蒙古马睾丸支持细胞的体外分离培养与鉴定

为研究一种简单快速分离蒙古马睾丸支持细胞并保证其活性的基本方法,本试验采集2岁蒙古马睾丸组织于低温环境下进行机械分离,将1~3 g睾丸组织剪碎,采用重力沉淀法去除游离的红细胞和间质细胞;使用0.1%胶原酶Ⅳ和0.25%胰蛋白酶+EDTA逐步进行组织消化,并用含有10%胎牛血清的培养基进行细胞培养;在接种后采用差异贴壁法分离纯化支持细胞,使用Tris-HCl低渗法去除杂质细胞,并采用碱性磷酸酶（AKP）染色、HE染色、实时荧光定量PCR方法进行鉴定。结果显示,支持细胞贴壁性能较强,培养24 h后大多数细胞开始贴壁,细胞形状呈椭圆形;培养48 h后胞质增多,折光性变强;培养3~4 d细胞胞质展开紧密连接,此时细胞呈三角形,有明显的核仁,培养6~7 d细胞生长状态进入稳定期。实时荧光定量PCR结果显示,GATA4和GDNF基因在培养细胞中极显著表达（P<0.01）,AKP染色支持细胞呈阴性表达,表明分离培养的细胞确为支持细胞。本试验使用机械分离法与两步酶消化法处理组织,可快速高效地获得睾丸支持细胞,成功构建了蒙古马睾丸支持细胞体外培养方法。     

Earthworm effects on selected physical and chemical properties of soil aggregates

Summary Some physical and chemical properties of 1-to 2-mm aggregates obtained from casts and the burrow-wall material of the earthworm species Lumbricus terrestris, Aporrectodea longa, and Aporrectodea caliginosa were determined in order to show the effects of earthworms on the stabilization of soil aggregates. The results were compared with those of the natural soil from the Ap horizon of a Parabraunerde (Luvisol, FAO). Both the tensile strength and the water stability of aggregates from casts and burrow-wall material were reduced compared with those of the natural aggregates but were increased compared with those of remoulded aggregates. These results indicate that to a great extent existing bonds are destroyed by earthworm ingestion. Nevertheless, earthworm activities are advantageous for the stabilization of reformed aggregates. The coarse sand fraction is reduced by selective ingestion by earthworms. The organic C content is increased by 4.1–21.0% for burrow-wall material and by 21.2–43.0% for casts. The carbonate content of aggregates from casts and burrow-wall material of L. terrestris was reduced by more than 50%, while that of A. longa showed no noticeable changes and that of A. caliginosa was increased by more than 60%. The total content of polysaccharides was increased by 35–87% for casts and by 33–46% for the burrow-wall material of all earthworm species. The most frequently detected monosaccharides were glucose, galactose, and glucosamine. L. terrestris appeared to have the strongest effect on the interparticle bonding of the reformed aggregates, measured both as tensile strength and water stability, followed by A. longa and A. caliginosa.     

熔喷过程湍流模型中的气流场数值模拟

以熔喷过程中的气流场为核心,建立熔喷过程的数学物理模型,采用数值模拟的方法进行研究。以Navier-Stocks方程为基础,应用基于同位网格的SIMPLER算法并行化计算气流场的速度分布,将试验测试值与数值模拟进行比较,结果表明:采用的数值模拟方法是有效的,完全可以用于模拟双槽钝头型模具的熔喷过程。     

Regeneration of compacted soil aggregates by earthworm activity

Soil compaction is a problem of modern agriculture, caused by heavy machinery when used in unsuitable, especially moist, conditions. Some regeneration processes in compacted loess soil were studied in a field experiment near Relliehausen, at the edge of the Solling mountains in Lower Saxony, Germany. Conventional tillage (CT) and conservation tillage (CS) systems were compared. The compaction was induced by the use of different wheel loads. The influence of earthworms was determined by comparing soil aggregates and casts with respect to dry and moist porosity, swelling, and water stable aggregation. For visualisation of the microstructure, a scanning electron microscope was used. The casts were obtained from two earthworm species living for 6 months in the laboratory in monoliths, taken on the plots after the wheeling procedure. The casts showed 10-20% higher values for porosity and about 50% higher swelling values than comparable soil aggregates, while the relative water stability was ca. 10% lower. We conclude that casts are looser and less stable than aggregates from the soil the earthworms ingested. To show the ecological relevance of the changes in the casts, the cast production per hectare per year was calculated. It was especially high in the most loaded soil under CS with endogeic species.     

Successful backcrosses of somatic hybrids between Sinapis alba and Brassica oleracea with the Brassica oleracea parent

Somatic hybrids between Sinapis alba (2n= 24) and Brassica oleracea (2n= 18) have been backcrossed with the B. oleracea parent. Whereas backcrosses with the diploid B. oleracea parent were unsuccessful, 344 BC₁ seeds could be obtained from inter-valence crosses with tetraploid B. oleracea (2n= 4x= 36). The investigated 96 BC₁ plants segregated for morphological traits and for fertility. They were backcrossed with diploid B. oleracea or self-pollinated, depending on their male fertility. The BC₁F₂ and BC₂ progenies segregated well for the morphological traits. Disturbances were observed especially in the generative phase (flower development and pollen fertility). Both male fertile and male sterile BC₁F₂ and BC₂ plants were obtained and backcrossed or self-pollinated with the B. oleracea parent. The presence of either one of the parental or the cybrid organelle genomes was detected. In the progenies, a stable maternal inheritance of the organelle genome patterns was observed. Isozyme analyses revealed polymorphism for the leucine aminopeptidase (LAP) which was used for the identification of S. alba genes in the progenies. Cytological investigations showed a clear differentiation between the BC₁F₂ and BC₂ plants. Whereas the BC₁F₂ plants possess large numbers of chromosomes ranging from 34 to 40, the BC₂ material was strongly reduced to chromosome numbers ranging from 20 to 22. Preliminary investigation of the meiosis suggests the possibility of introgressions of S. alba-DNA into the B. oleracea genome.     

Spatial analysis of seroconversion of sentinel cattle to bluetongue viruses in Queensland

Objective To assess quantitatively the spatial distribution of seroconversion of Queensland cattle to bluetongue viruses.
Design A sentinel herd study. Sample population Sixty-nine sentinel herds at 30 locations.
Procedure Spatial clustering of seroconversion to blue-tongue viruses was investigated during the period from 1990 to 1994.
Results Seroconversion to only two bluetongue virus serotypes, 1 and 21, was observed. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and subcoastal region of Queensland, and were significantly (P < 0.05) clustered. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field observations, except for the failure to detect seroconversion to bluetongue viruses in north-western Queensland.
Conclusion Bluetongue infection of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease status of animal populations.