A rice GT61 glycosyltransferase possesses dual activities mediating 2-O-xylosyl and 2-O-arabinosyl substitutions of xylan.

MAIN CONCLUSION: A member of the rice GT61 clade B is capable of transferring both 2-O-xylosyl and 2-O-arabinosyl residues onto xylan and another member specifically catalyses addition of 2-O-xylosyl residue onto xylan. Grass xylan is substituted predominantly with 3-O-arabinofuranose (Araf) as well as with some minor side chains, such as 2-O-Araf and 2-O-(methyl)glucuronic acid [(Me)GlcA]. 3-O-Arabinosylation of grass xylan has been shown to be catalysed by grass-expanded clade A members of the glycosyltransferase family 61. However, glycosyltransferases mediating 2-O-arabinosylation of grass xylan remain elusive. Here, we performed biochemical studies of two rice GT61 clade B members and found that one of them was capable of transferring both xylosyl (Xyl) and Araf residues from UDP-Xyl and UDP-Araf, respectively, onto xylooligomer acceptors, whereas the other specifically catalysed Xyl transfer onto xylooligomers, indicating that the former is a xylan xylosyl/arabinosyl transferase (named OsXXAT1 herein) and the latter is a xylan xylosyltransferase (named OsXYXT2). Structural analysis of the OsXXAT1- and OsXYXT2-catalysed reaction products revealed that the Xyl and Araf residues were transferred onto O-2 positions of xylooligomers. Furthermore, we demonstrated that OsXXAT1 and OsXYXT2 were able to substitute acetylated xylooligomers, but only OsXXAT1 could xylosylate GlcA-substituted xylooligomers. OsXXAT1 and OsXYXT2 were predicted to adopt a GT-B fold structure and molecular docking revealed candidate amino acid residues at the predicted active site involved in binding of the nucleotide sugar donor and the xylohexaose acceptor substrates. Together, our results establish that OsXXAT1 is a xylan 2-O-xylosyl/2-O-arabinosyl transferase and OsXYXT2 is a xylan 2-O-xylosyltransferase, which expands our knowledge of roles of the GT61 family in grass xylan synthesis.

Biochemical characterization of rice xylan biosynthetic enzymes in determining xylan chain elongation and substitutions.

Grass xylan consists of a linear chain of ß-1,4-linked xylosyl residues that often form domains substituted only with either arabinofuranose (Araf) or (methyl)glucuronic acid [(Me)GlcA] residues and it lacks the unique reducing end tetrasaccharide sequence found in dicot xylan. The mechanism of how grass xylan backbone elongation is initiated and how its distinctive substitution pattern is determined remain elusive. Here, we performed biochemical characterization of rice xylan biosynthetic enzymes, including xylan synthases, glucuronyltransferases and methyltransferases. Activity assays of rice xylan synthases demonstrated that they required short xylooligomers as acceptors for their activities. While rice xylan glucuronyltransferases effectively glucuronidated unsubstituted xylohexaose acceptors, they transferred little GlcA residues onto Araf-substituted xylohexaoses and rice xylan 3-O-arabinosyltransferase could not arabinosylate GlcA-substituted xylohexaoses, indicating that their intrinsic biochemical properties may contribute to the distinctive substitution pattern of rice xylan. In addition, we found that rice xylan methyltransferase exhibited a low substrate binding affinity, which may explain the partial GlcA methylation in rice xylan. Furthermore, immunolocalization of xylan in xylem cells of both rice and Arabidopsis showed that it was deposited together with cellulose in secondary walls without forming xylan-rich nanodomains. Together, our findings provide new insights into the biochemical mechanisms underlying xylan backbone elongation and substitutions in grass species.

A mechanism for hereditary angioedema caused by a methionine-379-to-lysine substitution in kininogens.

ABSTRACT: Hereditary angioedema (HAE) is associated with episodic kinin-induced swelling of the skin and mucosal membranes. Most patients with HAE have low plasma C1-inhibitor activity, leading to increased generation of the protease plasma kallikrein (PKa) and excessive release of the nanopeptide bradykinin from high-molecular-weight kininogen (HK). However, disease-causing mutations in at least 10% of patients with HAE appear to involve genes for proteins other than C1-inhibitor. A point mutation in the Kng1 gene encoding HK and low-molecular weight kininogen (LK) was identified recently in a family with HAE. The mutation changes a methionine (Met379) to lysine (Lys379) in both proteins. Met379 is adjacent to the Lys380-Arg381 cleavage site at the N-terminus of the bradykinin peptide. Recombinant wild-type (Met379) and variant (Lys379) versions of HK and LK were expressed in HEK293 cells. PKa-catalyzed kinin release from HK and LK was not affected by the Lys379 substitutions. However, kinin release from HK-Lys379 and LK-Lys379 catalyzed by the fibrinolytic protease plasmin was substantially greater than from wild-type HK-Met379 and LK-Met379. Increased kinin release was evident when fibrinolysis was induced in plasma containing HK-Lys379 or LK-Lys379 compared with plasma containing wild-type HK or LK. Mass spectrometry revealed that the kinin released from wild-type and variant kininogens by PKa is bradykinin. Plasmin also released bradykinin from wild-type kininogens but cleaved HK-Lys379 and LK-Lys379 after Lys379 rather than Lys380, releasing the decapeptide Lys-bradykinin (kallidin). The Met379Lys substitutions make HK and LK better plasmin substrates, reinforcing the relationship between fibrinolysis and kinin generation.

Intraobserver and Interobserver Reliability of the Snyder and Expanded SLAP Classification System: A Video Study.

Background: Superior labral anterior and posterior (SLAP) tears are a common finding in overhead athletes. The original classification system produced by Snyder in 1990 contained 4 types of SLAP tears and was later expanded to 10 types. The classification has been challenging because of inconsistencies between surgeons making diagnoses and treatments based on the diagnosis. Furthermore, patient factors-such as age and sports played-affect the treatment algorithms, even across similarly classified SLAP tears. Purpose: To (1) assess the interobserver and intraobserver reliability of the Snyder and expanded SLAP (ESLAP) classification systems and (2) determine the consistency of treatment for a given SLAP tear depending on different clinical scenarios. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: A total of 20 arthroscopic surgical videos and magnetic resonance imaging scans of patients with SLAP tears were sent to 20 orthopaedic sports medicine surgeons at various stages of training. Surgeons were asked to identify the type of SLAP tear using the Snyder and ESLAP classifications. Surgeons were then asked to determine the treatment for a SLAP tear using 4 clinical scenarios: (1) in the throwing arm of an 18-year-old pitcher; (2) in the dominant arm of an 18-year-old overhead athlete; (3) a 35-year-old overhead athlete; (4) or a 50-year-old overhead athlete. Responses were recorded, and the cases were shuffled and sent back 6 weeks after the initial responses. Results were then analyzed using the Fleiss kappa coefficient (κ) to determine interobserver and intraobserver degrees of agreement. Results: There was moderate intraobserver reliability in both the Snyder and ESLAP classifications (κ = 0.52) and fair interobserver reliability for both classification systems (Snyder, κ = 0.31; ESLAP, κ = 0.30; P < .0001) among all surgeons. Additionally, there was only fair agreement (κ = 0.30; P < .0001) for the treatment modalities chosen by the reviewers for each case. Conclusion: This study demonstrated that SLAP tears remain a challenging problem for orthopaedic surgeons in diagnostics and treatment plans. Therefore, care should be taken in the preoperative discussion with the patient to consider all the possible treatment options because this may affect the postoperative recovery period and patient expectations.

An Arabidopsis family GT106 glycosyltransferase is essential for xylan biosynthesis and secondary wall deposition.

MAIN CONCLUSION: We have demonstrated that the Arabidopsis FRA9 (fragile fiber 9) gene is specifically expressed in secondary wall-forming cells and essential for the synthesis of the unique xylan reducing end sequence. Xylan is made of a linear chain of ß-1,4-linked xylosyl (Xyl) residues that are often substituted with (methyl)glucuronic acid [(Me)GlcA] side chains and may be acetylated at O-2 and/or O-3. The reducing end of xylan from gymnosperms and dicots contains a unique tetrasaccharide sequence consisting of ß-D-Xylp-(1 → 3)-α-L-Rhap-(1 → 2)-α-D-GalpA-(1 → 4)-D-Xylp, the synthesis of which requires four different glycosyltransferase activities. Genetic analysis in Arabidopsis thaliana has so far implicated three glycosyltransferase genes, FRA8 (fragile fiber 8), IRX8 (irregular xylem 8) and PARVUS, in the synthesis of this unique xylan reducing end sequence. Here, we report the essential role of FRA9, a member of glycosyltransferase family 106 (GT106), in the synthesis of this sequence. The expression of the FRA9 gene was shown to be induced by secondary wall master transcriptional regulators and specifically associated with secondary wall-forming cells, including xylem and fiber cells. T-DNA knockout mutation of the FRA9 gene caused impaired secondary cell wall thickening in leaf veins and a severe arrest of plant growth. RNA interference (RNAi) downregulation of FRA9 led to a significant reduction in secondary wall thickening of fibers, a deformation of xylem vessels and a decrease in xylan content. Structural analysis of xylanase-released xylooligomers revealed that RNAi downregulation of FRA9 resulted in a diminishment of the unique xylan reducing end sequence and complete methylation of xylan GlcA side chains, chemotypes reminiscent of those of the fra8, irx8 and parvus mutants. Furthermore, two FRA9 close homologs from Populus trichocarpa were found to be wood-associated functional orthologs of FRA9. Together, our findings uncover a member of the GT106 family as a new player involved in the synthesis of the unique reducing end sequence of xylan.

Independent recruitment of glycosyltransferase family 61 members for xylan substitutions in conifers.

MAIN CONCLUSION: Several pine members of the gymnosperm-specific GT61 clades were demonstrated to be arabinosyltransferases and xylosyltransferases catalyzing the transfer of 2-O-Araf, 3-O-Araf and 2-O-Xyl side chains onto xylooligomer acceptors, indicating their possible involvement in Araf and Xyl substitutions of xylan in pine. Xylan in conifer wood is substituted at O-2 with methylglucuronic acid (MeGlcA) as well as at O-3 with arabinofuranose (Araf), which differs from xylan in dicot wood that is typically decorated with MeGlcA but not Araf. Currently, glycosyltransferases responsible for conifer xylan arabinosylation have not been identified. Here, we investigated the roles of pine glycosyltransferase family 61 (GT61) members in xylan substitutions. Biochemical characterization of four pine wood-associated GT61 members showed that they exhibited three distinct glycosyltransferase activities involved in xylan substitutions. Two of them catalyzed the addition of 2-O-α-Araf or 3-O-α-Araf side chains onto xylooligomer acceptors and thus were named Pinus taeda xylan 2-O-arabinosyltransferase 1 (PtX2AT1) and 3-O-arabinosyltransferase 1 (PtX3AT1), respectively. Two other pine GT61 members were found to be xylan 2-O-xylosyltransferases (PtXYXTs) adding 2-O-ß-Xyl side chains onto xylooligomer acceptors. Furthermore, sequential reactions with PtX3AT1 and the PtGUX1 xylan glucuronyltransferase demonstrated that PtX3AT1 could efficiently arabinosylate glucuronic acid (GlcA)-substituted xylooligomers and likewise, PtGUX1 was able to add GlcA side chains onto 3-O-Araf-substituted xylooligomers. Phylogenetic analysis revealed that PtX2AT1, PtX3AT1 and PtXYXTs resided in three gymnosperm-specific GT61 clades that are separated from the grass-expanded GT61 clade harboring xylan 3-O-arabinosyltransferases and 2-O-xylosyltransferases, suggesting that they might have been recruited independently for xylan substitutions in gymnosperms. Together, our findings have established several pine GT61 members as xylan 2-O- and 3-O-arabinosyltransferases and 2-O-xylosyltransferases and they indicate that pine xylan might also be substituted with 2-O-Araf and 2-O-Xyl side chains.

4-Oxo-2-nonenal (4-ONE)-Induced Degradation of Bovine Skeletal Muscle Proteins.

Lipids are an important component of meat, as they provide desirable sensory characteristics and nutritional benefits. However, lipids are susceptible to degradation through oxidation and produce toxic oxidative byproducts. 4-Oxo-2-nonenal (4-ONE) is an oxidative byproduct that is highly reactive and cytotoxic. In this study, we investigated the influence of 4-ONE-induced protein degradation on fresh and gastric digested bovine skeletal muscle proteins. The results indicated that 4-ONE naturally forms in fresh muscle proteins. We report here for the first time that 4-ONE causes severe degradation of bovine skeletal muscle proteins. An SDS-PAGE gel analysis showed evidence that the skeletal muscle proteins attenuated over the incubation time, as the density of the protein bands faded significantly after 120 h. Additionally, protein and band density analyses showed a significant decrease in protein abundance and band densities throughout the incubation time. This study revealed that the lipid oxidation byproduct, 4-oxo-2-nonenal (4-ONE) is responsible for causing skeletal muscle protein degradation. Future studies should assess the bioprotective role of antioxidants and other food ingredients for their potential to prevent the formation and/or detoxification of 4-ONE in meat.

Identification of xylan arabinosyl 2-O-xylosyltransferases catalyzing the addition of 2-O-xylosyl residue onto arabinosyl side chains of xylan in grass species.

Grass xylan, the major hemicellulose in both primary and secondary cell walls, is heavily decorated with α-1,3-linked arabinofuranosyl (Araf) residues that may be further substituted at O-2 with xylosyl (Xyl) or Araf residues. Although xylan 3-O-arabinosyltransferases (XATs) catalyzing 3-O-Araf addition onto xylan have been characterized, glycosyltransferases responsible for the transfer of 2-O-Xyl or 2-O-Araf onto 3-O-Araf residues of xylan to produce the Xyl-Araf and Araf-Araf disaccharide side chains remain to be identified. In this report, we showed that a rice GT61 member, named OsXAXT1 (xylan arabinosyl 2-O-xylosyltransferase 1) herein, was able to mediate the addition of Xyl-Araf disaccharide side chains onto xylan when heterologously co-expressed with OsXAT2 in the Arabidopsis gux1/2/3 (glucuronic acid substitution of xylan 1/2/3) triple mutant that lacks any glycosyl substitutions. Recombinant OsXAXT1 protein expressed in human embryonic kidney 293 cells exhibited a xylosyltransferase activity catalyzing the addition of Xyl from UDP-Xyl onto arabinosylated xylooligomers. Consistent with its function as a xylan arabinosyl 2-O-xylosyltransferase, CRISPR-Cas9-mediated mutations of the OsXAXT1 gene in transgenic rice plants resulted in a reduction in the level of Xyl-Araf disaccharide side chains in xylan. Furthermore, we revealed that XAXT1 close homologs from several other grass species, including switchgrass, maize, and Brachypodium, possessed the same functions as OsXAXT1, indicating functional conservation of XAXTs in grass species. Together, our findings establish that grass XAXTs are xylosyltransferases catalyzing Xyl transfer onto O-2 of Araf residues of xylan to form the Xyl-Araf disaccharide side chains, which furthers our understanding of genes involved in xylan biosynthesis.

Amiodarone induced movement disorder after cardiac arrest - A case report.

We describe a case of new onset movement disorder in a patient with ventricular tachycardia storm supported with peripheral VA ECMO. The differential diagnosis of abnormal movements in a post cardiac arrest patient requiring temporary mechanical circulatory support for cardiogenic shock is explored.

A mechanism for hereditary angioedema caused by a lysine 311-to-glutamic acid substitution in plasminogen.

Patients with hereditary angioedema (HAE) experience episodes of bradykinin (BK)-induced swelling of skin and mucosal membranes. The most common cause is reduced plasma activity of C1 inhibitor, the main regulator of the proteases plasma kallikrein (PKa) and factor XIIa (FXIIa). Recently, patients with HAE were described with a Lys311 to glutamic acid substitution in plasminogen (Plg), the zymogen of the protease plasmin (Plm). Adding tissue plasminogen activator to plasma containing Plg-Glu311 vs plasma containing wild-type Plg (Plg-Lys311) results in greater BK generation. Similar results were obtained in plasma lacking prekallikrein or FXII (the zymogens of PKa and FXIIa) and in normal plasma treated with a PKa inhibitor, indicating Plg-Glu311 induces BK generation independently of PKa and FXIIa. Plm-Glu311 cleaves high and low molecular weight kininogens (HK and LK, respectively), releasing BK more efficiently than Plm-Lys311. Based on the plasma concentrations of HK and LK, the latter may be the source of most of the BK generated by Plm-Glu311. The lysine analog ε-aminocaproic acid blocks Plm-catalyzed BK generation. The Glu311 substitution introduces a lysine-binding site into the Plg kringle 3 domain, perhaps altering binding to kininogens. Plg residue 311 is glutamic acid in most mammals. Glu311 in patients with HAE, therefore, represents reversion to the ancestral condition. Substantial BK generation occurs during Plm-Glu311 cleavage of human HK, but not mouse HK. Furthermore, mouse Plm, which has Glu311, did not liberate BK from human kininogens more rapidly than human Plg-Lys311. This indicates Glu311 is pathogenic in the context of human Plm when human kininogens are the substrates.

Functional analysis of GT61 glycosyltransferases from grass species in xylan substitutions.

MAIN CONCLUSION: Multiple rice GT61 members were demonstrated to be xylan arabinosyltransferases (XATs) mediating 3-O-arabinosylation of xylan and the functions of XATs and xylan 2-O-xylosyltransferases were shown to be conserved in grass species. Xylan is the major hemicellulose in the cell walls of grass species and it is typified by having arabinofuranosyl (Araf) substitutions. In this report, we demonstrated that four previously uncharacterized, Golgi-localized glycosyltransferases residing in clade A or B of the rice GT61 family were able to mediate 3-O-arabinosylation of xylan when heterologously expressed in the Arabidopsis gux1/2/3 triple mutant. Biochemical characterization of their recombinant proteins established that they were xylan arabinosyltransferases (XATs) capable of transferring Araf residues onto xylohexaose acceptors, and thus they were named OsXAT4, OsXAT5, OsXAT6 and OsXAT7. OsXAT5 and the previously identified OsXAT2 were shown to be able to arabinosylate xylooligomers with a degree of polymerization of as low as 3. Furthermore, a number of XAT homologs from maize, sorghum, Brachypodium and switchgrass were found to exhibit activities catalyzing Araf transfer onto xylohexaose, indicating that they are XATs involved in xylan arabinosylation in these grass species. Moreover, we revealed that homologs of another GT61 member, xylan 2-O-xylosyltransferase (XYXT1), from these grass species could mediate 2-O-xylosylation of xylan when expressed in the Arabidopsis gux1/2/3 mutant. Together, our findings indicate that multiple OsXATs are involved in 3-O-arabinosylation of xylan and the functions of XATs and XYXTs are conserved in grass species.

A Single Xyloglucan Xylosyltransferase Is Sufficient for Generation of the XXXG Xylosylation Pattern of Xyloglucan.

Xyloglucan is the most abundant hemicellulose in the primary cell walls of dicots. Dicot xyloglucan is the XXXG type consisting of repeating units of three consecutive xylosylated Glc residues followed by one unsubstituted Glc. Its xylosylation is catalyzed by xyloglucan 6-xylosyltransferases (XXTs) and there exist five XXTs (AtXXT1-5) in Arabidopsis. While AtXXT1 and AtXXT2 have been shown to add the first two Xyl residues in the XXXG repeat, which XXTs are responsible for the addition of the third Xyl residue remains elusive although AtXXT5 was a proposed candidate. In this report, we generated recombinant proteins of all five Arabidopsis XXTs and one rice XXT (OsXXT1) in the mammalian HEK293 cells and investigated their ability to sequentially xylosylate Glc residues to generate the XXXG xylosylation pattern. We found that like AtXXT1/2, AtXXT4 and OsXXT1 could efficiently xylosylate the cellohexaose (G6) acceptor to produce mono- and di-xylosylated G6, whereas AtXXT5 was only barely capable of adding one Xyl onto G6. When AtXXT1-catalyzed products were used as acceptors, AtXXT1/2/4 and OsXXT1, but not AtXXT5, were able to xylosylate additional Glc residues to generate tri- and tetra-xylosylated G6. Further characterization of the tri- and tetra-xylosylated G6 revealed that they had the sequence of GXXXGG and GXXXXG with three and four consecutive xylosylated Glc residues, respectively. In addition, we have found that although tri-xylosylation occurred on G6, cello-oligomers with a degree of polymerization of 3 to 5 could only be mono- and di-xylosylated. Together, these results indicate that each of AtXXT1/2/4 and OsXXT1 is capable of sequentially adding Xyl onto three contiguous Glc residues to generate the XXXG xylosylation pattern and these findings provide new insight into the biochemical mechanism underlying xyloglucan biosynthesis.

Comparison of Anticoagulation Strategies in Patients Requiring Venovenous Extracorporeal Membrane Oxygenation: Heparin Versus Bivalirudin.

OBJECTIVES: Extracorporeal membrane oxygenation is a life-sustaining therapy for severe respiratory failure. Extracorporeal membrane oxygenation circuits require systemic anticoagulation that creates a delicate balance between circuit-related thrombosis and bleeding-related complications. Although unfractionated heparin is most widely used anticoagulant, alternative agents such as bivalirudin have been used. We sought to compare extracorporeal membrane oxygenation circuit thrombosis and bleeding-related outcomes in respiratory failure patients receiving either unfractionated heparin or bivalirudin for anticoagulation on venovenous extracorporeal membrane oxygenation support. DESIGN: Retrospective cohort study. SETTING: Single-center, cardiothoracic ICU. PATIENTS: Consecutive patients requiring venovenous extracorporeal membrane oxygenation who were maintained on anticoagulation between 2013 and 2020. INTERNVENTIONS: IV bivalirudin or IV unfractionated heparin. MEASUREMENTS AND MAIN RESULTS: Primary outcomes were the presence of extracorporeal membrane oxygenation in-circuit-related thrombotic complications and volume of blood products administered during extracorporeal membrane oxygenation duration. One hundred sixty-two patients receiving unfractionated heparin were compared with 133 patients receiving bivalirudin for anticoagulation on venovenous extracorporeal membrane oxygenation. In patients receiving bivalirudin, there was an overall decrease in the number of extracorporeal membrane oxygenation circuit thrombotic complications (p < 0.005) and a significant increase in time to circuit thrombosis (p = 0.007). Multivariable Cox regression found that heparin was associated with a significant increase in risk of clots (Exp[B] = 2.31, p = 0.001). Patients who received bivalirudin received significantly less volume of packed RBCs, fresh frozen plasma, and platelet transfusion (p < 0.001 for each). There was a significant decrease in the number major bleeding events in patients receiving bivalirudin, 40.7% versus 11.7%, p < 0.001. CONCLUSIONS: Patients receiving bivalirudin for systemic anticoagulation on venovenous extracorporeal membrane oxygenation experienced a decrease in the number of extracorporeal membrane oxygenation circuit-related thrombotic events as well as a significant decrease in volume of blood products administered.

Propofol administration during catheter-directed interventions for intermediate-risk pulmonary embolism is associated with major adverse events.

OBJECTIVE: Catheter-directed interventions (CDIs) have been increasingly used for selected patients with acute intermediate-risk (submassive) pulmonary embolism (sPE) to prevent decompensation, mortality, and potentially long-term sequelae. The purpose of the present study was to determine whether the choice of anesthetic during these interventions has an effect on the postprocedural outcomes. METHODS: Patients who had undergone CDI for acute sPE from 2009 to 2019 were identified and grouped according to the intraprocedural use of propofol. The primary outcome was in-hospital intra- or postprocedural major adverse events, defined as the need for intubation, progression to massive pulmonary embolism, and in-hospital death. Major bleeding events (ie, intracerebral hemorrhage, transfusion of ≥2 U, the need for reintervention) were also assessed. Multivariate logistic regression analysis was used to evaluate the predictors of the studied outcomes. RESULTS: During the study period, 340 patients (age, 58.74 ± 15.22 years; 51.2% men) had undergone CDI for sPE (85 standard thrombolysis, 229 ultrasound-assisted thrombolysis, 26 suction thrombectomy). Propofol had been used for 36 patients (10.6%); the remaining 304 patients (89.4%) had received midazolam plus fentanyl, morphine, or hydromorphone for anesthesia. The baseline characteristics of both groups were similar, except for age, hypertension, American Society of Anesthesiologists class, and procedure type, with ultrasound-assisted thrombolysis the predominant procedure for the no-propofol group (74%). Overall, 18 patients had experienced ≥1 events of the composite outcome (ie, 10 intubations, 11 decompensations, 2 surgical conversions, 3 deaths). The propofol group had a significantly greater adverse event rate (13.8%; n = 5) compared with the no-propofol group (4.2%; n = 13; P = .015). On multivariate analysis, propofol was still a predictive factor for adverse events (odds ratio, 3.79; 95% confidence interval, 1.11-12.93; P = .03). A total of 16 patients had experienced major bleeding or other procedure-related events, including stroke in 4 (1.17%), coronary sinus perforation in 1, tricuspid valve rupture in 1, and the need for transfusion in 10 patients. The type of intervention (ie, standard thrombolysis, ultrasound-assisted thrombolysis, suction thrombectomy) was not a predictive factor for any studied outcome. CONCLUSIONS: CDIs are low-risk procedures with minimal postoperative morbidity and mortality in the setting of acute sPE. However, the use of propofol for intraprocedural sedation should be avoided because it can have detrimental effects.

A Group of O-Acetyltransferases Catalyze Xyloglucan Backbone Acetylation and Can Alter Xyloglucan Xylosylation Pattern and Plant Growth When Expressed in Arabidopsis.

Xyloglucan is a major hemicellulose in plant cell walls and exists in two distinct types, XXXG and XXGG. While the XXXG-type xyloglucan from dicot species only contains O-acetyl groups on side-chain galactose (Gal) residues, the XXGG-type xyloglucan from Poaceae (grasses) and Solanaceae bears O-acetyl groups on backbone glucosyl (Glc) residues. Although O-acetyltransferases responsible for xyloglucan Gal acetylation have been characterized, the biochemical mechanism underlying xyloglucan backbone acetylation remains to be elucidated. In this study, we showed that recombinant proteins of a group of DUF231 members from rice and tomato were capable of transferring acetyl groups onto O-6 of Glc residues in cello-oligomer acceptors, indicating that they are xyloglucan backbone 6-O-acetyltransferases (XyBATs). We further demonstrated that XyBAT-acetylated cellohexaose oligomers could be readily xylosylated by AtXXT1 (Arabidopsis xyloglucan xylosyltransferase 1) to generate acetylated, xylosylated cello-oligomers, whereas AtXXT1-xylosylated cellohexaose oligomers were much less effectively acetylated by XyBATs. Heterologous expression of a rice XyBAT in Arabidopsis led to a severe reduction in cell expansion and plant growth and a drastic alteration in xyloglucan xylosylation pattern with the formation of acetylated XXGG-type units, including XGG, XGGG, XXGG, XXGG,XXGGG and XXGGG (G denotes acetylated Glc). In addition, recombinant proteins of two Arabidopsis XyBAT homologs also exhibited O-acetyltransferase activity toward cellohexaose, suggesting their possible role in mediating xyloglucan backbone acetylation in vivo. Our findings provide new insights into the biochemical mechanism underlying xyloglucan backbone acetylation and indicate the importance of maintaining the regular xyloglucan xylosylation pattern in cell wall function.

Cytosolic Acetyl-CoA Generated by ATP-Citrate Lyase Is Essential for Acetylation of Cell Wall Polysaccharides.

Plant cell wall polysaccharides, including xylan, glucomannan, xyloglucan and pectin, are often acetylated. Although a number of acetyltransferases responsible for the acetylation of some of these polysaccharides have been biochemically characterized, little is known about the source of acetyl donors and how acetyl donors are translocated into the Golgi, where these polysaccharides are synthesized. In this report, we investigated roles of ATP-citrate lyase (ACL) that generates cytosolic acetyl-CoA in cell wall polysaccharide acetylation and effects of simultaneous mutations of four Reduced Wall Acetylation (RWA) genes on acetyl-CoA transport into the Golgi in Arabidopsis thaliana. Expression analyses of genes involved in the generation of acetyl-CoA in different subcellular compartments showed that the expression of several ACL genes responsible for cytosolic acetyl-CoA synthesis was elevated in interfascicular fiber cells and induced by secondary wall-associated transcriptional activators. Simultaneous downregulation of the expression of ACL genes was demonstrated to result in a substantial decrease in the degree of xylan acetylation and a severe alteration in secondary wall structure in xylem vessels. In addition, the degree of acetylation of other cell wall polysaccharides, including glucomannan, xyloglucan and pectin, was also reduced. Moreover, Golgi-enriched membrane vesicles isolated from the rwa1/2/3/4 quadruple mutant were found to exhibit a drastic reduction in acetyl-CoA transport activity compared with the wild type. These findings indicate that cytosolic acetyl-CoA generated by ACL is essential for cell wall polysaccharide acetylation and RWAs are required for its transport from the cytosol into the Golgi.

Severe Dizziness and Syncope After HeartMate 3 Implantation Requiring Pump Exchange.

Implantation of the HeartMate 3 (HM3) left ventricular assist device (Abbott Laboratories, Lake Bluff, IL) continues to increase as the results of European and U.S. clinical trials become available. Although the large trials adequately capture the more common and expected outcomes, rare and unexpected clinical complications will continue to appear with higher volumes of implantation. This report describes a rare complication of severe refractory postural dizziness and syncope after successful implantation of an HM3 in a patient who ultimately required pump exchange to a HeartWare HVAD (HeartWare, Framingham, MA) for resolution of symptoms.

A Copper10-Paclitaxel crystal; a medicinally active drug delivery platform.

Paclitaxel is a well-known cancer drug that functions as a mitotic inhibitor. This work focuses on a copper based crystal that encapsulates the pharmaceutical agent and serves as a drug delivery agent. A Copper10-Pacitaxil1 chloride (CU10PAC1) complex is synthesized and tested against the National Cancer Institute's sixty cell line panel. The 10:1 ratio results in a crystal that was examined by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spec (MALDI-TOF-MS), Scanning Electron Microscopy (SEM) and Proton (1H) and Carbon (13C) Nuclear Magnetic Resonance (NMR). The potential attributes of a copper based crystal as an in vivo drug carrier for Paclitaxel are discussed.

The Difficult Airway after Endoscopic Endonasal Skull Base Surgery: A Case Series and Management Algorithm.

OBJECTIVES: To analyze difficult airway situations affecting patients after endoscopic endonasal surgery (EES) for skull base tumors and to develop an airway management algorithm. STUDY DESIGN: Case series with chart review. SETTING: Single tertiary care center. SUBJECTS AND METHODS: Eleven difficult airway events occurred among patients after EES for skull base tumors, as identified through a retrospective review of our institutional Difficult Airway Management Team registry from January 2008 to March 2016. Data from these events included patient demographics, event characteristics, airway management techniques, and outcomes. Results were used to design a difficult airway protocol. RESULTS: The majority of patients were obese (63.6%) and had a dural defect (90.9%), each of which was repaired with a vascularized flap. The most common reasons for the difficult airway call were concern for using mask ventilation in a patient with a dural defect (27.3%) and difficult airway anatomy (27.3%). Two patients did not require airway intervention; 8 were intubated; and 1 underwent cricothyroidotomy. Videolaryngoscopy was the most common first-attempt intubation technique, followed by conventional direct laryngoscopy. Effective adjunctive techniques included intubation through a laryngeal mask airway and bougie-guided intubation. As compared with simple mask ventilation, laryngeal mask airway-assisted ventilation was associated with a decreased incidence of postevent cerebrospinal fluid leak. There were no incidences of postevent pneumocephalus, cardiopulmonary arrest, or mortality. CONCLUSIONS: We propose a difficult airway algorithm for patients following EES of the skull base, with sequential recommendations for airway management methods and commentary on adjunctive techniques.