This study was conducted to compare the pathogenesis of acute and latent infections with closely related bovine herpesvirus types 1 (BHV-1) and 5 (BHV-5) in their natural host. Two groups of eight calves were inoculated intranasally with BHV-1 or BHV-5. Although BHV-1 and BHV-5 similarly replicate in the nasal mucosa after inoculation, both viruses differ markedly in their ability to cause disease, BHV-5 being responsible of some fatal encephalitis while BHV-1 inducing rhinotracheitis. Virus isolation and immunohistochemistry demonstrated that BHV-5 replicates extensively in neurons of the central nervous system (CNS) and in respiratory cells of lungs, tracheal and nasal mucosae. Invasion of the CNS likely occurs through the trigeminal and olfactory pathways. Both groups developed cross-neutralising antibodies during this experiment suggesting partial clinical cross-protection afforded by the two infections. Three months after primary infection, experimental reactivation showed that BHV-5 was able to establish latency in the trigeminal ganglia but also the CNS of surviving calves. Moreover, laboratory findings suggested that BHV-5 could also persist in the tracheal and nasal mucosae. These results indicate that, after primary infection, BHV-1 and BHV-5 displayed similar biological features and consequently need to be considered together for the control of BHV-1 infection.

The morphological features gathered here reveal that EAM shares most of the characteristics of toxic myopathies.

By using a conditional gene targeting approach exploiting the cre-lox system, we show that postnatal inactivation of the myostatin gene in striated muscle is sufficient to cause a generalized muscular hypertrophy of the same magnitude as that observed for constitutive myostatin knockout mice. This formally demonstrates that striated muscle is the production site of functional myostatin and that this member of the TGFbeta family of growth and differentiation factors regulates muscle mass not only during early embryogenesis but throughout development. It indicates that myostatin antagonist could be used to treat muscle wasting and to promote muscle growth in man and animals.

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Abstract. Fifty-eight formalin-fi xed par affin-embedd ed canine mammar y tum or s, 19 malignant and 39 benign, were used in th is stud y. T umors were ob tai ned fro m dogs sub mi tte d for surgica l resection of lesions at privat e veterinary pra ctices in Brussels or fro m the su rgery unit of the Fac ulty of Veterinary Med icine, University of Liege. Immunoh isto chem ical eva luation was performed , usin g mon oclon al anti bod ies directed against keratins 8-18 and 19, vime ntin, desmi n, and a -actin and polyclonal anti bod ies directed against high-molecular-weight keratins and S-I 00 protein. Th e main cell types, epithelial, myoepithelial, and connective, were identifi ed , and myoep ith elial cells represent ed the major com po nent of most tum ors, both benign and malignan t. Myoep ith elial cells had five patt ern s: resting and proliferati ve supra basa l cells, spindle and sta r-shaped inters titial cells, and cartilage. Reactivity to keratin 19, vimen tin, a -actin, and S-I00 prot ein suggested a prog ressi ve transformation from resting cells to cartilage. Epithelial cell reac tivities were lim ited to keratins; only keratinized cells were posit ive for polyclonal keratins. Myofibroblasts were positive for both vime ntin and a -actin, and connective tissue cells were posit ive for vi me ntin. Myoepithelial cells appeared to be th e major com po nent of carcino mas , j ustifying reeva luation and sim plification of histomorphologic class ifications, with a " pleomorphic carci no ma" gro up incl uding all carcinomas exce pt squa mo us, mucino us, and comedo carcino ma s. Imm unoh istochem ical evaluation, in add itio n to routine hem atoxylin and eos in histop ath ologic eval uation is recommended for precise classificati on of canine mammary tumors.Key words: Canine species; im m uno histoc hemis try; mamm ar y tum ors ; myoepithelial cells. After skin tumor s, mammary tumors ar e th e seco nd acteriza tio n and histogenesis. ", , · ' 5. ' 9.23,28 Epithe lial cells most frequent neoplasm in dogs ." Malignant tumors express cyto keratin filam ents, mesenchymal cells exocc ur sponta neously in elde rly animals->' or often de-press vimentin filam ents, and mu scle cells express desvelop on ben ign lesions. 2 -4.32 Canine mammary tumors min fila me nts. Ab out 20 d ifferent subtypes of kerat in s a re an exce llent mod el for th e study of human breast ha ve been describ ed acco rd ing to th eir molecular ca ncer. 8 , 16,25 They have sim ilar histol ogic origin and weight, and th ey are characteristically found in certa in comparable regional and systemi c metastasis, and th ey epi the lia. For example, in hum an mamma ry glands, appear in signi ficant number s at a sim ilar relati ve age." epithe lial cells ex press keratins 14 and 18.14 Markers However , freq uency o f th e vario us histologic types is othe r than interme d iate filaments can also be used to d ifferenL ' 7 ,22,26 ide ntify cell types, for exa m ple, a -actin m icrofil am ents Charac teris tica lly, canine mammary tum ors ha ve ...