排序方式: 共有95条查询结果,搜索用时 375 毫秒
21.
Evolution of indirect reciprocity by social information: the role of trust and reputation in evolution of altruism 总被引:1,自引:0,他引:1
The complexity of human's cooperative behavior cannot be fully explained by theories of kin selection and group selection. If reciprocal altruism is to provide an explanation for altruistic behavior, it would have to depart from direct reciprocity, which requires dyads of individuals to interact repeatedly. For indirect reciprocity to rationalize cooperation among genetically unrelated or even culturally dissimilar individuals, information about the reputation of individuals must be assessed and propagated in a population. Here, we propose a new framework for the evolution of indirect reciprocity by social information: information selectively retrieved from and propagated through dynamically evolving networks of friends and acquaintances. We show that for indirect reciprocity to be evolutionarily stable, the differential probability of trusting and helping a reputable individual over a disreputable individual, at a point in time, must exceed the cost-to-benefit ratio of the altruistic act. In other words, the benefit received by the trustworthy must out-weigh the cost of helping the untrustworthy. 相似文献
22.
A dermal niche for multipotent adult skin-derived precursor cells 总被引:17,自引:0,他引:17
Fernandes KJ McKenzie IA Mill P Smith KM Akhavan M Barnabé-Heider F Biernaskie J Junek A Kobayashi NR Toma JG Kaplan DR Labosky PA Rafuse V Hui CC Miller FD 《Nature cell biology》2004,6(11):1082-1093
A fundamental question in stem cell research is whether cultured multipotent adult stem cells represent endogenous multipotent precursor cells. Here we address this question, focusing on SKPs, a cultured adult stem cell from the dermis that generates both neural and mesodermal progeny. We show that SKPs derive from endogenous adult dermal precursors that exhibit properties similar to embryonic neural-crest stem cells. We demonstrate that these endogenous SKPs can first be isolated from skin during embryogenesis and that they persist into adulthood, with a niche in the papillae of hair and whisker follicles. Furthermore, lineage analysis indicates that both hair and whisker follicle dermal papillae contain neural-crest-derived cells, and that SKPs from the whisker pad are of neural-crest origin. We propose that SKPs represent an endogenous embryonic precursor cell that arises in peripheral tissues such as skin during development and maintains multipotency into adulthood. 相似文献
23.
Ivan Babic Erik S. Anderson Kazuhiro Tanaka Deliang Guo Kenta Masui Bing Li Shaojun Zhu Yuchao Gu Genaro R. Villa David Akhavan David Nathanson Beatrice Gini Sergey Mareninov Rui Li Carolina Espindola Camacho Siavash K. Kurdistani Ascia Eskin Stanley F. Nelson Paul S. Mischel 《Cell metabolism》2013,17(6):1000-1008
- Download : Download high-res image (221KB)
- Download : Download full-size image
24.
Ali Bagheri Azadeh Akhavan Roofigar Shabnam Abbasi Ali Asghar Maassoumi Twan Rutten Frank R. Blattner 《Grana》2013,52(5):328-336
Astragalus is with nearly 3000 described species the largest genus of flowering plants. So far analyses of pollen characters have only been conducted for a few species of the groups within the genus. Here we analyse pollen grains of 22 species representative for Astragalus section Hymenostegis using scanning electron microscopy. We found the basic shape of the pollen grains to be oblate-spheroidal and apertures to be tricolpate as for other eudicots. The sculpturing pattern of the exine is micro-reticulate. Pollen grains show low morphological variation among different species of this section, but differences occur between sections of the genus. We conclude that the vast morphological differentiation that occurred during the rapid radiation of section Hymenostegis was not accompanied by comparable differentiation in pollen morphology. 相似文献
25.
Cécilia Szatkowski Judith Vallet Mojdeh Dormishian Nadia Messaddeq Phillippe Valet Mounia Boulberdaa Daniel Metzger Pierre Chambon Canan G. Nebigil 《PloS one》2013,8(12)
Background
Adipocyte renewal from preadipocytes occurs throughout the lifetime and contributes to obesity. To date, little is known about the mechanisms that control preadipocyte proliferation and differentiation. Prokineticin-2 is an angiogenic and anorexigenic hormone that activate two G protein-coupled receptors (GPCRs): PKR1 and PKR2. Prokineticin-2 regulates food intake and energy metabolism via central mechanisms (PKR2). The peripheral effect of prokineticin-2 on adipocytes/preadipocytes has not been studied yet.Methodology/Principal Findings
Since adipocytes and preadipocytes express mainly prokineticin receptor-1 (PKR1), here, we explored the role of PKR1 in adipose tissue expansion, generating PKR1-null (PKR1−/−) and adipocyte-specific (PKR1ad−/−) mutant mice, and using murine and human preadipocyte cell lines. Both PKR1−/− and PKR1ad−/− had excessive abdominal adipose tissue, but only PKR1−/− mice showed severe obesity and diabetes-like syndrome. PKR1ad−/−) mice had increased proliferating preadipocytes and newly formed adipocyte levels, leading to expansion of adipose tissue. Using PKR1-knockdown in 3T3-L1 preadipocytes, we show that PKR1 directly inhibits preadipocyte proliferation and differentiation. These PKR1 cell autonomous actions appear targeted at preadipocyte cell cycle regulatory pathways, through reducing cyclin D, E, cdk2, c-Myc levels.Conclusions/Significance
These results suggest PKR1 to be a crucial player in the preadipocyte proliferation and differentiation. Our data should facilitate studies of both the pathogenesis and therapy of obesity in humans. 相似文献26.
Tahmasebi Hamed Dehbashi Sanaz Jahantigh Mojdeh Arabestani Mohammad Reza 《Molecular biology reports》2020,47(2):1309-1320
Molecular Biology Reports - The ica genes in methicillin-resistant Staphylococcus aureus (MRSA) play an important role in biofilm formation. The aim of this study is to define effect of antibiotic... 相似文献
27.
Sepahvand A Shams-Ghahfarokhi M Allameh A Jahanshiri Z Jamali M Razzaghi-Abyaneh M 《Folia microbiologica》2011,56(6):527-534
In the present study, genetic diversity and mycotoxin profiles of Aspergillus flavus isolated from air (indoors and outdoors), levels (surfaces), and soils of five hospitals in Southwest Iran were examined.
From a total of 146 Aspergillus colonies, 63 isolates were finally identified as A. flavus by a combination of colony morphology, microscopic criteria, and mycotoxin profiles. No Aspergillus parasiticus was isolated from examined samples. Chromatographic analyses of A. flavus isolates cultured on yeast extract–sucrose broth by tip culture method showed that approximately 10% and 45% of the isolates
were able to produce aflatoxin B1 (AFB1) and cyclopiazonic acid (CPA), respectively. Around 40% of the isolates produced sclerotia on Czapek–Dox agar. The isolates
were classified into four chemotypes based on the ability to produce AF and CPA that majority of them (55.5%) belonged to
chemotype IV comprising non-mycotoxigenic isolates. Random amplified polymorphic DNA (RAPD) profiles generated by a combination
of four selected primers were used to assess genetic relatedness of 16 selected toxigenic and non-toxigenic isolates. The
resulting dendrogram demonstrated the formation of two separate clusters for the A. flavus comprised both mycotoxigenic and non-toxigenic isolates in a random distribution. The obtained results in this study showed
that RAPD profiling is a promising and efficient tool to determine intra-specific genetic variation among A. flavus populations from hospital environments. A. flavus isolates, either toxigenic or non-toxigenic, should be considered as potential threats for hospitalized patients due to their
obvious role in the etiology of nosocomial aspergillosis. 相似文献
28.
Zahra Rashidi Ashraf Aleyasin Mojtaba Eslami Saeid Nekoonam Adib Zendedel Mojdeh Bahramrezaie Fardin Amidi 《Reproductive biology》2019,19(3):245-254
Granulosa Cells (GCs) are sensitive to excessive production of reactive oxygen species (ROS). Quercetin (QUR) is a free radical scavenger which can alleviate oxidative stress through nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/antioxidant response element (ARE) pathway and thioredoxin (Trx) system. We aimed to explore the probable protective role of QUR on cultured human GCs treated with hydrogen peroxide (H2O2) as an inducer of oxidative stress. MTT assay was applied for evaluating the cell cytotoxicity of QUR and H2O2. The rate of apoptotic cells and intracellular ROS generation were determined by Annexin V-FITC/PI staining and 2′-7′-dichlorodihydro?uorescein diacetate ?uorescent probes (DCFH-DA), respectively. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis and western blot analysis were used to evaluate the gene and protein expression of Nrf2 and kelch-like ech-associated protein 1 (Keap1)1. The Nrf2 and Trx activities were measured by Enzyme-linked Immunosorbent Assay (ELISA). The results indicated that QUR pretreatment can decrease ROS production and apoptosis induced by H2O2. In addition, QUR increased Nrf2 gene and protein expression, as well as its nuclear translocation. Moreover, in QUR-treated group, a lower level of Keap1 protein was observed, which was not reported as significant. The results also indicated a significant correlation between the expression of Nrf2 and Keap1 in QUR-treated group. Further, QUR protected GCs from oxidative stress by increasing Trx gene expression and activity. This study suggests that QUR as a supplementary factor may protect GCs from oxidative stress in diseases related to this condition. 相似文献
29.
Primary malignant tumors of the spine are relatively rare, less than 5% of all spinal column tumors. However, these lesions are often among the most difficult to treat and encompass challenging pathologies such as chordoma and a variety of invasive sarcomas. The mechanisms of tumor recurrence after surgical intervention, as well as resistance to radiation and chemotherapy, remain a pervasive and costly problem. Recent evidence has emerged supporting the hypothesis that solid tumors contain a sub-population of cancer cells that possess characteristics normally associated with stem cells. Particularly, the potential for long-term proliferation appears to be restricted to subpopulations of cancer stem cells(CSCs) functionally defined by their capacity to self-renew and give rise to differentiated cells that phenotypically recapitulate the original tumor, thereby causing relapse and patient death. These cancer stem cells present a unique opportunity to better understand the biology of solid tumors in general, as well as targets for future therapeutics. The general objective of the current study is to discuss the fundamental concepts for understanding the role of CSCs with respect to chemoresistance, radioresistance, special cell surface markers, cancer recurrence and metastasis intumors of the osseous spine. This discussion is followed by a specific review of what is known about the role of CSCs in chordoma, the most common primary malignant osseous tumor of the spine. 相似文献
30.
Evgenia Alpert Armin Akhavan Arie Gruzman William
J. Hansen Joshua Lehrer-Graiwer Steven
C. Hall Eric Johansen Sean McAllister Mittul Gulati Ming-Fong Lin Vishwanath
R. Lingappa 《Bioscience reports》2021,41(10)
The role of human prostatic acid phosphatase (PAcP, |PPAP_HUMAN) in prostate cancer was investigated using a new proteomics tool termed signal sequence swapping (replacement of domains from the native cleaved amino terminal signal sequence of secretory/membrane proteins with corresponding regions of functionally distinct signal sequence subtypes). This manipulation preferentially redirects proteins to different pathways of biogenesis at the endoplasmic reticulum (ER), magnifying normally difficult to detect subsets of the protein of interest. For PAcP, this technique reveals three forms identical in amino acid sequence but profoundly different in physiological functions, subcellular location, and biochemical properties. These three forms of PAcP can also occur with the wildtype PAcP signal sequence. Clinical specimens from patients with prostate cancer demonstrate that one form, termed PLPAcP, correlates with early prostate cancer. These findings confirm the analytical power of this method, implicate PLPAcP in prostate cancer pathogenesis, and suggest novel anticancer therapeutic strategies. P15309相似文献