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1.
Coral reefs are generally considered to be the most biologically productive of all marine ecosystems, but in recent times these vulnerable aquatic resources have been subject to unusual degradation. The general decline in reefs has been greatly accelerated by mass bleaching in which corals whiten en masse and often fail to recover. Empirical evidence indicates a coral reef bleaching cycle in which major bleaching episodes are synchronized with El Niño events that occur every 3–4 years on average. By heating vast areas of the Pacific Ocean, and affecting the Indian and Atlantic Oceans as well, El Niño causes widespread damage to reefs largely because corals are very sensitive to temperature changes. However, mass bleaching events were rarely observed before the 1970s and their abrupt appearance two decades ago remains an enigma. Here we propose a new explanation for the sudden occurrence of mass bleaching and show that it may be a response to the relative increase in El Niño experienced over the last two decades. 相似文献
2.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
3.
One hundred and seventy normal male infants from Delhi were studied using the CBG technique to estimate Y-chromosome length heteromorphisms. The median class in Y/F [Y/F = total length of the Y chromosome/average total length of the F group chromosomes (19 and 20)] distribution was 0.75-0.79. The Y/F index in infants varied from 0.60 to 1.16 with a mean of 0.81 and a standard deviation of 0.09. A high incidence for very small (53.5 percent) and small (41.2 percent) categories of Y-chromosome length heteromorphisms was observed. Data were compared with other available reports; also possible mechanisms of the Y-chromosome length heteromorphisms and their role in ethnic/racial variation as well as in developmental disturbances are discussed. It is suggested there may be a need to redefine the long and short Y chromosome in a given population while studying different clinical disorders. 相似文献
4.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
5.
Two population groups of Jammu and Kashmir (India) — Muslims and Bodhs-have been typed for haptoglobin and for CG and PI subtype
polymorphisms. The allele frequencies do not show significant differences between these two populations. HP and GC allele
frequencies of Bodhs and Muslims differ considerably from with that observed in other North Indian populations. The PI allele
frequencies of Bohds and Muslims differ considerably from those found in other Indian populations and are more similar to
Mongoloid ones. 相似文献
6.
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8.
Devinder P. Bhasin Carl C. Gryte Joel F. Studebaker 《Biotechnology and bioengineering》1976,18(12):1777-1792
Since steroids are only slightly soluble in the aqueous solutions in which enzymatic reactions take place, it is difficult to obtain high effective concentrations per unit reactor volume when enzymes are used to catalyze steroid reactions. In order to obtain high effective concentrations in the present work, we have used small particles of a hydrophobic polymer, poly (dimethyl siloxane), as a reservoir for the steroid substrate and product. The activity of a bacterial hydroxysteroid dehydrogenase in a buffer solution declines much more slowly in the presence of those polymer particles than in the presence of a comparable amount of butyl acetate or ethyl acetate, the organic solvents used as steroid reservoirs in previous work with steroid transforming enzymes. When another substrate of the hydroxysteroid dehydrogenase is loaded into the polymer particles and the particles are suspended in an aqueous solution containing the enzyme and its cofactor, more product is formed that when a similar solution is emulsified with butyl acetate. 相似文献
9.
Tumor infiltrating lymphocytes (TIL), especially T-cells, have both prognostic and therapeutic applications. The presence of CD8+ effector T-cells and the ratio of CD8+ cells to FOXP3+ regulatory T-cells have been used as biomarkers of disease prognosis to predict response to various immunotherapies. Blocking the interaction between inhibitory receptors on T-cells and their ligands with therapeutic antibodies including atezolizumab, nivolumab, pembrolizumab and tremelimumab increases the immune response against cancer cells and has shown significant improvement in clinical benefits and survival in several different tumor types. The improved clinical outcome is presumed to be associated with a higher tumor infiltration; therefore, it is thought that more accurate methods for measuring the amount of TIL could assist prognosis and predict treatment response. We have developed and validated quantitative immunohistochemistry (IHC) assays for CD3, CD8 and FOXP3 for immunophenotyping T-lymphocytes in tumor tissue. Various types of formalin fixed, paraffin embedded (FFPE) tumor tissues were immunolabeled with anti-CD3, anti-CD8 and anti-FOXP3 antibodies using an IHC autostainer. The tumor area of stained tissues, including the invasive margin of the tumor, was scored by a pathologist (visual scoring) and by computer-based quantitative image analysis. Two image analysis scores were obtained for the staining of each biomarker: the percent positive cells in the tumor area and positive cells/mm2 tumor area. Comparison of visual vs. image analysis scoring methods using regression analysis showed high correlation and indicated that quantitative image analysis can be used to score the number of positive cells in IHC stained slides. To demonstrate that the IHC assays produce consistent results in normal daily testing, we evaluated the specificity, sensitivity and reproducibility of the IHC assays using both visual and image analysis scoring methods. We found that CD3, CD8 and FOXP3 IHC assays met the fit-for-purpose analytical acceptance validation criteria and that they can be used to support clinical studies. 相似文献
10.
Bhavna Bhasin Bryan Lau Mohamed G. Atta Derek M. Fine Michelle M. Estrella George J. Schwartz Gregory M. Lucas 《PloS one》2013,8(12)