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Biomedical subjects

T Miyata

Publications and source records attributed to T Miyata.

At least 361 records · Page 20Linked to original sources
PubMed1995

Somatic mutations of the PIG-A gene found in Japanese patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematologic disorder caused by deficient biosynthesis of the glycosylphosphatidylinositol (GPI) anchor. PIG-A, an X-linked gene that participates in the first step of GPI-anchor synthesis, is responsible for PNH. Abnormalities of the PIG-A gene have been demonstrated in all patients with PNH that have been studied to date. In this study, we analyzed 14 Japanese patients with PNH and identified 15 somatic mutations of PIG-A. The mutations included eight single-base changes and seven frame shift mutations. The single-base changes were two nonsense, three missense, and three splice site mutations. The frame shift mutations were four single-base deletions, two single-base insertions, and a replacement of two bases with one. They were all different, except for the same missense mutation being found in two patients. Moreover, these mutations were distributed in various regions of the gene. These results indicated that the mutations occurred at random sites and that there is no mutation hot spot in the PIG-A gene. All the mutations resulted in complete loss of function. Interestingly, the granulocytes in these patients contained variable proportions of mutant cells, suggesting that clonal expansion is not determined solely by mutations but is influenced by another factor(s).

Antigens, CD↗
PubMed1995

Retrievable, replaceable, macroencapsulated pancreatic islet xenografts. Long-term engraftment without immunosuppression.

Prevention of rejection and prolongation of graft survival are critical to achieving successful islet cell transplantation. Various techniques have been utilized to prolong graft survival. Recently, protection of pancreatic islets from host immune mechanisms by isolating the islets in artificial membranes has emerged as an attractive alternative to the use of immunosuppression. In this Rapid Communication, we describe a novel method for macroencapsulation of rat islets in hydrophilic macrobeads made with various combinations of agarose, collagen, and Gelfoam. Encapsulated xenotypic islets were placed intraperitoneally in mice in which diabetes was induced by streptozotocin. The encapsulated xenografts maintained normoglycemia > 170 days. Recipients mice had normal glucose tolerance tests, which indicates that the islets in the macrobeads were functioning as they would in an intact pancreas. Macrobeads retrieved up to 103 days after transplantation showed no evidence of tissue reaction or local inflammation. These retrieved macrobeads could also be retransplanted and replaced. Our studies indicate that the agarose-collagen/Gelfoam macrobeads we have developed serve both to protect islet xenografts from rejection and to provide a microenvironment in which the islets maintain and support their normal function in vivo. Because they may be retrieved after implantation and replaced, these macrobeads may be suitable for human clinical islet cell xenotransplantation.

Animals↗
PubMed1995

Phylogenetic position of Dictyostelium inferred from multiple protein data sets.

The phylogenetic position of Dictyostelium inferred from 18S rRNA data contradicts that from protein data. Protein trees always show the close affinity of Dictyostelium with animals, fungi, and plants, whereas in 18S rRNA trees the branching of Dictyostelium is placed at a position before the massive radiation of protist groups including the divergence of the three kingdoms. To settle this controversial issue and to determine the correct position of Dictyostelium, we inferred the phylogenetic relationship among Dictyostelium and the three kingdoms Animalia, Fungi, and Plantae by a maximum-likelihood method using 19 different protein data sets. It was shown at the significance level of 1 SE that the branching of Dictyostelium antedates the divergence of Animalia and Fungi, and Plantae is an outgroup of the Animalia-Fungi-Dictyostelium clade.

Amino Acid Sequence↗
PubMed1995

Biodegradation of glutaraldehyde-tanned human umbilical vein grafts.

A retrospective analysis of the long-term behavior of 111 glutaraldehyde-tanned human umbilical vein (HUV) grafts implanted between September 1977 and December 1993 was conducted. A total of 81 patients, with a mean age of 68.7 years, received the grafts and were followed up for between 1 and 131 months. The 5-year primary cumulative patency rate for above-knee femoropopliteal bypass was 83.1%, whereas that of other bypasses was 60.9%. An aneurysm of the graft was defined as a physically apparent localized dilatation, with diffuse ectasia being excluded. There were 11 aneurysms found in 9 grafts, 2 of which arose at the factory-made suture lines. The accumulated incidence of aneurysms had reached 21.9% by the 6th year. One aneurysm compressed the graft and resulted in limb-threatening ischemia and another resulted in frank rupture. Moreover, reinforcement of the mesh could not prevent aneurysm development, the repair of which is mandatory due to the risk of rupture and acute thrombosis. The HUV grafts showed an acceptable patency rate in the above-knee location, but the incidence of aneurysm formation after 5 years was abnormally high. Thus, both the risks and benefits of HUV grafts must be taken into account when considering their clinical application.

Adult↗
PubMed1995

Gender differences of disturbed hemostasis related to fasting insulin level in healthy very elderly Japanese aged > or = 75 years.

We investigated the relationship between fasting insulin level and various hemostatic factors, including fibrinolytic factors (active plasminogen activator inhibitor-1 (PAI-1), tissue type plasminogen activator (tPA)-PAI-1 complex, plasmin-alpha 2-plasmin inhibitor (PIC), and D-dimer), coagulation factors (activated factor VII, factor VII coagulant activity and antigen, factor VIII, factor X, and fibrinogen), coagulation inhibitors (antithrombin III, heparin cofactor II, and protein C), and an acute phase marker (sialic acid) in 102 healthy individuals aged > or = 75 years (46 men and 56 women). Active PAI-1 levels had a significant negative correlation with PIC levels (r = -0.342, P = 0.0006), indicating that PAI-1 influences in vivo fibrinolytic activity in the very elderly. Gender differences were found in the relationship between insulin and hemostatic abnormalities, with the insulin level being positively correlated with coagulation factors in men (factor VIII activity: r = 0.422, P < 0.01; factor VII activity: r = 0.386, P < 0.01) and with hypofibrinolysis in women (active PAI-1: r = 0.549, P < 0.0001). Insulin levels were positively correlated with the levels of factor VII antigen and factor VII activity in men (P < 0.01), but there was no correlation with activated factor VII levels. The fasting insulin level was also correlated with the levels of heparin cofactor II and sialic acid in men (P < 0.05). However, other hemostatic factors were not related to the insulin level in either sex.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Identification of rat urinary kinin as bradykinin.

Bradykinin (BK)-like activity, which was detected by BK-enzyme-immunoassay, was purified from 80 ml of ureter urine of Sprague-Dawley rats by Sephadex G 25 chromatography, FPLC, and reversed phase HPLC. The purified kinin fraction showed the same retention time as authentic BK on HPLC and produced contraction of isolated rat uterus, the contraction being suppressed by a B2-antagonist Hoe140. There was no other kinin detected on the HPLC at the corresponding retention time to kallidin, arginyl-BK or T-kinin. The peptide showed an amino acid sequence identical to that of BK by amino acid sequence analysis.

Amino Acid Sequence↗
PubMed1995

Intensive insulin therapy prevents the progression of diabetic microvascular complications in Japanese patients with non-insulin-dependent diabetes mellitus: a randomized prospective 6-year study.

To examine whether intensive glycemic control could decrease the frequency or severity of diabetic microvascular complications, we performed a prospective study of Japanese patients with non-insulin-dependent diabetes mellitus (NIDDM) treated with multiple insulin injection treatment. A total of 110 patients with NIDDM was randomly assigned to multiple insulin injection treatment group (MIT group) or to conventional insulin injection treatment group (CIT group). Fifty-five NIDDM patients who showed no retinopathy and urinary albumin excretions < 30 mg/24 h at the baseline were evaluated in the primary-prevention cohort, and the other 55 NIDDM patients who showed simple retinopathy and urinary albumin excretions < 300 mg/24 h were evaluated in the secondary-intervention cohort. The appearance and the progression of retinopathy, nephropathy and neuropathy were evaluated every 6 months over a 6-year period. The worsening of complications in this study was defined as an increase of 2 or more steps in the 19 stages of the modified ETDRS interim scale for retinopathy and an increase of one or more steps in 3 stages (normoalbuminuria, microalbuminuria and albuminuria) for nephropathy. The cumulative percentages of the development and the progression in retinopathy after 6 years were 7.7% for the MIT group and 32.0% for the CIT group in the primary-prevention cohort (P = 0.039), and 19.2% for MIT group and 44.0% for CIT group in the secondary-intervention cohort (P = 0.049). The cumulative percentages of the development and the progression in nephropathy after 6 years were 7.7% for the MIT group and 28.0% for the CIT group in the primary-prevention cohort (P = 0.032), and 11.5% and 32.0%, respectively, for the MIT and CIT groups in the secondary-intervention cohort (P = 0.044). In neurological tests after 6 years, MIT group showed significant improvement in the nerve conduction velocities, while the CIT group showed significant deterioration in the median nerve conduction velocities and vibration threshold. Although both postural hypotension and the coefficient of variation of R-R interval tended to improve in the MIT group, they deteriorated in the CIT group. In conclusion, intensive glycemic control by multiple insulin injection therapy can delay the onset and the progression of diabetic retinopathy, nephropathy and neuropathy in Japanese patients with NIDDM. From this study, the glycemic threshold to prevent the onset and the progression of diabetic microangiopathy is indicated as follows; HbA1c < 6.5%, FBG < 110 mg/dl, and 2-h post-prandial blood glucose concentration < 180 mg/dl.

Albuminuria↗
PubMed1995

The reeler gene-associated antigen on Cajal-Retzius neurons is a crucial molecule for laminar organization of cortical neurons.

In the neurological mutant mouse reeler, the histological organization of the neocortex develops abnormally and essentially results in an inversion of the relative positions of the cortical layers. The reeler mutation, therefore, provides an insight into the molecular mechanisms underlying the formation of the cortical layers. We have generated a monoclonal antibody (CR-50) that probes a distinct allelic antigen present in wild-type but not in reeler mutant mice. CR-50 reacted specifically with Cajal-Retzius neurons, one of the first cortical neurons to differentiate in the neocortex, but whose functional role is not known. When dissociated cerebral cortical cells were incubated with CR-50 in reaggregation culture, the genotype-dependent histogenetic assembly of wild-type cortical cells resembled that of reeler mutants. These findings revealed that the selective expression of a distinct molecule on Cajal-Retzius neurons is critical for the normal lamination of cortical neurons in the mammalian neocortex.

Animals↗
PubMed1995

Structures of cDNAs encoding the muscle-type and non-muscle-type isozymes of lamprey fructose bisphosphate aldolases and the evolution of aldolase genes.

Nearly full-length cDNA clones for muscle-type and non-muscle-type aldolase mRNAs were cloned from lambda gt10 cDNA libraries constructed from skeletal muscle and liver mRNAs of lamprey (Entosphenus japonicus). The cDNA-M8 has 2,240 bp carrying an open reading frame of 1,089 bp which encodes 362 amino acids without the amino terminal methionine, while the cDNA-L3 is 1,761 bp in length and has an open reading frame of 1,092 bp, which encodes 363 amino acids without the methionine. We designated the cDNA clones M8 and L3 as the muscle-type and non-muscle-type aldolase cDNAs, respectively. The entire amino acid sequences deduced from cDNA-M8 and -L3 show a high degree of identity to one another (76%) and also to vertebrate aldolases A (74-76%), B (68-70%), and C (71-76%) and Drosophila melanogaster aldolases alpha, beta, and gamma (66-67%). Northern blot analyses using the 3'-noncoding sequences of cDNA-M8 and -L3 as hybridization probes indicated that the muscle-type mRNA is expressed mainly in the skeletal muscle, heart muscle, brain, and some other tissues, but probably not in liver, while the non-muscle-type mRNA is expressed mainly in the liver and also in brain and other tissues, except for the heart muscle. Phylogenetic analyses showed that both muscle-type and non-muscle-type aldolases of lamprey resemble one another and might share a common ancestor with vertebrate aldolases A and C, but they are not direct ancestors of vertebrate aldolases.

Amino Acid Sequence↗
PubMed1995

Chemical cross-linking of activated coagulation factor VII with soluble tissue factor: calcium ions are not essential for full amidolytic activity of the factor VIIa-tissue factor complex after complex formation.

In the previous study involving a yeast expression system, a high molecular mass extracellular domain of human tissue factor (denoted as sTF alpha) with a high content of mannose residues was produced in abundance and 37 kDa sTF beta was obtained in a low yield [Shigematsu et al. (1992) J. Biol. Chem. 267, 21329-21337]. To obtain sTF beta in a high yield, we constructed four kinds of mutant sTF with partial or total replacement of the N-potential glycosylation Asn residues with Ala, and expressed them in yeast. We found that the yield of the beta form of the Asn137-to-Ala mutant (designated as sTF beta NNA) was threefold higher (3 mg/liter) than that of the wild type, suggesting that the replacement of one of the three potential N-glycosylation Asn residues with Ala could be a good way to minimize the addition of mannose repeats. Since it has been reported that calcium ions are required for the effective hydrolysis of peptidyl substrates by the factor VIIa-sTF complex, it is believed to be essential for the expression of full protease activity. Here, we report the enzymatic characterization of a factor VIIa-sTF beta NNA complex cross-linked with a homobifunctional reagent, bis(sulfosuccinimidyl) suberate. The factor VIIa-sTF beta NNA complex cross-linked in the presence of 5 mM calcium ions or 50 mM EDTA was purified. The cross-linked complex did not show factor X activation in the presence of phospholipids. However, it showed essentially the same activity toward peptidyl substrates as before cross-linking, even in the presence of EDTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amides↗
PubMed1995

Functional constraints against variations on molecules from the tissue level: slowly evolving brain-specific genes demonstrated by protein kinase and immunoglobulin supergene families.

In the protein kinase family, the basic function of kinase domain is similar among members. According to the standard view of functional constraint, the molecular evolutionary rate depends on functional and structural features characteristic of individual molecules (local constraint). Thus the evolutionary rate of the kinase domain is expected to be similar for different members. Contrary to this expectation, a comparison of the evolutionary rates revealed a wide difference among members; it amounts to about 100 times difference between the maximum and minimum rates. A similar result was also found in members of the immunoglobulin (Ig) family. In addition, significant correlations in evolutionary rate were observed between the kinase domain and the Ig-like domain in the receptor protein tyrosine kinases and between the kinase domain and the SH domain in the nonreceptor-type kinases. Furthermore, the evolutionary rates of family members that are expressed tissue specifically differ widely, depending on their tissue distribution: members expressed in the brain evolve with significantly slower rates than those expressed in the immune system. These results strongly suggest the presence of an alternative constraint (global constraint) against changes on molecules derived from higher levels like tissues or organs.

Animals↗
PubMed1995

Pathogenesis of dialysis-related amyloidosis.

Beta 2-microglobulin has been demonstrated to be a major constituent of amyloid fibrils in dialysis-related amyloidosis. However, the molecular pathogenesis of this complication remains unknown. Several lines of evidence suggest that beta 2-microglobulin is not an innocent bystander, but plays an active role in the development of dialysis-related amyloidosis. The evidence remains inconclusive, however, as to whether it is intact or modified beta 2-microglobulin which is amyloidogenic and contributes to bone and joint destruction. Recent biochemical and immunohistological studies have revealed a new modification of beta 2-microglobulin in amyloid fibrils, the advanced glycation end products formed nonenzymatically between aldoses and proteins. Further study has suggested that the interaction of advanced glycation end product-modified beta 2-microglobulin with monocytes/macrophages gives a plausible, albeit incomplete, explanation for the mechanism of bone and joint destruction in dialysis-related amyloidosis. This review focuses on new aspects of the pathogenesis of dialysis-related amyloidosis.

Amyloid beta-Peptides↗
PubMed1995

A point mutation (Arg271-->Cys) of a homozygote for dysfunctional prothrombin, prothrombin Obihiro, which has a region of high sequence variability.

The molecular defect of a congenitally dysfunctional form of prothrombin, prothrombin Obihiro, was identified in a patient with a severe bleeding tendency. He showed reduced fibrinogen clotting activity, despite a normal prothrombin antigen level. Nucleotide sequencing of amplified DNA revealed a C-->T change at nucleotide 7311 of exon VIII of the prothrombin gene. This resulted in the substitution of Arg271 by Cys at the factor Xa cleavage site which precludes normal activation of prothrombin Obihiro by factor Xa and the generation of thrombin. The proband was homozygous for this mutation. In addition, seven new nucleotide changes were identified in the prothrombin gene of this patient by comparison with the published gene sequence. Three polymorphisms at nucleotides 4291, 4298 and 7223 were exclusively identified in the prothrombin gene from Japanese. Particularly in the region containing exon VI and introns E and F (nucleotides 4048-4303), the prothrombin gene proved to be of high-sequence variability.

Base Sequence↗