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11.
The effects of wetting and drying and inorganic nitrogen (N) addition on carbon (C) and N turnover in fresh Douglas fir litter (Speuld forest, the Netherlands) were investigated. Litter was incubated for 9 days in the laboratory, receiving different moisture and N addition treatments. Following the additions, a series of reactions were observed of which most notable were a rapid retention of added ammonium and nitrate (NO 3 - ) and a sudden increase in CO2 respiration. For the rewetted-and-moist incubations, respiration levels remained elevated, N was net immobilized and nitrous oxide (N2O) production increased throughout the experiment. About 80% of the NO 3 - produced was lost again as N2O. In the rewetted-and-dried incubations, respiration decreased during the drying phase; no clear patterns in N mineralization were detected; and N2O production remained at constant levels, but still resulted in gaseous loss for half of the NO 3 - net produced. The experiments thus revealed two important NO 3 - sinks in LF1 litter, namely rapid retention of added NO 3 - and gaseous loss as N2O. The maximum NO 3 - loss via these sinks was estimated at 2 kg-N ha-1 yr-1, which is small compared to annual NO 3 - leaching at 90 cm soil depth (31 kg-N ha-1 yr-1). 相似文献
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Gladwin MT Raat NJ Shiva S Dezfulian C Hogg N Kim-Shapiro DB Patel RP 《American journal of physiology. Heart and circulatory physiology》2006,291(5):H2026-H2035
Accumulating evidence suggests that the simple and ubiquitous anion salt, nitrite (NO(2)(-)), is a physiological signaling molecule with potential roles in intravascular endocrine nitric oxide (NO) transport, hypoxic vasodilation, signaling, and cytoprotection after ischemia-reperfusion. Human and animal studies of nitrite treatment and NO gas inhalation provide evidence that nitrite mediates many of the systemic therapeutic effects of NO gas inhalation, including peripheral vasodilation and prevention of ischemia-reperfusion-mediated tissue infarction. With regard to nitrite-dependent hypoxic signaling, biochemical and physiological studies suggest that hemoglobin possesses an allosterically regulated nitrite reductase activity that reduces nitrite to NO along the physiological oxygen gradient, potentially contributing to hypoxic vasodilation. An expanded consideration of nitrite as a hypoxia-dependent intrinsic signaling molecule has opened up a new field of research and therapeutic opportunities for diseases associated with regional hypoxia and vasoconstriction. 相似文献
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Background
The KIPPPI (Brief Instrument Psychological and Pedagogical Problem Inventory) is a Dutch questionnaire that measures psychosocial and pedagogical problems in 2-year olds and consists of a KIPPPI Total score, Wellbeing scale, Competence scale, and Autonomy scale. This study examined the reliability, validity, screening accuracy and clinical application of the KIPPPI.Methods
Parents of 5959 2-year-old children in the Rotterdam area, the Netherlands, were invited to participate in the study. Parents of 3164 children (53.1% of all invited parents) completed the questionnaire. The internal consistency was evaluated and in subsamples the test-retest reliability and concurrent validity with regard to the Child Behavioral Checklist (CBCL). Discriminative validity was evaluated by comparing scores of parents who worried about their child’s upbringing and parent’s that did not. Screening accuracy of the KIPPPI was evaluated against the CBCL by calculating the Receiver Operating Characteristic (ROC) curves. The clinical application was evaluated by the relation between KIPPPI scores and the clinical decision made by the child health professionals.Results
Psychometric properties of the KIPPPI Total score, Wellbeing scale, Competence scale and Autonomy scale were respectively: Cronbach’s alphas: 0.88, 0.86, 0.83, 0.58. Test-retest correlations: 0.80, 0.76, 0.73, 0.60. Concurrent validity was as hypothesised. The KIPPPI was able to discriminate between parents that worried about their child and parents that did not. Screening accuracy was high (>0.90) for the KIPPPI Total score and for the Wellbeing scale. The KIPPPI scale scores and clinical decision of the child health professional were related (p<0.05), indicating a good clinical application.Conclusion
The results in this large-scale study of a diverse general population sample support the reliability, validity and clinical application of the KIPPPI Total score, Wellbeing scale and Competence scale. Also, the screening accuracy of the KIPPPI Total score and Wellbeing scale were supported. The Autonomy scale needs further study. 相似文献15.
W K de Raat 《Chemico-biological interactions》1978,20(2):163-170
Styrene and its metabolite styrene oxide were tested for their ability to induce sister chromatid exchanges (SCE) in CHO cells. Styrene oxide appeared to be a potent inducer of SCE. Styrene itself did not increase the number of SCE per metaphase, even in the presence of a metabolic activation system. The metabolic activation system decreased the SCE induction caused by styrene oxide. Induction of SCE by styrene in the presence of metabolic activation occurred when cyclohexene oxide was used as an inhibitor of the enzyme epoxide hydrase. 相似文献
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Utility of the white gene in estimating phylogenetic relationships among mosquitoes (Diptera: Culicidae) 总被引:2,自引:0,他引:2
The utility of a nuclear protein-coding gene for reconstructing
phylogenetic relationships within the family Culicidae was explored.
Relationships among 13 species representing three subfamilies and nine
genera of Culicidae were analyzed using a 762-bp fragment of coding
sequence from the eye color gene, white. Outgroups for the study were two
species from the sister group Chaoboridae. Sequences were determined from
clone PCR products amplified from genomic DNA, and aligned following
conceptual intron splicing and amino acid translation. Third codon
positions were characterized by high levels of divergence and biased
nucleotide composition, the intensity and direction of which varied among
taxa. Equal weighting of all characters resulted in parsimony and
neighboring-joining trees at odds with the generally accepted phylogenetic
hypothesis based on morphology and rDNA sequences. The application of
differential weighting schemes recovered the traditional hypothesis, in
which the subfamily Anophelinae formed the basal clade. The subfamily
Toxorhynchitinae occupied an intermediate position, and was a sister group
to the subfamily Culicinae. Within Culicinae, the genera Sabethes and
Tripteroides formed an ancestral clade, while the Culex-Deinocerites and
Aedes- Haemagogus clades occupied increasingly derived positions in the
molecular phylogeny. An intron present in the Culicinae- Toxorhynchitinae
lineage and one outgroup taxon was absent in the basal Anophelinae lineage
and the second outgroup taxon, suggesting that intron insertions or
deletions may not always be reliable systematic characters.
相似文献
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Egbert G Mik Ton G van Leeuwen Nicolaas J Raat Can Ince 《Journal of applied physiology》2004,97(5):1962-1969
This study describes the use of two-photon excitation phosphorescence lifetime measurements for quantitative oxygen determination in vivo. Doubling the excitation wavelength of Pd-porphyrin from visible light to the infrared allows for deeper tissue penetration and a more precise and confined selection of the excitation volume due to the nonlinear two-photon effect. By using a focused laser beam from a 1,064-nm Q-switched laser, providing 10-ns pulses of 10 mJ, albumin-bound Pd-porphyrin was effectively excited and oxygen-dependent decay of phosphorescence was observed. In vitro calibration of phosphorescence lifetime vs. oxygen tension was performed. The obtained calibration constants were kq = 356 Torr(-1) x s(-1) (quenching constant) and tau0 = 550 micros (lifetime at zero-oxygen conditions) at 37 degrees C. The phosphorescence intensity showed a squared dependency to the excitation intensity, typical for two-photon excitation. In vivo demonstration of two-photon excitation phosphorescence lifetime measurements is shown by step-wise PO2 measurements through the cortex of rat kidney. It is concluded that quantitative oxygen measurements can be made, both in vitro and in vivo, using two-photon excitation oxygen-dependent quenching of phosphorescence. The use of two-photon excitation has the potential to lead to new applications of the phosphorescence lifetime technique, e.g., noninvasive oxygen scanning in tissue at high spatial resolution. To our knowledge, this is the first report in which two-photon excitation is used in the setting of oxygen-dependent quenching of phosphorescence lifetime measurements. 相似文献
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M I Willems W K de Raat R A Baan J W Wilmer M J Lansbergen P H Lohman 《Mutation research》1987,176(2):211-223
The sensitivity of various methods suitable for biomonitoring the exposure to genotoxicants was compared in an animal model. The results were related to the presence of genotoxic effects in the target organ. Groups of male Wistar rats were given one oral dose of 0, 0.1, 10 or 200 mg 2-acetylaminofluorene (2-AAF)/5 ml dimethyl sulphoxide/kg body weight. Peripheral blood cells, excreta, liver and spleen were collected at different time intervals after dosing. Mutagenicity in urine and extracts of faeces was determined using the Ames test with Salmonella typhimurium TA98 with and without S9 and with and without beta-glucuronidase. Genotoxic effects were studied by measuring DNA-adduct formation in lymphocytes, liver and spleen, and sister-chromatid exchanges (SCEs) in lymphocytes. DNA adducts were measured with immunochemical techniques and postlabelling methods. Mutagenicity in urine and faeces, collected during the first 24 h after treatment, was detected at 2-AAF doses of 1 mg/kg b.w. and higher. At these doses DNA adducts also became apparent in the liver, the main target organ for tumour induction by 2-AAF. The adduct detected appeared to be the N-(deoxyguanosin-8-yl)-2-AAF adduct. There was no evidence of the presence of any other types of DNA adducts. At doses of 1 and 10 mg/kg b.w. no mutagenicity was detected in excreta collected during the second and third day after dosing. The DNA-adduct level in liver cells of the 1 mg/kg b.w. group was maximal 24 h after dosing. At 200 mg/kg b.w. a delay in excretion of mutagenicity with urine and faeces was seen and at 10 and 200 mg/kg b.w. the amount of DNA adducts continued to increase with time after dosing. At 24 and 48 h after treatment with 10 mg, the adduct levels were of the same order of magnitude as those found after the 20-fold higher dose. This points to overloading of the metabolizing system which in combination with the enterohepatic circulation, may lead to an increased retention of 2-AAF in the body. A slightly increased incidence of SCEs of doubtful significance was seen in lymphocytes, but only at the very high dose of 200 mg/kg b.w. No DNA adducts could be detected in blood lymphocytes or spleen cells at any of the dose levels applied, either with the immunochemical or with the postlabelling method.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献