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Biomedical subjects

Y Sato

Publications and source records attributed to Y Sato.

At least 379 records · Page 21Linked to original sources
PubMed2000

The zona pellucida-initiated acrosome reaction: defect due to mutations in the sperm glycine receptor/Cl(-) channel.

The mammalian sperm acrosome reaction (AR) is essential to fertilization, and the egg zona pellucida (ZP) is generally believed to be an in vivo initiator of the fertilizing sperm AR. Previously a neuronal glycine receptor/Cl(-) channel (GlyR) was detected on the plasma membrane of mammalian sperm and earlier pharmacological studies suggested that this receptor/channel is important to the ZP-initiated AR. Here, sperm from mice with mutations in the neuronal GlyR alpha or beta subunits (spasmodic and spastic) were shown to be deficient in their ability to undergo the AR initiated in vitro by glycine or by solubilized ZP from mouse eggs. However, both spontaneous and calcium ionophore (A23187)-initiated AR were unaffected. The ZP-initiated AR in wild-type sperm was maximal after 2 h of capacitation, but capacitation of sperm from spasmodic mice for up to 3 h did not result in significant ZP-initiated AR. Similar results were observed when sperm from wild-type and spastic mice were compared. Testis from mice with the beta subunit mutation contained truncated beta subunit mRNAs. Moreover, a monoclonal antibody against GlyR completely blocked ZP initiation of AR in normal mouse sperm. Our results are consistent with an essential role for the sperm GlyR in the ZP-initiated AR.

Acrosome Reaction↗
PubMed2000

Relationship between the configurations of 2-phenyltetrahydrothiophenium 1-methylides and their rearrangement products

trans-2-Phenyltetrahydrothiophenium 1-methylide (trans-3), which is generated by fluoride ion-induced desilylation of trans-2-phenyl-1-[(trimethylsilyl)methyl]tetrahydrothiophenium salt (trans-2), gave a mixture of 1,4,5,10a-tetrahydro-3H-2-benzothiocine (4) ([2,3]sigmatropic rearrangement product) and 4-methylsulfanyl-1-phenyl-1-butene (5) (Hofmann elimination product). Ylide trans-3 cannot undergo [2,3]sigmatropic rearrangement because the ylide-carbon is too far from the phenyl group, and trans-3 would instead isomerize to cis-3. In this paper, we discuss the mechanism of the isomerization of trans-3 to cis-3.

Journal Article↗
PubMed2000

The alpha-ketoisocaproate catabolism in human and rat livers.

Catabolism of alpha-ketoisocaproate in liver is mediated by cytosolic alpha-ketoisocaproate dioxygenase (KICD) and mitochondrial branched-chain alpha-keto acid dehydrogenase complex (BCKDC). The latter is believed to be involved in the main pathway of the KIC catabolism. In the present study, we measured the activities of KICD and BCKDC in human and rat livers. The KICD activity in human liver was 0.9 mU/g tissue, which was 14.2% of the total activity of BCKDC, and that in rat liver was 4.2 mU/g tissue, which was only 1.0% of the total activity, suggesting that KICD in human liver plays a relatively important role in the alpha-ketoisocaproate catabolism. The KICD activity in human liver was significantly increased by cirrhosis. In rat liver, the enzyme activity was markedly increased by physical training and streptozotocin-induced diabetes, but not by feeding of a diet rich in branched-chain amino acids, although BCKDC activity was increased by feeding of the diet.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed2000

Automatic auditory information processing in sleep.

STUDY OBJECTIVES: The mismatch negativity (MMN) component of the event-related potentials reflects the automatic detection of sound change. Only a few researchers have investigated the MMN elicitation during sleep in adult human and some of them reported that MMN amplitude was decreased in sleep compared to in waking. However, it is not clear that the decrease of MMN amplitude was due to increased drowsiness or long-term response decrement. Two experiments were conducted to clarify whether or not the MMN was elicited in each sleep stage. We presented auditory stimuli to subjects continuously from waking until sleep state (Experiment 1). Using the same experimental condition, we examined whether or not MMN amplitude was influenced by long-term stimulus presentation (80min.) and by vigilance level (Experiment 2). DESIGN: N/A SETTING: N/A PARTICIPANTS: N/A INTERVENTIONS: N/A MEASUREMENTS & RESULTS: Experiment 1: MMN was obtained in both drowsiness and REM sleep. MMN was significantly smaller in amplitude and shorter in latency in the both stages than in the waking state. However, MMN was not found in another sleep stage. Experiment 2: Amplitudes were no different among 0-20 min., 20-40 min., 60-80 min. But it was decreased in 40-60 min. and power value of alpha-wave was decreased in 40-60 min. CONCLUSIONS: To obtain the reliable data, by using the automatic spectral analysis, we confirmed that MMN was elicited in REM sleep. MMN was not influenced by long-term stimulation. The result suggested that auditory stimuli could be processed in the pre-attentive sensory memory even in REM sleep.

Adult↗
PubMed2000

An autopsy case of Klinefelter's syndrome suspected and its DNA analysis.

UNLABELLED: We experienced an autopsy case, small testes and tall stature, which suggested Klinefelter's syndrome. DNA analysis was performed to confirm the genetic abnormality. CASE HISTORY: A 28-year-old man who was single and lived with his parents. He suddenly lost his consciousness in a sitting room and died. Autopsy findings: He was 176 cm in height and 57 kg in weight. The post-mortem hypostasis was red-purple on his back, and rigor mortis was strong in each joint of the whole body. The heart weighted 340 g, in which dark red fluidal blood (300 ml) without coagulation was contained. The testes were smaller than normal adult male (left and right testes with epididymides weighted 8.1 g and 6.0 g, respectively). As a results of pathological examination, clumped Leydig cells, sclerotic and hyalined tubules were observed. Some germ cells with spermatozoid were also present. DNA Analysis: Generally, Klinefelter's syndrome is determined by karyotype analysis and/or the detection of sex chromatin. However, in this case, karyotype analysis and the detection of sex chromatin could not be demonstrated, because the blood which was collected in the autopsy became too old. Therefore, we tried sex determination and STR analysis (HPRT, HUMARA and DXS 1470) using DNA extracted from stored blood materials. Consequently, in the sex determination, no different situation was found in the X- and Y-specific bands from normal male's and as results of STR analyses, we could not corroborate the Klinefelter's syndrome.

Adult↗
PubMed2000

Bisphosphonate administration alters subcellular localization of vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts during experimental movement of rat molars.

This study was designed to clarify the effects of bisphosphonate (BP) administration on structure and functions of osteoclasts in alveolar bone resorption during experimental movement of rat molars. To produce orthodontic force, elastic band was inserted between the upper first and second molars for 4 days, and dissected maxillae were then examined by means of light and electron microscopic immunocytochemistry for vacuolar-type H(+)-ATPase and lysosomal cystein proteinase, cathepsin K in osteoclasts. Vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts are the most important enzymes for demineralization of apatite crystals and degradation of bone type-I collagen, respectively. At 1 day before elastic band insertion, BP was administered intraperitoneally. Control rats received the same volume of physiologic saline. In BP-administered rats, most osteoclasts exhibited either irregularly-formed ruffled borders and clear zones or only clear zones of various degrees of extension. Subcellular localization and expression of both vacuolar-type H(+)-ATPase and cathepsin K was significantly decreased in such osteoclasts with impaired ruffled borders and/or only clear zones by BP administration. In particular, cathepsin K secretion by osteoclasts towards resorption lacunae was markedly inhibited by BP administration. Our results indicate for the first time that BP administration significantly impair the osteoclast structure and reduces expression of both vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts during tooth movement.

Animals↗
PubMed2000

A Case of Proliferative Sarcoid Retinopathy with Sarcoid Nodules in Tissue Obtained During Vitrectomy.

Background: In previous studies, intraocular proliferative tissues obtained from proliferative sarcoid retinopathy cases during vitrectomy have been examined histopathologically. However, there is no report of identification of sarcoid nodules in examined tissues. We performed vitrectomy for a case of proliferative sarcoid retinopathy with extensive proliferative changes. Histopathologically, sarcoid nodules were identified in the fibrovascular membranes.Case: A 25-year-old man was treated for sarcoid uveitis in the right eye by his local ophthalmologist. Lens aspiration was performed for complicated cataract. He was referred to our hospital with vitreous opacity and traction retinal detachment which occurred after the surgery.Findings: The vitreous opacity was so severe that details of the fundus were not visible. Traction retinal detachment was suspected from findings of B-mode echography. Vitrectomy was performed, and total retinal detachment due to contraction of the fibrovascular membrane around the optic disc and posterior pole was observed. Sarcoid nodules were identified histopathologically in fibrovascular membranes obtained during vitrectomy.Conclusion: In proliferative sarcoid retinopathy cases, sarcoid lesions may be one of the causes of fibrovascular membrane formation.

Journal Article↗
PubMed2000

Anti-tumor immunity against CT26 colon tumor in mice immunized with plasmid DNA encoding beta-galactosidase fused to an envelope protein of endogenous retrovirus.

Endogenous retroviral gene products have been recognized as being expressed in human cancerous tissues. However, these products have not been shown to be antigenic targets for T-cells, possibly due to immune tolerance. Since carcinogen-induced colon tumor CT26 expresses an envelope protein, gp70, of an endogenous ecotropic murine leukemia virus that is comparable to human tumor-associated antigens, we examined whether a DNA vaccine containing the gp70 gene induces protective immunity against CT26 cells. Injection of mice with plasmid DNA (pDNA) encoding gp70 alone failed to induce anti-gp70 antibody (Ab) or anti-CT26 cytotoxic T lymphocyte (CTL) responses. However, immunization with pDNA encoding the beta-galactosidase (beta-gal)/gp70 fusion protein induced anti-gp70 Ab and anti-CT26 CTL responses and conferred protective immunity against CT26 cells. These results indicate that beta-gal acts as an immunogenic carrier protein that helps in the induction of immune responses against the poorly immunogenic gp70. Considering these results, it is possible that potential tolerance to the endogenous retroviral gene products expressed by human tumors may be overcome by DNA vaccines that contain an endogenous retroviral gene fused to genes encoding immunogenic carrier proteins.

Animals↗
PubMed2000

Aromatic residues and neighboring Arg414 in the (6R)-5,6,7, 8-tetrahydro-L-biopterin binding site of full-length neuronal nitric-oxide synthase are crucial in catalysis and heme reduction with NADPH.

Nitric-oxide synthase (NOS) requires the cofactor, (6R)-5,6,7, 8-tetrahydrobiopterin (H4B), for catalytic activity. The crystal structures of NOSs indicate that H4B is surrounded by aromatic residues. We have mutated the conserved aromatic acids, Trp(676), Trp(678), Phe(691), His(692), and Tyr(706), together with the neighboring Arg(414) residue within the H4B binding region of full-length neuronal NOS. The W676L, W678L, and F691L mutants had no NO formation activity and had very low heme reduction rates (<0.02 min(-1)) with NADPH. Thus, it appears that Trp(676), Trp(678), and Phe(691) are important to retain the appropriate active site conformation for H4B/l-Arg binding and/or electron transfer to the heme from NADPH. The mutation of Tyr(706) to Leu and Phe decreased the activity down to 13 and 29%, respectively, of that of the wild type together with a dramatically increased EC(50) value for H4B (30-40-fold of wild type). The Tyr(706) phenol group interacts with the heme propionate and Arg(414) amine via hydrogen bonds. The mutation of Arg(414) to Leu and Glu resulted in the total loss of NO formation activity and of the heme reduction with NADPH. Thus, hydrogen bond networks consisting of the heme carboxylate, Tyr(706), and Arg(414) are crucial in stabilizing the appropriate conformation(s) of the heme active site for H4B/l-Arg binding and/or efficient electron transfer to occur.

Amino Acid Sequence↗
PubMed2000

Genetic variation and relationships at five STR loci in five distinct ethnic groups in China.

Five short tandem repeat (STR) systems of TH01, vWA, LPL, F13B and FES/FPS were investigated in five ethnic groups living in China (Tujia, Miao, Bai, Chaoxian and Han). All five loci did not deviate from the Hardy-Weinberg equilibrium (P>0.05). At the five loci of each ethnic group, the observed heterozygosity, the mean exclusion chance (MEC), and the power of discrimination (PD) ranged from 0.42 to 0.86, from 0.20 to 0.66 and from 0.61 to 0.95, respectively. For the five ethnic groups, the combined MEC and combined PD were >0. 9360 and >0.9998, respectively, suggesting that combinations of these five systems are feasible for DNA typing in forensic investigations such as personal identification or paternity testing. Furthermore, the allelic frequencies at the five loci suggested that these five ethnic groups were distinctly different communities. Judging from the phylogenetic tree constructed based on the genetic distance among the five ethnic groups, Han, Chaoxian and Tujia were involved in an identical cluster, and Miao and Bai in another. These findings indicate that each of the five groups examined is not only a distinct community, but also has a relationship with each of the others.

Alleles↗
PubMed2000

Neocortical origin and tangential migration of guidepost neurons in the lateral olfactory tract.

The early-generated neurons designated as lot cells specifically mark the future site of the lateral olfactory tract (LOT) and guide LOT axons. We investigated the mechanism of how lot cells develop and get localized in the LOT position. Lot cells differentiated from neuroepithelial cells in all regions of the neocortex but not from those in the ganglionic eminence in culture. Cell tracing analyses demonstrated that lot cells generated from the neocortex subsequently followed a tangential migration stream ventrally toward the LOT position. Mutant mouse embryos lacking the function of transcription factor Gli3 showed disturbances of the migration stream and translocation of lot cells in the dorsal telencephalon. These results reveal a new type of neuronal migration in the telencephalon and introduce an unexpected dramatic feature of the earliest regionalization of the telencephalon.

Animals↗
PubMed2000

Postovulatory follicle: a model for experimental studies of programmed cell death or apoptosis in teleosts.

This is the first evidence of programmed cell death, or apoptosis, occurring in the postovulatory follicle (POF) of teleost fish. Females of Astyanax bimaculatus lacustris were submitted to induced ovulation through injecting pituitary extract. Ultrastructural analyses of POFs at time intervals varying from zero to four days postspawning showed several characteristic events of the apoptosis. Typical apoptotic figures, such as nucleus with chromatin condensation underlying the nuclear envelope in a crescent pattern and apoptotic bodies at different stages of formation and reabsorption, were observed in the follicular cells a few days after the onset of the postovulatory period. The results indicated that apoptosis is the major mechanism responsible for the elimination of the follicular cells in the POFs of A. bimaculatus lacustris during ovarian recovery postspawning. It is suggested that POFs might be used as an experimental model in dynamic studies involving cell death in teleosts.

Animals↗
PubMed2000

Observation of a spin-flip M1 transition in 7(lambda)Li.

Using a large-acceptance germanium detector array (Hyperball), we have observed a spin-flip M1 gamma transition between the ground-state spin doublet of (7)(Lambda)Li (3/2(+)-->1/2(+)). The observed energy of 691.7+/-0.6(stat)+/-1.0(syst) keV provides crucial information on the strength of the spin-spin interaction between a Lambda and a nucleon. This is the first observation of well-identified hypernuclear gamma transitions using germanium detectors.

Journal Article↗
PubMed2000

Mismatch negativity (MMN) reveals sound grouping in the human brain.

To investigate a part of the structure of the memory trace, auditory event-related potentials (ERPs) were recorded from reading subjects while they were presented with two different stimulus-series simultaneously. A clear mismatch negativity (MMN) was obtained from each series, when the stimulus sequence consisted of a high-frequency series and a low-frequency series. Moreover, the MMN showed independent elicitation within each series. However, if the frequency range of one series overlapped with that of the other series, the amplitude of the MMN was prominently reduced, suggesting that the two processing functions indexed by MMN coexisted simultaneously in the preattentive acoustic system and were produced by the respective grouping of high-frequency tones and low-frequency tones.

Acoustic Stimulation↗
PubMed2000

Expression of the 37-kDa laminin binding protein in murine lung tumor cell correlates with tumor angiogenesis.

Expression of the 37-kDa laminin binding protein (37LBP), a precursor protein of the 67-kDa laminin receptor, correlates well with the biological aggressiveness of cancer cells. Previously, we have established murine lung cancer cell lines T11 and T15, in which 37LBP expression was remarkably diminished, and reported that the mean survival time of the T11 and the T15-recipients was significantly prolonged compared with that of the control cell lines (P29 and T42). In the present study, immunohistochemical findings of the tumors demonstrated that the microvessel density in the T11 (28. 1+/-7.2/mm(2)) and in the T15 tumor (29.7+/-6.5/mm(2)) were significantly lower than that observed in P29 (46.3+/-8.7/mm(2)) or in T42 (50.5+/-4.4/mm(2)). Expression of vascular endothelial growth factor (VEGF) was repressed in T11 and T15 compared with its expression in P29 and T42. It was also shown that conditioned media of T11 and T15 cells exhibited significantly reduced proliferation and migration of the capillary endothelial cells. These results suggest that decreased expression of 37LBP in antisense-RNA transfectant may relate to its low tumorigenicity, and that this effect may be partly caused by the diminished tumor angiogenesis of murine lung cancer.

Animals↗
PubMed2000

Construction of region-specific partial duplication mutants (merodiploid mutants) to identify the regulatory gene for the glucan-binding protein C gene in vivo in Streptococcus mutans.

The gbpC gene encoding the glucan-binding protein C which is involved in dextran (glucan)-dependent aggregation (ddag) of Streptococcus mutans has been identified by random mutagenesis. We analyzed ddag(-) mutants containing the intact gbpC gene and found that these mutants possessed a large and characteristic duplication of a region of the chromosome which was responsible for the phenotype. Based upon characterization of these duplications, we developed a strategy to introduce a duplication into any specific region of the chromosome of these organisms. The 690-bp gene responsible for the ddag(-) phenotype was identified within a 60-kb region by observing ddag (positive or negative) phenotypes of successively constructed specific duplication mutants.

Bacterial Proteins↗
PubMed2000

Roles of two VEGF receptors, Flt-1 and KDR, in the signal transduction of VEGF effects in human vascular endothelial cells.

Vascular endothelial growth factor (VEGF) is a principal regulator of vasculogenesis and angiogenesis. VEGF expresses its effects by binding to two VEGF receptors, Flt-1 and KDR. However, properties of Flt-1 and KDR in the signal transduction of VEGF-mediated effects in endothelial cells (ECs) were not entirely clarified. We investigated this issue by using two newly developed blocking monoclonal antibodies (mAbs) against Flt-1 and KDR. VEGF elicits DNA synthesis and cell migration of human umbilical vein endothelial cells (HUVECs). The pattern of inhibition of these effects by two mAbs indicates that DNA synthesis is preferentially mediated by KDR. In contrast, the regulation of cell migration by VEGF appears to be more complicated. Flt-1 regulates cell migration through modulating actin reorganization, which is essential for cell motility. A distinct signal is generated by KDR, which influences cell migration by regulating cell adhesion via the assembly of vinculin in focal adhesion plaque and tyrosine-phosphorylation of focal adhesion kinase (FAK) and paxillin.

3T3 Cells↗