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Biomedical subjects

M Komiyama

Publications and source records attributed to M Komiyama.

At least 163 records · Page 9Linked to original sources
PubMed1993

Molecular design of artificial hydrolytic nucleases and ribonucleases.

Artificial nucleases and ribonucleases, which selectively hydrolyze the specific phosphodiester linkages in DNAs and RNAs, are prepared by the attachment of organic and inorganic catalysts to DNA oligomers as sequence-recognizing moieties. A hybrid of ethylenediamine and a 19-mer DNA selectively hydrolyzes tRNA(Phe) at the 3'-side of C63. Site-selective hydrolysis of DNAs has been accomplished by the lanthanide complexes bound to DNA oligomers. No concurrent oxidative cleavage of the ribose or the deoxyribose takes place.

Base Sequence↗
PubMed1993

[Surgical treatment of ruptured dissecting aneurysms: proximal clipping vs trapping].

The best surgical treatment for ruptured dissecting aneurysms of the vertebral artery is still controversial. Four patients (1 male, 3 female), age ranging from 43 to 62, were operated upon in our department during the last 6 years. Duration from rupture to the operation was 0 to 4 days. In 2 cases, proximal clipping was the primary treatment, while 2 had a trapping. Antiplatelet agents were given to prevent vasospasm in all cases postoperatively. In proximal clipping cases, one patient had suffered from fatal rerupture on the sixth postoperative day. In trapping cases, Wallenberg syndrome developed in one patient. These results suggest that a proximal clipping may not allow the treatment for the vasospasm because of the danger of rebleeding and also a trapped segment of vertebral artery should be as short as possible to avoid compromised perforators.

Adult↗
PubMed1993

[Hemorrhagic vascular lesions in facial injuries treated by intravascular embolization: report of two cases].

We have encountered 2 cases of hemorrhagic vascular lesion in the external carotid artery system caused by facial injury. In case 1, treatment of epistaxis by nasal packing was unsuccessful. Good result was obtained by intravascular embolization in the internal maxillary artery using polyvinyl alcohol particles and gelatin sponge pieces. In case 2, massive subgaleal hemorrhage due to tearing of the middle meningeal artery caused by a skull base fracture appeared following surgery for open skull fracture. Hemostasis was performed successfully by intravascular embolization in the middle meningeal artery using microcoils and gelatin sponge pieces. In cases of facial injuries with hemorrhagic lesions in the external carotid artery system, hemostasis is generally difficult. Referring to these two cases, we think that the treatment of choice is angiography followed by intravascular embolization.

Adult↗
PubMed1993

[Neurological deterioration induced by giant intracranial aneurysms even though these aneurysms had not ruptured; mural hemorrhage and intraluminal thrombosis].

The authors report two cases of intracranial giant aneurysms inducing acute neurological deterioration even though rupture of the aneurysms had not occurred. Neurological aggravation was attributable to the acute swelling of the aneurysmal mass after intramural hemorrhage in one case, and the formation of rapid and massive intraluminal thrombosis in another case. MRI confirmed these mechanisms in both cases. MRI is very useful for demonstrating mural and intraluminal pathologies involving giant aneurysms.

Aneurysm, Ruptured↗
PubMed1993

[MR findings in traumatic cerebrospinal fluid leakage with special reference to indications of the need for dural repair].

Eleven cases of traumatic cerebrospinal fluid (CSF) leakage (8 cases of rhinorrhea and 3 cases of otorrhea) were reviewed to discuss magnetic resonance (MR) findings and surgical indications of the need for dural repair. Five patients had delayed onset of CSF rhinorrhea, 12 to 66 days (mean 28 days) after the trauma, and in the remaining 6 patients (3 rhinorrhea and 3 otorrhea) CSF leakage was noted on admission. MR study was carried out within 7 days after the onset of CSF leakage using a 0.5 tesla imager. In 7 cases of rhinorrhea, MR images demonstrated brain herniation into the ethmoid or frontal sinuses and the dural defects were repaired with the vascularized periosteum flap taken from the frontal bone or the fascia lata. In the operations, brain parenchyma was found to be plugged into the fracture line as MR images showed, and also to adhere to the margin of dural fistula. In the remaining 4 patients (without the MR findings of brain herniation into the paranasal sinuses) spontaneous cessation of CSF leakage occurred and their clinical course was good. Spontaneous cessation of CSF leakage in these cases may suggest the complete healing of the lacerated dura. However, in cases with the brain herniated into the paranasal sinuses CSF leakage may not be observed, and natural healing of the dural defect cannot be expected. Therefore, such brain herniation indicates the absolute need for dural repair even if CSF leakage is not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Spatial relationship of nebulin relative to other myofibrillar proteins during myogenesis in embryonic chick skeletal muscle cells in vitro.

The developmental expression of nebulin was studied in embryonic chick skeletal muscle cells in vitro by means of immunofluorescence microscopy. Initially nebulin appeared homogeneously or in a punctate form in the cytoplasm, and then it was assembled into I-Z-I-like complexes containing actin and alpha-actinin but not myosin and connectin (titin). Striated patterns of nebulin ('singlets') in myofibrils appeared simultaneously with those of alpha-actinin (Z-bands), myosin (A-bands) and connectin ('doublets'), but earlier than those of actin. After actin striations were formed as myofibrils matured, each nebulin band started to exhibit 'droplets'. The delayed development of nebulin compared to the I-Z-I brush formation and the myofibril maturation seems to indicate that this giant myofibrillar protein is unnecessary for both the initial (formation of I-Z-I-like structures) and the subsequent (regular alignment of myofibrils) phases of myofibrillogenesis.

Animals↗
PubMed1992

Collaborative multicenter field trial of the Draft of ICD-10 in Japan--interdiagnostician reliability and disagreement: a report from the WHO project on "field trials of ICD-10, Chapter V".

The Draft of "ICD-10, Chapter V, Clinical Descriptions and Diagnostic Guidelines" was tested in a multicenter field trial in Japan. We have previously reported good results in suitability, confidence and ease of diagnosis, and adequacy of descriptions of the Draft. In this paper, the interdiagnostician reliability of the Draft is reported. Among the two-character categories, "Schizophrenia, Schizotypal States and Delusional Disorders (F2)" (ICC = .80) and "Mood Disorders (F3)" (ICC = .80) proved reliable. "Neurotic, Stress-Related, and Somatoform Disorders (F4)" was less reliable (ICC = .65). The ICCs of the 17 major categories (three-character code) and the 21 subcategories (four-character code) were also calculated. The finding that in Japan subtyping schizophrenia with ICD-10 was more reliable than that made using DSM-III Diagnostic Criteria supports the need to use a descriptive version of ICD-10 as the basis for several versions serving different purposes. The nature of disagreements with unreliable categories was also investigated. The results are discussed with special reference to the changes in the final Draft of Chapter V, which contained a feedback of the results from field trials from all over the world.

Delusions↗
PubMed1992

A provocative internal carotid artery balloon occlusion test with 99mTc-HM-PAO CBF mapping--report of three cases.

The balloon occlusion test (BOT) of the internal carotid artery (ICA), combined with induced hypotension and cerebral blood flow (CBF) mapping, was carried out in three patients with a large or giant aneurysm of the ICA. Occlusion of the ICA for 10 minutes in the normotensive state was followed by 5 minutes of induced hypotension. During the last 2 minutes of hypotensive occlusion, technetium-99m-hexamethyl-propyleneamine oxime was administered to study the CBF. All patients tolerated the procedure well. One patient with moderate CBF reduction developed ischemic complications 24 hours after permanent ICA occlusion. Another showed no significant change in CBF and tolerated permanent ICA occlusion well, while the third refused permanent occlusion. The provocative BOT combined with CBF mapping is a promising predictor of complications of ICA occlusion secondary to perfusion abnormalities.

Aged↗
PubMed1992

Significance of gadolinium-enhanced magnetic resonance imaging in differentiating spinal cord radiation myelopathy from tumor. Case report.

A young woman with a fourth ventricular ependymoma underwent radiotherapy following tumor excision. Twenty months later she developed a progressive neurological deficit at the C-2 vertebral level. Gadolinium-enhanced magnetic resonance imaging, showed an intramedullary lesion at the C-2 level. Although radiation myelopathy was suspected, tumor recurrence could not be excluded. Re-exploration and histopathology both confirmed a diagnosis of radiation myelopathy. A retrospective review of the case indicated findings favoring radiation myelopathy. The pertinent literature is reviewed and the findings discussed.

Adult↗
PubMed1992

Rare earth metal ions for unprecedentedly fast RNA hydrolysis.

Adenylyl(3'-5')adenosine (ApA) and uridyl(3'-5')uridine (UpU) are hydrolyzed at unprecedentedly large rates by rare earth metal ions at pH 8, 30 degrees C. With 0.01 M Tm(III), the half-lives are 10 min and 51 min, respectively. Potentiality of these ions as catalytic center of artificial ribonuclease is proposed.

Catalysis↗
PubMed1992

Substitution of non-catalytic stem and loop regions of hammerhead ribozyme with DNA counterparts only increases KM without sacrificing the catalytic step (kcat): a way to improve substrate-specificity.

In elucidating structure-function relationships and stabilizing ribozymes in vivo, several chimeric RNA/DNA ribozymes and substrates were chemically synthesized. Measurements of kinetic parameters revealed that the maximally deoxyribonucleotide-substituted ribozyme (DRDRD32) gained the highest catalytic activity reaching the kcat value of > 10 min-1, the highest value ever reported for hammerhead-type ribozymes. Since these chimeric ribozymes are more stable than the wild-type all-RNA ribozymes in vivo and they also possess higher substrate-specificity, they are considered to be better candidates for antiviral therapeutic agents.

Base Sequence↗
PubMed1992

Does RNA hydrolysis involve rate-limiting formation of the pentacoordinate intermediate or rate-limiting decomposition? Phenyl ester of adenosine 3'-phosphate as a novel probe.

The rate-limiting step of enzymatic and non-enzymatic hydrolysis of RNA has been experimentally determined by use of phenyl ester of adenosine 3'-phosphate as a novel probe. Alkaline hydrolysis of RNA involves rate-limiting decomposition of a pentacoordinate intermediate, and any catalyst, either enzymatic or non-enzymatic, should promote the decomposition step.

Adenosine Monophosphate↗
PubMed1992

OligoDNA-oligoamine hybrid for facile and sequence selective hydrolysis of RNA.

Oligoamines as catalytic sites for RNA hydrolysis are attached to 5'-end of [dT]16 using urethane bond. The [dT]16-pentaethylenehexamine hybrid promptly hydrolyzes poly[A] at pH 8, 50 degrees C. Definite importance of the complexation between the poly[A] and the [dT]16 moiety is confirmed by a marginal hydrolysis of poly[C]. Hydrolytic catalysis is ascribed to intramolecular acid-base cooperation of two or more amino residues in the oligoamines.

Catalysis↗
PubMed1992

DNA hydrolysis by rare-earth metal ions.

Plasmid DNA and poly(dA) are cleaved by rare-earth(III) ions at pH 7-8 and 50 degrees C. The cleavage has been confirmed by prompt conversion of supercoiled pBR 322 plasmid DNA (Form I) to a relaxed Form II. Furthermore, degradation of poly(dA) to shorter oligonucleotides is clearly evidenced by HPLC. A possible application of the metal ions (and their complexes) to artificial nucleases is indicated.

Catalysis↗
PubMed1992

Enormous catalyses of lanthanide metal ions for unprecedentedly fast hydrolysis of 3',5'-cyclic adenosine monophosphate.

3',5'-cyclic adenosine monophosphate (cAMP) is efficiently hydrolyzed by use of lanthanide metal(III) ions as catalysts. The acceleration by 10(-2) M of Ce(III) is remarkable (more than 10(11) fold) at pH 8.0, 30 degrees C, decreasing the half-life from a half million years to 35 seconds. The catalytic activity is in the following order: Ce >> Pr > Nd, La > Y, Sm, Dy > others. The catalysis is ascribed to cooperation of three or four lanthanide metal ions.

Catalysis↗
PubMed1992

[Therapeutic occlusion of unilateral vertebral artery for unclippable aneurysms; special reference to postoperative brainstem ischemia].

Seven cases of unclippable vertebral artery aneurysms (3 dissecting, 1 fusiform, 2 saccular and 1 giant) are reported. Five of these had subarachnoid hemorrhage, one showed mass effect and the other was found incidentally. Trapping of the involved portion of the vertebral artery was performed in 4 cases, proximal clip occlusion in 2 and proximal balloon occlusion in 1. There were no operative deaths and no rebleeding, but brainstem ischemia developed in 4 cases, two being transient and two permanent. The ischemic complications were possibly due to; (a) hypoperfusion in the transient cases and (b) thromboenbolism, from the partially thrombosed giant aneurysm or thrombosis of the cul-de-sac vertebral artery, in the permanent ones. Preoperative temporary vertebral artery occlusion with an inflatable balloon or postoperative anticoagulant therapy should be considered in the management protocol.

Aortic Dissection↗