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At least 649 records · Page 36Linked to original sources
PubMed2003

Reaction of arsenic vapor species with fly ash compounds: kinetics and speciation of the reaction with calcium silicates.

In coal combustion systems, the partitioning of arsenic between the vapor and solid phases is determined by the interaction of arsenic vapors with fly ash compounds under post-combustion conditions. This partitioning is affected by gas-solid reactions between the calcium components of the ash particles and arsenic vapors. In this study, bench scale experiments were conducted with calcium compounds typical of coal-derived fly ash to determine product formation, the extent of reaction and reaction rates when contacted by arsenic oxide vapors. Experiments conducted with arsenic trioxide (As(4)O(6(g))) vapors in contact with calcium oxide, di-calcium silicate and mono-calcium silicate over the temperature range 600-1000 degrees C indicated that these solids were capable of reacting with arsenic vapor species in both air and nitrogen. Calcium arsenate was the observed reaction product in all the samples analyzed. Maximum capture of arsenic occurred at 1000 degrees C with calcium oxide being the most effective of the three solids over the range of temperatures studied. Using a shrinking core model for a first order reaction and the results from intrinsic kinetic experiments conducted in air, the reaction rate constants were found to be 1.4 x 10(-3)exp(-2776/T) m/s for calcium oxide particles, 7.2 x 10(-3)exp(-3367/T) m/s for di-calcium silicate particles and 5.5 x 10(-3)exp(-3607/T) m/s for mono-calcium silicate particles. These results therefore suggest that any calcium present in fly ash can react with arsenic vapor and capture the metal in water-insoluble forms of the less hazardous As(V) oxidation state.

Arsenic↗
PubMed1976

[Therapeutic modification of blood circulation disorders of the intestine due to strophantin].

The vasoconstrictor effects of strophanthin on mesenteric hemodynamics were studied using mechanical ventricular massage to exclude the cardiac effects of the drug. The administration of a calcium antagonistic compound prior to digitalis, together with and after digitalis application, prevented the vasoconstrictor response completely. From our experimental experience the combination of cardiac glycosides with calcium antagonistic compounds seems rational.

Animals↗
PubMed2000

Intracellular calcium and protein kinase C mediate expression of receptor activator of nuclear factor-kappaB ligand and osteoprotegerin in osteoblasts.

Receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) produced by osteoblasts/stromal cells are involved as positive and negative regulators in osteoclast formation. Three independent signals have been proposed to induce RANKL expression in osteoblasts/stromal cells: vitamin D receptor-, cAMP-, and gp130-mediated signals. We previously reported that intracellular calcium-elevating compounds such as ionomycin, cyclopiazonic acid, and thapsigargin induced osteoclast formation in cocultures of mouse bone marrow cells and primary osteoblasts. Increases in calcium concentration in culture medium also induced osteoclast formation in cocultures. Treatment of primary osteoblasts with these compounds or with high calcium medium stimulated the expression of both RANKL and OPG messenger RNAs (mRNAs). 1,2-Bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid)-tetra(acetoxymethyl)ester, an intracellular calcium chelator, suppressed both ionomycin-induced osteoclast formation in cocultures and expression of RANKL and OPG mRNAs in primary osteoblasts. Phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, also stimulated osteoclast formation in these cocultures and the expression of RANKL and OPG mRNAs in primary osteoblasts. Protein kinase C inhibitors such as calphostin and staurosporin suppressed ionomycin- and PMA-induced osteoclast formation in cocultures and expression of RANKL and OPG mRNAs in primary osteoblasts. Ionomycin stimulated RANKL mRNA expression in ST2 and MC3T3-G2/PA6 cells, but not in MC3T3-E1 or NIH-3T3 cells. These effects were closely correlated with osteoclast formation in response to ionomycin in cocultures with these stromal cell lines. OPG strongly inhibited osteoclast formation induced by calcium-elevating compounds and PMA in cocultures, suggesting that RANKL expression in osteoblasts is a rate-limiting step for osteoclast induction. Forskolin, an activator of cAMP signals, also stimulated osteoclast formation in cocultures. Forskolin enhanced RANKL mRNA expression but suppressed OPG mRNA expression in primary osteoblasts. These results suggest that the calcium/protein kinase C signal in osteoblasts/stromal cells is the fourth signal for inducing RANKL mRNA expression, which, in turn, stimulates osteoclast formation.

3T3 Cells↗
PubMed2005

In vitro antimicrobial activity of Fill Canal, Sealapex, Mineral Trioxide Aggregate, Portland cement and EndoRez.

AIM: To determine in vitro the antimicrobial activity of Fill Canal, Sealapex, Mineral Trioxide Aggregate (MTA), Portland cement and EndoRez on various species of microorganisms. METHODOLOGY: The diffusion method on Müller-Hinton agar (MH) was employed. A base layer was made using MH agar and five wells were made by removing agar at equidistant points. Sealers were placed into the wells immediately after manipulation. The microorganisms Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Micrococcus luteus ATCC 9341, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228, Pseudomonas aeruginosa ATCC 27853 and Candida albicans ATCC 10231 were seeded by pour plate. The plates were kept at room temperature for 2 h for prediffusion and then incubated at 37 degrees C for 24 h. Aliquots of 10 mL of 0.05% triphenyltetrazolium chloride gel were added for optimization and the zones of inhibition were measured. RESULTS: Sealapex and Fill Canal demonstrated antimicrobial activity for all strains. For MTA and Portland cement, only E. coli was not inhibited. No antimicrobial activity was detected for EndoRez. CONCLUSIONS: In this laboratory study, Fill Canal, Sealapex, MTA and Portland cement presented antimicrobial activity whilst EndoRez did not.

Aluminum Compounds↗
PubMed2002

Vital pulp therapy in cariously exposed permanent teeth and its limitations.

Vital pulp therapy for cariously exposed permanent teeth remains one of the most controversial areas in dentistry. Because a vital, functioning pulp is capable of initiating several defence mechanisms to protect the body from bacterial invasion, it is beneficial to preserve the vitality and health of an exposed pulp rather than replace it with a root filling material following pulp exposure. There is no consensus on the survival rate of formerly cariously exposed pulps. Observation time, judgement criteria, pulpotomy/pulp capping technique and, most importantly, pulpal status at the time of treatment, vary to a great extent amongst studies. In mature teeth, a pulp exposed by caries is usually removed and the root canals are cleaned, shaped and filled. Amongst the methods for preservation of a cariously exposed pulp, partial pulpotomy has yielded a markedly high success rate in young teeth. Major limitations in the success of vital pulp therapy in cariously exposed permanent teeth exist. The lack of predictability and long-term success greatly influence decision-making. The decision-making itself is unreliable primarily due to the difficulty of accurately diagnosing the ability of the pulp to repair. While there are indications for vital pulp therapy in young permanent molars, it must be remembered that ultimately, none of these procedures enjoy the long-term success of complete root canal therapy.

Age Factors↗
PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗
PubMed2005

Purkinje cell long-term depression is prevented by T-588, a neuroprotective compound that reduces cytosolic calcium release from intracellular stores.

Long-term depression (LTD) of the parallel-fiber (PF) Purkinje synapse induced by four different experimental paradigms could be prevented in rat cerebellar slices by T-588, a neuroprotective compound. The paradigms consisted of pairing PF activation with climbing-fiber activation, direct depolarization, glutamic iontophoretic depolarization, or caffeine. In all cases, LTD was determined by patch-clamp recording of PF excitatory postsynaptic currents at the Purkinje cell somata. T-588 at 1 muM prevented the triggering of LTD reversibly and did not generate LTD on its own. Two-photon calcium-sensitive dye imaging demonstrated that T-588 reduces intracellular calcium concentration ([Ca(2+)](i)) increase by blocking calcium release from intracellular stores. Because [Ca(2+)](i) increase has been widely shown to trigger LTD and glutamate excitotoxicity, we propose that LTD may act as a neuroprotective mechanism. As such, LTD would serve to decrease glutamatergic-receptor sensitivity to limit deleterious [Ca(2+)](i) increase rather than to act as a mechanism for cerebellar learning.

Animals↗
PubMed2006

Comparison of antifungal activity of white-colored and gray-colored mineral trioxide aggregate (MTA) at similar concentrations against Candida albicans.

The killing effect of similar concentrations of white-colored MTA and gray-colored MTA against Candida albicans was assessed in vitro using the tube dilution test. A direct correlation was found between MTA concentration and its killing effect on C. albicans. At time period zero, both white-colored and gray-colored MTA samples showed Candida growth regardless of the concentration. Tubes containing gray-colored MTA in concentrations of 50, 25, 12.5, 6.25, and 3.125 mg/ml and tubes containing white-colored MTA in concentrations of 50 and 25 mg/ml did not show C. albicans growth at any of the other time periods tested. Tubes containing white-colored MTA in concentrations of 12.5 mg/ml or less showed Candida growth at all the time periods tested. Statistically, a significant difference was found between tubes containing either 50 mg/ml or 25 mg/ml and tubes containing lower concentrations of white-colored MTA (p < 0.001). A significant difference was also found between tubes containing gray-colored MTA in concentrations of 12.5 mg/ml or less and tubes containing similar concentrations of white-colored MTA (p < 0.001). It appears that both gray-colored and white-colored MTA in concentrations of 50 mg/ml and 25 mg/ml are effective in killing C. albicans for periods of up to 1 wk. Lower concentrations of gray-colored MTA may still be effective while lower concentrations of white-colored MTA may not.

Aluminum Compounds↗
PubMed2006

Effects of gray and white mineral trioxide aggregate on the proliferation of oral keratinocytes and cementoblasts.

Mineral trioxide aggregate (MTA) is used as a repair material and may directly contact cells from different cell lineages. The purpose of this study was to assess cell proliferation of immortalized Murine cementoblasts (OCCM.30) and immortalized keratinocytes (OKF6/TERT1) on gray MTA (GMTA) and white MTA (WMTA) with the DNA intercalating dye Hoechst 33342. Cells were grown for 72 hours on GMTA or WMTA that had been cured for 24 hours or 12 days. WMTA significantly (p < 0.001) increased the proliferation of OCCM.30 cementoblasts compared to control and OKF6/TERT1 keratinocytes. Both cell types grew significantly (p < 0.001) better on the surface of WMTA compared to GMTA. In addition, both cell types showed significantly (p < 0.005) higher proliferation when grown on 12-day-cured GMTA compared to 24-hour-cured GMTA.

Aluminum Compounds↗
PubMed2006

Comparison of the physical and mechanical properties of MTA and portland cement.

This study evaluated and compared the pH, radiopacity, setting time, solubility, dimensional change, and compressive strength of ProRoot MTA (PMTA), ProRoot MTA (tooth colored formula) (WMTA), white Portland cement (WP), and ordinary Portland cement (OP). The results showed that PMTA and Portland cement have very similar physical properties. However, the radiopacity of Portland cement is much lower than that of PMTA. The compressive strength of PMTA was greater than Portland cement at 28 days. The major constituent of PMTA is Portland cement. Given the low cost of Portland cement and similar properties when compared to PMTA, it is reasonable to consider Portland cement as a possible substitute for PMTA in endodontic applications. However, industrially manufactured Portland cement is not approved currently for use in the United States and therefore no clinical recommendation can be made for its use in the human body. Further in vitro and in vivo tests, especially with regards its biocompatibility, should be conducted to ascertain if it meets the FDA requirements for use as a medical device.

Aluminum Compounds↗