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971.
Frans M Helmerhorst Denise A M Perquin Diane Donker Marc J N C Keirse 《BMJ (Clinical research ed.)》2004,328(7434):261
Objective To compare the perinatal outcome of singleton and twin pregnancies between natural and assisted conceptions.Design Systematic review of controlled studies published 1985-2002.Studies reviewed 25 studies were included of which 17 had matched and 8 had non-matched controls.Main outcome measures Very preterm birth, preterm birth, very low birth weight, low birth weight, small for gestational age, caesarean section, admission to neonatal intensive care unit, and perinatal mortality.Results For singletons, studies with matched controls indicated a relative risk of 3.27 (95% confidence interval 2.03 to 5.28) for very preterm (< 32 weeks) and 2.04 (1.80 to 2.32) for preterm (< 37 weeks) birth in pregnancies after assisted conception. Relative risks were 3.00 (2.07 to 4.36) for very low birth weight (< 1500 g), 1.70 (1.50 to 1.92) for low birth weight (< 2500 g), 1.40 (1.15 to 1.71) for small for gestational age, 1.54 (1.44 to 1.66) for caesarean section, 1.27 (1.16 to 1.40) for admission to a neonatal intensive care unit, and 1.68 (1.11 to 2.55) for perinatal mortality. Results of the non-matched studies were similar. In matched studies of twin gestations, relative risks were 0.95 (0.78 to 1.15) for very preterm birth, 1.07 (1.02 to 1.13) for preterm birth, 0.89 (0.74 to 1.07) for very low birth weight, 1.03 (0.99 to 1.08) for low birth weight, 1.27 (0.97 to 1.65) for small for gestational age, 1.21 (1.11 to 1.32) for caesarean section, 1.05 (1.01 to 1.09) for admission to a neonatal intensive care unit, and 0.58 (0.44 to 0.77) for perinatal mortality. The non-matched studies mostly showed similar trends.Conclusions Singleton pregnancies from assisted reproduction have a significantly worse perinatal outcome than non-assisted singleton pregnancies, but this is less so for twin pregnancies. In twin pregnancies, perinatal mortality is about 40% lower after assisted compared with natural conception. 相似文献
972.
Maged1, a new regulator of skeletal myogenic differentiation and muscle regeneration 总被引:1,自引:0,他引:1
Tuan HN Nguyen Mathieu JM Bertrand Christiane Sterpin Younes Achouri Olivier RY De Backer 《BMC cell biology》2010,11(1):57
Background
In normal adult skeletal muscle, cell turnover is very slow. However, after an acute lesion or in chronic pathological conditions, such as primary myopathies, muscle stem cells, called satellite cells, are induced to proliferate, then withdraw definitively from the cell cycle and fuse to reconstitute functional myofibers. 相似文献973.
Ingrid Parmentier Ryan J. Harrigan Wolfgang Buermann Edward T. A. Mitchard Sassan Saatchi Yadvinder Malhi Frans Bongers William D. Hawthorne Miguel E. Leal Simon L. Lewis Louis Nusbaumer Douglas Sheil Marc S. M. Sosef Kofi Affum‐Baffoe Adama Bakayoko George B. Chuyong Cyrille Chatelain James A. Comiskey Gilles Dauby Jean‐Louis Doucet Sophie Fauset Laurent Gautier Jean‐François Gillet David Kenfack François N. Kouamé Edouard K. Kouassi Lazare A. Kouka Marc P. E. Parren Kelvin S.‐H. Peh Jan M. Reitsma Bruno Senterre Bonaventure Sonké Terry C. H. Sunderland Mike D. Swaine Mbatchou G. P. Tchouto Duncan Thomas Johan L. C. H. Van Valkenburg Olivier J. Hardy 《Journal of Biogeography》2011,38(6):1164-1176
Aim Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns. Location Tropical rain forest, West Africa and Atlantic Central Africa. Methods Alpha diversity estimates were compiled for trees with diameter at breast height ≥ 10 cm in 573 inventory plots. Linear regression (ordinary least squares, OLS) and random forest (RF) statistical techniques were used to project alpha diversity estimates at unsampled locations using climate data and remote sensing data [Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI), Quick Scatterometer (QSCAT), tree cover, elevation]. The prediction reliabilities of OLS and RF models were evaluated using a novel approach and compared to that of a kriging model based on geographic location alone. Results The predictive power of the kriging model was comparable to that of OLS and RF models based on climatic and remote sensing data. The three models provided congruent predictions of alpha diversity in well‐sampled areas but not in poorly inventoried locations. The reliability of the predictions of all three models declined markedly with distance from points with inventory data, becoming very low at distances > 50 km. According to inventory data, Atlantic Central African forests display a higher mean alpha diversity than do West African forests. Main conclusions The lower tree alpha diversity in West Africa than in Atlantic Central Africa may reflect a richer regional species pool in the latter. Our results emphasize and illustrate the need to test model predictions in a spatially explicit manner. Good OLS or RF model predictions from inventory data at short distance largely result from the strong spatial autocorrelation displayed by both the alpha diversity and the predictive variables rather than necessarily from causal relationships. Our results suggest that alpha diversity is driven by history rather than by the contemporary environment. Given the low predictive power of models, we call for a major effort to broaden the geographical extent and intensity of forest assessments to expand our knowledge of African rain forest diversity. 相似文献
974.
975.
Moshe Israeli Machteld Oudshoorn Geert W. Haasnoot Tirza Klein Bracha Zisser Gideon Bach Frans H. J. Claas 《Immunogenetics》2014,66(9-10):525-533
Approximately three million people have immigrated to the state of Israel since it was founded. Consequently, the immunogenetic profile of the younger generation may consist of a genetic mixture of formerly distinct population groups. We aimed to investigate whether HLA profiles in the Israeli population are age dependent and how this influences representation of various age groups in local donor registries. We determined HLA-A*, HLA-B*, and HLA-DRB1* low-resolution phenotypes of three age groups (n?=?4,169 in each): (1) cord blood units collected between 2009 and 2013 (BABIES) and adult registry donors (2) aged 18–28 years (YOUNG) and (3) aged 49–60 years (OLD). We compared the results with virtual groups that simulate the offspring of the actual study groups. None of the three actual age groups were in Hardy-Weinberg equilibrium. The YOUNG presented four HLA-B alleles that were absent in the OLD and BABIES. A significantly higher percentage among the OLD and BABIES had a “matched” individual within their group in comparison to the YOUNG. In the YOUNG, the 10 most common haplotypes account for 16.7 % of the population, in comparison to 18.2 % in the OLD or 19.8 % in the BABIES group. The BABIES group was genetically remote from all other groups. Further disparities were found between the actual and the corresponding virtual groups. We conclude that discrete age groups in Israel present distinct immunogenetic profiles, where the younger generation is more heterogeneous. The population dynamics of the age-dependent HLA profile is multifactorial: gradual intersubgroup admixture, nonrandom mating, and entry of new alleles. 相似文献
976.
977.
Boris Jansen Klaas G. J. Nierop Femke H. Tonneijck Frans W. M. van der Wielen Jacobus M. Verstraten 《Plant and Soil》2007,291(1-2):181-198
Large-scale clear-cutting and burning caused the altitude of the natural upper forest line (UFL) in the Northern Ecuadorian
Andes to decline to the point that its ‘natural’ position is now uncertain. To obtain a detailed reconstruction of the dynamics
of the UFL over the last few thousand years, traditional proxies alone do not suffice. For instance, pollen analysis suffers
from a low altitudinal resolution due to the large wind-blown component. In an attempt to find new, additional proxies to
study past UFL dynamics in the Ecuadorian Andes, we investigated the occurrence of isoprenoids (diterpenes, phytosterols and
pentacyclic triterpenoids) in the roots and leaves of 19 plant species responsible for the dominant biomass input in soil
and peat records along altitudinal transects covering approximately 500 m above and below the current UFL in two locations
in the Northern Ecuadorian Andes. Isoprenoids can serve as biomarker if they are uniquely present in a relevant plant species
and preserved well enough in chronological order in suitable records. Such biomarkers could help establish past vegetation
dynamics including the UFL position. For an isoprenoid to be a biomarker in soils normally it must be absent from the roots
of a plant species as roots do not enter soils in chronological order. For peat deposits this criteria only needs to be met
for the peat species themselves as only roots from peat species will be present. Two diterpenes, four phytosterols and six
pentacyclic triterpenoids met the criteria for biomarker in peat records. Of these, one diterpene, two phytosterols and three
pentacyclic triterpenoids also met the criteria for biomarker in soils. Samples from a soil under forest, a soil under the
adjacent páramo and a nearby peat deposit, 14C dated at approximately 1500 cal. AD and 200 cal. AD, were tested for the presence of isoprenoids that meet the criteria
for biomarker. Such isoprenoids were only found in the peat bog samples. However, we found that changes of number and concentrations
of isoprenoids with depth might provide additional information related to past vegetation changes. In conclusion, isoprenoids
show potential for use in a multi-proxy approach to reconstruct past UFL locations in the Northern Ecuadorian Andes and other
ecosystems with similar vegetation and soils. 相似文献
978.
Laurens M. Ni?ns Sten G. Zelle Cristina Gutiérrez-Delgado Gustavo Rivera Pe?a Blanca Rosa Hidalgo Balarezo Erick Rodriguez Steller Frans F. H. Rutten 《PloS one》2014,9(4)
This paper reports the most cost-effective policy options to support and improve breast cancer control in Costa Rica and Mexico. Total costs and effects of breast cancer interventions were estimated using the health care perspective and WHO-CHOICE methodology. Effects were measured in disability-adjusted life years (DALYs) averted. Costs were assessed in 2009 United States Dollars (US$). To the extent available, analyses were based on locally obtained data. In Costa Rica, the current strategy of treating breast cancer in stages I to IV at a 80% coverage level seems to be the most cost-effective with an incremental cost-effectiveness ratio (ICER) of US$4,739 per DALY averted. At a coverage level of 95%, biennial clinical breast examination (CBE) screening could improve Costa Rica''s population health twofold, and can still be considered very cost-effective (ICER US$5,964/DALY). For Mexico, our results indicate that at 95% coverage a mass-media awareness raising program (MAR) could be the most cost-effective (ICER US$5,021/DALY). If more resources are available in Mexico, biennial mammography screening for women 50–70 yrs (ICER US$12,718/DALY), adding trastuzumab (ICER US$13,994/DALY) or screening women 40–70 yrs biennially plus trastuzumab (ICER US$17,115/DALY) are less cost-effective options. We recommend both Costa Rica and Mexico to engage in MAR, CBE or mammography screening programs, depending on their budget. The results of this study should be interpreted with caution however, as the evidence on the intervention effectiveness is uncertain. Also, these programs require several organizational, budgetary and human resources, and the accessibility of breast cancer diagnostic, referral, treatment and palliative care facilities should be improved simultaneously. A gradual implementation of early detection programs should give the respective Ministries of Health the time to negotiate the required budget, train the required human resources and understand possible socioeconomic barriers. 相似文献
979.
980.