A physiological role for cyanate-induced carbonic anhydrase in Escherichia coli.

Cyanate induces expression of the cyn operon in Escherichia coli. The cyn operon includes the gene cynS, encoding cyanase, which catalyzes the reaction of cyanate with bicarbonate to give ammonia and carbon dioxide. A carbonic anhydrase activity was recently found to be encoded by the cynT gene, the first gene of the cyn operon; it was proposed that carbonic anhydrase prevents depletion of bicarbonate during cyanate decomposition due to loss of CO2 by diffusion out of the cell (M. B. Guilloton, J. J. Korte, A. F. Lamblin, J. A. Fuchs, and P. M. Anderson, J. Biol. Chem. 267:3731-3734, 1992). The function of the product of the third gene of this operon, cynX, is unknown. In the study reported here, the physiological roles of cynT and cynX were investigated by construction of chromosomal mutants in which each of the three genes was rendered inactive. The delta cynT chromosomal mutant expressed an active cyanase but no active carbonic anhydrase. In contrast to the wild-type strain, the growth of the delta cynT strain was inhibited by cyanate, and the mutant strain was unable to degrade cyanate and therefore could not use cyanate as the sole nitrogen source when grown at a partial CO2 pressures (pCO2) of 0.03% (air). At a high pCO2 (3%), however, the delta cynT strain behaved like the wild-type strain; it was significantly less sensitive to the toxic effects of cyanate and could degrade cyanate and use cyanate as the sole nitrogen source for growth. These results are consistent with the proposed function for carbonic anhydrase. The chromosomal mutant carrying cynS::kan expressed induced carbonic anhydrase activity but no active cyanase. The cynS::kan mutant was found to be much less sensitive to cyanate than the delta cynT mutant at a low pCO2, indicating that bicarbonate depletion due to the reaction of bicarbonate with cyanate catalyzed by cyanase is more deleterious to growth than direct inhibition by cyanate. Mutants carrying a nonfunctional cynX gene (cynX::kan and delta cynT cynX::kan) did not differ from the parental strains with respect to cyanate sensitivity, presence of carbonic anhydrase and cyanase, or degradation of cyanate by whole cells; the physiological role of the cynX product remains unknown.     

Biofiltration of paint solvent mixtures in two reactor types: overloading by hydrophobic components

Steady-state performance characteristics of a trickle bed reactor (TBR) and a biofilter (BF) in loading experiments with increasing toluene/xylenes inlet concentrations while maintaining a constant loading rate of hydrophilic components (methyl ethyl and methyl isobutyl ketones, acetone, and n-butyl acetate) of 4 g m⁻³ h⁻¹ were evaluated and compared, along with the systems’ dynamic responses. At the same combined substrate loading of 55 g m⁻³ h⁻¹ for both reactors, the TBR achieved more than 1.5 times higher overall removal efficiency (RE_W) than the BF. Increasing the loading rate of aromatics resulted in a gradual decrease of their REs. The degradation rates of acetone and n-butyl acetate were also inhibited at higher loads of aromatics, thus revealing a competition in cell catabolism. A step-drop in loading of aromatics resulted in an immediate increase of RE_W with variations in the TBR, while the new steady-state value in the BF took 6–7 h to achieve. The TBR consistently showed a greater performance than BF in removing toluene and xylenes. Increasing the loading rate of aromatics resulted in a gradual decrease of their REs. The degradation rates of acetone and n-butyl acetate were also lower at higher OL_AROM, revealing a competition in the cell catabolism. The results obtained are consistent with the proposed hypothesis of greater toxic effects under low water content, i.e., in the biofilter, caused by aromatic hydrocarbons in the presence of polar ketones and esters, which may improve the hydrocarbon partitioning into the aqueous phase.     

Expression of proteins encoded by the Escherichia coli cyn operon: carbon dioxide-enhanced degradation of carbonic anhydrase.

Cyanase catalyzes the reaction of cyanate with bicarbonate to give 2CO2. The cynS gene encoding cyanase, together with the cynT gene for carbonic anhydrase, is part of the cyn operon, the expression of which is induced in Escherichia coli by cyanate. The physiological role of carbonic anhydrase is to prevent depletion of cellular bicarbonate during cyanate decomposition due to loss of CO2 (M.B. Guilloton, A.F. Lamblin, E. I. Kozliak, M. Gerami-Nejad, C. Tu, D. Silverman, P.M. Anderson, and J.A. Fuchs, J. Bacteriol. 175:1443-1451, 1993). A delta cynT mutant strain was extremely sensitive to inhibition of growth by cyanate and did not catalyze decomposition of cyanate (even though an active cyanase was expressed) when grown at a low pCO2 (in air) but had a Cyn+ phenotype at a high pCO2. Here the expression of these two enzymes in this unusual system for cyanate degradation was characterized in more detail. Both enzymes were found to be located in the cytosol and to be present at approximately equal levels in the presence of cyanate. A delta cynT mutant strain could be complemented with high levels of expressed human carbonic anhydrase II; however, the mutant defect was not completely abolished, perhaps because the E. coli carbonic anhydrase is significantly less susceptible to inhibition by cyanate than mammalian carbonic anhydrases. The induced E. coli carbonic anhydrase appears to be particularly adapted to its function in cyanate degradation. Active cyanase remained in cells grown in the presence of either low or high pCO2 after the inducer cyanate was depleted; in contrast, carbonic anhydrase protein was degraded very rapidly (minutes) at a high pCO2 but much more slowly (hours) at a low pCO2. A physiological significance of these observations is suggested by the observation that expression of carbonic anhydrase at a high pCO2 decreased the growth rate.     

红腹锦鸡肺的组织结构与微血管构筑

为了了解红腹锦鸡(Chroysolophus pictus)肺的微细结构和微血管构筑特征,为呼吸生物学研究提供形态学依据,用组织学方法和微血管铸型技术在光镜和扫描电镜下观察研究了红腹锦鸡肺的组织结构与微血管构筑情况。结果表明,红腹锦鸡肺主要由各级支气管构成,从三级支气管上呈辅射状分出许多呼吸毛细管(微气管),并相互吻合成网状,呼吸毛细管外面包围有丰富的毛细血管;红腹锦鸡肺毛细血管垂直围绕在各微气管外,并相互吻合成密集的立体微血管网;毛细血管管径4.5~7.0μm,微气管直径11~50μm。并对肺微血管构筑情况与呼吸效率的关系作了探讨。     

Olive Phenolics as c-Met Inhibitors: (-)-Oleocanthal Attenuates Cell Proliferation,Invasiveness, and Tumor Growth in Breast Cancer Models

Dysregulation of the Hepatocyte growth factor (HGF)/c-Met signaling axis upregulates diverse tumor cell functions, including cell proliferation, survival, scattering and motility, epithelial-to-mesenchymal transition (EMT), angiogenesis, invasion, and metastasis. (-)-Oleocanthal is a naturally occurring secoiridoid from extra-virgin olive oil, which showed antiproliferative and antimigratory activity against different cancer cell lines. The aim of this study was to characterize the intracellular mechanisms involved in mediating the anticancer effects of (-)-oleocanthal treatment and the potential involvement of c-Met receptor signaling components in breast cancer. Results showed that (-)-oleocanthal inhibits the growth of human breast cancer cell lines MDA-MB-231, MCF-7 and BT-474 while similar treatment doses were found to have no effect on normal human MCF10A cell growth. In addition, (-)-oleocanthal treatment caused a dose-dependent inhibition of HGF-induced cell migration, invasion and G1/S cell cycle progression in breast cancer cell lines. Moreover, (-)-oleocanthal treatment effects were found to be mediated via inhibition of HGF-induced c-Met activation and its downstream mitogenic signaling pathways. This growth inhibitory effect is associated with blockade of EMT and reduction in cellular motility. Further results from in vivo studies showed that (-)-oleocanthal treatment suppressed tumor cell growth in an orthotopic model of breast cancer in athymic nude mice. Collectively, the findings of this study suggest that (-)-oleocanthal is a promising dietary supplement lead with potential for therapeutic use to control malignancies with aberrant c-Met activity.     

POTENTIATION OF CAFFEINEINDUCED CONTRACTURE BY RAISING EXTRACELLULAR POTASSIUM IN FROG SKELETAL MUSCLE

用蛙胫前肌小束为材料,研究了提高胞外钾［Ｋ＋］Ｏ对咖啡因挛缩的作用。［Ｋ＋］Ｏ从２ｍｍｏｌ／Ｌ提高到１０或２５ｍｍｏｌ／Ｌ,由３ｍｍｏｌ／Ｌ咖啡因引起的挛缩明显增强。以ＰＫＣ／ＰＣ（ＰＫＣ和ＰＣ分别为在高钾和正常钾条件下的咖啡因挛缩）表示的咖啡因挛缩增强,依赖［Ｋ＋］Ｏ和高钾作用时间。随着１０ｍｍｏｌ／Ｌ［Ｋ＋］Ｏ作用时间延长,直至１０ｍｉｎ,增强逐渐增加。但是,２５ｍｍｏｌ／Ｌ［Ｋ＋］Ｏ作用１ｍｉｎ时增强达到最大,然后下降到对照。ＰＫＣ／ＰＣ变化时程不能用高钾引起的去极化解释,而与由相似［Ｋ＋］Ｏ引起的胞浆自由钙变化时程相符。提示,至少在蛙骨骼肌,高钾引起的咖啡因挛缩增强主要是由胞浆自由钙升高引起的。     

Varied diet and opportunistic foraging in the Ethiopian Bush-crow Zavattariornis stresemanni,an Endangered generalist

The Ethiopian Bush-crow Zavattariornis stresemanni is an endangered, co-operatively breeding southern Ethiopian endemic with a remarkably restricted range (c. 6 000 km²). The species’ range was recently found to be almost perfectly predicted by an envelope of cooler, drier and more seasonal climate than surrounding areas, but the proximate determinants of this range restriction remain unclear. We assessed whether specialisation in diet or foraging may restrict the range of the species by conducting foraging watches to determine prey composition, augmented by observations of opportunistic foraging techniques, and by comparing our results to previously published information on diet. Prey composition comprised a range of arthropods, such as insect larvae (62.7%), beetles (Coleoptera) (15.6%), and grasshoppers and crickets (Orthoptera) (11.8%). Prey was primarily obtained by pecks above ground (74.2%) but also frequently dug up (23.8%). Prey capture was most successful during pecks and we also found chicks were preferentially fed larger prey items over smaller ones by adults. We documented opportunistic behaviours such as nest-raiding and ox-pecking. Diet and foraging are varied and unspecialised, and therefore do not appear to explain the restricted range of the Ethiopian Bush-crow.     

The European Renal Genome Project: An Integrated Approach Towards Understanding the Genetics of Kidney Development and Disease

Rapid progress in genome research creates a wealth of information on the functional annotation of mammalian genome sequences. However, as we accumulate large amounts of scientific information we are facing problems of how to integrate and relate the data produced by various genomic approaches. Here, we propose the novel concept of an organ atlas where diverse data from expression maps to histological findings to mutant phenotypes can be queried, compared and visualized in the context of a three-dimensional reconstruction of the organ. We will seek proof of concept for the organ atlas by elucidating genetic pathways involved in development and pathophysiology of the kidney. Such a kidney atlas may provide a paradigm for a new systems-biology approach in functional genome research aimed at understanding the genetic bases of organ development, physiology and disease.Key Words: EuReGene, kidney, genome, development, pathophysiology, genetics