Nonrandomness of point mutation as reflected in nucleotide substitutions in pseudogenes and its evolutionary implications

Summary We have obtained a revised estimate of the pattern of point mutation by considering more pseudogene sequences. Compared with our previous estimate, it agrees better with expectations based on the double-strand structure of DNA. The revised pattern, like the previous one, indicates that mutation occurs nonrandomly among the four nucleotides. In particular, the proportion of transitional mutations (59%) is almost twice as high as the value (33%) expected under random mutation. The same high proportion of transitions is observed in synonymous substitutions in genes. The proportion of transitional changes observed among electrophoretic variants of human hemoglobin is about the same as that predicted by the revised pattern of mutation. We also show that nonrandom mutation increases, by about 15%, the proportion of synonymous mutations due to single-nucleotide changes in the codon table, and increases, from 10% to 50%, the rate of synonymous mutation in the seven genes studied. However, nonrandom mutation reduces (by about 10%) the proportion of polar changes among nonsynonymous mutations in a gene. As far as single-nucleotide changes (in the codon table) are concerned, nonrandom mutation only slightly favors relatively conservative amino acid interchanges, and has virtually no effect on the proportions of radical changes and nonsense mutations.     

Magnetic field dependence of radical-pair decay kinetics and molecular triplet quantum yield in quinone-depleted reaction centers

Radical-pair decay kinetics and molecular triplet quantum yields at various magnetic fields are reported for quinone-depleted reaction centers from the photosynthetic bacterium Rhodopseudomonas sphaeroides R26. The radical-pair decay is observed by picosecond absorption spectroscopy to be a single exponential to within the experimental uncertainty at all fields. The decay time increases from 13 ns at zero field to 17 ns at 1 kG, and decreases to 9 ns at 50 kG. The orientation averaged quantum yield of formation of the molecular triplet of the primary electron donor, ³P, drops to 47% of its zero-field value at 1 kG and rises to 126% at 50 kG. Combined analysis of these data gives a singlet radical-pair decay rate constant of 5 · 10⁷s^?1, a lower limit for the triplet radical-pair decay rate constant of 1 · 10⁸s^?1 and a lower limit for the quantum yield of radical-pair decay by the triplet channel of 38% at zero field. The upper limit of the quantum yield of ³P formation at zero field is measured to be 32%. In order to explain this apparent discrepancy, decay of the radical pair by the triplet channel must lead to some rapid ground state formation as well as some ³P formation. It is proposed that the triplet radical pair decays to a triplet charge-transfer state which is strongly coupled to the ground state by spin-orbit interactions. Several possibilities for this charge-transfer state are discussed.     

Alterations of human erythrocyte membrane fluidity by oxygen-derived free radicals and calcium

Two possible reasons for the structural alterations of cell membranes caused by free radicals are lipid peroxidation and an increase in the intracellular calcium ion concentration. To characterize the alterations in membrane molecular dynamics caused by oxygen-derived free radicals and calcium, human erythrocytes were spin-labeled with 5-doxyl stearic acid, and alterations in membrane fluidity were quantified by electron spin resonance oxidase (0.07 U/mL) decreased membrane fluidity, and the addition of superoxide dismutase and catalase inhibited the effect on membrane fluidity of the hypoxanthine-xanthine oxidase system. Hydrogen peroxide (0.1 and 1 nM) also decreased membrane fluidity and caused alterations to erythrocyte morphology. In addition, a decrease in membrane fluidity was observed in erythrocytes incubated with 2.8 mM CaCl₂. On the other hand, incubation of erythrocytes with calcium-free solution decreased the changes in membrane fluidity caused by hydrogen peroxide.

These results suggest that changes in membrane fluidity are directly due to lipid peroxidation and are indirectly the result of increased intracellular calcium concentration. We support the hypothesis that alterations of the biophysical properties of membranes caused by free radicals play an important role in cell injury, and that the accumulation of calcium amplifies the damge to membranes weakened by free radicals.     

血清白介素8基因多态性与食管鳞癌根治术后的相关性分析

摘要 目的：探讨与分析血清白细胞介素8（IL-8）基因多态性与食管鳞癌（ESCC）根治术后的相关性。方法：2017年8月到2020年6月选择在本院诊治的食管鳞癌患者98例作为研究对象,检测血清IL-8表达水平。所有患者都给予根治手术治疗,随访患者的预后并进行相关性分析。结果：所有患者术后随访到2021年7月,平均随访时间为25.69±2.58个月,死亡28例,死亡率为28.6 %（死亡组）。两组血清IL-8表达水平表达具有差异（P<0.05）。所有患者的基因型频率均符合Hardy-Weinberg这一平衡法则,表明本文所选取的样本均具有群体代表性。IL-8基因启动子rs4073A/T的AA基因型较死亡组高,TT基因型较死亡组低,两组A、T等位基因频率分布对比有差异（P<0.05）。直线相关性分析显示：IL-8基因启动子rs4073A/T的AA基因型、A等位基因、血清IL-8表达水平与预后死亡率存在相关性（P<0.05）。多因素logistic回归分析显示：IL-8基因启动子rs4073A/T的AA基因型、A等位基因、血清IL-8表达水平为导致患者随访死亡的主要因素（OR=2.051,3.094,P<0.05）。结论：食管鳞癌根治术后患者依然存在一定的死亡率,患者死亡与血清IL-8基因多态性存在相关性,同时多伴随有IL-8的高表达。IL-8基因启动子rs4073A/T的AA基因型、A等位基因、血清IL-8表达水平为导致患者死亡的主要因素。     

肺癌根治术后并发症危险因素分析及其生活质量变化研究

摘要 目的：探讨肺癌根治术后并发症的危险因素,并分析其生活质量的变化。方法：纳入我院2018年9月～2020年7月收治的行肺癌根治术患者104例,对患者的临床资料进行回顾性分析。根据患者术后3个月的并发症发生情况,分成并发症组（n=32）和非并发症组（n=72）,分析肺癌根治术后并发症发生的影响因素,利用癌症病人生活质量测定量表（QLQ-C30）评估患者术前及术后3个月的生活质量。结果：肺癌根治术后32例出现并发症,其中切口感染6例,肺炎7例,肺不张9例,心律失常6例,脓胸4例。并发症组年龄≥60岁、烟龄≥10年、传统开胸术、慢性阻塞性肺疾病史人数占比高于非并发症组（P＜0.05）。多因素Logistic回归分析显示,年龄≥60岁（OR=2.978,95%CI：1.415-6.267）、烟龄≥10年（OR=3.847,95%CI：1.869-7.918）、传统开胸术（OR=3.065,95%CI：1.544-6.084）、慢性阻塞性肺疾病史（OR=2.848,95%CI：1.481-5.477）是肺癌根治术后患者发生并发症的危险因素（P＜0.05）。非并发症组术后3个月的总体生活质量量表、角色功能、躯体功能、情绪功能、社会功能评分高于术前与并发症组,且恶心呕吐、疲乏、疼痛、便秘、呼吸困难、食欲下降、睡眠障碍、腹泻评分较术前与并发症组明显降低（P＜0.05）。结论：肺癌根治术后并发症的发生主要与患者年龄、烟龄、手术方式、慢性阻塞性肺疾病史有关,且并发症对患者术后生活质量影响较大。     

Fluorescence Detection of Free Radicals by Nitroxide Scavenging

The fluorescence quantum yield of 4-(1-napthoyloxy)-2,2,6,6-tetramethylpiperidine-l-oxyl (I) in acetonitrile and hexane is 55 and 30-fold lower, respectively, than those of diamagnetic analogs. Experiments described herein demonstrate that this property makes possible the fluorescence detection of radical scavenging reactions in which the paramagnetic nitroxide-substituted naphthalene is converted to a diamagnetic N-alkoxy derivative. 2-Cyanopropyl free radicals were generated by the thermal decomposition of azobisisobutyronitrile (AIBN) in cyclohexane or in acetonitrile containing 1. The fluorescence intensity of the sample increased proportionally to the decrease in its ESR signal intensity, indicating the conversion of the paramagnetic nitroxide to the diamagnetic product. The linear relationship between the increase in fluorescence intensity and decrease in ESR signal intensity shows that the changes in the fluorescence intensity can serve as a sensitive means for optically detecting radicals.     

Free Radical Participation in Bacterial Bioluminescence

The metastable intermediate II produced on reaction of bacterial luciferase with reduced flavin mononucleotide and O₂, reacts with any of several stable free radicals to produce bioluminescence. The bioluminescence spectrum is very similar to that from the well-studied intermediate II and aldehyde reaction, and the number of photons per luciferase molecule reacted is at least 40% of the aldehyde reaction.     

Free radical scavenging activity,total phenolic content,total antioxidant status,and total oxidant status of endemic Thermopsis turcica

Thermopsis turcica, endemic to Turkey, is in danger of extinction. Studies on this species are very few due to the fact that it was only discovered in 1983 and grows in a small circumscribed area in Turkey. In this study, free radical scavenging activity, total phenolic content, total oxidant status (TOS), and total antioxidant status (TAS) of methanol (TTM) and acetone (TTA) extracts of T. turcica were measured spectroscopically. Free radical scavenging activity was determined according to the elimination of DPPH radicals and total phenol content was determined by the Folin–Ciocalteu reaction. Total oxidant status (TOS) and total antioxidant status (TAS) were measured with commercially available kits. Methanol and acetone extracts of T. turcica were found to have a specific radical scavenging effect. This effect was found to be related to the total phenolic content of the extracts. Since the TTA had a higher phenolic content than the methanol extract, it had a stronger radical scavenging effect. In addition, the total antioxidant capacity of the methanol extract was observed to be higher than that of its acetone counterpart. As a result, due to its antioxidative properties, T. turcica is thought to be a natural source of antioxidants.     

Dodonaea viscosa var. angustifolia leaf: New source of polysaccharide and its anti-oxidant activity

Ultrasonic technology was applied for polysaccharide extraction from the leaves of Dodonaea viscosa and response surface methodology (RSM) was used to optimize the effects of processing parameters on polysaccharide extraction yield. Three independent variables were extraction time (X₁), extraction temperature (X₂) and ultrasonic power (X₃), respectively. The statistical analysis indicated the independent variables (X₁, X₂, X₃), the quadratic terms (X₁₁ and X₃₃) and the interaction terms (X₁X₂, X₁X₃, X₂X₃) had significant effects on the yield of polysaccharides (P < 0.05). The optimal extraction conditions of D. viscosa leaf were determined as follows: extraction time 50.54 min, extraction temperature 85 °C and ultrasonic power 400 W. Under these conditions, the experimental yield of polysaccharides was 9.455 ± 0.24%, which was agreed closely with the predicted value (9.398%). The evaluation of anti-oxidant activity suggested that the polysaccharide exhibited significant protection against DPPH and hydroxyl radicals and could be explored as a nutraceutical agent.     

Hydroxylated chalcones with dual properties: Xanthine oxidase inhibitors and radical scavengers

In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen–Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure–activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones’ effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class.