Role of the vitellus in the block to polyspermy in golden hamster eggs

The block to polyspermy in golden hamster eggs is believed to operate only at the zona pellucida. However, changes in the egg vitellus also prevent further entry of capacitated sperm. When zona-free hamster eggs spontaneously activated in vitro, and in vivo fertilized eggs at pronuclear stage were inseminated with capacitated human sperm, penetration did not occur. In the case of a homologous system using hamster sperm and in vivo fertilized hamster eggs, slight attachment of sperm was observed but no penetration. The cortical granules were found to be released in spontaneously activated and in fertilized eggs as observed by phase contrast microscopy. These observations suggest that the egg vitellus plays a role in the block to poiyspermy in addition to that of the zona block.     

Egg white lysozyme is the major protein of the hen's egg vitelline membrane

Lysozyme accounts for 37% of the proteins of the hen's egg vitelline membrane. It can be extracted by salt solutions and purified by gel filtration on Sephadex G-50. There are no differences between the chemical and enzymic properties of egg white and vitelline membrane lysozymes. Vitelline membranes of ovarian eggs do not contain lysozyme. It is thus concluded that lysozyme is localized in the outer layer. Vitelline membranes from fertilized and unfertilized eggs contain the same amount of lysozyme; its percentage decreases after two days of incubation.     

Spatial distribution of abundant proteins in oocytes and fertilized eggs of the Mexican axolotl (Ambystoma mexicanum)

Two-dimensional protein patterns were compared from sections along the longitudinal axis of oocytes and fertilized eggs of the Mexican axolotl (Ambystoma mexicanum). Only a few differences were observed between four different sections through both oocyte and fertilized eggs. A set of proteins (14 out of 120 proteins) were found that reside only in the germinal vesicles (GV) of the fully grown oocyte. Two of these were observed exclusively in the vegetal half, and one in the animal half after GV breakdown, while other proteins were randomly distributed within the fertilized egg. One cytoplasmic protein was present only in the vegetal half of the mature oocyte and became present also in the animal half of the fertilized egg. Additional proteins were observed in all transverse sections of both mature oocyte and fertilized eggs. It is proposed that these proteins are modified rather than newly synthesized proteins.     

On protein fractions and inorganic ions in sea urchin eggs,unfertilized and fertilized

Frozen and dried unfertilized or fertilized eggs were subjected to extraction by 1-N KCl solution according to the method inaugurated by Mirsky.In confirmation of Mirsky's results a certain protein fraction seemed to become insoluble in normal fertilization of the egg.The differences proved almost to vanish if the eggs prior to fertilization were subjected to trypsin treatment which removes the vitelline membrane and thus inhibits the formation of a continuous fertilization membrane.An obvious correlation was found between the percentage of extracted proteins and the salt content of the egg samples (fig. 1). This is particularly high in frozen and dried fertilized eggs with the fertilization membrane normally formed. This probably accounts entirely for the previously reported differences between unfertilized and fertilized eggs.Extraction of the frozen and thawed eggs with distilled water gave the same general picture as extraction with N KCl. Here also the solubility of the proteins is correlated with the salt content of the samples.The dialyzed water extracts gave a strong precipitation upon addition of Ca (optimum at 0.0125-0.025 M). Freezing and thawing of the extracts likewise cause a precipitation of a certain fraction.The fraction which becomes insoluble in the presence of high salt content of the sample and that precipitated from extracts by additions of Ca or by freezing and thawing seem to be identical. It contains the soluble nucleoprotein of the eggs.No changes in Ca or Mg content was found to occur upon fertilization of the egg.     

Sperm environment affects offspring quality in broadcast spawning marine invertebrates

The provisioning of offspring can have far-reaching consequences for later life in a wide range of organisms and generally this provisioning is thought to be under maternal influence or control. In experiments with a broadcast-spawning ascidian, we found that the size of offspring was determined by egg size and the abundance of sperm present during fertilization. Larger eggs were fertilized at low sperm concentrations, whilst smaller eggs were successfully fertilized at high sperm concentrations. These differences in fertilized egg size resulted in differences in the development rate, hatching success and mean size of the subsequent larvae. Our results suggest that, in contrast to females that reproduce by other mating systems, free-spawning mothers lack some control over the provisioning of offspring. Furthermore, because males can alter the sperm environment, they can exert paternal (non-genetic) control over key offspring characteristics.     

The distribution of polymerized actin in the rat egg and its sensitivity to cytochalasin B during fertilization

The distribution of polymerized actin in rat eggs fertilized in vitro was determined using NBD-phallacidin (NBD-ph). Unfertilized and fertilized eggs exhibited a 3-5-micron-thick band of fluorescence that encompassed the entire cortical cytoplasm. There was no dramatic increase in the staining of the cortex in association with any component of the fertilizing sperm during its incorporation into the egg. Unfertilized eggs and fertilized eggs obtained at intervals after sperm-egg fusion were treated with cytochalasin B (CB; 5 micrograms/ml) and subsequently stained with NBD-ph. Unfertilized eggs treated with CB exhibited a continuous ring of cortical staining identical to that seen in untreated eggs. Eggs treated with CB 15 min after sperm-egg fusion exhibited small gaps in the cortical staining pattern, whereas those exposed to CB 1 hr after fusion exhibited larger gaps and the staining pattern appeared punctate. This pattern could be seen throughout the remainder of the 7 hr period of sperm incorporation and for at least 13 hr thereafter. CB-treated fertilized eggs that were washed to remove the drug again exhibited uninterrupted cortical staining on treatment with NBD-ph. CB also induced the resorption of surface elevations that are normally seen on the eggs during sperm incorporation, but it did not affect the morphology of unfertilized eggs. The sensitivity to CB during fertilization coincides with the onset of a variety of egg shape changes that occur during the period of sperm incorporation (Battaglia and Gaddum-Rosse, Gamete Res., 10:107-118, 1984a).(ABSTRACT TRUNCATED AT 250 WORDS)     

Suitability of non-fertilized eggs of Homalodisca vitripennis for the egg parasitoid Gonatocerus morrilli

Gonatocerus morrilli (Howard) (Hymenoptera: Mymaridae) is an egg parasitoid used in California, USA to control glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). Virgin GWSS females deposit non-fertilized eggs and mated females can exhaust sperm reserves for egg fertilization. However, nothing is known about Gonatocerus spp. performance when using non-fertilized GWSS eggs as hosts. Host age preference for oviposition and suitability of non-fertilized GWSS eggs as hosts for G. morrilli reproduction were investigated to determine whether non-fertilized eggs on sentinel plants could be used to monitor egg parasitoid populations. Gonatocerus morrilli parasitized all ages of GWSS eggs (1–8 days old) regardless if the host egg was fertilized or not. In choice tests (fertilized versus non-fertilized eggs), parasitoids failed to emerge as adults from non-fertilized eggs more often than from fertilized eggs. The results indicate that non-fertilized eggs were accepted by G. morrilli as suitable hosts for oviposition, but were less suitable for immature development compared to fertilized eggs.     

The genetics of egg retention and fertilization success in Drosophila: One step closer to understanding the transition from facultative to obligate viviparity

Oviparous, facultative egg retention enables Drosophila females to withhold fertilized eggs in their reproductive tracts until circumstances favor oviposition. The propensity to retain fertilized eggs varies greatly between species, and is correlated with other reproductive traits, such as egg size and ovariole number. While previous studies have described the phenomenon, no study to date has characterized within‐species variation or the genetic basis of the trait. Here, we develop a novel microscope‐based method for measuring egg retention in Drosophila females and determine the range of phenotypic variation in mated female egg retention in a subset of 91 Drosophila Genetic Reference Panel (DGRP) lines. We inferred the genetic basis of egg retention using a genome‐wide association study (GWAS). Further, the scoring of more than 95,000 stained, staged eggs enabled estimates of fertilization success for each line. We found evidence that ovary‐ and spermathecae‐related genes as well as genes affecting olfactory behavior, male mating behavior, male‐female attraction and sperm motility may play a crucial role in post‐mating physiology. Based on our findings we also propose potential evolutionary routes toward obligate viviparity. In particular, we propose that the loss of fecundity incurred by viviparity could be offset by benefits arising from enhanced mate discrimination, resource specialization, or modified egg morphology.     

Fertilization of the eggs ofCynops pyrrhogaster (japanese newt) after immersion in water

Summary Cynops pyrrhogaster oviducal eggs with and without jelly envelopes (jelly egg and dejellied egg respectively) were immersed in water, and then inseminated artificially. After 1 h of immersion in water, more than half the dejellied eggs were fertilized and developed, but no jelly eggs developed. The rapid decrease in the ability of jelly eggs to be fertilized after immersion in water is not due to a deficiency in the egg. Our results make it clear that hydrated jelly envelopes prevent the eggs from fertilizing. The ability of the egg to be fertilized decreases for a long time in water and this decrease proceeds more slowly in De Boer's solution or Holtfreter's balanced salt solution than in water.     

Comparison of heterospermic and homospermic inseminations as measures of male fertility

This study attempted to determine a basis for the previously observed greater sensitivity of heterospermic tests when compared to homospermic tests for detecting differences in fertility between males. In theory, the results of heterospermic tests are an indication of the proportion of eggs fertilized per unit time whereas results of homospermic inseminations measure only the cumulative or final proportion of eggs fertilized. The fertilizing ability of sperm from males of CF1 and C57BL/6N strains of mice was compared homospermically using both relatively high and low concentrations of sperm and by measuring the proportion of eggs penetrated per unit of time. The fertilizing ability of sperm from these strains was also compared using heterospermic inseminations. When females were inseminated with a high concentration of sperm, males of both strains fertilized a high and indistinguishable percentage of eggs when examined after 30 hr. When females were inseminated with either a low concentration of sperm or when the proportion of eggs penetrated was measured at 5 hr, differences between strains of mice were distinguishable. Heterospermic insemination further magnified the observed difference between strains. The results of this study confirm that measuring the percentage of eggs fertilized per unit of time can enhance the magnitude of differences between males in fertility as compared to measuring only the final percentage of eggs fertilized. Measuring the percentage of eggs fertilized per unit of time does not, however, entirely account for the large differences observed between fertility of males when they are compared using heterospermic inseminations.     

Hypotonic buffer induces meiosis and formation of anucleate cytoplasmic islands in the egg of the two-spotted cricket Gryllus bimaculatus

In insects, egg activation is known to occur in vivo and independently of fertilization, but its mechanisms are poorly understood. To gain understanding of these mechanisms, an attempt was made to activate the egg of Gryllus bimaculatus in vitro. It was found that meiosis resumed and was completed in unfertilized eggs treated with hypotonic buffer. Early developmental processes in activated, unfertilized eggs were investigated and compared with those in fertilized eggs. Mitosis did not progress, resulting in formation of anucleate cytoplasmic islands (pseudoenergids). Development in the activated, unfertilized eggs stopped at this stage and both yolk subdivision and cellularization did not occur. To elucidate the role of the nucleus in the developmental process to the syncytial stage in fertilized eggs, eggs were treated with aphidicolin to inhibit DNA polymerization. It was found that pseudoenergids also formed in these aphidicolin-treated fertilized eggs. These results demonstrate that pseudoenergids can increase in number independently of nuclei, suggesting that the cytoplasm rather than the nucleus plays the primary role in development to the syncytial stage in G. bimaculatus.     

Nuclear Involvement in Localization of the Initiation Site of Surface Contraction Waves in Xenopus Eggs

The initiation site of surface contraction waves (SCWs) was examined in fertilized, parthenogenetically activated and enucleated Xenopus eggs after either rotation through 90° off the vertical axis or injection of colchicine. In enucleated eggs, SCWs always started from a top site of the egg under all conditions examined. In fertilized or activated eggs, SCWs started, depending on the experimental conditions, from either the sperm entry point, the animal pole region located sideward or the top site of the egg. Histological examinations of fertilized and activated eggs revealed that the nucleus was in most cases positioned close to the initiation site of SCWs under various experimental conditions. It is suggested from these results that the egg cytoplasm has an intrinsic capability of causing the surface to generate SCWs, and that the nucleus is generally involved in localizing the initiation site of SCWs in fertilized or activated Xenopus eggs. A possible mechanism for localizing the initiation site of SCWs in Xenopus eggs is proposed.     

Hydrogen peroxide induces Src family tyrosine kinase-dependent activation of Xenopus eggs

Fertilization is accompanied by a rapid and transient calcium release in eggs, which is required for the onset of zygotic developmental program or 'egg activation'. Recently, it was found that Src family tyrosine kinase (SFK)-dependent phospholipase C (PLC) activity is necessary for the calcium transience in fertilized Xenopus eggs. The present study demonstrates that hydrogen peroxide (H2O2) stimulates protein-tyrosine phosphorylation in Xenopus eggs, which occurs primarily in the egg cortex of the animal hemisphere as revealed by indirect immunofluorescence study. Egg SFK was found to be upregulated by H2O2 while the SFK-specific inhibitor PP1 effectively blocked H2O2-induced tyrosine phosphorylation. As in fertilized eggs, PLCgamma, but not Shc, was tyrosine-phosphorylated in H2O2-treated eggs. H2O2 also caused inositol 1,4,5-trisphosphate (IP3) production and sustained calcium release. After limited application of H2O2, elevated SFK activity and tyrosine phosphorylation were quickly reversed. Under such conditions, eggs showed cortical contraction and dephosphorylation of p42 MAP kinase, both of which are indicative of egg activation. These egg activation events, as well as H2O2-induced IP3 production and calcium release, were sensitive to PP1 and PLC inhibitor U-73122. Together, the present study demonstrated that H2O2 can mimic, at least in part, early events of Xenopus egg activation that require an SFK-dependent PLC pathway.     

Incubation temperature and hemoglobin dielectric of chicken embryos incubated under the influence of electric field

Eggs from a layer-type breeder flock (Baladi, King Saud University) between 61 and 63 weeks of age were used in 3 trials to study the effects of electric field (EF) during incubation on the internal temperature of incubation, and eggs and hemoglobin (Hb) dielectric of chicken embryos at 18 days of age. Dielectric relative permittivity (epsilon') and conductivity (sigma) of Hb were examined in the range of frequency from 20 to 100 kHz. The values of dielectric increment (Deltaepsilon') and the relaxation times (tau) of Hb molecules were calculated. The internal temperature of eggs was measured in empty (following the removal of egg contents) and fertilized eggs in trials 1 and 2, respectively. The level of the EF was 30 kV/m, 60 Hz. EF incubation of embryos influenced the temperature of incubation and electrical properties of Hb molecules and did not influence the temperature of incubation and internal environment of eggs when empty eggs were incubated. EF incubation of fertilized eggs significantly raised the temperature of incubation, egg air cell, and at the surface of the egg yolk by approximately 0.09, 0.60, and 0.61 degrees F, respectively and Hb epsilon', sigma, Deltaepsilon', and tau as a function of the range of frequency of 20 to 100 kHz when compared with their counterparts of the control group. It was concluded that the exposure of fertilized chicken eggs to EF of 30 kV/m, 60 Hz, during incubation altered dielectric properties of Hb and that probably affected cell to cell communication and created the right environment for enhancing the growing process and heat production of embryos consequently increasing the temperature of the internal environment of the egg, and incubation.     

In vitro fertilization experiments using sockeye salmon reveal that bigger eggs are more fertilizable under sperm limitation

Although theory and widespread evidence show that the evolution of egg size is driven primarily by offspring and maternal fitness demands, an additional explanation invokes sperm limitation as a selective force that could also influence egg size optima. Levitan proposed that constraints from gamete encounter in external fertilization environments could select for enlargement of ova to increase the physical size of the fertilization target. We test this theory using in vitro fertilization experiments in an externally fertilizing fish. Sockeye salmon (Onchorhyncus nerka) females show considerable between-individual variation in ovum size, and we explored the consequences of this natural variation for the fertilization success of individual eggs under conditions of sperm limitation. By engineering consistent conditions where in vitro fertilization rate was always intermediate, we were able to compare the sizes of fertilized and unfertilized eggs across 20 fertilization replicates. After controlling for any changes in volume through incubation, results showed that successfully fertilized eggs were significantly larger than the eggs that failed to achieve fertilization. Under conditions without sperm limitation, fertility was unaffected by egg size. Our findings therefore support Levitan''s theory, demonstrating empirically that some element of egg size variation could be selected by fertilization demands under sperm limitation. However, further research on sperm limitation in natural spawnings is required to assess the selective importance of these results.     

鸡蛋胚下表层卵黄DNA的提取方法

利用Ficoll-400不连续密度梯度离心将受精和未受精鸡蛋的胚下表层卵黄进行纯化, 显微镜观察表明卵黄球形态良好, 没有胚细胞的存在.然后利用较高浓度的蛋白酶K消化,较长时间的酚抽提,最后提取了DNA. 电泳显示DNA条带清晰.该方法简便快速,从每个鸡蛋的胚下表层卵黄可回收10 ng DNA.     

Resting eggs in rotifers

The biology of resting eggs of monogonont rotifers is reviewed, covering literature published since the last major review by Gilbert (1974). The topics examined include resting egg production, morphology and species specificity, hatching, and evolutionary significance. Four major determinants of resting egg production are identified: mictic female production, male activity and fertility, female susceptibility to fertilization, and fertilized female fecundity. Recent work in these four areas is discussed as well as resting egg production in natural populations. Resting egg morphology, particularly shell structure and internal organization, is compared among species. Recent reports on the control of resting egg hatching in the laboratory are examined and the importance of temperature, light, diet, and salinity is reviewed. Two hatching patterns are contrasted, the first where eggs hatch at regular intervals over extended periods and the second where hatching is synchronized to some environmental cue. A latent period after resting egg formation, during which no hatching occurs, is defined for several species. The adaptive features of resting eggs are outlined including their contribution to genetic variability through recombination, their provision for environmental escape by dormancy, and their colonizing function resulting from their ease of dispersal. The type of cue utilized to initiate mictic female production as well as the pattern of resting egg hatching is related to environmental predictability.     

Dispersal of sperm surface antigens in the plasma membranes of polyspermically fertilized sea urchin eggs

Polyspermically fertilized Strongylocentrotus purpuratus eggs were fixed at varying times after insemination and exposed to a monoclonal antibody (mAb J18/29) directed against a group of sperm surface antigens. Indirect immunofluorescence microscopy reveals that the sperm surface components recognized by mAb J18/29 are quickly incorporated into the egg plasma membrane and begin to disperse as early as 1.5 min after insemination. At subsequent times after insemination, they undergo further dispersal so that by 45 min they are distributed evenly over the entire surface of the egg. These results provide evidence for the free lateral mobility of sperm membrane components in the fertilized egg.     

Egg transport in the coelom of the newt cynops pyrrhogaster. I. The ovulated egg is transported to the ostium by the ciliary movement of coelomic epithelial cells

We investigated the mechanism of egg transport in the newt not only by inserting various conditioned eggs into the recipient's body but also by placing them on the coelomic epithelia of the opened body cavity in the adult female newt. Most of the inserted coelomic eggs were oviposited, while 4 of 14 inserted de-jellied uterine eggs and 3 of 10 inserted de-jellied fertilized eggs were oviposited. The coelomic eggs placed on the coelomic epithelia were transported toward the ostium and entered the ostium. The de-jellied uterine eggs and the de-jellied fertilized eggs were transported to the ostium as well. Of all the eggs examined, the coelomic egg was transported the fastest. The transport speeds of coelomic eggs treated with periodic acid and the speed of boiled coelomic eggs were less than those of untreated coelomic eggs. In contrast, the transport speeds of coelomic eggs treated with trypsin and the speed of coelomic eggs removed from their vitelline envelopes (naked eggs) were faster than those of untreated coelomic eggs. Other experiments were carried out in order to ascertain the dependence of sexual activity on egg transport. The speed of coelomic egg transport in artificially sexually activated females was faster than in sexually inactive females, although the ciliary movement could always be observed in both sexually active females and sexually inactive females. This suggests that the speed of egg transport on the coelomic epithelia is controlled by the sexual activity of the female.     

Something Darwin didn't know about barnacles: spermcast mating in a common stalked species

Most free-living barnacles are hermaphroditic, and eggs are presumed to be fertilized either by pseudo-copulation or self-fertilization. Although the common northeast Pacific intertidal gooseneck barnacle, Pollicipes polymerus, is believed only to cross-fertilize, some isolated individuals well outside penis range nonetheless bear fertilized eggs. They must therefore either self-fertilize or—contrary to all prior expectations about barnacle mating—obtain sperm from the water. To test these alternative hypotheses, we collected isolated individuals bearing egg masses, as well as isolated pairs where at least one parent carried egg masses. Using 16 single nucleotide polymorphism markers, we confirmed that a high percentage of eggs were fertilized with sperm captured from the water. Sperm capture occurred in 100 per cent of isolated individuals and, remarkably, even in 24 per cent of individuals that had an adjacent partner. Replicate subsamples of individual egg masses confirmed that eggs fertilized by captured sperm occurred throughout the egg mass. Sperm capture may therefore be a common supplement to pseudo-copulation in this species. These observations (i) overturn over a century of beliefs about what barnacles can (or cannot) do in terms of sperm transfer, (ii) raise doubts about prior claims of self-fertilization in barnacles, (iii) raise interesting questions about the capacity for sperm capture in other species (particularly those with short penises), and (iv) show, we believe for the first time, that spermcast mating can occur in an aquatic arthropod.