生物修复菌剂的分类·应用及研究进展

由于人类的生产与社会活动,使得我们生存的自然环境遭到了前所未有的破坏。鉴于采用物理或化学方法修复环境,除去有害物质,易造成二次污染,寻找高效的生物修复方法成为了全世界的共同课题。微生物作为生态链中的分解者,由于其具有易繁殖、适应性强、代谢快等特性,是作为生物修复的极佳材料。对生物修复菌剂的分类、生产、应用及研究进展进行了综述。     

微生物代谢尼古丁的研究及其应用

尼古丁是烟叶中最主要的生物碱,也是影响烟叶品质的重要因素,其含量过高不但影响吸食的安全性,而且对环境也会造成危害。有些微生物能在烟叶醇化过程中代谢尼古丁,降低尼古丁的含量,而不影响烟叶原有的品质,并降低其对人类健康的危害。因此,尼古丁降解微生物有着非常好的应用潜力。本文综述了国内外尼古丁代谢微生物的种类、代谢途径、酶学研究、遗传研究以及相关应用研究的进展情况,展示了微生物方法和技术在处理烤烟尼古丁中的应用前景。     

Effects of a high-protein, low-energy diet in finishing lambs: 1. Feed intake, estimated nutrient uptake, and levels of plasma metabolites and metabolic hormones

Patterns of tissue mobilisation in ruminants are ill-understood. This hinders nutritional management to mitigate the effects of energy deprivation on protein mass, and nutritional regimens designed to change body composition. An experiment was conducted to comprehensively evaluate the effects of a low-energy high-protein diet in growing lambs. Three diets (CON = concentrate diet ad libitum, STR = straw ad libitum, SFM = straw ad libitum plus 150 g/d fish meal) were fed to growing white-face lambs. Analysis of feed intake and metabolite data provided evidence that greater available N did not have a synergistic effect on intake of low quality forage. Metabolite and hormone profiles of lambs in negative energy balance, supplemented with duodenally available protein, revealed that SFM animals did not respond with an accelerated rate of fat mobilization or maintain protein mass due to available N. This was particularly evident from the leptin profiles, which indicated higher circulating leptin levels for SFM compared to STR animals. Further, the data revealed that in sheep fed below requirements for maintenance, leptin levels did not correspond with acute ME intake, whereas the opposite was true for well-fed animals. Conversely, the response of the GH/IGF-1 axis to high protein–energy ratio (PER) diets was indicative of effects not explained by the difference in energy provided by the two experimental diets.

These results contrast with observations from intra-gastric infusion experiments testing similar PERs and previous conventional feeding trials and provide evidence of: (1) specific differences associated with PER in lambs fed via intra-gastric infusion vs. a conventional feeding approach, and (2) lack of usefulness of high PER diets in the post hoc modification of body composition of growing lambs. While positive N balance is known to occur in ruminants in negative energy balance, the determinants of relative proportions of muscle and adipose tissue catabolised under energy deprivation remain unknown.     

Altered tryptophan metabolism in FIV-positive cats

BACKGROUND: Feline immunodeficiency virus (FIV) is analogous to human immunodeficiency virus, the causative agent of human acquired immunodeficiency syndrome (AIDS). In AIDS patients, a progressive reduction in serum tryptophan concentration occurs because of activation of an inducible tryptophan degradation pathway mediated by elevated lamda-interferon production. HYPOTHESIS: Cats infected with FIV have increased tryptophan catabolism evidenced by reduced circulating concentrations of tryptophan and increased concentrations of the tryptophan catabolite kynurenine. ANIMALS: Convenience sample of 235 cats submitted for diagnostic FIV serology (115 FIV-negative and 120 FIV-positive cats). METHODS: Retrospective, cross-sectional study. Serum was assayed for tryptophan and kynurenine using a high performance liquid chromatography assay with fluorescence and ultraviolet detection, respectively. RESULTS: Tryptophan and kynurenine concentrations were log-normally distributed. Geometric mean concentrations were: tryptophan: FIV-positive 30.6 microM (95% CI: 26.8 34.8 microM), FIV-negative 48.9 [microM (95% CI: 43.6-54.9 microM) (P < .001); kynurenine: FIV-positive 22.7 microM (95% CI: 25.5-10.9 microM), FIV-negative 9.9 microM (95% CI: 20.3-9.03 microM) (P < .001). The ratio of kynurenine to tryptophan was: FIV-positive 4.93 (95% CI: 5.62-4.32), FIV-negative 1.34 (95% CI: 1.53 1.17) (P < .0001). CONCLUSIONS AND CLINICAL IMPORTANCE: Serum tryptophan concentration was significantly lower and serum kynurenine concentration was significantly higher in FIV-positive cats. The kynurenine: tryptophan ratio was >3-fold higher in FIV-positive animals, indicating increased tryptophan catabolism in this group. Dietary or pharmacologic intervention to support serum tryptophan concentrations has been shown to be clinically useful in humans with AIDS and might be applicable to cats with FIV infection.     

In vitro oxidation of essential amino acids by jejunal mucosal cells of growing pigs

This study was conducted to test the hypothesis that porcine jejunal mucosal cells can degrade all essential amino acids (EAA). Jejunal mucosal cells (primarily enterocytes) were isolated from 50-day-old healthy pigs and incubated at 37 °C for 45 min in Krebs buffer containing plasma concentrations of amino acids and one of the following l-[1-¹⁴C]- or l-[U-¹⁴C]-amino acids plus unlabeled tracers at 0.5, 2, or 5 mM: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. There was active transamination of leucine, isoleucine and valine in the cells (1.35–2.5 nmol/mg protein per 45 min at 2 mM), with most (67–71%) of their -ketoacids released into the medium. In contrast, catabolism of methionine and phenylalanine was negligible (0.04–0.05 nmol/mg protein per 45 min at 2 mM) and that of other EAA was completely absent in these cells. These results indicate that intestinal mucosal cells are a site for the substantial degradation of branched-chain amino acids but not other EAA in pigs.     

Increased microbial catabolic activity in diesel contaminated soil following addition of earthworms (Dendrobaena veneta) and compost

This study sought to assess the influence of compost and earthworms (Dendrobaena veneta) upon the level of hydrocarbon catabolism in petroleum contaminated forecourt soil (extractable petroleum hydrocarbons (EPH) 10 + 1.8 g kg⁻¹ and total 16 United States Environment Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAH) 1.62 ± 0.5 g kg⁻¹). The catabolic activity of the indigenous microorganisms within uncombined materials (soil and compost) and within the combined treatments (soil plus compost; either with or without earthworms) was assessed by ¹⁴C-radiorespirometry (¹⁴C-hexadecane, ¹⁴C-toluene and ¹⁴C-phenanthrene). Maximum levels of catabolic activity were observed (at the end of the incubation period; 84 d) for all three compounds in the combined contaminated soil, compost and earthworm mixtures. Significant (p < 0.05) enhancement factors (relative to the soil only control) in catabolic activity in the combined treatments (soil:compost (1:0.5)) of 3.6 times, 1.5 times and 3.5 times were observed for ¹⁴C-hexadecane, ¹⁴C-phenanthrene and ¹⁴C-toluene, respectively; with maximum levels of catabolic activity for these substrates being 68.6 ± 1.7%, 37.9 ± 5.3% and 85.9 ± 1.3%.     

高等植物脱落酸的代谢及调节机制

脱落酸(ABA)在种子的发育、休眠、萌发以及植物的营养生长、环境胁迫响应等过程中具有重要作用,植物体具有控制ABA的合成、降解、信号感知及其信号转导的调节机制。目前对高等植物ABA的合成途径及其调节机制的研究已比较深入,合成途径中的所有关键酶基因都已鉴定出,但对ABA分解代谢的研究则相对滞后。概述了ABA的生物合成、分解代谢途径及其调节机制。     

氟中毒对家蚕幼虫中肠组织糖原分解代谢调节的影响

用酶偶合系统测定了氟中毒对家蚕幼虫中肠组织糖原磷酸化酶活性的影响，其结果人氟中毒使中肠糖原磷酸化酶ａ型和ｂ型的活性均明显下降，特别是ｂ型的活性下降幅度较大。由此时以认为，氟中毒抑制了家蚕幼虫中肠组织内糖的分解代谢，使细胞的能量供应减少。     

母仔猪精氨酸的生理代谢与营养作用

精氨酸又称蛋白氨基酸,传统上,精氨酸不被认为是母仔猪的必需氨基酸,但是现代品种的猪生长更快,瘦肉率更高,孕育的胎儿更多,因此,对精氨酸有更高的生理需求量。大量研究表明,日粮中添加0.5%至1%精氨酸可以改善母仔猪的生产性能和繁殖性能。文章综合论述了母仔猪精氨酸的生理代谢和营养作用。