0.4% Dimeticone spray,a novel physically acting household treatment for control of cat fleas

The cat flea, Ctenocephalides felis, is the most important ectoparasite of cats and dogs worldwide as a cause of irritation and health problems. Most products to control these pests in the household environment rely upon a combination of neurotoxic insecticides and insect growth regulators to inhibit development of flea eggs and larvae into adults. However, some of these are affected by problems of insecticide resistance as well as public concerns about their potential for toxicity in domestic use. Heavy synthetic oils, like the siloxane dimeticone, are currently widely used to treat human ectoparasite infestations, acting by a physical mode of action, and have been used in a variety of presentations for killing all life stages of fleas. We have investigated the activity of low concentrations of high molecular weight dimeticone in a volatile silicone base for ability to immobilise flea life stages without asphyxiating them. We found that cat flea adults and larvae were immobilised by a surface film of dimeticone that inhibited movement of cuticular joints, apparently forming an effective sticky trap. When cocoons were treated the fleas continued to develop within the pupae but failed to emerge. An aerosol spray incorporating 0.4% concentration of dimeticone, for use as a residual household treatment, showed no significant difference in knock down capability compared with that of a widely used pyriproxifen/permethrin spray in a repeat challenge test, with effects persisting to inhibit adult flea emergence in the test arena area for more than 3 weeks after application.     

L-asparaginase-deficient mutants of yeast

Yeast L-asparaginase is a multimeric enzyme for which only a single structural gene has been found. Fourteen mutants deficient in L-asparaginase have been isolated, and they have been located at one site on the genetic map of Saccharomyces cerevisiae. The L-asparaginase gene (aspl) is located about 18 centimorgans from a gene governing tryptophan synthesis (trp4) on fragment 2 of the map.     

樟疫霉多聚半乳糖醛酸酶基因9和10的克隆、测序及其遗传转化研究

研究优化了樟疫霉多聚半乳糖醛酸酶基因9(Pcpg9)和Pcpg10基因克隆的PCR条件,并对其进行了克隆、测序和遗传转化研究。克隆获得了2个基因,其大小前者1059bp,后者1290bp;通过构建表达载体和遗传转化获得了2个基因的转基因菌系;2个基因均能指导合成相应的PG酶蛋白,其中转化Pcpg10基因的酵母菌所分泌的PG酶活性最强,对照Anpg 的PG酶活性次之,Pcpg9的PG酶活性最弱。Westernblotting表明,所克隆的2个基因所指导合成的PG酶蛋白均有不同程度的糖基化。     

A novel mode of arbovirus transmission involving a nonviremic host

In nature, infected and uninfected arthropod vectors often feed together on an animal. In mimicking this scenario in the laboratory, uninfected vectors were found to acquire virus while cofeeding on the same host as infected vectors. However, the vertebrate host on which they fed did not develop detectable levels of virus in its blood. These observations were made with Thogoto virus, an influenza-like virus of medical and veterinary significance. Rhipicephalus appendiculatus ticks were used as the vector and guinea pigs as the vertebrate host. The results demonstrate that a vertebrate that is apparently refractory to infection by an arthropod-borne virus can still play an important role in the epidemiology of the virus, and they suggest a novel mode of arthropod-borne virus transmission.     

Learning-set formation by mink, ferrets, skunks, and cats

The ability of mink, fer rets, skunks, and cats to learn to dis criminate between objects was com pared. Performance of mink and fer rets was similar to that reported for primates. This observation suggests that there is considerable overlap among mammals in ability to form learning sets.