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At least 1,063 records · Page 59Linked to original sources
PubMed1993

Sea urchin egg 100-kDa dynamin-related protein: identification of and localization to intracellular vesicles.

We have initiated a study to identify possible tubulin dimer binding proteins from unfertilized sea urchin eggs utilizing tubulin dimer coupled to Sepharose 4B. A 100-kDa polypeptide has been isolated and its interaction with tubulin/microtubules examined. Solution assembly studies indicated the 100-kDa polypeptide potentiated microtubule assembly. The 100-kDa protein also bundled and cosedimented with polymerized microtubules. Rabbit polyclonal anti-egg 100-kDa antibodies cross-reacted with a 100-kDa polypeptide in the eggs of several different sea urchin species and with mammalian brain dynamin, a 100-kDa microtubule binding protein. These biochemical characterizations and immunological results suggest that the sea urchin 100-kDa microtubule binding protein appears to be related to the dynamin protein family. To gain insight into the functional role of sea urchin egg 100-kDa dynamin-related protein, we immunolocalized egg 100-kDa protein in cryosections and isolated cortices of unfertilized eggs. Egg 100-kDa protein was localized to the monolayer of cortical granules that underlie the plasma membrane and to the inner cytoplasm. Immunolocalizations of egg 100-kDa protein in cortices isolated from fertilized eggs detailed the redistribution of the egg 100-kDa onto cortically positioned vesicles. Egg 100-kDa dynamin-related protein was expressed throughout early development with approximately equivalent amounts present in the unfertilized egg and embryo through early gastrulation, followed by an abrupt decrease in the level of expression by the pluteus larval stage.

Animals↗
PubMed1994

Evidence by a voltage clamp study of an electrically mediated block to polyspermy in the egg of the ascidian Phallusia mammillata.

Eggs of the ascidian Phallusia mammillata were voltage clamped (from -100 to +60 mV) and inseminated with a low or heavy sperm concentration. From inseminations with low sperm concentration (1 x 10(6) sp/ml), we found that fertilization currents occurred between -100 and +40 mV: they were always inward and displayed an analogous pattern whatever the clamped voltage. We established that the percentages of inseminated eggs that produced a fertilization current varied as a function of the clamped voltage. These percentages were not statistically different from 100% at clamped voltages between -100 and -30 mV, they decreased to 68 and 56% at clamped Vm of -10 and 0 mV, respectively, but were not statistically different from 0% at clamped Vm between +10 and +40 mV. We never obtained any egg electrical response at a clamped voltage of +50 mV. Almost all eggs (96%) which responded electrically were penetrated by one or several spermatozoa. These eggs were resuming meiosis (81 to 50%) at values of clamped Vm between -100 and 0 mV, respectively. At clamped Vm between +10 and +50 mV, the percentages of eggs resuming meiosis were not statistically different from 0. These results indicate that in P. mammillata eggs, the occurrence of an electrical response is voltage dependent and consequently that the initial depolarizing shift of the fertilization potential constitutes a fast block to polyspermy. However, in this species, the sperm penetration is not voltage dependent, since it occurred at clamped Vm from -100 to +40 mV. On the other hand, when eggs were clamped from -100 to +60 mV and inseminated with a heavy sperm concentration (2 x 10(7) sp/ml), the curves expressing, respectively, the percentages of eggs which responded electrically, the percentages of eggs which were penetrated by one or several spermatozoa, and the percentages of eggs resuming meiosis, as functions of the clamped Vm, were shifted by approximately 35 mV toward more positive voltages, compared to the corresponding curves obtained from eggs inseminated with a low sperm concentration. This last result means that the critical value of the membrane potential which characterizes the electrical block to polyspermy is dependent on the sperm concentrations used for inseminations.

Animals↗
PubMed2001

Chemical defense in the egg masses of benthic invertebrates: an assessment of antibacterial activity in 39 mollusks and 4 polychaetes.

Many marine invertebrates deposit benthic egg masses that are potentially vulnerable to microbial infection. To help counter this threat these species may have evolved some form of chemical protection for their encapsulated embryos. In this study the egg masses from 7 marine mollusks were tested for antibacterial activity against 4 marine pathogens: Enterococcus sericolicida, Vibrio anguillarum, Vibrio alginolyticus, and Vibrio harveyi. Extracts from all of these egg masses were found to inhibit the growth of at least 1 marine bacterium at concentrations that approximate the natural concentration of extract in the egg masses. The egg masses of 39 mollusks and 4 polychaetes were then tested for antibacterial activity against 3 human pathogenic bacteria; Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Activity was detected in the egg masses from 34 species, including 2 polychaetes and mollusks from two classes and 18 families. Antibacterial activity in molluskan egg masses was found to extend across the marine, estuarine, freshwater, and terrestrial environments. Both gelatinous egg masses and tough egg capsules were found to inhibit microbial growth, suggesting that physical protection alone may not be sufficient to protect the eggs. Antimicrobial activity was observed in the fresh egg masses but not in the well-developed egg masses of a subset of species. The results of this study indicate that a wide range of invertebrates use chemical defense to protect their early stage embryos against bacterial infection.

Animals↗
PubMed1975

The dependence of annulate lamellae formation on the nucleus in parthenogenetic rabbit eggs.

Previously it has been shown that, in the rabbit, although annulate lamellae (AL) are absent in the follicular oocytes, they appear in the fertilized eggs after the formation of the pronuclei. Furthermore, neither pronuclei nor AL appear when unfertilized eggs are aged in vivo or in vitro. This study was undertaken to determine whether AL formation requires presence of an intact nucleus, or whether the sperm alone contains the stimulatory factors essential to AL synthesis. Rabbit eggs were exposed to 10 degrees C, then incubated for 24 hours. Control eggs were incubated without cold-treatment. Electron microscopic observations indicated that two-thirds of the eggs formed one to two 'pronuclei', or subnuclei. The remainder one-third of the cold-treated eggs and the control eggs failed to form 'pronuclei'. AL were present in large amounts only in those activated eggs (parthenogenones) which formed 'pronuceli.' AL were absent in the control and the non-activated experimental eggs, both of which failed to form a 'pronucleus.' A few small AL were observed in eggs with subnuclei. Condensed fine textured nucleoli appeared precociously during cold-treatment in some eggs and they were present in the 'pronuclei' of activated eggs. It was concluded that the sperm is not necessary for AL formation, but the presence of an intact nucleus is mandatory.

Animals↗
PubMed2006

Polychlorinated biphenyl concentrations, congener profiles, and ratios in the fat tissue, eggs, and plasma of snapping turtles (Chelydra s. serpentina) from the Ohio Basin of Lake Erie, USA.

Concentrations and profiles of polychlorinated biphenyls (PCBs) were determined in three tissues of adult snapping turtles (Chelydra serpentina serpentina) from six locations in the Ohio Basin of Lake Erie to characterize tissue variation and geographic trends. The locations included the Ohio Areas of Concern, i.e., the Ashtabula, Black, and Maumee Rivers; the Ottawa River near Toledo; and two reference sites. Mean total PCBs were greatest in turtles from the Ottawa River followed by the Maumee, Ashtabula, and Black Rivers. All three types of samples-fat tissue (FT), eggs, and plasma-showed the same geographic trend in PCB levels. On a wet-weight basis, mean concentrations ranged from 2,148 to 18,669 ng/g in FT, from 183 to 3,683 ng/g in eggs, and from 18 to 201 ng/g in plasma. Across all sites, total PCB concentrations between the tissues were significantly correlated (0.001 < p < 0.005; Pearson correlation coefficient (r ( P )) was between 0.720 and 0.954). Two distinctly different profiles with respect to relative congener and homologue concentrations were found among the sites. One that included four of the six sites examined was characterized by hexa-chlorobiphenyl (hexa-CB) dominance followed by hepta-CBs, with PCBs no. 138 + 163, 153 + 132 + 105, and 180 being the most abundant congeners. The second profile, specific for turtles from the Ottawa River, was different from the first in that tetra-CBs were the most abundant congeners followed by hexa-CBs. Analysis of variance (ANOVA) indicated significant intertissue differences in the PCB homologue profiles, i.e., FT had a higher percentage of hepta-, octa-, and nona-CBs compared with eggs and plasma, whereas eggs showed a higher percentage of hexa-CBs. At any listed location, FT, eggs, and plasma had the same congener profile. An intertissue distribution of lipid-normalized individual congener concentrations examined by regression analyses revealed significant egg-FT, egg-plasma, and FT-plasma relations for >40 congeners (0.001 < p < 0.05). The distribution ratios determined for these congeners from the slope of the regression lines averaged 1.235 +/- 0.279, 0.430 +/- 0.170, and 0.387 +/- 0.115, respectively. The plasma wet weight-FT lipid-normalized concentration ratios for these congeners averaged 0.012 +/- 0.006. Both egg-FT and plasma wet weight-FT lipid-normalized ratios regressed against log K(ow) showed significant decreases, with increasing log K(ow), indicating greater accumulation of highly chlorinated congeners in FT than in other compartments. The estimated 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents ranged from 0.007 ng/g at reference sites to 0.060 ng/g at contaminated sites and from 0.099 to 1.992 ng/g in plasma and eggs, respectively. In both plasma and eggs, coplanar-CBs were the major contributors to total toxic equivalents (TEQs). Eggs from all contaminated sites had TEQs that exceeded the lowest observed effect level TEQs proposed for bald eagle chicks, in addition to high SigmaPCB levels at some of these sites, especially the Ottawa and Maumee River sites, indicate potentially increased risk to turtles and possibly other wildlife species inhabiting these ecosystems. Significant correlations of total PCBs and individual congeners between FT, eggs, and plasma indicate that blood sampling can provide a good nonlethal measure of PCB exposure and can be used to monitor environmental contamination.

Adipose Tissue↗
PubMed1988

A cell surface block to polyspermy occurs in golden hamster eggs.

We have examined the frequency and fate of supernumerary sperm in the perivitelline space (PVS) of in vitro fertilized hamster eggs to determine if there is a cell surface block to polyspermy. The zona pellucida block to polyspermy is very effective since only one sperm penetrated the zona pellucida in 72.8% of the 876 fertilized eggs examined. Of the polypenetrated eggs, 41.6% had a supernumerary sperm within the PVS. The proportion of polypenetrated eggs with PVS sperm did not change when the duration of coincubation was increased from 3 to 6 hr. PVS sperm were found in 67% of the inseminations. From these data we conclude that there is a cell surface block to polyspermy in the hamster. To investigate the mechanism of the cell surface block, we used the Hoechst-transfer technique (R. Hinkley, B. Wright, and J. Lynn, 1986, Dev. Biol. 118, 148-154) to monitor sperm-egg fusion. We first demonstrated that dye transfer from zona pellucida-free eggs to sperm only occurred when fusion was possible, i.e., in the presence of calcium, and that dye was transferred to all fused sperm. When cumulus-free, zona-intact eggs were preloaded with Hoechst dye and viewed 3 hr postinsemination, three classes of eggs with supernumerary sperm in the PVS were observed: eggs with only Hoechst-positive sperm (62%), eggs with only Hoechst-negative sperm (27%), and eggs with both a Hoechst-positive and a Hoechst-negative sperm (11%). Because of the limited time resolution of the Hoechst-transfer technique, the cell surface block could operate by preventing sperm fusion (Hoechst-negative), by the failure of the eggs to incorporate fused sperm (Hoechst-positive), and/or by the "unfusing" of fused sperm (Hoechst-positive and Hoechst-negative). We are unable at this time to differentiate between these mechanisms.

Animals↗
PubMed1992

Patterns of contamination by organochlorines and mercury in the eggs of two river passerines in Britain and Ireland with reference to individual PCB congeners.

Unhatched eggs were collected in 1988 and 1990 from nests of the Eurasian Dipper Cinclus cinclus and the Grey Wagtail Motacilla cinerea in Wales, eastern Scotland and south-western Ireland. Mercury concentrations in Dipper eggs (geometric means 0.45-0.91 ppm (microg g(-1)) dry mass) were significantly lower in eastern Scotland than in either south-western Ireland or Wales, where the incidence of detectable residues increased markedly between 1988 (2% of eggs) and 1990 (69%). By contrast, DDE (geometric means 0.63-3.54 ppm in lipid), TDE (<0.01-1.80 ppm), DDT (<0.01-0.65 ppm), total PCBs (3.99-10.47 ppm), HEOD (0.39-0.61 ppm) and HCB (0.02-0.13 ppm) were all significantly higher in Scottish eggs than others. Around 33-46% of the total PCB burden in Dipper and Grey Wagtail eggs could be accounted for by six congeners (IUPAC numbers 118, 180, 101, 153, 138 and 170). Amongst these attributable PCBs, Dipper eggs from eastern Scotland were dominated by congener 153 (2,2',4,4',5,5'-hexachlorobiphenyl), whilst Welsh and Irish eggs were dominated by congener 118 (2,3',4,4',5-pentachlorobiphenyl). With the latter exception, all the individual congeners were found at significantly higher concentrations in Scottish eggs than others. Grey Wagtail eggs were dominated by congeners 118 and 101 (2,2,4,5,5'-pentachlorobiphenyl). In general, these congeners are common, widespread, and dominant components in the eggs of other wild birds for which data are available. Consistent with the low to medium levels of contaminants found in Dipper eggs, there was only slight evidence of any toxic effects. These included moderate shell thinning in relation to increasing DDE, and some evidence that contaminants had contributed to egg failure.

Journal Article↗
PubMed1994

Novel cytoskeletal elements in mammalian eggs are composed of a unique arrangement of intermediate filaments.

Mammalian eggs and embryos contain a major network of specialized cytoskeletal components known as 'sheets' that have not been identified in any other cell type. Although eggs from at least seven different mammalian species have been shown to contain these cytoskeletal structures, embedment-free electron microscopic analysis of these eggs revealed that two basic forms of cytoskeletal sheets exist, a solid, planar type of sheet typical of hamster and rat eggs and a fibrous sheet typical of mouse, porcine, bovine, canine, and human eggs. In this study we have investigated the structural composition of the fibrous type of sheet in mouse eggs by employing biochemical approaches as well as two forms of ultrastructural analyses including: (1) analysis of thick, resin-embedded specimens using an intermediate voltage electron microscope (IVEM); (2) analysis of replicas from quick-frozen, deep-etched specimens. Our results indicate that the sheets of mouse eggs and preimplantation embryos are composed of cylindrical bundles of 10-11 nm filaments, with each of these filaments held in register by periodically arranged crossbridges spaced 23-25 nm apart. This sheet substructure of filaments and crossbridges is covered by a particulate material which can be removed by non-ionic detergent. Immunoelectron microscopic analysis of mouse eggs demonstrates that sheets bind antibodies to keratin and to a small extent, actin, but do not bind antibodies to vimentin or tubulin. Confirmation that keratin exists in these eggs was obtained by electrophoretic separation and one- and two-dimensional Western blot analysis demonstrating the existence of keratin types 5, 6, 8, 16, and type Z. The low abundancy of keratin type 8 compared to other keratin types explains the difficulties other investigators have had identifying intermediate filaments in mammalian embryos since most investigators have used antibodies directed specifically against keratin type 8 or its pair keratin type 18. Examination of compacted mouse embryos reveals that the filamentous framework of sheets disassembled and established close contact with the basolateral plasma membrane and the nucleus. However, sheets at the apical plasma membrane of blastomeres attach to the membrane but remain intact. Based on our biochemical and ultrastructural data, the fibrous sheets of mouse eggs appear to be cytoskeletal structures comparable to the solid, planar sheets of the Syrian hamster egg and probably serve similar function(s) in eggs and embryos of several mammalian species.

Animals↗
PubMedDate not supplied

Lifetime egg maturation by host-deprived Venturia canescens.

The study investigated egg maturation and deposition by the endoparasitoid wasp Venturia canescens under conditions of host deprivation. Female V. canescens maintained without hosts began to deposit eggs onto the sides of the culture vessel on the day of eclosion. The maturation of additional eggs was not inhibited once the maximum oviduct egg load was reached but rather continued for the duration of the experiment (up to 39 days), at a rate of around 5.8% of the remaining unmatured eggs per day. Following host access, wasps matured additional eggs at an increased rate. Artificial damage to the ovipositor resulted in a reduced rate of egg maturation even though the oviducts were partly egg depleted, while damage to the auxiliary valvulae had no effect. These results suggest two conclusions. Under conditions of host deprivation, the rate at which eggs are matured is determined by the rate of synthesis of precursors by the fat body that in turn is modified by feedback from the ovipositor, induced by physical stimulation. Further, the discarding of eggs is due to the involuntary unidirectional movement of eggs down the oviduct, facilitated by the ongoing maturation of additional eggs.

Animals↗
PubMed1987

Stage sensitivity of eggs of the teleost Oryzias latipes to cadmium exposure.

The stage sensitivity of eggs of the teleost Oryzias latipes to cadmium exposure was examined. First, using eggs at the blastula stage, the proper concentration of cadmium to which the eggs should be exposed was estimated. The eggs were, therefore, exposed to cadmium solutions ranging from 10.0 to 300.0 mg Cd/liter for 1 hr, and then they were transferred to cadmium-free medium. The cumulative mortality of the eggs was estimated by counting dead eggs within 24 hr. Mortality (1.1 +/- 0.7%) indistinguishable from that of the control (1.0 +/- 0.2%) was obtained in the solution of 10.0 mg Cd/liter. Relatively higher mortalities of 13.2 +/- 1.5, 18.0 +/- 1.0, and 20.7 +/- 3.1% could be seen in the solutions containing 50.0, 100.0, and 150.0 mg Cd/liter, respectively. Moreover, the exposure of the eggs to 200.0 and 300.0 mg Cd/liter increased mortality rates to 32.0 +/- 0.8 and 34.7 +/- 2.4%, respectively. Consequently, the concentration of 200.0 mg Cd/liter was selected for examining the stage sensitivity. Eggs at 11 different developmental stages were exposed to cadmium at a concentration of 200.0 mg Cd/liter for 1 hr. The mortalities obtained at the 4- to 16-cell stage, 32-cell stage, and morula stage were 99.2 +/- 1.0, 97.4 +/- 2.6, and 89.6 +/- 10.6%, respectively. With the progress of embryonic development, the eggs became more resistant to cadmium toxicity. After the morula stage, the mortalities decreased abruptly. In order to ascertain whether the change in mortalities of the eggs with development was related to the amount of cadmium combined with the eggs, the cadmium content was determined. In contrast to the remarkable change in the stage sensitivity to cadmium, the curve of cadmium content in the eggs remained constant at about 520 ng/egg throughout the experimental period.

Animals↗
PubMed2001

Egg hatching of mosquitoes Aedes caspius and Ae. vittatus stimulated by water vibrations.

Simple laboratory experiments with eggs of wild-caught Aedes caspius (Pallas) and Aedes vittatus (Bigot) mosquitoes (Diptera: Culicidae) demonstrated that egg hatch rates (i.e. percentage hatching daily) increased significantly in response to water vibrations caused by finger-tip drumming on containers of submerged eggs. When disturbed by daily vibrations for only 30 s, eggs hatched sooner than when they remained flooded or were periodically drained and reflooded without agitation. For autogenous Ae. caspius from saltmarsh, egg hatch rates were three- to four-fold greater for groups of 50 eggs than for solitary eggs, possibly due to chemicals (functional kairomones) emanating from other eggs or larvae. For anautogenous Ae. vittatus from freshwater rock-pools, tapping the container daily (for 30 s each 2 h in 8 h) hatched 93% of eggs, compared with only 42% hatch of eggs agitated only when first flooded or 55% hatch of eggs dried and reflooded three times during 17 days without other disturbance. It is concluded that, apart from flooding and other factors, vibrations - simulating the patter of rainfall provide a very significant hatching stimulus for Aedes eggs.

Aedes↗
PubMed1999

Protein tyrosine kinase-dependent release of intracellular calcium in the sea urchin egg.

The aminoguanide, methylglyoxal bis(guanylhydrazone) (MGBG), was shown to stimulate phosphorylation of RR-SRC, a synthetic protein tyrosine kinase (PTK) substrate, and different levels of tyrosyl phosphorylation of endogenous proteins in a sea urchin egg membrane-cortex preparation. Stimulating protein tyrosine kinase activity in the sea urchin egg stimulated intracellular Ca2+ release, because microinjection of 1-5 mM of MGBG into unfertilized eggs triggered a transient rise in intracellular Ca2+ activity ([Ca2+]i) after a brief latent period. Pretreating eggs with PTK-specific inhibitors, genistein or tyrphostin B42, significantly inhibited the MGBG-induced rise in [Ca2+]i. Methylglyoxal bis(guanylhydrazone) stimulation of PTK activities in the unfertilized sea urchin egg appeared to trigger Ca2+ release through phospholipase C (PLC)-dependent inositol 1,4,5-trisphosphate (InsP3) production. The MGBG-induced Ca2+ response could be suppressed in eggs preloaded with the InsP3 receptor antagonist, heparin, and was reduced in eggs pretreated with U73122, a PLC inhibitor. However, the response was unchanged in eggs treated with nicotinamide, an inhibitor of ADP-ribosyl cyclase, or nifedipine, an inhibitor of nicotinic acid adenine dinucleotide phosphate activity. These results suggest that MGBG may be useful as a chemical agonist of PTK in sea urchin eggs and allow direct testing of the PTK requirement for the transient rise in [Ca2+]i in sea urchin eggs during fertilization. Although genistein was observed to significantly delay the onset, the sperm-induced Ca2+ response in PTK inhibitor-loaded eggs otherwise appeared normal. Therefore, it was concluded that sea urchin eggs contain a PTK-dependent pathway that can mediate intracellular Ca2+ release, but PTK activity does not appear to be required for the fertilization response.

Animals↗
PubMed2001

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.

Animals↗
PubMed1993

Human bilharzial ureters. II. Cellular dynamic against deposited eggs.

The cellular dynamic against deposited Schistosoma haematobium eggs was studied in the submucosa and muscularis of the lower ureteral segments of Saudi patients with chronic urinary schistosomiasis. This dynamic activity was greatly affected by the damaged phase of the egg embryo. Freshly deposited eggs with "healthy" embryos were entirely surrounded by long cytoplasmic extensions of fibroblasts. Eggs with partially damaged embryos were surrounded by plasma cells which were focally adhered to spines of egg-shells and releasing their granular contents over their surface. Eggs with "dead" embryos, or empty egg-shells, were surrounded by actively mobile macrophages possessing numerous lysosomes, phagocytic vacuoles, and convoluted surface projections. After "peeling" off the outer and intermediate shell layers, macrophages invaded into eggs and fused together forming multinucleate giant macrophages. This study showed that the fibroblastic extensions acted as barriers between the parasite eggs or their products, and the host tissue; the plasma cell secretion over the egg surface may be involved in the migration of macrophages towards deposited eggs; and macrophages were the only dynamic cells responsible for the egg-shell invasion possibly for elimination.

Adult↗
PubMed1996

Response to long-term selection for egg production in laying hens.

1. A White Leghorn line was selected for part-record hen-housed number of eggs from 1962 to 1990. Genetic changes were estimated as deviations from its unselected control line. 2. Over the first 10 generations with selection almost exclusively for number of eggs to the age of 273 d, all traits, except rate of mortality, showed significant changes. Regressions per year were: 273 d production, 3.07 eggs; 497 d production, 5.18 eggs; production from 274 to 497 d, 2.43 eggs; age at first egg, -2.33 d; mean weight of first 10 eggs, -0.82 g; body weight at 497 d, -19.02 g and rate of mortality, 0.19%. 3. Over the rest of the period increasing selection pressure for egg weight has been applied. This resulted in positive changes for this trait and no or small negative changes in egg number. 4. In general, heritabilities and genetic correlations did not change over the period of selection. The heritability of the main trait of selection, production to 273 d was 0.19 +/- 0.04 and heritabilities of egg size traits about 0.50. 5. The genetic correlation between egg production to 273 d and mean weight of first 10 eggs was estimated as -0.37 +/- 0.06 but from the observed response a realised genetic correlation of -0.97 was calculated.

Aging↗
PubMed1961

Changes in the spermatozoon during fertilization in Hydroides hexagonus (Annelida). II. Incorporation with the egg.

This, the last of a series of three papers, deals with the final events which lead to the incorporation of the spermatozoon with the egg. The material used consisted of moderately polyspermic eggs of Hydroides hexagonus, osmium-fixed at various times up to five minutes after insemination. The first direct contact of sperm head with egg proper is by means of the acrosomal tubules. These deeply indent the egg plasma membrane, and consequently at the apex of the sperm head the surfaces of the two gametes become interdigitated. But at first the sperm and egg plasma membranes maintain their identity and a cross-section through the region of interdigitation shows these two membranes as a number of sets of two closely concentric rings. The egg plasma membrane rises to form a cone which starts to project into the hole which the spermatozoon earlier had produced in the vitelline membrane by means of lysis. But the cone does not literally engulf the sperm head. Instead, where they come into contact, sperm plasma membrane and egg plasma membrane fuse to form one continuous membranous sheet. At this juncture the two gametes have in effect become mutually incorporated and have formed a single fertilized cell with one continuous bounding membrane. At this time, at least, the membrane is a mosaic of mostly egg plasma membrane and a patch of sperm plasma membrane. The evidence indicates that the fusion of the two membranes results from vesiculation of the sperm and egg plasma membranes in the region at which they come to adjoin. Once this fusion of membranes is accomplished, the egg cytoplasm intrudes between the now common membrane and the internal sperm structures, such as the nucleus, and even extends into the flagellum; finally these sperm structures come to lie in the main body of the egg. The vesiculation suggested above appears possibly to resemble pinocytosis, with the difference that the vesicles are formed from the plasma membranes of two cells. At no time, however, is the sperm as a whole engulfed and brought to the interior of the egg within a large vesicle.

Animals↗
PubMed1953

Studies on the antibodies in rabbit antisera responsible for sensitization of human skin. I. The role of impurities in crystalline egg albumin in stimulating the production of skin-sensitizing antibody.

The capacity of rabbit anti-egg albumin sera to sensitize human skin has been studied. It has been shown that passive transfer by these sera is completely unrelated to the egg albumin-anti-egg albumin system, as demonstrated by a failure of passive transfer by some antisera containing ample anti-egg albumin and persistence of passive transfer in other antisera from which all anti-egg albumin had been removed by precipitation with homologous antigen. Three preparations of non-precipitating anti-egg albumin have been shown to have sensitizing capacities which bear no relation to their non-precipitating anti-egg albumin contents. From a portion of one of these the non-precipitating anti-egg albumin was removed without impairing its sensitizing ability, while in another portion obliteration of the sensitizing capacity was accomplished without reducing the anti-egg albumin. Evidence is presented to show that there are at least two possible antibodies in anti-egg albumin sera which are capable of inducing skin sensitivity and that they are antibodies against egg white impurities in crystalline egg albumin other than anti-conalbumin, anti-ovomucoid, and anti-lysozyme. The usefulness of a suitable quantitative precipitin technic for the analysis for antibodies against antigen impurities and for their selective absorption from sera is illustrated. The principle governing the procedure is described. The technic allows for the determination of a given trace antibody by working with such small concentrations of its purified specific antigen that whatever other antigen-antibody compounds are formed simultaneously with that to be determined will be below their solubility levels and consequently will not contribute appreciably to the precipitate.

Albumins↗
PubMed1974

Mechanism for increase in intracellular concentration of free calcium in fertilized sea urchin egg. A method for estimating intracellular concentration of free calcium.

Intracellular free calcium concentration in the sea urchin egg was calculated to increase from 0.1 mM in an unfertilized egg to 1 mM in a fertilized egg 10 min after fertilization, based on measurement of the dissociation constant between free calcium and sea urchin egg homogenate. The dissociation constant between free calcium (dialyzable calcium) and homogenate of sea urchin eggs was measured by means of dialysis equilibrium. The dissociation constant of the unfertilized egg was about 10(-4) M and that of the fertilized egg was about 10-3 M in three species of sea urchin, Hemicentrotus pulcherrimus, Anthocidaris crassispina, and Pseudocentrotus depressus. An increase in the dissociation constant of the unfertilized egg homogenate was observed after the addition of calcium ion at a concentration above 0.3 mM, the dissociation constant becoming the same as that observed in the fertilized egg homogenate after the administration of CaCl(2) at a concentration above 1 mM. Sodium ion also caused a decrease in the calcium-binding ability of the unfertilized egg homogenate. Therefore, penetration of calcium ion or sodium ion upon fertilization might induce an increase in the dissociation constant and then intracellular concentration of free calcium would increase at fertilization. Almost all calcium-binding ability of the egg homogenate was found in the microsomal fraction, and the substance which bound calcium was thought to be protein in nature, since trypsin could decrease the level of calcium-binding substance in the homogenate of the eggs.

Animals↗