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81.
The recent expansion of Pentecostalism and independent churches in Africa has generated growing interest among social scientists. This attention parallels a renewed interest among Africanists on witchcraft and occult activities, also believed by many to be increasing. Some suggest the two trends may be related, but it remains unclear how and why. Drawing on a study of Pentecostalism and health in the city of Chimoio, Mozambique, in 2002–03 that focused on attitudes toward recent social change, we argue that structural adjustment economic reforms have deepened economic inequality and exacerbated household stresses that affect men and women differently. Women increasingly seek spiritual help for reproductive health problems from Pentecostal churches, whereas men disproportionately pay traditional healers to engage "occult" practices to manage misfortune related to employment. The increased resort to both spiritual resources reveals social distress caused by economic adjustment, with important implications for health programs.  相似文献   
82.
We commonly read or hear that Charles Darwin successfully convinced the world about evolution and natural selection, but did not answer the question posed by his most famous book, ‘On the Origin of Species …’. Since the 1940s, Ernst Mayr has been one of the people who argued for this point of view, claiming that Darwin was not able to answer the question of speciation because he failed to define species properly. Mayr undoubtedly had an important and largely positive influence on the study of evolution by stimulating much evolutionary work, and also by promoting a ‘polytypic species concept’ in which multiple, geographically separated forms may be considered as subspecies within a larger species entity. However, Mayr became seduced by the symmetry of a pair of interlocking ideas: (1) that coexistence of divergent populations was not possible without reproductive isolation and (2) reproductive isolation could not evolve in populations that coexist. These beliefs led Mayr in 1942 to reject evidence of the importance of intermediate stages in speciation, particularly introgression between hybridizing species, which demonstrates that complete reproductive isolation is not necessary, and the existence of ecological races, which shows that ecological divergence can be maintained below the level of species, in the face of gene flow. Mayr's train of thought led him to the view that Darwin misunderstood species, and that species were fundamentally different from subspecific varieties in nature. Julian Huxley, reviewing similar data at the same time, came to the opposite conclusion, and argued that these were the intermediate stages of speciation expected under Darwinism. Mayr's arguments were, however, more convincing than Huxley's, and this caused a delay in the acceptance of a more balanced view of speciation for many decades. It is only now, with new molecular evidence, that we are beginning to appreciate more fully the expected Darwinian intermediates between coexisting species. © The Author. Journal compilation © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 3–16.  相似文献   
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Geographical variation in the reproductive biology of widespread species often occurs at their distributional boundaries. We sought to determine whether such variation has occurred in an invasive orchid, Oeceoclades maculata, across its naturalized range. We compared its reproductive biology in a Brazilian population with that published for a population on the Caribbean island of Puerto Rico. In the state of São Paulo, O. maculata flowers between December and February, at the height of the rainy season. Similar fruit sets were observed in manual self (76%) and cross (70.4%) pollination treatments. The fruit set of plants protected from both pollinators and rainfall was 6.1%, whereas plants exposed only to rainfall had a fruit set of 41.4%, slightly less than the controls (48.3%). Like the Puerto Rico population, reproduction is primarily through rain‐assisted autogamy, but unlike observations made on the island, outcrossing can eventually occur. We observed two butterfly species (Heliconius ethilla narcaea and Heliconius erato phyllis) pollinating O. maculata. Secretory epidermal cells and trichomes of the spur lumen produced 0.7 µL of 25% (sucrose equivalents) nectar per flower each morning, which was stored in a dilated basal portion of the spur and reabsorbed by the afternoon. Thus, geographical variation in reproductive biology exists across the broad invasive range of O. maculata.  相似文献   
87.
The phasmatodeans or stick and leaf insects are considered to be a mesodiverse insect order with more than 3000 species reported mainly from the tropics. The stick insect subfamily Necrosciinae comprises approximately 700 described species in more than 60 genera from the Oriental and Australian region, forming the most species‐rich subfamily traditionally recognized within Phasmatodea. However, the monophyly of this taxon has never been thoroughly tested and the evolutionary relationships among its members are unknown. We analyse three nuclear (18S and 28S rDNA, histone 3) and three mitochondrial (CO II, 12S and 16S rDNA) genes to infer the phylogeny of 60 species of stick insects that represent all recognized families and major subfamilies sensu Günther and the remarkable diversity within Necrosciinae. Maximum parsimony, maximum likelihood and Bayesian techniques largely recover the same substantial clades, albeit with highly discordant relationships between them. Most members of the subfamily Necrosciinae form a clade. However, the genus Neohirasea – currently classified within Lonchodinae – is strongly supported as subordinate to Necrosciinae, whereas Baculofractum, currently classified within Necrosciinae, is strongly supported within Lonchodinae. Accordingly, we formally transfer Neohirasea and allied taxa (namely Neohiraseini) to Necrosciinae sensu nova (s.n.) and Baculofractum to Lonchodinae s.n. We also provide further evidence that Leprocaulinus, until recently recognized as Necrosciinae, belongs to Lonchodinae, and forms the sister taxon of Baculofractum. Furthermore, Lonchodinae is paraphyletic under exclusion of Eurycantha and Neopromachus. We reinstate the traditional view that Neopromachus and related taxa (Neopromachini sensu Günther) are a subgroup of Lonchodinae and transfer those taxa + the New Guinean Eurycanthinae accordingly. Morphological evidence largely corroborates our molecular‐based findings and also reveals that Menexenus fruhstorferi is a member of the genus Neohirasea and is thus transferred from Menexenus (Lonchodinae) to Neohirasea, as Neohirasea fruhstorferi comb.n . (Necrosciinae s.n. ). Other phylogenetic results include Areolatae and Anareolatae each supported as polyphyletic, Heteropteryginae and Lanceocercata (Bayesian analysis) are monophyletic, albeit with low support, and Necrosciinae s.n. and Lonchodinae s.n. are recovered as sister taxa (Bayesian analysis).  相似文献   
88.

Background aims

Previous studies identified a circulating human osteoblastic population that expressed osteocalcin (OCN), increased following fracture and pubertal growth, and formed mineralized colonies in vitro and bone in vivo. A subpopulation expressed CD34, a hematopoietic/endothelial marker. These findings led to our hypothesis that hematopoietic-derived CD34+OCN+ cells exist in the circulation of mice and are modulated after fracture.

Methods

Flow cytometry was used to identify CD34+OCN+ cells in male B6.SJL-PtprcaPepcb/BoyJ and Vav-Cre/mTmG (VavR) mice. Non-stabilized tibial fractures were created by three-point bend. Fractures were longitudinally imaged by micro-computed tomography, and immunofluorescent staining was used to evaluate CD34+OCN+ cells within fracture callus. AMD3100 (10 mg/kg) was injected subcutaneously for 3 days and the CD34+OCN+ population was evaluated by flow cytometry.

Results

Circulating CD34+OCN+ cells were identified in mice and confirmed to be of hematopoietic origin (CD45+; Vav1+) using two mouse models. Both circulating and bone marrow-derived CD34+OCN+ cells peaked three weeks post-non-stabilized tibial fracture, suggesting association with cartilage callus transition to bone and early mineralization. Co-expression of CD34 and OCN in the fracture callus at two weeks post-fracture was observed. By three weeks, there was 2.1-fold increase in number of CD34+OCN+ cells, and these were observed throughout the fracture callus. AMD3100 altered CD34+OCN+ cell levels in peripheral blood and bone marrow.

Discussion

Together, these data demonstrate a murine CD34+OCN+ circulating population that may be directly involved in fracture repair. Future studies will molecularly characterize CD34+OCN+ cells, determine mechanisms regulating their contribution, and examine if their number correlates with improved fracture healing outcomes.  相似文献   
89.
1. Restoration of shallow turbid lakes to promote growth of submersed aquatic vegetation (SAV) requires knowledge of the environmental factors affecting SAV growth and persistence, and a means to predict the success of SAV reestablishment under different management scenarios to improve these environmental conditions. We used a dynamic ecological modelling approach relating SAV responses to changes in physical and chemical conditions, with information on water level, flow and transparency being provided by hydrodynamic and sediment transport models. 2. The potential persistence of Vallisneria americana was similar under simulated environmental conditions in 1946 and in 1954, as was the potential persistence of Potamogeton pectinatus, indicating that the disappearance of V. americana from Peoria Lake (U.S.A.) previously attributed to an extended spring flood in 1954, may have been related to the combined effects of changes in water level, flow and water transparency as well as possibly other factors. 3. Recent environmental conditions (for 2000) proved not to be conducive for the colonization and persistence potential of V. americana, but would allow colonization by P. pectinatus. The construction of a hypothetical levee along the eastern descending line of the navigation channel in Upper Peoria Lake, which was expected to reduce fetch‐ and navigation‐related turbidity, did not improve the situation for V. americana and overall deteriorated the situation for P. pectinatus. Thus, such a hydraulic alteration, generally considered as beneficial for SAV restoration, may not always be successful. 4. The results of the simulations indicated that the environmental conditions for potential persistence in Peoria Lake were generally less favourable for V. americana than for P. pectinatus. Measures suggested to restore SAV communities in such a lake should aim at reducing concentrations of total suspended solids at the point of inflow by a factor of three to four and limiting fetch‐ and navigation‐related resuspension.  相似文献   
90.
Strains of Escherichia coli are resistant to the antibiotic kasugamycin due to the partial non-methylation of 16S ribosomal RNA. An RNA methylase activity, absent from resistant strains, is shown here to methylate in vitro the 16S RNA of resistant as well as sensitive strains.  相似文献   
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