Herbstliche Nmin-Grenzwerte als Funktion von Bodenbeschaffenheit,Klima und Bodennutzung: Modellüberlegungen

Upper limits for soil nitrate in late fall as function of soil properties, climate and soil use: Model considerations Strategies and measures to reduce the leaching of nitrate from agricultural soils can only be successful if possibilities of control are available. In temperate regions measurement of soil mineral nitrogen (predominantly nitrate) in late fall, together with appropriate upper limits for tolerable soil nitrate, can be considered as an efficient control instrument. With assumptions about the mineralization of crop residues and the input of nitrate from the atmosphere, a procedure is developed with which the nitrate leaching in winter can be estimated if the amount of soil nitrate in late fall is known. With the procedure sample calculations for the crop rotation sugarbeets-summer wheat-winter barley are carried out for a variety of site conditions. The calculations show, that when no residual nitrate is left in the soil at the time of harvest, the cumulative amount of leached nitrate for the crop rotation (due to mineralization of residues) is 63.7 kg/ha NO₃^? N. However, when each year an amount of soil mineral nitrogen of 45 kg/ha in late fall is allowed for, the leached amount of soil nitrate can, for average site conditions, be as high as 133.6 kg/ha. It is shown how with the model in a rational way late fall site- and crop-specific upper limits for soil nitrate can be derived. However, the stipulation of such upper limits is not a matter of soil science only.     

Isoflavonoid composition of a callus culture of the relict tree Maackia amurensis Rupr. et Maxim

Isoflavonoids, an interesting and restricted group of secondary metabolites of legumes, exhibit estrogenic, antiangiogenic, and anticancer activities and are now popular as dietary supplements. Plant cell cultures that possess an increased ability to synthesize these metabolites were examined. During the investigation, cell cultures of the Far Eastern relict tree Maackia amurensis (Leguminosae) were established. A selection of seed-derived cell aggregates yielded the callus line designated A-18. This culture produces 20 isoflavonoids, namely, the isoflavones genistein, daidzein, formononetin, calycosin, derrone, and pseudobaptigenin and their glycosylated conjugates genistin, 6'-O-malonylgenistin, ononin, 6'-O-malonylononin, daidzin, 3'-methoxydaidzin, 4'-O-beta-D-glucopyranosyldaidzin, 4'-O-beta-D-glucopyranosylgenistin, and 7-O-beta-D-glucopyranosylcalycosin; the pterocarpans maackiain and medicarpin and their glycosylated conjugates 6'-O-malonyl-3-O-beta-D-glucopyranosylmaackiain and 6'-O-malonyl-3-O-beta-D-glucopyranosylmedicarpin; and the new pterocarpan glucoside 6'-O-malonyl-3-O-beta-D-glucopyranosyl-6,6a-dehydromaackiain. These isoflavonoids, possessing a hepatoprotective activity, were stably produced by the A-18 calli for prolonged periods of observation.     

Lignin deposition during earlywood and latewood formation in Scots pine stems

Lignin deposition at consecutive secondary wall thickening stages of early and late xylem cells during annual ring wood formation in Scots pine (Pinus sylvestris L.) stems was studied. Lignin patterns, isolated by thioglycolic acid method, consisted of alcohol-soluble (LTGA-I) and alkali-soluble (LTGA-II) fractions. The sum of two fractions, being the total lignin content, gradually increased in the course of lignification. However, the increments of lignin amount at each development stage of early and late tracheids were different. The intensity of lignin deposition increased in the course of earlywood tracheid maturation and decreased toward the end of latewood cell differentiation. The deposition of two lignin fractions in each layer of forming wood also occurred oppositely. The increment of LTGA-I descended, whereas that of LTGA-II increased from the beginning to the end of early xylem lignification. In contrast, LTGA-I increment dropped, whereas LTGA-II rose during late xylem lignification. Gel permeation chromatography showed that the lignins, formed at the beginning of lignification, were more homogeneous and had higher molecular weight compared with the lignins at the end of cell differentiation. Besides, the content of cellulose, estimated as the residue after lignin isolation, and of cell wall substances, presented as cell wall cross-section areas, at consecutive maturation stages of early and late xylem cells have been found to be different. The data show that lignin deposition occurred in different conditions and with opposite dynamics during early and late xylem formation.     

Computerized morphometry of mean nuclear diameter and nuclear roundness in canine mammary gland tumors on cytologic smears

BACKGROUND: The use of computer-based image analysis systems in veterinary oncology has increased. Computerized morphometry is a part of image analysis that describes geometric figures of cellular structures in any dimension. Most investigators have performed morphometric analysis on histologic specimens. Computer-assisted nuclear cytomorphometry can provide important preoperative information on neoplastic lesions in animals. OBJECTIVES: The aim of this study was to define whether the morphometric parameters of mean nuclear diameter and nuclear roundness could be used to differentiate benign from malignant canine mammary gland tumors on cytologic specimens. METHODS: Mean nuclear diameter and nuclear roundness were determined by computer-assisted morphometry of epithelial cells in Hemacolor-stained cytologic smears from normal canine mammary gland (n = 7) and from canine mammary adenomas (n = 8), tubulopapillary carcinomas (n = 9), and solid carcinomas (n = 6). Data were analyzed by the Mann-Whitney U test. RESULTS: Significant differences (P <.001) were found in mean nuclear diameter and nuclear roundness among all tumor types and in comparison with normal canine mammary gland epithelial cells (except for nuclear roundness between tubulopapillary carcinomas and solid carcinomas). CONCLUSIONS: The morphometric parameters of mean nuclear diameter and nuclear roundness can be used in the preoperative differentiation of benign from malignant canine mammary gland tumors.     

Embryo transfer,a useful technique to be applied in small community farms?

The objective of this study was to determine if the technique of embryo transfer in cattle can be commercially feasible in a region situated in the humid tropics of Mexico. Twenty-six Bos taurus and twenty-six Bos indicus cows were estrous synchronized and superovulated to obtain a total of 80 embryos of both sub-species. Embryos were classified using stereoscopic microscopy based on established criteria. Nine dual-purpose farms situated in the tropics of Mexico were chosen to provide ten recipient cows each to transfer one embryo per cow. The females were transferred using a fixed-time protocol after verifying the presence of a corpus luteum on the seventh day after the end of hormonal treatment. Pregnancy diagnosis was carried out 28 days after embryo transfer by ultrasonography. Estimation of the cost was determined by calculating the expenses for preparation of the donor and embryo recovery, which were US 633 and US633 and US 589 for B. taurus and B. indicus, respectively. The cost of each embryo was determined considering the number of transferable embryos recovered, which was 3.8 on mean. The cost of each conception was calculated taking into account the percentage of pregnant animals (27% on mean), and the cost for preparing donor and recipient cows, for transferring embryo. The overall cost per gestation was US 1,447. Considering a 50:50 ratio of male to female born, the cost for a replacement heifer calf was US1,447. Considering a 50:50 ratio of male to female born, the cost for a replacement heifer calf was US 2,894, which surpassed by far the commercial cost of a crossbred ready-to-bred heifer normally used as replacement (approximately US $900).     

Evidence of Damage in Cryopreserved and Fresh Bovine Embryos Using the Tunel Technique

The objective of the present study was to evaluate the quality of bovine embryos cryopreserved in different years in Chiapas, Mexico. The embryos were obtained from a government institution (FIMEGEN) dedicated to promoting embryo transfer among dual-purpose cattle farmers. Forty-three embryos frozen in 1988, 1989, 2000 and 2002 were analysed with the Tunel technique to detect programmed cell death (apoptosis). Eleven fresh embryos were used as controls. Analysis of variance was used in embryos stored in the different years with averages tested using Tukey's test. Student's t-test was employed to compare fresh and frozen cells. Embryos with shorter storage time presented a lower number (p < 0.001) of Tunel-positive cells compared with embryos stored for longer time. On the contrary, when comparing the number of apoptotic cells between frozen and fresh embryos a higher number of positive cells (p < 0.05) were found in the former. The present results suggest that the cryopreservation per se caused damage that compromises the viability of the embryo. Another explanation for the lower pregnancy rate found in the tropics could be irreversible damage caused by poor storage technique in these large operations.     

Lipid droplets in clusters negatively affect Bos indicus embryos during cryopreservation

Embryo transfer using cryopreserved B. indicus embryos results in low pregnancy rates. The low viability of B. indicus embryos is likely a result of their low freezability relative to embryos from other species, notably B. taurus. Freezability is probably related to the quantity of lipid droplets in the embryonic cells. However, the mechanism underlying this association is unknown. Using multiphoton and transmission electron microscopy, the proportion, volume, morphology and composition of lipid droplets in fresh and cryopreserved B. indicus and B. taurus embryos were studied. B. indicus embryos have more droplets than B. taurus and a greater percentage of lipid droplets in clusters (34% vs. 24%; p < 0.05). Also, B. indicus individual droplets are of greater volume than those of B. taurus (47 μm³ vs. 34 μm³; p < 0.05). After freezing, the percentage of clusters decreased in B. indicus (11% vs. 5%; p < 0.05), while in B. taurus they increased (2% vs. 7%; p < 0.05). Freezing influenced the lipid droplet morphology, increasing the number of cracked droplets in B. indicus embryos (33% fresh vs. 62% frozen; p < 0.05), but not in B. taurus embryos (35% fresh vs. 34% frozen; ns). Regarding composition, saturated lipid droplets prevail in B. indicus embryos, contrary to B. taurus embryos. We observed differences in lipid droplet organization, proportion, volume, morphology and composition between B. indicus and B. taurus embryos which are altered in opposite directions following freezing.