Magnesium in cystic fibrosis - Systematic review of the literature

BACKGROUND The metabolism of sodium, potassium, and chloride and the acid-base balance are sometimes altered in cystic fibrosis. Textbooks and reviews only marginally address the homeostasis of magnesium in cystic fibrosis. METHODS We performed a search of the Medical Subject Headings terms (cystic fibrosis OR mucoviscidosis) AND (magnesium OR hypomagnes[a]emia) in the US National Library of Medicine and Excerpta Medica databases. RESULTS We identified 25 reports dealing with magnesium and cystic fibrosis. The results of the review may be summarized as follows. First, hypomagnesemia affects more than half of the cystic fibrosis patients with advanced disease; second, magnesemia, which is normally age-independent, relevantly decreases with age in cystic fibrosis; third, aminoglycoside antimicrobials frequently induce both acute and chronic renal magnesium-wasting; fourth, sweat magnesium concentration was normal in cystic fibrosis patients; fifth, limited data suggest the existence of an impaired intestinal magnesium balance. Finally, stimulating observations suggest that magnesium supplements might achieve an improvement in respiratory muscle strength and mucolytic activity of both recombinant and endogenous deoxyribonuclease. CONCLUSIONS The first comprehensive review of the literature confirms that, despite being one of the most prevalent minerals in the body, the importance of magnesium in cystic fibrosis is largely overlooked. In these patients, hypomagnesemia should be sought once a year. Furthermore, the potential of supplementation with this cation deserves more attention.

ENaC activity in collecting ducts modulates NCC in cirrhotic mice.

Cirrhosis is a frequent and severe disease, complicated by renal sodium retention leading to ascites and oedema. A better understanding of the complex mechanisms responsible for renal sodium handling could improve clinical management of sodium retention. Our aim was to determine the importance of the amiloride-sensitive epithelial sodium channel (ENaC) in collecting ducts in compensate and decompensate cirrhosis. Bile duct ligation was performed in control mice (CTL) and collecting duct-specific αENaC knockout (KO) mice, and ascites development, aldosterone plasma concentration, urinary sodium/potassium ratio and sodium transporter expression were compared. Disruption of ENaC in collecting ducts (CDs) did not alter ascites development, urinary sodium/potassium ratio, plasma aldosterone concentrations or Na,K-ATPase abundance in CCDs. Total αENaC abundance in whole kidney increased in cirrhotic mice of both genotypes and cleaved forms of α and γ ENaC increased only in ascitic mice of both genotypes. The sodium chloride cotransporter (NCC) abundance was lower in non-ascitic KO, compared to non-ascitic CTL, and increased when ascites appeared. In ascitic mice, the lack of αENaC in CDs induced an upregulation of total ENaC and NCC and correlated with the cleavage of ENaC subunits. This revealed compensatory mechanisms which could also take place when treating the patients with diuretics. These compensatory mechanisms should be considered for future development of therapeutic strategies.

Chemical composition of interstitial waters from sediments of brine-bearing deeps of the Red Sea

Data on concentrations of the major ions (Cl, SO4, Alk, Na, K, Ca, Mg, NH4) in interstitial waters from sediments of three brine-bearing deeps of the Red Sea rift zone are reported. Interstitial waters of the Atlantis-II Deep have the highest salinity (310.1 g/l), of the Discovery Deep - slightly lower (298.8 g/l), and of the Suakin Deep - the lowest (159.9 g/l). Interstitial waters of all three deeps are characterized by low, compared with sea water, absolute and relative concentrations of Mg and SO4 ions and have extremely low alkaline reserve (0.15-0.64 meq/l). Concentrations of K, Ca and especially Na and Cl ions, as compared with sea water, are highly increased. Interstitial waters from the deeps in study have high, compared with sea water, concentrations of NH4 (12-62 mg/l).

Interstitial-water geochemistry of Kerguelen Plateau sediments

This report synthesizes all of the interstitial-water chemistry studies associated with the Kerguelen Plateau phase of ODP Leg 119. Sediments were cored at six sites (49°24'S to 59°36'S) in water depths ranging from 564 to 4082 m. A total of 77 interstitial-water samples was recovered as part of the routine sampling protocol. In addition, a novel, highresolution pore-water sampling program was tested during Leg 119 that enabled us to pinpoint reaction zones and extend our data base to deeper, drier levels that were heretofore inaccessible. Data collected include interstitial-water sodium, potassium, calcium, magnesium, pH, alkalinity, sulfate, ammonia, phosphate, aqueous silica, salinity, chloride, oxidation-reduction potentials, and sediment chemistry. The northern sector (Sites 736 and 737) is characterized by the highest sedimentation rates (up to 140 m/m.y.) and thermal gradients (70°-98°C/km) encountered on the Kerguelen Plateau during Leg 119. Site 737 represents the most reactive sediment column cored on the Kerguelen Plateau. Major cation fluxes at Site 737 are the strongest measured during Leg 119. High dissolved calcium concentrations (141.5 mM) were encountered near the bottom of Hole 737B. Elevated temperatures promote silica diagenesis and the alteration of volcanic material below 300 mbsf, and a diagenetic front was discovered near 370 mbsf at Site 737. The southern portion of the Kerguelen Plateau (Sites 738 and 744) records the lowest sedimentation rates (less than 5 m/m.y.) and thermal gradients (43°C/km) of the three study areas. Major cation fluxes at the southern sites are the lowest that we measured on the Kerguelen Plateau. High-resolution sampling provided evidence for significant silica release to the pore waters during the weathering of basement basalt. The relatively low thermal gradient does not appear to be sufficient for the formation of the opal-CT and quartz chert beds and nodules that were encountered below 120 mbsf at Site 738. Sediment-accumulation rates on the Eastern Kerguelen Sediment Ridge (Sites 745 and 746) are intermediate to those of the northern and southern sites. Deposition below the regional CCD accounts for the nearly carbonate-free, siliceous sediments. Despite their low organic carbon contents (mean = 0.15%), sediments on the Eastern Kerguelen Sediment Ridge exhibit the highest pore-water alkalinity (6.77 mM), ammonium (0.50 mM), and phosphate (23 µM) concentrations measured on the Kerguelen Plateau. Major cation fluxes are intermediate to those calculated for the northern and southern sites. The Eastern Kerguelen Sediment Ridge interstitial waters are unusual, however, in that the downward flux of magnesium is greater than the upward flux of calcium.

(Table 7) Composition of rainwater collected over the Pacific and Indian Oceans in 1955-1960

Devoted to chemical interaction between the ocean and the atmosphere in the Pacific and Indian Oceans measured in 1955-1960.

Vertical variations in basic salt composition of interstitial waters from Pacific sediments

Basic chemical composition of interstitial water in sediments of the Northwestern Pacific along a profile from the continental shelf of the Japan Trench to the ocean bed is discussed. Transformation of interstitial water in sediments rich in organic matter on the continental shelf and at the bottom of the Japan Trench is indicated. Variation in the vertical direction of elementary constituents of interstitial salt solution and variations in certain biogenic elements permit to make conclusions concerning processes taking place in sediments during sedimentation and diagenesis. These processes cause both metamorphism of water and transformation of organic and mineral content of sediments.

Investigation of pingos in Kuganguaq delta on Disko Island

The growth and collapse history of two pingos located approximately 18 m a.s.l, and 35 m a.s.l. in Kuganguag, Disko lsland, west-central Greenland were examined. The pingos of this area were formed on Tertiary basalt rocks. One of the pingos is located in the middle of an alluvial fan, the other is on a river bed. Both have already collapsed. The pingo on the river bed had already collapsed at least 3545±60 year BP (14C dating from base of the pond sediments in the pingo crater). Both pingos formed after the sea's retreat as permafrost developed in the newly exposed delta bottom.