Specific fixation of bovine brain and retinal acidic and basic fibroblast growth factors to mouse embryonic eye basement membranes

The labeling pattern of mouse embryonic eye frozen sections incubated with radioiodinated brain acidic and basic fibroblasts growth factors (aFGF and bFGF) was investigated by autoradiography. Both growth factors bind to basement membranes in a dose-dependent way, with a higher affinity for bFGF. Similar data were obtained with eye-derived growth factors (EDGF), the retinal forms of FGF. There was a heterogeneity in the affinity of the various basement membranes toward these growth factors. The inner limiting membrane of the retina and the posterior part of the lens capsule have a higher binding capacity than the posterior part of the Bruch's membrane. The specificity of the growth factor-basement membrane interaction was demonstrated by the following experiments: (i) an excess of unlabeled growth factor displaced the labeling; (ii) unrelated proteins with different isoelectric points--gelatin, serum albumin, histones--did not modify the labeling; and (iii) iodinated EGF or PDGF did not label basement membrane. In order to get a better understanding of the nature of this binding, we performed the incubation of the frozen sections with iodinated FGFs preincubated with various compounds: (i) heparin which is known to have a strong affinity for aFGF and bFGF partially decreases the labeling, and (ii) chondroitin sulfate B and dextran sulfate at high concentrations were also partially effective. In addition, enzymatic treatment of the sections reveals that only heparitinase, not collagenase or chondroitinase ABC, completely prevents the labeling without destroying the overall structure of the basement membrane. An antibody against the proteic part of EHS mouse proteoheparan sulfate does not affect the signal. Esterification of the acidic groups cancelled the binding. These results demonstrate that FGFs bind specifically to basement membranes, probably on the polysaccharidic part of the proteoheparan sulfate, and suggest that this type of interaction may be a general feature of the mechanism of action of these growth factors.     

In vivo study of free and esterified cholesterol turnover in various tissues of the rat.

Rats were infused for 3.5 to 10 hrs with either red cells or plasma previously labelled in vivo by [3H]-cholesterol. Cholesterol specific radioactivities were measured in plasma, HDL, LDL and VLDL, and various tissues. Red cell infusions led to a higher labelling of free than of esterified cholesterol in the plasma of infused rats. The opposite situation was observed following plasma infusion. Comparison of free and esterified cholesterol specific radioactivities in each tissue showed that esterified cholesterol was transferred from plasma to all the tissues, except the adrenals. Study of the ratios of cholesterol specific radioactivities from one experimental group to the other in each tissue, made it possible to demonstrate clearly the occurence of hydrolysis within all the studied tissues except 5 of them where its existence remains uncertain (lung, heart, kidney, tendon, muscle) and of esterification in 3 tissues (adrenal, liver lung). In addition, ratios of cholesterol radioactivities (free/ester) were found to be identical in plasma and in 4 tissues, where neither hydrolysis nor esterification were detected (heart, muscle, kidney, tendon). This finding is an argument in favor of a simultaneous transport of free and esterified cholesterol from plasma into these 4 tissues and suggests that the entire lipoprotein particles can penetrate these tissues, with no specificity of one special class. In adrenal, unlike all other tissues: 1) the turnover of esterified cholesterol was achieved mostly by hydrolysis and esterification in situ; 2) a preferential lipoprotein class (LDL) was responsible for the transport of free cholesterol from the plasma.     

Biological and biophysical properties of Haemophilus influenzae transforming DNA encapsided by viral proteins

Summary The expression of the transforming ability of Haemophilus influenzae DNA was investigated after its encapsidation by the coat protein of two different plant viruses, Brome Mosaic Virus (BMV) and Alfalfa Mosaic Virus (AMV). The influence of the encapsidation on the various steps of the transformation process was studied, as well as the protection of the DNA molecule inside of the DNA-protein complex particles against nucleolytic attack.The kinetics of uptake and penetration of free and encapsided DNA and their respective competitive abilities were compared in order to explain the differences which appeared between the rates of transformation by free and encapsided high molecular weight DNAs.Finally, some conclusions are drawn concerning the uncoating process of these nucleoprotein complex particles and the strength of the DNA-protein and protein-protein interactions existing in these particles.Abbreviations M.W. molecular weight - T.A. transforming ability     

Stoichiometry of calcium transport by sarcoplasmic reticulum: utilization of p-nitrophenylphosphate as an energy donor]

We have studied, under different conditions and through the hydrolysis of p-nitrophenylphosphate, the stoechiometry of the active transport of calcium by sarcoplasmic reticulum. According to a minimal kinetic model, it is possible to explain the variation of the coupling factor n(t) during the calcium accumulation in absence of precipitating agent. Under the described experimental conditions, at the beginning of the experiment, the coupling factor's value is slightly above 2.