A long way to stemness

Comment on: Tanaka Y, et al. Proc Natl Acad Sci USA 2012; 109:4515-20.     

Morphological specializations of the yolk sac for yolk processing in embryonic corn snakes (Pantherophis guttatus: Colubridae)

Non‐avian reptiles commonly are assumed to be like birds in their overall patterns of development. However, colubrid corn snakes (Pantherophis guttatus ) have mechanisms of yolk cellularization and processing that are entirely different from the avian pattern. In birds, a vascular “yolk sac” surrounds and digests the liquid yolk. In contrast, in corn snakes, the yolk material is converted into vascularized cords of yolk‐filled cells. In this study, we used stereomicroscopy, histology, and scanning electron microscopy to analyze this unusual developmental pattern in corn snakes. Our observations reveal that the yolk sac cavity is invaded by endodermal cells that proliferate, absorb yolk spheres, and form aggregates of interconnected cells within the liquid yolk mass. As development proceeds, small blood vessels arise from the yolk sac omphalopleure, penetrate into the yolk mass, and become tightly encased in the endodermal cells. The entire vitellus ultimately becomes converted into a mass of vascularized, “spaghetti‐like” strands of yolk‐laden cells. The resulting arrangement allows yolk to be digested intracellularly and yolk products to be transported to the developing embryo. Indirect evidence for this pattern in other species raises the possibility that it is ancestral for squamates and quite possibly Reptilia in general.     

Residual force enhancement contributes to increased performance during stretch-shortening cycles of human plantar flexor muscles in vivo

It is well known that muscular force production is history-dependent, which results in enhanced (RFE) and depressed (RFD) steady-state forces after stretching and shortening, respectively. However, it remains unclear if force-enhancing mechanisms can contribute to increased performance during in vivo stretch-shortening cycles (SSCs) of human locomotor muscles. The purpose of this study was to investigate whether RFE-related mechanisms contribute to enhanced force and power output during SSCs of the human plantar flexor muscles. Net ankle torques of fourteen participants were measured during and after pure isometric, pure stretch, pure shortening, and SSC contractions when the triceps surae muscles were electrically stimulated at a submaximal level that resulted in 30% of their maximum isometric torque. Dynamic contractions were performed over an amplitude of 15°, from 5° plantar flexion to 10° dorsiflexion, at a speed of 120° s⁻¹. External ankle work during shortening was 11.6% greater during SSCs compared to pure shortening contractions (p = .003). Additionally, RFD after SSCs (8.6%) was reduced compared to RFD after pure shortening contractions (12.0%; p < .05). It is therefore concluded that RFE-related mechanisms contribute to increased performance following SSCs of human locomotor muscles. Since RFD after SSCs decreased although work during shortening was increased, we speculate that the relevant mechanism lies outside actin-myosin interaction. Finally, our data suggests that RFE might be relevant and beneficial for human locomotion whenever a muscle is stretched, but this needs to be confirmed.     

鸡抗CHO细胞蛋白的IgY消长规律及其制备的试验研究

采用五种免疫程序分别免疫来亨鸡以制备抗体;ELISA检测不同免疫方案鸡抗体水平变化规律。结果显示,不同免疫程序接种来亨鸡后抗体产生水平不同。末针免疫28d后,4针低剂量肌肉免疫组抗体水平显著低于4针高剂量肌肉免疫组(P<0.01);3针低剂量肌肉免疫组抗体水平显著低于3针高剂量肌肉免疫组(P<0.01);肌肉免疫组抗体水平低于皮下免疫组(P<0.05)。所有组均在末针免疫20d后出现抗体高峰,抗体水平可持续30d以上;SDS-PAGE结果显示纯化IgY纯度可达99%,抗体ELISA效价大于1∶105。     

Egg yolk plasma can replace egg yolk in stallion freezing extenders

Hen egg yolk is normally used as a cryoprotective agent in semen freezing extenders, but its use has sanitary and practical disadvantages. Moreover the protection afforded by egg yolk has not yet been completely elucidated. The objective of this study was to compare the egg yolk plasma fraction to whole egg yolk in stallion freezing extender. Plasma contains mainly Low Density Lipoproteins (LDL), which are widely presumed to be the cryoprotective agent in egg yolk. Plasma can be produced on an industrial scale, sterilised by gamma-irradiation and incorporated in a ready-to-use extender (our ultimate objective). Plasma samples were subjected to different doses of gamma-irradiation (3, 5, 10 kGy) without dramatic chemical changes that may affect their cryoprotective properties. Stallion semen was frozen with whole egg yolk as a control and with sterilised egg yolk plasma. A fertility trial was conducted on a total of 70 mares' cycles. Fertility per cycle was 60% after insemination of semen frozen in our control extender containing egg yolk (EY), compared to 69% for the extender containing sterilised egg yolk plasma (EYP) (P > 0.05). Post-thaw motility and membrane integrity of spermatozoa were also analysed. Motility parameters were not significantly different between extenders except for the variable VAP (for EY versus EYP, VAP: 63 μm.s⁻¹ versus 59 μm.s⁻¹, a, b: P < 0.001; PROG: 41% versus 39%, RAP30: 56% versus 54%; RAP40: 51% versus 48%, P > 0.05). Membrane integrity was better preserved in EY than in EYP but the difference between extenders was small (P < 0.05). Our results demonstrated that sterilised egg yolk plasma has the potential to replace egg yolk in stallion freezing extender. This experiment led to the development of a ready-to-use extender called INRA-Freeze^® (IMV-Technologies, France).     

Egg size and offspring quality: a meta‐analysis in birds

Parents affect offspring fitness by propagule size and quality, selection of oviposition site, quality of incubation, feeding of dependent young, and their defence against predators and parasites. Despite many case studies on each of these topics, this knowledge has not been rigorously integrated into individual parental care traits for any taxon. Consequently, we lack a comprehensive, quantitative assessment of how parental care modifies offspring phenotypes. This meta‐analysis of 283 studies with 1805 correlations between egg size and offspring quality in birds is intended to fill this gap. The large sample size enabled testing of how the magnitude of the relationship between egg size and offspring quality depends on a number of variables. Egg size was positively related to nearly all studied offspring traits across all stages of the offspring life cycle. Not surprisingly, the relationship was strongest at hatching but persisted until the post‐fledging stage. Morphological traits were the most closely related to egg size but significant relationships were also found with hatching success, chick survival, and growth rate. Non‐significant effect sizes were found for egg fertility, chick immunity, behaviour, and life‐history or sexual traits. Effect size did not depend on whether chicks were raised by their natural parents or were cross‐fostered to other territories. Effect size did not depend on species‐specific traits such as developmental mode, clutch size, and relative size of the egg, but was larger if tested in captive compared to wild populations and between rather than within broods. In sum, published studies support the view that egg size affects juvenile survival. There are very few studies that tested the relationship between egg size and the fecundity component of offspring fitness, and no studies on offspring survival as adults or on global fitness. More data are also needed for the relationships between egg size and offspring behavioural and physiological traits. It remains to be established whether the relationship between egg size and offspring performance depends on the quality of the offspring environment. Positive effect sizes found in this study are likely to be driven by a causal effect of egg size on offspring quality. However, more studies that control for potential confounding effects of parental post‐hatching care, genes, and egg composition are needed to establish firmly this causal link.     

地衣芽孢杆菌对养殖水体氨氮、残饵降解特性研究

试验对从健康养殖大黄鱼肠道中分离筛选到的一株益生地衣芽孢杆菌X3914的氨氮、残饵降解特性进行了研究。结果表明,X3914菌株降解氨氮的最适温度、盐度和pH分别为30℃、2.0%和7.0,在氨氮初始浓度为100 mg/L时,24h内的氨氮降解率达到36.2%。通过向添加1%饲料的大黄鱼养殖用水中接种1%和5%(体积比)的菌量(菌浓度约为9.0×108 cfu/L)来研究地衣芽孢杆菌浓度对降解饲料中蛋白质、淀粉的影响。结果表明,接种5%菌量的降解率均高于1%菌量的降解率,其中,48h内接种5%菌量的蛋白质和淀粉的降解率分别为35.2%和52.6%。X3914菌株具有较好的氨氮、饲料蛋白质和淀粉的降解能力,在水产养殖上具有潜在的应用价值。     

Comparative toxicity,growth inhibitory and biochemical effects of terpenes and phenylpropenes on Spodoptera littoralis (Boisd.)

Eleven monoterpenes, phenylpropenes and sesquiterpenes were evaluated for their insecticidal and growth inhibitory activities against the second and fourth larval instars of Spodoptera littoralis. Among the tested compounds, 1,8-cineole revealed the highest fumigant toxicity against the 2nd and 4th larval instars with LC₅₀ values of 2.32 and 3.13 mg/L air, respectively. The monoterpenes, p-cymene, α-terpinene, (−)α-pinene and (−)-carvone were highly toxic to both larval stages as their LC₅₀ values ranged between 7.35 and 13.79 mg/L air against 2nd larval instar and between 14.66 and 32.02 mg/L air against 4th larval instar. In topical application assay against the 4th larval instar, (−)-carvone (LD₅₀ = 0.15 mg/larva) and cuminaldehyde (LD₅₀ = 0.27 mg/larva) were the most potent contact toxicants. In residual film assay, trans-cinnamaldehyde, (−)-citronellal and p-cymene showed the highest insecticidal activity against the 2nd larval instar, while α-terpinene and (−)-carvone were most effective compounds against the 4th larval instar. Moreover, the tested compounds caused strong growth reduction of both larval stages with growth inhibition higher than 80% in the 2nd larval instar and higher than 70% in the 4th larval instar. On the other hand, (−)-carvone, cuminaldehyde and (Z,E)-nerolidol showed pronounced inhibitory effects on acetylcholinesterase (AChE) and adenosine triphosphatases (ATPases) activity of S. littoralis larvae. Cuminaldehyde (IC₅₀ = 1.04 mM) and (Z,E)-nerolidol (IC₅₀ = 0.02 mM) caused the highest inhibition of AChE and ATPases, respectively. Taken together, the results indicate that monoterpenes, phenylpropenes and phenylpropenes could be used to develop new botanical insecticides for S. littoralis management.