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Biomedical subjects

S Kato

Publications and source records attributed to S Kato.

At least 703 records · Page 39Linked to original sources
PubMed1997

Gastric hyperemic response during vagally mediated acid secretion by TRH analog in rats.

The mechanisms of gastric hyperemic response during vagally mediated acid secretion induced by YM-14673, an analog of thyrotropin-releasing hormone, were investigated in urethane-anesthetized rats. The stomach was mounted on an ex vivo chamber and perfused with saline, and gastric mucosal blood flow (GMBF) was measured using a laser Doppler flowmeter, simultaneously with acid secretion. The i.v. injection of YM-14673 (0.1 approximately 1 mg/kg) increased both GMBF and acid secretion in a dose-dependent manner, and these responses persisted during a 90-min test period. The increases in GMBF and acid secretion induced by YM-14673 (0.3 mg/kg) were totally abolished by either bilateral vagotomy or atropine. Sensory ablation by capsaicin also significantly attenuated GMBF response without affecting acid secretion. On the other hand, N(G)-nitro-L-arginine methyl ester (L-NAME), but not D-NAME, significantly attenuated the increase in GMBF in an L-arginine-sensitive manner, although acid secretion was slightly augmented; in particular, gastric hyperemic response during the first 30 min (early period) was almost totally abolished. In contrast, omeprazole significantly attenuated GMBF response only in the late period, although it completely inhibited acid secretion in response to YM-14673. Combined treatment of omeprazole and L-NAME totally abolished hyperemic responses induced by YM-14673 during the test period. YM-14673 significantly elevated the release of nitrite and nitrate into the gastric lumen, and this response was inhibited by either atropine or L-NAME. These results suggest that YM-14673 increases GMBF as well as acid secretion, mediated by vagal-cholinergic pathways, and that gastric hyperemia is further regulated by two distinct mechanisms. The response in the early period is independent of acid secretion and mediated mainly by nitric oxide, whereas that in the later period occurs in association with acid secretion and may be mediated by nitric oxide and sensory neurons.

Animals↗
PubMed1997

Angiotensin receptor antagonists in experimental models of chronic renal failure.

The efficacy of angiotensin converting enzyme inhibitors (ACEI) in slowing the advancement of chronic renal disease attests to the importance of angiotensin II (Ang II) in the pathophysiological mechanisms underlying disease progression. It is apparent from studies of the effects of orally-active AT1 receptor antagonists (AT1RA) in experimental models of chronic progressive renal disease, that AT1RA have broadly similar effects to those of ACEI, implying that the favorable effects of ACEI on systemic and renal hemodynamics and indices of glomerular injury are mediated, in large part, by reducing the action of Ang II at AT1 receptors. The possibility remains, however, that differences in the modes of action of ACEI and AT1RA are significant in terms of renal protection and that the two classes of drugs are not therapeutically equivalent. Thus far, however, virtually all experimental studies comparing the renal protective effects of ACEI versus AT1RA have failed to show any convincing differences between the two classes of drug that cannot be attributed to discrepancies in the levels of blood pressure control achieved. As many rodent studies have adopted protocols originally designed to distinguish between the effects of treatment versus no treatment, however, it may be premature to conclude that ACEI and AT1RA are, essentially, therapeutically equivalent. Since both classes of drug have such potent renoprotective effects, the extent of injury that develops in treated rats may be so slight as to compromise the sensitivity of the experimental comparison. Fresh experimental approaches may be required to overcome this issue and resolve any outstanding questions concerning the therapeutic equivalence of AT1RA and ACEI in slowing the progression of renal disease.

Angiotensin II↗
PubMed1997

[Method for determining optimal intracavitary radiotherapy conditions for carcinoma of the uterine cervix with tumor infiltration of the vaginal wall].

Stage III carcinoma of the uterine cervix is occasionally accompanied by tumor infiltration of the vaginal wall. Currently, the vaginal wall has to be irradiated in the same manner as the uterine cervix. The authors have developed a system for determining the optimal irradiation conditions for treating the two regions, uterine cervix and vaginal wall, at the same time. A comparison of two methods is shown in simulation, and then a clinical case is reported. The first method consists of two treatment plans, one for the uterine cervix without tumor infiltration of the vaginal wall, and the other for the vaginal wall without carcinoma of the uterine cervix. The second, newly developed method considers the two regions together. Irradiation times of ovoid sources obtained with the second method are 15-25% less than those of the first method. Isodose curves obtained with the two methods are very different, and thus the uterine cervix and vaginal wall must be considered together in order to determine irradiation conditions.

Brachytherapy↗
PubMed1997

[Functions of the transforming growth factor-beta superfamily in eyes].

One human body is composed of 6 x 10(13) cells, and eyes are also composed of many cells of different functions. The cellular functions and intercellular interaction are regulated by many regulators including cytokines and growth factors to maintain the homeostasis. The transforming growth factor-beta (TGF-beta) superfamily, a large family of multifunctional factors, regulates various cellular functions, including cellular proliferation, migration, differentiation, apoptosis and extracellular matrix production. The TGF-beta superfamily contains about 30 multifunctional factors, and is divided into several families according to the sequence homology. The TGF-beta family, the activin family, and bone morphogenic proteins belong to the TGF-beta superfamily. TGF-beta superfamily members transduce signals through type I and type II serine/threonine type transmembrane receptors. The signals are transduced from receptors through nuclei by Smad family members, which are phosphorylated by the activated type I receptors and translocate from cytoplasm into nuclei. TGF-beta family members and the TGF-beta superfamily receptor family are expressed in ocular tissues including the cornea, ciliary epithelium, lens epithelium, retina, and blood vessels. This observation suggests the importance of the TGF-beta superfamily in eyes. Smad family members (Smad 1, Smad 2, Smad 3 and Smad 4) are expressed in the cultured retinal pigmant epithelial cell line (D407), in which TGF-beta and activin A stimulate the translocation of Smad 2, but not Smad 1 into nuclei, whereas bone morphogenetic protein (BMP) stimulates that of Smad 1, but not Smad 2. TGF-beta superfamily members play important roles in the pathogenesis of retinal neovascularization and in the wound healing process of corneal tissue. TGF-beta inhibits the endothelial functions, but, stimulates angiogenesis in vivo. TGF-beta is involved in the formation of abnormal connective tissue in corneal wound healing. In these processes, many cytokines and growth factors are involved, interacting with each other and forming networks. It is mandatory to clarify the networks to investigate molecular pathogenesis and new therapeutic agents.

Diabetic Retinopathy↗
PubMed1996

Differentiation-dependent enhanced expression of protein phosphatase 2Cbeta in germ cells of mouse seminiferous tubules.

The presence of five distinct isoforms of protein phosphatase 2Cbeta (PP2Cbeta-1 approximately -5) is known. In this study, we demonstrate that the mRNA levels of PP2Cbeta-3, -4 and -5 and PP2Cbeta protein level increased during the course of the first wave of spermatogenesis in neonatal mouse testis. Northern blot and in situ hybridization analyses revealed that PP2Cbeta-3, -4 and -5 were expressed predominantly in pachytene spermatocytes and in more highly differentiated germ cells. The substrate specificity of PP2Cbeta-4 determined with artificial substrates differed from those of PP2Cbeta-3 and -5, suggesting that the difference in the structure of PP2Cbeta-3, -4 and -5 reflect their unique physiological functions in testicular germ cells.

Animals↗
PubMed1996

A high frequency of defective vif genes in peripheral blood mononuclear cells from HIV type 1-infected individuals.

We studied the heterogeneity and intactness of the vif gene in six HIV-1-infected individuals at various clinical stages. The proviral vif sequences in peripheral blood mononuclear cells were amplified by PCR, followed by cloning and sequencing of 45 vif clones. The intraindividual diversity of the vif genes ranged from 0.45 to 3.3% and was not correlated with disease stage. Although the vif gene has been shown to be essential for infection of HIV-1 in vitro, a high frequency (31%) of defective vif genes was observed. In one patient, six vif clones carried double nonsense mutations at the same positions, five of which were clustered in the phylogenetic tree, suggesting that these vif-defective viruses may have replicated in vivo. Phylogenetic analysis revealed that the vif sequences from each individual were clustered into a separate group and that all of them belong to subtype B.

Adult↗
PubMed1996

Okadaic acid suppresses neural differentiation-dependent expression of the neurofilament-L gene in P19 embryonal carcinoma cells by post-transcriptional modification.

Mouse P19 embryonal carcinoma cells in aggregation culture in the presence of 10(-6) M retinoic acid followed by monolayer culture differentiate into nerve and glial cells. In this study, we demonstrated that the neurofilament-L (NF-L) mRNA and protein levels of these cells were enhanced in accordance with their retinoic acid-induced neural differentiation. Okadaic acid (OA) treatment of the cells markedly suppressed this differentiation-dependent NF-L gene expression increase and neurite outgrowth of the cells. Similar results were obtained when tautomycin was used instead of OA, suggesting that inhibition of protein phosphatase(s) is involved in the suppression of neural differentiation. OA treatment did not affect the NF-L gene transcription level, determined by the nuclear run-on transcription assay, but it did reduce the stability of both the 3.5- and 2.3-kilobase NF-L mRNAs. The expression and activity levels of protein phosphatase 2A (PP2A) and 2B (PP2B) but not protein phosphatase 1 (PP1) in P19 cells increased in accordance with the enhanced NF-L gene expression. The presence of OA in the culture medium during the course of the neural differentiation caused a reduced PP2A activity but not PP1 and PP2B activities of the cell extracts. On the other hand, both PP1 and PP2B activities but not PP2A activity of cell extracts were suppressed by the addition of cyclosporin A or FK506 in the culture medium. However, both cyclosporin A and FK506 treatments affected neither NF-L gene expression nor neurite outgrowth. These results demonstrate that the OA treatment inhibits the differentiation-dependent increase in NF-L gene expression by destabilizing its mRNAs and suggest that PP2A plays key roles in the differentiation-dependent enhanced expression of the NF-L gene and is the point of the action of OA.

Animals↗
PubMed1996

Development of porcine blastocysts from in vitro- matured and activated haploid and diploid oocytes.

The purpose of this study was to determine the developmental capacity of electro-activated porcine oocytes. Follicular oocytes collected from gilts at local slaughterhouses were matured for 48 h and were then subjected to a single square pulse of direct current for 100 rhojusec at 1,500 V/cm for activation. To obtain activated diploid oocytes, some were treated with 5.0 micro/ml cytochalasin B for 4 h immediately after electro-activation. The frequency of activation ranged from 96 to 100%. While 91% of activated oocytes that had not been treated with cytochalasin B had 2 polar bodies and a nucleus (haploids), 92% of the oocytes treated with cytochalasin B had only the first polar body and 2 nuclei (diploids). Haploids and diploids were further cultured in TCM-199 medium that contained 10% (v/v) heat- treated fetal calf serum (FCS) and 0.1 mg/ml sodium pyruvate (mTCM) or in Whittenk medium plus 0.4% (w/v) bovine serum albumin (BSA). The frequency of abnormal oocytes was significantly higher in mTCM (83%) than in Whitten's medium (65%) 96 h after the electro-activation (P < 0.01), suggesting that Whitten's medium supported the development of activated oocytes beyond the morula stage. In all cases, several oocytes developed to the blastocyst stage 144 h after electro- activation (1 to 12%). The frequency was significantly higher in the case of diploids cultured in Whitten's medium (12%) (P < 0.01) than in the case of haploids cultured in Whitten's medium (4%), or in the case of haploids cultured in mTCM (1%). The mean number of nuclei per blastocyst was significantly lower in mTCM (haploids, 15; diploids, 16.1) than in Whitten's medium (haploids, 35.7; diploids, 40.1; P < 0.01), suggesting that the number of nuclei in blastocysts was affected by the culture medium.

Journal Article↗
PubMed1996

Expression of bcl-2 protein, an inhibitor of apoptosis, and Bax, an accelerator of apoptosis, in ventricular myocytes of human hearts with myocardial infarction.

BACKGROUND: In general, myocyte death in myocardial infarctions (MIs) is attributed to necrosis, but recently the involvement of apoptosis has been suggested. The ratio of bcl-2 protein, an inhibitor of apoptosis, to Bax protein, an inducer of apoptosis, determines survival or death after an apoptotic stimulus. We speculated that bcl-2 or Bax expression is induced by ischemia and that it may be related to myocyte death in human hearts. METHODS AND RESULTS: We studied immunohistochemically 37 autopsied human hearts (acute MI, n = 15; old MI, n = 12; normal hearts as a control, n = 10) with the use of bcl-2 and Bax antibodies. There were no myocytes with positive bcl-2 immunoreactivity in the controls or hearts with old MI. However, myocytes with positive bcl-2 immunoreactivity were seen in 9 of 15 hearts (60%) with acute MI, in that it was localized only in salvaged areas surrounding the infarcted tissues. Myocytes with slightly positive Bax immunoreactivity were observed in the control hearts. In the salvaged myocytes surrounding the infarcted tissues, Bax was overexpressed in 2 of 15 hearts (13%) with acute MI but in 10 of 12 hearts (83%) with old MI. CONCLUSIONS: bcl-2 protein is induced in salvaged myocytes at the acute stage of infarction, but Bax protein is overexpressed at the old stage. The expression of bcl-2 and the overexpression of Bax may play an important pathophysiological role in the protection or acceleration of the apoptosis of human myocytes after ischemia and/or reperfusion.

Adult↗
PubMed1996

Ability to culture dermal papilla cells from red deer (Cervus elaphus) hair follicles with differing hormonal responses in vivo offers a new model for studying the control of hair follicle biology.

Red deer stags annually grow two distinct seasonal coats, a winter coat and a summer coat; in addition, they produce a mane during the breeding season when plasma testosterone levels are high, which is replaced by the short neck hairs of the summer coat when testosterone levels are low. As two very different hair types are produced from the same follicle under hormonal regulation, they offer an interesting model for studying the effects of hormones, particularly androgens, on mammalian hair growth. Since the dermal papilla of the hair follicle has a regulatory function and is probably the site of androgen action, we have investigated whether cells from the dermal papilla can be readily cultured from various types of red deer follicles; as the follicular connective tissue sheath may regenerate a new papilla in vivo, this was also examined. Individual dermal papillae and lower portions of the connective tissue sheath were microdissected from mane and flank follicles of red deer stags during the winter breeding season and from the summer coat during the nonbreeding season. Primary cultures were established from isolated dermal papillae, connective tissue sheath and dermal explants, subcultured and reestablished after freezing. Deer dermal papilla cells resembled sheep cells; they displayed a polygonal shape and irregular organisation, but did not form aggregates in contrast to human and rat vibrissa cells. Connective tissue sheath cell morphology was intermediate between that of dermal papilla cells and dermal fibroblasts. However, all three cell types derived during the breeding season grew at a much faster rate than the same cells derived during the nonbreeding season. Therefore, primary cell lines can be fairly readily derived from deer hair follicles. Since the red deer stag offers both androgen-dependent neck (mane) and control flank follicles in the breeding season, plus control nonbreeding season neck follicles, this means that stag follicular cells, particularly the dermal papilla cells, appear to offer a unique novel model system for the study of the hormonal regulation of hair growth.

Androgens↗
PubMed1996

cDNA cloning and functional analysis of the p97 subunit of the 26S proteasome, a polypeptide identical to the type-1 tumor-necrosis-factor-receptor-associated protein-2/55.11.

Molecular cloning of cDNA for a new regulatory subunit, designated p97, of the human 26S proteasome showed that the polypeptide consists of 908 amino acid residues with a calculated molecular mass of 100184 Da and an isoelectric point of 4.94. Computer analysis showed that p97 is very similar to type-1 tumor-necrosis-factor (TNF)-receptor-associated protein (TRAP)-2 and 55.11, both of which were identified recently as binding proteins of the cytoplasmic domain of type-1 TNF receptor by yeast two-hybrid screening. This finding suggests that the 26S proteasome might serve as a mediator molecule in the TNF signaling pathway in cells. Computer-assisted similarity analysis also revealed the high sequence similarity of p97 with a yeast protein whose function is yet unknown, the gene for which is here termed NAS1 (non-ATPase subunit 1). Disruption of NAS1 resulted in several phenotypes, including lethality and temperature-sensitive growth, depending on the genetic background of the cells used. The human p97 cDNA suppressed the growth defect of nas1 disruptant cells, when expressed from single-copy or multi-copy vectors, indicating that p97 is functionally equivalent to yeast Nas1p. Culturing of the temperature-sensitive nas1 cells at the restrictive temperature promoted the accumulation polyubiquitinated cellular proteins, implying that the 26S proteasome requires a functional Nas1p subunit for ubiquitin-dependent proteolysis. These results indicate that p97/Nas1p plays an important regulatory role in the function of the 26S proteasome.

Amino Acid Sequence↗
PubMed1996

Dopamine transporter gene polymorphism and psychiatric symptoms seen in schizophrenic patients at their first episode.

To investigate the possible role of the dopamine transporter (DAT) gene in determining the phenotype in human subjects, allele frequencies for the 40-bp variable number of tandem repeats (VNTR) polymorphism at this site were compared between 117 Japanese normal controls and 118 schizophrenic patients, including six subgroups: early-onset, those with a family history, and those suffering from one of the following psychiatric symptoms at their first episode: delusion and hallucination; disorganization; bizarre behavior; and negative symptoms. No significant differences were observed between the group as a whole or any subgroup of schizophrenic patients and controls. The results indicate that VNTR polymorphism in the DAT gene is unlikely to be a major contributor to any of the psychiatric parameters examined in the present population of schizophrenic subjects.

Adult↗
PubMed1996

Alterations in basal and glucose-stimulated voltage-dependent Ca2+ channel activities in pancreatic beta cells of non-insulin-dependent diabetes mellitus GK rats.

In genetically occurring non-insulin-dependent diabetes mellitus (NIDDM) model rats (GK rats), the activities of L- and T-type Ca2+ channels in pancreatic beta cells are found to be augmented, by measuring the Ba2+ currents via these channels using whole-cell patch-clamp technique, while the patterns of the current-voltage curves are indistinguishable. The hyper-responsiveness of insulin secretion to nonglucose depolarizing stimuli observed in NIDDM beta cells could be the result, therefore, of increased voltage-dependent Ca2+ channel activity. Perforated patch-clamp recordings reveal that the augmentation of L-type Ca2+ channel activity by glucose is markedly less pronounced in GK beta cells than in control beta cells, while glucose-induced augmentation of T-type Ca2+ channel activity is observed neither in the control nor in the GK beta cells. This lack of glucose-induced augmentation of L-type Ca2+ channel activity in GK beta cells might be causatively related to the selective impairment of glucose-induced insulin secretion in NIDDM beta cells, in conjunction with an insufficient plasma membrane depolarization due to impaired closure of the ATP-sensitive K+ channels caused by the disturbed intracellular glucose metabolism in NIDDM beta cells.

Animals↗
PubMed1996

Retinoic acid differentially up-regulates the gene expression of retinoic acid receptor alpha and gamma isoforms in embryo and adult rats.

The diverse biological effects of retinoic acid (RA) are exerted by its nuclear receptor-mediated gene expression. One of the two nuclear retinoic acid receptor subfamilies is composed of three subtypes of the all-transretinoic acid receptor (RAR-alpha, RAR-beta, and RAR-gamma). Furthermore, several isoforms are generated from each of three RARs by differential promoter usage and/or alternative splicing. It is thus thought that the developmental stage-specific actions of RA are modulated through the spatio-temporal expression of the subtype and isoforms of RARs. In this study, the auto-regulation of the RAR subtypes (RAR-alpha total, RAR-beta total and RAR-gamma total) and their major isoforms (RAR-alpha 1, alpha 2, RAR-beta 1, beta 2 and RAR-gamma 1, gamma 2) by RA was examined by means of Northern blotting in the 11.5 day embryo and maternal tissues by administering pregnant rats with an excess of all-trans RA. The expression of RAR-beta isoforms as well as the RAR-beta total was auto-regulated by RA in all maternal tissues and embryos examined. The gene expression of RAR-alpha 2, which was not affected by RA in the maternal tissues, was up-regulated in embryos, though there were no significant effects of RA on the levels of RAR-alpha 1 and the alpha total in the maternal tissues and the embryos. Likewise, RA did not affect the levels of RAR-gamma 1 and gamma total. However, unlike RAR-alpha 2, RAR-gamma 2 expression was up-regulated by RA only in the maternal tissues. Thus, these results indicates that two retinoic acid receptor isoforms (RAR-alpha 2 and RAR-gamma 2) are differentially auto-regulated in embryo and adult rats.

Animals↗
PubMed1996

Genetic polymorphisms of the cancer related gene and Helicobacter pylori infection in Japanese gastric cancer patients. An age and gender matched case-control study.

BACKGROUND: Gastric cancer is a multistage process, each caused by numerous factors. The objective of this study was to elucidate the risk factors for gastric cancer by using molecular epidemiologic techniques and serum markers. METHODS: Serum pepsinogen I levels, pepsinogen I/pepsinogen II (I/II) ratios, serum IgG antibody against Helicobacter pylori (H. pylori), and genetic polymorphisms of cytochrome p450 2E1 (CYP2E1), glutathione-S-transferase M1 (GSTM1), and L-myc protooncogenes were analyzed in 82 persons with gastric cancer and in 151 age- and sex-matched controls, who were selected from 208 gastric cancer patients and 375 noncancer patients, respectively. Statistical analysis was performed to elucidate which risk factors for gastric cancer were contributing the most to gastric carcinogenicity. RESULTS: Serum pepsinogen I level (odds ratio [OR] = 1.81; 95% confidence interval [CI], 1.04-3.16) and pepsinogen I/II ratios (OR = 3.09; 95% CI, 1.74-5.49) were significantly associated with gastric cancer risk in a case-control study. Seropositivity of serum IgG antibody against H. pylori (OR = 1.25; 95% CI, 0.84-1.85) and specific genotypes of a L-myc genetic polymorphism (OR = 1.33; 95% CI, 0.59-2.99) were more commonly observed in gastric cancer cases, but this was not statistically significant. Specific genotypes of the CYP2E1 RsaI polymorphism and GSTM1 gene deletion were not associated with gastric cancer. CONCLUSIONS: Atrophic mucosal change, indicated by serum pepsinogen levels, is possible a risk factor for gastric cancer. H. pylori infection and genetic polymorphisms of CYP2E1, L-myc, and GSTM1 genetic polymorphisms were not risk factors in this study.

Adult↗
PubMed1996

Enhanced UV sensitivity of yeast cells induced by overexpression of Mg(2+)-dependent protein phosphatase alpha (type 2C alpha).

The UV sensitivity of wild-type Saccharomyces cerevisiae cells was increased 2-fold when rat Mg(2+)-dependent protein phosphatase alpha (protein phosphatase type 2C alpha) was overexpressed in the cells. The overexpression of this enzyme rendered the rad 18 mutant (defective in postreplication repair) more UV-sensitive than was observed in the wild-type cells. However, this increase in UV sensitivity disappeared when the host cells had a rad 1 mutation (defective in excision repair). These results suggest that the Mg(2+)-dependent protein phosphatase overexpressed in the yeast cells inhibited their excision repair system.

Animals↗