Vascular medial thickening is a prominent finding in people and animals with refractory neonatal pulmonary hypertension. Smooth muscle cells are capable of 2 distinct growth responses in vivo: hypertrophy or hyperplasia. Hypertrophic smooth muscle cells may undergo DNA synthesis without cell division, leading to a polyploid state. To better understand the nature of smooth muscle cell growth in healthy and pulmonary hypertensive neonatal calves, we measured incorporation of the thymidine analog bromodeoxyuridine (BrdUrd) and total DNA content in medial cells from control (pulmonary arterial pressure = 32 +/- 2 mm of Hg) and hypobaric hypoxia-exposed (pulmonary arterial pressure = 120 +/- 7 mm of Hg) calves. Labeling of medial cells with BrdUrd measured by flow cytometry was increased (P < 0.02) in pulmonary arteries of hypoxia-exposed calves (n = 5), compared with control calves (n = 5). Immunohistochemical localization of BrdUrd indicated that BrdUrd labeling of large elastic pulmonary arteries from hypoxia-exposed calves was increased almost exclusively in the outer half of the medial wall. Increased BrdUrd labeling of muscular pulmonary arteries from hypoxia exposed calves was observed in the arterial media and adventitia, and tended to exit in clusters. Analysis of DNA content by flow cytometry indicated a decrease (P < 0.05) in percentage of tetraploid medial cells in pulmonary arteries from hypoxia-exposed calves, compared with control calves. Bivariate analysis for BrdUrd labeling and DNA content of cells from the pulmonary arteries of hypoxia-exposed calves indicated a subpopulation of diploid cells with positive BrdUrd labeling, suggestive of DNA synthesis and subsequent cell division. Results are suggestive of smooth muscle cell hyperplasia in the vascular media of hypoxia-exposed calves.

Tissues obtained from pigs inoculated with African swine fever virus (ASFV), fixed by vascular perfusion using glutaraldehyde, and embedded in paraffin or araldite were used for an immunohistologic electron microscopic study. To detect ASFV antigens, 4 methods were used on paraffin sections with or without pretreatment of the tissues. Use of biotinylated anti-ASFV antiserum combined with avidin -biotin complex and peroxidase proved to be the most suitable method, and antigen was detected in tissues infected with 2 ASF viruses of different virulence. Use of the glutaraldehyde fixation method should ensure optimal morphologic (structural and ultrastructural) data while allowing an immunohistologic study, and add to knowledge of the pathogenesis of ASF.

Expression of keratins (cytokeratins, CK) in healthy feline epithelia and 2 established feline mammary carcinoma cell lines was examined immunohistochemically and by use of immunoblotting analysis. A panel of specific anti-CK monoclonal antibodies (MAb) identifying epitopes unique to individual keratins or shared by 2 (or 3) CK polypeptides was used. Besides already available antihuman CK Mab, this panel of MAb consisted of 9 newly generated anti-human CK MAb and 1 newly generated anti-feline CK MAb. Immunohistochemical analysis on normal epithelia revealed that most of the anti-human CK MAb and the anti-feline CK MAb reacted with both feline and human epithelia, with a comparable tissue distribution pattern. However, slight differences in CK tissue distribution pattern between human beings and cats were detected by one MAb. Immunoblotting analysis revealed that all antihuman CK MAb that were immunohistochemically reactive with feline tissues detected analogous CK in cats, indicating the presence of a number of common epitopes on human and feline CK. Two continuous cell lines derived from 2 distinct feline mammary adenocarcinomas, K248C and K266, were analyzed with respect to their CK phenotype. Although no difference in CK expression between the 2 cell lines was detected in vitro, a difference in CK phenotype was detected on subcutaneous transplantation of the 2 cell lines into nude mice. Although the K248C-induced adenocarcinomas maintained the same CK phenotype as observed in vitro, the CK pattern of the K266 heterotransplants, growing as adenosquamous carcinomas, changed with squamous differentiation. Our findings confirm the high degree of homology between mammalian CK, and on the basis of those findings, we suggest that CK proteins provide a set of markers valuable for the characterization of normal and neoplastic feline tissues and for studies of squamous metaplasia.