Rabies virus infection in Aedes pseudoscutellaris cells: a study on receptorial structures

Rabies virus is able to infect in vitro a wide range of homeothermic and poikilothermic cells but little is known about its multiplication in arthropod cells. In this research the infection of rabies virus in Aedes pseudoscutellaris cells, a mosquito cell line susceptible to mosquito-borne viruses, was studied. After 60 days of incubation at 26 degrees C up to 70% of infected cells showed the synthesis of both viral nucleocapsid and envelope antigens, although viral yield and cell damage could not be detected. Research performed in order to investigate the role of membrane carbohydrate moieties in rabies virus-mosquito cell interaction suggested the participation of galactose and N-acetylglucosamine whereas sialic acid, known to be a rabies binding site in many homeothermic cell lines, was not involved.     

The influence of chronic pain on the analgesic effects of the α2-adrenoceptor agonist, xylazine, in sheep

A comparison of the analgesic potency of the alpha 2-adrenoceptor agonist, xylazine, in control healthy sheep and sheep suffering chronic pain from footrot, indicated that the analgesic effectiveness of xylazine was significantly reduced in the animals experiencing chronic pain. This was measured by recording the threshold to a mechanically applied pressure stimulus. Furthermore, when the condition was apparently resolved, by conventional treatment over a period of 2 to 3 weeks, the decreased analgesic effectiveness of the alpha 2-agonist was still apparent although the animals were clinically cured of the footrot.     

Milk fever and subclinical hypocalcaemia--an evaluation of parameters on incidence risk, diagnosis, risk factors and biological effects as input for a decision support system for disease control.

The present review analyses the documentation on incidence, diagnosis, risk factors and effects of milk fever and subclinical hypocalcaemia. It is hereby evaluated whether the existing documentation seems sufficient for further modelling in a decision support system for selection of a control strategy. Several studies have been carried out revealing an incidence of milk fever most often in the level of 5-10%. Few studies indicate that the incidence of subclinical hypocalcaemia is several times higher than milk fever. The diagnosis based on clinical or laboratory methods or based on presence of risk factors is outlined. The clinical symptoms of milk fever are highly specific and the disease level may thus be determined from recording of treatments. Diagnosis of subclinical hypocalcaemia needs to include laboratory examinations or it may be determined by multiplying the incidence of milk fever by a certain factor. From the documentation on risk factors, it is very complex to predict the incidence from the exposure level of the risk factors. Due to uncertainty, sensitivity analyses over a wide range of values for each parameter are needed. The documentation of cow characteristics, nutrition, environment and management as risk factors are described. Among cow characteristics, parity or age, body condition and production level were found to be important. Risk factors associated with nutrition included most importantly dietary cation-anion difference and calcium level whereas the importance of general feeding related factors like type of feed stuff and feeding level were less clear. Environment and management included season, climate, housing, pasturing, exercise, length of dry period and prepartum milking. Several of the parameters on environment and management were confounded among each other and therefore firm conclusions on the importance were difficult. The documentation of the effect of milk fever includes the downer cows, reproductive disorders, occurrence of other diseases and the effect on milk production, body weight and culling. The reproductive disorders included most importantly dystocia, uterine prolapse, retained placenta, metritis and repeat breeding, and occurrence of other diseases included ketosis, displaced abomasum and mastitis. The documentation was substantial and often quantifiable within certain limits. Overall it is concluded that the present documentation on milk fever concerning incidence, diagnosis, risk factors and effects seems sufficient for a systematic inclusion in a decision support system. A model on milk fever should take into consideration the variation in biological data and individual herd characteristics. The inclusion of subclinical hypocalcaemia would be more uncertain and probably should await further documentation on possibilities of determining the herd level incidence and also the effect of this condition on production.     

Molecular structure of troponin C from chicken skeletal muscle at 3-angstrom resolution

The x-ray structure of chicken skeletal muscle troponin C (TnC), the Ca2+-binding subunit of the troponin complex, shows that the protein is about 70 angstroms long with an unusual dumbbell shape. The carboxyl and amino domains are separated by a single long alpha helix of about nine turns. Only the two high-affinity Ca2+-Mg2+ sites of the COOH-domain are occupied by metal ions resulting in conformational differences between the COOH- and NH2-domains. These differences are probably important in the triggering of muscle contraction by TnC. Also the structure of TnC is relevant in understanding the function of other calcium-regulated proteins, in particular that of calmodulin because of its strong similarity in amino acid sequence.     

The Role of Hepatic Ultrasonography in Small Animal Medicine: From the Identification of the Lesions to Diagnosis

Veterinary Research Communications -     

Enhanced recovery of avian influenza virus isolates by a combination of chicken embryo inoculation methods.

Since 1993, 14 cases of avian influenza from four different states in the U.S.A. have been diagnosed by virus isolation from eight avian species. Only 11 of the 14 avian influenza virus (AIV) primary isolations would have been successful if only the standard protocol for AIV isolation, i.e., inoculation of specific-pathogen-free embryonating chicken eggs (ECEs) by the chorioallantoic sac (CAS) route, had been followed. Primary isolation attempts were negative for AIV in three cases in which ECEs were inoculated by the CAS route; AIV could not be detected by hemagglutinating activity, agar gel immunodiffusion test or negative stain electron microscopy. However, in these three cases, primary isolations of AIV were achieved by inoculation of ECEs into either the yolk sac or onto the chorioallantoic membrane.