Rapid screening of DOM's metal-binding ability using a fluorescence-based microplate assay

This note describes the development of a method to rapidly quantify the metal-binding ability of low-volume DOM samples based on their fluorescence properties. The method uses 96-well microplates to screen the fluorescence quenching observed when increasing concentrations of various metals are added to the pH-buffered DOM sample. Only 1.6 mL of DOM sample is required to quantify the binding affinity for each metal and the result is obtained in a few minutes. This study presents results for a surface soil DOM sample for which binding was assessed for Cu2+, Fe2+, Ni2+ at pH 5 and 9.

Management of cereal cyst nematodes, Heterodera spp., in Norway

Cereal cyst nematodes, Heterodera spp., are known worldwide as parasites of cereals and grasses. Surveys of cereal fields in Norway have revealed that nematodes belonging to the H. avenae complex occur throughout the country, and that H. avenae (the oat cyst nematode) is the most common species, followed by H. filipjevi (the rye cyst nematode). Both species are of economic importance in Scandinavia. H. avenae has been found in two common pathotypes, Ha 11 and Ha 12. Work in Sweden, however, has detected three additional pathotypes, H. avenae "Knislinge", H. avenae "Ringsisen" and H. avenae "Våxtorp". These pathotypes were found also in the Norwegian surveys. In Sweden H. filipjevi has two pathotypes, "East" and "West". In Norway, only pathotype "West" has been detected so far. Nematode management practices must be based on the knowledge of the relationship between initial nematode density and yield, the population dynamics, and the measures capable of reducing or keeping the population density below the threshold for economic damage. Crop rotation and the use of cultivars with resistance are important measures for controlling cereal cyst nematodes. Several cereal cultivars with resistance to H. avenae are on the market. As to H. filipjevi, resistance may be found in some commercial cultivars, although no intentional breeding for resistance against this nematode species has been attempted. In 2004 and 2005 the majority of the cereal cultivars on the Norwegian market were tested for susceptibility/resistance towards H. avenae pathotype Ha 11, H. avenae pathotype "Våxtorp" and H. filipjevi pathotype "West". Management systems, based on careful nematode identification and good knowledge of appropriate resistant cultivars, are in operation in Norway. Resistant barley is generally recommended when nematode populations are high due to its high tolerance compared to resistant oats. Farmers implementing this program have reported increased cereal yields on the average of 1000 kg/ha. It has been calculated that by implementing this program in full the county of Vestfold could make an economic gain of 800,000 Euro annually.

A fluorescence-based microplate assay to quantify DOM-induced catabolic activity

This note describes a novel method to quickly quantify the dissolved organic matter (DOM)-induced catabolic activity from low-volume samples. The concept is based on the catabolic response profiles (CRP) assay and is described as an inverse CRP, where the reactivity of a complex and diverse mixture of organic compounds towards single strains of bacteria is quantified. A strain of Pseudomonas fluorescens was grown and then transferred to an organic carbon-free mineral salt medium. 90 microL of a fluorogenic redox indicator was added to 90 microL of the bacterial suspension in a well on a 96-well microplate. The DOM sample (90 microL) was added to the well and the fluorescence emitted by the reduced indicator was read over the period of incubation. Only 0.8 mL of the DOM sample, including controls and replicates, was required to quantify the activity of each sample. Results are presented for a surface soil DOM sample and they were compared to glucose samples of various concentrations. The detection limit was reached for samples containing as little as 55 microM of glucose (0.3 mg C L(-1)). The assay showed that only 9% of the total carbon of the soil surface DOM sample was readily biodegradable.

First Report of the Root-Knot Nematode Meloidogyne ardenensis on Lady's Mantle in Norway

In August 2000, several small galls were observed on roots of lady's mantle (Alchemilla acutiloba Opiz) from an old grassland near Kristiansund in northern Norway. These plants, without clear above-ground symptoms, were infected with an unknown root-knot nematode. Soil and plant samples were collected in July 2001 at the previous year's location and sent for identification to the Plant Protection Service in Wageningen, the Netherlands. The smooth elongated galls included several males, swollen adult females with protruding small egg masses and hatching second-stage juveniles. Males and second-stage juveniles also were isolated from adhering soil. The root-knot nematode was identified as Meloidogyne ardenensis Santos (1). Identification was based on female, male, and second-stage juvenile morphology and female isozyme electrophoresis with malate dehydrogenase and esterase. M. ardenensis parasitizes several dicotyledonous hosts, primarily herbaceous and woody plants, and is distributed throughout Europe, with Scotland the most northern area (2). To our knowledge, this is not only the first published report of M. ardenensis in Scandinavia, but also the first report of this species on lady's mantle. References: (1) M. S. N. de A. Santos. Nematologica 13:593, 1968. (2) P. R. Thomas and D. J. F. Brown. Plant Pathol. 30:147, 1981.

Angiotensin II type 1 (AT1) receptor antagonists in the treatment of hypertension after renal transplantation

Hypertension is highly prevalent after renal transplantation and has been associated with lower graft survival. Optimum management of post-transplant hypertension remains to be defined. Losartan, a potent, orally active and selective non-peptide blocker of the angiotensin subtype 1 receptor, could represent a useful drug for treating post-transplant hypertension. Recently, a prospective study of 12 weeks treatment with losartan has showed a satisfactory control of arterial hypertension associated with a decrease in proteinuria in this high-risk group of renal transplant patients. A retrospective study was performed to review the role of losartan as a renoprotective agent (evaluating blood pressure and proteinuria) in renal transplant recipients in a long-term follow-up. A total of 150 transplant recipients were included in the study. None of the patients had a serum creatinine >3 mg/dl, or suspected renal artery stenosis, or other severe concomitant diseases. The indication for losartan therapy was hypertension, proteinuria and/or post-transplant erythrocytosis. The values of blood pressure, results of fasting haematology, blood chemistry and total proteinuria in 24-h urine samples were recorded at the time of initiation of losartan therapy, 6 and 3 months before the start, and at 3, 6, 12, 18 and 24 months thereafter. A tendency analysis by linear regression comparing two slopes before and after treatment was realized. A decrease in mean blood pressure and proteinuria, from 106.7+/-0.9 to 98.2+/-2.1 mmHg and from 1253.9+/-188 to 91.2+/-33.7 mg/24 h, P<0.05, respectively, was observed after introduction of losartan. A progressive increase in creatinine clearance was observed after the third month of losartan treatment. No significant changes were seen in haematocrit or serum potassium levels. We can conclude that a progressive decrease in mean arterial pressure associated with a decrease in proteinuria was observed during long-term follow-up. Based on the capacity of losartan to improve renal function, this drug could be decisive for the treatment and prevention of chronic allograft nephropathy.

Effect of a low calcium dialysate on parathyroid hormone secretion in diabetic patients on maintenance hemodialysis

Diabetic patients on maintenance dialysis often are characterized by a relative parathyroid hormone (PTH) deficiency and a form of renal osteodystrophy with low bone turnover known as adynamic bone. The goal of the present study was to determine whether a reduction in the dialysate calcium concentration would increase the predialysis (basal) PTH and maximal PTH level. Thirty-three diabetic maintenance hemodialysis patients with basal PTH values less than 300 pg/ml were randomized to be dialyzed with either a regular (3.0 mEq/liter or 3.5 mEq/liter, group I) or low (2.25 mEq/liter or 2.5 mEq/liter, group II) calcium dialysate for 1 year. At baseline and after 6 months and 12 months of study, low (1 mEq/liter) and high (4 mEq/liter) calcium dialysis studies were performed to determine parathyroid function. At baseline, basal (I, 126+/-20 vs. II, 108+/-19 pg/ml) and maximal (I, 269 pg/ml+/-40 pg/ml vs. II, 342 pg/ml+/-65 pg/ml) PTH levels were not different. By 6 months, basal (I, 98+/-18 vs. II, 200+/-34 pg/ml, p = 0.02) and maximal (I, 276 pg/ml+/-37 pg/ml vs. II, 529 pg/ml+/-115 pg/ml; p = 0.05) PTH levels were greater in group II. Repeated measures analysis of variance (ANOVA) of the 20 patients who completed the entire 12-month study showed that only in group II patients were basal PTH (p = 0.01), maximal PTH (p = 0.01), and the basal/maximal PTH ratio (p = 0.03) different; by post hoc test, each was greater (p < 0.05) at 6 months and 12 months than at baseline. When study values at 0, 6, and 12 months in all patients were combined, an inverse correlation was present between basal calcium and both the basal/maximal PTH ratio (r = -0.59; p < 0.001) and the basal PTH (r = -0.60; p < 0.001). In conclusion, in diabetic hemodialysis patients with a relative PTH deficiency (1) the use of a low calcium dialysate increases basal and maximal PTH levels, (2) the increased secretory capacity (maximal PTH) during treatment with a low calcium dialysate suggests the possibility of enhanced parathyroid gland growth, and (3) the inverse correlation between basal calcium and both the basal/maximal PTH ratio and the basal PTH suggests that the steady-state PTH level is largely determined by the prevailing serum calcium concentration.