bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of short‐term 17β‐estradiol treatment on the properties of t3‐binding proteins in the plasma of immature rainbow trout, salmo gairdneri
Authors: Cyr Daniel G. , Eales J. G. 
Published: June 2005

AbstractTo determine the effects of 17β‐estradiol (E2) on theproperties of the plasma proteins that bind 3,5,3′‐triiodo‐L‐thyronine (T3), immature rainbow trout, Salmo gairdneri, were intraperitoneally injected on days 0 and 3 with 0.5 mg E2‐3‐benzoate/100 g body weight, and plasma was sampled on days 4, 7, or 12. Control trout received peanut oil alone. E2 increased significantly the proportion of [125I]T3 bound to plasma‐binding sites. Separation of plasma proteins of control trout by agarose filtration on Bio‐Gel A‐1.5 m revealed that T3 bound to two main sites corresponding to molecular weights of 130 kDa (presumed prealbumin) and 55 kDa (presumed β‐globulin). Addition of a calculated amount of unlabeled T3 displaced [125I]T3 from the 55 kDa site, indicating its role as the T3 high‐affinity and low‐capacity site. E2 treatment initiated production of vitellogenin, which did not bind T3. Saturation analysis of [125I]T3 binding conducted on miniature G‐25 Sephadex columns indicated that E2 increased the capacity of the low‐affinity, high‐capacity T3‐binding site without effect on the high‐affinity, low‐capacity T3‐binding site. In conclusion, T3 binds to two main plasma sites and E2 causes an increase in the capacity of the low‐affinity site, resulting in a decrease in free T3 and in possible changes in T3 availability to tissues.
Ecdysteroid biosynthesis in the crustacean Y‐organ and control by an eyestalk neuropeptide
Authors: Spaziani Eugene , Watson R. Douglas , Mattson Mark P. , Chen Z.‐F. 
Published: June 2005

AbstractThe endocrine axis is described that controls growth, molting, and regeneration in crustaceans: The ecdysial glands (Y‐organs), sources of ecdysteroid hormones, and eyestalk neurosecretory centers, sources of a putative peptide (molt‐inhibiting hormone, MIH) that exerts negative control of Y‐organ function. Current knowledge of the physiology of these components is briefly reviewed, and in this context Y‐organs are discussed as useful models for study of steroidogenesis generally in animals at the cellular and molecular levels. Data are emphasized that demonstrate the utilization of cholesterol by Y‐organs for biosynthesis of at least two ecdysteroid secretion products, and suppression of the process by MIH. Evidence from radioactive tracer experiments is presented to show that (a) cholesterol in circulating hemolymph and in vitro in the presence of hemolymph serum is quantitatively bound to high‐density lipoprotein (HDL), (b) Y‐organs take up cholesterol by an active process, and (c) uptake is greatly accelerated in the absence of MIH (eyestalks absent) or inhibited by eyestalk extract. Results of in vitro experiments with 125I‐labeled HDL suggest that the HDL‐cholesterol complex is taken into Y‐organ cells mediated by receptors for the HDL apoprotein. Measured as a function of HDL concentration in the medium, cellular acid‐precipitable radioactivity (HDL uptake), acid‐soluble radioactivity (HDL degradation), and ecdysone secretion each exhibited saturation kinetics. Also, at saturation levels of external HDL, uptake, degradation, and secretion were significantly higher in Y‐organs from de‐eyestalked crabs than in glands from intact crabs.
Absence of temperature‐dependent sex determination in congeneric sexual and parthenogenetic Cnemidophorus lizards
Authors: Crews David 
Published: June 2005

AbstractEggs from congeneric gonochoristic and parthenogenetic whiptail lizards were incubated at various temperatures. There was no significant deviation from a sex ratio of one‐half in the sexual species at any temperature, whereas no males were produced in the parthenogenetic species. Temperature‐dependent sex determination appears to be completely absent in these lizards.
Effects of electric fields on fibroblast contractility and cytoskeleton
Authors: Harris Albert K. , Pryer Nancy K. , Paydarfar David 
Published: June 2005

AbstractWe used silicone rubber substrata and fluorescent staining of cytoskeletal components to study the mechanisms by which electrical voltage gradients cause reorientation of embryonic chick fibroblasts in tissue culture. No evidence was found for a direct stimulation of cell contractility, either parallel or perpendicular to the voltage gradient. Instead, there was a gradual weakening in cell contractility in the axis parallel to this gradient, accompanied by progressive retraction of lamellae oriented along this axis, apparently due to selective weakening of cell‐substratum adhesions. The cells then elongated perpendicular to the electric field, and strengthened their contractility in that axis.Fluorescence microscopy showed that cytoplasmic actin stress fibers and microtubules oriented perpendicular to the imposed voltage gradient. Many more cases were observed in which cell morphology had reoriented, but the actin fibers had not, as compared to the converse (cytoskeleton oriented, but not morphology). This disparity further supports the interpretation that the redirection of cell contractility is a consequence of morphological reorientation, rather than its cause.We also studied the effects of reversing the polarity of the electric fields at constant intervals (of as long as 1 minute). Fibroblasts failed to orient in response to such alternating fields, even after long exposure, but these same cells did reorient in response to pulsed currents in a consistent direction separated by “rest periods” (with no current). This combination of results is more consistent with an electrophoretic mechanism than with one depending on voltage‐induced changes in membrane permeabilities.
Steroidogenesis in Fundulus heteroclitus: III. Evidence for involvement of cAMP and protein synthesis in the gonadotropic modulation of ovarian steroid production and aromatase activity
Authors: Petrino Teresa R. , Hoch Kathryn L. , Lin Yu‐Wai P. , Wallace Robin A. 
Published: June 2005

AbstractThe role of cAMP and the involvement of protein synthesis in ovarian steroidogenesis and aromatase activity of the killifish Fundulus heteroclitus were examined by using isolated prematurational follicles (1.2–1.4 mm diameter) cultured in vitro. Addition of dibutyryl cAMP (dbcAMP) or cAMP in combination with an inhibitor of its catabolism [3‐isobutyl‐1‐methylxanthine (IBMX)] promoted a dose‐dependent increase of media 17α‐hydroxy,2β‐dihydroprogesterone (17α‐OH,20β‐DHP), testosterone (T), and 17β‐estradiol (E2) levels, comparable to the response invoked by a F. heteroclitus pituitary extract (FPE). In addition to steroid production, there was a two‐fold increment in follicular 3H‐leucine incorporation following FPE treatment, probably due to stimulation of protein synthesis. Cycloheximide blocked both 3H‐leucine incorporation and steroid production in a dose‐related manner. FPE also promoted a dose‐related enhancement (more than an additive effect) of E2 accumulation when T was included in the culture media. Results obtained with dbcAMP or cAMP + IBMX in combination with T were essentially the same as with FPE and T, indicating that FPE or increasing levels of cAMP are able to modify aromatase activity. When the endogenous production of E2 caused by FPE or cAMP (dbcAMP or cAMP + IBMX) treatment was suppressed by the use of trilostane (an inhibitor of Δ5‐3β‐hydroxysteroid dehydrogenase), the conversion of exogenous T to E2 was still significantly enhanced. However, no such stimulatory effect on aromatase activity was observed under the same conditions in the presence of cycloheximide. Taken together these results suggest that FPE‐stimulated follicular steroid production by large, prematurational follicles is likely mediated by an intracellular increase in cAMP levels and involves protein synthesis, including that of aromatase. Also, the production of maturation‐initiating steroid by F. heteroclitus follicles does not appear to be affected by physiological levels of E2, unlike the situation reported for other fish and amphibians.
Influence of pH on the regulatory properties of aerobic and anoxic forms of pyruvate kinase in a marine whelk
Authors: Michaelidis Basile , Storey Kenneth B. 
Published: June 2005

AbstractThe effects of pH on the kinetic properties of pyruvate kinase were determined for both the aerobic and anoxic (16 hours exposure to N2‐bubbled seawater) enzyme forms from foot muscle and gill of the marine whelk, Busycotypus canaliculatum. The two enzyme forms from each tissue had distinctly different properties; compared to the aerobic enzyme, the anoxic enzyme form had significantly increased values for S0.5 phosphoenolpyruvate and Ka fructose‐1,6‐bisphosphate and greatly reduced I50 values for L‐alanine. Effects of pH on kinetic constants were assessed at pH 6.6, 7.0, and 7.5. Both the aerobic and anoxic forms of pyruvate kinase in whelk foot showed minimal values for S0.5 PEP and Ka FBP at pH 7.0; these rose by up to twofold at the higher or lower pH values. I50 values for alanine and Mg.ATP were strongly affected by low pH; I50 Mg.ATP fell by tenfold at pH 6.6 compared to pH 7.0, whereas I50 ALA dropped eightfold for the aerobic and 2.5‐fold for the anoxic enzyme form over the same pH change. The qualitative effects of pH change were similar for the anoxic enzyme form from gill. PK‐aerobic from gill behaved differently, however; as pH decreased, S0.5 PEP increased, whereas Ka FBP and I50 ALA both decreased. Furthermore, inhibition by Mg‐ATP occurred only at low pH. Although anoxia‐induced phosphorylation of PK is clearly the primary mechanism for changing the activity state of PK during anaerobiosis, the results suggest that the progressive fall in intracellular pH that occurs during anoxia would enhance the inactivation of PK activity in whelk organs. In particular, the effect of low pH in increasing the sensitivity of the anoxic enzyme forms to inhibitors could facilitate the anoxia‐induced changes in carbon flow at the phosphoenolpyruvate branchpoint.
Excess retinoid acts through the stroma to produce mucous glands from newborn hamster cheek pouch in vitro
Authors: Covant H. A. , Hardy Margaret H. 
Published: June 2005

AbstractMany morphogenetic processes are modified or initiated by retinoids. The cheek pouch of the newborn hamster can be induced to develop mucous glands in vitro by adding excess retinoid. The objective of this study was to determine whether the retinoid acted through the epithelium or the mesenchymal stroma. Explants of cheek pouch were grown for 7 days in either standard medium, or medium supplemented with 6 μg/ml retinyl acetate (RAc; 1.8 × 10−5M). After separation of most explants into epithelium and mesenchyme by trypsinization, the separated tissues were recombined in all possible ways and cultured for a further 1–2 weeks in standard medium. All explants were analysed histologically and/or histochemically from complete serial paraffin sections. No glands were formed in 30 recombinants containing stroma that had not been exposed to RAc, but four of 25 recombinants containing previously exposed stroma had glands, as well as four of 18 unseparated explants exposed to RAc. Exposure of epithelium to RAc did not result in the incidence of glands. It was concluded that RAc acting through the stroma was responsible for the instructive interaction with the epithelium for gland formation. A molecular mechanism is suggested.
Effect of intermittent GnRH analogue treatments on hormonal levels and spermatogenesis in photostimulated red‐winged blackbirds (Agelaius phoeniceus)
Authors: Lacombe Diane , Matton Pierre , Cyr André 
Published: June 2005

AbstractIn photostimulated red‐winged blackbirds (Agelaius phoeniceus) receiving intermittent injections of 10.0 μg of a potent GnRH analogue (GnRH‐A), the pituitary gland was not desensitized, the androgen response was not clearly impaired, and the diameter of the seminiferous tubules was not modified in GnRH‐A‐treated birds compared to saline‐injected redwings. However, the thickness of the germinal epithelium was significantly reduced in redwings receiving 10.0 μg of GnRH‐A every 4th day and every 7th day compared to the saline‐injected redwings. Surprisingly, the group receiving the maximum number of injections (treated every 2nd day) had a thickness of the germinal epithelium and a proportion of individuals with normal spermatogenesis similar to the saline‐injected group and other GnRH‐A‐treated groups. The proportion of redwings with disturbed spermatogenesis was significantly higher in groups receiving GnRH‐A every 4th day and every 7th day compared to saline‐injected redwings. Impairment of spermatogenesis in redwings treated with GnRH‐A at different frequencies occurred without pituitary desensitization and the clear failure of the androgen response, suggesting that factors affecting Sertoli cell and Leydig cell function are involved.
Sex‐specific DNA in reptiles with temperature sex determination
Authors: Demas Suzanne , Duronslet Marcel , Wachtel Stephen , Caillouet Charles , Nakamura Dean 
Published: June 2005

AbstractBanded krait minor (“Bkm”) satellite DNA, originating in the W‐chromosome of the snake Bungarus fasciatus, has been found in the genome of diverse eukaryotic species including fruit fly, quail, and horse. Concentrations of Bkm have been found in the presumptive W‐chromosome of snakes with isomorphic sex chromosomes and in the male‐determining region of the Y‐chromosome in mouse and man. We therefore asked whether Bkm‐related DNA might be present in quantitative excess in DNA from males or females in two related species of sea turtle, Chelonia mydas, in which sex is determined by the temperature of the incubating egg, and Lepidochelys kempi, in which the critical sex‐determining temperature has recently been described. Filter hybridization with the Bkm 2(8) probe revealed male‐specific fragments in both species; female‐specific fragments were also revealed in C. mydas. Sex‐specific DNA sequences in temperature‐sex‐determined species such as Kemp's ridley and the green turtle were unexpected, but could be explained if there were an underlying genetic mode of sex determination in these animals, or alternatively, if temperature‐influenced sex determination involved structural modifications in DNA adjacent to, or directly concerned with, the sex‐determining genes. If these results are confirmed across a broader sample of sea turtles, the techniques described in this paper might be used routinely to identify gender in the young of these endangered animals, in which male and female are grossly indistinguishable.
Differentiation of the vitelline coat and the polarized site of sperm entrance in the egg of Unio elongatulus (Mollusca, Bivalvia)
Authors: Focarelli Riccardo , Rosa Domenico , Rosati Floriana 
Published: June 2005

AbstractWe studied the differentiation of the polarized site of sperm entrance in the egg of a freshwater bivalve, Unio elongatulus. As previously shown, in this egg model the property of sperm recognition and binding is restricted to a region characterized by a wrinkled surface which surrounds a truncated cone or crater region, at the vegetal pole of the egg. The crater is formed during oogenesis at a site opposite the occyte attachment to the ovarian wall. It first appears as a small bleb, and later detaches, leaving in the oocyte an open narrow process filled with an orderly array of microtubules. Here the vitelline coat differentiates from the rest of the oocyte. The role of the microtubules in the formation of the region and the differential distribution of the vitelline coat components is discussed. The synthesis during development of fucosyl containing glycoproteins and their presence in an electrophoretic pattern of isolated vitelline coats were also studied using Lotus tetragonolobus (LTA) conjugated with fluorescein and peroxidase.
Study of the differentiation of secretory cells in the golden hamster oviductal epithelium by use of a monoclonal antibody
Authors: Abe Hiroyuki , Oikawa Taneaki 
Published: June 2005

AbstractThe ontogeny of an oviductal zona pellucida glycoprotein, designated ZP‐0, in the golden hamster oviductal epithelium was investigated by means of light and electron microscopic immunolabeling studies using a monoclonal antibody. Light microscopic immunohistochemistry showed that ZP‐0 appeared in the oviductal epithelium from 9.5 to 10.5 days after birth. At first, ZP‐0 appeared in the Golgi region of the epithelial cells, and then increased in amount as development progressed to fill the supranuclear cytoplasm. Electron microscopic observations showed that rough endoplasmic reticulum and Golgi apparatus were well developed in non‐ciliated cells of the ampullar and isthmic segments at 10.5 days after birth. Secretory granules appeared near the Golgi apparatus and markedly increased in number until 15.5 days after birth. Ultrastructural immunocytochemistry showed that ZP‐0 appeared in the well‐developed Golgi apparatus and then was stored within the secretory granules of developing secretory cells. ZP‐0 was never present in the ciliated cells. These results indicate a coincidence between the beginning of ZP‐0 biosynthesis and the morphological cytodifferentiation of secretory cells in the golden hamster oviduct during postnatal development. This leads us to the conclusion that ZP‐0 is a possible differentiation marker of the golden hamster oviductal secretory cell.
Patterning of the head in hydra as visualized by a monoclonal antibody: III. The dynamics of head regeneration
Authors: Javois Lorette C. 
Published: June 2005

AbstractThe dynamics of the early patterning processes leading to the regeneration of a head in tissue excised from the body column of Hydra oligactis were examined by using a monoclonal antibody, CP8. This antibody displays position‐specific binding, labeling the head ectodermal epithelial cells. During regeneration of a head, antibody labeling is present well before morphological signs of the head, at a time correlated with the determination of the tissue (Javois et al., Dev. Biol., 117:607–618, '86). By quantifying antibody labeling during regeneration of three different pieces of tissue excised from the body column, it was found that the dynamics of the early patterning processes as visualized by CP8 labeling varied. The pattern of labeling observed as well as the spread of labeled tissue suggested that the amount and geometry of apical tissue in the regenerate played a critical role in the patterning processes. Contrary to the labeling pattern observed in heads which formed during bud development or which regenerated following decapitation (Javois et al., '86), not all the CP8+ tissue was confined to the head structures in these regenerates. Several alternative explanations for this surprising result are presented. The usefulness of these data in refining pattern formation models by more explicitly constraining their parameters is discussed.
A search for immunoreactive substance P and other neural peptides in the limb regenerate of the newt Notophthalmus viridescens
Authors: Globus Morton , Alles Paul 
Published: June 2005

AbstractImmunochemical studies demonstrate that the undecapeptide substance P (SP) may be detected by radioimmunoassay in newt limb regenerates and that SP is localized in the blastemal epidermis by immunofluorescence and peroxidase‐antiperoxidase staining. Immunoreactive SP is predominantly distributed at the periphery of epidermal cells, suggesting the presence of SP binding sites on the cell surface; the basal germinative layer of the epidermis and blastemal mesenchyme cells remain unreactive. The pattern of SP immunoreactivity in the blastema was compared with that of four other tachykinin‐family peptides (eledoisin, kassinin, substance K, and neuromedin K) and with three non‐tachykinin neural peptides (bombesin, neurotensin, and metenkephalin). With the exception of neurotensin, which showed weak staining in the basal layer but an absence in the peripheral layers of the epidermis, none of the peptides examined exhibited immunoreactivity in the blastema epidermis comparable to that of SP.
A model for studying isolation mechanisms in parasite populations: The genus Lepeophtheirus (Copepoda, Caligidae)
Authors: De Meeus T. , Renaud F. , Gabrion C. 
Published: June 2005

AbstractIn the Mediterranean, the parasitic copepod Lepeophtheirus thompsoni Baird, 1850 specifically infests turbot (Psetta maxima L., 1758), whereas L. europaensis Zeddam, Berrebi, Renaud, Raibaut, and Gabrion, 1988 infests brill (Scophthalmus rhombus L., 1758) and flounder (Platichthys flesus L., 1758). Experimental infestation of turbot by copepods from each of the three fish species showed an absence of any physiological incompatibility preventing natural development of the two parasite species, at least on one host species, i.e., the turbot. Moreover, interspecific hybrids were obtained experimentally, which implies that 1) there is no strict genetic barrier between the two species and 2) the natural prezygotic isolation results from a choice of the most favorable habitat. We discuss the origin and possible consequences of the presence, in the Mediteranean, of L. europaensis on brill and flounder, two hosts separated by their taxonomic status and ecobiology.
Natural freeze tolerance in the terrestrial turtle, Terrapene carolina
Authors: Costanzo Jon P. , Claussen Dennis L. 
Published: June 2005

AbstractTo investigate freeze tolerance in box turtles (Terrapene carolina), we froze 19 adults to body temperatures as low as −3.6°C under controlled laboratory conditions. Our data reveal that box turtles tolerate the freezing of at least 58% of their body water and can remain frozen, without injury, for at least 73 hr. Supercooling occurred in 63% of the turtles but only lasted from 0.1 to 2.0 hr. Supercooling points (X ± SEM = −1.1 ± 0.3°C) were high, and thus supercooling is not an effective strategy for freeze avoidance in T. carolina. Body ice contents (7–58% of total body water) of turtles frozen for 0.7–50 hr, determined calorimetrically, were inversely related to core body temperature. Significant thermal gradients occurred within the turtles' bodies during prefreeze cooling, freezing, and thawing. Since T. carolina hibernates in shallow terrestrial burrows, where exposure to subzero temperatures is likely, freeze tolerance represents a remarkable adaptation that probably enhances winter survival. These turtles are the largest (up to 0.5 kg) animals, by nearly an order of magnitude, for which natural freeze tolerance has been demonstrated.
Patterns of survival at subzero temperatures by hatchling painted turtles and snapping turtles
Authors: Packard Gary C. , Packard Mary J. 
Published: June 2005

AbstractNeonatal painted turtles (Chrysemys picta) do not emerge from their nest immediately upon hatching but instead remain inside the nest cavity until the following spring. Because the nest chamber is only 7–12 cm beneath the surface of the ground, hatchlings in northerly populations may be exposed to subzero temperatures during their first winter of life. We studied the pattern of survival by hatchling painted turtles exposed to subzero temperatures in a controlled laboratory experiment and discovered that 50% of the animals in our samples could withstand exposure to approximately −8.6°C for 18 hr. In contrast, hatchling snapping turtles (Chelydra serpentina) died at −2°C. This extraordinary ability for hatchling painted turtles to withstand exposure to subzero temperatures is a key feature in the unusual life history of the species and distinguishes painted turtles from other species occurring at high latitudes.