Plasma and platelet associated factors act in G1 to maintain proliferation and to stabilize arrested cells in a viable quiescent state : A temporal map of control points in the G1 phase

In medium supplemented with defibrinogenated, platelet-poor human plasma and a low molecular weight growth factor derived from human platelets (PDGF), Swiss 3T3 cells proliferate exponentially with the same cell cycle kinetics as cells cultured in medium supplemented with commercial calf serum. Removal of PDGF from the culture medium arrests proliferating cells in a stable, reversible G0/G1 quiescent state. This arrested state is similar to the known quiescent state induced by deprivation of calf serum in cell exit kinetics and cytoplasmic proteins synthesized. Cells are sensitive to PDGF deprivation only at the beginning of G1. Reduction of the plasma concentration in the culture medium also arrests cells in G1. The resulting arrested population is unstable and exhibits progressive cell death. Reduced levels of plasma block cellular transit through the cell cycle at a median time of approx. 2.1 h following mitosis, approx. 3.3 h prior to S phase initiation. In addition to being required by cycling cells, plasma associated factors are required to maintain G1 cells blocked by PDGF deprivation in a stable quiescent state. Establishment of a stable, viable G0/G1 growth-arrested state, therefore, apparently involves two distinct processes: arrest of cellular proliferation in G1 and stabilization of the arrested cells in a viable quiescent state. Together with previously reported findings on serum and isoleucine starvation, these results provide a temporal map of growth control points in the G1 phase.     

Euphorigenic drugs: effects on the reward pathways of the brain.

This report summarizes a number of experiments designed to examine the changes in the threshold for intracranial self-stimulation (ICSS) in the rat after the administration of morphine and a number of narcotic agonist-antagonists, as well as three nonnarcotic drugs that have extensive nonmedical use (cocaine, d-amphetamine, and phencyclidine). The results of these experiments clearly indicate that morphine lowers the threshold for ICSS and, furthermore, there appears to be little or no tolerance to this effect. The only mixed agonist-antagonist that consistently lowered the ICSS threshold was pentazocine. Cocaine, d-amphetamine, and to a lesser degree, phencyclidine also lowered the ICSS threshold. These results suggest that the abuse liability of these agents may be directly related to their ability to sensitize the neural substrate involved with natural reward.     

Effect of ethyl acetate on the transport of sodium and glucose in the hamster small intestine in vitro.

The effect of ethyl acetate on Na+, water and glucose transport, as well as on glucose and electrolyte intracellular concentrations in everted and cannulated sacs of hamster jejunum, have been studied.Ethyl acetate, a substance that easily penetrates and delivers energy to the cell, strongly stimulates net glucose and Na+ transport. The explanation of the experimental results takes into account the possibility of the existence of an active extrusion of glucose at the level of the basolateral membrane of the enterocyte.     

Effect on ethyl acetate on the transport of sodium and glucose in the hamster small intestine in vitro

The effect of ethyl acetate on Na⁺, water and glucose transport, as well as on glucose and electrolyte intracellular concentrations in everted and cannulated sacs of hamster jejunum, have been studied.Ethyl acetate, a substance that easily penetrates and delivers energy to the cell, strongly stimulates net glucose and Na⁺ transport.The explanation of the experimental results takes into account the possibility of the existence of an active extrusion of glucose at the level of the basolateral membrane of the enterocyte.     

Synthesis and some reactions of methyl 4,6-O-benzylidene-2,3-dideoxy-2-phenylazo-β-d-erythro-hex-2-enopyranoside

Methyl 4,6-O-benzylidene-2,3-dideoxy-2-phenylazo-β-d-erythro-hex-2-enopyranoside has been synthesised, and its addition reactions with methoxide, azide, hydride, and deuteride ions have been studied. Comment is made on the stereochemistry of addition reactions of 2- and 3-phenylazo derivatives of methyl 4,6-O-benzylidene-2,3-dideoxy-d-hex-2-enopyranosides.     

Validity of the reduced version of the Morningness-Eveningness Questionnaire

Sleep and Biological Rhythms - The aim of the present work was to validate the reduced version of the Morningness-Eveningness Questionnaire (MEQr) using circadian motor activity as external...