Functional Analysis of Multiple nifB Genes of Paenibacillus Strains in Synthesis of Mo-, Fe- and V-Nitrogenase

Background: Biological nitrogen fixation is catalyzed by Mo-, V- and Fe-nitrogenases that are encoded by nif, vnf and anf genes, respectively. NifB is the key protein in synthesis of the cofactors of all nitrogenases. Most diazotrophic Paenibacillus strains have only one nifB gene located in a compact nif gene cluster (nifBHDKENX(orf1)hesAnifV). But some Paenibacillus strains have multiple nifB genes and their functions are not known.Results: We have analyzed the genomes of the 116 diazotrophic Paenibacillus strains and found that some Paenibacillus strains have 2-4 nifB genes. Phylogeny analysis shows that all nifB genes in Paenibacillus fall into 4 subclasses: the nifB1 being the first gene within the compact nif gene cluster, the nifB2 being adjacent to anf or vnf genes, the other nifB3 and nifB4 being scattered on genomes. Transcriptional results demonstrate that nifB1 exhibits the greatest increase in expression under Mo-dependent conditions and nifB2 is even more induced under alternative fixation conditions. Functional analyses by complementation of the ∆nifB and ∆nifBHDK mutant of P. polymyxa WLY78 which has only one nifB gene and only Mo-nitrogenase showed that both nifB1 and nifB2 are active in synthesis of Mo-, Fe and V-nitrogenase. The nifB3 and nifB4 genes were not significantly expressed under N2-fixing conditions and could not restore the nitrogenase activity of P. polymyxa ∆nifB mutant, suggesting that nifB3 and nifB4 genes were not involved in nitrogen fixation. In addition, reconstruction of anf system comprising 8 genes (nifBanfHDGK and nifXhesAnifV) and vnf system comprising 10 genes (nifBvnfHDGKEN and nifXhesAnifV) supported synthesis of Fe-nitrogenase and V-nitrogenase in P. polymyxa, respectively. Conclusions: Our data and analysis reveal the contents and distribution of nifB genes in Paenibacillus. We demonstrated that the transcriptions of nifB being adjacent to nif or anf or vnf genes significantly expressed under N2-fixation conditions and are active in synthesis of Mo-, Fe and V-nitrogenase. Our study also provides guidance for engineering nitrogen fixation genes into heterologous hosts for nitrogen fixation.

Osteosynthesis materials in maxillofacial surgery: rejection, removal, corrosion and particle detection rates

Background Titanium is traditionally the material of choice for osteosynthesis in maxillofacial surgery and has a wide array of application in this field. Conversely, a growing interest for alternative fixation methods has emerged in the literature. Promising results have been reported for 3D-designed and manufactured (CAD/CAM) titanium materials, whereas the use of biodegradable materials seems to be a more controversial topic. Objective To conduct a narrative review on the complications related to osteosynthesis materials in maxillofacial surgery in terms of rejection-, removal-, corrosion- and particle detection rates. Data Sources A literature search was performed in April 2020 using the electronic database PubMed (National Library of Medicine, NCBI). The search included studies published between 1999 and March 2019. Study Selection Articles were eligible for inclusion when data for the outcomes of interest were available. Data Extraction Complication rates including rejection-, removal-, corrosion- and particle detection rates were extracted. Data Synthesis The data were synthesized and analyzed according to the different types of osteosynthesis materials and fixation methods. Finally, the results were summarized and recommendations were listed for different types of surgical indications.

Traumatic Craniocervical Dissociation in Patients with Congenital Assimilation of the Atlas to the Occiput

Traumatic atlantooccipital dissociation (AOD) is a severe and usually fatal injury. Patients with assimilation of the atlas to the skull are exposed to a higher risk of injury and delay diagnosis due to the abnormal anatomy. We report two cases of acute traumatic craniocervical dislocation in patients with baseline congenital assimilation of the atlas to the skull. Computer tomography (CT) was used to identify the injury. Computer tomography angiography (CTA) showed variations of the vertebral arteries’ location on both patients. Assimilation of the atlas was complete in patient one and partial in patient two. Emergent surgical instrumentation and fusion were performed with a very careful and meticulous posterior dissection. As general rule, most of the patients with CCD will undergo occiput to C2 posterior segmental instrumentation and fusion. In the presented cases, a more extensive fusion was necessary based on the type and severity of the CCJ injury and the anatomical anomalies associated. Postoperatively, patient one remained neurologically intact and patient two died. Alternative fixation techniques should be used to minimize risk of VA injury during the surgical procedures.

Variable Angle Locking Compression Plate as Alternative Fixation for Jones Fractures:

Introduction. Jones fractures pose many challenges for the treatingsurgeon and can cause significant disability for some patients. Theaim of this study was to review the results of using a variable anglelocking compression plate as an alternative fixation method in thetreatment of Jones fractures.Methods.xA retrospective chart review was conducted of patientswho had undergone fixation of Jones fracture with a variable anglelocking compression plate from September 2012 through February2016. Radiographs of the preoperative and six-week postoperativeand postoperative follow-up outcomes, including complication andhardware removal, were collected.Results. Twenty-three cases met the inclusion/exclusion criteria.The overall bony union rate was 96% at six-week postoperative and100% at 20-week postoperative. Mean age was 30 ± 16 years, andmean BMI was 30.7 ± 5.2 kg/m2. Three patients (13%) had plateremoval: two (9%) were due to irritation caused by shoe wearing andone patient (4%) had a skin infection (cellulitis) which was treatedwith intravenous antibiotics. One patient (4%) had developed deepvein thrombosis (DVT) that was resolved with anticoagulant withoutimplant removal. No fixation loss and no associated complicationsdeveloped from implant removal.Conclusions. Based on our limited experience, this study providedevidence that the variable angle locking compression plate may be analternative form of fixation for Jones fractures with a low complicationrate. This procedure seemed to provide a safe, reliable methodthat can achieve an anatomic reduction, stable fixation, rapid healing,and good results in the treatment of Jones fractures.Kans J Med 2019;12(2):28-32.

Comparison of Magnesium Versus Titanium Screw Fixation for Biplane Chevron Medial Malleolar Osteotomy in the Treatment of Osteochondral Lesions of the Talus

Background and objectives: The purpose of this retrospective study was to compare the clinical and radiological outcomes of patients who underwent biplane chevron medial malleolar osteotomy (MMO) for osteochondral lesions of the talus (OLT), fixed with either magnesium (Mg) or titanium (Ti) screws. Materials and Methods: A total of 22 patients (12 male, 10 female) with a mean age of 40.6±12.5 years (range, 18-56 years) who underwent MMO for OLT treatment were included in this retrospective study. Of the 22 patients, MMO was fixed with bioabsorbable Mg screws (Alloy: MgYREZr) in 11 patients, and in the remaining 11 patients (one bilateral) MMO were fixed with Ti screws.  All patients were followed up for at least one year with a mean of 20.7±8.9 months (range, 12–49 months). The American Orthopedic Foot and Ankle Society (AOFAS) scale and the visual analog scale (VAS) were used to evaluate the clinical results. Union of the osteotomy, postoperative displacement, and all other complications were followed and analyzed. Results: An improvement in the AOFAS scale and VAS points were recorded in both groups with no statistically significant difference between the groups (p: 0.079 and 0.107 respectively). Complete union of the osteotomy was obtained in all patients. One patient in the Ti group required implant removal due to pain and irritation. There were no other significant complications in either group. Conclusions: The results of this study showed that bioabsorbable Mg compression screws have similar therapeutic efficacy to Ti screws in respect to functional and radiological outcomes in MMO fixation. Bioabsorbable Mg screw is an alternative fixation material which can be safely used for MMO in ankle surgery.

C1-C2 screw fixation in the patient with anomalous course of vertebral artery: Case report

Introduction. The atlantoaxial complex is a very complicated structure and open reduction of C1-C2 subluxation is very demanding. Atlantoaxial instability may result from the traumatic, inflammatory, neoplastic, congenital or degenerative disorders. Anatomy of the vertebral artery is essential for surgical approach and sometimes the placement of C2 pedicle screw is not possible. In these instances, the translaminar screw placement in C2 can provide an alternative fixation point in C2, without threatening injury to the vertebral artery. Case report. We presented 54- year-old patient with cervical myelopathy according to traumatic atlantoaxial subluxation. Computed tomography angiography showed a bilateral vertebral artery anomaly of ?high-riding? type. The patient was operated and the posterior C1-C2 screws fixation was used. Due to the vertebral artery anomaly C2 screws were translaminary inserted. Complete reduction of C1-C2 subluxation and excellent neurological improvement were achieved. Conclusion. Surgical treatment of C1-C2 subluxation is very challenging. Many techniques of atlantoaxial fixation have been developed. The use of C2 translaminar screw is an alternative method of fixation in the treatment of atlantoaxial instability, especially in cases with the vertebral artery anomaly.

Alternative fixation system for implant-retained overdenture: case report

ABSTRACT The aim of this case report was to describe a prosthetic rehabilitation associated with an alternative model of polymer capsule for fixation system of implant-retained overdentures. Patient sought treatment at the clinic of School of Dentistry of Ribeirão Preto, due to lack of retention of their conventional total superior prostheses and inferior overdenture. The initial complaint was clinicallyconfirmed by altered intermaxillary relationships and severe reabsorption of the maxillary crest. In order to restore the function and improve its quality of life, it was proposed a prosthetic solution including implant fixed prosthesis to maxilla and a mandibular overdenture, with ball-type attachments associated with an alternative model of polymer capsule. This treatment was proposed inorder to reestablish the intermaxillary relationships and adequate occlusion, maintain retention and stability of the prosthesis. At the end of treatment and during a one-year follow-up of the case, the patient reported satisfaction and significant improvement in quality of life.