Dorothy Cheney (1950–2018)

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Expression and characterization of two glucuronoyl esterases from Thielavia terrestris and their application in enzymatic hydrolysis of corn bran

Abstract

The thermophilic fungus Thielavia terrestris when cultured on cellulose produces a cocktail of thermal hydrolases with potential application in saccharification of lignocellulosic biomass and other biotechnological areas. Glucuronoyl esterases are considered to play a unique role as accessory enzymes in lignocellulosic material biodegradation by cleaving the covalent ester linkage between 4-O-methyl-D-glucuronic acid (MeGlcA) and lignin in lignin-carbohydrate complexes (LCCs). Two glucuronoyl esterases from T. terrestris named TtGE1 and TtGE2 were expressed in Pichia pastoris. Both esterases displayed features of thermophilic enzymes, with the optimal temperature at 45 °C and 55 °C. TtGE1 and TtGE2 exhibited activity towards methyl (4-nitrophenyl β-D-glucopyranosid) uronate (Me-GlcA-pNP) but no catalytic activity to benzyl-D-glucuronate (BnzGlcA), indicating the difference in substrate specificity from previously studied fungal GEs. A substantial increase in the release of monomeric sugars and glucuronic acid from autohydrolysis of corn bran was observed by the supplementing TtGEs into commercial xylanase; the results clearly demonstrated that the TtGEs played a significant role in this degradation process. This research on TtGEs enriches our knowledge of this novel class of fungal GEs. These newly characterized TtGEs could be used as promising accessory enzymes to improve the hydrolysis efficiency of commercial enzymes in saccharification of lignocellulosic materials due to their thermophilic characteristics.

http://bit.ly/2RX7CSY

Combination of ssDNA recombineering and CRISPR-Cas9 for Pseudomonas putida KT2440 genome editing

Abstract

Pseudomonas putida KT2440 is a Gram-negative, biosafety strain that plays important roles in environmental and biotechnological applications. Highly efficient genome editing strategy is essential to the elucidation of gene function and construction of metabolic engineered strains. Building on our previously established recombineering-mediated markerless and scarless P. putida KT2440 chromosomal gene deletion methods, herein we combined single-stranded DNA (ssDNA) recombineering and CRISPR-Cas9 technologies for P. putida KT2440 genome editing. Firstly, an inactive kanamycin resistance gene was knocked into the P. putida KT2440 chromosome. Then, based on kanamycin selection, recombinase gene selection, ssDNA recombineering condition optimization, and gRNA expression promoter selection were performed. A two-plasmid genome editing system was established; the first is a broad host range, RK2 replicon–based plasmid cloned with the tightly regulated redβ and cas9 genes; the second is a broad host range, pBBR1 replicon–based, sgRNA expression plasmid. Gene point mutations and gene deletions were carried out; the genome editing efficiency is as high as 100%. The method will expedite the P. putida KT2440 metabolic engineering and synthetic biology studies.

http://bit.ly/2X2eUbN

Application of indocyanine green fluorescence endoscopic system in transsphenoidal surgery for pituitary tumors

Abstract

Background

For the precise removal of pituitary tumors, preserving the surrounding normal structures, we need real-time intraoperative information on tumor location, margins, and surrounding structures. The aim of this study was to evaluate the benefits of a new intraoperative real-time imaging modality using indocyanine green (ICG) fluorescence through an endoscopic system during transsphenoidal surgery (TSS) for pituitary tumors.

Methods

Between August 2013 and October 2014, 20 patients with pituitary and parasellar region tumors underwent TSS using the ICG fluorescence endoscopic system. We used a peripheral vein bolus dose of 6.25 mg/injection of ICG, started with a time counter, and examined how each tissue type increased and decreased in fluorescence through time.

Results

A total of 33 investigations were performed for 20 patients: 9 had growth hormone secreting adenomas, 6 non-functioning pituitary adenomas, 3 Rathke's cleft cysts, 1 meningioma, and 1 pituicytoma. After the injection of ICG, the intensity of fluorescence of tumor and normal tissues under near-infrared light showed clear differences. We could differentiate tumor margins from adjacent normal tissues and define clearly the surrounding normal structures using the different fluorescent intensities time changes and tissue-specific fluorescence patterns.

Conclusions

The ICG endoscopic system is simple, user-friendly, quick, cost-effective, and reliable. The method offered real-time information during TSS to delimit pituitary and parasellar region tumor tissue from surrounding normal structures. This method can contribute to the improvement of total removal rates of tumors, reduction of complications after TSS, saving surgical time, and preserving endocrinological functions.

http://bit.ly/2N69at9

Postoperative subdural hematoma with blood flow from an epidural hematoma through a tear at the suture point of an artificial dura substitute

Abstract

Objective

We have recently seen cases of postoperative epidural and subdural hematomas after duraplasty with an artificial dura substitute. In these cases, the epidural hematoma flowed into the subdural space through a tear at the suture point of the artificial dura substitute. In this study, whether such hematomas are specific to a certain artificial dura substitute was investigated, and the cause and risk factors were examined.

Methods

In our institute, 46 patients underwent brain tumor extirpation with duraplasty with an artificial dura substitute; Gore-Tex and SEAMDURA were used as the artificial dura substitutes. Patients with postoperative hemorrhage after brain tumor extirpation with duraplasty with an artificial dura substitute were retrospectively analyzed. Moreover, suture strength was compared experimentally between Gore-Tex and SEAMDURA.

Results

In patients who underwent brain tumor extirpation with duraplasty with an artificial dura substitute, the rate of postoperative hemorrhage was 8.6%. Epidural and subdural hematomas were seen in four patients after tumor extirpation with duraplasty with SEAMDURA, but there were none with Gore-Tex. Exposure of the superior sagittal sinus at craniotomy, older age, and longer operative time were seen more frequently in patients with hematoma than in patients without hematoma. The strength of the suture point was significantly weaker with SEAMDURA than with Gore-Tex (P = 0.00016).

Conclusions

Postoperative epidural and subdural hematomas seem to be specific for SEAMDURA and may be caused by the weak suture strength of SEAMDURA. In cases of duraplasty, a nonabsorbable artificial dura substitute may be suitable.

http://bit.ly/2SOSZpe

Mannitol-assisted synthesis of ultrathin Bi 2 MoO 6 architectures: excellent selective adsorption and photocatalytic performance

Abstract

Ultrathin structures have gained more and more attention due to their large surface area and abundant reactive sites, which are beneficial for the improvement of performances. Herein, we report an ultrathin Bi₂MoO₆ synthesized by a simple mannitol-assisted hydrothermal method for the first time. The as-synthesized ultrathin Bi₂MoO₆ exhibits highly selective adsorption efficiency toward various positively charged organic dyes. Moreover, the ultrathin Bi₂MoO₆ displays enhanced photocatalytic activity in comparison with pristine Bi₂MoO₆. Systematic photoelectrochemical measurements reveal that the higher separation efficiency of photogenerated carriers takes responsibility for the improved photocatalytic performance. This work provides a simple path for designing ultrathin nanoarchitectures and widening application for these ultrathin materials.

http://bit.ly/2SwWT6Q

Bedside ultrasound after aortic surgery

Abstract

Background

Early complications after aortic surgery, such as bleeding, vessel occlusion, and organ ischemia require quick and targeted diagnostics to reduce the morbidity and mortality. Ultrasound can be used for quick bedside diagnosis of vascular and organ complications.

Objective

The possibilities of color duplex and contrast-enhanced ultrasound for the detection of vascular and organ complications after aortic surgery are presented.

Results

Vascular access complications, such as acute vessel occlusion, stenosis, dissection, bleeding, hematoma, and false aneurysms can be detected by color duplex ultrasound. The differentiation between hematoma and active bleeding is possible with contrast-enhanced ultrasound. Ultrasound contrast imaging enables the evaluation of hemodynamically relevant dissections and intraluminal thrombi. Furthermore, contrast-enhanced ultrasound enables the differential diagnostics of acute kidney failure and a differentiation between complete or partial organ ischemia.

Conclusion

The use of bedside ultrasound for quick detection of early complications after aortic surgery enables optimization of the perioperative management of complications. Further diagnostic and therapeutic interventions can be used in a targeted manner, if necessary. Unnecessary exposure to nephrotoxic radiopaque agents and X‑rays and the risks involved in transportation of critically ill patients can therefore be avoided.

http://bit.ly/2X2oIm8