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Biomedical subjects

T Takai

Publications and source records attributed to T Takai.

At least 127 records · Page 7Linked to original sources
PubMed1984

Primary structure of gamma subunit precursor of calf-muscle acetylcholine receptor deduced from the cDNA sequence.

Clones carrying cDNA sequences for the gamma subunit precursor of the acetylcholine receptor from calf skeletal muscle have been isolated. Nucleotide sequence analysis of the cloned cDNA has revealed the primary structure of this polypeptide, which consists of 519 amino acids including a hydrophobic prepeptide of 22 amino acids. The gamma subunit of the calf muscle acetylcholine receptor, like the alpha subunit of the calf as well as the human muscle receptor, shares features characteristic of all four subunits of the Torpedo electroplax receptor, such as the putative disulphide bridge corresponding to that in the alpha subunit proposed as being in close proximity to the acetylcholine binding site and the four putative, hydrophobic transmembrane segments M1-M4. Thus, the calf gamma subunit molecule apparently exhibits the same transmembrane topology as proposed for the fish receptor subunits. The degree of sequence homology between the calf and Torpedo gamma subunits (56%) is lower than that between the alpha subunits of the two species (81%). Some regions of the gamma subunit molecule, including the region encompassing the putative disulphide bridge and the region containing the putative transmembrane segments M1, M2 and M3, are relatively well conserved between the two species.

Amino Acid Sequence↗
PubMed1984

Characteristics of the thyroid iodide translocator and of iodide-accumulating phospholipid vesicles.

Some biochemical characteristics of the thyroid I- translocator and of I- accumulating phospholipid vesicles (P-vesicles) were studied. P-vesicles were made from thyroid plasma membranes (PM) and soybean phospholipids by sonication. The optimal incubation temperature for Na+-dependent I- accumulation in P-vesicles was from 18-26 C. Only a small amount of Na+-independent I- accumulation was observed at various incubation temperatures, but it increased in proportion with the temperature up to 36 C. The optimal incubation pH (7.0-7.5) was near the physiological extracellular pH. When PM were heated at 55 C for 30 min before preparation of P-vesicles, Na+-dependent I- accumulation in the vesicles decreased by 35%. When they were heated at 65 C for 30 min, the I- -accumulating activity was almost completely lost. The translocator was also inactivated when PM were sonicated at 37 C in the presence of trypsin. The internal and external administration of ouabain to the vesicles did not affect the activity of Na+-dependent I- accumulation. When PM were treated with sodium dodecyl sulfate at a final concentration of 0.2-0.6 mg/ml, the I- translocator was inactivated or detached from PM, whereas the ouabain-sensitive Na+, K+-ATPase activity was preserved in the PM fragments. These observations suggest that the thyroid I- translocator consists of a protein component that is bound to PM at a site separate from Na+,K+-ATPase.

Adenosine Triphosphatases↗
PubMed1984

[Infectious urachal cyst: a case report].

A case of an infectious urachal cyst that presented as a lower abdominal mass in a 44-year-old man is reported. There was no urinary tract infection. Cystoscopy revealed the dome retracted. All other investigations were normal without microscopic hematuria. Laparotomy revealed the mass attached to the small intestine because of infection. The mass was excised after partial resection of small intestine and partial cystectomy.

Adult↗
PubMed1983

Analysis of sialic acids by gas chromatography of the mannosamine derivatives released by the action of N-acetylneuraminate lyase.

A convenient method for the analysis of sialic acids is proposed, which is based on their dissociation into pyruvate and N-acylmannosamines by the action of N-acetylneuraminate lyase, followed by gas-chromatographic analysis of the latter products as trimethylsilylated diethyl dithioacetals. Conjugated sialic acids should be freed with neuraminidase before being subjected to the action of the lyase, but these sequential enzymic reactions may be performed in one pot. N-Acetyl-, N-glycolyl- and N,O-diacetylneuraminic acids gave the corresponding mannosamines, and the dithioacetal derivatives of these mannosamines were well separated on a column of silicone OV-1. Quantitation of this enzymic and gas chromatographic method indicated that the error and coefficient of variation for free N-acetylneuraminic acid were 1.1% and 2.5%, respectively, for ten determinations at the 100 nmol level. The values for conjugated N-acetylneuraminic acid in N-acetylneuraminlactose were 2.9% and 5.9%, respectively. This method was applied to the analysis of sialic acids in some biological samples, and the results were compared with those obtained by the conventional colorimetric method. Preliminary data on urinary sialic acids indicated that cancerous patients gave significantly higher levels of urinary N-acetylneuraminic acid than normal subjects.

Adult↗
PubMed1983

Valinomycin-induced iodide leakage without impairment in sodium-dependent iodide transport in the thyroid.

The mechanism of inhibition of I- accumulation in the thyroid by valinomycin was investigated on a biological model. Phospholipid vesicles (P-vesicles) capable of Na+-dependent I- accumulation were reconstituted with thyroid plasma membrane (PM). In P-vesicles internally loaded with K+, Na+-dependant I- accumulation was observed in the presence of external Na+. The accumulated I- was discharged from the vesicles by addition of valinomycin. In P-vesicles with internal choline+, Na+-dependent I- accumulation also occurred, but I- discharge was not induced by the addition of valinomycin. P- vesicles without a PM component readily accumulated I- in the presence of both external K+ and valinomycin. P-vesicles with thyroid PM also accumulated I- rapidly in the presence of external K+ upon the addition of valinomycin; however, the accumulated I- was significantly discharged when the vesicles were loaded internally with Na+. A significant I- discharge was not observed in the vesicles with or without thyroid PM when they were loaded with choline+ instead of Na+. Valinomycin-induced I- uptake without leakage was observed in both Na+- and choline+-loaded P-vesicles containing liver PM instead of thyroid PM. These results indicate that valinomycin may inhibit I- accumulation in thyroid cells according to the following mechanism: 1) valinomycin, a K+ carrier, induces K+ efflux to form a gradient of electrical potential with a negative charge within the cells, and 2) I- is subsequently driven out down the gradient through the phospholipid bilayer. Na+-dependent I- transport may not be impaired by valinomycin.

Animals↗
PubMed1983

Visual field defects and pituitary enlargement in primary hypothyroidism.

In 14 patients with overt primary hypothyroidism, we examined visual fields by Goldmann's isopter perimetry. An unexpectedly high incidence (10 patients, 71.4%) of visual field defects was found. Two patients complained of visual failure, whereas 12 had no subjective symptoms. The extent of visual field change varied over a wide range, from early chiasmal compression to apparent bitemporal hemianopsia. The abnormality was characteristically restriction in the central visual field; peripheral vision was less often affected. The sella turcica was significantly enlarged in these patients as compared to controls. The volume of the sella turcica correlated significantly with both basal serum TSH and total pituitary reserve of TSH (r = 0.82, P less than 0.001). There was no correlation between the extent of visual field change and the volume of the sella turcica or pituitary TSH reserve. Of 10 patients with visual field defects, 8 improved during 1-4 months of T4 replacement. In 2 patients, however, the visual field defect deteriorated during replacement. The deterioration occurred when serum TSH levels had decreased to about 50% and 20% of pretreatment values, respectively. The peak serum TSH after TRH stimulation was higher at the time of deterioration than before treatment. Visual fields became normal during treatment with an increased dose of T4 (200 micrograms/day), when serum TSH was suppressed to an undetectable level. The paradoxical course of visual failure during T4 replacement may be due to an imbalance between TSH synthesis in the pituitary and TSH release which may induce an increase in pituitary size. The data suggest that visual field defects and their deterioration are due to pituitary hyperplasia and are reversible with T4 replacement. In order to rule out a pituitary tumor, hypothyroid patients with visual failure should be followed during T4 replacement therapy.

Adult↗
PubMed1983

Inhibition of iodide accumulation by perchlorate and thiocyanate in a model of the thyroid iodide transport system.

The manner of inhibition of thyroid I- accumulation by perchlorate (CIO4-) and thiocyanate (SCN-) was studied using a newly developed biological model of the I- transport system. CIO4- inhibited I- accumulation in phospholipid vesicles made from thyroid plasma membrane and soybean phospholipids by decreasing Na+-dependent I- influx. The anion did not at all induce I- leakage from the vesicles. On the basis of Lineweaver-Burk plot analysis, it did not change Vmax for I- concentration. These results suggest that CIO4- is a competitive inhibitor of thyroid I- transport. In contrast, SCN- did increase I- leakage from the phospholipid vesicles to diminish I- accumulation. This anion might cause only slight depression of Na+-dependent I- entry, if any. The results do not support the idea that SCN- may be a competitive inhibitor, in spite of the fact that the anion did not change Vmax for I- transport on the basis of Lineweaver-Burk plot analysis.

Cell Membrane↗
PubMed1983

Diagnosis of exophthalmos using orbital ultrasonography and treatment of malignant exophthalmos with steroid therapy, orbital radiation therapy, and plasmapheresis.

For the quantitative analysis of the extraocular muscle changes in Graves' disease, we used B-mode ultrasonography. 113 patients investigated in this study had no signs or symptoms of ophthalmopathy except proptosis. Muscle index was calculated as a sign of extraocular muscle enlargement. Muscle index of Graves' disease was significantly larger than that in controls (6.03 +/- 2.83 and 3.10 +/- 1.29, respectively). The muscle index in Graves' patients without clinical signs of exophthalmos was significantly increased when compared to control subjects, although both groups had the same degree of proptosis. The data show a uniform enlargement of the extraocular muscles in Graves' disease. The degree of proptosis is in close proportion to the quantitative change of the orbital soft tissue. Seven patients with malignant exophthalmos were treated with steroid therapy, supervoltage orbital radiotherapy or plasmapheresis. All patients had moderately severe ophthalmopathy due to Graves' disease. Both steroid therapy and orbital radiation therapy were effective in improving the symptoms of orbital soft tissue involvement and for diplopia. The effect of orbital radiation therapy was insufficient for the amelioration of proptosis in spite of a no significant decrease. The improvement of proptosis was evident only after 3-7 months of the radiotherapy. Plasmapheresis was effective in improving the ulceration of cornea and proptosis, but this was a transient effect.

Exophthalmos↗
PubMed1983

Unusual manifestations in primary hypothyroidism.

Nineteen patients with overt hypothyroidism were examined for the prevalence of myocardial disfunction, respiratory disturbances, peripheral neuropathy, and visual failure due to pituitary enlargement. Prevalences of pericardial effusion and myocardial disfunction (decrease PEP/LVET) were 50% and 75%, respectively. The degree of decreased myocardial function did not parallel with the grade of pericardial effusion. Arterial blood analysis indicated a frequent incidence of hypoxia in hypothyroidism. The incidence of hypoxia was 69%. The hypoxia was improved by thyroxine replacement therapy. In 6 patients examined for the ventilatory control, all had the index for hypercapnic ventilatory drive lower than normal control. It was suggested that the hypoxia in hypothyroidism was caused by a depression of the respiratory center in the brain and by anemia. Sensory nerve conduction was diminished in 6 of 11 hypothyroid patients and motor conduction in 6 of 15 was studied. In distal segments of sensory nerves, the abnormality frequently appeared before clinical symptoms of polyneuropathy. Visual field defect was detected in 71% of patients suffering of primary hypothyroidism. The most common characteristic change was the defect in the central visual field. All cases of visual field defect were cured by thyroid hormone replacement therapy. Two cases with deteriorated visual failure who did not improve during physiological replacement, were successively treated with over dosage of thyroid hormone.

Blood Gas Analysis↗
PubMed1982

Enzyme immunoassay for cytidine 3',5'-cyclic monophosphate (cyclic CMP).

An enzyme immunoassay for cytidine 3',5'-cyclic monophosphate (cyclic CMP) is presented. This assay is based upon the principles of competitive reaction and the double antibody solid phase method. Succinyl cyclic CMP-human serum albumin conjugate was injected into rabbits. Specific anti-cyclic CMP antibodies were incubated with a mixture of succinyl cyclic CMP labeled with beta-D-galactosidase and standard or sample cyclic CMP that had been succinylated prior to assay. The antibody-bound beta-D-galactosidase-cyclic CMP conjugate was separated from that of free with a second antibody, anti-rabbit immunoglobulin G, that was immobilized to a polystyrene ball. Then, activity of the enzyme on the solid phase was fluorometrically determined. When cyclic CMP contents in biological materials were estimated, acid extracts were partially purified by Dowex 1 x 8 formate column chromatography. The present immunoassay allows the detection of as little as 0.5 fmol of cyclic CMP with practically no interference from other cyclic nucleotides and cytidine analogs. By use of the enzyme immunoassay technique, we determined the amounts of cyclic CMP in various tissues of rats. They were found to be as little as 0.24-0.51 pmol/g wet weight, which was roughly 3000 to 20,000 and 100 to 500 times less than those of cyclic AMP and cyclic GMP, respectively.

Animals↗
PubMed1982

Double antibody enzyme immunoassay for the quantitation of adenosine 3', 5' -cyclic monophosphate (cyclic AMP) and guanosine 3', 5'-cyclic monophosphate (cyclic GMP) in tissue and plasma.

A sensitive double antibody enzyme immunoassay for the quantitation of cyclic AMP and cyclic GMP is presented. Specific antisera to each nucleotide were raised in rabbits by immunization with succinyl cyclic nucleotide-human serum albumin conjugates. For competitive reaction, antibodies were incubated with a mixture of succinyl cyclic nucleotide labelled with beta-D-galactosidase and unlabelled succinylated standard or sample cyclic nucleotides. The antibody-bound enzyme-hapten was separated from free hapten by anti-rabbit IgG immobilized to a polystyrene ball. Activity of the enzyme on the solid phase was fluorometrically determined. The assay system made it possible to ascertain values as low as 5 fmole of cyclic AMP or cyclic GMP. Cyclic nucleotides in plasma could be accurately determined by this method without requiring a deproteinizing reagent as the first step of assay.

Animals↗
PubMed1982

The sodium-dependent iodide transport by phospholipid vesicles reconstituted with the thyroid plasma membrane.

The I- transport system in the thyroid plasma membrane (PM) was successfully reconstituted in phospholipid vesicles (P-vesicles) by sonication. P-vesicles thus prepared were able to concentrate I- in the presence of external Na+. The activity of the I- transport increased with increase in the Na+ concentration outside the P-vesicles and with graded doses of PM protein used for the reconstitution in P-vesicles. When P-vesicles were prepared with only the lipid components extracted from PM instead of total PM, they were deprived of the biological activity to accumulate I-. Methimazole (MMI) did not change the Na+-dependent I- transport, but ClO4- and SCN- had inhibitory effects on the transport. These observations indicate that 1) a specific I- translocator is present in the thyroid PM, 2) the translocator is easily reconstituted in P-vesicles, 3) the translocator may not consist of phospholipids despite the theory of the I -concentrating thyroid phospholipids, and 4) Na+-I- cotransport through the translocator may be the mechanism for the accumulation of I- in the thyroid cells.

Animals↗
PubMed1982

Creutzfeldt-Jakob disease with demonstration of virus-like particles.

Two kinds of virus-like particles, doughnut-shaped particles and particles with dense core, were discovered in a brain tissue from a patient with Creutzfeldt-Jakob disease. The two types of virus-like particles are similar to immature type C and type C particles. although no direct relationship between Creutzfeldt-Jakob disease and these virus-like particles can be established, these facts may suggest that viruses play some role in the pathogenesis of Creutzfeldt-Jakob disease.

Aged↗
PubMed1982

Treatment of Graves' ophthalmopathy by steroid therapy, orbital radiation therapy, plasmapheresis and thyroxine replacement.

Thirteen patients with moderately severe ophthalmopathy due to Graves' disease were treated by steroid therapy, supervoltage orbital radiotherapy, plasmapheresis and thyroxine replacement. All patients complained of chemosis, ocular pain and diplopia. The mean value of proptosis was 21.3 mm. Eleven patients (84.6%) showed some improvement, but the effect was mostly on the symptoms of orbital soft tissue involvement. The effect on proptosis was rather unsatisfactory. In six patients (46.2%) proptosis decreased by 2.3 mm on the average, but they still had more noticeable exophthlamos than patients with Graves' disease without infiltrative ophthalmopathy. For regression of proptosis, radiation therapy was the most beneficial therapeutic regimen in this study, especially in the patients who received the treatment shortly after the beginning of malignant exophthlamos.

Female↗