Biomedical subjects

Y Eguchi

Publications and source records attributed to Y Eguchi.

At least 73 records · Page 4Linked to original sources

PubMed1997

Immunocytochemical changes in the fetal pancreatic islet following fetal administration of streptozotocin in the rat.

BACKGROUND: Streptozotocin (STZ) is selectively toxic to the B cells in the pancreatic islets. It is well known that in the adult rat, STZ causes the death of B cells, and it eventually induces diabetes mellitus. The present study was conducted to detect what morphological changes could be induced in the fetal B cells following a direct injection of STZ into the fetus in utero during late pregnancy in the rat. METHODS: STZ (400 micrograms/g body weight) was injected into the fetus in utero at 10:00 on day 19 of gestation. Three, 6, 24, and 48 hr after injection, the changes in the B cells (anti-insulin serum positive cells) were examined immunohistochemically. The total volume of the B cells was measured. Electron microscopic observation was made as well. RESULTS: Six hr after STZ injection, some B cells were destroyed so that their granules were distorted and burst. Twenty-four hr after STZ injection, a large majority of the existing B cells were disintegrated, and a number of small isletlike clusters of immature cells appeared among the exocrine acini. The total volume of anti-insulin serum positive cells was strikingly decreased. At 48 hr after injection, however, the volume returned to a level that was comparable to that of their littermate controls. CONCLUSIONS: The regeneration of the B cells may occur because of the high cell proliferative activity of undifferentiated cells following the destruction of the B cells caused by an injection of STZ.

Animals↗

PubMed1997

Essential role of active nuclear transport in apoptosis.

BACKGROUND: Apoptosis is defined by chromatin condensation, nuclear fragmentation and the formation of apoptotic bodies. Because apoptotic signals are transmitted through a common pathway that includes the target steps of death-driving ICE-family proteases and anti-cell death protein Bcl-2 in the cytoplasm, the signals must be transferred from the cytoplasm to the nucleus, at least to induce the apoptotic manifestation of the nucleus. Small signal molecules might diffuse across nuclear pores, but larger molecules are transported by active mechanisms requiring ATP and GTP hydrolysis. It is not known whether apoptotic signals are transmitted into the nucleus by the mechanisms of active nuclear transport. RESULTS: To test the possibility that active nuclear transport is involved in apoptotic signal transmission, we have analysed the effects of molecules that inhibit active nuclear transport on apoptosis. Wheat germ agglutinin (WGA), excess amounts of p10 protein, Ran-GTPgammaS complex, and anti-PTAC58 antibody, which all inhibit active nuclear transport when exogenously microinjected, prevent Fas-induced apoptotic nuclear manifestation. WGA also prevents apoptotic nuclear change promoted by microinjected active CPP32beta/Yama protease (an ICE family member), which plays an essential role in most apoptosis. CONCLUSIONS: The results presented here strongly suggest that active nuclear transport is essential for apoptotic signal transduction.

Antibodies↗

PubMed1997

Suppressive effect of perinatal testes on the differentiation of fetal ovaries transplanted into adult males in the rat.

A 14 d ovarian primordium was transplanted with a fetal testis (13-18 d and 21 d of gestation) or a neonatal testis (15, 20, 30 and 45 d after birth) into the renal subcapsular position of an adult male rat. Two weeks after transplantation, transplants were examined as to the degree of ovarian and testicular differentiation. In the combination of a 14 d ovary and a 13 d testis, there were 3 types of result: either the ovary or the testis alone developed or both gonads developed well. Ovaries transplanted in union with 15-18 d testes did not develop, although the testes developed normally. Some ovaries in union with 21 d testes developed normally. In combination with infantile testes, the incidence of developed ovaries increased as the age of testes advanced. These results suggest that the 13 d fetal testes begin to suppress the development of cotransplanted 14 d ovaries, that 14-18 d fetal testes maintain such suppressive effects and that this effect gradually diminishes in infantile testes as they progress toward 45 d after birth.

Animals↗

PubMed1997

Effects of brain temperature on calmodulin and microtubule-associated protein 2 immunoreactivity in the gerbil hippocampus following transient forebrain ischemia.

Increased intracellular calcium and cytoskeletal damage play a crucial role in neuronal death following injury such as cerebral ischemia. The effect of brain temperature on early intracellular calcium increase and neuronal cytoskeletal damage following cerebral ischemia has not been rigorously investigated. In the current communication we evaluated calmodulin (CaM) and microtubule-associated protein 2 (MAP2) in the same brain section using a double labeling immunohistochemical technique, and obtained evidence that the brain temperature has a significant effect on the early calcium increase and cytoskeletal damage as well as the delayed neuronal death occurring in CA1 sector of the gerbil hippocampus after transient forebrain ischemia. In the normothermia (36.7 degrees C) group, CaM and MAP2 immunoreactivity were markedly decreased within 48 h after ischemia and thereafter dramatic neuronal death (grade 3) was seen in the CA1 sector at 7 days. Mild hypothermia (33.3 degrees C) significantly protected against all these changes, whereas cytoskeletal damage and delayed neuronal death were aggravated by mild hyperthermia (39.7 degrees C). We conclude that mild hypothermia protects the brain against transient forebrain ischemia by reducing early cytoskeletal damage and subsequent neuronal death.

Animals↗

PubMed1997

Therapeutic efficacy of clenbuterol for urinary incontinence after radical prostatectomy.

BACKGROUND: Urinary incontinence is one of the most common complications occurring after radical prostatectomy. We evaluated the efficacy of clenbuterol, a selective beta 2-adrenoceptor agonist, in the treatment of incontinence occurring after radical prostatectomy, using urodynamic assessment. METHODS: Fourteen men (mean age, 68 years) with post-radical-prostatectomy incontinence were treated with 20 mg of clenbuterol twice a day for 1 month. The urodynamic assessment was performed on all patients before and after the administration of clenbuterol. A pad scoring system was used to gauge the severity of incontinence before and after treatment. RESULTS: At 1 month after administration of clenbuterol, 9 of the 14 patients (64%) had dramatic improvement in pad scores. Treatment failed in 5 patients (36%) with severe incontinence. The results of urodynamic studies showed that the mean functional urethral length of the patients with post-radical-prostatectomy incontinence increased significantly after treatment. CONCLUSION: These results suggest that clenbuterol can be used as an effective agent for treating mild-to-moderate stress incontinence after radical prostatectomy.

Aged↗

PubMed1997

Susceptibility of cerebellar granule neurons derived from Bcl-2-deficient and transgenic mice to cell death.

Overproduced Bcl-2 oncoprotein has been shown to suppress cell death induced by a variety of stimuli in many cell types, including neuronal cells. Because bcl-2 is expressed in the nervous system where massive cell death is observed during development, endogenous Bcl-2 is likely to be involved in regulating neuronal cell death. Here we examined the possible role of endogenous Bcl-2 in the regulation of neuronal cell survival in the central nervous system using primary cultured cerebellar granule neurons from bcl-2-deficient, wild-type and NSE-bcl-2-transgenic mice. Cerebellar granule neurons from bcl-2-deficient mice were more susceptible than those from normal littermates to death induced by reducing the K+ concentration of the medium from high (25 mM) to low (5 mM), and neurons from bcl-2-transgenic mice were least susceptible. Similar results were obtained when cell death was induced by serum withdrawal under high K+ conditions or by the presence of etoposide, A23187 or nimodipine. Consistently, bcl-2 deficiency reduced the number of cerebellar granule neurons per mouse. These results indicate that Bcl-2 impedes neuronal cell death induced by various stimuli in a dose-dependent manner, and that endogenous levels of Bcl-2 are able to regulate neuronal cell survival in the central nervous system.

Animals↗

PubMed1997

A functional role for death proteases in s-Myc- and c-Myc-mediated apoptosis.

Upon activation, cell surface death receptors, Fas/APO-1/CD95 and tumor necrosis factor receptor-1 (TNFR-1), are attached to cytosolic adaptor proteins, which in turn recruit caspase-8 (MACH/FLICE/Mch5) to activate the interleukin-1 beta-converting enzyme (ICE)/CED-3 family protease (caspase) cascade. However, it remains unknown whether these apoptotic proteases are generally involved in apoptosis triggered by other stimuli such as Myc and p53. In this study, we provide lines of evidence that a death protease cascade consisting of caspases and serine proteases plays an essential role in Myc-mediated apoptosis. When Rat-1 fibroblasts stably expressing either s-Myc or c-Myc were induced to undergo apoptosis by serum deprivation, a caspase-3 (CPP32)-like protease activity that cleaves a specific peptide substrate, Ac-DEVD-MCA, appeared in the cell lysates. Induction of s-Myc- and c-Myc-mediated apoptotic cell death was effectively prevented by caspase inhibitors such as Z-Asp-CH2-DCB and Ac-DEVD-CHO. Furthermore, exposing the cells to a serine protease inhibitor, 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), also significantly inhibited s-Myc- and c-Myc-mediated apoptosis and the appearance of the caspase-3-like protease activity in vivo. However, AEBSF did not directly inhibit caspase-3-like protease activity in the apoptotic cell lysates in vitro. Together, these results indicate that caspase-3-like proteases play a critical role in both s-Myc- and c-Myc-mediated apoptosis and that caspase-3-like proteases function downstream of the AEBSF-sensitive step in the signaling pathway of Myc-mediated apoptosis.

Animals↗

PubMed1997

Ontogeny of somatostatin cells in the rat fetal pancreas.

The growth pattern of somatostatin cells was clarified immunohistochemically from day 12 to day 18 of gestation in the rat fetus. On day 12, somatostatin cells first appeared within the pancreatic anlage. The total number of somatostatin cells was gradually increased from day 12 to day 16 and rapidly increased thereafter. It may be concluded that such a sequence of events of development in somatostatin cells occurs in a fashion similar to that in B cells.

Animals↗

PubMed1997

Effect of ethylene thiourea on cultured rat embryos in the presence of hepatic microsomal fraction.

To investigate whether teratogenicity of ethylene thiourea (ETU) is due to ETU per se or to its metabolites, rat embryos cultured in vitro were exposed to 10 and 30 micrograms/ml of ETU in the presence or absence of rat liver microsomal fraction (S9mix). In the absence of S9mix, the incidence of morphological abnormalities increased dose-dependently. In the presence of S9mix, abnormal morphogenesis was almost absent in all embryos. These findings suggest that teratogenicity of ETU is due to ETU per se.

Abnormalities, Drug-Induced↗

PubMed1997

[Molecular biology of apoptosis].

Apoptosis, a mechanism involving programmed cell death, is important for normal development and maintenance of tissue homeostasis of multicellular organisms. Apoptotic cells are defined by their fragmented nuclei with condensed chromatin, fragmented or condensed cytoplasm and formation of apoptotic bodies. The apoptotic signal transducing pathways activated by a variety of stimuli, including depletion of growth factors, heat shock, cytokines, DNA damaging reagents and crosslinking of Fas receptor, finally converge into the phylogenically conserved apoptotic main machinery, consisting of death-driving ICE-family proteases and anti-cell death protein Bcl-2. Recently, we noted that necrotic cell death induced by chemical hypoxia shares at least some part of the apoptotic main machinery. Using this system, we have shown that Bcl-2 prevents the loss of the mitochondrial membrane potential observed in both apoptotic and necrotic cell death. We also showed that the ICE protease cascade operates in apoptosis and that Bcl-2 functions upstream of the ICE prolease cascade. Here, we review the signal transducing pathway of the apoptotic main machinery.

Animals↗

PubMed1997

Protective effect of nafamostat mesilate in early wound healing.

BACKGROUND: Tensile strength in rat ileal anastomosis is diminished after injection with superoxide dismutase. We have studied the immunohistochemistry of extracellular matrix to investigate changes associated with this loss of tensile strength. A serine proteinase inhibitor, Nafamostat mesilate, was used to evaluate its potential for maintaining tensile strength. STUDY DESIGN: Four groups of rats underwent ileal anastomosis, Groups 1 and 2 were controls. Groups 3 and 4 were given superoxide dismutase and Nafamostat mesilate, respectively, after anastomosis. RESULTS: In controls, groups 1 and 2, tensile strength decreased to 58 percent and 57 percent, respectively, of the initial value measured immediately after anastomosis 1 day postoperatively and both dropped to 33 percent 3 days postoperatively. After 5 days, tensile strength recovered to 83 percent of initial value. In comparison with controls, administration of superoxide dismutase significantly attenuated the loss of tensile strength on day 1 (94 percent of initial value, p < 0.01) and on days 3, 5 and 7 (p < 0.05). Similar results were found after administration of Nafamostat mesilate on days 3 and 5 (p < 0.05). In group 1, degradation of the collagen layer in the anastomosis was observed, with disappearance of immunostaining for fibronectin and vitronectin on day 3. In both groups 3 and 4, these changes were significantly attenuated with intense immunostaining for plasminogen activator inhibitor-1; fibronectin and vitronectin were seen particularly among collagen fibers on both sides of the anastomosis. CONCLUSIONS: These findings suggest that degradation of extracellular matrix causes loss of tensile strength early after anastomosis. Nafamostat mesilate may be clinically useful to prevent breakdown of intestinal anastomoses.

Anastomosis, Surgical↗

PubMed1997

Bcl-2 and Bcl-xL block apoptosis as well as necrosis: possible involvement of common mediators in apoptotic and necrotic signal transduction pathways.

The proto-oncogene bcl-2 and a bcl-2-related gene bcl-x prevent apoptotic cell death induced by various treatments. Although a mechanism has been proposed that involves Bcl-2 activity on reactive oxygen species (ROS), we find that expression of Bcl-2 or Bcl-xL prevents cell death induced by withdrawal of oxygen (hypoxia) and that the cell death does not involve ROS, suggesting that Bcl-2 or Bcl-xL exerts an anti-cell death function by a mechanism other than through regulation of ROS activity. Using electron microscopy, and confocal and non-confocal fluorescence microscopy, we show that hypoxia induces both necrosis and apoptosis. Overexpression of Bcl-2 or Bcl-xL blocks hypoxia-induced apoptosis and, although to a lesser extent, necrosis. The anti-apoptotic proteins Bcl-2 and Bcl-xL effectively inhibit KCN-induced cell death which is characterized by necrotic features including apparently intact chromatin, remarkable mitochondrial swelling with loss of crista structure and loss of plasma membrane integrity. The necrotic cell death is also inhibited by inhibitors of ICE (interleukin-1 beta converting enzyme)(-like) proteases, the common mediators of apoptosis. These results indicate that Bcl-2/Bcl-xL and ICE(-like) proteases modulate both apoptotic and at least some forms of necrotic cell death, suggesting that both cell death pathways involve some common mediators.

Animals↗

PubMed1997

Habutobin splits the Arg16-Gly17 bond in the A alpha chain of rabbit fibrinogen.

We reported previously that habutobin, a thrombin-like enzyme from Trimeresurus flavoviridis venom, clotted only rabbit fibrinogen, whereas human, monkey, bovine, dog, rat and guinea-pig fibrinogens were unaffected. In the present study, we investigated the cleavage site of the rabbit A alpha chain by habutobin. The fibrinopeptide released by habutobin was identical to the fibrinopeptide A released by thrombin, and its amino acid sequence corresponded to A alpha 1-16 of rabbit fibrinogen. It was clarified therefore that habutobin cleaves the Arg16-Gly17 bond in the A alpha chain of rabbit fibrinogen.

Amino Acid Sequence↗

PubMed1997

Toward a virtual-labo-system for metabolic engineering: development of biochemical engineering system analyzing tool-kit (BEST-KIT).

BEST-KIT is an efficient and user-friendly "biochemical engineering system analyzing tool-kit" integrated the following key modules: 1) mathematical modeling and editing of reaction-scheme, 2) automatic derivation of differential equations, 3) numerical calculation, 4) nonlinear optimization, 5) visualization, 6) retrieve the information on reaction mechanism and kinetic parameters from data-base of metabolic pathways. The users of this simulator are assumed to be unfamiliar with computer technology and with computer programming. The integrated interface (UNIX version) is based on Xlib, XToolkit and OSF/Motif Widget.

Biochemistry↗

PubMed1996

Localization of bcl-2, bax, and bcl-x mRNAs in the developing inner ear of the mouse.

In situ hybridization was employed to study the expression of bcl-2 mRNA and its family members, bax and bcl-x mRNAs, in the developing inner ear. We found that in the cochlear structure, sensory epithelial cells, the spiral ganglion and stria vascularis expressed these mRNAs in postnatal period in a temporally similar manner, but in embryos, neither bax nor bcl-x mRNA were expressed in the sensory epithelium from embryonic day (E) 13 to 19. In contrast to these patterns, bcl-2 mRNA was expressed by E15 to E19, and the expression at E13 was below the lower limit of detection. Non-neuronal tissue (stria vascularis) also expressed these three transcripts during development. These results suggest that bcl-2 family members may be differentially involved in the differentiation of sensory epithelial cells, spiral ganglia, and stria vascularis. In particular, the differential expression patterns in the cochleovestibular neurons suggest that proliferating and differentiating neurons utilize distinct members of the bcl-2 family.

Animals↗

PubMed1996

Bcl-2 blocks loss of mitochondrial membrane potential while ICE inhibitors act at a different step during inhibition of death induced by respiratory chain inhibitors.

Bcl-2, Bcl-xL, CrmA and tetrapeptide ICE inhibitor reduce the extent of necrotic cell death induced by cyanide, which primarily damages mitochondria. Although none of them affects the drastic decrease in ATP levels induced by cyanide, Bcl-2 and Bcl-xL but not CrmA or ICE inhibitor inhibit the cyanide-induced decrease in mitochondrial membrane potential. A similar blocking effect is observed on necrotic cell death induced by other respiration inhibitors, rotenone and antimycin A, and on apoptotic cell death induced by etoposide or calcium ionophore. These results indicate that Bc1-2 and Bcl-xL protect mitochondria against the loss of function during both apoptosis and at least some forms of necrotic cell death. The ICE family proteases act at a different step other than the loss of mitochondrial membrane potential.

Adenosine Triphosphate↗

PubMed1996

Bcl-2 expression prevents activation of the ICE protease cascade.

The Bcl-2 family and the ICE family of cysteine proteases play important roles in regulating cell death. We show here that induction of cell death by a Ca2+ ionophore or hypoxia results in increased levels and activity of active ICE(-like) proteases and the subsequent activation of CPP32/Yama(-like) proteases, and that inhibition of these protease activities reduces the extent of cell death. Overexpression of the anti-apoptotic proteins Bcl-2 or Bcl-xL inhibits the cell death and the activation of ICE(-like) and CPP32/Yama(-like) proteases, indicating that Bcl-2 and Bcl-xL act upstream of these proteases. We also show that specific inhibition of ICE(-like) proteases in vivo prevents activation of CPP32/Yama(-like) proteases, whereas inhibition of CPP32/Yama(-like) proteases does not prevent activation of ICE(-like) proteases, suggesting the existence of a protease cascade in vivo that requires ICE(-like) proteases for activation of CPP32/Yama(-like) proteases. Induction of necrotic cell death by KCN also induces activation of ICE(-like) proteases but not of CPP32/Yama(-like) proteases, and Bcl-2 and Bcl-xL inhibit the activation and the cell death, suggesting that the functional site of Bcl-2 and Bcl-xL is also upstream of ICE(-like) proteases in at least some forms of necrosis.

Adrenal Gland Neoplasms↗

PubMed1996

Retardation of chemical hypoxia-induced necrotic cell death by Bcl-2 and ICE inhibitors: possible involvement of common mediators in apoptotic and necrotic signal transductions.

Inhibition of the respiratory chain reaction by cyanide, rotenone or antimycin A (chemical hypoxia) induces necrotic cell death characterized by apparently intact chromatin, remarkable mitochondrial swelling with loss of crista structure, and loss of plasma membrane integrity. The treatments induce no apoptotic cell death, as defined by fragmented nuclei with condensed chromatin, fragmented or condensed cytoplasm. The anti-apoptotic proteins Bcl-2 and Bcl-xL effectively retard the chemical hypoxia-induced necrotic cell death. The necrotic cell death is also retarded by inhibitors of ICE(-like) proteases, including interleukin-1beta converting enzyme (ICE), which are common mediators of apoptosis. These results indicate that Bcl-2/Bcl-xL and ICE(-like) proteases modulate apoptotic and at least some forms of necrotic cell death. Both cell death pathways appear to involve some common mediators; however necrotic or apoptotic cell death signals might be transduced through multiple pathways, because Bcl-2/ Bcl-xL or inhibitors of ICE(-like) proteases are relatively less potent in blocking necrotic cell death than in preventing apoptosis.

Amino Acid Sequence↗