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191.
192.
Esther Munalula‐Nkandu Paul Ndebele Seter Siziya JC Munthali 《Developing world bioethics》2015,15(3):248-256
We conducted a study to review the consenting process in a vaginal Microbicide feasibility study conducted in Mazabuka, Zambia. Participants were drawn from those participating in the microbicide study. A questionnaire and focus group discussion were used to collect information on participants understanding of study aims, risks and benefits. Altogether, 200 participants took part in this study. The results of the study showed that while all participants signed or endorsed their thumbprints to the consent forms, full informed consent was not attained from most of the participants since 77% (n = 154) of the participants had numerous questions about the study and 34% (n = 68) did not know who to get in touch with concerning the study. Study objectives were not fully understood by over 61% of the participants. Sixty four percent of the participants were not sure of the risks of taking part in the microbicide study. A significant number thought the study was all about determining their HIV status. Some participants were concerned that their partners were not on the trial as they were convinced that being on the study meant that that they had a lifetime protection from HIV infection. The process of obtaining consent was inadequate as various phases of the study were not fully understood. We recommend the need for researchers to reinforce the consenting process in all studies and more so when studies are conducted in low literacy populations. 相似文献
193.
Avise JC; Shapira JF; Daniel SW; Aquadro CF; Lansman RA 《Molecular biology and evolution》1983,1(1):38-56
We address the problem of the possible significance of biological
speciation to the magnitude and pattern of divergence of asexually
transmitted characters in bisexual species. The empirical data for this
report consist of restriction endonuclease site variability in maternally
transmitted mitochondrial DNA (mtDNA) isolated from 82 samples of
Peromyscus polionotus and P. leucopus collected from major portions of the
respective species' ranges. Data are analyzed together with previously
published information on P. maniculatus, a sibling species to polionotus.
Maps of restriction sites indicate that all of the variation observed can
be reasonably attributed to base substitutions leading to loss or gain of
particular recognition sites. Magnitude of mtDNA sequence divergence within
polionotus (maximum approximately equal to 2%) is roughly comparable to
that observed within any of five previously identified mtDNA assemblages in
maniculatus. Sequence divergence within leucopus (maximum approximately
equal to 4%) is somewhat greater than that within polionotus. Consideration
of probable evolutionary links among mtDNA restriction site maps allowed
estimation of matriarchal phylogenies within polionotus and leucopus.
Clustering algorithms and qualitative Wagner procedures were used to
generate phenograms and parsimony networks, respectively, for the
between-species comparisons. Three simple graphical models are presented to
illustrate some conceivable relationships of mtDNA differentiation to
speciation. In theoretical case I, each of two reproductively defined
species (A and B) is monophyletic in matriarchal genealogy; the common
female ancestor of either species can either predate or postdate the
speciation. In case II, neither species is monophyletic in matriarchal
genotype. In case III, species B is monophyletic but forms a subclade
within A which is thus paraphyletic with respect to B. The empirical
results for mtDNA in maniculatus and polionotus appear to conform closely
to case III. These theoretical and empirical considerations raise a number
of questions about the general relationship of the speciation process to
the evolution of uniparentally transmitted traits. Some of these
considerations are presented, and it is suggested that the distribution
patterns of mtDNA sequence variation within and among extant species should
be of considerable relevance to the particular demographies of speciation.
相似文献
194.
It has been well documented that the extracellular matrix components fibronectin and laminin promote or regulate morphogenesis of the myocardial cells in mammalian heart. However, their chronological change of expression (or localization) in the human heart remains elusive. In this study, fibronectin and laminin in the left ventricle of forty-two human fetuses aged from 8 to 26 weeks gestation and left ventricular tissues obtained from a 2-week old infant and two adults were investigated by Western blot analyses and indirect immunofluorescence technique with monoclonal antibodies. In the fetal heart, fibronectins were present along the endocardium, epicardium, and linings of larger blood vessels. In 14-16 weeks gestation, fibronectin immunofluorescence became stronger but not evenly dispersed in the interstitium. After 24 weeks gestation, they were strongly positive only in the relatively larger blood vessels, as well as those in the infant and adult cardiac tissues. Laminins were strongly positive along the endocardium and basement membrane of the myocardial cells and fibroblasts during fetal life. After birth, laminins formed fine fibrillar network along the basement membrane in association with the transverse tubules of myocardial cell; these morphological characteristics remained in the adult cardiac tissues. These results indicate that fibronectin expression is relatively constant during fetal life but decreases after birth; in contrast, laminin expression is not age-dependent and constant throughout the life. 相似文献
195.
Accessing genetic diversity for crop improvement 总被引:1,自引:0,他引:1
196.
Developing taste buds in the anterior mandibular floor of perihatching
chicks were studied by high voltage electron microscopic autoradiography in
order to identify proliferating gemmal cell types. Montaged profiles of 29
taste buds in five cases euthanized between embryonic day 21 and
posthatching day 2 were analyzed after a single [3H]thymidine injection
administered on embryonic day 16, 17 or 18. Results showed that dark cells
comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568
cells) gemmal cells as compared with light, intermediate, basal or
perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of
labeled cells and a greater amount of label (grains/nucleus) than the other
four bud cell types, irrespective of injection day. The nuclear area
(micron 2) of dark cells was not significantly larger (P > 0.05) than
that of the other gemmal cell types and therefore cannot account for the
greater amount for label in the dark cells. Interestingly, only dark cells
showed a positive correlation (P < 0.003) between amount of label and
nuclear area. Results suggest that, during the perihatching period of
robust cell proliferation, dividing dark cells may give rise primarily, but
not exclusively, to dark cell progeny.
相似文献
197.
Pollinator‐mediated selection in a specialized hummingbird–Heliconia system in the Eastern Caribbean
E. J. Temeles Y. J. Rah J. Andicoechea K. L. Byanova G. S. J. Giller S. B. Stolk W. J. Kress 《Journal of evolutionary biology》2013,26(2):347-356
Phenotypic matches between plants and their pollinators often are interpreted as examples of reciprocal selection and adaptation. For the two co‐occurring plant species, Heliconia bihai and H. caribaea in the Eastern Caribbean, we evaluated for five populations over 2 years the strength and direction of natural selection on corolla length and number of bracts per inflorescence. These plant traits correspond closely to the bill lengths and body masses of their primary pollinators, female or male purple‐throated carib hummingbirds (Eulampis jugularis). In H. bihai, directional selection for longer corollas was always significant with the exception of one population in 1 year, whereas selection on bract numbers was rare and found only in one population in 1 year. In contrast, significant directional selection for more bracts per inflorescence occurred in all three populations of the yellow morph and in two populations of the red morph of H. caribaea, whereas significant directional selection on corolla length occurred in only one population of the red morph and one population of the yellow morph. Selection for longer corollas in H. bihai may result from better mechanical fit, and hence pollination, by the long bills of female E. jugularis, their sole pollinator. In contrast, competition between males of E. jugularis for territories may drive selection for more bracts in H. caribaea. Competitive exclusion of female E. jugularis by territorial males also implicates pollinator competition as a possible ecological mechanism for trait diversification in these plants. 相似文献
198.
This study aimed to parameterize the effects of body and meal sizes on the gastric evacuation (GE) of farmed Russian sturgeon (Acipenser gueldenstaedtii) fed on live food (whiting fish) or commercial pellets. The radiography technique was used to monitor the evacuation of food from the stomach into the intestine at postprandial time. Acipenser gueldenstaedtii of different body sizes (total length ranged 82–105 cm) were fed on meal sizes ranged from 23 to 72 g composed of either live food or commercial pellets (had a 20% of BaSO4 as a radiopaque material). The square root model was found to adequality describe the process of GE in A. gueldenstaedtii independently of meal type and size. The effects of fish size on GER was described by simple power model and can be summarized by , where ρL was 0.000053 for live food and 0.000062 for commercial pellets (estimated from combined GE data), St is stomach contents (g), L is fish total length (cm) and t is time (h). The results of this study will provide a useful tool to estimate the stomach fullness of A. gueldenstaedtii at postprandial time t. Such information should assess the feeding strategy to minimize feed wastage and optimize the fish growth. 相似文献
199.