CO2 uptake by the cultivated hemiepiphytic cactus, Hylocereus undatus

The climate of the native tropical forest habitats of Hylocereus undatus, a hemiepiphytic cactus cultivated in 20 countries for its fruit, can help explain the response of its net CO2 uptake to environmental factors. Under wet conditions, about 85% of the total daily net CO₂ uptake occurs at night via Crassulacean acid metabolism, leading to a high water‐use efficiency. Total daily net CO₂ uptake is reduced 57% by only 10 days of drought, possibly involving stomatal closure induced by abscisic acid produced in the roots, which typically occupy a small substrate volume. Total daily net CO₂ uptake for H. undatus is maximal at day/night air temperatures of 30/20°C, optimal temperatures that are higher than those for desert cacti but representative of ambient temperatures in the tropics; its total daily net CO₂ uptake becomes zero at day/night air temperatures of 42/32°C. Stem damage occurs at 45°C for H. undatus, whose photosynthetic cells show little acclimation to high temperatures compared with other cacti and are also sensitive to low temperatures, ‐1.5°C killing half of these cells. Consistent with its shaded habitat, total daily net CO2 uptake is appreciable at a total daily PPF of only 2 mol m2 day' and is maximal at 20 mol m^?2 day^?1, above which photoinhibition reduces net CO₂ uptake. Net CO₂ uptake ability, which is highly correlated with stem nitrogen and chlorophyll contents, changes only gradually (halftimes of 2–3 months) as the concentration of applied N is changed. Doubling the atmospheric CO₂ concentration raises the total daily net CO₂ uptake of H. undatus by 34% under optimal conditions and by even larger percentages under adverse environmental conditions.     

Effect of rfaH (sfrB) and temperature on expression of rfa genes of Escherichia coli K-12.

In order to study the regulation of a large block of contiguous genes at the rfa locus of Escherichia coli K-12 which are involved in synthesis and modification of the lipopolysaccharide core, the transposon TnlacZ was used to generate in-frame lacZ fusions to the coding regions of five genes (rfaQ, -G, -P, -B and -J) within this block. The beta-galactosidase activity of strains in which these fusions had been crossed into the chromosomal rfa locus was significantly decreased when the rfaH11 (sfrB11) allele was introduced and was restored to wild-type levels when these strains were lysogenized with a lambda phage carrying wild-type rfaH. This indicates that the positive regulatory function encoded by rfaH is required throughout this block of genes. In addition, expression of the lacZ fusion to rfaJ was reduced by growth at 42 degrees C, and this correlated with a temperature-induced change in the electrophoretic profile of the core lipopolysaccharide.     

Comparison of lipopolysaccharide biosynthesis genes rfaK, rfaL, rfaY, and rfaZ of Escherichia coli K-12 and Salmonella typhimurium.

Analysis of the sequence of a 4.3-kb region downstream of rfaJ revealed four genes. The first two of these, which encode proteins of 27,441 and 32,890 Da, were identified as rfaY and rfaZ by homology of the derived protein sequences of their products to the products of similar genes of Salmonella typhimurium. The amino acid sequences of proteins RfaY and RfaZ showed, respectively, 70 and 72% identity. Genes 3 and 4 were identified as rfaK and rfaL on the basis of size and position, but the derived amino acid sequences of the products of these genes showed very little similarity (about 12% identity) between Escherichia coli K-12 and S. typhimurium. The next gene in the cluster, rfaC, encodes a product which also shows strong protein sequence homology between E. coli K-12 and S. typhimurium, as do the rfaF and rfaD genes which lie beyond it. Thus, the rfa gene cluster appears to consist of two blocks of genes which are conserved flanking a central region of two genes which are not conserved between these species. Although the RfaL protein sequence is not conserved, hydropathy plots of the two RfaL species are nearly identical and indicate that this is a typical integral membrane protein with 10 or more potential transmembrane domains. We noted the similarity of the structure of the rfa gene cluster to that of the rfb gene cluster, which has now been sequenced in several Salmonella serovars. The rfb cluster also contains a gene which lies within a central nonconserved region and encodes an integral membrane protein similar to protein RfaL. We speculate that protein RfaL may interact in a strain- or species-specific way with one or more Rfb proteins in the expression of surface O antigen.     

125I derivatives of prostaglandins. A novel approach in prostaglandin analysis by radioimmunoassay.

We report the production of radioactive iodinated (125 I) derivatives of prostaglandins E1, E2, F2alpha and their use in radioimmunological assays. Histamine or tyramine was coupled to the prostaglandins carboxyl group and the iodination was accomplished using the chloramine T method. The high specific radioactivity of these tracers and the resolution of the purification procedure allowed the detection of 0.5 pg of prostaglandins. A comparison with tritiated prostaglandin was made and showed a 10-fold gain in sensitivity. Furthermore in the case of the prostaglandin E1 system using 125I-labelled histamine or tyramine as tracer the cross reaction curves obtained were different from those obtained with [3H]prostaglandin E1; we suggest that the blocking of the carboxyl group alters the prostaglandin E1 structure, modifying its immunoreactivity.     

A 4-vinylprotochlorophyllide complex accumulated by "phofil" mutant of Rhodopseudomonas spheroides. An authentic intermediate in the development of the photosynthetic apparatus.

A photosynthetically competent mutant strain of Rhodopseudomonas spheroides was isolated. In addition to bacteriochlorophyll, this organism produced particle-bound precursor 4-vinylprotochlorophyllide. The spectral characteristics of the pigment complexes(es) accumulated in the culture medium were very variable. The spectral form occurring within the bacteria was characterized from fluorescence data. Its particle weight, 130 000, was determined by Sephadex G200 filtration. The main components of the complex were protein, lipid and pigment (6.8:61, w/w). As indicated by qualitative analysis, the lipid components were characteristic constituents of the photosynthetic membrane. Kinetics of pigments synthesis showed that the total pigment synthesis was not affected by the mutation; bacteriochlorophyll content was always lower in the mutant than in the parent strain. The repigmentation process was followed by fluorescence emission. The results indicated that the mutation affected membrane component synthesis required for the bacteriochlorophyll(ide) incorporation. The pigment complex was concluded to be an authentic intermediate in photosynthetic apparatus morphogenesis. The reasons for its excretion are discussed.     

The tyrosyl residues in creatine kinase. Modification by iodine.

The effect of the iodination of tyrosyl residues in creatine kinase from rabbit muscle has been investigated at alkaline pH after reversible masking of the reactive thiol groups. The conversion of 4-5 tyrosyl residues to monoiodotyrosines as measured by spectrotitration and by radioactive iodine labelling resulted in almost total loss of enzymic activity. The modified enzyme was unable to bind its nucleotide substrates but no significant conformational change was revealed by optical rotatory dispersion or Stokes radius measurements. However, change in the reactivity of some non-essential thiol groups, presumably those located near the active thiol groups, was observed.     

基于网络药理学的谷糠结合态多酚抗乳腺癌机制研究

本研究旨在探讨谷糠结合态多酚(bound phenol of inner shell,BPIS)发挥抗乳腺癌细胞活性的作用机制。首先采用细胞计数法检测BPIS对乳腺癌细胞以及正常乳腺细胞活性的影响;然后综合运用SEA、SIB以及GeneCards等数据库获得BPIS和乳腺癌的相关靶点,并分析活性成分与作用靶点的互作网络以及通路。本研究筛选得到BPIS抗乳腺癌相关靶点39个,主要涉及糖脂代谢和细胞自噬等生物过程以及MAPK、PI3K/AKT、FoxO等多条信号通,表明BPIS抗乳腺癌是多成分、多靶点、多通路协同作用的过程,而与细胞死亡相关的细胞自噬很可能在BPIS抑制乳腺癌过程中发挥主要作用。     

Sex-specific costs of reproduction on survival in a long-lived seabird

Costs of reproduction on survival have captured the attention of researchers since life history theory was formulated. Adults of long-lived species may increase survival by reducing their breeding effort or even skipping reproduction. In this study, we aimed to evaluate the costs of current reproduction on survival and whether skipping reproduction increases adult survival in a long-lived seabird. We used capture–mark–recapture data (1450 encounters) from two populations of Bulwer''s petrel (Bulweria bulwerii), breeding in the Azores and Canary Islands, North Atlantic Ocean. Using a multi-event model with two different breeding statuses (breeders versus non-breeders), we calculated probabilities of survival and of transitions between breeding statuses, evaluating potential differences between sexes. Females had lower survival probabilities than males, independent of their breeding status. When considering breeding status, breeding females had lower survival probabilities than non-breeding females, suggesting costs of reproduction on survival. Breeding males had higher survival probabilities than non-breeding males, suggesting that males do not incur costs of reproduction on survival and that only the highest quality males have access to breeding. The highest and the lowest probabilities of skipping reproduction were found in breeding males from the Azores and in breeding males from the Canary Islands, respectively. Intermediate values were observed in the females from both populations. This result is probably due to differences in the external factors affecting both populations, essentially predation pressure and competition. The existence of sex-specific costs of reproduction on survival in several populations of this long-lived species may have important implications for species population dynamics.     

小麦族植物的分类现状及主要存在的问题

小麦族(Triticeae)是禾本科、早熟禾亚科中一个有重要经济价值、以多年生植物占优势的族,族内绝大多数种类是重要的粮食作物和畜牧业上的优良牧草,饲用价值极高,有些种类具有耐寒、耐旱、耐碱等特性,是农牧业上良种繁育、牧草利用的重要基因资源。但该族同时又是分类学上的一个疑难族,各学者对族内系统分类意见不一、争议颇大,尤其在族的界限、族下类群划分以及类群演化关系上问题较多,至今尚未解决。查阅了国内外分类学文献,探讨其分类差异以及存在问题,为充分开发利用中国丰富的小麦族植物资源提供理论依据。