The effect of the source of nitrogen supplementation on nitrogen balance,rates of plasma leucine turnover,protein synthesis and degradation in sheep

Combined experiments of the isotope dilution method of [1-¹³C]leucine, open-circuit calorimetry and nitrogen (N) balance test were used to determine the effect of the source of N supplementation on N balance, whole body protein synthesis (WBPS) and degradation (WBPD) in sheep. The experiment was performed in a replicated 3 × 3 Latin square design. The control diet consisted of timothy hay, ground maize and soybean meal. The urea diet was the control diet supplemented with 1.5% urea. The SBM diet contained the same N and metabolisable energy as the urea diet, which was reached by changing ground maize and soybean meal weights of the control diet. Nitrogen retention was greater (p < 0.05) for the urea diet than the control and SBM diets. Plasma urea concentrations were highest for the SBM diet, followed by the urea diet, and the control diet was lowest. The WBPS and WBPD did not differ between diets, but were numerically lower for the urea and SBM diets. These results suggest that in sheep, urea supplementation influenced N retention without clear changes in WBPS and WBPD.     

Downscaling Aggregate Urban Metabolism Accounts to Local Districts

Urban metabolism accounts of total annual energy, water, and other resource flows are increasingly available for a variety of world cities. For local decision makers, however, it may be important to understand the variations of resource consumption within the city. Given the difficulty of gathering suburban resource consumption data for many cities, this article investigates the potential of statistical downscaling methods to estimate local resource consumption using socioeconomic or other data sources. We evaluate six classes of downscaling methods: ratio‐based normalization; linear regression (both internally and externally calibrated); linear regression with spatial autocorrelation; multilevel linear regression; and a basic Bayesian analysis. The methods were applied to domestic energy consumption in London, UK, and our results show that it is possible to downscale aggregate resource consumption to smaller geographies with an average absolute prediction error of around 20%; however, performance varies widely by method, geography size, and fuel type. We also show how mapping these results can quickly identify districts with noteworthy resource consumption profiles. Further work should explore the design of local data collection strategies to enhance these methods and apply the techniques to other urban resources such as water or waste.     

Excretion of radiolabeled estradiol in the cat (Felis catus,L): A preliminary report

The time course and end products of estradiol metabolism were studied in the domestic cat, which has been chosen as a model for steroid metabolism studies in nondomestic felidae. Radiolabeled estradiol was injected intravenously into three adult female cats; one had a spontaneous estrus, one was induced with follicle-stimulating hormone, and one had been ovariohysterectomized; feces, urine, and blood were collected daily, and the radioactivity content was determined. Feces and urine contained 47 and 1% of the injected dose (0.33 μCi), respectively. Metabolites appeared earlier in the urine than in feces (d 1 vs d 2 postinjection), and excretion was completed on d 5; no radioactivity was detected in plasma 24 h postinjection. Estradiol metabolites were excreted as unconjugated estrogens (22%) and as conjugates hydrolyzable with β-glucuronidase and acid solvolysis (7 and 50%, respectively); the remaining 14% were not recoverable with any of the above methods. The major portion of the conjugates was estradiol-17β (64–80%) while 11–16% appeared as estrone. Endogenous cycles related to the spontaneous and induced ovarian activity were monitored by observation of estrous behavior, vaginal epithelium cornification, and plasma estradiol determination. The reproductive state of each animal had no effect on the time course or type of metabolite excreted. We found low proportions of injected radioactivity excreted in the urine and high residual levels remaining after hydrolysis and extraction in the feces. These findings suggest that although feces are an abundant source of estradiol metabolite in the cat, and probably in the exotic felidae, development of noninvasive methods for monitoring ovarian cycles in these species will depend on more efficient methods for urine hydrolysis, on the resolution of problems encountered in fecal steroid analysis, or on the identification of metabolites which may be measured directly in the urine without hydrolysis or extraction.     

外源H2O2对盐碱混合胁迫下裸燕麦幼苗生长和抗性生理的影响

为探讨信号分子过氧化氢（H₂O₂）增强裸燕麦盐碱耐性的作用及其生理机制,以裸燕麦品种‘定莜6号’为材料,在日光温室内用珍珠岩培养幼苗至三叶一心期时叶面喷施0.01 mmol·L^-1 H₂O₂的同时根部浇灌75 mmol·L^-1盐碱混合溶液（NaCl：Na₂SO₄：NaHCO₃：Na₂CO₃=12：8：9：1）或添加H₂O₂淬灭剂二甲基硫脲（DMTU）,研究对幼苗生长及叶片光合色素含量、活性氧代谢和渗透调节物质积累的影响。结果表明：喷施H₂O₂能够缓解盐碱混合胁迫对裸燕麦幼苗生长的抑制,提高幼苗根长、株高和植株干重及叶片叶绿素a、叶绿素b、总叶绿素、类胡萝卜素含量和超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶活性,降低超氧阴离子、H₂O₂、丙二醛、抗坏血酸、谷胱甘肽和游离氨基酸含量,促进抗氧化物质类黄酮、总酚和原花青素及渗透调节物质可溶性蛋白质、可溶性糖和脯氨酸积累。添加DMTU部分或完全逆转了H₂O₂的上述作用。采用隶属函数综合评价显示,喷施H₂O₂提高了盐碱混合胁迫下裸燕麦幼苗的综合评价值D,添加DMTU完全逆转了H₂O₂对D值的提升作用。表明外源H₂O₂通过参与活性氧代谢和渗透调节物质积累等生理代谢调控缓解盐碱混合胁迫诱导的氧化伤害和生长抑制,从而提高裸燕麦对盐碱胁迫的适应能力。     

Endogenous indoles and the biosynthesis and metabolism of indole-3-acetic acid in cultures of Rhizobium phaseoli

Gas chromatography-mass spectrometric analyses of purified extracts from cultures of Rhizobium phaseoli wild-type strain 8002, grown in a non-tryptophan-supplemented liquid medium, demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol (IEt), indole-3-aldehyde and indole-3-methanol (IM). In metabolism studies with ³H-, ¹⁴C- and ²H-labelled substrates the bacterium was shown to convert tryptophan to IEt, IAA and IM; IEt to IAA and IM; and IAA to IM. Indole-3-acetamide (IAAm) could not be detected as either an endogenous constituent or a metabolite of [³H]tryptophan nor did cultures convert [¹⁴C]IAAm to IAA. Biosynthesis of IAA in R. phaseoli, thus, involves a different pathway from that operating in Pseudomonas savastanio and Agrobacterium tumefaciens-induced crown-gall tumours.Abbreviations IAA indole-3-acetic acid - IAld indole-3-aldehyde - IAAm indole-3-acetamide - IEt indole-3-ethanol - IM indole-3-methanol - HPLC-RC high-performance liquid chromatography-radio counting - GC-MS gas chromatography-mass spectrometry     

Thyroid hormone regulation of cell migration and oxidative metabolism in polymorphonuclear leukocytes: clinical evidence in thyroidectomized subjects on thyroxine replacement therapy

Migration and superoxide anion (O2-) generation were studied in polymorphonuclear leukocytes (PMNs) from 14 athyreotic patients, previously treated by total thyroidectomy and radioiodine therapy for differentiated thyroid carcinoma, and from age- and sex-matched euthyroid healthy controls. Patients were studied twice: in hypothyroidism (visit 1) and after TSH-suppressive L-T4 replacement therapy (visit 2). Random migration and N-formyl-Met-Leu-Phe (fMLP) 0.1-microM induced chemotaxis were similar in cells from patients at both visit 1 and visit 2 and from healthy controls. On the contrary, resting O2- generation in cells from patients was significantly lower than control values, both at visit 1 and 2. At visit 1, fMLP 0.1 muM-induced O2- generation was significantly lower than control values, while phorbol-myristate acetate (PMA) 100-ng/ml induced O2- generation was similar in cells from patients and from controls. At visit 2 both responses increased, resulting in fMLP-induced O2- generation superimposable to control values and PMA-induced O2- generation significantly higher with respect to both visit 1 and cells from controls. In vitro exposure of PMNs from healthy subjects to L-T4 did not affect O2- generation in resting cells, and significantly increased that induced by fMLP or PMA only at high, supra-physiological concentrations. Neither TSH nor T3 had significant effects at any of the concentrations tested. The present results document the existence of a correlation between thyroid status and oxidative metabolism of human PMNs, which is however unlikely to depend upon a direct action of thyroid hormones on these cells.     

Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves ofClusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela

Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (), hydrogen isotope ratio (D) and N-levels, and with altitude were assessed. In the samples, where values of above 15 indicate predominant performance of C₃ photosynthesis, there were slight tendencies of increasing , D and N-levels with increasing altitude and of increasing with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of with altitude in the samples, where values of below 10 indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C₃-CAM transitions in C₃/CAM intermediate species, low availability of water is the most important.     

Proteomics of chloroplast envelope membranes

Proteomics is a very powerful approach to link the information contained in sequenced genomes, like Arabidopsis, to the functional knowledge provided by studies of plant cell compartments, such as chloroplast envelope membranes. This review summarizes the present state of proteomic analyses of highly purified spinach and Arabidopsis envelope membranes. Methods targeted towards the hydrophobic core of the envelope allow identifying new proteins, and especially new transport systems. Common features were identified among the known and newly identified putative envelope inner membrane transporters and were used to mine the complete Arabidopsis genome to establish a virtual plastid envelope integral protein database. Arabidopsis envelope membrane proteins were extracted using different methods, that is, chloroform/methanol extraction, alkaline or saline treatments, in order to retrieve as many proteins as possible, from the most to the less hydrophobic ones. Mass spectrometry analyses lead to the identification of more than 100 proteins. More than 50% of the identified proteins have functions known or very likely to be associated with the chloroplast envelope. These proteins are (a) involved in ion and metabolite transport, (b) components of the protein import machinery and (c) involved in chloroplast lipid metabolism. Some soluble proteins, like proteases, proteins involved in carbon metabolism or in responses to oxidative stress, were associated with envelope membranes. Almost one third of the newly identified proteins have no known function. The present stage of the work demonstrates that a combination of different proteomics approaches together with bioinformatics and the use of different biological models indeed provide a better understanding of chloroplast envelope biochemical machinery at the molecular level.     

Resting Energy Expenditure: Systematic Organization and Critique of Prediction Methods

There are many published methods for predicting resting energy expenditure (REE) from measured body composition. Although these published reports extend back almost a century, new related studies appear on a regular basis. It remains unclear what the similarities and differences are among these various methods and what, if any, advantages the newly introduced REE prediction models offer. These issues led us to develop an organizational system for REE prediction methods with the goal of clarifying prevailing ambiguities in the field. Our classification scheme is founded on body composition level (whole‐body, tissue‐organ, cellular, and molecular) and related components as the REE predictor variables. Each existing REE prediction method by body composition must belong to one body composition level. The suggested classification system, founded on a conceptual basis, highlights similarities and differences among the diverse REE‐body composition prediction methods, provides a framework for teaching REE‐body composition relationships, and identifies important future research opportunities.