The effect of limb ischaemia on the serum glycerol concentration of the rat

Résumé Le sérum des rats présente une concentration élevée de glycérine après l'application de garrots aux membres postérieurs pendant quatre heures. L'auteur compare ses résultats avec ceux des recherches dans lesquelles les acides gras non-estérifiés ont été soumis à des mesures quantitatives.     

Demonstration of specific receptors for angiotensin III in rat adrenal glands]

Distinct and specific binding sites for 3H-angiotensin II (A II) AND 3H-angiotensin III (A III) have been demonstrated in Rat adrenal gland preparations. A III binding sites have the highest affinity (KD29C1-2.10(-10)M) for the 2-8 heptapeptide. This suggests the possibility of a separate and distinct physiological role for the 2-8 heptapeptide, mediated via such A III binding sites.     

Ancestral lysozymes reconstructed, neutrality tested, and thermostability linked to hydrocarbon packing

The controversy surrounding the idea that neutral mutations dominate protein evolution is attributable in part to the inadequacy of the tools available to evolutionary investigators. With a few exceptions, most investigations into the force driving protein evolution have relied on indirect criteria for distinguishing neutral and non-neutral variants. To investigate a particular pathway of molecular evolution, we have reconstructed by site-directed mutagenesis likely ancestral variants of the lysozymes of modern game birds (order Galliformes), tested their activity and thermostability and determined their three-dimensional structure. We focused on amino acids at three positions that are occupied in all known game birds either by the triplet Thr 40, Ile 55, Ser 91, or by the triplet Ser 40, Val 55, Thr 91. We have synthesized proteins representing intermediates along the possible three-step evolutionary pathways between these triplets. Although all of these are active and stable, none of these intermediates is found in known lysozymes. A comparison of the structures and thermostabilities of the variants reveals a linear correlation between the side-chain volume of the triplet and the thermostability of the protein. Each pathway connecting the two extant triplet sequences includes a variant with a thermostability outside the range of the extant proteins. This observation is consistent with a non-neutral evolutionary pathway. The existence of variants that are more stable than the extant proteins suggests that selection for maximum thermostability may not have been an important factor in the evolution of this enzyme.