Production and characterization of saratin, an inhibitor of von Willebrand factor-dependent platelet adhesion to collagen.

Platelets tether to collagen in both a von Willebrand factor (vWF)-dependent and a vWF-independent manner. We have recently characterized a recombinant protein, saratin, isolated from the saliva of the leech Hirudo medicinalis, expressed it in Hansenula polymorpha, and studied its effect on direct and indirect platelet-collagen interactions. Saratin dose dependently inhibited the binding of purified human vWF to human type I and III collagens (IC(50)= 0.23 +/- 0.004 and 0.81 +/- 0.04 microg mL(-1), respectively) and to calf skin collagen (IC(50)= 0.44 +/- 0.008 microg mL(-1)). Furthermore, saratin showed a similar inhibitory potency against the binding of human, rodent, and porcine plasma vWF to these collagens. In a flow chamber under conditions of elevated shear (2700 s(-1)), saratin dose dependently and potently inhibited platelet aggregate formation on a collagen-coated surface (IC(50)= 0.96 +/- 0.25 microg mL(-1)), but at reduced shear (1300 s(-1)) a rightward shift in the dose-response curve was noted (IC(50)= 5.2 +/- 1.4 microg mL(-1)). Surface plasmon resonance analysis revealed both high and low affinity binding sites for saratin on human collagen type III (K(d) 5 x 10(-8) M and 2 x 10(-6) M, respectively). Although low concentrations of saratin, which inhibited platelet adhesion under increased shear (i.e., saturation of high-affinity binding sites), had no effect on vWF-independent collagen-induced platelet aggregation, high concentrations (i.e., saturation of low-affinity binding sites) were found to inhibit platelet aggregation. These data demonstrate that saratin is a potent inhibitor of vWF-dependent platelet adhesion to collagen and hence may have therapeutic potential as an antithrombotic agent.

One-step purification of the NADH dehydrogenase fragment of the Escherichia coli complex I by means of Strep-tag affinity chromatography.

The proton-pumping NADH:ubiquinone oxidoreductase, also called complex I, is the first energy-transducing complex of many respiratory chains. Complex I of Escherichia coli can be split into three fragments. One of these fragments, the soluble NADH dehydrogenase fragment, represents the electron input part of complex I. It comprises the subunits NuoE, F and G and harbors one flavin mononucleotide and up to six iron-sulfur clusters. Here, we report the one-step purification of this fragment by means of affinity chromatography on StrepTactin. This was achieved by fusing the Strep-tag II peptide to the C-terminus of NuoF or NuoG. Fusion of this peptide to the N-terminus of either NuoE or NuoF disturbed the assembly of the NADH dehydrogenase fragment.

Collective decision-making in social spiders: dragline-mediated amplification process acts as a recruitment mechanism

Amplification mechanisms involved in group cohesion and coordination of several individuals' activities are a major research topic in social arthropod biology. In this paper, we investigate how recruitment processes can be mediated by the use of silk draglines in the case of social spiders. Our intent is to demonstrate how a behavioural feature common to all spider species can induce positive feedback, potentially leading to collective decision-making in a social context. Dragline-mediated amplification mechanisms are investigated in a simulated "Y" choice set-up. Numerical experiments involve two distinct models: a simplified one, devoted to the exploration of the most basic amplifying properties of the system, and a more complex simulation platform, taking into account the geometrical properties of a growing network (two-dimensional web). The effect of hypothetical subpopulations, as well as variations in silk attractivity in the case of mixed populations (originating from multiple nests) are also discussed. Results fit experimental data and demonstrate that spiders' behaviour exhibits very strong amplifying properties that can play a crucial part in the organization of social life. Copyright 1999 Academic Press.

X-ray crystal structure of arrestin from bovine rod outer segments.

Retinal arrestin is the essential protein for the termination of the light response in vertebrate rod outer segments. It plays an important role in quenching the light-induced enzyme cascade by its ability to bind to phosphorylated light-activated rhodopsin (P-Rh*). Arrestins are found in various G-protein-coupled amplification cascades. Here we report on the three-dimensional structure of bovine arrestin (relative molecular mass, 45,300) at 3.3 A resolution. The crystal structure comprises two domains of antiparallel beta-sheets connected through a hinge region and one short alpha-helix on the back of the amino-terminal fold. The binding region for phosphorylated light-activated rhodopsin is located at the N-terminal domain, as indicated by the docking of the photoreceptor to the three-dimensional structure of arrestin. This agrees with the interpretation of binding studies on partially digested and mutated arrestin.

Crystallization and preliminary X-ray analysis of arrestin from bovine rod outer segment.

We present the first X-ray study of a member of the arrestin family, the bovine retinal arrestin. Arrestin is essential for the fine regulation and termination of the light-induced enzyme cascade in vertebrate rod outer segments. It plays an important role in quenching phototransduction by its ability to preferentially bind to phosphorylated light-activated rhodopsin. The crystals diffract between 3 angstroms and 3.5 angstroms (space group P2(1)2(1)2, cell dimensions a = 169.17 angstroms, b = 185.53 angstroms, c = 90.93 angstroms, T = 100 K). The asymmetric unit contains four molecules with a solvent content of 68.5% by volume.

Behavioral differentiation of mice exposed to a water tank social interaction test.

Male or female C57BL/6J mice were exposed to a water tank in which food could be obtained only by wading in the water towards a feeder. Behavioral differentiation occurred in that three distinct categories could be distinguished: major carriers (transporting over 80% of the food pellets), sporadic carriers (transporting less than 20% of the food pellets) and non-carriers. In the elevated + -maze, major carriers were more willing to explore open spaces than non-carriers. Sporadic carriers showed some evidence of the same tendency of decreased anxiety, but in a minor way. The willingness of mice to become carriers is associated with their willingness to explore novel areas. This test may be useful for the assessment of anxiolytic compounds in a social situation.

Spatial navigation of staggerer and normal mice during juvenile and adult stages.

Staggerer mutant mice were compared to normal mice of two different ages (2-6 mo) in two tasks requiring navigational skills in a circular maze visible platform condition and a T-maze. Staggerer mutants had higher latencies than normal mice in both tests. The performance of normal mice worsened with age for both tests. The aging factor interacted with the genotype factor only in the circular maze, where the mutant-nonmutant differential was wider among juvenile animals. In neither task was there evidence of a more pronounced impairment with aging in staggerer mutants. It remains to be determined in this mutant at more advanced stages of aging or in other models of chronic neural disease whether early neuropathology accelerates brain aging.

Behavioral profiles of adult rats in a difficult food supply social situation, related to certain early behavioral features.

Behavioral profiles of male rats were defined in nine intralitter groups of six individuals at various stages of their development: (a) at pup stage in individual situations (uncomfortable positions) and social situations (removal away from the mother), and (b) at adult stage in a difficult food supply social situation (complete immersion of the food access way). The male population was split into two sets, both at pup stage (the most and the least swift and efficient of each group to overcome uncomfortable situations), and at adult stage (carriers and noncarriers of food in each group tested). Our results showed an important relation between these pup and adult behavioral profiles: the swiftest and most efficient individuals of a group at pup stage adopted more often a food carrier behavioral profile at adult stage. Assumptions about the predictive value of some behavioral features of a young rat in regard to its adult behavioral profile are discussed.

Effect of group size on social organization in rats with restricted access to food.

In groups of rats subjected to a experimental design in which access to the feeder was made difficult, a behavioural differentiation developed. Some rats brought back food pellets to the cage (carrier rats) while the others stayed in the home cage (noncarrier rats). We compared the social organization underlying the adoption of these roles in groups of three and six rats. Reducing group size increased the incidence of carrier rats, leading to a smaller number of differentiated groups. However, differentiated groups seemed to adapt to the situation in the same way as the groups of six rats. In both cases, carriers could be distinguished from noncarriers by their way of obtaining food and by how food possession stopped. Moreover, behavioural variables generally exhibited better stability in small groups and noncarrier/carrier rat relations were more extensive, resulting in more typical organization. The potential use of such groups for pharmacological studies is discussed.

Ingestive behaviors of the rat deficient in vasopressin synthesis (Brattleboro strain). Effect of chronic treatment by dDAVP.

Spontaneous manipulator and locomotor activities, food and fluid intake have been recorded from rats suffering from a genetic lack of central vasopressin (VP) synthesis (Brattleboro strain, DI), their heterozygous litter mates (HZ) or Long Evans (LE) rats. The daily patterns of activities did not differ, except for their drinking behavior. This was mainly associated with food intake during the dark period with LE rats but was distributed equally during light and dark periods with DI rats. HZ rats showed a behavioral heterogeneity, some of them following the daily pattern of LE rats, and others, that of DI rats. The daily feeding pattern was identical in the three genotypes but the selection between two isocaloric contrasted diets was different. When they were fed ad lib, HZ and DI rats consumed less carbohydrate than LE rats, the protein intake being unchanged. On the contrary, when the DI rats were only fed during the dark period, they ate more carbohydrate than LE rats. The peripheral infusion of a V2 AVP agonist (dDAVP) restored a normal hydric balance in DI rats but failed to modify the diet selection. These data show that in the rats, the lack of central VP synthesis disturbs both the selection of diets and the efficiency of the satiety signals. These disturbances were unchanged by the peripheral VP treatment which suggested the direct involvement of the central release of the neuropeptide.

Maternal behavior variations and adaptations, and pup development within litters of various sizes in Wistar rat.

Variations of two maternal behavior components (time spent with litter and rapidity of pup retrieving) as well as certain physical and developmental characteristics of pups (weight, relative weight gain, and neuromotor maturation) in rats were simultaneously studied in 29 various-sized litters in which interindividual variations were not experimentally amplified. Results showed mothers' behavioral adaptations to litters' characteristics (size and weight). Time spent with young was linked to litter size, whereas rapidity of pup retrieving was related to the pups' physical characteristic. Beyond these adaptive variabilities, residual variations subsisted between mothers. These variations were determinant for differences in pup development for only one component: the time that mothers spent with their litters, while pup retrieving component variations did not have any effect.

[Maternal behaviour and mother-young relationships in spiders]. / Comportement maternel et relations mères-jeunes chez les araignées.

Most species of spiders leave their egg-sacs in a sheltered place. However, some of them look after or carry their egg-sacs until the spiderlings hatch. Others extend their maternal behaviour to feeding their young by regurgitation or by the distribution of prey. The adaptative aspect of this maternal behaviour is shown by a reduced rate of reproduction in the species whose care of progeny is the most sophisticated. The maternal care of the egg-sac depends on the physiological state of the female, that state, in turn, being maintained by the presence of the egg-sac. The tolerance exhibited by the mother towards her offspring implies at least two mechanisms: (i) inhibition of predatory behaviour in response to the movements of an offspring at a distance, (ii) inhibition of cannibalism when in contact with an offspring. The parental relationship can be complemented by cooperation between the young that involves a tolerance mechanism probably close to that of social spiders.

[Effect of diphenylhydantoin administered during gestation and lactation on the motor development and cerebellar histology of the young rat]. / Action de la diphénylhydantoïne administrée pendant la gestation et l'allaitement, sur le développement moteur et l'histologie du cervelet du jeune rat.

Rattus norvegicus females were treated by diphenylhydantoin (D.P.H.), all along pregnancy and lactation. 4 groups were constituted: a 100 mg DPH/kg/day group, a 50 mg DPH/kg/day group; a placebo group (treated with pure water), and control group. D.P.H. was given twice a day by a gastric tube. The cerebellar Purkinje cells studied through light microscopy and transmission electron microscopy in young rats (25 days old) showed no visible alteration. 2 motorcoordination tests were applied to the young rats, during their 2nd and 3rd weeks of post-natal life. Young rats of DPH 100, DPH 50 and placebo groups showed a backwardness relatively to control. This backwardness may be attributed to the maternal forced feeding stress, but not to a specific action of the DPH.