Analysis of major repetitive DNA sequences in the dog (Canis familiaris) genome.

A systematic screening and analysis of repeated DNA sequences from a dog genomic library composed of small DNA inserts enabled us to characterize abundant canine repetitive DNA families. Four main families were identified: i) a group of highly repeated tRNA-derived short interspersed repetitive DNA elements (tRNA-SINEs); ii) another type of SINE-like element that was mainly found inserted into long interspersed repetitive elements (LINEs); iii) LINEs of the L1 type; and iv) satellite or satellite-like DNA. Surprisingly, no SINEs derived from 7SL RNA were found in the dog genome. These data should help in the analysis of canine DNA sequences and in the design of canine genome mapping reagents.

Bizarre "sawtooth" tympanogram in a patient with otitis media.

A patient evaluated for otitis media had a bizarre tympanogram with a "sawtooth" configuration. Acute otitis media with a pinpoint perforation was diagnosed. After resolution of the acute infection, a 2-mm diameter perforation remained and the presence of a patulous eustachian tube was documented. Tympanoplasty was eventually required, after which a normal tympanogram was recorded. Our interpretation of the tympanogram is discussed and the literature reviewed.

Partial characterization of a familial B lymphosarcoma with a thymic localization in cattle.

We recently described an original epidemiological form of bovine leukosis in cattle. In the young female offspring of one bull, more than 3% of animals developed a thymic lymphoblastic lymphosarcoma. Of these, 31 cases, together with a lymphoid cell line established from one of the tumours, were phenotypically characterized. Characterization was done using a large combination of well clustered monoclonal antibodies, and monoclonal antibodies prepared in our laboratory by immunizing mice either with bovine normal lymphocytes or with tumour thymic cells. The thymic tumours and the cell line did not express any T lymphoid antigens but they did express some B lymphoid markers. The phenotype of the tumour cells was CD45+/-, CD44+/- TdT+, class II-DR+/-, CD19+/-, CD21-, Ig- and HBM 57+ (recognizing the mb-1 chains of the B-cell receptor). The cell line expressed a more mature phenotype: TdT-, CD45-, CD44+, class II-DR+, CD19+, CD21+/- and sIgG+. These results allow us to consider these tumours as B-cell derived. These B lymphosarcomas with a thymic localization are reminiscent of a human mediastinal non-lymphoblastic lymphoma reported as a primary mediastinal clear cell lymphoma. The possibility of a thymic or extrathymic origin for this B lymphosarcoma is discussed.

[Preparation and characterization of a monoclonal antibody directed against bovine leukocytes]. / Préparation et caractérisation d'un anticorps monoclonal dirigé contre des leucocytes bovins.

A monoclonal antibody (MAb-M25) was obtained by immunizing BALB/C mice with tumour cells isoled from a familial thymic lymphosarcoma observed in Friesian cattle. The specificity of this MAb was assessed using PBL, lymphoids organs (lymph node, spleen, tonsil, Pleyer's patch) and non lymphoid tissues (liver, skin) from clinical normal cattle. Immunofluorescence and immunohistochemistry methods were used to characterise this monoclonal antibody. It reacted with 27% of peripheral blood lymphocytes and a large proportion of mononuclear cell in the lymphoid organ, in the thymic cortical, in the dermis and in the liver. It also stained lymphocytes of the mantle of follicules and thymocytes of the thymus cortex. The tissue distribution of M25 have a similarity with the human CD1c Mab and the bovine 20-27 MAb.

Epidemiological and pathological studies of a familial thymic lymphosarcoma in bovine species.

A total of 216 cases of the thymic form of bovine leukosis were observed in Holstein calves in several departments of France over a period of 18 months. Almost all of these calves were sired by the same bull. The calves were negative for bovine leukemia virus-specific antibodies. Morphological studies, including light and electron microscopic cytology, and immunophenotyping were performed in 38 cases. The tumor cells exhibit membrane markers (T-cell antigens) at variable levels, which indicate that they are T-lymphoid derived. The cells are maintained at a very early stage of differentiation as indicated by TdT enzyme activity and the presence of MHC class II antigen.

Preparation and characterization of a monoclonal antibody against bovine CD5 lymphocyte surface antigen.

The M1 monoclonal antibody (mAb) was proved to recognize 51-70% of Bovine peripheral blood lymphocytes (PBL). The M1+ cells were SIg-. In spleen and lymph nodes, the M1 positive lymphocytes were located within the T cell areas. All the lymphoid follicles remained negative. In the thymus, 10% of thymocytes were M1+, most of them were located in the medulla. The M1 mAb did not inhibit spontaneous rosette formation by sheep erythrocytes and bovine lymphocytes. On the other hand, biochemical analysis of membrane antigen with bovine thymic tumor cell line LB203 gave a molecular weight of 75 kDa. Despite a slight difference in biochemical results (75 vs 67-69 kDa). Our data permit us to consider M1 mAb as a possible homologous of human anti-CD5 mAb. Finally, M1 cross-reacted with sheep peripheral blood T lymphocytes.