Einfluß von alimentärem Zn-Mangel auf die Stickstoffelimination und Enzymaktivitäten des Harnstoffzyklus

Influence of alimentary zinc deficiency on nitrogen elimination and activities of urea cycle enzymes
This study was conducted to investigate whether the hyperammonaemia shown in earlier zinc-deficiency experiments was the result of disturbed enzyme activities of the urea cycle. For this study 36 male Sprague-Dawley rats with an average body weight of 85 g were divided into three experimental groups of 12 animals each. Group 1 received the semisynthetic zinc-deficient diet (AIN-93G; 1.2 mg Zn/kg DM) ad libitum over 33 experimental days. Group 2 received the zinc-sulphate-supplemented control diet (60 mg Zn/kg DM) ad libitum and group 3 received the same diet matched to the feed intake of the zinc-deficient rats. Alimentary zinc deficiency reduced the zinc concentration and the activity of the alkaline phosphatase in serum by 75 and 67%, respectively. The activity of the glutamate dehydrogenase and the concentrations of ammonia and urea in the serum of the zinc-deficient rats showed no significant differences compared with pair-fed control rats. On the other hand the hepatic activity of the mitochondrial localized glutamate dehydrogenase of the zinc-deficient rats was significantly increased and the carbamoylphosphate synthetase and ornithine carbamoyltransferase were reduced about half in comparison with both control groups. The activities of the cytosolic liver enzymes such as argininosuccinate synthetase, argininosuccinase and arginase were again significantly increased in zinc-deficient rats compared with both control groups. The increased hepatic activity of the glutamate dehydrogenase possibly led to an enhanced NH₃ elimination in addition to urea synthesis. The typical reduction of feed intake in consequence of zinc deficiency is therefore not the cause of hyperammonaemia due to disturbed urea synthesis, as has been hypothesized in earlier studies.     

A grading system for lymphocytic plasmacytic colitis in dogs

Colonic mucosal samples were obtained every 4 weeks for 13 months from 6 clinically normal dogs and from 47 dogs with a clinical diagnosis of chronic inflammatory bowel disease. All samples were graded on a scale of 0-5, based upon the quantity of lymphocytes and plasma cells in the lamina propria, epithelial changes, and the presence of ulcers and erosions. A grade of less than or equal to 2.0 was considered normal and was assigned to 77 of 78 samples from clinically normal dogs and 28 of 48 samples from dogs with diarrhea. A transient increase in cellularity was noted in 1 sample from 1 control dog. Nineteen dogs with clinical disease had obvious histologic abnormalities. The grading scheme described provides the pathologist with an objective criterion for the microscopic evaluation of colonic mucosal samples obtained by endoscopic techniques and offers clinicians a method of assessing the dog's progress and response to therapy.     

Large-sample hypothesis tests for stratified group-testing data

Insect-vectored plant diseases impact the agricultural community each year by affecting the economic value, the quantity, and the quality of crops. Controlling the spread of disease is an important area in risk assessment, and understanding the dynamics of vector populations helps researchers to develop effective treatments. In this article, we consider an experimental design commonly used by researchers who study plant disease and examine large-sample, likelihood-based hypothesis tests that can be used to characterize disease-transmission behavior in a stratified population. Small-sample size and power results along with design considerations are provided. We illustrate our testing procedures using two real data examples and provide recommendations for plant-disease researchers in the field.     

Effect of non-linear adsorption on the transport behaviour of Brilliant Blue in a field soil

The food dye Brilliant Blue FCF (Color Index 42090) is often used as dye tracer in field studies for visualizing the flow pathways of water in soils. Batch studies confirmed findings of other researchers that non‐linear sorption is important for Brilliant Blue, especially at small concentrations (< 10 g l^?1 for our soil), and that retardation increases with decreasing concentrations as well as with increasing ionic strength of solutions. Therefore, it is not obvious if it can be used as an indicator for water flow paths as is often done. In this study, we compared the mobility of Brilliant Blue in a field soil (gleyic Luvisol) with that of bromide. Brilliant Blue and potassium bromide were simultaneously applied as a 6‐mm pulse on a small plot in the field, and the tracers were displaced with 89 mm of tracer‐free water using a constant intensity of 3.9 ± 0.2 mm hour^?1. Both tracer concentrations were determined on 144 soil cores taken from a 1 m × 1 m vertical soil profile. The transport behaviour differed in both (i) mean displacement and (ii) spatial concentration pattern. We found the retardation of Brilliant Blue could not be neglected and, in contrast to the bromide pattern, a pulse splitting was observed at the plough pan. Numerical simulations with a particle tracking code revealed that the one‐dimensional concentration profile of bromide was represented fairly well by the model, but the prediction of the double peak in the Brilliant Blue concentration profile failed. With additional assumptions, there were indications that Brilliant Blue does not follow the same flow paths as bromide. However, the question of Brilliant Blue taking the same flow pathways as bromide cannot be adequately answered by comparing both concentration distributions, because we look at two different transport distances due to the retardation of Brilliant Blue. It became obvious, however, that Brilliant Blue is not a suitable compound for tracing the travel time of water itself.     

Effects of fertilization and irrigation on American sycamore and black locust planted on a reclaimed surface mine in Appalachia

Short rotation woody biofuel plantations on reclaimed surface mines in Appalachia can diversify domestic energy supplies and facilitate the reforestation of these disturbed lands. This study examined growth, survival, biomass accumulation and allocation, and nitrogen concentrations following two growing seasons in American sycamore (Platanus occidentalis L.) and black locust (Robinia pseudoacacia L.) seedlings receiving irrigation, granular fertilization, and irrigation + fertilization compared with untreated controls. Fertilization increased basal diameter, height, and stem mass of American sycamore following two growing seasons. Increased stem production was attributed to accelerated development and not shifts in biomass allocation due to treatment. Irrigation and irrigation + fertilization treatments did not enhance growth or biomass accumulation of American sycamore. Similarly, black locust basal diameter, height, and stem mass did not differ among the treatments. Browse surveys showed that more than 76% of black locust seedlings experienced arrested or retrogressed growth due to browse; less than 3% of American sycamores were browsed. This intensive browse by ungulates, likely including reintroduced elk, may have affected growth differences among species and confounded the effects of treatments on black locust. Survival was unaffected by treatment in both species, but mean survival was greatest in American sycamore (80%) compared to black locust (58%). Per tree total nitrogen uptake was highest in fertilized American sycamore (7.9 g) and lowest in irrigated American sycamore (0.9 g). The results of our study suggest that granular fertilizer applications can accelerate seedling growth on reclaimed surface mines in the Appalachian region.     

Potential role of soil calcium in recovery of paper birch following ice storm injury in Vermont, USA

In recent years, an increased number of mature paper birch (Betula papyrifera Marsh.) and heart-leafed paper birch (B. papyrifera var. cordifolia (Regel) Fern.) in northeastern United States forests have exhibited decline symptoms including foliar loss, reduced fine branching, and tree mortality. We assessed crown health, radial growth, and available soil cations in 2006 as a preliminary assessment of factors that may be influencing paper birch decline. Tree rings began to decrease in width in 1998—the year of a severe region-wide ice storm. All trees (regardless of their current decline status) experienced reduced growth starting in 1998 and tree growth continued to decrease for two years following the ice storm. After this generalized growth decrease, trees that now have vigorous crowns showed a marked increase in growth, whereas trees that now have low crown vigor did not rebound in growth, but instead exhibited a significantly higher incidence of locally absent annual rings. Extractable soil-aluminum (Al), a phytotoxic element mobilized by acid deposition, was significantly higher in soils associated with declining trees compared to those adjacent to vigorous trees. Higher soil calcium (Ca) availability was associated with both vigorous crowns and increased radial growth following the 1998 ice storm. Furthermore, increased soil Ca availability was negatively correlated to the percentage of declining trees, and positively related to increased radial growth, whereas elevation was not significantly associated with either parameter. Although previously overlooked as a factor influencing paper birch recovery from injury, we found that available soil Ca was linked to crown vigor and rebounds in growth following an inciting event.     

Foliar application of the exogenous plant hormones at pre-blooming stage improves flowering and fruiting in cashew (<Emphasis Type="Italic">Anacardium occidentale</Emphasis> L.)

The problem of declining tree yield has led to an investigation into the effectiveness of foliar application of exogenous hormones to improve flowering, fruit set, and fruit retention in cashew. Five exogenous hormones, one Gibberellic Acid (GA₃) and four Auxins (IAA, IBA, NAA, and 2,4-D) at seven different rates of application (0 mg L⁻¹, 10 mg L⁻¹, 25 mg L⁻¹, 50 mg L⁻¹, 100 mg L⁻¹, 250 mg L⁻¹, and 500 mg L⁻¹) were tested on six yield-related components of the two Brazilian cashew genotypes. This trial was a factorial split-split-plot design with each treatment replicated five times within a tree and three replications (three trees) per genotype. Responses varied significantly between exogenous hormones, concentrations and genotypes. The cashew plants used showed hormone-specific and optimum concentration response patterns. Of the five exogenous hormones tested, GA₃ was most effective as its application at 50–100 mg L⁻¹ gave five-fold improvements in flowering (precocity and number of hermaphrodite flowers) and fruiting, and about 69% increase in fruit retention ability and 25% in nut size. Panicles treated with GA₃ also produced relatively bigger nuts compared to the untreated. Days to flowering was found to be hormone sensitive, while production of hermaphrodite flowers, fruit set, and nut development tended to be concentration specific. The GA₃ exhibited a broad concentration tolerance among the five exogenous hormones investigated. Our data showed that using GA₃ at 50 mg L⁻¹ will enhance flowering precocity, shorten flowering duration, increase production of hermaphrodite flowers and fruit set significantly, and resultant nuts develop optimally with high percentage retention. Thus, it suggests cashew yield could be increased by exogenous foliar application of GA₃ at 50–100 mg L⁻¹ at pre-blooming stage.     

Ras p21 as a potential mediator of insulin action in Xenopus oocytes

The oncogene protein product (p21) of the ras gene has been implicated in mediating the effects of a variety of growth factors and hormones. Microinjection of monoclonal antibody 6B7, which is directed against a synthetic peptide corresponding to a highly conserved region of p21 (amino acids 29 to 44) required for p21 function, specifically inhibited Xenopus oocyte maturation induced by incubation with insulin. The inhibition was dose-dependent and specific since (i) the same antibody had no effect on progesterone-induced maturation, (ii) immunoprecipitation and Western blotting indicated that the antibody recognized a single protein of molecular weight 21,000 in oocyte extracts, and (iii) inhibition was not observed with identical concentrations of normal immunoglobulin. Thus, p21 appears to be involved in mediating insulin-induced maturation of Xenopus oocytes. Furthermore, the mechanism may involve phosphorylation of p21, as p21 was found to be a substrate of the insulin receptor kinase.