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PubMed1988

Gas exchange and development of chicken embryos with widely altered shell conductance from the beginning of incubation.

The O2 uptake of chicken embryos confined in the eggshell (MO2) is governed by a shell diffusive conductance (GO2) and PO2 difference between ambience and air space, suggesting that a relation between GO2 and air space PO2 (PAO2) is hyperbolic at constant MO2. Upon wide alteration of GO2 from the beginning of incubation, the MO2 was measured on day 16 of incubation and the relation between GO2 and PAO2 examined. The MO2 increased hyperbolically with increasing GO2, reached maximum at control conductances and decreased with further increase in GO2. From these changes in MO2 with GO2, an equation was derived predicting PAO2 as a quadratic function of inverse gO2 (mass-specific conductance, i.e., GO2 standardized by fresh egg mass), and the relation between air space PO2 and shell conductance was no longer hyperbolic. The arterialized blood PO2 (PaO2) of the allantoic vein measured individually was also expressed by a quadratic equation of inverse gO2. While for widely altered conductance the MO2 was little related to PaO2, the mass (embryo)-specific O2 uptake increased with PaO2. The excess water loss associated with increased conductance was involved in changes in these variables.

Animals↗
PubMedDate not supplied

Metabolic responses of chicken embryos and hatchlings to altered O2 environments.

The oxygen consumption (MO2) response over a 4 h period of exposure to altered ambient O2 (air, 10, 15, 40, 60, 80 and 100%), helium (He) and sulfur hexafluoride (SF6) environments was determined for young (12 days old) and late (16 and 18 days old) embryos, externally pipped (EP) eggs and just hatched chicks (hatchlings) of the domestic fowl. The young embryos were insensitive to hyperoxic gas mixtures and to He exposure, while the late embryos increase their MO2 in hyperoxic environments, independently of O2 concentration, and also in a He atmosphere. Both the young and late embryos responded to SF6 exposure with decreasing MO2, as SF6 reduces O2 diffusivity through the eggshell. The MO2 of EP eggs and hatchlings in He and SF6 varied very widely, the effects of altered diffusivity being insignificant. In hypoxic environments in which the MO2 decreased, the fall of MO2 became smaller as embryos developed and particularly after they pipped the shell and hatched. In an atmosphere of 10% O2, the MO2 of all embryos in the egg before hatching decreased to below 10% of the control after 4 h, while in hatchlings the MO2 remained above 80% of the control. As all embryos in situ in the egg depend entirely or partly on diffusion in order to obtain O2, this emphasizes the limitation of the diffusive process. A 4 h exposure to 10% O2 was lethal for embryos in the egg even if they had pipped the shell and were breathing air with the lungs.

Animals↗
PubMed1980

Density regulation of domestic populations of Triatoma infestans in Brazil.

Twenty old houses in a rural area of central Brazil were sampled monthly for Triatoma infestans during 16 months. The samples indicated peak adult emergence between January and May, preceded by peak emergence of stage V, IV and III nymphs respectively. Stage I and II nymphs were rarely taken in the samples. A much smaller peak of adult emergence occurred in September; thus the two peaks of adult emergence during the year were consistent with the approximately six months duration of egg-to-adult development usually recorded in laboratory studies. During January, 1977, when the study began, all houses were searched for dead bugs, exuviae, eggs and eggshells. These samples were used to calculate stage mortalities, from which a simple life-table was constructed. These data were combined with laboratory data concerning stage development times and female longevity and fecundity. Sensitivity analysis of the life-table showed it to be most sensitive to small changes in daily mortality rate and total egg-to-adult development time. The data were used to advance an hypothesis that the size of domestic populations of T. infestans is mainly controlled by changes in the egg-to-adult development time and, to a lesser extent, by changes in female reproductivity. Both these factors are in turn controlled by the nutritional status of the bug population, which, if the supply of food, i.e. number of hosts, is constant, is dependent upon the density of the bug population. It is argued that this mechanism of density regulation functions within limits set by the prevailing ambient temperature.

Animals↗
PubMed1991

Control of follicular epithelium development and vitelline envelope formation in the mosquito; role of juvenile hormone and 20-hydroxyecdysone.

Using microsurgical manipulations, hormone applications, and transmission electron microscopy we have investigated the regulation of differentiation of the follicular epithelium and formation of the vitelline envelope (VE) in primary follicles in the ovary of the mosquito, Aedes aegypti. During the first 3 days after eclosion, the primary follicle grows, and cells of the follicular epithelium differentiate, their content of mitochondria, rough endoplasmic reticulum, and Golgi complexes increases significantly. Growth and differentiation of the follicular epithelium appear to be under the control of juvenile hormone (JH), because they are blocked by removal of corpora allata in newly closed adult females and can be restored by either implantation of corpora allata or application of JH III. In insects, including mosquitoes, VE is the first layer of the eggshell to be deposited. It is formed from the secretory products of the follicle cells and its deposition coincides with yolk accumulation by developing oocytes. Only follicle cells adjacent to the oocyte deposit VE. In decapitated females, given a blood meal by enema and injected with picogram doses of 20-hydroxyecdysone (20-HE), follicle cells synthesize the VE precursors and deposit morphologically normal VE, in contrast to saline injected controls which deposit no VE. We conclude that 20-HE, as well as factors originating from the blood meal and the oocyte, are required for the normal formation of VE in the mosquito follicles.

Aedes↗
PubMed1996

Concentration and bioaccumulation of organochlorine pesticide residues in herons and their prey in wetlands of Thermaikos Gulf, Macedonia, Greece.

Concentrations of the principal organochlorine insecticides were determined in eggs and freshly dead chicks of the Squacco heron (Ardeola ralloides), Little Egret (Egretta garzetta) and Night Heron (Nycticorax nycticorax), as well as in frogs (Rana sp.), the main heron prey. Material was collected from the wetlands of the Thermaikos Gulf (Macedonia, northern Greece) in 1992 and 1993. Residues of the organochlorine pesticides alpha-BHC, beta-BHC, lindane, 4,4'-DDD, 4,4'-DDE, heptachlor and dieldrin were found in the eggs, chicks and prey of the herons. alpha-BHC, beta-BHC, and lindane had highest concentration in the Night Heron and lowest in the Little Egret. In all samples examined, the bioconcentration factors (BCF) of these compounds had very high values. BCF of pollutants for the eggs of the Squacco Heron were at lower levels than those of its chicks. BCF for frogs were in almost all cases lower than those for the other samples. Biomagnification factor (BMF) for 4,4'-DDE and beta-BHC had the highest values of all other compounds (except in the Night Heron). BMF for the eggs of the Squacco Heron were greater than for its chicks. Variation in the pesticide contents in the different heron species is attributed to different feeding habits; the exception being the occurrence of dieldrin in eggs only and 4,4'-DDE as a remnant of past spraying. Amounts of pesticides detected in this study are too low to affect eggshell thickness in the Squacco Heron or have other effects on the wildlife of the area.

Animals↗
PubMed1989

The maternal ventralizing locus torpedo is allelic to faint little ball, an embryonic lethal, and encodes the Drosophila EGF receptor homolog.

The torpedo gene of Drosophila melanogaster is involved in the establishment of the dorsoventral pattern of eggshell and embryo. We have isolated new alleles of torpedo and have found that torpedo is allelic to the zygotic embryonic lethal faint little ball. We have shown that torpedo resides in subdivision 57F on the second chromosome--at the same location as the Drosophila homolog of the EGF receptor (DER). Using a cosmid that contains most of the DER coding region as a hybridization probe, we have shown that a cytologically small deficiency that eliminates torpedo activity also removes the DER gene, and that an inversion that was isolated as a strong torpedo allele breaks the coding region of the DER gene. We conclude that torpedo is the DER gene.

Alleles↗
PubMed1993

Spatially localized rhomboid is required for establishment of the dorsal-ventral axis in Drosophila oogenesis.

The establishment of dorsal-ventral asymmetry of the Drosophila embryo requires a group of genes that act maternally. None of the previously identified dorsal-ventral axis genes are known to produce asymmetrically localized gene products during oogenesis. We show that rhomboid (rho), a novel member of this group, encodes a protein that is localized on the apical surface of the dorsal-anterior follicle cells surrounding the oocyte. Loss of rho function causes ventralization of the eggshell and the embryo, whereas ectopic expression leads to dorsalization of both structures. Thus, spatially restricted rho is necessary and sufficient for dorsal-ventral axis formation. We propose, based on these observations and double mutant experiments, that the spatially restricted rho protein leads to selective activation of the epidermal growth factor receptor in the dorsal follicle cells and subsequently the specification of the dorsal follicle cells.

Animals↗
PubMedDate not supplied

Immunoglobulin in the eggs of the channel catfish (Ictalurus punctatus).

Egg yolk proteins obtained from 2-3-day-old fertilized channel catfish eggs were analyzed to determine if immunoglobulin (Ig) was present. Using both monoclonal and polyclonal antibodies to catfish Ig, egg Ig was isolated and structurally characterized. The egg Ig when analyzed in SDS-gels under nonreducing conditions dissociated into eight distinct subpopulations with relative mobilities identical to that previously described for the serum Ig of the channel catfish. In addition, the component heavy (H) and light (L) chains of the egg Ig had similar relative mobilities as the H and L chains identified in serum Ig. Immunocytological studies using both polyclonal and monoclonal anti-catfish Ig showed that Ig was dispersed throughout the yolk of the egg. In addition these analyses indicated that Ig was localized within the external membranes (eggshell) of the egg.

Animals↗
PubMed1994

An analysis of avian reproduction studies submitted for pesticide registration.

Avian reproduction studies are currently part of the regulatory ecotoxicology requirements for pesticides in many countries. In the study, 134 avian reproduction studies were reviewed to determine their ability to identify pesticides that have the potential to affect reproduction in wild birds. A clustering procedure was first used to assign measured variables to parental, developmental, or eggshell effects. This assignation was found to be identical in the two bird species tested. Nineteen of 69 pesticides tested were found to cause developmental effects at levels lower than those giving rise to detectable parental toxicity. At least some of these should not have been registered without some assurance that developmental effects would not occur in the wild. The analysis also found very little similarity in the effects of pesticides on the two bird species commonly used in avian reproduction tests. This casts serious doubts on the ability to extend the results of avian reproduction studies to any potentially affected bird species. Modifications to the avian reproduction test, based on results of the analysis conducted, are suggested. It is recommended that the avian reproduction study be recognized as a rough screening tool only and that efforts not be made to make it more realistic, e.g., such as through a reduced exposure period.

Animals↗
PubMed1982

Laryngeal foreign bodies in children.

Laryngeal foreign bodies (F.B.) in children are relative rare, especially in infants under one year of age, and the diagnosis and removal are difficult. The history, the clinical and radiologic findings can be misleading. Seventeen patients with laryngeal F.B. (10 of them under one year of age) are presented, and the diagnostic problems and treatment are discussed. Foreign bodies were either objects of a sharp and thin quality, e.g. an eggshell fragment, or large, e.g. a piece of meat, causing apnea and death.

Bronchoscopy↗
PubMed1987

Cloning of a Schistosoma japonicum gene encoding a major immunogen recognized by hyperinfected rabbits.

A library of randomly sheared Schistosoma japonicum genomic DNA fragments was constructed in the bacteriophage expression vector lambda gt11. A portion of the library was screened with sera collected from rabbits 8 weeks after they were infected with 1000 cercariae. Four clones whose recombinant gene products react with the rabbit sera were purified to homogeneity. Clone SjIR-12A was chosen for detailed study because of its very intense reaction with the rabbit sera. SjIR-12A was found to encode part of a 70 kDa protein (Sj70) that is present in both soluble egg antigen (SEA) and soluble worm antigen preparations (SWAP). Western blot analysis suggests that Sj70 is the only SWAP component that is strongly immunoreactive with the rabbit sera. Rabbit antibodies that react with the SjIR-12A fusion protein were immunoaffinity purified and used to localize immunoreactive product to the nervous tissue of male and female adult worms, the dorsal and lateral tegument of male adult worms, and in eggs to the miracidial tegument and the area between the eggshell and miracidium. Southern hybridization analysis suggests there are approximately four copies of the Sj70 gene per haploid genome.

Animals↗
PubMed1994

The role of dityrosine formation in the crosslinking of CUT-2, the product of a second cuticlin gene of Caenorhabditis elegans.

A second cuticlin gene, cut-2, of the nematode Caenorhabditis elegans, has been isolated and its genomic and cDNA sequences determined. The gene codes for a component of cuticlin, the insoluble residue of nematode cuticles. Conceptual translation of cut-2 reveals a 231-amino acid secreted protein which, like CUT-1, begins with a putative signal peptide of 16 residues. The central part of the protein consists of 13 repetitions of a short hydrophobic motif, which is often degenerated with substitutions and deletions. Parts of this motif are present also in CUT-1 (Caenorhabditis elegans) as well as in several protein components of the larval cuticle and of the eggshell layers of various insects (Locusta migratoria, Ceratitis capitata and Drosophila species). These sequence similarities are related to the similar functions of these proteins: they are all components of extracellular insoluble protective layers. Immunolocalisation and transcription analysis suggest that CUT-2 contributes to the cuticles of all larval stages and that it is not stage-specific. Analysis by reverse transcriptase-PCR suggests that it is not stage-specific. Analysis by reverse transcriptase-PCR suggests that transcription is not continuous throughout larval development but occurs in peaks which precede the moults. Dityrosine has been detected in the cuticle of nematodes and of insects; formation of dityrosine bridges may be one of the cross-linking mechanisms contributing to the insolubility of cuticlins. Recombinant, soluble CUT-2 is shown to be an excellent substrate for an in vitro cross-linking reaction, catalysed by horseradish peroxidase in the presence of H2O2, which results in the formation of insoluble, high-molecular weight CUT-2 and of dityrosine.

Amino Acid Sequence↗
PubMed1989

Dormancy and hatching of nematode eggs.

The sequence of events during the hatching process of some parasitic nematodes has been the subject of recent detailed study. Certain factors, such as the trehalose content of the perivitelline fluid and the permeability characteristics of the eggshell, are influential in hatching and are also important for the survival of dormant, unhatched juveniles. In this review, Roland Perry examines some attributes of the egg that are involved in dormancy and survival of nematodes and details the changes that occur during the hatching process.

Journal Article↗
PubMed1987

Trends of organochlorine residues in eggs of birds from Italy, 1977 to 1985.

All the eggs, collected in Italy in 1982 and 1983, of two species of passerine birds, three gulls, four terns and the night heron, contained DDE and, with lower frequencies, other organochlorine contaminants. Organochlorines were more concentrated in the species of higher trophic level. DDE contamination showed a decreasing trend from 1978 to 1985 in one passerine, two terns and in the heron. After 1980-1982, the level of contamination was below the critical threshold beyond which reproduction is affected, eggshell thickness was only slightly or not reduced; therefore, the current impact of organochlorines on these birds is probably negligible. Detrimental effects may have occurred during the 1970s, when some of the eggs were contaminated beyond the critical threshold.

Journal Article↗
PubMed1987

Influence of a diet of fluoride-fed cockerels on reproductive performance of captive American kestrels.

In 1982, twenty-four pairs of captive American kestrels (Falco sparverius) were forced to renest by removal of their first clutches 6 days after their completion. Immediately following, each of three groups of eight pairs was randomly assigned to one of three daily dietary regimes for 10 days: (1) three 1-day old cockerels with background levels of F(-) (62.4+/-51ppm, mean+/-SD) in their femurae, (2) two 10-day old cockerels with 4512+/-810ppm of F(-) in their femurae, (3) two 10-day old cockerels with 7690+/-417ppm of F(-) in their femurae. Fluoride levels in femurae of treated kestrels were significantly (P<0.0025) higher than those of control birds. Clutch sizes tended to be smaller as more fluoride was added to the diet, but not significantly so, due to an increase of the variance in the treatment group. Per cent fertility and per cent hatchability were not significantly affected by treatment. The fluoride content in eggshells in the fluoride-treated groups differed significantly from those of the control group (P<0.001).

Journal Article↗
PubMed1989

Environmental contaminants and reproductive success of great blue herons Ardea herodias in British Columbia, 1986-1987.

In 1986, eggs were collected and productivity estimated at four great blue heron (Ardea herodias) colonies on the coast of British Columbia. Polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were present in all eggs in a qualitatively similar pattern among colonies. PCDD levels were significantly elevated at a colony near a kraft pulp mill at Crofton on Vancouver Island, although there was no correlation between the number of young raised in a nest and levels of either PCDDs, PCDFs, PCBs, organochlorine pesticides or mercury. In 1987, heron productivity was normal at three colonies, while the colony at Crofton failed to raise any young. A normal complement of eggs were apparently laid in about 57 nests, but during incubation they were destroyed and the broken eggshells were found in and beneath the nests. Analysis of eggs salvaged from nests showed that 2378-TCDD levels were about three times higher in 1987 than in 1986. At a colony in Vancouver, 2378-TCDF levels were significantly higher in 1987 than 1986 eggs. Levels of organochlorine pesticides and total mercury in eggs were generally low; highest residue levels were found in two mainland colonies, particularly at one adjacent to an agricultural area. Total PCB levels were low and did not differ significantly among locations. Analysis of PCB congener ratios indicated different sources of PCBs. Regurgitated prey samples collected in 1986 from four locations had generally low levels of PCDD, PCDF, mercury, lead and cadmium contamination.

Journal Article↗
PubMed1989

Organochlorine contaminants in eggs of Common Terns from the Canadian Great Lakes, 1981.

To determine if contaminant levels in Common Terns had changed over the last decade, we collected and analyzed eggs from four nesting colonies on the three lower Great Lakes during 1981. DDE and PCBs were detected in every egg from the four colonies. Dieldrin, mirex and trans-nonachlor were detected in more than 45% of the eggs. Seven other organochlorine contaminants (DDD, DDT, hexachlorobenzene, oxychlordane, cis-chlordane, cis-nonachlor and toxaphene) were detected in less than 25% of the eggs. Eggs from the Lake Ontario colony were generally the most heavily contaminated. Comparisons of DDE and PCB data with earlier studies of Common Terns indicated that contaminant levels in eggs from the four sampled colonies, or nearby sites, have decreased by up to 80-90% from 1969-1973 to 1981. Interspecies comparisons showed that Common Tern eggs have lower organochlorine residue levels than eggs of Caspian Terns or Herring Gulls. Dietary variation and migratory status are possible explanations for the differences in residue levels among species. Eggshell thickness, log-PCBs, and log-DDE were not significantly intercorrelated. Elevated contaminant levels in the early 1970s might be at least partly responsible for the decline of the Great Lakes Common Tern population over the past decade. Stabilization of population numbers during the early 1980s suggests that organochlorine pollution levels have been reduced to a point where they are no longer an important factor in the population dynamics of this species on the Great Lakes.

Journal Article↗
PubMed1991

Effects of acidification on the availability of toxic metals and calcium to wild birds and mammals.

The effects of acidification on wildlife inhabiting aquatic or semi-aquatic environments are reviewed, with particular reference to the possibility for increased dietary exposure to Hg, Cd, Pb and/or Al, and decreased availability of essential dietary minerals such as Ca. It is concluded that: (1) piscivores risk increased exposure to dietary methyl-Hg in acidified habitats, and Hg concentrations in prey may reach levels known to cause reproductive impairment in birds and mammals; (2) piscivores do not risk increased exposure to dietary Cd, Pb or Al because these metals are either not increased in fish due to acidification, or increase are trivial from a toxicological perspective; (3) insectivores and omnivores may, under certain conditions, experience increased exposure to toxic metals in some acidified environments. Exposure levels are likely to be sufficiently low, however, that significant risks to health or reproduction are unlikely. More importantly, these wildlife species may experience a drastic decrease in the availability of dietary Ca due to the pH-related extinction of high-Ca aquatic invertebrate taxa (molluscs, crustaceans). Decreased availability of dietary Ca is known to adversely affect egg laying and eggshell integrity in birds, and the growth of hatchling birds and neonatal mammals. Acidification-related changes in the dietary availability of other essential elements, such as Mg, Se and P, have not been established and require further investigation; (4) herbivores may risk increased exposure to Al and Pb, and perhaps Cd, in acidified environments because certain macrophytes can accumulate high concentrations of these metals under acidic conditions. The relative importance of pH in determining the metal concentrations of major browse species, and the toxicological consequences for herbivores wildlife, is not well established and requires further study. A decreased availability of dietary Ca is also likely for herbivores inhabiting acidified environments.

Journal Article↗