Oxygen metabolism,oxidative stress and acid-base physiology of dental plaque biofilms

Dental plaque is a natural biofilm which has been a focus of attention for many years because of its known roles in caries and periodontal diseases. Acid production by plaque bacteria leads to the erosion of tooth mineral in caries, and the cariogenicity of plaque is related to population levels of acid-tolerant organisms such as mutants streptococci. However, the biofilm character of plaque allows for survival of a diverse flora, including less acid-tolerant organisms, some of which can produce ammonia from arginine or urea to counter acidification. Plaque is often considered to be relatively anaerobic. However, evidence is presented here that both supragingival and subgingival plaque have active oxygen metabolism and that plaque bacteria, including anaerobes, have developed defenses against oxidative stress. Even in subgingival plaque associated with periodontitis, measured residual oxygen levels are sufficient to allow for oxygen metabolism by organisms considered to be extremely anaerobic such asTreponema denticola, which metabolizes oxygen by means of NADH oxidases and produces the protective enzymes superoxide dismutase and NADH peroxidase. The finding that plaque bacteria produce a variety of protective enzymes is a good indicator that oxidative stress is a part of their everyday life. The biofilm character of plaque allows for population diversity and coexistence of aerobes, anaerobes and microaerophiles. Overall, agents that affect oxidative metabolism offer possibilities for reducing the pathogenic activities of plaque.     

A Synthetic Peptide Based on a Natural Salivary Protein Reduces Demineralisation in Model Systems for Dental Caries and Erosion

The salivary protein statherin is an inhibitor of spontaneous and secondary precipitation of hydroxyapatite (HAp). It is also detected in enamel pellicle. The N-terminal region of statherin is involved in its adsorption onto tooth surfaces, and, calcium binding. A peptide (StN21) was designed with a 21 amino acid sequence identical to the N-terminus of statherin. The aim was to measure the effect of StN21 on the rate of mineral loss in a model system for dental caries and erosion using HAp subjected to artificial carious and erosive conditions. StN21 was synthesised using Fmoc chemistry. A surface of each HAp block was exposed to solution containing StN21 at concentrations 9.4–376 μmol L⁻¹ (in phosphate buffer) for 24 h. Controls were HAp exposed to buffer only, and HAp exposed to lysozyme. Demineralising solution (0.1 mol L⁻¹ acetic acid, pH 4.5, 1.0 mmol L⁻¹ calcium and 0.6 mmol L⁻¹ phosphate) was circulated past the HAp blocks at 0.4 mL min^-1 to mimic carious and erosive conditions. Scanning microradiography was used to measure the rate of mineral loss for demineralisation periods of 3 weeks. The rate of mineral loss of the samples exposed to StN21 was reduced by ∼40% compared to the controls, but no dependence on the concentration of StN21 was observed at the concentrations used. StN21 has been shown to be a potent and stable peptide that has potential as a preventive/therapeutic agent in the treatment of enamel erosion and dental caries.     

Recovery of Crystallographic Texture in Remineralized Dental Enamel

Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain structural integrity.     

Effect of ecdysterone on the metabolism of purine and pyrimidine nucleotides in chicken tissues]

Hormonal amounts (10(-7) M) of ecdysterone phytoecdysteroid have been studied for their effect on the metabolic processes in the chicken tissues. Changes in the blood serum parameters which characterize the state of the integral systems of mineral, lipid, protein and nucleotide metabolism as well as the dynamics of metabolism of nucleic acids and their precursors--purine and pyrimidine nucleotides in the tissues with actively functioning protein-synthesizing system prove that the biological effect of ecdysterone after its introduction to the bird organism manifests both in the non-genome early phase of the action (0-1 h) and in the late genome phase (24-72 h), i.e. in analogy to the time of response to the introduction of classical steroid hormones. It is supposed that polyfunctional early effect of ecdysterone is mediated by its action on one of universal transmembrane signal systems of the cells--adenylate cyclase or polyphosphoinosite one, while the presence of the expressed changes in metabolism of nucleic acids in the late phase unambiguously indicate to its action in the bird organism as that of a typical steroid hormone.     

Physiologic functions of vitamin D3 and its metabolism in the body in normal states and in some pathologies

In the review there are some results of investigations of the laboratory summarized on the mechanisms of vitamin D3 metabolism and its functioning in organism; investigation of infringement of mineral, lipid and protein metabolic processes with vitamin D3 deficiency and with different pathologies and the ways of their regulation as well as the data about some new high-effective forms of vitamin D3 for their implementation in medicine and agriculture.     

Conformational and constitutional analysis of dental caries following radiotherapy for head and neck cancer

BackgroundThis study aimed to investigate the morphology and chemical composition of dental caries related to ionizing radiation (DCIR), an aggressive and progressive disease that affects dental hard tissues.Materials and methodsEight human teeth with DCIR were paired with sixteen control teeth (8 teeth with conventional caries and 8 without caries) and included in this study. An analysis of the morphology of the lesions was performed using the following techniques: periapical radiography, cone beam computed tomography, computed microtomography, and scanning electron microscopy. The chemical composition was assessed using X-ray dispersive spectroscopy.ResultsThere was more demineralization in DCIR lesions when compared to conventional dental caries, even though there was no cavitation in the cervical region of the teeth. The superficial roughness and topography of DCIR lesions were similar to those of healthy teeth. On the other hand, lesions of conventional dental caries showed greater surface and topographic irregularity when compared to DCIR and healthy teeth (p = 0.001). Calcium (Ca) and phosphorus (P) levels were lower in DCIR lesions when compared to controls. However, higher levels of carbon (C) have been observed in DCIR lesions. There was a greater loss of the mineral matrix in DCIR followed by conventional caries. The reduction in the mineral matrix (Ca and P) was compatible with the imaging patterns observed in teeth with DCIR and conventional caries.ConclusionDespite their rapid evolution, DCIR presents an irregular, apparently intact surface with significant changes in the amount of Ca, P, and C.     

Effect of 6-mercaptopurine on mineral and metallothionein metabolism in the mouse

The effect of the anticancer drug 6-mercaptopurine (6-MP) on mineral metabolism was investigated in mice. C57Bl/6J female mice were injected intraperitoneally with 6-MP at 100 mg/kg body wt for one, two, four, or five consecutive days. On d 6 of the study, liver, kidney, and intestine were removed, and concentrations of zinc, copper, iron, manganese, magnesium, and calcium were measured. Hepatic concentrations of zinc, copper, iron, and calcium became higher as the number of drug injections increased. To determine if the altered mineral metabolism was a function of a drug-induced, acute-phase response, liver metallothionein and plasma ceruloplasmin were measured. Metallothionein concentrations in the liver became higher with increased number of injections, correlating with the stepwise increase in hepatic zinc. Gel filtration chromatography showed that most of the increase in liver zinc concentration was associated with a protein of mol wt of 6000–8000, the approximate weight of metallothionein. Ceruloplasmin concentrations were not affected by 6-MP injection. These results suggested that 6-MP alters zinc metabolism by sequestering zinc into the liver via induction of metallothionein synthesis and that the drug may induce an acute-phase response with an atypical acute-phase protein profile.     

Influence of vitamin E application period on the mineral and D-vitamin metabolism in the organism

It was shown, that influence of vitamin E on mineral and D-vitamin metabolism depends on its doses and application period: physiological doses of vitamin E activate and large doses - inhibit the effect of vitamin D3 in regulation of mineral metabolism in the organism. The duration of application of large doses of vitamin E (higher than 20 physiological doses) during which the negative changes are not determined has not to exceed 10 days.     

The impact on production and mechanisms of pathogenesis of trematode infections in cattle and sheep

Trematodes can have marked effects on several components of individual animal productivity—particularly growth and wool production, but there is a need for better definition of their effects upon overall flock and herd productivity and of the economic benefits to be derived from their control by chemical, immunological and/or genetic approaches. The reasons for reduced productivity are complex and include reduced appetite coupled with a protein/energy drain arising from increased protein turnover, and in some cases derangements in gastrointestinal function and mineral metabolism are to be anticipated. Knowledge of the effects of trematodes on animal productivity and metabolism lags far behind that of gastrointestinal nematodes and while there is certainly a need for more study of the effects of trematodes per se, there is perhaps an even more pressing need for experimental and field work on mixed infections.     

Vitamin D metabolism and expression in rats fed on low-calcium and low-phosphorus diets

1. Cholecalciferol, radioactively labelled with both (14)C and (3)H, was administered weekly for 7 weeks to rats that had been depleted of vitamin D for 4 weeks before repletion with the radioactive vitamin. This permitted measurement of the steady-state effect on vitamin D metabolism of low-calcium and low-phosphorus regimens, as compared with a normal mineral intake. These dietary manoeuvres were carried out during the last 3 weeks of repletion. Cholecalciferol, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol were determined in plasma, intestine, kidney and bone. Ca(2+)-binding-protein content was measured in intestine and kidneys of comparable animals. 2. In rats on the low-calcium diets, 1,25-dihydroxycholecalciferol concentration was elevated in plasma, bone, kidney and intestine, and intestinal Ca(2+)-binding protein was increased to over twice the concentration found in the control animals. 3. The low-phosphorus regimens led to a decrease in plasma phosphate and 1,25-dihydroxycholecalciferol in all tissues studied, for the latter to the point where it was undetectable in plasma and bone. Intestinal and renal concentrations of Ca(2+)-binding protein were unchanged in the low-phosphate-intake group and decreased in the very-low-phosphate-intake group. 4. It is concluded that in the rat, unlike in the chick, hypophosphataemia is not associated with a stimulation of the production of 1,25-dihydroxycholecalciferol or its expression in the synthesis of Ca(2+)-binding protein. Therefore the plasma phosphate concentration does not appear to be directly involved in the regulation of the functional metabolism of vitamin D.     

The effect of sodium humate on metabolism and resistance in highly productive poultry]

Natrium humate introduced into broiler chickens Broiler-6 line increases mass on 5-7% on the average and poultry safety on 3-5%. In chicken tissues the indexes of protein, mineral and lipid metabolism normalize, the organism's protection and adaptation opportunities improve as a result of peat preparation influence on fodder component mastering and regulatory processes.     

The impact of mycorrhizal colonization upon nitrogen source utilization and metabolism in seedlings of Eucalyptus grandis Hill ex Maiden and Eucalyptus maculata Hook

Analysis of soil solution from forest sites dominated by Eucalyptus grandis and Eucalyptus maculata indicates that soluble forms of organic nitrogen (amino acids and protein) are present in concentrations similar to those of mineral nitrogen (nitrate and ammonium). Experiments were conducted to determine the extent to which mycorrhizal associations might broaden nitrogen source utilization in Eucalyptus seedlings to include organic nitrogen. In isolation, species of ectomycorrhizal fungi from northern Australia show varying abilities to utilize mineral and organic forms of nitrogen as sole sources. Pisolithus sp. displayed strongest growth on NH₄⁺, glutamine and asparagine, but grew poorly on protein, while Amanita sp. grew well both on mineral sources and on a range of organic sources (e.g. arginine, asparagine, glutamine and protein). In sterile culture, non-mycorrhizal seedlings of Eucalyptus grandis and Eucalyptus maculata grew well on mineral sources of nitrogen, but showed no ability to grow on sources of organic nitrogen other than glutamine. In contrast, mycorrhizal seedlings grew well on a range of organic nitrogen sources. These observations indicate that mycorrhizal associations confer on species of Eucalyptus the ability to broaden their resource base substantially with respect to nitrogen. This ability to utilize organic nitrogen was not directly related to that of the fungal symbiont in isolation. Seedlings mycorrhizal with Pisolithus sp. were able to assimilate sources of nitrogen (in particular histidine and protein) on which the fungus in pure culture appeared to grow weakly. Experiments in which plants were fed ¹⁵N-labelled ammonium were undertaken in order to investigate the influence of mycorrhizal colonization on the pathway of nitrogen metabolism. In roots and shoots of all seedlings, ¹⁵N was incorporated into the amide group of glutamine, and label was also found in the amino groups of glutamine, glutamic acid, γ-aminobutyric acid and alanine. Mycorrhizal colonization appeared to have no effect on the assimilation pathway and metabolism of [¹⁵N]H₄⁺; labelling data were consistent with the operation of the glutamate synthase cycle in plants infected with either Pisolithus sp. (which in isolation assimilates via the glutamate synthase cycle) or Elaphomyces sp. (which assimilates via glutamate dehydrogenase). It is likely that the control of carbon supply to the mycorrhizal fungus from the host may have a profound effect on both the assimilatory pathway and the range of nitrogen sources that can be utilized by the association.     

拒避-诱杀组合技术对橘小实蝇产卵的影响

本文研究了以矿物油(mineral spray oil)乳剂为保护剂、"猎蝇"蛋白质毒饵为诱杀剂组成的拒避-诱杀组合技术对橘小实蝇Bactrocera dorsalis (Hendel)产卵的控制作用。结果显示:橘小实蝇在采用拒避-诱杀组合技术保护的供试香蕉上平均产卵孔数为0.000±0.000个,果实完好率达到100%,而单独使用"猎蝇"蛋白质毒饵的平均产卵孔数为27.000±1.732个,果实完好率仅为5.55%,表明该组合技术对橘小实蝇产卵的控制效果显著。在100倍～300倍浓度范围内,矿物油浓度越高,拒避-诱杀组合对橘小实蝇产卵的控制效果越好;随着虫口密度的增加,毒饵使用量和施用面积也须相应增加,才能取得更好的防治效果。     

A stepwise approach to the understanding of extracellular enzyme activity in soil. II. Competitive effects on the adsorption of a beta-D-glucosidase in mixed mineral or organo-mineral systems

A previous study has shown the effect of individual mineral surfaces on the activity of sweet almond beta-D-glucosidase. We now consider more complex situations likely to occur in soil, such as adsorption onto mixtures of different mineral surfaces, and the effect on enzyme activity of mineral surfaces with organic coatings. The effect of the order of addition of the minerals to enzyme suggests that the rate of adsorption is limited by the diffusion of the protein towards the interface and is not influenced by the magnitude of attractive forces between the protein and the surface. Adsorption is found to be quasi-irreversible. A study of the effect of artificial coatings of montmorillonite on enzyme activity led to the conclusion that an exchange of the enzyme with molecules of the coating occurs. This exchange is dependent upon the adsorption energy of the molecules of the coating and the electric charge of beta-D-glucosidase. This model is used for the interpretation of the effect of natural clay-humic complexes on enzyme activity.     

Effect of mutacin administration on Streptococcus mutans-induced dental caries in rats

A bacteriocin from serotype c Streptococcus mutans strain C3603 was examined for its inhibitory effect on experimental dental caries in rats infected with S. mutans MT8148R (serotype c). Significant reduction in the incidence of dental caries was found only when bacteriocin was incorporated both in the drinking water and in the diet at a high concentration. However, caries reduction was not as great as expected and the addition of bacteriocin to drinking water alone had no effect on the recovery of S. mutans, plaque deposition or caries incidence. The bacteriocin activity must have been reduced in the oral cavity of rats, and the reasons were examined. Bacteriocin-resistant mutants were not detected and the bacteriocin was not inactivated by saliva. Whereas the bacteriocin did not kill the S. mutans cells grown in a sucrose-containing medium, it completely killed the cells grown in a sucrose-free medium.     

Quantitative proteomics to study the response of potato to contrasting fertilisation regimes

There is concern over the sustainability and environmental impact of mineral fertilisers and crop protection inputs used in intensive arable crop production systems. However, replacing mineral with organic fertilisers (animal and green manures) and restricting the use of chemosynthetic crop protection may significantly reduce crop yields. The effects of (a) replacing mineral with composted cattle manure fertiliser input and (b) omitting pesticide-based crop protection on potato (Solanum tuberosum) tuber yield, leaf and tuber mineral nutrient content and leaf protein profiles were investigated. Switching to organic fertiliser had a greater effect on yield and protein profiles than the omission of chemosynthetic crop protection. Leaf N and P composition were significant drivers of protein expression, particularly proteins involved in photosynthesis such as the large subunit of RuBisCO, RuBisCO activase and the photosystem I reaction centre, which were at higher abundances in potato leaves grown under mineral fertiliser regimes. Proteins known to be induced in response to stress, such as dehydroascorbate reductase and Glutathione S-transferases, were also shown to be up-regulated under mineral fertilisation, possibly associated with higher Cd composition, whereas two proteins known to be involved in biotic stress (1,3-β-d-glucan glucanohydrolase; putative Kunitz-type tuber invertase inhibitor) were more abundant under compost fertilisation. Results showed that switching from mineral to organic fertilisers led to reduced N availability, a significant change in leaf protein expression and lower tuber yield. In contrast, omission of chemosynthetic crop protection inputs had limited effects on protein expression and no significant effect on tuber yield. This study provides information on the effects of changes in nutrient supply on protein expression patterns. It is a prerequisite for the development of functional molecular markers for a directed strategy to inform breeding programmes to improve potato nutrient use efficiency.     

Association between ENAM polymorphisms and dental caries in children

AimDental enamel, the most rigid biological tissue of the tooth known to mankind, is the most integral and fundamental part of the tooth. Enamel matrixes compile 5% of Enamelin peptides and at the time of tooth development, they are considered to effect the formation and elongation of enamel crystallites. ENAM plays critical role in enamel formation. Any changes in ENAM may affect the thickness of enamel and may lead to dental caries. The present study is aimed to evaluate the association of ENAM gene polymorphisms and susceptibility of dental caries development risk.Material and methodsThe present study was carried out on 168 South Indian children, children’s with dental caries were included in study. Written consent was taken from their parents/guardians. Additionally 193 healthy individuals were enrolled as controls. Sampling was done after dental examination of the individuals. Three ENAM gene single nucleotide polymorphisms (SNPs) were rs7671281, rs3796704 and rs12640848 was genotyped to check their role in susceptibility of dental caries development risk.ResultsOut of three SNPs rs7671281 showed statistically significant risk association with dental caries susceptibility in this ethnic population at heterozygous allele CT (OR: 1.939, p = .01865) and with minor allele T (OR: 1.451, p = .001292). SNP rs3796704 showed significant protective association with dental caries in Indian population at heterozygous allele GA (OR: 0.409, p = .0192) and with minor allele A (OR: 0.645, p = .00875). SNP rs12640848 showed significant protective association with dental caries in Indian population at heterozygous allele AG (OR: 3.041, p = .00642) and with minor allele G (OR: 1.478, p = .02184). Preliminary insilico analysis also showed that rs7671281 (Ile648Thr) amino acid change will cause the structural and functional changes in ENAM protein.ConclusionsIn the present study significant association was observed between ENAM gene SNP rs7671281 and dental caries susceptibility in South Indian children. These results suggested that ENAM gene variants may contribute to dental caries in children.     

An in vitro dynamic microcosm biofilm model for caries lesion development and antimicrobial dose-response studies

Some dynamic biofilm models for dental caries development are limited as they require multiple experiments and do not allow independent biofilm growth units, making them expensive and time-consuming. This study aimed to develop and test an in vitro dynamic microcosm biofilm model for caries lesion development and for dose-response to chlorhexidine. Microcosm biofilms were grown under two different protocols from saliva on bovine enamel discs for up to 21 days. The study outcomes were as follows: the percentage of enamel surface hardness change, integrated hardness loss, and the CFU counts from the biofilms formed. The measured outcomes, mineral loss and CFU counts showed dose-response effects as a result of the treatment with chlorhexidine. Overall, the findings suggest that biofilm growth for seven days with 0.06 ml min^?1 salivary flow under exposure to 5% sucrose (3 × daily, 0.25 ml min^?1, 6 min) was suitable as a pre-clinical model for enamel demineralization and antimicrobial studies.