Vitamin K requirement and reproduction in bromadiolone-resistant Norway rats

BACKGROUND: Nucleotide polymorphisms in the VKORC1 gene can be linked to anticoagulant rodenticide resistance in Norway rats (Rattus norvegicus Berkenhout). This provides a fitness advantage to rats exposed to anticoagulant actives, but may also cause fitness costs. The vitamin K requirement and reproductive parameters of bromadiolone‐resistant rats (Westphalian resistant strain; VKOR variant Tyr139Cys) and bromadiolone‐susceptible Norway rats were compared. RESULTS: At vitamin K deficiency, blood clotting times increased in all homozygous resistant males within 8 days and in 80% of homozygous resistant females within 15 days. There was little effect on blood clotting in heterozygous males and no effect in heterozygous females and VKOR wild‐type individuals. Litter size was about 20% higher in sensitive pairs compared with resistant pairs. Testes growth, male gonad weight, sperm motility and testis cell concentration were unaffected by the mutation. CONCLUSIONS: The VKOR variant Tyr139Cys causes considerable physiological cost in Norway rats in terms of vitamin K requirement and reproduction. This may affect the distribution and spread of resistant individuals in the wild. Decreased litter size of resistant parents seems to be due to lowered female reproductive performance, as there was no significant effect of the mutation on any aspects of male reproduction considered, but this requires further study. Copyright © 2011 Society of Chemical Industry     

Growth of the native oyster Ostrea angasi using raft culture in Tasmania,Australia

Native oyster spat set on scallop shells in a hatchery showed seasonal growth and reached a mean shell length of 78.7 mm, 2 years after being suspended from a raft at North West Bay, Tasmania.Growth varied with suspension depth and to a lesser extent between ropes on the raft. Average dry weight condition index at harvest (115.6) indicated that the oysters were in very good condition although 42.7% died during the 2-year trial.     

The use of computer-generated electrostatic surface maps for the design of new ‘GABA-ergic’ insecticides

A computer model was constructed based on the observation that a number of structurally dissimilar compounds gave rise to similar biological activity. Mode of action work confirmed the link. The model was then used to prioritise targets for synthesis and successfully predicted many active series. The major limitation of the model was that it was unable to predict potency or spectrum. It is thought likely that the factors controlling these limitations are linked with LUMO energies, but this hypothesis has not been proven.     

Challenging diagnosis--icterus associated with a single perforating duodenal ulcer after long-term nonsteroidal antiinflammatory drug administration in a dog

A dog developed icterus, vomiting, and anorexia 2 wk after orthopedic surgery and treatment with meloxicam for approximately 1 y. Exploratory laparotomy revealed a single perforated duodenal ulcer. The most likely cause of the hyperbilirubinemia was intrahepatic cholestasis resulting from peritonitis associated with the perforation.     

Down-regulation of MHC class II receptors of DH82 cells, following infection with Ehrlichia canis

In order to evaluate whether infection with E. canis alters the expression of major histocompatibility complex (MHC) class I and/or MHC class II receptors, and by doing so alters the immune response to the organism, flow cytometry was performed on DH82 cells infected with Ehrlichia canis (90% infection) and on uninfected DH82 cells of the same passage, using anti-canine MHC class I and II antibodies. MHC class II expression was evident in 47.6 and 46.2% (mean 46.9%) of uninfected DH82 cells using two different anti-MHC class II antibodies, while no MHC class II expression was evident in DH82 cells infected with E. canis. The present results indicate that infection of DH82 macrophages with E. canis down-regulates their MHC class II receptors. These results suggest a possible mechanism by which E. canis evades the immune system.     

Temporal Dynamics of the Biocontrol Agent Pseudomonas fluorescens Strain A506 in Flowers in Inoculated Pear Trees

ABSTRACT The colonization of individual flowers in mature pear orchards by Pseudomonas fluorescens strain A506 applied at different times during bloom was measured to determine the receptivity of flowers to colonization and the extent of intra-tree movement over time. Strain A506 populations in flowers open at inoculation were initially about 10(4) cells per flower and increased to approximately 10(6) cells per flower in flowers that were inoculated within about 5 days of opening. However, eventual populations decreased with further increases in flower age at inoculation to as few as about 10(3) cells per flower when inoculated flowers were more than 10 days old. Populations of strain A506 on flowers that opened after inoculation was initially very low at the time of petal expansion (<100 cells per flower) but increased rapidly with time after flower opening. The maximum population of strain A506 that developed on such flowers decreased with increasing time between inoculation and petal expansion; 10(4) to 10(5) cells of strain A506 eventually colonized flowers that opened within 7 days of inoculation, whereas fewer than 100 cells colonized flowers that opened 24 days or more after inoculation. Large total bacterial populations on A506-treated trees were associated with significant reductions in populations of Erwinia amylovora and reduced incidence of fire blight and severity of fruit russet.