The equivalence of the Calcium‐Acetate‐Lactate and Double‐Lactate extraction methods to assess soil phosphorus fertility

A large variety of extraction methods are used worldwide for the estimation of “plant‐available P” in soils. In Germany, the standard extractants are Calcium‐Acetate‐Lactate (CAL) and Double‐Lactate (DL). Until now there is no validated transformation procedure available and studies on the comparability of both methods have reported conflicting evidence. The uncertainty about the equivalence of CAL‐P and DL‐P hinders a direct comparison of the P fertility status and P fertilizer recommendations across Germany. Based on 136 datasets for soil samples from an interlaboratory comparison program and three P fertilization field trial sites, for which plant‐available P had been determined by both the CAL and DL method, we assessed the comparability of both extraction methods and derived simple and multiple regression equations to transform DL‐P into CAL‐P values. On average, DL extracted 30% more P than CAL. However, this strongly depended on soil pH and carbonate content. A simple linear regression model explained 70% of the variance. However, if simple linear regression models were fitted to pH‐specific samples (pH range 4.5 to 7.0) the R² increased to 0.96. Based on an independent validation dataset (n = 48) we demonstrated that such pH‐specific models were more accurate than models that did not consider pH when transforming DL‐P to CAL‐P values. Multiple regression results showed that out of soil pH, C_org, N_t, and C : N ratio, only soil pH improved the model. The transformation equations in this study provide a step towards an improved comparability of P fertility status assessments of soils across Germany.     

Do woodlice (Isopoda: Oniscidea) produce endogenous cellulases?

In studies on digestive processes and microorganisms in the gut of the common woodlouse, Porcellio scaber (Isopoda: Oniscidea), we observed marked contradictions between the activity of cellulolytic enzymes and the number of microorganisms. The anterior hindgut exhibited the highest cellulolytic activity, but was characterized by low microbial counts. Due to the presence of endosymbiotic bacteria in the midgut lobes that appear to produce cellulases, we suggest that the cellulases that are active in the hindgut of woodlice are of endogenous origin. Received: 4 April 1997     

The diversification of terpene emissions in Mediterranean oaks: lessons from a study of Quercus suber, Quercus canariensis and its hybrid Quercus afares

Interspecific gene flow is common in oaks. In the Mediterranean, this process produced geographical differentiations and new species, which may have contributed to the diversification of the production of volatile terpenes in the oak species of this region. The endemic North African deciduous oak Quercus afares (Pomel) is considered to be a stabilized hybrid between the evergreen Quercus suber (L.) and the deciduous Quercus canariensis (Willd.), presumably being monoterpene and isoprene emitters, respectively. In a common garden experiment, we examined the terpene emission capacities, terpene synthase (TPS) activities and nuclear genetic markers in 52 trees of these three oak species. All but one of the Q. suber and Q. canariensis trees were found to be genetically pure, whereas most Q. afares trees possessed a mixed genotype with a predominance of Q. suber alleles. Analysis of the foliar terpene emissions and TPS activities revealed that all the Q. canariensis trees strongly produced isoprene while all the Q. suber trees were strong monoterpene producers. Quercus afares trees produced monoterpenes as well but at more variable and significantly lower rates, and with a monoterpene pattern different than that observed in Q. suber. Among 17 individuals tested, one Q. afares tree emitted only an insignificant amount of terpenes. No mixed isoprene/monoterpene emitter was detected. Our results suggest that the capacity and pattern of volatile terpene production in Algerian Q. afares populations have strongly diverged from those of its parental species and became quantitatively and qualitatively reduced, including the complete suppression of isoprene production.     

Why do farmers still grow corn on steep slopes in northwest Vietnam?

Intense cultivation of annual crops on steep slopes in northwest Vietnam has resulted in widespread and severe erosion. This has led to myriad problems including siltation of dams critical for hydroelectricity generation, and increasing levels of rural poverty due to declining crop yields. The solution to these problems is sustainable land management, in particular sloping land agricultural technologies. Our study focuses on defining, and finding solutions to, a second-order problem: that farmers are reluctant to adopt sustainable land management practices, despite numerous projects demonstrating their effectiveness. Interviews with farmers in northwest Vietnam confirmed that intense corn cultivation on steep slopes provided the majority of income for most households. The financial security associated with growing corn (compared to alternative crops) was the deciding factor in land management choices. However, interviews also revealed that farmers were dissatisfied with growing corn because of low income and high input costs. Farmers’ replies indicated that they thought they had no alternative to growing corn. However, farmers were aware of alternative crops, and were particularly interested in growing grass, fruit trees and timber trees, although few farmers were keen to be first to adopt these alternative species extensively. Further research is required on development of production-to-commercialization chains for alternative crops, and more generally, to find ways to increase farmer financial security during transition to sustainable land management.     

Cortisol/creatinine ratio in urine (UCC) of healthy cats

In 31 healthy cats urine samples were taken to determine the cortisol/creatinine ratio (UCC) during hospitalisation and at home. The UCC of the samples, which had been taken in the clinic, was significantly higher (0-19 x 10(-6), Median 3 x 10(-6)) than the one of the samples taken at home (0-4 x 10(-6), Median 1 x 10(-6)). The parameter was neither influenced by the cat's age, sex or the fact that the cat stayed inside or outside, nor by the degree of visible agitation. Assay validation achieved good results regarding precision and accuracy of the measuring of cortisol and creatinine in the urine. The study shows that stress--caused by the visit to the veterinarian--can provoke a significant increase of UCC. Therefore, the parameter should be determined only from urine samples taken at home. Furthermore, it is important to notice that cortisol metabolites are measured in varying degree with the different assays. Therefore, it is inevitable that each laboratory generates its own reference values.     

Evaluation of the low-dose dexamethasone suppression test and ultrasonographic measurements of the adrenal glands in cats with diabetes mellitus

The objectives of the study were to evaluate the low-dose dexamethasone suppression (LDDS) test and the size of the adrenal glands via ultrasonography in cats with diabetes mellitus. Twenty-two cats were enrolled in the study. In 19 cats, suppression of cortisol concentrations below 5.5 nmol/litre occurred four and eight hours after intravenous administration of dexamethasone (0.1 mg/kg). In one other cat, the cortisol concentration was also below 5.5 nmol/litre at eight hours but was 11.0 nmol/litre at four hours. The results were in agreement with those of healthy cats in a previous study. The cortisol concentrations four and eight hours after administration of dexamethasone did not differ between cats with good glycemic control (n = 8) and those with moderate to poor control (n = 12). The adrenal glands of the diabetic cats were not enlarged compared with those of healthy cats. In two diabetic cats, the LDDS test results were abnormal. One cat had a pituitary adenoma and adrenal glands of normal size as determined by ultrasonography. The size of the adrenal glands of the other cat clearly differed; histological examination of the larger adrenal gland revealed an adrenocortical adenoma. Based on our findings, the results of the LDDS test using 0.1 mg/kg of dexamethasone are normal in cats with diabetes mellitus independent of the quality of glycemic control. In addition, diabetes mellitus does not lead to a measurable increase in the size of the adrenal glands in cats. Further studies are needed to evaluate if the dexamethasone dosage used in this study is useful to diagnose mild form of hypercortisolism.     

GlyR alpha3: an essential target for spinal PGE2-mediated inflammatory pain sensitization

Prostaglandin E2 (PGE2) is a crucial mediator of inflammatory pain sensitization. Here, we demonstrate that inhibition of a specific glycine receptor subtype (GlyR alpha3) by PGE2-induced receptor phosphorylation underlies central inflammatory pain sensitization. We show that GlyR alpha3 is distinctly expressed in superficial layers of the spinal cord dorsal horn. Mice deficient in GlyR alpha3 not only lack the inhibition of glycinergic neurotransmission by PGE2 seen in wild-type mice but also show a reduction in pain sensitization induced by spinal PGE2 injection or peripheral inflammation. Thus, GlyR alpha3 may provide a previously unrecognized molecular target in pain therapy.     

Using stable isotope data to quantify niche overlap and diets of muskellunge,northern pike and walleye in a deep Minnesota lake

Muskellunge (Esox masquinongy Mitchill), northern pike (Esox lucius L.) and walleye (Sander vitreus Mitchill) often coexist in lake communities, yet uncertainty exists about the potential for interspecific competition among these top predators. Stable isotope data were used to assess niche overlap and diets of these predators in Elk Lake (Minnesota, U.S.A). δ¹³C indicated primary production sources (e.g. pelagic v. littoral) and δ¹⁵N indicated trophic position; the bivariate distribution of these isotopes defined the species’ isotopic niche. Niche overlap probabilities were calculated and stable isotope mixing models were used to quantify diet proportions. Muskellunge and northern pike niches overlapped little (<10%), while walleye overlapped muskellunge (15%–60%) and northern pike (33%–53%) more extensively. Muskellunge diets focused (50%) on cisco (Coregonus artedi Lesueur), walleye primarily assimilated non-cisco prey fish (80%), and northern pike diets were dominated by non-cisco prey fish (45%) and invertebrates (40%). The presence of a cisco population and the flexibility of northern pike to use invertebrate resources may decrease potential competition among these predators. However, cisco are threatened by climate change and eutrophication, and our results suggest that extirpation of cisco may cause major changes in potential competitive interactions among these top predators. Moreover, cisco were unique among prey species in their ability to exploit pelagic energy, such that loss of cisco will likely alter energy flow in lake food webs where they currently exist.