Wear Performance of Dental Materials: A Comparison of Substructure Ceramics,Veneering Ceramics,and Non‐Precious Alloys

The aim of this in vitro study was to compare the two‐body wear resistance of different dental ceramics and non‐precious alloys. Two‐body wear tests were performed in a chewing simulator with steatite antagonists. A pin‐on‐block design with a vertical load of 50 N for 1.2 × 10⁵ cycles (f = 1.6 Hz; lateral movement: 1 mm, mouth opening: 2 mm) was used for the wear test. Surface roughness R_a (SP6, Perthen‐Feinprüf, G) and wear depth were determined using a 3D‐Profilometer (Laserscan 3D, Willytec, G). Scanning electron microscopy (Quanta FEG 400, FEI, NL) was applied for evaluating wear performance of both, materials and antagonists. Statistics: one‐way ANOVA (α = 0.05). The in vitro wear test showed that the wear performance of dental materials is strongly influenced by the type of material (ceramic, zirconia, or alloy). Zirconia and alloy provided low wear in contrast to glass‐ceramic systems. In contradiction to common expectations, hard zirconia and alloy systems showed even lower antagonistic wear than glass‐ceramics.     

Enhancement of secretagogue-induced adrenocorticotropic hormone release from cultured sheep anterior pituitary cells by recombinant ovine interleukin 1

Interaction between protein disulfide isomerase, possessing not only isomerase but also chaperone-like activity, and olygomeric enzyme, GAPDH, has been studied using technique of immobilization on insoluble support. PDI dimers bound to CNBr-activated Sepharose were shown to possess high TPOR activity as well as the ability to reactivate lysozyme. Immobilized PDI was not found to interact neither with soluble tetrameric GAPDH, nor with soluble denatured GAPDH. However, soluble PDI binds effectively to immobilized GAPDH monomers; Kd was found to be 3.7 x 10(-6) M, stoichiometry 0.824 mole PDI monomers per mole GAPDH monomers. Immobilized GAPDH tetramers do not interact with PDI. These observations are also confirmed by the data on electrophoresis of proteins bound to immobilized GAPDH monomers and tetramers. The ability of PDI to interact with denatured protein form, but not with the native one, is considered to be evidence of chaperone-like activity of the enzyme.     

Effect of N-palmitoylethanolamine on energy-dependent transport of Ca2+ in vesicles of myometrium sarcolemma and their phospholipid composition

N-palmitoylethanolamine (NPE) was studied for their effect on calcium pump of pig myometrium sarcolemma. NPE in concentration of 10 microM, stimulated by 28-46% Mg2+, ATP-dependent accumulation of Ca2+ in vesicles of plasmatic membrane of uterus myocytes taking absolutely no effect on passive release of this cation from them. NPE modified phospholipid composition of sarcolemma, causing the increase of percentage content of phosphatidylinositol (by 20.2%) and lysophosphatidylcholine (2.7 times). While NPE effects transport Ca2+, Mg(2+)-ATPase solubilized from plasmatic membrane and purified due to the method of affinity chromatography on calmodulin-sepharose 4B, no activating effect of NPE on the calcium pump was observed. And what is more, a weakly expressed tendency to inhibition (by 14-15%, respectively) of the rate of Ca2+, Mg(2+)-dependent enzymic hydrolysis of ATP has been revealed. It is supposed that the effect of NPE on active transmembrane transport of Ca2+ is an important link in the general mechanism of contraction-relax of the myometrium and is, apparently, connected with its modifying effect on the lipid composition of the sarcolemma.     

Increased expression of monoamine oxidase-B results in enhanced neurite degeneration in methamphetamine-treated PC12 cells

In vivo administration of methamphetamine (MA) produces selective damage to dopaminergic nerve terminals, which is hypothesized to be due to release of dopamine from synaptic vesicles within the terminals, allowing the generation of reactive oxygen species (ROS) via dopamine metabolism. Hydrogen peroxide formed during this reaction can interact with free iron to form hydroxyl radicals, which can oxidize proteins, nucleic acids, and membrane lipids, leading to terminal degeneration. Elevation of activity of the dopamine-metabolizing enzyme monoamine oxidase (MAO) in nerve growth factor-treated PC12 cells resulted in a substantial rise in products of dopamine metabolism following MA treatment, including 3,4-dihydroxyphenylacetic acid and hydroperoxides, as well as an increase in lipid peroxidation and a decrease in neurite number and length compared with control cells. These latter effects could be reversed by treatment with the MAO-B specific inhibitor, deprenyl. These data suggest that dopamine metabolism and subsequent ROS production may be key elements in MA-induced neurite degeneration in dopaminergic neurons.     

Fusion between retinal rod outer segment membranes and model membranes: a role for photoreceptor peripherin/rds

Peripherin/rds plays an essential role in the maintenance of photoreceptor rod cell disk membrane structure. The purification of this protein to homogeneity [Boesze-Battaglia, K., et al. (1997) Biochemistry 36, 6835-6846] has allowed us to characterize the functional role of peripherin/rds in the maintenance of rod outer segment (ROS) membrane fusion processes. Utilizing a cell-free fusion assay system, we report that the fusion of R18-labeled ROS plasma membrane (R18-PM) with disk membranes or peripherin/rds-enriched large unilammellar vesicles (LUVs) is inhibited upon trypsinolysis of peripherin/rds. To understand this phenomenon, we tested the ability of a series of overlapping synthetic C-terminal peripherin/rds peptides to mediate model membrane fusion. Within the 63 amino acid long region of the C-terminus, we identified a minimal 15 residue long amino acid sequence (PP-5), which is necessary to promote membrane fusion. PP-5 was able to inhibit R18-PM disk membrane fusion and promoted ANTS/DPX contents mixing in a pure vesicle system. This peptide (PP-5) promoted calcium-induced vesicle aggregation of phosphatidylethanolamine:phosphatidylserine LUVs. FTIR analysis confirmed the structural prediction of this peptide as alpha-helical. When modeled as an alpha-helix, this peptide is amphiphilic with a hydrophobicity index of 0.75 and a hydrophobic moment of 0.59. PP-5 has substantial biochemical and functional homology with other well-characterized membrane fusion proteins. These results demonstrate the necessity for peripherin/rds in ROS membrane fusion, specifically the requirement for an intact C-terminal region of this protein.     

Personality prototypes and ego development: conceptual similarities and relations in adult women

Three studies investigated how three personality prototypes (K. York & O.P. John, 1992) relate to J. Loevinger's (1976) stages of ego development (ED). Study 1 examined their conceptual similarities, and Study 2 their relations in a sample of adult women. In both studies, the personality prototypes mapped onto regions defined by multiple ED stages: The Individuated prototype was most likely to reach the high region of ED (Individualistic, Autonomous, and Integrated); the Traditional prototype was most likely to function in the middle region (Conformist, Self-aware, and Conscientious); and the Conflicted prototype was more likely to remain in the low region (Impulsive and Self-protective). In addition to these between-prototype differences, Study 3 explored whether differences in life outcomes within the prototypes are also related to ED; findings suggest that personality prototype and ego development may interact in shaping the life course.     

Adenosine deaminase activity in protein-energy malnutrition

Cell-mediated immunity (CMI) was evaluated in 69 children with protein-energy malnutrition (PEM) and 20 healthy controls. Significantly decreased responses to purified protein derivative (PPD) (p < 0.02) and absolute lymphocyte count (ALC) (p < 0.01) and increased serum adenosine deaminase (ADA) activity (p < 0.001) were observed in PEM cases compared with the controls. The mean values of ALC and ADA activity in PEM patients were 85.9% and 158.7% of the normal mean, respectively. A significant negative correlation was observed between the two parameters (r=- 0.2765, p < 0.01). The CMI tests were abnormal in all three grades of PEM, except for the response to PPD in grade I, when compared with the controls. No significant differences were found between infected and uninfected PEM cases. Thus, impaired CMI was observed not only in grades II and III but also in grade I PEM patients and the concomitant infection did not affect its status. However, ADA activity demonstrated a more pronounced change than the other tests.     

Decreased erythrocyte Na+,K(+)-ATPase activity associated with cellular potassium loss in extremely low birth weight infants with nonoliguric hyperkalemia

To determine whether a shift of potassium ions from the intracellular space to the extracellular space accounts, in part, for the hyperkalemia seen in extremely low birth weight infants, we examined potassium concentration in serum and erythrocytes from extremely low birth weight infants with hyperkalemia (n = 12) or with normokalemia (n = 27). In addition, to determine whether the shift of potassium was associated with low sodium-potassium-adenosinetriphosphatase (Na+,K(+)-ATPase) activity, we studied the activity of ATPase in the last 16 infants enrolled in the study. Fluid intake and output were measured during the first 3 days of life. Infants were considered to have hyperkalemia if the serum potassium concentration was 6.8 mmol/L or greater. Blood was obtained daily for intracellular sodium and potassium levels by means of lysis of erythrocytes. The remaining erythrocyte membranes were frozen and analyzed for Na+,K(+)-ATPase activity. There were significantly lower intracellular potassium/serum potassium ratios in the infants with hyperkalemia for each day of the 3-day study (p < 0.001). In the hyperkalemic group, there was lower Na+,K(+)-ATPase activity than in the infants with normokalemia (p = 0.006). Low Na+,K(+)-ATPase activity was associated with lower intracellular potassium/serum potassium ratios (p = 0.006), higher serum potassium values (p = 0.02), and lower intracellular potassium concentration (p = 0.009). The urinary data demonstrated that there was no difference in glomerulotubular balance between the two groups. We conclude that nonoliguric hyperkalemia in extremely low birth weight infants may be due, in part, to a shift of potassium from the intracellular space to the extracellular space associated with a decrease in Na+,K(+)-ATPase activity.     

Cross-infection control in Malaysian dental practice

STUDY OBJECTIVE: The aim was to study the spectrum of clinical problems and outcomes in infants born at an urban academic hospital. In consequence, as part of the overall study, the incidence of congenital anomalies and the outcomes of affected infants were recorded. DESIGN: This was a prospective, hospital-based study, undertaken on liveborn infants born over a 3-year period, 1 May 1986 to 30 April 1989. SETTING: Kalafong Hospital, Pretoria. MAIN RESULTS: A total of 17,351 liveborn infants was examined and the total congenital anomalies incidence was 11.87 per 1,000 livebirths. The central nervous system was the system most frequently involved (2.30 per 1,000 livebirths), followed by the musculoskeletal system (2.13 per 1,000 livebirths). The commonest individual congenital anomaly was Down syndrome (1.33 per 1,000 livebirths), followed by neural tube defects (0.99 per 1,000 livebirths) and ventricular septal defects (0.69 per 1,000 livebirths). In 11% (2.25 per 1,000 livebirths) of neonatal deaths, infant loss was attributable to congenital anomalies. CONCLUSIONS: The incidence of congenital anomalies in black South African neonates, born in an urban setting, is as high as in other First- and Third-World countries, and the incidence of some individual congenital anomalies is higher. This study indicates the need for further research and the establishment of prenatal, genetics and paediatric facilities to manage these problems.