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Biomedical subjects

R Nagata

Publications and source records attributed to R Nagata.

At least 55 records · Page 3Linked to original sources
PubMed1991

Mechanisms of veratramine-induced 5-HT syndrome in mice.

Regional monoamine assays revealed that during veratramine-induced myoclonic movements, the contents of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in the cerebral cortex were reduced with a slight increase in dopamine metabolites in the midbrain and brainstem. A similar tendency to decrease 5-HT and 5-HIAA contents was observed in the hypothalamus and hippocampus without increase in the contents of dopamine and its metabolites. Norepinephrine levels were not modified in any brain region at any time after the administration of the veratrum alkaloid. It was found that the veratramine evoked 3H-5-HT release from the frontal cortical slices was Ca+(+)-independent and persistent, and it continued approximately 20 min after the 2-min exposure to veratramine. The uptake of 3H-5-HT into the frontal cortical slices was inhibited competitively by veratramine. These results suggest that veratramine is both a releaser and uptake inhibitor of 5-HT and that the veratramine-induced involuntary movements may be mediated by serotonergic hyperfunction.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

[The effect of inhalation of sevoflurane for an hour on the liver of beagles].

The effect of sevoflurane in comparison with that of enflurane and halothane, each at 1.8 MAC, on the liver was examined after inhalation exposure to beagles under controlled respiration for 1 hr. No abnormalities were observed in general conditions in the animals exposed to any of these anesthetics. Recovery time to spontaneous respiration after the end of anesthesia was similar for each group, but the awakening was quickest in sevoflurane exposed group. Blood pressure dropped immediately after the initiation of exposure in each group, but it recovered quickly to preexposure levels after the end of the exposure. Minor and reversible elevations in the values of GOT, GPT, LDH and bilirubin were noted without the organic change of the liver in beagles after the inhalation exposure to 1.8 MAC of each anesthetic. Since similar changes were observed in beagles exposed to enflurane or halothane, we conclude that no change in the liver specifically associated with sevoflurane was found under these experimental conditions.

Anesthesia, Inhalation↗
PubMed1989

Expression and processing of cyanobacterial Mn-stabilizing protein in Escherichia coli.

The woxA gene of cyanobacterium Anacystis nidulans R2, which encodes the precursor of the Mn-stabilizing protein involved in photosynthetic water oxidation, was found to be expressed in Escherichia coli. The 30-kDa expression product was indistinguishable from the authentic mature protein on SDS/PAGE. Upon fractionation of E. coli cells, the expression product was co-precipitated with the membrane fraction, which is consistent with the water-insoluble nature of the authentic mature protein. Analysis of the amino-terminal amino acid sequence of the product revealed that it is identical to the sequence from the 28th residue of the precursor, indicating that the precursor is processed in E. coli. The expression product was digested by trypsinization of E. coli spheroplasts, but not by that of intact cells. This observation suggests that the product is secreted from the cytoplasmic membrane, but not from the outer membrane. The occurrence of both processing and secretion suggests that a signal peptidase of E. coli can recognize the structure for translocation across the thylakoid membrane. Comparison of the signal sequence and the presequence of sweet potato sporamin A suggests that the processing enzymes of the thylakoid membrane and endoplasmic reticulum possess a common substrate specificity.

Amino Acid Sequence↗
PubMed1989

Preventive effect of taurine against acute paraquat intoxication in beagles.

The continuous infusion of taurine markedly protected against paraquat (PQ)-induced oliguria in beagles. Pharmacokinetic studies revealed that taurine infusion increased the blood concentration of PQ and reduced the net content in the kidney and, to a lesser extent, in the lung. The excretion of PQ into the urine was unaltered. The infusion of glycine did not have such effects.

Animals↗
PubMed1989

Potentiality of protamine sulfate as mutagen.

The mutagenicity of protamine sulfate has been clarified based on chromosomal aberration of cultured chinese hamster lung cells (cell line) in direct and metabolic activation methods and microbial mutagenesis (Ames test). In chromosomal aberration test, protamine sulfate caused cytotoxicity in the high doses (2500 and 5000 micrograms/ml) in the presence of rat liver homogenates (S-9). But very negligible or no cytotoxicity occurred in direct method at high dose (5000 micrograms/ml). Structural aberration of chromosome was not occurred in either of the methods. In microbial mutagenesis study, protamine sulfate did not show any cytotoxicity to microbes up to the dose of 5000 micrograms per plate. Furthermore, it did not have any effect in microbes like mutagens or like some toxic agent. The study reveals that protamine sulfate is not mutagen.

Animals↗
PubMed1987

New singlet oxygen source and trapping reagent for peroxide intermediates.

Application of newly-developed water-soluble singlet oxygen sources in the oxidation of biologically important compounds and the electron-transfer process involving singlet oxygen has been reviewed. Particularly, oxidation products of tryptophan by chemically generated singlet oxygen were compared to those obtained in dye-sensitized photooxygenation. The usefulness of trimethylsilyl cyanide as a trapping reagent for dipolar peroxide intermediates has been demonstrated in the photooxygenation of N-methylindoles, 2-(methoxymethylene)adamantane and adamantylideneadamantane in aprotic solvents. Based on these trapping reactions mechanism of singlet oxygen reaction of electron-rich enol ethers and enamines is discussed in light of theoretical calculation.

Cyanides↗
PubMed1987

[Chronic toxicity and recovery tests of rokitamycin in beagle dogs].

Six-month oral chronic toxicity study and two-month recovery tests on rokitamycin (TMS-19-Q) were performed in Beagle dogs at daily doses of 90, 180 and 360 mg/kg. The results were summarized as follows: No death occurred to any animals in these experiments. In higher dosage groups (180 and 360 mg/kg), vomiting, salivation and reduction of body weight gain with decrease in food intake were observed. Body temperature and pulse rate were normal, and ECG, sperm and vaginal smear tests, urinalysis, blood and biochemical examinations also revealed normal values. No marked changes in organ weights, necropsy, histopathological and electron microscopic observations were detected.

Administration, Oral↗
PubMed1986

Saccade-related activity of periaqueductal gray matter of the monkey.

Single unit activity was recorded extracellularly from the periaqueductal gray matter (PAG) and the superior colliculus of three monkeys during spontaneous saccades and fixation. Most saccade-related cells were found in the dorsal and lateral regions of the PAG and they paused with saccades. The pause preceded the onset of saccades by 34.5 +/- 6.8 msec (n = 31). In 90% of the 31 PAG cells, the saccade-related modulation in activity occurred in all directions. There was a linear relationship between pause duration and saccade duration with correlation coefficients larger than 0.70 in most cells. Superior colliculus cells showed bursts preceding onset of saccades. The lead times averaged 25.3 msec (n = 35). There was no linear relationship between burst duration and saccade duration. These results suggest that the dorsal and lateral regions of PAG play an important role in the saccadic system, probably through long lead burst units in the deep layer of the superior colliculus and/or pontine reticular formation.

Animals↗
PubMed1986

[Chronic intravenous toxicity studies of potassium clavulanate and BRL28500 in dogs].

The chronic toxicity of potassium clavulanate (CVA-K) and BRL28500 were evaluated using dogs in 26-week intravenous administration studies followed by a 5-week off-dose period. The doses for CVA-K and BRL28500 were 10, 20, 50 and 100 mg/kg (p.f.a.), and 80, 160, 320 and 800 mg/kg (p.f.a.) respectively. There were no deaths in either of the groups. For general condition, dogs dosed with CVA-K at 100 mg/kg showed reddening of the skin and mucous membranes, shaking of the head, facial oedema, a decrease in food intake and a reduction in body weight. Also some dogs of the same group showed decreased spontaneous activity, emaciation and signs of dehydration. In the BRL28500 treatment groups, there was reddening of the skin and mucous membranes, vomiting and salivation at 800 mg/kg. Urinalysis of dogs dosed with CVA-K showed occasional dark yellow coloration of the urine. There was also a very weak and equivocal response or positive reaction for protein, occult blood, and urine sugar in some animals at 100 mg/kg. Some dogs dosed with BRL28500 also showed either a very weak and equivocal response or slight positive reaction for occult blood at 320 mg/kg and above, and dark yellow coloration of the urine at 800 mg/kg. Haematological examination of the CVA-K groups showed increases in leukocyte count and platelet count at the highest dose of 100 mg/kg. No haematological abnormalities were noted in any of the BRL28500 groups. Serum biochemical studies of dogs dosed with CVA-K revealed a decrease in total protein at 50 mg/kg and above, and increases in Al-P, total bilirubin, GPT, BUN and creatinine at 100 mg/kg. In the BRL28500 treatment groups, there were increases in total cholesterol and triglyceride at 160 mg/kg and above. In dogs dosed with CVA-K there was an increase in liver weight at 100 mg/kg. Histopathological examination showed a ground glass-like appearance of the hepatocyte cytoplasm and also altered distribution of PAS positive material at 50 mg/kg and above. In the BRL28500 groups, there was an increase in liver weight at 320 mg/kg and above. There were the same ground glass-like appearance in hepatocytes and altered distribution of PAS positive material at 800 mg/kg. In view of the above results, the maximum non-effect dose levels in the present studies were considered to be 20 mg/kg for CVA-K and 80 mg/kg for BRL28500.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Macrosaccadic oscillation, saccadic dysmetria and motor error in spinocerebellar degeneration.

The macrosaccadic oscillation was analyzed quantitatively in a 31-year-old man with spinocerebellar degeneration, using DC electrooculogram. Over a follow-up period of one year the macrosaccadic oscillation changed into saccadic dysmetria where square oscillations were suppressed during fixation and occurred only after visually guided saccades. The initial movements in the oscillation followed the main saccades with a mean latency of 147.6 msec. When a saccade showed an overshoot, a fast movement occurred in the opposite direction, and with undershoot of the saccade, the fast movement occurred in the same direction as that of the saccade. Furthermore, the amplitudes of the oscillation had a close correlation with those of the motor error, ie, the difference in the amplitudes between the target displacement and saccade. The results suggest that square oscillations in the macrosaccadic oscillation and saccadic dysmetria may be caused by an elevation of the gain in the corrective saccadic system.

Adult↗
PubMed1984

Pupillary light reflex in amblyopia.

The pupillary light reflex of 15 strabismic and anisometropic amblyopes, and eight subjects who had recovered from functional amblyopia was studied by using an infrared electropupillogram. Ten of the fifteen amblyopes had significantly longer latencies of contraction when the amblyopic eyes were stimulated than when the normal eyes were stimulated. However, there was no relationship between the delay in pupillary light reflexes and reduced visual acuity of amblyopic eyes. The amplitudes and maximum velocities of the contraction were not altered significantly in amblyopic and normal eyes. All of the subjects who had recovered showed no significant difference of the latencies of the pupillary responses to stimulation between normal and amblyopic eyes. These findings indicate that a retinal mechanism in amblyopic eyes may be responsible for the abnormally long pupillary light reflex latency.

Adolescent↗