Stable isotope studies in human evolution

The discipline of human evolution usually involves the evaluation of changes in gross and molecular morphology or changes in artifact assemblages. In contrast, stable isotope analysis is an indirect line of investigation. Understanding the human evolutionary sequence requires information on nutritional, biobehavioral, and general ecology. These are the kinds of information that stable isotope analysis can provide. Such studies may not identify the mechanisms for change, but their application serves to elucidate the situations under which change occurred.     

A segmentation clock patterns cellular differentiation in a bacterial biofilm

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Some effects of shark nets in the Natal nearshore environment

Synopsis Protective gillnets (shark nets) have been successful in reducing the frequency of shark attacks on the coast of Natal, South Africa. This is achieved primarily through a reduction in numbers of large sharks. The nets also take a by catch of dolphins, sea turtles, batoids and teleosts. Concern has been expressed over the direct effect of mortalities on the various stocks and also the broader, indirect effects on the inshore system. Catch rates of most shark species declined initially but have shown no trend since the mid-1970s. A first estimate of the reduction in total shark numbers is provided, and factors such as stock identity and net avoidance are discussed. Turtle and teleost stocks do not appear to be threatened by net mortalities but marine mammalogists are investigating the sustainability of catches of two dolphin species. Certain batoids may have declined despite a high release rate, but more data are needed. A published contention that shark netting has resulted in a proliferation of small sharks through reduced predation is re-examined and considered to be exaggerated. Reduced predation on dolphins, as a result of shark netting, is estimated.     

Characterising the morphological characters and carbohydrate metabolism of oat culms and their association with lodging resistance

• Lodging resistance can be improved by enhancing the mechanical strength of culms, and culm carbohydrates could improve this mechanical strength. Culm carbohydrates can regulate development of the culm and affect its toughness.
• The present study determines the relationship between lodging and carbohydrate content in oat culms. Field experiments were conducted in alpine regions in 2017 and 2018 using three oat varieties with different lodging resistance. Lodging‐related morphological characteristics were directly determined and culm carbohydrate content and enzyme activity related to cellulose synthesis and sucrose metabolism were evaluated with ultraviolet spectrophotometry.
• Results showed that the lower the gravity height or the lower ratio of gravity height to plant height, the stronger the lodging resistance of the varieties. Higher culm nonstructural (NSC) and structural (SC) carbohydrate content contributed to the ability of culms to resist lodging, especially the content of cellulose and sucrose. PCA showed that sucrose metabolism and SC content were closely related to lodging resistance. Correlation analysis showed that the lodging index (LI) was significantly negatively correlated with NSC. Sucrose content was highly and significantly positively correlated with NSC. Additionally, the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS) were highly and significantly positively correlated with sucrose and cellulose content.
• The relationship between field characters and oat lodging, as well as the regulatory mechanism of carbohydrate content on lodging resistance of the culm are discussed.

     

α-Tocopherol supplementation reduces 5-nitro-γ-tocopherol accumulation by decreasing γ-tocopherol in young adult smokers

Abstract

γ-Tocopherol (γ-T) scavenges reactive nitrogen species (RNS) to form 5-NO₂-γ-T (NGT). However, α-T supplementation decreases circulating γ-T, which could limit its RNS scavenging activities. We hypothesized that α-T supplementation would mitigate NGT accumulation by impairing γ-T status. Healthy smokers (21 ± 1 y, n = 11) and non-smokers (21 ± 2 y, n = 10) ingested 75 mg/d each of RRR- and all-rac-α-tocopheryl acetate for 6 d. Plasma α-T, γ-T, γ-carboxyethyl hydroxychromanol (CEHC), NGT, and nitrate/nitrite were measured prior to supplementation (Pre), the morning after 6 consecutive evenings of supplementation (Post 1), and on the mornings of d 6 (Post 6) and d 14 (Post 14) during the post-supplementation period. α-T supplementation increased plasma α-T, and decreased γ-T, in both groups and these returned to Pre concentrations on Post 6 regardless of smoking status. Plasma γ-CEHC increased after the first dose of supplementation in both groups, suggesting that α-T supplementation decreased plasma γ-T in part by increasing its metabolism. Plasma NGT and nitrate/nitrite concentrations at Pre were greater in smokers, indicating greater nitrative stress due to cigarette smoking. Plasma NGT concentration was lowered only in smokers on Post 1 and Post 6 and was restored to Pre levels on Post 14. Plasma nitrate/nitrite tended (P = 0.07) to increase post-supplementation only in smokers, supporting decreases in RNS scavenging by γ-T. Plasma NGT concentration was more strongly correlated (P < 0.05) with γ-T in smokers (R = 0.83) compared with non-smokers (R = 0.50), supporting that α-T-mediated decreases in γ-T reduces NGT formation. These data indicate that α-T supplementation limits γ-T scavenging of RNS in smokers by decreasing γ-T availability.     

Play and Intentionality Among Today's Preschoolers

A comparison is made of data on the level of development of play activity and its influence on the volitional behavior of today's preschoolers and the preschoolers of the 1940s–1950s. The results of the comparison point to a substantial decrease in the level of narrative role-playing among children today. The study reproduces the widely known experiment of Z.V. Manuilenko (1948). The comparison of data on preschoolers of the mid-twentieth century and the beginning of the twenty-first shows a significant decrease in the level of volitional behavior in both play and nonplay situations. The results suggest that primitive, underdeveloped play cannot define a zone of proximal development and fulfill the status of primary activity.     

不同含湿率及加载条件对人皮质骨纳米压痕测试的影响

目的:探讨不同含湿率及加载条件对人皮质骨纳米压痕测试的影响。方法:采用美国Hysitron纳米压痕仪,设定不同加载模式(高峰载荷分别为300、400、500 nm;加载速度分别为6、8、10 nm/s)对不同含湿率(20‰、30‰、40‰、50‰、60‰)人皮质骨进行弹性模量及硬度测量。结果:在同一加载模式下,不同含湿率标本的测试值随着含湿率增高,弹性模量及硬度值均显著降低(P0.01);三种不同加载模式对含湿率为20‰标本测试值无明显变化;对含湿率60‰标本测试值有显著性影响(P0.02)。结论:纳米压痕仪测试骨微观力学特性时,测试值不仅受标本本身含湿率的影响,当测试条件改变,对湿润标本测试结果也完全不同。当使用纳米压痕技术时,通常采用脱水包埋处理的标本测试出的机械性能,对我们在微观层面认识人体骨在湿润的生理环境下的机械性能是不够全面的。     

Tracking wind‐dispersed seeds using 15N‐isotope enrichment

Seed dispersal influences a wide range of ecological processes. However, measuring dispersal patterns, particularly long‐distance dispersal, has been a difficult task. Marking bird‐dispersed seeds with stable ¹⁵N isotopes has been shown to be a user‐friendly method to trace seed dispersal. In this study, we determined whether ¹⁵N urea solution could be used to enrich seeds of two common wind‐dispersed plants, Eupatorium glaucescens (Asteraceae) and Sericocarpus tortifolius (Asteraceae). We further tested if the water type (distilled versus tap) in ¹⁵N urea solutions influences the level and variability of enrichment of plant seeds, and if increasing spraying frequency per se increases enrichment. Because droughts may lower seed set or kill plants, we wanted to investigate if the additional use of an externally applied anti‐transpirant affects the intake of externally applied ¹⁵N into seeds. The results demonstrate that ¹⁵N enrichment of seeds can facilitate dispersal experiments with wind‐dispersed plants. The use of distilled water in ¹⁵N urea solutions did not increase ¹⁵N enrichment compared to tap water. Further, enrichment was more efficient at lower spray frequencies. Both the use of tap water and low frequencies could lower time, effort and project costs. The results suggest that species can be protected from drought using an anti‐transpirant without decreasing the incorporation of ¹⁵N into seeds.     

Analysis of the pathways of nitric oxide utilization in mitochondria

The regulatory role that mitochondria play in cell dysfunction and cell-death pathways involves the concept of a complex and multisite regulation of cellular respiration and energy production signaled by cellular and intercellular messengers. Hence, the role of nitric oxide, as a physiological regulator acting directly on the mitochondrial respiratory chain acquires further relevance. This article provides a survey of the major regulatory roles of nitric oxide on mitochondrial functions as an expression of two major metabolic pathways for nitric oxide consumption: a reductive pathway, involving mitochondrial ubiquinol and yielding nitroxyl anion and an oxidative pathway involving superoxide anion and yielding peroxynitrite. The modulation of the decay pathways for nitrogen-and oxygen-centered radicals is further analyzed as a function of the redox transitions of mitochondrial ubiquinol. The interplay among these redox processes and its implications for mitochondrial function is discussed in terms of the mitochondrial steady-state levels (and gradients) of nitric oxide and superoxide anion.     

饵料蛋白水平对德国小蠊肠道细菌群落的影响

昆虫肠道微生物在宿主营养代谢、生长发育、免疫以及抵御病原菌等方面具有重要作用。研究不同蛋白水平饵料饲养对德国小蠊（Blattella germanica）雄成虫肠道细菌群落组成及其功能的作用，探究德国小蠊肠道细菌对宿主营养和健康的影响，以期为发展生物防治的诱食性饵料提供理论支持。分别取连续饲喂低蛋白（LP2组：5%）、高蛋白（HP3组：65%）以及正常蛋白水平饵料（CD1组：25%）21 d的德国小蠊雄成虫，饥饿24 h后无菌条件下分离并提取肠道总基因组DNA，采用特异引物扩增细菌16S rDNA的V4可变区并进行高通量测序，分析德国小蠊肠道细菌群落组成及其功能特征。结果表明德国小蠊肠道细菌主要由拟杆菌门（Bacteroidetes）、变形菌门（Proteobacteria）、梭杆菌门（Fusobacteria）和厚壁菌门（Firmicutes）等细菌群落组成。饲喂低蛋白饵料LP2组的德国小蠊肠道细菌中拟杆菌属（Bacteroides）细菌丰度（47.44%）显著高于HP3组（23.97%）和对照CD1（7.04%）。饲喂高蛋白饵料的HP3组梭杆菌门丰度显著高于其他两组。LEfSe物种差异分析也表明HP3组德国小蠊肠道细菌中梭杆菌属（Fusobacterium）细菌与低蛋白饵料LP2组和对照CD1组有显著差异。基于Tax4Fun功能预测显示，HP3高蛋白饵料组的德国小蠊肠道细菌中与能量代谢功能相关基因的相对丰度极显著高于对照组CD1组，外源性物质代谢与降解和其他氨基酸代谢功能基因的相对丰度显著高于低蛋白LP2组。本研究结果表明饵料中蛋白质水平的差异能够显著改变德国小蠊肠道中细菌群落结构组成，并影响其代谢功能。