Influence of the blood concentration of prolactin on the length of the sensitive period for establishing maternal behavior in sheep at parturition

The fading of postpartum maternal interest for the neonate (sensitive period) in ewes separated from their young at lambing is delayed when parturition is induced with 20 mg of estradiol benzoate (EB). An experiment was carried out to investigate the role of prolactin in this phenomenon. The sensitive period was studied in three groups of parturient ewes. In all groups lambs were removed at birth and reintroduced to their mothers 24 hr later. Maternal acceptance was tested at this time. In group 1 (dexamethasone D), ewes were induced to lamb with dexamethasone (15 mg im). In group 2 (EB), ewes were treated with 20 mg of estradiol benzoate (im). In group 3 (EB + CB 154) ewes received 20 mg of EB as in group 2 and 1 mg of CB 154 (sc) every 12 hr to prevent the enhanced secretion of prolactin which normally occurs after EB injection. The concentration of prolactin was highest in group 2 (EB), lowest in group 3 (EB + CB), and intermediate in group 1 (D) (p ? 0.001 between groups). By contrast, the proportion of ewes showing maternal behavior was similar in groups 2 and 3 ($\text{15}\text{23}$ and $\text{17}\text{22}$), both of which differed from group 1 ($\text{3}\text{22}\text{; p ? 0.005}$). It is concluded that the lengthening of the sensitive period for establishing maternal behavior in sheep following EB induced parturition is not related with high levels of prolactin in the peripheral circulation.     

Une faune de petits mammiferes d'age turolien moyen(Miocene superieur) a Cucuron (Vaucluse); donnees nouvelles sur le genre Stephanomys (Rodentia) et consequences stratigraphiques

A small mammal fauna, including rodents and a new species of Murid, Stephanomys stadii n. sp., has been found in a continental formation underlying the deposits with the famous big mammal fauna of Mont Luberon. This fauna of small mammals is a little younger than the fauna of Los Mansuetos (Spain), so, the Pikermian fauna of Mont Luberon, which is said to be of the same age as the fauna of Pikermi is younger than the fauna of big and small mammals of Los Mansuetos.     

Solubilisation et caractérisation d'une glycoprotéine : fucosyl-transférase cérébrale

1. A glycoprotein: fucosyl-transferase activity was demonstrated in sheep cerebral cortex, using desialylated fetuin as exogenous acceptor and detergent Trition X 100 for solubilization.

2. Addition of Triton X 100 to the membrane suspension gave first an activation then a solubilization of the cerebral fucosyl-transferase.

3. Hydrophobic chromatography was investigated for purification of the enzyme. Binding was effective using alkyl-agarose chromatographic columns with two or more than two atoms of carbon, but elution was only possible with ethyl and butyl-agarose.

4. Combination of subcellular fractionation and hydrophobic chromatography on ethylagarose led to a 30 fold purification.

5. After ethyl-agarose chromatography, some properties of fucosyl-transferase were studied: the optimal temperature was 25°C. The optimum pH was about neutrality. Light activation was observed with Mn²⁺ concentration below 1 mM.

6. Homogeneity was tested using Ultrogel chromatography, polyacrylamide gel electrophoresis and ultracentrifugation.

7. It was concluded that ethyl-agarose hydrophobic chromatography easily bind a few solubilized proteins (about 20 per cent of the ST supernatant). When elution was performed, these proteins, including fucosyl-transferase, were released from ethyl-agarose columns as a stable aggregate, only dissociated with lower ionic strength.

Ethyl-agarose fraction (eluted with KCl 120 mM) showed homogeneity:

— with Ultrogel AcA 22 chromatography (Mw = 300.000).

— with polyacrylamide gel electrophoresis without S.D.S.

— with the analytical ultracentrifugo giving Mw = 280.000; S₂₀ = 10.

But after dialysis overnight against a buffer without KCl, ultracentrifugation technics showed no homogeneity. Futhermore, SDS gel electrophoresis gave more than four bands.     

Ultrahistochemical study on the ruthenium red surface staining

Summary The electron-dense marker which is thought to produce the ruthenium red surface staining is studied. This stain is prepared under conditions which should give its rise in cell surface membrane, and its nature and charge are tested electrophoretically and by measuring the turbidity, respectively. It is a positive colloid resulting from the recharging of colloidal osmium dioxide by RR polycations. Controls on the affinity are carried out by applying positive sol to gelled agarose sections containing hyaluronic acid, polyvinyl sulfate or polylysine. Controls are also carried out on ascites Ehrlich carcinoma and Zajdela ascites hepatoma cells subjected to prior enzymatic and chemical treatments. It is found that the osmium-RR system visualizes all acidic groups in the outer hydrophilic leaflet, that is the greater part of compounds in this external cell layer. A model is presented for the mechanism underlying its rise in cell surface membrane.     

Cooperative properties of hormone receptors in cell membranes

The binding of many polypeptide hormones to cell surface receptors does not appear to follow the law of mass action. While steady–state binding data are consistent in many cases with either heterogeneous populations of binding sites or interactions of the type known as negative cooperativity, study of the kinetics of dissociation of the hormone receptor complex allows an unambiguous demonstration of cooperative interactions. Negative cooperativity, which seems to be wide-spread among hormone receptors, provides exquisite sensitivity of the cell at low hormone concentrations while buffering against acutely elevated hormone levels. The molecular mechanisms underlying the cooperativity are still largely unknown. Cooperativity may stem from a conformational transition in individual receptors or involve receptor aggregation in the fluid membrane (clustering) or more extensive membrane phenomena. Thus, new models of hormone action must be considered which integrate the progress in our knowledge of both the complex mechanisms regulating hormone binding to their surface receptors, and the dynamic properties of the cell membrane.     

Amino acid sequence and immunological properties of chachalaca egg white lysozyme

Summary The amino acid sequence of lysozyme c from chachalaca egg white was determined. Like other bird lysozymes c, that of the chachalaca has 129 amino acid residues. It differs from other avian lysozymes c by 27 to 31 amino acid substitutions as well as by being devoid of phenylalanine. It contains substitutions at 9 positions which are invariant in the other 7 bird lysozymes of known sequence. Although the chachalaca is classified zoologically in the order Galliformes, which includes chickens and other pheasant-like birds, its lysozyme differs more from those of pheasant-like birds than do the lysozymes c of ducks. Phylogenetic analysis of the sequence comparisons confirms that the lineage leading to chachalaca lysozyme c separated from that leading to other galliform lysozymes c before the duck lysozyme c lineage did. This indicates a contrast between protein evolution and evolution at the organismal level. Immunological comparison of chachalacalysozyme c with other lysozymes of known sequence provides further support for the proposal that immunological cross-reactivity is strongly dependent on degree of sequence resemblance among bird lysozymes.103rd communication on lysozymes from the Laboratory of P. Jollès. Supported in part by grants from C.N.R.S. (ER 102), I.N.S.E.R.M. (Groupe de recherche U-116), N.S.F. (GB-42028X), and N.I.H. (GM-21509).     

On the origin of molecular “handedness” in living systems

Elementary particle effects (beta-decay) provide at best only a weakly handed radiation in the biologically effective energy ranges. Global magnetic effects coupled to sunlight are randomized by paleomagnetic reversals. Hence a persistent terrestrial handed bias at possible local biopoetic sites offers a more promising explanation for the origin of the "handedness" of the molecules found among living systems on earth. Magnetite in lava flows maintains a handed bias for surface catalysis through many magnetic reversals. Magnetite contaminated with sulfur has already been proposed by Granick as a biopoetic site because it provides a weak source of chemical energy derived by photochemical conversion. Indirect evidence for this hypothesis has been provided by the molecular structure of ferredoxin - a single strand of the 14 primordial amino acids wrapped around an FeS core. Lava flows have been suggested as biopoetic sites by Fox, since their temperature and chemical composition might allow for the rapid synthesis of prebiotic compounds at the surface of the primitive earth. The additional fact that magnetite in lave flows also provides a persistent handed site for surface catalysis offers a further argument for the experimental investigation of this specific biopoetic environment.