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Biomedical subjects

T Tsuchiya

Publications and source records attributed to T Tsuchiya.

At least 865 records · Page 48Linked to original sources
PubMed1976

Adenosine 5'-triphosphate synthesis energized by an artificially imposed membrane potential in membrane vesicles of Escherichia coli.

Adenosine 5'-triphosphate (ATP) synthesis driven by an artificially imposed membrane potential in right-side-out membrane vesicles of Escherichia coli was investigated. Membrane vesicles prepared in the presence of adenosine diphosphate were loaded with K+ by incubation with 0.5 M potassium phosphate. Addition of valinomycin resulted in the synthesis of 0.2 to 0.3 nmol of ATP/mg of membrane protein, whereas no synthesis was observed after addition of nigericin. Addition of K+, dicyclohexylcarbodiimide, carbonylcyanide p-trifluoromethoxyphenylhydrazone, or azide to the assay buffer inhibited ATP synthesis. Adenosine diphosphate and Mg2+ were found to be required. Ca2+, which can replace Mg2+ for the hydrolytic activity of the Mg2+-adenosine triphosphatase (ATPase) (EC 3.6.1.3), could not replace Mg2+ in the synthetic reaction and, in fact, inhibited ATP synthesis even in the presence of Mg2+. Strain NR-70, a mutant lacking the Mg2+-ATPase, was unable to synthesize ATP using an artificially imposed membrane potential. Additionally, the Mg2+-ATPase was found to contain tightly bound ATP.

Adenosine Diphosphate↗
PubMed1976

Effects of benzodiazepines and pentobarbital on the evoked potentials in the cat brain.

The sites of action of benzodiazepines, diazepam and ID-540 [7-chloro-5-(o-fluorophenyl)-1-methyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one) on the central nervous system were examined and compared with those of pentobarbital using evoked potentials recorded on the limbic system and hypothalamus in the cat brain. Benzodiazepines affected the various neuronal connections of the intra-limbic, limbic-hypothalamic and midbrain-limbic systems; especially the amygdala (AMYG)-, ventromedial hypothalamus (VMH)- and central gray matter (SGC)-hippocampal (HIPP) evoked potentials were attenuated, whereas the AMYG-VMH, VMH-AMYG and the septum (SP)-VMH evoked potentials were facilitated. Pentobarbital selectively attenuated the SGC-, VMH- and AMYG-HIPP evoked potentials, or facilitated the VMH-AMYG and the SP-HIPP evoked potentials. Both benzodiazepines and pentobarbital affected three afferent hippocampal neuronal connections, areas of the reticulo-hypothalamic systems regulating hippocampal activity, while only benzodiazepines affected the neuronal influence of the amygdaloid and septal areas on the hypothalamus.

Amygdala↗
PubMed1976

[Depressive effects of benzodiazepines on penicillin-induced epileptic discharges].

Effects of clonazepam, nitrazepam and diazepam on penicillin induced primary, spread and reactive epileptoform discharges were investigated in gallamine immobilized cats. Different strengths of seizure foci were induced by penicillin G 1000, 3000 and 6000 U injected into the cortex, amygdala and intralaminal thalamus, and the spread of epileptic discharges in the subcortex or surrounding area and to the contralateral area was followed. Benzodiazepines 5 mg/kg i.v. shortened the duration of primary epileptoform discharges and prolonged the interictal interval in the cortical, amygdaloid and intralaminal thalamic epileptogenesis induced by a high concentration of penicillin G. When a low concentration of penicillin G was injected into the cortex, amygdala and intralaminal thalamus, benzodiazepines abolished the spread of primary epileptoform discharges and the reactive discharges, but did not suppress completely the primary epileptogenic discharges and the contralateral reflective activity. Suppression of the discharges necessitated administration of a high dose. The greatest degree of suppression was seen with clonazepam. It is concluded that the anticonvulsive effect of benzodiazepines may be due to the blackades of neuronal pathways which spread the seizure discharges from the site of origin (focus) to the effector organ, and the elevation of convulsive thresholds.

Animals↗
PubMed1975

Energy transduction in Escherichia coli. The role of the Mg2+ATPase.

Inverted membrane vesicles from strain 7, a wild type Escherichia coli K12 strain, actively transport calcium with energy supplied either by respiration or by ATP. These vesicles also have energy-linked quenching of quinacrine fluorescence. Membranes of strain 7, depleted of Mg2+ATPase by EDTA treatment, lack both activities. Membrane vesicles from strain NR70, a mutant lacking the Mg2+ATPase, show neither calcium transport nor energy-linked fluorescence quenching. Neither EDTA treatment nor genetic loss of the Mg2+atpase causes a reduction in respiration. Purified Mg2+ATPase from strain 7 can bind to EDTA-treated membrane vesicles from either strain 7 or NR70. This binding restored both calcium transport and fluorescence quenching, driven either by respiration or by ATP. Dicyclohexylcarbodiimide treatment mimics the effect of the Mg2+ATPase in the case of respiration-driven reactions. Treatment with EDTA, while not essential for the binding of the Mg2+ATPase to membrane vesicles of NR70, produced better restoration of both activities. The rate of restoration of fluorescence quenching showed a time lag which may indicate that binding of the Mg2+ATPase is a relatively slow process. Antiserum prepared against the Mg2+ATPase inhibited the quenching of quinacrine fluorescence when driven by ATP but not when driven by respiration. Addition of antiserum prior to addition of Mg2+ATPase prevented the restoration of fluorescence quenching, whether driven by respiration or ATP. These results clearly show that MG2+ATPase has an important role not only in catalyzing ATP synthesis and hydrolysis but also in maintaining the energized membrane state.

Adenosine Triphosphatases↗
PubMed1975

Characterization of an active transport system for calcium in inverted membrane vesicles of Escherichia coli.

The energy-dependent uptake of calcium by inverted membrane vesicles of Escherichia coli was investigated. Methods for preparation and storage of the vesicles were devised to allow for the maximal activity and stability of the calcium transport system. The pH and temperature optima for the reaction were observed to occur at pH 8.0 AND 30 DEGREES, RESPECTIVELY. The eft was found that the extent of the reaction depended on the presence of phosphate or oxalate. Phosphate was found to enter the vesicles at a rate slower than that of calcium. A Ca2+:Pi ratio of approximately 1.5 was found, suggesting formation of Ca3(PO4)2. Monovalent cations stimulated calcium uptake, with the order of effectiveness being K+ is greater than Na+ is greater than Li+ is greater than NH4+. Inhibition was found with certain divalent cations, but these also inhibited the electron transport chain. Of the divalent cations examined only Mg2+ and Sr2+ inhibited calcium transport without a corresponding inhibition of respiration. Calcium transport exhibited biphasic Kinetics, with a low affinity system and a high affinity system. The low affinity system showed a Km of 0.34 mM and a Vmax of 85 nmol/min/mg of protein. The kinetic constants of the high affinity system were 4.5 muM and 2 nmol/min/mg of protein. The energy for calcium transport could be derived from the electron transport chain by oxidation of NADH, D-lactate, and succinate, in order of their effectiveness. Respiration-driven calcium transport was inhibited by inhibitors of the electron transport chain and by uncouplers of oxidative phosphorylation. ATP could also be used to supply enerty for calcium transport. The ATP-driven reaction was inhibited by inhibitors of the Mg2+ATPase and by an antiserum prepared against that protein, demonstrating that that enzyme is involved in the utilization of ATP for active transport in inverted vesicles.

Adenosine Triphosphatases↗
PubMed1975

Reassembly of functionally active 50S ribosomal particles from proteins and RNAs of Escherichia coli. Dependency of 50S ribosomal reassembly on 30S subunits.

Further studies were made on the reassembly of 50S ribosomal subunits from proteins and RNAs of E. coli. The reassembled particles had high activity in poly U-directed polyphenylalanine synthesis and their sucrose sedimentation properties were similar to those of the original intact particles. Several factors affecting the reassembly were examined. The optimal pH for solubilization of ribosomal proteins was pH 9.5, and the optimal Tris concentration was 0.75 to 1.00 M. In the reassembly mixture the pH was adjusted to 8.2 A sharp optimum magnesium ion concentration of 6 to 10 mM was observed. The reassembly required 0.2 to 0.5 M KCl, the optimum concentration being 0.40 M. On incubation for 20 min a temperature of 34 and 40 degrees was necessary, 37 degrees being best. Oligonucleotides, which we previously added to the reassembly mixture were found not to be necessary for inhibition of RNase II [EC 3.1.4.20] activity remaining in the reaction was found necessary to dialyze the reassembly mixture against a buffer containing 10 mM magnesium ion after the incubation. Simultaneous reassembly of 30 and 50S subunits with time was observed, showing that 70S ribosomes were formed first and that they then dissociated into subunits. Reassembly of 50S subunits from their component proteins and RNAs was completely dependent on either 30S particles or the simultaneous reassembly of 30S subunits. Other critical factors affecting the reassembly of 50S subunits must be examined, since the reproducibility of this reassembly is only about 60%, even under the above controlled conditions.

Bacterial Proteins↗
PubMed1975

Prevention of freeze denaturation of carp actomyosin by sodium glutamate.

1) Denaturation of carp actomyosin during storage at -20 degrees was studied with particular interest in the cryoprotective effect of sodium glutamate, the most cryoprotective of the compounds tested previously. 2) Storage with glutamate prevented the rapid decrease in solubility, viscosity, and ATPase (EC 3.6.1.3)activity of actomyosin during storage. Ultracentrifugal studies suggested that aggregation occurred in the frozen state without glutamate, but that added glutamate prevented aggregation or denaturation. 3) Electron microscopy showed that the original actomyosin consisted of long filaments with typical "arrowhead" structures, and that these decomposed into small fragments and sticked with globular portions, forming loosely packed aggregates during storage without glutamate. On storage with glutamate, the filaments were well preserved, and their fine structure was clearer than that of the original sample. 4) Preparations of actomyosin extracted with 10 mM glutamate were of better quality and their ultrastructure and physicochemical and biochemical properties showed increased stability on freezing. 5) Freeze-denaturation seems to involve complicated aggregation with transconformation of proteins besides the side-to-side aggregation discussed previously.

Actomyosin↗
PubMed1975

Electrophysiological and behavioral effects of 1-methyl-5-(o-fluorophenyl)-7-chloro-1,3-dihydro-2H-1,4-benzodiazepin-2-one (ID-540) in cats and rabbits.

Effects of ID-540 (1-methyl-5-(o-fluorophenyl)-7-chloro-1,3-dihydro-2H-1,4-benzodiazepin-2-one) on the central nervous system were evaluated electrophysiologically and behaviorally in cats and rabbits. The reference compound used was diazepam. 1. ID-540 as well as diazepam produced muscle relaxation, grooming, facilitation of appetite and suppression of defensive behaviors. ID-540 made the animals lie on their side during sleep, but diazepam did not. 2. Though more effectively inducing an increase in fast activity and a decrease in frequency of hippocampal theta-waves than diazepam, ID-540 scarcely affected the amplitude of subcortical EEG (hippocampus, amygdala and hypothalamus), which diazepam decreased in cats. 3. ID-540 and diazepam increased the waking phase and decreased the paradoxical sleep phase. 4. ID-540 and diazepam at a dose of 1 mg/kg decreased the duration of amygdala after-discharge for 1 h in cats. Diazepam increased the duration of the after-discharge after it had been decreased, but ID-540 did not. ID-540 did not affect the duration of hippocampal after-discharge whereas diazepam prolonged it. 5. ID-540 depressed more effectively the hippocampal arousal response to stimulation of the ventro-medial hypothalamus than did diazepam in rabbits. 6. ID-540 depressed amygdalo-hippocampal evoked potential in cats. 7. ID-540 did not affect norepinephrine-induced pressor response but reduced hypothalamic pressor response in cats.

Animals↗