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231.
We have found that the potentiation of antiproliferative effects by buthionine sulfoximine (BSO) of cell growth inhibition induced by cisplatin are highly schedule dependent in resistant BE colon carcinoma cells. Maintenance of low GSH levels during the 12-h interval after cisplatin (cis-DDP) treatment is critical. A schedule of BSO exposure that results in low GSH levels for 12 h after cisplatin exposure is associated with a marked increase in DNA interstrand cross-link formation as analyzed by alkaline elution. These findings are consistent with a central role of GSH in interfering with the conversion of cis-DDP DNA monoadducts to DNA interstrand cross-links and may prove relevant to the design of clinical trials of BSO with cisplatin. 相似文献
232.
233.
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
234.
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
235.
Gustine Rebecca N. Hanan Erin J. Robichaud Peter R. Elliot William J. 《Biogeochemistry》2022,157(1):51-68
Biogeochemistry - Wildfire is a major driver of nitrogen (N) cycling and export from terrestrial to aquatic systems. While fire is a natural process in many watersheds, it can still degrade water... 相似文献
236.
Accessing genetic diversity for crop improvement 总被引:1,自引:0,他引:1
237.
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
238.
The reactivity of a series of potentially tetradentate hydrazone ligands, involving pyridyl and imidazolyl substituent groups, towards copper(II) salts has been examined. Both mononuclear and polynuclear derivatives are obtained with some ligands and in some cases redox reactions are observed in which, when water is a significant solvent component, nitrogen gas evolution indicates the formation of copper(I) derivatives. The reduction is assumed to occur by initial hydrolysis of the hydrazone ligand, forming hydrazine as one product, which reduces copper(II) to copper(I). However the copper(I) ions bind preferentially to unoxidized ligand thus limiting the extent to which reduction occurs. In the presence of electronegative ligands the copper(II) complexes are stabilized in some cases, while in one case a mixed valence polynuclear species is produced. Preliminary details of the X-ray structure of [Cu(IMAA)Br2]·H2O (IMAA = (1-methyl-2-imidazolyl)aldazine) indicate a mononuclear, five-coordinate, system involving unsymmetrical tridentate ligand, a structural feature which is apparent in most other mononuclear species. 相似文献
239.
Larval release in a sub-euphotic zone invertebrate triggered by sinking phytoplankton particles 总被引:1,自引:0,他引:1
Starr Michel; Therriault Jean-Claude; Conan Gerard Y.; Comeau Michel; Robichaud Guy 《Journal of plankton research》1994,16(9):1137-1147
This paper reports field results showing that the larval releaseof the snow crab, Chionoecetes opilio, in a subarctic fjordis phased with the sedimentation peak of phytoplankton particlesoriginating from the surface spring bloom, but with a lag of23 weeks. Further laboratory experiments with egg-bearingfemales showed a significant induction of larval release whenthey were exposed to senescent cultures of different phytoplanktonspecies, as opposed to controls and females exposed to freshcultures. These results are interpreted and discussed in thecontext of possible strategies evolved by the snow crab to enhanceits reproductive success. The field and laboratory evidencepresented here represents the first instance indicating thatphyto-detritus can act as a chemical cue for initiating andsynchronizing reproductive activities in sub-euphotic invertebrates.Selection for control of larval release by downward flux ofalgal particles may be especially important for invertebratepopulations in high-latitude areas, where the development ofplankton communities shows a high level of seasonality. 相似文献
240.