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Biomedical subjects

T Sakamoto

Publications and source records attributed to T Sakamoto.

At least 271 records · Page 15Linked to original sources

A new-type titanium intervertebral spacer and its insertion device used in posterior lumbar interbody fusion.

We have recently developed a new-type trapezoid mesh cage (TPM cage) together with an insertion device, which for use as a new titanium mesh intervertebral spacer in posterior lumbar interbody fusion (PLIF). The TPM cage has sufficient mechanical strength, a large contact area that gives good long-term stability, and preserves the initial disc height to provide good balance. The insertion device for the TPM cage is useful not only for handling the implant but also for controlling the implant insertion direction. The TPM cage and its insertion device are promising for use in PLIF.

Biocompatible Materials↗

[Two cases of ischemic changes indicated in the amplitude of motor evoked potentials during thoracoabdominal aortic aneurysm repair].

Monitoring of motor-evoked potentials (MEPs) is employed to examine functional integrity of descending motor pathway during thoracic aortic surgery. We experienced two cases of intraoperative changes in MEPs during thoracic aortic replacement. In one case, MEPs recovered after the intercostal artery reattachment, and in another case after the release of aortic clamping. No postoperative paraplegia was found in both cases. We conclude that monitoring of MEPs is useful not only because we can detect symptoms of the spinal cord injury from ischemia immediately but also because they give us a clue to decide operative procedures.

Aged↗

[Familial summer-type hypersensitivity pneumonitis in a grandfather and his two-and-a-half-year-old grandson].

We encountered a family in which two of the six members, the grandfather and his grandson, had summer-type hypersensitivity pneumonitis in late summer. Chest computed tomography of these patients showed small, diffuse nodular shadows in both lung fields, with mosaic-like opacities in the grandfather and ground glass opacity of both lung fields in the grandson. Bronchoalveolar lavage fluid from the grandfather disclosed high total cell counts, high percentages of lymphocytes, and a low ratio of CD 4+ cells to CD 8+ cells. Transbronchial lung biopsy specimens obtained from the same patient revealed alveolitis with non-caseous epithelioid cell granulomas in the interstitium and Masson bodies in the alveolar septa. These two patients recovered spontaneously after hospital admission. They had positive results in provocation tests for their home and were positive for serum anti-Trichosporon cutaneum (T. asahii, T. mucoides) antibodies. Both cases were accordingly diagnosed as summer-type hypersensitivity pneumonitis.

Aged↗

[Central necrosis of the lumbo-sacral segment of the spinal cord associated with multiple cholesterin emboli, clinically presenting as acute paraplegia].

A seventy-six-year-old man suddenly suffered from paraplegia and pain in both legs. He had been maintained on hemodialysis and committed a suicide attempt by cutting the shunt at the paraplegic attack. He was brought to the emergency ward for the treatment of hemorrhagic preshock. Neurological examination demonstrated flaccid paraplegia, loss of tendon reflex in the lower extremities, dissociated sensory loss below the fourth lumbar level; and incontinence in defecation. MRI showed T2 shortening in the ventral spinal cord caudal below the level of the eleventh thoracic cord. Postmortem examination confirmed ischemic infarct in the central area of the spinal cord, associated with disseminated cholesterin emboli in the small arteries. This case was the first MRI demonstration of central necrosis caused by cholesterin emboli, and may emphasize the significance of cholesterin emboli in the spinal arterial disorders in the aged.

Acute Disease↗

Soluble Fas and soluble Fas L levels in patients with acute pancreatitis.

The FasL-Fas system is an apoptosis induction system and plays an important role in homeostasis and biophylaxis. The present study was conducted to investigate soluble Fas (sFas), soluble Fas ligand (sFasL), and tumor necrosis factor alpha (TNF-alpha) in patients with acute pancreatitis. As acute pancreatitis became severe, the levels of sFas in the serum increased significantly, while those of sFasL decreased significantly. A significant inverse correlation was observed between the serum levels of sFas and those of sFasL. Also, a significant positive correlation was observed between the levels of TNF-alpha and sFas. A greater increase in serum sFas and decrease in serum sFasL levels was observed in patients with complicating multiple organ dysfunction syndrome (MODS) than in those without it. The results of the study suggest that the pathological aggravation of acute pancreatitis could be related to changes in the Fas-FasL system.

Acute Disease↗

Unique recognition style of tRNA(Leu) by Haloferax volcanii leucyl-tRNA synthetase.

The recognition manner of tRNA(Leu), a class II tRNA characterized by a long variable arm, by leucyl-tRNA synthetase from an extreme halophilic archaea, Haloferax volcanii, was studied using the in vitro transcription system. It was found that the discriminator base (A73) and the long variable arm, especially the specific loop sequence A47CG47D and U47H at the base of this helix, are significant for recognition by LeuRS. An appropriate stem length of the variable arm was also required. Base substitutions in the anticodon arm did not affect the leucylation activity. Transplantation of both the discriminator base and the variable arm of tRNA(Leu) was not sufficient to introduce leucylation activity to tRNA(Ser). Insertion of an additional nucleotide into the D-loop, which is not involved in the direct interaction with LeuRS, converted tRNA(Ser) to an efficient leucine acceptor. This suggests that differences in the tertiary structure play a key role in eliminating tRNA(Ser). The sequence-specific recognition of the long variable arm of tRNA(Leu) has not been observed in any of other organisms reported, such as Escherichia coli, yeast or human. On the other hand, the mode of discrimination from non-cognate tRNAs is similar to that in E. coli in that differences in the tertiary structure play a key role. Similarity extends to the substrate stringency, exemplified by a cross-species aminoacylation study showing that no class II tRNAs from E. coli or yeast can be leucylated by H. volcanii LeuRS. Our results have implications for the understanding of the evolution of the recognition system of class II tRNA.

Acylation↗

Expression of a dominant negative SHP-2 in transgenic mice induces insulin resistance.

To elucidate the roles of SHP-2, we generated transgenic (Tg) mice expressing a dominant negative mutant lacking protein tyrosine phosphatase domain (DeltaPTP). On examining two lines of Tg mice identified by Southern blot, the transgene product was expressed in skeletal muscle, liver, and adipose tissues, and insulin-induced association of insulin receptor substrate 1 with endogenous SHP-2 was inhibited, confirming that DeltaPTP has a dominant negative property. The intraperitoneal glucose loading test demonstrated an increase in blood glucose levels in Tg mice. Plasma insulin levels in Tg mice after 4 h fasting were 3 times greater with comparable blood glucose levels. To estimate insulin sensitivity by a constant glucose, insulin, and somatostatin infusion, steady state blood glucose levels were higher, suggesting the presence of insulin resistance. Furthermore, we observed the impairment of insulin-stimulated glucose uptake in muscle and adipocytes in the presence of physiological concentrations of insulin. Moreover, tyrosine phosphorylation of insulin receptor substrate-1 and stimulation of phosphatidylinositol 3-kinase and Akt kinase activities by insulin were attenuated in muscle and liver. These results indicate that the inhibition of endogenous SHP-2 function by the overexpression of a dominant negative mutant may lead to impaired insulin sensitivity of glucose metabolism, and thus SHP-2 may function to modulate insulin signaling in target tissues.

Animals↗

Target gene transfer of tissue plasminogen activator to cornea by electric pulse inhibits intracameral fibrin formation and corneal cloudiness.

Intracameral fibrin formation, a complication of ocular inflammation and intraocular operations, sometimes results in glaucoma and/or corneal damage leading to permanent visual loss. We transferred a therapeutic gene to the corneal endothelium in order to use it as a therapeutic organ. A plasmid encoding tissue plasminogen activator (tPA) was injected into the anterior chamber of rats and electric pulses (EPs) were given subsequently, which transferred a plasmid gene to a highly selected area of corneal endothelium with no inflammation. The biologically active tPA was clearly present for 4 days after treatment. Fibrin formation induced by YAG laser-generated bleeding in the anterior chamber decreased significantly more in treated eyes than in control eyes. Corneal opacity was significantly lower in treated eyes than in control eyes and histological damage was not apparent in the treated eyes. This genetic modification allows us to use the corneal endothelium to treat various ocular diseases and could be a new and effective type of pharmacologic gene therapy.

Animals↗

Circulating levels of secretory type II phospholipase A(2) predict coronary events in patients with coronary artery disease.

Background-The circulating levels of secretory nonpancreatic type II phospholipase A(2) (sPLA(2)) are increased in various chronic inflammatory diseases and the increase in the levels correlates with the disease severity. sPLA(2) may possibly play a role in atherogenesis and is highly expressed in atherosclerotic arterial walls that are known to have inflammatory features. Thus, this study prospectively examined whether circulating levels of sPLA(2) may have a significant risk and prognostic values in patients with coronary artery disease (CAD). Methods and Results-Plasma levels of sPLA(2) were measured in 142 patients with CAD and in 93 control subjects by a radioimmunoassay. The sPLA(2) levels had a significant and positive relations with serum levels of C-reactive protein, a marker of systemic inflammation, and with the number of the traditional coronary risk factors associated with individuals. Multivariate logistic regression analysis showed that higher levels of sPLA(2) (>246 ng/dL; 75th percentile of sPLA(2) distribution in controls) were a significant and independent risk factor for the presence of CAD. In multivariate Cox hazard analysis, the higher levels of sPLA(2) were a significant predictor of developing coronary events (ie, coronary revascularization, myocardial infarction, coronary death) during a 2-year follow-up period in patients with CAD independent of other risk factors, including CRP levels, an established inflammatory predictor. Conclusions-The increase in circulating levels of sPLA(2) is a significant risk factor for the presence of CAD and predicts clinical coronary events independent of other risk factors in patients with CAD; these results may reflect possible relation of sPLA(2) levels with inflammatory activity in atherosclerotic arteries.

Aged↗

An NMR analysis of ubiquitin recognition by yeast ubiquitin hydrolase: evidence for novel substrate recognition by a cysteine protease.

Yeast ubiquitin hydrolase 1 (YUH1), a cysteine protease that catalyzes the removal of ubiquitin C-terminal adducts, is important for the generation of monomeric ubiquitin. Heteronuclear NMR spectroscopy has been utilized to map the YUH1 binding surface on ubiquitin. When YUH1 was titrated into a sample of ubiquitin, approximately 50% of the (1)H-(15)N correlation peaks of ubiquitin were affected to some degree, as a result of binding to YUH1. It is noteworthy that the amide resonances of the basic residues (Arg42, Lys48, Arg72, and Lys74) were highly perturbed. These positively charged basic residues may be involved in direct interactions with the negatively charged acidic residues on YUH1. In addition to the electrostatic surface, the hydrophobic surfaces on ubiquitin (Leu8, Ile44, Phe45, Val70, Leu71, and Leu73) and YUH1 are also likely to contribute to the binding interaction. Furthermore, the amide resonances of Ile13, Leu43, Leu50, and Leu69, the side chains of which are not on the surface, were also highly perturbed, indicating substrate-induced changes in the environments of these residues as well. These large changes, observed from residues located throughout the five-stranded beta-sheet surface and the C-terminus, suggest that substrate recognition by YUH1 involves a wider area on ubiquitin.

Amino Acid Sequence↗

Structural analysis of the titin gene in hypertrophic cardiomyopathy: identification of a novel disease gene.

Hypertrophic cardiomyopathy (HCM) is characterized by ventricular hypertrophy accompanied by myofibrillar disarrays. Molecular genetic analyses have revealed that mutations in 8 different genes cause HCM. Mutations in these disease genes, however, could be found in about half of HCM patients, suggesting that there are other unknown disease gene(s). Because the known disease genes encode sarcomeric proteins expressed in the cardiac muscle, we searched for a disease-associated mutation in the titin gene in 82 HCM patients who had no mutation in the known disease genes. A G to T transversion in codon 740, from CGC to CTC, replacing Arginine with Leucine was found in a patient. This mutation was not found in more than 500 normal chromosomes and increased the binding affinity of titin to alpha-actitin in the yeast two-hybrid assay. These observations suggest that the titin mutation may cause HCM in this patient via altered affinity to alpha-actinin.

Actinin↗

Preparation of recombinant rat interleukin-5 by baculovirus expression system and analysis of its biological activities.

Rat interleukin-5 (IL-5) cDNA was subcloned from peritoneal cells collected 4 h after intraperitoneal injection of Ascaris suum antigen solution into the immunized rats. Cysteine proteinase-deleted (CPd) rat IL-5 recombinant virus was constructed by inserting rat IL-5 cDNA into CPd virus having a deletion in the cysteine proteinase gene of the silkworm Bombyx mori nuclear polyhedrosis virus. On infection with the CPd rat IL-5 recombinant virus, the silkworm B. mori larvae produced rat IL-5 as a dimeric form in hemolymph. Recombinant rat IL-5 was purified more than 95.5% by anion-exchange chromatography and hydrophobic chromatography. The purified recombinant rat IL-5 promoted the proliferation of T88-M cells in a concentration-dependent manner, and its effect was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. When bone marrow cells from normal rats were incubated with recombinant rat IL-5 in medium containing methylcellulose, the colony formation by eosinophilic cells was induced. Furthermore, when rat peritoneal eosinophils were incubated with recombinant rat IL-5, the spontaneous decrease in the eosinophil viability was inhibited in time- and concentration-dependent manners. In addition, the recombinant rat IL-5-induced eosinophil survival was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. These findings suggest that rat IL-5 acts as B-cell growth factor II (BCGF-II), eosinophil differentiation factor (EDF), and eosinophil survival-enhancing factor.

Animals↗

Ubiquitin binding interface mapping on yeast ubiquitin hydrolase by NMR chemical shift perturbation.

The interaction between the 26 kDa yeast ubiquitin hydrolase (YUH1), involved in maintaining the monomeric ubiquitin pool in cells, and the 8.5 kDa yeast ubiquitin protein has been studied by heteronuclear multidimensional NMR spectroscopy. Chemical shift perturbation of backbone (1)H(N), (15)N, and (13)C(alpha) resonances of YUH1, in a YUH1-ubiquitin mixture and in a 35 kDa covalent complex with ubiquitin (a stable analogue of the tetrahedral reaction intermediate), was employed to identify the ubiquitin binding interface of YUH1. This interface mapped on the secondary structure of YUH1 suggests a wide area of contact for ubiquitin, encompassing the N-terminus, alpha1, alpha4, beta2, beta3, and beta6, coincident with the high specificity of YUH1 for ubiquitin. The presence of several hydrophobic clusters in the ubiquitin binding interface of YUH1 suggests that hydrophobic interactions are equally important as ionic interactions in contacting ubiquitin. The residues in the binding interface exhibit a high percentage of homology among the members of the ubiquitin C-terminal hydrolase family, indicating the well-conserved nature of the ubiquitin binding interface reported in this study. The secondary structure of YUH1, from our NMR studies, was similar to the recently determined structure of its human homologue ubiquitin C-terminal hydrolase L3 (UCH-L3), except for the absence of the helix H3 of UCH-L3. This region in YUH1 (helix H3 of UCH-L3) was least perturbed upon ubiquitin binding. Therefore, the binding interface was mapped onto the corresponding residues in the UCH-L3 crystal structure. A model for ubiquitin binding to YUH1 is proposed, in which a good correlation was observed for the lateral binding of ubiquitin to UCH-L3 (YUH1), stabilized by the electrostatic and hydrophobic interactions.

Amino Acid Sequence↗

Transcriptional regulation of a receptor protein tyrosine phosphatase gene hPTP-J by PKC-mediated signaling pathways in Jurkat and Molt-4 T lymphoma cells.

The recently cloned type II receptor protein tyrosine phosphatase (RPTP) gene hPTP-J is a new member of the MAM (meprin, A5, PTPmicro) domain subfamily. We previously reported that hPTP-J mRNA was detected significantly in Jurkat T lymphoma cells and its expression was completely down-regulated by phorbol myristate acetate (PMA). In this study, we investigated what signaling pathways/molecules are involved in the transcriptional regulation of hPTP-J expression in Jurkat and Molt-4 T cell lines. The hPTP-J transcription was transiently up-regulated 20 min after the addition of PMA (20 ng/ml) to the Jurkat culture, followed by the complete down-regulation in 8 h after PMA addition. The transient up-regulation and the complete down-regulation induced by PMA was blocked by a PKC-specific inhibitor, GF109203X, suggesting that the regulatory effect of PMA on the hPTP-J transcription depends on protein kinase C activation. hPTP-J transcription was down-regulated not only by PMA but also by several signaling modulators including 1-oleoyl-2-acetylglycerol, forskolin, orthovanadate, manumycin and okadaic acid. Therefore, several signaling molecules such as protein tyrosine phosphatases, PP2A/CaMKIV and Ras are required for hPTP-J transcription in Jurkat and Molt-4 cells.

Cyclic AMP↗

Association of plasma levels of activated protein C with recanalization of the infarct-related coronary artery after thrombolytic therapy in acute myocardial infarction.

Protein C is one of the most important antithrombotic components. After activation by the thrombin-thrombomodulin complex on endothelial cells, activated protein C (APC) inactivates factors Va and VIIIa, which leads to the inhibition of thrombin formation. We examined the association of plasma levels of APC with the responsiveness to coronary thrombolytic therapy of the infarct-related coronary artery in patients with acute myocardial infarction (AMI). Plasma levels of APC, thrombin-antithrombin III complex (TAT), and plasminogen activator inhibitor (PAI) activity were measured in 32 consecutive AMI patients who underwent coronary angiography followed by thrombolytic therapy, and compared to the measurements in 23 control subjects. On admission, APC levels (ng/mL) were significantly elevated in patients with AMI, as compared with controls (2.5+/-0.4 vs. 1.2+/-0.2, 1.3+/-0.2, respectively, p<0.01). At discharge, plasma levels in AMI patients decline to values not significantly different from those in controls. (1.2+/-0.2, 1.3+/-0.2, respectively). TAT levels (ng/mL) were different among the groups in a fashion similar to that of APC (14.1+/-3.1 on admission vs. 3.3+/-0.4 at discharge, 1.8+/-0.1 in the control subjects, respectively, p<0.01). PAI activity levels (IU/mL) were higher on admission than at discharge and higher than the control subjects (19.7+/-1.8 vs. 10.5+/-1.0, 5.4 +/- 0.7, respectively, p<0.01). Thirty-two patients with AMI were classified into two groups according to the results of thrombolysis: the success group (24 patients) and the failure group (eight patients). APC levels were higher in the failure group than in the success group (5.1+/-0.7 vs. 1.6+/-0.2, p<0.01). TAT levels were also higher in the failure group than in the success group (30.8+/-9.6 vs. 8.6+/-1.7, p<0.01). PAI activity levels (IU/mL) were lower in the failure group than in the success group (13.5+/-3.1 vs. 21.7+/-2.1, p<0.05). There were correlations between APC and TAT levels both on admission (r=0.75, p<0.0001) and at discharge (r=0.71, p<0.0001). Elevated APC was thought to correlate with increased thrombin generation in patients with AMI. This study demonstrated that there was a significant relation between plasma APC level and the responsiveness to thrombolytic therapy of the infarct artery. This study may also indicate that increased thrombin generation is a cause of the resistance to thrombolytic therapy.

Acute Disease↗