Three SNPs within exons of INHA and ACVR2B genes are significantly associated with litter size in Dazu black goats

The aim of this study was to analyse the association between single-nucleotide polymorphisms within INHA and ACVR2B and litter size in Dazu black goats. In total, twenty-two SNPs were genotyped in 190 individuals by SNaPshot and resequencing. The results showed that three SNPs (SNP_1, SNP_12 and SNP_13 in this study) were detected to have significant additive genetic effect on the recorded goat litter size (p < .05). The SNP_1 (NC_030809.1), a non-synonymous substitution of G for T at chr2-g. 28314990 in the exon 2 of INHA gene (NM_001285606.1), resulted in homozygote 2 (HOM2) contributed 0.25 and heterozygote (HET) contributed 0.12 larger litter than homozygote 1 (HOM1). Meanwhile, SNP_12 (Chr22-g. 11721225 A > T) and SNP_13 (Chr22-g. 11721227 A > C) (NC_030829.1) simultaneously mutated at the first and third position of a triplet AAA (lysine, K) in the exon 4 of ACVR2B gene (XM_018066623.1) had estimated genetic effects of HOM1 (0.00) and HOM2 (0.03) larger than HET (−0.12). In conclusion, one SNPs (chr2-g. 28314990 T > G) within the exon 2 of INHA and two SNPs (Chr22-g. 11721225 A > T and Chr22-g. 11721227 A > C) i n the exon 4 of ACVR2B gene were highly recommended as candidate markers of litter size in Dazu black goats. A large-scale association study to assess the impact of these variants on litter size is still necessary.     

猪血浆转铁蛋白与部分经济性状关系的研究——Ⅰ. 多态性与产仔数和日增重的关系

用经改进的聚丙烯酰胺凝胶电泳铁染法,测定了二花脸猪血浆转铁蛋白多态类型,分析了其基因型频率和基因频率,并探讨了猪血浆转铁蛋白多态性与产仔性能和增重速度的相关性。     

Reproductive roles predict sexual dimorphism in internal and external morphology of lake whitefish,Coregonus clupeaformis

Abstract – The different reproductive roles of the sexes can predict the direction and magnitude of sexual dimorphism of external and internal morphology. Males should have enlarged structures that enhance the acquisition of mating opportunities, whereas females are predicted to have enlarged organs that are associated with the production of eggs. We tested these predictions in male and female lake whitefish, a species in which both sexes have similar overall body size and shape. After controlling for body size, male lake whitefish had significantly longer jaws and pectoral and pelvic fins, larger hearts, and more muscle than females. Sexual dimorphism in relative muscle mass may be one of the most fundamental morphological differences between males and females. Females had relatively heavier livers than males. Because the liver is important for the breakdown of fats and vitellogenesis, selection should favour an enlarged liver in females for the processing of energy and the production of large numbers of eggs.     

农业土地规模经营的理论探讨

实现农业土地规模经营,有利于生产力有效运转并取得最佳的规模效益。其适度性受各种因素的影响,具有区域性和动态性。规模经营与劳动生产率有着密切的关系,应该在确保提高土地生产率的基础上来提高劳动生产和土地规模经营的效益。土地适当集中、土地经营主体的总人数尽量精简和劳动组合的优化是优化土地经营规模的三个相互制约的因素。要采取积极的措施逐步实现土地的规模经营。对现有土地经营形式要做具体分析,其调整应从有利于生产力发展出发,在尊重群众意愿的基础上稳步进行。     

A leakiness index for assessing landscape function using remote sensing

The cover, number, size, shape, spatial arrangement and orientation of vegetation patches are attributes that have been used to indicate how well landscapes function to retain, not ‘leak’, vital system resources such as rainwater and soil. We derived and tested a directional leakiness index (DLI) for this resource retention function. We used simulated landscape maps where resource flows over map surfaces were directional and where landscape patch attributes were known. Although DLI was most strongly related to patch cover, it also logically related to patch number, size, shape, arrangement and orientation. If the direction of resource flow is multi-directional, a variant of DLI, the multi-directional leakiness index (MDLI) can be used. The utility of DLI and MDLI was demonstrated by applying these indices to three Australian savanna landscapes differing in their remotely sensed vegetation patch attributes. These leakiness indices clearly positioned these three landscapes along a function-dysfunction continuum, where dysfunctional landscapes are leaky (poorly retain resources). This revised version was published online in July 2006 with corrections to the Cover Date.     

Osmolarity,cell volume and proliferation in nasopharyngeal carcinoma cells

AIM: To investigate the relationship between osmolarity, cell volume and cell proliferation in nasopharyngeal carcinoma cells. METHODS: MTT method was applied to detect the proliferation ability of the poorly-differentiated nasopharyngeal carcinoma cell (CNE-2Z) under various osmolarity conditions. The flow cytometry was used to analyse cell cycle distribution. Cell volume was obtained by the image analysis of living cells and cell viability was determined by the trypan blue assay. RESULTS: Cultivation of cells under the hypertonic conditions of 370 and 440 mOsmol/L increased cell volume by 8.7% and 27.8% and facilitated cell proliferation by 22.2% and 33.9%, respectively. However, hypotonic incubation of cells with osmolarity of 160 and 230 mOsmol/L decreased cell volume by 12.8% and 4.1% and inhibited cell proliferation by 34.0% and 15.6%, respectively. Cell volume was positively correlated with cell proliferation rate. Long-term cultivation of cells under anisotonic conditions did not significantly alter cell cycle distribution, but hypotonic cultivation decreased cell viability. CONCLUSION: Proliferation of nasopharyngeal carcinoma cells was closely correlated with the osmolarity of culture medium and cell volume. Hypotonic cultivation may inhibit cell proliferation by decreasing cell volume to facilitate cell death mechanisms.     

Evaluation of sampling methods and assessment of the sample size to estimate the weed seedbank in soil, taking into account spatial variability

As field sampling is time consuming, it is necessary to develop efficient sampling techniques to obtain accurate estimates of the weed seedbank in soil. The relative efficiency between sampling schemes depends on the spatial variability in weed seed density across agricultural fields. Spatial variability of the weed seed density was characterized by theoretical correlograms. A systematic sampling (square grill) scheme was considered and it was found that, taking into account spatial variability, this sampling scheme was more efficient than simple random sampling. As a result, the sample size can be reduced in comparison with that given in previous studies, where spatial correlation was ignored. The reduction depends on the correlation structure defined as a function of the ratio, τ, between the nugget effect and the sill of the variogram. The maximum reduction of the sample size, without loss of either precision or confidence level corresponds to the case where there is no nugget effect, τ = 0. The opposite extreme case, where the reduction is nil, corresponds to the case of a pure nugget effect τ = 1. The abaci based on given expressions are provided to determine the sample size in species whose spatial pattern can be fitted either to a Poisson or to a negative binomial distribution.     

黄鳍棘鲷标志放流群体的规格适宜性评价

合理选取标志放流鱼的规格是成功监测放流鱼类动态及评估增殖效果的关键步骤。本研究以黄鳍棘鲷为对象,通过2个实验评价标志鱼的适宜规格。实验1对比了4种体长的黄鳍棘鲷(平均体长5、7、11和14 cm)作T型标志后其生长、存活和标志保留情况,并利用逻辑斯蒂回归模型分别分析标志鱼存活率和标志保留率的规格特异性;实验2模拟了不同混合比例下2种体长黄鳍棘鲷标志鱼与不标志鱼的捕捞情况,并利用重抽样方法对捕捞结果作计算机重抽样,分析2种鱼能否充分混合以及标志鱼的规格、比例对捕捞结果的影响。结果显示:(1)7、11和14 cm标志组的特定生长率与对照组无显著差异;(2)标志鱼的存活率随体长的增加而增加(5 cm标志组的鱼在标志后7 d内全部死亡,7、11和14 cm标志组的存活率分别为77.5%、92.5%和100.0%)。标志鱼的存活率与初始体长的逻辑斯蒂回归关系式为P=exp(0.099X-6.900)/[1+exp(0.099X-6.900)];(3)各组的标志保留率较高(7、11和14 cm标志组的标志保留率分别为97.5%、100.0%和100.0%),但与体长无明显关系;(4)模拟捕捞结果与计算机重抽样结果无显著差异,二者均不受鱼体规格的影响,但受标志鱼比例的影响极显著,标志鱼比例越高,其捕获率也越高。综上,建议今后采用T型标志方法开展增殖放流品种(如黄鳍棘鲷)的相关研究时,应综合考虑成本和可接受的误差范围以选择符合研究目的的标志鱼规格,若需标志鱼的存活率高于50.0%,则体长至少为7 cm,高于75.0%则体长至少为8 cm,高于95.0%则体长至少为10 cm。此外,在成本允许的条件下,建议尽可能增加放流鱼类中标志鱼的比例以提高增殖效果评估的代表性,而具体适宜的比例值得深入研究。     

鹰爪虾形态性状和体重的通径分析及灰色关联分析

为探究鹰爪虾(Trachypenaeus curvirostirs)形态性状和体重的关系,本研究测定了体重(Y)及全长(X₁)、体长(X₂)、头胸甲长(X₃)、头胸甲宽(X₄)、头胸甲高(X₅)、第1腹节长(X₆)、第1腹节宽(X₇)、第1腹节高(X₈)、第6腹节长(X₉)、第6腹节宽(X₁₀)、第6腹节高(X₁₁)、尾节长(X₁₂)、尾扇长(X₁₃)13个形态性状,通过通径分析和灰色关联分析等方法研究了各性状之间的关系。结果显示,雌性鹰爪虾各生物学指标均大于雄性,雌、雄群体各性状之间均呈极显著正相关关系(P<0.01),体长(X₂)与体重的相关系数均最大(分别为0.972和0.969);通径分析和决定系数分析发现,雌、雄群体体长(X₂)对体重的直接影响和直接决定系数均最大(通径系数分别为0.443和0.519),雌、雄群体对体重间接作用最大的形态性状分别为第1腹节宽(X₇)(作用系数之和为0.750)和尾节长(X₁₂)(作用系数之和为0.887),雌性群体体长(X₂)和头胸甲高(X₅)的共同决定系数最大(0.167),雄性群体全长(X₁)和体长(X₂)的共同决定系数最大(0.248)。采用逐步回归法建立雌、雄群体形态性状与体重的多元回归方程分别为Y₁=–14.563+0.133X₂+0.374X₇+0.282X₅+0.225X₁₃(R₂=0.978)、Y₂=–7.947+0.092X₂+0.309X₄+0.203X₁₀+0.036X₁–0.087X₁₂(R₂=0.980)。雌性群体形态性状与体重的关联系数平均值在0.868~0.941之间,雄性群体的平均值在0.793~0.906之间,从同一形态性状来看,雌性群体与体重关联系数的平均值均大于雄性群体。雌、雄群体体长(X₂)与体重的关联度均为最高。通径分析结果和灰色关联分析结果并不完全相同,综合比较分析得出,在进行鹰爪虾选育时,雌、雄群体以体长(X₂)作为主要选择性状,雌性群体辅助选择头胸甲高(X₅)和第1腹节宽(X₇);雄性群体辅助选择头胸甲宽(X₄)和全长(X₁)。