Sediment-related growth limitation of Elodea nuttallii as indicated by a fertilization experiment

1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes.     

Sediment-related growth limitation of Elodea nuttallii as indicated by a fertilization experiment

1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes.     

Maturational changes in responses of tissue and airway resistance to histamine

Dreshaj, Ismail A., Musa A. Haxhiu, Charles F. Potter, FatonH. Agani, and Richard J. Martin. Maturational changes in responsesof tissue and airway resistance to histamine. J. Appl.Physiol. 81(4): 1785-1791, 1996.We determinedhow postnatal maturation affects the relative contributions of airwaysand lung parenchyma to pulmonary resistance(RL) and whether there are developmental differences in their respective responses to constrictive agents. We studied open-chest ventilated anesthetized piglets of threeages: 2-4 days, 2-3 wk, and 10 wk.RL was partitioned into tissue(Rti) and airway (Raw) resistance by means of alveolar capsules underbaseline conditions and after intravenous histamine. Postnatalmaturation was associated with a progressive decline inRL, Rti, and Raw and with anincrease in the contribution of Rti toRL from 38 ± 8% at 2-4days to 72 ± 2% at both 2-3 and 10 wk. Histamine causedRL to increase at all ages. Whenpartitioned into Rti and Raw, the percent increase in Rti significantlyexceeded that of Raw at both 2-4 days and 2-3 wk. Incontrast, the percent increase in Raw significantly exceeded that ofRti at 10 wk. Administration of atropine before histamine in pigletsaged 10 wk reduced the response of Rti and Raw to histamine.Histamine-induced responses ofRL were blocked by priorH₁-receptor blockade withpyrilamine (2 mg/kg). These results indicate that1) the contribution of Rti and Rawto RL changes during maturationand that 2) contractile responses toexogenous histamine are manifest predominantly in most distal airwaysand lung parenchyma during early postnatal life; with advancingmaturation there is greater contribution of airways to the increase inRL induced by histamine.

     

Cellulose-bound Peptide Arrays: Preparation and Applications

Spatial organization of metabolic enzymes may represent a general cellular mechanism to regulate metabolic flux. One recent example of this type of cellular phenomenon is the purinosome, a newly discovered multi-enzyme metabolic assembly that includes all of the enzymes within the de novo purine biosynthetic pathway. Our understanding of the components and regulation of purinosomes has significantly grown in recent years. This paper reviews the purine de novo biosynthesis pathway and its regulation, and presents the evidence supporting the purinosome assembly and disassembly processes under the control of G-protein-coupled receptor (GPCR) signaling. This paper also discusses the implications of purinosome and GPCR regulation in drug discovery.     

Optimisation of a quantitative polymerase chain reaction-based strategy for the detection and quantification of human herpesvirus 6 DNA in patients undergoing allogeneic haematopoietic stem cell transplantation

Human herpesvirus 6 (HHV-6) may cause severe complications after haematopoietic stem cell transplantation (HSCT). Monitoring this virus and providing precise, rapid and early diagnosis of related clinical diseases, constitute essential measures to improve outcomes. A prospective survey on the incidence and clinical features of HHV-6 infections after HSCT has not yet been conducted in Brazilian patients and the impact of this infection on HSCT outcome remains unclear. A rapid test based on real-time quantitative polymerase chain reaction (qPCR) has been optimised to screen and quantify clinical samples for HHV-6. The detection step was based on reaction with TaqMan^® hydrolysis probes. A set of previously described primers and probes have been tested to evaluate efficiency, sensitivity and reproducibility. The target efficiency range was 91.4% with linearity ranging from 10-10⁶ copies/reaction and a limit of detection of five copies/reaction or 250 copies/mL of plasma. The qPCR assay developed in the present study was simple, rapid and sensitive, allowing the detection of a wide range of HHV-6 loads. In conclusion, this test may be useful as a practical tool to help elucidate the clinical relevance of HHV-6 infection and reactivation in different scenarios and to determine the need for surveillance.     

Oligomycin inhibits HIF-1alpha expression in hypoxic tumor cells

Hypoxia-inducible factor-1 (HIF-1) is a key regulator of cellular responses to reduced oxygen availability. The contribution of mitochondria in regulation of HIF-1 in hypoxic cells has received recent attention. We demonstrate that inhibition of electron transport complexes I, III, and IV diminished hypoxic HIF-1 accumulation in different tumor cell lines. Hypoxia-induced HIF-1 accumulation was not prevented by the antioxidants Trolox and N-acetyl-cysteine. Oligomycin, inhibitor of F₀F₁-ATPase, prevented hypoxia-induced HIF-1 protein accumulation and had no effect on HIF-1 induction by hypoxia-mimicking agents desferrioxamine or dimethyloxalylglycine. The inhibitory effect of mitochondrial respiratory chain inhibitors and oligomycin on hypoxic HIF-1 content was pronounced in cells exposed to hypoxia (1.5% O₂) but decreased markedly when cells were exposed to severe oxygen deprivation (anoxia). Taken together, these results do not support the role for mitochondrial reactive oxygen species in HIF-1 regulation, but rather suggest that inhibition of electron transport chain and impaired oxygen consumption affect HIF-1 accumulation in hypoxic cells indirectly via effects on prolyl hydroxylase function. hypoxia-inducible factor 1; oxygen sensing     

The effects of forskolin and rolipram on cAMP,cGMP and free fatty acid levels in diet induced obesity

Obesity is a major health problem. We investigated the effects of forskolin and rolipram in the diet of animals in which obesity had been induced. We used 50 female albino Wistar rats that were assigned randomly into five groups as follows: group 1, control; group 2, high fat diet; group 3, high fat diet + forskolin; group 4, high fat diet + rolipram; and group 5, high fat diet + rolipram + forskolin. The rats were fed for 10 weeks and rolipram and forskolin were administered during last two weeks. The animals were sacrificed and blood samples were obtained. Serum cAMP, cGMP and free fatty acids (FFA) levels were measured using ELISA assays. We also measured weight gain during the 10 week period. cAMP and FFA levels of groups 3, 4 and 5 were significantly higher than those of groups 1 and 2. We found no significant differences in serum cGMP levels among the groups. The weight gain in groups 3, 4 and 5 was significantly less than for group 2. We also found that the weight gain in group 5 was significantly less than in groups 3 and 4. We found that both forskolin and rolipram stimulated lipolysis and inhibited body weight increase by increasing cAMP levels. Also, combination therapy using the two agents may be more effective in preventing diet induced obesity than either agent alone. We found also that these agents did not effect cellular cGMP levels in diet induced obesity.