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71.
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Dietmar Zinner Jenny Wertheimer Rasmus Liedigk Linn F. Groeneveld Christian Roos 《American journal of physical anthropology》2013,150(1):133-140
Baboons (genus Papio) are an interesting phylogeographical primate model for the evolution of savanna species during the Pleistocene. Earlier studies, based on partial mitochondrial sequence information, revealed seven major haplogroups indicating multiple para‐ and polyphylies among the six baboon species. The most basal splits among baboon lineages remained unresolved and the credibility intervals for divergence time estimates were rather large. Assuming that genetic variation within the two studied mitochondrial loci so far was insufficient to infer the apparently rapid early radiation of baboons we used complete mitochondrial sequence information of ten specimens, representing all major baboon lineages, to reconstruct a baboon phylogeny and to re‐estimate divergence times. Our data confirmed the earlier tree topology including the para‐ and polyphyletic relationships of most baboon species; divergence time estimates are slightly younger and credibility intervals narrowed substantially, thus making the estimates more precise. However, the most basal relationships could not be resolved and it remains open whether (1) the most southern population of baboons diverged first or (2) a major split occurred between southern and northern clades. Our study shows that complete mitochondrial genome sequences are more effective to reconstruct robust phylogenies and to narrow down estimated divergence time intervals than only short portions of the mitochondrial genome, although there are also limitations in resolving phylogenetic relationships. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
73.
M Van de Casteele G Leuckx L Baeyens Y Cai Y Yuchi V Coppens S De Groef M Eriksson C Svensson U Ahlgren J Ahnfelt-R?nne O D Madsen A Waisman Y Dor J N Jensen H Heimberg 《Cell death & disease》2013,4(3):e523
We previously showed that injury by partial duct ligation (PDL) in adult mouse pancreas activates Neurogenin 3 (Ngn3)+ progenitor cells that can differentiate to β cells ex vivo. Here we evaluate the role of Ngn3+ cells in β cell expansion in situ. PDL not only induced doubling of the β cell volume but also increased the total number of islets. β cells proliferated without extended delay (the so-called ‘refractory'' period), their proliferation potential was highest in small islets, and 86% of the β cell expansion was attributable to proliferation of pre-existing β cells. At sufficiently high Ngn3 expression level, upto 14% of all β cells and 40% of small islet β cells derived from non-β cells. Moreover, β cell proliferation was blunted by a selective ablation of Ngn3+ cells but not by conditional knockout of Ngn3 in pre-existing β cells supporting a key role for Ngn3+ insulin− cells in β cell proliferation and expansion. We conclude that Ngn3+ cell-dependent proliferation of pre-existing and newly-formed β cells as well as reprogramming of non-β cells contribute to in vivo β cell expansion in the injured pancreas of adult mice. 相似文献
74.
Kristin E Svensson Marianne I Velandia Ann-Sofi T Matthiesen Barbara L Welles-Nyström Ann-Marie E Widström 《International breastfeeding journal》2013,8(1):1-13
Background
Infants with latch-on problems cause stress for parents and staff, often resulting in early termination of breastfeeding. Healthy newborns experiencing skin-to-skin contact at birth are pre-programmed to find the mother’s breast. This study investigates if skin-to-skin contact between mothers with older infants having severe latching on problems would resolve the problem.Methods
Mother-infant pairs with severe latch-on problems, that were not resolved during screening procedures at two maternity hospitals in Stockholm 1998–2004, were randomly assigned to skin-to-skin contact (experimental group) or not (control group) during breastfeeding. Breastfeeding counseling was given to both groups according to a standard model. Participants were unaware of their treatment group. Objectives were to compare treatment groups concerning the proportion of infants regularly latching on, the time from intervention to regular latching on and maternal emotions and pain before and during breastfeeding.Results
On hundred and three mother-infant pairs with severe latch-on problems 1–16 weeks postpartum were randomly assigned and analyzed. There was no significant difference between the groups in the proportion of infants starting regular latching-on (75% experimental group, vs. 86% control group). Experimental group infants, who latched on, had a significantly shorter median time from start of intervention to regular latching on than control infants, 2.0 weeks (Q1 = 1.0, Q3 = 3.7) vs. 4.7 weeks (Q1 = 2.0, Q3 = 8.0), (p-value = 0.020). However, more infants in the experimental group (94%), with a history of “strong reaction” during “hands-on latch intervention”, latched-on within 3 weeks compared to 33% in the control infants (Fisher Exact test p-value = 0.0001). Mothers in the experimental group (n = 53) had a more positive breastfeeding experience according to the Breastfeeding Emotional Scale during the intervention than mothers in the control group (n = 50) (p-value = 0.022).Conclusions
Skin-to-skin contact during breastfeeding seems to immediately enhance maternal positive feelings and shorten the time it takes to resolve severe latch-on problems in the infants who started to latch. An underlying mechanism may be that skin-to-skin contact with the mother during breastfeeding may calm infants with earlier strong reaction to “hands on latch intervention” and relieve the stress which may have blocked the infant’s inborn biological program to find the breast and latch on.Trial registration
Karolinska Clinical Trial Registration number CT20100055 相似文献75.
Alcohol consumption and alcohol problems after bariatric surgery in the swedish obese subjects study
76.
77.
Recombination is an engine of genetic diversity and therefore constitutes a key process in evolutionary biology and genetics. While the outcome of crossover recombination can readily be detected as shuffled alleles by following the inheritance of markers in pedigreed families, the more precise location of both crossover and non-crossover recombination events has been difficult to pinpoint. As a consequence, we lack a detailed portrait of the recombination landscape for most organisms and knowledge on how this landscape impacts on sequence evolution at a local scale. To localize recombination events with high resolution in an avian system, we performed whole-genome re-sequencing at high coverage of a complete three-generation collared flycatcher pedigree. We identified 325 crossovers at a median resolution of 1.4 kb, with 86% of the events localized to <10 kb intervals. Observed crossover rates were in excellent agreement with data from linkage mapping, were 52% higher in male (3.56 cM/Mb) than in female meiosis (2.28 cM/Mb), and increased towards chromosome ends in male but not female meiosis. Crossover events were non-randomly distributed in the genome with several distinct hot-spots and a concentration to genic regions, with the highest density in promoters and CpG islands. We further identified 267 non-crossovers, whose location was significantly associated with crossover locations. We detected a significant transmission bias (0.18) in favour of ‘strong’ (G, C) over ‘weak’ (A, T) alleles at non-crossover events, providing direct evidence for the process of GC-biased gene conversion in an avian system. The approach taken in this study should be applicable to any species and would thereby help to provide a more comprehensive portray of the recombination landscape across organism groups. 相似文献
78.
Combined observational and experimental data provide limited support for facilitation in lichens 下载免费PDF全文
Måns Svensson Alexandro Caruso Rebecca Yahr Christopher Ellis Göran Thor Tord Snäll 《Oikos》2016,125(2):278-283
It is increasingly recognized that facilitative interactions can shape communities. One of the mechanisms through which facilitation may operate is when one species facilitates the colonization of another through the exchange of shared symbionts. Lichens are symbiotic associations composed of a mycobiont (lichenised‐fungus) and one or two photobionts (algae or cyanobacteria). Different lichen species may have overlapping specificity for photobionts, creating the possibility that facilitation drives lichen community assembly. To investigate whether facilitation occurs in lichens, we combined an observational study (a) with a manipulative field experiment (b). For (a), we quantified the effect of local patch conditions, facilitation and the size of the surrounding metapopulation on colonizations of an epixylic lichen species (Cladonia botrytes) in an area of managed boreal forest. This was done by twice surveying lichens on 293 stumps, located in stands of three age classes. For (b), we treated unoccupied surfaces of 56 cut stumps with algal mixtures of an Asterochloris photobiont and recorded C. botrytes colonizations over three years. In (a), colonization rates of C. botrytes increased with increasing abundance of other lichen species with specificity for Asterochloris photobionts, consistent with an effect of facilitation. However, in the field experiment (b), colonizations of the focal species did not provide support for facilitation. We conclude that our study provides limited support for facilitation in green‐algal lichens, underscoring the importance of combining observational studies with experiments when studying species interactions. 相似文献
79.
80.
Lindgren K Ormestad M Persson M Martinsson S Svensson LT Mahlapuu M 《The FEBS journal》2007,274(11):2887-2896
The AMP-activated protein kinase is an evolutionarily conserved heterotrimer that is important for metabolic sensing in all eukaryotes. The muscle-specific isoform of the regulatory gamma-subunit of the kinase, AMP-activated protein kinase gamma3, has a key role in glucose and fat metabolism in skeletal muscle, as suggested by metabolic characterization of humans, pigs and mice harboring substitutions in the AMP-binding Bateman domains of gamma3. We demonstrate that AMP-activated protein kinase alpha2beta2gamma3 trimers are allosterically activated approximately three-fold by AMP with a half-maximal stimulation (A(0.5)) at 1.9 +/- 0.5 or 2.6 +/- 0.3 microm, as measured for complexes expressed in Escherichia coli or mammalian cells, respectively. We show that mutations in the N-terminal Bateman domain of gamma3 (R225Q, H306R and R307G) increased the A(0.5) values for AMP, whereas the fold activation of the enzyme by 200 microm AMP remained unchanged in comparison to the wild-type complex. The mutations in the C-terminal Bateman domain of gamma3 (H453R and R454G), on the other hand, substantially reduced the fold stimulation of the complex by 200 microm AMP, and resulted in AMP dependence curves similar to those of the double mutant, R225Q/R454G. A V224I mutation in gamma3, known to result in a reduced glycogen content in pigs, did not affect the fold activation or the A(0.5) values for AMP. Importantly, we did not detect any increase in phosphorylation of Thr172 of alpha2 by the upstream kinases in the presence of increasing concentrations of AMP. Taken together, the data show that different mutations in gamma3 exert different effects on the allosteric regulation of the alpha2beta2gamma3 complex by AMP, whereas we find no evidence for their role in regulating the level of phosphorylation of alpha2 by upstream kinases. 相似文献