Fertilizer, tillage, and dairy manure contributions to nitrate and herbicide leaching.

Few studies have examined the water quality impact of manure use in no-tillage systems. A lysimeter study in continuous corn (Zea mays L.) was performed on Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalf) to evaluate the effect(s) of tillage (no-till [NT] and chisel-disk [CD]), nitrogen fertilizer rate (0 and 168 kg N ha(-1)), and dairy manure application timing (none, spring, fall, or fall plus spring) on NO3-N, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), and alachlor [2-chloro-2'-6'-diethyl-N-(methoxymethyl)acetanilide] concentrations in leachate collected at a 90-cm depth. Herbicides were highest immediately after application, declining to less than 4 mug L(-1) in about two months. Manure and manure timing by tillage interactions had little effect on leachate herbicides; rather, the data suggest that macropores rapidly transmitted atrazine and alachlor through the soil. Tillage usually did not significantly affect leachate NO3-N, but no-tillage tended to cause higher NO(3)-N. Manuring caused higher NO3-N concentrations; spring manuring had more impact than fall, but fall manure contained about 78% of the N found in spring manure. Nitrate under spring "only fertilizer" treatment exceeded 10 mg L(-1) 38% of the time, compared with 15% for spring only manure treatment. After three years, manured soil leachate NO3-N exceeded that for soil receiving only N fertilizer. Soil profile (90 cm) NO3-N after corn harvest exceeding 22 kg N ha(-1) was associated with winter leachate NO3-N greater than 10 mg N L(-1). Manure can be used effectively in conservation tillage systems on this and similar soils. Accounting for all N inputs, including previous manure applications, will be important.

Functional and biochemical characterization of B-cell differentiation factor (BCDF) produced by an HTLV-I-transformed human T-cell clone and demonstration of specific binding of the factor to a BCDF responsive cell line.

We have previously described YA2, a human T-cell clone that secretes B-cell differentiation factor (BCDF) but not B-cell growth factor (BCGF). The BCDFs secreted by YA2 and HTLV-I-transformed YA2 (TYA2) were functionally similar in their ability to stimulate Ig secretion by Staphylococcus aureus Cowan strain I-activated B cells and IgM secretion by SKW6.4 cells. In addition, they were biochemically similar with a MW of 30 kDa by high-performance liquid chromatography (HPLC) sieving, and a pI of 6.0-6.8 by isoelectric focusing. The BCDF activity was not blocked by antibodies to interleukin 2 and BCGF. BCDF was purified from TYA2 supernatant by sequential media protein immunoadsorption, flat bed isoelectric focusing, HPLC TSK 2000 sieving, and repeated immunoadsorption and was then iodinated. The iodinated material had functional BCDF activity and migrated to a single band at MW 30 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and at pI of 6.8 by polyacrylamide gel isoelectric focusing. 125I-BCDF purified in this manner bound specifically to a BCDF-responsive cell line and not to phytohemagglutinin-activated T cells. 125I binding to the BCDF-responsive cell line was competitively inhibitable by the addition of cold BCDF. Thus we have purified and characterized a factor with BCDF activity and demonstrated that this factor binds specifically to a BCDF-responsive cell line.

B cell growth and differentiation factors interact with receptors distinct from the interleukin 2 receptor.

Human B lymphocytes preactivated with Staphylococcus aureus Cowan strain I can proliferate and differentiate to Ig-secreting cells when cultured in the presence of recombinant interleukin 2 (IL2). We have compared 2 different B cell growth factors (BCGF) and a B cell differentiation factor (BCDF) to IL2 in the regulation of human B lymphocyte growth and differentiation. Utilizing a competitive binding assay, neither a high molecular weight BCGF (HMW-BCGF) nor a low molecular weight BCGF (LMW-BCGF) competitively inhibited the binding of radiolabeled IL2. Blocking studies with the anti-Tac monoclonal antibody demonstrated that B cell proliferation to IL2 was inhibited while a crude supernatant containing BCGF and IL2 was only partially inhibited. B cell Ig secretion induced by IL2 was also inhibited by anti-Tac while a crude supernatant and partially purified BCDF were not. Furthermore, IL2 plus BCGF was shown to enhance B cell proliferation better than either factor alone and IL2 plus a BCDF enhanced B cell Ig secretion better than either factor alone. By separating activated B cells into Tac-positive and Tac-negative fractions, much of the previously noted enhancement with the 2 factors was found to be secondary to the differential sensitivity of the 2 populations to BCGF and IL2 or BCDF and IL2. Thus, LMW-BCGF, HMW-BCGF and a partially purified BCDF appear to interact with receptors distinct from the IL2 receptor in mediating their effects on B cell growth and differentiation.