Genetic diversity of Pueraria lobata (kudzu) and closely related taxa as revealed by inter-simple sequence repeat analysis

Kudzu (Pueraria lobata) is a noxious weed infesting some areas of the USA. Knowledge of its genetic variation in both native and invasive areas can lead to effective biological control measures. Inter-simple sequence repeat (ISSR) variations were studied in P. lobata and its four closely related congeneric species (P. edulis, P. montana, P. phaseoloides and P. thomsoni). ISSR results allowed a clear separation of these five species. For P. lobata, 108 plants from China and USA were analysed. The samples from the US were genetically closer to Chinese P. lobata populations than to other congeneric populations. High genetic differentiation was found for P. lobata, P. montana and P. thomsoni in Chinese samples. High genetic diversity and low population differentiation was found in P. lobata samples of the US. This supports the hypothesis of multiple introductions into the USA from different sources in Japan or China, followed by subsequent gene exchange and recombination.     

The action of phosphine against the eggs of phosphine-resistant and -susceptible strains of Rhyzopertha dominica F

The effect of phosphine at exposure periods of 24, 48 and 120 h on hatching and mortality of 0- to 1-day-old eggs of susceptible (TN6) and resistant (FC10) strains of Rhyzopertha dominica of field origin was investigated. The fumigant affected hatching in both the strains. In a 48-h exposure at 27 (+/- 2) degrees C, the LD99 doses for the eggs of TN6 and FC10 were 0.56 and 3.25 mg litre-1, respectively. Significant reduction in hatching was observed in treated batches with progressive increase of phosphine dose in the first 2-3 days. On subsequent days the numbers hatching were often similar to those in controls, and sometimes exceeded control hatch, especially following a 5-day exposure. A critical change in the order of susceptibility of egg and adult stages of the two strains was noticed. In 48-h exposures, eggs of the susceptible strain were more tolerant than their adults, whilst the reverse was true in the resistant strain.     

Pathogenesis of BSE

Before the emergence of bovine spongiform encephalopathy (BSE) and recognition of its zoonotic potential, the major example of the transmissible spongiform encephalopathies (TSEs) of animals was scrapie of sheep. But there is no evidence that scrapie transmits naturally to any species other than sheep and goats. The pathogenesis of scrapie has been studied most in experimental laboratory rodent species. In most experimental models of scrapie, after peripheral non-neural routes of infection, replication of the agent can first be detected in lymphoreticular system (LRS) tissue. When the route of introduction of agent into the body is localized, initial involvement will be in LRS tissue draining the infection site. Thereafter, there is a striking amplification of the agent in the LRS and spread by lymphatic/haematogenous routes, giving widespread dissemination in the LRS. This precedes replication in the CNS, but is not the means by which infection reaches the CNS. There is now substantial evidence from experimental models of scrapie that involvement of the CNS is by peripheral nervous system (PNS) pathways. In some models employing oral exposure the earliest localized LRS replication is in the gut-associated lymphoid tissue (GALT) and autonomic PNS routing to the CNS has been implicated. However, the relative importance of different routes of spread of TSEs within the body is determined by a number of host- and agent-dependent factors and, therefore, generalizations from an experimental model to a natural disease across a species barrier may not be appropriate. With the occurrence of BSE and recognition of its food-borne route of transmission via meat and bone meal, has come greater awareness of the probable importance of the oral route of infection in ruminant species affected by TSEs. In consequence, studies have increasingly focused on the natural host species to examine pathogenetic events.     

五日龄窝活仔数对窝断奶仔猪数及仔猪成活率的影响

1992年以来,通过对丹麦长白猪及约克夏猪的总产仔数进行选育,使这一性状得到了显著的增长,但同时仔猪死亡率也大大增加。本研究的目标是估算出窝产仔数及成活率遗传和表型参数来寻找一种新的选育标准以改善窝断奶仔猪数。研究共收集了9300窝长白猪及6861窝约克夏猪的数据并利用了基于线性模型的REML进行分析,包括了母猪和与配公猪的遗传效应。结果表明,5日龄窝活仔数（N5D）的选育可以作为改善丹麦长白猪和丹麦约克夏猪的窝断奶仔猪数及仔猪成活率替代选育标准。     

不同蛋能比对凡纳滨对虾幼虾生长、饲料转化、血清指标和体组成的影响

导读：虾料配制时首先考虑的因子。 前言 凡纳滨对虾原产于美洲中南部的太平洋沿岸,我国于1988年引进,由于该虾生长快、适应性强、食性广、价格高、抗病力强等优点,迅速成为主要养殖品种。当前,饲料成本占总养殖成本的50～60％,而蛋白水平又是影响生长性能和饲料成本的主要因素。那么怎样才能降低饲料成本呢？通过优化蛋白能量和非蛋白能量在饲料中的比例,可以达到这一目的。如果蛋白相对于能量过量,那么,     

Detection of Actinobacillus pleuropneumoniae Infection in Pigs

It is difficult to control the spread of porcine haemophilus pleuropneumonia caused by Actinobacillus pleuropneumoniae because there is no sensitive and specific way to accurately determine whether or not a pig herd is infected. This paper reports bacteriological and serological techniques used to detect A. pleuropneumoniae infection in pigs from a herd with endemic disease.

The bacteria were isolated from the anterior nasal mucosa of grower pigs, but not from younger or older pigs. Bacteriological culture of several tissues from the respiratory tract showed that nine of ten young finishing pigs were infected, but culture of lung tissue from slaughtered hogs detected infection in only 39 of 288 (13.5%). Both cooler storage temperature and use of selective medium prolonged the time that lung tissue could be stored and the organism still recovered. An enzyme-linked immunosorbent assay detected serotype-specific antibodies in serum of infected pigs.

     

Enzymatic profiles of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillae

The enzymatic activities of 39 strains of Erysipelothrix rhusiopathiae and 34 of E tonsillae were determined with the API ZYM system. The profiles of these two species were very similar, differing solely in N-acetyl-beta-glucosaminidase activity. Whereas 90 per cent of strains of E rhusiopathiae exhibited strong activity with N-acetyl-beta-glucosaminidase, positive reactions were observed for this enzyme in only 24 per cent of strains of E tonsillae. These results support previous DNA-DNA hybridisation studies and suggest that E tonsillae is a new species of the genus Erysipelothrix.