南方鲇泌尿系统的结构

南方鲇肾前部分离,中后部相连,有两条肾索,属于硬骨鱼类的Ⅱ-B型肾,有2-9个斯坦尼斯小体.肾单位弥散分布于肾组织中,肾小体单个分布,肾前中后三部分别为3.8,3.4,2.6个/mm^2,平均直径66.5μm.肾小球毛细血管为有孔型,其间有系膜细胞.足细胞的足突与肾小球毛细血管紧贴并形成滤过孔.肾小管分化为颈段、第一近端小管（PⅠ）、第二近端小管（PⅡ）、远端小管（DS）、集合小管（CS）.颈段（NS）为立方上皮;PⅠ、PⅡ细胞柱状,有丰富的纹状缘.PⅠ细胞顶部有明显PAS阳性带,含有粗面内质网、线粒体及大量电子致密物质.与PⅠ、PⅡ伴行的毛细血管均为有孔型.DS、CS为立方上皮,线粒体、质膜内褶丰富.肾单位除颈段外的各段上皮均有大量游走细胞.各级收集管汇成中肾管通入膀胱.     

The effects of birth weight and estimated breeding value for protein deposition on nitrogen efficiency in growing pigs

The effects of birth weight (BiW; low BiW [LBW] vs. high BiW [HBW]) and estimated breeding value (EBV) for protein deposition (low EBV [LBV] vs. high EBV [HBV]) on N retention, N efficiency, and concentrations of metabolites in plasma and urine related to N efficiency in growing pigs were studied. At an age of 14 wk, 10 LBW–LBV (BiW: 1.07 ± 0.09 [SD] kg; EBV: −2.52 ± 3.97 g/d, compared with an average crossbred pig with a protein deposition of 165 g/d), 10 LBW–HBV (BiW: 1.02 ± 0.13 kg; EBV: 10.47 ± 4.26 g/d), 10 HBW–LBV (BiW: 1.80 ± 0.13 kg; EBV: −2.15 ± 2.28 g/d), and 10 HBW–HBV (BiW: 1.80 ± 0.15 kg; EBV: 11.18 ± 3.68 g/d) male growing pigs were allotted to the experiment. The pigs were individually housed in metabolism cages and were subjected to an N balance study in two sequential periods of 5 d, after an 11-d dietary adaptation period. Pigs were assigned to a protein adequate (A) or protein restricted (R, 70% of A) regime in a change-over design. Pigs were fed 2.8 times the energy requirements for maintenance. Nontargeted metabolomics analyses were performed in urine and blood plasma samples. The N retention (in g/d) was higher in the HBW than in the LBW pigs (P < 0.001). The N retention (in g/[kg metabolic body weight (BW^0.75) · d]) and N efficiency, however, were not affected by the BiW of the pigs. The N retention (P = 0.04) and N efficiency (P = 0.04) were higher in HBV than in LVB pigs on the A regime but were not affected by EBV in pigs on the R regime. Restricting the dietary protein supply with 30% decreased the N retention (P < 0.001) but increased the N efficiency (P = 0.003). Nontargeted metabolomics showed that a hexose, free amino acids (AA), and lysophosphatidylcholines were the most important metabolites in plasma for the discrimination between HBV and LBV pigs, whereas metabolites of microbial origin contributed to the discrimination between HBV and LBV pigs in urine. This study shows that BiW does not affect N efficiency in the later life of pigs. Nitrogen efficiency and N retention were higher in HBV than in LBV pigs on the A regime but similar in HBV and LBV pigs on the R regime. In precision feeding concepts aiming to further optimize protein and AA efficiency in pigs, the variation in EBV for protein deposition of pigs should be considered as a factor determining N retention, growth performance, and N efficiency.     

microRNA调控动物皮下脂肪组织和肌内脂肪沉积的研究进展

脂肪组织是动物机体重要的能量代谢及内分泌器官,选择性的脂肪沉积对动物肉类的感官品质、风味性和加工特性具有至关重要的作用,因此动物不同部位脂肪沉积的特异性调控因子及其作用分子机理备受研究者的关注。microRNA（miRNA）是一类长度为22 nt左右的非编码小RNA,近年来采用组学技术对具有表型差异的脂肪组织和脂肪细胞进行高通量测序,筛选发现了许多差异表达的miRNAs,这些miRNAs可通过与靶基因mRNA相结合发挥生物学功能,对不同部位脂肪沉积调控具有重要作用。鉴于此,本文将从miRNA在动物皮下脂肪组织和肌内脂肪的调控作用等方面进行综述,为后续研究miRNA调控动物脂肪组织沉积的作用及机制提供理论参考和新的思路。     

猪肌纤维性状形成和肌内脂肪沉积的遗传机制

近年来,通过改变肌纤维性状和肌内脂肪含量改善猪肌肉品质成为科学家们研究的热点。肌纤维性状形成和肌内脂肪沉积是内因与外因共同作用的结果。作者对猪肌纤维性状形成和和肌内脂肪沉积的遗传机制进行了综述,以期寻求调控及改善猪肌肉品质的方法。猪肌纤维性状形成和肌内脂肪沉积的遗传机制非常复杂,受基因、转录因子及信号通路的复杂网络调控。猪肌纤维的生长发育主要受生肌决定因子（myogenic determinant,MyoD）基因家族和肌肉生长抑制素（myostatin,MSTN）基因一正一负协同调控。能量感应网络AMPK/SIRT1/PGC-1α在猪肌纤维类型转化中起重要作用。脂肪沉积相关基因的表达量与猪肌内脂肪沉积有密切关系。随着分子生物技术的不断发展,许多与肌纤维性状形成和肌内脂肪沉积的相关基因已被鉴定出来,有助于进一步揭示猪肌纤维性状形成和肌内脂肪沉积的遗传机制。     

Evaporation ponds as a drainwater disposal management option

Constructed evaporation ponds are being utilized for disposalof saline subsurface drainage waters in San Joaquin Valley,California. These terminal evaporation ponds are located inhydrologically closed basins and/or regions with no surfacedrainage out of the valley. The saline drainwaters disposedinto the ponds are sodium-sulfate or sodium-sulfate-chloridetype waters and upon desiccation produces mirabilite andhalite. The drainwaters contain excessive levels of traceelements from geochemical origins. The trace element of mostconcern, is selenium because it bioaccumulates in the aquaticfood chain and causes death and deformity of waterbirdsattracted to the pond environment. At the present, the onlyeconomic drainwater disposal option in the southern. portionof the valley is evaporation ponds. The operation of theseponds is heavily regulated by waste discharge requirements toreduce and mitigate wildlife impacts. A case study onevaporation ponds and bird usage from a drainage districtillustrates the extensive monitoring and mitigation required.The prognosis is evaporation basins will be needed for theforeseeable future unless breakthroughs occur in economic andeffective drainwater treatment and drainwater reuseoptions.     

Effect of liming on some chemical,biochemical, and microbiological properties of acid soils under spruce (Picea abies L.)

Summary Soil pH, total organic C, total N, exchangeable Al, available P, CO₂ evolution, microbial biomass C and N, phosphatase and dehydrogenase activities were determined in acid soils sampled under spruce subjected to acid deposition, before and after liming. A slight decrease in pH values was observed from the edge of a tree canopy to the base of the trunk in acid soils. Liming drastically reduced exchangeable Al and increased CO₂ evolution, microbial biomass, and the metabolic quotient. The microbial biomass C to total organic C ratio increased after liming but did not reach 2%, the average value considered valid in soils where the C content is in equilibrium, that is when C inputs are equal to C outputs. The microbial biomass C:N ratio decreased after liming, thus indicating that bacteria became predominant over fungi when soil acidity decreased. Dehydrogenase activity but not phosphatase activity was increased by liming. The decrease in phosphatase activity was not completely related to the increase in available P, but was also dependent on microbial growth and the decrease in acid phosphatase, the predominant component of acid soils.     

土壤硒区域环境分异及安全阈值的研究

影响土壤硒区域贫民是的因子很多。本文通过主因子地计算，在影响土壤硒的诸因子中提纯出四个主因子（即土壤类型，土壤母质，土地利用类型及植被类型），并对我国４１个土类中的硒进行了区划，最后针对不同区域确定出土壤硒的安全阈值。这将为我国判定土壤硒的环境质量标准提供科学依据。     

Five-year trends in soil arthropod densities in pine forests with various levels of vitality

Summary A comparative field study was conducted to study the correlation between forest vitality and the abundance of soil microarthropods. During 5 years the vitality of six pine forests within the Veluwe area, the Netherlands, was estimated by the number of needle year-classes, while soils were sampled and extracted for various soil microarthropod groups. Within sites the number of needle year-classes in the forest stands fluctuated over the 5 years, while the collembolan family Sminthuridae showed a trend towards a decreasing population density and the density of the cryptostigmatid mite Platynothrus peltifer Koch increased. Among sites there was a significant positive correlation between the number of needle year-classes and the relative abundance of P. peltifer. The results imply that soil microarthropods may indicate changes in physical and chemical factors in relation to soil fertility and vitality of the trees.