Rearrangement of erythrocyte band 3 molecules and reversible formation of osmotic holes under hypotonic conditions

The complex phenomenon of rearrangement of band 3 molecules after erythrocyte swelling under hypotonic condition is considered. The rearrangement includes the increase of the mobile fraction and clustering of band 3. The self-associative tendency and the action of the elastic field generated within the lipid membrane after erythrocyte swelling result in equilibration of the number of molecules per cluster and the number of clusters. The local perturbation of the elastic field induces excitation of the cluster in the nearest neighbor and changes its packing state generating changes in the free volume within the cluster. The local perturbation could result in the reversible formation of osmotic hole. We formulated a model to predict changes of the cluster packing states generated by rearrangement of band 3 molecules on two time-scales. The phenomenon is examined on the basis of two experimental sets, i.e. low (5.2 mM Na₃PO₄ solution) and high (46.0 mM Na₃PO₄ solution) hypotonicities at 21°C, from Golan and Veatch (Proc Natl Acad Sci 77(5):2537–2541, 1980). Modeling considerations suggested that lower hypotonic conditions resulted in higher values of: the driving force of agglomeration of band 3 as a measure of self-associative tendency, the specific rate of cluster breaking, the specific rate of increase of the mobile fraction of band 3, and the dispersion of cluster sizes. Lower hypotonic conditions ensure the generation of a higher average value of the free energy within the membrane after erythrocyte swelling, which enables more intensive rearrangement of band 3 molecules.     

Algebraic connectivity may explain the evolution of gene regulatory networks

Gene expression is a result of the interplay between the structure, type, kinetics, and specificity of gene regulatory interactions, whose diversity gives rise to the variety of life forms. As the dynamic behavior of gene regulatory networks depends on their structure, here we attempt to determine structural reasons which, despite the similarities in global network properties, may explain the large differences in organismal complexity. We demonstrate that the algebraic connectivity, the smallest non-trivial eigenvalue of the Laplacian, of the directed gene regulatory networks decreases with the increase of organismal complexity, and may therefore explain the difference between the variety of analyzed regulatory networks. In addition, our results point out that, for the species considered in this study, evolution favours decreasing concentration of strategically positioned feed forward loops, so that the network as a whole can increase the specificity towards changing environments. Moreover, contrary to the existing results, we show that the average degree, the length of the longest cascade, and the average cascade length of gene regulatory networks cannot recover the evolutionary relationships between organisms. Whereas the dynamical properties of special subnetworks are relatively well understood, there is still limited knowledge about the evolutionary reasons for the already identified design principles pertaining to these special subnetworks, underlying the global quantitative features of gene regulatory networks of different organisms. The behavior of the algebraic connectivity, which we show valid on gene regulatory networks extracted from curated databases, can serve as an additional evolutionary principle of organism-specific regulatory networks.     

Implementation of contact definitions calculated by FEA to describe the healing process of basal implants

Aims: Bone structure around basal implants shows a dual healing mode: direct contact areas manifest primary osteonal remodeling, in the void osteotomy-induced spaces, the repair begins with woven bone formation. This woven bone is later converted into osteonal bone. The purpose of this study was to develop a model to accurately represent the interface between bone and basal implant throughout the healing process. The model was applied to the biological scenario of changing load distribution in a basal implant system over time. Methods: Computations were made through finite element analysis using multiple models with changing boneimplant contact definitions which reflected the dynamic nature of the interface throughout the bony healing process. Five stages of bony healing were calculated taking into account the changes in mineral content of bone in the vicinity of the load transmitting implant surfaces. Results: As the bony integration of basal implants proceeds during healing, peak stresses within the metal structure shift geographically. While bony repair may still weaken osteonal bone, woven bone has already matured. This leads to changes in the load distribution between and within the direct contact areas, and bone areas which make later contact with implant. Conclusions: This study shows that basal implants undergo an intrinsic shift of maximum stress regions during osseointegration. Fatigue testing methods in the case of basal implants must therefore take into account this gradual shift from early healing phase until full osseointegration is achieved.     

Weight loss of black, white, and Hispanic men and women in the Diabetes Prevention Program

Objective: To provide the specific weight loss outcomes for African‐American, Hispanic, and white men and women in the lifestyle and metformin treatment arms of the Diabetes Prevention Program (DPP) by race‐gender group to facilitate researchers translating similar interventions to minority populations, as well as provide realistic weight loss expectations for clinicians. Methods and Procedures: Secondary analyses of weight loss of 2,921 overweight participants (22% black; 17% Hispanic; 61% white; and 68% women) with impaired glucose tolerance randomized in the DPP to intensive lifestyle modification, metformin or placebo. Data over a 30‐month period are examined for comparability across treatment arms by race and gender. Results: Within lifestyle treatment, all race‐gender groups lost comparable amounts of weight with the exception of black women who exhibited significantly smaller weight losses (P < 0.01). For example, at 12 months, weight losses for white men (?8.4%), white women (?8.1%), Hispanic men (?7.8%), Hispanic women (?7.1%), and black men (?7.1%) were similar and significantly higher than black women (?4.5%). In contrast, within metformin treatment, all race‐gender groups including black women lost similar amounts of weight. Race‐gender specific mean weight loss data are provided by treatment arm for each follow‐up period. Discussion: Diminished weight losses were apparent among black women in comparison with other race‐gender groups in a lifestyle intervention but not metformin, underscoring the critical nature of examining sociocultural and environmental contributors to successful lifestyle intervention for black women.     

Kinetics of sunflower oil methanolysis at low temperatures

The kinetics of the sunflower oil methanolysis process was studied at lower temperatures (10-30 degrees C). The sigmoidal kinetics of the process was explained by the mass transfer controlled region in the initial heterogenous regime, followed by the chemical reaction controlled region in the pseudo-homogenous regime. A simple kinetic model, which did not require complex computation of the kinetic constants, was used for simulation of the TG conversion and the FAME formation in the latter regime: the fast irreversible second-order reaction was followed by the slow reversible second-order reaction close to the completion of the methanolysis reaction. The mass transfer was related to the drop size of the dispersed (methanol) phase, which reduced rapidly with the progress of the methanolysis reaction. This was attributed to the formation of the emulsifying agents stabilizing the emulsion of methanol drops into the oil.     

Biparental Inheritance of γ-Tubulin during Human Fertilization: Molecular Reconstitution of Functional Zygotic Centrosomes in Inseminated Human Oocytes and in Cell-free Extracts Nucleated by Human Sperm

Human sperm centrosome reconstitution and the parental contributions to the zygotic centrosome are examined in mammalian zygotes and after exposure of spermatozoa to Xenopus laevis cell-free extracts. The presence and inheritance of the conserved centrosomal constituents γ-tubulin, centrin, and MPM-2 (which detects phosphorylated epitopes) are traced, as is the sperm microtubule-nucleating capability on reconstituted centrosomes. γ-Tubulin is biparentally inherited in humans (maternal >> than paternal): Western blots detect the presence of paternal γ-tubulin. Recruitment of maternal γ-tubulin to the sperm centrosome occurs after sperm incorporation in vivo or exposure to cell-free extract, especially after sperm “priming” induced by disulfide bond reduction. Centrin is found in the proximal sperm centrosomal region, demonstrates expected calcium sensitivity, but appears absent from the zygotic centrosome after sperm incorporation or exposure to extracts. Sperm centrosome phosphorylation is detected after exposure of primed sperm to egg extracts as well as during the early stages of sperm incorporation after fertilization. Finally, centrosome reconstitution in cell-free extracts permits sperm aster microtubule assembly in vitro. Collectively, these results support a model of a blended zygotic centrosome composed of maternal constituents attracted to an introduced paternal template after insemination.     

Structure and properties of polyurethanes prepared from triglyceride polyols by ozonolysis

Ozonolysis was used to obtain polyols with terminal primary hydroxyl groups and different functionalities from trilinolein (or triolein), low-saturation canola oil, and soybean oil. The functionality of the model polyol from triolein (trilinolein) was 3.0 and that of soy polyol was 2.5, due to the presence of unreactive saturated fatty acids, while canola gave a polyol with a functionality of 2.8. All polyols exhibited a high tendency to crystallize at room temperature. The resulting waxes had melting points comparable to that of paraffin and very low viscosities in the liquid state. The polyols were cross-linked using 4,4'-methylenebis(phenyl isocyanate) to give polyurethanes. Glass transitions (T(g)) for the model-, canola-, and soy-based polyurethanes were 53, 36, and 22 degrees C, respectively. The about 30 degrees C lower T(g) of the soy-based polyurethane than that of the model polyurethane was the result not only of lower functionality but also of the presence of saturated fatty acids in the former. Polyurethane from the canola polyol had intermediate cross-linking density and properties. These polyurethanes displayed excellent mechanical properties and higher glass transition temperatures compared to polyurethanes from epoxidized and hydroformylated polyols of the same functionality, presumably due to the absence or lower content of dangling chains in the former.     

Optimizing long intrinsic disorder predictors with protein evolutionary information

Protein existing as an ensemble of structures, called intrinsically disordered, has been shown to be responsible for a wide variety of biological functions and to be common in nature. Here we focus on improving sequence-based predictions of long (>30 amino acid residues) regions lacking specific 3-D structure by means of four new neural-network-based Predictors Of Natural Disordered Regions (PONDRs): VL3, VL3H, VL3P, and VL3E. PONDR VL3 used several features from a previously introduced PONDR VL2, but benefitted from optimized predictor models and a slightly larger (152 vs. 145) set of disordered proteins that were cleaned of mislabeling errors found in the smaller set. PONDR VL3H utilized homologues of the disordered proteins in the training stage, while PONDR VL3P used attributes derived from sequence profiles obtained by PSI-BLAST searches. The measure of accuracy was the average between accuracies on disordered and ordered protein regions. By this measure, the 30-fold cross-validation accuracies of VL3, VL3H, and VL3P were, respectively, 83.6 +/- 1.4%, 85.3 +/- 1.4%, and 85.2 +/- 1.5%. By combining VL3H and VL3P, the resulting PONDR VL3E achieved an accuracy of 86.7 +/- 1.4%. This is a significant improvement over our previous PONDRs VLXT (71.6 +/- 1.3%) and VL2 (80.9 +/- 1.4%). The new disorder predictors with the corresponding datasets are freely accessible through the web server at http://www.ist.temple.edu/disprot.     

Quality of screening for diabetic retinopathy in the Rijeka region of Croatia

The aim of this study was to compare the quality of screening for diabetic retinopathy in cities of Rijeka and Zagreb, Croatia. Review of a random sample of 500 diabetic patient records and prospective ophthalmologic survey of 466 randomly selected diabetic patients in a secondary level diabetologic service in Rijeka (coastal region of Croatia). The main outcome measures were proportion of diabetic patient records with notes on ophthalmologic examination; rate of diabetic patients involved with screening for diabetic retinopathy; comparison with rates in Zagreb (Croatian capital). A total of 67% patients visited the ophthalmologist at least once after diagnosed with diabetes, and notes on ophthalmologic examination were found in only 28% patient records. Fifty percent of patients underwent an ophthalmologic examination within two years. Only one third of patients diagnosed with DM in last two years visited the ophthalmologist within this time, and 14% of patients older than 50 years never visited the ophthalmologist. Model of screening for diabetic retinopathy in Croatia works better in Zagreb than in Rijeka region, and needs certain improvements. The authors suggested modern methods of screening, the incorporation of the mechanisms of quality control, the obligatory reporting of newly diagnosed diabetic patients to the national registry, and the direct referral from diabetologist to ophthalmologist.