Studies on experimental chlamydial mastitis in goat histoenzymology

Clinical and Diagnostic Significance of Lactate Dehydrogenase and Its Isoenzymes in Animals

Lactate dehydrogenase (LDH) is widely distributed enzyme in cells of various living systems where it is involved in carbohydrate metabolism catalyzing interconversion of lactate and pyruvate with NAD⁺/NADH coenzyme system. Cells of tissues are direct source of lactate dehydrogenase isoenzymes that are naturally distributed in blood plasma/serum of animals and humans producing characteristic profile. This profile depends on intracellular isoenzyme concentration in all tissues that contribute to the common pool of lactate dehydrogenases in plasma/serum as a consequence of natural cell degradation. LDH is widely distributed in the body, high activities are found in the heart, liver, skeletal muscle, kidney, and erytrocytes, whereas lesser amounts are found in the lung, smooth muscle, and brain. Because of its widespread activities in numerous body tissues, LDH is elevated in a variety of disorders. There are many conditions that contribute to increased activity of LDH. An elevated total LDH value is a rather nonspecific finding. Therefore, LDH assays assume a more clinical significance when separated into isoenzyme fractions. The activity of LDH and its serum and tissue patterns and composition show great variations between the species. These differences do not allow using catalytic activities of LDH isoenzymes from one species to another. Instead, the pattern of serum LDH isoenzymes should be interpreted in respect to its species origin that is important in particular in veterinary medicine. Determination of total LDH activity and its isoenzyme pattern in serum of mammals had become one of the biochemical indicators in the assessment of organ disorders. When the content of cells is released from tissue to plasma, as on cell injury, the LDH isoenzyme pattern of the serum changes in favour of the profile of the affected organ (tissue) that can be used in the diagnostic practice.

Pathogenesis and inflammatory response in experimental caprine mastitis due to Staphylococcus chromogenes

Coagulase-negative staphylococci (CNS) are the most frequently isolated bacteria in cases of subclinical mastitis in dairy cows. CNS species may differ in their pathogenicity, but very little is known about their virulence factors or their immune response in intramammary infections. To our knowledge, no experimental studies into the mastitis pathogenesis caused by CNS have been described in lactating goats. The aim of this study was to induce an experimentally Staphylococcus chromogenes mastitis in lactating goats aimed at verifying if the model can be used to evaluate the inflammatory response, the dynamics of infection and the pathological findings within the first hours of intramammary inoculation. Six Saanen goats in mid-lactation were inoculated with 1 × 10⁷ colony forming units of S. chromogenes. Bacterial growth peaked in milk from the challenged right halves of the mammary glands (RMG) at 4 h post inoculation (PI). Shedding of viable bacteria showed a marked decrease at 12 h PI. An increase in mean somatic cell counts was observed in the milk samples from 8 h PI onwards. Mild clinical signs were evoked by intramammary inoculation. Staphylococcus chromogenes could be isolated in tissue from all RMG. Histological examination of specimens of the RMG and lymph nodes of the goats showed an increased inflammatory response throughout the experiment with respect to control halves. In conclusion, the experimental inoculation of S. chromogenes in lactating goats is capable of eliciting an inflammatory response and capable of causing pathological changes. This research represents a preliminary study for a better knowledge of the mastitis pathogenesis caused by S. chromogenes.

Development of an experimentally induced Streptococcus uberis subclinical mastitis in goats

Streptococcus uberis is a major environmental mastitis-causing pathogen. The infections are predominantly subclinical and are frequently undetected and untreated for extended periods of time. More information about the pathogenesis of S. uberis mastitis would be useful. To our knowledge, no experimental studies into the mastitis pathogenesis caused by S. uberis have been described in lactating goats. The aim of this study was to reproduce an experimentally induced S. uberis subclinical mastitis in lactating goats aimed to evaluate the inflammatory response, dynamics of infection and the pathological findings within the first hours of intramammary inoculation with S. uberis. Six Saanen goats in mid-lactation were inoculated with 1.7 × 10(8)cfu of S. uberis. Bacterial growth peaked in milk from challenged right mammary halves (RMH) at 4h PI. Shedding of viable bacteria showed a marked decrease at 20 h PI. Mean somatic cell counts in milk from the RMH peaked at 20 h PI. Inoculation with S. uberis was followed by a decrease in the mean total number of leukocytes. Signs and systemic symptoms were not evoked by intramammary inoculation. S. uberis could be isolated in tissue from all RMH. Histological examination of specimens of the RMH and lymph nodes of the goats showed an increased inflammatory response throughout the experiment. The histological findings correlated with the immunohistochemical detection of S. uberis in RMH. In conclusion, the experimental inoculation of S. uberis in lactating goats is capable of eliciting an inflammatory response and causing pathological changes, resulting in a subclinical mastitis. This investigation shows that goat might to represent a valuable model for the study of the mastitis pathogenesis caused by S. uberis.

Characterization of the caprine (Capra hircus) beta-2 integrin CD18-encoding cDNA and identification of mutations potentially responsible for the ruminant-specific virulence ofMannheimia haemolytica

The leukocyte integrins play a critical role in a great number of cellular adhesive interactions during the immune response. We describe here the isolation and characterization of the caprine beta(2) (CD18) sub-unit, common to the leukocyte beta(2)-integrin family. The deduced 770-amino-acid sequence reveals a transmembrane protein with 80, 81, 83, 96 and 99% identity with its canine, murine, human, bovine and ovine homologues respectively. Analysis of CD18 sequences emphasizes the functional importance of the beta(2) sub-unit I-like domain, and included metal ion-dependent adhesion site-like motif and confirms that of the cytoplasmic tail. Moreover, comparisons of ruminant versus non-ruminant CD18 sequences allowed the identification of 16 potential mutation sites that could be held responsible for the unique virulence of Mannheimia haemolytica for ruminants. Mannheimiosis is known to be the major respiratory disease among ruminants, whereas it is not pathogenic for other mammals, an observation that has been attributed to a specific interaction between M. haemolytica leukotoxin and ruminants' CD18. Therefore, the data provided here offer the possibility to explore new avenues in studies based on the caprine model and provide key information for future studies aimed at elucidating the molecular mechanisms underlying the ruminant-specific virulence of M. haemolytica.

Molecular characterisation of the caprine (Capra hircus) lymphocyte function-associated antigen-1 alpha subunit-encoding cDNA

Background

Lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alpha L beta 2) is required for many cellular adhesive interactions during the immune response.

Results

The Capra hircus CD11a-encoding cDNA was sequenced and compared with its human, murine, rat, bovine and ovine counterparts. Despite some focal differences, it shares all the main characteristics of its known mammalian homologues.

Conclusion

Therefore, along with the caprine CD18-encoding cDNA, which has been available for a few months, the sequence data revealed here will allow the Capra hircus LFA-1 expression in vitro as a tool to explore the specificities of inflammation in the caprine species.