RESUMO
BACKGROUND: With the decreasing age threshold for patients undergoing total hip arthroplasty (THA), there is an escalating demand for enhanced polyethylene durability. Although reports assessing wear in remelted highly cross-linked polyethylene (HXLPE) through radiographic imaging exist, a consensus regarding its oxidation level is lacking. This study investigated the wear, oxidation levels, and degradation of remelted HXLPE that was retrieved at least 10 years after THA. METHODS: Our analysis focused on 7 cases of melted HXLPE liners retrieved ≥10 years after THA. All patients were women, who had an average age of 64 ± 6.5 years at the initial operation, and the mean postoperative period after THA was 12 years and 11 months ±1 year and 5 months. The wear conditions were measured by matching the shape analysis data obtained from a coordinate-measuring machine with a spherical model. Fourier-transform infrared spectroscopy was used to study the oxidation of polyethylene, and the polyethylene structure was evaluated using scanning electron microscopy. RESULTS: Osteolysis was not observed in any case on X-rays, computed tomography, or intraoperative findings during revision surgery. The average oxidation index (OI) of the sliding surface under load was 0.31 ± 0.22 in the 6 cases calculated after hexane treatment, and 0.69 for one case without hexane treatment. In the 6 cases calculated after hexane treatment, the average OI of the non-load-bearing sliding surface was 0.11 ± 0.20. Average wear values were 0.33 ± 0.11 mm at 45 degrees from the equatorial direction and 0.04 ± 0.07 mm in the opposite direction. The initial structure of the polyethylene was preserved at all sites with low oxidation levels; however, in one case with stem subsidence, morphological changes and a high OI were observed. CONCLUSIONS: Long-term oxidation and wear of remelted HXLPE liners retrieved from THA patients were minimal.
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Cytochrome c oxidase (CcO), a membrane enzyme in the respiratory chain, catalyzes oxygen reduction by coupling electron and proton transfer through the enzyme with a proton pump across the membrane. In all crystals reported to date, bovine CcO exists as a dimer with the same intermonomer contacts, whereas CcOs and related enzymes from prokaryotes exist as monomers. Recent structural analyses of the mitochondrial respiratory supercomplex revealed that CcO monomer associates with complex I and complex III, indicating that the monomeric state is functionally important. In this study, we prepared monomeric and dimeric bovine CcO, stabilized using amphipol, and showed that the monomer had high activity. In addition, using a newly synthesized detergent, we determined the oxidized and reduced structures of monomer with resolutions of 1.85 and 1.95 Å, respectively. Structural comparison of the monomer and dimer revealed that a hydrogen bond network of water molecules is formed at the entry surface of the proton transfer pathway, termed the K-pathway, in monomeric CcO, whereas this network is altered in dimeric CcO. Based on these results, we propose that the monomer is the activated form, whereas the dimer can be regarded as a physiological standby form in the mitochondrial membrane. We also determined phospholipid structures based on electron density together with the anomalous scattering effect of phosphorus atoms. Two cardiolipins are found at the interface region of the supercomplex. We discuss formation of the monomeric CcO, dimeric CcO, and supercomplex, as well as their role in regulation of CcO activity.
Assuntos
Complexo IV da Cadeia de Transporte de Elétrons/química , Mitocôndrias Cardíacas/enzimologia , Animais , Cardiolipinas/química , Bovinos , Cristalografia por Raios X , Digitonina/química , Transporte de Elétrons , Complexo I de Transporte de Elétrons/química , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Membranas Mitocondriais/enzimologia , Conformação Molecular , Oxirredução , Oxigênio/química , Fosfolipídeos/química , Fósforo/química , Ligação Proteica , Conformação Proteica , Multimerização ProteicaRESUMO
A 1,4-addition reaction of 5H-oxazol-4-ones to alkylidene ß-ketoesters, which was catalyzed by using chiral guanidines via a dynamic kinetic resolution process that involved geometric isomerization of the alkylidene ß-ketoesters, was developed. This method allowed using E,Z isomeric mixture of various acyclic alkylidene ß-ketoesters to obtain the products stereoselectively. The relation between the geometry and the stereoselectivity of products was investigated, and the derivatization of the products to the corresponding α-acyl-γ-lactone was performed.
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A unique electron-accepting analog of vitamin K1 found in photosystem I in several species of oxygenic photosynthetic microorganisms was confirmed to be 5'-hydroxyphylloquinone (1) through stereo-uncontrolled synthesis. Furthermore, the stereochemistry of 1 obtained from Synechococcus sp. PCC 7942 was assigned to be 5'S using proline-catalyzed stereocontrolled reactions.
Assuntos
Complexo de Proteína do Fotossistema I/metabolismo , Vitamina K 1/análogos & derivados , Transporte de Elétrons , Estereoisomerismo , Synechococcus/metabolismo , Vitamina K 1/química , Vitamina K 1/metabolismoRESUMO
2-Formyl(thio)esters were utilized as pronucleophiles to obtain less-accessible acyclic chiral building blocks bearing versatile functional groups on a quaternary carbon atom for enantioselective 1,4-addition to vinylketones. To achieve high enantioselectivity in the present 1,4-addition reaction, thiourea-tertiary amines containing a bulky chiral backbone were developed as catalysts, and several derivatizations of the products were performed to demonstrate the synthetic utility of the products.
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ABSTRACT: Immune checkpoint inhibitors can revive exhausted helper T-cells, and inflammatory cell reactivation may cause autoimmune disease-like conditions. Drug-induced arthritis is an immune-related adverse event, but the diagnostic approach is undefined. We present the diagnostic utility of 99m Tc-MDP bone scintigraphy for nivolumab-induced inflammatory arthritis. A 67-year-old man with hypopharyngeal carcinoma presented bilateral multiple metacarpophalangeal joint pain and swelling at each nivolumab administration. Regular imaging findings were atypical for inflammatory arthritis and did not fulfill the criteria for rheumatoid arthritis. We diagnosed nivolumab-induced inflammatory arthritis based on clinical symptoms and the symmetrical moderate uptake of the affected joints on 99m Tc-MDP bone scintigraphy.
Assuntos
Artrite Reumatoide , Nivolumabe , Masculino , Humanos , Idoso , Nivolumabe/efeitos adversos , Medronato de Tecnécio Tc 99m , Cintilografia , Tomografia Computadorizada por Raios X , Tecnécio , Artrite Reumatoide/diagnóstico por imagem , Artrite Reumatoide/tratamento farmacológicoRESUMO
An asymmetric 1,4-addition reaction of 5H-oxazol-4-ones with alkynyl carbonyl compounds was developed, and, for the first time, high enantiomeric and geometric control was achieved to afford the thermodynamically unstable Z-isomer predominantly using chiral guanidine catalysts bearing a hydroxy group at the appropriate position. The method provides synthetically useful γ-butenolide ester bearing a chiral quaternary stereogenic center.
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A new chiral bicyclic guanidine-catalyzed direct catalytic aldol reaction of 5H-oxazol-4-ones with aldehydes has been developed. The present aldol reaction proceeds smoothly with high enantioselectivity using bicyclic guanidines bearing a hydroxy group at the appropriate position, and various combinations of 5H-oxazol-4-ones and aldehydes are applicable. The method provides synthetically useful alpha,beta-dihydroxycarboxylates bearing a chiral quaternary stereogenic center at the alpha-carbon atom.
Assuntos
Aldeídos/química , Guanidina/química , Oxazóis/química , Catálise , EstereoisomerismoRESUMO
We have developed a general, robust, and cost-effective method for the (E)- or (Z)-stereocomplementary enol tosylation of beta-ketoesters using TsCl- N-methylimidazole (NMI)-Et3N or LiOH. TsCl coupled with NMI formed a highly reactive N-sulfonylammonium intermediate. Stereocongested secondary alcohols were smoothly sulfonylated using Ts(Ms)Cl-NMI-Et3N. beta-Ketoesters underwent (E)-selective tosylation using TsCl-NMI-Et3N and (Z)-selective tosylation using TsCl-NMI-LiOH (total of 23 examples; 60%-99% yield). Stereoretentive Negishi and Sonogashira couplings using enol tosylates proceeded successfully to give trisubstituted alpha,beta-unsaturated esters.
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A pentafluorophenylammonium triflate (PFPAT) catalyst (5 mol %) successfully promoted C-acylation of enol silyl ethers with acid chloride to produce various beta-diketones (12 examples; 62-92% yield). Similarly, C-acylation of ketene silyl acetals or ketene silyl thioacetals (i.e., crossed Claisen condensation) proceeded smoothly to provide not only alpha-monoalkylated beta-keto (thio)esters but also thermodynamically unfavorable (less accessible) alpha,alpha-dialkylated beta-keto (thio)esters in good to excellent yield (38 examples; 60-92% yield).
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[Structure: see text] A powerful Ti-crossed Claisen condensation between ketene silyl acetals (KSAs) and acid chlorides was successfully performed to give alpha-monoalkylated esters and thermodynamically unfavorable (less accessible) alpha,alpha-dialkylated beta-keto esters in good yield (46 examples; 41-98% yield). A closely related reaction between ketene silyl thioacetals (KSTAs) and acid chlorides also proceeded smoothly to give alpha-monoalkylated and alpha,alpha-dialkylated beta-keto thioesters (21 examples; 61-97% yield). The present protocol was extended to the direct condensation of KSAs with carboxylic acids (14 examples; 71-97% yield).
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We have developed a practical crossed Claisen condensation between ketene silyl acetals and methyl esters using catalytic NaOH to obtain alpha-monoalkylated beta-keto esters and inaccessible alpha,alpha-dialkylated beta-keto esters.
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We have developed an efficient method for the preparation of enol silyl ethers using novel agents, silazanes together with NaH or DBU catalyst, wherein TMS and TBDMS groups were smoothly and chemoselectively introduced into ketones and aldehydes under mild conditions.
RESUMO
Asymmetric Ti-crossed Claisen condensation utilizing the dioxane-2,5-dione chiral template and its successful application to total synthesis of chiral alternaric acid are described.
Assuntos
Ácidos/síntese química , Titânio/química , Ácidos/química , Estrutura MolecularRESUMO
BACKGROUND: Venous thromboembolism (VTE) is a critical complication after hip replacement surgery, so both early diagnosis and prophylaxis are important. The purpose of this study was to clarify the rapid changes of the fibrin monomer complex (FMC) and soluble fibrin (SF) during the perioperative period of hip replacement surgery. METHODS: The subjects were 32 patients (7 men, 25 women) who underwent elective hip replacement surgery between November 2004 and January 2006. Their ages ranged between 34 to 82 years (mean 56.8 years). According to their thromboembolic risk, the patients received different prophylaxis: unfractionated heparin (4 patients), danaparoid sodium (14 patients), or mechanical therapy only (14 patients). RESULTS: FMC and SF became rapidly elevated during the operation and just after surgery but declined to preoperational levels 3 days after surgery; they were higher in lupus anticoagulant (LA)-positive patients. In contrast, FDP and D-dimer had gradually become elevated 3 and 7 days after surgery. According to venous ultrasonography and lung perfusion scintigraphy, VTE occurred in 7 patients overall (21.9%). The incidence of VTE was 7.1% in the danaparoid group, whereas it was 35.7% in the mechanical therapy group. We also found that danaparoid sodium rapidly decreased FMC and SF within 3 days. CONCLUSIONS: FMC and SF were rapidly elevated during hip replacement surgery and differentiated in LA-positive and LA-negative patients.
Assuntos
Artroplastia de Quadril , Produtos de Degradação da Fibrina e do Fibrinogênio/análise , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticoagulantes/uso terapêutico , Artroplastia de Quadril/efeitos adversos , Sulfatos de Condroitina/uso terapêutico , Dermatan Sulfato/uso terapêutico , Feminino , Fibrina/análise , Heparina/uso terapêutico , Heparitina Sulfato/uso terapêutico , Humanos , Período Intraoperatório , Inibidor de Coagulação do Lúpus/sangue , Masculino , Pessoa de Meia-Idade , Período Pós-Operatório , Tromboembolia Venosa/sangue , Tromboembolia Venosa/etiologia , Tromboembolia Venosa/prevenção & controleRESUMO
We developed an efficient, practical, robust method for the regio- and stereoselective preparation of (E)-ketene trimethylsilyl acetals (KSAs) derived from tert-butyl esters 1. The reaction was performed under convenient reaction conditions; LDA-TMSCl, 0-5 degrees C, and cyclopentyl methyl ether (CPME) solvent. Two kinds of (Z)- and (E)-KSAs derived from alpha-oxygen and alpha-nitrogen-substituted tert-butyl esters, respectively, were also obtained in good yield. The present protocol was successfully applied to a stereocontrolled preparation of useful, but highly reactive (less accessible) beta-ketoester-derived tert-butyl (1Z,3E)-1,3-bis(TMS)dienol ethers 2.
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An efficient TiCl(4)-Et(3)N or Bu(3)N-promoted aldol-type addition of phenyl and thiophenyl esters or thioaryl esters with aldehydes and ketones was performed (total 46 examples). The present method is advantageous from atom-economical and cost-effective viewpoints; good to excellent yields, moderate to good syn-selectivity, substrate variations, reagent availability, and simple procedures. Utilizing the present reaction as the key step, an efficient short synthesis of three lactone [2(5H)-furanone] analogs of jasmine perfumes was performed. Among them, the lactone analog of cis-jasmone had a unique perfume property (tabac).
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We encountered a unique phenomenon of reaction velocity reversal during the silylation between mixed simple alcohols (A; AOH) and alpha- or beta-hydroxyketones (B; BOH). The present reaction system using anilinosilanes 1a [PhNH(TMS)] (TMS-A) and 1b [PhNH(TES)] (TES-A) with the catalytic TBAF (0.02 equiv) reagent showed that the order of silylation-velocity between the independent system and the mixed system was distinctively reversed [nu(A) > nu(B) approximately nu(B(mix)) > nu(A(mix))]. A total of seven examples indicate its high generality: AOH = linalool, 3-octanol; BOH = valeroin, benzoin, 5-hydroxy-4-methyl-3-undecanone. Time-dependent IR spectroscopy analysis rationally supported this speculation.
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TiCl4-Lewis base (AcOEt, CH3NO2) complexes smoothly deprotected tert-butyldimethylsilyl (TBDMS) ethers. The reaction velocity with these complexes, which seemed less reactive due to the influence of Lewis bases, was considerably greater than that with TiCl4 alone. Selective desilylations between aliphatic and aromatic TBDMS ethers (1 and 5), between 1 and benzyl, allyl, tosyl, methoxyphenyl, and chloroacetyl ethers (13, 14, 15, 16, and 17), and between TBDMS and TBDPS ethers (18 and 19) were successfully performed. Desilylation of TBDMS-aldol, acyloin, and beta-lactam analogues 9-12 proceeded smoothly due to anchimeric assistance by the neighboring carbonyl groups. The present method was successfully applied to the practical synthesis of 1beta-methylcarbapenems 20a'-f'.
Assuntos
Carbapenêmicos/síntese química , Éteres/química , Nitritos/química , Compostos de Organossilício/química , Titânio/química , Carbapenêmicos/química , Estrutura Molecular , EstereoisomerismoRESUMO
Ti-crossed-Claisen condensation between a 1:1 mixture of carboxylic esters and acid chlorides promoted by TiCl4-Bu3N-N-methylimidazole proceeded successfully to give various beta-keto esters in good yields with excellent selectivities (19 examples, approximately 48-95% yield; cross/self-selectivity = approximately 96/4-99/1). The present method was extended to the condensation between a 1:1 mixture of carboxylic acids and carboxylic esters (six examples, approximately 70-92% yield; cross/self-selectivity = approximately 91/9-99/1). To demonstrate the utility of the present two Ti-crossed-Claisen condensations, we performed a couple of efficient short-step syntheses of two natural, representative, and useful perfumes, cis-jasmone and (R)-muscone.