Comparison of German and Swiss Rainfall Simulators - Utility,Labour Demands and Costs

The utility, vehicle required, the time needed for assembly and relocation and the costs associated with six different rainfall simulators were studied. The results can be summarized as follows:

• 1 The simulator designed by Kainz & Eicher (1990) is the least expensive to operate. This simulator also has excellent experimental versatility. Its only restriction is a short slope length.
• 2 The rainfall simulator of Karl & Toldrian (1973) is also inexpensive to operate, but because of disadvantages such as low falling height, wind susceptibility, and the need for more workers than other simulators, it should be used mainly where other simulators are not practical (forests, steep slopes, or long slopes).
• 3 The rainfall simulator of Richter et al. (1988) has limited mobility in the field and is highly susceptible to wind drift. Moreover, its narrow plots do not cover a representative unit of a cultivated field.
• 4 The modified Swanson-type simulator (Auerswald, (1986) is suitable for large plots if a sufficient water supply is available.
• 5 The simulator of Kromer & Vöhringer (1988) has the highest fixed costs, but labour is used efficiently.
• 6 The simulator of Schmidt (1983) can only be considered for stationary use because of its long assembly time. Other disadvantages are narrow plot size and high wind susceptibility.

Depending on the selection of the simulator, total costs of between 400 DM and 2000 DM per plot should be expected even with high use rates.     

Managing Insect Resistance to Bacillus thuringiensis Toxins

Bacillus thuringiensis (B.t.) delta-endotoxins provide an alternative to chemical insecticides for controlling many species of pest insects. Recent biotechnological developments offer the promise of even greater use of B.t. toxins in genetically transformed pest-resistant crops. However, the discovery that insects can adapt to these toxins raises concerns about the long-term usefulness of B.t. toxins. Several methods for managing the development of resistance to B.t. toxins have been suggested, but none of these approaches offer clear advantages in all situations.     

Cytochemical staining characteristics of lymph nodes from normal and lymphoma-affected dogs

Frozen sections and imprint smears were used to evaluate the presence and pattern of cytochemical staining reactions in the B- and T-cell regions of lymph nodes from normal dogs and dogs with lymphoma. Staining procedures evaluated included peroxidase (PER), Sudan black B (SBB), naphthol AS-D chloroacetate esterase (CAE), alpha-naphthyl butyrate esterase (NBE), acid phosphatase (ACP), and leukocyte alkaline phosphatase (LAP). In normal lymph nodes, macrophages and some lymphocytes within the interfollicular (T-cell) region and medulla stained positive with ACP and NBE. Smaller numbers of macrophages also occurred sporadically within the germinal follicles. Cells positive for PER, SBB, and CAE were scattered infrequently throughout all regions of the normal lymph node, consistent with granulocytes and mast cells. The LAP stained cells were predominantly and prominently located within the mantle zone of secondary follicles and to a much lesser extent within the germinal centers, compatible with B-cell lymphocytes derived from follicular center cells. Of the 12 dogs with lymphoma, 7 cases (4 immunoblastic, 2 large noncleaved, 1 small noncleaved) stained diffusely positive with LAP, 4 cases (all lymphoblastic) had numerous focally positive lymphocytes using ACP and NBE, and 1 case (immunoblastic) did not stain positive with any of the cytochemical reactions. Cytochemical staining of canine lymph nodes with NBE, ACP, and LAP proved useful in distinguishing between B- or T-cell regions and detecting different cell types of canine lymphoma.