Molecular basis of bunyavirus transmission by mosquitoes: role of the middle-sized RNA segment

In an examination of the molecular basis of oral transmission of bunyaviruses by mosquitoes., La Crosse (LAC), snowshoe hare (SSH), and LAC-SSH reassortant viruses were compared in their ability to be transmitted to laboratory mice by the natural mosquito vector of LAC virus, Aedes triseriatus. Both LAC virus and the reassortment viruses containing the middle-sized (M) segment from the LAC parent were efficiently transmitted. In contrast, SSH virus and reassortment viruses containing the M RNA from the SSH parent were inefficiently transmitted. Thus, the M RNA segment, which codes for the virion glycoproteins, may be a major determinant of oral transmission of bunyaviruses by mosquitoes.     

山东茶山植物群落结构及物种多样性

茶山地处鲁东南地区,为全面了解其植物群落结构及物种多样性,2006年7月和10月对茶山植物群落结构及物种多样性进行野外调查,记录到高等植物352种,隶属90科250属,获得标准样方11个,面积6 600 m2。样方数据显示,该区域乔木种类匮乏,乔木层平均物种数2.55,Shannon-Wiener指数平均值0.48;灌木层平均物种数10.55,Shannon-Wiener指数平均值1.68。该区域受人为干扰影响显著,正处于群落演替早期,物种多样性偏低。     

Free and HF-HO-extractable amino acids determined by high performance liquid chromatography in a loamy sand soil

Summary Amino acids were extracted from fertility plots of a loamy sand soil with 0.05 M HF-HCl and with a 10% ethanol solution (free amino acids) and analysed by reverse-phase high performance liquid chromatography (HPLC). The total quantities of amino-N compounds analysed were 4.4 g/g soil for the acid treatment and 22.6 g/g soil for the 10% ethanol extract. Glycine and glutamic acid were the most abundant of 15 amino-N compounds in the HF-HCl extracts, whereas glutamic acid and ornithine + NH⁺ ₄ were found in the highest concentration in the 10% ethanol extracts. The HF-HCI pretreatment is used to increase the efficiency of the extraction of soil organic matter. Although this pretreatment removed some amino acids, the acids extract less than 1% of the total amino-N content of the crude soil extracts. The pretreatment, therefore, was not overly destructive. Comparisons between the amino acids extracted from the fertility plots were not conclusive, except for glycine, which was greater in concentration in the higher fertilizer N plots of the same crop rotation.     

Cokriging particle size fractions of the soil

It is often necessary to predict the distribution of mineral particles in soil between size fractions, given observations at sample sites. Because the contents in each fraction necessarily sum to 100%, these values constitute a composition, which we may assume is drawn from a random compositional variate. Elements of a D‐component composition are subject to non‐stochastic constraints; they are constrained to lie on a D– 1 dimensional simplex. This means we cannot treat them as realizations of unbounded random variables such as the multivariate Gaussian. For this reason, there are theoretical reasons not to use ordinary cokriging (or ordinary kriging) to map particle size distributions. Despite this, the compositional constraints on data on particle size fractions are not always accounted for by soil scientists. The additive log‐ratio (alr) transform can be used to transform data from a compositional variate into a form that can be treated as a realization of an unbounded random variable. Until now, while soil scientists have made use of the alr transform for the spatial prediction of particle size, there has been concern that the simple back‐transform of the optimal estimate of the alr‐transformed variables does not yield the optimal estimate of the composition. A numerical approximation to the conditional expectation of the composition has been proposed, but we are not aware of examples of its application and it has not been used in soil science. In this paper, we report two case studies in which we predicted clay, silt and sand contents of the soil at test sites by ordinary cokriging of the alr‐transformed data followed by both the direct (biased) back‐transform of the estimates and the unbiased back‐transform. We also computed estimates by ordinary cokriging of the untransformed data (which ignores the compositional constraints on the variables) for comparison. In one of our case studies, the benefit of using the alr transform was apparent, although there was no consistent advantage in using the unbiased back‐transform. In the other case study, there was no consistent advantage in using the alr transform, although the bias of the simple back‐transform was apparent. The differences between these case studies could be explained with respect to the distribution on the simplex of the particle size fractions at the two sites.     

Effect of Anticoagulants and Sampling Time on Results of Progesterone Determination in Canine Blood Samples

The concentration of plasma progesterone was measured by ELISA, in serum and samples prepared with three different anticoagulant agents – namely ethylenediaminetetraacetic acid (EDTA), heparine and sodium fluoride oxalate potassium(NaFK). Forty clinically healthy bitches were selected based on the signs of pro‐oestrus or oestrus. Values of progesterone concentration were significantly higher in serum than in EDTA‐plasma (p < 0.0005); heparin‐plasma (p < 0.05) and NaFK‐plasma (p < 0.005). During pro‐oestrus and oestrus until the time of ovulation, progesterone exhibited a conspicuous and statistically verified diurnal pattern (p < 0.05), its serum concentration being higher during 6.00–7.00 p.m. than 8.00–9.00 a.m. By the time of ovulation tendency of higher p.m. progesterone level reverses and from this point on the a.m. progesterone concentration is higher. The results of these experiments indicate that the concentration of canine progesterone assayed with ELISA may be affected by the time of collection and the method of preservation used.