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1.
Shaun E. Hunter Emily F. Finnegan Dimitrios G. Zisoulis Michael T. Lovci Katya V. Melnik-Martinez Gene W. Yeo Amy E. Pasquinelli 《PLoS genetics》2013,9(3)
The let-7 microRNA (miRNA) regulates cellular differentiation across many animal species. Loss of let-7 activity causes abnormal development in Caenorhabditis elegans and unchecked cellular proliferation in human cells, which contributes to tumorigenesis. These defects are due to improper expression of protein-coding genes normally under let-7 regulation. While some direct targets of let-7 have been identified, the genome-wide effect of let-7 insufficiency in a developing animal has not been fully investigated. Here we report the results of molecular and genetic assays aimed at determining the global network of genes regulated by let-7 in C. elegans. By screening for mis-regulated genes that also contribute to let-7 mutant phenotypes, we derived a list of physiologically relevant potential targets of let-7 regulation. Twenty new suppressors of the rupturing vulva or extra seam cell division phenotypes characteristic of let-7 mutants emerged. Three of these genes, opt-2, prmt-1, and T27D12.1, were found to associate with Argonaute in a let-7–dependent manner and are likely novel direct targets of this miRNA. Overall, a complex network of genes with various activities is subject to let-7 regulation to coordinate developmental timing across tissues during worm development. 相似文献
2.
Chad D. Edwards Joseph C. Beatty Jacqueline B. R. Loiselle Katya A. Vlassov Daniel D. Lefebvre 《Applied microbiology and biotechnology》2013,97(8):3613-3623
Industrial activity over the last two centuries has increased heavy metal contamination worldwide, leading to greater human exposure. Zinc is particularly common in industrial effluents and although an essential nutrient, it is highly toxic at elevated concentrations. Photoautotrophic microbes hold promise for heavy metal bioremediation applications because of their ease of culture and their ability to produce sulfide through metabolic processes that in turn are known to complex with the metal ion, Hg(II). The green alga Chlamydomonas reinhardtii, the red alga Cyanidioschyzon merolae, and the cyanobacterium Synechococcus leopoliensis were all able to synthesize sulfide and form zinc sulfide when exposed to Zn(II). Supplementation of their respective media with sulfite and cysteine had deleterious effects on growth, although ZnS still formed in Cyanidioschyzon cells to the same extent as in unsupplemented cells. The simultaneous addition of sulfate and Zn(II) had similar effects to that of Zn(II) alone in all three species, whereas supplying sulfate prior to exposure to Zn(II) enhanced metal sulfide production. The coupled activities of serine acetyltransferase and O-acetylserine(thiol)lyase (SAT/OASTL) did not increase significantly in response to conditions in which enhanced ZnS formation occurred; sulfate added prior to and simultaneously with Zn(II). However, even low activity could provide sufficient sulfate assimilation over this relatively long-term study. Because the extractable activity of cysteine desulfhydrase was elevated in cells that produced higher amounts of zinc sulfide, cysteine is the probable source of the sulfide in this aerobic process. 相似文献
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Virjinia Doltchinkova Tonya Andreeva Katya Georgieva Gergana Mihailova Konstantin Balashev 《Physiologia plantarum》2019,166(2):585-595
With their ability to survive complete desiccation, resurrection plants are a suitable model system for studying the mechanisms of drought tolerance. In the present study, we investigated desiccation‐induced alterations in surface topography of thylakoids isolated from well‐hydrated, moderately dehydrated, severely desiccated and rehydrated Haberlea rhodopensis plants by means of atomic force microscopy (AFM), electrokinetic and optical measurements. According to our knowledge, so far, there were no reports on the characterization of surface topography and polydispersity of thylakoid membranes from resurrection plants using AFM and dynamic light scattering. To study the physicochemical properties of thylakoids from well‐hydrated H. rhodopensis plants, we used spinach thylakoids for comparison as a classical model from higher plants. The thylakoids from well‐hydrated H. rhodopensis had a grainy surface, significantly different from the well‐structured spinach thylakoids with distinct grana and lamella, they had twice smaller cross‐sectional area and were 1.5 times less voluminous than that of spinach. Significant differences in their physicochemical properties were observed. The dehydration and subsequent rehydration of plants affected the size, shape, morphology, roughness and therefore the structure of the studied thylakoids. Drought resulted in significant enhancement of negative charges on the outer surface of thylakoid membranes which correlated with the increased roughness of thylakoid surface. This enhancement in surface charge density could be due to the partial unstacking of thylakoids exposing more negatively charged groups from protein complexes on the membrane surface that prevent from possible aggregation upon drought stress. 相似文献
6.
Miyake K Tsukui T Shinji Y Shinoki K Hiratsuka T Nishigaki H Futagami S Wada K Gudis K Iwakiri K Yamada N Sakamoto C 《Helicobacter》2004,9(2):130-137
Background. The role of teprenone in Helicobacter pylori‐associated gastritis has yet to be determined. To investigate the effect of teprenone on inflammatory cell infiltration, and on H. pylori colonization of the gastric mucosa in H. pylori‐infected patients, we first compared the effect of teprenone with that of both histamine H2 receptor antagonists (H2‐RA) and sucralfate on the histological scores of H. pylori gastritis. We then examined its in vitro effect on H. pylori‐induced interleukin (IL)‐8 production in MKN28 gastric epithelial cells. Materials and Methods. A total of 68 patients were divided into three groups, each group undergoing a 3‐month treatment with either teprenone (150 mg/day), H2‐RA (nizatidine, 300 mg/day), or sucralfate (3 g/day). All subjects underwent endoscopic examination of the stomach before and after treatment. IL‐8 production in MKN28 gastric epithelial cells was measured by enzyme‐linked immunosorbent assay (ELISA). Results. Following treatment, the teprenone group showed a significant decrease in both neutrophil infiltration and H. pylori density of the corpus (before vs. after: 2.49 ± 0.22 vs. 2.15 ± 0.23, p = .009; 2.36 ± 0.25 vs. 2.00 ± 0.24, p = .035, respectively), with no significant differences seen in either the sucralfate or H2‐RA groups. Teprenone inhibited H. pylori‐enhanced IL‐8 production in MKN28 gastric epithelial cells in vitro, in a dose‐dependent manner. Conclusions. Teprenone may modify corpus H. pylori‐associated gastritis through its effect on neutrophil infiltration and H. pylori density, in part by its inhibition of IL‐8 production in the gastric mucosa. 相似文献
7.
Stefanov K Nechev J Lavchieva-Nacheva G Nikolova N Seizova K Kwartirnikov M Lavchiev V Popov S 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2002,131(3):543-550
Total lipid, fatty acid and sterol composition of larvae and adults of Musca domestica was investigated before and after feeding on sucrose syrup or on the same syrup containing 1% lead nitrate. The effects of sucrose and of lead ions were found to be different. In larvae sucrose diet inhibited the fatty acid elongation and stimulated the first stages of their unsaturation. A significant increase of phytosterol concentrations was obtained. These changes increased the cell membrane permeability. The addition of lead caused a decrease of the fatty acid unsaturation, which decreased the cell membrane permeability. In adults the sucrose diet had no effect on the lipid and sterol composition, while the addition of lead decreased the cholesterol concentration. The composition of lipids and sterols also depends on the diet of larvae before pupation. The data obtained suggested that changes in lipid and sterol composition, which control the permeability of the cell membrane, might be an adaptive response of the organism to the changes of the environment. 相似文献
8.
The accumulation of beneficial mutations on competing genetic backgrounds in rapidly adapting populations has a striking impact on evolutionary dynamics. This effect, known as clonal interference, causes erratic fluctuations in the frequencies of observed mutations, randomizes the fixation times of successful mutations, and leaves distinct signatures on patterns of genetic variation. Here, we show how this form of “genetic draft” affects the forward-time dynamics of site frequencies in rapidly adapting asexual populations. We calculate the probability that mutations at individual sites shift in frequency over a characteristic timescale, extending Gillespie’s original model of draft to the case where many strongly selected beneficial mutations segregate simultaneously. We then derive the sojourn time of mutant alleles, the expected fixation time of successful mutants, and the site frequency spectrum of beneficial and neutral mutations. Finally, we show how this form of draft affects inferences in the McDonald–Kreitman test and how it relates to recent observations that some aspects of genetic diversity are described by the Bolthausen–Sznitman coalescent in the limit of very rapid adaptation. 相似文献
9.
Abstract The bubble crab Dotilla fenestrata forms very dense populations on the sand flats of the eastern coast of Inhaca Island, Mozambique, making it an interesting biological model to examine spatial distribution patterns and test the relative efficiency of common sampling methods. Due to its apparent ecological importance within the sandy intertidal community, understanding the factors ruling the dynamics of Dotilla populations is also a key issue. In this study, different techniques of estimating crab density are described, and the trends of spatial distribution of the different population categories are shown. The studied populations are arranged in discrete patches located at the well‐drained crests of nearly parallel mega sand ripples. For a given sample size, there was an obvious gain in precision by using a stratified random sampling technique, considering discrete patches as strata, compared to the simple random design. Density average and variance differed considerably among patches since juveniles and ovigerous females were found clumped, with higher densities at the lower and upper shore levels, respectively. Burrow counting was found to be an adequate method for large‐scale sampling, although consistently underestimating actual crab density by nearly half. Regression analyses suggested that crabs smaller than 2.9 mm carapace width tend to be undetected in visual burrow counts. A visual survey of sampling plots over several patches of a large Dotilla population showed that crab density varied in an interesting oscillating pattern, apparently following the topography of the sand flat. Patches extending to the lower shore contained higher densities than those mostly covering the higher shore. Within‐patch density variability also pointed to the same trend, but the density increment towards the lowest shore level varied greatly among the patches compared. 相似文献
10.
Scale-up of malaria preventive and control interventions over the last decade resulted in substantial declines in mortality and morbidity from the disease in sub-Saharan Africa and many other parts of the world. Sustaining these gains will depend on the health system performance. Treatment provides individual benefits by curing infection and preventing progression to severe disease as well as community-level benefits by reducing the infectious reservoir and averting emergence and spread of drug resistance. However many patients with malaria do not access care, providers do not comply with treatment guidelines, and hence, patients do not necessarily receive the correct regimen. Even when the correct regimen is administered some patients will not adhere and others will be treated with counterfeit or substandard medication leading to treatment failures and spread of drug resistance. We apply systems effectiveness concepts that explicitly consider implications of health system factors such as treatment seeking, provider compliance, adherence, and quality of medication to estimate treatment outcomes for malaria case management. We compile data for these indicators to derive estimates of effective coverage for 43 high-burden Sub-Saharan African countries. Parameters are populated from the Demographic and Health Surveys and other published sources. We assess the relative importance of these factors on the level of effective coverage and consider variation in these health systems indicators across countries. Our findings suggest that effective coverage for malaria case management ranges from 8% to 72% in the region. Different factors account for health system inefficiencies in different countries. Significant losses in effectiveness of treatment are estimated in all countries. The patterns of inter-country variation suggest that these are system failures that are amenable to change. Identifying the reasons for the poor health system performance and intervening to tackle them become key priority areas for malaria control and elimination policies in the region. 相似文献