Polyester synthesis by lipase catalyst involves two major polymerization modes: i) ring‐opening polymerization of lactones, and, ii) polycondensation. Ring‐opening polymerization includes the finding ...of lipase catalyst; scope of reactions; polymerization mechanism; ring‐opening polymerization reactivity of lactones; enantio‐, chemo‐ and regio‐selective polymerizations; and, chemoenzymatic polymerizations. Polycondensation includes polymerizations involving condensation reactions between carboxylic acid and alcohol functional groups to form an ester bond. In most cases, a carboxylic acid group is activated as an ester form, such as a vinyl ester. Many recently developed polymerizations demonstrate lipase catalysis specific to enzymatic polymerization and appear very useful. Also, since lipase‐catalyzed polyester synthesis provides a good opportunity for conducting “green polymer chemistry”, the importance of this is described
This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are ...prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester synthesis is, therefore, a reaction in reverse way of in vivo lipase catalysis of ester bond-cleavage with hydrolysis. The lipase-catalyzed polymerizations show very high chemo-, regio-, and enantio-selectivities and involve various advantageous characteristics. Lipase is robust and compatible with other chemical catalysts, which allows novel chemoenzymatic processes. New syntheses of a variety of functional polyesters and a plausible reaction mechanism of lipase catalysis are mentioned. The polymerization characteristics are of green nature currently demanded for sustainable society, and hence, desirable for conducting ‘green polymer chemistry’. (Communicated by Ryoji NOYORI, M.J.A.)
Mechanistic aspects of lipase‐catalyzed ring‐opening polymerization (ROP) of lactones to give polyesters are discussed from accumulated experimental data and new insight. Comparison of the ROP ...reactivity by lipase catalyst with the anionic ROP reactivity by a metal‐catalyst clearly demonstrates the characteristics of lipase catalysis; the larger ring‐sized monomers with lower ring strain showed higher polymerizability than medium ring‐sized ones, in contrast to the anionic ROP showing the reverse direction where the ring strain of monomer is operative. The enzyme‐catalysis involves an acyl‐enzyme intermediate formation as a key‐step. From the copolymerization results a new mechanism is proposed, that involves the formation of the acyl‐enzyme intermediate (acylation step) and/or the nucleophilic attack of the propagationg alcohol end to the carbonyl carbon of the intermediate to open the monomer ring (deacylation step) as the rate‐determining step. The structure of the propagating alcohol end (primary or secondary) affects much on which step is more operative.
Aneurysmal subarachnoid hemorrhage (SAH) can result in poor outcomes, and biomarkers for predicting poor prognosis have not yet been established. The aim of this study was to clarify the significance ...of the serum glucose/potassium ratio for predicting the prognosis of aneurysmal SAH.
The authors retrospectively reviewed the records of 565 patients with aneurysmal SAH between 2006 and 2016. The patient group comprised 208 men and 357 women (mean age 61.5 years, range 10-95 years). A statistical analysis was conducted of the clinical and laboratory risk factors of poor outcome, including the serum glucose/potassium ratio.
On estimation of the initial assessment using Hunt and Kosnik (H-K) grading, 233 patients (41.2%) were classified as the severe SAH group (H-K Grade IV or V). There were significant correlations between the severe SAH group and serum glucose/potassium ratio (p < 0.0001). Serum glucose/potassium ratio was elevated in an H-K grade-dependent manner (Spearman's r = 0.5374, p < 0.0001). With the estimation of the Glasgow Outcome Scale (GOS) score at discharge, 355 patients (62.8%) were classified as poor outcome (GOS score 1-3). The serum glucose/potassium ratio was elevated in a GOS score at discharge-dependent manner (Spearman's r = 0.4006, p < 0.0001), and was significantly elevated in the poor outcome group compared with the good outcome group (GOS score 4 or 5; p = 0.0245). There were significant correlations between poor outcome and serum glucose/potassium ratio (p < 0.0001), age (p < 0.0001), brain natriuretic peptide levels (p = 0.011), cerebral infarction due to vasospasm (p < 0.0001), and H-K grade (p < 0.0001). Multivariate logistic regression analyses showed significant correlations between poor outcome and serum glucose/potassium ratio (p = 0.009).
In this study, the serum glucose/potassium ratio of patients with aneurysmal SAH at admission was significantly correlated with H-K grade and GOS score at discharge. Therefore, this ratio was useful for predicting prognosis of aneurysmal SAH, especially in severe cases.
Abstract Introduction Few reports of delirium-related risk factors have focused on environmental risk factors and clinical risk factors, such as white matter signal abnormalities on magnetic ...resonance imaging (MRI) FLAIR images. Material & Methods We prospectively enrolled 253 patients admitted to our neurosurgical center between December 2014 and June 2015 and analyzed a total of 220 patients (100 males; mean age, 64.1 years; age range, 17–92 years). The upper 4 points of the Intensive Care Delirium Screening Checklist (ICDSC) indicated delirium. We evaluated patient factors consisting of baseline characteristics and related factors, such as white matter lesions (WMLs), and we also evaluated the surrounding environment. Results Delirium occurred in 29/220 cases (13.2%) in the present study. Regarding the baseline characteristics, there were significant statistical correlations between delirium and age ( P = 0.0187), Hasegawa Dementia Scale-Revised score ( P = 0.0022) on admission, and WMLs ( P <0.0001). WMLs were related to age ( P < 0.0001) and atherosclerotic disease ( P = 0.004). Regarding related factors, there were significant statistical correlations between delirium and staying at a neurosurgical care unit (NCU; P = 0.0245). Multivariate logistic regression analyses showed statistically significant correlations of delirium with WMLs ( P <0.0001) and surrounding delirium patients ( P = 0.026). Conclusion WMLs in patients and the environmental situation are risk factors for delirium in a neurosurgical center. Therefore, to prevent delirium, we must recognize risk factors, such as high grade WMLs, and manage environmental factors, such as the surrounding situation.
This review focuses on the in vitro synthesis of polysaccharides, the method of which is “enzymatic polymerization” mainly developed by our group. Polysaccharides are formed by repeated glycosylation ...reactions between a glycosyl donor and a glycosyl acceptor. A hydrolysis enzyme was found very efficient as catalyst, where the monomer is designed based on the new concept of a “transition-state analogue substrate” (TSAS); sugar fluoride monomers for polycondensation and sugar oxazoline monomers for ring-opening polyaddition. Enzymatic polymerization enabled the first in vitro synthesis of natural polysaccharides such as cellulose, xylan, chitin, hyaluronan and chondroitin, and also of unnatural polysaccharides such as a cellulose–chitin hybrid, a hyaluronan–chondroitin hybrid, and others. Supercatalysis of hyaluronidase was disclosed as unusual enzymatic multi-catalyst functions. Mutant enzymes were very useful for synthetic and mechanistic studies. In situ observations of enzymatic polymerization by SEM, TEM, and combined SAS methods revealed mechanisms of the polymerization and of the self-assembling of high-order molecular structure formed by elongating polysaccharide molecules. (Communicated by Hitosi NOZAKI, M.J.A.)
OBJECT The tentorial branch of the posterior cerebral artery was first identified in a cadaver dissection study. However, the tentorial branch of the superior cerebellar artery (SCA) has not been ...clearly described in autopsy or normal anatomical studies. In this study, a dural branch of the SCA that was found during the surgical treatment of trigeminal neuralgia is described. METHODS Between April 2011 and March 2014, 70 patients with idiopathic trigeminal neuralgia underwent microvascular decompression. The records of 58 patients were reviewed to investigate the meningeal branch of the SCA. RESULTS The meningeal branch of the SCA was visualized in 15 of the 58 patients (25.9%). In 4 patients, it was necessary to divide this branch in order to achieve decompression of the trigeminal nerve without eliciting postoperative neurological deficits. CONCLUSIONS This is the first identification of the meningeal branch of the SCA in living subjects, and such branches were rather frequently found. Recognition of this branch is important for the management of lesions in the cerebellopontine angle and tentorial lesions, using either an open microsurgical or endovascular method.
The present article reports a new method for the synthesis of 'artificial urushi' using cardanol, a major ingredient of cashew nutshell liquid, as the starting monomer. Natural urushi sap is ...polymerized in a water-in-urushiol (w/o) emulsion system; here, we mimic this system for the polymerization of cardanol. The combination of a weak amine base and a weak carboxylic acid functions as efficient emulsifier. The polymerization of cardanol is carried out in a water-in-cardanol (w/o) emulsion to produce a prepolymer emulsion, which is further cured by crosslinking, resulting in the biomimetic polymerization of cardanol. The prepolymer emulsion is stable for storage. The films were prepared from the prepolymer emulsion; the curing of these films was achieved by thermal annealing or by cobalt naphthenate-catalyzed crosslinking in air to generate 'artificial urushi'. The rheological properties of the cardanol monomer and the prepolymer emulsions resulted in excellent film formation on the substrate. Physical property examinations of the cured films showed sufficient hardness for use as a coating layer. Cardanol is a renewable resource, and no organic solvent was used, and thus, this polymerization is a green chemical process.
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