Variations in the life-history parameters of Hemipyrellia ligurriens (Diptera: Calliphoridae) in response to larval competition for food

Abstract. 1. Larval rearing densities of Hemipyrellia ligurriens (Wiedemann) (Diptera: Calliphoridae) in standardized carrion were manipulated in order to investigate changes in life-history parameters in response to larval competition for food.
2. Competition was of the typical scramble type. Survivorship remained high at densities up to 32 larvae g liver^-1 but decreased rapidly as larval density increased further.
3. Emergent adults were undersized with reduced fecundity and longevity. Variations in adult body size apparently reduced the effects of competition on larval mortality.
4. Females of dry weight corresponding to only 10.4% of the potential maximum emerged at the highest rearing densities of 128 larvae g liver-1. However, these females had a nearly four-fold increase in reproductive investment (per unit weight) when compared to the largest individuals.
5. The duration of larval development declined when competition was intense (i.e. at high larval densities).
6. The short adult life of H.ligurriens, combined with the unpredictability of larval habitat availability, may reduce the value of long-range dispersal so that females 'do better' by maintaining reproductive investment despite a concomitant decline in dispersal ability.     

Investigations of the possible role of proteases in altering surface proteins of virally transformed hamster fibroblasts

Virally transformed fibroblasts have on their surfaces zero or reduced amounts of a large external transformation-sensitive (LETS) glycoprotein. This protein is extremely sensitive to proteolysis. When prelabeled normal fibroblasts are cocultivated with transformed cells, the LETS glycoprotein of the normal cells shows an increased rate of turnover. Experiments are described which investigate the possibility that this phenomenon and the absence of LETS glycoprotein are due to proteolysis by the transformed cells. In particular, the role of plasminogen activation is examined by the use of protease inhibitors and plasminogen-depleted serum. It is concluded that activation of plasminogen is not required for the disappearance of the LETS glycoprotein although the involvement of other proteases cannot be ruled out. The role of proteases in affecting cell growth and behavior is discussed.     

ErbB-2, the preferred heterodimerization partner of all ErbB receptors, is a mediator of lateral signaling.

We have analyzed ErbB receptor interplay induced by the epidermal growth factor (EGF)-related peptides in cell lines naturally expressing the four ErbB receptors. Down-regulation of cell surface ErbB-1 or ErbB-2 by intracellular expression of specific antibodies has allowed us to delineate the role of these receptors during signaling elicited by: EGF and heparin binding EGF (HB-EGF), ligands of ErbB-1; betacellulin (BTC), a ligand of ErbB-1 and ErbB-4; and neu differentiation factor (NDF), a ligand of ErbB-3 and ErbB-4. Ligand-induced ErbB receptor heterodimerization follows a strict hierarchy and ErbB-2 is the preferred heterodimerization partner of all ErbB proteins. NDF-activated ErbB-3 or ErbB-4 heterodimerize with ErbB-1 only when no ErbB-2 is available. If all ErbB receptors are present, NDF receptors preferentially dimerize with ErbB-2. Furthermore, EGF- and BTC-induced activation of ErbB-3 is impaired in the absence of ErbB-2, suggesting that ErbB-2 has a role in the lateral transmission of signals between other ErbB receptors. Finally, ErbB-1 activated by all EGF-related peptides (EGF, HB-EGF, BTC and NDF) couples to SHC, whereas only ErbB-1 activated by its own ligands associates with and phosphorylates Cbl. These results provide the first biochemical evidence that a given ErbB receptor has distinct signaling properties depending on its dimerization.     

Assessment of viability and mitochondrial function of equine spermatozoa using double staining and flow cytometry

An objective double-staining method was developed to evaluate viability and mitochondrial function of stallion spermatozoa using flow cytometry. Sperm viability was assessed by propidium iodide (PI) exclusion, and mitochondrial function was measured by the intensity of rhodamine 123 (R123) fluorescence. Flow cytometry estimates of sperm viability measured by PI were equivalent (P > 0.05) to estimates made using Hoechst 33258 stain and fluorescent microscopy (% dead: 25 +/- 2.4 vs 21.5 +/- 3.5). The use of both PI and R123 was validated by addition of various proportions of freeze-shocked (membrane damaged) cells to viable spermatozoa. There was a high correlation (r(2) = 0.996) between increased PI positivestained (dead) cells and the number of membrane-damaged spermatozoa added (% dead: 29 +/- 0.4, 44 +/- 1.4, 58 +/- 0.9, 75 +/- 0.7 and 91+/- 0.25 vs 0, 25, 50, 75 and 100% damaged cells, respectively). Optimal mitochondrial activity (OMA), as assessed by R123 uptake, was also reduced proportionally (r(2) = 0.976) by the percentage of membrane-damaged cells added (% OMA: 48 +/- 0.6, 37 +/- 1.7, 29 +/- 0.5, 16 +/- 1, 3.8 +/- 1.3 vs 0, 25, 50, 75 and 100% damaged cells, respectively). The mitochondrial inhibitors rotenone and monensin significantly depressed optimal mitochondrial activity (P < 0.001), and there was a significant positive correlation (r(2) = 0.959) between the dose of inhibitors added and the population of sperm cells exhibiting minimal R123 staining (4 -/+ 0.9, 12 -/+ 1.6, 14 -/+ 0.1 and 28 -/+ 2% for treatments with 0, 0.5, 1 and 2 x 10(-5) M rotenone and 0, 0.5, 1, and 2 x 10(-4) M monensin, respectively). Finally, it was shown that treatments containing identical proportions of membrane-damaged cells yielded similar results in terms of viability and mitochondrial activity, irrespective of whether the staining procedure was single or double (P > 0.05). The results of the double-staining method revealed that the percentage of spermatozoa with optimally functioning mitochondria was significantly correlated with the percentage of viable (PI negative) sperm cells (r(2) = 0.998). Flow cytometric analyses using this staining procedure provides reliable and rapid (10,000 cells/min) qualitative assessment of stallion semen.     

Pleiotropic mutants affecting the control of nitrogen metabolism in Aspergillus nidulans

Summary Mutants of Aspergillus nidulans with lesions in gene amdT are pleiotropically affected in their ability to utilize a wide variety of nitrogen sources in the presence of glucose. Ability to utilize a number of these compounds as sole sources of carbon and nitrogen is not altered. One of these mutants, amdT102, has properties consistent with it being derepressed for glucose repression of the utilization of most (but not all) nitrogen sources. The amdT102 mutant can grow strongly on histidine, lysine and cystine as sole nitrogen sources while the wild type strain grows extremely poorly on these amino acids. Similar but less extreme effects apply to many other nitrogen sources. The amdT19 mutant is unable to utilize most nitrogen sources in the presence of glucose, suggesting that it is subject to greatly increased repression of nitrogen source utilization. The amdT mutants are not affected in their ability to use many compounds as sole carbon sources. Carbon sources other than glucose also affect utilization of nitrogen sources in the amdT mutants.     

Structural studies on lipopolysaccharides of serologically non-typable strains of Helicobacter pylori, AF1 and 007, expressing Lewis antigenic determinants.

In contrast to other Helicobacter pylori strains, which have serologically detectable Lewis(x)+ (Le(x)) and Lewis(y)++ (++Le(y)) antigenic determinants in the O-specific polysaccharide chains of the lipopolysaccharides, H. pylori AF1 and 007 were non-typable with anti-Le(x) and anti-Le(y) antibodies. The carbohydrate portions of the lipopolysaccharides were liberated by mild acid hydrolysis and subsequently studied by sugar and methylation analyses, 1H-NMR spectroscopy and electrospray ionization-mass spectrometry. Compared with each other, and with lipopolysaccharides of strains studied previously, the lipopolysaccharides of both AF1 and 007 showed similarities, but also differences, in the structures of the core region and O-specific polysaccharide chains. The O-specific polysaccharide chains of both strains consisted of a short or long polyfucosylated poly-N-acetyl-beta-lactosamine chains, which were distinguished from those of other strains by a high degree of fucosylation producing a polymeric Le(x)chain terminating with Le(x) or Le(y) units:[sequence: see text] where n = 0 or 1 in strain AF1 and 0 in strain 007, m = 0-2, 6-7 in strain AF1 and m = 0-2, 6-7 or approximately 40 in strain 007, the medium-size species being predominant. Therefore, compared with other strains, the lack of reactivity of lipopolysaccharide of H. pylori AF1 and 007 with anti-Le(x) and anti-Le(y) may reflect the presence of a polymeric Le(x) chain and has important implications for serological and pathogenesis studies. As the substitution pattern of a D-glycero-D-manno-heptose residue in the outer core varied in the two strains, and an extended DD-heptan chain was present in some lipopolysaccharide species but not in others, this region was less conservative than the inner core region. The inner core L-glycero-D-manno-heptose region of both strains carried a 2-aminoethyl phosphate group, rather than a phosphate group, as reported previously for other H. pylori strains.     

AnCF, the CCAAT Binding Complex of Aspergillus nidulans, Contains Products of the hapB, hapC, and hapE Genes and Is Required for Activation by the Pathway-Specific Regulatory Gene amdR

CCAAT binding factors (CBFs) positively regulating the expression of the amdS gene (encoding acetamidase) and two penicillin biosynthesis genes (ipnA and aatA) have been previously found in Aspergillus nidulans. The factors were called AnCF and PENR1, respectively. Deletion of the hapC gene, encoding a protein with significant similarity to Hap3p of Saccharomyces cerevisiae, eliminated both AnCF and PENR1 binding activities. We now report the isolation of the genes hapB and hapE, which encode proteins with central regions of high similarity to Hap2p and Hap5p of S. cerevisiae and to the CBF-B and CBF-C proteins of mammals. An additional fungus-specific domain present in HapE was revealed by comparisons with the homologs from S. cerevisiae, Neurospora crassa, and Schizosaccharomyces pombe. The HapB, HapC, and HapE proteins have been shown to be necessary and sufficient for the formation of a CCAAT binding complex in vitro. Strains with deletions of each of the hapB, hapC, and hapE genes have identical phenotypes of slow growth, poor conidiation, and reduced expression of amdS. Furthermore, induction of amdS by omega amino acids, which is mediated by the AmdR pathway-specific activator, is abolished in the hap deletion mutants, as is growth on γ-aminobutyric acid as a sole nitrogen or carbon source. AmdR and AnCF bind to overlapping sites in the promoters of the amdS and gatA genes. It is known that AnCF can bind independently of AmdR. We suggest that AnCF binding is required for AmdR binding in vivo.     

Identification of highly potent and selective PI3Kδ inhibitors

Selective PI3Kδ inhibitors have recently been hypothesized to be appropriate immunosuppressive agents for the treatment of immunological disorders such as rheumatoid arthritis. However, few reports have highlighted molecules that are highly selective for PI3Kδ over the other PI3K isoforms. In this letter, isoform and kinome selective PI3Kδ inhibitors are presented. The Structural Activity Relationship leading to such molecules is outlined.