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At least 865 records · Page 48Linked to original sources
PubMed1996

The role of gonadal hormones in gene expression of calbindin (Mr 28,000) in the laying hen.

Acute and chronic changes in calbindin (Mr 28,000) mRNA and calbindin concentrations were determined to assess the roles of steroid hormones in calbindin mRNA and calbindin synthesis in the eggshell gland (ESG). The results support an earlier suggestion that calbindin gene expression in the ESG is associated with Ca2+ flux through the ESG. The evidence includes wide oscillation of the mRNA during the diurnal egg cycle, in close temporal association with egg shell calcification. Progesterone (single im injection of 1 mg/kg body weight, BW) prolonged the period of egg formation and reduced the rate of Ca2+ transport and the concentration of calbindin mRNA in the ESG. Dexamethasone (single im injection of 5 mg/kg BW) prolonged the period of egg formation, increased shell Ca2+, and reduced calbindin mRNA in the ESG and intestine. Testosterone (single im injection of 2 mg/kg BW) did not affect calbindin mRNA synthesis in the ESG. The effects of estradiol on the synthesis of calbindin mRNA in the ESG of sexually immature or laying birds were minor, while it affected plasma Ca in the same birds. The antiestrogen Tamoxifen (60 mg/kg BW, given orally) reduced plasma Ca, but did not affect the synthesis of calbindin mRNA in the ESG. The antiprogesterone RU-38486 (20 mg/kg BW, orally) increased shell Ca2+ but had no effect on plasma Ca or the synthesis of calbindin mRNA. It appears that estrogens alone cannot account for the markedly elevated synthesis of calbindin mRNA in the ESG of the laying bird. The hypothesis that the regulatory mechanism for the synthesis of calbindin mRNA in the ESG may involve a stimulator(s), associated with the onset of production, and an oscillating depressor(s) is supported and both appear to be closely linked to the reproductive cycle. The specific in vivo effect of progesterone on calbindin mRNA in the ESG, together with its already known changes during the ovulatory cycle in birds, supports the idea that it is a depressor.

Animals↗
PubMed2000

Changes in parathyroid hormone-related peptide receptor binding in the shell gland of laying hens (Gallus domesticus) during the oviposition cycle.

In this study, parathyroid hormone (PTH) receptor binding was examined in the membrane fraction of the endometrium of the shell gland of laying and nonlaying hens by the use of (125)I-PTH-related peptide (PTHrP) binding assays. Specific (125)I-PTHrP binding was found in the endometrium of the shell gland and increased during the first 1 h of incubation and then reached a plateau. Specific (125)I-PTHrP binding increased in line with an increase in protein concentration from 10 to 80 microg. The membrane fraction had specific binding to (125)I-PTHrP. The Scatchard plot analysis revealed a linear profile that indicated the presence of one type of receptor. The equilibrium dissociation constant (K(d)) and the maximum binding capacity (B(max)) in the shell gland decreased 19 h before oviposition in egg-laying hens and remained low for about 20 h during the period of calcification. In contrast, the K(d) and the B(max) in nonlaying hens were constant throughout a 24-h period. These results suggest that PTH acts on the endometrium of the shell gland during the eggshell calcification.

Animals↗
PubMed2001

Pattern of plasma sex steroid hormone levels during reproductive cycles of male and female tropical lizard, Calotes versicolor.

Annual changes in gonadal activity and plasma sex steroid hormone levels in male and female Calotes versicolor [plasma testosterone (T) levels in males and 17 beta-estradiol (E(2)) and progesterone (P) levels in females] are described. In females both plasma E(2) (32.80 +/- 12.91 pg/ml) and P (1.72 +/- 0.79 ng/ml) levels are at their low levels during the postbreeding season when the gonads are regressed. With the onset of recruitment of vitellogenic follicles, E(2) levels begin to rise, reaching peak values (1306.00 +/- 407.01 pg/ml) when the follicles are preovulatory. During this time, plasma levels of P are low. Plasma E(2) levels decline (285.60 +/- 143.0 pg/ml) soon after ovulation, and circulating concentrations of P begin to rise, reaching peak value (19.24 +/- 10.03 ng/ml), during eggshell formation. In gravid females, at mid-gestation, the same pattern of E(2) secretion is found when a second set of follicles undergoes vitellogenesis. However, P levels remain low from mid-gestation (4.06 +/- 2.17 ng/ml) until oviposition. These findings suggest that high P levels are not needed for oviductal egg retention during late gestation and that low levels of P may facilitate growth of a new batch of vitellogenic follicles. In males, plasma levels of T are correlated with the spermatogenetic activity that accompanies breeding.

Animals↗
PubMed1999

Mass determination of the unit cell of the innermost chorionic layer in Drosophilidae by scanning transmission electron microscopy.

The innermost chorionic layer (ICL) in eggshells of Drosophila melanogaster is a naturally occurring patchwork of thin three-dimensional crystalline plates located between the inner endochorion and the vitelline envelope. The mass-per-unit area of the ICL has been measured from scanning transmission electron microscope images of isolated unstained material and it was possible to distinguish up to four layers with the majority of the crystalline sheets being one to three layers thick. Taking into account the unit cell areas for the different crystals, we have estimated the mean ICL subunit sizes to be 36 kDa for Drosophila melanogaster, 35 kDa for Drosophila auraria, and 33 kDa for Drosophila teissieri. The results suggest that the three different Drosophilidae species have very similar average subunit masses.

Animals↗
PubMed1995

Saltationist and punctuated equilibrium models for the evolution of viviparity and placentation.

Vertebrate viviparity (live-bearing reproduction), placentation, and placentotrophy are widely assumed to have evolved as three successive, gradualistic transformations. From empirical data and predictive tests on lizards and snakes, this paper indicates that placentae and a degree of placentotrophy have evolved repeatedly as necessary correlates of viviparity, not as subsequent modifications. In addition, information derived from studies of anatomy, physiology, biogeography and systematics is used to evaluate new saltationist and punctuated equilibrium models for the evolution of viviparity. Phylogenetic reconstruction reveals that more than 100 squamate clades have made the transition to viviparity and placentation. However, various phenotypic intermediates postulated by the gradualistic model are either scarce or unrepresented among known forms, including those in which viviparity has evolved at specific and subspecific levels. Evolution in squamates seems to have produced a dichotomy between two evolutionarily stable patterns: (i) retention of weakly shelled or shell-free eggs to term (viviparity), with development of fully functional placentae; and (ii) deposition of shelled eggs at or near the limb bud stage of development (typical oviparity). Conflicting functional demands placed on eggshell morphology may constrain establishment of prolonged, oviparous egg-retention as a viable, historically stable pattern. Alternatively, the costs of prolonged egg-retention associated with decreased female mobility or decreased fecundity may exceed the benefits in oviparous forms.

Animals↗
PubMed1997

Phylogeny of the island populations of the Hawaiian Drosophila grimshawi complex: evidence from combined data.

The picture-winged species Drosophila grimshawi is unique among Hawaiian Drosophila in its wide geographic range, having populations on several islands of the Hawaiian archipelago. This distribution contrasts with the pattern of single-island endemism observed in most of the picture-winged group; significantly, it does not concur with predictions of the founder theory, where speciation is the typical outcome of founder events involving colonization of a new island. To examine this anomalous situation, we have taken a phylogenetic approach in an attempt to resolve the relationships among taxa and decipher the most probable colonization scenario. We have obtained both morphological and molecular data for all the D. grimshawi populations as well as the closely related species D. pullipes, and two outgroup species, using scanning electron microscopy to score ultrastructural features of the chorion or eggshell, and PCR amplification and nucleotide sequencing to acquire sequence data on Yp1, one of the three Yolk protein genes. In addition, we have used available data on Yolk Protein electrophoretic pattern and jousting, oviposition, and mating behavioral characters. Analyses of these data sets, either individually or in combination, indicate that there are two separate and ecologically distinct clades within this species complex. One clade includes the Kauai and Oahu populations of grimshawi, as well as the closely related species D. pullipes from Hawaii, all of which are classified as ecological specialists with respect to their oviposition and breeding substrate. The other clade includes all the ecologically generalist grimshawi populations of the Maui Nui island complex. The phylogenetic results do not concur with the previously proposed hypothesis that D. pullipes originated from a founder derived from the Maui Nui complex and further suggest that these taxa are in need of taxonomic revision.

Animals↗
PubMed1998

Molecular evidence for parallel evolution of adaptive syndromes in fig-breeding Lissocephala (Drosophilidae).

Afrotropical Lissocephala (Drosophilidae) breed strictly in syconia (figs) of Ficus (Moraceae) and have accordingly evolved specific features including modified female and eggshell morphologies, ovipositing, larval foraging, and mating behaviors. These various traits may exist as two or three alternative states. Each species displays a specific suite of traits so closely coordinated with one another that alternative states of the overall suites of traits can be seen as "adaptive syndromes." Three clear-cut adaptive syndromes can be recognized while two taxonomic lineages (juncta and sanu species groups) are traditionally accepted on the basis of male terminalia. A crucial evolutionary question results from the consideration that ecological clusters and taxonomic groups have conflicting compositions: the three syndromes are found in the juncta group while two of them occur in the sanu group. To resolve this conflict, we present molecular data which provide a robust phylogeny: mitochondrial DNA (12S + 16S ribosomal DNA and cytochrome b) sequence data are in agreement with one another regardless of the algorithm used. All molecular data consistently support male terminalia dichotomy. Such a level of consistency unambiguously indicates that parallel evolution of adaptive syndromes occurred. Thus, homoplasy may affect morphological and behavioral traits concomitantly when these are involved in a network of functional relationships.

Adaptation, Physiological↗
PubMed1988

The analysis of PO2 difference between air space and arterialized blood in chicken eggs with respect to widely altered shell conductance.

The gas exchange of chicken eggs takes place by molecular diffusion. The diffusion barrier between ambient atmosphere and erythrocyte hemoglobin of the gas exchanger (the vascularized chorioallantoic membrane) is conveniently divided into two parts by the air space in the fibrous shell membranes; i.e., the outer barrier (mainly the porous eggshell) and the inner barrier (the chorioallantoic membrane and the chemical reaction with hemoglobin). In contrast to the alveolar-arterial Po2 difference in vertebrate lungs, the difference of Po2 between the air space and the arterialized blood in the allantoic vein (delta PAo2.Pao2) is large in chick embryos. The present study analyzed the delta PAo2.Pao2 in relation to the diffusing capacity of the chorioallantoic membrane (inner barrier) and physiological shunt in the allantoic circulation with respect to widely altered diffusive conductance of the shell (outer barrier). The shell diffusive conductance (Go2) was altered of the beginning of incubation, and the O2 consumption (Mo2) was measured on day 16. The Mo2 increased hyperbolically with increasing Go2, reached a maximum at control values of Go2 and decreased with further increases in Go2. From Go2 and Mo2, the air space Po2 was determined. The delta PAo2.Pao2 was increased in eggs with augmented Go2 (from about 50 torr in control eggs to 70 torr in conductance-increased eggs). The diffusing capacity and allantoic shunt which produce a given delta PAo2.Pao2 were estimated employing a microcomputer performing the Bohr integration procedure so that a calculated Pao2 agreed with the measured Pao2. The allantoic shunt is not more than 20%; 10% is likely. The diffusing capacity becomes maximum in intact control eggs and is decreased at both lowered and augmented Go2. At lowered Go2, diffusion limitation is responsible for about 90% of delta Pao2.Pao2 even in the presence of a 10% shunt. The diffusion limitation to blood oxygenation decreases as Go2 increases, but it is still predominant at augmented Go2. In control eggs, the resistance of the inner barrier to O2 diffusion is about 1.7-fold that of the shell (outer barrier) which agrees with the previous reports.

Animals↗
PubMed1991

[Idiopathic aseptic osteonecrosis of the capitate bone. Literature review apropos of 3 new cases].

The authors report 3 cases of idiopathic avascular necrosis of the capitate and review them together with published reports of 16 further cases. The patients are normally young and the diagnosis delayed. The radiographs may demonstrate an eggshell appearance, a sequestrum, marked sclerosis, or cystic changes. A classification is proposed based on the portion of the bone involved. Early osteoarthritic changes occur and carpal instability may develop. It is suggested that there are features in the blood supply which may be significant. Treatment is by operation, involving either excision of the capitate with replacement with a prosthetic spacer, or else by arthrodesis.

Adult↗
PubMed1992

Subchronic toxicity and reproduction effects of tri-n-butyltin oxide in Japanese quail.

A subchronic toxicity/reproduction study was performed in Japanese quails that were fed a diet containing 0, 24, 60, and 150 mg tri-n-butyltin oxide (TBTO) per kg basal diet for 6 weeks. Eggs produced during the 6 weeks of treatment were incubated and hatched, and chicks hatched from eggs collected in weeks 5 and 6 of exposure were reared for 2 weeks. In parent quail, neither diminished food consumption nor any overt toxic or histopathologic signs were observed following exposure to TBTO. A statistically significant decrease in hatch-ability and increase in percent of chicks found dead in the shell were observed following TBTO exposure at concentrations of 60 and 150 mg/kg food. However, no significant, adverse effects were recorded on total egg production, eggshell thickness and cracked eggs. Blood chemistry parameters of birds measured at the last day of TBTO treatment revealed a statistically significant decrease in serum aspartate aminotransferase (ASAT) enzyme activity among both sexes in all treatment groups. In addition, a statistically significant dose-related decrease in serum calcium level was observed in females only, while serum follicle stimulating hormone (FSH) levels were statistically significantly reduced in male birds in all treatment groups (approximately 50% of the controls). Moreover, a significant decrease in hepatic microsomal 7-ethoxyresorufin (EROD) activity was recorded in females fed 24 and 60 mg TBTO/kg diet and males fed 60 and 150 mg TBTO/kg diet, whereas pentoxyresorufin-o-deetylase (PROD) activity was only significantly decreased in males fed 150 mg TBTO/kg diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Blocked endocytotic uptake by the oocyte causes accumulation of vitellogenins in the haemolymph of the female-sterile mutants quitPX61 and stand stillPS34 of Drosophila.

The developmental lesions in two female-sterile mutants, quitPX61 (qui) and stand stillPS34 (stil), of Drosophila have been analysed. Previtellogenic development is normal in mutant qui ovarioles but, during vitellogenic stages, only small quantities of yolk accumulate in the oocyte. The nurse-cell cytoplasm does not stream into the oocyte. However, the follicle cells continue their developmental program and synthesize an excessive quantity of eggshell material. In the mutant stil, the oocyte remains small and contains only a fraction of the yolk proteins present in wild-type follicles. Histological and ultrastructural observations and the failure to incorporate trypan blue indicate that the yolk proteins present in the mutant follicles are neither derived from the fat body nor from the follicle cells. Since, in both mutants, the uptake mechanism of vitellogenin is affected, the 3 polypeptides accumulate in the haemolymph (in stil, the protein concentration is up to 4 times higher than in wild-type females) and the haemolymph volume increases. Reciprocal transplantations of ovarioles show that the developmental lesions in both mutants are ovary-autonomous. Furthermore, genetic chimeras of stil show that the activity of the stil gene is required in the germline cells and not in the somatic tissues.

Animals↗
PubMed1985

Trichuris muris: structure and formation of the egg polar plugs.

The structure and development of the polar plugs of Trichuris muris eggs were observed by light and electron microscopy. Initial stages in plug formation commenced in the spermatheca of the adult female where two polar papillae became delimited from the remainder of the oocyte cytoplasm. These papillae exhibited a discrete PAS positive reaction and were regarded as prospective plug regions from which cytoplasmic granules were absent. Glycogen rosettes, initially concentrated in these prospective areas, were later transformed into an irregular fine network of chitin-protein microfibrils. This arrangement of microfibrils was in contrast to that of the surrounding collar region which displayed a distinct lamellate organization. The fully developed polar plug was of lower electron density than the shell. Each plug was covered externally by the vitelline layer and lined internally by the lipid layer of the eggshell.

Animals↗
PubMed1991

Autoradiographic and morphological investigations on the uptake and incorporation of tritiated lysin by acanthocephalans.

Four palaeacanthocephalans and two eoacanthocephalans from fish were autoradiographically investigated for their in vitro uptake of tritiated lysin. All worms took up the labelled amino acid at their surface without showing a species-specific pattern. The tegument of the metasoma was more heavily labelled than the presomal tegument, suggesting that the worms predominantly absorb the nutrient from the food inside the host's gut in vivo. Within the metasomal tegument the nuclei revealed the most intense labelling. In the muscles the outer myogenic belt absorbed more radioactivity than did the enclosed cytoplasmic core. In female worms the ovarian balls and eggs that showed incomplete eggshell formation were highly labelled. In male worms the cement glands showed the most intense labelling of all organs inside the body cavity. We conclude that the investigated acanthocephalans require lysin for protein synthesis and for the coding of protein synthesis in the tegumental nuclei.

Acanthocephala↗
PubMed1990

The fine structure of the embryonic envelopes before and after hatching in bothriocephalids: physiological and ecological significance.

The fine structure and differentiation of the embryonic envelopes before and after hatching in two bothriocephalid species of teleostean fish are described. Scanning electron microscopic observation of the egg surface confirmed the specific ornamentation of the capsule. Its thickness and topographic morphology reflect the physiocochemical characteristics of the environment. Beneath the eggshell, two syncytial layers were observed around the oncosphere. The outer envelope, visible during the preoncospheral phase, degenerated before the liberation of the coracidium. Glycoconjugate labelling confirmed the nutritive character of this layer. After hatching, the inner envelope was the only layer covering the oncosphere. The apical plasma membrane of the coracidial sheath bore cilia and numerous clublike microvilli. Beneath the cortical zone, the syncytial cytoplasm was vacuolated, resembling a honeycomb; the electron-dense zone, described from other pseudophyllideans, was not present. The basal membrane of the inner envelope, uniformly electron-dense, was assimilated by the oncospheral membrane. Comparison of the composition of the embryonic envelopes of pseudophyllideans with those of other tapeworm orders and trematodes revealed ontogenetic, structural and functional similarities between the embryotrophic layers. The physiological and ecological significance of the structure of the free-swimming coracidium is discussed. In this respect, the inner envelope around the oncosphere appears to be responsible for the inability of the larva to detect and invade the intermediate host.

Animals↗
PubMed1993

Schistosoma mansoni: analysis of monoclonal antibodies reactive with gut-associated antigens.

The analysis of a series of monoclonal antibodies (mAbs) developed in our laboratory against gut-associated antigens of Schistosoma mansoni is described. It was found that mAbs that recognized epitopes of antigens in the gut and on the eggshell were mainly of the IgM isotype; these epitopes are likely to be carbohydrate in composition. Of a number of mAbs that were reactive with antigens important to the human humoral immune response, 75% appeared to be reactive with the circulating cathodic antigen.

Animals↗
PubMed1994

Light and scanning electron microscopic observations of the eggs, daughter rediae, cercariae, and encysted metacercariae of Echinostoma trivolvis and E. caproni.

Light microscopy (LM) and scanning electron microscopy (SEM) were used to determine interspecific differences between various larval stages of 2 allopatric species of 37-collar-spined echinostomes, Echinostoma caproni and E. trivolvis. The abopercular and embryo diameters of the eggs of E. trivolvis were significantly different from those of E. caproni. The abopercular knobs of E. caproni and E. trivolvis have shallow and deep infoldings in the eggshells, respectively. Interspecific differences were noted in the tegument, tegumentary papillae, and spherical bodies around the mouth and in the papilliform process of the two rediae. The cercaria of E. caproni has one ventral tail fin-fold, whereas that of E. trivolvis has two; both species have two dorsal tail fin-folds. The outer metacercarial cyst diameter of E. caproni was significantly greater than that of E. trivolvis. E. caproni has a smoother outer cyst wall than does E. trivolvis.

Animals↗
PubMed1985

Histochemical studies of Ca-ATPase, succinate and NAD+-dependent isocitrate dehydrogenases in the shell gland of laying Japanese quails: with special reference to calcium-transporting cells.

In order to elucidate the problem of which cells are involved in calcium transport and to estimate the role of mitochondria in calcium transport in the avian shell gland, the fine structure and the Ca-ATPase, succinate dehydrogenase (SDH) and nicotinamide adenine dinucleotide (NAD+)-dependent isocitrate dehydrogenase (NAD+-ICDH) activity of the shell gland of egg-laying Japanese quails were examined. The surface epithelial cells, consisting of ciliated cells with cilia and microvilli and non-ciliated cells with microvilli, had many large and electron-dense granules. The tubular-gland cells occupied the proprial layer and lacked secretory granules. When an egg was in the shell gland, the well-developed mitochondria of tubular-gland cells characteristically tended to accumulate in the apical cytoplasm, while they were scattered throughout the cytoplasm when an egg was not in the shell gland. Intense Ca-ATPase activity was found on the microvilli of tubular-gland cells, and moderate activity was found on the lateral-cell surface. In the surface epithelial cells, the basolateral cell surface showed moderate enzymatic activity. Both SDH and NAD+-ICDH activity were found in tubular-gland cells when an egg was in the shell gland. These results strongly suggest that calcium for eggshell calcification is actively transported by the tubular-gland (depending on Ca-ATPase activity) and that the mitochondria of gland cells may play an important role in this process as an energy source.

Animals↗
PubMed1980

Reproductive success of screech owls fed Aroclor 1248.

Aroclor 1248 was fed to captive screech owls (Otus asio) at the rate of three ppm in the diet to determine if reproductive effects such as fewer eggs per clutch, lower hatchability, malformation of the chicks, or higher mortality rates of chicks would appear in this raptorial species as they did in chickens. There were no effects on eggshell thickness, number of eggs laid, young hatched, and young fledged from feeding a low level of Aroclor 1248 to captive screech owls. The polychlorinated biphenyl (PCB) residues found in the eggs of the dosed birds ranged from 3.9 ppm to 17.8 ppm. Background PCB residues in the diet of all experimental birds ranged from non-detected to 0.62 ppm.

Animals↗