Role of hydrophobic interaction in the enantioselective solvolyses of amino acid p-nitrophenyl esters by optically active imidazole-containing polymers

Solvolytic reactions of N-benzyloxycarbonyl-D -phenylalanine p-nitrophenyl ester and N-benzyloxycarbonyl-L -phenylalanine p-nitrophenyl ester by optically active imidazole-containing polymers were performed at different temperatures and in aq. ethanol of different water contents. The catalyst polymers employed were homopolymers of N-methacryloyl-L -histidine ( 1a ) and N-methacryloyl-L -histidine methyl ester ( 1b ), as well as copolymers of 1a with dodecyl methacrylate (DMA) and 1b with DMA. In 30 vol. -% aqueous ethanol at pH 7,02 the homopolymers did not show any enantioselective catalysis. However, the copolymers did exhibit enantioselective catalysis, viz., k_cat(L )/k_cat(D ) = 1,25 for poly ( 1b -co-DMA) containing 5,7 mol-% of DMA. As the reaction temperature was lowered, the reaction rate increased and the enantioselectivity was enhanced (k_cat(L )/k_cat(D ) = 1,67 for poly ( 1b -co-DMA) at 10°C). When the ethanol content was decreased, enhanced reaction rates and enantioselectivity (k_cat(L )/k_cat(D ) = 1,65 for poly ( 1 b -co-DMA) in 20 vol.-% aqueous ethanol) were observed. From these results it is concluded that hydrophobic interaction plays an important role in the enantioselective catalysis of optically active imidazole-containing polymers.     

Dental restorative composites containing 2,2-bis-[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane derivatives and spiro orthocarbonates

Various dental restorative composite resins containing 2,2-bis-[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) derivatives and spiro orthocarbonates (SOCs) were explored for minimizing the volumetric shrinkage that generally occurs during polymerization. Previous reports suggested mixing Bis-GMA with its derivative TMBis-GMA (2,2-bis[3,5-dimethyl-4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) to obtain a dental composite with low volumetric shrinkage. It was hypothesized that spiro orthocarbonates would expand volumetrically during polymerization, because of their sophisticated ring-opening reactions; therefore several of them were added to the mixture of Bis-GMA and TMBis-GMA to bring about further reductions in volumetric shrinkage. It was indeed possible to reduce the extent of volumetric shrinkage of dental composites containing SOCs, and to do so without compromising these resins' mechanical properties.     

Serum-catalyzed hydrolysis of metronidazole amino acid esters

Glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), phenylalanine (Phe), and lysine (Lys) esters of metronidazole were synthesized using dicyclohexylcarbodiimide (DCC) coupling or a mixed-anhydride route, using tert-butyloxycarbonyl (tert-Boc) amino acids. Human serum-catalyzed hydrolysis of these esters at 37 degrees C give half-lives varying from 4.5 min for the Phe ester to 96 h for the Ile ester. Also determined was the pH-rate profile for hydrolysis in aqueous buffers at 25 degrees C. A linear relationship was observed between the logarithmic value of the hydrolysis rate constant in serum and that of the OH- -catalyzed hydrolysis of cationic esters. This finding may indicate that the esters studied are "equally" poor substrates for binding to the enzymes in serum and, thus, the difference observed in the serum-catalyzed hydrolysis rate is solely derived from the chemical lability of an ester bond. Interestingly, the extent of chemical activation observed in the buffer system appears to be amplified in the serum-catalyzed hydrolysis.     

Sociodemographic Patterns of Exclusive,Dual, and Polytobacco Use Among U.S. High School Students: A Comparison of Three Nationally Representative Surveys

PurposeThis study examines sociodemographic patterns of exclusive/dual/polytobacco use among U.S. high school students using multiple national surveys.MethodsUsing three national youth surveys (Population Assessment of Tobacco and Health [PATH] Wave 4 [2016–2017], 2017 Youth Risk Behavior Survey, and 2017 National Youth Tobacco Survey), we classified tobacco products into four groups: (1) electronic nicotine delivery systems (ENDS), (2) conventional cigarettes (CCs), (3) other combustible tobacco products, and (4) smokeless tobacco products. We created 16 categories of non/exclusive/dual/polytobacco use within the past 30 days using the four product groups and calculated weighted population prevalence by sex and race/ethnicity (all surveys) and parental education and income (PATH), based on variable availability.ResultsThe results from 9,331, 12,407, and 9,699 high school students in PATH, Youth Risk Behavior Survey, and National Youth Tobacco Survey, respectively, largely agreed and pointed to similar conclusions. ENDS was the most prevalent exclusive use product (3.8%–5.2% across surveys), with CCs falling to second or third (1.2%–2.0% across surveys). By sex, exclusive, dual, and poly smokeless tobacco product use were more common for males, whereas exclusive CC use was more common for females. By race/ethnicity, non-Hispanic Whites had a higher prevalence of exclusive ENDS use and ENDS/CC dual use than non-Hispanic Blacks. As income and parental education levels increased from low to high, the prevalence of exclusive CC use decreased, whereas the prevalence of exclusive ENDS use increased.ConclusionUnderstanding sociodemographic patterns of tobacco use can help identify groups who may be at greater risk for tobacco-related health outcomes.     

Clinical Significance of De Novo Malignancy After Liver Transplant: A Single-Center Study

BackgroundSeveral studies have reported that solid organ transplant recipients have a high risk for malignant tumors because the suppressed immune system fails in preventing malignant transformations. De novo malignancy after transplantation is the most common cause of death in the late period after liver transplant (LT). This study investigated the clinical significance of de novo malignancy after LT, and it is the largest study based in Korea to report long-term follow-up results associated with de novo malignancy after LT.MethodsData of 1793 adults who underwent LT in Seoul National University Hospital were retrospectively collected, and medical charts and data from the Ministry of Public Administration and Security were reviewed to examine the causes of death and de novo malignancy status. The Fisher exact test and Kaplan-Meier survival analysis were used to analyze the data.ResultsOf the 1793 recipients, 27 died of de novo malignancies. Of 875 hepatocellular carcinoma (HCC) patients, 12 died, and of 918 non-HCC patients, 15 died. De novo malignancy was the main cause of death at 5 years after LT but was not in the initial 5 years. In Korea the most common cancers that developed after LT were gastric cancer (21.4%) and lymphoma (14.3%). De novo HCC in non-HCC cases was found in 2 patients.ConclusionDe novo malignancy is a key factor affecting long-term survival after LT. Therefore, regular screening and education are important for improving long-term survival and quality of life in these patients after LT.     

Direct versus indirect transfer for traumatic brain injury to James Cook University Hospital: a retrospective study

IntroductionPatients with traumatic brain injury are referred to the neurosurgical unit at James Cook University Hospital, Middlesbrough, either from local accident and emergency departments (direct transfer from the scene) or from other hospitals (indirect transfer). This study looked at the outcome in both groups.Material and methodsThis was a retrospective observational study using trauma audit research network data for patients treated for traumatic brain injury at the neurosurgery department at the neurosurgical unit at James Cook University Hospital.ResultsA total of 356 patients with traumatic brain injury were admitted under the care of neurosurgeons; 143 (40%) of these patients had a neurosurgical procedure. Of the patients undergoing a neurological procedure, 111 patients were transferred directly while 32 were indirect transfers; 213 patients were managed conservatively. Of those managed conservatively, 165 were transferred directly while 48 were indirect transfers.We compared the length of hospital stay and Glasgow Outcome Scale score for the patients based on whether they were conservatively managed or required surgery in the direct and indirect transfer groups. The difference in the length of stay in the surgical and conservative groups following direct and indirect transfer was insignificant (p = 0.07). The time to the operation in direct and indirect transfer was also not statistically significant (p = 0.06).ConclusionPatients are as safe, if not safer, by reaching the nearest trauma unit with facilities for resuscitation and imaging.     

Knotless All-Inside Arthroscopic Modified Broström Procedure for Lateral Ankle Instability

One reported complication of the arthroscopic modified Broström operation is pain caused by the suture anchoring knot. We hypothesized that a knotless technique could reduce such pain. Therefore, in this study we evaluated the clinical and radiological outcomes after knotless all-inside arthroscopic modified Broström operation for lateral ankle instability. From July 2017 to November 2017, 28 patients were treated. Clinical and radiological features were evaluated preoperatively and 3, 6, and 12 months postoperatively using the American Orthopaedic Foot & Ankle Society ankle-hindfoot scale score, visual analogue scale score for pain, anterior talar drawer test, and talar tilt angle. The mean age of the 28 patients (14 men, 14 women) was 41.71 ± 17.19 years. Three (10.7%) complications, but no knot-associated pain, occurred. The clinical and radiological outcomes were significantly improved 12 months postoperatively compared with preoperative outcomes (all p < .05). Knotless all-inside arthroscopic modified Broström operation for lateral ankle instability avoided knot-associated pain and improved not only patient satisfaction but also clinical and radiological outcomes.