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31.
Niraj Shrestha Pallavi Chaturvedi Xiaoyun Zhu Michael J. Dee Varghese George Christopher Janney Jack O. Egan Bai Liu Mark Foster Lynne Marsala Pamela Wong Celia C. Cubitt Jennifer A. Foltz Jennifer Tran Timothy Schappe Karin Hsiao Gilles M. Leclerc Lijing You Christian Echeverri Catherine Spanoudis Ana Carvalho Leah Kanakaraj Crystal Gilkes Nicole Encalada Lin Kong Meng Wang Byron Fang Zheng Wang Jin-an Jiao Gabriela J. Muniz Emily K. Jeng Nicole Valdivieso Liying Li Richard Deth Melissa M. Berrien-Elliott Todd A. Fehniger Peter R. Rhode Hing C. Wong 《Aging cell》2023,22(5):e13806
32.
Paulino Bambi Alan M. Tonin Renan de Souza Rezende Fernando Carvalho Vieira Fernanda Gabriela Graciano Miranda Luz Boyero José F. Gonçalves Júnior 《Biotropica》2023,55(1):40-52
Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear-cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast-growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear-cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest-stream interfaces. 相似文献
33.
Solana Abraham Andrea Moyano Viviana Díaz M. Gabriela Murúa Juan Rull 《Insect Science》2023,30(4):1183-1190
Promiscuous mating systems provide the opportunity for females to bias fertilization toward particular males. However, distinguishing between male sperm competition and active female sperm choice is difficult for species with internal fertilization. Nevertheless, species that store and use sperm of different males in different storing structures and species where females are able to expel all or part of the ejaculates after copulation may be able to bias fertilization. We report a series of experiments aimed at providing evidence of female sperm choice in Euxesta eluta (Hendel), a species of ulidiid fly that expels and consumes ejaculates after copulation. We found no evidence of greater reproductive success for females mated singly, multiply with the same male, or mated multiply with different males. Female E. eluta possesses two spherical spermathecae and a bursa copulatrix for sperm storage, with a ventral receptacle. There was no significant difference in storing more sperm in spermathecae 24 h after copulation than immediately after copulation. Females mated with protein-fed males had greater reproductive success than similar females mated to protein-deprived males. Protein-fed females prevented to consume the ejaculate, retained more sperm when mated to protein-fed males than when mated to protein-deprived males. Our results suggest that female E. eluta can exert control of sperm retention of higher quality males through ejaculate ejection. 相似文献
34.
In marine benthic invertebrates with complex life cycles, recruitment success, juvenile survival, and growth may be affected by variation in both maternal factors and environmental conditions prevailing during preceding embryonic or larval development. In an estuarine crab, Chasmagnathus granulata, previous investigations have shown that initial larval biomass is positively correlated with the biomass of recently extruded eggs, and it depends also on the salinity experienced during embryogenesis. Biomass at hatching has consequences for the subsequent larval development which, in this species, comprises two alternative developmental pathways with four or five zoeal instars (short or long pathway) and a megalopa. Larvae hatching with a lower than average biomass tend to develop through the long pathway and metamorphose to megalopae with higher biomass. In the present study, we show experimentally that the long pathway produces also significantly larger juveniles (crab size measured as carapace width, biomass as dry mass, carbon and nitrogen contents). Compared with juveniles originating from the short pathway, those from the long pathway showed in successive instars longer moulting cycles and larger carapace width, but lower size increments at ecdysis. In consequence, differences in size or biomass of long pathway vs short pathway crabs tended to disappear in later instars (after stage V). Furthermore, we tested in juveniles the tolerance of starvation at three salinities (5‰, 15‰, 32‰). Tolerance of starvation was significantly higher in juveniles originating from the long pathway, indicating higher energy reserves. While salinity played only a minor role for survival, it exerted significant effects on the time of moulting to the second juvenile instar, regardless of the preceding developmental pathway. The biomass of first juveniles obtained from the short pathway showed a significant positive correlation with the biomass of the freshly hatched zoea I, but not in those from the long pathway. In conclusion, the fitness of juvenile C. granulata is linked with previous developmental processes and environmental conditions during the embryonic and larval phase. Hence, a better understanding and prediction of the recruitment success of marine benthic invertebrates with a complex life cycle may require more comprehensive life‐history investigations. 相似文献
35.
Oxidative stress and antioxidant content in Chlorella vulgaris after exposure to ultraviolet-B radiation 总被引:4,自引:0,他引:4
Growth of Chlorella vulgaris was measured in cultures irradiated with 0, 0.8, 2.0 and 4.4 kJ m2 UV-B. Growth expressed as chlorophyll content, declined significantly with increased UV-B dose. Ultraviolet-B irradiated cultures in log phase of growth showed a 284% increase in oxygen radical generation and a 145% increase in lipid peroxidation compared with unirradiated cultures, whereas cultures in the stationary growth phase showed no significant changes in these parameters. The activities of superoxide dismutase and catalase increased by 40 and 500%, respectively, after exposure to a UV-B dose of 4.4 kJ m−2 . Contents of the lipophilic antioxidants α-tocopherol and β-carotene increased by 180 and 63 amol cell−1 respectively, between log and stationary phases in unirradiated cultures; but in UV-B-irradiated cultures these increases were significantly depressed. Photoreducing capacities of chloroplasts were decreased following UV-B irradiation of both isolated chloroplasts and those isolated from irradiated algae. Cells exposed to UV-B exhibited increased size and starch accumulation. These results suggest that oxidative stress conditions related to UV-B exposure trigger an antioxidant response that includes an increase in the activity of the antioxidant enzymes (superoxide dismutase and catalase). 相似文献
36.
Phosphorylation and dephosphorylation of ribosomal proteins have been suggested to participate in the regulation of protein synthesis in eukaryotic organisms. The present research focuses on the purification and partial characterization of a protein kinase from maize ribosomes that specifically phosphorylates acidic ribosomal proteins. Ribosomes purified from maize axes were used as the enzyme source. Purification of ribosomes was performed by centrifugation through a 0.5 M sucrose, 0.8 M KCl cushion. A protein kinase activity present in this fraction was released by extraction with 1.5 M KCl and further purified by diethylaminoethyl cellulose column chromatography. A peak containing protein kinase activity was eluted around 400 m M KCl. Analysis of this fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one band of 38 kDa molecular mass, which cross-reacted in a western blot with antibodies raised against proteins from the large ribosomal subunit. This enzyme specifically phosphorylates one of the acidic ribosomal proteins (P2 ). Its activity is inhibited by Ca2+ and Zn2+ and is activated by Mg2+ , polylysine and spermine. The relevance of this protein kinase in reinitiating the protein synthesis process during germination is discussed. 相似文献
37.
Spontaneous Cell Fusion in Macrophage Cultures Expressing High Levels of the P2Z/P2X7 Receptor 总被引:6,自引:0,他引:6 下载免费PDF全文
Paola Chiozzi Juana M. Sanz Davide Ferrari Simonetta Falzoni Arrigo Aleotti Gary N. Buell Ginetta Collo Francesco Di Virgilio 《The Journal of cell biology》1997,138(3):697-706
Mouse and human macrophages express a plasma membrane receptor for extracellular ATP named P2Z/P2X7. This molecule, recently cloned, is endowed with the intriguing property of forming an aqueous pore that allows transmembrane fluxes of hydrophylic molecules of molecular weight below 900. The physiological function of this receptor is unknown. In a previous study we reported experiments suggesting that the P2Z/P2X7 receptor is involved in the formation of macrophage-derived multinucleated giant cells (MGCs; Falzoni, S., M. Munerati, D. Ferrari, S. Spisani, S. Moretti, and F. Di Virgilio. 1995. J. Clin. Invest. 95:1207– 1216). We have selected several clones of mouse J774 macrophages that are characterized by either high or low expression of the P2Z/P2X7 receptor and named these clones P2Zhyper or P2Zhypo, respectively. P2Zhyper, but not P2Zhypo, cells grown to confluence in culture spontaneously fuse to form MGCs. As previously shown for human macrophages, fusion is inhibited by the P2Z/P2X7 blocker oxidized ATP. MGCs die shortly after fusion through a dramatic process of cytoplasmic sepimentation followed by fragmentation. These observations support our previous hypothesis that the P2Z/P2X7 receptor is involved in macrophage fusion. 相似文献
38.
Tunicamycin, an inhibitor of the asparagine-linked protein N-glycosylation, blocks the initiation of DNA synthesis in Swiss 3T3 cells stimulated by prostaglandin F2α alone or with insulin. This effect is exerted only when tunicamycin is added from 0 to 8 h after stimulation and it decreases the rate of entry into S phase. Blocking of labeled sugar incorporation to proteins occurs regardless of the time of PGF2α stimulation. In contrast tunicamicin does not inhibit protein synthesis. These results suggest that N-glycoprotein synthesis early during the prereplicative phase is an important event controlling the mitogenic action of PGF2α 相似文献
39.
The apoptosis of human peripheral blood lymphocytes was analyzed by the breakdown of DNA into oligonucleosome-sized fragments. The mature lymphocytes were rendered sensitive to apoptosis by either the omission of fetal bovine serum in the culture medium or the addition of polymyxin B. In the first case it was counteracted by phorbol myristate acetate. The possible involvement of protein kinase C in cell survival is pointed out. 相似文献
40.
Isolation and biochemical characterization of a zona pellucida-binding glycoprotein of boar spermatozoa. 总被引:1,自引:0,他引:1
V Jonákova L Sanz J J Calvete A Henschen D Cechová E T?pfer-Petersen 《FEBS letters》1991,280(1):183-186
Lectin-like molecules on the sperm surface are implicated in the process of gamete recognition and adhesion. We have isolated and biochemically characterized a 15 kDa glycoprotein from ejaculated boar sperm which possess zona pellucida-binding- and haemagglutinating-activity. The zona/15 kDa protein interaction is inhibited by fucoidan, suggesting that the glycoprotein is one of the sperm components which participate in the initial gamete interaction. N-Terminal sequence analysis of the isolated 15 kDa glycoprotein showed that it may belong to the same sperm/egg recognition-mediating protein family as the sea urchin sperm protein binding. 相似文献