Life table characteristics of Macrolophus caliginosus preying upon Tetranychus urticae

The life table characteristics of the polyphagous mirid Macrolophus caliginosus Wagner (Heteroptera: Miridae) preying on various stages of Tetranychus urticae Koch (Acari: Tetranychidae) with tomato as host plant were described at 22 °C. The following average parameters were obtained: Female longevity: 28.7 days; fecundity: 0.7 eggs/female/day; egg mortality: 2.6%; pre-oviposition period: 5.5 days; oviposition period: 18.1 days; post-oviposition period: 3.2 days; juvenile development time: 26.8 days; juvenile mortality: 34.9%; and sex ratio (/(+): 0.46. Life table parameters were estimated as net reproduction rate (R ₀): 6.15; intrinsic rate of increase (r _m): 0.031 day^–1; finite rate of increase (): 1.032; mean generation time (T _c): 58.17 days; and doubling time (T ₂) 22.2 days. The parameters obtained were in accordance with those reported for M. caliginosus fed on another mite species (T. turkestani Ugarov & Nikolski (Acari: Tetranychidae)). However, compared to the performance of M. caliginosus fed on common glasshouse insect pests, a diet consisting of only mites appeared to be inferior. However, being a voracious predator, M. caliginosus may be a valuable addition to existing methods of mite control.     

Transfer of the Pheromone-Inducible Plasmid pCF10 among Enterococcus faecalis Microorganisms Colonizing the Intestine of Mini-Pigs

A new animal model, the streptomycin-treated mini-pig, was developed in order to allow colonization of defined strains of Enterococcus faecalis in numbers sufficient to study plasmid transfer. Transfer of the pheromone-inducible pCF10 plasmid between streptomycin-resistant strains of E. faecalis OG1 was investigated in the model. The plasmid encodes resistance to tetracycline. Numbers of recipient, donor, and transconjugant bacteria were monitored by selective plating of fecal samples, and transconjugants were subsequently verified by PCR. After being ingested by the mini-pigs, the recipient strain persisted in the intestine at levels between 10⁶ and 10⁷ CFU per g of feces throughout the experiment. The donor strain, which carried different resistance markers but was otherwise chromosomally isogenic to the recipient strain, was given to the pigs 3 weeks after the recipient strain. The donor cells were initially present in high numbers (10⁶ CFU per g) in feces, but they did not persist in the intestine at detectable levels. Immediately after introduction of the donor bacteria, transconjugant cells appeared and persisted in fecal samples at levels between 10³ and 10⁴ CFU per g until the end of the experiment. These observations showed that even in the absence of selective tetracycline pressure, plasmid pCF10 was transferred from ingested E. faecalis cells to other E. faecalis organisms already present in the intestinal environment and that the plasmid subsequently persisted in the intestine.     

Analysis of the leukemia inhibitory factor receptor functional domains by chimeric receptors and cytokines

In contrast to other hematopoietic cytokine receptors, the leukemia inhibitory factor receptor (LIFR) possesses two cytokine binding modules (CBMs). Previous studies suggested that the NH(2)-terminal CBM and the Ig-like domain of the LIFR are most important for LIF binding and activity. Using the recently engineered designer cytokine IC7, which induces an active heterodimer of the LIFR and gp130 after binding to the IL-6R, and several receptor chimeras of the LIFR and the interleukin-6 receptor (IL-6R) carrying the CBM of the IL-6R in place of the COOH-terminal LIFR CBM, we could assign individual receptor subdomains to individual binding sites of the ligand. The NH(2)-terminal CBM and the Ig-like domain of the LIFR bind to ligand site III, whereas the COOH-terminal CBM contacts site I. Furthermore, we show that LIFR mutants carrying the IL-6R CBM instead of the COOH-terminal CBM can replace the IL-6R by acting as an alpha-receptor for IL-6. However, in situations where a signaling competent receptor is bound at IL-6 site I, ligand binding to site III is an absolute requirement for participation of the receptor in a signaling heterodimer with gp130; i.e., a functional receptor complex of IL-6 type cytokines cannot be assembled solely via site I and II as in the growth hormone receptor complex.     

Genome sequencing of a single cell of the widely distributed marine subsurface Dehalococcoidia,phylum Chloroflexi

Bacteria of the class Dehalococcoidia (DEH), phylum Chloroflexi, are widely distributed in the marine subsurface, yet metabolic properties of the many uncultivated lineages are completely unknown. This study therefore analysed genomic content from a single DEH cell designated ‘DEH-J10'' obtained from the sediments of Aarhus Bay, Denmark. Real-time PCR showed the DEH-J10 phylotype was abundant in upper sediments but was absent below 160 cm below sea floor. A 1.44 Mbp assembly was obtained and was estimated to represent up to 60.8% of the full genome. The predicted genome is much larger than genomes of cultivated DEH and appears to confer metabolic versatility. Numerous genes encoding enzymes of core and auxiliary beta-oxidation pathways were identified, suggesting that this organism is capable of oxidising various fatty acids and/or structurally related substrates. Additional substrate versatility was indicated by genes, which may enable the bacterium to oxidise aromatic compounds. Genes encoding enzymes of the reductive acetyl-CoA pathway were identified, which may also enable the fixation of CO₂ or oxidation of organics completely to CO₂. Genes encoding a putative dimethylsulphoxide reductase were the only evidence for a respiratory terminal reductase. No evidence for reductive dehalogenase genes was found. Genetic evidence also suggests that the organism could synthesise ATP by converting acetyl-CoA to acetate by substrate-level phosphorylation. Other encoded enzymes putatively conferring marine adaptations such as salt tolerance and organo-sulphate sulfohydrolysis were identified. Together, these analyses provide the first insights into the potential metabolic traits that may enable members of the DEH to occupy an ecological niche in marine sediments.     

The chromatin-remodeling factor CHD4 coordinates signaling and repair after DNA damage

In response to ionizing radiation (IR), cells delay cell cycle progression and activate DNA repair. Both processes are vital for genome integrity, but the mechanisms involved in their coordination are not fully understood. In a mass spectrometry screen, we identified the adenosine triphosphate–dependent chromatin-remodeling protein CHD4 (chromodomain helicase DNA-binding protein 4) as a factor that becomes transiently immobilized on chromatin after IR. Knockdown of CHD4 triggers enhanced Cdc25A degradation and p21^Cip1 accumulation, which lead to more pronounced cyclin-dependent kinase inhibition and extended cell cycle delay. At DNA double-strand breaks, depletion of CHD4 disrupts the chromatin response at the level of the RNF168 ubiquitin ligase, which in turn impairs local ubiquitylation and BRCA1 assembly. These cell cycle and chromatin defects are accompanied by elevated spontaneous and IR-induced DNA breakage, reduced efficiency of DNA repair, and decreased clonogenic survival. Thus, CHD4 emerges as a novel genome caretaker and a factor that facilitates both checkpoint signaling and repair events after DNA damage.     

Estrogenic effect of propylparaben (propylhydroxybenzoate) in rainbow trout Oncorhynchus mykiss after exposure via food and water

The estrogenic effect of propylparaben was investigated in a rainbow trout Oncorhynchus mykiss test system. Propylparaben was administered orally to sexually immature rainbow trout every second day for up to 10 days in doses between 7 and 1830 mg kg(-1) 2 d(-1) and in the water at 50 and 225 microg l(-1) for 12 days. Plasma vitellogenin was measured before and during the exposures and the concentrations of propylparaben in liver and muscle were determined at the end of experiments. Increases in average plasma vitellogenin levels were seen at oral exposure to 33 mg propylparabenkg(-1) 2 d(-1); the most sensitive fish responded to 7 mg kg(-1). The ED(50) values for increase in vitellogenin synthesis were 35, 31 and 22 mg kg(-1) 2 d(-1) at day 3, 6 and 11, respectively. Exposure to 225 microg propylparabenl(-1) increased vitellogenin synthesis, but exposure to 50 microg l(-1) did not. Propylparaben showed little tendency to bioaccumulation in rainbow trout; less than 1 per thousand of the total amount of propylparaben administered orally at 1830 mg kg(-1) 2 d(-1) over the 10-d experimental period was retained in muscle and liver 24 h after the end of the experiment. Exposure to 225 microg propylparabenl(-1) for 12 d led to concentrations of 6700 and 870 microg propylparabenkg(-1) liver and muscle, respectively. Half lives for propylparaben were 8.6 h in liver and 1.5 h in muscle.     

Characterisation of Age-Dependent Beta Cell Dynamics in the Male db/db Mice

Aim

To characterise changes in pancreatic beta cell mass during the development of diabetes in untreated male C57BLKS/J db/db mice.

Methods

Blood samples were collected from a total of 72 untreated male db/db mice aged 5, 6, 8, 10, 12, 14, 18, 24 and 34 weeks, for measurement of terminal blood glucose, HbA_1c, plasma insulin, and C-peptide. Pancreata were removed for quantification of beta cell mass, islet numbers as well as proliferation and apoptosis by immunohistochemistry and stereology.

Results

Total pancreatic beta cell mass increased significantly from 2.1 ± 0.3 mg in mice aged 5 weeks to a peak value of 4.84 ± 0.26 mg (P < 0.05) in 12-week-old mice, then gradually decreased to 3.27 ± 0.44 mg in mice aged 34 weeks. Analysis of islets in the 5-, 10-, and 24-week age groups showed increased beta cell proliferation in the 10-week-old animals whereas a low proliferation is seen in older animals. The expansion in beta cell mass was driven by an increase in mean islet mass as the total number of islets was unchanged in the three groups.

Conclusions/Interpretation

The age-dependent beta cell dynamics in male db/db mice has been described from 5-34 weeks of age and at the same time alterations in insulin/glucose homeostasis were assessed. High beta cell proliferation and increased beta cell mass occur in young animals followed by a gradual decline characterised by a low beta cell proliferation in older animals. The expansion of beta cell mass was caused by an increase in mean islet mass and not islet number.