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PubMed1971

Lytic enzyme from lysates of Streptomyces venezuelae infected with actinophage MSP2.

A lytic enzyme was purified 600-fold with 12% recovery from lysates of Streptomyces venezuelae S13 infected with actinophage MSP2. The purified enzyme preparation was homogeneous as shown by polyacrylamide electrophoresis. The enzyme was active over a pH range 6.0 to 9.0 with a maximum at pH 7.5. The pH profile for stability was sharp, with an optimum at pH 7.5. Maximal activity occurred between 30 and 35 C. The enzyme was stable at 20 C or less. A 30-min exposure to 25, 30, 35, 40, 45, and 50 C produced an inactivation of 3, 40, 77, 82, 93, and 100%, respectively. Lytic activity was stimulated fivefold by either 5 x 10(-3)m Mg(2+) or Mn(2+) and three- and twofold by Ca(2+) and Ba(2+), respectively. Addition of Na(+), K(+), NH(4) (+), or Li(+) to the tris(hydroxymethyl)aminomethane-hydrochloride buffer did not alter the rate of lysis. Enzyme activity was inhibited 74 and 27% by 10(-4) and 10(-5)m ethylenediaminetetraacetic acid (EDTA), respectively. The inhibition by EDTA was reversed partially by addition of Mg(2+). Lytic activity was abolished by either 5 x 10(-4)m HgCl(2) or p-hydroxymercuribenzoate, whereas 5 x 10(-4)m CuSO(4) inhibited 72%. Cell wall solubilization paralleled the release of N-terminal amino groups and reached a level of 0.23 mumole per mg of cell walls. No release of reducing power was detected in treated or untreated cell wall suspensions. Tests for proteolytic activity were negative.

Acrylates↗
PubMed1976

Control of tumbling in bacterial chemotaxis by divalent cation.

Chemotaxis is migration of organisms to higher concentrations of attractant or lower concentrations of repellent. Understanding the switch than controls whether the flagella rotate counterclockwise for swimming or clockwise for tumbling (thrashing about without making much forward progress) is central to understanding chemotaxis of peritrichous bacteria, since chemotaxis results from selective suppression of tumbles. Depletion of divalent cation by chelating agents in the presence of A23187, an ionophore that conveys divalent cation across membrane, causes incessant tumbling in Bacillus subtilis. Small additions of MgCl2 prevent this tumbling. In this tumbling condition, the bacteria which normally swim extensively when given attractant, do not respond even to 10 mM alanine, a strong attractant. MnCl2, by contrast to others potentiated by the ionophore. Permanent cations, including tetraphenylarsonium ion and triphenylmethylphosphonium ion, cause permanent swimming, even in the presence of A23187 and chelating agents. We propose that divalent cation, probably Mg2+ ion, binds to the switch to cause swimming and that, in the absence of divalent cation at the switch, the bacterium tumbles.

Alanine↗
PubMed1975

Calcium balance in children treated with diphosphonates.

Serial mineral balances have been obtained in 3 children undergoing therapy with EHDP (ethane-1-hydroxy-1, 1-diphosphonate) for diseases involving ectopic calcification. Although clinical outcome was not uniformly satisfactory, all cases showed an overall reduction in calcium balance. This was due to increased faecal excretion of calcium and was most marked after a long duration of therapy. Although these results conflict with reported experience in adults, they are in agreement with published observations of the effects of EHDP on calcium absorption in experimental animals.

Adenosine Monophosphate↗
PubMed1976

Binding of methylmercuric hydroxide by 4-thiouridine of N-formylmethionyl-tRNA from Escherichia coli.

The binding of methylmercuric hydroxide to N-formylmethionyl-tRNA of Escherichia coli has been studied. In the absence of magnesium ions, methylmercury binds strongly to 4-thiouridine in the eighth position from the 5' end: the dissociation constant is (1.0 +/- 0.2) X 10(-5) M, and the forward and reverse rate constants for binding are (5.3 +/- 0.5) X 10(4) M-1S-1 and 0.38 +/- 0.02S-1, respectively. The presence of Mg2+ prevents this binding, presumably through some conformational change induced in the structure of N-formylmethionyl-tRNA.

Binding Sites↗
PubMed1996

Zinc-ion-dependent acid phosphatase exhibits magnesium-ion-dependent myo-inositol-1-phosphatase activity.

We have purified bovine brain Zn(2+)-dependent acid phosphatase (Zn(2+)-APase), which requires Zn2+ ions to hydrolyze the substrate p-nitrophenyl phosphate (pNPP) in an acidic environment. The substrate specificity and metal requirement of Zn(2+)-APase at a physiological pH was also studied. The enzyme exhibited hydrolytic activity on myo-inositol-1- and -2-monophosphates, 2'-adenosine monophosphate, 2'-guanosine monophosphate, and the alpha- and beta-glycerophosphates, glucose-1-phosphate, and fructose-6-phosphate in 50 mM Tris-HCl buffer (pH 7.4) in the presence of Mg2+ ions, but not on pNPP and phosphotyrosine. Zn2+, Mn2+ and Co2+ ions were less effective for activation. Among the above substrates, myo-inositol-1-phosphate was the most susceptible to hydrolysis by the enzyme in the presence of 3 mM Mg2+ ions. The enzyme exhibited an optimum pH at around 8 for myo-inositol-1-phosphate in the presence of 3 mM Mg2+ ions. The Mg(2+)-dependent myo-inositol-1-phosphatase activity of the enzyme was significantly inhibited by Li+ ions. The Zn(2+)-dependent p-nitrophenyl phosphatase activity and Mg(2+)-dependent myo-inositol-1-phosphatase activity of the purified enzyme fraction exhibited similar behavior on Sephadex G-100 and Mono Q colomns. These findings suggest that Zn(2+)-APase also exhibits Mg(2+)-dependent myo-inositol-1-phosphatase activity under physiological conditions.

Acid Phosphatase↗
PubMed1987

The effect of oral magnesium-containing bowel preparation agents on mucosal coating by barium sulphate suspensions.

Alteration in the quality of mucosal coating by barium sulphate suspension observed during double-contrast barium enema (DCBE) examinations when an oral magnesium-containing purgative (Picolax) was used as sole bowel preparation has been investigated in vivo. Small amounts of Picolax were found to produce a linear increase in apparent viscosity and thixotropy, due to flocculation. The effect of equivalent concentrations of acid was significantly less (p less than 0.01), and of magnesium chloride was significantly greater (p less than 0.05), whereas magnesium citrate was comparable to Picolax, demonstrating the deflocculating effect of citrate on the flocculating action of magnesium ions. It is suggested that colonic residue from orally ingested magnesium-containing purgatives may contain sufficient magnesium ions to increase viscosity of the barium suspension and visibly affect its coating during DCBE.

Barium Sulfate↗
PubMedDate not supplied

Soil and tree-ring chemistry response to liming in a sugar maple stand.

An evaluation of the impact of dolomitic lime [CaMg(CO3)2] on soils (five years after treatment) and sapwood chemistry (after four growing seasons) was realized for a Ca-deficient sugar maple stand at the lake Clair watershed. The effect on humus chemistry was significant: exchangeable Mg and Ca, effective acidity (EA), base saturation (BSe), pH, and effective cation exchange capacity (CECe) significantly increased, while exchangeable Fe significantly decreased. In the B horizon, liming increased exchangeable Ca, Mg, and Mn concentrations while decreasing other acid cations. No significant temporal trends in element concentrations in tree rings could be detected, although the lime treatment significantly changed the average xylem Mg and Mn concentrations as well as the average Mg/Mn and Ca/Mn ratios of the sapwood. The absence of temporal trends in rings from the last 20 yr implied a significant re-equilibration of elements through the sapwood. Significant relationships were found between averaged xylem Ca/Mn and Mg/Mn ratios and exchangeable humus Ca, Mg, Mn, Al, Fe, and H+ concentration, EA, CECe, and BSe, suggesting that the average xylem Ca/Mn and Mg/Mn ratios are strong indicators of the soil acid-base status.

Acer↗
PubMed1999

Antacids revisited: a review of their clinical pharmacology and recommended therapeutic use.

Antacids are commonly used self-prescribed medications. They consist of calcium carbonate and magnesium and aluminum salts in various compounds or combinations. The effect of antacids on the stomach is due to partial neutralisation of gastric hydrochloric acid and inhibition of the proteolytic enzyme, pepsin. Each cation salt has its own pharmacological characteristics that are important for determination of which product can be used for certain indications. Antacids have been used for duodenal and gastric ulcers, stress gastritis, gastro-oesophageal reflux disease, pancreatic insufficiency, non-ulcer dyspepsia, bile acid mediated diarrhoea, biliary reflux, constipation, osteoporosis, urinary alkalinisation and chronic renal failure as a dietary phosphate binder. The development of histamine H2-receptor antagonists and proton pump inhibitors has significantly reduced usage for duodenal and gastric ulcers and gastro-oesophageal reflux disease. However, antacids can still be useful for stress gastritis and non-ulcer dyspepsia. The recent release of proprietary H2 antagonists has likely further reduced antacid use for non-ulcer dyspepsia. Other indications are still valid but represent minor uses. Antacid drug interactions are well noted, but can be avoided by rescheduling medication administration times. This can be inconvenient and discourage compliance with other medications. All antacids can produce drug interactions by changing gastric pH, thus altering drug dissolution of dosage forms, reduction of gastric acid hydrolysis of drugs, or alter drug elimination by changing urinary pH. Most antacids, except sodium bicarbonate, may decrease drug absorption by adsorption or chelation of other drugs. Most adverse effects from antacids are minor with periodic use of small amounts. However, when large doses are taken for long periods of time, significant adverse effects may occur especially patients with underlying diseases such as chronic renal failure. These adverse effects can be reduced by monitoring of electrolyte status and avoiding aluminum-containing antacids to bind dietary phosphate in chronic renal failure. Antacids, although effective for discussed indications of duodenal and gastric ulcer and gastro-oesophageal reflux disease, have been replaced by newer, more effective agents that are more palatable to patients. Antacids are likely to continue to be used for non-ulcer dyspepsia, minor episodes of heartburn (gastro-oesophageal reflux disease) and other clear indications. Although their wide-spread use may decline, these drugs will still be used, and clinicians should be aware of their potential drug interactions and adverse effects.

Antacids↗
PubMed2006

Cathartic-induced fatal hypermagnesemia in the elderly.

Symptomatic hypermagnesemia is rare and can be induced by exogenous magnesium-containing cathartics or antacids. We report a patient with hypermagnesemia. The patient was treated with continuous hemodiafiltration (CHDF); however, he died on the 4th hospital day. Hypermagnesemia is not easily detected because the magnesium level is not examined during routine investigations, and many physicians are relatively unfamiliar with hypermagnesemia. Hypermagnesemia should be considered in elderly patients presenting with hypotension, bradycardia, hyporeflexia, or respiratory depression, and particularly in patients with abnormal renal function or small bowel hypomotility. Magnesium-containing cathartics or antacids should be used more carefully in the elderly.

Aged, 80 and over↗
PubMed1997

Native corn starch versus either cellulose or glucose in the diet and the effects on apparent magnesium absorption in goats.

The objective of this study was to determine whether dietary glucose or starch would reduce the inhibitory effect of high K intake on Mg absorption in ruminants. In a 6 x 6 Latin square design, six goats were fed diets with or without added KHCO3 containing either cellulose, glucose, or native corn starch. The K concentrations of the diets were 7.8 or 34.0 g or K/kg of dry matter, and carbohydrates were incorporated so that their concentrations were identical on a glucose equivalent basis (331 g of glucose/kg of dry matter). The intake of extra K significantly reduced apparent Mg absorption from 29.8 to 22.1% on average. Glucose, instead of cellulose, in the diet did not affect Mg absorption. Replacement of dietary cellulose by corn starch enhanced the mean efficiency of Mg absorption from 21.8 to 30.9%. Starch versus glucose increased Mg absorption by 5.8 percentage units. No statistically significant interaction was observed between the type of carbohydrate and the amount of K in the diet with regard to Mg absorption. This study showed that the inhibitory effect of dietary KHCO3 on Mg absorption in goats was fully counteracted by the replacement of cellulose with starch in the diet. Possible changes in the pH of ruminal fluid might have mediated the dietary effects on Mg absorption.

Absorption↗