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Biomedical subjects

J Hashimoto

Publications and source records attributed to J Hashimoto.

108 records · Page 6Linked to original sources
PubMed1977

Importance of 5'-terminal blocking structure to stabilize mRNA in eukaryotic protein synthesis.

The 7-methylguanylic acid residue confronting the 5'-terminal nucleotide of mRNA through two pyrophosphate linkages was completely removed by tobacco pyrophosphatase from mRNAs of cytoplasmic polyhedrosis virus, tobacco mosaic virus (viral RNA), and globin without any scission in the inner part of the RNA chain. Protein synthesis ability in a wheat germ cell-free system was lost after this treatment of all three kinds of mRNA. The initiation complexes for protein synthesis of these three RNAs were not obtained after using tobacco phosphodiesterase-treated mRNA. On incubation of mRNA in a wheat germ extract, the mRNA lacking m7G was quickly degraded from the 5' terminus in an exonucleolytic way, whereas the intact mRNA remained stable. These results show that one of the confronting nucleotide structure's functions is to stabilize the mRNA, to prevent its degradation.

Animals↗
PubMed1977

Chemical modifications of ribonuclease U1.

In order to obtain information on the nature of the amino acid residues involved in the activity of ribonuclease U1 [EC 3.1.4.8], various chemical modifications of the enzyme were carried out. RNase U1 was inactivated by reaction with iodoacetate at pH 5.5 with concomitant incorporation of 1 carboxymethyl group per molecule of the enzyme. The residue specifically modified by iodoacetate was identified as one of the glutamic acid residues, as in the case of RNase T1. The enzyme was also inactivated extensively by reaction with iodoacetamide at pH 8.0 with the loss of about one residue each of histidine and lysine. When RNase U1 was treated with a large excess of phenylglyoxal, the enzymatic activity and binding ability toward 3'-GMP were lost, with simultaneous modification of about 1 residue of arginine. The reaction of citraconic anhydride with RNase U1 led to the loss of enzymatic activity and modification of about 1 residue of lysine. The inactivated enzyme, however, retained binding ability toward 3'-GMP. These results indicate that there are marked similarities in the active sites of RNases T1 and U1.

Amino Acids↗
PubMedDate not supplied

Comparison of nonradioactive cDNA probes for detection of potato spindle tuber viroid by dot-blot hybridization assay.

Six nonradioactive cDNA probes were compared for their sensitivities for detecting potato spindle tuber viroid (PSTVd) by dot-blot hybridization assay. Three biotinylated PSTVd cDNA probes, labeled by photoactivation with photobiotin, by nick translation or by random priming with biotinylated deoxyribonucleotides, were all capable of detecting 20 pg of purified PSTVd by a colorimetric assay and 2-20 pg by a chemiluminescent assay. Digoxigenin-labeled probe was able to detect 200 pg of purified PSTVd. Two biotinylated probes prepared with polymerase chain reaction (PCR) incorporating biotinylated dUTP or dATP were the most sensitive: 0.2-2 pg of PSTVd was detectable by both assays. All six probes could detect PSTVd also in extracts of infected tomato leaves at a dilution of up to 1/250-1/1250. These nonradioactive probes are equal to radioactive probes in their sensitivity, and the biotinylated probes produced with PCR amplification are particularly suitable for practical diagnosis, as they are sensitive and rapidly prepared in large quantities.

Base Sequence↗
PubMedDate not supplied

Meniscal repair using fibrin sealant and endothelial cell growth factor. An experimental study in dogs.

The effect of fibrin sealant and endothelial cell growth factor on the healing of defects of the avascular portion of canine menisci was investigated in 30 menisci of 15 adult mongrel dogs. The defects were treated in one of three ways: Group 1, the defect was left empty; Group 2, the defect was filled with fibrin sealant; and Group 3, the defect was filled with fibrin sealant and endothelial cell growth factor. The healing process was evaluated macroscopically and histologically at intervals of 1, 2, 6, 12, and 24 weeks. The average percentage of each defect that was filled with connective tissue was 5% in Group 1, 76.6% in Group 2, and 89.4% in Group 3. In the early phase of this repair, the extrinsic pannus-like tissue that contained many capillary vessels extended from the meniscosynovial junction into the defect. Subsequently, organized fibrous connective tissue was formed, which had changed to cartilaginous tissue at 12 to 24 weeks. The combination of fibrin sealant and endothelial cell growth factor enhanced the neovascularization and formation of granulation tissue, which accounted for the increased healing level in the avascular portion of the meniscus.

Animals↗
PubMedDate not supplied

The microvasculature of the sesamoid complex: its clinical significance.

The microvascular anatomy of the sesamoid complex was investigated in 15 cadaver specimens using histology and tissue clearing (Spalteholz) techniques. It was found that both sesamoids appeared equally well vascularized and the vascular supply to each sesamoid originated from two major sources (proximal and plantar) and one minor source (distal). Proximally, vessels originating from the first plantar metatarsal artery enter the sesamoid at its attachment to the flexor hallucis brevis. In addition, vessels enter the plantar surface of the sesamoid near the midline and arborize throughout the bone, anastamosing with the proximal vessels. The distal vascular supply to the sesamoids originates from its distal capsular attachment and appears to contribute minimally to the overall vascular scheme. The lateral attachments of the sesamoids to the plantar plate and joint capsule were relatively avascular. In two bipartite specimens examined, the major blood supply originated from the proximal and distal poles of the sesamoid. No vessels were observed entering the plantar surface of these specimens. The results of this study suggest that injury to the proximal or plantar aspects of the sesamoids could disrupt the vascular supply to these bones. These areas should, therefore, be avoided during the surgical approach to the sesamoids.

Hallux↗
PubMedDate not supplied

Scanning electron microscopic study on the shape of infertile seminiferous tubules: a hypothesis of pathogenesis of idiopathic male infertility.

The shape of infertile seminiferous tubules was studied on testicular biopsied specimens from patients with idiopathic male infertility using the scanning electron microscope. A parallel study of the same sections was performed by ordinary light microscopy. Normal seminiferous tubules were revealed to be shaped like a weaving cylinder, whereas infertile seminiferous tubules were strangulated in various places, or appeared similar to a tail-like rope which became gradually more slender. These strangulated or slender parts of tubules seemed to correspond to the smaller tubules with thickened tubular walls that were recognized under the light microscope. It is suggested that these thickened tubular walls suppress spermatogenesis by a nutritional disturbance, and the strangulations of infertile tubules interfere with sperm transport by tubular blockage or germinal disorganization and interrupted contractions of the tubules.

Adult↗