Comparative analysis of influence of promoters and inhibitors onin vitroavailable iron using two methods

The investigation was undertaken with the objective of comparing two in vitro techniques, measuring dialyzable iron (method A) and measuring ionizable iron (method B), for iron bioavailability in a model system. The effect of the time of introduction of the additives on the available iron was also determined. FeSO4 solution was used as the reference source of iron, to which a series of enhancers (ascorbic acid, citric acid, maleic acid and tartaric acid) and inhibitors (tannic acid, calcium oxalate, oxalic acid, calcium carbonate and sodium phytate) were added individually at various concentrations, and available iron was estimated. From FeSO4 solution, 0.1% (method A) and 3.9% (method B) of iron was available. The addition of ascorbic acid, citric acid and tartaric acid increased this by 33-50%, 28-57% and 23-90%, respectively, for method A and by 15-89%, 24-78% and 24-93% for method B. Tannic acid, sodium phytate and calcium oxalate exhibited an inhibitory effect irrespective of the concentrations, while oxalic acid and calcium carbonate exhibited a dose-dependent inhibitory pattern. The iron availability analyzed by both methods showed a positive correlation with seven out of nine additives. An inverse relation was seen between the inhibitory effect of calcium carbonate and calcium oxalate and their time of introduction into the system. The overall observations showed that although absolute values varied widely, a positive correlation existed between the methods.

Heavy metal distribution between contaminated soil and Paulownia tomentosa, in a pilot-scale assisted phytoremediation study: influence of different complexing agents

The distribution of Cd, Cu, Pb and Zn between a contaminated soil and the tree species Paulownia tomentosa was investigated in a pilot-scale assisted phytoremediation study. The influence of the addition of EDTA, tartrate and glutamate at 1, 5 and 10mM concentrations on metal accumulation by the plant and on metal mobilization in soil was evaluated. Root/shoot metal concentration ratios were in the range of 3-5 for Zn, 7-17 for Cu, 9-18 for Cd and 11-39 for Pb, depending on the type and concentration of complexing agent. A significant enhancement of metal uptake in response to complexing agent application was mainly obtained in roots for Pb (i.e. 359 mg kg(-1) for EDTA 10mM and 128 mg kg(-1) for the control), Cu (i.e. 594 mg kg(-1) for glutamate 10mM and 146 mg kg(-1) for the control) and, with the exception of glutamate, also for Zn (i.e. 670 mg kg(-1) for tartrate 10mM and 237 mg kg(-1) for the control). Despite its higher metal mobilization capacity, EDTA produced a metal accumulation in plants quite similar to those obtained with tartrate and glutamate. Consequently the concentration gradient between soil pore water and plant tissues does not seem to be the predominant mechanism for metal accumulation in Paulownia tomentosa and a role of the plant should be invoked in the selection of the chemical species taken up. Metal bioavailability in soil at the end of the experiment was higher in the trials treated with EDTA than in those treated with tartrate and glutamate, the latter not being significantly different from the control. These findings indicated the persistence of a leaching risk associated to the use of this chelator, while an increase of the environmental impact is not expected when glutamate and tartrate are applied.

Octa-O-bis-(R,R)-Tartarate Ditellurane (SAS)—a Novel Bioactive Organotellurium(IV) Compound: Synthesis, Characterization, and Protease Inhibitory Activity

Octa-O-bis-(R,R)-Tartarate Ditellurane (SAS) is a new Te(IV) compound, comprised of two tellurium atoms, each liganded by four oxygen atoms from two carboxylates and two alkoxides of two tartaric acids. Unlike many other Te(IV) compounds, SAS was highly stable in aqueous solution. It interacted with thiols to form an unstable Te(SR)(4) product. The product of the interaction of SAS with cysteine was isolated and characterized by mass spectroscopy and elemental analysis. SAS selectively inactivated cysteine proteases, but it did not inactivate other families of proteolytic enzymes. It displayed selectivity towards the cysteine protease cathepsin B, a human enzyme of pharmaceutical interest, with a second order rate constant k(i)/K(i)=5900 M(-1) s(-1).

Partitioning of ochratoxin A in mycelium and conidia ofAspergillus carbonariusand the impact on toxin contamination of grapes and wine

AIMS

Aspergillus carbonarius is an important ochratoxin A (OTA)-producing fungus which is responsible for toxin contamination of grapes and wine. The objectives of this study were to examine the partitioning of OTA in mycelium and conidia of a range of A. carbonarius strains on artificial grape juice and defined media, to determine the excretion patterns of OTA from these spores, and the effect of organic acids used in wine production on OTA excretion from conidia.

METHODS AND RESULTS

The results showed that 60-70% of the OTA was accumulated in the conidia of a number of different isolates of A. carbonarius. Calculations showed that on different defined media, an amount of 0.011- to 0.1-pg OTA was present per conidium. The OTA in spores was found to be rapidly excreted into the medium during the initial few hours after conidial germination leading to an increase of OTA in must during maceration for wine production. The presence of tartaric acid inhibited OTA production, but malic acid enhanced this production during mycelial growth. These acids were also shown to affect the time course of germination and the rate of OTA excretion from conidia during germination.

CONCLUSIONS

This study is the first to examine and show the partitioning of OTA into spores of strains of A. carbonarius and that rapid excretion of OTA from spores could be a reason for OTA accumulation in musts during wine production.

SIGNIFICANCE AND IMPACT OF THE STUDY

Conidia of A. carbonarius could be a major source of OTA contamination of grapes used in wine production. This information could help in the development of effective prevention strategies to minimize wine contamination with this important mycotoxin.

Effects of exogenous chelators on phytoavailability and toxicity of Pb in Zinnia elegans Jacq

Chelate-enhanced phytoremediation is considered as an effective method for the extraction of lead (Pb) by plants. However, more detailed studies are needed to evaluate the effect of exogenous chelators on phytoavailability and toxicity of Pb in plants, then to find out the proper applied concentration of chelators to minimize the combined toxicity to the plants and maximize phytoavailable Pb. To clarify these questions, the seed germination test of Zinnia elegans Jacq. exposed to solutions containing Pb and four types of chelators including sodium ethylenediamine tetra-acetic acid (Na2EDTA), oxalic acid, tartaric acid and citric acid was observed. The results showed that the roots and shoots treated with equimolar chelators and Pb were longer than those treated with half and two folds of the molar concentrations of Pb. The growth of seedlings was inhibited by surplus addition of chelators, and the toxicity of complexes was less than that of Pb and chelators. In particular, 2.4 mM EDTA and 1.2 mM oxalic acid significantly (P<0.05) increased Pb uptake when the seeds were treated with 2.4 mM Pb. In the 4.8 mM Pb solution, Pb accumulation in the seedlings was markedly (P<0.05) increased by 4.8 mM EDTA, 2.4 mM tartaric acid, 4.8 mM tartaric acid and 2.4 mM citric acid, and amounted to 6752.4, 6453.8, 6541.4 and 6598.3 microg g(-1), respectively. With the superfluous addition of chelators, Pb accumulation in the seedlings decreased in a concentration-dependent manner. When Pb was used at 2.4 mM, an equimolar concentration of EDTA not only increased Pb uptake but also stimulated the seedling growth. Thus, chelating agents in their appropriately concentrations could counteract Pb toxicity, but superfluous chelators resulted in less Pb uptake and growth inhibition of the seedlings.

6-Methylprednisolone down-regulates IRAK-M in human and murine osteoclasts and boosts bone-resorbing activity: a putative mechanism for corticoid-induced osteoporosis

Osteoclasts are large, multinucleated cells, which originate from the fusion of macrophages. They play a central role in bone development and remodeling via the resorption of bone and are thus important mediators of bone loss, which leads to osteoporosis. IL-1R-associated kinase (IRAK)-M is a pseudokinase, which acts as a negative modulator of innate immune responses mediated by TLRs and IL-1R. Recently, it has been reported that IRAK-M also participates in the control of macrophage differentiation into osteoclasts. In addition, it was shown that IRAK-M knockout mice develop a strong osteoporosis phenotype, suggesting that down-regulation of this molecule activates osteoclast-mediated bone resorption. We studied the effect of the osteoporosis-inducing glucocorticoid, 6-methylprednisolone (6-MP), on IRAK-M expression in osteoclasts. Our results showed that osteoclasts, derived from THP-1 and RAW cells as well as human blood monocytes, differentiated into osteoclasts, express high levels of IRAK-M at mRNA and protein levels. In addition, 6-MP down-regulates IRAK-M expression, which correlates with an increased activation of bone resorption. These findings suggest a mechanism of corticosteroid-induced osteoporosis and open new avenues for treating this endemic disease of Western societies.

Antitumor effect of an injectable in-situ forming drug delivery system composed of a novel tissue adhesive containing doxorubicin hydrochloride

Our group has developed a novel tissue adhesive composed of biomacromolecules and organic acid derivatives which have good biocompatibility and exhibit high bonding strength to living tissues. We propose to use this tissue adhesive for in-situ forming drug delivery system (DDS) for cancer chemotherapy. In a previous work, we had prepared a novel in-situ forming DDS composed of human serum albumin (HSA) and tartaric acid derivative (TAD) containing doxorubicin hydrochloride (DOX), and we had demonstrated an in vitro release profile of DOX from HSA-TAD gel for approximately up to 100h. Here, we report on antitumor effect of this injectable in-situ forming DDS. Local injection of DOX by the HSA-TAD was administered to human colon carcinoma (WiDr) implanted subcutaneously onto the immunodeficient mouse. The results of the in vivo experiments showed that the presence of DOX in blood of mice was detectable for up to 3days, and that the tumor volume was effectively minimized with injection of HSA-TAD containing DOX. The in-situ forming DDS with the novel tissue adhesive containing DOX, therefore, is a useful technique for cancer chemotherapy.

RESPONSES OF CRITERION VARIABLES TO DIFFERENT SUPPLEMENTAL DOSES OF L-CARNITINE L-TARTRATE

L-carnitine L-tartrate (LCLT) supplementation beneficially affects markers of postexercise metabolic stress and muscle damage. However, to date, no study has determined the dose response of LCLT to elicit such responses. Therefore, the purpose of this study was to determine the effects of different doses of LCLT on criterion variables previously shown to be responsive to LCLT supplementation. Eight healthy men (22 +/- 3 y, 174 +/- 5 cm, 83.0 +/- 15.3 kg) were supplemented with 0 g, 1 g, and 2 g of LCLT for 3 weeks and then performed a bout of resistance exercise (5 sets of 15-20 repetition maximum with a 2-min rest between sets) with associated blood draws. This procedure was performed in a balanced, randomized, repeated measures design. Serum carnitine concentrations increased (p < or = 0.05) following the 1 g and 2 g doses, with the 2-g dose providing the highest carnitine concentrations. The 1- and 2-g doses reduced postexercise serum hypoxanthine, serum xanthine oxidase, serum myoglobin, and perceived muscle soreness. In conclusion, both the 1- and 2-g doses were effective in mediating various markers of metabolic stress and of muscle soreness. Use of LCLT appears to attenuate metabolic stress and the hypoxic chain of events leading to muscle damage after exercise.

Investigations on the interaction of tartaric acid derivative/human serum albumin tissue adhesive with J774A.1 mouse macrophage cells through SEM, IL-6 cytokine and gene expression techniques

We developed a novel tissue adhesive consisting of human serum albumin (HSA) and tartaric acid derivative (TAD). Four different concentrations of TAD namely, 0.05 mM, 0.1 mM, 0.2 mM and 0.3 mM were mixed with 40%, 42% and 44% HSA individually and were made in the form of disks. J774A.1 mouse macrophage cells were seeded on top of these disks. The disks were pre-treated with sterile water and Eagle's medium before every seeding. All the seeding was incubated from 1 day to 3 days before making any investigations on it. SEM images were recorded and it was observed that these cells adhered to these materials very well. Mouse IL-6 cytokine expressions were studied using ELISA. It was seen from the cytokine expression results that the release of IL-6 was minimum at 0.3 mM TAD concentrations with 44% HSA disks. No significant difference was observed in the cytokine expressions of IL-6 at 42% and 44% HSA at all concentrations of TAD studied in this work. mRNA gene expressions of IL-6 were investigated using RT-PCR technique. In 40% HSA, the gene expression level of IL-6 gene did not change during 3-day-culture in the range of TAD concentration of 0.05 mmol to 0.2 mmol. However, 0.3 mM TAD suppressed the gene expression at all concentration of HSA. In 42% HSA, although 0.05 mM and 0.1 mM TAD did not affect the gene expression, 0.2 mM and 0.3 mM TAD induced the expression level with incubation time. In 44% HSA, all the concentration of TAD increased the expression level even though the cytokine expression levels were quite low. Hence it could be thought that the expression at the cytokine level is quite insignificant where as it is to be considered at the gene expression level. On the whole, 0.3 mM TAD with 44% HSA could be considered as a challenging material as a tissue adhesive material for use in the field of tissue engineering.

Mechanistic Analysis for Drug Permeation Through Intestinal Membrane

For drug absorption, intestinal drug permeability's through both the paracellular and transcellular routes were analyzed. Absorption enhancers, such as sodium caprate (C10), decanoylcarnitine (DC) and tartaric acid (TA), increased the paracellular permeability of water-soluble, low lipophilic and poorly absorbable drugs by enlargement of tight junction (TJ) adhering to the intercellular portion; that is, expansion of the paracellular routes. C10 increased the intracellular calcium level to induce contraction of calmodulin-dependent actin filaments. Although DC also increased the intracellular calcium level, the action was independent of calmodulin, and thus the action mechanism of DC was considered to differ from that of C10. DC and TA decreased the intracellular ATP level and the intracellular pH, suggesting that intracellular acidosis increases the calcium level through decrease in ATP level followed by opening TJ. TA had no effect on Western blot analysis, but TA significantly inhibited excretion of rhodamine 123, one of the P-glycoprotein (P-gp) substrates, from the serosal to mucosal side, suggesting that TA increases the intestinal absorption of P-gp substrates, possibly by inhibiting the P-gp function without changing the expression of P-gp. During ischemia/reperfusion (I/R) injury during small intestine grafting, TJ opening and decrease in P-gp function simultaneously occurred. The in vitro model of I/R showed that lipid peroxidation is a trigger of the injury, and superoxide and iron ion participate in TJ opening and decrease in P-gp function. Colonic epithelial cells have the specific transcellular transport systems for lipopolysaccharide (LPS), one of which shows substrate specificity in the interaction with CD14 and/or that of TLR4. In the infective disease induced by LPS, the mucosal LPS sensitive transport capability was decreased and in the secretory direction, the receptor-mediated uptake mechanism disappeared. LPS taken up into the cells can be excreted by P-gp or mrp. The expression levels and function of the secretory transporters were considered to be increased in the infective condition. In conclusion, changes in TJ as the membrane structure and P-gp as the membrane function are important factors controlling intestinal membrane transport.

Enhancement effect study of some organic acids on the calcium availability of vegetables: application of the dynamic in vitro simulated gastrointestinal digestion method with continuous-flow dialysis

The effect of added organic acids on the calcium availability of vegetables was investigated using the dialysis profiles obtained from an in vitro simulated gastrointestinal digestion with continuous-flow dialysis method. Citric acid was the most effective enhancer followed by tartaric, malic, and ascorbic acids. For amaranth, which has a low calcium availability (5.4%), a significant increase of availability was observed with increasing concentrations of all acids studied. With the continuous-flow dialysis approach, organic acids could be observed to promote the dialyzability even at an elevated intestinal pH. An enhancement effect from added organic acids was not clearly observed for Chinese kale, which itself contains a high amount of available calcium (52.9%).

L-Carnitine L-tartrate (LCLT) and dehydroepiandrosterone sulfate (DHEAS) affect red and white blood cells in aged Sprague-Dawley rats

Supplementation with either L-carnitine or DHEAS was separately suggested to counteract age-related declines. However, little is known about any interactive effects of these substances, independently promoting mitochondrial energy metabolism, in older individuals. We thus studied the effects of 3 months of daily oral combined supplementation with LCLT and DHEAS on red (RBCs) and white blood cells (WBCs) in male Sprague-Dawley rats by determining RBC and WBC counts, lymphocyte proliferation and interleukin-2 (IL-2) synthesis in spleen lymphocytes after Concanavalin A (ConA) stimulation. Supplementation with LCLT in addition to DHEAS decreased RBCs and increased platelets in the blood of 25-month-old Sprague-Dawley rats, whereas supplementation with DHEAS alone shifted the balance from segmented neutrophile granulocytes to large lymphocytes in differential WBC counts. Based on these results, interactive effects of supplementation with L-carnitine and DHEAS on RBCs and platelets are suggested.

Functional identification of ygiP as a positive regulator of the ttdA-ttdB-ygjE operon

Functional characterization of unknown genes is currently a major task in biology. The search for gene function involves a combination of various in silico, in vitro and in vivo approaches. Available knowledge from the study of more than 21 LysR-type regulators in Escherichia coli has facilitated the classification of new members of the family. From sequence similarities and its location on the E. coli chromosome, it is suggested that ygiP encodes a lysR regulator controlling the expression of a neighbouring operon; this operon encodes the two subunits of tartrate dehydratase (TtdA, TtdB) and YgiE, an integral inner-membrane protein possibly involved in tartrate uptake. Expression of tartrate dehydratase, which converts tartrate to oxaloacetate, is required for anaerobic growth on glycerol as carbon source in the presence of tartrate. Here, it has been demonstrated that disruption of ygiP, ttdA or ygjE abolishes tartrate-dependent anaerobic growth on glycerol. It has also been shown that tartrate-dependent induction of the ttdA-ttdB-ygjE operon requires a functional YgiP.

Enhancement of intestinal absorption of poorly absorbed hydrophilic compounds by simultaneous use of mucolytic agent and non-ionic surfactant

The effect of co-administration of a mucolytic agent with a penetration enhancer was assessed on the intestinal absorption of poorly absorbed hydrophilic compounds. Fluorescein isothiocyanate-labeled dextran with average molecular weight of ca. 4.4 kDa (FD-4) was used as a model compound, and N-acetylcysteine (NAC) was used as a mucolytic agent. Sodium caprate (C10), tartaric acid (TA), sodium taurodeoxycholate (TDC), sodium dodecyl sulfate (SDS), p-t-octyl phenol polyoxyethylene-9.5 (Triton X-100, TX-100) were selected as penetration enhancers with different mechanisms of action. Various dosing solutions containing a penetration enhancer in the absence or in the presence of NAC were directly administered into the exposed rat jejunum, and the bioavailability of FD-4 up to 2 h was determined. The extent of improvement by co-administration was highly dependent on the penetration enhancer species applied. The observed enhancement was thought to result from the mucolytic activity of NAC, which can reduce the mucus viscosity and facilitate the penetration of FD-4 to mucosal membrane. Among the combinations tested, the simultaneous administration of NAC and TX-100 provided the highest enhancement (22.5-fold) of intestinal FD-4 absorption compared to the control. Although the detailed mechanism for the observed drastic improvement is unclear, one possible reason was thought to be due to the improved diffusivity of TX-100 micellar system in the mucus layer. All these results suggest that the combination of a mucolytic agent and a non-ionic surfactant may have potential as an enhancing system for peroral delivery of poorly absorbed hydrophilic compounds like protein and peptide drugs.

Improvement of Intestinal Absorption of P­glycoprotein Substrate by D­tartaric Acid

The purpose of the present experiment was to examine the effects of D-tartaric acid (TA) on intestinal drug absorption under both in situ and in vitro experimental conditions. In the in vitro diffusion chamber experiments, TA (10 mM) added to the mucosal side of rat colon significantly decreased rhodamine123 (Rho 123) transport from the serosal to mucosal side. Since TA has been shown to change the integrity of the epithelial tight junctions in rat colon at low pH conditions, resulting in improved paracellular drug transport, the effect of TA on membrane resistance was examined at pH 7.4 in the present study. It was found that membrane resistance, an indicator of paracellular integrity, did not change at pH 7.4. In the in situ loop method, TA (20 mM) increased the absorption of Rho123 in both ileum and colon but not in jejunum. TA (20 mM) also increased the absorption of daunorubicin in the ileum, but TA (20 mM) did not change the expression level of P-glycoprotein (P-gp). TA (20 mM) significantly inhibited excretion of i.v.-administered Rho123 and daunorubicin into the ileal lumen. In conclusion, for the first time we demonstrated that TA increases the intestinal absorption of P-gp substrates Rho123 and daunorubicin, possibly by modulating the P-gp function without changing the expression level of P-gp in the rat intestine.

Phytoestrogenic effects of black tea extract (Camellia sinensis) in an oophorectomized rat (Rattus norvegicus) model of osteoporosis

The adverse side effects of currently available anti-osteoporotic agents warrant the search for compounds with less toxic effects. In this study, we assessed the phytoestrogenic potentiality of whole aqueous extract of black tea (BTE) in a bilaterally oophorectomized rat model (2.5%, 1 ml/100 g body weight/day for 28 days). Although the supplementation was given for 28 days but, sign of revival of copulation period (estrous stage) from non-receptive diestrous stage was first noticed after 21 days of BTE supplementation in bilaterally oophorectomized rats. This was accompanied by a significant increase in serum estradiol level. To test whether this increase in serum estradiol level could have an influence upon the oophorectomy-induced damage of bone, we assessed marker parameters of bone resorption and osteoclastic activity (tartrate-resistant acid phosphatase), collagen degradation (urinary hydroxyproline), bone loss (bone ash mineral content) and bone breaking strength (bone density). Results indicated that increase in serum estradiol level after BTE supplementation could significantly diminish oophorectomy-induced decaying changes in bone. This study proposes that aqueous BTE may be assessed as a phytoestrogenic compound for prevention against estrogen deficiency-related osteoporotic damages.

Preparation and Characterization of Chitosan-Based Nanoparticles

The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan for biomedical applications. Natural di- and tricarboxylic acids were used for intramolecular cross-linking of the chitosan linear chains. The condensation reaction of carboxylic groups and pendant amino groups of chitosan was performed by using water-soluble carbodiimide. This method allows the formation of polycations, polyanions, and polyampholyte nanoparticles. The prepared nanosystems were stable in aqueous media at low pH, neutral, and mild alkaline conditions. The structure of products was determined by NMR spectroscopy, and the particle size was identified by laser light scattering (DLS) and transmission electron microscopy (TEM) measurements. It was found that particle size depends on the pH, but at a given pH, it was independent of the ratio of cross-linking and the cross-linking agent. Particle size measured by TEM varied in the range 60-280 nm. In the swollen state, the average size of the particles measured by DLS was in the range 270-370 nm depending on the pH. The biodegradable cross-linked chitosan nanoparticles, as solutions or dispersions in aqueous media, might be useful for various biomedical applications.

Differential effects of ammonia on the benzodiazepine modulatory site on the GABA-A receptor complex of human brain

Ammonia is a key factor in the pathogenesis of encephalopathies associated with liver failure. A direct effect of ammonia on GABAergic neurotransmission was proposed as a mechanism that may explain its neurotoxic effect on the basis of electrophysiological and biochemical studies performed in animal models of liver failure. In the present study, we investigated using a radiometric assay the effect of ammonia on the binding of GABA-A receptor ligands to membranes from normal human brains. Ammonium tartrate significantly decreased the maximal binding of [3H]flunitrazepam to well-washed frontal cortical membranes (366+/-63 fmol/mg protein in absence of ammonia versus 294.1+/-51 fmol/mg protein in presence of 2 mM ammonia; p<0.05). The efficacy of the effects of ammonia was within the millimolar range (IC50=4.8 mM). This effect was not seen in cerebellum or hippocampus. Ammonia exposure decreased the maximal binding of [3H]flumazenil (284.9+/-24.2 fmol/mg protein in absence of ammonia versus 146.4+/-15.6 fmol/mg protein in presence of 2 mM ammonia; p<0.01). This effect was seen with a greater potency (Imax=32.4%) and a lower IC50 (0.1 mM). Inhibition of [3H]flumazenil binding was significant in all brain regions. The apparent ammonia-induced decrease of [3H]flunitrazepam and [3H]flumazenil binding was due to a decrease in the binding affinities of these ligands for the benzodiazepine site. In contrast, ammonium tartrate exposure did not cause significant changes to the binding of [3H]muscimol in any brain region. These findings demonstrate that ammonia interacts negatively with components of the benzodiazepine-associated site at the GABA-A receptor complex in human brain in contrast to previous reports in the rat, and thus, does not support the notion that ammonia directly activates the GABA-A receptor complex resulting in increased GABAergic neurotransmission in human hepatic encephalopathy. These findings also suggest that positron emission tomography studies in cirrhotic patients using [11C]flumazenil may be underestimating GABA-A receptor sites depending upon the degree of hyperammonemia of the patient.

Erosive effects of different acids on bovine enamel: release of calcium and phosphate in vitro

The present study intended to investigate minimal erosive effects of different acids on enamel during short time incubation via determination of calcium and phosphate dissolution. Bovine enamel specimens were eroded for 1-5 min with eight different acids of pH 2, 2.3 and 3 (citric (CA), maleic (MA), lactic (LA), tartaric (TA), phosphoric (PA), oxalic (OA), acetic (AA) and hydrochloric acid (HCl)). Calcium (Ca) and phosphate (P) release were determined photometrically using arsenazo III (calcium) and malachite green (phosphate) as substrates. Each subgroup contained eight enamel specimens. Amount of titratable acid was determined for all acidic solutions. MA, LA, TA, AA and HCl caused linear release of Ca and P, PA of Ca, CA of P. For CA, MA, LA, TA, AA, PA and HCl mineral loss was shown to be pH-dependent. Ca dissolution varied between 28.6+/-4.4 (LA, pH 2) and 2.4+/-0.7 nmol mm(-2)min(-1) (HCl, pH 3), P dissolution ranged between 17.2+/-2.6 (LA, pH 2) and 1.4+/-0.4 nmol mm(-2)min(-1) (HCl, pH 3). LA was one of the most erosive acids. AA was very erosive at pH 3. HCl and MA were shown to have the lowest erosive effects. There was only a weak correlation (r=0.28) between P and Ca release and the amount of titratable acid. The method of the present study allows investigation of minimal erosive effects via direct determination of P and Ca dissolution. During short time exposition at constant pH level, erosive effects mainly depend on pH and type of acid but not on amount of titratable acid.

The Nature of the Stimulus and of the Fumarate Binding Site of the Fumarate Sensor DcuS of Escherichia coli

DcuS is a membrane-associated sensory histidine kinase of Escherichia coli specific for C(4) -dicarboxylates. The nature of the stimulus and its structural prerequisites were determined by measuring the induction of DcuS-dependent dcuB'-'lacZ gene expression. C(4)-dicarboxylates without or with substitutions at C2/C3 by hydrophilic (hydroxy, amino, or thiolate) groups stimulated gene expression in a similar way. When one carboxylate was replaced by sulfonate, methoxy, or nitro groups, only the latter (3-nitropropionate) was active. Thus, the ligand of DcuS has to carry two carboxylate or carboxylate/nitro groups 3.1-3.8 A apart from each other. The effector concentrations for half-maximal induction of dcuB'-'lacZ expression were 2-3 mm for the C(4)-dicarboxylates and 0.5 mm for 3-nitropropionate or d-tartrate. The periplasmic domain of DcuS contains a conserved cluster of positively charged or polar amino acid residues (Arg(107)-X(2)-His(110)-X(9)-Phe(120)-X(26)-Arg(147)-X-Phe(149)) that were essential for fumarate-dependent transcriptional regulation. The presence of fumarate or d-tartrate caused sharpening of peaks or chemical shift changes in HSQC NMR spectra of the isolated C(4)-dicarboylate binding domain. The amino acid residues responding to fumarate or d-tartrate were in the region comprising residues 89-150 and including the supposed binding site. DcuS(R147A) mutant with an inactivated binding site was isolated and reconstituted in liposomes. The protein showed the same (activation-independent) kinase activity as DcuS, but autophosphorylation of DcuS was no longer stimulated by C(4)-dicarboxylates. Therefore, the R147A mutation affected signal perception and transfer to the kinase but not the kinase activity per se.

Effects of 24,25(OH)2D3, 1,25(OH)2D3 and 25(OH)D3 on alkaline and tartrate-resistant acid phosphatase activities in fetal rat calvaria

The aim of this work was to evaluate the effects of 24,25-dihydroxyvitamin D3, 24,25(OH)2D3, on alkaline phosphatase (AP) and tartrate-resistant acid phosphatase (TRAP) activities in fetal rat calvaria cultures. These actions were compared with those of 1,25-dihydroxyvitamin D3, 1,25(OH)2D3, and 25-hydroxyvitamin D3, 25(OH)D3, in similar experimental conditions. At 10 min, 30 min and at 24 h incubation time, 1,25(OH)2D3 (10(-10)M) and 25(OH)D3 (10(-7) M) produced a significant increase in AP and TRAP activities compared to control group (without vitamin D metabolites). However, 24,25(OH)2D3 (10(-7) M) only produced effects on phosphatase activities similar to those produced by 1,25(OH)2D3 and 25(OH)D3, after 24 h incubation time. These findings suggest that 1,25(OH)2D3 and 25(OH)2D3 could carry out actions in minutes (nongenomic mechanism), while 24,25(OH)2D3 needs longer periods of time to perform its biological actions (genomic mechanism).

Purification and characterization of an acid phosphatase from the commercial mushroom Agaricus bisporus

Acid phosphatase [AP; EC 3.1.3.2], a key enzyme involved in the synthesis of mannitol in Agaricus bisporus, was purified to homogeneity and characterized. The native enzyme appeared to be a high molecular weight type glycoprotein. It has a molecular weight of 145 kDa and consists of four identical 39-kDa subunits. The isoelectric point of the enzyme was found at 4.7. Maximum activity occurred at 65 degrees C. The optimum pH range was between 3.5 and 5.5, with maximum activity at pH 4.75. The enzyme was unaffected by EDTA, and inhibited by tartrate and inorganic phosphate. The enzyme exhibits a Km for p-nitrophenylphosphate and fructose-6-phosphate of 370 microM and 3.1 mM, respectively. A broad substrate specificity was observed with significant activities for fructose-6-phosphate, glucose-6-phosphate, mannitol-1-phosphate, AMP and beta-glycerol phosphate. Only phosphomonoesters were dephosphorylated. Antibodies raised against the purified enzyme could precipitate AP activity from a cell-free extract in an anticatalytic immunoprecipitation test.

Anomaly and correlation of killing in the therapeutic properties of silver (I) chelation with glutamic and tartaric acids

OBJECTIVES

To investigate whether silver chelates or silver ions are more effective as therapeutic agents, and to examine their mode of action so that safer and stable compounds that have a broad spectrum of therapeutic activities can be developed.

METHODS

Efficacy was investigated against Pseudomonas aeruginosa (ATCC 15442) by determining MIC via a broth macrodilution procedure using NCCLS methods for antibiotic susceptibility testing.

RESULTS

It was found that the responsible agent for silver therapeutic properties is the silver chelates rather than silver ions, contradicting previous findings, and the efficacy profiles mimic that of free silver ions present in solution.

CONCLUSIONS

Silver therapeutic activities seem to be more effective as complexes-an intracellular package-rather than free silver ions, demonstrating that the effect of silver is linked to cells' DNA unwinding, and not respiratory or membrane functionality as was traditionally recognized.