Character displacement in the fighting colours of Hetaerina damselflies

Aggression between species is a seldom-considered but potentially widespread mechanism of character displacement in secondary sexual characters. Based on previous research showing that similarity in wing coloration directly influences interspecific territorial aggression in Hetaerina damselflies, we predicted that wing coloration would show a pattern of character displacement (divergence in sympatry). A geographical survey of four Hetaerina damselfly species in Mexico and Texas showed evidence for character displacement in both species pairs that regularly occurs sympatrically. Hetaerina titia, a species that typically has large black wing spots and small red wing spots, shifted to having even larger black spots and smaller red wing spots at sites where a congener with large red wing spots is numerically dominant (Hetaerina americana or Hetaerina occisa). Hetaerina americana showed the reverse pattern, shifting towards larger red wing spots where H. titia is numerically dominant. This pattern is consistent with the process of agonistic character displacement, but the ontogenetic basis of the shift remains to be demonstrated.     

Poly(ADP-ribose) polymerase forms loops with DNA

The interaction between highly purified poly(ADP-ribose) polymerase from calf thymus and different topological forms of pBR322 DNA has been studied by gel retardation electrophoresis and electron microscopy. We show that: (i) in the absence of nicks on DNA the enzyme has a marked affinity for supercoiled (form I) DNA, (ii) in the presence of single stranded breaks poly(ADP-ribose) polymerase preferentially binds to form II, (iii) in all cases enzyme molecules are frequently located at DNA intersections, (iv) a cooperative binding of the enzyme on DNA occurs.     

Results of the study of bird droppings collected in the Lithuanian SSR for the purpose of searching out tularemia epizootics

There are practically no records of cases of tularemia among humans in the Lithuanian SSR. Nevertheless, the mass sero-allergic survey of the population for tularemia, carried out 10-12 years ago, showed that 2.3% of the adult population in the Republic had had contacts with the causative agent of this infection. The work was aimed at the determination of the present activity of the foci of tularemia. During 6 years in 22 rural districts 2582 samples of avian excrements, containing bones and wool of small animals, were collected and studied by means of the antibody neutralization test (ANT). In 132 (5.1 +/- 0.4%) excrement samples collected on the territory of 12 districts Francisella tularensis antigen was detected. The average ANT titer was 45.2, the maximum titer (10 excrement samples) reached 1: 160. The study revealed the existence of the natural foci of tularemia in Lithuania at present, but their activity proved to be low. The most unfavorable situation was found to exist in western districts of the Republic.     

Human endothelin converting enzyme-2 (ECE2): characterization of mRNA species and chromosomal localization.

Generation of the functionally pleiotropic members of the endothelin vasoactive peptide family is critically catalyzed by unique type II metalloproteases, termed endothelin converting enzymes (ECE). Isolation of human ECE-2 (EC 3.4.24.71) cDNAs revealed deduced open reading frames of 787 and 765 amino acids with approximately 60% identity with human ECE-1. Characterization of mRNA variants revealed mRNA structural diversity at the 5'-terminus. Two mRNA species exist containing distinct first and second exons. Furthermore, in one of these species, an in-frame deletion of the intracytoplasmic domain removed 29 amino acids. Because of the previously reported human genetic diseases ascribed to germline mutations of member genes of the endothelin family, ECE2 was localized in human chromosomes with fluorescence in situ hybridization and radiation hybrid mapping to 3q28-q29 and SHGC-20171/D3S1571, respectively.     

Selective increase in cytokeratin synthesis in cultured rat hepatocytes in response to hormonal stimulation

Addition of a combination of insulin, dexamethasone and EGF at seeding time to cultured rat hepatocytes in serum-free medium caused a selective increase in the biosynthesis of particular cytokeratin components. This increase was prominent during the first day in culture. No significant increases were detected in the absence of hormones or in the presence of either hormones added alone or in pairs, except in the case of insulin plus dexamethasone, which yielded an effect close to that obtained with the three factors. Interestingly, the latter condition also maintained a high level of albumin production over a 6-day period in culture.     

Methods for study of mutations and mutagenesis in human lymphocytes

Detailed methods are presented for measurement and study of in vivo mutations and in vitro mutagenesis in human lymphocytes. The methods described include preparation of conditioned medium containing interleukin-2, enumeration of mutant clones, in vitro mutagenesis, and expansion of mutant clones for further study.     

Enhancement of eosinophil effector function by soluble factors released by S. mansoni: role of proteases

Schistosomulum-released products (SRP) have been shown to enhance both expression of rat and human eosinophil Fc receptors and IgG-dependent cytotoxicity. The present work provides additional evidence of the secretion of eosinophil-enhancing factors by schistosomula and other developmental stages of schistosomes, including adult worms. The heat lability, as well as the strong inhibition of the stimulating activity of SRP by the protease inhibitor Trasylol, suggest that thermolabile proteases secreted by the parasite are involved in this mechanism. The purification of the schistosome proteases by preparative isoelectric focusing and gel filtration demonstrated that neutral proteases able to hydrolyze the collagenase substrates Azocoll and Z-Gly-Pro-Leu-Gly-Pro are able to significantly enhance eosinophil effector functions. Purified Clostridium histolyticum collagenase was also able to mimic the enhancing effect of schistosome proteases, suggesting involvement of a collagenase-like activity of the enzymes in the eosinophil stimulation.     

Glycerolipid formation and PGE2 and PGF2α production of rat renal papillae in vitro, the effects of urea

The glycerolipid production by rat renal papillary slices varied inversely with the urea concentration (0a–1660 mM) whether the production was measured as labelling of the glycerol backbone from glucose or as incorporation of labelled arachidonic acid and palmitic acid. The rate of phospholipid formation was most dependent on medium urea concentrations in the range between 0 and 1100 mM. The production of prostaglandins PGE₂ and PGF_2α, measured radioimmunologically or by an isotope derivative method was in the same range inversely related to the production of glycerolipids and chain elongations. The effect of urea on prostaglandin formation is probably indirectly caused by the inhibition of the phospholipid formation and chain elongation, since the effect was abolished by 1% defatted albumin in the medium. The data suggest that the level of free arachidonic acid within the cells is controlled to an important extent by glycerolipid formation and chain elongation.