Effect of opiate receptor agonists and antagonists on maternal aggression in rats

The behavioral effects of opiate agonists and antagonists were studied on the female aggression model. Mu-agonist buprenorphine more selectively decreased maternal aggression than kappa-agonist tifluadom. Kappa-agonists (bremazocine, tifluadom) increased passive defence in lactating female rats. Ethopharmacological data shows predominant involvement of brain mu-opiate receptor system in the integrative processes of maternal behavior and maternal aggression in particular.     

Phase changes in the population of group A streptococci and their influence on the course of the epidemic process of tonsillitis

This work presents the data on the complex evaluation of the population of group A streptococci, studied at each of four phases (reservation, epidemic transformation, epidemic spread, reservational transformation) of the course of the epidemic process of streptococcal infection of the respiratory tracts (tonsillitis) in an organized group of adults. The characterization of the phases of the infective agent in accordance with the level of the carrier state, the size of streptococcal foci and the virulence of streptococci is given. Thus, the study shows that the heterogeneity of group A streptococci with respect to their virulence reaches its maximum level at the phases of reservation and epidemic spread and its minimum level at the phases of epidemic and reservational transformation. The size of streptococcal foci in carriers and the virulence of streptococci isolated from them are the inter-related unidirectional signs of the population of the infective agent and, at the same time, the main factors responsible for the phase character of the epidemic process and the morbidity level in tonsillitis.     

The conformation of calmodulin: a substantial environmentally sensitive helical transition in Ca4-calmodulin with potential mechanistic function

The conformation of Ca4-calmodulin in solution, as assessed by far-UV peptide circular dichroism, contains significantly less alpha-helix than the proposed X-ray crystal structure. We now show that Ca4-calmodulin adopts significant additional helical structure in solution in the presence of a helicogenic solvent (50%, v/v, aqueous 2,2,2-trifluoroethanol or 50%, v/v, methylpentane-5,5-diol). We suggest that the long continuous helix (residues 66-92 of the crystal structure) is not necessarily a normal feature of the calmodulin structure in solution, and may be due in part to the conditions of crystallisation. This result is supported by time-resolved tyrosine fluorescence anisotropy studies indicating that Ca4-calmodulin in solution is an essentially compact globular structure which undergoes isotropic rotational motion. We conclude that, under appropriate ionic and apolar environmental conditions, Ca4-calmodulin undergoes a substantial helical transition, which may involve residues in the central region of the molecule. Such a transition could have an important function in determining specificity and affinity in interactions of calmodulin with different target sequences of Ca2+-dependent regulatory enzymes.     

Quantitative structure activity relationship studies on 3-triazines using van der Waal volume and molecular connectivity index

QSAR studies have been performed on the homologues of 3-triazines, using molecular connectivity index and van der Waal volume as structural parameters. The regression analysis has shown good correlation between antitumour activity and the two structural parameters.     

Evidence for a Ca2+-independent association between calpain II and phospholipid vesicles

Possible interactions between calpain II and phospholipids such as phosphatidylinositol, phosphatidylserine and phosphatidylcholine were studied using fluorescence and gel filtration techniques. Changes in fluorescence intensity of purified calpain II show that the enzyme strongly interacts with phosphatidylinositol and phosphatidylserine and to a lesser extent with phosphatidylcholine. These results are corroborated by the gel filtration technique which permits the isolation of the enzyme phospholipid complex. Association between calpain II and various phospholipid vesicles can occur in the absence of calcium. Such binding occurs without any observable change of the molecular mass of the two subunits on SDS-polyacrylamide gel electrophoresis.     

Phospholipase of rat intestine: mode of action]

Phospholipase activities of rat intestinal mucosa homogenate have been determined from lysophosphatidylcholines [14C] and phosphatidylcholines [-3H-14C]. In the presence of phosphatidylcholines, at pH 6.5, the homogenate has a phospholipase B activity. At pH 8.5, a phospholipase A2 activity was shown. In the presence of lysophospatidylcholines, at pH 6.5, we notice a lysophospholipase A1 activity. A kinetic study of the reactions allows us to separate the activity B into a phospholipase A2 activity and a lysophospholipase A1 activity. Thus, it appears that the total phospholipase activity of rat intestinal mucosa would results from a phospholipase A2 activity and a lysophospholipase A1 activity.     

A fluorescence study of the binding of cytochrome C to mixed-phospholipid microvesicles : evidence for a preferred orientation of the bound protein.

Kinetic and equilibrium experiments are reported on the binding of the fluorescent probe 1,8-anilino-naphtalene sulfonate (ANS) to microvesicles of natural lecithin containing 10 per cent of an anionic phospholipip (90 : 10 mixtures). Kinetics discriminated between fast binding to the outer leaflet of the bilayer and apparently slow binding to the inner leaflet controlled by the diffusion of the probe across the bilayer. The equilibrium distribution of ANS between the two leaflets was not dependent on the nature of the anionic species and the spectral properties of bound ANS were identical in all cases investigated. A hyperbolic saturation was observed allowing to propose an affinity scale for the binding of ANS to mixtures of lecithin with phosphatidic acid, phosphatidylinositol, and cardiolipin. The effects on binding of ionic strength and sodium dodecylsulfate were also considered. The binding of horse heart ferricytochrome c to ANS-labelled microvesicles was studied quantitatively making use of the quenching of the probes fluorescence by the heme. Perrin-F?rster energy transfer could be analysed on the basis of a simple model of the physical arrangement of the system which was elaborated from published data referring to ANS and cytochrome c binding to phospholipids. Experimental and theoretical computed values of the quenching efficiency were compared and led to conclude in favor of a preferred orientation of the heme crevice fully accessible from the external space at the lipid interface.