Microplastics evidence in yolk and liver of loggerhead sea turtles (Caretta caretta), a pilot study

The potential toxicity of microplastics is a growing concern for the scientific community. The loggerhead sea turtle (Caretta caretta) is particularly inclined to accidently ingest plastic and microplastic due to its long-life cycle features. The possible transfer of microplastics from the female to the eggs should be investigated. The present study investigated the presence of microplastics in yolk and liver samples evaluating the number of melanomacrophages in the hepatic tissue as a possible biomarker of microplastics impact on the embryonic health status. The biometric parameters and liver histological analysis of 27 and 48 embryos (from two different nests respectively) at the 30 stage of development were analyzed. Raman Microspectroscopy was performed to identify the microplastics after alkaline digestion (10% KOH) of yolk and portion of liver from 5 embryos at the 30 developmental stage per nest. Microplastics were found in yolk and liver of loggerhead sea turtles at late embryonic stage for the first time. All microplastics were smaller than 5 μm and were made of polymers and colors suggesting their diverse origins. A total number of 21 microplastics, with dimensions lower than 5 μm, were found between the two nests (11 and 10 microplastics respectively). Only two shape categories were identified: spheres and fragments. The most frequent polymers observed were polyethylene, polyvinyl chloride and acrylonitrile butadiene styrene (31.5%, 21.1% and 15.8% respectively). Despite the eggs showing a higher number of microplastics in yolk samples than liver (15 and 6 microplastics in yolk and liver respectively), a positive correlation was observed only between the number of melanomacrophages (r = 0.863 p < 0.001) and microplastics in the liver. This result may suggest that microplastics could exert some effects on the hepatic tissues. Future studies should investigate this aspect and the possible relation between microplastics and other stress biomarkers.

Measurement of ultrasound velocity in yolk and blastula of fish embryo in vivo

An acoustic microscopy method for measuring the velocity of ultrasound in the yolk and blastula of bony fish embryos at early stages of development was proposed. The yolk and blastula were approximated as a sphere and a spherical dome, respectively, consisting of a homogeneous liquid. A theoretical model of ultrasonic wave propagation through a spherical liquid drop located on a solid substrate was developed in the ray approximation. The dependence of the wave propagation time on the speed of sound in the drop, its diameter, and the position of the focus of the ultrasonic transducer has been determined. It was shown that the velocity in the drop can be found by solving the inverse problem by minimizing the discrepancy between the experimental and model spatial distributions of the propagation time, assuming that the velocity in the immersion liquid and the radius of the drop are known. The velocities in the yolk and blastula of the loach (Misgurnus fossilis) embryo at the stage of development of the middle blastula were measured in vivo using a pulsed scanning acoustic microscope operating at a central frequency of 50 MHz. The yolk and blastula radii were determined from ultrasound images of the embryo. Acoustic microscopy measurements conducted with four embryos provide velocities of the acoustic longitudinal wave in the yolk and blastula. They were measured to be 1581 ± 5 m/s and 1525 ± 4 m/s when the temperature of the liquid in the water tank was kept at 22 ± 2 °C.

Effects of cadmium, lead, mercury, chromium, and selenium co-treatment on egg quality and fatty acids

This study aimed to reveal the effect of selenium (Se) and heavy metals (chromium (Cr), cadmium (Cd), lead (Pb), and mercury (Hg)) on the quality, fatty acids, and 13 kinds of ions in the egg yolk and albumen. Four experimental groups were established, including a control group (control; basal diet), Se group (basal diet + Se), heavy metals group (basal diet + CdCl₂ + Pb(NO₃)₂ + HgCl₂ + CrCl₃), and Se + heavy metal (HM) group (basal diet + Se + CdCl₂ + Pb(NO₃)₂ + HgCl₂ + CrCl₃). Se supplementation significantly increased the experimental egg yolk percentage since Se accumulation mainly occurred in the yolks of the eggs. The Cr content in the yolks of the Se + heavy metal groups decreased at 28 days, while a significant reduction was evident in the Cd and Hg levels of the Se + heavy metal yolks compared to the heavy metal group at 84 days. The complex interactions between the elements were analyzed to determine the positive and negative correlations. Se displayed a high positive correlation with Cd and Pb in the yolk and albumen, while the heavy metals minimally affected the fatty acids in the egg yolk.

The evolution of gastrulation morphologies

During gastrulation, early embryos specify and reorganise the topology of their germ layers. Surprisingly, this fundamental and early process does not appear to be rigidly constrained by evolutionary pressures; instead, the morphology of gastrulation is highly variable throughout the animal kingdom. Recent experimental results demonstrate that it is possible to generate different alternative gastrulation modes in single organisms, such as in early cnidarian, arthropod and vertebrate embryos. Here, we review the mechanisms that underlie the plasticity of vertebrate gastrulation both when experimentally manipulated and during evolution. Using the insights obtained from these experiments we discuss the effects of the increase in yolk volume on the morphology of gastrulation and provide new insights into two crucial innovations during amniote gastrulation: the transition from a ring-shaped mesoderm domain in anamniotes to a crescent-shaped domain in amniotes, and the evolution of the reptilian blastoporal plate/canal into the avian primitive streak.

The complete dorsal structure is formed from only the blastocoel roof of Xenopus blastula: insight into the gastrulation movement evolutionarily conserved among chordates

Gastrulation is a critical event whose molecular mechanisms are thought to be conserved among vertebrates. However, the morphological movement during gastrulation appears to be divergent across species, making it difficult to discuss the evolution of the process. Previously, we proposed a novel amphibian gastrulation model, the "subduction and zippering (S&Z) model". In this model, the organizer and the prospective neuroectoderm are originally localized in the blastula's blastocoel roof, and these embryonic regions move downward to make physical contact of their inner surfaces with each other at the dorsal marginal zone. The developmental stage when contact between the head organizer and the anterior-most neuroectoderm is established is called "anterior contact establishment (ACE)." After ACE, the A-P body axis elongates posteriorly. According to this model, the body axis is derived from limited regions of the dorsal marginal zone at ACE. To investigate this possibility, we conducted stepwise tissue deletions using Xenopus laevis embryos and revealed that the dorsal one-third of the marginal zone had the ability to form the complete dorsal structure by itself. Furthermore, a blastocoel roof explant of the blastula, which should contain the organizer and the prospective neuroectoderm in the S&Z model, autonomously underwent gastrulation and formed the complete dorsal structure. Collectively, these results are consistent with the S&Z gastrulation model and identify the embryonic region sufficient for construction of the complete dorsal structure. Finally, by comparing amphibian gastrulation to gastrulation of protochordates and amniotes, we discuss the gastrulation movement evolutionarily conserved among chordates.

Fusion and expansion of vitellogenin vesicles during Caenorhabditis elegans intestinal senescence

Some of the most conspicuous aging phenotypes of C. elegans are related to post-reproductive production of vitellogenins (Vtg), which form yolk protein (YP) complexes after processing and lipid loading. Vtg/YP levels show huge increases with age, and inhibition of this extends lifespan, but how subcellular and organism-wide distribution of these proteins changes with age has not been systematically explored. Here, this has been done to understand how vitellogenesis promotes aging. The age-associated changes of intestinal vitellogenin vesicles (VVs), pseudocoelomic yolk patches (PYPs), and gonadal yolk organelles (YOs) have been characterized by immuno-electron microscopy. We find that from reproductive adult day 2 (AD 2) to post-reproductive AD 6 and AD 9, intestinal VVs expand from 0.2 to 3-4 μm in diameter or by >3000 times in volume, PYPs increase by >3 times in YP concentration and volume, while YOs in oocytes shrink slightly from 0.5 to 0.4 μm in diameter or by 49% in volume. In AD 6 and AD 9 worms, mislocalized YOs found in the hypodermis, uterine cells, and the somatic gonadal sheath can reach a size of 10 μm across in the former two tissues. This remarkable size increase of VVs and that of mislocalized YOs in post-reproductive worms are accompanied by extensive fusion between these Vtg/YP-containing vesicular structures in somatic cells. In contrast, no fusion is seen between YOs in oocytes. We propose that in addition to the continued production of Vtg, excessive fusion between VVs and mislocalized YOs in the soma worsen the aging pathologies seen in C. elegans.

Prefertilization Exposure of Rainbow Trout Eggs to Per- and Polyfluoroalkyl Substances to Simulate Accumulation During Oogenesis

Aqueous film-forming foams (AFFFs) are used in firefighting and are sources of per- and polyfluoroalkyl substances (PFAS) to the environment through surface runoff and groundwater contamination at defense and transportation sites. Little is known regarding the toxicity and bioaccumulation of newer AFFF formulations containing novel PFAS. To mimic maternal transfer of PFAS, prefertilization rainbow trout eggs were exposed to three PFAS using novel methodologies. Batches of unfertilized oocytes were exposed for 3 h to 0, 0.01, 0.1, 1, or 10 µg/ml separately to perfluorooctanoic acid, perfluorohexanoic acid, or perfluorooctanesulfonic acid in either coelomic fluid or Cortland's solution. After exposure, the gametes were fertilized and rinsed with dechlorinated water. Egg yolk was aspirated from a subset of fertilized eggs for PFAS quantification. Each PFAS was detected in yolks of eggs exposed to the respective PFAS, and yolk concentrations were directly proportional to concentrations in aqueous media to which they were exposed. Exposure in coelomic fluid or Cortland's solution resulted in similar concentrations of PFAS in egg yolks. Ratios of PFAS concentrations in oocytes to concentrations in exposure media (oocyte fluid ratios) were <0.99 when exposed from 0.01 to 10 µg/ml and <0.45 when exposed from 0.1 to 10 µg/ml for both media and all three PFAS, demonstrating that the water solubility of the chemicals was relatively great. Prefertilization exposure of eggs effectively introduced PFAS into unfertilized egg yolk. This method provided a means of mimicking maternal transfer to evaluate toxicity to developing embryos from an early stage. This method is more rapid and efficient than injection of individual fertilized eggs and avoids trauma from inserting needles into eggs. Environ Toxicol Chem 2021;40:3159-3165. © 2021 SETAC.

Alterations on vitamin C synthesis and transportation and egg deposition induced by dietary vitamin C supplementation in Hy-Line Brown layer model

In ovo feeding of vitamin C (VC) has positive effects on the growth performance, immune and antioxidant function in poultry, which indicates that increasing VC content in eggs may be of benefit. This study was to investigate the effects of dietary VC supplementation on VC synthesis and transportation and egg deposition. In Exp. 1, in order to select a suitable animal model, VC content was detected in different eggs from different layer species. Vitamin C content was lower in ISA Brown breeder eggs and Hy-Line Brown layer eggs (P < 0.05) then in Arbor Acres breeder eggs. In Exp. 2, a total of 24 Hy-Line Brown layers (42-week-old) were randomly divided into 3 treatments with 8 replicates and fed a basal diet with VC at 0, 200 and 400 mg/kg. Sodium-dependent VC transporter 1 and 2 (SVCT1 and SVCT2) expressions were higher in ileum than in duodenum and jejunum (P < 0.05). SVCT1 expression was higher but SVCT2 expression was lower in the magnum than in the ovary (P < 0.05). L-Gulonolactone oxidase (GLO) and SVCT1 expressions were higher but SVCT2 was lower in the kidney than in the liver (P < 0.05). Dietary VC supplementation at 400 mg/kg increased SVCT1 expression in duodenum, ovary and magnum, but decreased GLO and SVCT1 expression in liver (P < 0.05). Dietary VC supplementation at 200 and 400 mg/kg increased SVCT2 expression in duodenum, but decreased GLO and SVCT1 expression in kidney and SVCT2 expression in liver (P < 0.05). Dietary VC supplementation promoted VC absorption in duodenum and jejunum, but reduced endogenous VC synthesis in liver and kidney. Although dietary VC supplementation enhanced VC transportation in ovary and magnum, it did not increase VC deposition in produced eggs.

Exploring the effectiveness of in ovo feeding of vitamin C based on the embryonic vitamin C synthesis and absorption in broiler chickens

BACKGROUND

Many researches about in ovo feeding (IOF) of vitamin C (VC) are gradually carried out to explore physiological development in chicken, but little studies focus on VC synthesis capacity of the embryo itself, the selection of injection site and the effectiveness of IOF of VC. This study aims to explore the above problems.

RESULTS

Kidney and yolk sac were the main organs for VC synthesis and L-gulonolactone oxidase (GLO) expression was lower during pre-hatch development than that during post-hatch development. Sodium-dependent vitamin C transporter 1 (SVCT1) expression was increased continuously in yolk sac from embryonic age 19 (E19) to post-hatch day 1 (D1) and in intestine (duodenum, jejunum and ileum) from E17 to D1. Plasma VC content was higher at D1 than that at D21 and D42. IOF of VC significantly reduced GLO expression in liver, kidney and yolk sac as well as SVCT1 expression in duodenum, jejunum and ileum, but increased the VC content in plasma, brain, kidney and liver. In addition, IOF of VC obviously reduced the embryonic morality and increased the hatchability under heat stress.

CONCLUSIONS

This study suggested that IOF of VC at E11 in yolk was effective for embryonic VC supplementation. These findings provide a theoretical reference about the method of embryonic VC supplementation and effective methodology on embryonic VC nutrition in broiler chickens.

Oogenesis in the tardigrade Hypsibius exemplaris Gąsiorek, Stec, Morek & Michalczyk, 2018 (Eutardigrada, Hypsibiidae)

Tardigrades are small, globally widespred invertebrates that need at least a thin layer of water to be active. There are gonochoric, hermaphroditic, and parthenogenetic species among them. The main aim of this study was to analyze the structure of the ovary, the structure of female germ cell clusters, and the course of oogenesis in the parthenogenetic species Hypsibius exemplaris, which in 2007 was recognized as a model organism. The material was analyzed using light and confocal microscopy as well as transmission and scanning electron microscopy. Histochemical and immunohistochemical methods were used. Our study showed that in the meroistic-polytrophic ovary of the examined species, branched germ cell clusters are formed in which one cell differentiates into an oocyte while the remaining cells become trophocytes. Vitellogenesis is of the mixed type: the first part of the yolk is synthesized by the oocyte (autosynthesis); the second part is synthesized by trophocytes and transported to the oocyte by cytoplasmic bridges; and the third part is synthesized outside the ovary (in storage cells) and transported to the oocyte by endocytosis. At the end of oogenesis, the trophocytes die by apoptosis. Parthenogenetic female of H. exemplaris lays from one to a dozen smooth eggs into exuviae.

Can phthalates move into the eggs of the loggerhead sea turtle Caretta caretta? The case of the nests on the Linosa Island in the Mediterranean Sea

During the monitoring of Caretta caretta nests on the island of Linosa, 30 unhatched eggs from four nests were collected to study the presence of phthalates in their three components (shell, yolk, and albumen). Four phthalates, namely diethyl (DEP), dibutyl (DBP), di-(2-ethylhexyl) (DEHP), and dioctyl (DOTP) phthalic acid esters (PAE), which are widely used as additives in plastics, were detected in all egg components. The most frequently found phthalate was DBP, followed by DEHP in eggshell and yolk. Dimethyl- (DMP) and butylbenzyl-phthalate (BBP) were below the limits of detection for all samples. The high total phthalate recorded in the yolk suggests that contamination could arise by vitellogenesis. PERMANOVA analysis (p = 0.01) confirmed significant differences in the PAEs contamination profiles in the eggs from the four nests. This study confirms the negative impact of plastic related compounds posing questions about the potential adverse effects on organisms and their conservation status.

Production of YP170 Vitellogenins Promotes Intestinal Senescence in Caenorhabditis elegans

During aging, etiologies of senescence cause multiple pathologies, leading to morbidity and death. To understand aging requires identification of these etiologies. For example, Caenorhabditis elegans hermaphrodites consume their own intestinal biomass to support yolk production, which in later life drives intestinal atrophy and ectopic yolk deposition. Yolk proteins (YPs; vitellogenins) exist as three abundant species: YP170, derived from vit-1–vit-5; and YP115 and YP88, derived from vit-6. Here, we show that inhibiting YP170 synthesis leads to a reciprocal increase in YP115/YP88 levels and vice versa, an effect involving posttranscriptional mechanisms. Inhibiting YP170 production alone, despite increasing YP115/YP88 synthesis, reduces intestinal atrophy as much as inhibition of all YP synthesis, which increases life span. By contrast, inhibiting YP115/YP88 production alone accelerates intestinal atrophy and reduces life span, an effect that is dependent on increased YP170 production. Thus, despite copious abundance of both YP170 and YP115/YP88, only YP170 production is coupled to intestinal atrophy and shortened life span. In addition, increasing levels of YP115/YP88 but not of YP170 increases resistance to oxidative stress; thus, longevity resulting from reduced vitellogenin synthesis is not attributable to oxidative stress resistance.

The effects of varied food acid ratios and egg components on Salmonella Typhimurium culturability from raw egg-based sauces

Raw egg-based sauces, such as mayonnaise and aioli, are frequently identified as sources of Salmonella during outbreaks of human cases of foodborne gastrointestinal disease. In this study, we surveyed aioli and mayonnaise recipes from different popular food websites to identify potential risk factors that may lead to the survival of Salmonella Typhimurium. In laboratory experiments, different ratios of food acids were used to determine if lemon juice, vinegar, or a combination of both restricted Salmonella Typhimurium culturability. We found that as long as the pH was below 4.2, bacterial culturability was limited. The use of whole egg alone or in combination with egg yolk was also investigated. Sauce preparations containing whole egg exhibited higher pH and supported Salmonella Typhimurium culturability longer than those containing yolk only. Ten restaurant prepared sauces were also obtained to further characterize the effect of preparation variability. Sauce preparations with a pH ≤ 3.8 did not support bacterial culturability after 4 h incubation at any temperature. The higher the pH the longer Salmonella Typhimurium remained culturable. Based on this study, it is recommended that raw egg-based foods are acidified, then stored at room temperature for at least 4 h prior to consumption.

Carboxyl ester lipase is highly conserved in utilizing maternal supplied lipids during early development of zebrafish and human

Carboxyl ester lipase (Cel), is a lipolytic enzyme secreted by the pancreas, which hydrolyzes various species of lipids in the gut. Cel is also secreted by mammary gland during lactation and exists in breast milk. It facilitates dietary fat digestion and absorption, thus contributing to normal infant development. This study aimed to examine whether the Cel in zebrafish embryos has a similar role of maternal lipid utilization as in human infants, and how Cel contributes to the utilization of yolk lipids in zebrafish. The cel1 and cel2 genes were expressed ubiquitously in the blastodisc and yolk syncytial layer before 24 hpf, and in the exocrine pancreas after 72 hpf. The cel1 and cel2 morphants exhibited developmental retardation and yolk sac retention. The total cholesterol, cholesterol ester, free cholesterol, and triglyceride were reduced in the morphants' body while accumulated in the yolk (except triglyceride). The FFA content of whole embryos was much lower in morphants than in standard controls. Moreover, the delayed development in cel (cel1/cel2) double morphants was partially rescued by FFA and cholesterol supplementation. Delayed and weakened cholesterol ester transport to the brain and eyes was observed in cel morphants. Correspondingly, shrunken midbrain tectum, microphthalmia, pigmentation-delayed eyes as well as down-regulated Shh target genes were observed in the CNS of double morphants. Interestingly, cholesterol injections reversed these CNS alterations. Our findings suggested that cel genes participate in the lipid releasing from yolk sac to developing body, thereby contributing to the normal growth rate and CNS development in zebrafish.

Effect of dietary sesame (Sesame indicum L) seed meal level supplemented with lysine and phytase on performance traits and antioxidant status of late-phase laying hens

Objective

This study was performed to investigate the effects of supplementing sesame seed meal (SSM) with phytase and lysine on performance, egg quality, blood biochemical and antioxidant status of laying hens.

Methods

A total of 960, 56-wk-old laying hens were divided into 12 dietary groups with eight replicates per group (10 birds per replicate). A completely randomized design with factorial arrangement 2×3×2 consisted of two levels of lysine supplement (0 and 10% over requirement), three SSM levels (0, 10 and 20%) with or without phytase (0 and 300 g/ton). The feeding trial lasted 10 weeks.

Results

From findings, birds fed diets with 10% SSM had higher feed intake than groups fed 0 and 20% SSM. The addition of phytase to experimental feeds, improved feed conversion ratio (FCR), increased egg weight and mass (P<0.01). Egg quality criteria was not affected by supplementing phytase; however, supplementing 300 g/ton phytase to hens diet, led to a significant (P<0. 05) increase in egg shell strength. Egg yolk cholesterol and serum low-density lipoprotein cholesterol (LDL-C), atherogenic index and total cholesterol were decreased (P<0.01) by diet containing 20% SSM. The high-density lipoprotein cholesterol (HDL-C) was increased (P<0.05) in serum of hens fed 20% SSM than the other groups. It was also observed that total antioxidant capacity (TAC) and total superoxide dismutase (TSOD) content of hens fed 20% SSM was significantly upper than control group (P<0.05).

Conclusion

As from results, dietary supplementation of SSM and phytase had no negative effects on laying hens performance or egg quality improving also the egg oxidative stability.

Zebrafish as a Model for Toxicological Perturbation of Yolk and Nutrition in the Early Embryo

PURPOSE OF REVIEW

Developmental toxicity assessments often focus on structural outcomes and overlook subtle metabolic differences which occur during the early embryonic period. Deviant embryonic nutrition can result in later-life disease, including diabetes, obesity, and cardiovascular disease. Prior to placenta-mediated nutrient exchange, the human embryo requires maternally supplied nutritional substrates for growth, called yolk. Here, we compare the biology of the human and zebrafish yolk and review examples of toxicant-mediated perturbation of yolk defects, composition, and utilization.

RECENT FINDINGS

Zebrafish embryos, like human embryos, have a protruding yolk sac that serves as a nutritional cache. Aberrant yolk morphology is a common qualitative finding in fish embryotoxicity studies, but quantitative assessment and characterization provides an opportunity to uncover mechanistic targets of toxicant effects on embryonic nutrition. The zebrafish and the study of its yolk sac is an excellent model for uncovering toxicant disruptions to early embryonic nutrition and has potential to discover mechanistic insights into the developmental origins of health and disease.

Modeling Embryonic Cleavage Patterns

The division patterns of early invertebrate and vertebrate embryos are key to the specification of cell fates and embryo body axes. We here describe a generic computational modeling method to quantitatively test mechanisms which specify successive division position and orientation of eggs and early blastomeres in 3D. This approach should serve to motivate and guide future experimental work on the mechanisms controlling early embryo morphogenesis.

Microinjection of Marine Fish Eggs

Microinjection is a powerful tool for studying embryonic development and analyzing gene functions in fish. This technique was first applied to model species of fish such as zebrafish and medaka whose egg chorions could be removed or softened before microinjection. Recent progress in genome editing using TALEN and CRISPR has opened the opportunity to analyze gene functions in a much wider range of fish including those important to marine aquaculture. Therefore, application of the microinjection technique is also required in these species. However, the characteristics of fish eggs vary widely between species and several technical difficulties need to be overcome in order to use microinjection in a wider range of species. To obtain consistent results with microinjection, an optimal method has to be developed for each target species. In this chapter, we describe the physical characteristics of the eggs of fish species that have been used in microinjection experiments in our laboratory and detail the microinjection system we developed for fish eggs with a hard chorion, such as those of marine species.

Azadirachtin impairs egg production in Atta sexdens leaf-cutting ant queens

Leaf-cutting ants are important pests of forests and agricultural crops in the Neotropical region. Atta sexdens colonies can be composed of thousands of individuals, which form a highly complex society with a single reproductive queen. Successful control of this species is achieved only if the queen is affected. Few data are available on the lethal or sublethal effects of toxic compounds on leaf-cutting ant queens. Azadirachtin has been claimed as an effective biopesticide for insect control, but its action on leaf-cutting ants has been little explored. This study shows that azadirachtin affects oviposition in A. sexdens queens, impairing egg development by decreasing protein reserves. Azadirachtin inhibits the synthesis of vitellogenin, the major yolk protein precursor. The negative effects of azadirachtin on the reproduction of leaf-cutting ant queens suggest a potential use for the control of these insects.

Vitellogenin transcytosis in follicular cells of the honeybee Apis mellifera and the wasp Polistes simillimus

Vitellogenin receptor (VgR) is a low-density lipoprotein receptor responsible for the mediated endocytosis of vitellogenin (Vg) during egg formation in insects. The maturing oocyte is enveloped by a follicular epithelium, which has large intercellular spaces during Vg accumulation (patency). However, Vg has been reported in the cytoplasm of follicular cells, indicating that there may be a transcellular route for its transport. This study verified the presence of VgR in the follicular cells of the ovaries of the honeybee Apis mellifera and the wasp Polistes simillimus in order to evaluate if Vg is transported via transcytosis in these insects. Antibodies specific for vitellogenin receptor (anti-VgR), vitellogenin (anti-Vg), and clathrin (anti-Clt) were used for immunolocalization. The results showed the presence of VgR on the apical and basal plasma membranes of follicular cells of the vitellogenic follicles in both species, indicating that VgR may have been transported from the basal to the apical cell domain, followed by its release into the perivitelline space, evidenced by the presence of apical plasma membrane projections containing VgR. Co-localization proved that Vg bind to VgR and that the transport of this protein is mediated by clathrin. These data suggest that, in these social insects, Vg is transported via clathrin-mediated VgR transcytosis in follicular cells.

Expression of Yolk Processing Enzyme Genes in Fertilized Eggs from Artificially Matured Female Eel, Anguilla japonica

Large quantity of eggs fail to be fertilized and many of fertilized eggs are unable to hatch in the eel, Anguilla japonica. Larvae of eel absorb egg yolk up to 8 days after hatching but the majority of hatched larvae die before they reach the stage of first feeding in this species. Genes of key enzymes for yolk processing (cathepsin B, D, L and lipoprotein lipase - abbreviated as ctsb, ctsd, ctsl and lpl, respectively) could be associated with egg quality. In this study, we investigated differences in the expression of these genes between floating eggs and sinking eggs, and also the relationship between the gene expressions of the enzymes and fertilization rates in the fertilized eggs obtained from artificially matured female eels. Expressions of yolk processing enzyme genes did not show significant difference between floating and sinking egg groups. Expression of ctsb decreased when fertilization rate was high. Expression of ctsd, ctsl and lpl, however, did not show any significant differences. These results suggest that ctsb expression could be an indicator of egg quality, and that some proteins prone to be digested by ctsb could be very important in the process of fertilization and normal cleavage in this species. Further study should identify these critical proteins to improve our understanding on the quality of fish eggs.

Roles of the sire and dam quail in egg, yolk, albumen, and shell weight alterations due to the parthenogenetic trait

Infertile eggs from Chinese Painted quail exhibit parthenogenesis, and the 1st egg in a clutch sequence is more likely to develop a parthenogenetic embryo. Also, hens that exhibit parthenogenesis have shorter clutches and heavier egg weights. These larger eggs may be a result of the egg residing in the oviduct longer, allowing more time for the parthenote to develop. However, it is unknown which components of the egg are altered due to the parthenogenetic trait or the role of dams and sires from the parthenogenetic line of quails in these alterations. Therefore, our objective was to determine if the parthenogenetic trait in dams, sires, or both contributes to alterations in egg components, such as yolk, albumen, and shell weights. Two selected lines of quail, 1 line selected for parthenogenesis and 1 line that was unselected for the parthenogenetic trait (control), were utilized in a 2 x 2 factorial arrangement of dam and sire lines to create 4 breeding treatments: control dams + control sires (CC), control dams + parthenogenetic sires (CP), parthenogenetic dams + control sires (PC), parthenogenetic dams + parthenogenetic sires (PP). Daily, fresh eggs were collected, labeled, weighed, and the germinal disc was classified as fertile, unfertilized without development, or parthenote. Yolk, albumen, and shell weights were obtained, and their weights were also calculated as percentage of total egg weight. A dam main effect revealed heavier weights for total egg, yolk, albumen, and shell as well as a larger percentage of albumen and ratio of albumen to yolk in parthenogenetic line dams versus control line dams. However, the percentage of yolk was higher for control than parthenogenetic line dams. The increase in total egg and egg component weights due to the parthenogenetic trait suggests that the transit time of the egg through the oviduct is altered. Perhaps transit through the magnum and uterus is delayed the most yielding greater albumen and shell weights, respectively.

Laying hen performance, egg quality improved and yolk 5-methyltetrahydrofolate content increased by dietary supplementation of folic acid

This study was performed to evaluate the effect of folic acid (FA) on performance, egg quality and yolk 5-methyltetrahydrofolate (5-MTHF) content. A total of 384 Hy-line W36 strain hens from 52 to 58 weeks of age were randomly assigned to 4 groups, and each group received one of following dietary treatments: 0, 5, 10 and 15 mg FA/kg diet. A completely randomized design was used. Egg production percentage, egg mass and egg weight were increased significantly (P < 0.05) and feed conversion ratio (FCR) was reduced significantly (P < 0.05) by increasing FA content in diets. No significant differences were detected among treatments on egg quality except for shell thickness. The dietary supplementations of laying hens diets with FA significantly increased yolk 5-MTHF content (P = 0.02). Overall, these data demonstrate that dietary supplementation with FA raised 5-MTHF content of yolk and productivity of egg production in laying hens.

Health Risk Contamination of Heavy Metals in Yolk and Albumen of Duck Eggs Collected in Central and Western Thailand

Two hundred duck egg samples were collected from 20 farms in Central and Western Thailand. The levels of Zn, Co, Mn, Fe, and Cr in yolks were found significantly higher than in albumen, whereas the levels of Cd and Cu contaminations in egg albumen were significantly higher than in yolks. The mean level of Pb contamination in whole eggs was 4.06 ± 2.70 mg kg^-1 dry weight. This level was higher than the Thai agricultural standard no. 6703-2005 for duck eggs set at 0.1 ppm for the magnitude of 40.6 times. In addition, 98% (196/200) of duck egg samples had Pb levels higher than the standard limit. However, the calculation of daily intakes of Pb, Cd, and Cu contamination in the current study of duck eggs shows that these metals were lower than the World Health Organization and the Food and Agriculture Organization provisional tolerated daily intake. These levels may, however, present a health risk resulting from a long-term exposure. It can be concluded that consumers may be at risk of Pb, Cd, and Cu contamination if they consume contaminated duck eggs. In addition, long-term monitoring of the health risks of heavy metals contamination should be conducted concerning the duck egg production system in Thailand.

Multiplication in Egg Yolk and Survival in Egg Albumen of Genetically and Phenotypically Characterized Salmonella Enteritidis Strains

Prompt refrigeration of eggs to prevent the multiplication of Salmonella Enteritidis to high levels during storage is an important practice for reducing the risk of egg-transmitted human illness. The efficacy of egg refrigeration for achieving this goal depends on the interaction among the location of contamination, the ability of contaminant strains to survive or multiply, and the rate at which growth-restricting temperatures are attained. The present study assessed the significance of several characterized genetic and phenotypic properties for the capabilities of 10 Salmonella Enteritidis isolates to multiply rapidly in egg yolk and survive for several days in egg albumen during unrefrigerated (25°C) storage. The growth of small numbers of each Salmonella Enteritidis strain (approximately 10¹ CFU/mL) inoculated into egg yolk samples was determined after 6 and 24 h of incubation. The survival of larger numbers of Salmonella Enteritidis (approximately 10⁵ CFU/mL) inoculated into albumen samples was determined at 24 and 96 h of incubation. In yolk, the inoculated Salmonella Enteritidis strains multiplied to mean levels of approximately 10^2.6 CFU/mL after 6 h of incubation and 10^8.3 CFU/mL after 24 h. In albumen, mean levels of approximately 10^4.6 CFU/mL Salmonella Enteritidis were maintained through 96 h. The concentrations of the various Salmonella strains after incubation in either yolk or albumen were distributed over relatively narrow ranges of values. Significant ( P < 0.01) differences observed among individual strains suggested that maintenance of the fimbrial gene sefD may have positive genetic selection value by improving fitness to grow inside egg yolk, whereas the antibiotic resistance gene bla_TEM-1 tet(A) appeared to have negative genetic selection value by decreasing fitness to survive in egg albumen.

Pre-gastrula Development of Non-eutherian Mammals

Marsupials and monotremes differ from eutherian mammals in many features of their reproduction and development. Some features appear to be representative of transitional stages in evolution from therapsid reptiles to humans and mice, particularly with respect to the extraembryonic tissues that have undergone remarkable modifications to accommodate reduced egg size and quantity of yolk/deutoplasm, and increasing emphasis on viviparity and placentation. Trophoblast and hypoblast contribute the epithelial layers in most of the extraembryonic membranes and are the first two lineages to differentiate from the embryonic lineage. How they are specified varies greatly among mammals, perhaps largely due to heterochrony in the stage at which they must function. Differences probably also exist in the stage at which lineages are specified relative to the stage at which they fully commit to differentiation. The dogma of sequential commitment to trophoblast and hypoblast with progressive loss of potency may not be a fundamental feature of early mammalian development, but merely a recently acquired developmental pattern in eutherians, or at least mice.

Quantitative Proteomics of Xenopus Embryos I, Sample Preparation

Xenopus oocytes and embryos are model systems optimally suited for quantitative proteomics. This is due to the availability of large amount of protein material and the ease of physical manipulation. Furthermore, facile in vitro fertilization provides superbly synchronized embryos for cell cycle and developmental stages. Here, we detail protocols developed over the last few years for sample preparation of multiplexed proteomics with TMT-tags followed by quantitative mass spectrometry analysis using the MultiNotch MS3 approach. In this approach, each condition is barcoded with an isobaric tag at the peptide level. After barcoding, samples are combined and the relative abundance of ~100,000 peptides is quantified on a mass spectrometer. High reproducibility of the sample preparation process prior to peptides being tagged and combined is of upmost importance for obtaining unbiased data. Otherwise, differences in sample handling can inadvertently appear as biological changes. We detail and exemplify the application of our sample workflow on an embryonic time-series of ten developmental stages of Xenopus laevis embryos ranging from the egg to stage 35 (just before hatching). Our accompanying paper (Chapter 14 ) details a bioinformatics pipeline to analyze the quality of the given sample preparation and strategies to convert spectra of X. laevis peptides into biologically interpretable data.

Rates of parasitism, but not allocation of egg resources, vary among and within hosts of a generalist avian brood parasite

Brown-headed cowbirds (Molothrus ater) deposit their eggs into the nests of other birds, which then raise the cowbird chick. Female cowbirds thus have limited options for impacting their offspring's development via maternal effects compared to most other passerines. Cowbirds can impact their offspring's phenotype by choosing among potential host nests, and by adjusting egg resources based on host characteristics. To examine whether cowbirds exhibit either or both of these strategies, we investigated rates of cowbird parasitism and egg investment (egg size, yolk-to-albumen ratio, and yolk testosterone and androstenedione) among and within host species in a shrubland bird community. We found that the probability of being parasitized by cowbirds, controlling for host status as a cowbird egg accepter or rejecter and ordinal date, varied significantly among host species, indicating an apparent preference for some hosts. Parasitism rates did not differ with host size, however, and despite variation in cowbird egg size among host species, this variation was not related to host size or cowbird preference. Among host species with eggs that are larger than those of the cowbird, cowbirds were significantly more likely to parasitize nests with relatively smaller eggs, whereas parasitism rates did not vary with relative egg size in host species with smaller eggs. There was no evidence for variation in cowbird egg components among or within host species. Our data indicate that cowbirds discriminate among host nests, but do not appear to adjust the composition of their eggs based on inter- or intraspecific host variation.

Adult pollen diet essential for egg maturation by a solitary Osmia bee

Reproduction is a nutritionally costly activity for many insects, as their eggs are rich in lipids and proteins. That cost seems especially acute for non-social bees, which for their size, lay enormous eggs. All adult female bees visit flowers, most of them to collect pollen and nectar, or sometimes oils, to feed their progeny. For adult bees, the need for pollen feeding has only been detailed for the honey bee, Apis mellifera. To experimentally test for the reproductive value of adult pollen feeding by a non-social bee, Osmia californica (Hymenoptera: Apiformes: Megachilidae), young female bees plus males were released into large glasshouse cages provided with either a male-fertile sunflower cultivar or a pollen-less one. Females regularly visited and drank nectar from flowers of both cultivars. Abundant orange pollen was seen regularly in guts of females confined with the male-fertile sunflowers, indicative of active pollen ingestion. All females' terminal oocytes (next egg to be laid) were small at emergence. Oocytes of females confined with the pollen-less sunflowers remained small, despite frequent nectaring and exposure to other floral stimuli. In contrast, the basal oocytes of female O. californica with access to pollen had swelled to full size within ten days following emergence, enabling them to lay eggs in provided nest tubes. Adult females of this solitary bee required dietary pollen to reproduce; nitrogen stores acquired as larvae were inadequate. Early and regular pollen feeding in part paces the onset and maximum tempo of solitary bees' lifetime reproductive output.

Isolation and detection of microRNA from the egg of chickens

Background

The egg is a vital part of the chicken developmental process and an important protein source for humans. Despite the chicken egg being a subject of intense research little attention has been given to the role of microRNAs within the egg.

Findings

We report a method for the reproducible and reliable isolation of miRNA from the albumen and yolk of chicken eggs. We also report the detection via real-time PCR of a number of miRNAs from both of these biological fluids.

Conclusions

These findings provide an interesting look into the chicken egg and raise questions as to the role that miRNAs maybe playing in the chicken egg. This method of detecting miRNAs in chicken eggs will allow researchers to investigate the presence of an additional level of epigenetic programming in chick development previously unknown and also how this impacts the nutritional value of eggs for human consumption.

Changes in follicular cells architecture during vitellogenin transport in the ovary of social Hymenoptera

Vitellogenins are the major yolk proteins, synthesized in the fat body, released into the hemolymph and captured by the developing oocytes, but the mechanisms by which these proteins cross the follicular cell layer are still poorly understood. This study describes the actin distribution in follicular cells during vitellogenin transport to the oocyte in social Hymenoptera represented by bees Apis mellifera and Melipona quadrifasciata, the wasp Mischocyttarus cassununga and the ant Pachycondyla curvinodis. In oocytic chambers of vitellogenic follicles, vitellogenin was found within the follicular cells, perivitelline space and oocyte, indicating a transcellular route from the hemolymph to the perivitelline space. The cortical actin cytoskeleton in follicular cells underwent reorganization during transport of vitellogenin across this epithelium suggesting that in the ovary of social hymenopterans, vitellogenin delivery to oocytes requires a dynamic cytoskeletal rearrangement of actin filaments in the follicular cells.

The effect of hatching time on the bioenergetics of northern pike (Esox lucius) larvae from a single egg batch during the endogenous feeding period

Size, caloric value and chemical composition were measured separately in the progeny of two northern pike (Esox lucius) females at 3-day intervals during the endogenous feeding period from hatching to final yolk resorption. Tissue, yolk and entire larvae were analysed separately in three groups of larvae that hatched at different times (between 88 and 106 degree-days post-fertilization). An integrated approach with the Gompertz model was used to compute the yolk conversion efficiency and time to maximum tissue size in early, mid and late hatched larvae. At hatching, unresorbed yolk of early hatched larvae contained more energy (39.20 J) and more protein (0.99 mg) compared to the yolk of larvae that hatched later (38.13 J and 0.92 mg protein for late hatched larvae, p < 0.05). In contrast, a significant reduction in tissue weight (-0.7 mg DW) and protein content (-0.5 mg) was found in early hatched larvae compared to those which hatched later (p < 0.05). Between days 9 and 12 post-hatching (108 and 144 degree-days post-hatching), close to the final yolk resorption, late hatched larvae stopped growing and their tissue began to be resorbed. This tissue resorption time was delayed in early hatched larvae which presented at the end of the experiment a greater tissue weight than late hatched ones. Yolk conversion efficiency in term of energy from hatching to complete yolk resorption stage was significantly higher for early and mid hatched larvae (51%) compared to late hatched ones (44%) (p = 0.004). Furthermore, the time to maximum tissue size was found to be negatively related to hatching time which implies that early hatched larvae take longer time to switch from one developmental stage to the next. The maximum tissue dry weight and energy content were found to be reached at approximately the same age post-fertilization for both early hatched and late hatched larvae, suggesting that the principal steps in a fish's lifespan are better correlated with time of fertilization than hatching time.

Lxr regulates lipid metabolic and visual perception pathways during zebrafish development

The Liver X Receptors (LXRs) play important roles in multiple metabolic pathways, including fatty acid, cholesterol, carbohydrate and energy metabolism. To expand the knowledge of the functions of LXR signaling during embryonic development, we performed a whole-genome microarray analysis of Lxr target genes in zebrafish larvae treated with either one of the synthetic LXR ligands T0901317 or GW3965. Assessment of the biological processes enriched by differentially expressed genes revealed a prime role for Lxr in regulating lipid metabolic processes, similarly to the function of LXR in mammals. In addition, exposure to the Lxr ligands induced changes in expression of genes in the neural retina and lens of the zebrafish eye, including the photoreceptor guanylate cyclase activators and lens gamma crystallins, suggesting a potential novel role for Lxr in modulating the transcription of genes associated with visual function in zebrafish. The regulation of expression of metabolic genes was phenotypically reflected in an increased absorption of yolk in the zebrafish larvae, and changes in the expression of genes involved in visual perception were associated with morphological alterations in the retina and lens of the developing zebrafish eye. The regulation of expression of both lipid metabolic and eye specific genes was sustained in 1 month old fish. The transcriptional networks demonstrated several conserved effects of LXR activation between zebrafish and mammals, and also identified potential novel functions of Lxr, supporting zebrafish as a promising model for investigating the role of Lxr during development.

Multiple vitellogenins and product yolk proteins in European sea bass (Dicentrarchus labrax): Molecular characterization, quantification in plasma, liver and ovary, and maturational proteolysis

Three complete vitellogenin (Vtg) polypeptides of European sea bass (Dicentrarchus labrax), an acanthomorph teleost spawning pelagic eggs in seawater, were deduced from cDNA and identified as VtgAa, VtgAb and VtgC based on current Vtg nomenclature and phylogeny. Label free quantitative mass spectrometry verified the presence of the three sea bass Vtgs or their product yolk proteins (YPs) in liver, plasma and ovary of postvitellogenic females. As evidenced by normalized spectral counts, VtgAb-derived protein was 2- to 5-fold more abundant, depending on sample type, than for VtgAa, while VtgC-derived protein was less abundant, albeit only 3-fold lower than for VtgAb in the ovary. Western blotting with Vtg type-specific antisera raised against corresponding gray mullet (Mugil cephalus) lipovitellins (Lvs) detected all three types of sea bass Vtg in the blood plasma of gravid females and/or estrogenized males and showed that all three forms of sea bass Lv undergo limited partial degradation during oocyte maturation. The comparatively high levels of VtgC-derived YPs in fully-grown oocytes and the maturational proteolysis of all three types of Lv differ from what has been reported for other teleosts spawning pelagic eggs in seawater but are similar to recent findings for two species of North American Moronidae, the striped bass (Morone saxatilis) and white perch (Morone americana), which spawn pelagic and demersal eggs, respectively in fresh water. Together with the high Vtg sequence homologies and virtually identical structural features of each type of Vtg between species, these findings indicate that the moronid multiple Vtg systems do not substantially vary with reproductive environment.

Regulation of Ahr signaling by Nrf2 during development: Effects of Nrf2a deficiency on PCB126 embryotoxicity in zebrafish (Danio rerio)

The embryotoxicity of co-planar PCBs is regulated by the aryl hydrocarbon receptor (Ahr), and has been reported to involve oxidative stress. Ahr participates in crosstalk with another transcription factor, Nfe2l2, or Nrf2. Nrf2 binds to antioxidant response elements to regulate the adaptive response to oxidative stress. To explore aspects of the crosstalk between Nrf2 and Ahr and its impact on development, we used zebrafish (Danio rerio) with a mutated DNA binding domain in Nrf2a (nrf2a(fh318/fh318)), rendering these embryos more sensitive to oxidative stress. Embryos were exposed to 2 nM or 5 nM PCB126 at 24 h post fertilization (prim-5 stage of pharyngula) and examined for gene expression and morphology at 4 days post fertilization (dpf; protruding - mouth stage). Nrf2a mutant eleutheroembryos were more sensitive to PCB126 toxicity at 4 dpf, and in the absence of treatment also displayed some subtle developmental differences from wildtype embryos, including delayed inflation of the swim bladder and smaller yolk sacs. We used qPCR to measure changes in expression of the nrf gene family, keap1a, keap1b, the ahr gene family, and known target genes. cyp1a induction by PCB126 was enhanced in the Nrf2a mutants (156-fold in wildtypes vs. 228-fold in mutants exposed to 5 nM). Decreased expression of heme oxygenase (decycling) 1 (hmox1) in the Nrf2a mutants was accompanied by increased nrf2b expression. Target genes of Nrf2a and AhR2, NAD(P)H:quinone oxidoreductase 1 (nqo1) and glutathione S-transferase, alpha-like (gsta1), showed a 2-5-fold increase in expression in the Nrf2a mutants as compared to wildtype. This study elucidates the interaction between two important transcription factor pathways in the developmental toxicity of co-planar PCBs.

The Atg1-Tor pathway regulates yolk catabolism in Drosophila embryos

Yolk provides an important source of nutrients during the early development of oviparous organisms. It is composed mainly of vitellogenin proteins packed into membrane-bound compartments called yolk platelets. Catabolism of yolk is initiated by acidification of the yolk platelet, leading to the activation of Cathepsin-like proteinases, but it is unknown how this process is triggered. Yolk catabolism initiates at cellularization in Drosophila melanogaster embryos. Using maternal shRNA technology we found that yolk catabolism depends on the Tor pathway and on the autophagy-initiating kinase Atg1. Whereas Atg1 was required for a burst of spatially regulated autophagy during late cellularization, autophagy was not required for initiating yolk catabolism. We propose that the conserved Tor metabolic sensing pathway regulates yolk catabolism, similar to Tor-dependent metabolic regulation on the lysosome.

Ovarian yolk formation in fishes: Molecular mechanisms underlying formation of lipid droplets and vitellogenin-derived yolk proteins

Fish egg yolk is largely derived from vitellogenins, which are synthesized in the liver, taken up from the maternal circulation by growing oocytes via receptor-mediated endocytosis and enzymatically processed into yolk proteins that are stored in the ooplasm. Lipid droplets are another major component of fish egg yolk, and these are mainly composed of neutral lipids that may originate from maternal plasma lipoproteins. This review aims to briefly summarize our current understanding of the molecular mechanisms underlying yolk formation in fishes. A hypothetical model of oocyte growth is proposed based on recent advances in our knowledge of fish yolk formation.

Estrogen-induced yolk precursors in European sea bass, Dicentrarchus labrax: Status and perspectives on multiplicity and functioning of vitellogenins

The estrogen-inducible egg yolk precursor, vitellogenin, of the European sea bass (Dicentrarchus labrax) has received considerable scientific attention by virtue of its central importance in determination of oocyte growth and egg quality in this important aquaculture species. However, the multiplicity of vitellogenins in the sea bass has only recently been examined. Recent cloning and homology analyses have revealed that the sea bass possesses the three forms of vitellogenin, VtgAa, VtgAb and VtgC, reported to occur in some other highly evolved teleosts. Progress has been made in assessing the relative abundance and special structural features of the three Vtgs and their likely roles in oocyte maturation and embryonic nutrition. This report discusses these findings in the context of our prior knowledge of vitellogenesis in this species and of the latest advances in our understanding of the evolution and function of multiple Vtgs in acanthomorph fishes.

Identification of environmental chemicals that induce yolk malabsorption in zebrafish using automated image segmentation

Environmental factors affecting nutrient availability during development can cause predisposition to diseases later in life. To identify chemicals in the environment capable of altering nutrient mobilization, we analyzed yolk malabsorption in the zebrafish embryo, which relies on maternally-derived yolk for nutrition during its first week of life. Embryos of the transgenic zebrafish line HGn50D, which fluoresce in the yolk syncytial layer, were exposed from two to five days post fertilization to different chemicals. We developed a software package to automatically and accurately segment and quantify the area of the fluorescing yolk in images captured at the end of the treatment period. Based on this quantification, we found that prochloraz decreased yolk absorption, while butralin, tetrabromobisphenol A, tetrachlorobisphenol A and tributyltin increased yolk absorption. Given the number and variety of industrial chemicals in commerce today, development of automated image processing to perform high-speed quantitative analysis of biological effects is an important step for enabling high throughput screening to identify chemicals altering nutrient absorption.

Comparison of three spectrophotometric methods for analysis of egg yolk carotenoids

Carotenoids accumulated in the egg yolk are of importance for two reasons. Firstly they are important pigments influencing customer acceptance and secondly they are essential components with positive health effects either as antioxidants or as precursor of vitamin A. Different analytical methods are available to quantitatively identify carotenoids from egg yolk such as spectrophotometric methods described by AOAC (Association of Official Analytical Chemists) and HPLC (High Performance Liquid Chromatography). Both methods have in common that they are time consuming, need a laboratory environment and well trained technical operators. Recently, a rapid lab-independent spectrophotometric method (iCheck, BioAnalyt GmbH, Germany) has been introduced that claims to be less time consuming and easy to operate. The aim of the current study was therefore to compare the novel method with the two standard methods. Yolks of 80 eggs were analysed as aliquots by the three methods in parallel. While both spectrometric methods are only able measure total carotenoids as total ß-carotene, HPLC enables the determination of individual carotenoids such lutein, zeaxanthin, canthaxanthin, ß-carotene and β-apocarotenoic ester. In general, total carotenoids levels as obtained by AOAC were in average 27% higher than those obtained by HPLC. Carotenoid values obtained by the reference methods AOAC and HPLC are highly correlated with the iCheck method with r(2) of 0.99 and 0.94 for iCheck vs. AOAC and iCheck vs. HPLC, respectively (both p<0.001). Bland Altman analysis showed that the novel iCheck method is comparable to the reference methods. In conclusion, the novel rapid and portable iCheck method is a valid and effective tool to determine total carotenoid of egg yolk under laboratory-independent conditions with little trained personal.

A novel estrogen-regulated avian apolipoprotein

In search for yet uncharacterized proteins involved in lipid metabolism of the chicken, we have isolated a hitherto unknown protein from the serum lipoprotein fraction with a buoyant density of ≤1.063 g/ml. Data obtained by protein microsequencing and molecular cloning of cDNA defined a 537 bp cDNA encoding a precursor molecule of 178 residues. As determined by SDS-PAGE, the major circulating form of the protein, which we designate apolipoprotein-VLDL-IV (Apo-IV), has an apparent M_r of approximately 17 kDa. Northern Blot analysis of different tissues of laying hens revealed Apo-IV expression mainly in the liver and small intestine, compatible with an involvement of the protein in lipoprotein metabolism. To further investigate the biology of Apo-IV, we raised an antibody against a GST-Apo-IV fusion protein, which allowed the detection of the 17-kDa protein in rooster plasma, whereas in laying hens it was detectable only in the isolated ≤1.063 g/ml density lipoprotein fraction. Interestingly, estrogen treatment of roosters caused a reduction of Apo-IV in the liver and in the circulation to levels similar to those in mature hens. Furthermore, the antibody crossreacted with a 17-kDa protein in quail plasma, indicating conservation of Apo-IV in avian species. In search for mammalian counterparts of Apo-IV, alignment of the sequence of the novel chicken protein with those of different mammalian apolipoproteins revealed stretches with limited similarity to regions of ApoC-IV and possibly with ApoE from various mammalian species. These data suggest that Apo-IV is a newly identified avian apolipoprotein.

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Apo-VLDL-IV (Apo-IV) is a newly identified avian apolipoprotein.

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Apo-IV expression is suppressed by estrogen.

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Apo-IV containing VLDL particles are excluded from uptake into yolk.

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Apo-IV has limited similarity to mammalian ApoC-IV.

Egg size, postembryonic yolk, and survival ability

Neonates of many species are dependent upon a post-embryonic yolk (PEY), a residual of the energy reserve of the developing embryo. Offspring hatching from large eggs have relatively more PEY than offspring from small eggs. Among daphniid Cladocera, large species produce larger eggs than smaller species. We have found that the proportional amount of energy reserve in eggs of five species of Cladocera is similar, but neonates of the larger Cladocera are born with a greater relative amount of postembryonic yolk, as triacylglycerol, than small species. Apparently, more of the reserve is metabolized by embryos of small species. This is correlated with the higher unitweight metabolic rates of smaller animals. It has been argued that animals should produce relatively larger eggs when exposed to low or unpredictable food conditions to increase the survivorship of their offspring. The physiological constraint of greater relative energy requirements of small embryos may limit PEY and explain why offspring of larger eggs survive better in low or unpredictable food resource environments.