-neurite interaction.

Animals↗
PubMed2001

Structural requirements of sphingosine molecules for inhibition of DNA primase: biochemical and computational analyses.

Using 28 chemically well-defined compounds containing D-erythro-sphingosine and its analogues, we analyzed structure-activity relationships for DNA primase inhibition. Biochemical studies demonstrated a positively charged amino group at C2 and a long aliphatic chain to be absolutely required for inhibition. Whereas C2-amino group is intact, sphingosine 1-phosphate was totally inactive. This result could be due to cancellation of positive charge of the amino group by the interaction with negatively charged C1-phosphate, since simulations with the software INSIGHT II showed these two groups to be close enough to interact. The hydroxyl group at C3 and trans-double bond at C4-C5 were also found to be important for the inhibition. Dehydroxylation of C3, as well as saturation or cis-conversion of the trans-double bond led to decrease of inhibitory activity. Despite saturation of the double bond, introduction of a hydroxyl group into C4 of dihydrosphingosine resulted in restoration of inhibition. Conversion of the double bond into a triple bond did not abolish but rather enhanced the inhibitory activity. Among sphingosine stereoisomers, the naturally occurring D-erythro-sphingosine proved to be the strongest inhibitor. To ascertain the contribution of the total conformation to the inhibition, especially of the long aliphatic chain, we constructed a 3D-quantitative structure-activity relationship model using the computer program Catalyst/HipHop on the basis of information described above. Analysis of the hypothesis model for active compounds revealed that the orientation of aliphatic chain, represented by the dihedral angle of C2-3-4-5, correlated well with the inhibition. Modifications such as deletion of the hydroxyl group at C3 or saturation of the C4-C5 double bond caused shifts in the dihedral angle of C2-3-4-5, with concomitant decrease in inhibitory activity.

Animals↗
PubMed2001

Chloroplast targeting of chloroplast division FtsZ2 proteins in Arabidopsis.

Plant nuclear genomes encode chloroplast division proteins homologous to the eubacterial cell division protein FtsZ. In higher plants, FtsZ genes constitute a small gene family that consists of two subgroups, FtsZ1 and FtsZ2. It was previously hypothesized that members of one family (FtsZ1) targeted chloroplasts, while members of the other family (FtsZ2) localized in the cytoplasm. We determined the full-length cDNA sequences of two FtsZ2 genes from Arabidopsis thaliana (AtFtsZ2-1 and AtFtsZ2-2) and found that the genes encode polypeptides of 478 and 473 amino acids, respectively, and both contain N-terminal extensions beyond what have previously been predicted. The N-terminal regions of both AtFtsZ2-1 and AtFtsZ2-2 were expressed as green fluorescent protein (GFP) fusions under the cauliflower mosaic virus 35S promoter in bombarded tobacco cells. Confocal laser scanning microscopy revealed both fusions exclusively localized to chloroplasts, demonstrating that the N-terminal regions function as chloroplast-targeting signals in vivo. Thus, FtsZ2 proteins function within chloroplasts.

Amino Acid Sequence↗
PubMed2001

Combinatorial roles of olig2 and neurogenin2 in the coordinated induction of pan-neuronal and subtype-specific properties of motoneurons.

Distinct classes of neurons are generated at defined times and positions during development of the nervous system. It remains elusive how specification of neuronal identity coordinates with acquisition of pan-neuronal properties. Here we show that basic helix-loop-helix (bHLH) transcription factors Olig2 and Neurogenin2 (Ngn2) play vital roles in the coordinated induction of pan-neuronal and subtype-specific properties of motoneurons. Olig2 and Ngn2 are specifically coexpressed in motoneuron progenitors. Misexpression studies in chick demonstrate the specific, combinatorial actions of Olig2 and Ngn2 in motoneuron generation. Our results further revealed crossregulatory interactions between bHLH and homeodomain transcription factors in the specification of motoneurons. We suggest that distinct classes of transcription factors collaborate to generate motoneurons in the ventral neural tube.

Animals↗
PubMed2001

Effect of ACTH on the imipramine- and desipramine-induced decrease in duration of immobility time as measured in a rat forced swimming test.

In a rat forced swimming test (FS), we examined the effect of repeated injections of ACTH (adrenocorticotropic hormone) for 14 days on the decreased duration of immobility time produced by imipramine and desipramine. Both imipramine (15 and 30 mg/kg, p.o.) and desipramine (15 and 30 mg/kg, p.o.) significantly decreased the duration of immobility time in the FS. On the other hand, ACTH (100 microg/kg, i.p.) alone did not affect the duration of immobility time in FS. When ACTH (100 microg/kg, i.p.) was injected for 14 days before the 15-min swim session, it counteracted the decreased duration of immobility time induced by both imipramine and desipramine. Thus, ACTH seems to play a key role in decreasing the duration of immobility time of antidepressants in this test.

Adrenocorticotropic Hormone↗
PubMed2001

Repeated treatment with imipramine, fluvoxamine and tranylcypromine decreases the number of escape failures by activating dopaminergic systems in a rat learned helplessness test.

Chronic administration of antidepressants has been shown to reduce the number of escape failures in the rat learned helplessness test (LH). In the present study we investigated the role of D1, D2 and D3 receptors in mediating this effect. In our first series of experiments, we demonstrated that SKF38393, D1 receptor agonist, in a dose of 2.5 mg/kg (i.p.) and quinpirole, D2 receptor agonist in a dose of 0.5 mg/kg (i.p.), significantly decreased the number of escape failures in LH, and these were reversed by SCH23390 (0.015 mg/kg), D1 receptor antagonist, and by sulpiride (25 mg/kg), D2 receptor antagonist, respectively. In contrast, 7-OH-DPAT, a D3 receptor agonist, in a dose of 10 mg/kg (i.p.) did not affect the number of escape failures in LH. In a second series of experiments, we showed that eight days of repeated treatment with imipramine (10 mg/kg, p.o.), fluvoxamine (1.25 mg/kg, p.o.) and tranylcypromine (1.25 mg/kg, p.o.) significantly decreased the number of escape failures in LH. The decrease in escape failures seen with use of imipramine and tranylcypromine was reversed by sulpiride in LH, but not by SCH23390. On the other hand, the effect of fluvoxamine was reversed by both SCH23390 and sulpiride. These findings indicate that stimulation of D1 and D2 receptors decreased the number of escape failures in LH, respectively. Thus, D2 and/or D1 receptors are probably involved in the decreased number of escape failures in case of repeated treatment with antidepressants in LH.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2001

An essential role of a TatC homologue of a Delta pH- dependent protein transporter in thylakoid membrane formation during chloroplast development in Arabidopsis thaliana.

At least three transport systems function in targeting nuclear-encoded chloroplast proteins to the chloroplast thylakoid membrane. One of these systems requires a thylakoid pH gradient and is named the DeltapH-dependent protein transport system. A similar DeltapH export system of Escherichia coli contains four components, twin arginine translocation A (TatA), TatB, TatC, and TatE. TatC is a major component of the DeltapH-dependent protein transporter in E. coli and functions in the translocation of tightly folded proteins across membranes. We have isolated four transposon-inserted albino mutants named albino and pale green 2 (apg2) from Arabidopsis thaliana and showed that the transposons were inserted into different sites of a single gene. The APG2 gene product (named cpTatC) has sequence similarity with bacterial TatC and contains six putative transmembrane domains, including bacterial TatC proteins and a transit peptide in its N terminus. apg2 mutants showed albino phenotypes and could not grow in soil. The apg2 plastids were highly vacuolated, lacked internal membrane structures and lamellae of the thylakoid membrane, and contained many densely stained globule structures, like undifferentiated proplastids. Immunoblot analysis detected no thylakoid membrane proteins such as D1, light-harvesting complex, and OE23 in apg2 plastids, whereas soluble proteins such as rubisco large and small subunits were not decreased. These results indicate an essential role of cpTatC in chloroplast development, especially in thylakoid membrane formation.

Amino Acid Sequence↗
PubMed2001

Expression of the kallikrein gene family in normal and Alzheimer's disease brain.

The human kallikrein gene family consists of 15 serine proteases. We examined the expression of the kallikrein genes in human cerebral cortex and hippocampus by RT-PCR and compared their expression between Alzheimer's disease (AD) and control tissue. KLK1, 4, 5, 6, 7, 8, 10, 11, 13 and 14 are expressed in both cerebral cortex and hippocampus. KLK9 is expressed in cortex but not hippocampus, whereas KLK2, 3, 12 and 15 are not expressed in either tissue. We demonstrate an 11.5-fold increase in KLK8 mRNA levels in AD hippocampus compared to controls. The KLK8 gene product, neuropsin, processes extracellular matrix and is important for neuronal plasticity. Therefore, the increase in KLK8 could have detrimental effects on hippocampal function in AD.

Aged↗
PubMed2001

Influence of anesthesia on brain distribution of [(11)C]methamphetamine in monkeys in positron emission tomography (PET) study.

We investigated the influence of anesthesia on the brain distribution of [11C]methamphetamine (MAP) obtained by the positron emission tomography (PET) using the normal rhesus monkeys. We clarified that the brain uptake of [11C]MAP under halothane anesthesia was faster and higher than that under pentobarbital. The difference of the effect of anesthesia is an important problem in pharmacokinetic study in PET with experimental animals.

Adjuvants, Anesthesia↗
PubMed2001

Atypical multidrug resistance may be associated with catalytically active mutants of human DNA topoisomerase II alpha.

In human cells, atypical drug resistance was previously identified with reduced catalytic activity or nuclear localization efficiency of DNA topoisomerase II alpha (TOP2 alpha). We have shown two etoposide resistant hTOP2 alpha mutants, K798L and K798P confer resistance to etoposide. In this work, we showed these mutants are also resistant against doxorubicin and mAMSA in vivo in the yeast strain ISE2, rad52, top2-4 at the non-permissive temperature. We purified these mutants to characterize the drug resistant mechanism. Purified recombinant proteins were 8- to 12-fold more resistant to etoposide and doxorubicin than wild type TOP2 alpha, and 2-fold more resistant to amsacrine, as measured by accumulation of cleavable DNA. These data show that K798L and K798P may be intrinsically resistant against these drugs in vitro and that this character may confer atypical multidrug resistant phenotype in vivo in yeast.

Amino Acid Substitution↗
PubMed2001

Obtusifoliol 14alpha-demethylase (CYP51) antisense Arabidopsis shows slow growth and long life.

Obtusifoliol 14alpha-demethylase is a plant orthologue of sterol 14alpha-demethylase (CYP51) essential in sterol biosynthesis. We have prepared CYP51 antisense Arabidopsis in order to shed light on the sterol and steroid hormone biosynthesis in plants. Arabidopsis putative CYP51 cDNA (AtCYP51) was obtained from Arabidopsis expressed sequence tag (EST) library and its function was examined in a yeast lanosterol 14alpha-demethylase (Erg11) deficient mutant. A recombinant AtCYP51 protein fused with a yeast Erg11 signal-anchor peptide was able to complement the erg11 mutation, which confirmed AtCYP51 to be a functional sterol 14alpha-demethylase. AtCYP51 was then used to generate transgenic Arabidopsis by transforming with pBI vector harboring AtCYP51 in the antisense direction under CaMV35S promoter. The resulting transgenic plants were decreased in accumulation of AtCYP51 mRNA and increased in the amount of endogenous obtusifoliol. They showed a semidwarf phenotype in the early growth stage and a longer life span than control plants. This newly found phenotype is different from previously characterized brassinosteroid (BR)-deficient campesterol biosynthesis mutants.

Amino Acid Sequence↗
PubMed2001

Shigella invasion of macrophage requires the insertion of IpaC into the host plasma membrane. Functional analysis of IpaC.

Shigella infects residential macrophages via the M cell entry, after which the pathogen induces macrophage cell death. The bacterial strategy of macrophage infection, however, remains largely speculative. Wild type Shigella flexneri (YSH6000) invaded macrophages more efficiently than the noninvasive mutants, where YSH6000 induced large scale lamellipodial extension including ruffle formation around the bacteria. When macrophages were infected with the noninvasive ipaC mutant, the invasiveness and induction of membrane extension were dramatically reduced as compared with that of YSH6000. J774 macrophages infected with YSH6000 showed tyrosine phosphorylation of several proteins including paxillin and c-Cbl, and this pattern was distinctive from those stimulated by Salmonella typhimurium or phorbol ester. Upon addition of IpaC into the external medium of macrophages, membrane extensions were rapidly induced, and this promoted uptake of Escherichia coli. The exogenously added IpaC was found to be integrated into the host cell membrane as detected by immunostaining. The IpaC domain required for the induction of membrane extension from J774 was narrowed down within the region of residues 117-169, which contains a putative membrane-spanning sequence. Our data indicate that Shigella directs its own entry into macrophages, and the IpaC domain which is required for the association with its host membrane is crucial.

Amino Acid Sequence↗
PubMed2001

Light and brassinosteroid signals are integrated via a dark-induced small G protein in etiolated seedling growth.

Plant growth and development are regulated through coordinated interactions between light and phytohormones. Here, we demonstrate that a dark-induced small G protein, pea Pra2, regulates a variant cytochrome P450 that catalyzes C-2 hydroxylation in brassinosteroid biosynthesis. The cytochrome P450 is dark-induced and predominantly expressed in the rapidly elongating zone of etiolated pea epicotyls, where Pra2 is also most abundant. Transgenic plants with reduced Pra2 exhibit a dark-specific dwarfism, which is completely rescued by exogenous brassinolide. Overexpression of the cytochrome P450 results in enhanced hypocotyl growth even in the light, which phenocopies the etiolated hypocotyls. We therefore propose that Pra2 and its orthologs are molecular mediators for the cross-talk between light and brassinosteroids in the etiolation process in plants.

Amino Acid Sequence↗
PubMed2001

Direct measurement of the pion valence-quark momentum distribution, the pion light-cone wave function squared.

We present the first direct measurements of the pion valence-quark momentum distribution which is related to the square of the pion light-cone wave function. The measurements were carried out using data on diffractive dissociation of 500 GeV/c pi(-) into dijets from a platinum target at Fermilab experiment E791. The results show that the /q&q> light-cone asymptotic wave function describes the data well for Q2 approximately 10 (GeV/c)(2) or more. We also measured the transverse momentum distribution of the diffractive dijets.

Journal Article↗
PubMed2001

Observation of color-transparency in diffractive dissociation of pions.

We have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t(min)-->0), we find that when the per-nucleus cross section for this process is parametrized as sigma = sigma0Aalpha, alpha has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.

Journal Article↗
PubMed2001

Ganglioside G(D2) in small cell lung cancer cell lines: enhancement of cell proliferation and mediation of apoptosis.

Expression levels of gangliosides and glycosyltransferase genes responsible for their syntheses in human lung cancer cell lines and a normal bronchial epithelial cell line were analyzed. Both non-small cell lung cancers and small cell lung cancers (SCLCs) mainly expressed G(M2) and G(M1), whereas only SCLCs expressed b-series gangliosides, such as G(D2), G(D1b), and G(T1b). Accordingly, many SCLC cell lines showed up-regulation of the G(D3) synthase gene. Consequently, we introduced G(D3) synthase cDNA into a SCLC line with low expression of b-series gangliosides and analyzed the effects of newly expressed gangliosides on tumor phenotypes. The transfectant cells expressing high levels of G(D2) and G(D3) exhibited markedly increased growth rates and strongly enhanced invasion activities. Addition of anti-G(D2) monoclonal antibodies into the culture medium of these cells resulted in the marked growth suppression of G(D2)-expressing cell lines with reduced activation levels of mitogen-activated protein kinases but not of nonexpressants, suggesting that G(D2) plays important roles in cell proliferation. Moreover, G(D2)-expressing cells treated with anti-G(D2) antibodies showed features of apoptotic cell death at 30 min after addition of antibodies, i.e., shrinkage of cytoplasm, binding of Annexin V, and staining with propidium iodide, followed by DNA fragmentation. This G(D2)-mediated apoptosis was associated with caspase-3 activation and partly inhibited by a caspase inhibitor, z-Val-Ala-Asp-fluoromethyl ketone. The finding that anti-G(D2) antibodies suppressed the cell growth and induced apoptosis of SCLC cells strongly suggested the usefulness of G(D2) as a target for the therapy of disastrous cancer, although the precise mechanisms for apoptosis remain to be clarified.

Antibodies, Monoclonal↗