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Australian Family Physician 2017Cryosurgery is an effective, simple and inexpensive treatment used extensively in general practice and dermatology. It is used most commonly for actinic keratoses and...
BACKGROUND
Cryosurgery is an effective, simple and inexpensive treatment used extensively in general practice and dermatology. It is used most commonly for actinic keratoses and warts; however, a large number of benign, premalignant and malignant skin diseases can also be treated.
OBJECTIVE
The objective of this article is to help readers improve their cryosurgery technique.
DISCUSSION
Application of the cryogenic agent (most commonly liquid nitrogen) to the skin induces rapid freezing followed by slow thawing. This produces cell injury, vascular stasis and occlusion, and inflammation. The quantity of cryogen delivered onto the skin (dose), technique, duration of thawing and amount of surrounding tissue frozen are dependent on the body region and type of lesion. If clinical diagnosis is not possible, either a skin biopsy or referral to a dermatologist is recommended. We strongly discourage blind treatment of undiagnosed skin lesions.
Topics: Contraindications; Cryosurgery; Humans; Nitrogen; Skin; Skin Diseases
PubMed: 28472571
DOI: No ID Found -
Journal of Experimental Botany May 2017
Topics: Nitrogen; Nutritional Physiological Phenomena; Plant Physiological Phenomena
PubMed: 30053117
DOI: 10.1093/jxb/erx171 -
Chemical Reviews Jun 2020Nitrogenase is the enzyme that catalyzes biological N reduction to NH. This enzyme achieves an impressive rate enhancement over the uncatalyzed reaction. Given the high... (Review)
Review
Nitrogenase is the enzyme that catalyzes biological N reduction to NH. This enzyme achieves an impressive rate enhancement over the uncatalyzed reaction. Given the high demand for N fixation to support food and chemical production and the heavy reliance of the industrial Haber-Bosch nitrogen fixation reaction on fossil fuels, there is a strong need to elucidate how nitrogenase achieves this difficult reaction under benign conditions as a means of informing the design of next generation synthetic catalysts. This Review summarizes recent progress in addressing how nitrogenase catalyzes the reduction of an array of substrates. New insights into the mechanism of N and proton reduction are first considered. This is followed by a summary of recent gains in understanding the reduction of a number of other nitrogenous compounds not considered to be physiological substrates. Progress in understanding the reduction of a wide range of C-based substrates, including CO and CO, is also discussed, and remaining challenges in understanding nitrogenase substrate reduction are considered.
Topics: Biocatalysis; Carbon Dioxide; Carbon Monoxide; Isoenzymes; Models, Molecular; Nitrogen; Nitrogenase; Oxidation-Reduction; Substrate Specificity
PubMed: 32176472
DOI: 10.1021/acs.chemrev.9b00556 -
Chemical Reviews Jun 2020The reduction of dinitrogen to ammonia by nitrogenase reflects a complex choreography involving two component proteins, MgATP and reductant. At center stage of this... (Review)
Review
The reduction of dinitrogen to ammonia by nitrogenase reflects a complex choreography involving two component proteins, MgATP and reductant. At center stage of this process resides the active site cofactor, a complex metallocluster organized around a trigonal prismatic arrangement of iron sites surrounding an interstitial carbon. As a consequence of the choreography, electrons and protons are delivered to the active site for transfer to the bound N. While the detailed mechanism for the substrate reduction remains enigmatic, recent developments highlight the role of hydrides and the privileged role for two irons of the trigonal prism in the binding of exogenous ligands. Outstanding questions concern the precise nature of the intermediates between N and NH, and whether the cofactor undergoes significant rearrangement during turnover; resolution of these issues will require the convergence of biochemistry, structure, spectroscopy, computation, and model chemistry.
Topics: Ammonia; Crystallization; Metals, Heavy; Models, Molecular; Nitrogen; Nitrogenase; Protein Conformation
PubMed: 32538623
DOI: 10.1021/acs.chemrev.0c00067 -
Annals of Botany Jun 2010Productive agriculture needs a large amount of expensive nitrogenous fertilizers. Improving nitrogen use efficiency (NUE) of crop plants is thus of key importance. NUE... (Review)
Review
BACKGROUND
Productive agriculture needs a large amount of expensive nitrogenous fertilizers. Improving nitrogen use efficiency (NUE) of crop plants is thus of key importance. NUE definitions differ depending on whether plants are cultivated to produce biomass or grain yields. However, for most plant species, NUE mainly depends on how plants extract inorganic nitrogen from the soil, assimilate nitrate and ammonium, and recycle organic nitrogen. Efforts have been made to study the genetic basis as well as the biochemical and enzymatic mechanisms involved in nitrogen uptake, assimilation, and remobilization in crops and model plants. The detection of the limiting factors that could be manipulated to increase NUE is the major goal of such research.
SCOPE
An overall examination of the physiological, metabolic, and genetic aspects of nitrogen uptake, assimilation and remobilization is presented in this review. The enzymes and regulatory processes manipulated to improve NUE components are presented. Results obtained from natural variation and quantitative trait loci studies are also discussed.
CONCLUSIONS
This review presents the complexity of NUE and supports the idea that the integration of the numerous data coming from transcriptome studies, functional genomics, quantitative genetics, ecophysiology and soil science into explanatory models of whole-plant behaviour will be promising.
Topics: Nitrogen; Plant Proteins; Plants; Quantitative Trait Loci
PubMed: 20299346
DOI: 10.1093/aob/mcq028 -
Oecologia Jun 2017Amino acid nitrogen isotopic analysis is a relatively new method for estimating trophic position. It uses the isotopic difference between an individual's 'trophic' and... (Review)
Review
Amino acid nitrogen isotopic analysis is a relatively new method for estimating trophic position. It uses the isotopic difference between an individual's 'trophic' and 'source' amino acids to determine its trophic position. So far, there is no accepted explanation for the mechanism by which the isotopic signals in 'trophic' and 'source' amino acids arise. Yet without a metabolic understanding, the utility of nitrogen isotopic analyses as a method for probing trophic relations, at either bulk tissue or amino acid level, is limited. I draw on isotopic tracer studies of protein metabolism, together with a consideration of amino acid metabolic pathways, to suggest that the 'trophic'/'source' groupings have a fundamental metabolic origin, to do with the cycling of amino-nitrogen between amino acids. 'Trophic' amino acids are those whose amino-nitrogens are interchangeable, part of a metabolic amino-nitrogen pool, and 'source' amino acids are those whose amino-nitrogens are not interchangeable with the metabolic pool. Nitrogen isotopic values of 'trophic' amino acids will reflect an averaged isotopic signal of all such dietary amino acids, offset by the integrated effect of isotopic fractionation from nitrogen cycling, and modulated by metabolic and physiological effects. Isotopic values of 'source' amino acids will be more closely linked to those of equivalent dietary amino acids, but also modulated by metabolism and physiology. The complexity of nitrogen cycling suggests that a single identifiable value for 'trophic discrimination factors' is unlikely to exist. Greater consideration of physiology and metabolism should help in better understanding observed patterns in nitrogen isotopic values.
Topics: Amino Acids; Animals; Carbon Isotopes; Diet; Food Chain; Nitrogen; Nitrogen Isotopes; Nutritional Status; Proteins
PubMed: 28584941
DOI: 10.1007/s00442-017-3881-9 -
Environmental Science and Pollution... Feb 2022The efficiency of nitrogenous fertilizers in South Asia is on a declining trajectory due to increased losses. Biochar (BC) and slow-releasing nitrogen fertilizers (SRNF)...
The efficiency of nitrogenous fertilizers in South Asia is on a declining trajectory due to increased losses. Biochar (BC) and slow-releasing nitrogen fertilizers (SRNF) have been found to improve nitrogen use efficiency (NUE) in certain cases. However, field-scale studies to explore the potential of BC and SRNF in south Asian arid climate are lacking. Here we conducted a field experiment in the arid environment to demonstrate the response of BC and SRNF on cotton growth and yield quality. The treatments were comprised of two factors, (A) nitrogen sources, (i) simple urea, (ii)neem-coated urea, (iii)sulfur-coated urea, (iv) bacterial coated urea, and cotton stalks biochar impregnated with simple urea, and (B) nitrogen application rates, N=160 kg ha, N = 120 kg ha, and N = 80 kg ha. Different SRNF differentially affected cotton growth, morphological and physiological attributes, and seed cotton yield (SCY). The bacterial coated urea at the highest rate of N application (160 kg ha) resulted in a higher net leaf photosynthetic rate (32.8 μmol m s), leaf transpiration rate (8.10 mmol s), and stomatal conductance (0.502 mol m s), while leaf area index (LAI), crop growth rate (CGR), and seed cotton yield (4513 kg ha) were increased by bacterial coated urea at 120 kg ha than simple urea. However, low rate N application (80 kg ha) of bacterial coated urea showed higher nitrogen use efficiency (39.6 kg SCY kg N). The fiber quality (fiber length, fiber strength, ginning outturn, fiber index, and seed index) was also increased with the high N application rates than N2 and N3 application. To summarize, the bacterial coated urea with recommended N (160 kg ha) and 75% of recommended N application (120 kg ha) may be recommended for farmers in the arid climatic conditions of Punjab to enhance the seed cotton yield, thereby reducing nitrogen losses.
Topics: Agriculture; Charcoal; Fertilizers; Nitrogen; Soil
PubMed: 34595718
DOI: 10.1007/s11356-021-16576-6 -
Plant Physiology and Biochemistry : PPB Jun 2021We investigated the within- and between-leaf variability in the carbon and nitrogen isotope composition (δC and δN) and total nitrogen (TN) content in two grapevine...
We investigated the within- and between-leaf variability in the carbon and nitrogen isotope composition (δC and δN) and total nitrogen (TN) content in two grapevine cultivars (Vitis vinifera cv. Chasselas and Pinot noir) field-grown under rain-fed conditions. The within-leaf variability was studied in discs sampled from base-to-tip and left and right regions from the margin to midrib. The intra- and interplant variability was studied by comparing leaves at different positions along the shoot (basal, median, apical). In leaves from both cultivars, a decrease in δC from base to tip was observed, which is in line with an upward gradient of stomatal density and chlorophyll concentration. Less important, but still significant differences were observed between the right and left discs. The leaf TN and δN values differed between cultivars, showed smaller variations than the δC values, and no systematic spatial trends. The intraleaf variations in δC, δN, and TN suggest that stomatal behavior, CO fixation, chlorophyll concentrations, and the chemical composition of leaf components were heterogeneous in the leaves. At the canopy scale, the apical leaves had less C and more N and TN than the basal leaves, indicating differences in their photosynthetic capacity and remobilizations from old, senescing leaves to younger leaves. Overall, this study demonstrates patchiness in the δC and δN values of grapevine leaves and species-specificity of the nitrogen assimilation and N fractionation. These findings suggest that care must be taken not to overinterpret foliar δC and δN values in studies based on fragmented material as markers of physiological and biochemical responses to environmental factors.
Topics: Carbon; Carbon Isotopes; Nitrogen; Nitrogen Isotopes; Plant Leaves
PubMed: 33812226
DOI: 10.1016/j.plaphy.2021.03.048 -
Chemosphere Aug 2018It is crucial to have a review on the role of iron in water treatment for the guidance towards the selection of appropriate processes, content of iron, and application... (Review)
Review
It is crucial to have a review on the role of iron in water treatment for the guidance towards the selection of appropriate processes, content of iron, and application conditions, as there are few reviews available at present and the systematic information is lacking for both researchers and engineers. The objectives of this review are to summarize the state of arts with respect to iron applied in nitrogen removal, discuss chemical and biological or bio-chemical combined nitrogen removal pathways and processes coupled with iron, and to reveal reaction mechanisms as well as providing references or even solutions to pertinent the practical engineering application of nitrate removal coupling with iron. The following information have been summarized and discussed in details: (1) iron based materials with varieties of preparations and forms, (2) major coupling ways of nitrogen removal methods or processes with iron application, (3) chemical reaction equations about a variety of chemical and biological or bio-chemical combined processes and the main mechanisms. In addition, challenges and/or drawbacks during the nitrogen removal processes will also be discussed in this paper, which is aimed to seek better practical engineering applications of nitrate removal coupling with iron.
Topics: Denitrification; Iron; Nitrogen; Water Pollutants, Chemical; Water Purification
PubMed: 29653322
DOI: 10.1016/j.chemosphere.2018.04.019 -
G3 (Bethesda, Md.) Mar 2022In yeast physiology, a commonly used reference condition for many experiments, including those involving nitrogen catabolite repression (NCR), is growth in synthetic...
In yeast physiology, a commonly used reference condition for many experiments, including those involving nitrogen catabolite repression (NCR), is growth in synthetic complete (SC) medium. Four SC formulations, SCCSH,1990, SCCSH,1994, SCCSH,2005, and SCME, have been used interchangeably as the nitrogen-rich medium of choice [Cold Spring Harbor Yeast Course Manuals (SCCSH) and a formulation in the methods in enzymology (SCME)]. It has been tacitly presumed that all of these formulations support equivalent responses. However, a recent report concluded that (i) TorC1 activity is downregulated by the lower concentration of primarily leucine in SCME relative to SCCSH. (ii) The Whi2-Psr1/2 complex is responsible for this downregulation. TorC1 is a primary nitrogen-responsive regulator in yeast. Among its downstream targets is control of NCR-sensitive transcription activators Gln3 and Gat1. They in turn control production of catabolic transporters and enzymes needed to scavenge poor nitrogen sources (e.g., Proline) and activate autophagy (ATG14). One of the reporters used in Chen et al. was an NCR-sensitive DAL80-GFP promoter fusion. This intrigued us because we expected minimal if any DAL80 expression in SC medium. Therefore, we investigated the source of the Dal80-GFP production and the proteomes of wild-type and whi2Δ cells cultured in SCCSH and SCME. We found a massive and equivalent reorientation of amino acid biosynthetic proteins in both wild-type and whi2Δ cells even though both media contained high overall concentrations of amino acids. Gcn2 appears to play a significant regulatory role in this reorientation. NCR-sensitive DAL80 expression and overall NCR-sensitive protein production were only marginally affected by the whi2Δ. In contrast, the levels of 58 proteins changed by an absolute value of log2 between 3 and 8 when Whi2 was abolished relative to wild type. Surprisingly, with only two exceptions could those proteins be related in GO analyses, i.e., GO terms associated with carbohydrate metabolism and oxidative stress after shifting a whi2Δ from SCCSH to SCME for 6 h. What was conspicuously missing were proteins related by TorC1- and NCR-associated GO terms.
Topics: Catabolite Repression; GATA Transcription Factors; Gene Expression Regulation, Fungal; Nitrogen; Proteome; Saccharomyces cerevisiae Proteins
PubMed: 35100365
DOI: 10.1093/g3journal/jkab432