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S Hamaguchi

Publications and source records attributed to S Hamaguchi.

At least 37 records · Page 2Linked to original sources
PubMed1997

Inhibition of colony formation of NIH 3T3 cells by the expression of the small molecular weight heat shock protein HSP27: involvement of its phosphorylation and aggregation at the C-terminal region.

The ectopic expression of the small molecular weight heat shock protein HSP27 reportedly confers resistance to heat and other types of stress, but our recent findings indicated that it rendered human immortalized fibroblast cells (KMST-6) more sensitive to oxidative stress and caused irreversible growth arrest (Arata et al., 1995, J. Cell. Physiol., 163:458-465). To clarify the relationship between HSP27 and growth regulation, we investigated the effect of overexpression of HSP27 and its mutants on the growth potential of several cell lines. Mammalian expression vectors of the wild-type, hypophosphorylatable, or C-terminal deletion mutants of human HSP27 were constructed from the pRc/CMV plasmid that contained the neomycin-resistant gene. The plasmid was introduced into mouse fibroblasts (NIH 3T3), normal human fibroblasts (TIG-3), Chinese hamster ovary (CHO-K1), or mammary tumor cells (MCF-7), which were then selected in medium containing G418. The number of drug-resistant colonies was significantly decreased by transfection with the expression vector for wild-type HSP27 compared with vector alone, whereas the overexpression of HSP27 in CHO-K1 cells had essentially no effect. The expression vectors of an hypophosphorylatable mutant (pKSm, human HSP27 gene in which codons for Ser-15, -78, and -82 were converted to code for Gly by site-directed mutagenesis) as well as C-terminal deletion mutants in which 12-36 amino acid residues from the C-terminus were deleted had no significant effect on the colony-forming efficiency of NIH 3T3 cells. Cells isolated from G418-resistant colonies formed by transfection of NIH 3T3 cells with the HSP27 expression vector expressed no detectable levels of wild-type HSP27 and did not form stable clonal transformants expressing high levels of HSP27 from NIH 3T3 cells. In contrast, several clones expressing high levels of HSP27 were obtained from CHO-K1 cells transfected with the HSP27 expression vector. In KMST-6 clones expressing high levels of HSP27, the wild-type HSP27 formed aggregates with a mean molecular mass of about 200 kDa as determined by gel filtration, and the size of the oligomers changed with oxidative stress. On the other hand, the size of aggregates of HSP27 encoded by pKSm or C-terminal deletion mutants did not change. These observations indicated that the forced expression of wild-type HSP27 participates in inhibiting the growth of some cell types and that the inhibition may be associated with its phosphorylation and aggregation.

3T3 Cells↗
PubMed1995

Effects of the overexpression of the small heat shock protein, HSP27, on the sensitivity of human fibroblast cells exposed to oxidative stress.

The role of the human small heat shock protein (HSP27) in oxidative stress was examined using stable transformants of an immortalized human fibroblast cell line (KMST-6) isolated by transfection of HSP27 expression vectors. Several stable transformants that expressed high or low levels of HSP27 protein were obtained. Clones expressing high levels of HSP27 were more sensitive to growth inhibition by a low dose of hydrogen peroxide (0.1 mM) than those expressing low levels. Clones expressing high levels of HSP27 did not acquire obvious resistance to hyperthermy and cytotoxic agents, except for one (#13), in which resistance to cytotoxic agents was increased. The level of phosphorylated HSP27 in clones expressing high levels of this protein increased at 30 min and was sustained even 4 hours after exposing the cells to 0.1 mM of hydrogen peroxide. On the other hand, the levels in clones expressing low levels of HSP27 were reduced within 4 hours after exposure to hydrogen peroxide. Furthermore, overexpression of nonphosphorylatable mutant HSP27 did not affect sensitivity to oxidative stress. These results suggested that constitutively high expression of HSP27 in KMST-6 cells make them susceptible to oxidative stress resulting in growth arrest, and this mechanism could involve the phosphorylation of HSP27.

Cell Line, Transformed↗
PubMed1995

Does hypertonic saline have preventive effects against delayed neuronal death in gerbil hippocampus?

This experiment was conducted to ascertain whether or not hypertonic saline solution (HSS) has preventive effects on delayed neuronal death in the hippocampal CA1 subfield of the gerbil. Twenty-eight gerbils were anesthetized with 1% halothane and 50% nitrous oxide during the experimental period. Their common carotid arteries were occluded bilaterally for 2.5 min, immediately after which 2 mL/kg of 10% NaCl was infused via the tail vein. Two mL/kg of physiological saline solution (PSS) was used for the control group in the same manner. 5 days later, after the cerebrum was removed, the hippocampus was stained with hematoxylin-eosin, and histopathological changes in the CA1 subfield were observed under the light microscope. Degenerative or necrotic pyramidal cells were compared among groups. The degeneration rates of the pyramidal cells were as follows; after sham operation with PSS, 4.2 +/- 1.8%; after sham operation with HSS, 6.5 +/- 3.3%; on ischemia-reperfusion with PSS, 95.6 +/- 1.6%; on ischemia-reperfusion with HSS, 7.1 +/- 3.0%. This study suggested that hypertonic saline might prevent delayed neuronal death in the hippocampal CA1 subfield of gerbils subjected to cerebral ischemia-reperfusion.

Animals↗
PubMed1995

Tumor-specific mutations in the tyrosine kinase domain of the RET proto-oncogene in pheochromocytomas of sporadic type.

Sporadic pheochromocytomas, sporadic medullary thyroid carcinomas (MTCs), pheochromocytomas and/or MTCs in multiple endocrine neoplasia (MEN) 2A or 2B were screened for mutations in the tyrosine kinase domain of the RET proto-oncogene by direct sequencing of PCR-amplified products or sequencing subcloned DNAs from PCR-products. All tumors of 4 MEN 2B patients were confirmed to contain a heterozygous missense mutation at codon 918 (ATG-->ACG; Met-->Thr) of the RET proto-oncogene as well as their leukocytes. The same tumor-specific mutations at codon 918 were also found in 5/16 (31%) sporadic pheochromocytomas. These results suggest that mutations of the RET proto-oncogene in its tyrosine kinase domain play a role not only as the predisposing gene for MEN 2B, but also as a tumorigenic factor for pheochromocytomas of sporadic type.

Adolescent↗
PubMed1994

Purification and characterization of a novel calcium-binding protein, S100C, from porcine heart.

A novel Ca(2+)-binding protein, which we have named S100C (Ohta et al. (1991) FEBS Lett. 295, 93-96), was purified to homogeneity from porcine heart by Ca(2+)-dependent dye-affinity chromatography. S100C possesses some properties of S100 proteins, such as self-association and exposure of a hydrophobic site upon binding of Ca2+ but it differs from S100 proteins in forms of its isoelectric point (pI = 6.2), cross-reactivity with antibodies, staining by Stains-all, and its Ca(2+)-dependent interaction with the immobilized dye. S100C bound to cytoskeletal components at physiological concentrations of Ca2+. Moreover, it was found that 125I-labeled S100C interacted with annexin I in a Ca(2+)-dependent manner. S100C also inhibited the phosphorylation of annexin I by protein kinase C. These data suggest that S100C might act to regulate the cytoskeleton in a Ca(2+)-dependent manner via interactions with annexin I.

Animals↗
PubMed1994

Foreign gene transfer into nigorobuna (Carassius auratus grandoculis).

Supercoiled and linear plasmid DNA containing the Escherichia coli beta-galactosidase gene was injected into dechorionated nigorobuna (Carassius auratus grandoculis) eggs prior to first cleavage. The survival rates in the hatching stage were 73% to 89% for injected eggs in comparison with controls (non-injected chorionated eggs). The exogenous DNA was detected by polymerase chain reaction (PCR) in all of the three-day-old larvae analyzed and in about 20% of two-year-old adult fish. Expression of the transgene was easily examined by a histochemical method using dechorionated eggs. The incidence of beta-galactosidase-positive embryos was highest in the gastrula or embryonic-body-formation stage and became low in the embryonic-body-movement stage. These results suggest the usefulness of funa (Carassius fishes) as a model fish in transgenic experiments, and the applicability of the transgenic technique to the improvement of funa as a food source.

Animals↗
PubMed1994

[Effect of hypertonic saline solution on delayed neuronal death].

This experiment was performed to investigate whether hypertonic saline has a preventive effect on delayed neuronal death in the CA1 subfield of the hippocampus. Twenty gerbils were used, and after being anesthetized by inhalation of 1% halothane, both common carotid arteries were occluded for 2.5 min. The animals were injected intravenously with 2 ml/kg of 10% NaCl immediately after reperfusion, and 2 ml/kg of physiological saline solution was used in the same manner in a control group. Five days later, histopathological changes in the CA1 subfield were observed by staining with hematoxylin-eosin and examining sections of the brain under a light microscope. Degenerative or necrotic pyramidal cells exhibited cell shrinkage, nuclear pyknosis, dark staining of the cytoplasm vacuolation and disappearance of the radial striated zone. The pyramidal cell degeneration rate in a 1 mm length of CA1 subfield was 95.6 +/- 1.6% in the ischemia-reperfusion-saline group and 7.1 +/- 3.0% in ischemia-reperfusion-hypertonic saline group, and the difference was statistically significant. This study verified that hypertonic saline prevented delayed neuronal death in the CA1 subfield of hippocampal area after ischemia-reperfusion.

Animals↗
PubMed1993

Alterations in the morphology of nuages in spermatogonia of the fish, Oryzias latipes, treated with puromycin or actinomycin D.

A germ-cell specific organelle, nuage, in Oryzias latipes is polymorphic. Nuages with a strand-like structure and amorphous fibrous bodies can be discriminated from each other; furthermore 2 types of nuages of intermediate morphology are also present. After the administration of puromycin or actinomycin D, nuage morphology in spermatogonia was examined by electron microscopy. Puromycin as well as actinomycin D caused a significant increase in the incidence of nuages with a strand-like structure. These observations indicate that the loss of supply of some materials can induce morphological changes in nuages, suggesting that the polymorphism in nuages of O latipes possibly results from the turnover of nuage materials.

Animals↗
PubMed1992

Sexually differentiated mechanisms of sterility in interspecific hybrids between Oryzias latipes and O. curvinotus.

Fertility of interspecific hybrids between Oryzias latipes and O. curvinotus was examined. F1 females were able to lay eggs but males were sterile. Histological examination of the ovaries of hybrids revealed that oogenesis does not proceed normally in spite of the apparent fertility. Most oocytes degenerated at the pachytene stage of the meiotic prophase, and only a few entered the diplotene stage to develop into ova. Hybrid males could induce females to spawn eggs, an indication that they had differentiated completely into true males. However, they did not produce fertile sperm. Most germ cells in testes of hybrids passes through almost the entire process of spermatogenesis, but deviations from the normal course of events were observed during spermiogenesis. The condensation of chromatin in spermatids occurred, but the diameters of sperm heads were about 1.5-fold larger than those of normal ones. Prominent abnormalities were apparent in the quantity and arrangement of microtubules in the cytoplasm. Abnormal spermatozoa were phagocytized by Sertoli cells. These observations indicate that the mechanisms of impaired gametogenesis in these interspecific hybrids are sexually differentiated.

Animals↗
PubMed1989

[The interproximal periodontal pocket and its measurement].

Periodontal probing is the most important examination to determine the presence and severity of periodontal lesions. In the interproximal contact areas, probing depth is not accurate because there are some errors in angulating the probe. The purpose of this study was to establish the correct probing method in these areas. Therefore a new interproximal periodontal probe was developed. It eliminated the errors which arise from angulating a probe. The effectiveness of the 8-point method which uses both a conventional probe and the new type interproximal one was determined. The results were as follows: 1. 20 human dry skulls were selected to indicate the necessary angle at which a probe could reach the center of the interproximal contact area. Approximately 30 degrees was needed in molars. This was the most popular angle for measurement in these places. 2. 12 periodontal patients were selected to determine the errors in probing depth between a conventional probe and the new type interproximal one when a probe angulated 30 degrees. The average error was 0.56 mm, indicating that the new type interproximal probe must be used when a probe was angulates 30 degrees. 3. 19 periodontal patients who received a flap operation were selected to determine the effective probing method which could predict the alveolar bone defects in the interproximal contact areas. Measurement of 3 points (bucco-mesial or distal line-angle, linguo-mesial or distal line-angle and center of mesial or distal) could estimate the form of interproximal bone defects. 4. 45 periodontal patients were selected to determine the condition of interproximal periodontal pockets. Marked periodontal damage was present not only at the center of interproximal contact areas but also in the other sites. These results suggest that the new interproximal periodontal probe is a reasonable instrument for angled probing in the interproximal contact areas, and the 8-point method is the most effective one to reveal the periodontal condition in detail.

Humans↗