Sexual receptivity and post-emergence ovarian development in females of Coproica vagans (Diptera: Sphaeroceridae)

Abstract .Males and females of the dung fly species Coproica vagans Haliday 1833 (Diptera: Sphaeroceridae) mate soon after emergence from the puparium. At this time females still have immature ovaries. Therefore, mating precedes vitellogenesis in this species. Data presented here show that mating enhances oogenesis in C. vagans females. Mated females mature their first egg batch sooner and oviposit four days earlier than virgin conspecifics. Mating-related enhancement of oogenesis could be explained either through nutritional benefits to females or male chemical or stimulatory manipulation of the females. Oogenesis was divided into six arbitrary stages, with vitellogenesis beginning in stage 4. Ovarian development beyond stage 4 is rapid compared with pre-vitellogenetic development. Virgin females pause oogenesis in stage 4. The genital opening of mated females is blocked by a mating plug that persists until oviposition begins. The plug seems to ensure the paternity of the last male to mate by preventing females from remating. The operational sex ratio in C. vagans populations is presumed to be strongly male-biased.     

Pulmonary clearance of inhaled 99mTc-DTPA: effects of surfactant depletion by lung lavage

The influence of surfactant depletion on clearance from the lungs of inhaled technetium-99m-labeled diethylenetriamine pentaacetate (99mTc-DTPA) was studied in rabbits. Surfactant was removed by repeated lung lavage with isotone saline. To minimize structural damage to the lungs, pressure generated insufflation with short expiration was utilized. Aerosolized 99mTc-DTPA was administered via a bag-in-bottle system. Radioactivity was measured with a gamma camera and time-activity curves were obtained over the base of the right lung. Six nonlavaged rabbits served as controls. In six lavaged rabbits clearance of 99mTc-DTPA was significantly faster than in controls. In three rabbits given natural surfactant into the trachea after lung lavage, 99mTc-DTPA was eliminated faster than in controls but slower than in surfactant-depleted animals. The results indicate a role of surfactant on clearance rate of 99mTc-DTPA from rabbit lungs. Measurements of 99mTc-DTPA clearance may be useful in studying the function of the surfactant system in different lung disorders.     

Anaerobic degradation of papermill sludge in a two-phase digester containing rumen microorganisms and colonized polyurethane foam

Summary The use of reticulated polyurethane foam as a support material for the immobilization of methanogenic associations and its application to the anaerobic treatment of fine particulate solid wastes was investigated. The colonization of polyurethane support particles in a continuous upflow reactor fed on a mixture of acetate, propionate and butyrate, was both rapid and dense. The combination of rumen microorganisms and colonized support particles in a two-phase digester resulted in an efficient anaerobic decomposition of papermill sludge.     

Bovine conglutinin is a collagen-like protein

Conglutinin is a bovine plasma protein which is relatively large and asymmetric with elevated contents of glycine and, to some extent, proline. Although its physiologic function is unknown, conglutinin is known to bind, in the presence of calcium, to yeast cell walls and to the solid-phase-inactivated third component of complement. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions, isolated conglutinin appeared to consist of a single polypeptide chain (Mr 48 000). Unreduced conglutinin consisted of a single stained band with an apparent molecular weight of approximately 300 000. Cross-linking experiments with glutaraldehyde and dimethyl suberimidate suggested that this Mr 300 000 molecule consists of six of the disulfide-linked polypeptide chains. Amino acid composition revealed hydroxylysine and hydroxyproline together with elevated glycine and proline contents. Digestion of reduced, alkylated conglutinin with bacterial collagenase resulted in formation of a precipitate which consisted of an Mr 24 000 peptide which was digested to Mr 21 000 with large quantities of collagenase. These peptides contained less glycine, proline, hydroxylysine, and hydroxyproline than did the intact protein. The supernatant from this digestion mixture was, however, enriched in these four amino acids, with glycine making up nearly one-third of the total. Prolonged digestion with pepsin at 37 degrees C resulted in an Mr 20 000 peptide which was enriched in glycine, proline, hydroxyproline, and hydroxylysine. Amino-terminal sequence analysis showed that the glycine-X-Y repeating sequence begins at residue 26.(ABSTRACT TRUNCATED AT 250 WORDS)     

Activation of complement by Schistosoma mansoni schistosomula: killing of parasites by the alternative pathway and requirement of IgG for classical pathway activation.

Living Schistosoma mansoni schistosomula incubated with normal chicken, guinea pig, human, and monkey sera were killed after 4 hr contact at 37 degrees C. The following data indicate that this action is dependent on the activation of the alternative complement pathway (AP): a) the inactivity of RB, RD, and zymosan-treated serum against schistosomula; b) the partial activity of RD restored in FD; c) the full effect of the C4-deficient guinea pig, C2-deficient human, and the agammaglobulinemic human sera; d) the consumption of both the AP and FB after the incubation of NHS with schistosomula; e) the detection of C3d breakdown product during the contact of the C2-deficient human serum with these young parasites. Killing by serum was decreased as the immature schistosomes developed and was completely absent against 4-day-old lung schistosomula (LS). In other experiments, it was demonstrated that schistosomula, in the presence of IgG, were able to initiate complement activation also through the classical pathway (CP). However, the CP does not appear to play a role in the schistosomulicidal activity of complement. The in vivo relevance of these observations is considered.     

Activation of the alternative complement pathway by lymphoblastoid cell lines derived from patients with Burkitt's lymphoma and infectious mononucleosis.

Cultured human lymphoblastoid cell lines derived from patients with Burkitt's lymphoma or infectious mononucleosis were shown to activate the alternative pathway of complement fixation. This reaction does not require any conventional antibody directed against the cells. Although the reaction showed an absolute dependence on the presence of factor B it was relatively independent of the presence of factor D or of properdin. To this extent activation of the alternative pathway by lymphoblastoid cells resembles that produced by “C3-nephritic factor.” Rat and mouse complement were activated in a manner similar to human complement, but guinea pig complement was inactive. Chicken complement, unlike any of the mammalian complements tested, was able to bring about lysis of the lymphoblastoid cell lines by the alternative pathway.     

Deficiency of factor B of the complement system in sickle cell anaemia.

Factors B and D as well as the total activity of the alternative pathway of complement activation were measured using a functional assay in sera from 29 patients with sickle cell anaemia and 18 normal controls. Total alternative pathway activity was reduced in the patients compared with controls. In patients with abnormally low total alternative pathway activity factor D levels were normal, whereas factor B levels were significantly depressed to a mean level of about half of normal. Regression analysis in patients also showed a significant relation between total alternative pathway activity and factor B levels. A deficiency of factor B is the likely cause of the defect in the complement system in patients with sickle cell anaemia. Such a defect may contribute to the excessive proneness of such patients to severe infection.     

The BLOC-1 complex promotes endosomal maturation by recruiting the Rab5 GTPase-activating protein Msb3

Membrane microcompartments of the early endosomes serve as a sorting and signaling platform, where receptors are either recycled back to the plasma membrane or forwarded to the lysosome for destruction. In metazoan cells, three complexes, termed BLOC-1 to -3, mediate protein sorting from the early endosome to lysosomes and lysosome-related organelles. We now demonstrate that BLOC-1 is an endosomal Rab-GAP (GTPase-activating protein) adapter complex in yeast. The yeast BLOC-1 consisted of six subunits, which localized interdependently to the endosomes in a Rab5/Vps21-dependent manner. In the absence of BLOC-1 subunits, the balance between recycling and degradation of selected cargoes was impaired. Additionally, our data show that BLOC-1 is both a Vps21 effector and an adapter for its GAP Msb3. BLOC-1 and Msb3 interacted in vivo, and both mutants resulted in a redistribution of active Vps21 to the vacuole surface. We thus conclude that BLOC-1 controls the lifetime of active Rab5/Vps21 and thus endosomal maturation along the endocytic pathway.     

The effect of genomic information on optimal contribution selection in livestock breeding programs

Background

Long-term benefits in animal breeding programs require that increases in genetic merit be balanced with the need to maintain diversity (lost due to inbreeding). This can be achieved by using optimal contribution selection. The availability of high-density DNA marker information enables the incorporation of genomic data into optimal contribution selection but this raises the question about how this information affects the balance between genetic merit and diversity.

Methods

The effect of using genomic information in optimal contribution selection was examined based on simulated and real data on dairy bulls. We compared the genetic merit of selected animals at various levels of co-ancestry restrictions when using estimated breeding values based on parent average, genomic or progeny test information. Furthermore, we estimated the proportion of variation in estimated breeding values that is due to within-family differences.

Results

Optimal selection on genomic estimated breeding values increased genetic gain. Genetic merit was further increased using genomic rather than pedigree-based measures of co-ancestry under an inbreeding restriction policy. Using genomic instead of pedigree relationships to restrict inbreeding had a significant effect only when the population consisted of many large full-sib families; with a half-sib family structure, no difference was observed. In real data from dairy bulls, optimal contribution selection based on genomic estimated breeding values allowed for additional improvements in genetic merit at low to moderate inbreeding levels. Genomic estimated breeding values were more accurate and showed more within-family variation than parent average breeding values; for genomic estimated breeding values, 30 to 40% of the variation was due to within-family differences. Finally, there was no difference between constraining inbreeding via pedigree or genomic relationships in the real data.

Conclusions

The use of genomic estimated breeding values increased genetic gain in optimal contribution selection. Genomic estimated breeding values were more accurate and showed more within-family variation, which led to higher genetic gains for the same restriction on inbreeding. Using genomic relationships to restrict inbreeding provided no additional gain, except in the case of very large full-sib families.     

Nutrient induced fluorescence transients (NIFTs) provide a rapid measure of P and C (co-)limitation in a green alga

Nutrient Induced Fluorescence Transients (NIFTs) have been shown to be a possible way of testing for the limiting nutrient in algal populations. In this study we tested the hypothesis that NIFTs can be used to detect a (co-)limitation for inorganic phosphorus (Pi) and CO₂ in the green alga Chlamydomonas acidophila and that the magnitude of the NIFTs can be related to cellular P:C ratios. We show a co-limitation response for Pi and CO₂ via traditional nutrient enrichment experiments in natural phytoplankton populations dominated by C. acidophila. We measured NIFT responses after a Pi- or a CO₂-spike in C. acidophila batch cultures at various stages of Pi and inorganic C limitation. Significant NIFTs were observed in response to spikes in both nutrients. The NIFT response to a Pi-spike showed a strong negative correlation with cellular P:C ratio that was pronounced below 3 mmol P: mol C (equivalent to 0.2 pg P cell^–1). Both cellular P and C content influenced the extent of the Pi-NIFT response. The NIFT response to a CO₂-spike correlated to low CO₂ culturing conditions and also had a negative correlation with cellular P content. A secondary response within the Pi-NIFT response was related to the CO₂ concentration and potentially reflected co-limitation. In conclusion, NIFTs provided a quick and reliable method to detect the growth-limiting nutrient in an extremophile green alga, under Pi-, CO_2- and Pi/CO₂ (co-)limited growth conditions.