Heme-protein vibrational couplings in cytochrome c provide a dynamic link that connects the heme-iron and the protein surface

The active site of cytochrome c (Cyt c) consists of a heme covalently linked to a pentapeptide segment (Cys-X-X-Cys-His), which provides a link between the heme and the protein surface, where the redox partners of Cyt c bind. To elucidate the vibrational properties of heme c, nuclear resonance vibrational spectroscopy (NRVS) measurements were performed on (57)Fe-labeled ferric Hydrogenobacter thermophilus cytochrome c(552), including (13)C(8)-heme-, (13)C(5)(15)N-Met-, and (13)C(15)N-polypeptide (pp)-labeled samples, revealing heme-based vibrational modes in the 200- to 450-cm(-1) spectral region. Simulations of the NRVS spectra of H. thermophilus cytochrome c(552) allowed for a complete assignment of the Fe vibrational spectrum of the protein-bound heme, as well as the quantitative determination of the amount of mixing between local heme vibrations and pp modes from the Cys-X-X-Cys-His motif. These results provide the basis to propose that heme-pp vibrational dynamic couplings play a role in electron transfer (ET) by coupling vibrations of the heme directly to vibrations of the pp at the protein-protein interface. This could allow for the direct transduction of the thermal (vibrational) energy from the protein surface to the heme that is released on protein/protein complex formation, or it could modulate the heme vibrations in the protein/protein complex to minimize reorganization energy. Both mechanisms lower energy barriers for ET. Notably, the conformation of the distal Met side chain is fine-tuned in the protein to localize heme-pp mixed vibrations within the 250- to 400-cm(-1) spectral region. These findings point to a particular orientation of the distal Met that maximizes ET.     

Inhibition of cell survival, viability and proliferation by dentin adhesives after direct and indirect exposure in vitro

Objectives

The influence of dentin adhesive systems (Scotchbond Multi-Purpose, XP Bond, Xeno V, Clearfil Protect Bond, AdheSE) on cell survival, viability and proliferation was characterized after direct and indirect exposure using different cell culture techniques.

Materials and methods

The primers and cured bonding parts were directly exposed to cells using cell culture inserts, and complete materials were analyzed in a dentin barrier test. Cell responses were examined in 3T3 mouse fibroblasts after 24- and 72-h exposure periods by the estimation of total cell numbers (survival), apoptosis (viability) and cell proliferation.

Results

Cell numbers were effectively reduced by the primers of AdheSE, Protect Bond, and Scotchbond Multi-Purpose as well as XP bond after direct exposure in a cell culture insert test device. Likewise, Scotchbond Multi-Purpose primer induced a rate of apoptosis (93.9%) even higher than detected with Protect Bond primer (91.6%). Cell proliferation was entirely inhibited by primers and by Xp Bond as well. The Scotchbond Multi-Purpose was most cytotoxic in a dentin barrier test device after a 24-h indirect exposure. It also increased the percentage of cells in apoptosis to 15.4% compared to untreated controls.

Conclusion

Unpolymerized primers of dentin adhesives were more cytotoxic than polymerized bonding counterparts. Moreover, total etch dentin adhesives were more cytotoxic than self-etch adhesives.

Clinical relevance

When dentin adhesives are used in deep cavities without a protective dentin barrier the leachable hydrophobic and hydrophilic component of dentin adhesive systems can penetrate to the pulp and may induce cytotoxic responses in pulp tissues.     

Segmental vitiligo in a patient with thoracic outlet syndrome

Reported here is a 35-year-old man with findings of thoracic outlet syndrome and bilateral segmental vitiligo on C8–T1 dermatomes. The possible causal relationship between the two disorders under the common denominator of cervical sympathetic involvement is discussed for the first time in the literature.     

Utility of the Rey-15 Recognition Trial to Detect Invalid Performance in a Forensic Neuropsychological Sample

The current study sought to address the utility of the Rey Fifteen Item Test (Rey-15), with the use of a combined score [recall correct + (recognition correct – false positives)], to distinguish between valid and invalid performance among a sample of litigating persons referred for neuropsychological evaluation. Scores on the Rey-15 were analyzed across four comparison groups: (1) litigating persons with evidence of invalid performance (n = 29), (2) litigating persons with valid performance (n = 63), (3) learning-disabled patients (n = 36), and (4) a mixed clinical neuropsychological sample not involved in litigation (n = 54). A Rey-15 combined cutoff score of < 21 yielded the highest sensitivity (70%) and specificity (92.8%) rates. If the Rey-15 is to be used in clinical practice to detect invalid performance, the recognition trial with combined score < 21 should be used. Findings support the use of the combined Rey-15 score in place of the previously used recall Rey-15 score to improve sensitivity and specificity rates for detection of invalid performance in litigating neuropsychological referrals.     

The Prevalence and Course of Pulmonary Hypertension and Right Ventricular Dysfunction in Patients Undergoing Orthotopic Heart Transplantation

BackgroundPulmonary hypertension (PHT) and right ventricular (RV) dysfunction are among the commonly observed and potentially serious complications following heart transplantation. RV dysfunction is reported to occur in as much as half of these patients. In this study, the authors sought to examine the prevalence and the course of these prognostically important complications.MethodsThe records of 30 patients who had undergone orthotopic heart transplantation at our center were examined. Demographic and clinical variables were noted; RV dysfunction, pulmonary artery pressure on Doppler echocardiographic examination, and catheter findings were recorded.ResultsThe mean age of the study population was 31.3 years. On preoperative assessment, PHT was present in 21 (70%) patients. The average value of systolic pulmonary artery pressure was 44.5 ± 5.9 mm Hg. The mean value of pulmonary vascular resistance was 3.3 ± 1.8 hybrid reference unit (HRU). RV dysfunction was detected on postoperative assessment in 17 (56.7%) patients. The mean ischemia time was 216 ± 77 minutes; in 3 cases it exceeded 5 hours but in none of the cases did it reach 6 hours. Rejection was detected in 14 (46.7%) patients. Most of the patients received inotropic agents in the early postoperative period. When compared with preoperative values, on follow up at the end of the first year, a significant decrease in pulmonary artery pressure was observed (47.4 ± 4.8 vs 38.5 ± 7.5 mm Hg; P = .03), and the ratio of patients experiencing RV dysfunction decreased to 16.6% (n = 5).ConclusionThe findings of this study indicate that RV dysfunction and PHT are common complications following heart transplantation and improve with appropriate management over time with monitoring.     

Effects of different surface treatments on shear bond strength in two different ceramic systems

The purpose of this study was to evaluate the influence of different surface treatments (sandblasting, acid etching, and laser irradiation) on the shear bond strength of lithium disilicate-based core (IPS Empress 2) and feldspathic ceramics (VITA VM 9). One hundred ceramic discs were divided into two groups of 50 discs each for two ceramic systems: IPS Empress 2 (group I) and VITA VM 9 (group II). Each of the two groups was further divided into five surface treatment groups (ten each) as follows: group SB, sandblasting with alumina particles (50 μm); group HF, 5 % hydrofluoric acid etching; group L, Er:YAG laser irradiation (distance, 1 mm; 500 mJ; 20 Hz; 10 W; manually, noncontact R14 handpiece); group SB–L, sandblasting + Er:YAG laser; and group HF–L, 5 % hydrofluoric acid + Er:YAG laser. Luting cement (Panavia 2.0) was bonded to the ceramic specimens using Teflon tubes. After 24 h of water storage, a shear bond strength test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed with a two-way analysis of variance (ANOVA) and Tukey's honestly significant difference tests (α?=?0.05). The two-way ANOVA indicated that the shear bond strength was significantly affected by the surface treatment methods (p?<?0.05), but there was no significant interaction between the ceramic systems. Group SB–L had the highest mean values for each ceramic system. Sandblasting, followed by Er:YAG laser irradiation, enhanced the bond strength, indicating its potential use as an alternative method. The atomic force microscopic evaluation revealed that group SB had the most distinct sharp peaks among the groups.