Milk yield and reproductive performance of Holstein cows testing positive for bovine tuberculosis.

The objective of this study was to determine if high milk-yielding Holstein cows testing positive for bovine tuberculosis (bTB) are affected in their reproductive performance and milk yield. For this purpose, 1044 healthy cows and 105 bTB reactor cows were used. Tuberculosis reactor cows were from four large commercial dairy operations from the same region which were transferred from their barns to an isolated dairy facility. Cows free from this disease were placed in the same barn as the bTB reactor cows but in an isolated division and served as control animals. The analysis of variance with a general linear model for binary data showed that the reproductive performance of bTB reactors was impaired; overall pregnancy per artificial insemination differed (P < 0.05) between bTB reactor and non-reactor cows (16.9 vs. 20.7%). Cows that were TB reactors required 4.7 ± 2.9 services per pregnancy compared with 4.3 ± 2.8 for control cows (P > 0.05). The intervals between calving and conception were similar between bTB reactors (154 ± 78 days) and control animals (150 ± 80 days). Control cows tended (P = 0.08) to produce more milk than bTB reactors over a 305-day lactation (10,684 ± 1720 vs. 10,345 ± 1736; mean ± SD). Serum metabolites indicative of nutritional stress did not differ between bTB reactor and non-reactor cows. It was concluded that both reproductive performance and milk yield decreased marginally in bTB reactor cows, which explains the reluctance of milk producers to get rid of these animals.

Maturation-associated immunophenotypic abnormalities in bone marrow B-lymphocytes in myelodysplastic syndromes.

Recent studies concerning the pathophysiology of myelodysplastic syndromes (MDS) have shown evidences for the existence of complex interactions between hematopoietic stem cells and the bone marrow (BM) microenvironment. We analyzed the B-lymphocyte maturation in BM of patients with MDS. For this purpose, 41 newly-diagnosed patients were analyzed. Enumeration and characterization of CD34+ and CD34- B-cell precursors and mature B-lymphocytes was performed using multiparameter flow cytometry. BM from eight transplant donors and six orthopedic surgery patients were used as controls. CD34+/CD45(lo) B-cells were found in 17/22 patients with RA/RARS and in 5/13 with RAEB. In patients with RAEB-t and CMML no CD34+ B-cell precursors could be detected. A positive correlation was found between CD34+ and CD34- B-cell precursors (r=0.52). CD34+ B-cell precursors presented an inverse correlation with BM percentage of blasts and peripheral leukocytes and a positive one with hemoglobin. Asynchronous antigen expression (CD19+/CD79a- cells) was found in 7/11 cases of RA/RARS and 6/18 cases of RAEB in which this phenotype was examined. Abnormal patterns of expression for at least one antigen was found in 91% of RA/RARS cases and in 74% of RAEB. Underexpression of TdT and CD79a were the most frequent abnormalities. Our results present evidences of an abnormal B-cell maturation in MDS. This may be an evidence that B-lymphocytes are derived of the abnormal clone. But it may also be the consequence of influences of abnormalities of BM microenvironment leading to an impaired commitment and maturation of the B-cell line in MDS. Studies performed with purified well-characterized B-cells may further elucidate these abnormalities.