Biology of microbes
Philip A. Geis in Cosmetic Microbiology, 2006
Simply put, the amino acids come from the digested polymers ingested by the cells. They can come from protein catabolism or from the intermediates of carbohydrate catabolism that are diverted from the catabolic process into the anabolic process of making amino acids. The production of amino acids requires energy in the form of ATP. Thus, these synthetic processes only occur when plenty of ATP is available from catabolism and the intermediates can be diverted away from the process of energy generation. The first step in synthesizing amino acids is to assimilate nitrogen. One mechanism to do this is nitrogen fixation. The process occurs predominantly in ecologically related bacteria such as Rhizobium, Azotobacter, and the cyanobacteria. It also occurs in certain Klebsiella and Clostridium organisms. The latter two are sometimes contaminants of personal care products, so we will touch briefly on nitrogen fixation. Realize, however, that nitrogen fixation is primarily a function of organisms that are not of concern to the cosmetic or drug microbiologist. Nitrogen fixation is the reduction of atmospheric gaseous nitrogen into ammonia by nitrogenase. It requires at least 6 electrons for reducing power and 12 ATP molecules. Other more common mechanisms for assimilating nitrogen are ammonia incorporation and assimilatory nitrate reduction. Ammonia is easily incorporated into amino acids by forming the alanine amino acid directly by amination of pyruvate using the alanine dehydrogenase enzyme. Alternatively, a cell can form glutamate (an amino acid) by aminating α-ketoglutarate (a TCA cycle intermediate) using the glutamate dehydrogenase enzyme. Once these two amino acids have been formed, the ammonia they carry (now called an α-amino group) can be transferred to other carbon skeletons of other catabolic intermediates by transamination to form several other amino acids. Other mechanisms of assimilating nitrogen include use of two enzymes in tandem (glutamine synthetase and glutamate synthetase) with the same net result of the formation of glutamate from α-ketoglutarate. Nitrate can also be assimilated by forming ammonia using the nitrate reductase enzyme and electrons from the reaction of NADPH + H; the ammonia formed is then assimilated using the processes described above. Most bacteria assimilate nitrogen by the processes described above. Once assimilated, the nitrogen is then transformed into the 20 amino acids that constitute the proteins organisms use. Other microbes assimilate nitrogen already in the form of amino acids via the breakdown of proteins.
Cellular Grafting Techniques
Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan in Comprehensive Textbook on Vitiligo, 2020
Liquid nitrogen is commonly used in cryosurgery as a method of selective tissue destruction through the rapid formation of intracellular and extracellular ice crystals. This selective destruction can be utilized in recipient site preparation to induce blister formation. The patient is called in on the day before the surgery and the recipient area is prepared using liquid nitrogen spray. Blisters will be formed in the treated area. The blister fluid is removed, and cellular suspension is injected into this pocket (Figure 38.1.6). This method is very useful in treating palmer and acral areas. Repigmentation is better compared with conventional dermabrasion or laser abrasion. It has to be restricted to the recipient site, as cryo-separation at the donor site for harvesting the blister roof will destroy the melanocytes.
Protein and amino acids
Geoffrey P. Webb in Nutrition, 2019
A positive nitrogen balance indicates a net accumulation of body protein. Healthy adults do not go into sustained positive nitrogen balance if dietary protein intake is stepped up but utilise the excess protein as an energy source and excrete the associated nitrogen as urea. Growing children would be expected to be in positive nitrogen balance, as would pregnant women, those recovering after illness, injury or starvation, and those actively accumulating extra muscle such as body-builders. One would expect these groups, particularly rapidly growing children, to have a relatively higher protein requirement than other adults i.e. they would be expected to require more protein per kilogram of body weight. Lactating women would be expected to have a higher protein requirement because they are secreting protein in their milk. Note that the daily positive nitrogen balance in body-builders is very small and would not of itself indicate a significant increase in their protein requirements.
Wear Evaluation of High Interstitial Stainless Steels
Published in Tribology Transactions, 2008
J. Rawers, J. Tylczak, D. Alman
A new series of high nitrogen-carbon manganese stainless steel alloys are studied for their wear resistance. High nitrogen and carbon concentrations were obtained by melting elemental iron-chromium-manganese (several with minor alloy additions of nickel, silicon, and molybdenum) in a nitrogen atmosphere and adding elemental graphite. The improvement in material properties (hardness and strength) with increasing nitrogen and carbon interstitial concentration was consistent with previously reported improvements in similar material properties alloyed with nitrogen only. Wear tests included: scratch, pin-on-disk, sand-rubber-wheel, impeller, and jet erosion. Additions of interstitial nitrogen and carbon as well as interstitial nitrogen and carbide precipitates were found to greatly improve material properties. In general, with increasing nitrogen and carbon concentrations, strength, hardness, and wear resistance increased.
The effects of acute clostridium difficile diarrhea on fecal nitrogen content in adult hospitalized patients.
Published in Journal of the American College of Nutrition, 1987
J A Tayek, B R Bistrian, G L Blackburn
Clostridium difficile diarrhea (CDD) is a frequent cause of hospital-associated infectious diarrhea and a common reason for nutritional consultation. Limited data are available on fecal nitrogen losses during infectious diarrhea in adults. Eleven patients with acute CDD were studied for stool volume and fecal nitrogen. The mean stool output was 630 +/− 110 g/day and fecal nitrogen 2.5 +/− 0.3 g per 24 hour period (mean +/− SEM). Fecal nitrogen loss was increased from the predicted 12.0 mg/kg BW/day to 38.0 +/− 5.9 mg/kg BW/day. Fecal nitrogen loss in CDD can be an important source of nitrogen loss and should be measured in nitrogen balance studies in such patients.
Nitrogen Absorption following Small-Intestinal Resection
Published in Scandinavian Journal of Gastroenterology, 1980
E. Hylander, K. Ladefoged, S. Jarnum
A nitrogen balance study was performed in 40 patients with various small-bowel resections. Twenty-two patients had part of or the whole colon in function; 18 had an ileostomy. The patients had body weights that were about 95% of their ideal body weight (range, 133% to 71%). Net nitrogen absorption was significantly lower in patients with extensive small-bowel resection (≥150 cm) (median, 8.0 g/day ˜64% of the dietary nitrogen intake) compared with patients with small-bowel resection
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