to evaluate the effect of Taqi genotypes of vitamin D receptor (VDR) gene polymorphism on bone mineral density (BMD) and the risk for secondary osteoporosis (OP) in patients on programmed ...hemodialysis.
Eighty-two patients treated with long-term hemodialysis were examined. Along with physical examination, osteodensitometry was carried out and VDR gene polymorphism was studied in all the patients.
OP in the study skeletal parts was more common in the TT-genotype group. The serum concentration of intact parathyroid hormone and the activity of alkaline phosphatase were also higher in the TT-genotype group. However, the diferences were statistically insignificant between the TT-, Tt-, and tt- genotype groups. BMD was lowest in each study skeletal parts in the TT-genotype group and this difference was statistically significant in the proximal femur, which was estimated by the Z index (p = 0.02).
The results of the present study confirm the hypothesis that the VRD gene is a genetic determinant of bone metabolism in patients with chronic renal disease who receive long-term hemodialysis.
The solubilization of integral membrane proteins with detergents produces protein–detergent complexes (PDCs). Interactions between the detergent moieties of PDCs contribute significantly to their ...behavior. The effects of the precipitating agent polyethylene glycol (PEG) upon these detergent–detergent interactions have been examined, focusing on the detergent system used to crystallize the bacterial outer membrane protein OmpF porin. Static and dynamic light scattering were used to assess the effects of temperature and concentration upon the hydrodynamic size distribution and the aggregation state of detergent micelles and a phase diagram for micellar solutions was mapped. Estimates of the second osmotic virial coefficient obtained from static light‐scattering measurements on micelles were shown to accurately reflect the thermodynamic quality of the solvent. Solvent quality decreases as the consolute boundary is approached, suggesting micelle–micelle attractive forces help to organize PDCs into crystalline aggregates near the cloud point. An apparent increase in micelle mass is observed as the solution approaches the cloud point. These results raise the possibility that the detergent‐mediated aggregation of PDCs and/or slight changes in micelle geometry may prove to be important in the nucleation of membrane protein crystals.
Complex formation between a natural polysaccharide – gellan and an antimicrobial drug – ofloxacin was studied in aqueous solution. Conductimetric and potentiometric titration curves revealed that ...gellan and ofloxacin forms a water-soluble complex of composition 2:1 mol/mol stabilized by ionic and hydrogen bonds. The formation of the gellan-ofloxacin complex was confirmed by FTIR spectroscopy, dynamic light scattering, zeta-potential and thermogravimetric analysis. The average hydrodynamic size of the complex was found 307±5 nm and its zeta-potential was negative and equal to -15 mV. Thin films of the gellan-ofloxacin complex, gelled in 0.3 wt.% of CaCl2, were used to study the release kinetics of ofloxacin in distilled water and phosphate buffer. The drug release kinetics evaluated by UV-Vis spectroscopy at λmax = 289 nm and calculated by the Ritger-Peppas model correspond to non-Fickian diffusion in distilled water and Case II transport (zero-order kinetics) in phosphate buffer. The cumulative release of ofloxacin from the gellan-ofloxacin films was equal to 96±2% and 36±2% in phosphate buffer and distilled water, respectively. It is expected that the gellan-ofloxacin complex is able to form in situ gel on the surface of the eye and to prolong the drug residence time in the tear fluid.
Objective: to substantiate a procedure for predicting the severity of postperfusion acute heart failure (AHF) from the baseline level of NT-proBNP during myocardial revascularization in patients with ...a left ventricular ejection fraction (LVEF) of less than 35%. Subjects and materials. Fifty-six patients with a LVEF of less than 35% were examined. A total of 3.5±0.1 (range 2—4) coronary arteries were shunted under cardio-pulmonary bypass (CPB) (71.0±5.5 min). The concentration of NT-proBNP was measured before surgery (Cardiac Reader®, Roche). Mortality rates, sympathomimetic agents’ dosages required after EC, and the frequency of use of intraaortic balloon pumping (IABP) were analyzed. Results. A good clinical course was observed in 47 cases (Group 1). AHF was recorded in 9 patients (Group 2). Comparative analysis demonstrated that the preoperative concentration of NT-proBNP (871±111 pg/ml in Group 1 and 1946±236 pg/ml in Group 2) was of the highest prognostic value as compared with the traditional indicators (p=0.0015). Patients with a NT-proBNP concentration of less than 600 pg/ml did not virtually need inotropic therapy after EC. In a group with a biomarker level of 600—1200 mg/ml, the infusion of dopamine and dobutamine achieved the traditional cardiotonic dosages and every three patients needed epinephrine. With NT-proBNP of 1200-2000 pg/ml, mortality from AHF was 15.4%; a need for epinephrine and IABC was 46.4 and 7.7%, respectively. The peptide concentration of more than 2000 pg/ml indicated the extremely high risk of severe AHF. In the postperfusion period, each patient was given epinephrine and an IABC system was installed in half of them. In this group mortality achieved 50%. Conclusion. It is expedient to determine a preoperative NT-proBNP concentration in a LVEF of less than 35% to predict AHF to be occurred after myocardial revascularization. The concentration of less than 1200 pg/ml may be considered to be a safe level of the peptide. Its content increase more than 2000 pg/ml suggests that there is an extremely high risk of severe AHF. The level of this biomarker may be a guide to choose an anesthetic tactic. Key words: NT-proBNP, cardiosurgery, heart failure.
The colloidal stability and characteristics of particles formed by homopolymers of poly(
N-vinyl caprolactam), poly(
N-isopropyl acrylamide) and poly(vinyl methyl ether) in dilute aqueous solutions ...above the lower critical solution temperature, LCST, was followed by means of dynamic and static light scattering. Depending on the solution concentration, the homopolymers precipitate or form stable dispersions of monodisperse spherical particles. To obtain colloidally stable aggregates, also called mesoglobules, no stabilising agent was added. The stability of the mesoglobules upon time and dilution at temperatures above the LCST suggests that the particle surfaces possess a hydrophilic character. The size of the formed particles depends on the concentration and the heating rate of the solutions. However, internal structure and shape of mesoglobules are affected neither by the way, how the mesoglobules were prepared, nor by molar mass of individual macromolecules. Mesoglobules of PNIPAM obey the
M∝
R
2.7 scaling law. Origin of stability of the dispersions vs. expected precipitation is discussed.
The three human β-defensins, HBD1–3, are 33–47-residue, cationic antimicrobial proteins expressed by epithelial cells. All three proteins have broad spectrum antimicrobial activity, with HBD3 ...consistently being the most potent. Additionally, HBD3 has significant bactericidal activity against Gram-positive Staphylococcus aureus at physiological salt concentrations. We have compared the multimeric state of the three β-defensins using NMR diffusion spectroscopy, dynamic and static light scattering, and analysis of the migration of the three β-defensins on a native gel. All three techniques are in agreement, suggesting that HBD-3 is a dimer, while HBD-1 and HBD-2 are monomeric. Subsequently, the NMR solution structures of HBD1 and HBD3 were determined using standard homonuclear techniques and compared with the previously determined solution structure of HBD2. Both HBD1 and HBD3 form well defined structures with backbone root mean square deviations of 0.451 and 0.616 Å, respectively. The tertiary structures of all three β-defensins are similar, with a short helical segment preceding a three-stranded antiparallel β-sheet. The surface charge density of each of the defensins is markedly different, with the surface of HBD3 significantly more basic. Analysis of the NMR data and structures led us to suggest that HBD3 forms a symmetrical dimer through strand β2 of the β-sheet. The increased anti-Staphylococcalactivity of HBD3 may be explained by the capacity of the protein to form dimers in solution at low concentrations, an amphipathic dimer structure, and the increased positive surface charge compared with HBD1 and HBD2.
A superhigh-molar-mass polyelectrolyte, poly(methacryloylethyl trimethylammonium methyl sulfate) (PMETMMS), with molar mass 26 × 106 has been studied by viscosity and light scattering in saltless ...water−acetone mixtures of various compositions. PMETMMS is known to collapse on addition of acetone into an aqueous solution. It has been shown that the collapse of the polyelectrolyte chains may be induced also by dilution of the polymer solutions, leaving the solvent composition constant. The scattered light intensity measured as a function of polymer concentration shows a maximum at a certain concentration. The position of the maximum is dependent on the solvent composition. A compact structure with the radius of gyration R g ≈ 50 nm and the hydrodynamic radius R h ≈ 30−40 nm is formed in a very dilute solution where the value of the second virial coefficient A 2 is close to zero. The values of M w measured by static light scattering in solutions with various solvent compositions were constant. Correlation functions measured using dynamic light scattering unambiguously show a decrease of the relaxation times as well as the narrowing of the size distribution of the polymer with dilution. This most probably is due to the change of the balance of inter- and intramolecular interactions upon dilution.
A polycation poly(methacryloylethyl trimethylammonium methylsulfate), PMETMMS, with molar mass M w = 26 × 106 has been studied by viscosity and light scattering in a mixture of water and acetone. ...Various amounts of a base (sodium hydroxide) or acids (hydrochloric, sulfuric, or phosphoric acid) have been added to the samples. PMETMMS shows typical polyelectrolyte behavior of the reduced viscosity in water−acetone mixtures with acetone mass fraction, γ, below 0.80. When γ ≥ 0.80, PMETMMS undergoes a reversible coil-to-globule transition. The collapse can also be induced by dilution of the polymer solution, keeping the solvent composition constant, γ = 0.70. Correlation functions measured using dynamic light scattering show a decrease of the relaxation time as well as the narrowing of the size distribution of the polymer with dilution. It has been shown that a compact structure instead of an extended coil is formed in a very dilute solution. Base or acid added into the solvent increases the value of the critical polymer concentration at which the collapse occurs. In a medium with low dielectric constant, base or acid molecules strongly interact with the charged groups of the polycation. Addition of NaOH into the solvent (less than 6 × 10-4 mol/L) decreases the degree of ionization of the polycation. However, the addition of acid (0.3 × 10-4 mol/L) introduces counterions that not only screen the positive charges of the polymer chain but also form inter- and intramolecular links. The latter effect becomes more profound with increasing the counterion valency. Upon dilution of the polymer solution, the number of the contacts between the polymer and added base/acid increases, but the number of inter- and intramolecular ion pairs of the polycation decreases. The balance of inter- and intramolecular interactions changes, and at high dilution, the intramolecular interactions dominate, owing to the poor quality of the solvent.
Silicifying organisms (diatom algae, sponges, etc.) build multifarious silica and composite nano-structures which attracts rapt attention of specialists in nanotechnology. These organisms can capture ...monomeric silicic acid from diluted solutions (<1
mM) and molecular mechanism of this process is still unknown. Some hypotheses include mediatorial role of zinc ions coordinated with a special protein transporter. We have studied several basic hydrogels and their complexes with double charged metal ions in sorption of silicic acid from non-saturated solutions. Cross-linked poly(vinylamine) coordinated with Zn
2+ was able to capture silicic acid from 0.1 to 1.7
mM solutions. The other ions (Cu
2+, Fe
2+, Ni
2+, Co
2+, Cd
2+ and Mn
2+) and less basic poly(1-vinylimiazole) were not active in the sorption. A mechanism included oligomerization of silicic acid and formation of triple complex poly(vinylamine)-Zn
2+-oligosiloxane was proposed. FTIR, NMR and EDS data confirm this conclusion. The found capture of silicic acid from diluted solutions with polyamine–zinc complex shows possibility in principle of the zinc-mediated transmembrane transport of Si(OH)
4 in silicifying organisms. On the other hand, the ability of zinc ions immobilized on the polyamine support to capture oligosilicates could be used in directed assembly of nanocomposite structures by the “bottom-up” approaches.
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