Cílem práce bylo zhodnocení účinku samotného mléka a fluoridovaného mléka s obsahem 2,5 a 5,0 ppm fluoru na progresi a remineralizaci kariézních lézí na povrchu zubního kořene při cyklických změnách pH prostředí. Kariézní leze na kořeni zubu byly vytvořeny za použití kyseliny mléčné při pH 4,6. Takto vytvořené leze byly podílně nařezány a analyzovány pomocí mikroskopie v polarizovaném světle (PLM) a mikroradiografie (MRG). Jednotlivé vzorky byly potom pokryty acidorezistentním lakem kromě vytvořené kazivé leze. Kariézní leze byly následně vystaveny působení vody, mléka nebo fluoridovaného mléka v průběhu cyklických změn pH prostředí -demineralizace a remineralizace po dobu 2 týdnů. Po skončení experimentu byly leze opět hodnoceny pomocí PLM a MRG. Obě metody prokázaly signifikantní redukci progrese kazivé leze (33,2%), a to jak v případě mléka samotného, tak mléka fluoridovaného ve srovnání s kontrolou (voda). Kvantitativní mikroradiografie (MRG) sledovala změny minerálního obsahu a distribuce minerálů uvnitř leze. Výsledky potvrdily předpokládaný protektivní efekt fluoridavaného mléka na kaz zubního kořene, neboť došlo jak k redukci progrese leze tak ke zvýšení obsahu minerálů uvnitř leze.
The aim of this study was to assess the effect of milk with 0, 2.5 or 5 ppm F- on progression and remineralization of caries-like root-surface lesions using a pH cycling model. The root-surface lesions were crea-ted utilizing a partially saturated lactic acid buffer at pH 4.6. Longitudinal sections were cut through the lesion and analyzed using polarized light microscopy (PLM) and microradiography (MRG). The sections were then coa-ted with an acid resistant varnish, except the outer natural surface that would be exposed to water, milk or fluoridated milk for 2 weeks and cycled in a de- and remineralizing systém. The lesions were characterized again by PLM and MRG after treatment. A significant reduction in lesion progression (33.2%) was found by PLM and MRG after treatment with either non-fluoridated or fluoridated milk when compared to the control group. Using quan-titative MRG, minerál change and distribution in the lesions were recorded. A possible protective effect of fluoridated milk on root surface caries was supported by a reduction in the progression of the lesions and an increase in the minerál content within the lesion.
Some time ago, we published an announcement that the azo group that closes model cyclic peptides is often reduced in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) in the presence of 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix. In this work, we demonstrate that these peptides are ionized in all DHB matrix isomers, although threshold ionization laser energies as well as the reduction ratios differ in each matrix. Using a NALDI plate, we confirmed that their reduction depends on the presence of DHB matrix and that the hydrogen atoms participating in the reaction come from the DHB matrix hydroxyl group. We show that the reduction ratio is affected by the overall covalent structure of the peptide, by the presence of a free carboxyl group in DHB matrix, by the mutual position of the hydroxyl and carboxyl groups, as well as the laser beam intensity. Based on these results, it can be concluded that the azo-group reduction in cyclic peptides is a very complex process and we are far from fully understanding its nature. We hope that our experimental results will help to shed some light on the MALDI process that still remains mysterious in some of its aspects.
- MeSH
- Azo Compounds chemistry metabolism MeSH
- Peptides, Cyclic chemistry metabolism MeSH
- Gentisates chemistry MeSH
- Hydroxyl Radical chemistry MeSH
- Isomerism MeSH
- Oxidation-Reduction MeSH
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization methods MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
There is virtually no information on spontaneous variability of ECG body surface potential maps (BSPMs) and on dynamics of their reactive changes in healthy subjects. This study evaluated quantitatively the depolarization (QRS) and repolarization (QRST) parameters derived from the respective integral BSPMs, constructed beat-to-beat, from continual body surface ECG records in 9 healthy men resting supine, during head-up tilting and sitting. Spontaneous variability of the BSPMs parameters, both at rest and during postural reactions, was characterized by significant respiratory and low frequency oscillations, more pronounced when related to repolarization. Head-up tilting and sitting-up evoked significant decrease in the QRST-BSPM amplitudes, widening of the angle ? and reduction of nondipolarity indexes, compared to the respective supine values. All these changes were gradual, characterized by transition phenomena and prolonged after-effects. Tilting back to horizontal restored the resting supine values. The postural effects on depolarization were individually more variable and in the average showed a minimal QRS-BSPM amplitude increase. Beat-to-beat analysis of a train of ECG BSPMs provided the first evidence of spontaneous, non-random, respiratory and low frequency oscillations of the ventricular repolarization pattern, and the first insight into the dynamics of body posture associated changes in ventricular recovery.
In the present study the treatment by three chemical solutions (5%) of travertine is considered. The overall process assumes the structural pore reduction due to the continuous controlled crystallization of low soluble inorganic salts such as calcium sulfate and calcium oxalate. Travertine samples of monolithic blocks of Turkish origin previously cut in form of parallelepiped blocs with length of 25 ± 1mm, width and thickness of 7 mm are employed in this study. The prepared samples were dipped in distilled water for 2-3 hours followed by drying up to 6 hours at 70 °C, 6 hours at 100 °C and 12 hours to 125 °C. Consolidation of travertine samples is carried out by treatment in three stages: the first stage involves treatment with calcium acetate (Ca(CH3COO)2• H2O), the second stage involves the treatment with ammonium sulphate (NH4)2SO4 followed by the third stage includes the treatment with ammonium oxalate (NH4)2C2O4•H2O. The decreasing of porosity and surface area is monitored by continuous gravimetric measurements followed by gas- and mercury porosimetry measurements. After each treatment, the sample weight increases and its porosity decreases. All samples were subject of: 10, 20, 30, 40, 50 treatments respectively.
The impact of four pre-treatment techniques on the surface morphology and chemistry, residual stress, mechanical properties, corrosion resistance in a physiological saline solution and cell colonization of commercially pure titanium is examined in detail. Mechanical polishing, electrochemical etching, chemical etching in Kroll's reagent, and ion sputter etching with argon ions were applied. Surface morphologies reflect the nature of surface layer removal. Significant roughening of the surface and a characteristic microtopology become apparent as a result of the sensitivity of chemical and ion sputter etching to the grain orientation. The hardness in the near surface region was controlled by the amount of residual stress. Etching of the stressed surface layer led to a reduction in residual stress and surface hardness. A compact passivation layer composed of TiO, TiO2 and Ti2O3 native oxides imparted high corrosion resistance to the surface after mechanical polishing, chemical and electrochemical etching. The ion sputter etched surface showed substantially reduced corrosion resistance, where the corrosion process was controlled by electron transfer. The specific topology affected the adhesion of the cell to the surface rather than the cell area coverage. The cell area coverage increased with the corrosion stability of the surface.
Iron uptake by diatoms is a biochemical process with global biogeochemical implications. In large regions of the surface ocean diatoms are both responsible for the majority of primary production and frequently experiencing iron limitation of growth. The strategies used by these phytoplankton to extract iron from seawater constrain carbon flux into higher trophic levels and sequestration into sediments. In this study we use reverse genetic techniques to target putative iron-acquisition genes in the model pennate diatom Phaeodactylum tricornutum We describe components of a reduction-dependent siderophore acquisition pathway that relies on a bacterial-derived receptor protein and provides a viable alternative to inorganic iron uptake under certain conditions. This form of iron uptake entails a close association between diatoms and siderophore-producing organisms during low-iron conditions. Homologs of these proteins are found distributed across diatom lineages, suggesting the significance of siderophore utilization by diatoms in the marine environment. Evaluation of specific proteins enables us to confirm independent iron-acquisition pathways in diatoms and characterize their preferred substrates. These findings refine our mechanistic understanding of the multiple iron-uptake systems used by diatoms and help us better predict the influence of iron speciation on taxa-specific iron bioavailability.
- MeSH
- Biological Availability MeSH
- Biological Transport MeSH
- CRISPR-Cas Systems MeSH
- Species Specificity MeSH
- FMN Reductase genetics metabolism MeSH
- Phylogeny MeSH
- Gallium metabolism MeSH
- Gene Knockout Techniques MeSH
- Climate Change MeSH
- Membrane Transport Proteins genetics metabolism MeSH
- Microbiota MeSH
- Seawater chemistry MeSH
- Oxidation-Reduction MeSH
- Bacterial Outer Membrane Proteins metabolism MeSH
- Receptors, Cell Surface metabolism MeSH
- Recombinant Fusion Proteins metabolism MeSH
- Diatoms genetics growth & development metabolism MeSH
- Siderophores metabolism MeSH
- Iron metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
