Crystal structures of a new class of pyrimidine/purine nucleoside phosphorylase (ppnP) revealed a Cupin fold

Nucleotides metabolism is a fundamental process in all organisms. Two families of nucleoside phosphorylases (NP) that catalyze the phosphorolytic cleavage of the glycosidic bond in nucleosides have been found, including the trimeric or hexameric NP-I and dimeric NP-II family enzymes. Recently studies revealed another class of NP protein in E. coli named Pyrimidine/purine nucleoside phosphorylase (ppnP), which can catalyze the phosphorolysis of diverse nucleosides and yield D-ribose 1-phosphate and the respective free bases. Here, we solve the crystal structures of ppnP from E. coli and the other three species. Our studies revealed that the structure of ppnP belongs to the Rlmc-like cupin fold and showed as a rigid dimeric conformation. Detail analysis revealed a potential nucleoside binding pocket full of hydrophobic residues. And the residues involved in the dimer and pocket formation are all well conserved in bacteria. Since the cupin fold is a large superfamily in the biosynthesis of natural products, our studies provide the structural basis for understanding and the directed evolution of NP proteins.

s-Processing in Asymptotic Giant Branch Stars in the Light of Revised Neutron-Capture Cross Sections

Current AGB stellar models provide an adequate description of the s-process nucleosynthesis that occurs. Nonetheless, they still suffer from many uncertainties related to the modeling of the 13C pocket formation and the adopted nuclear reaction rates. For many important s-process isotopes, a best set of neutron-capture cross sections was recently re-evaluated. Using stellar models prescribing that the 13C pocket is a by-product of magnetic-buoyancy-induced mixing phenomena, s-process calculations were carried out with this database. Significant effects are found for a few s-only and branching point isotopes, pointing out the need for improved neutron-capture cross section measurements at low energy.

A Review of Periodontal Ligament-Derived Mesenchymal Stem Cells Being Used to Regenerate the Periodontal Ligament and Periodontium

Periodontal disease is an inflammatory disease of the tissues making up the periodontium that consists of alveolar bone resorption, recession of the gingiva, as well as damage to the periodontal ligament and cementum caused by accumulation of bacteria in the oral cavity. The method of treatment is dependent upon the depth of pocket formation and stage of disease advancement. When pockets are at a depth between 4 and 5 mm, nonsurgical treatments such as scaling, root planning, and antibiotics are used to treat. Surgical methods are used, however, when pockets are deeper than 5 mm. Both nonsurgical and surgical treatments currently used have limited capabilities to regenerate parts of the periodontium. The discovery of periodontal ligament-derived mesenchymal stem cells and their ability to generate cementoblasts, osteoblasts, adipocytes, chondroblasts, and fibroblasts in vitro that all contribute to the formation of the periodontium. This paper discusses the aims of current and future research on periodontal ligament stem cells and their potential to regenerate the periodontal ligament, as well as the entire periodontium.

Comparison of endoscopic and microscopic management of attic cholesteatoma: A randomized controlled trial

Objectives: To compare the endoscopic approach to manage attic cholesteatoma with conventional microscopic technique. Design: Randomized controlled trial. Participants: A total of 190 patients (192 ears) diagnosed with attic cholesteatoma extending to the antrum area (stages Ib and II) were randomly assigned into two groups: one undergoing endoscopic approach and the other undergoing the microscopic technique. Main outcome measures: The two groups were compared in terms of preoperative and intraoperative findings, access to hidden areas expressed in terms of the Middle Ear Structural Visibility Index (MESVI), mean operative time, and postoperative findings. Results: No difference in the parameters of the preoperative and intraoperative findings analyzed (patient age, computed tomography findings, disease stage, and intraoperative cholesteatoma characteristics) was observed between the endoscopic and microscopic groups. The median MESVI for the endoscopic group was better than that for the microscopic group (P<0.05). The mean operating time using the endoscopic approach was less than that using the microscopic approach (P<0.05). The median postoperative pain score in the endoscopic group was lower than that in the microscopic group (P<0.05). No significant difference was found between the two groups in terms of taste sensation, air-bone gap closure at the end of 4 weeks, and vertigo experienced at the end of the first week. When long-term surgical outcomes were assessed 1 year postoperatively, five patients in the microscopic group had recurrence, four had cartilage displacement, three had perforation, and five had retraction pocket formation. In the endoscopic group, four patients had disease recurrence, three had cartilage displacement, two had perforation, and four had retraction pocket formation. Conclusion: Endoscopic management of limited attic cholesteatoma showed definite advantages over the conventional microscopic approach, such as providing better visualization, requiring less postoperative time, subjecting the patients to less pain, and decreasing the incidence of complications.

Alveolar Preservation with Albumin and Gentamycin-Coated Allograft after Third Molar Tooth Removal: A Randomized Clinical Trial

Alveolar preservation can minimize bone resorption after tooth removal and additional topical antibiotics might also be considered. The goal of this study was to observe alveolar preservation with albumin and gentamycin-coated allograft compared to unfilled control sockets after mandibular third molar removal. Twenty-two patients were involved, 11 in the control group and 11 in the test group. CBCT analysis and micromorphometric analysis were performed. After one year, graft integration was observed with remaining graft particles. Micromorphometric analysis showed increased density and lower trabeculae formation in the grafted group. The buccal height reduction of the alveolar ridge was significantly lower when alveolar preservation was applied (control: 2.54 ± 2.01 mm, graft: 1.37 ± 1.04 mm, p < 0.05). Horizontal bone loss prevention was not significant. At the distal site of the second molar, the marginal bone level (MBL) was significantly lower in the control group. At the control group, five pockets persisted from the eight initial and all healed in the graft group. Alveolar preservation improves bone formation, helps to preserve the buccal bone crest, and minimizes MBL loss and pocket formation on the adjacent teeth. Thus, it needs to be also considered after third molar surgical removal.

Conformational flexibility Of A Highly Conserved Helix Controls Cryptic Pocket Formation In FtsZ

Mycobacterium tuberculosis is responsible for more than 1.6 million deaths per year. Overcoming failure from established therapies owing to multidrug resistance requires the identification of novel targets. One potential antibacterial target is filamentous temperature sensitive protein Z (FtsZ), which is the bacterial homologue of mammalian tubulin, a validated cancer target. M. tuberculosis FtsZ function is essential, with its inhibition leading to arrest of cell division, elongation of the bacterial cell and eventual cell death. However, the development of potent inhibitors against FtsZ has been a challenge due to the lack of structural information. Here we have solved multiple crystal structures of M. tuberculosis FtsZ in complex with coumarin analogues. Coumarins bind exclusively to two novel cryptic pockets in nucleotide-free FtsZ but not to the binary FtsZ-GTP or GDP complexes. Our findings provide a detailed understanding of the molecular basis for cryptic pocket formation, controlled by the conformational flexibility of the H7 helix, and thus reveal an important structural and mechanistic rationale for coumarin’s antibacterial activity.

Guided Tissue Regeneration – A Boon to Surgical Periodontal Therapy

Periodontitis has been a chronic inflammatory disease of the gingiva which eventually result in periodontal pocket formation with loss of the associated periodontal ligament and alveolar bone around teeth. Guided tissue regeneration (GTR), which is often a target for periodontal treatment, has the ability to promote periodontal regeneration. The development of the periodontal attachment is primarily concerned with tissue regeneration.Based on such concept, guided tissue regeneration is being utilized to varying degree of success to restore periodontal defects. In order to remove epithelium as well as gingival corium from the root and/or existing bone walls on the assumption that they interfere with regeneration, barrier techniques have been applied, using elements like expanded polytetrafluoroethylene, polyglactine, polylactic acid, calcium sulfate and collagen.

Non-surgical periodontal therapy: Case Report

Chronic periodontitis is the inflammatory diseases of the supporting tissues of teeth caused by micro-organisms resulting in progressive destruction of the periodontal ligament and alveolar bone with pocket formation, recession, or both. Mechanical debridement of supra-gingival and subgingival biofilms, together with adequate oral hygiene measures is the standard periodontal therapy. Nonsurgical periodontal therapy which aims to eliminate both living bacteria in the microbial biofilm and calcified biofilm microorganisms still remains the gold standard and first recommended approach to control periodontal infection. This article would highlight about the long term follow-up and management of chronic periodontitis cases through non-surgical periodontal therapy and its importance and efficacy in day to day clinical practice. Key words: Chronic periodontitis, nonsurgical periodontal therapy, efficacy.