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Biomedical subjects

N Takeuchi

Publications and source records attributed to N Takeuchi.

At least 397 records · Page 22Linked to original sources
PubMed1967

Anion permeability of the inhibitory post-synaptic membrane of the crayfish neuromuscular junction.

1. The membrane conductance of the crayfish muscle fibre was calculated and the increase in the membrane conductance brought about by the application of gamma-aminobutyric acid (GABA) was investigated under various conditions. The permeability of the activated inhibitory post-synaptic membrane was estimated from the conductance change.2. When the concentration of Cl(-) was changed by substituting Cl(-) with methylsulphate, a linear relation was obtained between the membrane conductance change produced by GABA and the concentration of Cl(-). Cations have no appreciable effect on the GABA induced conductance change (less than 0.4%).3. The conductance change produced by GABA on the inhibitory post-synaptic membrane was measured in various solutions in which the Cl(-) was replaced by various anions. The degree of permeability depended on the anion species in the following order:Br(-) > Cl(-) > SCN(-) > I(-) > NO(3) (-) > HCOO(-) > ClO(3) (-) > ClO(4) (-) > BrO(3) (-)4. At high pH the conductance change produced by GABA was decreased, while at low pH it increased.5. These results show that the activated inhibitory post-synaptic membrane of crayfish muscle fibres has the characteristics of an anion selective membrane, suggesting the fixed positive charges in the inhibitory membrane.

Aminobutyrates↗
PubMed1966

A study of the inhibitory action of gamma-amino-butyric acid on neuromuscular transmission in the crayfish.

1. The effect of gamma-aminobutyric acid (GABA) on the neuromuscular junction of the crayfish (Cambarus clarkii) was investigated. The drug was applied iontophoretically to a junction and the potential changes were recorded intracellularly as well as extracellularly with micro-electrodes.2. The amplitude of the potential produced by iontophoretically applied L-glutamate was decreased by simultaneous application of GABA to the same junctional area. When the membrane potential was clamped at the resting level the clamping current for the L-glutamate injection was not changed by GABA application, indicating that there is no appreciable competition between L-glutamate and GABA for the glutamate-sensitive receptor.3. The excitatory nerve was stimulated repetitively and the excitatory junctional potentials (e.j.p.s) were recorded extracellularly with a micro-electrode placed on the surface of the muscle. The average size of the extracellular e.j.p.s was reduced by the application of GABA.4. The number of quanta released per impulse calculated from the extracellular e.j.p.s was decreased during the application of GABA, while the quantum size remained unchanged.5. The size of the excitatory presynaptic nerve spike was decreased by the application of GABA. However, no appreciable change was observed in the inhibitory nerve spike.6. These results indicate that in addition to its post-synaptic action GABA acts on the excitatory presynaptic nerve terminal and reduces the release of the transmitter.

Aminobutyrates↗
PubMed1966

On the permeability of the presynaptic terminal of the crayfish neuromuscular junction during synaptic inhibition and the action of gamma-aminobutyric acid.

1. The contribution of chloride to presynaptic inhibition of the crayfish neuromuscular junction during the action of gamma-aminobutyric acid (GABA) and the inhibitory transmitter was investigated. Chloride in van Harreveld's solution was replaced with propionate, acetate, methylsulphate or glycerophosphate and electrical changes were recorded intracellularly and extracellularly with micro-electrodes.2. When the preparation was soaked in Cl-deficient solutions, the quantum content of the excitatory junctional potentials (e.j.p.s), calculated from the number of failures, was increased.3. The presynaptic inhibitory action of GABA was reduced or almost absent when the preparation was soaked in Cl-deficient solution. In Cl-deficient solution the stimulation of the inhibitory axon showed little or no inhibitory action on e.j.p.s.4. If GABA was applied shortly after the outside solution was changed to the Cl-deficient one, the frequency of the spontaneous e.j.p.s was increased transiently.5. It is suggested that GABA or the inhibitory transmitter act on the presynaptic excitatory terminal and predominantly increase its permeability to chloride.

Journal Article↗
PubMedDate not supplied

Age-related changes of bile acid metabolism in rats.

Cholesterol and bile acid leves were examined in young (8 weeks), middle-aged (12 months) and old (24 months) germ-free male rats, and young (8 weeks) and middle-aged (12 months) conventional male rats. The plasma cholesterol levels were higher in the aged rats, being more marked in the conventional rats. The liver cholesterol levels also increased with age and the increases were almost identical for both groups. No age-related changes were found in the biliary bile acid secretion, the pool size and distribution of bile acids in the bile, small intestine and large intestine, nor in the turnover frequency of bile acids, but the pool size in the young and middle-aged germ-free rats was much larger than that in the conventional rats. The turnover frequency was less in the germ-free rats. The bile acid synthesis presumed from the fecal bile acid excretion decreased in the aged germ-free rats but not in the conventional rats. A most remarkable age-related change was found in the bile acid composition; cholic acid increased and beta-muricholic acid derived from chenodeoxycholic acid in the rat decreased by aging, resulting in an increase of the CA/CDCA ratio (bile acids belonging to the cholic acid group/bile acids to the chenodeoxycholic acid group) in the bile, feces and pool. These results suggest that cholic acid synthesis increases while chenodeoxycholic acid synthesis is impaired by aging in rats.

Journal Article↗
PubMedDate not supplied

Bile acid synthesis in young and old rats.

Bile acid synthesis from orally administered (14)C-cholesterol or from (14)C-mevalonic acid administered intravenously were examined in male and female 2-, 12- and 24-month-old rats. About 5-9% of the '4C-cholesterol administered was recovered as bile acids from the small intestine 3 days after administration. The value in the case of (14)C-mevalonic acid was about 1/10 that of (14)C-cholesterol. Major bile acids were cholic acid and beta-muricholic acid, and the formation ratio of cholic acid increased in aged rats, although no further difference was found between 12- and 24-month-old animals of either sex. Male rats formed more beta-muricholic acid than females at all ages examined. In addition, no significant difference was found in the bile acid composition between both precursors, (14)C-cholesterol and (14)C-mevalonic acid.

Journal Article↗
PubMedDate not supplied

Permanent cell culture lines of rat erythroleukemia and growth inhibition by dexamethasone in vitro.

Four erythroleukemia cell lines were established in vitro from rats with primary leukemias induced by a set of intravenous injections of 7,8,12-trimethylbenz[a] anthracene (TMBA). These cell lines were grown in Dulbecco's medium with 20% inactivated fetal calf serum; they were characterized by specific consistent chromosome abnormalities, related to No. 2 chromosome, which were maintained in culture for more than 1 year. Addition of dexamethasone prevented the cell growth of 2 of the cell lines in this medium but failed to alter the growth rate of the other 2 cell lines. These findings are correlated with karyotype abnormalities involving chromosome No. 2.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

Head and neck carcinoma: detection of extraorgan spread with MR imaging and CT.

A retrospective analysis of the Magnetic resonance (MR) and CT findings in 18 untreated carcinomas of the oral cavity (7), oropharynx (2), hypopharynx (7), and larynx (2) was performed to assess the accuracy in evaluating extraorgan tumor spread and nodal involvement. Surgical and pathologic correlation was available for 13 primary tumors and nodal status was analyzed in 18. Nine primary tumors had extraorgan extension. MR had a tendency to be superior to CT in predicting tumor invasion of the cartilage and muscle. Sensitivity, specificity and accuracy for extraorgan spread of primary tumors were 89%, 100% and 92%, respectively, for MR and 78%, 75% and 77% for CT. Accuracy for nodal classification (83%) and carotid invasion (94%) of MR was equal to that of CT. CT was more sensitive than MR for demonstrating necrosis within the nodes and vice versa for detecting retropharyngeal nodes. MR imaging is a useful radiologic modality in evaluating extraorgan tumor spread and nodal levels of the head and neck carcinomas.

Adult↗
PubMedDate not supplied

Inclined coronal scans in thoracic MR imaging.

To determine the value of inclined coronal MR in diagnosing thoracic abnormalities, the multiscan coronal and inclined coronal spin echo MR images of 4 normal subjects and 10 patients with thoracic abnormalities were reviewed. The major airway such as trachea, main bronchi and lobar bronchi, left atrium and its junctions with pulmonary veins required less slices for visualization on inclined coronal images than on standard coronal images, and these normal structures and the lesions located in this region were easy to evaluate in several cases. The left pulmonary artery, especially the upper and lower lobe branches were better visualized on inclined coronal images. The pericardium and the other great vessels were equally visualized on inclined and on standard coronal images. There was no case in which normal structures or lesions were more difficult to demonstrate on inclined coronal images compared with standard coronal images. We conclude that an inclined coronal MR scan of the thorax is valuable to evaluate the mediastinal structures and lesions, especially in diagnosing the abnormalities of the airway, left atrium and its junctions with pulmonary veins.

Adult↗
PubMedDate not supplied

Mediastinal lymph node metastases from nonsmall cell bronchogenic carcinoma: reevaluation with CT.

We evaluated the sensitivity of CT for detecting mediastinal lymph node metastases in patients with nonsmall cell bronchogenic carcinoma. Computed tomography of 208 cases of surgically proven bronchogenic carcinoma from three institutes was evaluated retrospectively using specific diagnostic criteria. These consisted of two size thresholds for specific mediastinal node regions: 13 mm short transverse diameter for nodes in the subcarinal, precarinal, and tracheobronchial regions and 10 mm for other regions. Based on these criteria, the overall sensitivity of CT was 69%, specificity 94%, and accuracy 86% for detection of metastasis. In cases of adenocarcinoma, sensitivity was 61%, specificity 93%, and accuracy 81%, and in those of squamous cell carcinoma the respective values were 86, 94, and 92%. Comparison between the results using the present criteria with the former criterion of 10 mm short transverse diameter for all mediastinal nodes revealed that the number of false-positive cases decreased markedly. We conclude that more accurate CT evaluation of mediastinal lymph node metastasis in nonsmall cell bronchogenic carcinoma can be achieved with specific size criteria for specific mediastinal regions.

Adenocarcinoma↗
PubMedDate not supplied

MR imaging of Sjögren syndrome: correlation with sialography and pathology.

Magnetic resonance (MR) imaging of the parotid glands were performed in 13 cases of Sjögren syndrome to assess if there are any typical MR features. The MR findings were compared with sialography and pathology results. Signal intensity ratios of parotid (minus background noise) to skeletal muscle (minus background noise) were measured in these 13 cases as well as in 10 normal controls. Both T1- and T2-weighted images showed multiple hypointense mixed with hyperintense foci (salt-and-pepper appearance) throughout the glands in the six Sjögren cases of intermediate severity (46%), inhomogeneous glands in five cases with early or advanced disease, and homogeneous glands in the remaining two cases with the earliest stage of disease. Mean intensity ratios in T2-weighted pulse sequences in patients with salt-and-pepper appearance and inhomogeneous glands were significantly smaller than those in normal controls (p less than 0.05 and p less than 0.001, respectively). Pathologic studies tend to indicate that focal lymphocytic aggregates associated with increased interlobular fibrosis are probably responsible for the hypointense foci and the decrease in intensity ratios. We think that the salt-and-pepper appearance is suggestive of Sjögren syndrome and that the decreased intensity ratios combined with a typical clinical picture may lead to a highly probable diagnosis of this disorder.

Adult↗