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41.
Mouse maelstrom, a component of nuage, is essential for spermatogenesis and transposon repression in meiosis 总被引:1,自引:0,他引:1
Soper SF van der Heijden GW Hardiman TC Goodheart M Martin SL de Boer P Bortvin A 《Developmental cell》2008,15(2):285-297
Tight control of transposon activity is essential for the integrity of the germline. Recently, a germ-cell-specific organelle, nuage, was proposed to play a role in transposon repression. To test this hypothesis, we disrupted a murine homolog of a Drosophila nuage protein Maelstrom. Effects on male meiotic chromosome synapsis and derepression of transposable elements (TEs) were observed. In the adult Mael(-/-) testes, LINE-1 (L1) derepression occurred at the onset of meiosis. As a result, Mael(-/-) spermatocytes were flooded with L1 ribonucleoproteins (RNPs) that accumulated in large cytoplasmic enclaves and nuclei. Mael(-/-) spermatocytes with nuclear L1 RNPs exhibited massive DNA damage and severe chromosome asynapsis even in the absence of SPO11-generated meiotic double-strand breaks. This study demonstrates that MAEL, a nuage component, is indispensable for the silencing of TEs and identifies the initiation of meiosis as an important step in TE control in the male germline. 相似文献
42.
Miriam C.J. de With E.P.A. Brigitte van der Heijden Matthijs F. van Oosterhout M. Kon Alfons B.A. Kroese 《Cryobiology》2009,59(3):308-316
Introduction
Cold hypoxia is a common factor in cold tissue preservation and mammalian hibernation. The purpose of this study was to determine the effects of cold preservation on the function of the retractor (RET) muscle of the hamster in the non-hibernating state and compare these with previously published data (van der Heijden et al., 2000) [52] on the rat cutaneus trunci (CT) muscle.Materials and methods
After cold storage (16 h at 4 °C), muscles were stimulated electrically to measure maximum tetanus tension (P0) and histologically analyzed. The protective effects of addition of the antioxidants trolox and deferiprone and the calcium release inhibitor BDM to the storage fluid were determined.Results
After storage, the twitch threshold current was increased (from 60 to 500 μA) and P0 was decreased to 27% of control. RET morphology remained unaffected. RET muscle function was protected by trolox and deferiprone (P0, resp., 43% and 59% of control). Addition of BDM had no effect on the RET.Conclusions
The observed effects of cold preservation and of trolox and deferiprone on the RET were comparable to those on CT muscle function, as reported in a previously published study (van der Heijden et al., 2000) [52]. Both hamster RET and rat CT muscles show considerable functional damage due to actions of reactive oxygen species. In contrast to the CT, in the RET cold preservation-induced functional injury could not be prevented by BDM and was not accompanied by morphological damage such as necrosis and edema. This suggests that the RET myocytes possess a specific adaptation to withstand the Ca2+ overload induced by cold ischemia. 相似文献43.
Marijn T. J. van Loenhout Thijn van der Heijden Roland Kanaar Claire Wyman Cees Dekker 《Nucleic acids research》2009,37(12):4089-4099
RecA, the key protein in homologous recombination, performs its actions as a helical filament on single-stranded DNA (ssDNA). ATP hydrolysis makes the RecA–ssDNA filament dynamic and is essential for successful recombination. RecA has been studied extensively by single-molecule techniques on double-stranded DNA (dsDNA). Here we directly probe the structure and kinetics of RecA interaction with its biologically most relevant substrate, long ssDNA molecules. We find that RecA ATPase activity is required for the formation of long continuous filaments on ssDNA. These filaments both nucleate and extend with a multimeric unit as indicated by the Hill coefficient of 5.4 for filament nucleation. Disassembly rates of RecA from ssDNA decrease with applied stretching force, corresponding to a mechanism where protein-induced stretching of the ssDNA aids in the disassembly. Finally, we show that RecA–ssDNA filaments can reversibly interconvert between an extended, ATP-bound, and a compressed, ADP-bound state. Taken together, our results demonstrate that ATP hydrolysis has a major influence on the structure and state of RecA filaments on ssDNA. 相似文献
44.
Gert‐Jan van der Heijden Zhiyue J. Wang Zili D. Chu Pieter J.J. Sauer Morey W. Haymond Luisa M. Rodriguez Agneta L. Sunehag 《Obesity (Silver Spring, Md.)》2010,18(2):384-390
The rise in obesity‐related morbidity in children and adolescents requires urgent prevention and treatment strategies. Currently, only limited data are available on the effects of exercise programs on insulin resistance, and visceral, hepatic, and intramyocellular fat accumulation. We hypothesized that a 12‐week controlled aerobic exercise program without weight loss reduces visceral, hepatic, and intramyocellular fat content and decreases insulin resistance in sedentary Hispanic adolescents. Twenty‐nine postpubertal (Tanner stage IV and V), Hispanic adolescents, 15 obese (7 boys, 8 girls; 15.6 ± 0.4 years; 33.7 ± 1.1 kg/m2; 38.3 ± 1.5% body fat) and 14 lean (10 boys, 4 girls; 15.1 ± 0.3 years; 20.6 ± 0.8 kg/m2; 18.9 ± 1.5% body fat), completed a 12‐week aerobic exercise program (4 × 30 min/week at ≥70% of peak oxygen consumption (VO2peak)). Measurements of cardiovascular fitness, visceral, hepatic, and intramyocellular fat content (magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS)), and insulin resistance were obtained at baseline and postexercise. In both groups, fitness increased (obese: 13 ± 2%, lean: 16 ± 4%; both P < 0.01). In obese participants, intramyocellular fat remained unchanged, whereas hepatic fat content decreased from 8.9 ± 3.2 to 5.6 ± 1.8%; P < 0.05 and visceral fat content from 54.7 ± 6.0 to 49.6 ± 5.5 cm2; P < 0.05. Insulin resistance decreased indicated by decreased fasting insulin (21.8 ± 2.7 to 18.2 ± 2.4 µU/ml; P < 0.01) and homeostasis model assessment of insulin resistance (HOMAIR) (4.9 ± 0.7 to 4.1 ± 0.6; P < 0.01). The decrease in visceral fat correlated with the decrease in fasting insulin (R2 = 0.40; P < 0.05). No significant changes were observed in any parameter in lean participants except a small increase in lean body mass (LBM). Thus, a controlled aerobic exercise program, without weight loss, reduced hepatic and visceral fat accumulation, and decreased insulin resistance in obese adolescents. 相似文献
45.
Liping Qiu Qian Zhang Hansong Zhu Peter B. Reich Samiran Banerjee Marcel G. A. van der Heijden Michael J. Sadowsky Satoshi Ishii Xiaoxu Jia Mingan Shao Baoyuan Liu Huan Jiao Haiqiang Li Xiaorong Wei 《The ISME journal》2021,15(8):2474
While soil erosion drives land degradation, the impact of erosion on soil microbial communities and multiple soil functions remains unclear. This hinders our ability to assess the true impact of erosion on soil ecosystem services and our ability to restore eroded environments. Here we examined the effect of erosion on microbial communities at two sites with contrasting soil texture and climates. Eroded plots had lower microbial network complexity, fewer microbial taxa, and fewer associations among microbial taxa, relative to non-eroded plots. Soil erosion also shifted microbial community composition, with decreased relative abundances of dominant phyla such as Proteobacteria, Bacteroidetes, and Gemmatimonadetes. In contrast, erosion led to an increase in the relative abundances of some bacterial families involved in N cycling, such as Acetobacteraceae and Beijerinckiaceae. Changes in microbiota characteristics were strongly related with erosion-induced changes in soil multifunctionality. Together, these results demonstrate that soil erosion has a significant negative impact on soil microbial diversity and functionality.Subject terms: Soil microbiology, Microbial ecology 相似文献
46.
van der Heijden AM Lee TC van Rantwijk F van Bekkum H 《Carbohydrate research》2002,337(21-23):1993-1998
Glycosidation of saccharides combines the essential characteristics of two major renewable classes, viz. triglycerides and carbohydrates, leading to biofriendly surfactants and emulsifiers. The development of the alkylglycosides derived from reducing disaccharides has lagged, because no efficient synthesis was available. We have found that ordered mesoporous materials of the MCM-41 type are active and selective catalysts for the glycosidation of disaccharides containing fructose at the reducing end, i.e., isomaltulose, lactulose and leucrose. No alcoholysis or hydrolysis of the glycosidic bond was observed, demonstrating the mildness of the MCM-41 catalyst. Leucrose was found to be less reactive than the two other disaccharides, in accordance with the absence of furanose forms in leucrose. 相似文献
47.
48.
Karin M. van der Heijden Inneke M. van der Heijden Flavio H. Galvao Camila G. Lopes Silvia F. Costa Edson Abdala Luiz A. D’Albuquerque Anna S. Levin 《PloS one》2014,9(9)
The objectives of this study were to develop a rat model of gastrointestinal colonization with vancomycin-resistant Enterococcus faecalis (VRE) and extended-spectrum beta-lactamase (ESBL)-producing E. coli and to evaluate intestinal translocation to blood and tissues after total and partial hepatic ischemia.
Methods
- We developed a model of rat colonization with VRE and ESBL-E coli. Then we studied four groups of colonized rats: Group I (with hepatic pedicle occlusion causing complete liver ischemia and intestinal stasis); Group II (with partial liver ischemia without intestinal stasis); Group III (surgical manipulation without hepatic ischemia or intestinal stasis); Group IV (anesthetized without surgical manipulation). After sacrifice, portal and systemic blood, large intestine, small intestine, spleen, liver, lungs, and cervical and mesenteric lymph nodes were cultured. Endotoxin concentrations in portal and systemic blood were determined. Results – The best inocula were: VRE: 2.4×1010 cfu and ESBL-E. coli: 1.12×1010 cfu. The best results occurred 24 hours after inoculation and antibiotic doses of 750 µg/mL of water for vancomycin and 2.1 mg/mL for ceftriaxone. There was a significantly higher proportion of positive cultures for ESBL-E. coli in the lungs in Groups I, II and III when compared with Group IV (67%; 60%; 75% and 13%, respectively; p:0.04). VRE growth was more frequent in mesenteric lymph nodes for Groups I (67%) and III (38%) than for Groups II (13%) and IV (none) (p:0.002). LPS was significantly higher in systemic blood of Group I (9.761±13.804 EU/mL−p:0.01). No differences for endotoxin occurred in portal blood. Conclusion –We developed a model of rats colonized with resistant bacteria useful to study intestinal translocation. Translocation occurred in surgical procedures with and without hepatic ischemia-reperfusion and probably occurred via the bloodstream. Translocation was probably lymphatic in the ischemia-reperfusion groups. Systemic blood endotoxin levels were higher in the group with complete hepatic ischemia. 相似文献
49.
Arbuscular mycorrhizal fungi influence life history traits of a lepidopteran herbivore 总被引:5,自引:0,他引:5
Results from pot and microcosm studies in the greenhouse have shown that plant growth and foliar chemistry is altered by the presence and species composition of arbuscular mycorrhizal fungi (AMF). The growth and survival of herbivores which feed on plants could, as a consequence, also be affected by these mutualistic soil fungi. Consequently, interactions between AMF, plants and herbivores could occur. To test this, larvae of the common blue butterfly, Polyommatus icarus (Lycaenidae), were fed with sprigs of Lotus corniculatus (Fabaceae) plants which were inoculated with one of two different AMF species, with a mixture of these AMF species or with sprigs of plants which were not inoculated with AMF. Survival and larval weight of third instar larvae fed with plants colonised by AMF were greater than those of larvae fed with non-mycorrhizal plants. Survival of larvae feeding on non-mycorrhizal plants was 1.6 times lower than that of larvae feeding on plants inoculated with a mixture of AMF species and 3.8 times lower than that of larvae feeding on plants inoculated with single AMF species. Furthermore, larvae fed with non-mycorrhizal plants attained only about half the weight of larvae fed with mycorrhizal plants after 11 days of growth. These differences in larval performance might be explained by differences in leaf chemistry, since mycorrhizal plants had a 3 times higher leaf P concentration and a higher C/N-ratio. Our results, thus, show that the presence of belowground mutualistic soil fungi influences the performance of aboveground herbivores by altering their food quality. Larval consumption, larval food use and adult lipid concentrations of the common blue butterfly differed between larvae which were fed with plants inoculated with different AMF species. This suggests that the performance of herbivores is not only influenced by the presence of AMF but also depends on the identity of the AMF species colonising the host plants. Moreover, a significant interaction term between AMF species and maternal identity of the larvae occurred for adult dry weight, indicating that the performance of offspring from different females was differently influenced by AMF species composition. To our knowledge, these results show for the first time that the species composition of AMF communities can influence life-history traits of butterfly larvae and possibly herbivores in general. 相似文献
50.
Edwin Van Der Heijden Steven K. Verbeek Pieter J. C. Kuiper 《Global Change Biology》2000,6(2):201-212
Sphagnum bogs play an important role when considering the impacts of global change on global carbon and nitrogen cycles. Sphagnum recurvum P. Beauv. var. mucronatum (Russ.) was grown at 360 (ambient) and 700 μL L?1 (elevated) atmospheric [CO2] in combination with different nitrogen deposition rates (6, 15, 23 g N m?2 y?1), in a short‐ and long‐term growth chamber experiment. After 6 months, elevated atmospheric [CO2] in combination with the lowest nitrogen deposition rate, increased plant dry mass by 17%. In combination with a high nitrogen deposition rate, biomass production was not significantly stimulated. At the start of the experiment, photosynthesis was stimulated by elevated atmospheric [CO2], but it was downregulated to control levels after three days of exposure. Elevated [CO2] substantially reduced dark respiration, which resulted in a continuous increase in soluble sugar content in capitula. Differences in growth response among different nitrogen and CO2 treatments could not be related to measured carbon exchange rates, which was mainly due to interference of microbial respiration. Doubling atmospheric [CO2] reduced total nitrogen content in capitula but not in stems at all nitrogen deposition rates. Reduction in total nitrogen content coincided with a decrease in amino acids, but soluble protein levels remained unaffected. Thus, elevated [CO2] induced a substantial shift in the partitioning of nitrogen compounds in capitula. Soluble sugar concentration was negatively correlated with total nitrogen content, which implies that the reduction in amino acid content in capitula, exposed to elevated [CO2], might be caused by the accumulation of soluble sugars. Growth was not stimulated by increased nitrogen deposition. High nitrogen deposition, resulting in a capitulum nitrogen content in excess of 15 mg g?1 dw, was detrimental to photosynthesis, reduced water content and induced necrosis. We propose a capitulum nitrogen content of 15 mg g?1 dw as a possible bioindicator for the detection of nitrogen pollution stress in oligo‐mesotrophic peat bog ecosystems. At the lowest nitrogen deposition level, nitrogen recovery was higher than 100%, which indicates substantial dry deposition and/or gaseous nitrogen fixation by bacteria, associated with Sphagnum. Increasing nitrogen deposition rates decreased nitrogen recovery percentages, which indicates reduced efficiency of nitrogen fixation. 相似文献