ospC diversity in Borrelia burgdorferi: different hosts are different niches

The outer surface protein C (ospC) locus of the Lyme disease bacterium, Borrelia burgdorferi, is at least an order of magnitude more variable than other genes in the species. This variation is classified into 22 ospC major groups, 15 of which are found in the northeastern United States. The frequency distributions of ospC within populations suggest that this locus is under balancing selection. In multiple-niche polymorphism, a type of balancing selection, diversity within a population can be maintained when the environment is heterogeneous and no one genotype has the highest fitness in all environments. Genetically different individuals within vertebrate species and different vertebrate species constitute diverse environments for B. burgdorferi. We examined four important host species of B. burgdorferi and found that the strains that infected each species had different sets of ospC major groups. We found no variation among conspecific hosts in the ospC major groups of their infecting strains. These results suggest multiple niches create balancing selection at the ospC locus.     

Activities of RNases in different cell compartments in different regions of pea roots

RNase activity in three different regions of pea roots—thetip, middle and basal regions—was analyzed. There werethree types of RNases differing from each other in their intracellularlocalization; the enzymes in a soluble form and two bound formsassociated with unknown, small particles or ribosomes and withthe microsomal membrane. The top region showed a high activityper DNA content of RNase in the microsomal membrane and lowactivities for the other two RNases, as compared with the otherregions. The middle region contained a low amount of RNA perDNA and showed a higher activity per DNA content of RNase inthe unknown particles or ribosomes than in the basal region.The activity of RNase in the unknown particles or ribosomesvaried greatly among the regions, but that in microsomal membranevaried only slightly. ¹ Present address: Okitsu Branch, Fruit Tree Research Station,Okitsu, Shizuoka, Japan. ² Present address: Asahi Denka Co. Ltd., 7–1 Higashiogu,Arakawa, Tokyo, Japan. (Received July 25, 1974; )     

Sexual dimorphism in snakes: different reproductive roles favour different body plans

Because snakes have a highly simplified morphology, and many species have a wide (and broadly overlapping) range of adult body sizes within each sex, they offer an excellent opportunity to compare body composition of males and females. Evolutionary theory predicts that particular body components should be differentially enlarged in the two sexes. For example, we might expect the reproductive success of females to be enhanced by enlargement of organ systems involved in the processing and storage of energy (e.g. alimentary tract, liver, fat stores) whereas males would benefit from the enlargement of systems important for mate-searching, male–male combat and sperm competition (e.g. larger mass of skeletal muscles, tail, and kidneys). Dissection of 243 specimens of three snake species (117 Vipera aspis, 43 Elaphe longissima, 83 Coluber viridflavus) broadly supported these predictions. Strong sex differences were apparent in relative sizes (masses) of all the non-gonadal body components that we weighed. For example, males consistently had more musculature (relative to body length) than did conspecific females. Dimorphism in relative muscle mass is likely to be one of the most fundamental and widespread morphological differences between males and females in the Animal Kingdom.     

不同土壤类型和肥力玉米地土壤养分根际效应研究

采集吉林省玉米植株及土壤样品,研究不同土壤类型和肥力,玉米不同品种和生育时期土壤－植物系统根际养分动态变化及植物吸收的相互关系,结果表明,玉米地土壤ＮＨ＾＋４－Ｎ、ＮＯ＾－３－Ｎ在根际富集,其变化主要与化肥供应有关,高肥力土壤根际有效磷亏缺,种植密度越大,根际亏缺率超大;低肥力土壤则有效磷在根际略高。高肥力土壤有效钾较高,根际有效钾富集也更明显,茎叶、根对养分的吸收量顺序为：Ｎ     

Genetic polymorphisms of proteins in different breeds and different populations of chickens

Six polymorphic protein systems in 15 chicken breeds have been investigated. In the Silkie breed another variant of G3 proteins (G₃ A^F Silkie) has been observed characterized by higher electrophoretic mobility than G₃ A. The frequencies of individual alleles in various lines and different generations have been determined in two breeds (White Leghorn and White Cornish).     

The potency of acyclovir can be markedly different in different cell types

Acyclovir is an acyclic guanine analog with a considerable activity against herpes simplex viruses. We studied the antiherpetic activity of acyclovir in macrophages and fibroblast cell lines. Utilising a plaque reduction assay we found that acyclovir potently inhibited the HSV-1 replication in macrophages (EC50) = 0.0025 microM) compared to Vero (EC50 = 8.5 microM) and MRC-5 (EC50 = 3.3 microM) cells. The cytotoxicity of acyclovir was not detected at concentrations < or = 20 microM, thus the selective index in macrophages was >8000. This marked difference in antiherpetic activity between macrophages and fibroblasts was not observed with Foscarnet and PMEA. We suggest that this potent antiviral effect of acyclovir is mainly due to a proficient phosphorylation of the drug and/or a favourable dGTP/acyclovir triphosphate ratio in macrophage cells.     

Papillomaviruses: different genes have different histories

Papillomaviruses (PVs) infect stratified squamous epithelia in vertebrates. Some PVs are associated with different types of cancer and with certain benign lesions. It has been assumed that PVs coevolved with their hosts. However, recently it has been shown that different regions of the genome have different evolutionary histories. The PV genome has a modular nature and appeared after the addition of pre-existent blocks. This order of appearance in the PV genome is evident today in the different evolutionary rates of the different genes, with new genes--E5, E6 and E7--diverging faster than old genes--E1, E2, L2 and L1. Here, we propose an evolutionary framework aiming to integrate genome evolution, PV biology and epidemiology of PV infections.     

Abrasions and lameness in piglets born in different farrowing systems with different types of floor

Background  

The quality of the floor is essential to the welfare of piglets as abrasions often are recorded in newborn piglets, and such lesions may lead to lameness. Apart from animal suffering, lameness contributes to losses in form of dead piglets, decreased growth, and increased use of antibiotics and manual labour.     

甜荞不同品种不同海拔地区种子蛋白组分含量研究

该研究通过分析甜荞10个品种在4个不同海拔栽培的种子蛋白质组分(清蛋白、球蛋白、醇溶蛋白和谷蛋白)的含量变异,以揭示不同荞麦品种之间以及不同栽培地点甜荞种子蛋白组分的变异规律。结果表明:在所有甜荞品种种子蛋白组分含量中清蛋白谷蛋白球蛋白醇溶蛋白。其中,种植于海拔最低的内蒙古通辽的甜荞种子平均球蛋白含量最高(1.081%),而种植于海拔1 450 m的河北甜荞谷蛋白平均含量最高(2.805%);海拔2 620 m的青海甜荞清蛋白平均含量为4.750%,而在海拔最高的西藏日喀则收获的甜荞种子的醇溶蛋白最高(平均为0.393%)。另外,蒙0530在4个地区的平均种子清蛋白和谷蛋白含量都最高,而球蛋白含量最高的品种是赤甜荞1号,定甜荞2号的种子醇溶蛋白含量最高。双因素方差分析表明,种子清蛋白含量品种间变异达极显著水平,不同地点间的种子醇溶蛋白含量达极显著水平,而地点和品种两个因素对种子球蛋白含量和谷蛋白含量的变异都有极显著影响。相关性分析表明,赤甜荞1号的醇溶蛋白含量与海拔呈显著正相关,蒙0530的球蛋白含量与海拔呈显著负相关,其他品种蛋白组分与海拔的相关性不显著。该研究结果对于甜荞优质品种培育和栽培以及推广都有一定的指导意义。     

Cell cycle dependent genes inducible by different mitogens in cells from different species

Summary A number of genes and cDNA sequences (including at least four oncogenes) are known to be expressed in a cell cycle-dependent manner, i.e. the levels of specific mRNAs vary with the phases of the cell cycle. In order to explore the significance of some of these sequences in the mitogenic response, we have investigated the expression of 8 cell cycle-dependent sequences (plus two control sequences, not expressed in a cell cycle-dependent manner) under a variety of conditions. These conditions included cells of different types, from different species, stimulated to proliferate by different mitogens. The genes (or sequences) studied included five cDNA clones whose sequences are preferentially expressed in early G₁, i.e. two cDNA clones inducible by platelet-derived growth factor (JE-3 and KC-1), and three cDNA clones inducible by serum (2A9, 2F1, 4F1); and three oncogenes (c-myc, c-ras^Ha and p53) whose expression is known to be cell cycle-dependent. All of the tested genes, except 2A9, c-ras^Ha and the control genes, are expressed in a cell cycle-dependent manner in human peripheral blood mononuclear cells stimulated by phytohemagglutinin and in serum-stimulated mouse and Syrian hamster fibroblasts. The inducibility of these genes by different mitogens in cells of different types and from different species strongly suggests that these genes play a role in cell cycle progression. This conclusion is further supported by the known structural and functional similarities between cell-cycle dependent genes, oncogenes and genes coding for cell-cycle related molecules.     

氮素调控剂对不同类型土壤氮素转化的影响

采用室内培养试验方法,比较了硝化抑制剂双氰胺（DCD）和3,5-二甲基吡唑（DMP）对华北平原两种主要土壤类型潮褐土和潮土中氮素转化的调控效果,并进一步研究了DMP与脲酶抑制剂氢醌（HQ）的配合施用对潮土中氮素转化的影响.结果表明： 在两种供试类型土壤上DMP对尿素氮的硝化抑制作用均强于DCD.与单施尿素相比,在氮素转化高峰时,DMP可使土壤中NH₄⁺-N含量显著提高149.5%～387.2%,NO₃^--N含量降低22.3%～55.3%;同一抑制剂对潮土中氮素转化的调控效应较潮褐土更为明显;与DMP单施相比,DMP和HQ配施表现出明显的对氮素转化的协同抑制效果.