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Differential Utilization (differential + utilization)
Selected AbstractsGenetic and ecological divergence of a monophyletic cichlid species pair under fully sympatric conditions in Lake Ejagham, CameroonMOLECULAR ECOLOGY, Issue 6 2001Ulrich Schliewen Abstract Although there is mounting evidence that speciation can occur under sympatric conditions, unambiguous examples from nature are rare and it is almost always possible to propose alternative allopatric or parapatric scenarios. To identify an unequivocal case of sympatric speciation it is, therefore, necessary to analyse natural settings where recent monophyletic species flocks have evolved within a small and confined spatial range. We have studied such a case with a cichlid species flock that comprises five Tilapia forms endemic to a tiny lake (Lake Ejagham with a surface area of approximately 0.49 km2) in Western Cameroon. Analysis of mitochondrial D-Loop sequences shows that the flock is very young (approximately 104 years) and has originated from an adjacent riverine founder population. We have focused our study on a particular pair of forms within the lake that currently appears to be in the process of speciation. This pair is characterized by an unique breeding colouration and specific morphological aspects, which can serve as synapomorphic characters to prove monophyly. It has differentiated into a large inshore and a small pelagic form, apparently as a response to differential utilization of food resources. Still, breeding and brood care occurs in overlapping areas, both in time and space. Analysis of nuclear gene flow on the basis of microsatellite polymorphisms shows a highly restricted gene flow between the forms, suggesting reproductive isolation between them. This reproductive isolation is apparently achieved by size assortative mating, although occasional mixed pairs can be observed. Our findings are congruent with recent theoretical models for sympatric speciation, which show that differential ecological adaptations in combination with assortative mating could easily lead to speciation in sympatry. [source] Regulation of the Nanog gene by both positive and negative cis -regulatory elements in embryonal carcinoma cells and embryonic stem cellsMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2009Brian Boer Abstract The transcription factor Nanog is essential for mammalian embryogenesis, as well as the pluripotency of embryonic stem (ES) cells. Work with ES cells and embryonal carcinoma (EC) cells previously identified positive and negative cis -regulatory elements that influence the activity of the Nanog promoter, including adjacent cis -regulatory elements that bind Sox2 and Oct-3/4. Given the importance of Nanog during mammalian development, we examined the cis -regulatory elements required for Nanog promoter activity more closely. In this study, we demonstrate that two positive cis -regulatory elements previously shown to be active in F9 EC cells are also active in ES cells. We also identify a novel negative regulatory region that is located in close proximity to two other positive Nanog cis -regulatory elements. Although this negative regulatory region is active in F9 EC cells and ES cells, it is inactive in P19 EC cells. Furthermore, we demonstrate that one of the positive cis -regulatory elements active in F9 EC cells and ES cells is inactive in P19 EC cells. Together, these and other studies suggest that Nanog transcription is regulated by the interplay of positive and negative cis -regulatory elements. Given that P19 appears to be more closely related to a later developmental stage of mammalian development than F9 and ES cells, differential utilization of cis -regulatory elements may reflect mechanisms used during development to achieve the correct level of Nanog expression as embryogenesis unfolds. Mol. Reprod. Dev. 76: 173,182, 2009. © 2008 Wiley-Liss, Inc. [source] Differential regulation of the Oct-3/4 gene in cell culture model systems that parallel different stages of mammalian developmentMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 8 2008Sunil Kumar Mallanna Abstract Oct-3/4 is an essential transcription factor that regulates stem cell fate during embryogenesis. Previous reports have shown that the Oct-3/4 gene utilizes different enhancers to regulate its expression as development proceeds. However, the cis -elements contributing to the differential activity of these enhancers require further study. Here, we investigated the function of the HMG/POU cassette and LRH-1 site present in the distal enhancer (DE) and the proximal enhancer, respectively. F9 and P19 EC cells were the focus of this study because their differential utilization of Oct-3/4 enhancers parallels the use of these enhancers during different stages of development. We determined that the LRH-1 site functions as a positive and a negative cis -regulatory element in P19 and F9 EC cells, respectively. Furthermore, we determined that the HMG/POU cassette in the DE strongly activates the Oct-3/4 promoter in F9 cells, but is a much weaker positive regulatory element in P19 cells. Given that HMG/POU cassettes play key roles in the regulation of at least seven essential genes, the Oct-3/4 HMG/POU cassette was examined more closely by focusing on Sox2, which can bind to HMG/POU cassettes. Although chromatin immunoprecipitation demonstrated that Sox2 binds to the Oct-3/4 gene equally well in both EC cell lines, tethering Sox2 to the region of the HMG/POU cassette only activated the Oct-3/4 promoter in F9 EC cells. These and other findings suggest that the differential activity of the HMG/POU cassette of the Oct-3/4 gene in EC cells is due to differential action of Sox2 and its associated co-factors. Mol. Reprod. Dev. 75: 1247,1257, 2008. © 2008 Wiley-Liss, Inc. [source] Simultaneous measurement of 13C- and 15N-isotopic enrichments of threonine by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Jean-Philippe Godin Under conditions of high isotopic dilution, e.g. in a tracer study, the ability to determine accurately and quantitatively small variations in isotopic enrichments of differently labelled chemical compounds (e.g. 13C and 15N in threonine) in a single run by gas chromatography/mass spectrometry (GC/MS) is desirable but remains a technological challenge. Here, we report a new, rapid and simple GC/MS method for simultaneously measuring the isotopic enrichments of doubly labelled threonine ([U13C] and 15N) with isotopic enrichment lower than 1.5 Molar Percent Excess (MPE). The long-term reproducibility measured was around 0.09 MPE for both tracers (throughout a 6 week period). The intra-day repeatability was lower than 0.05 and 0.06 MPE for [U13C]-Thr and 15N-Thr, respectively. To calculate both isotopic enrichments, two modes of calculations were used: one based on work by Rosenblatt et al. in 1992 and the other one using a matrix approach. Both methods gave similar results (ANOVA, P >0.05) with close precision for each mode of calculation. The GC/MS method was then used to investigate the differential utilization of threonine in different organs according to its route of administration in minipigs after administration of both tracers. In plasma samples, the lowest isotopic enrichment measured between two successive time points was at 0.01 and 0.02 MPE for [U13C]-Thr and 15N-Thr, respectively. Moreover, the accuracy of GC/MS 13C-isotopic enrichment measured was validated by analyzing the same plasma samples by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Statistical analysis showed that both techniques gave the same results (ANOVA, P >0.05). This new GC/MS method offers the possibility to measure 13C- and 15N-isotopic enrichments with higher throughput, and using a lower amount of sample, than using GC/C/IRMS. Copyright © 2009 John Wiley & Sons, Ltd. [source] Recent trends and racial/ethnic differences in the incidence and treatment of ductal carcinoma in situ of the breast in California women ,CANCER, Issue 4 2003Kaire Innos M.D., Ph.D. Abstract BACKGROUND The rapid increase in the incidence of ductal carcinoma in situ (DCIS) of the breast in the U.S. has been associated with the widespread adoption of screening mammography. Little is known regarding the incidence and treatment of DCIS in women of racial/ethnic groups other than white and black. The current investigation examined recent trends and racial/ethnic differences in the incidence and treatment of DCIS in California. METHODS All cases of DCIS diagnosed in women age , 40 years in California between 1988,1999 were included. Age-adjusted incidence rates for white, black, Hispanic, and Asian-Pacific Islander women were calculated using the 2000 U.S. female population as the standard. The estimated annual percent change (EAPC) in the rates was calculated using least squares regression. RESULTS The average annual age-adjusted incidence of DCIS (1988,1999) was 45.3 per 100,000 in white women, 35.0 in black women, 30.9 in Asian-Pacific Islander women, and 21.8 in Hispanic women. Although a steady increase in the incidence of DCIS was noted in all racial/ethnic groups over the study period, Asian-Pacific Islander women were found to have experienced the steepest increase (EAPC = 9.1%), particularly in the age group 50,64 years (EAPC = 12.0%). The DCIS incidence was reported to increase with age in white, black, and Hispanic women, but remained fairly constant after the age of 50 years in Asian-Pacific Islanders. The proportion of women with DCIS treated with mastectomy decreased from 53% in 1988 to 32% in 1999. Younger women and Asian-Pacific Islander women reportedly were more likely to undergo mastectomy. CONCLUSIONS Considerable differences by race/ethnicity and age were observed in DCIS incidence and the change in the incidence in California between 1988 and 1999. Further information is needed to determine whether these differences are because of differential utilization of screening mammography or biologic characteristics of DCIS lesions. Cancer 2003;97:1099,106. © 2003 American Cancer Society. DOI 10.1002/cncr.11104 [source] | ||||||||||