Depressed immunoconglutinin responses in calves experimentally infected with Trypanosoma congolense

Contrary to expectation, immunoconglutinin levels failed to rise significantly in calves infected with Trypanosoma congolense. In addition, it was shown that trypanosome infection appeared to inhibit the immunoconglutinin response to Brucella abortus strain 19. The possible reasons for these findings are discussed.     

Intoxication in cattle caused by a batch of sugar beet pulp (author's transl)]

During the period from Dec. 7th 1972 to Jan. 8th 1973 76 cattle deaths were reported in 20 herds on the island of M?on and the adjacent south-eastern area of Sealand. The disease was characterized by a sudden onset and a rapid and invariably fatal course. Initially, there was a loss of appetite, depression, excessive salivation and incoordination. These symptoms progressed to paralysis and, in some animals, trmor and convulsions. Death usually ensued less than 2 hours after the first observation of symptoms. Losses in the herds varied from 1 to 12 animals. In herds with multiple incidents the majority of deaths occurred in the 24-hour-period following observation of the first case. Pathology: Gross lesions were few and inconclusive. Histology revealed marked dilatation of cerebral and maningeal blood vessels (arterioles, venoles and capillaries), with perivascular edema and haemorrhage. Adjacent neurons and glia cells showed various degrees of degeneration, apparently secondary to the vascular lesion. In all affected herds sugar beet pulp from one particular sugar mill had been used during the period preceding the outbreak. The syndrome was reproduced by feeding sugar beet pulp from this batch to two heifers. The heifers showed symptoms after 19 and 32 days' feeding, resp. and died after a few hours. Clinical and pathological features were identical with those observed in the spontaneous disease. Thus, it was proved that the particular batch of pulp was responsible for the disease. The investigation did not, however, reveal a toxic factor in this batch. Analyses for lead, arsenic, mercury, nitrite, alkyl phosphates, chlorinated insecticides and Cl. botulinum toxin were negative. Batches of the sugar beet pulp showed pronounced microbial deterioration, the flora being dominated by yeasts and filamentous fungi (moulds). Several species of fungi have been isolated but so fat their possible role in the etiology of the syndrome remains unsettled. The syndrome bears some resemblance to cerebrocortical necrosis (C.C.N.) but differs in several clinical and pathological details. It is tentatively suggested that the beet pulp may have contained one or more toxic substances that interfere with microbial activity in the rumen, resulting in a disturbance of synthesis or absorption of essential metabolites. The clinical, epidemiological and pathological findings are compatible with the hypothesis that the syndrome might be due to fungal toxins. Accordingly, the isolated fungi are now being studied in more detail.     

Use of an immortalized bovine mammary epithelial cell line (MAC-T) to measure the mitogenic activity of extracts from heifer mammary tissue: effects of nutrition and ovariectomy

The objectives of the experiment were (1) to determine whether MAC-T cells would accurately mimic the previously observed proliferative responses of primary mammary epithelial cells (MEC) to mammary tissue extracts from high and low-fed heifers and (2) to determine whether mammary tissue extracts from ovariectomized (OVX) heifers would have lower mitogenic activity than intact controls. Addition of mammary tissue extracts to cell culture media of MAC-T cells plated on plastic or collagen-coated plastic to a range of concentrations between 1 and 8% resulted in dose-dependent increases in cell proliferation. Furthermore, mammary tissue extracts from low-fed prepubertal heifers aged 9 months, stimulated significantly more proliferation of MAC-T cells, as measured by 3H-thymidine incorporation into DNA than mammary tissue extracts from high-fed heifers (40.6 cpm x 10(3) per well versus 21.9+/-1.8 cpm x 10(3) per well). These observations suggested that MAC-T cells would be a suitable alternative to primary MECs for measuring the mitogenic activity of mammary tissue extracts. Conversely, no difference was observed in the mitogenic activity of mammary tissue extracts from OVX or control heifers. Possibly, MAC-T cells provide a good model for nutrition- but not ovarian-induced changes in mammary growth. Alternatively, that reduction of in vivo mammary development following OVX did not result in reduced mitogenic activity of the mammary tissue extracts emphasizes that heifer mammary development is the result of complex interactions between local growth factors and systemic hormones.     

Critical perspectives in animal agriculture: a response

People who work in the animal industries are faced with questions and criticisms about a variety of contentious issues, including animal management practices, ethics, diversity in animal agriculture, and animal welfare. Formulating responses to these questions requires a critical evaluation of our own work and open discussion of these controversial issues. Effective debate on these issues can be accomplished only with input from philosophers and social scientists skilled in such discussions, in addition to animal scientists. Therefore, animal scientists must engage in discussions of controversial issues among themselves and with entities outside agriculture. Furthermore, we must accept responsibility for the application of research results and any potential negative consequences. Because society is increasingly concerned with issues of animal welfare and the effects of new technologies, we should increase communications and transparency with the public. Increased diversity of race and gender will increase the ability of animal agriculture to connect with our stakeholders and to communicate the relevance of our work to society. Animal scientists need a professional ethic that espouses a higher level of understanding and commitment to philosophical discussions of contentious issues.     

Diagnostic peritoneal lavage for identification of blastomycosis in a dog with peritoneal involvement

A 6-year-old castrated male Dalmatian was evaluated because of hematemesis. The dog had lived its entire life in South Dakota and Wyoming and had never traveled outside of these states. Results of laboratory testing were compatible with iatrogenic acute renal failure and gastrointestinal tract ulceration secondary to previous nonsteroidal anti-inflammatory drug and corticosteroid administration. Differential diagnoses for clinical signs and laboratory abnormalities that existed prior to these treatments included multisystemic infectious or inflammatory disease and neoplasia. Four-quadrant abdominocentesis did not yield any fluid, but because intra-abdominal disease was still suspected, diagnostic peritoneal lavage was performed. Fluid that was obtained was markedly cellular, and there were numerous extracellular structures with a round to oval shape; a 1-microm-thick, clear-staining capsule; a basophilic interior; and broad-based budding. Organisms were consistent with Blastomyces spp, and fungal culture yielded Blastomyces dermatitidis. Treatment with liposomal amphotericin B and itraconazole was recommended but could not be initiated because of the client's financial constraints. At necropsy, disseminated blastomycosis involving the stomach, small intestines, urinary bladder, omentum, mesentery of the small intestine, and abdominal wall musculature was seen. To our knowledge, peritoneal involvement has not been reported in dogs with blastomycosis, and gastrointestinal tract involvement has only rarely been reported. Findings in this dog suggest that diagnostic peritoneal lavage may be a useful technique in determining the cause of infectious peritonitis when the amount of abdominal fluid is below the limit of detection for abdominocentesis.     

Use of plasma clearance of technetium Tc 99m pentetate to estimate renal clearance during postnatal development in pigs

OBJECTIVE: To compare renal clearance of technetium Tc 99m pentetate with plasma clearance by use of a glomerular filtration rate technique in pigs from 3 to 24 weeks of age. Animals: 24 female pigs. Procedure: At the time of investigation, 5 pigs were 3 weeks old, 6 pigs were 6 weeks old, 8 pigs were 12 weeks old, and 5 pigs were 24 weeks old. Plasma clearance of technetium Tc 99m pentetate was measured by the use of a single injection technique followed by collection of multiple blood samples until 5 hours after the injection. Simultaneously, urine was collected through a urinary catheter, and the renal clearance of technetiumTc 99m pentetate was calculated. Plasma clearance of technetium Tc 99m pentetate was correlated with the renal clearance (r = 0.95). Plasma clearance was higher than renal clearance at all ages (mean, 5.8%), indicating extrarenal clearance of technetium Tc 99m pentetate or methodologic errors. Volume of distribution increased with increasing age but decreased as a fraction of body weight. CONCLUSIONS: Plasma clearance of technetium Tc 99m pentetate estimates renal clearance with acceptable precision when using single injection technique and multiple biood samples in pigs from 3 to 24 weeks of age.     

Development of a rapid in vitro protein refolding assay which discriminates between peptide-bound and peptide-free forms of recombinant porcine major histocompatibility class I complex (SLA-I)

The extracellular domains of swine leukocyte antigen class I (SLA-I, major histocompatibility complex protein class I) were cloned and sequenced for two haplotypes (H4 and H7) which do not share any alleles based on serological typing, and which are the most important in Danish farmed pigs. The extracellular domain of SLA-I was connected to porcine beta2 microglobulin by glycine-rich linkers. The engineered single-chain proteins, consisting of fused SLA-I and beta2 microglobulin, were overexpressed as inclusion bodies in Escherichia coli. Also, variants were made of the single-chain proteins, by linking them through glycine-rich linkers to peptides representing T-cell epitopes from classical swine fever virus (CSFV) and foot-and-mouth disease virus (FMDV). An in vitro refold assay was developed, using a monoclonal anti-SLA antibody (PT85A) to gauge refolding. The single best-defined, SLA-I restricted porcine CD8(+) T-cell epitope currently known is a 9-residue peptide from the polyprotein of CSFV (J. Gen. Virol. 76 (1995) 3039). Based on results with the CSFV epitope and two porcine haplotypes (H4 and H7), the in vitro refold assay appeared able to discriminate between peptide-free and peptide-occupied forms of SLA-I. It remains to be seen whether the rapid and technically very simple in vitro refold assay described here will prove generally applicable for the screening of virus-derived peptides for SLA-I binding.     

Maximum-likelihood estimation of sensitivity and specificity of ELISAs and faecal culture for diagnosis of paratuberculosis

The accuracy of three diagnostic tests for paratuberculosis was evaluated using maximum-likelihood estimation of sensitivity and specificity. We also explored the variety of estimates that can be obtained if the tests are to be used in populations of different composition with regard to infection and disease states. Two enzyme-linked immunosorbent assays (ELISAs) were evaluated separately with the faecal culture (FC). The study was carried out as a cross-sectional field study to cover all likely states of infection with Mycobacterium avium subsp. paratuberculosis.The three basic assumptions for the maximum-likelihood technique were evaluated to validate the results. Our accuracy estimates for the ELISAs were not very different from those previously published, but those for faecal culture differed if a different cut-off value was chosen for the ELISA. If faecal culture was used for screening in a Danish dairy region where the median ELISA reading was a measure of the general disease situation, the sensitivity of the faecal culture was 20-25%. If faecal culture was used as a confirmatory test on cows with a high ELISA reading (and thus high level of antibodies), the sensitivity of the faecal culture would be in the range 60-70%. These results emphasise the importance of the composition of a target population before selecting a specific diagnostic test for a given purpose. We concluded that faecal culture is useful for confirmation but not for screening purposes.