Ligand effects on the dephosphorylation of heart and skeletal muscle specific phosphorylases

Pseudo first order rate constants were determined for the dephosphorylation of heart and skeletal muscle specific phosphorylase a isoenzymes isolated from rabbit and pig using rabbit muscle phosphorylase phosphatase (mol. wt 34,000). The rate constants determined in the absence of ligands, were 4-5 fold lower for heart specific phosphorylases than for skeletal muscle specific ones. Glucose 6-phosphate (0.5-1 mM) enhances the rate of dephosphorylation of heart specific isophosphorylases 3-fold and suspends inhibition by 10(-5) M AMP, however, it has no significant effect on the dephosphorylation of skeletal muscle specific enzymes under the same conditions. Our data support characteristic functional differences between heart and skeletal muscle specific phosphorylases both in rabbit and pig.     

Free radical signal of bile pigment in paraffin embedded liver tissue

A linear correlation have been found between the amplitude of the free radical signal of the electron spin resonance (ESR) spectrum of paraffin embedded liver blocks and the number of bile casts in the histological sections made from these blocks. It has been suggested that the major part of the ESR free radical signal arises from bile pigment, but the contribution of "age pigment" cannot be excluded. On the basis of model experiments the majority of these radical centers was assigned to protein bound bilirubin. In the course of histological processing more than 80% of various free radical centers arising in air dried liver tissue is extracted.     

New technique in optical resolutions

The present paper illustrates the development of an advanced technique in optical resolution. Both of the amphetamine enantiomers can be obtained by a two-step distillation in nearly quantitative yield without any loss of the resolving agent. It is proved that the second-order interactions (H-bond) are sufficient for separation of enantiomers by distillation. © 1994 Wiley-Liss, Inc.     

Study of the imprinting and overlap of insulin and concanavalin-A at the receptor level in a protozoan (Tetrahymena) model system

In a protozoan (Tetrahymena) model system, insulin treatment produced a long-term imprinting which upon re-exposure to the hormone resulted in an enhanced binding of the hormone. Insulin pretreatment produced similar effect with regard to the binding of concanavalin-A. Concanavalin-A could only induce a short-term imprinting for itself and was not capable at all of inducing imprinting for insulin. Based on the results of this study it appears that the binding of the sugar component of the receptor, which can be achieved also by lectin, is not sufficient to induce imprinting but the whole (hormone) molecule is needed.     

Involvement of the phosphoinositol (PI) system in the mechanism of hormonal imprinting

Certain components of the phosphoinositol (PI) system are present in the unicellular Tetrahymena. Treatment of Tetrahymena with insulin did not alter the relative proportions of the examined six phospholipid components (PIP2, PIP, phosphatidylcholine, phosphatidylethanolamine, PI, PA), but the primary interaction (imprinting) with insulin accounted for an about 75% decrease in the PIP2-level and an about 20% increase in the phosphatidylethanolamine level. The experimental results strongly suggest that hormonal imprinting accounted for adjustment of the second messenger systems of Tetrahymena to an energy saving level.