A yield-independent, 15N-isotope dilution method to estimate legume symbiotic dependence without a non-N2-fixing reference plant

The proportional contribution of atmospheric N₂ to the N nutrition of lupin (P _atm) was estimated in a field experiment following addition of NH₄Cl of KNO₃ to unconfined microplots (1.5 m²) at 2.5 g N m^-2 (10 atom% ¹⁵N). The integrated ¹⁵N enrichment, or mean pool abundance, of nitrate extracted from 0- to 15-cm samples taken under the lupin crop on eight occasion between 28 and 190 days after sowing was used as the reference criterion to estimate P _atm by the ¹⁵N-isotope dilution technique. Estimates of P _atm were similar to those obtained using canola as a non-fixing reference plant, but were higher than estimates obtained using a yield-dependent model. Use of mean pool abundance obviates the need for a non-fixing reference plant, and the frequent sampling and isotope-ratio analysis of the legume biomass required with the yield-dependent model is unnecessary. However, further work is needed to validate a sampling strategy commensurate with the growth of the legume roots.     

Nitrate leaching loss following application of organic manures to sandy soils in arable cropping.

Abstract. Experiments were set up at two sites to measure nitrogen (N) leaching loss from applications of separated pig/cattle slurry and cattle farmyard manure(FYM), during winters 1990/91–1993/94 (site A) and from broiler litter and FYM, during winters 1990/91–1992/93 (site B). The manures were applied at a target rate of 200 kg ha^-1 total N during the autumn and winter to overwinter fallow or top dressed onto winter rye. The total N in leachate was calculated from leachate N concentrations, in samples collected using ceramic cups buried at 90 cm, and an estimate of drainage volume. Nitrogen losses were greatest following manure applications in September, October and November but losses following applications in December or January were not significantly elevated above those from untreated controls. Losses were consistently lower from FYM than from broiler litter or separated slurry. The presence of a cover crop (winter rye) significantly reduced overall N leaching compared with the fallow, but only reduced the manure N leaching losses at one site during one winter when a high proportion of drainage occurred late. The incorporation of a nitrification inhibitor (DCD) with manures applied in October did not significantly reduce the manure N leaching.     

Determination of ractopamine in cattle and sheep urine samples using an optical biosensor analysis: comparative study with HPLC and ELISA

A biosensor method, using the surface plasmon resonance (SPR) principle, was developed for the determination of ractopamine in cattle and sheep urine. A monoclonal antibody was used to compete with ractopamine in the sample and ractopamine immobilized on the sensor chip. Addition of bovine serum albumin (BSA, 1 mg/mL) as an antibody stabilizer to the incubation buffer was required to achieve a stable biosensor response throughout each sample set. The calibration curve gave a mean IC(50) of 4.7 +/- 0.21 ng/mL (n = 7). Over sample concentrations from 2.5 to 10 ng/mL recoveries were typically approximately 100-110%, whereas inter- and intra-assay reproducibilities (% CV) were usually less than 10 and 6%, respectively. Comparison of biosensor results with results obtained from high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assays (ELISA) using enzyme-hydrolyzed urine (to convert ractopamine conjugates to free ractopamine) gave correlation coefficients of 0.94 for sheep and 0.86 for cattle. Slopes of the lines, with zero intercepts, equaled 0.80 for sheep and 0.74 for cattle. For untreated (nonhydrolyzed) urine samples, the correlations between biosensor and HPLC results were 0.95 for sheep and 0.72 for cattle with slopes of 1.18 (sheep) and 1.69 (cattle). The slopes greater than unity indicate that the biosensor responded to ractopamine metabolites in addition to free ractopamine. The biosensor assay is an excellent analytical tool to screen ractopamine residues in sheep or cattle urine, and the results should be extendible to other species with suitable validation.     

Chemical comparison of goldenseal (Hydrastis canadensis L.) root powder from three commercial suppliers

The characterization of herbal materials is a significant challenge to analytical chemists. Goldenseal (Hydrastis canadensis L.), which has been chosen for toxicity evaluation by NIEHS, is among the top 15 herbal supplements currently on the market and contains a complex mixture of indigenous components ranging from carbohydrates and amino acids to isoquinoline alkaloids. One key component of herbal supplement production is botanical authentication, which is also recommended prior to initiation of efficacy or toxicological studies. To evaluate material available to consumers, goldenseal root powder was obtained from three commercial suppliers and a strategy was developed for characterization and comparison that included Soxhlet extraction, HPLC, GC-MS, and LC-MS analyses. HPLC was used to determine the weight percentages of the goldenseal alkaloids berberine, hydrastine, and canadine in the various extract residues. Palmatine, an isoquinoline alkaloid native to Coptis spp. and other common goldenseal adulterants, was also quantitated using HPLC. GC-MS was used to identify non-alkaloid constituents in goldenseal root powder, whereas LC-MS was used to identify alkaloid components. After review of the characterization data, it was determined that alkaloid content was the best biomarker for goldenseal. A 20-min ambient extraction method for the determination of alkaloid content was also developed and used to analyze the commercial material. All three lots of purchased material contained goldenseal alkaloids hydrastinine, berberastine, tetrahydroberberastine, canadaline, berberine, hydrastine, and canadine. Material from a single supplier also contained palmatine, coptisine, and jatrorrhizine, thus indicating that the material was not pure goldenseal. Comparative data for three commercial sources of goldenseal root powder are presented.     

Microbial activity affected by lime in a long-term no-till soil

Under conventional farming practices, lime is usually applied on the soil surface and then incorporated into the soil to correct soil acidity. In no-till (NT) systems, where lime is surface applied or only incorporated into the soil to very shallow depth, lime will likely not move to where it is required within reasonable time. Consequently, lime may have to be incorporated into the soil by mechanical means. The objective of this laboratory study was to characterize the effect of lime, incorporated to different depths, on chemical and biological soil properties in a long-term NT soil. Soil samples taken from the 0–5, 0–10, and 0–20 cm depths were analyzed in incubation studies for soil pH, nitrate, CO₂ respiration, and microbial biomass-C (MBC). Lime (CaCO₃) was applied at rates equivalent to 0, 4.4, 8.8, and 17.6 Mg ha⁻¹. Application of lime to both 0–10 and 0–20 cm depths increased soil pH from about 4.9 by 1, 1.7, and 2.8 units for the low, medium, and high liming rates, respectively. Soil nitrate increased over time and in proportion to liming rate, suggesting that conditions were favorable for N-mineralization and nitrification. Greater respiration rates and greater MBC found in lime-treated than in non-limed soils were attributed to higher soil pH. Faster turnover rates and increased mineralization of organic matter were found in lime-treated than in non-limed soils. These studies show that below-surface lime placement is effective for correcting soil acidity under NT and that microbial activity and nitrification can be enhanced.     

Uptake of veterinary medicines from soils into plants

Medicines play an important role in the treatment and prevention of disease. Whereas the side effects on human and animal health resulting directly from treatment have been widely documented, only recently have the occurrence and fate of medicines in the environment and the potential consequences for human health been recognized as an issue warranting consideration. Medicines have been shown to be released to soils and to persist in the environment. This study was performed to investigate the potential for a range of veterinary medicines to be taken up from soil by plants used for human consumption and to assess the potential significance of this exposure route in terms of human health. Soil analyses indicated that, for selected substances, measurable residues of these are likely to occur in soils for at least 5 months following application of manure containing these compounds. Experimental studies on the uptake of veterinary medicines into carrot roots (tubers) and lettuce leaves showed that only florfenicol, levamisole, and trimethoprim were taken up by lettuces, whereas diazinon, enrofloxacin, florfenicol, and trimethoprim were detected in carrot roots. Measured concentrations in plant material were used to model potential adult human exposure to these compounds. Although exposure concentrations were appreciable in a few instances, accounting for approximately 10% of the acceptable daily intake values (ADI), all were lower than the ADI values, indicating that, at least for compounds with properties similar to those considered here, there is little evidence of an appreciable risk. This exposure route may, however, be important when veterinary medicines have a very low ADI, at which they elicit subtle effects over prolonged periods, or when exposure is occurring via a number of routes at once. Although degradation products (produced in the soil or the plant) were not measured, it is possible for some substances that these could increase the risks to consumers.     

Genetic manipulation for enhancing calcium content in potato tuber

Increased calcium (Ca) in potatoes may increase the production rate by enhancing tuber quality and storability. Additionally, increased Ca levels in important agricultural crops may help ameliorate the incidence of osteoporosis. However, the capacity to alter Ca levels in potato tubers through genetic manipulations has not been previously addressed. Here we demonstrate that potato tubers expressing the Arabidopsis H+/Ca2+ transporter sCAX1 (N-terminal autoinhibitory domain truncated version of CAtion eXchanger 1) contain up to 3-fold more Ca than wild-type tubers. The increased Ca appears to be distributed throughout the tuber. The sCAX1-expressing potatoes have normally undergone the tuber/plant/tuber cycle for three generations; the trait appeared stable through successive generations. The expression of sCAX1 does not appear to alter potato growth and development. Furthermore, increased Ca levels in sCAX1-expressing tubers do not appear to alter tuber morphology or yield. Given the preponderance of potato consumption worldwide, these transgenic plants may be a means of marginally increasing Ca intake levels in the population. To our knowledge, this study represents the first attempts to use biotechnology to increase the Ca content of potatoes.     

Creatine phosphokinase in thyroid: isoenzyme composition compared with other tissues

Considerable creatine phosphokinase activity was demonstrated in thyroid glands of several species. After starch gel electrophoresis, thyroid exhibited a creatine phosphokinase isoenzyme pattern different from that of muscle, heart, and brain. The isoenzyme repertory of various tissues and a hybrid enzyme produced from muscle and brain enzyme are consistent with the postulated dimeric structure of creatine phosphokinase.     

Descriptive epidemiology of culling in dairy cows from 34 herds in New York State

Data on parity, disease, farmers' stated primary reasons for culling and stage of lactation at diagnosis and at culling were used to describe patterns of culling in Holstein lactations from 34 New York herds. Of 7763 lactations, 18.7% ended in culling [death (95 cows), sales for dairy purposes (104 cows), or slaughter]. The culling rates for specific reasons were: dairy purposes 1.3%, low production 3.8%, reproduction 4.8%, udder problems 4.0%, feet and legs 1.2%, old age 0.3%, accidents 0.3% and miscellaneous reasons 2.9%. Culling increased with parity (at least through Lactation 6) and primarily was due to production, reproduction and udder problems. Culling for these 3 reasons peaked immediately after calving, again between 151 and 240 days post-partum (poor milk production) and at >240 days post-partum (poor reproductive performance). First-lactation cows sold for dairy use tended to be sold in early lactation. Death in older cows usually occurred early in lactation and was due to udder problems or to miscellaneous causes.

Compared to lactations without the disease, lactations with a diagnosis of downer cow, clinical mastitis or treat problems were 3.5, 2.0 and 2.7 times more likely to end in culling, respectively. Among cows diagnosed with a disease and culled, many were culled the same day or within 30 days of the diagnosis. Such “immediate” culling upon diagnosis was especially typical of cows with milk fever, downer cow syndrome, left displaced abomasum, teat problems, and foot and leg problems (and for some cases of clinical mastitis), implying that these disorders led to “forced” culling, which was particularly costly to the farmers.     

A biotyping scheme for Salmonella livingstone

Salmonella livingstone is one of the more common salmonella serotypes isolated in the United Kingdom. The characterization of 70 different isolates of S. livingstone using biochemical tests and plasmid profile analysis is described. The isolates could be divided into four groups by their ability to grow in d-tartrate, l-tartrate and Stern's glycerol. Further subdivision was achieved by the use of plasmid profile analysis; 24 of the isolates possessed light plasmids (less than 9.5 MD) and four possessed heavy plasmids (greater than 30 MD). The combination of biotyping and plasmid profile analysis can be used as the basis of a scheme to 'fingerprint' S. livingstone for epidemiological studies.