First 20 years of DNDC: Model evolution and GRAMP.

The DNDC (DeNitrification and DeComposition) model was first developed by Li et al. (1992) as a rain event-driven process-orientated simulation model for nitrous oxide, carbon dioxide and nitrogen gas emissions from the agricultural soils in the U.S. Over the last 20 years, the model has been modified and adapted by various research groups around the world to suit specific purposes and circumstances. The Global Research Alliance Modelling Platform (GRAMP) is a UK-led initiative for the establishment of a purposeful and credible web-based platform initially aimed at users of the DNDC model. With the aim of improving the predictions of soil C and N cycling in the context of climate change the objectives of GRAMP are to: 1) to document the existing versions of the DNDC model; 2) to create a family tree of the individual DNDC versions; 3) to provide information on model use and development; and 4) to identify strengths, weaknesses and potential improvements for the model.

The chemistry of the S-nitrosoglutathione/glutathione system

S-Nitrosothiols have generated considerable interest due to their ability to act as nitric oxide (NO) donors and due to their possible involvement in bioregulatory systems—e.g., NO transfer reactions. Elucidation of the reaction pathways involved in the modification of the thiol group by S-nitrosothiols is important for understanding the role of S-nitroso compounds in vivo. The modification of glutathione (GSH) in the presence of S-nitrosoglutathione (GSNO) was examined as a model reaction. Incubation of GSNO (1 mM) with GSH at various concentrations (1–10 mM) in phosphate buffer (pH 7.4) yielded oxidized glutathione, nitrite, nitrous oxide, and ammonia as end products. The product yields were dependent on the concentrations of GSH and oxygen. Transient signals corresponding to GSH conjugates, which increased by one mass unit when the reaction was carried out with 15N-labeled GSNO, were identified by electrospray ionization mass spectrometry. When morpholine was present in the reaction system, N-nitrosomorpholine was formed. Increasing concentrations of either phosphate or GSH led to lower yields of N-nitrosomorpholine. The inhibitory effect of phosphate may be due to reaction with the nitrosating agent, nitrous anhydride (N2O3), formed by oxidation of NO. This supports the release of NO during the reaction of GSNO with GSH. The products noted above account quantitatively for virtually all of the GSNO nitrogen consumed during the reaction, and it is now possible to construct a complete set of pathways for the complex transformations arising from GSNO + GSH.

Emissions of greenhouse gases in the United States 1985-1990

Mode of access: Internet.

High altitude pollution program stratospheric measurement system feasibility study /

Mode of access: Internet.

Humphry Davy's Chemische und physiologische Untersuchungen über das oxydirte Stickgas und das Athmen desselben .. Aus dem englischen übersezt. ...

"Vorrede," v. 2, signed: D. Nasse.

The collected works of Sir Humphry Davy ...

v. 1. Memoirs of the life of Sir Humphry Davy, by his brother, John Davy.--v. 2. Early miscellaneous papers from 1799 to 1805, with an introductory lecture and outlines of lectures on chemistry, delivered in 1802 and 1804.--v. 3. Researches, chemical and philosophical, chiefly concerning nitrous oxide ... and its respiration.--v. 4. Elements of chemical philosophy.--v. 5. Bakerian lectures and miscellaneous papers from 1806 to 1815.--v. 6. Miscellaneous papers and researches, especially on the safety-lamp, and flame, and on the protection of the copper sheathing of ships, from 1815 to 1828.--v. 7. Discourses delivered before the Royal society. Elements of agricultural chemistry, pt. I.--v. 8. Elements of agricultural chemistry, pt. II. Miscellaneous lectures and extracts from lectures.--v. 9. Salmonia, or Days of fly-fishing. Consolation in travel, or The last days of a philosopher.

Topographic plasticity in primary visual cortex is mediated by local corticocortical connections

The placement of monocular laser lesions in the adult cat retina produces a lesion projection zone (LPZ) in primary visual cortex (V1) in which the majority of neurons have a normally located receptive field (RF) for stimulation of the intact eye and an ectopically located RF ( displaced to intact retina at the edge of the lesion) for stimulation of the lesioned eye. Animals that had such lesions for 14 - 85 d were studied under halothane and nitrous oxide anesthesia with conventional neurophysiological recording techniques and stimulation of moving light bars. Previous work suggested that a candidate source of input, which could account for the development of the ectopic RFs, was long-range horizontal connections within V1. The critical contribution of such input was examined by placing a pipette containing the neurotoxin kainic acid at a site in the normal V1 visual representation that overlapped with the ectopic RF recorded at a site within the LPZ. Continuation of well defined responses to stimulation of the intact eye served as a control against direct effects of the kainic acid at the LPZ recording site. In six of seven cases examined, kainic acid deactivation of neurons at the injection site blocked responsiveness to lesioned-eye stimulation at the ectopic RF for the LPZ recording site. We therefore conclude that long-range horizontal projections contribute to the dominant input underlying the capacity for retinal lesion-induced plasticity in V1.

Oxidation effects on tetrahydropterin metabolism

The susceptibility of tetrahydropterins to oxidation was investigated in vitro and related to in vivo metabolism. At physiological pH, tetrahydrobiopterin (BH4) was oxidized, with considerable loss of the biopterin skeleton, by molecular oxygen. The hydroxyl radical (.OH) was found to increase this oxidation and degradation, whilst physiological concentrations of glutathione (GSH) retarded both the dioxygen and .OH mediated oxidation. Nitrite, at acid pH, oxidized BH4 to biopterin and tetrahydrofolates to products devoid of folate structure. Loss of dietary folates, from the stomach, due to nitrite mediated catabolism is suggested. The in vivo response of BH4 metabolism to oxidising conditions was examined in the rat brain and liver. Acute starvation depressed brain biopterins and transiently BH4 biosynthetic and salvage (dihydropteridine reductase, DHPR) pathways. Loss of biopterins, in starvation, is suggested to arise primarily from catabolism, due to oxygen radical formation and GSH depletion. L-cysteine administration to starving rats was found to elevate tissue biopterins, whilst depletion of GSH in feeding rats, by L-buthionine sulfoximine, decreased biopterins. An in vivo role for GSH to protect tetrahydropterins from oxidation is suggested. The in vivo effect of phenelzine dosing was investigated. Administration lowered brain biopterins, in the presence of dietary tyrosine. This loss is considered to arise from p-tyramine generation and subsequent DHPR inhibition. Observed elevations in plasma biopterins were in line with this mechanism. In conditions other than gross inhibition of DHPR or BH4 biosynthesis, plasma total biopterins were seen to be poor indicators of tissue BH4 metabolism. Evidence is presented indicating that the pterin formed in tissue samples by acid iodine oxidation originates from the tetrahydrofolate pool and 7,8-dihydropterin derived from BH4 oxidation. The observed reduction in this pterin by prior in vivo nitrous oxide exposure and elevation by starvation and phenelzine administration is discussed in this light. The biochemical importance of the changes in tetrahydropterin metabolism observed in this thesis are discussed with extrapolation to the situation in man, where appropriate. An additional role for BH4 as a tissue antioxidant and reductant is also considered.