Synthetic Tyr-phospho and non-hydrolyzable phosphonopeptides as PTKs and TC-PTP inhibitors*

Tyrosine-specific protein kinases and phosphatases are important signal transducing enzymes in normal cellular growth and differentiation and have been implicated in the etiology of a number of human neoplastic processes. In order to develop agents which inhibit the function of these two classes of enzymes by interfering with the binding of their substrates, we synthesized analogs derived from the peptide EDNEYTA. This sequence reproduces the main autophosphorylation site of Src tyrosine kinases. In this work we report the synthesis, by classical solution methods, of the phosphotyrosyl peptide ED-NEYpTA as well as of three analogs in which the phosphotyrosine is replaced by a phosphinotyrosine and by two unnatural, non-hydrolyzable amino acids 4-phosphonomethyl-l -phenylalanine and 4-phosphono-l -phenylalanine. The Src peptide and its derivatives were tested as inhibitors of three non-receptor tyrosine kinases (Lyn, belonging to the Src family, CSK and PTK-IIB) and a non-receptor protein tyrosine phosphatase obtained from human T-cell (TC-PTP). The biomimetic analogues, which do not significantly affect the activity of CSK, PTK-IIB and TC-PTP, act:is efficient inhibitors on Lyn, influencing both the exogenous phosphorylation and, especially, its autophosphorylation. In particular, the Pphe derivative may provide a basis for the design of a class of inhibitors specific for Lyn and possibly Src tyrosine kinases, capable of being used in vivo and in vitro conditions. © Munksgaard 1995.     

Sleep and time course of consolidation of visual discrimination skills in patients with narcolepsy–cataplexy

The level of procedural skills improves in normal individuals when the acquisition is followed by a period of sleep rather than wake. If sleep plays an important role in the consolidation process the advantage it provides should be reduced or delayed when its organization is altered, as in patients with chronic sleep disorders. To test this prediction in patients with narcolepsy–cataplexy (NC), who usually have a more fragmented organization of sleep than normals, we compared the initial, intermediate and delayed level of consolidation of visual skills . Twenty-two drug-naive NC patients and 22 individually-matched controls underwent training at a texture discrimination task (TDT) and were re-tested on the next morning (after a night spent in laboratory with polysomnography) and after another six nights (spent at home). TDT performance was worse in patients than controls at training and at both retrieval sessions and the time course of consolidation was different in NC patients (who improved mainly from next-day to 7th-day retrieval session) compared with controls. Moreover, the less-improving patients at next-day retrieval had a wider disorganization of sleep, probably because of an episode of rapid eye movement (REM) sleep at sleep onset REM, on post-training night more frequently than more-improving patients. These findings suggest that the time course of the consolidation process of procedural skills may be widely influenced by the characteristics of sleep organization (varying night-by-night much more in NC patients than controls) during post-training night.     

Glycated plasma proteins in experimentally induced acute toxic renal failure by dichromate injection: evidence for loss with urine and decreased plasma levels.

In the rat, a single subcutaneous injection of sodium dichromate (20 mg/kg) causes acute renal injury and significant polyuria, proteinuria, and glycosuria (peaking 2–3 days after treatment, and returning to normal by day 5) without any changes in the plasma levels of protein, glucose, and glycated haemoglobin. Surprisingly, the percentage levels of glycated plasma total proteins and albumin (assayed by boronate affinity chromatography) transiently and significantly decrease during recovery from proteinuria (days 4 and 10 after treatment) and were found in the normal range of values by day 18. These changes are concomitant with a significant increase in the percentage level of glycated albumin in urine. Constancy of total plasma protein and the temporal pattern of levels of glycation suggest that changes in the percentage values of glycated proteins are secondary to a transient selective loss of glycated plasma proteins in urine.     

DIFFERENT AFFINITY OF CORTICAL GHB BINDING SITES IN SARDINIAN ALCOHOL-PREFERRING (sP) AND-NON PREFERRING (sNP) RATS

Specific gamma-hydroxybutyric acid (GHB) binding sites in corticalmembranes of selectively bred alcohol-preferring sP and alcohol-nonpreferring sNP rats were compared using [2,3³H]GHB ligand. ThesP rat line showed an increased affinity (-40% lower K_d) ofboth the high- and low-affinity sites in comparison with thesNP line. No significant difference in GHB receptor density(B_max) was detected between the two rat lines. The results raisethe possibility that differences in GHB binding sites may playa role in the genetic predisposition to ethanol preference inour rat line.