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Biomedical subjects

T Ohtani

Publications and source records attributed to T Ohtani.

At least 163 records · Page 9Linked to original sources
PubMed1983

"Convulsoid responses" suggesting development of autonomous epileptogenicity.

To test a convenient and reliable neuronal index that suggests the development of autonomous epileptogenicity, we conducted in acute experiments on rabbits a comparative study of the changes in direct cortical responses (DCRs) in primary and mirror sites during electrically induced primary (PRID) and projected seizure discharges (PROD). It has been assumed that the primary site shows autonomous epileptogenicity during the PRID, whereas the mirror site during the PROD does not. We observed that in the primary site, the dendritic potentials (field EPSPs) were remarkably suppressed in amplitude or disappeared during the PRID and that there was a loss of the after-positivity (field IPSPs); these DCRs recovered gradually after termination of the PRID. Instead of DCRs, "convulsoid responses" (a general term for responses similar to the individual spontaneous waves which occur in all types of seizures discharges) were usually elicited in the primary site during PRID. In the mirror site during PROD, the DCRs showed three different behaviors: they were either unaffected, increased, or suppressed. Convulsoid responses were never elicited. In a few cases, independent seizure discharges were induced in the mirror site. During the independent seizure discharges, the DCRs in the mirror site disappeared and convulsoid responses similar to the individual independent waves were usually elicited, as in the primary site during PRID. We conclude that the convulsoid response was the most reliable indicator of the development of autonomous epileptogenicity, and that suppression or disappearance of DCRs was the supplementary sign of that development. These neuronal indexes may be useful for identification of secondary epileptogenesis.

Animals↗
PubMed1983

Indications for endoscopic Nd-YAG laser surgery in the trachea and bronchus.

Nd-YAG laser surgery via the fiberoptic bronchoscope can vaporize lesions causing airway obstruction or stenosis located from the trachea to segmental bronchi with minimized danger of bleeding, and improve ventilatory disturbances. 35 lesions in the trachea and bronchus consisting of 27 malignant lesions and 8 benign lesions were treated with endoscopic Nd-YAG laser surgery. The procedures were performed under local anesthesia, and no significant side effects were recognized. The lesions was irradiated with 20-80 W. power. In most cases a continuous wave was used, but in cases of early stage squamous cell carcinoma intermittent irradiation of 0.5 second laser spots were used. In 21 of 35 cases effective results were obtained. The non-effective results obtained in 14 cases were considered to be due to inexact preprocedural evaluation of the extent of the lesions. Effective results were obtained in 11 of 13 lesions located in the trachea, in 3 of 5 lesions in the trachea and bronchus and in 7 of 17 lesions in the bronchus. Tumor in the trachea with severe ventilatory disturbance is a good indication for Nd-YAG laser surgery to rapidly alleviate symptoms. But in cases of lung cancer, indications even as a palliative procedure are limited to those cases in which the lung parenchyma distal to the stenotic portion is viable. However, the indications for this procedure as a curative modality are extremely limited.

Adult↗
PubMed1982

D-loop cycle. A circular reaction sequence which comprises formation and dissociation of D-loops and inactivation and reactivation of superhelical closed circular DNA promoted by recA protein of Escherichia coli.

Excess recA protein, a protein essential to general genetic recombination in Escherichia coli, promotes a sequence of formation and dissociation of D-loops from negative superhelical closed circular double-stranded DNA (form I DNA) and homologous single-stranded fragments in the presence of excess ATP, resulting in inactivation of the form I DNA without apparent damage to the DNA. The dissociation of D-loops is accompanied by hydrolysis of ATP to ADP that apparently depends on homologous DNA molecules (homology-dependent ATP hydrolysis). However, at a lower concentrations of ATP, we observed anomalous kinetics in the formation and dissociation of D-loops; as the concentration of ATP was decreased, there was a progressively smaller dissociation of D-loops and a faster resynthesis in the second phase, without changing the rate of the first formation of D-loops. This anomaly might suggest that, as the increase in the amount of ADP relative to that of ATP, dissociation form I DNA is stimulated before formation of D-loops is inhibited. We found that addition of ADP inhibited competitively both formation and dissociation of D-loops and that the latter process was more sensitive to the inhibition than was the former process. Addition of a sufficient amount of ADP to inhibit both formation and dissociation of D-loops, cessation of homology-dependent hydrolysis of ATP, or incubation at low temperature resulted in reactivation of form I DNA that had been inactivated by the sequence. In the presence of an ATP-regenerating system, we confirmed our previous result that limiting the amount of recA protein also causes anomalous kinetics in the formation and dissociation of D-loops. These observations indicate that the formation and dissociation of D-loops and the inactivation and reactivation of form I DNA make a circular reaction sequence.

Bacterial Proteins↗
PubMed1982

Role of superhelicity in homologous pairing of DNA molecules promoted by Escherichia coli recA protein.

In the presence of ATP and an excess of recA protein, superhelical closed circular DNA (form I DNA) and homologous single-stranded fragments paired to form D-loops in the early stage of incubation and dissociated during subsequent incubation. RecA protein that was not bound to single-stranded DNA ("free recA protein") was shown to be responsible for the dissociation of D-loops. Larger amount of free recA protein gave a lower final yield of D-loops. When the concentration of form I DNA was increased in the presence of a fixed amount of single-stranded DNA, larger amounts of free recA protein were required to produce a certain extent of dissociation. When form I DNA, excess recA protein, and ATP were incubated without single-stranded DNA, or with heterologous single-stranded fragments before the addition of homologous single-stranded fragments, formation and subsequent dissociation of D-loops were observed as in the case when all components of the reaction were added from the start. Therefore, the dissociation of D-loops is a result of the stoichiometric interaction between free recA protein and form I DNA bearing D-loops. In the process of formation and dissociation of D-loops, form I DNA was converted to an inactive substrate without any apparent damage to the DNA. The concentration of free recA protein appeared to decrease during the reaction. These observations revealed that formation and dissociation of D-loops are sequential reactions when form I DNA is the substrate and recA protein is present in excess. The dissociation of D-loops and the inactivation of form I DNA can be explained by a model in which recA protein cooperatively binds to form I DNA from the site of D-loop, resulting in stimulation of unidirectional unwinding of the double helix.

Bacterial Proteins↗
PubMed1982

Hydrolysis of ATP dependent on homologous double-stranded DNA and single-stranded fragments promoted by RecA protein of Escherichia coli.

RecA protein is essential to general genetic recombination in Escherichia coli. In the presence of ATP, a stoichiometric amount of recA protein forms D-loops from superhelical closed-circular DNA (form I DNA) and homologous single-stranded fragments, and subsequently dissociates the D-loops. Under appropriate conditions, the hydrolysis of ATP by recA protein depends on the presence of both double-stranded DNA and homologous single-stranded fragments (homology-dependent hydrolysis). In the presence of form I DNA, most of the homology-dependent hydrolysis of ATP by recA protein is related to the dissociation of D-loops rather than the formation of D-loops. RecA protein also promoted the homology-dependent hydrolysis of ATP in the presence of nicked-circular DNA (form II DNA), but unlike the case of form I DNA, this hydrolysis was associated with an increase in the amount of mature D-loops that were detected by the D-loop assay. When double-stranded DNA was superhelical, the homology-dependent hydrolysis of ATP continued at the same rate even after all the D-loops were dissociated. This correlates with our earlier observation that in the process of formation and dissociation of D-loops, form I DNA was converted to an inactive substrate without any apparent damage to the DNA, probably by the formation of a complex with recA protein. All of the observations described above can be explained by a model in which a common mechanism causes dissociation of D-loops from form I DNA, inactivation of form I DNA, and growth of D-loops in form II DNA. The mechanism might involve cooperative binding of recA protein to the duplex DNA from the site of the nascent D-loop, resulting in unidirectional unwinding of the duplex DNA.

Adenosine Triphosphate↗
PubMed1982

Enhancement of non-specific resistance to Pseudomonas pneumonia by a synthetic derivative of muramoyl dipeptide in immunosuppressed guinea pigs.

A synthetic derivative of muramoyl dipeptide, 6-O-stearoyl-N-acetylmuramoyl-L-alanyl-D-isoglutamine [L18-MDP(A)], showed a protective effect against bacteraemic and non-bacteraemic pneumonia caused by Pseudomonas aeruginosa in immunosuppressed guinea pigs. In about half of the animals treated with the compound before infection, death from bacteraemic pneumonia produced by intratracheal inoculation of P. aeruginosa was delayed for 7 d, although all of the animals infected without prior treatment with the compound died within 4 d of infection. Multiplication of the organisms in the lung was also suppressed for at least 10 d by treatment with the compound when the animals inhaled an aerosol of P. aeruginosa. In contrast, in untreated animals the numbers of bacteria in the lung gradually increased from 10(6) to 10(9) c.f.u. g-1, and a few animals in which the organism increased to 10(9) c.f.u. g-1 had died by 6 and 10 d after infection. In both healthy and immunosuppressed animals, the accumulation of polymorphonuclear leukocytes (PMNs) in a subcutaneous air-pouch injected with heat-killed organisms was augmented by subcutaneous treatment with L18-MDP(A) 1 d before bacterial injection. The phagocytic activity of peritoneal PMNs was also increased by treatment with this compound. The augmentation of protective mechanisms against pseudomonas pneumonia by L18-MDP(A) may be attributed at least partly to the increased chemotactic and phagocytic activity of PMNs.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1981

[Study of cefamandole in neonatal purulent meningitis caused by E. coli (author's transl)].

Cefamandole (CMD) was intravenously drip infusion administered at daily dose of 400 mg/kg to the neonate with purulent meningitis caused by E. coli which was resistant to ABPC. In clinical application, CMD was evaluated as effective, although 6 mg/kg/day of GM given concomitantly. No adverse effect and abnormal laboratory findings were observed. This study would support the clinical usefulness of CMD in severe neonatal infection especially like meningitis.

Cefamandole↗
PubMed1979

Oral rehabilitation by prosthetic restoration after maxillectomy for malignant tumors.

In maxillectomy patients, speech intelligibility between before and after insertion of prostheses has been reviewed by many investigators. Speech intelligibility was not related to the size of the defect, but rather to the defect region. Speech intelligibility was considerably improved by the use of prostheses. A great difference could not be found in escape rate from the nasal cavity between before and after insertion of prostheses, but there was a remarkable change in the spirometer. Postmaxillectomy functions are also easily restored by prosthetic oral rehabilitation, necessary to aid surgical procedure.

Adult↗