Equilibrium constant for calcium ion and ascorbate ion

Tsao, Constance S.

doi:10.1007/bf01963581

Cited by 11 publications

(9 citation statements)

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“…28 In aqueous solutions, ascorbic acid undergoes ionisation to form singly-and doubly-charged anions, and each of these anionic species may couple with calcium ions to form a complex of the 1:1 type. 17 Such a property can help to reduce the availability of ionic calcium in the presence of a relatively large quantity of ascorbate. This reducing agent interfered with dentin hybridisation when CSE was used (Figs.…”

Section: [ ( ) T D $ F I G ]mentioning

confidence: 99%

“…Two mechanisms may be advocated to explain the stability of this resin-dentin interface: (1) the preservation of collagen integrity promoted by ascorbic acid incorporation. 17 Type I collagen is a major organic component of the dentin matrix and has several important functions. It determines the shape of dentin, and is responsible for anchoring structures bonded to the hybrid layer to the underlying mineralised dentin.…”

Section: [ ( ) T D $ F I G ]mentioning

confidence: 99%

“…15,16 Reactive oxygen species can 'abstract' a hydrogen from ascorbate, which becomes monodehydroascorbate and soon gains another electron to become dehydroascorbate. 17 The oxidised forms of ascorbate are relatively stable. 14,15 Ascorbic acid may suppress the denaturing effect of etching on dentin collagen, 18 offering protection against the degradation of compositedentin bonds.…”

Section: Introductionmentioning

confidence: 99%

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Adjunctive use of an anti-oxidant agent to improve resistance of hybrid layers to degradation

Erhardt

Osorio

Viseras

et al. 2011

Journal of Dentistry

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Section: [ ( ) T D $ F I G ]mentioning

confidence: 99%

Section: [ ( ) T D $ F I G ]mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Adjunctive use of an anti-oxidant agent to improve resistance of hybrid layers to degradation

Erhardt

Osorio

Viseras

et al. 2011

Journal of Dentistry

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“…32 In our endothelial cell model, millimolar concentrations of ascorbic acid had no effect on basal [ 34 Alternative mechanisms of action of ascorbic acid relate to its reducing and radical scavenger properties. As a reducing agent, ascorbic acid may alter the redox state of soluble guanylyl cyclase in vascular smooth muscle cells, which is sensitized to NO, thus mediating relaxation.…”

Section: Involvement Of Endothelium-dependent Factors In Ascorbic Acimentioning

confidence: 99%

Ascorbic Acid–Induced Modulation of Venous Tone in Humans

et al. 2001

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Abstract-Ascorbic acid appears to have vasodilatory properties, but the underlying mechanisms are not well understood.The aims of this study were to define the acute effects of locally infused ascorbic acid in human veins and to explore underlying mechanisms by using pharmacological tools in vivo. Ascorbic acid was infused in dorsal hand veins submaximally preconstricted with the ␣ 1 -adrenoceptor agonist phenylephrine or with prostaglandin F 2␣ in 23 healthy male nonsmokers, and the venodilator response was measured. Ascorbic acid produced dose-dependent dilation with maximum reversal of constriction of 38Ϯ4% in phenylephrine-preconstricted veins and of 51Ϯ13% in prostaglandin F 2␣ -preconstricted veins. Oral pretreatment with the cyclooxygenase inhibitor acetylsalicylic acid or local coinfusion of ascorbic acid and the nitric oxide synthase inhibitor N G -monomethyl-L-arginine had no effect, but coinfusion of ascorbic acid and methylene blue (to inhibit cGMP generation) abolished venodilation. Coinfusion of ascorbic acid and the nonselective potassium channel blocker quinidine abolished venodilation, whereas the inhibitor of ATP-dependent potassium channels glibenclamide had no effect. In cultured bovine endothelial cells, ascorbic acid did not affect intracellular calcium concentration but blunted the response to ATP or digitonin exposure. Ascorbic acid, in millimolar concentrations, dilates human hand veins, presumably by activation of vascular smooth muscle potassium channels through cGMP. This activation is independent of eNOS-mediated nitric oxide synthesis and cyclooxygenase products and does not involve ATP-dependent potassium channels.

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“…Vitamin C, owever, didn't exert a positive effect on femoral BMD and strength. Vitamin C has been reported to stimulate intestinal Ca absorption because of the chelating action of ascorbate with calcium ion (23,24), and Deuchi et al (8) found that, in rats fed a diet containing 5% chi tosan, 1.5% sodium ascorbate supplementation could increase Ca absorption. In the present study, there was no significant difference in Ca absorption between the CH and CHVC groups.…”

Section: Discussionmentioning

confidence: 99%

Effects of Habitual Chitosan Intake on Bone Mass, Bone-Related Metabolic Markers and Duodenum CaBP D9K mRNA in Ovariectomized SHRSP Rats.

Yang

Nakajima

et al. 2002

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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SummaryWe have demonstrated that the habitual intake of chitosan can decrease bone mass in ovariectomized (OVX) SHRSP rats fed a low-Ca diet (0.1%). In the present study, we examined both the etiology of bone loss induced by dietary chitosan and the preventive ef fect of vitamin C supplementation. Rats were OVX and maintained on one of the following diets for 6 wk: 10% cellulose (CE), 10% chitosan (CH) or 10% chitosan with sodium ascor bate (CHVC). CH caused a significant reduction in bone mineral density (BMD) and stiffness in femurs and the fourth lumbar vertebrae (L4). There was no significant difference in intes tinal Ca absorption between CH and CE, whereas CH intake significantly reduced intestinal P absorption. The bone loss in CH rats was accompanied with an increase in urinary Ca ex cretion and a decrease in serum Ca as well as a significant increment in serum PTH and 1,25(OH)2D3. The vitamin D receptor and calcium binding protein D9K mRNAs were also significantly increased in the duodenum of CH rats. Vitamin C supplementation to CH caused an increase in the Ca and P contents of femurs as well as BMD of the L4, with a de crease in urinary Ca excretion. These results indicate that dietary chitosan with low Ca in take possibly induces the loss of bone mass by enhancing urinary Ca excretion rather than by inhibiting Ca absorption, and that vitamin C supplementation could prevent bone loss caused by chitosan through the increment of retained Ca followed by suppression of urinary Ca excretion. Key Words dietary chitosan, OVX rats, bone loss, serum 1,25(OH)2D3, CaBP D9K mRNA Chitosan, a polymer of glucosamine and a type of water insoluble dietary fiber, is prepared by the deacety lation of chitin, which constitutes the exoskeletons of arthropods such as crabs, shrimp, lobsters and insects (1). Chitosan has been shown to have a hypocholes terolemic effect in humans and animals (2-5), and also an inhibitory effect on intestinal fat digestion and ab sorption in rats (6). It has also been reported to be of low toxicity (7), and has come to be widely used as a food supplement to lower blood cholesterol and prevent weight gain. However, in spite of a number of nutri tional advantages, chitosan may serve as a chelator of several minerals and hence impair their bioavailabili ties. Deuchi et al. discovered that decreased intestinal absorption of calcium (Ca) and bone mineral contents of femurs were induced in male rats when fed diets con taining 5% chitosan for 2 wk (8). Moreover, Wada et al., in an experiment using 47Ca, observed that there was no discriminatory difference in fecal Ca excretion in rats fed chitosan or cellulose, but a significant increase in urinary Ca excretion with chitosan intake (9). These studies suggested that dietary chitosan might influence calcium and bone metabolism through inhibiting Ca absorption and/or by accelerating its urinary excretion.The decrease in net Ca retention as a consequence of habitual intake of chitosan with a low-Ca diet may en hance the risk of osteopenia or osteoporosi...

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Equilibrium constant for calcium ion and ascorbate ion

Cited by 11 publications

References 11 publications

Adjunctive use of an anti-oxidant agent to improve resistance of hybrid layers to degradation

Adjunctive use of an anti-oxidant agent to improve resistance of hybrid layers to degradation

Ascorbic Acid–Induced Modulation of Venous Tone in Humans

Effects of Habitual Chitosan Intake on Bone Mass, Bone-Related Metabolic Markers and Duodenum CaBP D9K mRNA in Ovariectomized SHRSP Rats.

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