ABSTRACT

Fragile X Chromosome in Baldy Calf Syndrome

Alain Bouvet, D.M.V., M.Sc.

Supervisor: Dr. P.K. Basrur

Chromosome evaluation was carried out on blood culture samples of 40 animals including six baldy calves, to determine whether the Fragile X chromosome reported previously in baldy calves is a consistent feature of this syndrome. Influence of the baldy calf environment on the integrity of chromosome was tested by inoculating cultures of lymphocytes from normal heifers, with either varous concentrations of plasma from baldy calves or Mycoplasma arginini isolated from clinical cases of Baldy Calf Syndrome. The possible association between the Fragile X trait and the altered immunocompetence evident in baldy calves was tested using various lymphocyte parameters including differential count, blast transformation response to mitogens, antibody levels and ultrastructural features, in normal and affected animals. Medical records, necropsy reports and results of morphological studies on skin and tongue lesions of baldy calves were compiled to characterize the syndrome.

Results of our study indicate that a Fragile X is present only in cultures of blood samples from female Holstein-Friesians, and that an elevated but variable percentage of cells with a Fragile X chromosome is a consistant f cature of the Baldy Calf Syndrome. Exposure to Mycoplasma arginini or baldy calf plasma did not significantly alter the frequency of Fragile X in cultured lymphocytes from normal heifers, suggesting that the Fragile X trait, like the skin lesions, may be one of the pleiotropic expressions of the mutant gene for Baldy Calf Syndrome.

Some of the features of this syndrome were similar to those reported in the human Fragile X Syndrome. Similarities of this syndrome with inherited zinc deficiency in cattle with regard to chromosome features, clinical signs of reduced immunocompetence and morphological atterations in the skin, suggest that the mutant gene for Baldy Calf Syndrome could also be interfering with chromosome integrity and zinc metabolism.


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