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S Ura

Publications and source records attributed to S Ura.

At least 19 recordsLinked to original sources
PubMed2001

Caspase cleavage of MST1 promotes nuclear translocation and chromatin condensation.

MST1, mammalian STE20-like kinase 1, is a serine/threonine kinase that is cleaved and activated by caspases during apoptosis. MST1 is capable of inducing apoptotic morphological changes such as chromatin condensation upon overexpression. In this study, we show that MST1 contains two functional nuclear export signals (NESs) in the C-terminal domain, which is released from the N-terminal kinase domain upon caspase-mediated cleavage. Full-length MST1 is excluded from the nucleus and localized to the cytoplasm. However, either truncation of the C-terminal domain, point mutation of the two putative NESs, or treatment with leptomycin B, an inhibitor of the NES receptor, results in nuclear localization of MST1. Staurosporine treatment induces chromatin condensation, MST1 cleavage, and nuclear translocation. Staurosporine-induced chromatin condensation is partially inhibited by expressing a kinase-negative mutant of MST1, suggesting an important role of MST1 in this process. Significantly, MST1 is more efficient at inducing chromatin condensation when it is constitutively localized to the nucleus by mutation of its NESs. Moreover, inhibition of MST1 nuclear translocation by mutation of its cleavage sites reduces its ability to induce chromatin condensation. Taken together, these results suggest that truncation of the C-terminal domain of MST1 by caspases may result in translocation of MST1 into the nucleus, where it promotes chromatin condensation.

Active Transport, Cell Nucleus↗
PubMed2001

MST1-JNK promotes apoptosis via caspase-dependent and independent pathways.

BACKGROUND: MST1 is an upstream kinase of the JNK and p38 MAPK pathways whose expression induces apoptotic morphological changes such as nuclear condensation. During apoptosis, caspase cleavage of MST1 removes a C-terminal regulatory domain, increasing the kinase activity of the MST1 N-terminal domain. Downstream pathways of MST1 in the induction of apoptosis remain to be clarified. RESULTS: In this study, we found that the expression of MST1 resulted in caspase-3 activation. Therefore, MST1 is not only a target of caspases but also an activator of caspases. This caspase activation and apoptotic changes occur through JNK, since the co-expression of a dominant-negative mutant of JNK inhibited MST1-induced morphological changes as well as caspase activation. In contrast, neither a dominant-negative p38 nor the p38 inhibitor SB203580 inhibited them. MST1 induced nucleosomal DNA fragmentation, which was suppressed by caspase inhibitors or ICAD (Inhibitor of Caspase-Activated DNase). Surprisingly, however, other changes such as membrane blebbing and chromatin condensation were not inhibited by caspase inhibitors. CONCLUSION: These results suggest that MST1 most likely promotes two events through JNK activation; first, MST1 induces the activation of caspases, resulting in CAD-mediated DNA fragmentation, and second, MST1 induces chromatin condensation and membrane blebbing without utilizing downstream caspases.

Animals↗
PubMed2001

Renal lesions in leprosy: a retrospective study of 199 autopsies.

In the present work, 199 patients with leprosy who underwent autopsy between 1970 and 1986 were retrospectively studied to determine the prevalence, types, clinical characteristics, and etiologic factors of renal lesions (RLs) in leprosy. Patients were divided into two groups: 144 patients with RLs (RL+) and 55 patients without RLs (RL-). RLs observed in 72% of the autopsied patients were amyloidosis (AMY) in 61 patients (31%), glomerulonephritis (GN) in 29 patients (14%), nephrosclerosis (NPS) in 22 patients (11%), tubulointerstitial nephritis (TIN) in 18 patients (9%), granuloma in 2 patients (1%), and other lesions in 12 patients (6%). AMY occurred most frequently in patients with lepromatous leprosy (36%; nonlepromatous leprosy, 5%; P < 0.01), recurrent erythema nodosum leprosum (33%; P < 0.02), and trophic ulcers (27%; 0.05 < P < 0.10). Ninety-seven percent of AMY was found in patients with lepromatous leprosy, 88% showed recurrent trophic ulcers, and 76% presented with erythema nodosum leprosum. NPS was found in older patients with arterial hypertension, neoplastic diseases, infectious diseases, and vasculitis associated with GN. Most patients with AMY presented with proteinuria (95%) and renal failure (88%). The most frequent causes of death were renal failure in patients with AMY (57%), infectious diseases in patients with GN (41%) and TIN (45%), and cardiovascular diseases in patients with NPS (41%). No difference in survival rates was observed among RL- patients and those with AMY, GN, NPS, or TIN.

Aged↗
PubMed2001

[Two adult cases of nemaline myopathy presenting different clinical symptoms and CT findings].

We report herein two cases of nemaline myopathy which showed peculiar muscle involvement and clinical symptoms. Case 1: A 44-year-old woman had developed gradual woresening of muscle weakness. Neurologically, only flexion of her neck was found to be weak. Her muscular CT revealed mild atrophy of four extremities and the sternocleidomastoid muscles. Histological examinations with Gomori-trichrome staining revealed tiny structures whose form was compatible with nemaline rods. Moreover, electronmicroscopic examination demonstrated the lattice pattern of electron-dense structures, and they also appeared to possess structural continuity with the Z-band. Case 2: A 56-year-old woman visited our department because of neck pulsations. Neurological examinations revealed bilateral hearing disturbance, marked atrophy of neck muscles, muscle weakness in four extremities and hypoactive deep tendon reflexes. She also exhibited steppage and waddling gaits. Her muscular CT demonstrated degenerative processes in the neck muscles(splenius muscles and semispinal muscles), trapezius muscles, para-spinal muscles, deltoid muscles and gluteal muscles. Among them, the para-spinal muscles and extensor muscles of the lower limbs showed marked degeneration and had been partly replaced by fatty tissues. A muscle biopsy was performed, and the presence of nemaline rods was confirmed by Gomori-trichrome staining. Although these two cases could be diagnosed as nemaline myopathy, the clinical symptoms and muscular CT findings were not quite the same. Whether these differences might simply indicate different clinical phases during the disease progression or be of further pathogenic significance still remains unclear. Additionally, since long-term follow-up studies of nemaline myopathy are quite rare, further follow-up examinations of these cases are necessary in order to understand the clinical and pathological alterations of nemaline myopathy.

Adult↗
PubMed1998

Anti-neutrophil cytoplasmic antibodies (ANCA) in the clinical forms of leprosy.

Anti-neutrophil cytoplasmic antibodies (ANCA) are autoantibodies against enzymes present in primary granules of neutrophils and lysosomes of monocytes detected in systemic vasculitis and in other diseases, including infections. ANCA are markers of active Wegener granulomatosis, which presents some anatomo-pathologic and immune response features similar to those of leprosy. Thus, we raised the hypothesis that ANCA may be present in leprosy as markers specifically linked to the presence of vasculitis. The aim of this study was to determine the presence of ANCA in leprosy and its correlation with the clinical forms of the disease. Sera from 60 normal individuals and from 59 patients with different clinical forms of leprosy were studied. The patients were also allocated into reactional and nonreactional groups. By indirect immunofluorescence, ANCA were positive, an atypical pattern (A-ANCA), in 28.8% of the patient sera. A-ANCA predominated, although not significantly (p > 0.05), in the reactional groups 37.9% vs 20.0%), and in those at the lepromatous pole (41.6% vs 20.0%). There was no correlation between ANCA positivity and either disease duration, disease activity, or therapeutic regimen (p > 0.05). An interesting finding was the correlation between ANCA and gender: 94.1% of ANCA-positive patients were males (p < 0.01), a feature that so far has not been reported in ANCA-related diseases and for which there is no explanation at the moment. By ELISA, the sera of the lepromatous leprosy patients did not show activity against either PR3, MPO, HLE, the most common ANCA antigens. Because A-ANCA are nonspecific, this finding requires further investigation for the determination of the responsible antigen(s). In conclusion, A-ANCA are present in 28.8% of leprosy patients but are not related to vasculitis in the erythema nodosum leprosum reaction and are not a marker of a specific clinical form.

Adolescent↗
PubMed1997

Impact of natural IRS-1 mutations on insulin signals: mutations of IRS-1 in the PTB domain and near SH2 protein binding sites result in impaired function at different steps of IRS-1 signaling.

Insulin receptor substrate-1 (IRS-1) is one of the major substrates of insulin receptor tyrosine kinase and mediates various insulin signals downstream. In this study, we have examined the impact of three natural IRS-1 mutations identified in NIDDM patients (G971R, P170R, and M209T) on insulin signaling. G971R is located near src homology 2 protein binding sites, and P170R and M209T are located in the phosphotyrosine binding domain of IRS-1. 32D-IR cells, stably overexpressing human insulin receptor, were transfected with wild-type human IRS-1 cDNA (WT) or three mutant IRS-1 cDNAs and analyzed. All the cell lines expressing mutant IRS-1 showed a significant reduction in [3H]thymidine incorporation compared with WT. Upon insulin stimulation, cells expressing G971R showed a 39% decrease (P < 0.005) in phosphatidylinositol 3-kinase (PI 3-kinase) activity, a 43% decrease (P < 0.01) in binding of the 85-kDa regulatory subunit of PI 3-kinase, and a 22% decrease (P < 0.05) in mitogen-activated protein kinase activity compared with those expressing WT. Cells expressing P170R and M209T showed slight but significant decreases in PI 3-kinase activity (17 and 14%, respectively; both P < 0.05) and in binding of p85 (22 and 16%, respectively; both P < 0.05) and a greater decrease in mitogen-activated protein kinase activity (41 and 43%, respectively; both P < 0.005) compared with WT. After insulin stimulation, cells expressing P170R and M209T showed significant decreases in IRS-1 phosphorylation (37 and 42%, respectively; both P < 0.05) and in IRS-1 binding to the insulin receptor (48 and 53%, respectively; P < 0.01) compared with WT. G971R showed no changes in IRS-1 phosphorylation and in IRS-1 binding to the insulin receptor compared with WT. These data suggest that the impaired mitogenic response of P170R and M209T was mainly due to reduced binding to the insulin receptor, whereas the impaired response of G971R was mainly due to reduced association with PI 3-kinase p85.

Animals↗
PubMed1996

Bradykinin enhances GLUT4 translocation through the increase of insulin receptor tyrosine kinase in primary adipocytes: evidence that bradykinin stimulates the insulin signalling pathway.

It has been suggested that bradykinin stimulates glucose uptake in experiments in vivo and in cultured cells. However, its mechanism has not yet been fully elucidated. In this study, the effects of bradykinin on the insulin signalling pathway were evaluated in isolated dog adipocytes. The bradykinin receptor binding study revealed that dog adipocytes possessed significant numbers of bradykinin receptors (Kd = 83 pmol/l, binding sites = 1.7 x 10(4) site/ cell). Reverse transcription-polymerase chain reaction amplification showed the mRNA specific for bradykinin B2 receptor in the adipocytes. Bradykinin alone did not increase 2-deoxyglucose uptake in adipocytes; however, in the presence of insulin (10(-7) mol/l) it significantly increased 2-deoxyglucose uptake in a dose-dependent manner. Bradykinin also enhanced insulin stimulated GLUT4 translocation from the intracellular fraction to the cell membrane, and insulin induced phosphorylation of the insulin receptor beta subunit and insulin receptor substrate-1 (IRS-1) without affecting the binding affinities or numbers of cell surface insulin receptors in dog adipocytes. The time-course of insulin stimulated phosphorylation of the insulin receptor beta subunit revealed that phosphorylation reached significantly higher levels at 10 min, and stayed at the higher levels until 120 min in the presence of bradykinin, suggesting that bradykinin delayed the dephosphorylation of the insulin receptor. It is concluded that bradykinin could potentiate insulin induced glucose uptake through GLUT4 translocation. This effect could be explained by the potency of bradykinin to upregulate the insulin receptor tyrosine kinase activity which stimulates phosphorylation of IRS-1, followed by GLUT4 translocation.

Adipocytes↗
PubMed1996

Molecular scanning of the insulin receptor substrate-1 (IRS-1) gene in Japanese patients with NIDDM: identification of five novel polymorphisms.

Since the insulin receptor substrate-1 (IRS-1) is the major substrate of the insulin receptor tyrosine kinase and has been shown to activate phosphatidylinositol (PI) 3-kinase and promote GLUT4 translocation, the IRS-1 gene is a potential candidate for development of non-insulin-dependent diabetes mellitus (NIDDM). In this study, we have identified IRS-1 gene polymorphisms, evaluated their frequencies in Japanese subjects, and analysed the contribution of these polymorphisms to the development of NIDDM. The entire coding region of the IRS-1 gene of 94 subjects (47 NIDDM and 47 control subjects) was screened by polymerase chain reaction-single stranded conformation polymorphism (PCR-SSCP) analysis. Seven SSCP polymorphisms were identified. These corresponded to two previously identified polymorphisms [Gly971 --> Arg (GGG --> AGG) and Ala804 (GCA --> GCG)] as well as five novel polymorphisms [Pro190 --> Arg (CCC --> CGC), Met209 --> Thr (ATG --> ACG), Ser809 --> Phe (TCT --> TTT), Leu142 (CTT --> CTC), and Gly625 (GGC --> GGT)]. Although the prevalence of each of these polymorphisms was not statistically different between NIDDM and control subjects, the prevalence of the four IRS-1 polymorphisms with an amino acid substitution together was significantly higher in NIDDM than in control subjects (23.4 vs 8.5%, p < 0.05), and two substitutions (Met 209 --> Thr and Ser809 --> Phe) were found only in NIDDM patients. Equilibrium glucose infusion rates during a euglycaemic clamp in NIDDM and control subjects with the IRS-1 polymorphisms decreased by 29.5 and 22.0%, respectively on the average when compared to those in comparable groups without polymorphisms, although they were not statistically significant. Thus, IRS-1 polymorphisms may contribute in part to the insulin resistance and development of NIDDM in Japanese subjects; however, they do not account for the major part of the decrease in insulin-stimulated glucose uptake which is observed in subjects with clinically apparent NIDDM.

Amino Acid Sequence↗
PubMed1995

Expression of insulin receptor on clonal pancreatic alpha cells and its possible role for insulin-stimulated negative regulation of glucagon secretion.

In pancreatic alpha cells, the existence and function of the insulin receptor has not yet been fully established. In this study, to confirm the expression of functional insulin receptors in pancreatic alpha cells, we performed: 1) insulin receptor binding assay, 2) Northern blot analysis and RT-PCR (reverse transcription-polymerase chain reaction) amplification of insulin receptor mRNA, 3) immunocytochemical staining, 4) biosynthetic labelling of insulin receptor protein using [35S]methionine, 5) analysis of insulin-stimulated autophosphorylation of the insulin receptor in glucagon secreting cell lines, In-R1-G9 and alpha TC clone 6 cells. Glucagon secretion decreased with the addition of insulin in both cells. The receptor binding studies using [125I-Tyr-A14] insulin revealed that both cells possessed a significant number of insulin receptors (In-R1-G9:K1 = 2.1 x 10(9) mol/l-1, K2 = 6.2 x 10(7) mol/l-1, R1 = 0.27 x 10(4), R2 = 1.86 x 10(4) sites/cell; alpha TC clone 6: K1 = 2.1 x 10(9) mol/l-1, K2 = 7.3 x 10(7) mol/l-1, R1 = 0.27 x 10(4), R2 = 1.95 x 10(4) sites/cell). Northern blot analysis as well as RT-PCR amplification showed the mRNA specific for insulin receptor in both cells. By immunocytochemical staining using anti-insulin receptor alpha-subunit antibody, positive immunostaining for insulin receptor was observed in both cells. [35S]Methionine labelling of both cells followed by immunoprecipitation using anti-insulin receptor antibody showed the correct size of the insulin receptor protein. The insulin receptor expressed in these cells underwent autophosphorylation by insulin stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Sudden death of calves by experimental infection with Strongyloides papillosus. IV. Electrocardiographic and pneumographic observations at critical moments of the disease.

Electrocardiographic and pneumographic observations at critical moments were carried out on five calves that died suddenly following experimental infections with Strongyloides papillosus. Time which elapsed during these critical moments was calculated from the time of observation of ventricular flutter (VF) to the appearance of accelerated respiration and cessation of respiration. The beginning of accelerated respiration ranged from -19 to 41 s after VF. Time (minutes:seconds) of cessation of respiration ranged from 2:10 to 3:50 after VF. The results of the experiment suggested sudden cardiac death as the cause of death in calves following infection with Strongyloides papillosus.

Animals↗
PubMed1993

Sudden death of calves by experimental infection with Strongyloides papillosus. III. Hematological, biochemical and histological examinations.

Nine calves infected percutaneously with graded doses of Strongyloides papillosus (SPL) were examined for hematological, biochemical and histological changes during the infection. Six of the calves infected with the highest larval doses died suddenly and the three calves given lower doses survived. No changes were observed in blood cell counts except for a transient eosinophilia. Parameters of the blood coagulation system and blood gas remained normal. A decrease in blood glucose was observed in four of the calves that died after the prepatent period of the parasite. However, endotoxic shock could be ruled out as a cause of death because of normal platelet counts, no intravascular coagulation and low levels of serum endotoxin. A transient increase of creatine kinase was observed in three of the calves that died; however, myocardial infarction or myocarditis were not observed. No lesions were observed except for minor inflammatory changes in the lungs and slight cellular infiltrations in the heart. In the absence of any consistent hematological, biochemical or histological changes in the calves that died, the present study failed to demonstrate mechanisms underlying sudden death due to SPL infection.

Animals↗
PubMed1992

Sudden death of calves by experimental infection with Strongyloides papillosus. I. Parasitological observations.

Recently, an unknown disease, 'sudden death', in calves has been found in Japanese beef production farms. A previous study conducted by Taira and Ura indicated that sudden death can be effected in calves by hyperinfection of Strongyloides papillosus (SPL) and that the disease is possibly caused by SPL infection. In the present work, an experimental infection of SPL in calves was conducted to confirm the field occurrence. Fifteen Holstein Friesian calves, ranging from 45.5 to 85.6 kg in body weight, were divided into six groups. Calves of Groups A, B, C, D, E and F were infected once at the rate of 100,000, 320,000, 1,000,000, 3,200,000, 10,000,000 and 32,000,000 SPL larvae per 100 kg of body weight, respectively. Five calves were assigned to Group B, while two calves were assigned to the other groups. After showing no premonitory signs, sudden death of ten calves took place. The survival time of these calves was 27.4 and 16.8 days (Group B), 14.8 and 14.8 days (Group C), 13.3 and 14.2 days (Group D), 11.0 and 11.1 days (Group E) and 11.6 and 10.8 days (Group F). Three calves of Group B did not exhibit sudden death. The results of this study demonstrate that strongyloidiasis was the cause of sudden death.

Animals↗
PubMed1992

Sudden death of calves by experimental infection with Strongyloides papillosus. II. Clinical observations and analysis of critical moments of the disease recorded on videotape.

Four calves experimentally infected with different doses of Strongyloides papillosus were examined for changes of body temperature and other clinical parameters. Also, the critical moments of death, which were recorded on videotape, were analyzed in detail. The first clinical signs included initial accelerated respiration. In general, body temperature was almost normal; however, one calf showed a slight increase after 2 or 3 days of infection, and two calves a gradual increase 7 days after infection. Vocal noises and general spasms were observed 5-14 times during the course of death. Initial vocal noises were heard between 0:50 and 1:30 (minute:second) after the appearance of the initial clinical signs. The final spasm, preceding death, occurred between 3:05 and 3:40 after the appearance of the initial clinical signs.

Animals↗
PubMed1992

Sudden cardiac death in calves with experimental heavy infection of Strongyloides papillosus.

For obtaining the preliminary data on the pathogenesis of sudden death in calves naturally heavily infected with Strongyloides papillosus, we monitored 8 Holstein calves experimentally infected with the larvae on electrocardiographic and pneumographic changes. Six calves died suddenly on days 11 to 17 after infection. Sinus tachycardia had been recorded continuously since 1 to 6 days before death. Heart rates increased gradually until death. Since 1 or 2 days before death, various patterns of tachyarrhythmia and bradyarrhythmia had been observed among patterns of sinus tachycardia. Arrhythmias included serious ventricular premature beat, paroxysmal ventricular tachycardia, complete atrioventricular block and so on. The terminal pattern observed suddenly in all of the cases was ventricular arrhythmias consisting of serial ventricular tachycardia, flutter and fibrillation, which were followed by respiratory arrest. Abnormal pneumograms were not obtained before the terminal ventricular fibrillation. Two of 8 calves recovered from the infection, only one of which showed sinus arrest and the second degree of atrioventricular block transiently. We concluded that calves heavily infected with the larvae died due to sudden cardiac arrest.

Animals↗
PubMed1991

Sudden death in calves associated with Strongyloides papillosus infection.

In recent years, a total of 152 calves have died suddenly on three farms in the southern part of Japan which used sawdust as litter. Calves often died within a few minutes of a violent fall without showing previous clinical signs. On necropsy of these cases, only a slight lesion was observed, although all showed heavy infection with Strongyloides papillosus (SPL). They appeared to have not only a large number of SPL eggs in the faeces, together with many adult SPL worms in the intestine, but also many migratory SPL larvae in tissues such as the lung and muscle. These outbreaks ceased following medication with thiabendazole or ivermectin. It is concluded that 'sudden death' is associated with heavy infection with SPL.

Animal Husbandry↗