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131.
132.
Long-Evans rats were exposed to a single dose of head X-irradiation (600 rads) at 2 days of age. Experimental and sham irradiated rats were sacrificed at 14, 20-21, 23, 41-45, and 70-71 days. Tibial epiphyseal width and the number of cells in the epiphyseal plate were determined. Histochemical and electron microscopic studies were carried out on both costal and epiphyseal cartilage. Histochemical techniques revealed a reduction in chondroitin sulfate at 14 days in both costal and epiphyseal cartilage of X-irradiated rats. Epiphyseal cartilage demonstrated recovery subsequently, and this was followed by a normal decrease of chondroitin sulfate with increasing age, but costal cartilage did not recover. Collagen synthesis was also reduced in both costal and epiphyseal cartilage, but not as dramatically as chondroitin sulfate. Except for some electron dense cells and reduced scalloping of the cell membrane, costal chondrocytes from irradiated rats did not show major ultrastructural alterations. In contrast, epiphyseal chondrocytes demonstrated radiation induced alterations in organelles, in enhanced glycogen deposition, and in retardation of chondrocyte maturation. Extracellularly in both costal and epiphyseal cartilage of irradiated rats, collagen density and matrix granules were reduced, while calcification of the matrix was enhanced. Beyond 45 days, the effects of irradiation were markedly reduced. Comparisons of the histochemical results with metabolic studies carried out previously in cartilage from the same animals indicated a more direct concordance of the histochemical results with the pattern of physical growth and supported the usefulness of morphologic and histochemical techniques in the analysis of the growth disorder in the head-irradiated rat. 相似文献
133.
Timm Konold A Robin Sayers Amanda Sach Gemma E Bone Steven van Winden Gerald AH Wells Marion M Simmons Michael J Stack Angus Wear Steve AC Hawkins 《BMC veterinary research》2010,6(1):53
Background
Various clinical protocols have been developed to aid in the clinical diagnosis of classical bovine spongiform encephalopathy (BSE), which is confirmed by postmortem examinations based on vacuolation and accumulation of disease-associated prion protein (PrPd) in the brain. The present study investigated the occurrence and progression of sixty selected clinical signs and behaviour combinations in 513 experimentally exposed cattle subsequently categorised postmortem as confirmed or unconfirmed BSE cases. Appropriate undosed or saline inoculated controls were examined similarly and the data analysed to explore the possible occurrence of BSE-specific clinical expression in animals unconfirmed by postmortem examinations. 相似文献134.
Nitrous oxide (N2O) is primarily produced by the microbially-mediated nitrification and denitrification processes in soils. It is influenced by a suite of climate (i.e. temperature and rainfall) and soil (physical and chemical) variables, interacting soil and plant nitrogen (N) transformations (either competing or supplying substrates) as well as land management practices. It is not surprising that N2O emissions are highly variable both spatially and temporally. Computer simulation models, which can integrate all of these variables, are required for the complex task of providing quantitative determinations of N2O emissions. Numerous simulation models have been developed to predict N2O production. Each model has its own philosophy in constructing simulation components as well as performance strengths. The models range from those that attempt to comprehensively simulate all soil processes to more empirical approaches requiring minimal input data. These N2O simulation models can be classified into three categories: laboratory, field and regional/global levels. Process-based field-scale N2O simulation models, which simulate whole agroecosystems and can be used to develop N2O mitigation measures, are the most widely used. The current challenge is how to scale up the relatively more robust field-scale model to catchment, regional and national scales. This paper reviews the development history, main construction components, strengths, limitations and applications of N2O emissions models, which have been published in the literature. The three scale levels are considered and the current knowledge gaps and challenges in modelling N2O emissions from soils are discussed. 相似文献
135.
RENAN MILAGRES LAGE NOVAES JOSÉ PIRES DE LEMOS FILHO RENATA ACÁCIO RIBEIRO MARIA BERNADETE LOVATO 《Molecular ecology》2010,19(5):985-998
Little is known about past vegetation dynamics in Eastern Tropical South America (ETSA). Here we describe patterns of chloroplast (cp) DNA variation in Plathymenia reticulata, a widespread tree in the ETSA Atlantic Forest and Cerrado biomes, but not found in the xeromorphic Caatinga. Forty one populations, comprising 220 individuals, were analysed by sequencing the trnS‐trnG and trnL‐trnL‐trnF cpDNA regions. Combined, they resulted in 18 geographically structured haplotypes. The central region of the sampling area, comprising Minas Gerais and Goiás Brazilian states, is a centre of genetic diversity and probably the most longstanding area of the distribution range of the species. In contrast, populations from northeastern Brazil and the southern Cerrados showed very low diversity levels, almost exclusively with common haplotypes which are also found in the central region. Coupled with a long‐branched star‐like network, these patterns suggest a recent range expansion of P. reticulata to those regions from central region sources. The recent origin of the species (in the early Pleistocene) or the extinction of some populations due to drier and cooler climate during the last glacial maximum could have been responsible for that phylogeographic pattern. The populations from northeastern Brazil originated from two colonization routes, one eastern (Atlantic) and one western (inland). Due to its high diversity and complex landscape, the central region, especially central‐north Minas Gerais (between 15°–18° S and 42°–46° W), should be given the highest priority for conservation. 相似文献
136.
Background
The fish, Erythrinus erythrinus, shows an interpopulation diversity, with four karyomorphs differing by chromosomal number, chromosomal morphology and heteromorphic sex chromosomes. Karyomorph A has a diploid number of 2n = 54 and does not have differentiated sex chromosomes. Karyomorph D has 2n = 52 chromosomes in females and 2n = 51 in males, and it is most likely derived from karyomorph A by the differentiation of a multiple X1X2Y sex chromosome system. In this study, we analyzed karyomorphs A and D by means of cytogenetic approaches to evaluate their evolutionary relationship. 相似文献137.
Jennie Ursum Wouter H Bos Nancy van Dillen Ben AC Dijkmans Dirkjan van Schaardenburg 《Arthritis research & therapy》2010,12(1):R8
Introduction
To investigate whether baseline levels of anti-citrullinated protein antibody (ACPA) or IgM rheumatoid factor (IgM-RF) and changes in the year thereafter are associated with disease activity, functional and radiographic outcome in early arthritis patients, and provide additional information over baseline autoantibody status. 相似文献138.
Rebecca Nedellec Mia Coetzer Michael M. Lederman Robin E. Offord Oliver Hartley Donald E. Mosier 《Journal of virology》2010,84(11):5842-5845
Resistance of human immunodeficiency virus type 1 (HIV-1) to small-molecule CCR5 inhibitors is well demonstrated, but resistance to macromolecular CCR5 inhibitors (e.g., PSC-RANTES) that act by both CCR5 internalization and receptor blockade had not been reported until recently (3). The report of a single simian-human immunodeficiency virus SHIVSF162-p3 variant with one V3 and one gp41 sequence change in gp160 that conferred both altered replicative fitness and resistance to PSC-RANTES was therefore surprising. We introduced the same two mutations into both the parental HIV-1SF162 and the macaque-adapted SHIVSF162-p3 and found minor differences in entry fitness but no changes in sensitivity to inhibition by either PSC-RANTES or the small-molecule allosteric inhibitor TAK-779. We attribute the earlier finding to confounding fitness effects with inhibitor sensitivity.A recent study by Dudley et al. (3) claimed to be “the first to describe the immediate selection and infection of a drug-resistant SHIV [simian-human immunodeficiency virus] variant in the face of a protective vaginal microbicide, PSC-RANTES.” The article further concluded, “This rhesus CCR5-specific/PSC-RANTES resistance selection is particularly alarming given the relative homogeneity of the SHIVSF162-p3 stock compared to the potential exposure to a heterogeneous HIV-1 [human immunodeficiency virus type 1] population in human transmission.” The study described a SHIVSF162-p3 variant with two amino acid substitutions, K315R in the V3 loop region (present as a minor component of the p3 challenge stock) and N640D in HR2 of gp41, that conferred greater replicative fitness and greater relative resistance to both the CCR5 inhibitor PSC-RANTES (to which the single macaque harboring this variant had been exposed prior to infection) and the small-molecule allosteric CCR5 inhibitor TAK-779 (1).While the development of HIV-1 strains resistant to small-molecule CCR5 inhibitors has been observed (11, 14), this result was surprising for several reasons. First, the inhibitory mechanism of PSC-RANTES is different from those of the small-molecule allosteric inhibitors; the ability of the macromolecule to induce profound and prolonged intracellular coreceptor sequestration, together with its ability to sterically block coreceptor use, should provide additional barriers to the development of resistant viruses that retain use of CCR5 (10). Second, this interpretation is supported by the failure to generate PSC-RANTES-resistant strains in multiple long-term in vitro selection studies (R.N. and D.E.M., unpublished results). Finally, the development of escape mutants in an in vivo setting would be expected to require sustained inhibitory concentrations of the drug at sites of replication. The Dudley et al. study was based on a single-dose experiment under conditions in which even at the highest dose used, no detectable systemic exposure occurred (6).The determination of resistance can be confounded by the fitness of a virus isolate (7), and the claim of resistance to PSC-RANTES was surprising given that infection with the parental HIV-1SF162 isolate with the consensus GPGR315 sequence is highly susceptible to PSC-RANTES inhibition (D.E.M., unpublished data) (Fig. (Fig.11 and Table Table1).1). These concerns prompted us to determine the impact of the K315R and N640D sequence variants on the entry fitness and sensitivity of both HIV-1SF162 and SHIVSF162-p3 to PSC-RANTES or TAK-779 in a single-round infection assay using either human or rhesus CCR5-expressing U87.CD4 target cells. We felt that it was important to extend the experiments of Dudley et al. (3) to HIV-1 since it is inhibition of HIV-1 infection of humans that is the intended application of a microbicide containing PSC-RANTES or related recombinant molecules (4, 12). We used site-directed mutagenesis to create three variants of the wild-type SF162 env sequence (R315, N640): K315, N640; R315, D640 (equivalent to the “resistant” SHIVSF162-p3 variant from macaque 584), and K315, D640. These four env genes were used to complement a luciferase reporter HIV-1 construct in a standard single-round infection assay that has the advantage of a dynamic range of up to 8 logs (9, 15). We found that D640 conferred a small but significant entry advantage over N640 in the single-cycle assay (Table (Table1),1), in agreement with the results reported by Dudley et al. (3). However, none of the SF162 mutations conferred any significant resistance to either PSC-RANTES or TAK-779 (Fig. (Fig.11 and Table Table1),1), whether or not we corrected for the modest difference in entry efficiency. We repeated these experiments using the SHIVSF162-p3 env clone that has the same sequence as that used in the experiments of Dudley et al. (3, 5) to determine if the finding of resistance was related to the other sequence differences between the macaque-adapted SHIV and SF162. Neither R315, D640, nor the combination of the two “resistance” mutations conferred resistance to either PSC-RANTES or TAK-779 on target cells expressing either human or rhesus CCR5 (Table (Table11 and Fig. 1C and D). The D640 substitution again conveyed a small entry advantage over N640 (data not shown). We thus conclude that the two mutations in SHIVSF162-p3 that were claimed to confer resistance to PSC-RANTES using either human or rhesus CCR5 for entry were selected by replicative fitness in macaque 584 and not by drug resistance. We find no evidence that the two mutations have any impact on the PSC-RANTES sensitivity of either HIV-1SF162 or SHIVSF162-p3 (Fig. (Fig.1),1), and we were unable to confirm the 5.5-fold increase in resistance to PSC-RANTES on target cells expressing human CCR5 or the 7-fold increase on target cells expressing rhesus CCR5 reported by Dudley et al. (3). We therefore attribute the conclusions of Dudley et al. (3) to confounding fitness effects with inhibitor sensitivity. Multiple rounds of replication in the assays employed by Dudley et al. (3) likely amplified the relatively minor differences in entry fitness that we (and they) observed and made the precise assessment of 50% inhibitory concentration (IC50) values more difficult, particularly given that 10-fold dilutions of inhibitors were used in their experiments.Open in a separate windowFIG. 1.Inhibition of HIV-1SF162 env mutants by PSC-RANTES. (A) Single-round infection assay performed with U87.CD4.human CCR5 target cells using the four SF162 sequence variants with half-log dilutions of PSC-RANTES added 30 min prior to infection. Data are relative light units (RLU) and are summarized in a different format in the first row of data in Table Table1.1. (B) Means ± standard errors (SE) of the 50% inhibitory concentration of PSC-RANTES on each SF162 variant from three replicate experiments plotted as the reciprocal of the log IC50 (pIC50) in moles. Higher pIC50 values indicate greater sensitivity to inhibition, but the differences depicted are not statistically significant. (C) Means ± SE of the 50% inhibitory concentrations of PSC-RANTES from three replicate experiments using the four sequence variants of SHIVSF162-p3 with target cells expressing human CCR5. Note the different order of the columns for the SHIVSF162-p3 variants; the “wild-type” SHIV has a different V3 sequence than the “wild-type” HIV-1SF162, as well as 31 amino acid substitutions in other regions of envelope (5). (D) Means ± SE of the 50% inhibitory concentration of PSC-RANTES from three replicate experiments using the four sequence variants of SHIVSF162-p3 with rhesus CCR5-expressing U87.CD4 target cells. WT, wild type; M, moles.
Open in a separate window
Open in a separate windowaCorrected virus input for infectivity differences; equal relative light units (RLU).bThe 95% confidence intervals (CI) of sigmoidal curve fitting (Prism 5.0, GraphPad) of triplicate values for each inhibitor concentration are shown.cr2, correlation coefficient for the individual data points fitted to the calculated inhibition curve.dVirus input not corrected for minor increases (∼0.3 log RLU) in infectivity associated with D640.eRLU at equivalent p24 content of pseudoviruses containing the four variant HIV-1SF162 env sequences. Titration of input viruses showed parallel slopes of infectivity (RLU versus input p24; data not shown). SEM, standard error of the mean.fEntry via rhesus CCR5 was lower than via human CCR5 because of lower expression levels following transient transfection as opposed to stable transduction; no adjustment for infectivity was necessary, because all four SHIV162-p3 envelopes mediated similar entry.We observed similar inhibitory activity of PSC-RANTES on entry of both HIV-1SF162 and SHIVSF162-p3 via both human and macaque CCR5, even though SHIVSF162-p3 has many mutations in env that occurred during multiple passages in macaques (5), and macaque CCR5 has 7 to 8 amino acid differences from human CCR5 (8, 13), including one polymorphic site that contributes to resistance to small-molecule CCR5 inhibitors (2). While it is possible that selection for either fitness or resistance to CCR5 inhibitors may show subtle differences between SHIV-infected macaques and HIV-1 infected humans, and may even vary between macaques with different CCR5 alleles, no such differences were observed in our experiments. Although we were unable to achieve the very high levels of macaque CCR5 expression reported by Dudley et al. (3), differences in coreceptor levels would be expected to affect all four SHIVSF162-p3 variants equally. Our results argue strongly that there is no simple mutational pathway that results in resistance to PSC-RANTES for either HIV-1SF162 or SHIVSF162-p3. We conclude that the results reported by Dudley et al. (3) give no cause for concern about the development of resistance to microbicides containing PSC-RANTES or similar compounds. 相似文献
TABLE 1.
HIV-1 SF162 or SHIVSF162-p3 V3 and/or HR2 mutations do not confer resistance to CCR5 inhibitors for entry via either human or rhesus CCR5Parameter | Result for indicated variant | |||
---|---|---|---|---|
HIV-1SF162 (R315+N640) “wild type” | HIV-1SF162 (K315+N640) “SHIVp3 like” | HIV-1SF162 (R315+D640) “resistant variant” | HIV-1SF162 (K315+D640) D640 gp41 change | |
Human CCR5 | ||||
PSC-RANTESa IC50 (pM) (95% CIb) | 36 (21-60) | 18 (5.7-55) | 29 (20-42) | 13 (3.5-47) |
r2c | 0.936 | 0.868 | 0.964 | 0.899 |
TAK-779 IC50 (nM) (95% CI) | 0.24 (0.11-0.53) | 0.28 (0.14-0.55) | 0.39 (0.10-1.50) | 0.39 (0.12-1.20) |
r2 | 0.896 | 0.919 | 0.858 | 0.842 |
PSC-RANTESd IC50 (pM) (95% CI) | 65 (47-92) | 82 (56-120) | 79 (49-130) | 66 (44-100) |
r2 | 0.937 | 0.893 | 0.918 | 0.937 |
Mean log RLU (±SEM)e | 6.631 (0.047) | 6.636 (0.019) | 6.977 (0.026) | 6.952 (0.023) |
SHIVSF162-p3 (R+N) R315 V3 change | SHIVSF162-p3 (K+N) SHIV “wild type” | SHIVSF162-p3 (R+D) “resistant variant” | SHIVSF162-p3 (K+D) D640 gp41 change | |
---|---|---|---|---|
PSC-RANTESa IC50 (pM) (95% CI) | 26 (16-43) | 21 (15-28) | 16 (10-28) | 23 (15-35) |
r2 | 0.918 | 0.969 | 0.904 | 0.939 |
TAK-779 IC50 (nM) (95% CI) | 0.69 (0.47-1.02) | 0.46 (0.28-0.77) | 0.60 (0.32-1.13) | 0.68 (0.46-0.99) |
r2 | 0.949 | 0.921 | 0.877 | 0.949 |
Rhesus CCR5 | ||||
PSC-RANTES IC50 (pM) (95% CI) | 14 (0.4-50) | 65 (14.5-294) | 3.09 (1.4-7.1) | 9.89 (0.5-20.4) |
r2 | 0.690 | 0.615 | 0.839 | 0.866 |
Mean log RLUf (±SEM) | 4.80 (0.245) | 4.58 (0.519) | 4.66 (0.360) | 4.74 (0.517) |
139.
140.
Nitrogen (N) availability is a key role in food and fiber production. Providing plant-available N through synthetic fertilizer in the 20th and early 21st century has been a major contributor to the increased production required to feed and clothe the growing human population. To continue to meet the global demands and to minimize environmental problems, significant improvements are needed in the efficiency with which fertilizer N is utilized within production systems. There are still major uncertainties regarding the fate of fertilizer N added to agricultural soils and the potential for reducing losses to the environment. Enhancing the technical and economic efficiency of fertilizer N is seen to promote a favorable situation for both agricultural production and the environment, and this has provided much of the impetus for a new N fertilizer project. To address this important issue, a rapid assessment project on N fertilizer (NFRAP) was conducted by SCOPE (the Scientific Committee on Problems of the Environment) during late 2003 and early 2004. This was the first formal project of the International Nitrogen Initiative (INI). As part of this assessment, a successful international workshop was held in Kampala, Uganda on 12 - 16 January, 2004. This workshop brought together scientists from around the world to assess the fate of synthetic fertilizer N in the context of overall N inputs to agricultural systems, with a view to enhancing the efficiency of N use and reducing negative impacts on the environment. Regionalization of the assessment highlighted the problems of too little N for crop production to meet the nutrient requirements of sub-Saharan Africa and the oversupply of N in the major rice-growing areas of China. The results of the assessment are presented in a book (SCOPE 65) which is now available to provide a basis for further discussions on N fertilizer. 相似文献