Biomedical subjects

S Nagata

Publications and source records attributed to S Nagata.

At least 181 records · Page 10Linked to original sources

PubMed1998

Human autoimmune lymphoproliferative syndrome, a defect in the apoptosis-inducing Fas receptor: a lesson from the mouse model.

The immune response is regulated not only by the proliferation, differentiation, and activation of cells, but also by programmed cell death, called apoptosis. Fas ligand expressed in activated T cells binds to its receptor, Fas, and induces apoptosis in target cells. Two mouse mutations that cause autoimmune disease, lpr (lymphoproliferation) and gld (generalized lymphoproliferative disease), are mutations in Fas and FasL genes, respectively. Human patients showing phenotypes (Canale-Smith syndrome or autoimmune lymphoproliferative syndrome) similar to those in lpr mice also carry mutations in Fas. This is a good example of a case in which the identification of a mouse mutation has led to the understanding of a human disease.

Amino Acid Sequence↗

PubMed1998

Serial Doppler echocardiographic evaluation of Carpentier-Edwards pericardial valve dysfunction: comparison with Ionescu-Shiley valve.

BACKGROUND: Doppler echocardiography is a valuable noninvasive method for evaluating of the occurrence and degree of either prosthetic valve stenosis or regurgitation. By using serial Doppler echocardiographic examination, we evaluated the incidence and the mode of the Carpentier-Edwards pericardial valve (CEPX) dysfunction compared with that of the Ionescu-Shiley valve (IS). METHODS AND RESULTS: After aortic and/or mitral valve replacement, 80 patients with CEPX and 111 with IS underwent Doppler echocardiography at intervals of at least 2 years after surgery. The average durations of follow-up were 6.1 +/- 2.9 years for patients with CEPX and 7.2 +/- 3.0 years for those with IS. Bioprosthetic valve stenosis was defined as reduced excursion of the bioprosthetic valve leaflets and peak gradient > or =60 mm Hg after aortic valve replacement and mean gradient > or =7 mm Hg after mitral valve replacement. Bioprosthetic valve regurgitation caused by bioprosthetic valve dysfunction was defined as grade > or =3 transvalvular regurgitation. In the aortic position, although there was no significant difference in the actuarial rate of freedom from bioprosthetic valve stenosis between patients with IS and those with CEPX (10 years after surgery, 88% +/- 7% vs 90%, NS), bioprosthetic regurgitation caused by bioprosthetic valve dysfunction occurred less frequently in patients with CEPX than in those with IS (10 years after surgery, 86% vs 54% +/- 9%, p < 0.05). In the mitral position, bioprosthetic valve stenosis occurred more frequently in patients with CEPX than in those with IS (10 years after surgery, 54% +/- 11% vs 72% +/- 8%, p < 0.01). Although grade > or =3 transvalvular bioprosthetic regurgitation occurred later in patients with CEPX than in those with IS, there was no significant difference in the actuarial rate of freedom from that regurgitation between patients with CEPX and those with IS (10 years after surgery, 63% +/- 10% vs 54% +/- 7%, NS). CONCLUSIONS: For aortic valve replacement, CEPX has good long-term durability because of the low incidence of bioprosthetic regurgitation. For mitral valve replacement, long-term durability of CEPX is poor, although medium-term durability is satisfactory.

Aortic Valve↗

PubMed1998

Anti-idiotype monoclonal antibodies against anti-microcystin antibody and their use in enzyme immunoassay.

Microcystins (MCs), a group of heptapeptide hepatotoxins produced by cyanobacteria, are suspected as tumor-promoter contaminants of environmental water. We have previously developed an enzyme-linked immunosorbent assay (ELISA) for MCs based on an anti-MC MAb (MAb-mc). We describe here the production of anti-idiotype MAbs (MAb-ids) which react with MAb-mc and their use in a new ELISA for MCs. For the production of MAb-id, hybridoma cells were generated from mice immunized with MAb-mc. Two MAbs were selected for their ability to inhibit the binding of MAb-mc to microcystin-LR (MCLR)-bovine serum albumin conjugate in ELISA. The one with the higher inhibitory activity, designated Id7 (IgG1, kappa), was further characterized. ELISA and immunoprecipitation analysis revealed that Id7 specifically bound to MAb-mc but not to control IgG1, and the binding was inhibited by free MCLR. Therefore, Id7 is a MAb-id to MAb-mc and potentially possesses the structural image of MCLR. To establish MAb-id based ELISA, Id7 was tested for use in three types of competitive ELISA for MCs. The best format enabled reliable measurements of MCLR in the range of 100-1000 pg/ml with a coefficient of variation of less than 3%. In addition, microcystin-RR and microcystin-YR, principal MCs found in environmental water, were cross-reacted well (67-111% of MCLR) in the ELISA although 6(Z)-MCLR, a minor component, was less reactive (7% of MCLR). A comparative study of the MAb-id based ELISA with previously established MAb-mc based ELISA revealed good correlation (n = 14, r = 0.97) between the two methods for measurements of MCs content in freshwater samples. Thus, developed MAb-id based ELISA is an useful alternative for environmental monitoring of MCs.

Animals↗

PubMed1998

Effect of passive immunization against inhibin on FSH secretion, folliculogenesis and ovulation rate during the follicular phase of the estrous cycle in mares.

Physiological roles of inhibin in mares were investigated by means of passive immunization using an antiserum to inhibin that had been raised in a castrated goat. Eight mares were given an intravenous injection of either 100 mL (n = 4) or 200 mL (n = 4) of inhibin antiserum 4 d after a single intramuscular injection of PGF2 alpha on Day 8 after ovulation, 4 control mares were treated with 100 mL castrated goat serum in the same manner. Jugular vein blood samples were collected after treatment with the serum until 192 h post treatment. Follicular growth and ovulations were monitored by ultrasound examination at 24-h intervals. The ability of the inhibin antiserum to neutralize the bioactivity of equine inhibin was examined in vitro using a rat pituitary cell culture system. Suppression of secretion of FSH from cultured rat pituitary cells by equine follicular fluid was reversed by the addition of increasing doses of the inhibin antiserum, thereby indicating its bioactivity. Plasma levels of FSH and estradiol-17 beta were higher in mares treated with the inhibin antiserum. The ovulation rate was significantly higher in mares treated with antiserum (100 mL = 3.75 +/- 0.63; 200 mL = 4.50 +/- 0.65) than in control mares (1.25 +/- 0.25). These results demonstrate that inhibin is important in regulating FSH secretion and folliculogenesis in mares. They also show that neutralization of the bioactivity of inhibin may become a new method for the control of folliculogenesis and ovulation rate in mares.

Animals↗

PubMed1998

Can positive affect items be used to assess depressive disorders in the Japanese population?

BACKGROUND: The purpose of the present study was to examine the measurement properties of positive affect items among the Japanese population. METHODS: Responses to the Japanese version of the Center for Epidemiologic Studies Depression Scale and four additional negatively revised items of the original positive affect items were compared for 85 Japanese psychiatric out-patients with dysphoric-mood-related symptoms and 255 demographically matched controls. RESULTS: Responses to positive affect items were generally comparable between the two groups, whereas responses to negative symptom items were markedly different (P < 0.002 for all comparisons). The group difference was most marked for symptom persistence. Responses to the four negatively revised items of positive affect revealed a similar picture to that of the negative symptom items. The internal consistency of the scale significantly improved when the original positive affect items were replaced by the negatively revised items (P < 0.001 for both). CONCLUSIONS: Positive affect items with positive wording cannot be used to assess depressive disorders in the Japanese population adequately, but this can be done with the corresponding negatively revised items.

Adult↗

PubMed1998

Caspase 1-independent IL-1beta release and inflammation induced by the apoptosis inducer Fas ligand.

Fas ligand is a well-characterized apoptosis inducer. Here we demonstrate that Fas ligand induces the processing and secretion of interleukin-1beta (IL-1beta) in peritoneal exudate cells. This IL-1beta secretion is independent of IL-1beta converting enzyme (caspase 1), yet it is inhibited by caspase inhibitors, indicating that a caspase(s) in addition to IL-1beta converting enzyme can process IL-1beta. Inoculation of tumor cells expressing Fas ligand into wild-type mice induces a massive neutrophil infiltration that is, in contrast, suppressed in IL-1alpha/beta knockout mice. These results demonstrate a newly discovered role for Fas ligand in inflammation, and challenge the dogma that apoptosis does not induce inflammation.

Animals↗

PubMed1998

Downregulation of Fas ligand by shedding.

Apoptosis-inducing Fas ligand (FasL) is a type II membrane protein, predominantly expressed in the activated T cells. FasL is cleaved by a putative metalloproteinase to produce a soluble form. Here, we blocked the shedding of human FasL by deleting its cleavage site. Although human Jurkat cells and mouse primary hepatocytes that express a low level of Fas were resistant to the soluble form of FasL, they were efficiently killed by membrane-bound FasL. Furthermore, soluble FasL inhibited cytotoxicity of the membrane-bound FasL. These results indicate that the membrane-bound form of FasL is the functional form and suggest that shedding of FasL is to prevent the killing of the healthy bystander cells by cytotoxic T cells.

Animals↗

PubMed1998

Fas-induced DNA fragmentation and proteolysis of nuclear proteins.

BACKGROUND: Fas is a member of the tumour necrosis factor (TNF) receptor family. Activation of Fas by its ligand or an agonistic anti-Fas antibody causes apoptosis in Fas-bearing cells, by activating various members of the caspase family. RESULTS: Specific fluorogenic substrates (MCA-DEVDAPK[dnp] and MCA-VEVDAPK[dnp]) for caspases 3 and 6 were prepared. Using these substrates, a gradual increase of the caspase 3-and 6-like proteases were detected during the Fas engagement in human Jurkat. This activation of caspases correlated well with the cleavage of poly(ADP-ribose) polymerase and lamin B1, as well as with DNA fragmentation. When the recombinant caspases were added to the extracts from Jurkat cells, caspase 3 produced active caspase 6-like protease, while caspase 6 activated the caspase 3 protease, suggesting that these proteases can activate each other. The caspase-treated cell extracts, as well as the extracts from the Fas-activated cells, caused the proteolysis of nuclear proteins and DNA degradation. The cleavage of nuclear proteins was inhibited by caspase inhibitors, while the same inhibitors had no effect on DNA degradation. CONCLUSIONS: At one stage of the caspase cascade, caspases activate each other, and amplify the apoptotic signal. Caspases downstream of the cascade then cause the proteolysis of nuclear proteins and DNA degradation.

Apoptosis↗

PubMed1998

Downstream of phosphatidylinositol-3 kinase, a multifunctional signaling molecule, and its regulation in cell responses.

Phosphatidylinositol (PI)-3 kinase is an enzyme that phosphorylates the D-3 position of PI and its derivatives. It is activated immediately after growth factor or differentiation factor stimulation, suggesting that PI-3 kinase is involved in signal transduction of the stimulation. PI-3 kinase appears to play various important roles including signaling to the nucleus, vesicle transport, and rearrangement of the cytoskeleton since many cell responses which require these events are affected by inhibition or activation of PI-3 kinase. To understand how PI-3 kinase can act in such multiple ways, it is important to identify the factors downstream of PI-3 kinase. In this review, we discuss the factors downstream of PI-3 kinase and the methods used to identify them. Recent studies revealed that some proteins involved in vesicle transport or in rearrangement of the cytoskeleton are regulated by the phospholipids generated by PI-3 kinase, implying the mechanism by which PI-3 kinase regulates these cell responses.

Animals↗

PubMed1998

Testicular inhibin in the stallion: cellular source and seasonal changes in its secretion.

The cellular localization of inhibin alpha, betaA, and betaB subunits, 3beta-hydroxysteroid dehydrogenase (3beta-HSD), and cytochrome P450 aromatase (aromatase) in stallion testes was investigated. In addition, detailed seasonal changes in circulating immunoreactive (ir)-inhibin were investigated in correlation with testosterone, estradiol, LH, and FSH. Inhibin alpha subunit-positive staining was observed in Sertoli cells, and more clearly positive staining was noted in Leydig cells. Inhibin betaA and betaB subunits were also stained in both types of cells. Immunoreactivity of 3beta-HSD and aromatase was confined to the Leydig cells. There was no seasonal effect on the percentage of the areas within seminiferous tubules and interstitial tissues that stained positive for the inhibin alpha subunit. The highest plasma concentrations of ir-inhibin were observed in the breeding season, and the lowest levels were noted during the nonbreeding season. The circulating concentrations of ir-inhibin, steroid hormones, and gonadotropins were positively correlated with each other throughout the 2 years studied. The presence of the inhibin alpha and beta subunits in Leydig cells and Sertoli cells in the equine testis suggests that these cells may secrete dimetric (bioactive) inhibin in circulation of stallions, and that the circulating ir-inhibin may be a useful indicator of the testicular function of stallions.

3-Hydroxysteroid Dehydrogenases↗

PubMed1998

Inhibin secretion in the mare: localization of inhibin alpha, betaA, and betaB subunits in the ovary.

To determine the source of circulating inhibin and estradiol-17beta during the estrous cycle in mares, the cellular localization of the inhibin alpha, betaA, and betaB subunits and aromatase in the ovary was determined by immunohistochemistry. Concentrations of immunoreactive (ir-) inhibin, estradiol-17beta, progesterone, LH, and FSH in peripheral blood were also measured during the estrous cycle in mares. Immunohistochemically, inhibin alpha subunits were localized in the granulosa cells of small and large follicles and in the theca interna cells of large follicles, whereas inhibin betaA and betaB subunits were localized in the granulosa cells and in the theca interna cells of large follicles. On the other hand, aromatase was restricted to only the granulosa cells of large follicles. Plasma ir-inhibin concentrations began to increase 9 days before ovulation; they remained high until 2 days before ovulation, after which they decreased when the LH surge was initiated. Thereafter, a further sharp rise in circulating ir-inhibin concentrations occurred during the process of ovulation, followed by a second abrupt decline. After the decline, plasma concentrations of ir-inhibin remained low during the luteal phase. Plasma estradiol-17beta concentrations followed a profile similar to that of ir-inhibin, except during ovulation, and these two hormones were positively correlated throughout the estrous cycle. Plasma FSH concentrations were inversely related to ir-inhibin and estradiol-17beta. These findings suggest that the dimeric inhibin is mainly secreted by the granulosa cells and the theca cells of large follicles; granulosa cells of small follicles may secrete inhibin alpha subunit, and estradiol-17beta is secreted by the granulosa cells of only large follicles in mares.

Animals↗

PubMed1998

Flame figures associated with bullous pemphigoid.

We report a case of bullous pemphigoid showing the histological features of flame figures. An 80-year-old man was admitted with multiple, tense, thumb-sized blisters among erythematous plaques on his trunk and limbs. A biopsy showed accumulations of eosinophil granules on the collagen fibers, forming characteristic "flame figures", in addition to the features of bullous pemphigoid. We retrospectively examined biopsy specimens from 34 patients with bullous pemphigoid treated in our department over the last 10 years for the presence of flame figures. They were observed in 3 of these patients (8.8%), all of whom were more than 80 years of age. Our retrospective study indicates that the association of flame figures with bullous pemphigoid is not rare, considering the fact that the present case is only the third report of this association. Our data also suggest that the degree of dermal eosinophilia and the formation of flame figures could be related.

Age Factors↗

PubMed1998

Inhibin secretion in the stallion.

To examine the physiological role of inhibin in the stallion, a heterologous radioimmunoassay (RIA) based on a bovine RIA was validated and used to measure immunoreactive (ir)-inhibin concentrations in plasma and testicular homogenates. The bioactivity of equine testicular inhibin was also examined using an assay for suppression of FSH secretion from rat anterior pituitary cells. In addition, to identify the cell responsible for secreting testicular inhibin, the localisation of inhibin in the testis was investigated by an immunohistochemical method using a polyclonal antibody against (Tyr30)-porcine inhibin alpha(1-30) NH2. In the RIA, parallel dose response curves were obtained for the bovine inhibin standard and serial dilutions of stallion plasma and equine testicular homogenates. Parallel FSH inhibition curves were also observed for the bovine inhibin standard and serial dilutions of equine testicular homogenates in the bioassay. The inhibition of FSH secretion from rat pituitary cells by equine testicular homogenates was neutralised by an antiserum against bovine inhibin in vitro. Plasma concentrations of ir-inhibin, testosterone and oestradiol-17beta in stallions decreased abruptly after bilateral gonadectomy and FSH and LH concentrations in the plasma subsequently increased. Therefore, circulating inhibin in the stallion appeared to be largely of testicular origin. The histochemical results showed for the first time that strong immunopositive staining for inhibin occurred in the Leydig cells of the testes. Sertoli cells were also stained by the inhibin antibody but the reaction was weaker than that in Leydig cells. These results indicate clearly that both Leydig and Sertoli cells are potential sources of testicular inhibin in the stallion. A clear increase in plasma ir-inhibin concentrations was observed during the natural breeding season. Similar seasonal changes in the plasma concentrations of testicular steroid hormones and pituitary gonadotrophins occurred throughout the year. In conclusion, the testes appear to be the main source of inhibin, and testicular inhibin is secreted by Leydig and Sertoli cells in stallions. The positive correlations between plasma ir-inhibin and testicular activity during both the breeding and nonbreeding seasons indicate that plasma ir-inhibin is a useful indicator of reproductive activity in the stallion.

Animals↗

PubMed1998

Intracellular changes in ions and organic solutes in halotolerant brevibacterium sp. Strain JCM 6894 after exposure to hyperosmotic shock

In the present study we aimed to observe the intracellular responses when there was a hyperosmotic shock with a large shift in ionic strength in nutrient-rich and nutrient-poor external environments in order to clarify the availability of substrates. To do this, we used the halotolerant organism Brevibacterium sp. strain JCM 6894, which is able to grow in the presence of a wide range of salt concentrations. Hyperosmotic shock was induced by transferring cells in the late exponential phase of growth in a complex medium containing 0.5 M NaCl into either old or fresh culture medium containing 2 M NaCl. Changes in the growth rate, in the pH of the medium, and in the internal cation or organic solute concentrations in the cytosol after an upshock were analyzed as a function of incubation time. The cells exhibited very different responses to upshocks in fresh culture medium and in old culture medium; in fresh culture medium, growth was stimulated and the medium became more acidic, whereas the old culture medium repressed growth and the medium became more alkaline. The intracellular free Na+ concentrations remained low (80 nmol mg of protein-1) after an upshock in fresh culture medium, although they quickly increased twofold in the old culture medium. In contrast, K+ ions immediately accumulated in the cells in fresh culture medium, whereas K+ ions were taken up quite slowly in old culture medium. Furthermore, the cells placed in fresh culture medium transiently accumulated alanine and glutamine in response to the upshock, but the cells placed in old culture medium did not. Growth of the Brevibacterium strain at higher levels of salinity was supported by ectoine synthesis but was not observed after the shift to high-osmolarity conditions in the old culture. In the fresh culture, however, ectoine was vigorously synthesized in cells for more than 5 h after the upshock; the concentration of ectoine in cells was more than 3,500 nmol mg of protein-1 at 10 h, which corresponded to a ninefold increase compared to the concentration before the shock. These findings are consistent with the results of an analysis of the extracellular medium composition before and after the upshock.

Journal Article↗

PubMed1998

High Fas ligand expression on lymphocytes in lesions of ulcerative colitis.

BACKGROUND: The pathogenesis of ulcerative colitis is unclear, but cytotoxic T lymphocytes infiltrating the mucosa have been implicated in mucosal damage. The Fas ligand (FasL), expressed on cytotoxic T lymphocytes, induces apoptosis in cells expressing Fas. AIM: To analyse FasL expression in affected colonic mucosa to ascertain Fas-FasL interaction in ulcerative colitis. METHODS: FasL mRNA was quantified in colonic mucosal specimens from healthy subjects and patients with ulcerative colitis or Crohn's disease, using the competitive reverse transcription polymerase chain reaction. FasL mRNA localisation was determined by in situ hybridisation. Expression of Fas in colonic mucosa was analysed immunohistochemically. Phenotypes of lamina propria lymphocytes that expressed FasL were analysed by flow cytometry. RESULTS: FasL mRNA was strongly expressed in active ulcerative colitis lesions, but not in those associated with active Crohn's disease or active proctitis-type ulcerative colitis. In situ hybridisation showed that FasL mRNA expression occurred in mononuclear cells infiltrating lesions. Fas was expressed in epithelial cells in ulcerative colitis and Crohn's disease, and in normal subjects. Cytometry showed that FasL was expressed in CD3 lymphocytes infiltrating the lamina propria in active lesions. CONCLUSIONS: FasL is expressed in CD3 lymphocytes infiltrating into ulcerative colitis but not Crohn's disease lesions, suggesting that Fas-FasL induced apoptosis participates in the mucosal damage of ulcerative colitis.

Acute Disease↗

PubMed1998

Chronic oral antigen exposure induces lymphocyte migration in anaphylactic mouse intestine.

Persistent diarrhea, vomiting, and dehydration are symptoms often seen in patients suffering from food allergy after chronic antigen exposure; however, the precise mechanisms involved have not been well defined. In an effort to clarify the mechanisms of the chronic intestinal changes attributable to genuine IgE-mediated anaphylactic reactions induced by orally administered antigen, a mouse model was established by s.c. implantation of a murine hybridoma capable of producing monoclonal anti-trinitrophenyl IgE antibody, and the morphologic and immunologic changes occurring in the intestine upon chronic antigen exposure were investigated. In the early stage after ingestion of the antigen, diarrhea and noticeable infiltration of mast cells as well as eosinophils into the lamina propria were observed. A substantial increase in serum histamine levels as well as an increase in leukotriene C4 synthesis in the jejunal mucosa were observed 1 h after antigen challenge. Also, the synthesis of leukotriene B4 was significantly elevated for up to 9 h after antigen challenge. The expression of both intercellular adhesion molecule-1 (ICAM-1) on mucosal vascular endothelial cells and IAd on epithelial cells was markedly enhanced, and noticeable infiltration of eosinophils and lymphocytes was also confirmed in the mouse model after chronic antigen exposure. These findings suggest that oral antigen exposure induces anaphylactic reactions in the intestine mediated by mast cells and eosinophils in response to the IgE-antigen complex in the early phase, and also induces lymphocyte migration after chronic antigen exposure.

Administration, Oral↗

PubMed1998

Microinjection of activated phosphatidylinositol-3 kinase induces process outgrowth in rat PC12 cells through the Rac-JNK signal transduction pathway.

We have previously shown that sustained phosphatidylinositol (PI)-3 kinase activity is necessary for neurite outgrowth of PC12 cells induced by nerve growth factor (NGF). Microinjection of a constitutively active mutant of PI-3 kinase induced process formation suggesting that PI-3 kinase is indeed involved in the neurite outgrowth. However, the processes appeared to be incomplete neurites as they had very poor organization of F-actin and GAP43 antigen. The microtubule network was enhanced in the process-bearing cells and process formation was inhibited by colchicine suggesting that microtubules play an important role in process formation downstream of PI-3 kinase. These cell responses were inhibited by dominant-negative mutants of Rac and Sek1/SAPK but not by a dominant-negative mutant Ras and PD98059, a MAP kinase kinase (MEK) inhibitor, suggesting that not the Ras-MAP kinase pathway but the Rac-Jun N-terminal kinase (JNK) pathway is involved in process formation.

Animals↗

PubMed1998

[Amyloidogenic peptides such as beta-amyloid, amylin and calcitonin strongly enhance the susceptibility of rat hippocampal neurons to excitatory amino acids in vivo].

We have previously shown that in vivo injection of beta-amyloid (beta 1-40, beta 25-35) with non-toxic amounts of ibotenic acid, an excitatory amino acid, causes synergistic and drastic neuronal degeneration in rat hippocampus. It was, however, yet not clear whether the neuronal degeneration in vivo was associated with their primary amino acid sequences, their secondary beta-structure or their activities to suppress MTT reduction activity in vitro. In addition to beta-amyloid, other amyloidogenic peptides such as human amylin or calcitonin are known to deposit extracellularly in systemic and peripheral amyloidosis. In this study, we measured the activity of amyloidogenic peptides (beta 1-40, human amylin and calcitonin) to suppress cellular MTT reduction activity in vitro and their synergistic neurodegeneration with ibotenic acid in vivo. All amyloidogenic peptides, but not non-amyloidogenic peptides (beta 40-1, BSA), suppressed the MTT reduction activity in HeLa cells and in the primary cultured neurons in vitro, and also produced the synergistic neuronal cell loss in rat hippocampal region by enhancing the toxicity of ibotenic acid in vivo. The deposits of amyloidogenic peptides at the injection sites were thioflavin S fluorescence positive, suggesting the fibrillary beta-structures. These results indicate that the neurodegeneration in vivo by amyloidogenic peptides is strongly associated with their fibrillary beta-structure and their activity to suppress MTT reduction activity in vitro.

Amyloid↗