Biomedical subjects

T Ohtsuki

Publications and source records attributed to T Ohtsuki.

At least 73 records · Page 4Linked to original sources

PubMed1999

Species differences in fodrin proteolysis in the ischemic brain.

There has been growing evidence that the breakdown of cytoskeletal proteins is an important biochemical change leading to ischemic neuronal death. In the present study, we investigated species differences in the susceptibility of fodrin to calpain activation induced by cerebral ischemia in gerbils, rats, and mice. In vivo fodrin proteolysis and degradation of microtubule-associated protein 2 after complete ischemia occurred more rapidly in the hippocampus and cerebral cortex of the gerbil brain than in the corresponding area of the rat and mouse brain. The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 injected intraperitoneally before ischemia did not diminish fodrin degradation in the gerbil hippocampus. In vivo fodrin proteolysis was inhibited at 33 degrees C and enhanced at 41 degrees C compared with proteolysis at 37 degrees C during ischemia. However, in vitro fodrin proteolysis after addition of Ca2+ into the crude membrane fraction did not show any differences among three species. Although it is highly unlikely that the difference in the sensitivity of NMDA receptor or the sensitivity of calpain activation to calcium was the crucial determinant of susceptibility of fodrin degradation in the gerbil brain, the present study clearly demonstrated that fodrin in the gerbil brain was more susceptible to calpain activation induced by ischemia than that in the rat and mouse brains. Enhanced proteolysis may be one of the reasons neurons in the gerbil brain are highly vulnerable to ischemia.

Animals↗

PubMed1999

Direct preparation of radioactive fullerenes as a tracer for applications.

The C60 and C70 fullerenes were irradiated by high-energy gamma-rays and charged particles. The irradiated samples were dissolved in CS2 and/or toluene and filtered to remove insoluble by-products. Finally, radioactive fullerenes and products labeled with 11C or 13N were isolated and detected in the liquid phase by radiochromatography. It was found that (1) not only 11C or 13N radioactive monomer fullerenes but also their dimers (trimers and, possibly, tetramers) were produced by recoil implantation process following nuclear reaction and (2) the radioactive fullerene labeled with 11C yields has led to high yields.

Carbon↗

PubMed1999

DNA cleavage and proteolysis of microtubule-associated protein 2 after cerebral ischemia of different severity.

We report temporal profiles of cytoplasmic proteolysis and genomic DNA cleavage after cerebral ischemia of different severity in gerbils. Global forebrain ischemia by bilateral common carotid artery occlusion for 5 min with reperfusion, severe unilateral hemispheric ischemia by unilateral common carotid artery occlusion for 30 min with reperfusion, and complete ischemia by decapitation were used. The hippocampus was examined for proteolysis by using immunohistochemistry for microtubule-associated protein 2, DNA cleavage by using in situ nick-end labelling, and nuclear morphology by Hematoxylin staining. During evolution of delayed neuronal death after transient forebrain ischemia, loss of the immunoreaction for microtubule-associated protein 2 occurred almost in parallel with DNA cleavage in the CA1 region. In contrast, disappearance of the immunoreaction for microtubule-associated protein 2 was much faster than genomic DNA cleavage after unilateral hemispheric ischemia and reperfusion. The microtubule-associated protein 2 immunoreactivity was completely lost before development of changes in nuclear morphology or DNA cleavage after complete ischemia. The present study demonstrated the differences between necrosis and delayed neuronal death, but the nuclear morphology in the latter was not exactly the same as seen in apoptosis. Some elements of both necrotic and apoptotic machineries may work following transient ischemia, and the degree of ischemic insult may determine the character of cell death process.

Animals↗

PubMed1999

Supportive evidence for contribution of the dopamine D2 receptor gene to heritability of stature: linkage and association studies.

Increases in height were reported in children chronically exposed prenatally and postnatally to D2 receptor-blocking drugs. A possible haplotypic association between stature and the DRD2 gene was also reported. In this study, we examined linkage between stature and DRD2 by genotyping a dinucleotide repeat polymorphism in 79 sib-pairs aged 8-17 years. An association between stature and a putative functional polymorphism in the promoter region of the DRD2 gene was examined in the sib-pairs and in 125 unrelated male adults. All the subjects were Japanese. Linkage (p = 0.004, SIBPAL) and an association (p = 0.009, paired t-test, in the sib-pairs; p = 0.006, ANOVA, in the adults) with stature were suggested. These findings indicate that DRD2 is one of the genes that contribute to heritability of stature.

Adolescent↗

PubMed1999

Molecular cloning of a novel member of the HSP110 family of genes, ischemia-responsive protein 94 kDa (irp94), expressed in rat brain after transient forebrain ischemia.

To identify genes induced by transient forebrain ischemia, we used the mRNA differential display technique in the four-vessel occlusion model in rats. Some genes were identified as candidates that encode ischemia-responsive protein, and one of them was cloned as ischemia-responsive protein 94 kDa (irp94) from the rat hippocampal cDNA library. Sequence analysis suggested that rat irp94 was a transcriptional variant or a homologue of mouse apg-2 and human heat shock protein (hsp) 70RY and a member of the HSP110 family, because IRP94 was >90% identical to APG-2 and HSP70RY and approximately 60% identical to the other members of the HSP110 family. Although irp94 mRNA was constitutively expressed in the normal hippocampus, it was clearly enhanced 4-24 h after ischemia for 10 (1.9-fold increase) and 15 min (3.4-fold increase). These changes mainly occurred in neuronal cells, as judged by the localization of irp94 mRNA using in situ hybridization histochemistry. On the other hand, hyperthermic stress did not enhance irp94 mRNA expression, suggesting that irp94 expression was enhanced under ischemic stress and not related to the heat shock signaling mechanism. Our study suggested that irp94, a novel member of the HSP110 family, might play an important role in the environment altering neuronal functions, especially after transient forebrain ischemia.

Animals↗

PubMed1999

Core 2-containing O-glycans on CD43 are preferentially expressed in the memory subset of human CD4 T cells.

Human CD4 T cells can be divided into two functionally distinct subsets: a CD45RO+ memory subset and a CD45RA+ naive subset. In an attempt to identify novel cell surface molecules on these cells, we have developed a mAb, anti-1D4. The antigen defined by anti-1D4 was preferentially expressed on the memory subset of freshly isolated peripheral CD4 T cells and 1D4+ CD4 T cells functionally corresponded to memory T cells. Retrovirus-mediated expression cloning revealed that the 1 D4 antigen is human CD43. Transfection of CHO-leu cells, which stably express human CD43, with core 2 beta-1,6-N-acetylglucosaminyltransferase (C2GnT) conferred expression of the 1D4 antigen and mRNA of C2GnT was detected by RT-PCR only in 1D4+ T cells but not in 1D4- T cells, implying that the 1 D4 antigen is composed of core 2-containing O-glycans on CD43. Reactivity with anti-1 D4 was completely abolished when cells were treated with neuraminidase, while them remained weak binding of anti-T305, a previously described mAb which also reacts with CD43 modified with core 2-containing O-glycans. Moreover, anti-1D4 markedly reacted with NIH-3T3 cells expressing human CD43 and low levels of endogenous C2GnT, whereas anti-T305 reacted slightly. These results indicate that the 1D4 antigen is distinct from the epitope defined by anti-T305 and anti-1D4 is a more sensitive probe to detect core 2-containing O-glycans than anti-T305. Taken together, our results indicate that core 2-containing O-glycans, whose expression can easily be detected with anti-1D4, are preferentially expressed in the CD45RO+ memory subset of CD4 T cells.

Animals↗

PubMed1999

The guanosine binding mechanism of the Tetrahymena group I intron.

The Tetrahymena group I intron catalyzes self-splicing through two consecutive transesterification reactions, using a single guanosine-binding site (GBS). In this study, we constructed a model RNA that contains the GBS and a conserved guanosine nucleotide at the 3'-terminus of the intron (omegaG). We determined by NMR the solution structure of this model RNA, and revealed the guanosine binding mechanism of the group I intron. The G22 residue, corresponding to omegaG, participates in a base triple, G22 xx G3 x C12, hydrogen-bonding to the major groove edge of the Watson-Crick G3 x C12 pair. The G22 residue also interacts with A2, which is semi-conserved in all sequenced group I introns.

Animals↗

PubMed1999

NMR signal assignment of the polyuridine tract of the single-stranded RNA complexed with Sxl RBD1-RBD2 by using residue selective [5-(2)H]uridine substitutions.

Using [5-(2)H]uridine phosphoramidite, we synthesized a series of 2H-labeled Drosophila Sex-lethal (Sxl) target RNAs, in which all the uridine residues except one were specifically replaced by [5-(2)H]uridine. By observing the H5-H6 cross peaks of RNA in the TOCSY spectra, we unambiguously assigned all the base proton resonances of the target RNA in a Sxl x RNA complex. Furthermore, it was shown that Sxl differently recognizes A and G in a position prior to the polyuridine tract.

Animals↗

PubMed1999

Efficacy and safety of infrared warming of the eyelids.

PURPOSE: To evaluate our newly developed infrared heater (IRH) and compare it to a broad-spectrum heater (BSH) for warming the eyelids. MATERIALS AND METHODS: Ten normal subjects were enrolled in this study. All measurements were recorded in a room with temperature 23 degrees C, 40% humidity, and no wind. The IRH is composed of two hard eye patches that have light-emitting diodes (LEDs) emitting near-infrared radiation. We first compared the temperature rises in the cornea, lacrimal gland, and eyelids after warming through closed eyelids with the IRH for 5 and 10 min. Next, we compared warming with the IRH or BSH for 30 min. We then used the IRH for 5 min with the eyes open to confirm its safety. Finally, we determined subjective feeling after warming the eyes. RESULTS: Direct comparison of 5 versus 10 min of warming with the IRH showed no significant differences in temperature rises in the upper eyelid (p = 0.09). The IRH caused significantly more heating (p < 0.05) than did the BSH everywhere except the cornea. The temperatures never rose above 37.7 degrees C for either heater during 30 min or with the IRH with the eyes open for 5 min. The subjects' comfort level rose significantly (p < 0.05) after treatment with the IRH. CONCLUSIONS: Our study showed the efficacy and safety of warming the eyelids with a newly developed IRH. Only 5 min is necessary to increase ocular temperature and enhance comfort.

Adult↗

PubMed1999

A synergistic effect of serotonin transporter gene polymorphism and smoking in association with CHD.

Serotonin induces vasoconstriction in the presence of atherosclerotic lesions. Platelets acquire serotonin from the extracellular space by serotonin transporter and release it following aggregation. There is a functional polymorphism in the serotonin transporter (5-HTT) gene promoter associated with transcriptional efficacy and plasma serotonin levels. To examine whether the polymorphism is associated with coronary heart disease (CHD) in the Japanese, we analyzed 144 male CHD patients with an onset age before 65 and 222 apparently healthy men. The L allele was observed significantly more frequently in the CHD patients (26%) than in the control subjects (19%); the odds ratio was 1.48 (p <0.03). A significant interaction between the polymorphism and smoking was observed for CHD (p = 0.03), suggesting that the two have a synergistic effect on CHD. Odds ratio of the combination of the L allele and smoking was 1.95 (p <0.003). The 5-HTT gene promoter polymorphism may play a role in susceptibility to CHD, particularly when it is combined with smoking.

Adult↗

PubMed1999

Association between serotonin transporter gene polymorphism and smoking among Japanese males.

The serotoninergic system may be involved in smoking behavior because nicotine increases brain serotonin secretion, nicotine withdrawal decreases serotonin levels, and a selective serotonin reuptake inhibitor antagonizes the response to nicotine. Compared with the L allele, the S allele of the polymorphism in the upstream regulatory region of the serotonin transporter gene is associated with decreased transcription efficiency of the 5-HTT gene promoter. We examined this polymorphism in a Japanese population consisting of 387 males from two different areas in Japan. The L allele was observed significantly more often in smokers (21%) than in nonsmokers (lifetime nonsmokers + ex-smokers, 14%; P = 0.005). The presence of the L allele (the L/L + L/S genotypes) was also significantly increased in smokers (37%) compared with that in nonsmokers (24%; P = 0.003). The present study suggests that individuals with the S/S genotype are less inclined to smoke and/or can more easily stop smoking than others, supporting a role of the serotoninergic system in smoking behavior.

Adult↗

PubMed1998

Association between polymorphisms in the type 1 sigma receptor gene and schizophrenia.

Several antipsychotic agents such as haloperidol and rimcazole are known to bind to sigma receptors with high affinity, and evidence for a potential link between sigma receptors and the etiology of schizophrenia has been reported. The present study was conducted to systematically search for nucleotide variants of the type 1 sigma receptor gene in 48 schizophrenics. Two polymorphisms were found: GC-241-240TT in the 5' flanking region and Gln2Pro. These two polymorphisms were in nearly complete linkage disequilibrium with each other. The Pro2 variant of the Gln2Pro polymorphism changes the endoplasmic reticulum retention signal motif. These polymorphisms were examined in an extended sample of schizophrenics (n = 308) and controls (n = 433) and a significant association between the presence of the TT/Pro2 haplotype and schizophrenia was observed (odds ratio = 1.27, P = 0.04).

Adolescent↗

PubMed1998

Activated endothelial cells induce apoptosis in leukemic cells by endothelial interleukin-8.

Tumor cells are eradicated by several systems, including Fas ligand-Fas and tumor necrosis factor (TNF)-tumor necrosis factor receptor (TNFR). In the previous study, we purified an apoptosis-inducing factor (AIF) to homogeneity from a medium conditioned by PDBu-treated HL-60 cells. N-terminal sequence analysis showed that AIF is identical to endothelial interleukin-8 (IL-8). A novel apoptosis system, in which endothelial cells participate via endothelial IL-8 release, is identified here. Human umbilical vein cells (VE cells) produce and secrete IL-8 by stimulation of IL-1alpha and TNF-alpha. Endothelial IL-8, which is secreted from VE cells by stimulation of IL-1alpha and TNF-alpha , induces apoptosis in myelogenous leukemia cell line K562 cells. Monocyte-derived IL-8 could not induce apoptosis in K562 cells. Moreover, interaction between VE cells and K562 cells induces the release of endothelial IL-8 from VE cells, and the attached K562 cells undergo apoptosis. Moreover, interactions between VE cell and other cell lines, such as HL-60, U937, Jurkat, and Daudi, induce the secretion of endothelial IL-8 and the induction of apoptosis in cell lines. Endothelial IL-8 significantly inhibits tumor growth of intraperitoneal and subcutaneous tumor mass of K562 cells and induces apoptosis in their cells in vivo. Endothelial IL-8 plays an important role in apoptosis involving endothelial cells, which may provide us with a new therapy for hematological malignancies.

Animals↗

PubMed1998

Negative regulation of the anti-human immunodeficiency virus and chemotactic activity of human stromal cell-derived factor 1alpha by CD26/dipeptidyl peptidase IV.

Stromal cell-derived factor 1alpha (SDF-1alpha) is a chemokine that has been shown to prevent infection of T-tropic HIV strains and is a possible substrate of CD26/dipeptidyl peptidase IV (DPPIV). In this study, we show that SDF-1alpha was cleaved at the N-terminal region by CD26/DPPIV and as a result the inhibitory activity of SDF-1alpha against HIV infection disappeared. Moreover, the chemotactic activity of SDF-1alpha also disappeared specifically by DPPIV activity of recombinant soluble CD26. These results suggested that dissemination of T-tropic HIV strains in vivo may be facilitated by CD26/DPPIV via inactivation of functional SDF-1alpha.

Animals↗

PubMed1998

Identification of a novel apoptosis-inducing factor derived from leukemic cells: endothelial interleukin-8, but not monocyte-derived, induces apoptosis in leukemic cells.

The human myelogenous leukemia cell line HL-60, treated with phorbol 12, 13-dibutyrate (PDBu), produces apoptosis-inducing factors (AIFs) in leukemic cells. We have purified AIF against leukemic cell line K562 as target cells, and N-terminal amino acid sequencing analysis revealed that this purified protein is identical to endothelial cell-derived interleukin-8 ([(Ala)-IL-8]77). In Western blot analysis of supernatants of PDBu-treated HL-60 cells, only [(Ala)-IL-8]77 was detected. Moreover, recombinant human [(Ala)-IL-8]77 induced apoptosis in leukemic cell lines such as K562, HL-60, KG-1, U937, THP-1 and Jurkat, but monocyte-derived IL-8 ([(Ser)-IL-8]72) did not. Therefore [(Ala)-IL-8]77 plays an important role in inducing apoptosis against leukemic cells and may lead to a new therapy for leukemia.

Apoptosis↗

PubMed1998

Functional modification of agonist-antagonist electromyographic activity for rapid movement inhibition.

Subjects made a fast elbow extension movement to designated target in response to a go signal. In 45% of trials a stop signal was presented after the go signal, to which subjects were asked to stop the movement as rapidly as possible. The interstimulus interval (ISI), or time interval between the go and stop signals, was randomly varied between 0 and 200 ms. Electromyographic (EMG) activity was recorded from biceps brachii and triceps brachii. Subjects could sometimes completely inhibit initiation of the movements when the ISI was 0 ms, but could rarely do so when the ISI exceeded 100 ms. For responses that were initiated but stopped on the way, the amplitude of the movement decreased linearly as the time interval (=modification time) from the stop signal to EMG onset increased. The peak velocity increased linearly as the movement amplitude increased. This tendency was similar to those previously reported in step-tracking movements with various amplitudes. In spite of the similarity in the kinematics of the movement, the EMG pattern was different from that of step-tracking movement. While the initial agonist burst (AG1) decreased linearly after the modification time exceeded 100 ms, the antagonist burst (ANT) increased compared with the go trial for the modification time from 0 to 200 ms and decreased after the modification time exceeded 300 ms. This change of activation is analogous to functional modification of middle-latency reflex EMG response to load, or cutaneous perturbation. In conclusion, it is suggested that adaptive mechanisms, which would functionally modify the reflex responses, are also continuously working during voluntary movements in response to sudden changes in environmental information.

Adaptation, Physiological↗

PubMed1998

Gene expression of noncollagenous bone matrix proteins in the limb joints and intervertebral disks of the twy mouse.

The twy (tiptoe walking Yoshimura) mouse is an autosomal recessive mutant manifesting multiple osteochondral lesions characterized by pathologic calcium deposition. To elucidate the pathophysiology of the limb joint lesions and the intervertebral disk lesions of the twy mouse, we assessed the mRNA expression of noncollagenous bone matrix proteins such as osteocalcin, osteonectin, osteopontin, and matrix Gla protein (MGP) by in situ hybridization, but only expression of MGP was observed in association with the pathologic calcium deposits in twy mice. Mild degeneration and abnormal growth of the cartilage in contact with the joint capsule was observed at 5 weeks in the articular cartilage of the ankle joint of the twy mouse, and MGP gene expression was observed at the same time. Simultaneous growth of synovial membrane cells and relatively undifferentiated articular cartilage cells in the knee joint, and of cartilage-like cells near the insertion of the cruciate ligament was observed in the twy mouse, and MGP gene expression was found to be present at the same time. Hypertrophy of abnormally proliferated chondrocyte-like cells, which are different from fibrocartilaginous cells of the annulus fibrosus, was observed in the intervertebral disks of the twy mouse at 3 weeks of age, and MGP gene expression was noted at the same time. These findings suggest that abnormal expression of MGP plays a major role in the pathologic calcification of the twy mouse.

Animals↗

PubMed1998

Stable isotope-edited NMR analysis of Ascaris suum mitochondrial tRNAMet having a TV-replacement loop.

Most nematode mitochondrial (mt) tRNAs have a TV-replacement loop (TV loop) which replaces the normal T arm and the variable loop in standard tRNAs with a less-structured loop. The tertiary structure of such tRNAs has been discussed theoretically with reference to the crystal structure of yeast tRNAPhe [Wolstenholme et al. (1994) Nucleic Acids Res. 22, 4300-4306] and examined experimentally by chemical and enzymatic probing [Watanabe et al. (1994) J. Biol. Chem. 269, 22902-22906]. The results suggest that most regions of the tRNA other than the TV loop are folded in a similar manner to yeast tRNAPhe. To confirm this notion more clearly, the tertiary structure of Ascaris suum mt tRNAMet was analyzed by NMR using various synthetic tRNAs site-specifically labeled with stable isotopes, which were prepared by a combination of chemical synthesis and enzymatic ligation. Tertiary interactions involving G(L2), G(L3), U(L4), and U8 were observed in the NMR spectra of the labeled tRNAs, but those relating to G(L5) were not. On the basis of these results, a possible tertiary structural model of nematode mitochondrial tRNAMet was constructed.

Animals↗