Search PubMed⌕ Search

Biomedical subjects

A Shinohara

Publications and source records attributed to A Shinohara.

At least 91 records · Page 5Linked to original sources
PubMed1995

RAD51 homologues in Xenopus laevis: two distinct genes are highly expressed in ovary and testis.

The RAD51 gene is a eukaryotic counterpart of the Escherichia coli recA gene which is involved in genetic recombination. Two distinct Xenopus laevis RAD51 cDNA clones (XRAD51.1 and XRAD51.2) were isolated from an oocyte cDNA library using the human RAD51 cDNA (HsRAD51) as a probe. Sequence analysis revealed that 98.2% of the amino-acid residues were identical between XRAD51.1 and XRAD51.2, and that both were 95% identical to HsRAD51. Both of the XRAD51 genes were expressed at a higher level in ovary and testis than in other somatic tissues, suggesting their involvement in meiotic recombination. The expression of XRAD51.1 was about eightfold in excess of that of XRAD51.2 in all of the tissues examined. Analysis of the rates of synonymous substitution in the coding sequences of the two XRAD51 suggests that these two genes diverged about 50 million years ago. The structural similarities of the XRAD51 proteins to RecA in E. coli and Rad51 in yeasts or vertebrates are discussed.

Amino Acid Sequence↗
PubMed1995

Localization of RecA-like recombination proteins on chromosomes of the lily at various meiotic stages.

The Rad51 and Lim15 proteins of lily, which are homologs of the bacterial RecA protein, were found on chromosomes in various stages of meiotic prophase 1. The presence of both Rad51 and Lim15 proteins as discrete foci on leptotene and zygotene chromosomes and their colocalization suggest that meiotic recombination begins at the leptotene stage with the cooperation of these proteins and continues in zygotene. Localization of the foci on or adjacent to the chromosomes suggests that these proteins bind to the chromatin loops that extend from the axial cores. The proteins in these foci may participate in the searching and pairing of homologous DNA sequences, as the RecA protein does. The different pattern of localization of the Rad51 protein between the leptotene and pachytene stages and the absence of the Lim15 protein in the pachytene stage suggest that the Rad51 protein plays different roles in these stages.

Amino Acid Sequence↗
PubMed1995

A species-specific interaction of rad51 and rad52 proteins in eukaryotes.

The structures and properties of the Rad51 and Rad52 proteins in eukaryotes are described. Both proteins form a complex and are responsible for recombination and repair reactions. The N-terminal region of the Rad51 protein interacts with the C-terminal region of the Rad52 protein. Species-specific interaction is probably essential for the functioning of these genes.

Animals↗
PubMed1995

Homologous recombination and the roles of double-strand breaks.

Double-strand breaks (DSBs) and single-strand gaps in damaged DNA are efficiently repaired by mechanisms associated with recombination. Recombination is a series of complex biochemical reactions, requiring at least 20 gene products, even in Escherichia coli. Genes homologous to bacterial and yeast recombination genes have been cloned in higher eukaryotes, suggesting there might be a common fundamental mechanism of recombination among a wide variety of species. In eukaryotes, protein-protein interactions play important roles in recombination: by interacting with a specific protein(s), the complex involved in repair of DSBs is modified to carry out specialized cellular functions, such as meiotic recombination and switching of mating types in yeast.

Animals↗
PubMed1995

Dichotic listening in patients with partial section of the corpus callosum.

Patients with a complete section of the corpus callosum have been observed to exhibit strong left-ear suppression when different speech stimuli are presented to both ears simultaneously (so-called dichotic listening). Data concerning the locus of corpus callosum damage that causes strong left-ear suppression remains scanty. In the present investigation, a consonant-vowel syllable dichotic listening test was given to five right-handed patients with partial sections of the corpus callosum, which were located using MRI and accurately defined measurement procedures. The following two measurement methods were used: (i) the genu-splenium (G-S) method, in which a lesion was localized in the anteroposterior dimension relative to the total length of the corpus callosum, defined as the distance between the most anterior point of the genu to the most posterior point of the splenium; and (ii) the rostrum-splenium (R-S) method, which takes into account the curvature of the corpus callosum, and in which a lesion was localized relative to the total length of the corpus callosum, defined as the length of the curved line from the tip of the rostrum to the end of the splenium. Results were compared with scores from 50 normal control subjects. Strong left-ear suppression was observed in two patients, who had surgical sections of the posterior 15.5-18.5% of the corpus callosum as measured with the G-S method, or the posterior 20-24% of the corpus callosum as measured with the R-S method. The suppression phenomenon persisted for more than 10 years post-surgery. On the other hand, the remaining three patients, who had lesions anterior to the posterior 17-28% of the corpus callosum as measured with the G-S method or 20-33% as measured with the R-S method exhibited no left-ear extinction. Despite the common assumption that damage to the posterior part of the trunk of the corpus callosum causes strong left-ear suppression, the results from the G-S method indicated that damage to the splenium defined as the posterior one-fifth of the segment between the anterior-most and posterior-most points of the corpus callosum, cause strong left-ear suppression. By the R-S method, results showed that damage to the splenium (the posterior one-fifth of the curvature of the corpus callosum) and possibly the part extending to the most posterior part of the trunk (the posterior one-quarter of the curvature) causes strong left-ear suppression.

Adult↗
PubMed1995

[Initial and short-term results of percutaneous transluminal coronary angioplasty in patients over 70 years old: recent improvements in effectiveness].

Elderly patients have a higher incidence of procedure-related complications and recurrent angina after percutaneous transluminal coronary angioplasty (PTCA). However, early success rates seem to have improved. To determine whether outcome of PTCA in the elderly has changed recently, we compared initial results and short-term outcome in patients over 70 years old in two groups; 64 patients with 70 PTCA lesions who underwent first elective PTCA in 1982-1989 (early group) and 140 patients with 153 PTCA lesions in 1990-1993 (late group). The mean age of the late group was significantly older than that of the early group (74 +/- 3 vs 73 +/- 2 years, p < 0.01). The two groups had similar clinical characteristics including sex, prior myocardial infarction and multivessel disease. The overall success rate of PTCA was significantly higher in the late group than in the early group (92.8% vs 82.8%, p < 0.05). The rate of abrupt closure was similar in the two groups (2.9% vs 2.6%). Major complications (procedural myocardial infarction, emergency bypass surgery, hospital death) occurred in 4.7% of the early group and in 3.6% of the late group. Angiographic restenosis occurred in 41.5% of the early group and in 33.6% of the late group. Cardiac events (cardiac death and/or myocardial infarction) occurred in 6.6% of the early group and in 1.5% of the late group (p = 0.06). The initial success rate of PTCA has improved in the elderly as well as younger patients (< 70; 92.8% vs 91.6%). We conclude that PTCA can be performed with high initial success and satisfactory short-term outcome in patients over 70 years old.

Aged↗
PubMed1995

BONSAI Garden: parallel knowledge discovery system for amino acid sequences.

We have developed a machine discovery system BONSAI which receives positive and negative examples as inputs and produces as a hypothesis a pair of a decision tree over regular patterns and an alphabet indexing. This system has succeeded in discovering reasonable knowledge on transmembrane domain sequences and signal peptide sequences by computer experiments. However, when several kinds of sequences are mixed in the data, it does not seem reasonable for a single BONSAI system to find a hypothesis of a reasonably small size with high accuracy. For this purpose, we have designed a system BONSAI Garden, in which several BONSAI's and a program called Gardener run over a network in parallel, to partition the data into some number of classes together with hypotheses explaining these classes accurately.

Algorithms↗
PubMed1995

[Structure and function of RAD51 gene in eukaryote].

RAD51 gene of S. cerevisiae is involved in DNA repair of double-strand breaks, mitotic and meiotic recombination. Rad51 protein is structurally similar to bacterial RecA proteins, which play crucial roles in recombination and DNA repair. Like RecA, Rad51 protein forms nucleofilament with a right handed helical structure, in which the DNA is extended 1.5 times than B-form DNA. Structural homologs have been cloned from various organisms including human and mouse. These results suggest that Rad51 is an essential recombination protein conserved from yeasts to human. Different from RecA, Rad51 protein requires at least an another protein, Rad52, to carry out recombination through the interaction between them.

Animals↗
PubMed1994

Comparative study of methods for determining lanthanide elements in biological materials by using NAA, HPLC postcolumn reaction, and ICP-MS.

Mice were injected intravenously with one of the following elements: Y, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, or Yb, at a dose of 25 mg/kg body wt. After 20 h, the various organs were taken out, and the element concentrations were determined by NAA, HPLC postcolumn reaction, or ICP-MS. The results by these three methods were within the acceptable range. About 85% of the amount administered of each element was found in liver, lung, and spleen.

Animals↗
PubMed1994

[Analysis of trace elements in biological materials by microwave induced plasma-mass spectrometry].

Analytical conditions have been established for determination of trace elements in biological materials by microwave induced plasma-mass spectrometry (MIP-MS). Possible elemental contaminants were checked in the water and reagents used, and during the wet-ashing process. Among 72 elements tested, contamination by Na, Mg, K, Ca, Fe, Ba, and Pb were observed. This contamination was estimated to occur mainly during the process of preparing samples due to the water, reagents and surroundings. Contamination by Ca, Mg, Zn and Pb from tubes for storage was also observed. Adequate conditions for multielement analyses in plasma and bone samples were evaluated. Both plasma and bone samples were digested by the wet-ashing technique before applying MIP-MS. The recovery rates of elements added were decreased depending on the contents of plasma or bone samples in the measuring solutions. The interfering effects of matrix modification due to organs were improved by correction with an internal standard. Recovery rates of elements added, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn, Ba, Pb and fourteen lanthanide elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were within 100 +/- 5% in analytical samples containing 1% volume of human plasma when Ga or Tl was used as the internal standard. Recoveries of Sn and Zn in the bone samples containing 0.1% bone as the original bone material, however, were 100 +/- 10% even after correction by the internal standard, suggesting the necessity of combined use of standard addition methods. The concentrations of V, Cr, Mn, Fe, Cu, Zn, Rb, Sr, Mg, and Ca in plasma from two healthy women were determined by MIP-MS. The data were consistent with the values reported elsewhere, and agreed very closely with those obtained by atomic absorption spectrometry. The accuracy of the values obtained by this method was confirmed using standard reference materials. These results indicate that MIP-MS is a useful method for multielement determination of biological materials.

Animals↗
PubMed1993

A chicken RAD51 homologue is expressed at high levels in lymphoid and reproductive organs.

Comparisons of the amino acid sequences of three yeast RecA-like proteins, Rad51 and DMC1 from S.cerevisiae and Rad51 from S.pombe, revealed several highly conserved regions. Degenerated oligonucleotides encoding two of these regions were used for the polymerase chain reaction to clone a chicken RecA-like gene. The encoded protein shares 68% and 49% identical amino acids with the Rad51 and DMC1 proteins. The strong sequence conservation between the yeast and chicken genes indicates that RecA homologues are conserved throughout evolution from prokaryotes to higher eukaryotes. High expression of the chicken Rad51 gene was found within the organs of lymphoid and germ cell development suggesting its involvement in lymphoid and meiotic recombination.

Amino Acid Sequence↗
PubMed1993

Similarity of the yeast RAD51 filament to the bacterial RecA filament.

The RAD51 protein functions in the processes of DNA repair and in mitotic and meiotic genetic recombination in the yeast Saccharomyces cerevisiae. The protein has adenosine triphosphate-dependent DNA binding activities similar to those of the Escherichia coli RecA protein, and the two proteins have 30 percent sequence homology. RAD51 polymerized on double-stranded DNA to form a helical filament nearly identical in low-resolution, three-dimensional structure to that formed by RecA. Like RecA, RAD51 also appears to force DNA into a conformation of approximately a 5.1-angstrom rise per base pair and 18.6 base pairs per turn. As in other protein families, its structural conservation appears to be stronger than its sequence conservation. Both the structure of the protein polymer formed by RecA and the DNA conformation induced by RecA appear to be general properties of a class of recombination proteins found in prokaryotes as well as eukaryotes.

Adenosine Triphosphate↗
PubMed1993

Intrusion of an incisor tooth into the contralateral frontal sinus following trauma.

Although intrusions of glass fragments into the frontal sinuses are not uncommon in traffic accidents, a case with a tooth in the frontal sinus has never been reported. We report a patient with traumatic inclusion of an incisor tooth in the contralateral frontal sinus. Radiographic investigations demonstrated the tooth in the frontal sinus though no skin damage was recognized on the upper face. The usefulness of CT scan in localizing the missing tooth after facial trauma and its route of entry into the contralateral frontal sinus is discussed.

Accidents, Traffic↗
PubMed1993

Cloning of human, mouse and fission yeast recombination genes homologous to RAD51 and recA.

Rad51, of Saccharomyces cerevisiae, is a homologue of recA of Escherichia coli and plays crucial roles in both mitotic and meiotic recombination and in repair of double-strand breaks of DNA. We have cloned genes from human, mouse and fission yeast that are homologous to rad51. The 339 amino acid proteins predicted for the two mammalian genes are almost identical and are highly homologous (83%) with the yeast proteins. The mouse gene is transcribed at a high level in thymus, spleen, testis and ovary and at a lower level in brain and other tissues. The rad51 homologues fail to complement the DNA repair defect of rad51 mutants of S. cerevisiae. The mouse gene is located in the F1 region of chromosome 2 and the human gene maps to chromosome 15.

Amino Acid Sequence↗
PubMed1993

Catheter ablation therapy in a case with WPW syndrome complicated by multiple tachyarrhythmias.

WPW syndrome is of importance because of the frequent association of tachyarrhythmias. However, its complication by 3 or more different tachyarrhythmias simultaneously is rare. This paper reports a case of WPW syndrome complicated by paroxysmal atrial fibrillation, atrial flutter, and 2 types of atrioventricular reentrant tachycardia. The tachyarrhythmias could be cured by cauterizing the accessory pathway using catheter ablation with radiofrequency electric current. A 30-year-old man visited to a local physician with an episode of tachycardia which failed to resolve, and a diagnosis of WPW syndrome associated with paroxysmal atrial fibrillation was made. The patient was referred to our hospital for further examination and treatment, and electrophysiological study was performed. During the examination, 2 types of atrioventricular reentrant tachycardia with different heart rates were induced, as well as atrial fibrillation and 2:1 atrial flutter. The presence of a left-sided accessory atrioventricular pathway was confirmed by coronary sinus mapping, and the following day catheter ablation was performed and the accessory pathway was cauterized. Subsequently, the delta wave disappeared from the ECG and no additional episodes of tachycardia occurred. Catheter ablation is still undergoing research as a therapeutic modality. However, because the ablation technique entails little invasion or risk, and is economical, it may well become a mainstream treatment for tachycardia in patients with WPW syndrome in the future.

Adult↗
PubMed1992

Functional structures of the recA protein found by chimera analysis.

We developed a novel genetic method for finding functional regions of a protein by the analysis of chimeras formed between homologous proteins. Sets of chimeric genes were made by intramolecular homologous recombination in a linearized plasmid DNA carrying both recA genes of Escherichia coli and Pseudomonas aeruginosa. A recBCsbcA strain of E. coli was used for isolation of plasmids carrying recombinants between these genes. Examination of properties of E. coli strains deleting the recA gene and carrying a plasmid with a chimeric gene shows that chimera formation at certain positions inactivates a RecA function. Frequently, all chimeras with a junction in a certain region of the protein inactivate a function. Rather than a direct effect of the presence of the junction at a particular position, mismatching of the regions both sides of the junction that are derived from the different species is responsible for the inactivation. For a chimeric protein to be functional, certain pairs of sequences in different regions of the protein must derive from the same parent. Four pairs of such sequences were found: two are involved in activities for genetic recombination and for resistance to ultraviolet light irradiation and the others in formation of active oligomers. Regions defined by these sequences are located in the looped regions of the protein. A pair of regions may co-operate to form a functional folded structure.

Amino Acid Sequence↗