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PubMed2025

Genome-Wide Mining of lncRNAs Reveals Their Potential Regulatory Role in the Evolution of Viviparity.

Reproduction in vertebrates usually involves egg-laying (oviparity) or live-bearing (viviparity). Oviparity is the ancestral trait from which viviparity has independently evolved more than 100 times in squamate reptiles. This transition involves a series of physiological and structural changes, including the degeneration of eggshell and the evolution of a placenta and differences in the temporal and spatial expression patterns of some functional genes that drive the structural transformation. Long non-coding RNAs (lncRNAs) play important roles in the regulation of gene expression, yet it remains unclear whether they participate in gene expression shifts during the transition from oviparity to viviparity, and if so how. Therefore, we employ deep mining to identify novel lncRNAs of a closely related oviparous-viviparous pair of lizards (Phrynocephalus przewalskii and P. vlangalii). We construct cis- and trans-regulatory networks between lncRNAs and target genes using the transcriptomic data of oviduct or uteri tissues across reproductive periods. Results show that lncRNAs that regulate eggshell gland developmental genes in the oviparous lizard are lost or less expressed in the viviparous lizard. A number of lncRNAs involved in the regulation of placental development and embryo attachment in viviparous species have no orthologs in oviparous species, and others show little or no expression. Accordingly, lncRNAs may play important regulatory roles in the physiological and structural changes in the transition from oviparity to viviparity. These results open doors to the further elucidation of genetic regulatory networks.

Animals↗
PubMed1970

p,p'-DDT: effect on calcium metabolism and concentration of estradiol in the blood.

Ringdoves given 10 parts per million p,p'-DDT showed a decrease of estradiol in the blood early in the breeding cycle and egg-laying was delayed. There was also a decrease in deposition of medullary calcium and in eggshell weight. Injection of p,p'-DDE (150 milligrams per kilogram of body weight) caused reduction of eggshell weight and inhibition of carbonic anhydrase in the oviduct.

Animals↗
PubMed1991

Laser ablation studies of the role of the Drosophila oocyte nucleus in pattern formation.

Somatic and germline cells interact during oogenesis to establish the pattern axes of the Drosophila eggshell and embryo. The role of the oocyte nucleus in pattern formation was tested with the use of laser ablation. Ablation in stage 6 to 9 egg chambers caused partial or complete ventralization of the eggshell, phenotypes similar to those of eggs produced by gurken or torpedo females. Accumulation of vasa protein at the posterior pole of treated oocytes was also disrupted. Thus the oocyte nucleus is required as late as stage 9 for dorsoventral patterning within the follicle cells and for polar plasm assembly in the oocyte.

Animals↗
PubMed2006

Inactivation of single-celled Ascaris suum eggs by low-pressure UV radiation.

Intact and decorticated single-celled Ascaris suum eggs were exposed to UV radiation from low-pressure, germicidal lamps at fluences (doses) ranging from 0 to 8,000 J/m2 for intact eggs and from 0 to 500 J/m2 for decorticated eggs. With a UV fluence of 500 J/m2, 0.44-+/-0.20-log inactivation (mean+/-95% confidence interval) (63.7%) of intact eggs was observed, while a fluence of 4,000 J/m2 resulted in 2.23-+/-0.49-log inactivation (99.4%). (The maximum quantifiable inactivation was 2.5 log units.) Thus, according to the methods used here, Ascaris eggs are the most UV-resistant water-related pathogen identified to date. For the range of fluences recommended for disinfecting drinking water and wastewater (200 to 2,000 J/m2), from 0- to 1.5-log inactivation can be expected, although at typical fluences (less than 1,000 J/m2), the inactivation may be less than 1 log. When the eggs were decorticated (the outer egg shell layers were removed with sodium hypochlorite, leaving only the lipoprotein ascaroside layer) before exposure to UV, 1.80-+/-0.32-log reduction (98.4%) was achieved with a fluence of 500 J/m2, suggesting that the outer eggshell layers protected A. suum eggs from inactivation by UV radiation. This protection may have been due to UV absorption by proteins in the outer layers of the 3- to 4-microm-thick eggshell. Stirring alone (without UV exposure) also inactivated some of the Ascaris eggs (approximately 20% after 75 min), which complicated determination of the inactivation caused by UV radiation alone.

Animals↗
PubMed1996

Regulation of schistosome egg granuloma formation: host-soluble L-selectin enters tissue-trapped eggs and binds to carbohydrate antigens on surface membranes of miracidia.

Immunogenic carbohydrate epitopes are prominent in soluble egg antigens (SEA) of Schistosoma mansoni and in vivo are released through ultramicroscopic pores in the eggshell. Previously, one immunogenic carbohydrate was identified as lacto-N-fucopentaose III (LNFPIII), which contains the biologically important trisaccharide Lewis(x) (Le(x)), a weak ligand for E-, L-, and P-selectins. Selectins are involved in various inflammatory reactions, including recruitment of granulocytes. Further, L-selectin molecules are shed from leukocyte cell surfaces upon activation. These independent observations suggest that selectins may play various roles in granuloma formation and/or regulation. We tested in situ for alterations in expression of host E-, L-, or P-selectin in murine liver tissue at various times postinfection with schistosome cercariae. We found that L-selectin was expressed on cells surrounding egg granulomas, but surprisingly we also found mouse L-selectin on the surface membranes of larval miracidia within the S. mansoni ova. In contrast, neither E- nor P-selectin was found within ova. Antibodies to human or rat L-selectin or 15 other distinct mouse leukocyte surface molecules did not bind to the miracidial surface. The anti-mouse L-selectin staining of miracidia could be inhibited by wash buffer containing sulfated carbohydrates such as sulfated Le(x), heparan sulfate, fucoidan, and carrageenan. The elution studies imply that the miracidial surface and, therefore, schistosomes express sulfated glycans. The binding of soluble L-selectin to miracidia was not restricted by the genetic background of the host, as mouse L-selectin was detected on the surface of S. mansoni miracidia in livers from BALB/C, CBA/J, C57BL/6, and outbred Swiss mice. We also detected soluble mouse L-selectin binding to Schistosoma japonicum miracidia, indicating that these observations can be generalized to all schistosome infections. On the basis of these observations we hypothesize that host-soluble L-selectin traverses through pores in the eggshell and binds to target ligands on the surface membranes of miracidia; this complex formation might ultimately impede the release of soluble antigens from the eggs. The intraovum binding of mouse L-selectin to immunogenic carbohydrate antigens is a novel role for selectins, and this model may, in part, explain the down-regulation in granulomatous pathology observed following the acute phase of the disease.

Animals↗
PubMed2004

Developmental gene amplification and origin regulation.

Developmentally regulated gene amplification serves to increase the number of templates for transcription, yielding greatly increased protein and/or RNA product for gene(s) at the amplified loci. It is observed with genes that are very actively transcribed and during narrow windows of developmental time where copious amounts of those particular gene products are required. Amplification results from repeated firing of origins at a few genomic loci, while the rest of the genome either does not replicate, or replicates to a lesser extent. As such, amplification is a striking exception to the once-and-only-once rule of DNA replication and may be informative as to that mechanism. Drosophila amplifies eggshell (chorion) genes in the follicle cells of the ovary to allow for rapid eggshell synthesis. Sciara amplifies multiple genes in larval salivary gland cells that encode proteins secreted in the saliva for the pupal case. Finally, Tetrahymena amplifies its rRNA genes several thousand-fold in the creation of the transcriptionally active macronucleus. Due to the ease of molecular and genetic analysis with these systems, the study of origin regulation has advanced rapidly. Comparisons reveal an evolutionarily conserved trans-regulatory apparatus and a similar organization of sequence-specific cis-regulatory replicator and origin elements. The studies indicate a regulatory role for chromatin structure and transcriptionally active genes near the origins.

Animals↗
PubMed1982

Embryonic oxygen consumption and growth of Laysan and black-footed albatross.

The constraints placed on diffusive gas exchange by the eggshell and the adaptive features of embryonic respiration and metabolism in large Laysan and black-footed albatross eggs (300 g) during prolonged incubation (65 days) were examined in naturally incubated eggs on Sand Island, Midway, in the Northwestern Hawaiian Islands. A low eggshell gas conductance and slow growth rate were associated with a relatively low oxygen consumption (MO2) throughout incubation. Just prior to internal pipping (IP) of the inner shell membrane and penetration of the air space, the MO2 (pre-IP MO2) was approximately 1,250 ml O2 (STPD).day-1 for both species, resulting in air cell O2 and CO2 tensions of 106 and 40 Torr, respectively. During the 4- to 5-day pipping-to-hatching interval, O2 uptake increases rapidly as pulmonary respiration is initiated. Hatchling O2 consumption averaged 3,700 ml O2 (STPD).day-1 or about three times the pre-IP MO2. Data support the hypothesis that embryonic metabolism among Procellariiformes is related to the extent to which the incubation period deviates from the expected value based on initial egg mass.

Animals↗
PubMed1989

Mobilization of calcium, phosphorus, and magnesium by embryonic alligators (Alligator mississippiensis).

The yolk of an alligator (Alligator mississippiensis) egg contains approximately 115 mg of Ca, 180 mg of P, and 17 mg of Mg at oviposition. This compartment is the primary (or sole) source of P and Mg for the forming embryo. Both of these elements are depleted rapidly from the yolk once the embryo enters the growth phase of development. The yolk also is an important source of Ca for the embryo, particularly during the first two-thirds of incubation. During the last trimester of development, however, the embryo supplements Ca from the yolk with Ca mobilized from the eggshell. Indeed, more Ca is withdrawn from the eggshell during the last 2 wk of incubation than can be used by the embryo in skeletogenesis. The excess Ca is stored in the yolk, thereby causing net transfer of Ca to shift from withdrawal from the yolk to deposition in the yolk. Consequently, the residual yolk in the hatchling alligator contains a substantial reserve of Ca to support skeletal growth during the neonatal period. The pattern of mobilization and deposition of Ca during embryogenesis in alligators is similar to that characterizing avian embryos, but is distinct from that characterizing embryos of all other oviparous reptiles.

Alligators and Crocodiles↗
PubMed2003

Mechanisms of cell positioning during C. elegans gastrulation.

Cell rearrangements are crucial during development. In this study, we use C. elegans gastrulation as a simple model to investigate the mechanisms of cell positioning. During C. elegans gastrulation, two endodermal precursor cells move from the ventral surface to the center of the embryo, leaving a gap between these ingressing cells and the eggshell. Six neighboring cells converge under the endodermal precursors, filling this gap. Using an in vitro system, we observed that these movements occurred consistently in the absence of the eggshell and the vitelline envelope. We found that movement of the neighbors towards each other is not dependent on chemotactic signaling between these cells. We further found that C. elegans gastrulation requires intact microfilaments, but not microtubules. The primary mechanism of microfilament-based motility does not appear to be through protrusive structures, such as lamellipodia or filopodia. Instead, our results suggest an alternative mechanism. We found that myosin activity is required for gastrulation, that the apical sides of the ingressing cells contract, and that the ingressing cells determine the direction of movement of their neighboring cells. Based on these results, we propose that ingression is driven by an actomyosin-based contraction of the apical side of the ingressing cells, which pulls neighboring cells underneath. We conclude that apical constriction can function to position blastomeres in early embryos, even before anchoring junctions form between cells.

Actin Cytoskeleton↗
PubMed2003

bullwinkle and shark regulate dorsal-appendage morphogenesis in Drosophila oogenesis.

bullwinkle (bwk) regulates embryonic anteroposterior patterning and, through a novel germline-to-soma signal, morphogenesis of the eggshell dorsal appendages. We screened for dominant modifiers of the bullwinkle mooseantler eggshell phenotype and identified shark, which encodes an SH2-domain, ankyrin-repeat tyrosine kinase. At the onset of dorsal-appendage formation, shark is expressed in a punctate pattern in the squamous stretch cells overlying the nurse cells. Confocal microscopy with cell-type-specific markers demonstrates that the stretch cells act as a substrate for the migrating dorsal-appendage-forming cells and extend cellular projections towards them. Mosaic analyses reveal that shark is required in follicle cells for cell migration and chorion deposition. Proper shark RNA expression in the stretch cells requires bwk activity, while restoration of shark expression in the stretch cells suppresses the bwk dorsal-appendage phenotype. These results suggest that shark plays an important downstream role in the bwk-signaling pathway. Candidate testing implicates Src42A in a similar role, suggesting conservation with a vertebrate signaling pathway involving non-receptor tyrosine kinases.

Animals↗
PubMed2002

Mosaic analyses reveal the function of Drosophila Ras in embryonic dorsoventral patterning and dorsal follicle cell morphogenesis.

In Drosophila melanogaster, the Ras signal transduction pathway is the primary effector of receptor tyrosine kinases, which govern diverse developmental programs. During oogenesis, epidermal growth factor receptor signaling through the Ras pathway patterns the somatic follicular epithelium, establishing the dorsoventral asymmetry of eggshell and embryo. Analysis of follicle cell clones homozygous for a null allele of Ras demonstrates that Ras is required cell-autonomously to repress pipe transcription, the critical first step in embryonic dorsoventral patterning. The effects of aberrant pipe expression in Ras mosaic egg chambers can be ameliorated, however, by post-pipe patterning events, which salvage normal dorsoventral polarity in most embryos derived from egg chambers with dorsal Ras clones. The patterned follicular epithelium also determines the final shape of the eggshell, including the dorsal respiratory appendages, which are formed by the migration of two dorsolateral follicle cell populations. Confocal analyses of mosaic egg chambers demonstrate that Ras is required both cell- and non cell-autonomously for morphogenetic behaviors characteristic of dorsal follicle cell migration, and reveal a novel, Ras-dependent pattern of basal E-cadherin localization in dorsal midline follicle cells.

Animals↗
PubMed2003

Endogenous and exogenous ice-nucleating agents constrain supercooling in the hatchling painted turtle.

Hatchlings of the painted turtle (Chrysemys picta) commonly hibernate in their shallow, natal nests. Survival at temperatures below the limit of freeze tolerance (approximately -4 degrees C) apparently depends on their ability to remain supercooled, and, whereas previous studies have reported that supercooling capacity improves markedly with cold acclimation, the mechanistic basis for this change is incompletely understood. We report that the crystallization temperature (T(c)) of recently hatched (summer) turtles acclimated to 22 degrees C and reared on a substratum of vermiculite or nesting soil was approximately 5 degrees C higher than the T(c) determined for turtles acclimated to 4 degrees C and tested in winter. This increase in supercooling capacity coincided with elimination of substratum (and, in fewer cases, eggshell) that the hatchlings had ingested; however, this association was not necessarily causal because turtles reared on a paper-covered substratum did not ingest exogenous matter but nevertheless showed a similar increase in supercooling capacity. Our results for turtles reared on paper revealed that seasonal development of supercooling capacity fundamentally requires elimination of ice-nucleating agents (INA) of endogenous origin: summer turtles, but not winter turtles, produced feces (perhaps derived from residual yolk) that expressed ice-nucleating activity. Ingestion of vermiculite or eggshell, which had modest ice-nucleating activity, had no effect on the T(c), whereas ingestion of nesting soil, which contained two classes of potent INA, markedly reduced the supercooling capacity of summer turtles. This effect persisted long after the turtles had purged their guts of soil particles, because the T(c) of winter turtles reared on nesting soil (mean +/- S.E.M.=-11.6+/-1.4 degrees C) was approximately 6 degrees C higher than the T(c) of winter turtles reared on vermiculite or paper. Experiments in which winter turtles were fed INA commonly found in nesting soil showed that water-soluble, organic agents can remain fully active for at least one month. Such INA may account for the limited supercooling capacity (T(c) approximately -7.5 degrees C) we found in turtles overwintering in natural nests and may therefore pose a formidable challenge to the winter survival of hatchling C. picta.

Acclimatization↗
PubMed2004

Temperature-dependent oxygen limitation in insect eggs.

Most terrestrial insect embryos support metabolism with oxygen from the environment by diffusion across the eggshell. Because metabolism is more temperature sensitive than diffusion, embryos should be relatively oxygen-limited at high temperatures. We tested whether survival, development time and metabolism of eggs of a moth, Manduca sexta, were sensitive to experimentally imposed variation in atmospheric oxygen availability (5-50 kPa; normoxia at sea level is 21 kPa) across a range of biologically realistic temperatures. Temperature-oxygen interactions were apparent in most experiments. Hypoxia affected survival more strongly at warmer temperatures. Metabolic rates, measured as rates of CO2 emission, were virtually insensitive to hypo- and hyperoxia at 22 degrees C but were strongly influenced at 37 degrees C. Radial profiles of P(O2) inside eggs, measured using an oxygen microelectrode, demonstrated that 3-day-old eggs had broad central volumes with P(O2) less than 2 kPa, and that higher temperature led to lower P(O2). These data indicate that at realistically high temperatures (32-37 degrees C) eggs of M. sexta were oxygen limited, even in normoxia. This result has important implications for insect population ecology and the evolution of eggshell structures, and it suggests a novel hypothesis about insect gigantism during Paleozoic hyperoxia.

Analysis of Variance↗
PubMed2001

Seasonal change in the capacity for supercooling by neonatal painted turtles.

Hatchlings of the North American painted turtle (Chrysemys picta) typically spend their first winter of life inside the shallow, subterranean nest where they completed incubation the preceding summer. This facet of their natural history commonly causes neonates in northerly populations to be exposed in mid-winter to ice and cold, which many animals survive by remaining unfrozen and supercooled. We measured the limit of supercooling in samples of turtles taken shortly after hatching and in other samples after 2 months of acclimation (or acclimatization) to a reduced temperature in the laboratory or field. Animals initially had only a limited capacity for supercooling, but they acquired an ability to undergo deeper supercooling during the course of acclimation. The gut of most turtles was packed with particles of soil and eggshell shortly after hatching, but not after acclimation. Thus, the relatively high limit of supercooling for turtles in the days immediately after hatching may have resulted from the ingestion of soil (and associated nucleating agents) by the animals as they were freeing themselves from their eggshell, whereas the relatively low limit of supercooling attained by acclimated turtles may have resulted from their purging their gut of its contents. Parallels may, therefore, exist between the natural-history strategy expressed by hatchling painted turtles and that expressed by numerous terrestrial arthropods that withstand the cold of winter by sustaining a state of supercooling.

Acclimatization↗
PubMed2006

New perspectives on host-parasite interplay by comparative transcriptomic and proteomic analyses of Schistosoma japonicum.

Schistosomiasis remains a serious public health problem with an estimated 200 million people infected in 76 countries. Here we isolated ~ 8,400 potential protein-encoding cDNA contigs from Schistosoma japonicum after sequencing circa 84,000 expressed sequence tags. In tandem, we undertook a high-throughput proteomics approach to characterize the protein expression profiles of a number of developmental stages (cercariae, hepatic schistosomula, female and male adults, eggs, and miracidia) and tissues at the host-parasite interface (eggshell and tegument) by interrogating the protein database deduced from the contigs. Comparative analysis of these transcriptomic and proteomic data, the latter including 3,260 proteins with putative identities, revealed differential expression of genes among the various developmental stages and sexes of S. japonicum and localization of putative secretory and membrane antigens, enzymes, and other gene products on the adult tegument and eggshell, many of which displayed genetic polymorphisms. Numerous S. japonicum genes exhibited high levels of identity with those of their mammalian hosts, whereas many others appeared to be conserved only across the genus Schistosoma or Phylum Platyhelminthes. These findings are expected to provide new insights into the pathophysiology of schistosomiasis and for the development of improved interventions for disease control and will facilitate a more fundamental understanding of schistosome biology, evolution, and the host-parasite interplay.

Amino Acid Sequence↗
PubMed2002

Effects of dietary chromium and zinc on egg production, egg quality, and some blood metabolites of laying hens reared under low ambient temperature.

This experiment was conducted to evaluate the effects of chromium (chromium picolinate, CrPic) and zinc (ZnSO4 x H2O) on egg production, egg quality, and serum insulin, corticosterone, glucose, cholesterol, and total protein concentrations of laying hens reared under a low ambient temperature (6.8 degrees C). One hundred twenty laying hens (Hy-Line; 32 wk old) were divided into 4 groups, 30 hens per group. The laying hens were fed the control diet (T1) or the control diet supplemented with either 400 microg of Cr/kg of diet (T2), 30 mg of Zn/kg of diet (T3), or 400 microg of Cr plus 30 mg of Zn/kg of diet (T4). Although the dry matter intake (DMI) was similar (p > 0.05) for all treatment groups, supplemental chromium and zinc either individually or together increased live-weight change, egg production, and improved feed efficiency (p < 0.05). However, no significant differences were observed between T4 and T2 or T3. Compared to T1, supplemental chromium and zinc increased egg weight, eggshell weight, eggshell thickness, egg specific gravity, and Haugh unit (p < 0.05) in T2, T3, and T4 groups, among which there was no significant difference. Serum insulin concentration increased (p < 0.05) and corticosterone concentration decreased (p < 0.05) with dietary chromium and zinc supplementation. Serum glucose and choles- terol concentrations decreased (p < 0.05) and protein concentrations increased (p < 0.001) with dietary chromium and zinc supplementation in all treatment groups. The results of this study indicated that either supplemental dietary chromium or zinc increased plasma insulin and decreased corticosterone concentrations and that had a positive effect on performance of laying hens under low ambient temperature.

Animals↗
PubMedDate not supplied

[Immunological aspects of the phenoloxidase enzymatic system of Schistosoma mansoni].

The phenol oxidase enzymatic system (EC 1.10.3.1, EC 1.10.3.2) is widespread in different species of the animal and vegetal kingdom. Despite its importance in the eggshell formation of the trematodes phenol oxidase (PO) has been little studied in these organisms, mainly in S. mansoni. This report presents the initial results concerning the immunization of rabbits with PO of S. mansoni and mushroom tyrosinase. The immunological analysis done by means of double immunodifusion (Ouchterlony) and immunoelectrophoresis techniques revealed some immunological identity between the PO of males and females. It was not seen cross reaction between the antisera against PO and tyrosinase, what suggests that the antigenic determinants of both enzymes are different in spite of their catalytic sites being similar, since they act over the same substrate. The results reported here represent a first step in way to obtain the PO isoenzymes in their pure form and should open new insights for further studies on the molecular mechanisms involved in the sclerotization process of the S. mansoni eggshell.

Animals↗
PubMed2001

Ootaxonomic investigation of five Lutzomyia species (Diptera, Psychodidae) from Venezuela.

The eggshell fine structure of five sand fly species from Venezuela belonging to the genus Lutzomyia (L. migonei, L. ovallesi, L. absonodonta, L. gomezi and L. panamensis) was examined by scanning electron microscopy. The chorionic sculpturing of L. migonei, L. ovallesi, L. absonodonta and L. gomezi was characterized by series of columns arranged in palisade to form sinuous ridges. In inter-ridge areas, the basal layer was covered with fibrous material. The outer chorion of L. panamensis had a pattern known as "mountain- or volcano-like". The morphology of the posterior pole and aeropyle had a common structure in the five species, with some species-specific characters. The eggshell features of the five species are compared with those of other phlebotomine sand flies.

Animals↗