阳离子诱导大叶藻叶绿体膜中激发能在PSⅡ和PSⅠ之间分配变化的机理(英文)

用Ｃａ２＋ 和胰酶处理大叶藻（Ｚｏｓｔｅｒａ ｍ ａｒｉｎａ）叶绿体膜研究了其类囊体膜多肽成分与Ｍｇ２＋ 诱导其Ｃｈｌａ荧光和类囊体膜表面电荷变化之间的相互关系,观察到：１．在正常的叶绿体膜中,Ｍｇ２＋ 诱导ＰＳⅡ荧光强度的增高与其诱导类囊体膜表面电荷密度的降低密切相关;２．用Ｃａ２＋ 处理这种叶绿体膜,除去类囊体膜表面的３２～３４ ｋＤ多肽对Ｍｇ２＋ 诱导的上述现象无影响;３．如果用胰酶消化Ｃａ２＋ 处理过的叶绿体膜,进一步除去膜表面的２６ ｋＤ多肽,Ｍｇ２＋诱导的这些现象则全部消失。这些实验结果清楚地表明,在大叶藻的叶绿体膜中,类囊体膜表面的２６ ｋＤ 多肽是阳离子诱导这两种相关现象的特异性作用部位。对阳离子调节激发能在ＰＳⅡ和ＰＳⅠ之间分配的机理进行了讨论     

Characterization of Herpes Simplex Virus Type 1 RNA Present in the Absence of De Novo Protein Synthesis

We used herpes simplex virus type 1 (HSV-1) DNA and restriction fragments of HSV-1 DNA covalently coupled to cellulose as a reagent to isolate for further characterization the major and minor HSV-1 immediate-early mRNA species in HeLa cells infected and maintained in the absence of de novo protein synthesis. Five major and several minor immediate-early mRNA species were characterized. One major species was a 4.2-kilobase mRNA mapping in the TR(S)/IR(S) region with its 3' end distal to the U(S) region; this mRNA encoded a 170,000-dalton polypeptide in vitro. A 2.8-kilobase mRNA, encoding a 120,000-dalton polypeptide, was mapped in the TR(L)/IR(L) region with its 3' end directed toward the U(L) region. Three 1.8-kilobase mRNA species were mapped. One, mapping in the IR(S) region with its 3' end in the U(S), encoded a 68,000-dalton polypeptide. One mapped in the TR(S) region and had its 3' end in the U(S) region; the third one encoded a 64,000-dalton polypeptide and mapped in the U(L) region near the IR(L) region. One minor species 5.2 kilobases in size was clearly detectable mapping in the U(L) region. Furthermore, there were indications that one or more immediate-early mRNA species approximately 3 kilobases in size hybridized to regions near the TR(L) and in or near the TR(S)/IR(S) regions. Nuclear immediate-early RNA mapped only in those regions where polyribosomal immediate-early mRNA mapped, although minor differences were seen. Finally, we demonstrated that at least three major immediate-early mRNA's-4.2 kilobases, 2.8 kilobases, and the 1.8-kilobase one mapping in the IR(S)/U(S) region-continued to appear on polyribosomes as functional mRNA late after infection.     

In vitro assessment of the toxicity of metal compounds

A review has been compiled illustrating the directions taken in examining the genotoxic effects of metals and their compounds centering only on those studies pertaining to effects of metals and their compounds on DNA structure and function, such as the induction of DNA strand breaks, production of DNA-protein crosslinks, induction of chromosomal aberrations, and sister chromatid exchanges. Although it is premature to declare a cause and effect relationship between the carcinogenic activity of metals and their ability to induce one or more lesions in DNA, strong evidence is emerging to suggest such a relationship. Low concentrations of metals induce the appearance of DNA lesions, such as strand breaks and crosslinks, or induce sister chromatid exchanges or DNA repair synthesis. Assays based upon these events constitute extremely sensitive probes for genotoxic effects of metals and their compounds. These effects of metals on DNA are consistent with the currently accepted mechanism of chemical carcinogenesis, allowing the acquisition and propagation of altered DNA function. The lack of complete information on the activity of metals in producing DNA lesions allow only preliminary conclusions to be drawn. Certain compounds containing potentially or actually carcinogenic elements, such as Ni, Be, As, Cr, Cd, and to a minor extent Pb, have yielded positive responses in one or more DNA lesion assays. At relatively nontoxic levels of Ni and Cr, considerable evidence suggests that multiple types of DNA lesions are induced.     

Respiratory depression produced by centrally administered taurine in the cat

The effects of taurine (0.8-64.8 mumol) were studied on respiratory activity following intracisternal (cisterna magna) and intracerebroventricular (lateral ventricle) injections in cats anesthetized with alpha-chloralose. Respiratory activity was measured by using a Fleisch pneumotachograph and monitoring tracheal airflow. The flow signal was integrated to obtain tidal volume (VT) and respiratory rate (f) was obtained by counting the number of VT excursions over one minute. Inspiratory (TI), expiratory (TE) and total (TTOT) cycle durations were also determined during this time period. In addition, end-tidal CO2 was continuously monitored. Associated changes in arterial pressure (femoral artery cannula) and heart rate were also determined. After injections into the cisterna magna, taurine caused dose-related decreases in minute ventilation (VE). The maximal decrease in VE was from 495 +/- 59 to 64 +/- 14 ml/min (p less than 0.05), and was due to both decreases in VT (from 27 +/- 3 to 5 +/- 1 ml; p less than 0.05) and f (from 18 +/- 1 to 12 +/- 2 breaths/min; p less than 0.05). TE and TTOT were increased from 2.4 +/- 0.4 to 4.5 +/- 0.6 sec (p less than 0.05) and from 3.7 +/- 0.4 to 6.4 +/- 0.8 sec (p less than 0.05), respectively. Mean inspiratory flow (VT/TI), a measure of inspiratory drive, was decreased from 21 +/- 4 to 4 +/- 2 ml/sec (p less than 0.05). Apnea occurred in 5 of 6 animals after the 64.8 mumol dose. This respiratory depression occurred without any significant change in arterial pressure. After lateral ventricle injections, taurine also caused dose-related, but not as pronounced, decreases in respiratory activity. In addition, taurine caused significant decreases (p less than 0.05) in arterial pressure in doses that decreased VE. Taurine administered intravenously had no significant cardiorespiratory depressant effects. These data indicate that centrally administered taurine produces respiratory depression and, depending on the route of CNS administration, also produces hypotension.     

Amazonia trees have limited capacity to acclimate plant hydraulic properties in response to long‐term drought

The fate of tropical forests under future climate change is dependent on the capacity of their trees to adjust to drier conditions. The capacity of trees to withstand drought is likely to be determined by traits associated with their hydraulic systems. However, data on whether tropical trees can adjust hydraulic traits when experiencing drought remain rare. We measured plant hydraulic traits (e.g. hydraulic conductivity and embolism resistance) and plant hydraulic system status (e.g. leaf water potential, native embolism and safety margin) on >150 trees from 12 genera (36 species) and spanning a stem size range from 14 to 68 cm diameter at breast height at the world's only long‐running tropical forest drought experiment. Hydraulic traits showed no adjustment following 15 years of experimentally imposed moisture deficit. This failure to adjust resulted in these drought‐stressed trees experiencing significantly lower leaf water potentials, and higher, but variable, levels of native embolism in the branches. This result suggests that hydraulic damage caused by elevated levels of embolism is likely to be one of the key drivers of drought‐induced mortality following long‐term soil moisture deficit. We demonstrate that some hydraulic traits changed with tree size, however, the direction and magnitude of the change was controlled by taxonomic identity. Our results suggest that Amazonian trees, both small and large, have limited capacity to acclimate their hydraulic systems to future droughts, potentially making them more at risk of drought‐induced mortality.     

Nucleotide Diversity of the Coding and Promoter Regions of <Emphasis Type="Italic">DREB1D</Emphasis>, a Candidate Gene for Drought Tolerance in <Emphasis Type="Italic">Coffea</Emphasis> Species

Climate change is posing a major challenge to coffee production worldwide leading to a need for the development of coffee cultivars with increased drought tolerance. In several plant species, the use of DREB genes in crop improvement has achieved promising results to desiccation tolerance engineering. Recent studies reported CcDREB1D specific patterns of expression in Coffea canephora and functional evidence of this gene involvement in drought stress responses. However, knowledge on natural diversity of this gene is largely unknown. In this context, this study aimed at evaluating the sequence variability of the DREB1D gene in several Coffea genotypes. Nucleotide variation in promoters and coding regions of this gene were evaluated in a population consisting of 38 genotypes of C. canephora, C. arabica and C. eugenioides, most of them characterized by different phenotypes (tolerance vs. susceptibility) in relation to drought. The genetic diversity of the loci revealed different haplotypes for the promoter and coding regions. In particular, our findings suggest association between drought tolerance and the genetic variations on DREB1D promoter regions, but not with those from its corresponding coding regions. Gene expression studies revealed up-regulated expression of DREB1D gene upon drought mainly in leaves of drought-tolerant clones of C. canephora, and in response to drought, high, and low temperatures in leaves of C. arabica, suggesting a key role of this gene in coffee responses to abiotic stress.     

Population structure,relative growth and morphological sexual maturity of the snapping shrimp Alpheus brasileiro Anker, 2012 (Caridea: Alpheidae) from the south-eastern coast of Brazil

The present study investigated the population structure of the snapping shrimp Alpheus brasileiro. We tested the hypotheses that the sex ratio of the population differs from the expected 1:1 and that the growth pattern differs between adults and juveniles and between sexes. Reproductive period, juvenile recruitment and morphological sexual maturity were estimated. Samples were collected in two periods. The first sampling occurred bimonthly from March 2013 to January 2014. The second sampling occurred monthly from April 2015 to March 2016. The population structure was determined based on the size-frequency distribution of different demographic categories. To analyse the relative growth, we measured the second pleuron length, major cheliped propodus length, major cheliped propodus width, major cheliped propodus height, appendix interna length, appendix masculina length. The results showed that the sex ratio did not differ from 1:1 (male:female). Reproduction and juvenile recruitment were continuous throughout the study period. The analysis of relative growth confirmed the hypothesis that males and females, and juveniles and adults, have different growth patterns, indicating distinct strategies of energy allocation. The estimated carapace length at the onset of morphological sexual maturity was 4.9?mm in males and 4.7?mm in females. The results obtained in this study are probably related to the monogamous social behaviour of A. brasileiro. Monogamy can influence demographic parameters such as sex ratio and the size at which males and females reach morphological sexual maturity.