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PubMed2006

Accurate enthalpies of formation of alkali and alkaline earth metal oxides and hydroxides: assessment of the correlation consistent composite approach (ccCA).

Computing the enthalpies of formation for alkali metal and alkaline earth metal oxides (M(x)O) and hydroxides [M(OH)(n)] using the Gaussian-n (Gn) and Weismann-n (Wn) ab initio model chemistries is difficult due to an improper treatment of core-valence electron correlation effects. Using a new model chemistry called the correlation consistent Composite Approach (ccCA), enthalpies of formation were determined for eight different alkali/alkaline earth metal oxides and hydroxides. Unlike the Gn and Wn model chemistries, which must be modified to properly account for core-valence electron correlation, the standard implementations of the ccCA provide acceptable results, and all enthalpies of formation obtained with the ccCA are within the accepted range of recommended values.

Computer Simulation↗
PubMed2006

Alkali metal counterion control of enolate protonation stereoselectivity.

[reaction: see text] Generation of the lithium salt of the norbornenol shown (M = H) followed by quenching with aqueous NH(4)Cl solution gives predominantly the beta-epimeric ketone 6. Similar production of the potassium alkoxide leads instead to the alpha-epimer (99:1). These results reveal the potential importance of alkali metal counterions as stereocontrol elements.

Ammonium Chloride↗
PubMed1971

Structure of glycoproteins of human erythrocytes. Alkali-stable oligosaccharides.

Studies have been made on the oligosaccharide residues of the alkali-stable carbohydrate-protein linkage of sialoglycopeptides derived from human erythrocytes. Four glycopeptides were isolated after alkaline borohydride treatment and Pronase digestion of MN-active sialoglycopeptides. The structure of one of these glycopeptides (GPIV) has been studied by sequential hydrolysis with specific glycosidases. Glycopeptide GPIV contained (per mol): 1mol of fucose, 1mol of sialic acid, 3mol of galactose, 3mol of mannose, 4mol of acetylglucosamine, 1mol of aspartic acid and fractional amounts of threonine, serine and glycine. The molecular weight of the glycopeptide was estimated to be 2330 by gel filtration. On the basis of glycosidase-digestion results, a tentative structure is proposed for the oligosaccharide moiety of glycopeptide GPIV.

Alkalies↗
PubMed1980

Structural studies on heparan sulphate from human lung fibroblasts. Characterization of oligosaccharides obtained by selective periodate oxidation of D-glucuronic acid residues followed by scission in alkali.

1. (3)H- and (35)S-labelled heparan sulphate was isolated from monolayers of human lung fibroblasts and subjected to degradations by (a) deaminative cleavage and (b) periodate oxidation/alkaline elimination. Fragments were resolved by gel- and ion-exchange-chromatography. 2. Deaminative cleavage of the radioactive glycan afforded mainly disaccharides with a low content of ester-sulphate and free sulphate, indicating that a large part (approx. 80%) of the repeating units consisted of uronosyl-glucosamine-N-sulphate. Blocks of non-sulphated [glucuronosyl-N-acetyl glucosamine] repeats (3-4 consecutive units) accounted for the remainder of the chains. 3. By selective oxidation of glucuronic acid residues associated with N-acetylglucosamine, followed by scission in alkali, the radioactive glycan was degraded into a series of fragments. The glucuronosyl-N-acetylglucosamine-containing block regions yielded a compound N-acetylglucosamine-R, where R is the remnant of an oxidized and degraded glucuronic acid. Periodate-insensitive uronic acid residues were recovered in saccharides of the general structure glucosamine-(uronic acid-glucosamine)(n)-R. 4. Further degradations of these saccharides via deaminative cleavage and re-oxidations with periodate revealed that iduronic acid may be located in sequences such as glucosamine-N-sulphate-->iduronic acid-->N-acetylglucosamine. Occasionally the iduronic acid was sulphated. Blocks of iduronic acid-containing repeats may contain up to five consecutive units. Alternating arrangements of iduronic acid- and glucuronic acid-containing repeats were also observed. 5. (3)H- and (35)S-labelled heparan sulphates from sequential extracts of fibroblasts (medium, EDTA, trypsin digest, dithiothreitol extract, cell-soluble and cell-insoluble material) afforded similar profiles after both periodate oxidation/alkaline elimination and deaminative cleavage.

Alkalies↗
PubMed2002

Characterization of a HKT-type transporter in rice as a general alkali cation transporter.

We report the characterization of rice OsHKT1 (Oryza sativa ssp. indica) homologous to the wheat K+/Na+-symporter HKT1. Expression of OsHKT1 in the yeast strain CY162 defective in K+-uptake restored growth at mM and micro M concentrations of K+ and mediated hypersensitivity to Na+. When expressed in Xenopus oocytes, rice OsHKT1 showed uptake characteristics of a Na+-transporter but mediated transport of other alkali cations as well. OsHKT1 expression was analysed in salt-tolerant rice Pokkali and salt-sensitive IR29 in response to external cation concentrations. OsHKT1 is expressed in roots and leaves. Exposure to Na+, Rb+, Li+, and Cs+ reduced OsHKT1 transcript amounts in both varieties and, in some cases, incompletely spliced transcripts were observed. By in situ hybridizations the expression of OsHKT1 was localized to the root epidermis and the vascular tissue inside the endodermis. In leaves, OsHKT1 showed strongest signals in cells surrounding the vasculature. The repression of OsHKT1 in the two rice varieties during salt stress was different in various cell types with main differences in the root vascular tissue. The data suggest control over HKT expression as a factor that may distinguish salt stress-sensitive and stress-tolerant lines. Differences in transcript expression in space and time in different lines of the same species appear to be a component of ion homeostasis correlated with salt sensitivity and tolerance.

Animals↗
PubMed1986

Effects of supplements on intake, rumen function and nutrient supply and growth in cattle eating alkali-treated oat straw.

1. Expt 1. Six 200 kg Hereford heifers fitted with rumen and abomasal cannulas were fed ad lib. on alkali-treated oat straw sprayed with urea and minerals, with no supplement (O), or 700 g rolled barley (B) or cottonseed meal (C)/d, in a 3 x 3 Latin square with two replicates. 2. Intakes of the basal diet were not significantly affected by the supplements. Intakes of digestible organic matter (OM) were 3135, 3325 and 3515 g/d on diets O, B and C respectively. Abomasal OM flow on diet C was 13 and 12% higher than on diets O and B respectively (P less than 0.05) which was associated with a decrease in the proportion of OM intake apparently digested in the rumen (P less than 0.05) and an increase in the proportion of abomasal OM digested in the lower gut (P less than 0.05). 3. Total nitrogen and bacterial N flows at the abomasum were significantly higher (P less than 0.01 and P less than 0.05 respectively) on diet C than on diets O and B. Efficiency of bacterial N synthesis on diet C was 19 and 28% higher than on diets O and B respectively (P less than 0.05). 4. Dry matter (DM) pool size in the rumen was greater on diet C than on diets O and B (P less than 0.05). 5. Expt 2. Thirty-three 210 kg Friesian heifers were allocated to the same treatments as in Expt 1. Intakes of the basal straw diet were not significantly affected by the supplements.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkalies↗
PubMedDate not supplied

Respiratory health effects of alkali dust in residents near desiccated Old Wives Lake.

Several years of drought have contributed to the desiccation of Old Wives Lake, a shallow, alkaline lake in southern Saskatchewan. The prevailing northwest wind, which blows across the 177-km2 dry lake bed, has generated airborne sodium sulfate, silt, and clay. Residents have reported nasal, eye, and respiratory irritation. A cross-sectional design that included 300 controls and 300 exposed subjects elucidated the potential adverse respiratory health effects of exposure to blowing alkali salt and dust. An increased prevalence of current cough, current wheeze, chronic cough, chronic wheeze, chronic eye irritation, and chronic nasal irritation was identified in the exposed population. Smoking-adjusted odds ratios were consistent with the prevalence ratios. Lung function did not differ between the exposed and the control populations. Rainfall during the study period reduced airborne dust levels and may have precluded demonstration of previously reported adverse effects.

Adult↗
PubMed2004

Alkali-urea extraction of demineralized bone matrix removes noggin, an inhibitor of bone morphogenetic proteins.

Demineralized bone matrix (DBM) and native bone morphogenetic protein (nBMP) are complex mixtures of non-collagenous bone proteins. These mixtures contain many of the BMPs that are available as recombinant molecules. Information regarding the presence in these materials of molecules that may affect the availability and activity of the BMPs is very limited. We have devised a simple chemical extraction of DBM using alkali-urea that produces a water soluble extractate that inhibits the osteogenic activity of DBM. We have demonstrated the presence of noggin, an extracellular BMP ligand antagonist, in this material. We conclude that differential chemical extraction may be a useful means of removing inhibitory molecules from DBM and nBMP.

Alkalies↗
PubMed1955

Factors influencing the ability of isolated cell nuclei to from gels in dilute alkali.

1. Known methods for isolating cell nuclei are divided into two classes, depending on whether or not the nuclei are capable of forming gels in dilute alkali or strong saline solutions. Methods which produce nuclei that can form gels apparently prevent the action of an intramitochondrial enzyme capable of destroying the gel-forming capacity of the nuclei. Methods in the other class are believed to permit this enzyme to act on the nuclei during the isolation procedure, causing detachment of DNA from some nuclear constituent (probably protein). 2. It is shown that heating in alkaline solution and x-irradiation can destroy nuclear gels. Heating in acid or neutral solutions can destroy the capacity of isolated nuclei to form gels. 3. Chemical and biological evidence is summarized in favor of the hypothesis that DNA is normally bound firmly to some nuclear component by non-ionic linkages.

Alkalies↗
PubMed1983

Cell volume regulation by Amphiuma red blood cells. The role of Ca+2 as a modulator of alkali metal/H+ exchange.

In response to osmotic perturbation, the Amphiuma red blood cell regulates volume back to "normal" levels. After osmotic swelling, the cells lose K, Cl, and osmotically obliged H2O (regulatory volume decrease [RVD] ). After osmotic shrinkage, cell volume is regulated as a result of Na, Cl, and H2O uptake (regulatory volume increase [RVI] ). As previously shown (Cala, 1980 alpha), ion fluxes responsible for volume regulation are electroneutral, with alkali metal ions obligatorily counter-coupled to H, whereas net Cl flux is in exchange for HCO3. When they were exposed to the Ca ionophore A23187, Amphiuma red blood cells lost K, Cl, and H2O with kinetics (time course) similar to those observed during RVD. In contrast, when cells were osmotically swollen in Ca-free media, net K loss during RVD was inhibited by approximately 60%. A role for Ca in the activation of K/H exchange during RVD was suggested from these experiments, but interpretation was complicated by the fact that an increase in cellular Ca resulted in an increase in the membrane conductance to K (GK). To determine the relative contributions of conductive K flux and K/H exchange to total K flux, electrical studies were performed and the correspondence of net K flux to thermodynamic models for conductive vs. K/H exchange was evaluated. These studies led to the conclusion that although Ca activates both conductive and electroneutral K flux pathways, only the latter pathways contribute significantly to net K flux. On the basis of observations that A23187 did not activate K loss from cells during RVI (when the Na/H exchange was functioning) and that amiloride inhibited K/H exchange by swollen cells only when cells had previously been shrunk in the presence of amiloride, I concluded that Na/H and K/H exchange are mediated by the same membrane transport moiety.

Amiloride↗
PubMed1987

Inhibition of the alkali burn-induced lipoxygenation of arachidonic acid in the rabbit cornea in vivo by a platelet activating factor antagonist.

We have evaluated the involvement of 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor, PAF), a membrane derived lipid mediator, in the inflammatory response of the anterior segment of the rabbit eye after corneal injury. The action of BN 52021, an antagonist of PAF receptor, was tested in vivo in models of corneal injury by alkali burn. The sodium salt of 1-14C-arachidonic acid was injected in the anterior chamber and the production of labeled prostaglandins and hydroxyeicosatetraenoic acid (HETE) was monitored as an index of the activation of the cyclooxygenase and lipoxygenase pathways. Topically applied BN 52021 produced a specific inhibition of the formation of labeled 5- and 12-HETE. This inhibition was maximal when the drug was applied during the first few hours after the injury. The drug does not affect the increased protein concentration in the aqueous humor after injury. These results suggest involvement of PAF in the inflammatory response in the cornea that could be blocked by the antagonist.

Alkalies↗
PubMed1992

Eicosanoid modulation and epithelial wound healing kinetics of the alkali-burned cornea.

The cyclooxygenase and lipoxygenase enzyme systems can metabolize a number of C20 polyunsaturated fatty acids. Although arachidonic acid is the usual substrate for these pathways, the eicosanoid precursor pool can be nutritionally manipulated by supplementation with alternative precursors, often generating less active or down-regulatory metabolic products. Prefeeding with gamma-linolenic acid, eicosapentaenoic acid, or a combination of both failed to influence the lagphase, epithelial migration rate, or epithelial wound healing kinetics after either 1N or 4N NaOH alkali burning of the rabbit cornea. Initial epithelial wound healing probably does not involve eicosanoid-mediated processes. Essentially linear epithelial healing kinetics continued to closure without a late decrease in wound edge velocity.

Alkalies↗
PubMed2003

Towards artificial repair of UV-damaged DNA: studies on drug binding and alkali hydrolysis.

Properties of the DNA containing the (6-4) photoproduct, one of the major UV-induced lesions, were analyzed. Two basic studies towards artificial recognition and repair of this type of damaged DNA are presented here. One is recognition of the UV-damaged DNA by a minor groove-binding drug. It was found by CD spectroscopy that distamycin could bind DNA duplexes containing the (6-4) photoproduct as effectively as the unmodified DNA, whereas a DNA duplex containing the cyclobutane pyrimidine dimer was not recognized by this drug. The other is a mechanistic study on alkali degradation of this photoproduct. HPLC and NMR analyses revealed that hydrolysis between the N3 and C4 positions of the 5' pyrimidine component occurred first. This intermediate was relatively stable, and further degradation to the strand break required severe conditions like the hot piperidine treatment.

Alkalies↗
PubMed1981

Intragastric alkali infusion: a simple, accurate provocative test for diagnosis of symptomatic alkaline reflux gastritis.

Alkaline reflex gastritis is a disabling clinical syndrome, occurring most often after gastric surgery. It is characterized by abdominal pain and bilious vomiting, and, presumably, is due to gastric irritation by regurgitated duodenal contents. The only known effective treatment is by surgical diversion to prevent the duodenal reflux. Unfortunately, the clinical diagnosis is difficult to prove, and the results of surgery are too often disappointing because of inaccurate patient selection. This is a report of a new test for distinguishing patients with symptomatic bile reflux gastritis. The test consists of blind sequential infusion into the stomach, via nasogastric tube, of 20 ml of 0.1 N HCl, normal saline, 0.1 N NaOH, and the patient's own gastric contents. Each solution is given twice. A positive test is defined as reproduction of the patient's usual pain by NaOH, and/or gastric contents, but not by acid or saline. Fifteen of 21 patients with clinical symptoms and endoscopic findings suggesting bile gastritis had a positive alkali infusion test, while only one of 18 normal controls and none of 17 controls with other causes of abdominal pain had a positive test (p less than 0.001). Of the 21 patients with clinical-endoscopic bile gastritis, 15 have had surgical treatment by Roux-en-Y gastrojejunostomy. Nine of ten patients with positive test had excellent symptomatic relief after surgery. Zero of five patients with a negative test were relieved of pain after the operation. Tis simple test appears to be a sensitive, specific, and accurate means for selecting patients for surgical treatment of alkaline reflux gastritis.

Alkalies↗
PubMed2005

Crystallization and preliminary X-ray study of a family 10 alkali-thermostable xylanase from alkalophilic Bacillus sp. strain NG-27.

Xylanases (EC 3.2.1.8) catalyze the hydrolysis of beta-1,4-glycosidic linkages within xylan, a major hemicellulose component in the biosphere. The extracellular endoxylanase (XylnA) from the alkalophilic Bacillus sp. strain NG-27 belongs to family 10 of the glycoside hydrolases. It is active at 343 K and pH 8.4. Moreover, it has attractive features from the point of view of utilization in the paper pulp, animal feed and baking industries since it is an alkali-thermostable protein. In this study, XylnA was purified from the native host source and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the monoclinic space group C2, with unit-cell parameters a = 174.5, b = 54.7, c = 131.5 A, beta = 131.2 degrees, and diffract to better than 2.2 A resolution.

Alkalies↗