Acute Insulin-induced Hypoglycaemia does not alter IGF-1 and LH Release in Cyclic Mares

Lactation in the mare is associated with changes in the release of metabolic as well as reproductive hormones. Plasma glucose concentration is constantly reduced in lactating compared with non-lactating mares. Several metabolic signals have been proposed to link nutrition and somatic metabolism with reproductive function. The following experiment was performed to study the effect of acute hypoglycaemia on the release of insulin-like growth factor-1 (IGF-1) and luteinizing hormone (LH) in cyclic mares. Different doses of insulin (0.1 and 0.2 IU/kg body weight) were given to induce a decrease in plasma glucose concentration, as existent in lactating mares. All horses treated with insulin developed a hypoglycaemia over a time period of nearly 10 h. The IGF-1 and LH were analysed before and after insulin administration. At no point of time, a significant difference between the two insulin treatments and the control treatment was observed. Therefore, the hypoglycaemic horse is apparently able to provide the brain with sufficient glucose. Short-term hypoglycaemia does not affect the hypothalamo-pituitary-ovarian axis, and concentrations of IGF-1 and LH remained stable during insulin-induced hypoglycaemia. An acute change in plasma glucose concentration is thus not or at least not the only metabolic signal that links nutrition and somatic metabolism with reproductive function in the horse mare.     

Anti‐microbial Susceptibility of Streptococcus spp. Isolated from Bovine Mastitis in Argentina

The in vitro susceptibility to penicillin G, erythromycin and clindamycin was determined by the disc diffusion test and by E‐test for a total of 47 streptococcal strains (three Streptococcus uberis, 36 Streptococcus agalactiae, eight Streptococcus dysgalactiae spp. dysgalactiae) isolated from bovine intramammary infections in Argentina. Moreover, resistance phenotypes of erythromycin‐resistant streptococcal isolates was characterized. MIC₉₀ of penicillin G, erythromycin and clindamycin for S. agalactiae were 0.75, 8.0 and 12.0 μg/ml respectively. Resistance to erythromycin and clindamycin was detected in 13 (27.6%) and 12 (25.5%) isolates respectively. No isolate was resistant to penicillin G. Resistance against macrolides, lincosamides and streptogramin B (MLS_B) represented by the constitutive MLS_B phenotype was present in 11 (23.4%) erythromycin‐resistant isolates and two isolates (4.3%) expressed the M phenotype. The inducible MLS_B phenotype was not identified. Results suggest that beta‐lactams are the first‐line antibiotics when treating streptococcal udder infections; however, the continuous monitoring of the antibiotic resistance is essential, as the emergence of resistant strains has become a growing concern on the therapy of bovine mastitis.     

Culture of Differentiated Adult Rabbit Auricular Chondrocytes

Chondrocytes dedifferentiate to a fibroblast‐like phenotype on plastic surfaces. Dedifferentiation is reversible if these cells are then cultured embedded in gels as alginate, agarose or collagen. Chondrocytes cultured in suspension on a non‐adherent surface are also known to form aggregates of differentiated cells. The knowledge of chondrocyte behavior in culture is relevant for tissue engineering purposes. In this report we describe a simple method to culture differentiated or redifferentiated rabbit auricular chondrocytes on plastic surfaces with a stable phenotype. When chondrocyte aggregates formed in suspension are next seeded on plastic surfaces, most of them attach to the plastic as round or polygonal cells, and this morphological differentiation, confirmed by the presence of type II collagen, is stable for long culture periods. We also report that the addition of aggregates to monolayer cultures of dedifferentiated chondrocytes results in their redifferentiation, as is shown by their morphological changes and the synthesis of type II collagen. Therefore, this simple method can be useful for the study of chondrocyte behavior on plastic surfaces and for redifferentiating previously proliferated chondrocytes in tissue engineering techniques. Furthermore, these results demonstrate that, in addition to culture conditions such as cell isolation method or cell‐density, chondrocyte behavior on plastic depends on the presence or absence of aggregates resulting from the dissociation process.     

Occurrence and Distribution of Lactate Dehydrogenase in Knee Joint Carilage in Healthy and Osteoarthrotic Dogs

According to clinical studies, degenerative diseases of canine joints lead to higher lactate dehydrogenase (LDH) levels in synovial fluid. The goal of the present study was to examine the intraarticular distribution of LDH in healthy and osteoarthrotic knee joints in order to identify possible sources of LDH in synovial fluid. As synovial LDH concentrations neither correlate with the number of leukocytes nor with synovitis, our investigation focused on the articular cartilage. Samples from healthy and osteoarthrotic knee joints were fixed and processed for transmission electron microscopy (TEM), immunohistochemistry (IHC), and immunocytochemistry (ICC). In addition, fresh cartilage samples were investigated cytochemically by the tetrazolium‐formazan reaction. Analyses of blood and synovial fluid samples were used to confirm the absence of inflammatory disease. Morphology of articular cartilage was assessed macroscopically and by means of TEM. IHC revealed highest levels of LDH in chondrones and a diffuse labelling of the matrix with a distinctive decrease in signal from superficial to deeper cartilage layers. Ultrastructural localization by ICC showed LDH to be present in the cytoplasm of all chondrocytes and confirmed the density gradient in the matrix. Labelling was absent from nuclei and from pericellular rims. Cytochemistry confirmed the distribution pattern and, thus, expanded our findings beyond immunological evidence by providing proof of enzymatic activity of LDH in articular cartilage. The present results indicate that LDH is transferred from chondrocytes to the cartilaginous matrix. We suggest, therefore, that LDH found in synovial fluid originates from the articular cartilage and that osteoarthrotic processes promote LDH release from the cartilaginous matrix.     

Distribution and Activity of Fatty Acid Amide Hydralase (FAAH) in the Gastrointestinal Neurons of Mouse

The endocannabinoid anandamide may regulate intestinal motility through activation of CB1 receptors. Anandamide is then inactivated by fatty acid amide hydrolase (FAAH), a membrane bound enzyme. Under pathological conditions, inactivation of such enzymatic activity may lead to inhibition of the intestinal motility. Here, preliminary reports on the distribution of Fatty Acid Amide Hydrolase (FAAH) immunoreactivity in the mouse gastrointestinal neurons, and the pharmacological effects of N‐arachidonoylserotonin (AA‐5HT), a selective inhibitor of FAAH, are reported. FAAH was revealed by an indirect immunofluorescence. Laminar preparations containing the myenteric or the submucous plexus adhered, were peeled off after the whole gut wall had been stretched out and fixed in 4% paraformaldehyde. They were subsequently incubated with a polyclonal anti‐serum directed against a region near the N‐terminus of the human FAAH and revealed by a FITC‐conjugated goat anti‐rabbit secondary anti‐serum. FAAH‐immunoreactive neurons were observed within the myenteric ganglia throughout the GIT. The positive nerve cells varied in size and density of immunoreactivity. Stomach and large intestine showed the highest neuronal density. AA‐5HT significantly reduced both gastric emptying and gastrointestinal tract transit. Such inhibitory effect was reduced by the C1 receptor antagonist SR141716A. Both morphological and pharmacological results suggest that FAAH may play a critical role in controlling gut anandamide levels.     

Serodiagnosis of Burkholderia mallei Infections in Horses: State‐of‐the‐art and Perspectives

Burkholderia mallei causes glanders or farcy in solipeds, a disease that must be reported to the OIE (Office International des Epizooties, Paris, France). The number of reported outbreaks has increased steadily during the last decade. Serodiagnosis is hampered by the considerable number of false‐positives and ‐negatives of the internationally prescribed tests. The major problem leading to low sensitivity and specificity of complement fixation test (CFT) and enzyme‐linked immunosorbent assay (ELISA) has been linked to the test antigens currently used, i.e. crude preparations of whole cells. Future perspectives for the development and evaluation of serological test kits using well‐characterized single antigens are discussed in the light of recent molecular research on B. mallei and the closely related saprozoonotic agent B. pseudomallei.     

Morphological Studies on the Development of the Bronchial Epithelium of the Fetal Camel Lung

Light microscopic observations revealed that in camel foetuses of 25 mm crown‐to‐rump length (CRL) the primordial tubular system of the prospective lung was formed of several tubules lined by undifferentiated columnar epithelium. Intra‐epithelial neuroendocrine cells were the first elements to be differentiated in the lining epithelium of the primordial tubular system of the prospective lung as early as 25 mm CRL. On reaching 50–67 mm CRL, the primordial tubular system started to differentiate into two systems of primordial tubules, the prospective bronchial or light tubules and the future respiratory or dark tubules. The lining epithelium of the prospective bronchial tubules revealed a clear evidence of ciliogenesis as early as 80 mm CRL. From 800 mm CRL onwards, the bronchial epithelium demonstrated ciliated and non‐ciliated secretory cells. The non‐ciliated secretory cells of the bronchial epithelium of fetal camel lung showed moderate reaction to AB/PAS technique, for the first time, in fetuses reaching 600 mm CRL.     

Secondary or Accessory Glomerular Layer in Mice During Growth

Most mammals have two different structures in which we found glomerular layers at the same time: the main olfactory bulb (MOB) and the accessory olfactory bulb (AOB). Both bulbs have the same pattern of organization, but there are some differences: although the size is considerably bigger in MOB than in AOB, probably the most important difference is that the principal cells are not differentiated into mitral and tufted cells in the AOB, and are usually described as mitral/tufted cells. We have previously observed that in some mammals, like pigs and sheep, the AOB reaches maturity before birth, but this is not a rule for other species. Surprisingly, mice need several days of life to achieve full stratification of its cellular components. We have studied the chronology of this process, focusing our attention on the glomerular layer, the last to appear. We concluded that there are two critical periods, between E11.5 and E16.5 (migration phase) and between E17.5 and P3.5–7 (true morphological constitution).