Ovarian adenocarcinoma with metastases in a white rhinoceros

A 36-y-old white rhinoceros (Ceratotherium simum) was presented with respiratory distress, sanguineous vaginal exudate, and anorexia. The clinical signs progressed over 40 d, and the rhinoceros died. Autopsy revealed significant ascites; a unilateral, 12.5-cm diameter, polypoid mass in the left ovary; a white, firm transmural mass in the right uterine horn; a white, friable mass in the lung; and white-to-tan, friable small nodules in the diaphragm. Histologic examination revealed similar neoplastic cells in the masses in all 4 locations, composed predominantly of epithelial cells proliferating in a tubulopapillary pattern with significant nuclear atypia and numerous atypical mitotic figures (18–42 per 2.37 mm²). Immunohistochemistry for CK7 (cytokeratin 7) and CK20 (cytokeratin 20) suggest that the ovarian, pulmonary, and diaphragmatic lesions were of ovarian origin and that the ovary was the primary tumor site.     

Chalastospora gossypii in a Maine Coon cat: case report and literature review

A 15-y-old castrated male Maine Coon cat was evaluated for an ulcerated soft tissue mass on the right hindlimb that had been observed for 4 mo and had grown rapidly. A 3 × 3 cm soft, raised, amorphous, and ulcerated subcutaneous mass was observed on the lateral right metatarsus. In-house cytology via fine-needle aspiration was nondiagnostic. Incisional biopsy of the mass and further staging was declined, and amputation was elected. The amputated limb was submitted for histopathology, which revealed severe chronic nodular granulomatous dermatitis and multifocal granulomatous popliteal lymphadenitis with large numbers of intralesional fungal hyphae. Fungal PCR and sequencing on formalin-fixed, paraffin-embedded tissue identified Chalastospora gossypii. No adjunctive therapy was elected at the time. The patient has done well clinically 1 y post-operatively. C. gossypii is a rare microfungus found worldwide and is considered a minor pathogen of several plants. To our knowledge, infection by this fungus has not been reported previously in veterinary species. Features in our case are comparable to other mycotic infections. Nodular granulomatous mycotic dermatitis and cellulitis, although uncommon, should be a differential for soft tissue masses in veterinary species; C. gossypii is a novel isolate.     

Complex mammary carcinoma with metastases to lymph nodes,subcutaneous tissue,and multiple joints in a dog

An 8‐year‐old, intact female, mixed‐breed dog presented to the Oklahoma State University Boren Veterinary Medical Teaching Hospital for evaluation of progressive lameness and joint effusion of multiple joints. Physical examination revealed joint effusion of the elbow, hock, and stifle joints bilaterally, enlarged left axillary and right popliteal lymph nodes, a subcutaneous mass over the left elbow, and a subcutaneous mass involving the left second and third mammary glands. Cytologic examination of the mammary mass, enlarged lymph nodes, and joint fluid from most affected joints revealed a monomorphic population of loosely cohesive neoplastic epithelial cells. The patient was humanely euthanized, and subsequent necropsy with histopathologic examination revealed a complex mammary carcinoma with metastases to enlarged lymph nodes, subcutaneous tissue over the left elbow, and the synovium of multiple joints. Immunohistochemical stains were performed and showed diffusely positive pan cytokeratin, CK8/18, and CK19 staining in the neoplastic luminal epithelial cells of the mammary carcinoma, synovium, and lymph nodes, and showed diffusely positive vimentin staining of the myoepithelial cells. Myoepithelial calponin positivity was diffuse in the mammary mass and lymph nodes but minimal in the synovium. Only the mammary mass showed p63 positivity. Metastatic mammary neoplasia is relatively common in dogs; however, metastasis to the synovium has only been reported once previously in the literature. This is the first case utilizing immunohistochemistry for confirmation and characterization of metastases.     

Carcinoma of the mammary gland in a mare

A 20‐year‐old Quarter Horse mare was presented with a firm, nonpainful swelling near the axial margin of the left mammary gland. Ultrasound examination of the mass revealed a 35 mm poorly encapsulated, homogeneous mass within the parenchyma of the left mammary gland. Using histopathology and immunohistochemistry, the mass was diagnosed as a mammary carcinoma and showed positivity for cytokeratin 18 (CK18), vimentin and α‐smooth muscle actin. Additionally, the mRNA expression level of the oncogene cMyc did not show a significant upregulation, whereas p53, a well‐known tumour suppressor gene in breast cancer, was significantly reduced in comparison with healthy equine mammary gland tissue. To the authors' knowledge, this is the first report of a significant downregulation of p53 expression in a mammary carcinoma of a mare.     

Expression of fibronectin and its integrin receptor α5β1 in canine mammary tumours

Fibronectin and its integrin receptor α5β1 were studied by immunohistochemical methods in five normal canine mammary glands, four dysplastic glands and 18 mammary tumours. The aim of the study was to evaluate the possible changes in the α5β1 integrin receptor and its ligand fibronectin in relation to the metastatic capacity of canine mammary neoplasms. The immunostaining of α5β1 was very uniform in the hyperplastic glands but uneven in the mammary tumours. The expression of α5 and β1 was diminished in metastatic tumours but there were some α5-positive cells with pronounced features of malignancy and immaturity. Stromal fibronectin was increased in most cases and cytoplasmic staining of fibronectin was observed in epithelial and myoepithelial cells in mammary neoplasms but not in normal or dysplastic mammary tissue. There was no relationship between the content of α5β1 and the expression of fibronectin in canine mammary tumours.     

Immunocytochemical differentiation of neoplastic and hyperplastic canine epithelial lesions in cytologic imprint preparations

The aim of the study was to test the potential use of commercially available antibodies generated against human cytokeratins in differentiating canine epithelial tumours in cytological samples. Immunocytochemical staining procedures were performed on 183 different primary epithelial canine tissues (including hyperplasia [n=7], dysplasia [n=3], benign [n=54] and malignant [n=119] neoplasia) and 20 distant metastases of 13 of the malignant tumours. All epithelial tumours and their metastases stained distinctly positive with broad spectrum anti-cytokeratin AE1/AE3. Immunocytological reactions with broad spectrum anti-cytokeratin KL1 produced less reliable results. Numerous negative reactions were found, especially in columnar epithelium tumours, whereas squamous epithelium tumours were KL1-positive. In most cases specific antibodies CK7, CK8,CK14,CK18 and CK20 showed similar reaction patterns when compared to reactivity in human tissues. Immunocytological staining was found to be a reliable and valuable diagnostic technique when combined with conventional cytology and may be especially suitable for the differentiation of undifferentiated epithelial tumours and distant metastases of unknown origin.     

Risk factors for Coxiella burnetii antibodies in bulk tank milk from Danish dairy herds

The aim was to identify risk factors associated with Coxiella burnetii antibody positivity in bulk tank milk (BTM) samples from 100 randomly selected Danish dairy cattle herds. Antibody levels were measured by an enzyme-linked immuno-sorbent assay. Before testing the herds, the farm managers were interviewed about hired labour, biosecurity, housing and herd health during the 12 months prior to the study. Variables considered important for C. burnetii antibody positivity in multivariable logistic regression analysis included the sharing of machines between farms (OR = 3.6), human contacts (OR = 4.2), artificial insemination by other people than artificial insemination technicians (OR = 7.7), routine herd health contract with the veterinarian (OR = 4.3) and hygiene precautions taken by veterinarians (OR = 5). In addition, herd size, hired labour, trading of cattle between farms, quarantine and use of calving and disease pens also showed significant association in univariable analysis. This study demonstrates that strict biosecurity is important for the prevention of infections with C. burnetii.     

Bovine mammary epithelial cells retain stem-like phenotype in long-term cultures

The detection and characterization of bovine mammary stem cells may give a better understanding of the cyclic characteristic of mammary gland development. In turn, this could potentially offer techniques to manipulate lactation yield and for regenerative medicine. We previously demonstrated that adult stem cells reside in the bovine mammary gland and possess an intrinsic regenerative potential. In vitro maintenance and expansion of this primitive population is a challenging task that could make easier the study of adult mammary stem cells. The aim of this study is to investigate this possibility. Different subpopulations of mammary epithelial cells emerge when they are cultured in two defined culture conditions. Specific cell differentiation markers as cytokeratin 18 (CK18) and cytokeratin 14 (CK14) were expressed with significant differences according to culture conditions. Vimentin, a well-known fibroblast marker was observed to increase significantly (P < 0.5) only after day 20. In both conditions, after prolonged culture (25 days) a subset of cells still retained regenerative capabilities. These cells were able to form organized pseudo-alveoli when transplanted in immunodeficient mice as shown by the expression of cytokeratin 14 (CK14), cytokeratin 18 (CK18), p63 (a mammary basal cell layer marker) and Epithelial Cell Adhesion Molecule (EpCAM). We also were able to observe the presence of milk proteins signal in these regenerated structures, which is a specific marker of functional mammary alveoli. Progenitor content was also analyzed in vitro through Colony-Forming Cell (CFC) assays with no substantial differences among culture conditions and time points. These results demonstrate that long-term culture of a multipotent cell subpopulation with intrinsic regenerative potential is possible.     

Effect of storage time on the urine protein: creatinine ratio in alkaline ovine urine

The urine protein:creatinine (UPC) ratio is considered the reference method to assess proteinuria. Its diagnostic value in ovine medicine needs further elucidation. In population monitoring and/or for research purposes, it is convenient to collect many samples simultaneously and store them for later analysis. However, analyte stability data are required to ensure reliable results. We used 15 of 90 urine samples collected from sheep to assess the effect of storage time on the UPC ratio. After centrifugation, the supernatant of each sample was divided into 6 aliquots. Urine protein and creatinine concentrations were determined immediately in one aliquot using the pyrogallol red and a modified Jaffè method, respectively. The other aliquots were stored at −18°C. Based on the absence of active sediment, alkaline urine pH, and UPC ratio ≥0.2, we included 15 samples in our study. The UPC ratio was determined in the stored aliquots 2, 7, 14, 21, and 60 d after collection. The data were analyzed with univariate ANOVA. No significant difference was observed in the urinary concentrations of protein, creatinine, and the UPC ratio (0.8 ± 0.84 in conventional units and 0.09 ± 0.095 in SI units) among different times (p > 0.05). The UPC ratio remained stable for 2 mo in ovine urine samples stored at −18°C.     

Secretory component and IgA expression by epithelial cells in sow mammary gland and mammary secretions

Secretory component (SC) and IgA expression of epithelial cells were studied in the mammary tissue and mammary secretions of sows. In mammary tissue, SC was not detected until day 105 of gestation. From the time of delivery (day 115) to the time of established lactation, the proportion of epithelial cells containing sc rose from 20 per cent to nearly 100 per cent. There was no IgA in alveolar epithelial cells until day 105 of gestation; on day 115, IgA positive epithelial cells were present in 10 per cent of the alveoli, which increased to 80 per cent during lactation. Epithelial cells represented more than 20 per cent of the total cells in colostrum, and predominated over leucocytes in milk. In colostrum, these epithelial cells (9 to 15 μm) showed weakly positive membrane, sc, contained cytoplasmic SC and had a limited capacity for in vitro proliferation. Ten per cent of epithelial cells contained intracytroplasmic IgA. In milk, the epithelial cells were larger (15 to 40 μm) with a higher expression of both membrane and intracytoplasmic sc; 66 per cent of these cells expressed intracytoplasmic IgA. These data showed that the capacity of mammary epithelium to process IgA to secretory IgA was complete at the end of mammary gland organisation, and established that the epithelial cells of milk contribute to the transfer of IgA to neonates.     

Spontaneous Adenosquamous Carcinoma with Rapid Growth and EMT-like Changes in the Mammary Gland of a Young Adult Female BALB/c Mouse

This study histopathologically and immunohistochemically investigated a spontaneously occurring single mass subcutaneously located in the left lower abdomen of a female BALB/cAJcl−nu/+ mouse at 10 weeks of age. The mass was about 20 × 15 × 10 mm in size after formalin fixation; nevertheless, it was not detected by clinical observations at 9 weeks of age. H&E staining revealed the tumor origin was epithelial and probably arose from the mammary gland, and the tumor cells demonstrated a squamous, acinar or polyhedral/basal pattern. A cell kinetics analysis revealed that many of the tumor cells of the squamous, acinar or polyhedral/basal component were positive for PCNA and cyclin D1, although there were a few of TUNEL-positive tumor cells in all of the components. An epithelial/mesenchymal analysis demonstrated that most of the tumor cells of the squamous and acinar components contained keratin and E-cadherin; however, most of the tumor cells of the polyhedral/basal component were less or very weakly positive for these markers. The tumor cells of the squamous component were negative for vimentin and SMA; however, many of the tumor cells of the polyhedral/basal component exhibited vimentin. In addition, expression of SMA was confirmed in some tumor cells of the acinar and basal components. Based on the microscopic and immunohistochemical characterizations, the tumor was diagnosed to be adenosquamous carcinoma that originated from the mammary gland with rapid growth, and the tumor cells demonstrated epithelial-mesenchymal transition-like changes.     

Progesterone receptors in normal,dysplastic and tumourous feline mammary glands. Comparison with oestrogen receptors status

The aims of the study were to standardise an immunohistochemical (IHC) method for the detection of progesterone receptors (PR) on formalin-fixed, paraffin wax-embedded tissue sections of feline mammary gland tumours and dysplasias, comparing the results with those obtained using the radiolabelled ligand dextran coated charcoal (DCC) assay applied to frozen tissue samples from the same cases. Also, to define the immunohistochemical distribution of PR in the different cellular compartments of the lesions and to compare the oestrogen receptor (ER) and PR status of the feline mammary lesions. Proliferative mammary lesions collected from 34 cats were studied; 25 malignant tumours and 9 benign tumours and dysplasias. PR protein was present at a concentration of 5 fmol mg(-1) (positivity threshold) in 37.5 per cent of malignant tumours and 66.7 per cent of benign tumours and dysplasias while immunoreative products to PR antibody were found in the nuclei of tumour cells in 38.5 per cent and 66.7 per cent of the cases, respectively. Concordance between DCC-PR and IHC-PR was 88.5 per cent (P<0.001). The specificity (true negatives) and sensitivity (true positives) of the IHC method were 89.4 per cent and 87.5 per cent respectively. The presence of PR was linked to the absence of ovariectomy (P<0.02). Oestrogen receptors, detected by either method, were also detected in half the cases in which PR had been detected. In malignant tumours, the most prevalent groups were the ER + PR + and ER-PR + groups.     

Expression of cytokeratin 18 during pre- and post-natal porcine lung development

The expression pattern of the intermediate filament protein cytokeratin 18 (CK 18) is described during pre- and post-natal development of the porcine lung using a monoclonal antibody against human CK 18. Lungs from 16 foetuses in pseudoglandular, canalicular, saccular and alveolar stages of lung development and lungs from 12 pigs ranging in age from birth to 49 days after birth were studied by immunohistochemistry.In the early pseudoglandular stage of development (day 70 of gestation) all the columnar epithelial cells lining the tubular endbuds strongly expressed CK 18 predominantly in the apical cell compartment. A modest staining was found in the more cuboidal cells of the canalicular stage (day 80 of gestation) where the labelling occurred as a distinct positive rim at the apical cell membrane in most of the cells lining the canaliculi. In 96- and 100-day-old foetuses, parts of the gas exchanging area were formed as terminal sacs by extreme attenuation of the epithelium. In this stage, CK 18 was clearly detectable in the flat type I as well as in the cuboidal type II alveolar epithelial cells. A marked change of the CK 18 expression pattern occurred during formation of the alveoli by septal outgrowth and maturation of the epithelium in 105- and 111-day-old foetuses. Differentiated type I cells no longer expressed CK 18, whereas type II cells were still labelled. Moreover, a specific change in the subcellular distribution pattern from the luminal periphery in immature porcine type II cells to a cytoplasmic localization in differentiated type II cells could be observed. Our investigation additionally demonstrated that the epithelium of bronchi, bronchioli and terminal bronchioli expressed CK 18 in all pre- and post-natal developmental stages. From the 96 days of gestation onwards the epithelial cells of developing bronchial glands were also labelled. Our results clearly show that during porcine lung development profound changes in the cellular expression pattern of CK 18 occur and that CK 18 can be regarded as a selective marker for differentiated porcine alveolar type II cells from the 105th day of gestation onwards. We also assume that the intermediate filament CK 18 could be of significance in the maturation process of the type II alveolar cells.     

Immunolocalization of insulin-like growth factor-I (IGF-I) and its receptors (IGF-IR) in the equine epididymis

Insulin-like growth factor plays a paracrine/autocrine role in regulating testicular function in the stallion, but its presence in the equine epididymis remains unknown. The aim of this study was to test the hypothesis that insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) are localized in the caput, corpus, and cauda of the epididymis in an age-dependent manner. Immediately after castration, epididymal tissue was fixed, paraffin-embedded, and processed for immunohistochemistry (IHC). Western blot was also performed using equine epididymal extracts to verify the specificity of the antibodies against IGF-I and IGF-IR. Immunolabeling of IGF-I was observed in the cytoplasm of principal and basal cells in the caput, corpus, and cauda at the pre-pubertal (3–7 months), pubertal (12–18 months), post-pubertal (2–4 years), and adult stages (4.5–8 years). Immunolabeling of IGF-IR was observed in the cytoplasm of principal cells in all regions of the epididymis in each age group. Immunolabeling of IGF-IR was also detected in the cytoplasm of basal cells from animals of all ages. Bands observed by Western blot corresponded to the molecular weights of IGF-I and IGF-IR, ~23 kDa and 95 kDa, respectively. These results suggest that IGF-I might function as an autocrine and/or paracrine factor during the development, maintenance and/or secretions of the stallion epididymis.     

Basket and Basal-duct Cells in Domestic Animals: Different Cytokeratin Expression and Shape

Cytokeratins (CKs) are a multigenic family of proteins constituting intermediate filaments in epithelia, indicated in humans by the numbers 1–20. Different cell-types can be immunocytochemically identified on the grounds of their CK expression. This investigation was designed to study CK expression of basket cells (BCs) and basal-duct cells (BDCs) in some domestic animals. Frozen sections of mammary and major salivary glands from cows, sheep, pigs and rabbits were treated using the immunofluorescent method, using as monoclonal antibodies clones CK-E3, CKB1, KS-1A3, and LDS-68, respectively, revealing the human CKs 17, 14, 13, 7. BCs surrounding acini and BDCs were stained by CK 17 antibody only in the rabbit. CK 14 was detectable in both cell types in cows, sheep and pigs, except in the case of bovine salivary BCs. CK 13 was revealed in BCs and BDCs of all mammary glands and also rabbit salivary glands. In the salivary glands of the other species, only BDCs were stained. CK 7 gave unreliable results in all the species and cell types examined. Interestingly, in the rabbit, also BDCs are basket-like in shape. The antibodies employed showed different staining depending on species and gland. On the grounds of immuno-reactivity and shape. BCs and BDCs can be considered the same cell type in the rabbit. In the other species, they appear to be different, since BDCs may express additional CKs and are triangular-shaped, whereas BCs are truly basket-like. It is worth noting that clone KS-1A3 in the rabbit and CKB1 in the sheep and pig can be considered markers of the basket/basal system.     

Poor maternal nutrition inhibits muscle development in ovine offspring

Background

Maternal over and restricted nutrition has negative consequences on the muscle of offspring by reducing muscle fiber number and altering regulators of muscle growth. To determine if over and restricted maternal nutrition affected muscle growth and gene and protein expression in offspring, 36 pregnant ewes were fed 60%, 100% or 140% of National Research Council requirements from d 31 ± 1.3 of gestation until parturition. Lambs from control-fed (CON), restricted-fed (RES) or over-fed (OVER) ewes were necropsied within 1 d of birth (n = 18) or maintained on a control diet for 3 mo (n = 15). Semitendinosus muscle was collected for immunohistochemistry, and protein and gene expression analysis.

Results

Compared with CON, muscle fiber cross-sectional area (CSA) increased in RES (58%) and OVER (47%) lambs at 1 d of age (P < 0.01); however at 3 mo, CSA decreased 15% and 17% compared with CON, respectively (P < 0.01). Compared with CON, muscle lipid content was increased in OVER (212.4%) and RES (92.5%) at d 1 (P < 0.0001). Muscle lipid content was increased 36.1% in OVER and decreased 23.6% in RES compared with CON at 3 mo (P < 0.0001). At d 1, myostatin mRNA abundance in whole muscle tended to be greater in OVER (P = 0.07) than CON. Follistatin mRNA abundance increased in OVER (P = 0.04) and tended to increase in RES (P = 0.06) compared with CON at d 1. However, there was no difference in myostatin or follistatin protein expression (P > 0.3). Phosphorylated Akt (ser473) was increased in RES at 3 mo compared with CON (P = 0.006).

Conclusions

In conclusion, maternal over and restricted nutrient intake alters muscle lipid content and growth of offspring, possibly through altered gene and protein expression.     

Immunolocalization of lingual antimicrobial peptide (LAP) in the bovine mammary gland

Lingual antimicrobial peptide (LAP), a member of the β-defensin family in cows, is involved in the innate immune system and plays a crucial role in killing a large variety of microorganisms. The aim of the present study was to demonstrate the immunolocalization of LAP in the mammary glands of cows. A LAP antibody was raised in a rabbit by immunity with a synthetic 11 amino acid sequence out of a 42-amino acid sequence of the mature form of LAP. The specificity of the LAP antibody was checked using a competitive immunoassay and Western blotting. Paraffin sections of the mammary gland were immunostained with LAP antibody. In the competitive immunoassay, an increase of synthetic LAP concentration suppressed the optical density. Western blotting analysis for LAP revealed the presence of the LAP peptide in mammary alveolar tissue. When the mammary gland was immunostained with LAP antibody, epithelial cells of both infected and non-infected alveoli were immunopositive. These results indicate that LAP is localized in the epithelium of non-infected as well as infected alveolus in the mammary gland in cows.     

Occurrence of congenital disorders in Swiss sheep

Background

The rates of congenital disorders in Swiss sheep were determined by a questionnaire which was sent to 3,183 members of the Swiss Sheep Breeders’ Association.

Findings

A total of 993 questionnaires were returned, giving a response rate of 31.2%. Of these, 862 questionnaires originated from farms keeping one of the predominant Swiss sheep breeds: Swiss White Alpine sheep, Brown-Headed Meat sheep, Swiss Black Brown Mountain sheep and Valais Blacknose sheep. During a 10-year-period, entropion was reported in 33.6% of the farms, brachygnathia inferior in 29.5%, abdominal/umbilical hernia in 15.9%, cryptorchidism in 10.5% and torticollis in 10.5%. The most significant difference between the four breeds (P < 0.001) occurred for entropion in Swiss White Alpine sheep and Brown-Headed Meat sheep, brachygnathia inferior in Swiss Black Brown Mountain sheep, and scrotal/inguinal hernia in Valais Blacknose sheep. The Swiss White Alpine breed showed a significantly higher animal prevalence of entropion (6.2% in 2011 and 5.5% in 2012) than other breeds (P < 0.001).

Conclusions

These findings indicate a breed-specific necessity for action, particularly regarding Swiss animal welfare legislation, especially entropion in Swiss White Alpine sheep is concerned. In general, careful selection of breeding stock is to be recommended.     

不同培养方法对山羊瘤胃上皮细胞生长及角蛋白18表达量的影响

本试验旨在研究不同培养方法对山羊瘤胃上皮细胞生长及角蛋白18(CK18)表达量的影响。采集42日龄山羊的瘤胃上皮组织,分别采用酶消化法和组织块法对其进行体外培养。通过光学显微镜观察原代培养和传代培养阶段的细胞形态,检测第5代山羊瘤胃上皮细胞的生长曲线,并采用细胞免疫荧光法对山羊瘤胃上皮细胞进行鉴定。结果显示:1)经0.25%胰蛋白酶+0.02%乙二胺四乙酸消化获得的原代培养山羊瘤胃上皮细胞于2 d开始贴壁生长,5 d细胞开始明显增多,10 d细胞数量达到最大。2)经组织块法获得的原代培养山羊瘤胃上皮细胞于4 d开始"爬出"组织块,8 d细胞开始明显增多,14 d细胞数量达到最大。3)经免疫荧光染色显示2种方法获得的细胞胞浆内CK18均呈阳性表达且细胞纯度后者明显高于前者。4)组织块法获得的细胞CK18表达量显著高于酶消化法(P0.05)。综合得出,与酶消化法相比,应用组织块法可成功获得纯度更高的山羊瘤胃上皮细胞。     

Distribution of cytokeratin polypeptides detected by monoclonal antibodies K8.13 and K8.12 in the fetal bovine ruminal epithelium.

Temporal and spatial distributions of cytokeratin (CK) polypeptides were detected by monoclonal antibodies (mAbs) K8.13 and K8.12 during the development of the bovine ruminal epithelium. By the Western blotting analysis after the sodium dodecyl sulfate-polyacrilamide gel electrophoresis, mAb K8.13 confirmed 60.8 and 63.0 kD CK polypeptides in the fetal ruminal epithelial extract, and mAb K8.12 also 48.0 and 54.0 kD CK polypeptides. Immunohistochemical reactivities against both mAbs were detected only in the epithelial cells throughout the fetal periods. Distributions of CK polypeptides detected only by mAb K8.13 were observed on the basal side of the epitherial layer, but not by mAb K8.12 in the 7 cm fetus in crown-rump length. MAb K8.13 reacted also intensely with columnar-shaped cells in the basal layer in the fetuses of the later developmental periods. These results suggest that CK polypeptides detected by mAb K8.13 might be involved in the differentiation and/or the maintenance of the basal layer in the ruminal epithelial development.