Serial sections of bone and soft tissue from the metacarpophalangeal joints of 2 mature and 2 immature horses were evaluated for substance P immunoreactive sensory nerve fibers. Formalin-fixed specimens were sectioned, either nondemineralized or demineralized with formic acid or EDTA. Rabbit antiserum to substance P (SP) was used in the strep. tavidin-biotin-peraxidase complex method for immunolocalization of SP antigen, and staining with 3,3'- diaminobenzidine was used for permanent identification of SP fibers. Abundant sensory nerve fibers were identified in the joint capsule, synovial membrane subintimal layers, collateral ligaments, suspensory ligament and distal sesamoidean ligament attachments to the sesamoid bones, and the periarticular periosteal layers. Sparse SP-immunoreactive nerve fibers were found in subchondral bone plates of the metacarpus, proximal first phalanx, and dorsal articular surface of the sesamoid bones. Most SP fibers were associated with blood vessels in the small cancellous spaces and haversian canals of the subchondral bone. The deeper marrow spaces contained increased numbers of SP sensory fibers; a few appeared in small groups and as several SP-immunoreactive fibers in a larger nerve. Cortical bone contained only a few SP fibers in the haversian canals. Substance P fibers were not identified in the osteocytic lacunae, canaliculi, or the bony lamellae of the haversian systems of the subchondral bone plate, and its extension to the metaphyseal and diaphyseal cortical bone. Equine metacarpophalangeal joint soft tissues have an abundant sensory nerve supply, similar to that of other species. However, the subchondral bone plate also has sparse sensory nerve fibers, which is a unique finding, and may help explain signs of bone pain associated with disease states of the fetlock.

Twelve biotinylated lectins and an avidin-biotin-peroxidase method were used to detect and localize specific carbohydrate residues on formalin-fixed, paraffin-embedded female canine mammary gland sections. Histologic sections from 3 lactating and 7 nonlactating mixed-breed dogs (age 5.6 +/- 0.35 years) were incubated with Arachis hypogea agglutinin (peanut agglutinin; PNA), Concanavalia ensiformis agglutinin (conA), Dolichos biflorus agglutinin (DBA), Glycine max agglutinin (SBA), Griffonia simplicifolia agglutinin-I (GS-I), Lens culinaris agglutinin (LCA), Lycopersicon esculentum agglutinin (LEA), Phytolacca americana mitogen (pokeweed mitogen; PWM), Ricinus communis agglutinin-I and-II (RCA-I and -II), Triticum vulgaris (WGA), and Ulex europaeus agglutinin-I (UEA-I). Each lectin had a specific binding pattern, except SBA and DBA. In nonlactating glands, PNA, conA, LEA, and UEA-I stained duct cells in a linear-binding pattern, with a mean percentage of positive ducts per section of 28.7 (+/- 0.6), 65.7 (+/- 0.3), 100 (+/- 0), and 8.4 (+/- 0.2), respectively. Strong apical, lateral, basal, and cytoplasmic positivity on duct cells was seen after incubation of the sections with RCA-I, RCA-II, and WGA in all ducts. In acinar cells, the binding pattern and the staining distribution of all the lectins studied were similar to those in duct cells. However, for PNA, conA, and UEA-I, the mean percentage of positive lobules per section was 33.7 (+/- 0.9), 62 (+/- 0.5), and 10.5 (+/- 0.2), respectively. In glands from lactating dogs, conA and UEA-I did not stain. The cytoplasm of all myoepithelial cells was moderately stained with RCA-I, RCA-II, and WGA. Endothelial cells stained with GS-I, PWM, RCA-I, RCA-II, WGA, conA, and LCA. The extracellular matrix, especially the periacinar and periduct regions, and the interstitial fibroblasts were positive for LCA, RCA-I, RCA-II, and WGA. Peripheral unmyelinated nerve fibers of the nipple were strongly positive for GS-I, PWM, RCA-1, RCA-II, and WGA. Some of the lectins used (ie, PNA, conA, UEA-I, GS-I, PWM, and LEA) appear to have selective staining of mammary gland structures that seems to be correlated with various physiologic functions. The contrasting binding pattern of lectins specific for the same sugar indicates a lack of knowledge of interactions between lectins and carbohydrate residues in tissue sections.

The in vitro and in vivo binding of a monoclonal antibody (MAB) that recognizes a tumor-associated carbohydrate antigen was studied in dogs. Monoclonal antibody 155H.7 was raised in response to inoculation of mice with beta-galactose(1-3)betaN-acetylgalactosamine conjugated to human serum albumin. Avidin-biotin-complex immunohistochemical staining of cryostat sections of normal and neoplastic canine tissue specimens revealed heterogenous binding of MAB 155H.7 to the cells of many canine mammary and lung carcinomas and homogenous staining of many sarcomas, including osteogenic sarcoma. In addition, there was variable staining of a variety of normal tissues including some ductual epithelium, peripheral nerve fibers, and some endothelial cells and fibroblasts. Immunoscintigraphy with 131I-labeled MAB 155H.7 was used to study the in vitro distribution of the antibody. The 131I-labeled MAB 155.H.7 was administered to 1 clinically normal dog, 7 dogs with osteogenic sarcoma, 1 dog with undifferentiated sarcoma, and 2 dogs with mammary tumor. Scintigraphy revealed concentration of radioactivity in 8 of 10 tumor sites within 24 hours after MAB administration. The ratio of 131I in tumor sites to 131I in the surrounding normal tissues, compared with the similar ratio of 99mTc-labeled erythrocytes ranged from 1.1 to 4.3 in tumor vs normal tissue with a mean value of 2, confirming tumor localization of the radiolabeled MAB in excess of that associated with enhanced tumor vascularization.

We studied the uptake and sequential transneuronal passage of pseudorabies virus (PRV) in rat CNS by use of a combination of immunohistochemistry and in situ hybridization. Protocols for rapid detection of PRV by immunohistochemistry and in situ hybridization in rats with PRV infection of the CNS after intranasal instillation of a wild-type strain of PRV were optimized in vitro, using porcine kidney-15 cells. Pseudorabies virus-specific hybridization signals appeared in the cytoplasm and nucleus of PRV-infected porcine kidney-15 cells by postinoculation (PI) hour 6. In tissue sections of PRV-infected rats, PRV nucleic acids were detected in areas of the rat brain in close proximity to the areas in which PRV antigens were evident. The PRV was initially found in the nucleus of trigeminal ganglion neurons at PI hour 24. At PI hour 72, PRV antigens were observed in the mid-brain, and 24 hours later, in the telencephalon. We also found evidence of specific progressive transsynaptic transmission of the virus, and, on the basis of that, we have constructed a map of the synaptic contacts and pathways in the brain. Therefore, combined use of immunohistochemistry and in situ hybridization was useful for characterizing the pathogenesis of PRV in the CNS of rats after intranasal inoculation, following a pattern that mimics PRV infection of the natural host.