Search PubMed⌕ Search

Biomedical subjects

T Yoshimi

Publications and source records attributed to T Yoshimi.

At least 109 records · Page 6Linked to original sources
PubMed1987

[Studies on cytosol thyroid hormone binding proteins in the rat liver: Part III. Partial purification and binding characteristics of thyroxine-binding protein in hypothyroid rat liver cytosol and serum].

Cytosolic thyroxine-binding protein (CT4BP) was partially purified from rat liver cytosol obtained 10 days after thyroidectomy using Sephadex G-200 gel filtration, and its binding characteristics were analyzed in displacement experiments using a charcoal binding method to separate bound and free hormones. Serum T4-binding proteins were also partially purified, and their binding characteristics were similarly determined. Sephadex G-200 gel filtration of liver cytosol from thyroidectomized rats revealed that CT4BP had an apparent molecular weight of 100 X 10(3) daltons. CT4BP had a very high affinity constant (Ka) of 2.2 +/- 10(10) M-1 and a small maximum binding capacity (MBC) of 5.1 X 10(-9) g/mg. protein for T4. Relative affinities of T4 analogues for CT4BP (if the affinity of L-T4 was assigned a value of 100, then D-T4 would have a value of 25.3; L-T3, 16.6; D-T3, 2.3; reverse T3, 1.4 and both Tetrac and Triac less than 1) showed that CT4BP had a rigid specificity for alanine-side chain of T4-molecule. This CT4BP was not demonstrated when cytosol from normal rat liver was used. Sephadex G-200 gel filtration of rat serum obtained 10 days after thyroidectomy revealed two T4-binding proteins. The faster peak (Peak I; MW about 100 X 10(3) daltons) was eluted before the albumin peak, and the slower peak (Peak II; MW about 56 X 10(3) daltons) appeared after the albumin peak. Peak I was barely detectable when normal rat serum was used. Peak I had a higher Ka of 2.0 X 10(10) M-1 and a smaller MBC of 3.9 X 10(-9) g/mg. protein than Peak II (Ka; 8.9 X 10(8) M-1, MBC; 3.7 +/- 10(-7) g/mg. protein). Relative affinities of T4 analogues for Peak I (L-T4 100, D-T4, 34.9, L-T3 11.1, D-T3 1.8, reverse T3 6.8, Tetrac 0.25 and Triac 0.1) showed that Peak I had a rigid specificity to alanine-side chain of T4 molecule, but Peak II had little specificity to this side chain (L-T4 100, D-T4 9.2, L-T3 2.1, D-T3 1.0, reverse T3 14.3, Tetrac 69 and Triac 26.3). Thus, Peak I had a similar binding characteristics to those of human thyroxine-binding globulin (TBG), and Peak II was comparable to human thyroxine-binding prealbumin (TBPA). The results that both molecular weight and binding characteristics were similar between CT4BP and Peak I suggest that both proteins are identical, being comparable to human TBG. This must be clarified in future.

Animals↗
PubMed1985

Effects of water deprivation and administration of hypertonic saline on dopamine concentrations in posterior pituitary and vasopressin release in rats.

Changes in concentrations of arginine vasopressin (AVP) in plasma and the neurointermediate lobe of the pituitary and those in dopamine (DA) in the neurointermediate lobe in rats were studied simultaneously after depriving the animals of water as well as after giving intraperitoneal (i.p.) injections of hypertonic saline (4.5% saline, 25 ml/kg of body weight). After water deprivation for 24 h, both AVP in plasma and DA in the neurointermediate lobe increased without any changes in AVP in the neurointermediate lobe. Water deprivation for 48-72 h caused further increases in both AVP in plasma and DA in the neurointermediate lobe with a significant decrease in AVP in the neurointermediate lobe. Rehydration for 24 h subsequent to 72 h of water deprivation made AVP in plasma and DA in the neurointermediate lobe return to the values of normally hydrated rats, whereas AVP in the neurointermediate lobe was still depressed. Thirty min after the i.p. injection of hypertonic saline, both AVP in plasma and DA in the neurointermediate lobe increased markedly with no change in AVP in the neurointermediate lobe. The time course of change in DA in the neurointermediate lobe was similar to that in plasma AVP when plasma osmolality was changed chronically or acutely. These results may make questionable the preconception that the tuberohypophyseal DA neurons are not involved in or regulated by early changes in vasopressin secretion.

Animals↗
PubMed1984

[A sensitive and specific radioimmunoassay for arginine vasopressin and its validation].

A sensitive and specific radioimmunoassay (RIA) for arginine vasopressin (AVP) has been developed and validated. Synthetic AVP was coupled to bovine serum albumin (BSA) with glutaraldehyde. Antisera against AVP were raised in three rabbits immunized with AVP-BSA complex. After 6 months, at the 16th injection, one of the antisera had a titer high enough to be utilizable for RIA at a final dilution of 1:400,000. The labeling of AVP with 125I Na was performed with the modified chloramine T method, and the purification of iodinated AVP was done with gel filtration chromatography on a Sephadex G-25 fine column (1 X 20 cm) with an elution buffer of 0.01 M acetic acid containing 0.1% BSA. Radioactivities from the Sephadex G-25 were eluted in three peaks. 125I-AVP, which was reactive to the antiserum, was contained in the third peak, and 125I-AVP in the fractions on the down slope of the peak was used for the radioligand in the amount of 1000 cpm. The specific activity of purified 125I-AVP was about 400 muCi/microgram. Diluted antiserum and samples, unlabeled AVP or related peptides were preincubated at 4 degrees C for 24 hr, and then 125I-AVP was added to the mixture and incubated for a further 72 hr. Separation of B and F was done with polyethyleneglycol. The minimal detection limit of AVP, which was 95% of the confidence limit of the mean value of B0, was 0.4 pg/tube. The cross-reactivities with lysine vasopressin, arginine vasotocin, DDAVP and oxytocin were 0.1%, 30%, 1% and 0%, respectively. AVP in plasma was extracted with cold acetone and petroleum ether. The recoveries of synthetic AVP from plasma which was added (2-16 pg) were more than 94%. The intra and inter-assay coefficients of variation determined by plasma of AVP concentration of about 4.8 pg/ml were 8.7% and 11.3%, respectively. The RIA detected AVP of concentration as low as 1 pg/ml following the extraction procedure. AVP immunoreactivity was detected without extraction in urine, and the lyophilized cerebrospinal fluid and acid extract of tissues of the central nervous system, and the reactivities in these samples were demonstrated to be immunologically identical to that of synthetic AVP when diluted serially. The changes of plasma and urinary AVP concentration on water intake, water deprivation and smoking in humans were clearly demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Effects of branched chain amino acid infusion on glucose metabolism in cirrhotic patients with encephalopathy.

An amino acid solution enriched in branched chain amino acids (BCAA) was administered to cirrhotic patients with encephalopathy and serial determinations of serum glucose, IRI and IRG were performed. Slight decrease of serum glucose was observed when only BCAA was given. On the other hand, when BCAA was infused with glucose, the serum glucose level decreased significantly after infusion (-77.5 +/- 26.2 mg/dl, p less than 0.01) and two cases of hypoglycemic shock were observed. Although both serum insulin and glucagon increased in these cases, the IRI/IRG molar ratio which was 8.9 at the start of infusion increased to 20.6 at the end of infusion. It was suggested that administration of BCAA with glucose caused hypoglycemia in cirrhotics with encephalopathy, possibly by synergistic action of BCAA and glucose on serum insulin level.

Amino Acids↗
PubMed1983

[Amerlex TSH].

Explore the source record for details and available documents.

Antibodies↗