A role for tryptophan in immune control of chlamydial abortion in sheep

Tryptophan (Trp) catabolism appears to be an important mechanism for regulation of inflammatory responses, resulting in T-cell tolerance and survival of semi-allogeneic concepti during pregnancy. Trp catabolism can be induced by IFN-gamma, and is therefore an important host defence mechanism against intracellular pathogens. Chlamydophila abortus is a bacterial pathogen that can cause persistent infection in non-pregnant sheep, but invades the placenta and causes abortion in late pregnancy. IFN-gamma was found to control the growth of Chlamydophila abortus in ovine cells in a highly dose-dependent manner. Addition of 200U/ml IFN-gamma eradicated all traces of infection from the cultures, whereas concentrations less than 50U/ml failed to control the growth of the organism, resulting in cell lysis. However, concentrations in the range of 50-100U/ml were found to restrict growth to an extent that a persistent infection was established, allowing survival of the organism in tissue culture for several months. Removal of IFN-gamma resulted in the re-appearance of infectious organisms. Addition of exogenous Trp to the cells treated with 50-100U/ml IFN-gamma prevented the establishment of persistence. These effects in tissue culture are analogous to the persistent infection observed in pregnant sheep prior to abortion. These data suggest that control of C. abortus growth in the periphery is linked to the balance of pro-inflammatory cytokine production and availability of Trp during pregnancy.     

Canine model and genomic structural organization of glycogen storage disease type Ia (GSD Ia)

A canine model of glycogen storage disease Ia (GSD Ia), similar clinically, biochemically, and pathologically to the human disease, was established by crossbreeding Maltese and Beagle dogs carrying a mutated, defective glucose-6-phosphatase (G-6-Pase) gene. Ten puppies were born in three litters from these crossbreedings. Six were homozygous for the previously described M121I GSD Ia mutation. Of these six affecteds, two were stillborn, and one died at 2, 32, and 60 days of life, respectively (puppies A, B, C, D, E), while one is alive at age 15 months (puppy F). Affected puppies exhibited tremors, weakness, and neurologic signs when hypoglycemic. They had postnatal growth retardation and progressive hepatomegaly. Biochemical abnormalities included fasting hypoglycemia, hyperlactacidemia, hypercholesterolemia, hypertriglyceridemia, and hyperuricemia. Microscopic examination of tissues from affected puppies showed diffuse, marked hepatocellular vacuolation, with distended clear hepatocytes and central to marginally located rounded nuclei. In the kidneys of puppies D and E, there was segmental glomerular sclerosis and vacuolation of proximal convoluted tubular epithelium. Biochemical analysis revealed increased liver glycogen content and isolated markedly reduced G-6-Pase enzyme activity in liver and kidney. The canine G-6-Pase gene was characterized by screening a canine genomic library. It spans approximately 11.8 kb and consists of five exons with >90% amino acid sequence homology to the derived human sequence. The first 1.5 kb of the 5' region was sequenced and contains several putative response element motifs homologous to the human 5' region. Establishment of this canine colony of GSD Ia that closely resembles human disease and isolation of the canine genomic gene provides an excellent model for studying pathophysiology and long-term complications and an opportunity to develop novel therapeutic approaches such as drug and gene therapy.     

Client donation program for acquiring dogs and cats to teach veterinary gross anatomy

A donor program for procuring dogs and cats to meet the needs of anatomical instruction was initiated six years ago at Tufts University School of Veterinary Medicine. The program was initiated in order to comply with state regulations that preclude the use of shelter animals and to satisfy ethical objections of students and faculty. The donor program has successfully met the animal needs for teaching gross anatomy and, in addition, provides opportunities to integrate clinical perspectives and ethics beginning from the first year of veterinary education.     

Preparing the veterinary profession for corporate and trade issues in the Americas: proceedings of a conference on synergism and globalization, Santiago, Chile, May 6-8, 2001

The complex and rapid-paced development of international trade, coupled with increasing societal demands for the production not only of abundant and inexpensive food, but also of food that is safe and has been raised in a humane and environmentally friendly manner, demands immediate attention from the veterinary community. The new culture of global trade agreements, spurred by the development of the WTO, dictates massive changes and increasing integration of public and private sectors. This is a huge growth area for our profession and will require individuals with a skill set we do not yet provide in our educational framework. In North America, veterinary education is parochial and focused on specialization. This strong orientation toward companion animals fails to provide adequate training for those interested in acquiring the necessary skills for the emerging area of globalization and trade. In South America, curricula are less harmonized with one another and there is tremendous variation in degree programs, rendering it difficult to ascertain whether veterinarians are prepared to assume decision-making responsibilities regarding international transport of food. If we do not begin to prepare our graduates adequately for this emerging market demand, the positions will be filled by other professions. These other professions lack broad-based scientific knowledge about animal physiology and disease causation. Decisions made without adequate background could have devastating consequences for society, including incursions of unwelcome diseases, food safety problems, and public health issues. To prepare our new veterinary graduates for the future and this emerging market, it is important to nurture a global mindset within our academic communities and to promote communications, languages, and an interdependent team mentality. Areas of technical expertise that need a place, perhaps a parallel track, in the curriculum include production medicine, public health, food safety, and international veterinary medicine. The major trade corridors of the future regarding animal-based protein flow between North and South America. It is absolutely essential that we find areas of consensus and deficiencies so that we can harmonize our trade agreements and ensure adequate flow of safe food products from one continent to the other.     

Pyrethroid insecticide residues on vegetable crops

Pyrethroid insecticides were applied on various vegetable crops as foliar treatments to determine dissipation rates. On Chinese broccoli (Guy Lon), Chinese mustard (Pak Choi) and Chinese cabbage (Kasumi, napa), fenvalerate was persistent with residues of 0.10, 0.14 and 0.11 mg kg-1, respectively, by day 21. Cypermethrin residues on head lettuce were below 0.1 mg kg-1 by day 10 but on the leafier romaine and endive varieties it was more persistent and required 14-19 days to dissipate below this concentration. After three applications, residues of cypermethrin in harvested carrots and of permethrin in eggplant were not detected on the day of application. On asparagus, deltamethrin and cypermethrin residues declined to less than 0.1 mg kg-1 by days 1 and 2, respectively; permethrin was more persistent, requiring more than 2 days to decline to less than 0.1 mg kg-1. Deltamethrin on dry (cooking) and Spanish onions was not detected on the day of application. On tomatoes, the concentration of permethrin was 0.093 mg kg-1 on the day of application and declined to about 0.05 mg kg-1 after 2-4 days. In general, permethrin, cypermethrin and deltamethrin residues declined to acceptable concentrations within an acceptable pre-harvest interval. Fenvalerate may be too persistent on these speciality crops unless a maximum residue limit > 0.1 mg kg-1 is permitted.     

Use of standard toxicity tests with Typhlodromus pyri and Aphidius rhopalosiphi to establish a dose-response relationship

The existing standardised test systems for assessing the toxicity of crop protection products to the non-target arthropods Typhlodromus pyri (Acari: Phytoseiidae) and Aphidius rhopalosiphi (Hymenoptera: Aphidiidae) are limit tests designed to compare a single-use rate of the product with a water control. The suitability of these test systems for generating dose-response data as required for refined ecotoxicological risk assessment was evaluated. Data on dose-response toxicity of crop protection products to T. pyri and A. rhopalosiphi were generated under worst-case laboratory and to T. pyri under extended laboratory conditions and analysed using the standard Probit method, a logistic regression, a generalised Probit analysis, and the moving average-angle method in order to calculate the LR₅₀-values (application rate killing 50% of the exposed organisms). The fit of the models, the precision of the resulting LR₅₀ values, and the required minimum number of replicates were compared. In 85% of the studies, at least one of the statistical methods led to satisfactory results. The moving average-angle method was the most widely applicable method. The results show that the existing guidelines can be used to perform dose-response tests. Implications for risk assessment are discussed.     

Evaluation of uncalibrated preferential flow models against data for isoproturon movement to drains through a heavy clay soil

The uncalibrated predictive ability of four preferential flow models (CRACK‐NP, MACRO/MACRO_DB, PLM, SWAT) has been evaluated against point rates of drainflow and associated concentrations of isoproturon from a highly structured and heterogeneous clay soil in the south of England. Data were available for four plots for a number of storm events in each of three successive growing seasons. The mechanistic models CRACK‐NP and MACRO generally gave reasonable estimates of drainflow over the three seasons, but under‐estimated concentrations of isoproturon over a prolonged period in the first season and over‐estimated them in the two remaining seasons. CRACK‐NP simulated maximum concentrations of isoproturon over the first two events of each of the three seasons of 156, 527 and 24.4 µg litre^?1, respectively, and matched the observed data (465, 65.1 and 0.65 µg litre^?1) slightly better than MACRO (69.1, 566 and 58.5 µg litre^?1). Automatic selection of parameters from soils information within MACRO_DB reduced the emphasis on preferential flow relative to the stand‐alone version of MACRO. This gave a poor simulation of isoproturon breakthrough and simulated maximum concentrations were 0, 50.1 and 35.1 µg litre^?1, respectively. The capacity model PLM gave the best overall simulation of total drainflow for the first two events in each season, but over‐estimated concentrations of isoproturon (967, 808 and 51.3 µg litre^?1). The simple model SWAT represented total drainflow reasonably well and gave the best simulation of maximum isoproturon concentrations (140, 80.2 and 8.2 µg litre^?1). There was no clear advantage here in using the mechanistic models rather than the simpler models. None of the models tested was able to simulate consistently the data set, and uncalibrated modelling cannot be recommended for such artificially drained heavy clay soils. © 2001 Society of Chemical Industry     

The transmission by nematodes of tobraviruses is not determined exclusively by the virus coat protein

The coat protein gene of the nematode non-transmissible, SP5 isolate of pea early-browning tobravius was replaced with that of the highly nematode transmissible, PPK20 isolate of tobacco rattle tobravirus. Plants were infected with the recombinant virus when mechanically inoculated and the virus invaded the plants systemically. However, although the PPK20 isolate of TRV was transmitted by nematodes from these plants, the recombinant virus was not transmitted. Therefore, the virus coat protein is not the exclusive determinant of nematode transmission.     

Characterization of residues in soybeans grown in soil treated with 1,3-dichloropropene soil fumigant

The metabolism of cis- and trans-1,3-dichloropropene (1,3-D) was studied in soybean plants grown in soil treated 24 days prior to planting with [U-¹⁴C]E- and Z-1,3-dichloropropene at 380 liters ha^?1. Isolation and identification of the ¹⁴C residue from soybean plants at 84 days (forage) and 176 days (mature) after application showed that no 1,3-dichloropropene or its putative metabolites, 3-chloroallyl alcohol and 3-chloroacrylic acid, could be detected in any of the tissues. The components of the ¹⁴C residue included major plant constituents (i.e. fatty acids, protein, pigments, organic acids, sucrose and other carbohydrates, and lignin).