Biomedical subjects
Publications and source records attributed to R Larochelle.
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Fifteen Canadian field isolates of porcine reproductive and respiratory syndrome (PRRS) virus from Quebec and Ontario were compared with 5 US PRRS virus (PRRSV) isolates and with the European Lelystad isolate using monoclonal antibodies (MAbs) SDOW17, EP147, and VO17 directed to the 15-kDa nucleocapsid protein of PRRSV. All Canadian and US isolates tested by indirect immunofluorescence were recognized by the 3 MAbs, and individual titers of MAbs towards Canadian and US PRRSV isolates were similar as well. In contrast, the Lelystad virus isolate reacted only with the SDOW17 MAb and showed no reactivity with either EP147 or VO17. The reactivity pattern with these MAbs suggests that the Canadian isolates of PRRSV tested are antigenically similar to US isolates of PRRSV, and that these North American isolates share highly conserved epitopes on the 15-kDa nucleocapsid protein that clearly differentiate them from the European Lelystad virus isolate.
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Protein A-gold (PAG) and a primary porcine antiserum were used in immunogold silver staining (IGSS) for the detection of transmissible gastroenteritis virus (TGEV) in formalin-fixed paraffin-embedded tissue sections of small intestine originating from infected pigs. Immunogold electron microscopy was used to evaluate the reactivity of the prepared PAG marker with the specific porcine TGEV antiserum. Gold particles were closely associated with single virions and immune aggregates of TGEV. When IGSS, using PAG as the marker, was applied to tissue sections, dark staining of TGEV-infected villous enterocytes was observed. Background was low, allowing good visualization by light microscopy of the distribution of viral antigen. Two other gold conjugates, protein A/G-gold (PA/GG) and protein G-gold (PGG), were tested in IGSS. The labeling with PA/GG was comparable to that obtained with PAG. However, no staining was observed when PGG was used. The use of IGSS and PAG offers advantages and may represent a useful technique for the detection of other viral pathogens.
Two cytopathic agents were isolated on porcine alveolar macrophages following inoculation with homogenates of lung tissues from pigs showing respiratory problems. These isolates were identified as porcine reproductive and respiratory syndrome (PRRS) virus isolates by indirect immunofluorescence using a PRRS virus (PRRSV) specific monoclonal antibody (MAb) and were designated as LHVA-92-1 and LHVA-92-2. Immunogold electron microscopy using a porcine PRRS positive serum pool and protein A-gold resulted in an intense labelling of aggregates of viral particles. Dark specific cytoplasmic staining of porcine alveolar macrophages infected with both virus isolates could be observed by immunogold silver staining (IGSS) using the specific MAb. This method proved effective in detecting PRRSV antigens in several ethanol-fixed tissues of piglets intranasally inoculated with the supernatants of macrophages infected with each isolate. Immunogold silver staining was also successfully used for the detection of PRRSV antigens on sections of formalin-fixed paraffin-embedded lung tissues and on frozen sections of lungs. The present results indicate that colloidal gold may be useful for the identification and immunohistochemical detection of PRRSV in tissues.
Immunogold silver staining (IGSS) was applied for the detection of porcine group A rotavirus in formalin-fixed paraffin-embedded tissue sections of small intestine. Prior to the application of IGSS, the reactivity of protein A-gold as a marker was tested with group-specific antiserum in immunogold electron microscopy. Immune aggregates were intensely and specifically labeled with the gold complex. Application of IGSS to tissue sections resulted in specific dark staining of villous enterocytes infected by group A rotavirus. This method also proved effective for the detection of rotaviral antigen in infected cultured cells. The IGSS method may be suitable for routine diagnostic detection of rotaviral infections and may have application for detection of other viral pathogens of veterinary importance.
The present study was designed to compare the distribution of goblet cells and the histochemical composition of mucosubstances produced by these cells in the nasal cavity of piglets aged from 1 to 28 days. Serial transverse sections were stained to demonstrate neutral, acidic, and sulfated mucosubstances. Sections located at eight reference levels rostrocaudally in the nasal cavity and defined regions on these sections were used for goblet-cell counting. There was a nonhomogeneous distribution of goblet cells in the nasal cavity of piglets. A rostrocaudal increase in goblet-cell density was observed with the highest densities found in the ventral meatus and on the septum. There was no difference in this pattern of distribution according to age of the piglets. However, age-related differences were observed in the prevalence of goblet cells containing sialomucins, sulfomucins, or both. While sialomucins were prevalent at 1 and 14 days, sulfomucins predominated in the rostral half of the cavity at 28 days. Our results indicate a maturation of the products of secretion with aging in piglets. The affinity of infectious agents for sialylated glycoconjugates and the predominance of sialomucins in the nasal cavity of newborn piglets could account for their greater susceptibility to bacterial infection.
In order to study the distribution and the extent of atrophy caused by Pasteurella multocida in the nasal conchae, experimental piglets were injected intramuscularly at seven days of age with either two or four 50% mouse lethal doses per kg body weight of P. multocida type D dermonecrotoxin. Experimental and control piglets were killed four, six and ten days postinjection. Serial transverse paraffin embedded sections of the noses were cut throughout the entire length of the nasal conchae. The area of the nasal ventral conchae was measured and the morphometric index of the nasal cavity was calculated. It was observed that P. multocida type D dermonecrotoxin induced severe atrophy of the nasal ventral conchae. This atrophy was present along the entire conchae. However, it was most severe at the level of the first and second premolar teeth.
The epithelial distribution in the nasal cavity of piglets was studied by serial transverse sections. The epithelial distribution in the nasal cavity of healthy piglets varied according to the age of the animal. The transitional epithelium, which contained goblet cells but no ciliated cells, occupied a smaller proportion of the nasal cavity in the newborn piglets than in the 4-week-old piglets. The ciliated epithelium extended more rostrally in the newborn piglets and covered the non-mineralized rostral portion of the nasal ventral concha. At 28 days of age, the rostral cartilaginous concha is overlaid by the transitional epithelium, the respiratory epithelium covering the mineralized nasal ventral concha. The variations in the epithelial distribution according to age are discussed with regard to the greater susceptibility of newborn piglets to bacterial infection.
The present study compares the morphology of the nasal conchae and the relative development (i.e., surface area and neurosensory cell number) of the olfactory epithelium between four species of shrews occupying different ecotopes (Blarina brevicauda, Sorex cinereus, S. fumeus, S. palustris). The number of olfactory cells was corrected for split cell error. Data were analyzed by using size indices based on the allometric method. The convoluted shape of the maxilloturbinal in Blarina, with large respiratory epithelial surface area, could not be related with certainty to the subterranean ecotope. From the comparison between Soricinae and Crocidurinae, one major difference concerned the shape and attachment of ectoturbinal 3. Differences in the relative development of the olfactory organ are discussed with regard to differences in the use of chemical signals. The semi-fossorial B. brevicauda, with the more developed olfactory organ, is reported to possess more scent-glands and to manifest active scent-marking behaviors and fecal deposits associated with territoriality. The two terrestrial species, S. cinereus and S. fumeus, have olfactory epithelia showing an intermediate development. Published accounts of fewer scent-glands and a lack of active scent-marking behavior indicate a lesser use of olfactory communication in these two species where mutual avoidance seems the rule. Indication of an even more reduced use of olfactory signals in social interactions by the semiaquatic S. palustris is suggested by its least-developed olfactory epithelium. The comparison between Soricinae and Crocidurinae supports a relationship between the development of the olfactory organ and the relative use of olfactory communication known to occur in social interactions.