Biomedical subjects

M Hoshi

Publications and source records attributed to M Hoshi.

At least 145 records · Page 8Linked to original sources

PubMed1995

Amyloid beta peptide induces cytoplasmic accumulation of amyloid protein precursor via tau protein kinase I/glycogen synthase kinase-3 beta in rat hippocampal neurons.

Exogenous application of synthetic amyloid beta protein (A beta) is known to induce neurotoxic effects in rat hippocampal culture. We report here that A beta (25-35) induces accumulation of amyloid precursor protein (APP) derivatives in the cytoplasm of neurons. At the same time, the level of the secreted form of APP released into the culture medium decreases. Tau protein kinase I/glycogen synthase kinase-3 beta (TPK I/GSK-3 beta) antisense oligonucleotide blocked APP accumulation and prevented neuronal death. These results provide evidence that APP accumulation after A beta treatment is regulated by TPK I/GSK-3 beta. A beta neurotoxicity is probably mediated via phosphorylation of tau by TPK I/GSK-3 beta, resulting in an impairment of axonal transport, and cytoplasmic accumulation of APP.

Amyloid beta-Peptides↗

PubMed1995

Identification and synthetic pathway of sialyl-Lewisx-containing neolacto-series gangliosides in lens tissues. 1. Characterization of gangliosides in human senile cataractous lens.

Human lens accumulates gangliosides in association with aging and senile cataract progression. In this study we purified and characterized five major gangliosides in human cataractous lenses. Structural analyses and immunological studies revealed the presence of ganglio-series gangliosides, GM3, GM2, GM1 and GD1a, and a sialyl-Lewisx-containing neolacto-series ganglioside, NeuAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1ceramide (IV3NeuAcIII3FucnLc4). Slow-moving gangliosides, although minor components, were also found to have sialyl-Lewisx-related structures, based on anti-Lewisx antiserum binding to their asialo forms. However, sialyl-paragloboside, a possible precursor of the sialyl-Lewisx ganglioside, was not identified.

Aged↗

PubMed1995

Buckling of a single microtubule by optical trapping forces: direct measurement of microtubule rigidity.

As major determinants of cell shape and polarity, microtubules are required to have suitable rigidity. However, our knowledge of the mechanical properties of microtubules is far from satisfactory. We report here a new method of measuring the flexural rigidity of a single microtubule by direct buckling using the optical trapping technique. Microtubule buckling was induced by applying a small longitudinal compressing force through an optically trapped microsphere that was firmly attached to the microtubule. Three ways of estimating the flexural rigidity of a continuous slender rod, one from the observed critical load of buckling and two from deflected lengths and angles of bending, yielded values which agreed well when applied to the analysis of buckling microtubules. Unexpectedly, we found that the rigidity was not constant as expected but was dependent on microtubule length. This length dependency explains the discrepancies among reported values of microtubule flexural rigidity measured by different methods. Comparing microtubules of identical lengths, microtubules assembled with brain-derived associated proteins (4 x 10(-23) Nm2 at around 10 microns in length) were four times more rigid than those assembled from purified tubulin and stabilized with taxol (1 x 10(-23) Nm2).

Animals↗

PubMed1995

Ultrastructural localization of acrosome reaction-inducing substance (ARIS) on sperm of the starfish Asterias amurensis.

Using colloidal gold tagged ligands we have identified the ultrastructural site of ARIS binding to intact and acrosome-reacted starfish sperm. In intact sperm, colloidal gold conjugated ARIS was specifically localized to a single domain (0.1-0.3 micron in diameter) on the plasma membrane. This site was located on the anterior-lateral aspect of the sperm head, that is, just peripheral to the region occupied by the acrosomal vesicle and periacrosomal components. When sperm were labeled with colloidal gold conjugated ARIS, washed to remove unbound label, and then induced to undergo the acrosome reaction, the labeled patch remained associated with the plasma membrane and was positioned just lateral to the acrosomal process. However, when sperm were suspended in labeled ARIS and induced to undergo the acrosome reaction, label was observed along the entire anterior aspect of the sperm head with the exception of the acrosomal process. Labeling along the entire anterior aspect of the sperm head in this case was deemed to be nonspecific and due to binding of colloidal gold tagged molecules to components formerly located within the acrosomal vesicle, as the same pattern was obtained using colloidal gold tagged bovine serum albumin. Quantitative and qualitative aspects of ARIS binding observed here by electron microscopy are in agreement with measured binding characteristics previously reported (Ushiyama et al., 1993a: Zygote 1:121-127; Ushiyama et al., 1993b: J Reprod Dev 39:53-54), and indicate that the site of labeled ARIS binding represents a specific plasma membrane domain occupied by ARIS receptors.

Animals↗

PubMed1995

A periodic network of G protein beta gamma subunit coexisting with cytokeratin filament in starfish oocytes.

Heterotrimeric G proteins are membrane-bound and carry signals from activated receptors on plasma membranes to cytoplasmic effector enzymes and channels. In starfish oocytes, the beta gamma subunit of G protein mediates 1-methyladenine stimulation of oocyte maturation. In order to investigate the localization of beta gamma subunits in starfish oocytes during oocyte maturation, we raised a monoclonal antibody against the beta subunit. By immunofluorescence microscopy using the antibody, immature oocytes show a network of fibers in the cytoplasm. The staining of fibers is beaded with a periodicity of 0.7 microns. The same staining pattern is obtained by anti-gamma subunit antibody. In addition, the fibers are stained by anti-cytokeratin antibody. These results indicate that the G protein beta gamma subunit coexists with cytokeratin filaments in starfish oocytes. Stimulation of oocyte maturation by 1-methyladenine causes the beta gamma subunit to be disassembled.

Animals↗

PubMed1995

G-protein-mediated signal transduction for meiosis reinitiation in starfish oocyte.

Starfish oocyte maturation is induced by 1-methyladenine. There were apparently two forms of 1-methyladenine receptor affected by GTP gamma S. Pertussis toxin ADP-ribosylated the 39-kDa alpha subunit of a G protein and inhibited maturation. Also, the G protein was ADP-ribosylated by cholera toxin only when 1-methyladenine was added. The purified G protein had an heterotrimeric structure consisting of 39 kDa alpha, 37 kDa beta, and 8 kDa gamma subunits. The deduced amino acid sequence of the cDNA of starfish G alpha was 89% identical to mammalian Gi-1 alpha. The purified starfish beta gamma-subunits induced maturation when they were microinjected into oocytes.

Adenosine Diphosphate Ribose↗

PubMed1995

Effects of heparin, sperm concentration and bull variation on in vitro fertilization of bovine oocytes in a protein-free medium.

The present study was conducted to examine the effects of heparin, sperm concentration and bull variation on the fertilization of bovine oocytes in a protein-free medium supplemented with polyvinyl alcohol and subsequent in vitro development of fertilized embryos. The effects in protein-free medium were compared with those in medium supplemented with bovine serum albumin (BSA). In the presence of heparin (1, 10 and 100 microg/ml), nearly all the oocytes were fertilized with and without BSA. In the absence of BSA, polyspermy was lower (4 to 15%) than in its presence (15 to 48%; P < 0.05). An increase in sperm concentration from 1 x 10(4) cells/ml during insemination enhanced fertilization rate up to 1 x 10(6) cells/ml with and without BSA (14 to 90% and 3 to 77%, respectively). In the absence of BSA, the highest concentration of spermatozoa (1 x 10(7) cells/ml) gave a lower fertilization rate (55%) than that at 1 x 10(6) cells/ml (77%; P < 0.05). Polyspermy neither increased nor decreased sperm concentration without BSA (0 to 8%; P > 0.05). The effects of spermatozoa from 5 different bulls chosen randomly on in vitro fertilization in medium without BSA were examined. Individual bull variation in fertilization rate (36 to 95%) was noted at 3 different heparin concentrations (1, 10 and 100 microg/ml). Polyspermic fertilization was low (0 to 14%) and was the same for all bulls at all heparin concentrations. Embryos fertilized without BSA developed to the blastocyst stage at the same rate (27%) as those with BSA (33%; P > 0.05).

Journal Article↗

PubMed1995

Effects of water quality on in vitro fertilization and development of bovine oocytes in protein-free medium.

Examination was made of the effects of water quality in medium preparation on fertilization and early development of bovine in vitro matured (IVM) oocytes in a protein-free medium. The IVM oocytes were inseminated and cultured for 7 d in protein-free media prepared with 4 different types of water preparations: tap, deionized, twice-distilled, and purified water using the Milli-Q system (Milli-Q water). High frequencies (70 to 83%) of normal fertilization were obtained in media prepared with all types of water. However, the frequency of development to the blastocyst stage in media prepared with Milli-Q water (31 +/- 3%) was significantly higher than with the 3 other types of water (11 to 13%). Moreover, the effects of storage period of Milli-Q water on early development of bovine embryos was also examined. The frequency of development to the blastocyst stage in media prepared with Milli-Q water immediately after preparation (fresh Milli-Q water; 35 +/- 4%) was significantly higher than for Milli-Q water stored for 1 wk (18 +/- 4%) or 2 wk (18 +/- 3%). Effects of commercially available purified water on early development of bovine embryos were also examined. The frequency of development to the blastocyst stage in media prepared with Milli-Q water (33 +/- 5%) was significantly higher than for purified water purchased from 3 different suppliers (Brand A; 21 +/- 6%, Brand B; 21 +/- 2%, Brand C; 21 +/- 4%). Each water sample was analyzed by the measurement of electrical conductivity, organic compounds and/or inorganic ion and endotoxin concentrations to evaluate purity. Fresh Milli-Q water showed the lowest level of electrical conductivity and contained the lowest concentration of organic compounds. These results indicate that in vitro fertilization of bovine oocytes is not affected by the water quality in the preparation of medium; however, early development of bovine embryos is seriously affected by the purification method and the storage period of water used for medium preparation.

Journal Article↗

PubMed1995

Glycemic control, growth and complications in children with insulin-dependent diabetes mellitus--a study of children enrolled in a Summer camp program for diabetics in Kinki district, Japan.

The influence of glycemic control on growth and on the development of complications in diabetic children was studied. The subjects of the study were 107 children with insulin-dependent diabetes mellitus (IDDM), who were enrolled in a Summer camp program for diabetic children in Kinki District, Japan from 1972 to 1990, and who had at least three determinations of HbA1 during the observation period. Many of the children had high mean levels of HbA1, regardless of age. The height and weight were below the standards for the respective ages in many children, indicating the retardation of growth. However, S.D. scores for height and weight and other physical indices were not related to the mean levels of HbA1. By contrast, the prevalence of diabetic retinopathy was related to an elevated mean level of HbA1, but that of albuminuria was not. Serum cholesterol levels were higher in children with higher mean levels of HbA1, but serum triglycerides appeared not to be related to glycemic control. The incidence of retinopathy during the observation period closely related to the degree of the mean levels of HbA1, but that of albuminuria did not.

Adolescent↗

PubMed1995

Age-related changes in ganglioside composition in human lens.

We previously reported that human lens accumulates gangliosides in association with aging and senile cataract progression. Structural analysis revealed that gangliosides in human cataractous lenses were composed of ganglio-series gangliosides, such as GM3, GM2, GM1 and GD1a, and sialyl-Lewisx-containing neolacto-series gangliosides. Although Lewisx-containing neolacto-series glycolipid was found to accumulate in association with aging and cataract progression, the sialyl-Lewisx gangliosides did not show much accumulation in individual lenses from subjects between 16 and 80 years old. The content of sialyl-Lewisx gangliosides was about two to four times higher than that of Lewisx glycolipids, suggesting the possibility that the increase in Le(x) glycolipid is partly due to the desialylation of sialyl-Le(x) gangliosides. On the other hand, the expression of ganglio-series gangliosides increased in an age-related manner. Thus, age-related changes in lens glycolipids may modify the cell-to-cell interaction induced by cell surface sugar chains, leading to the initiation and progression of cataract.

Adolescent↗

PubMed1995

Characterization of neutral glycosphingolipids in rat lens.

Neutral glycosphingolipids were purified from non-cataractous lenses of Sprague-Dawley rats by a combination of solvent extraction, Folch's partition, and column chromatography using DEAE-Sephadex and Iatrobeads. Six major GSLs from monohexosylceramide to pentahexosylceramide were identified by sugar composition analysis, methylation analysis and glycosidase digestion. Structural relationships among the six neutral glycosphingolipids revealed metabolic pathways leading to the synthesis of Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1 ceramide (IV3Gal alpha nLc4), instead of a Lewis(x) glycolipid (Gal beta 1- 4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1 ceramide, III3FucnLc4), from neolactotetraosylceramide (nLc4), together with isoglobotriaosylceramide (iGb3). The alpha-galactosyl epitope, Gal alpha 1-3Gal-R, is evolutionarily conserved in many types of cells of non-primate mammals, prosimians and New World monkeys, but not in those of Old World monkeys or humans. This evolution-related difference in carbohydrate epitopes suggests different cell-to-cell attachments, which may be mediated through cell surface glycosphingolipids, between rat and human lenses.

Animals↗

PubMed1995

Cortical changes in starfish (Asterina pectinifera) oocytes during 1-methyladenine-induced maturation and fertilisation/activation.

Maturation of the starfish oocyte cortex to produce an effective cortical granule reaction and fertilisation envelope is believed to develop in three phases: (1) pre-methyladenine (1-MA) stimulation; (2) post-1-MA stimulation, pregerminal vesicle breakdown; and (3) post-germinal vesicle breakdown. The present study was initiated to identify what each of these phases may encompass, specifically with respect to structures associated with the oocyte cortex, including cortical granules, microvilli and vitelline layer. 1-MA treatment brought about an orientation of cortical granules such that they became positioned perpendicular to the oocyte surface, and an approximately 4-fold decrease in microvillar length. A-23187 activation of immature oocytes treated with (10 min; pregerminal vesicle breakdown) or without 1-MA resulted in a reduction in cortical granule number of 21% and 41%, respectively (mature oocytes underwent a 96% reduction in cortical granules). Elevation of the fertilisation envelope in both cases was significantly retarded compared with activated mature oocytes. In activated mature oocytes, the vitelline layer elevated 20.0 +/- 5.4 mu m from the egg's surface, whereas in immature oocytes treated with just A-23187 or with 1-MA (10 min) and A-23187, it lifted 0.35 +/- 0.1 and 0.17 +/- 0.04 mu m, respectively. The fertilisation envelopes of activated (or fertilised) immature oocytes also differed morphologically from those of mature oocytes. In activated, immature oocytes, the fertilisation envelope was not uniform in its thickness and possessed thick and thin regions as well as fenestrations. Additionally, it lacked a complete electron-dense stratum that characterised the fertilisation envelopes of mature oocytes. The nascent perivitelline space of immature oocytes was also distinguished by the presence of numerous vesicles which appeared to be derived from microvilli. Differences in the morphology of cortices from activated (fertilised) and non-activated, immature and mature oocytes substantiate previous investigations demonstrating three phases of cortical maturation, and are consistent with physiological changes that occur during oocyte maturation, involving ionic conductance of the plasma membrane, establishment of slow and fast blocks to polyspermy and elevation of a fertilisation envelope.

Adenine↗

PubMed1995

Estimation by radiation inactivation of the minimum functional size of acrosome-reaction-inducing substance (ARIS) in the starfish, Asterias amurensis.

In the starfish Asterias amurensis, the jelly coat of the eggs contains a glycoprotein essential for the induction of the acrosome reaction in homologous spermatozoa that is termed the acrosome-reaction-inducing substance (ARIS). ARIS is a highly sulphated and fucose-rich glycoprotein of extremely high molecular mass (> 10(4) kDa). ARIS was irradiated with high-energy electrons in order to estimate the minimum size required for its biological activity. The minimum functional unit or target size of ARIS was estimated to be c. 14 kDa by target size analysis. ARIS was significantly disintegrated by the irradiation, yet the total sugar content was not apparently reduced. The binding of 125I-labelled ARIS to spermatozoa competed with that of irradiated ARIS, although the affinity of ARIS was much reduced after irradiation.

Acrosome↗

PubMed1995

Regulatory mechanisms of the acrosome reaction revealed by multiview microscopy of single starfish sperm.

The acrosome reaction in many animals is a coupled reaction involving an exocytotic step and a dramatic change in cell shape. It has been proposed that these morphological changes are regulated by intracellular ions such as Ca2+ and H+. We report here simultaneous visualization, under a multiview microscope, of intracellular free Ca2+ concentration ([Ca2+]i), intracellular pH (pHi), and morphological changes in a single starfish sperm (Asterina pectinifera). [Ca2+]i and pHi were monitored with the fluorescent probes indo-1 and SNARF-1, respectively. The acrosome reaction was induced with ionomycin. After the introduction of ionomycin in the medium, [Ca2+]i increased gradually and reached a plateau in approximately 30 s. The fusion of the acrosomal vacuole took place abruptly before the plateau, during the rising phase. Although the speed of the [Ca2+]i increase varied among the many sperm tested, exocytosis in all cases occurred at the same [Ca2+]i of approximately 2 microM (estimated using the dissociation constant of indo-1 for Ca2+ of 1.1 microM). This result suggests that the exocytotic mechanism in starfish sperm responds to [Ca2+]i rapidly, with a reaction time of the order of one second or less. Unlike the change in [Ca2+]i, an abrupt increase in pHi was observed immediately after exocytosis, suggesting the presence of a proton mobilizing system that is triggered by exocytosis. The rapid increase in pHi coincided with the formation of the acrosomal rod and the beginning of vigorous movement of the flagellum, both of which have been proposed to be pHi dependent. The exocytotic event itself was visualized with the fluorescent membrane probe RH292. The membrane of the acrosomal vacuole, concealed from the external medium in an unreacted sperm, was seen to fuse with the plasma membrane.

Acrosome↗

PubMed1995

Childhood thyroid diseases around Chernobyl evaluated by ultrasound examination and fine needle aspiration cytology.

Screening by ultrasound examination and fine-needle aspiration cytological biopsy (FNA) was conducted in five regions in Belarus, Ukraine, and Russia to investigate the prevalence of childhood thyroid diseases around Chernobyl. Gomel, Zhitomir, Kiev, and the western area of Bryansk are the administrative regions where severe radioactive contamination occurred. The subjects from Mogilev, where contamination was relatively low, served as controls. Among 55,054 subjects (26,406 boys and 28,648 girls), the prevalence of ultrasonographic thyroid abnormalities such as nodule, cyst, and abnormal echogenity was significantly higher in the regions with severe contamination than in Mogilev. Of the 1,396 children showing echographic thyroid abnormalities 197 were selected for FNA, and a sample was successfully obtained for diagnosis from 171 (51 boys and 120 girls) of the 197 subjects. The aspirate was insufficient for diagnosis in the remaining 26 subjects. Thyroid cancer was encountered in four children (2.3%) from the contaminated regions, two children being from Gomel. The other thyroid diseases were follicular neoplasm, 6.4%; adenomatous goiter, 18.7%; chronic thyroiditis, 31.0%; and cyst, 24.0%, suggesting that a major cause of thyroid nodularity is nonneoplastic changes, mainly chronic thyroiditis and cysts. These results will serve as an important data base for further analyses and suggest that childhood thyroid diseases, including both neoplasms and immunological disorders, are consequences of radioactive fallout.

Adenocarcinoma, Follicular↗

PubMed1995

Localization of neutral and acidic glycosphingolipids in rat lens.

Rat lens was found to contain several neutral and acidic glycosphingolipids in lens epithelia, cortex and nucleus, and showed developmental changes in their content and localization. TLC-immunostaining of gangliosides revealed the enrichment of some ganglio-series gangliosides (GM3, GM1, GD3 and GD1b) in lens epithelia and the presence of GM3 and GD3 in the lens nucleus. Immunohistochemical studies confirmed the distribution of GM3 and GM1 in anterior lens epithelial cells and the cortex, with expression decreasing toward the lens nucleus. Immunoreaction to GD3 was more intense in the lens nucleus than in epithelial cells. In contrast, the expression of neolacto-series glycosphingolipids was restricted to the lens nucleus. In order to investigate the pathological changes of glycosphingolipids in cataract, galactose-induced cataractous lenses were examined. However, no significant changes were observed in the content and composition of glycosphingolipids. In addition, Lewisx epitopes found in human cataractous lenses were not detected in the cataractous lenses of galactosaemic rats and hereditary cataractous Emory mice.

Aging↗

PubMed1995

Differential distribution of gangliosides in adult rat ovary during the oestrous cycle.

Gangliosides are ubiquitous membrane components in mammalian cells and are suggested to play important roles in various cell functions, such as cell-cell recognition, differentiation and transmembrane signalling. Rat ovary contained GM3, GD3 and GD1a as major gangliosides, and GM1 as a minor one. In order to study their distribution in the rat ovary and its possible changes during the oestrous cycle, frozen sections were stained with specific monoclonal antibodies against 11 ganglio-series gangliosides including those mentioned above. GM3, GM1 and GD1a were expressed in a spatio-temporally different manner during the oestrous cycle, but GD3 and other gangliosides were not immunohistochemically detected. In primary and secondary follicles, GM3, GM1 and GD1a were expressed in theca cells, but not in granulosa cells. The oocyte in primary, but not secondary, follicles was positive to the anti-GD1a antibody. In Graafian follicles, GM1 and GD1a were similarly expressed as in secondary follicles, however, the expression of GM3 spread gradually from theca cells to granulosa cells. In early Graafian follicles, only GM3 was expressed to a detectable extent from the outer part of the granulosa layer to the inner part. Shortly before ovulation, all granulosa cells and cumulus cells became positive to anti-GM3 antibody. After ovulation, differential distribution of GM3, GM1 and GD1a was also observed in luteal cells. GD1a was localized in thread-like structures, while GM3 was distributed throughout the cytoplasm, but not in the nucleus. GM1 was localized only in the plasma membrane and/or its close vicinity. Other ganglio-series gangliosides, including GD3, were not detected to an appreciable extent in the ovaries by immunohistochemistry.

Animals↗

PubMed1995

Protoplast fusion method for efficient transformation of mouse spermatogenic cells.

The efficiencies of methods for introducing DNAs into spermatogenic cells were investigated. The calcium phosphate method has been most commonly used to transfect DNA into cultured cells, but this method severely damages spermatogenic cells. Therefore, we investigated the efficiencies of transfection of spermatogenic cells by DEAE-dextran, modified liposome, and protoplast fusion methods, which seemed to cause less damage to spermatogenic cells than the calcium phosphate method. The protoplast fusion method was the most suitable for transfection of spermatogenic cells.

Animals↗