Binding pattern of 125Iodine thyroxine and tri-iodothyronine in skin and liver tissues of spotted munia, Lonchura punctulata: Co-relation to seasonal cycles of breeding and molting.

Prevalent notion about thyroid hormones is that thyroxine (T4) is a mere precursor and physiological effects of thyroid hormones are elicited by tri-iodothyronine (T3) after mono-deiodination of T4. Earlier studies on feather regeneration and molt done on spotted munia L. punctulata suggest that T4 (mono-deiodination suppressed by iopanoic acid and thyroidectomized birds) is more effective than T3 in inducing feather regeneration. The binding pattern of 125I labeled T4 and T3 has been investigated in the nuclei prepared from skin and liver tissues (samples obtained during different months) of spotted munia using scatchard plot analysis. The results show that binding capacity (Bmax – pmole/80 µgm DNA) of 125I-T3 to nuclei of skin was significantly higher in November as compared to April and June, whereas the binding affinity (Kd-10-9M-1) was significantly lower in November as compared to April and June. During November, Bmax for binding of T3 and T4 did not vary in liver and skin nuclei but Kd varied significantly. Binding capacity of 125I- T3 to skin and liver did not vary but binding affinity of 125I- T4 to skin was approximately 7 times higher than that of liver. The results suggest that T4 does show a variation in binding pattern that co-relates to the molting pattern of spotted munia. These variations might play important role in different physiological phenomenon in this tropical bird. The experiments do point towards the possibility of independent role of T4 as a hormone, however, further experiments need to be done to ascertain the role of T4 in this model and work out the exact molecular mechanism of action.

In-vitro interaction of verapamil hydrochloride with magnesium sulphate (anhydrous) and its influence on protein binding of verapamil hydrochloride.

The interaction between Verapamil Hydrochloride and Magnesium Sulphate (anhydrous) has been studied in an aqueous system at pH 7.4 and 2.4. From spectrophotometric study, it has been found that Verapamil Hydrochloride form 1:1 complex with Magnesium Sulphate (anhydrous). Spectral studies helps to detect the initial complexation between drug and metal. Job’s plot at 7.4 and 2.4 provides same type of information. The Ardon’s spectrophotometric method confirmed the 1:1 complexation and the value of stability constants was calculated using Ardon’s plot. An in vitro study of protein binding of Verapamil Hydrochloride and their 1:1 mixture with Magnesium Sulphate (anhydrous) has been conducted by equilibrium dialysis method at (37 ± 0.5)0C and at pH 7.4. The Scatchard plots were prepared to reveal the number of binding sites and the affinity for protein binding. It has been found that interaction of the drug with Magnesium Sulphate (anhydrous) results into increasing the affinity and increasing the protein binding of Verapamil Hydrochloride.

Irreversibility of the interaction of human growth hormone with its receptor and analysis of irreversible reactions in radioreceptor assays—Theoretical considerations.

Kinetic studies of the binding and dissociation of [125I]-human growth hormone to rabbit liver and mammary gland membrane receptors have showed that the binding of [125I]- human growth hormone was largely irreversible to liver membrane receptors and completely to the solubilised mammary gland receptor. As Scatchard analysis assumes complete reversibility of the hormone-receptor interaction the validity of estimates of affinity and capacity of receptors derived by this analysis may be questionable. Theoretical considerations show that in unimolecular irreversible interactions of hormone and receptor, a nonlinear (concave) or a linear Scatchard plot can be obtained. In linear Scatchard plots the capacity of the receptor obtained by extrapolation represents an overestimation of true capacity. This overestimation correlates with the value of the intercept in the Scatchard plot.

The establishment of ACTHR detecting method and assay of ACTHR on rat thymocytes / 中国免疫学杂志

In this paper, it was reported that rat thymocytes harbor both high and low affinity ACTHR. The proper number of thymocytes used for deterting ACTHR varies from 1?10~6 /0.2 ml to 2 ?10~6 /ml, the maximum binding of ACTH to ACTHR occurs at 20 minutes. The IC_(50) for ACTH concentration is 800 nM or so. The saturation curves show that thymocyte ACTHRs are saturated at the concentration of 2.5 nM of ~(125)IACTH. There are high affinity ACTHR of 840 sites/cell on thymocyte (KD=0.15nM, Bmax = 2. 8 fmol/2 ? 10~6 cells); whereas low affinity ACTHRs are 12400 sites/cell (KD=4.2 nM, Bmax = 41.5 fmol/2 ? 10~6 cells).Moreover amputation stress can reduce thymocyte ACTHR remarkably.