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摘要： eP225

关键词： autolysin   bacterial cell wall   Clostridioides difficile   cysteine endopeptidase   peptidoglycan   X‐   ray structure  

摘要： Autolysin is a lytic enzyme that hydrolyzes peptidoglycans of the bacterial cell wall, with a catalytic domain and cell wall-binding (CWB) domains, to be involved in different physiological functions that require bacterial cell wall remodeling. We identified a novel autolysin, Acd24020, from Clostridioides (Clostridium) difficile (C. difficile), with an endopeptidase catalytic domain belonging to the NlpC/P60 family and three bacterial Src-homology 3 domains as CWB domains. The catalytic domain of Acd24020 (Acd24020-CD) exhibited C. difficile-specific lytic activity equivalent to Acd24020, indicating that Acd24020-CD has full-function as a lytic enzyme by itself. To elucidate the specific peptidoglycan-recognition and catalytic reaction mechanisms of Acd24020-CD, biochemical characterization, X-ray structure determination, a modeling study of the enzyme/substrate complex, and mutagenesis analysis were performed. Acd24020-CD has an hourglass-shaped substrate-binding groove across the molecule, which is responsible for recognizing the direct 3-4 cross-linking structure unique to C. difficile peptidoglycan. Based on the X-ray structure and modeling study, we propose a dynamic Cys/His catalyzing mechanism, in which the catalytic Cys299 and His354 residues dynamically change their conformations to complement each step of the enzyme catalytic reaction.

关键词： grape seed extract   antioxidants   cadmium   rattus norvegicus   biochemical markers   protective effect  

摘要： Cadmium (Cd) is a heavy metal that occurs in all areas of the environment, including the food chain. In the body, it causes oxidative stress by producing free radicals that are harmful to the cells. Grape seed extract (GSE) contains a wide range of biologically active components that help to neutralize the adverse effects of free radicals. In this study, the effects of GSE prepared form semi-resistant grapevine cultivar Cerason, which is rich in phenolics, on biochemical markers of brown rats exposed to the effects of cadmium were monitored. GSE increased the plasma antioxidant activity and, in the kidneys and the liver, Cd content was significantly lowered by GSE co-administration. Accordingly, the increase in creatinine content and alanine aminotransferase activity and the decrease of catalase and superoxide dismutase activities caused by cadmium were slowed down by GSE co-administration. The results of this work reveal that grape seed extract offers a protective effect against the intake of heavy metals into the organism.

关键词： Listeria monocytogenes   Queso fresco   Nisin derivatives   Endolysin   PlyP100  

摘要： Nisin is an antimicrobial peptide that is commonly used as a food preservative and capable of inhibiting the pathogen Listeria monocytogenes. However, nisin is ineffective in controlling L. monocytogenes in Queso Fresco (QF). To address the challenge, in this work, we used synthetic biology strategies to create a series of nisin A derivatives by substituting residues 27, 30, 31 and 32 with positively charged amino acids (H, K and R). Our results showed that nisin derivatives exhibited reduced antilisterial activity in vitro compared to nisin A;however, they were all more stable under QF-like experimental conditions (pH 7 + 22% milk fat), notably H27/31K. Compared to nisin A, the derivatives H31K and V32K exhibited slight antilisterial improvement in QF and H27/ 31K was able to reduce the initial population of L. monocytogenes by up to 1.5 Log CFU/g. L. monocytogenes isolates exhibited similar susceptibility to nisin A or H27/31K after 7 or 14 days of nisin exposure in QF. Notably, when combined with endolysin PlyP100, the application of H27/31K resulted in non-enumerable levels of L. monocytogenes after 14 days of cold storage. Our results highlight the potential of bioengineered nisin derivatives for stabilized and enhanced control of L. monocytogenes in QF.

关键词： O. niloticus   ZnOBPs   ZnONPs   Antioxidant enzymes   Vitamins (E and C)  

摘要： The comparison between bulk and nano ZnO particles were antecedently studied but describing the dose-dependent toxicity and the ameliorative effect of vitamins (E and C) in Oreochromis niloticus, have not been previously documented. Therefore, the present study was designed to investigate the ameliorative effect of vitamins (E and C) against oxidative stress and biochemical alterations induced by sublethal concentrations of zinc oxide bulk particles (ZnOBPs) and zinc oxide nanoparticles (ZnONPs). Toxicity tests were carried out on O. niloticus and showed that 96 h LC50 values of ZnOBPs and ZnONPs were 84 mg/l and 5.6 mg/l respectively. Exposure of the studied fish to these sublethel concentrations for 7, 14, 21 & 28 days showed a significant increase (p < 0.05) in serum glucose, AST, ALT, creatinine, urea and uric acid compared to control groups while, fish groups exposed to ZnOBPs or ZnONPs and supplemented with vitamins E and C, their serum enzyme concentrations were decreased compared to the groups without supplementation after 7, 14, 21 and 28 day. On the other hand, antioxidant defense enzymes (SOD, CAT and GST) activity in *** fish were increased significantly (p < 0.05) when exposed to sublethal concentrations of ZnOBPs or ZnONPs compared to the control value. However, fish groups supplemented with vitamins (E and C) have a decrease in SOD, CAT and GST enzymes activity when compared to unsupplemented groups and the values returned to similar levels established in the control at low concentrations but still higher than control at the high concentrations.

关键词： Biochemical analytes   Neonates   Reference intervals   Enzymes   Lipids  

摘要： BackgroundBiochemical analytes provide information for neonatal disease management and therapy, and population-based reference intervals (RIs) are essential to accurately interpret laboratory test results. This study aimed to establish local RIs for biochemical assays in term *** total of 195 healthy term neonates from birth to 3rd day were recruited as reference individuals prospectively. Analytes of 26 common biochemistries were measured using the VITROS 5600 Integrated System. The 3-level nested ANOVA was performed to assess the need for partitioning RIs of each analyte, and RIs were derived by a nonparametric method or robust method. Multiple regression analysis was used to evaluate specific correlations between the analytes and individual characteristics including age, gender, gestational age, birthweight and delivery *** were no between-sex differences in all analytes, whereas there were significant between-day-age differences in 6 analytes. Small between-delivery-mode differences were observed in the results for potassium, phosphorus, and urea. The major related factor of most analytes was postnatal age. During the first 3days, values of iron, lipids and lipoproteins increased;creatinine, urea, uric acid, creatine kinase and lactate dehydrogenase decreased;other analytes showed slight changes or relatively stable trends. Reference limits of some analytes, particularly lactate dehydrogenase and alkaline phosphatase, were significantly different from adult and pediatric *** of 26 common biochemical analytes are established for term neonates aged 0 to 3days in northeast China. Additionally, it is suggested that age-related changes should be valued in the clinical decision-making process for newborns.

关键词： Antioxidant capacity   ER stress   Litopenaeus vannamei   Selenium   Transcriptome  

摘要： This study investigated the effects of different levels of dietary selenium (Se) on the growth, antioxidant capacity, hepatopancreas health, and transcriptional-level responses of Litopenaeus vannamei. Sodium selenite was added to basal diet formulations at 0, 0.2, 0.4, and 0.8 mg/kg, with final Se concentrations of 0.13, 0.20, 0.45, and 0.81 mg/kg, respectively. Shrimp were fed the experimental diets for 8 weeks, after which the following parameters were measured: growth performance, antioxidant enzymes activity, ALT, AST activity, endoplasmic reticulum stress and transcriptome. Shrimp fed the 0.45 and 0.81 mg/kg Se diets (P < 0.05) showed the highest weight gain, shrimp fed the 0.13 mg/kg Se diet had the highest hepatosomatic index (P < 0.05), and the endoplasmic reticulum stress related genes were down-regulated (P < 0.05) in shrimp fed the 0.45 mg/kg Se diet. Antioxidant enzyme activity (SOD, CAT, and GPx) was enhanced with the increase in the Se level. The transcriptome results showed that glycine, serine, and threonine metabolism, the pentose phosphate pathway, and ascorbate and aldarate metabolism were enriched in shrimp fed the 0.45 mg/kg Se diet, while focal adhesions, gap junctions, tight junctions, and adhesion junctions were found in shrimp fed the 0.13 and 0.81 mg/kg Se diets. Co-expression analysis showed that genes PINKI and Innexin (among others), were involved in the influence of Se levels on shrimp. Our results suggested that Se supplementation improved the growth and antioxidant capacity of L. vannamei by promoting the biosynthesis of glutathione and enhancing the activity of antioxidant enzymes. However, high levels of dietary Se can cause endoplasmic reticulum stress and hepatopancreas tissue damage.

关键词： Hypoxia tolerance   Hematology   Biochemistry   Turbot   Scophthalmus maximus. L  

摘要： Hypoxia is a critical issue in aquaculture which affects the metabolism and survival of fish. The critical oxygen tension (Pcrit), loss of equilibrium (LOE), respiration frequency (RF), plasma cortisol, glucose, lactate, cholesterol (CHO), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), total protein, albumin, globulin, albumin/globulin, white blood cell (WBC), red blood cell (RBC), hemoglobin (Hb) and hematocrit (Hct) of turbot (male vs female) were determined during hypoxia and reoxygenation to evaluate their hypoxia tolerance and underlying physiological response. Results showed that dissolved oxygen (DO) values at Pcrit and LOE were 3.34 +/- 0.17 mg/L and 1.30 +/- 0.16 mg/L, respectively. RF significantly increased at Pcrit and LOE. Meanwhile, abnormal swimming behaviors were observed at DO values lower than 5 mg/L. Male and female showed no significant difference in above indexes. Hypoxia stress significantly increased plasma cortisol, glucose, and lactate contents at Pcrit and LOE, with the highest value obtained at LOE. Female plasma cortisol and glucose content were significantly higher than males at LOE, whereas the male lactate was significantly higher than females. Hypoxia stress did not affect the WBC number, plasma CHO, HDL, LDL levels and albumin/globulin of the male and female turbot. Plasma TG and total protein, albumin, globulin levels significantly increased at LOE and Pcrit, respectively. Female total protein significantly higher than males at Pcrit, but the opposite trend was found at LOE. RBC, Hb and Hct manifested similar cortisol results, the male and female showed no significant difference. The aforementioned parameters except for cortisol were recovered to normal levels after reoxygenation for 12 h. In conclusion, turbot manifest sex dimorphism difference during hypoxia stress-induced hematological and biochemical response.

关键词： Omega-3 fatty acids   Coronavirus   Kidney function   Respiratory function  

摘要： Background: Omega-3 polyunsaturated fatty acids (n3-PUFAs) may exert beneficial effects on the immune system of patients with viral infections. This paper aimed to examine the effect of n3-PUFA supplementation on inflammatory and biochemical markers in critically ill patients with COVID-19. Methods: A double-blind, randomized clinical trial study was conducted on 128 critically ill patients infected with COVID-19 who were randomly assigned to the intervention (fortified formula with n3-PUFA) (n = 42) and control (n = 86) groups. Data on 1 month survival rate, blood glucose, sodium (Na), potassium (K), blood urea nitrogen (BUN), creatinine (Cr), albumin, hematocrit (HCT), calcium (Ca), phosphorus (P), mean arterial pressure (MAP), O-2 saturation (O(2)sat), arterial pH, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), bicarbonate (HCO3), base excess (Be), white blood cells (WBCs), Glasgow Coma Scale (GCS), hemoglobin (Hb), platelet (Plt), and the partial thromboplastin time (PTT) were collected at baseline and after 14 days of the intervention. Results: The intervention group had significantly higher 1-month survival rate and higher levels of arterial pH, HCO3, and Be and lower levels of BUN, Cr, and K compared with the control group after intervention (all P <0.05). There were no significant differences between blood glucose, Na, HCT, Ca, P, MAP, O2sat, PO2, PCO2, WBCs, GCS, Hb, Plt, PTT, and albumin between two groups. Conclusion: Omega-3 supplementation improved the levels of several parameters of respiratory and renal function in critically ill patients with COVID-19. Further clinical studies are warranted.