Julia T. Blue

Canine X-linked muscular dystrophy: An animal model of Duchenne muscular dystrophy: Clinical studies

The progression of clinical disease and serum creatine kinase (CK) levels in canine X-linked muscular dystrophy (CXMD) was studied in 7 dogs from birth to 12-14 months and in 18 dogs at varying intervals from birth to 8 weeks. One affected male was studied from age 3.5 to 6 years, and all pups were descendants of this dog. A lethal neonatal form was recognized in some pups. In the more typical form, clinical signs of stunting, weakness and gait abnormalities were evident by 6-9 weeks and were progressive, leading to marked muscle atrophy, fibrosis and contractures by 6 months. Serum CK levels were markedly elevated, such that affected pups could be identified by 1 week. CK values increased until 6-8 weeks, then plateaued at approx. 100 times normal. Affected females and beagle-cross dogs were less severely affected than large breed-cross dogs. In the 2 adult dogs with cardiac insufficiency CK levels had decreased to 5-15 times normal. These studies show that CXMD and Duchenne muscular dystrophy have striking phenotypic as well as genotypic similarities. In addition, these studies of CXMD suggest that in females and in smaller dogs the same genetic defect results in a less severe clinical disease.

Longitudinal evaluation of bovine mammary gland health status by somatic cell counting, flow cytometry, and cytology

Bovine mastitis phases induced by Staphylococcus aureus were assessed in 6 lactating cows before challenge and at 1, 4–8, and 9–14 days postinoculation (dpi). Milk lymphocytes, macrophages, and polymorphonuclear cells (PMN) were counted by conventional (manual) cytology, identified by CD3+ and CD11b+ immunofluorescence and counted by flow cytometry (based on leukocyte forward and side light scatter values). Somatic cell counts (SCC) and recovery of bacteria were recorded at the same times. Preinoculation samples showed a lymphocyte-dominated composition. At 1 dpi, the percentage of PMN increased and that of lymphocytes decreased. At 4–8 dpi, PMN were predominant, but the percentage of mononuclear cells increased above that at 1 dpi and further increased by 9–14 dpi (when lymphocytes approached prechallenge values). Based on leukocyte percentages, 3 indices were created from the data: 1) the PMN/lymphocyte percentage ratio (PMN/L), 2) the PMN/macrophage percentage ratio (PMN/M), and 3) the phagocyte (PMN and macrophage)/lymphocyte percentage ratio (Phago/L). Significant correlations were found between cytologic and flow cytometric data in all of these indicators (all with P ≤ 0.01). These indices identified nonmastitic, early inflammatory (1–8 dpi), and late inflammatory (9–14 dpi) animals. In contrast, SCC and bacteriology did not. Although sensitivity of the SCC was similar to that of Phago/L, the specificity of SCC was almost half that of the Phago/L index. Based on flow cytometry indicators, an algorithm for presumptive diagnosis of bovine mastitis was developed. Flow cytometry provides results as valid as those obtained by conventional (manual) cytology, shows greater ability to identify mastitic cases than does SCC, and may identify 3 mammary gland health-related conditions.

Lead in tissues of woodchucks fed crown vetch growing adjacent to a highway

Woodchucks (Marmota monax) were fed crown vetch (Coronilla varia) growing along a major highway that was harvested in 1979, before unleaded gas was widely used, and again in 1985. Crown vetch, harvested 300 m from the nearest road, was fed as the control. The crops were fed as 50% dry weight of the diet for 58 d. The concentrations of lead in the control, 1979 crop, and 1985 crop were, respectively, 0.74, 50.65, and 6.78 ppm dry weight. The average +/- SE) concentrations (ppm, dry weight) of lead found in the tissues of the control, 1979, and 1985 dietary-treatment animals were, respectively, kidney, 0.36 +/- 0.05, 5.78 +/- 0.72, and 0.79 +/- 0.09; liver, 0.09 +/- 0.01, 4.71 +/- 0.17, and 0.46 +/- 0.06; muscle, 0.07 +/- 0.01, 0.14 +/- 0.02, and 0.07 +/- 0.00; blood, 0.09 +/- 0.02, 2.17 +/- 0.13, and 0.31 +/- 0.05; and bone, 1.27 +/- 0.25, 47.52 +/- 7.05, and 3.71 +/- 0.65. No significant differences (p greater than 0.05) between dietary treatments were found in the general hematological analyses of the woodchucks. The ecological significance of these findings is discussed.

1,25-Dihydroxy vitamin D2 induces leukemia cell differentiation.

Dear Editor: 1,25-dihydroxy vitamin D2, like 1,25-dihydroxy vitamin D3, can modulate the proliferation and differentiation of human promyelocytic leukemia cells. HL-60 human promyelocytic leukemia cells, which are known to undergo terminal differentiation along the monocytic lineage in response to 1,25-dihydroxy vitamin D3, were cultured in the presence of varying concentrations of 1,25-dihydroxy vitamin D2. The cells underwent G1/0 specific growth arrest and monocytic differentiation. The kinetics of growth arrest and phenotypic differentiation were similar to that observed previously for 1,25-dihydroxy vitanfin D3. 1,25-dihydroxy vitamin D2 was effective at concentrations of 10 -6 M at effecting growth arrest and phenotypic differentiation. Reducing the concentration to 10 -s M resulted in no apparent growth arrest or differentiation. Dose-response studies indicate that G1/0 specific growth arrest and phenotypic differentiation due to 1,25-dihydroxy vitamin D2 are coupled. Vitamin D3 is the vitamin historically most well known for its role in mediating intestinal calcium absorption, as well as in bone calcium metabolism. It is a dietary factor which is required for proper animal development. It has also been found to have activity in the treatment of the childhood neoplasia, retinoblastoma (1). In this regard, at the cellular level it can control proliferation and differentiation, presumably acting through its ligand-receptor complex which binds DNA to regulate gene expression (11). It has thus been studied extensively in investigations of cell proliferation and differentiation, gene expression and cancer therapy, as well as its traditional setting in nutrition. In one well studied in vitro model for cell growth and differentiation, HL-60 human promyelocytic leukemia cells (4), the active metabolite of vitamin D3, 1,25-dihydroxy vitamin D3, is well known to induce these promyelocytic cells to terminally differentiate into monocytes (8-10,14). Its cellular and genetic effects have thus been well studied in this context. In contrast, vitamin D2 has been less studied. Vitamin D2 is chemically similar to vitamin D3, diverging by only one double bond and a methyl group on its alkyl chain. However, their metabolism is not always the same (7). Nevertheless they can have similar vitamin D receptor interactions in the cases of both the intestinal (2) and thymus derived receptors (6). They can also have similar metabolic and pharmacological effects (3,5,6). Given this, an obvious question is whether the active metabolite of vitamin D2, 1,25-dihydroxy vitamin D2, has activity to induce the differentiation of HL-60 human promyelocytic leukemia cells similar to that of 1,25-dihydroxy vitamin D3. A positive indication in this case would suggest that both had similar capability to induce programs of cell differentiation. 1,25-dihydroxy vitamin D2 at a concentration of 10 -6 M causes G1/0 specific growth arrest of HL-60 cells. Exponentially growing HL-60 ceils were placed in culture with 1,25-dihydroxy vitamin D2 and samples were harvested at periodic intervals to determine the relative number of ceils in each of the cell cycle phases G1/0, S, G2+M by flow cytometry (15). G1/0 specific growth arrest would