Implications of flexible-shelled eggs in a Cretaceous choristoderan reptile

Flexible, or soft-shelled, eggs are almost unknown in the fossil record, leaving large gaps in our knowledge of the reproductive biology of many tetrapod clades. Here, we report two flexible-shelled eggs of the hyphalosaurid choristodere Hyphalosaurus baitaigouensis from the Early Cretaceous of China, one containing an embryo and the second associated with a neonate. Choristoderes are an enigmatic group of aquatic reptiles that survived the K–T extinction but died out in the Miocene. Hyphalosaurids, a specialized clade of Choristodera, resemble miniature plesiosaurs and are considered to be primarily aquatic in habit. Scanning electron microscopy of samples from the eggs reveals a thin, non-columnar external mineralized layer characterized by rounded nodes and tentatively identified poorly structured irregular pores, with an underlying amorphous layer presumably representing decomposed protein fibrils. While the relationships of Choristodera remain controversial, eggshell microstructure more closely resembles that of Lepidosauromorpha (the lineage including lizards) as opposed to that of Archosauromorpha (the lineage including birds and crocodiles).     

Syphacia muris: Water permeability of eggs and its effect on hatching

As a result of a previous study, it appeared that hatching of eggs of Syphacia muris is activated by the application of heat (37 °C) or cysteine or trypsin but that these are not the essential stimuli. In the present study it has been established that exposure of eggs prior to hatching for several hours to 37 °C or cysteine or trypsin, or for 3 days to 22 °C, accelerated hatching. Pretreatment with 37 °C or cysteine or trypsin also increased permeability of the eggshell to water; however, it did not induce the operculum to open. The operculum opened only if the eggs, after pretreatment, were immersed in water. The larvae could leave the opened eggs only in water and not in any other medium such as paraffin oil. These data made it possible to distinguish between three stages in the hatching process. During Stage 1, the eggshell becomes permeable to water. This can be induced by dissolving the proteins of the eggshell in a trypsin solution or by stimulating the larvae with temperature or cysteine. The permeability of the eggshell is essential to successful hatching. In Stage 2, which occurs only in the presence of water, the larvae dissolve the chitinous seal between the operculum and the eggshell. In Stage 3 the larvae probably increase their size by water absorption and leave the eggs. In the discussion it has been proposed that all nematodes, both those hatching in the intestine and the species hatching in the open, could well have an identical hatching mechanism to the one observed in Syphacia muris.     

Water exchange of flexible-shelled eggs and its effect on hatchling traits in the Chinese skink,<Emphasis Type="Italic"> Eumeces chinensis</Emphasis>

Flexible-shelled eggs of the Chinese skink (Eumeces chinensis) were used to determine the routes of water exchange with the environment and the effects of water exchange on hatchling traits. Eggs were incubated under three different hydric conditions at 28 °C. One group (ground eggs) was half-buried in incubation substrate. The second group (upper eggs) rested on the ground eggs but did not contact the substrate directly, and the third group was placed on a plastic platform above the substrate. Ground and upper eggs increased in mass and hatched successfully, while all eggs resting on the plastic platform lost mass and died within a week. Hence, E. chinensis eggs cannot sustain water balance through exchange of water vapor in air alone, but can absorb water from the substrate and other eggs and develop well. Water gained by upper eggs was only 20% of that absorbed by ground eggs, but hatchlings from the two treatments did not differ in morphology or locomotor performance. Therefore, the degree of water exchange of E. chinesis eggs has little effect on embryonic development and hatchling traits. The insensitivity of the eggs to variations in water exchange may be an adaptation against extreme hydric conditions in a species that deposits its eggs close to the soil surface.Communicated by I.D. Hume     

不同孵化湿度下的乌龟卵孵化成功率及新生幼体特征

A total of 51 Chinese three-keeled pond turtle Chinemys reevesii eggs were incubated on wet and dry substrates (water potentials of - 12 kPa and - 300 kPa, respectively) at 30℃ to assess the influence of the hydric environments on egg survival and hatchling traits. Eggs incubated in the dry condition lost weight, whereas those incubated in the wet condition did not. The hydric environments did not affect incubation lengths (60.3 vs 60.7 days) as well as hatching successes (69.2% vs 88.0% ). Except for wet body mass and carapace width, which were larger for hatchlings from the -12 kPa treatment than from the -300 kPa treatment, the hydric environments did not affect most hatchling traits. These unaffected traits included dry body mass, carapace length, tail length, limb length, hatehling components (carcass, residual yolk and fat bodies), swimming performance and critical thermal minimum. In conclusion, within the water potential of -12 to -300 kPa, hydric environments have little effect on embryonic development and hatchling traits in Chinese three-keeled pond turtles [Acta Zoologica Sinica 50 (1) : 133 - 136, 2004].     

水热环境对白条草蜥孵化卵和孵出幼体表型特征的影响

用4×2(温度×湿度)八种水热环境孵化安徽滁州琅琊山白条草蜥(Takydromus wolteri)卵,观测孵化卵重量变化、胚胎利用卵内物质和能量以及孵出幼体的特征。卵从孵化环境中吸水导致重量增加,卵重量的增加与入孵卵重量、孵化温度和基质湿度有关。两种孵化基质湿度对孵化期、孵化成功率、孵出幼体性比和大小都无显著影响。孵化期随恒定孵化温度的升高而缩短,27℃、30℃和33℃孵化期分别为32.5、24.9和23.0d,波动温度孵化期为31.1d。33℃孵化成功率最低(42.8%)。温度对孵化成功率和孵出幼体的性别无显著影响,但显著影响胚胎对卵内物质的动用、幼体的大小和重量。33℃不适宜孵化白条草蜥卵,该温度下孵出的幼体躯干小,剩余卵黄多,运动能力差。27℃和波动温度中孵出幼体躯干发育良好,各项被测定的特征指标极其相似。     

Early breeding protects anuran eggs from Saprolegnia infection

Here, we studied the ecological significance of Saprolegnia infections (‘saprolegniasis’) on the survival and development of two populations of the endemic Patagonian anuran Pleurodema thaul (Anura, Leiuperidae). We found that four different Saprolegnia species infected eggs and embryos of P. thaul, indicating that the infection by these ‘zoosporic fungi’ was different in each anuran population and among different cohorts. Late anuran cohorts generally showed a higher incidence of infection than early cohorts, but we observed no clear overall pattern between populations. In addition, in laboratory experiments, we determined that some of the Saprolegnia species induce early hatching, and that hatching timing was variable between populations. In summary, we found that early breeding (by underlying priority effects) could improve the survival of the earliest cohorts of P. thaul by allowing them to survive the stress imposed by epidemic events of Saprolegnia.     

Selenium interactions with essential and toxic elements in egg yolk from commercial and fortified eggs

The main objective of this work was to evaluate the interaction between selenium concentration in both commercial and Se-enriched eggs and other essential/toxic elements (Ca, Mg, Fe, Zn, Pb, and Cd), taking into account a possible synergic action of iodine. Commercial eggs were purchased from several sale points or directly from the producers (farmyard eggs). Fortified eggs were obtained by supplementing chickenfeed for 6 weeks with Se as sodium selenite (1.0mug/g Se) or Se plus iodine (1.0mug/g Se+3.7mug/g I). Se in experimental egg yolks significantly increased over the basic value by 39% in the Se group and 61% in the Se+I group, suggesting that I addition may enhance Se absorption. Levels of Se in commercial yolks were identical in free-range, barn or battery eggs, but significantly lower in farmyard and higher in organic eggs where the Se content approximated that found in Se fortified eggs. A significant reduction in Cd was observed in Se+I treated yolks compared to both control and Se alone diet, thus suggesting a high sensitivity of Cd to the detoxifying effect of Se combined with I. Furthermore, Se+I supplementation was associated with a significant Zn reduction, a finding which needs clarification to avoid attempts to maximize one component affecting the levels of other essential elements.     

ER stress protects from retinal degeneration

The unfolded protein response (UPR) is a specific cellular process that allows the cell to cope with the overload of unfolded/misfolded proteins in the endoplasmic reticulum (ER). ER stress is commonly associated with degenerative pathologies, but its role in disease progression is still a matter for debate. Here, we found that mutations in the ER‐resident chaperone, neither inactivation nor afterpotential A (NinaA), lead to mild ER stress, protecting photoreceptor neurons from various death stimuli in adult Drosophila. In addition, Drosophila S2 cultured cells, when pre‐exposed to mild ER stress, are protected from H₂O₂, cycloheximide‐ or ultraviolet‐induced cell death. We show that a specific ER‐mediated signal promotes antioxidant defences and inhibits caspase‐dependent cell death. We propose that an immediate consequence of the UPR not only limits the accumulation of misfolded proteins but also protects tissues from harmful exogenous stresses.     

Hydroxytyrosol protects retinal pigment epithelial cells from acrolein-induced oxidative stress and mitochondrial dysfunction

Hydroxytyrosol (HTS) is a natural polyphenol abundant in olive oil. Increasing evidence indicates HTS has beneficial effect on human health for preventing various diseases. In the present study, we investigated the protective effects of HTS on acrolein-induced toxicity in human retinal pigment epithelial cell line, ARPE-19, a cellular model of smoking- and age-related macular degeneration. Acrolein, a major component of the gas phase cigarette smoke and also a product of lipid peroxidation in vivo , at 75 μmol/L for 24 h caused significant loss of cell viability, oxidative damage (increase in oxidant generation and oxidative damage to proteins and DNA, decrease in antioxidants and antioxidant enzymes, and also inactivation of the Keap1/Nrf2 pathway), and mitochondrial dysfunction (decrease in membrane potential, activities of mitochondrial complexes, viable mitochondria, oxygen consumption, and factors for mitochondrial biogenesis, and increase in calcium). Pre-treatment with HTS dose dependently and also time dependently protected the ARPE-19 cells from acrolein-induced oxidative damage and mitochondrial dysfunction. A short-term pre-treatment with HTS (48 h) required > 75 μmol/L for showing protection while a long-term pre-treatment (7 days) showed protective effect from 5 μmol/L on. The protective effect of HTS in this model was as potent as that of established mitochondria-targeting antioxidant nutrients. These results suggest that HTS is also a mitochondrial-targeting antioxidant nutrient and that dietary administration of HTS may be an effective measure in reducing and or preventing cigarette smoke-induced or age-related retinal pigment epithelial degeneration, such as age-associated macular degeneration.     

Effect of caulerpenyne,a toxin extracted from Caulerpa taxifolia on mechanisms regulating intracellular pH in sea urchin eggs and sea bream hepatocytes

The proliferation of the green marine alga Caulerpa taxifolia in the Mediterranean led us to investigate the toxic effects on marine organisms of caulerpenyne (Cyn), the major secondary metabolite synthesized by the alga. This study was performed on sea urchin eggs (Paracentrotus lividus) and isolated hepatocytes from the sea bream (Sparus aurata), in which accumulation of the toxins by metabolic processes may be of significance. Cyn provoked an acidification of seawater containing both unfertilized and fertilized eggs, as revealed by a titrable efflux of protons. The pHi in unfertilized eggs continuously increased in the presence of Cyn, whereas there was a biphasic response in both fertilized eggs and isolated hepatocytes, with a decrease of the pHi followed by recovery to the initial value. Cyn inhibited the accumulation of ¹⁴C-methylamine in acidic granules present in the cortical zone of sea urchin eggs. Dicyclocarbodiimide (DCCD), a well-known H⁺-ATPase inhibitor, provoked a similar inhibition. Both molecules increased pH in the acidic compartments of isolated bream hepatocytes. These results suggest that Cyn inhibits intracellular sequestration of protons and thus liberates protons into the cell cytoplasm from which they leak toward the extracellular medium. © 1997 John Wiley & Sons, Inc.     

歪水蚤两种生理型卵的季节变化及其温度效应

实验室观测表明,3种歪水蚤的卵皆覆以半透明外鞘,仅特氏歪水蚤生产一定数量的不孵的无鞘卵。特氏歪水蚤夏卵与滞育卵的外鞘形态不同,前者较窄(≤15μm)且折皱均匀,后者多宽而折皱不均匀,随其外鞘加宽,活力明显提高。在钳形歪水蚤,两种卵的形态无明显差异;而右突歪水蚤尚未发现能够生产滞育卵。歪水蚤卵型的复杂多变,可能与其能够生产两种不同生理型卵的遗传特性正相适应。在短至12小时和6天的驯养期内,右突歪水蚤所产卵的卵径和鞘宽均分别与温度呈显著负相关及正相关,并随季节而异;这进一步表明动物对本海区温度季节性变化的适应。     

Oviposition deterrents from eggs of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae): chemical identification and analysis by electroantennogram

Our previous results showed that an extract of the abdomens of mated females of the cotton bollworm, Helicoverpa armigera, deterred oviposition of conspecifics. In this paper, we found that the extract, in addition to reducing conspecifics’ oviposition, could elicit strong electroantennogram responses from mated females. The EAG elicitors mainly came from mature chorionated eggs in the ovarioles. Laid eggs or their surface extract evoked similar EAG responses. The main chemical components of the EAG elicitors from mature chorionated and laid eggs were myristic, palmitic, stearic, and oleic acids. A blend of authentic fatty acids at the ratio found in the laid eggs and in an amount equivalent to 100 laid eggs mimicked the EAG response and deterring effect. Moreover, these four oviposition-deterring fatty acids and their corresponding methyl esters evoked significantly higher EAG responses from both mated females and males than hexane blank and background. The EAG values differed among the test chemicals and between sexes. These results demonstrate that the four fatty acids from eggs are at least partially responsible for the oviposition-deterring effect of the extract from the abdomens of mated female H. armigera and that the moths may detect these chemicals olfactorily by antennae.     

恒定和波动温度下丽斑麻蜥孵出幼体的表型变异

作者以丽斑麻蜥(Eremias argus)为模型动物研究恒定和波动孵化温度对孵化成功率和孵出幼体表型的影响。卵在四个恒定[24 ,27 ,30 and 33 (±0·3)℃]、一个波动温度下孵化。不同温度处理下的孵化成功率相同,但孵出幼体表型不同。孵化期随孵化温度升高呈指数式缩短;在相同平均温度下,波动温度孵化卵的孵化期比恒温孵化卵长。在所有被检表型特征中,幼体的干重、剩余卵黄干重和运动表现更易受孵化温度影响。总体而言,低温(24℃、27℃)孵出幼体运动表现最佳,高温(33℃)孵出幼体最差、温和温度(30℃和波动温度)孵出幼体居中。本文研究数据显示: (1)丽斑麻蜥卵每日短期暴露于潜在致死的极端温度下对孵化成功率和孵出幼体形态特征无明显的不利效应; (2)温度波动对孵出幼体运动表现无促进作用,对孵化期的影响则不同于平均值相同的恒定温度。     

Treatment with acetyl salicylic acid protects muskmelon seedlings against drought stress

Salicylic acid (SA) is a common plant-produced signal molecule that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was, therefore, conducted to test whether acetyl salicylic acid (ASA) application at various concentrations through seed soaking or foliar spray would protect muskmelon [Cucumis melo L. (reticulatus group)] seedlings, subjected to drought stress. Twenty-three-day-old plants pre-treated with ASA (0, 0.1, 0.25, 0.50 or 1.0 mM) were subjected to drought stress for 1 week in a greenhouse. ASA applied either through seed soaking or through foliar spray was effective within the range of 0.1–1 mM in providing drought stress protection in muskmelon seedlings; however, there was no difference between application methods indicating that both methods provided similar levels of protection. ASA significantly affected all seedling growth and stress indicator variables measured except leaf number and root dry weight. The best protection appeared to be obtained from seedlings pre-treated with lower concentrations of ASA. Even though both methods provided similar means of protection, due to its simplicity and practicality, soaking muskmelon seeds prior to sowing in up to 0.5 mM ASA would be a more desirable method.     

Isoprene synthesis protects transgenic tobacco plants from oxidative stress

Isoprene emission represents a significant loss of carbon to those plant species that synthesize this highly volatile and reactive compound. As a tool for studying the role of isoprene in plant physiology and biochemistry, we developed transgenic tobacco plants capable of emitting isoprene in a similar manner to and at rates comparable to a naturally emitting species. Thermotolerance of photosynthesis against transient high-temperature episodes could only be observed in lines emitting high levels of isoprene; the effect was very mild and could only be identified over repetitive stress events. However, isoprene-emitting plants were highly resistant to ozone-induced oxidative damage compared with their non-emitting azygous controls. In ozone-treated plants, accumulation of toxic reactive oxygen species (ROS) was inhibited, and antioxidant levels were higher. Isoprene-emitting plants showed remarkably decreased foliar damage and higher rates of photosynthesis compared to non-emitting plants immediately following oxidative stress events. An inhibition of hydrogen peroxide accumulation in isoprene-emitting plants may stall the programmed cell death response which would otherwise lead to foliar necrosis. These results demonstrate that endogenously produced isoprene provides protection from oxidative damage.     

Nanoparticle-mediated catalase delivery protects human neurons from oxidative stress

Several neurodegenerative diseases and brain injury involve reactive oxygen species and implicate oxidative stress in disease mechanisms. Hydrogen peroxide (H₂O₂) formation due to mitochondrial superoxide leakage perpetuates oxidative stress in neuronal injury. Catalase, an H₂O₂-degrading enzyme, thus remains an important antioxidant therapy target. However, catalase therapy is restricted by its labile nature and inadequate delivery. Here, a nanotechnology approach was evaluated using catalase-loaded, poly(lactic co-glycolic acid) nanoparticles (NPs) in human neuronal protection against oxidative damage. This study showed highly efficient catalase encapsulation capable of retaining∼99% enzymatic activity. NPs released catalase rapidly, and antioxidant activity was sustained for over a month. NP uptake in human neurons was rapid and nontoxic. Although human neurons were highly sensitive to H₂O₂, NP-mediated catalase delivery successfully protected cultured neurons from H₂O₂-induced oxidative stress. Catalase-loaded NPs significantly reduced H₂O₂-induced protein oxidation, DNA damage, mitochondrial membrane transition pore opening and loss of cell membrane integrity and restored neuronal morphology, neurite network and microtubule-associated protein-2 levels. Further, catalase-loaded NPs improved neuronal recovery from H₂O₂ pre-exposure better than free catalase, suggesting possible applications in ameliorating stroke-relevant oxidative stress. Brain targeting of catalase-loaded NPs may find wide therapeutic applications for oxidative stress-associated acute and chronic neurodegenerative disorders.