Publications by authors named "Miguel A Ramirez"

52 Publications

E. coli Nickel-Iron Hydrogenase 1 Catalyses Non-native Reduction of Flavins: Demonstration for Alkene Hydrogenation by Old Yellow Enzyme Ene-reductases*.

Angew Chem Int Ed Engl 2021 Mar 15. Epub 2021 Mar 15.

Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Rd, Oxford, OX1 3QR, United Kingdom.

A new activity for the [NiFe] uptake hydrogenase 1 of Escherichia coli (Hyd1) is presented. Direct reduction of biological flavin cofactors FMN and FAD is achieved using H as a simple, completely atom-economical reductant. The robust nature of Hyd1 is exploited for flavin reduction across a broad range of temperatures (25-70 °C) and extended reaction times. The utility of this system as a simple, easy to implement FMNH or FADH regenerating system is then demonstrated by supplying reduced flavin to Old Yellow Enzyme "ene-reductases" to support asymmetric alkene reductions with up to 100 % conversion. Hyd1 turnover frequencies up to 20.4 min and total turnover numbers up to 20 200 were recorded during flavin recycling.
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http://dx.doi.org/10.1002/anie.202101186DOI Listing
March 2021

Noise Exposures Causing Hearing Loss Generate Proteotoxic Stress and Activate the Proteostasis Network.

Cell Rep 2020 11;33(8):108431

Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA. Electronic address:

Exposure to excessive sound causes noise-induced hearing loss through complex mechanisms and represents a common and unmet neurological condition. We investigate how noise insults affect the cochlea with proteomics and functional assays. Quantitative proteomics reveals that exposure to loud noise causes proteotoxicity. We identify and confirm hundreds of proteins that accumulate, including cytoskeletal proteins, and several nodes of the proteostasis network. Transcriptomic analysis reveals that a subset of the genes encoding these proteins also increases acutely after noise exposure, including numerous proteasome subunits. Global cochlear protein ubiquitylation levels build up after exposure to excess noise, and we map numerous posttranslationally modified lysines residues. Several collagen proteins decrease in abundance, and Col9a1 specifically localizes to pillar cell heads. After two weeks of recovery, the cochlea selectively elevates the abundance of the protein synthesis machinery. We report that overstimulation of the auditory system drives a robust cochlear proteotoxic stress response.
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http://dx.doi.org/10.1016/j.celrep.2020.108431DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7722268PMC
November 2020

Catastrophic Failure of Reverse Shoulder Arthroplasty from a Broken Screw: A Case Report.

JBJS Case Connect 2020 Jul-Sep;10(3):e19.00504

Department of Orthopedic Surgery, University of Illinois College of Medicine at Peoria (UICOMP), Peoria, Illinois.

Case: A 63-year-old woman presented with pain and limited range of motion 2 years after undergoing reverse shoulder arthroplasty (RSA). She underwent revision RSA for catastrophic implant failure caused by central screw breakage, subsequent polyethylene wear, and glenosphere loosening, and achieved excellent outcomes.

Conclusion: This is a unique case of a salvage procedure with satisfactory outcomes for a rare complication of RSA. It demonstrates the importance of clinical vigilance notwithstanding the absence of radiographic abnormalities in long-term monitoring of patient implant failure.
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http://dx.doi.org/10.2106/JBJS.CC.19.00504DOI Listing
April 2021

Management of irreparable massive rotator cuff tears: a systematic review and meta-analysis of patient-reported outcomes, reoperation rates, and treatment response.

J Shoulder Elbow Surg 2020 Dec 4;29(12):2459-2475. Epub 2020 Aug 4.

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.

Background: There is no consensus on the treatment of irreparable massive rotator cuff tears. The goal of this systematic review and meta-analysis was to (1) compare patient-reported outcome scores, (2) define failure and reoperation rates, and (3) quantify the magnitude of patient response across treatment strategies.

Methods: The MEDLINE, Embase, CENTRAL (Cochrane Central Register of Controlled Trials), and Scopus databases were searched for studies including physical therapy and operative treatment of massive rotator cuff tears. The criteria of the Methodological Index for Non-randomized Studies were used to assess study quality. Primary outcome measures were patient-reported outcome scores as well as failure, complication, and reoperation rates. To quantify patient response to treatment, we compared changes in the Constant-Murley score and American Shoulder and Elbow Surgeons (ASES) score with previously reported minimal clinically important difference (MCID) thresholds.

Results: No level I or II studies that met the inclusion and exclusion criteria were found. Physical therapy was associated with a 30% failure rate among the included patients, and another 30% went on to undergo surgery. Partial repair was associated with a 45% retear rate and 10% reoperation rate. Only graft interposition was associated with a weighted average change that exceeded the MCID for both the Constant-Murley score and ASES score. Latissimus tendon transfer techniques using humeral bone tunnel fixation were associated with a 77% failure rate. Superior capsular reconstruction with fascia lata autograft was associated with a weighted average change that exceeded the MCID for the ASES score. Reverse arthroplasty was associated with a 10% prosthesis failure rate and 8% reoperation rate.

Conclusion: There is a lack of high-quality comparative studies to guide treatment recommendations. Compared with surgery, physical therapy is associated with less improvement in perceived functional outcomes and a higher clinical failure rate.
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http://dx.doi.org/10.1016/j.jse.2020.07.030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7669555PMC
December 2020

Novel Approaches of Nanoceria with Magnetic, Photoluminescent, and Gas-Sensing Properties.

ACS Omega 2020 Jun 15;5(25):14879-14889. Epub 2020 Jun 15.

School of Engineering, Sao Paulo State University (UNESP), Guaratinguetá, São Paulo 12516-410, Brazil.

The modification of CeO with rare-earth elements opens up a wide range of applications as biomedical devices using infrared emission as well as magnetic and gas-sensing devices, once the structural, morphological, photoluminescent, magnetic, electric, and gas-sensing properties of these systems are strongly correlated to quantum electronic transitions between rare-earth f-states among defective species. Quantitative phase analysis revealed that the nanopowders are free from secondary phases and crystallize in the fluorite-type cubic structure. Magnetic coercive field measurements on the powders indicate that the substitution of cerium with lanthanum (8 wt %), in a fluorite-type cubic structure, created oxygen vacancies and led to a decrease in the fraction of Ce species in the 3+ state, resulting in a stronger room-temperature ferromagnetic response along with high coercivity (160 Oe). In addition to the magnetic and photoluminescent behavior, a fast response time (5.5 s) was observed after CO exposure, indicating that the defective structure of ceria-based materials corresponds to the key of success in terms of applications using photoluminescent, magnetic, or electrical behaviors.
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http://dx.doi.org/10.1021/acsomega.9b04250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7330910PMC
June 2020

Stereoselective Synthesis of Highly Substituted Tetrahydropyrans through an Evans Aldol-Prins Strategy.

J Org Chem 2018 08 6;83(16):9039-9066. Epub 2018 Aug 6.

Instituto Universitario de Bio-Orgánica "Antonio González" (IUBO-AG), Centro de Investigaciones Biomédicas de Canarias (CIBICAN), Departamento de Química Orgánica , Universidad de La Laguna (ULL) , Avda. Astrofísico Francisco Sánchez 2 , 38206 San Cristóbal de La Laguna , Tenerife , Spain.

A direct and general method for the synthesis of naturally occurring 2,3,4,5,6-pentasubstituted tetrahydropyrans has been developed, employing β,γ-unsaturated N-acyl oxazolidin-2-ones as key starting materials. The combination of the Evans aldol addition and the Prins cyclization allowed the diastereoselective and efficient generation of the desired oxacycles in two fashions: a one-pot Evans aldol-Prins protocol, in which five new σ bonds and five contiguous stereocenters were straightforwardly generated, and a two-step version, which additionally permitted the isolation of β,γ-unsaturated alcohol precursors bearing an N-acyl oxazolidin-2-one in the α position. From these alcohols were also obtained halogenated pentasubstituted tetrahydropyrans as well as 2,3,4,5-tetrasubstituted tetrahydrofurans, shedding light on the mechanism of the process. Computational studies were consistent with the experimental findings, and this innovative Evans aldol-Prins strategy was performed for the preparation of a battery of more than 30 densely substituted tetrahydropyrans, unprecedentedly fused to a 1,3-oxazinane-2,4-dione ring, both in a racemic fashion and in an enantiomeric fashion. These novel molecules were successfully submitted to several transformations to permit simple access to a variety of differently functionalized tetrahydropyrans. Most of these unique molecules were evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and the yeast Candida albicans, and some structure-activity relationships were established.
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http://dx.doi.org/10.1021/acs.joc.8b01182DOI Listing
August 2018

Lacertus Fibrosus Versus Achilles Allograft Reconstruction for Distal Biceps Tears: A Biomechanical Study.

Am J Sports Med 2017 Dec 22;45(14):3340-3344. Epub 2017 Sep 22.

Department of Orthopaedic Surgery, MedStar Union Memorial Hospital, Baltimore, Maryland, USA.

Background: The bicipital aponeurosis, or lacertus fibrosus, can potentially be used as a reconstruction graft in chronic distal biceps tendon tears.

Purpose: To evaluate construct stiffness, load to failure, and failure mechanism with lacertus fibrosus versus Achilles allograft for distal biceps tendon reconstruction.

Study Design: Controlled laboratory study.

Methods: Ten fresh-frozen matched cadaveric pairs of elbows were used. Three centimeters of the distal biceps tendon was resected. Specimens were randomized to the lacertus fibrosus or Achilles tendon group. In one group, the lacertus fibrosus was released from its distal attachment and then tubularized and repaired intraosseously to the radius. In the other group, an Achilles tendon graft was sutured to the biceps muscle and repaired to the ulna. The prepared radii were rigidly mounted at a 45° angle on a load frame. The proximal biceps muscle was secured in a custom-fabricated cryogenic grip. Displacement was measured using a differential variable reluctance transducer mounted at the radius-soft tissue junction and in the muscle- or muscle allograft-tissue junction proximal to the repair. Specimens were loaded at 20 mm/min until failure, defined as a 3-mm displacement at the radius-soft tissue junction.

Results: No significant difference was found in mean load to failure between the lacertus fibrosus and Achilles tendon group (mean ± SD, 20.2 ± 5.5 N vs 16.89 ± 4.54 N; P = .18). Stiffness also did not differ significantly between the lacertus fibrosus and Achilles tendon group (12.3 ± 7.1 kPa vs 10.5 ± 5.7 kPa; P = .34). The primary mode of failure in the lacertus fibrosus group was suture pullout from the tissue at the musculotendinous junction (7 of 10). In the Achilles group, failures were observed at the muscle-allograft interface (3) and the allograft-bone (radial tuberosity) interface (3), and 3 suture failures were observed. The button fixation did not fail in any specimens.

Conclusion: The mean stiffness and load-to-failure values were not significantly different between a lacertus fibrosus construct and Achilles tendon allograft.

Clinical Relevance: Use of the lacertus fibrosus may be a potential alternative to Achilles tendon allograft reconstruction of chronic distal biceps tears when primary repair is not possible.
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http://dx.doi.org/10.1177/0363546517727511DOI Listing
December 2017

Revision Total Elbow Arthroplasty.

J Am Acad Orthop Surg 2017 Aug;25(8):e166-e174

From the Department of Orthopaedic Surgery, MedStar Union Memorial Hospital, Baltimore, MD (Dr. Ramirez and Dr. Murthi) and the Department of Orthopaedic Surgery, Stanford University, Stanford Health Care, Redwood City, CA (Dr. Cheung).

Despite recent technologic advances, total elbow arthroplasty has complication rates higher than that of total joint arthroplasty in other joints. With new antirheumatic treatments, the population receiving total elbow arthroplasty has shifted from patients with rheumatoid arthritis to those with posttraumatic arthritis, further compounding the high complication rate. The most common reasons for revision include infection, aseptic loosening, fracture, and component failure. Common mechanisms of total elbow arthroplasty failure include infection, aseptic loosening, fracture, component failure, and instability. Tension band fixation, allograft struts with cerclage wire, and/or plate and screw constructs can be used for fracture stabilization.
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http://dx.doi.org/10.5435/JAAOS-D-15-00479DOI Listing
August 2017

Split-Intein Triggered Protein Hydrogels.

Methods Mol Biol 2017 ;1495:161-171

Department of Chemical Engineering, Texas A&M University, College Station, TX, 77843, USA.

Proteins are nature's building blocks and indispensable in living organisms. Protein-based hydrogels have a wide variety of applications in research and biotechnology. In this chapter, we describe an intein-mediated protein hydrogel that utilizes two synthetic soluble protein block copolymers, each containing a subunit of a trimeric protein that serves as a cross-linker and one half of the naturally split DnaE intein from Nostoc punctiforme. Mixing of these two protein block copolymers initiates an intein trans-splicing reaction that constitutes a self-assembling polypeptide flanked by cross-linkers, triggering protein hydrogel formation. The generated hydrogels are highly stable under both acidic and basic conditions, and at temperatures up to 50 °C. In addition, these hydrogels are able to undergo rapid reassembly after shear-induced rupture. Incorporation of an appropriate binding motif into the protein block copolymers enables the convenient site-specific incorporation of functional globular proteins into the hydrogel network.
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http://dx.doi.org/10.1007/978-1-4939-6451-2_11DOI Listing
January 2018

Enantiodivergent Synthesis of (+)- and (-)-Pyrrolidine 197B: Synthesis of trans-2,5-Disubstituted Pyrrolidines by Intramolecular Hydroamination.

Chemistry 2016 Oct 14;22(43):15529-15535. Epub 2016 Sep 14.

Instituto Universitario de Bio-Orgánica "Antonio González" (CIBICAN), "Síntesis Orgánica Sostenible, Unidad Asociada al CSIC", Departamento de Química Orgánica, Universidad de La Laguna, C/Francisco Sánchez 2, 38206, La Laguna, Tenerife, Spain.

A highly efficient, diastereoselective, iron(III)-catalyzed intramolecular hydroamination/cyclization reaction involving α-substituted amino alkenes is described. Thus, enantiopure trans-2,5-disubstituted pyrrolidines and trans-5-substituted proline derivatives were synthesized by means of a combination of enantiopure starting materials, easily available from l-α-amino acids, with sustainable metal catalysts such as iron(III) salts. The scope of this methodology is highlighted in an enantiodivergent approach to the synthesis of both (+)- and (-)-pyrrolidine 197B alkaloids from l-glutamic acid. In addition, a computational study was carried out to gain insight into the complete diastereoselectivity of the transformation.
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http://dx.doi.org/10.1002/chem.201602708DOI Listing
October 2016

Whither life? Conjectures on the future evolution of biochemistry.

Biol Lett 2016 08;12(8)

Department of Biochemistry, University of Otago, Dunedin, New Zealand

Life has existed on the Earth for approximately four billion years. The sheer depth of evolutionary time, and the diversity of extant species, makes it tempting to assume that all the key biochemical innovations underpinning life have already happened. But we are only a little over halfway through the trajectory of life on our planet. In this Opinion piece, we argue: (i) that sufficient time remains for the evolution of new processes at the heart of metabolic biochemistry and (ii) that synthetic biology is providing predictive insights into the nature of these innovations. By way of example, we focus on engineered solutions to existing inefficiencies in energy generation, and on the complex, synthetic regulatory circuits that are currently being implemented.
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http://dx.doi.org/10.1098/rsbl.2016.0269DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5014022PMC
August 2016

Emerging role of extracellular vesicles in communication of preimplantation embryos in vitro.

Reprod Fertil Dev 2016 Jan;29(1):66-83

Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, University of Ghent, Salisburylaan 133, B-9820 Merelbeke, Belgium.

In vitro, efficient communication between mammalian embryos in groups or between embryos and cocultured somatic cells implies that there is a sender, a message and a receiver that is able to decode the message. Embryos secrete a variety of autocrine and paracrine factors and, of these, extracellular vesicles have recently been implicated as putative messengers in embryo-embryo communication, as well as in communication of the embryo with the maternal tract. Extracellular vesicles (EVs) are membrane-bound vesicles that are found in biofluids and in culture media conditioned by the presence of embryos or cells. EVs carry and transfer regulatory molecules, such as microRNAs, mRNAs, lipids and proteins. We conducted a systematic search of the literature to review and present the currently available evidence regarding the possible roles of EVs in in vitro embryo communication and embryo development. It is important to note that there is limited information available on the molecular mechanisms and many of the biologically plausible functions of EVs in embryo communication have not yet been substantiated by conclusive experimental evidence. However, indirect evidence, such as the use of media conditioned by embryos or by somatic cells with improved embryo development as a result, may indicate that EVs can be an important asset for the development of tailor-made media, allowing better embryo development in vitro, even for single embryo culture.
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http://dx.doi.org/10.1071/RD16318DOI Listing
January 2016

Olecranon tip osteoarticular autograft transfer for irreparable coronoid process fracture: a biomechanical study.

Hand (N Y) 2015 Dec 3;10(4):695-700. Epub 2015 Jun 3.

c/o Lyn Camire, Editor, Department of Orthopaedic Surgery, MedStar Union Memorial Hospital, 3333 North Calvert Street, Suite 400, Baltimore, MD 21218 USA.

Background: We hypothesized that transfer of the olecranon tip for simulated type III coronoid fracture would restore posterior ulnohumeral translation to a level not different from that in the intact state.

Methods: The collateral ligaments were left intact in 12 fresh-frozen cadaveric elbows, and all other soft tissues were removed. The entire coronoid process was osteotomized flush with the ventral aspect of the ulna and was reconstructed using the tip of the olecranon process. Specimens were tested with an axial load of 100 N at 0.25 mm/s in 15° increments from 15 to 120° of flexion. Intact, osteotomized, and reconstructed posterior ulnohumeral displacement was measured.

Results: The bony reconstruction did not obstruct range of motion of the elbow. Intact translation (mean ± SD) ranged from 0.3 ± 0.1 to 1.1 ± 0.6 mm, and translation in the osteotomized state ranged from 1.3 ± 1.0 to 2.0 ± 1.0 mm. Resection of the coronoid resulted in a significant increase in posterior ulnar translation compared with intact at all flexion angles (p < 0.05) except at 75°. Reconstruction decreased translation versus the osteotomized state at all flexion angles, significantly at 60 and 120°. No significant difference in translation was found between reconstructed and intact states at five of eight positions tested.

Conclusions: In this biomechanical study of irreparable coronoid fracture, autograft olecranon tip transfer restored posterior elbow stability to a level not significantly different from the intact elbow in five of eight elbow positions tested.
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http://dx.doi.org/10.1007/s11552-015-9776-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4641086PMC
December 2015

Varus Posteromedial Instability.

Hand Clin 2015 Nov 7;31(4):557-63. Epub 2015 Aug 7.

Department of Orthopaedic Surgery, MedStar Union Memorial Hospital, 3333 North Calvert Street, Suite 400, Baltimore, MD 21218, USA. Electronic address:

Varus posteromedial instability of the elbow is a result of traumatic injury to the medial facet of the coronoid and usually the lateral collateral ligament. Treatment of these fractures is usually surgical; poor outcomes have been described with nonoperative treatment. Surgical management consists of coronoid fracture fixation with plates, screws, or sutures and radial collateral ligament repair. Outcomes of these injuries are mixed, but most series report fair to good objective scores. The purpose of this article is to describe the pathophysiology of varus posteromedial instability, discuss the management of this injury, and report the outcomes of treatment.
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http://dx.doi.org/10.1016/j.hcl.2015.06.005DOI Listing
November 2015

Signature Patterns of MHC Diversity in Three Gombe Communities of Wild Chimpanzees Reflect Fitness in Reproduction and Immune Defense against SIVcpz.

PLoS Biol 2015 May 28;13(5):e1002144. Epub 2015 May 28.

Department of Structural Biology and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America.

Major histocompatibility complex (MHC) class I molecules determine immune responses to viral infections. These polymorphic cell-surface glycoproteins bind peptide antigens, forming ligands for cytotoxic T and natural killer cell receptors. Under pressure from rapidly evolving viruses, hominoid MHC class I molecules also evolve rapidly, becoming diverse and species-specific. Little is known of the impact of infectious disease epidemics on MHC class I variant distributions in human populations, a context in which the chimpanzee is the superior animal model. Population dynamics of the chimpanzees inhabiting Gombe National Park, Tanzania have been studied for over 50 years. This population is infected with SIVcpz, the precursor of human HIV-1. Because HLA-B is the most polymorphic human MHC class I molecule and correlates strongly with HIV-1 progression, we determined sequences for its ortholog, Patr-B, in 125 Gombe chimpanzees. Eleven Patr-B variants were defined, as were their frequencies in Gombe's three communities, changes in frequency with time, and effect of SIVcpz infection. The growing populations of the northern and central communities, where SIVcpz is less prevalent, have stable distributions comprising a majority of low-frequency Patr-B variants and a few high-frequency variants. Driving the latter to high frequency has been the fecundity of immigrants to the northern community, whereas in the central community, it has been the fecundity of socially dominant individuals. In the declining population of the southern community, where greater SIVcpz prevalence is associated with mortality and emigration, Patr-B variant distributions have been changing. Enriched in this community are Patr-B variants that engage with natural killer cell receptors. Elevated among SIVcpz-infected chimpanzees, the Patr-B*06:03 variant has striking structural and functional similarities to HLA-B*57, the human allotype most strongly associated with delayed HIV-1 progression. Like HLA-B*57, Patr-B*06:03 correlates with reduced viral load, as assessed by detection of SIVcpz RNA in feces.
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http://dx.doi.org/10.1371/journal.pbio.1002144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4447270PMC
May 2015

Arthroscopic Management of a Glenohumeral Osteochondral Defect Using Particulated Juvenile Cartilage Allograft: A Case Report.

JBJS Case Connect 2015 Apr-Jun;5(2):e56

c/o Lyn Camire, Editor, Department of Orthopaedic Surgery, MedStar Union Memorial Hospital, 3333 North Calvert Street, Suite 400, Baltimore, MD 21218. E-mail address:

Case: A sixteen-year-old high school varsity quarterback was referred to us for evaluation of right shoulder pain two months after an injury sustained during a football tackle. The patient reported being substantially limited in his ability to perform vigorous activity because of pain and the sensation that his shoulder was about to dislocate. Evaluation showed a Bankart tear and a focal full-thickness glenoid osteochondral defect. The tear was treated with Bankart repair, and the osteochondral defect was filled arthroscopically with particulated juvenile cartilage graft. The patient returned to full sports activity without restriction at nine months after surgery and, at two years of follow-up, remained pain free with full range of motion and strength and no symptoms of instability.

Conclusion: The current case suggests that particulated juvenile cartilage may be effective in the treatment of osteochondral lesions of the glenoid.
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http://dx.doi.org/10.2106/JBJS.CC.N.00189DOI Listing
December 2017

Glenohumeral pressure with surface replacement arthroplasty versus hemiarthroplasty.

Orthopedics 2014 Oct;37(10):e892-6

It is not known whether significant differences in the glenohumeral center of pressure and contact pressure exist between surface replacement arthroplasty and hemiarthroplasty compared with the native joint. Twelve fresh-frozen cadaveric shoulders were dissected free of soft tissue, and the joint capsule was removed. The scapula was potted with the glenoid parallel to the ground. A pressure-sensitive sensor was placed in the glenohumeral joint, and each specimen was tested in sequence: intact, surface replacement, and hemiarthroplasty. Loading was done with a 440-N compression load at 0.5 Hz with the shoulder in 4 different positions. The center of pressure and contact pressure were measured at each position. The glenohumeral contact pressure with surface replacement was not different from intact pressure in 2 arm positions. Pressure with hemiarthroplasty was significantly different compared with the intact shoulder at all 4 arm positions and compared with the surface replacement group at 2 arm positions (P≤.05). Change in the anterior-posterior center of pressure from intact was significantly smaller with surface replacement compared with hemiarthroplasty with the humerus at 0° flexion/0° abduction and at 0° flexion/90° abduction (1.11±0.89 mm vs 2.38±1.62 mm, P=.02, and 0.68±0.50 mm vs 2.37±2.0 mm, P=.01, respectively). Change in the superior-inferior center of pressure was significantly smaller with surface replacement vs hemiarthroplasty at 0° flexion/0° abduction and at 90° flexion/90° abduction (0.98±1.16 mm vs 2.33±1.38 mm, P=.02, and 1.50±1.28 mm vs 2.90±1.92 mm, P=.04, respectively). Compared with hemiarthroplasty, surface replacement arthroplasty more closely replicated the contact pressure and center of pressure in the intact glenohumeral joint.
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http://dx.doi.org/10.3928/01477447-20140924-55DOI Listing
October 2014

Multimodal local infiltration analgesia in total shoulder replacement.

Pain Manag 2013 Jul;3(4):253-5

Department of Orthopedic Surgery, MedStar Union Memorial Hospital, 333 North Calvert Street, Suite 400, Baltimore, MD 21218, USA.

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http://dx.doi.org/10.2217/pmt.13.17DOI Listing
July 2013

African origin of the malaria parasite Plasmodium vivax.

Nat Commun 2014 ;5:3346

Division of Biological Anthropology, University of Cambridge, Cambridge CB2 1QH, UK.

Plasmodium vivax is the leading cause of human malaria in Asia and Latin America but is absent from most of central Africa due to the near fixation of a mutation that inhibits the expression of its receptor, the Duffy antigen, on human erythrocytes. The emergence of this protective allele is not understood because P. vivax is believed to have originated in Asia. Here we show, using a non-invasive approach, that wild chimpanzees and gorillas throughout central Africa are endemically infected with parasites that are closely related to human P. vivax. Sequence analyses reveal that ape parasites lack host specificity and are much more diverse than human parasites, which form a monophyletic lineage within the ape parasite radiation. These findings indicate that human P. vivax is of African origin and likely selected for the Duffy-negative mutation. All extant human P. vivax parasites are derived from a single ancestor that escaped out of Africa.
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http://dx.doi.org/10.1038/ncomms4346DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4089193PMC
November 2015

Synthesis of an intein-mediated artificial protein hydrogel.

J Vis Exp 2014 Jan 27(83):e51202. Epub 2014 Jan 27.

Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station.

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of this hydrogel are two protein block-copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. A highly hydrophilic random coil is inserted into one of the block-copolymers for water retention. Mixing of the two protein block copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit with crosslinkers at either end that rapidly self-assembles into a hydrogel. This hydrogel is very stable under both acidic and basic conditions, at temperatures up to 50 °C, and in organic solvents. The hydrogel rapidly reforms after shear-induced rupture. Incorporation of a "docking station peptide" into the hydrogel building block enables convenient incorporation of "docking protein"-tagged target proteins. The hydrogel is compatible with tissue culture growth media, supports the diffusion of 20 kDa molecules, and enables the immobilization of bioactive globular proteins. The application of the intein-mediated protein hydrogel as an organic-solvent-compatible biocatalyst was demonstrated by encapsulating the horseradish peroxidase enzyme and corroborating its activity.
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http://dx.doi.org/10.3791/51202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4091093PMC
January 2014

Roundworm-associated median nerve compression: a case report.

Iowa Orthop J 2013 ;33:225-7

Columbia University College of Physicians & Surgeons.

Human dirofilariasis is a rare zoonotic infection caused by the bite of a blood-feeding mosquito infected with a filarial nematode (roundworm). these infections can manifest as stationary or migratory subcutaneous or conjunctival nodules. We report an unusual case of Dirofilaria tenuis (D.tenuis) infection that developed into a space- occupying lesion in the wrist leading to median nerve compression pathology in an otherwise healthy young woman. We also comment on the natural history of the disease and report the outcome after surgical excision. To our knowledge, we are the first to report a case of median nerve compression caused by a growing subcutaneous nodule from a D.tenuis infection.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3748886PMC
May 2014

The malagarasi river does not form an absolute barrier to chimpanzee movement in Western Tanzania.

PLoS One 2013 11;8(3):e58965. Epub 2013 Mar 11.

Department of Anthropology, University of California San Diego, San Diego, California, United States of America.

The Malagarasi River has long been thought to be a barrier to chimpanzee movements in western Tanzania. This potential geographic boundary could affect chimpanzee ranging behavior, population connectivity and pathogen transmission, and thus has implications for conservation strategies and government policy. Indeed, based on mitochondrial DNA sequence comparisons it was recently argued that chimpanzees from communities to the north and to the south of the Malagarasi are surprisingly distantly related, suggesting that the river prevents gene flow. To investigate this, we conducted a survey along the Malagarasi River. We found a ford comprised of rocks that researchers could cross on foot. On a trail leading to this ford, we collected 13 fresh fecal samples containing chimpanzee DNA, two of which tested positive for SIVcpz. We also found chimpanzee feces within the riverbed. Taken together, this evidence suggests that the Malagarasi River is not an absolute barrier to chimpanzee movements and communities from the areas to the north and south should be considered a single population. These results have important consequences for our understanding of gene flow, disease dynamics and conservation management.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0058965PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3594223PMC
December 2013

Iron(III) catalyzed direct synthesis of cis-2,7-disubstituted oxepanes. The shortest total synthesis of (+)-isolaurepan.

Org Lett 2012 Dec 20;14(23):5904-7. Epub 2012 Nov 20.

Instituto Universitario de Bio-Orgánica Antonio González, Departamento de Química Orgánica, Universidad de La Laguna, C/Astrofísico Francisco Sánchez 2, 38206 La Laguna, Tenerife, Spain.

Prins cyclization of bis-homoallylic alcohols with aldehydes catalyzed by iron(III) salts shows excellent cis selectivity and yields to form 2,7-disubstituted oxepanes. The iron(III) is able to catalyze this process with unactivated olefins. This cyclization was used as the key step in the shortest total synthesis of (+)-isolaurepan.
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http://dx.doi.org/10.1021/ol3028016DOI Listing
December 2012

Reverse total shoulder arthroplasty for irreparable rotator cuff tears and cuff tear arthropathy.

Clin Sports Med 2012 Oct;31(4):749-59

Department of Orthopaedic Surgery, Union Memorial Hospital, 3333 North Calvert Street, Suite 400, Baltimore, MD 21218, USA.

Based on the available literature, we believe that reverse shoulder arthroplasty is a reasonable treatment modality in patients with CTA and massive irreparable cuff tears. RSA has been shown to increase patient function and decrease pain. There are still a high number of complications related to this procedure; however, with stringent patient selection criteria and meticulous technique, high patient satisfaction scores are typically achieved in these patients, at least in the short term. Further studies are required to evaluate the efficacy these devices in the long term.
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http://dx.doi.org/10.1016/j.csm.2012.07.009DOI Listing
October 2012

Shoulder dislocation in the older patient.

J Am Acad Orthop Surg 2012 Oct;20(10):615-22

Department of Orthopedics, Union Memorial Hospital, Baltimore, MD, USA.

Approximately 20% of all shoulder dislocations occur in patients aged >60 years. Older patients who sustain a primary shoulder dislocation are much less likely than younger patients to suffer from recurrence. However, older patients are more likely than younger patients to sustain injuries to the rotator cuff, axillary nerve, or brachial plexus. Rotator cuff tears are significantly more common than nerve palsies, and rotator cuff tears can be mistaken for nerve palsies. Older patients with persistent shoulder pain and dysfunction after dislocation should be carefully evaluated for rotator cuff pathology. Although dislocation is a common injury in the older population, these concomitant injuries-especially of the rotator cuff-are often missed.
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http://dx.doi.org/10.5435/JAAOS-20-10-615DOI Listing
October 2012

Eastern chimpanzees, but not bonobos, represent a simian immunodeficiency virus reservoir.

J Virol 2012 Oct 25;86(19):10776-91. Epub 2012 Jul 25.

Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

Chimpanzees in west central Africa (Pan troglodytes troglodytes) are endemically infected with simian immunodeficiency viruses (SIVcpzPtt) that have crossed the species barrier to humans and gorillas on at least five occasions, generating pandemic and nonpandemic forms of human immunodeficiency virus type 1 (HIV-1) as well as gorilla SIV (SIVgor). Chimpanzees in east Africa (Pan troglodytes schweinfurthii) are also infected with SIVcpz; however, their viruses (SIVcpzPts) have never been found in humans. To examine whether this is due to a paucity of natural infections, we used noninvasive methods to screen wild-living eastern chimpanzees in the Democratic Republic of the Congo (DRC), Uganda, and Rwanda. We also screened bonobos (Pan paniscus) in the DRC, a species not previously tested for SIV in the wild. Fecal samples (n = 3,108) were collected at 50 field sites, tested for species and subspecies origin, and screened for SIVcpz antibodies and nucleic acids. Of 2,565 samples from eastern chimpanzees, 323 were antibody positive and 92 contained viral RNA. The antibody-positive samples represented 76 individuals from 19 field sites, all sampled north of the Congo River in an area spanning 250,000 km(2). In this region, SIVcpzPts was common and widespread, with seven field sites exhibiting infection rates of 30% or greater. The overall prevalence of SIVcpzPts infection was 13.4% (95% confidence interval, 10.7% to 16.5%). In contrast, none of the 543 bonobo samples from six sites was antibody positive. All newly identified SIVcpzPts strains clustered in strict accordance to their subspecies origin; however, they exhibited considerable genetic diversity, especially in protein domains known to be under strong host selection pressure. Thus, the absence of SIVcpzPts zoonoses cannot be explained by an insufficient primate reservoir. Instead, greater adaptive hurdles may have prevented the successful colonization of humans by P. t. schweinfurthii viruses.
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http://dx.doi.org/10.1128/JVI.01498-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457319PMC
October 2012

Digital soft tissue trauma: a concise primer of soft tissue reconstruction of traumatic hand injuries.

Iowa Orthop J 2011 ;31:110-20

Department of Orthopedic Surgery, Union Memorial Hospital, Baltimore, MD, USA.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3215123PMC
March 2012

Does late night hip surgery affect outcome?

J Trauma 2011 Aug;71(2):447-53; discussion 453

Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA.

Background: There is a perception that after-hours hip surgery may result in increased complication rates. Surgeon fatigue, decreased availability of support staff, and other logistical factors may play an adverse role. However, there are little data supporting this perception in the hip fracture literature. We present a retrospective study comparing outcomes of hip fracture surgeries performed after hours versus regular daytime hours and outcomes before and after implementation of a dedicated orthopedic trauma room staffed by a fellowship trained traumatologist.

Methods: A retrospective study of 767 consecutive patients with intertrochanteric, subtrochanteric, or femoral neck fractures was performed for the years 2000 to 2006. Surgeries were stratified by time of incision into two groups: day (07:00 AM-05:59 PM) and night (06:00 PM-06:59 PM). Each group was further divided into a period before the implementation of a trauma room and the period after (August 2004). Records were examined for procedure length, intraoperative blood loss, complications (nonunion, implant failure, infection, deep vein thrombosis, pulmonary embolus, and refracture), reoperation, and mortality.

Results: Four hundred ninety-nine patients were included the day group and 268 in the night group. There were no differences in terms of age, ethnicity, American Society of Anesthesiologists status, total number of comorbidities, and fracture type between groups. There were significantly more females in the night group than the day group. Intertrochanteric fractures were 64% of all fractures, femoral neck fractures were 34%, and subtrochanteric fractures were 2%. Duration of surgery for Dynamic Hip System procedures was significantly longer in the night group and also before the trauma room became available. These differences in duration of surgery also correlate with blood loss differences between the groups. Intramedullary nails also took longer to do at night. Hemiarthroplasties demonstrated no significant differences. The 1-year and 2-year mortalities of hip fracture patients operated during daytime hours in a trauma room (13 and 15%, respectively) were significantly less than they were before the implementation of the trauma room (25 and 37%, respectively). When the effect of the trauma room was eliminated, there were no significant differences between overall daytime and nighttime mortalities at 1 month, 1 year, and 2 years. There were no significant differences in other complications noted between the different groups.

Conclusions: We recommend that nighttime surgery should not be dismissed in hip fracture patients that would otherwise benefit from an early operation. However, there seems to be a decreasing trend in mortality when hip fractures are operated in a dedicated daytime trauma room staffed by a dedicated traumatologist.
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http://dx.doi.org/10.1097/TA.0b013e3182231ad7DOI Listing
August 2011

A microwave-assisted domino rearrangement of propargyl vinyl ethers to multifunctionalized aromatic platforms.

Chemistry 2011 Mar 15;17(12):3318-21. Epub 2011 Feb 15.

Química Biológica y Biotecnología, Instituto de Productos Naturales y Agrobiología, Consejo Superior de Investigaciones Científicas, Avda. Astrofísico Francisco Sánchez 3, 38206 La Laguna, Tenerife, Spain.

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http://dx.doi.org/10.1002/chem.201003532DOI Listing
March 2011