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Biomedical subjects

T Deguchi

Publications and source records attributed to T Deguchi.

At least 361 records · Page 20Linked to original sources
PubMed1978

Binding of aminoglycoside antibiotics to acidic mucopolysaccharides.

Binding of aminoglycoside antibiotics to acidic mucopolysaccharides has been studied by means of physicochemical methods. Reactivity was affected markedly by the ionic environment , e.g. pH and ionic strength of the medium, the concentrations and the molar ratios of the constituents. The ionic character of binding was further confirmed by gel chromatography. The reduction of metachromasis by an aminoglycoside was also observed. Their affinity is correlated with localization of the aminoglycosides in vivo. According to reactivity, the following descending order of affinity was obtained for each family: neomycin, gentamicin, sagamicin, kanamycin and streptomycin; heparin, chondroitin sulfate and hyaluronic acid. This sequence of aminoglycosides corresponds to the extent of oto-, nephro- and neuro-(acute)toxicity, suggesting that their affinity for acidic mucopolysaccharides contribute to their tissue toxicity.

Aminoglycosides↗
PubMed1978

Ontogenesis of circadian rhythm of melatonin synthesis in pineal gland of rat.

Serotonin N-acetyltransferase (NAT) activity regulates the circadian rhythm of melatonin synthesis in pineal gland. NAT rhythm persisted in continuous darkness or in blinded rats. Development of the circadian rhythm of NAT activity was followed in the infant rats raised under various lighting schedules. The pups born and raised in continuous darkness or under constant illumination showed a rhythmic change indicating that the biological clock for NAT is generated inborn independent of environmental light-dark schedules. In the absence of light, the rhythms of pups synchronized with mother's rhythm. When rats were maintained under a ultradian light-dark schedule (LD 6:6), NAT activity showed a circadian change increasing once a day. When pups were born and raised under the ultradian lighting condition, NAT activity rhythm coincided with mother's rhythm. When pups were raised by a foster mother who had an inverted rhythm from that of an original mother, the rhythm of the pups synchronized with that of the foster mother. Whe pups were separated from their mother daily for 12 hours, their NAT rhythms reappeared when they were separated from their mother. These observations indicated a novel mechanism that in the absence of light-dark schedule, mothers taught the circadian rhythm to the pups as they raised them.

Acetyltransferases↗
PubMed1978

[Radioimmunoassay of 125I-sagamicin (author's transl)].

A radioimmunoassay for an aminoglycoside antibiotic, sagamicin, was developed using antisera from rabbits injected with a sagamicin-bovine serum albumin conjugate. Sagamicin was iodinated by a modified Bolton & Hunter method. The standard curve was linear on a logit-log plot yielding an sensitivity of 0.5ng/tube. A correlation coefficient of 0.95 was obtained between the radioimmunoassay and a microbioassay for sagamicin in human sera. Cross-reaction occurred with gentamicin components and some of sagamicin subunits, but there was no cross-reactivity to neomycin, kanamycin and amikacin. Antibody was purified by affinity chromatography on sagamicin bound agarose.

Animals↗
PubMed1977

Endogenous activating factor for guanylate cyclase in synaptosomal-soluble fraction of rat brain.

When the crude mitochondrial fraction of rat brain was homogenized with distilled water and centrifuged, most of guanylate cyclase activity was detected in the soluble fraction. The total guanylate cyclase activity recovered in the soluble fraction was 5- to 8-fold higher than that of the crude mitochondrial fraction. The greater recovery of guanylate cyclase activity was found to be due to a release of an endogenous activating factor for guanylate cyclase. The activating factor was partially purified by acid extraction followed by a gel filtration and ion exchange resin columns. The factor was a dialyzable small molecule. The molecular weight was estimated to be between 300 and 600 by a Sephadex G-15 column and Diaflo ultrafilter membranes. It was stable in dilute acids, but labile in alkaline solution. It was readily soluble in water, but insoluble in organic solvents. Treatment with various enzymes, so far as tested, failed to abolish the activity. The activating factor stimulated the initial velocity of the reaction. It altered neither the Km value for GTP nor the dependency of the enzyme on divalent metals. The activation by the factor was due to an increase in the Vmax of the reaction. The activation was prevented by lysolecithin, Lubrol PX, hydroxylamine, methylhydroxylamine, or hemoglobin.

Animals↗
PubMed1977

Activation of guanylate cyclase in cerebral cortex of rat by hydroxylamine.

Hydroxylamine actived guanylate cyclase in particulate fraction of cerebral cortex of rat. Activation was most remarkable in crude mitochondrial fraction. When the crude mitochondrial fraction was subjected to osmotic shock and fractionated, guanylate cyclase activity recovered in the subfractions as assayed with hydroxylamine was only one-third of the starting material. Recombination of the soluble and the particulate fractions, however, restored guanylate cyclase activity to the same level as that of the starting material. When varying quantities of the particulate and soluble fractions were combined, enzyme activity was proportional to the quantity of the soluble fraction. Heating of the soluble or particulate fraction at 55 degrees for 5 min inactivated guanylate cyclase. The heated particulate fraction markedly activated guanylate cyclase activity in the native soluble fraction, while the heated soluble fraction did not stimulate enzyme activity in the particulate. The particulate fraction preincubated with hydroxylamine at 37 degrees for 5 min followed by washing activated guanylate cyclase activity in the soluble fraction in the absence of hydroxylamine. Further fractionation of the crude mitochondrial fraction revealed that the factor(s) needed for the activation by hydroxylamine is associated with the mitochondria. The mitochondrial fraction of cerebral cortex activated guanylate cyclase in supernatant of brain, liver, or kidney in the presence of hydroxylamine. The mitochondrial fraction prepared from liver or kidney, in turn, activated soluble guanylate cyclase in brain. Activation of guanylate cyclase by hydroxylamine was compared with that of sodium azide. Azide activated guanylate cyclase in the synaptosomal soluble fraction, while hydroxylamine inhibited it. The particulate fraction preincubated with azide followed by washing did not stimulate guanylate cyclase activity in the absence of azide. The activation of guanylate cyclase by hydroxylamine is not due to a change in the concentration of the substrate GTP, Addition of hydroxylamine did not alter the apparent Km value of guanylate cyclase for GTP. Guanylate cyclase became less dependent on manganese in the presence of hydroxylamine. Thus the activation of guanylate cyclase by hydroxylamine is due to the change in the Vmax of the reaction.

Animals↗
PubMed1977

Circadian rhythms of enzyme and running activity under ultradian lighting schedule.

Serotonin N-acetyltransferase activity in the pineal gland and running acitvity of rats were measured under an ultradian lighting schedule (light/dark 6:6). When rats were moved from a diurnal lighting condition to the ultradian conditions, N-acetyltransferase activity showed a circadian rhythm, increasing once a day. N-acetyltransferase activity in the pups born and raised under the ultradian lighting conditions also exhibited a circadian change, the phase of which coincided with that of their mothers. When pups were raised by a foster mother with an inverted rhythmic phase from that of the original mother, the phase of the rhythm in N-acetyltransferase activity of the pups synchronized with that of the foster mother. When pups were separated from their mothers for 12 h/day, the circadian increase of N-acetyltransferase activity appeared during the dark period when they were separated from their mothers. The circadian rhythms of running acitvity were in phase with those of N-acetyltransferase activity in the pineal gland.

Acetyltransferases↗
PubMed1977

Synthesis of carbon-14 and tritium labeled sagamicin.

Sagamicin, an aminoglycoside antibiotic, was labeled with tritium by means of a platinum catalyzed hydrogen exchange reaction and by carbon-14 in two biosynthetic procedures. 14C-Methyl-L-methionine was used as the radioactive precursor in these biological processes involving Micromonospora sagamiensis. The distribution of radioactivity in 14C-sagamicin and gentamicin C1 was studied by mild acid hydrolysis and Hofmann degradation. The results showed that both C- and N-methyl groups were derived from methionine. One of the biosynthetic processes involved the conversion of gentamicin into sagamicin with resting cells and labeled methionine.

Carbon Radioisotopes↗
PubMed1976

Subcellular distribution and activation by non-ionic detergents of guanylate cyclase in cerebral cortex of rat.

Non-ionic detergents stimulated particulate guanylate cyclase activity in cerebral cortex of rat 8- to 12-fold while stimulation of soluble enzyme was 1.3- to 2.5-fold. Among various detergents, Lubrol PX was the most effective one. The subcellular distribution of guanylate cyclase activity was examined with or without 0.5% Lubrol PX. Without Lubrol PX two-thirds of the enzyme activity was detected in the soluble fraction. In the presence of Lubrol PX, however, two-thirds of guanylate cyclase activity was recovered in the crude mitochondrial fraction. Further fractionation revealed that most of the particulate guanylate cyclase activity was associated with synaptosomes. The sedimentation characteristic of the particulate guanylate cyclase activity was very close to those of choline acetyltransferase and acetylcholine esterase activities, two synaptosomal enzymes. When the crude mitochondrial fraction was subfractionated after osmotic shock, most of guanylate cyclase activity as assayed in the absence of Lubrol PX was released into the soluble fraction while the rest of the enzyme activity was tightly bound to synaptic membrane fractions. The total guanylate cyclase activity recovered in the synaptosomal soluble fraction was 6 to 7 times higher than that of the starting material. The specific enzyme activity reached more than 1000 pmol per min per mg protein, which was 35-fold higher than that of the starting material. The membrane bound guanylate cyclase activity was markedly stimulated by Lubrol PX. Guanylate cyclase activity in the synaptosomal soluble fraction, in contrast, was suppressed by the addition of Lubrol PX. The observation that most of guanylate cyclase activity was detected in synaptosomes, some of which was tightly bound to the synaptic membrane fraction upon hypoosmotic treatment, is consistent with the concept that cyclic GMP is involved in neural transmission.

Animals↗
PubMed1976

Effects of palytoxin on isolated intestinal and vascular smooth muscles.

Palytoxin (PTX), the most potent marine toxin isolated from the Zoanthid, Palythoa tuberculosa, was studied to determine the effect on isolated smooth muscles. In guinea pig taenia coli PTX at above 3 X 10(-10) g/ml caused a contraction which slowly subsided under isotonic recording. Under isometric recording PTX at above 1 X 10(-10) g/ml caused a contraction which depended on the spontaneous activity. The PTX-induced contraction was not affected by atropine, tripelenmamine or tetrodotoxin but was inhibited by 5 mM Mg, norephinrphrine, isoprenaline or papaverine. PTX at above 1 X 10(-9) g/ml induced an increase in spike frequency and a slight depolarization accompanied with a contraction when measured using a sucrose gap method. In some cases the spike generation was almost abolished after a long exposure to higher dose of PTX and the developed tension gradually decreased. Under isometric recording PTX caused a sustained contraction in rabbit aorta, dog mesenteric and coronary arteries at above 1 X 10(-10) and 1 X 10(-11) g/ml, respectively, in a dose-dependent manner. The coronary artery was most sensitive among the preparation used. PTX-induced contraction in aorta was irreversible, was not influenced by phentolamine but diminished with 5 mM Mg and disappeared in a D-600 or Ca-free medium. PTX is thus an extremely potent and direct stimulant which acts on smooth muscles.

Acrylamides↗
PubMed1975

Ontogenesis of a biological clock for serotonin:acetyl coenzyme A N-acetyltransferase in pineal gland of rat.

Serotonin:acetyl coenzyme A N-acetyltransferase (EC 2.3.1.5) Activity in pineal gland was assayed in rats which were born and raised under diurnal lighting conditions, in continuous darkness, or in constant light. N-Acetyltransferase activity in the pups raised under diurnal lighting showed a rhythmic pattern, with high enzyme activity during dark period. The pups raised in continuous darkness also showed a rhythmic pattern, the phase of which was delayed by 8 hr in 7-week-old pups; the rhythmic phase of N-acetyltransferase began in the evening in 12-day-old pups and was regularly delayed by 1 hr every week. The pups raised in constant illumination also showed a rhythmic pattern; the rhythmic phase was delayed by 3 hr every week. When the mother rats were coupled in darkness and maintained in darkness during pregnancy and after the pups were born, their pups again showed a rhythmic pattern. These observations indicate that the biological clock for N-acetyltransferase is generated independently of environmental lighting. When mothers were coupled under reversed lighting conditions and transferred into darkness or light, the rhythmic pattern in their pups was inverted 180 degrees from that of pups born of diurnal mothers. When the pups were raised in darkness, the rhythmic phase of N-acetyltransferase in the pups was similar to that of their mothers. It is suggested that in the absence of light-darkness cycle, the mother rat sets the rhythm of the pups to synchronize with her own rhythm. When pups were reared by a foster mother with a different rhythmic pattern from that of their original mother, the rhythmic phase in the pups was closer to that of the original mother, suggesting that the original mother plays the predominant role setting the rhythm of the pups.

Acetyltransferases↗