Chemical Factors
Michael J. Kennish in Ecology of Estuaries Physical and Chemical Aspects, 2019
Ammonium (NH+4) is the predominant inorganic nitrogen species in estuarine sediments, being stable under anaerobic conditions. Denitrification occurs within anaerobic sediments near the redox discontinuity layer, whereas nitrification takes place in the aerobic surface layer and the oxygenated water column. As nitrification proceeds in the upper, oxidized sediments, nitrate is produced and diffuses across the redox discontinuity layer into the anaerobic zone. Denitrifying bacteria utilize the nitrate within this zone. Hence, intense microbial action at the redox discontinuity layer facilitates the downward movement of nitrate into the anaerobic zone, where denitrification occurs, and the upward diffusion of ammonium into the aerobic zone, where nitrification takes place.192 An important process affecting dissolved ammonium distribution in sediments is reversible adsorption on sedimentary particles.193
Culture systems for the human embryo
David K. Gardner, Ariel Weissman, Colin M. Howles, Zeev Shoham in Textbook of Assisted Reproductive Techniques, 2017
Although there is some debate as to the level of concern one should place on ammonium toxicity in culture medium (96, 97), there are growing data to support the appearance of ammonium in the culture medium over time (72,90,98,99) (Figure 16.3a) and its toxicity to embryos, including those of humans (90, 93). Indeed, an analysis of the impact of culture media composition on live birth rates and the subsequent development of the children conceived has been reported by Dumoulin and colleagues (100, 101). In their studies, the effects of two commercial media were analyzed in a day-2 transfer program, and it was determined that differences existed in embryo growth kinetics and subsequent birth weight, which persisted through the first two years of life. Only one of the two culture media used contained free glutamine, and it was culture in this medium that resulted in delays in development and reduced birth weight, likely because the embryos were exposed to levels of ammonium known to adversely effect human embryo development and physiology (Figure 16.3b through 16.3d).
NUTRIENT HOMEOSTASIS
David M. Gibson, Robert A. Harris in Metabolic Regulation in Mammals, 2001
Similarly the liver can utilize the twenty different amino acids arriving in the portal blood for its own oxidative metabolism and protein synthesis. However the bulk of the inllux passes into the general circulation for uptake by the peripheral tissues. If there is a prolonged dietary surfeit of amino acids (roast beef) the carbon skeletons will be oxidized in the liver w hile the amino groups are pruned and incorporated into urea for linai excretion by the kidney. In this situation the systemic blood is spared an excess of amino acids which could exceed the abilit\ of peripheral cells to manage the disposal of amino groups. Ammonia (NH,) and its protonated form, the ammonium cation (NH/), are toxic. Tissues incorporate N11,' into the amide ol the amino acid glutamic for transport to the liver, the exclusive site of urea formation, Chapter 8.
Effects of rosiglitazone/PHBV drug delivery system on postoperative fibrosis in rabbit glaucoma filtration surgery model
Published in Drug Delivery, 2019
Feng Zhang, Ke Liu, Zheng Pan, Mengdan Cao, Dengming Zhou, Hairong Liu, Yuting Huang, Xuanchu Duan
The assays include chloroform (TCM), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and PHBV, which were purchased from Sigma (USA). Rosiglitazone was obtained from BioVision (USA). Ammonium formate came from Fisher scientific (USA). Acetonitrile was obtained from Merck Millipore (Germany). Filed emission scanning electron microscope SU8010 was obtained from Hitachi (Tokyo, Japan). LC-20A high-performance liquid chromatography (HPLC) were obtained from Shimadzu equipped with an autosampler (Model SIL-20A), a column temperature controller compartment (CTO-10AS) and ultraviolet detector (SPD-M20A). Diamonsil C18 column (5 μ 250 × 4.6 mm) were purchased from Dikma Technologies Inc., China. PH meter came from Denver Instrument, USA. TonoVet were obtain from Icare, Finland. In the vivo experiments, the assays include pentobarbital sodium (30 mg/kg) (Solarbio, Beijing, China), Benoxil (Santen, Japan), Tobramycin Dexamethasone Eye Ointment (Alcon, USA), 0.5% Levofloxacin Eye Drops (Santen, Japan), 4% Paraformaldehyde (Solarbio, Beijing, China), suture line (10-0 nylon; Alcon; USA), 8-0 Vicryl suture (Ethicon; USA), Normal Saline (Second Xiangya Hospital, Changsha, China), Mitomycin C (Sigma, USA), anti-Collagen I antibody (Abcam, UK), anti-α-SMA antibody (Abcam, UK), and anti-connective tissue growth factor (CTGF) antibody (Abcam, UK).
Bioanalytical strategies in drug discovery and development
Published in Drug Metabolism Reviews, 2021
Aarzoo Thakur, Zhiyuan Tan, Tsubasa Kameyama, Eman El-Khateeb, Shakti Nagpal, Stephanie Malone, Rohitash Jamwal, Chukwunonso K. Nwabufo
MWCO ultrafiltration is a method that utilizes a cut-off for the molecular weight of a protein to be retained while the rest will pass through into the filtrate. MWCO ultrafiltration can be done with a membrane, which can remove dissolved solids up to a certain molecular weight on a filter plate. This is a good sample clean-up option and, in some cases offers better retention than SPE. In MWCO ultrafiltration, non-volatile salt adducts are buffer exchanged into the solution with volatile salts. In all cases, the cut-off should not be more than half of the molecular mass. MWCO-ultrafiltration devices are rinsed with a buffer before loading the sample. Ammonium acetate is often used. The number of buffer exchanges and ratio depends upon the protein (DelGuidice et al. 2020).
Destruction of Pseudomonas aeruginosa pre-formed biofilms by cationic polymer micelles bearing silver nanoparticles
Published in Biofouling, 2020
Tsvetelina Paunova-Krasteva, Emi Haladjova, Petar Petrov, Aleksander Forys, Barbara Trzebicka, Tanya Topouzova-Hristova, Stoyanka R. Stoitsova
The potential of cationic polymers and polymer micelles to compete with the chemical stability of the biofilm matrices has been shown as a novel successful approach to biofilm dispersal (Chen et al. 2014; Joseph et al. 2016; Borisova et al. 2018; Kamaruzzaman et al. 2019). Their efficiency, due to the presence of positive charges, usually quaternary ammonium groups, allows them to penetrate through the bacterial cell walls, interact with the biofilm extracellular matrix and disintegrate biofilms without exerting antibacterial action (Francolini et al. 2015; Liu et al. 2018; Liu Y et al. 2019). The presence of quaternary ammonium moieties, however, may cause some harmful effects. Recently, the successful application was demonstrated of cationic polymer micelles bearing both quaternized poly (2-vinylpyridine) and PDMAEMA moieties as anti-biofilm agents on pre-formed biofilms of Gram-positive and Gram-negative bacteria (Borisova et al. 2018). The results revealed that particle size was essential for the anti-biofilm effect. The structure of polymer micelles (presence of a hydrophobic core and a hydrophilic cationic corona) in combination with the smaller size of PDMAEMA-based micelles provided a large surface area and respectively a high density of positive charges. This allowed increasing the antibacterial activity while avoiding the high toxic effects caused by quaternary ammonium functionalities (Nederberg et al. 2011; Chen et al. 2014).
Related Knowledge Centers
- Amine
- Ammonia
- Atom
- Organic Compound
- Protonation
- Ion
- Chemical Formula
- Quaternary Ammonium Cation
- Hydrogen
- Brønsted–Lowry Acid–Base Theory