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At least 631 records · Page 35Linked to original sources
PubMed1982

Selection for high specific gravity of eggs in a flock of Australorp hens.

1. A realised heritability of 0.23 was obtained in an Australorp flock (S) selected for five generations for high egg specific gravity. 2. A comparison with an unselected control flock (C) over 50 weeks of lay in the final generation indicated a number of statistically significant correlated responses in commercially important traits in the S line in addition to the direct response of +0.004 in specific gravity. 3. With an increase in specific gravity, there was a decrease of 3.4 in the percentage of soft-shelled eggs laid. 4. The weight and albumen height of eggs measured within 1 hour of lay declined by 1.8 g and 2.1 Haugh units respectively. 5. There were reductions in the weight and albumen height losses of eggs stored over a 10-d period (C 0.74, S 0.62 g and C 17.9, S 15.0 Haugh units respectively), so that at the end of this period the albumen heights in both lines were the same. 6. Average body weight and daily food intake were less by 0.28 kg and 7.5 g respectively. 7. Although there was no change in egg production, the average age at first egg was reduced by 11.3 d.

Animals↗
PubMed2001

Molecular cloning of a second prophenoloxidase cDNA from the mosquito Armigeres subalbatus: prophenoloxidase expression in blood-fed and microfilariae-inoculated mosquitoes.

Melanization constitutes an important component in various aspects of insect life, including cuticular sclerotization, egg-shell tanning, melanization of parasites and wound healing. Recently, a cDNA encoding prophenoloxidase (pro-PO), a key enzyme in the biosynthesis of melanotic material in insects, was cloned from microfilariae (mf)-inoculated mosquitoes, Armigeres subalbatus. However, results of Northern blot analyses indicated that two pro-POs might be present in Ar. subalbatus and these pro-POs might be responsible for two distinct physiological functions, egg-shell tanning and melanization of parasites. Subsequently, the second pro-PO cDNA (As-pro-PO II) was cloned from blood-fed Ar. subalbatus by rapid amplification of cDNA ends polymerase chain reaction. The 2210 bp As-pro-PO II cDNA contains a 41 bp 5'-non-coding region, a 2064 bp open reading frame and a 105 bp 3'-non-coding region. A hydrophobic signal peptide for endoplasmic reticulum targeting is not found in the N-terminal region. The deduced amino acid sequence of As-pro-PO II shares a high degree of identity (81.5%) with that of the As-pro-PO I obtained from mf-inoculated Ar. subalbatus. Both Northern blot and reverse transcription polymerase chain reaction analysis demonstrated that these two mosquito pro-POs are persistently expressed in mosquito haemocytes and not in fat body, midgut, or ovaries. The expression of As-pro-PO I and As-pro-PO II in mosquitoes is associated with melanization of mf and blood feeding, respectively.

Amino Acid Sequence↗
PubMed2006

[Construction of the female subtractive cDNA library and screening of the specific expressing genes].

OBJECTIVE: To screen the Schistosoma japonicum female specific expressing genes. METHODS: S. japonicum adult worms were collected from the rabbits' vein after six-week infection by affusing method. The adult worms were stabilized by RNA-later liquid, the male and female worms were carefully separated with nipper. The high quality total RNA was extracted and mRNA was obtained after purification. Double stranded cDNAs were synthesized after reverse transcription. Female subtractive (female as tester, male as driver) and male subtractive (male as tester, female as driver) cDNA libraries were constructed. The differentially expressed genes were further screened by dot-blot hybridization. The clones were selected and sequenced, which showed apparently higher signals when hybridizing with the female subtracting male probes, than those signals when hybridizing with the male subtracting female probes. The homology of these sequences was searched with BLAST program. The semi-quantitative PCR was applied to test the differential gene expression in female and male adult worms. RESULT: Female subtracting male and male subtracting female cDNA libraries were constructed with SSH technique. After dot-blot hybridization, 50 clones were tested to be the potential female differentially expressed genes and were sequenced. 42 expressing sequence tags (ESTs) were received. After bioinformatics analysis, 17 fragments (about 40.5%) showed high identity with the S. japonicum egg-shell protein genes, 17 sequences (about 40.5%) were highly homologous to unknown S. japonicum genes and partly homologous to female specific 800 protein. 8 fragments (about 19.0%) showed high identity with other S. japonicum unknown genes. The fragments in clones of 577, 579, 668, 695, 720, and 708 were tested by RT-PCR to be the differentially expressed genes in female adult worms using S. japonicum actin gene as the internal standard. These fragments were highly homologous to S. japonicum egg shell protein gene AY222885, AY222895, AB017097, AF519182, M32281, and S. japonicum unknown gene AY813556 respectively. CONCLUSION: SSH is essential to screen the differentially expressed genes of S. japonicum female worms. A number of female specific genes have been found by this method.

Animals↗
PubMed1997

Glycosidases are present on the surface of Drosophila melanogaster spermatozoa.

We investigated the presence of enzymes on the surface of Drosophila melanogaster spermatozoa that might bind the carbohydrate residues of the egg shell. Spectrophotometric and fluorimetric studies were used on whole spermatozoa to assay galactosyltransferase and glycosidase activities. No galactosyltransferase is present on the sperm surface, whereas two glycosidases, beta-N-acetylglucosaminidase (GlcNAc'ase) and alpha-mannosidase (Man'ase), have been evidenced. They have an optimal pH of 6-6.5 and 4, respectively. The same glycosidases were detected as soluble forms probably secreted by the seminal vesicle epithelium. We suggest that these enzymes might be involved in the recognition of alpha-mannose and beta-N-acetylglucosamine residues present on the egg shell at the site of sperm entry.

Acetylglucosaminidase↗
PubMed1990

Carbonic anhydrase and its isozymes in heat stressed white Leghorn hens.

Experiments were conducted to study the effect of heat stress on uterine tissue carbonic anhydrase levels and their isozyme patterns in relation to production of no- and thin-shelled eggs. Birds exposed to naturally occurring heat stress had lower enzyme levels in their uteri than birds kept in an air-conditioned pen. 4 isozyme bands of carbonic anhydrase were visible in uterine tissue homogenate from both groups of birds. Isozymes were suppressed in heat-stressed birds, as was evident from staining intensities of the bands. This provided evidence to the effect that heat stress not only decreased the total quantity of carbonic anhydrase in the uteri of the hens but also suppressed its isozyme fractions, leading to greater production of no-shell and thin-shelled eggs.

Animals↗
PubMed2006

Drop of egg production in chickens by experimental infection with an avian metapneumovirus strain PLE8T1 derived from swollen head syndrome and the application to evaluate vaccine.

Decreases in egg production and increased incidence of abnormal eggs due to malformation of egg shells were observed in specific pathogen free (SPF) 173-day-old laying hens inoculated intravenously with an avian metapneumovirus (aMPV) strain PLE8T1. This strain was derived from an isolate from broiler birds exhibiting swollen head syndrome (SHS). Some SPF birds inoculated with the virus showed, slight diarrhea without any respiratory symptoms. Thus, the PLE8T1 strain was used as a challenge virus to evaluate efficacy of aMPV vaccines. SPF chickens which received a live attenuated aMPV vaccine (NEMOVAC; Merial) at 7 or 77 days old and an inactivated aMPV vaccine (OVO-4; Merial) at 105 days old were protected against poor egg production caused by the challenge with the PLE8T1 strain. Thus, aMPV, the PLE8T1 strain passaged 22 times after isolation, from birds exhibiting SHS, could induce a drop in egg production in laying hens accompanied by malformation of egg shells. It was suggested that this challenge system could be applied to evaluate the efficacy of aMPV vaccine.

Aging↗
PubMed1990

Morphology of medullary bone during the egg formation cycle.

The medullary bone of birds is known to function as a calcium store for egg shell production, but it is not known if the stage of shell formation within the egg formation cycle is reflected by the thickness of osteoid seams on the medullary bone. Adult laying hens were killed at two points in the formation cycle to determine the effects of shell formation on medullary bone using histological techniques. No differences in medullary bone volume or osteoid thickness were apparent at either of the two points. Fluorochrome bone labelling techniques demonstrated, however, that less medullary bone mineralisation occurred during the active period of shell formation.

Animals↗
PubMed1986

Campylobacter jejuni in broilers: the role of vertical transmission.

The role of broiler eggs in the transmission of Campylobacter jejuni to broiler grow-out flocks was investigated. Six breeder flocks supplying broiler eggs to hatcheries were examined for cloacal carriage of C. jejuni. Of 240 birds tested, 178 (74%) were C. jejuni-positive. Eggs from these birds examined for C. jejuni penetration of the egg shell indicated that 185 of 187 were campylobacter-free. Eggs from breeder flocks of unknown C. jejuni status were also examined for C. jejuni shell penetration. C. jejuni was not isolated from 142 eggs examined. A further 193 hatchery eggs incubated and hatched in the laboratory were campylobacter-free. Six farms containing the progeny of C. jejuni-positive breeder flocks were monitored. Eight hundred and forty birds from 14 flocks in these grow-out farms were campylobacter-free during their 6-week grow-out period. Experimental egg-penetration studies indicated that C. jejuni transmission via the egg is not easily effected. Of 257 eggs surface-challenged with C. jejuni, 162 hatched; all were campylobacter-free. Of 167 eggs injected with C. jejuni, 12 hatched; 2 of these were colonized with C. jejuni. Our data do not support a role for vertical transmission of C. jejuni in commercial broiler production.

Animals↗
PubMed2000

[Ultrastructural organization of hypodermis and formation of cuticle in pharate larva of Leptotrombidium orientale (Acariformes: Trombiculidae)].

The ultrastructural organization of hypodermis and the process of cuticle deposition is described for the pharate larvae of a trombiculid mite, Leptotrombidium orientale, being under the egg-shell and prelarval covering. The thin single-layered hypodermis consists of flattened epithelial cells containing oval or stretched nuclei and smooth basal plasma membrane. The apical membrane forms short scarce microvilli participating in the cuticle deposition. First of all, upper layers of the epicuticle, such as cuticulin lamella, wax and cement layers, are formed above the microvilli with plasma membrane plaques. Cuticulin layer is seen smooth at the early steps of this process. Very soon, however, epicuticle starts to be curved and forms particular high and tightly packed ridges, whereas the surface of hypodermal cells remains flat. Then a thick layer of the protein epicuticle is deposited due to secretory activity of hypodermal cells. Nearly simultaneously the thick lamellar procuticle starts to form through the deposition of their microfibrils at the tips of microvilli of the apical plasma membrane. Procuticle, as such, remains flat, is situated beneath the epicuticular ridges and contains curved pore canals. Cup-like pores in the epicuticle provide augmentation of the protein epicuticle mass due to secretion of particular substances by cells and to their transportation through the pore canals towards these epicuticular pores. The very beginning of the larval cuticle formation apparently indicates the starting point of the larval stage in ontogenesis, even though it remains for some time enveloped by the prelarval covering or sometimes by the egg-shell. When all the processes of formation are over, hungry larvae with a fully formed cuticle are actively hatched from two splitted halves of prelarval covering.

Acari↗
PubMed1987

The innermost chorionic layer of Drosophila. I. The role of chorin octamers in the formation of a family of interdigitating crystalline plates.

The innermost chorionic layer (ICL) within egg shells of Drosophila melanogaster is composed of thin, abutting three-dimensional crystalline plates which form a closed, membrane-like sheath. Collectively, the crystals within the sheath appear to form a family of related three-dimensional crystals in space group C222; however, specimens prepared for electron microscopy are actually two-dimensional crystals in c222. The projected structures of the negatively stained crystals have been studied by minimal dose electron microscopy employing image reconstruction methods. Thin sections indicate that unit cells within the ICL are composed of paired layers; top and bottom layers are related by centrally located 2-fold axes, aligned parallel to the surface of the ICL. The most probable structural unit of the crystals is a tetramer of chorin dimers with a point group symmetry of 222, which is denoted a chorin octamer. Projection maps were computed from average transforms of two-dimensional crystals for delta (the primitive unit cell angle) equal to 84 degrees, 90 degrees and 97 degrees (+/- 1.5 degrees). The maps indicate that the molecular transitions responsible for the observed family of crystals involve concerted intramolecular rearrangements about molecular 2-fold axes. The significance in vivo of the family of crystals within the ICL is not known; however, structural considerations suggest that the observed polymorphism may reflect one facet of an intrinsic bonding flexibility of the ICL octamer that may play a role in the formation of interplate junctions and the assembly of a continuous closed sheath. The ICL may therefore serve as a structural bridge between the vitelline membrane-wax layer and the endochondrial floor, allowing the larva to shed the inner egg shell layers during hatching.

Animals↗
PubMed1998

Salmonellosis in Trinidad: evidence for transovarian transmission of Salmonella in farm eggs.

The aim of this study was to determine whether the contents of farm eggs in Trinidad are contaminated with Salmonella and if transovarian transmission occurs. 750 fresh eggs from 10 farms supplying 75% of the country's eggs were cultured for Salmonella. Salmonella was found on the egg shells' surfaces from all farms, and in the egg contents from three farms. Isolates were obtained from the cultures of the contents and shells of nine (1.2%) and 35 (4.66%) eggs, respectively (p < 0.005). Serotypes found in the contents were S. enteritidis (0.8%; deduced to be contaminated by transovarian transmission) and S. typhimurium (0.4%); those isolated from the shells (contaminated by faecal transmission) were S. typhimurium (3.06%), S. enteritidis (0.67%), S. ohio (0.27%), S. cerro (0.27%), S. infantis (0.27%) and S. heidelberg (0.13%). This study provides the first evidence for Salmonella and, more importantly, S. enteritidis, in eggs in Trinidad. This is of major public health significance because S. enteritidis infected eggs appear normal and the organism is difficult to detect and control. The consumption of these eggs may increase the risk of Salmonella infection. Food safety practices, particularly the thorough cooking (> or = 70 degrees C) of all egg dishes and the refrigeration (< 10 degrees C) of shell eggs and egg dishes, are recommended.

Animals↗
PubMed1990

The egg bundles of the monogenean Dionchus remorae and their attachment to the gills of the remora, Echeneis naucrates.

Gills of three remoras, Echeneis naucrates L., from Heron Island, Queensland, Australia had few adults but many attached egg bundles of the monogenean, Dionchus remorae. Studies of fresh, and preserved and cleared, primary gill lamellae bearing egg bundles and investigations with scanning electron microscopy and serial wax sections reveal proliferated host epithelium surrounding and embedding part of a loop of egg-shell material to which eggs are tethered, but eggs in each bundle hang free of gill tissue. This hyperplasia appears to anchor egg bundles to the host's gills. However, hyperplasia will take time to develop and cannot play a part in tethering newly laid egg bundles. Possible advantages to the parasite by attaching eggs to the gills of its host include improved oxygenation of the eggs, and a reduced risk of egg predation. Egg attachment by D. remorae to their remora hosts seems well adapted to successful larval invasion of fish which exhibit phoresy.

Animals↗
PubMed1986

Toxicity of petroleum crude oils and their effect on xenobiotic metabolizing enzyme activities in the chicken embryo in ovo.

Microliter quantities of a Prudhoe Bay crude oil (PBCO) applied to the shell of fertile chick eggs during various stages of development induced cytochrome P-450 levels and mixed-function oxidase activities within the liver of the embryo. PBCO (5 microliter) applied on Day 11 of incubation was found to maximally induce within 24 hr embryo hepatic cytochrome P-450 levels (fourfold), naphthalene hydroxylase (sixfold), benzo[a]pyrene 3-hydroxylase (14-fold), and 7-ethoxyresorufin O-deethylase (24-fold). Glutathione S-transferase was not induced. Crude oils are known to be highly toxic to avian embryos, especially during the early stages of development. The LD50 of PBCO and Hibernia crude oil applied to the egg shell on Day 8 of incubation was found to be 1.3 and 2.2 microliter, respectively. Mixed-function oxidase-dependent metabolism of crude oil components may be required for toxicity since administration of 20 micrograms of disulfiram in dioxane 1 hr prior to application of 1.3 microliter of PBCO reduced embryo mortality from 60 to 20%.

Animals↗
PubMed2001

The schistosome egg: development and secretions.

We have investigated the development of the schistosome egg and its secretions in order to understand how it migrates through gut tissues and also initiates pathology in the liver. We show by electron microscopy that the subshell envelope is absent in the newly deposited egg, but appears very early and differentiates as development progresses. In the mature egg, this nucleated envelope contains extensive endoplasmic reticulum, suggestive of a protein synthetic capacity. Furthermore, Reynolds' layer only appears between the envelope and the egg-shell in the mature egg and may represent its accumulated secretions. We have biosynthetically labelled and collected the secretions (ESP) released by mature but not immature eggs during culture. Their fractionation by SDS-PAGE reveals a simple pattern of 6 bands, differing markedly in composition from soluble egg antigen preparations. Electrophoresis in casein substrate gels demonstrates the presence of 2 distinct proteases in the egg secretions. By immunocytochemistry, ESP localized predominantly to the envelope of the mature egg, suggesting that this layer rather than the miracidium is the source of egg secretions.

Animals↗
PubMed1997

In vivo gene transfer into the blastoderm of early developmental stage of chicken.

An attempt was made to improve gene transfer into chick embryos in order to produce transgenic chickens. The beta-actin-lacZ/MiwZ, a marker gene in transfection reagent, was injected into the blastodisc of either unincubated fertilized eggs (stage X) or eggs induced from the shell gland by treating the hens intravenously with oxytocin or arginine vasotocin (stages IV-VI). All the manipulated embryos were incubated to reach stage XIV, the period at which primordial germ cells (PGCs) migrate from the germinal crescent to the gonadal anlage via the blood stream. MiwZ was detected in the embryos, extraembryonic tissues and blood by the histochemical staining method of beta-galactosidase. The MiwZ DNA was detected in 57% (127/221) of the survival embryos and in 9% (12/127) of the embryonic tissues. The expression was observed mosaically in the epidermis, heart and neural tube. The PGCs in the blood collected from the vitelline artery or dorsal aorta also showed a positive histochemical staining. However, the expression of MiwZ using the soft shelled eggs was more intense in the extraembryonic tissues, although it did not emerge in the embryos. Thus, it is possible to introduce an exogenous gene into the embryonic tissues using incubated fertilized eggs without sacrificing the hens. This technique for successive genetic operations should facilitate the production of transgenic chickens.

Actins↗
PubMed1998

Arginine vasotocin receptor in the vagina of the oviduct of the hen.

The presence of receptor for arginine vasotocin (AVT) in the vagina of the oviduct of the hen was demonstrated by the use of radioligand binding assays on membrane fractions of the tissue. The binding to [125I]AVT was highly competitive with unlabeled AVT. Scatchard analysis revealed that the binding sites are of a single class. The equilibrium dissociation constant (Kd) was 0.48+/-0.05 nM (x+/-SEM; n = 6) in laying hens holding a hard-shelled egg in the uterus (shell gland) and 1.01+/-0.02 nM (n = 6) in nonlaying hens. The maximum binding capacity (Bmax) was 0.41+/-0.04 pmol/mg protein (n = 6) in laying hens and 0.81+/-0.01 pmol/mg protein (n = 6) in nonlaying hens. The Kd value of the laying hens varied from 0.39 to 1.20 nM during an oviposition cycle, showing an increase just prior to oviposition, and the Bmax value also varied from 0.30 to 0.66 pmol/mg protein, showing a gradual increase after 6 h prior to oviposition. In the nonlaying hen, both values were almost constant during a 24-h day. The changes in the binding affinity and capacity of AVT receptor of the vagina may be related to oviposition in the hen.

Animals↗
PubMed2006

Comparison of forecasting methodologies using egg price as a test case.

Egg price forecasting of shelled eggs is a complex problem. Traditionally, future egg price has been predicted using a combination of regression analysis and experienced-based intuition to build a model, which is then fine-tuned to prevalent market conditions. Even after collecting reliable and expensive data, the subsequent analysis, in many cases, does not produce a high confidence to explain the variations in egg price. In the current project, a different approach using neural networks was used to forecast egg price. A neural network is a mathematical model of an information-processing structure that is loosely based on our present understanding of the working of human brain. An artificial neural network consists of a large number of simple processing elements connected to each other in a network. Urner Barry egg quotes from 1991 to 2002 as well as number of hens, egg storage capacity, and number of eggs placed for hatching from the USDA databases (1993 to 2000) were used to forecast egg price. Regression analysis explained only 37% of the variation in egg price due to the above-mentioned 3 factors. Neural networks, on the other hand, recognize the pattern in previous years' egg prices and then predict the future price more efficiently. The 3 networks used in this research (Ward, back-propagation, and general regression neural networks) fit the forecast line more tightly to the previous year's egg price line than did regression analysis. In the case of general regression neural networks, the R2 value was as high as 60%. Results suggest that neural networks may be a more reliable method of egg price forecasting than simple regression analysis if reliable data are collected and manipulated for such models.

Agriculture↗