HorkaD, a Chromosome Instability-Causing Mutation in Drosophila, Is a Dominant-Negative Allele of lodestar

Correct segregation of chromosomes is particularly challenging during the rapid nuclear divisions of early embryogenesis. This process is disrupted by Horka^D, a dominant-negative mutation in Drosophila melanogaster that causes female sterility due to chromosome tangling and nondisjunction during oogenesis and early embryogenesis. Horka^D also renders chromosomes unstable during spermatogenesis, which leads to the formation of diplo//haplo mosaics, including the gynandromorphs. Complete loss of gene function brings about maternal-effect lethality: embryos of the females without the Horka^D-identified gene perish due to disrupted centrosome function, defective spindle assembly, formation of chromatin bridges, and abnormal chromosome segregation during the cleavage divisions. These defects are indicators of mitotic catastrophe and suggest that the gene product acts during the meiotic and the cleavage divisions, an idea that is supported by the observation that germ-line chimeras exhibit excessive germ-line and cleavage function. The gene affected by the Horka^D mutation is lodestar, a member of the helicase-related genes. The Horka^D mutation results in replacement of Ala777 with Thr, which we suggest causes chromosome instability by increasing the affinity of Lodestar for chromatin.     

The importance of sedimenting organic matter, relative to oxygen and temperature, in structuring lake profundal macroinvertebrate assemblages

We quantified the role of a main food resource, sedimenting organic matter (SOM), relative to oxygen (DO) and temperature (TEMP) in structuring profundal macroinvertebrate assemblages in boreal lakes. SOM from 26 basins of 11 Finnish lakes was analysed for quantity (sedimentation rates), quality (C:N:P stoichiometry) and origin (carbon stable isotopes, δ¹³C). Hypolimnetic oxygen and temperature were measured from each site during summer stratification. Partial canonical correspondence analysis (CCA) and partial regression analyses were used to quantify contributions of SOM, DO and TEMP to community composition and three macroinvertebrate metrics. The results suggested a major contribution of SOM in regulating the community composition and total biomass. Oxygen best explained the Shannon diversity, whereas TEMP had largest contribution to the variation of Benthic Quality Index. Community composition was most strongly related to δ¹³C of SOM. Based on additional δ¹³C and stoichiometric analyses of chironomid taxa, marked differences were apparent in their utilization of SOM and body stoichiometry; taxa characteristic of oligotrophic conditions exhibited higher C:N ratios and lower C:P and N:P ratios compared to the species typical of eutrophic lakes. The results highlight the role of SOM in regulating benthic communities and the distributions of individual species, particularly in oligotrophic systems.     

Periosteal microcirculatory action of chronic estrogen supplementation in osteoporotic rats challenged with tourniquet ischemia

AimsTransient ischemia of osteoporotic bones during elective orthopedic surgery or fracture repair carries risks for serious complications, and estrogen loss or replacement has a potential to influence ischemia–reperfusion-induced inflammatory activation. To clarify this, we investigated the periosteal inflammatory changes in a clinically relevant time frame in ovariectomized rats, an experimental model of postmenopausal bone loss. Furthermore, the effects of chronic estrogen supplementation on the postischemic local and systemic inflammatory reactions were assessed.Main methodsBilateral ovariectomy or sham operation was performed in 3-month-old female Sprague–Dawley rats. Five months later, estrogen replacement therapy with 17β-estradiol (20 μg^? 1 kg^? 1 day^? 1) or vehicle treatment was initiated. The microcirculatory inflammatory consequences of 60-min total hindlimb ischemia followed by 180-min reperfusion were examined 11 months after ovariectomy and were compared with those in 3-month-old animals.Key findingsThe osteoporosis that developed 5 months after ovariectomy was significantly ameliorated by estrogen replacement therapy. Both in ovariectomized and in non-ovariectomized animals, ischemia–reperfusion elevated the neutrophil adherence ~ 3-fold in the postcapillary venules of the periosteum (intravital microscopy), with an ~ 50–60% increase in intravascular neutrophil activation (CD11b; FACS analysis), an enhanced TNF-α release (ELISA) and periosteal expression of ICAM-1 (the endothelial ligand of CD11b; immunohistochemistry). Exogenous 17β-estradiol considerably reduced TNF-α release and the number of neutrophil–endothelial interactions in the periosteum, without affecting the CD11b and ICAM-1 expression changes.SignificanceOsteoporosis itself does not increase the magnitude of the limb ischemia–reperfusion-associated periosteal inflammatory reaction. Chronic estrogen supplementation, however, reverses osteoporosis and significantly ameliorates the microcirculatory consequences of transient ischemia.     

Notes on the Deficiency-One Theorem: multiple linkage classes

The Deficiency-One Theorem tells us about certain chemical reaction systems that they cannot admit multiple interior equilibria. The theorem was proven by Feinberg. In this paper we provide a relatively short proof of that theorem. We also extend that result by giving an equivalent condition to the fact that the set of interior equilibria is nonempty for a chemical reaction system considered in the Deficiency-One Theorem.     

High-copy-number derivatives of the plasmid cloning vector pBR322

A stable copy-number mutant of a pBR322-derived plasmid was isolated. The mutation was found to be a single G → T transversion located near the 3' end of a DNA segment coding for the regulatory RNA I. The resulting copy number for this plasmid is approx. 1000 per cell or 65 % of total cellular DNA. Several cloning vectors have been constructed from this copy-number mutant and their practical application is discussed.     

Characterization of regulatory (interferon-alpha/beta) and accessory (LAF/IL 1) monokine activities from liver granuloma macrophages of Schistosoma mansoni-infected mice

Previously it was shown that macrophages (M phi) isolated from the vigorous (Vig) or modulated (Mod) liver granulomas (Gr) of Schistosoma mansoni-infected mice restored mitogen and parasite egg antigen-induced proliferative responses to accessory cell-depleted lymphocytes. Furthermore, supraoptimal concentrations of highly activated VigGrM phi suppressed lymphoproliferation to a greater extent than did the lesser activated ModGrM phi. In this study we investigated the role of soluble mediators in GrM phi accessory/regulatory activity. Indomethacin released VigGrM phi-mediated inhibition of mitogen but not antigen-induced lymphoproliferation. Extensively dialyzed serum-free GrM phi culture supernatant nonspecifically suppressed SEA- or KLH-induced blastogenesis. Culture supernatants also reduced vesicular stomatitis virus-induced plaque formation in supernatant-pretreated L-929 fibroblasts. The 20 to 45 Kd GrM phi-derived lymphoproliferation suppressive factor (SF) and the 20 to 50 Kd viral plaque-reducing factor (PRF) were stable at low pH, but became inactivated by heat and trypsin digestion. Although freshly isolated Vig or ModGrM phi contained preformed SF and PRF, in vitro production of the factors were depressed by protein synthesis inhibitors. Moreover, SF was active only when added to cultures before day 3 of the 6-day proliferation assay. Both SF and PRF were specifically retained on rabbit anti-murine IFN-alpha/beta immunoaffinity columns. Thus, the suppressive activity of Vig or ModGrM phi is in part mediated by a monokine that shares physical, biological, and antigenic characteristics with murine IFN-alpha/beta. In contrast to the suppression of antigen-driven proliferation, GrM phi culture supernatant costimulated PHA-induced mitogenesis. The 13 to 21 Kd GrM phi-derived lymphocyte-activating factor (LAF) was stable to heat, low pH, and trypsin digestion. Freshly isolated Vig or ModGrM phi contained preformed LAF, although its in vitro production was depressed by protein synthesis inhibitors. The physical and biological characteristics of GrM phi-derived LAF appear similar to IL 1. It is concluded that both Vig and ModGrM phi secrete regulatory/accessory monokines that may contribute to the initiation and maintenance of the focal inflammatory granulomatous response.     

Characterization of granuloma T lymphocyte function from Schistosoma mansoni-infected mice

This study was undertaken to characterize and compare T lymphocyte function from the vigorous and modulated liver granulomas of Schistosoma mansoni-infected mice. Although both types of lesion contained equal percentages of T lymphocytes, the T cell subset distribution was different. For vigorous lesions, the ratio of helper/effector to suppressor/cytotoxic T cells was 2 to 3:1. For modulated lesions the ratio was lower (1:1). Differences in the phenotypic profiles of vigorous and modulated granuloma (Gr) T cells were reflected in their functional activity. Vigorous Gr T cells were more active in lymphoproliferation, IL-2 production, and granuloma formation than those from modulated lesions. Moreover, modulated Gr T cells suppressed the functional activity of vigorous Gr T cells in a dose-dependent manner. The selective depletion of T cell subsets showed that phenotypically, the Gr delayed-hypersensitivity T cell is L3T4+, Lyt-1+ whereas the Gr Ts cell is an Lyt-2+ lymphocyte. Both of these T cell subsets are present in vigorous and modulated lesions. During acute infection, delayed-hypersensitivity T cell lymphocyte functions predominate, whereas Ts lymphocyte functions appear to prevail during chronic infection.