Residues Distal to the Active Site Contribute to Enhanced Catalytic Activity of Variant and Hybrid β-Lactamases Derived from CTX-M-14 and CTX-M-15

A variety of CTX-M-type extended-spectrum β-lactamases (ESBLs), including hybrid ones, have been reported in China that are uncommon elsewhere. To better characterize the substrate profiles and enzymatic mechanisms of these enzymes, we performed comparative kinetic analyses of both parental and hybrid CTX-M enzymes, including CTX-M-15, -132, -123, -64, -14 and -55, that are known to confer variable levels of β-lactam resistance in the host strains. All tested enzymes were susceptible to serine β-lactamase inhibitors, with sulbactam exhibiting the weakest inhibitory effects. CTX-M-55, which differs from CTX-M-15 by one substitution, A⁷⁷V, displayed enhanced catalytic activity (k_cat/K_m) against expanded-spectrum cephalosporins (ESCs). CTX-M-55 exhibits higher structure stability, most likely by forming hydrophobic interactions between A⁷⁷V and various key residues in different helices, thereby stabilizing the core architecture of the helix cluster, and indirectly contributes to a more stable active site conformation, which in turn shows higher catalytic efficiency and is more tolerant to temperature change. Analyses of the hybrids and their parental prototypes showed that evolution from CTX-M-15 to CTX-M-132, CTX-M-123, and CTX-M-64, characterized by gradual enhancement of catalytic activity to ESCs, was attributed to introduction of different substitutions to amino acids distal to the active site of CTX-M-15. Similarly, the increased hydrolytic activities against cephalosporins and sensitivity to β-lactamase inhibitors, clavulanic acid and sulbactam, of CTX-M-64 were partly due to the amino acids that were different from CTX-M-14 and located at both the C and N termini of CTX-M-64. These data indicate that residues distal to the active site of CTX-Ms contributed to their enhanced catalytic activities to ESCs.     

Comparison of age and sex regarding gingival and papillary recession

No studies have been published concerning the comparison between gingival and papillary recession in the maxillary esthetic zone (including incisors, canines, and premolars) regarding age and sex. This study addressed this issue. Adults (n = 250) with fully erupted permanent dentitions, healthy gingivae, and natural teeth in the maxillary esthetic area were included. Visual examinations were performed to detect papillary and gingival recession. Space evident apical to the contact area of adjacent teeth was recorded as papillary recession; a cementoenamel junction visible coronal to the buccal gingival margin was recorded as gingival recession. All sites with papillary and gingival recession were significantly associated with age; however, only some sites with gingival and papillary recession were associated with sex. Papillary recession was more severe than gingival recession in both extent and prevalence in subjects older than 30 years of age. Thus, papillary recession may be expected to be a more common esthetic dental problem.     

Suitable restriction enzymes for pulsed-field gel electrophoresis analysis of Candida tropicalis

This study was designed to pursue the identification of optimal restriction enzyme for pulsed-field gel electrophoresis (PFGE) analysis of Candida tropicalis. Twelve restriction enzymes were tested on C. tropicalis strains. Our results indicate that BssHII, NaeI, and RsrII were useful enzymes for PFGE analysis, and NaeI was the best for PFGE analysis of C. tropicalis isolates.     

Frowning and Jaw Clenching Muscle Activity Reflects the Perception of Effort During Incremental Workload Cycling

The present study aimed to investigate whether facial electromyography (EMG) recordings reflect the perception of effort and primary active lower limb muscle activity during incremental workload cycling. The effects of exercise intensity on EMG activity of the corrugator supercilii (CS), masseter and vastus lateralis (VL) muscles, heart rate (HR) and the rating of perceived exertion (RPE) were investigated, and the correlations among these parameters were determined. Eighteen males and 15 females performed continuous incremental workload cycling exercise until exhaustion. CS, masseter and VL muscle activities were continuously recorded using EMG during exercise. HR was also continuously monitored during the test. During the final 30 s of each stage of cycle ergometer exercise, participants were asked to report their feeling of exertion on the adult OMNI-Cycle RPE. HR and EMG activity of the facial muscles and the primary active lower limb muscle were strongly correlated with RPE; they increased with power output. Furthermore, facial muscle activity increased significantly during high-intensity exercise. Masseter muscle activity was strongly and positively correlated with HR, RPE and VL activity. The present investigation supports the view that facial EMG activity reflects the perception of effort. The jaw clenching facial expression can be considered an important factor for improving the reporting of perceived effort during high-intensity exercise in males and females.

Key points

• Frowning and jaw clenching muscle activity reflects the perception of effort during incremental workload cycling.
• EMG activity of the masseter muscle was strongly and positively correlated with RPE, HR and lower limb EMG activity during incremental workload cycling.
• The jaw clenching facial expression can be considered an important factor for estimating the intensity of effort.

Key words: Perceived exertion, facial electromyography, masseter muscle, corrugator supercilii muscle, incremental exercise testing     

Poor prognosis of end-stage renal disease in systemic lupus erythematosus: a cohort of Chinese patients

We studied the clinical course of 26 systemic lupus erythematosus (SLE) patients who started regular dialysis at our hospital and whose stay exceeded a three-month duration in order to investigate the long-term prognosis in a Chinese cohort. Clinical and serological activities of lupus before and after dialysis were analysed. To compare the long-term survival rate, controls were set using 78 age-matched end-stage renal disease (ESRD) patients who did not have SLE or diabetes mellitus and entered the chronic dialysis program at a similar period with SLE dialysis patients. There was a significant decrease in clinical lupus activity after starting regular dialysis (P < 0.05); however, the serological activity remained the same. The five-and ten-year survival rates were significantly lower in the SLE patients (73 and 38% in the SLE group versus 95 and 88% in the non-SLE group, P < 0.05). SLE patients had a 4.3-times higher risk of death than non-SLE patients (P < 0.05, 95% confidence interval, 1.2-15.2). Also, the deceased SLE patients had persistent lower serum levels of complement 3. SLE patients with ESRD remain clinically quiescent despite persistent serological abnormalities and have a worse prognosis than other uremia patients in the Chinese population.     

Antiatherogenic effect of Pistacia lentiscus via GSH restoration and downregulation of CD36 mRNA expression

Pistacia lentiscus var. Chia (Anacardiaceae) grows almost exclusively on Chios Island, Greece, and gives a resinous exudate resin used for culinary purposes by Mediterranean people. We investigated the molecular mechanisms through which total polar extract of the resin inhibits oxidized low-density lipoprotein (oxLDL) cytotoxic effect on peripheral blood mononuclear cell (PBMC). Cells exposed to oxLDL underwent apoptosis and necrosis, dependent on the duration of exposure. When culturing cells with oxLDL and the polar extract concurrently, we observed inhibition of both the phenomena. Because under oxidative stress the pro-oxidant systems outbalance the antioxidant, potentially producing oxidative damage and ultimately leading to cell death, we measured the levels of intracellular antioxidant glutathione (GSH). Additionally, we measured CD36 expression, a class B scavenger receptor, on CD14-positive cells, as CD36 has been identified as the oxLDL receptor in macrophages and may play a pivotal role in atherosclerotic foam cell formation. oxLDL decreased GSH levels and upregulated CD36 expression. P. lentiscus extract restored GSH levels and downregulated CD36 expression, even at the mRNA level. In order to find out the biologically drastic constituents of the resin's polar extract, fractions derived from RP-HPLC analysis were examined for their antioxidant effect on oxidatively stressed PBMC. The triterpenoid fraction revealed remarkable increase in intracellular GSH. We suggest GSH restoration and downregulation of CD36 mRNA expression as the pathways via which P. lentiscus triterpenes exert antioxidant/antiatherogenic effect. Additionally, our results provide strong evidence of the resin's antiatherogenic effect; therefore it is credited with beneficial health aspects.