Heart rate variability parameters as markers of the adaptation to a sealed environment (a hypoxic normobaric chamber) in the horse

Simulated hypoxic normobaric devices have been used in human beings in order to enhance endurance capacity. These devices are sealed chambers where the athletes are supposed to stay for at least 6–8 hr daily. The current research assesses the changes in time‐domain, spectral and non‐geometrical heart rate variability (HRV) parameters in 6 horses subjected to progressive duration periods inside of a hermetically sealed chamber. It was pursued, firstly to evaluate the intensity of the stress experienced by the animals and secondly to elucidate whether the horses might require an acclimation period before implementation of hypoxic conditions. HRV parameters were monitored for 6 days: day 0 (6‐hr duration; in paddocks; basal conditions), and days 1, 2, 3, 4 and 5 (1, 2, 3, 4 and 6 hr inside the chamber every day respectively). During day 1 and during the first hours of days 2 and 3, compared to day 0, horses presented increased HR and SDHR values and decreased RR interval duration. SD1 values decreased on some hours of days 2 and 3, but differences with day 0 were not found on day 1. Increased SDNN, RMSSD, SD1 and SD2 values were observed on days 4 and 5. These results showed an activation of the sympathetic activity together with an attenuation of the parasympathetic activity during the days 1 to 3. Increased parasympathetic activity was found only during the first hours of days 4 and 5. Spectral parameters experienced minor variations, with increased LF_peak and LF% during some hours of days 4 and 5. In conclusion, at least 3 days are needed to adapt the horse to a sealed environment before starting to subject the animals to hypoxic conditions. When the horses were acclimatized, however, a minor stress was detected with they spent more than 4 hr inside of the chamber.     

Linkage disequilibrium and effective population size in Gir cattle selected for yearling weight

Linkage disequilibrium (LD) plays an important role in genomic selection and mapping of quantitative trait loci (QTL). This study investigated the pattern of LD and effective population size (N_e) in Gir cattle selected for yearling weight. For this purpose, 173 animals with imputed genotypes (from 18 animals genotyped with the Illumina BovineHD BeadChip and 155 animals genotyped with the Bovine LDv4 panel) were analysed. The LD was evaluated at distances of 25–50 kb, 50–100 kb, 100–500 kb and 0.5–1 Mb. The N_e was estimated based on 5 past generations. The r² values (a measure of LD) were, respectively, .35, .29, .18 and .032 for the distances evaluated. The LD estimates decreased with increasing distance of SNP pairs and LD persisted up to a distance of 100 kb (r² = .29). The N_e was greater in generations 4 and 5 (24 and 30 animals, respectively) and declined drastically after the last generation (12 animals). The results showed high levels of LD and low N_e, which were probably due to the loss of genetic variability as a consequence of the structure of the Gir population studied.     

不同放牧强度下羊草十大针茅草地植被与土壤氮素的空间异质性分析

以河北坝上的羊草(Leymus chinensis)+大针茅(Stipa grandis)典型草原为研究对象,用方差和地统计分析相结合的方法,研究了不同放牧强度对植被和土壤氮素的空间分布格局的影响.结果表明,植被密度与土壤氮素的变异函数大多符合球状和指数模型;轻牧与中牧的植被群落密度的空间分布受随机因素的影响较大,禁牧与重牧地受空间结构性因素影响较大,但重牧区土壤氮素的空间分布受随机因素影响相对较大;放牧降低了植被密度的空间异质性,而禁牧区的空间异质性(基台值0.116 8)大于放牧区(基台值均值0.019 5);随放牧强度的增加,土壤铵态氮、硝态氮的空间异质性均呈降低-增加的趋势,且重牧明显增加了土壤铵态氮和硝态氮的空间异质性,基台值分别为5.642 0和2.681 0,大于其余3个处理铵态氮和硝态氮的均值(0.315 8和0.168 7);整体上,在相同放牧处理的植被密度与土壤硝态氮的空间分布有相近的变化趋势.     

准噶尔荒漠区域尺度浅层土壤化学计量特征及其空间分布格局

干旱荒漠生态系统具有降水稀少、土壤贫瘠、生物多样性低的特点,对荒漠土壤生态化学计量特征的研究有助于深入了解荒漠土壤养分供给能力及其对生物多样性和生态系统稳定性的影响。对准噶尔荒漠79个样点浅层(0~10cm)土壤及环境因子进行调查取样,分析了土壤有机碳(C)、全氮(N)及全磷(P)化学计量特征、空间分布及其影响因素。结果表明,准噶尔荒漠土壤C、N、P平均含量分别为(5.73±0.49),(0.207±0.009)和(0.347±0.004)g/kg,C∶N、C∶P、N∶P分别为(29.92±2.55),(15.97±1.23)和(0.498±0.024)。土壤P稳定性最高(CV=0.098),而C、C∶N和C∶P的变异性较强(CV=0.687~0.758)。C、P、C∶N及C∶P在不同生境(沙漠、戈壁和盐碱荒漠)、不同群落(白梭梭、梭梭及小灌木)间均存在差异。与全国及全球平均水平相比,准噶尔荒漠土壤C、N、P含量、C∶P及N∶P均较低而C∶N较高,养分元素缺乏程度表现为NCP。土壤养分元素及其化学计量比之间多具有显著的二次函数关系,且化学计量比主要受C和N的制约。在区域尺度上,各化学计量参数表现出明显的空间异质性,其中C、C∶N和C∶P分布格局相似,并受年降水量、纬度和经度的影响;N与N∶P分布格局相似,受经度、海拔和年均温的影响。     

The biological and practical significance of antigenic variability in protective T cell responses against Theileria parva

The evolution of antigenically distinct pathogen strains that fail to cross-protect is well documented for pathogens controlled primarily by humoral immune responses. Unlike antibodies, which recognise native proteins, protective T cells can potentially recognise epitopes in a variety of proteins that are not necessarily displayed on the pathogen surface. Moreover, individual hosts of different MHC genotypes generally respond to different sets of epitopes. It is therefore less easy to envisage how strain restricted immunity can arise for pathogens controlled by T cell responses, particularly in antigenically complex parasites. Nevertheless, strain restricted immunity is clearly a feature of a number of parasitic infections, where immunity is known to be mediated by T cell responses. One such parasite is Theileria parva which induces potent CD8 T cell responses that play an important role in immunity. CD8 T cells specific for parasitized lymphoblasts exhibit strain specificity, which appears to correlate with the ability of parasite strains to cross-protect. Studies using recently identified T. parva antigens recognised by CD8 T cells have shown that the strain restricted nature of immunity is a consequence of the CD8 T cell response in individual animals being focused on a limited number of dominant polymorphic antigenic determinants. Responses in animals of different MHC genotypes are often directed to different parasite antigens, indicating that, at the host population level, a larger number of parasite proteins can serve as targets for the protective T cell response. Nevertheless, the finding that parasite strains show overlapping antigenic profiles, probably as a consequence of sexual recombination, suggests that induction of responses to an extended but limited set of antigens in individual animals may overcome the strain restricted nature of immunity.     

Platelet function in dogs: breed differences and effect of acetylsalicylic acid administration

BACKGROUND: Clinical studies investigating platelet function in dogs have had conflicting results that may be caused by normal physiologic variation in platelet response to agonists. OBJECTIVES: The objective of this study was to investigate platelet function in clinically healthy dogs of 4 different breeds by whole-blood aggregometry and with a point-of-care platelet function analyzer (PFA-100), and to evaluate the effect of acetylsalicylic acid (ASA) administration on the results from both methods. METHODS: Forty-five clinically healthy dogs (12 Cavalier King Charles Spaniels [CKCS], 12 Cairn Terriers, 10 Boxers, and 11 Labrador Retrievers) were included in the study. Platelet function was assessed by whole-blood aggregation with ADP (1, 5, 10, and 20 microM) as agonist and by PFA-100 using collagen and epinephrine (Col + Epi) and Col + ADP as agonists. Plasma thromboxane B(2) concentration was determined by an enzyme immunoassay. To investigate the effect of ASA, 10 dogs were dosed daily (75 or 250 mg ASA orally) for 4 consecutive days. RESULTS: A higher platelet aggregation response was found in CKCS compared to the other breeds. Longer PFA-100 closure time (Col + Epi) was found in Cairn Terriers compared to Boxers. Plasma thromboxane B(2) concentration was not statistically different between groups. Administration of ASA prolonged the PFA-100 closure times, using Col + Epi (but not Col + ADP) as agonists. Furthermore, ASA resulted in a decrease in whole-blood platelet aggregation. CONCLUSIONS: Platelet function is influenced by breed, depending upon the methodology applied. However, the importance of these breed differences remains to be investigated. The PFA-100 method with Col + Epi as agonists, and ADP-induced platelet aggregation appear to be sensitive to ASA in dogs.     

格氏栲种群生态学研究Ⅶ.格氏栲种群分布格局的强度与纹理分析

前人都是采用样方方法对格氏栲种群数量的空间格局进行测定,而格局分布有可能受样方大小的影响,且分析过程中没有涉及聚块间密度差的问题,因而无法掌握种群的聚块大小差别及聚块内个体间的离散程度．本研究采用无样方距离法,测定不同生境的格氏栲种群空间格局,分析格氏栲种群格局的强度和纹理．强度以聚块和间隙的密度差来定义,纹理则是体现聚块内个体间的离散程度与诸聚块间的分离程度．测定结果表明,格氏栲种群格局强度从高到低排列次序为：木姜子＞蚊母树＞冬青＞茜草树＞格氏栲＞米槠＞虎皮楠＞木荷;格局纹理从粗到细的顺序是：木荷＝木姜子＞茜草树＞格氏栲＝冬青＞米槠＞蚊母树＞虎皮楠．这一测定结果与作者采用聚集度指标测定相同样地格氏栲种群空间格局的结果基本相符．因此,格氏栲空间格局类型及分布与格氏栲生物学特性及生境的关系密切     

松红蜡蚧成虫空间分布及抽样技术

分别选择被松红蜡蚧（CeroplastesrubensMaskell）为害的马尾松10株,为害程度为轻、中、重,从东、南、西、北、顶5个方位,每株5个轮次进行全面的虫口、枝条长度调查,结果表明：不同轮次之间差异极显著;不同方向的多重比较差异显著;不同方位的虫口密度板显著。该虫空间分布为聚集分布,回归方程为：M＝2．42＋0．69X,相关系数γ＝0．9745,平均拥挤度与均数相关性极显著;应用I(wao．s)提出的贯序抽样公式,在T（m）≥T（0）时,需要进行防治。     

Analysis of genetic variability of aluminium tolerance response in triticale

Comparative analyses of genetic variability of aluminium tolerance response were made in a range of triticale genotypes of two sets, one consisting of six Australian cultivars (or lines), the other consisting of eight South African lines and an Australian check, by following solution culture and screening under controlled growth cabinet conditions. Results showed that Tahara, Tahara ‘S’ and Abacus were the most Al-tolerant triticales among the Australian genotypes in terms of root regrowth characteristics at 10 μg.g^-1 Al. The 19th ITSN 70-4, along with the standard cultivar Tahara was superior to all other South African genotypes; the eight South African genotypes spanned the range from Al-tolerant, moderately Al-tolerant to Al-sensitive. Regrown root length and percentage of seedlings with root regrowth were the two key indicators for screening and evaluating Al tolerance response. Considerable genetic variability of tolerance to Al stress among the two sets of tested genotypes was revealed by the estimates of genetic parameters. High heritability values were recorded for those two indicators, with associated high levels of relative genetic advance (RGA). Further improvement of varietal tolerance to Al stress in triticale could be anticipated through selection and breeding. This revised version was published online in July 2006 with corrections to the Cover Date.