Calcium interactions

The effects of calcium on polymer-solvent and polymer-surface interactions are dependent on polymer ionicity a maximum intrinsic viscosity and a minimum adsorption density as a function of polymer ionicity are obtained. For xanthan, on the other hand, no influence of specific polymer-calcium interaction is detected either on solution or on adsorption properties, and the increase in adsorption due to calcium addition is mainly due to reduction in electrostatic repulsion. The maximum adsorption density of xanthan is also found to be independent of the nature of the adsorbent surface, and the value is close to that calculated for a closely-packed monolayer of aligned molecules. 

Kerper LE University of Rochester, Rochester, NY Intracellular lead-calcium interactions (bovine brain endothelial cells) National Institute of Environmental Health Sciences... 

The importance of dietary or endogenously synthesized vitamin D has long been recognized as a primary factor influencing the bioavailability of calcium. Some of the most exciting biochemical-nutritional research in recent years has been devoted to determining the mechanisms involved in vitamin D-calcium interactions. This research has been well reviewed in other publications. The objective of the symposium upon which this book is based was to review some of the other lesser-known dietary factors that appear to have an impact on the bioavailability of calcium. 

Similarly, the serum electrolytes (sodium, potassium, and calcium) interact with each other a decrease in one is frequently tied, for instance, to an increase in one of the others. Furthermore, the nature of the data (in the case of some parameters), either because of the biological nature of the parameter or the way in which it is measured, is frequently either not normally distributed (particularly because of being markedly skewed) or not continuous in nature. This can be seen in some of the reference data for experimental animals in Mitruka and Rawnsley (1957) or Weil (1982) in, for example, creatinine, sodium, potassium, chloride, calcium and blood. 

The interaction of Ca2+ with pectins is discussed. The role of carboxylic acid salt formation and the degree of polymerization are first considered in terms of electrostatic and/or cooperative specific interactions. Then the effect of the degree of esterification and that of the pattern of carboxylic group distribution are discussed pectin esterase forms blocks which behave as fully hydrolyzed polymers and favor aggregation. Finally, the role of the calcium addition on the degree of aggregation was established. All the data show the important role of molecular structure of the pectins on calcium interactions. 

Mehansho, H., Kanerva, R. L., Hudepohl, G. R., and Smith, K. T. (1989a). Calcium bioavailability and iron-calcium interaction in orange juice. /. Am. Coll. Nutr. 8, 61-68. 

Drugs may bind to other drugs in the gut. We have already met the iron/calcium interaction with tetracyclines, which reduces the absorption of the antibiotic. 

Chatteijee, C., P. Sinha, N. Nautiyal, S.C. Agarwala, and C.P Sharma. 1987. Metabolic changes associated with boron-calcium interactions in maize. Soil Sci. Plant Nutr. 33 607-617. 

The accumulated phosphate reacts with calcium available to form apatite. Calcium may be concentrated within the vesicles by virtue of a lipid-calcium interaction and possibly by active calcium transport across the vesicle membrane458. Recent studies have led to the discovery of PL-Ca-Prcomplexes in calcifying tissues. These Pl-Ca-Pj complexes110 and certain proteolipids122,491 have been shown to rapidly nucleate HA from metastable Ca-P04 solutions. There is evidence for the existence of these complexes in matrix vesicles135. ... 

Gastrointestinal distress (nausea, vomiting, diarrhea) may be a problem with tetracycline use. Hypersensitivity reactions (such as rashes) may also occur, as well as an increase in skin sensitivity to ultraviolet light (photosensitivity).16 Tetracyclines form chemical complexes with calcium that may impair the growth and development of calcified tissues such as bone and teeth, especially in children.69 Tetracyclines also cause discoloration of teeth in children and pregnant women, apparently because of the tetracycline-calcium interaction.69 As mentioned previously, development of tetracycline-resistant strains and resulting superinfections may be a serious problem during tetracycline therapy. 

Pharmacologic Consequences of Calcium Interactions with Opioid Alkaloids and Peptides... 

The veratridine concentrations employed in the various studies differ widely. Some such differences can be explained by the different temperatures at which the experiments are performed since the effects are much reduced in the cold (see Sect. 6). The alkaloid action also depends on pH, with, as mentioned above, more alkaline values increasing the effect. Another modulator may be the Ca + concentration, whose increase shifts the relationship between the permeability of modified channels and membrane potential to more positive potentials and leads to a reduced effect over a wider potential range (see Ulbricht 1969a, Fig. 31). This paper also discusses earlier hypotheses of a more direct veratridine-calcium interaction. More recently a direct competition between Ca and veratridine has been postulated from Na" uptake studies, as mentioned above (Cat-terall 1975a). For frog muscle the apparent Kd of such veratridine-en-hanced uptake is reported to decrease considerably when the membrane is depolarized by doubling [K ]o from 2.5 to 5 mM (McKinney and Ratzlaff 1987). 

Figure 13-4. Schematic diagram of a cardiac sarcomere with the cellular components Involved In excitation-contraction coupling. Factors involved in excitation-contraction coupling are numbered 1. Na+/K ATPase 2, Na+/Ca2+ exchanger 3, voltage-gated calcium channel 4, calcium pump in the wall of the sarcoplasmic reticulum (SR) 5, calcium release channel in the SR, 6, site of calcium interaction with the troponin-tropomyosin system. (Reproduced, with permission, from Katzung BG [editor] Basic Clinical Pharmacology, 8th ed. McGraw-Hill, 2001.)...

The focus of this monograph is a comparison of natural organics rejection potential and fouling mechanisms of three membrane processes which are commonly used in water treatment - micro- (MF), ultra- (UU, and nanofiltration (NF). This comparative treatment study is combined with the science of natural organics and surface water systems, including an examination of natural organic-colloid-calcium interactions and solution speciation. 

Theoretical Studies of Metal/Conjugated Polymer Interfaces Aluminum and Calcium Interacting with 7i-Conjugated Systems... 

The conformation of acidic polysaccharides and their interactions with calcium ions was examined by molecular simulation, and the authors demonstrated the existence of specific calcium binding with poly-a-L-guluronate [56, 57], The mechanism of complex formation involves calcium interactions with different oxygen atoms of two adjacent guluronic acid units and with two inter-chain units, as visualized in the egg-box model (Fig. 24.7). The mechanism of gelation is a two-step process first step is a dimer formation, followed by precipitation for small chains, or gelation for long ones formed with different types of blocks. 

Drug-drug iuteractions Calcium salts A previous warning from the FDA that ceftriaxone and intravenous calcium products should not be co-administered to any patient to prevent precipitation leading to end-organ damage [SEDA-33, 494] was retracted in April 2009. In a search of the FDA Adverse Event Reporting System for reports of ceftriaxone-calcium interactions that resulted in serious adverse events, with ceftazidime-calcium as a comparator, 104 and 99 events respectively were identified [23 ]. For ceftriaxone-calcium-related adverse events, 7.7% and 20% were classified as probable and possible respectively for embolism. Ceftazidime-calcium resulted in fewer probable embolic events (4%) but more possible embolic events (30%). The authors claimed that their analysis supported the revised FDA recommendation that patients over 28 days old may receive ceftriaxone and calcium sequentially. This has been supported by the results of a matched cohort study in 142 patients who were exposed to the combination of ceftriaxone and intravenous calcium and in whom mortality and other adverse outcomes were not increased... 

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