Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of aeration, pH and iron concentration on the growth of yeast C. lipolytica 704 on the hexadecane medium and on the synthesis of citric and isocitric acids was investigated. The yeast synthesized citric acids actively during intensive aeration. The acid formation was strongly dependent on the medium acidity: pH 6.0 was most favourable for the synthesis of citric acids. The Fe concentration influenced significantly the ratio of the acids synthesized. At a low concentration of iron (0.005 mg Fe/l) equal amounts of citrate and isocitrate were formed; at an increased concentration isocitrate was in predominant formation.
 ...
PMID:[Effect of cultivation conditions on the synthesis of citric and isocitric acids in Candida lipolytica on hexadecane medium]. 0 20

The paper confirms the existence of a peroxide mechanism involved in oxidation of iron and manganeses by the most typical iron bacteria growing at neutral acidity of the medium. Oxidation of bivalent iron and manganese is accomplished by the simultaneous action of catalase and hydrogen peroxide produced in the respiratory chain in the course of oxidation of organic substances. Catalase performs the peroxidase function in these processes. The possibility of these biological reactions to occur and the necessary conditions have been studied in vitro. Possible variants of iron and manganese oxidation by iron bacteria are discussed, including the conditions for "symbiotic" oxidation of manganese by mixed cultures of microorganisms.
 ...
PMID:[Mechanism of the oxidation of divalent iron and manganese by iron bacteria developing in a neutral acidic medium]. 3 22

The role of acidity in determining and restricting plant distribution and performance is discussed. In soils especially, a key effect of H+ ion concentration is on the solubility of potentially toxic heavy metals such as aluminum, managenese, zinc, iron, copper, and nickel. Al has been reported from many studies since the 1920's as the key determining toxic factor in acid soils. Some acid-tolerant species have been shown to be especially tolerant of Al, and mechanisms of tolerance have been suggested. Mn is also a commonly toxic factor at soil pH less than 5.0. Calcium has been shown to alleviate Mn toxicity. Low pH soils are also generally low in Ca, K, Na, and P; all essential major elements for plant growth. In lakes and marine situations acidic waters are uncommon as the waters are buffered. Calcium is again ameliorative of metal toxicities. The pH, redox, and valency state are critical in determining nutrient availability and metal speciation. Recent increases in the H+ ion content of precipitation have caused increased acidities of freshwater lakes in Scandinavia and eastern North America, which have depleted biota, including fish populations.
 ...
PMID:Effect of H+ ion activity and Ca2+ on the toxicity of metals in the environment. 3 Dec 77

The polysaccharides were studied in an electroreceptor organ, the tuberous organ of Gnathonemus petersii (Mormyridae). Histochemical methods (P.A.S., alcian blue, toluidine blue and iron colloidal reactions) allowed us to demonstrate the existence of glycogen in the sensory cytoplasm, and P.A.S. positive polysaccharides in the sensory cavity. The polysaccharides were shown to be amylase proof; they display an acidity due to the existence of sulphated radicals. The histochemical study was completed by a cytochemical analysis: a treatment with thiocarbohydrazide (TCH) according to the Thiery's method. This method allowed us to estimate the glycogen concentration, its localization, and relationship with cellular organites within the sensory cytoplasm, as well as to differentiate the highly glycogenous type II cells of the platform from the other accessory cells (Derbin and Szabo, 1968). After a treatment for 20 hours with TCH, silver stained grains were visible on the polysaccharide filaments of the sensory chamber, between the microvilli and the vacuoles of the epidermal cells lining to the sensory cavity. Silver grains coated the outer surface of the microvilli. Such polysaccharides were not identical to the filamentous polysaccharides of the cavity. In order to determine the cytochemical localization of the polysaccharide acid groups, sections were stained with iron salts. The colloidal iron constitutes a deposit opaque to electrons and located both on the filamentous polysaccharides of the sensory cavity and in the vacuoles of the epidermal cells, indicating that only these filamentous polysaccharides display acid radicals.
 ...
PMID:Cytochemistry and distribution of polysaccharides in an electroreceptor: the tuberous organ of Gnathonemus petersii (Mormyrids). 4 39

The duodenal glands of cat and horse were studied using PAS, Alcian blue, dialysed iron, aldehyde fuchsin-Alcian blue and high iron diamine stains. It was found that the duodenal glands of the horse reacted positively to Alcian blue, dialysed iron stains and also took the Alcian blue stain in the combined aldehyde fuchsin-Alcian blue and high iron diamine-Alcian blue stains. Those of the cat gave negative results. These results suggest the presence of acidic groups in the mucosubstances secreted by the horse's duodenal glands. A suggestion is put forward on the strength of the high iron diamine-Alcian blue combined stains that the acidity is due to the presence of carboxyl groups. It is suggested that the acidity may be significant in either cellulose metabolism or the digestion of the bacterial microflora from the stomach of herbivores.
 ...
PMID:Histochemistry of the duodenal glands of the cat and horse. 7 85

An artificial pyritic coal spoil was prepared and examined over a period of 1.5 years for changes in the population of various physiological varieties of bacteria and also for mineral leaching. Heterotrophic bacteria were the first to dominate the spoil, acquiring a population of 10(7) cells per g within 2 weeks. Bacteria capable of utilizing choline sulfate as the sole source of energy comprised approximately 1% of the total heterotrophic bacteria. Sulfur-oxidizing autotrophic bacteria (Thiobacillus) and finally iron-oxidizing bacteria (Thiobacillus ferrooxidans) increased in the population, the latter becoming the dominant species where acidity was greatest. Partition of species paralleled partition of acidity in the spoil. Maximum acidity (pH 2.6) and maximum population of T. ferrooxidans (greater than 10(7) cells per g) occurred at the summit. Molds (notably, Aspergillus), algae (Chlorococcales, Oscillatoria, Navicula), cilliated and flagellated protozoa, an arthropod (Podura aquatica), and a moss (aberrant Physcomitrium pyriforme) were observed. The mineral salts leached from the spoil, in decreasing order, were the sulfates of magnesium (predominantly hexahydrite), calcium (gypsum), sodium, aluminum (alunogenite), and iron.
 ...
PMID:Microbial succession and mineral leaching in an artificial coal spoil. 73 42

The published procedure for the synthesis of pyrrolidone-5-hydroxamic acid was improved. The acidity constant of the pyrrolidone-5-hydroxamic acid was determined as pKa = 8.65. In an aqueous solution of iron (III) ions, pyrrolidone-5-hydroxamic acid binds ferric ion, forming a mixture of mono-, bis-, and tris(pyrrolidone-5-hydroxamato)iron (III) complexes. These complexes were studied by potentiometric and spectrophotometric methods. The tris compound was isolated as dark orange-red crystals and identified according to elemental analysis and IR spectral data as C15H21FeN6O9.6H2O, having the magnetic moment of 5.67 B.M.
 ...
PMID:Aqueous mixture of pyrrolidone-5-hydroxamic acid-iron (III) complexes: isolation and characterization of tris (pyrrolidone-5-hydroxamato) iron (III). 113 53

The localization of neutral mucin and acidic mucins in both control and fasted rat gastric fundic mucosa were examined by microscopic and electron microscopic histochemical methods. By Carnoy's fixation, the surface mucous coat of the control rat gastric fundic mucosa was found to be composed of alternating layers of acidic mucins and neutral mucin, indicating the synchronous and cyclic secretions of them. In many gastric pits of the fundic glands, the acidic mucins were found to spring out from the deep foveolar regions like volcanoes. This phenomenon may suggest that the acidic mucins play a fundamental role in protecting the pit cells against HCl during its passage, and the layers of neutral mucin and acidic mucins in the surface coat is the safeguard against the HCl and digestive enzymes in the gastric lumen. In the fasting rat gastric fundic mucosa, the acidity and the amount of the gastric juice were markedly decreased, indicating the suppressed secretions of mucins and HCl. The decreased production of sulfomucin was directly demonstrated by 35SO4-autoradiography. Many mucous neck cells existing in close association with the parietal cells were ballooned due to accumulation of alcian blue (AB)-positive but high iron-diamine (HID)-negative sialomucin, which was not demonstrable in the control. The secretory granules of sialomucin contained in the ballooned mucous neck cells were positively stained ultrastructurally with cacodylate-ferric colloid to stain acid mucopolysaccharides.
 ...
PMID:Importance of acidic mucin secretions by foveolar and mucous neck cells of rat fundic mucosa as the defence mechanisms against HCl as revealed by fasting. 138 Aug 50

Ascorbic acid (AsA), after being oxidized in 0.1 M phosphate (pH 7.0) buffer under the catalytic influence of adventitious iron, reacted with glutamine (Gln) derivatives with the formation of stable fluorophores showing lipofuscin-like blue (350/430 nm) fluorescence. The fluorescence was reversibly quenched by acidity and enhanced by alkaline conditions, and the fluorescence intensity was directly proportional to the Gln and AsA concentrations. Addition of H2O2 considerably increased the velocity of the fluorescence formation. Incubation of AsA/Gln in 0.1 M phosphate buffer at pH 5.0 gave a slower fluorophore formation as compared with incubation at pH 7.0. The iron chelators DTPA and desferrioxamine inhibited the fluorophore development by preventing the iron catalyzed AsA oxidation. This was in contrast to the effects of the chelators ADP and EDTA which did not show such preventive activity. The fluorophores produced by the AsA/Gln reaction are thought to be Schiff bases formed secondary to Maillard reactions involving oxidized AsA. Considering that ascorbic and dehydroascorbic acid are active and common reductones, the oxidation-enhanced carbonyl-protein cross-linking is suggested to be an important chemical reaction which may take place during ageing and be involved in lipofuscinogenesis.
 ...
PMID:Lipofuscin-like fluorophores can result from reactions between oxidized ascorbic acid and glutamine. Carbonyl-protein cross-linking may represent a common reaction in oxygen radical and glycosylation-related ageing processes. 156 Jun 82

Fluorescence and non-enzymatic browning were observed in reactions between ascorbic acid (AH2) and amino acids (AA) as well as in reactions involving AH2 autoxidation and/or polymerization in the presence of trace amounts of adventitious iron (less than or equal to 10 microM). These reaction products exhibited fluorescent spectra (400-490 nm) akin to those of extracts from lipofuscin-rich tissues. Lengthy incubation of AH2 at 37 degrees C in phosphate buffer (pH 7.0) caused a concentration- and time-dependent increase in absorbance at 412 nm, paralleling increase in 377/440 nm fluorescence, due to formation of autoxidation/polymerization products. The fluorescences of these substances were increased by acidity and quenched at alkaline conditions but restored by neutralization. The reactions between AH2 (0.1-2.0 mM) and a number of AA (1.0-4.0 mM) were also found to result in products with blue fluorescence. Following TBA test, the AH2 autoxidation/polymerization products and AH2/AA reaction products showed only moderate and slight absorbance at 535 nm, respectively, indicating a little or minute formation of aldehydes with MDA-like reactivity. The findings in this study, nevertheless, suggest possible misinterpretations of results in previous studies dealing with AH2-dependent, oxygen free radical induced, 'lipofuscin-related fluorescence'. Thus, similar to nonenzymatic glycosylation (Maillard) reactions, AH2 autoxidation as well as reactions between AH2 and AA may result in 'lipofuscin-like material', as judged from their fluorescence spectral patterns.
 ...
PMID:Oxidized ascorbic acid and reaction products between ascorbic and amino acids might constitute part of age pigments. 177 4


1 2 3 4 5 6 7 8 9 10 Next >>