bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of excitatory amino acids on in vivo and in vitro gonadotropin and growth hormone secretion in testosterone‐primed immature rainbow trout, Oncorhynchus mykiss
Authors: Flett Peter A. , van der Kraak Glen , Leatherland John F. 
Published: June 2005

AbstractThe present studies were conducted to evaluate the effects of excitatory amino acids (EAAs) on gonadotropin II (GtH II) and growth hormone (GH) secretion in testosteroneprimed immature rainbow trout, Oncorhynchus mykiss. Intraperitoneal injections of N‐methyl‐DL‐aspartate (NMA) elevated both plasma GtH II and GH levels. By comparison, Des Gly10 [D‐Ala6] LHRH‐ethylamide (LHRH‐A) elevated plasma GtH II levels but had no effect on plasma GH levels. The GtH II response to NMA was not evident in sexually regressing adult rainbow trout. GtH II secretion by perifused pituitary glands of testosterone‐primed immature rainbow trout was elevated following NMA or salmon GnRH analogue (sGnRH‐A) challenge. The GtH II response to NMA was eliminated in pituitaries previously exposed to either the NMA receptor antagonist, AP5, or a GnRH receptor antagonist (D‐pGlu1,D‐Phe2,D‐Trp3,6‐LHRH), suggesting that NMA operates by stimulating the secretion of GnRH rather than by direct actions on the pituitary gonadotropic cells. The results of these studies provide evidence of the presence of NMA‐specific receptors in the hypothalamo‐hypophyseal system that when activated led to the release of GtH II. L‐glutamic acid (GLU) also stimulated GtH II secretion from perifused pituitary glands. However, the response to GLU was only partly blocked by AP5, suggesting that GLU exerted some of its effect via non‐NMA type receptors, in addition to its actions on NMA receptors. The results of these studies support the contention that EAA receptor activation may play a role in regulating the onset of sexual maturation in teleosts, as it seems to do in mammals. © 1994 Wiley‐Liss, Inc.
A Xenopus maternal effect mutant gene affects oocyte meiotic reinitiation and fertilization
Authors: de Vantéry Corinne , Schorderet‐Slatkine Sabine , Droin Anne 
Published: June 2005

AbstractNo cleavage (nc) is a maternal effect mutant gene, recessive and sex limited. It affects the eggs laid by homozygous mutant females, independently of the male genotype.Contrary to normal oocytes, following germinal vesicle breakdown (GVBD) during maturation, the transient microtubular array (TMA) is not formed, nor are the meiotic spindles. Cytoplasmic asters with condensed chromosomes are present in the majority of oocytes, as well as microtubular bundles and sometimes cytoplasmic spindle‐like asters. These mature oocytes exhibit a disturbance in yolk platelet arrangements. The white spot is rather irregular, and the maturation period is longer than normal. Transfers of cytoplasm from nc mature oocytes into normal stage VI oocytes resulted in abnormal maturation of the normal oocytes. Reciprocal transfers (cytoplasm from normal mature oocytes into nc stage VI oocytes) induce the formation of spindles, usually cytoplasmic; this indicates that the deficiency can be partly rescued.Following fertilization, the nc eggs show neither contraction nor rotation; polyspermy is present in the majority of cases. Even in the same egg, simultaneous spindles and nuclei can be observed, revealing a disturbance in the spatial localization of regulators of the cell cycle. Cytokinesis never occurs. Polyspermy results from the absence of cortical reaction following sperm entry. However, when mature nc oocytes are treated with PMA, they show cortical granule exocytosis and the formation of an altered vitelline envelope.The different factors possibly involved in these anomalies are discussed in relation to cytoarchitectural disorganization of the cell and abnormal cell cycle regulation. © 1994 Wiley‐Liss, Inc.
Effects of the pineal gland and melatonin on the metabolism of oocytes in vitro and on ovulation in Bufo arenarum
Authors: de Atenor M. S. B. , de Romero I. R. , Brauckmann E. , Pisanó A. , Legname A. H. 
Published: June 2005

AbstractThe pineal gland and the hormone melatonin appear to be responsible to some extent for the metabolic behaviour of Bufo arenarum oocytes during the winter. This assumption is supported by the observation that, in isolated mitochondria, both elements stimulate the rate of oxidation of citrate and inhibit that of fumarate, thus raising the oxidizing ratio that relates these parameters (C/F) to values close to or above 1, which is characteristic of these animals in winter.The sensitivity of oocytes to melatonin, in terms of the C/F ratio, varies throughout the year. It is maximal in fall and early winter at a dose of 1.8 μg/ml after 30 min treatment, minimal or nonexistent in late winter, and it increases gradually during the spring and summer. The response of oocytes to melatonin is more significant if the animals have been previously injected with a homogenate of homologous hypophysis.A direct metabolic effect of melatonin on oocytes was observed when coelomic oocytes, without follicle cells, responded to hormonal treatment.Both an extract of pineal gland and melatonin inhibit in vitro ovulation, the inhibitory effect of the extract being greater than that of the hormone. © 1994 Wiley‐Liss, Inc.
Effects of Ddc cluster lethal alleles on ovary growth, attachment, and egg production in Drosophila
Authors: McCrady Edward , Tolin David J. 
Published: June 2005

AbstractThe Ddc cluster of genes on the left arm of chromosome 2 in Drosophila has been extensively characterized by Wright and coworkers (Wright, '87b). Many of the genes in the cluster are associated with the pigmentation and sclerotization of the cuticle, and at least 12 have been shown to play a role in female fertility. To characterize further the actions of genes in the cluster, we have investigated the effect on fertility of a total of five of the previously untested genes (l(2)37Be, Bb, Bg, Bd, and Cg), and three of the partially characterized genes (l(2)37Ce, Ddc, and amd). Each allele was crossed to Df(2L)TW130 or49h flies in order to make it hemizygous over the 8–12 band deficiency covering the Ddc region, 37B9‐C1,2;37D1‐2. Ovaries taken from larvae produced by this cross were transplanted into female larval hosts of y f mal genotype, that were then mated to v f mal males. The wild type allele of mal in implanted tissue allowed identification and study of surviving implants by staining for the presence of aldehyde oxidase. Of the 18 alleles available, amdH149, l(2)37Bb1, Bb9, Bb11, Bd6, Be1, Bd7, Be2, Be3, Ce4, and Cg1 did not allow enough growth to form transplantable ovaries; l(2)37Bg1, Bg2, and Cgtsl prevented development of transplanted ovaries in their hosts; l(2)37Ce5 allowed implanted ovaries to attach to oviducts and grow, but insufficiently for production of eggs; and DdcN27, amd29, and l(2)37Bd4 appeared not to restrict ovary development. Heteroallelic heterozygotes of Bd7 × Bd4 also produced fully fertile ovaries, but no other heteroallelic combinations did so. No obvious correlation exists between this pattern of effects on ovarian fertility and the overall organization of the gene cluster. © 1994 Wiley‐Liss, Inc.
Embryonic development of the cornea in the eye of the clearnose skate, Raja eglanteria: I. Stromal development in the absence of an endothelium
Authors: Conrad Gary W. , Paulsen Avelina Q. , Luer Carl A. 
Published: June 2005

AbstractEmbryos of the clearnose skate, Raja eglanteria, develop in sea water at 20–22°C, hatching after 82 ± 4 days (Luer and Gilbert, Environ. Biol. Fishes, 13:161–171, 1985). Eyes develop as steadily enlarging spheres whose corneas have the same radius of curvature as the sclera. The cornea begins development as a 2‐cell thick epithelium beneath which by Day 12 there is only a basal lamina and a wispy matrix separating it from the underlying lens. This matrix, modified by Day 16, is displaced on Day 22 by a few orthogonal plies of fibrillar primary stroma. Ply number increases to at least 13 by Day 30, reaching the final number of 20 ± 2 by Day 42. Stromal fibroblasts (keratocytes) appear at the corneal periphery by Day 22, and in increased numbers by Day 30, a time at which no keratocytes are seen in the central stroma. However, by Day 40, many fibroblasts are present at the corneal periphery, invading the primary stroma between plies, occasionally reaching even the central cornea. By Day 53, keratocytes are present between all plies, from corneal periphery to center. Thickness of each ply in this secondary stroma increases, but the number of plies remains the same as in the primary stroma. Bowman's layer, non‐invaded matrix beneath the epithelial basal lamina, is not evident until Day 53. Sutural fibers, first seen on Day 22, originate in the corneal epithelial basal lamina, traversing perpendicularly the plies of the primary stroma. Sutural fibers persist throughout development of the secondary stroma and into adulthood. In contrast to chicks, skate corneas remain transparent throughout development, and never form an endothelium. © 1994 Wiley‐Liss, Inc.
Concomitant effects of sulfide and hypoxia on the aerobic metabolism of the marine oligochaete Tubificoides benedii
Authors: Dubilier Nicole , Giere Olav , Grieshaber Manfred K. 
Published: June 2005

AbstractSulfide is toxic for most aerobic organisms and inhibits the key enzyme of aerobic respiration, cytochrome c oxidase, at low μM concentrations. Tubificoides benedii is a ubiquitous marine oligochaete that regularly occurs in polluted, poorly oxidized coastal muds with high sulfide concentrations. The questions posed in this study were: Can T. benedii maintain aerobic pathways despite the occurrence in its habitat of sulfide concentrations that are toxic for many marine invertebrates? What influence does the ambient oxygen concentration have on the sulfide effects? To answer these questions animals were incubated under flow‐through conditions in various sulfide and oxygen concentrations. As an indicator of an anaerobic metabolism succinate was measured, a metabolite which accumulates in high concentrations in T. benedii under hypoxic conditions. The results show that under normoxic conditions, T. benedii can maintain a completely aerobic metabolism at sulfide concentrations up to 175 μM. At 300 μM sulfide, anaerobic pathways are utilized to only a small extent and even at sulfide concentrations as high as 450 μM and 600 μM a partially aerobic metabolism is sustained. However, if ambient oxygen concentrations are decreased, much lower sulfide concentrations cause the animal to utilize anaerobic pathways. At oxygen concentrations as low as 20 μM (= 1.5 kPa O2 or 7% air saturation), where the worms can maintain a fully aerobic metabolism in the absence of sulfide, minimal concentrations of sulfide (40 μM) are sufficient to give rise to an anaerobic metabolism. © 1994 Wiley‐Liss, Inc.
Further characterization of the pituitary‐adrenocortical responses to stress in Chiroptera
Authors: Widmaier Eric P. , Harmer Tara L. , Sulak Adriana M. , Kunz Thomas H. 
Published: June 2005

AbstractPrevious studies on bats from this laboratory have revealed the presence of exceptionally high circulating levels of glucocorticoids in two species of the sub‐order Megachiroptera. In the present study, the following questions were asked: (1) what effect does the routine handling and examination of captive bats have on the activity of their hypothalamic‐pituitary‐adrenocortical (HPA) axis?; (2) are the unusually high plasma levels of cortisol and corticosterone found in Pteropus hypomelanus associated with high levels of circulating adrenocorticotropic hormone (ACTH)?; (3) are there diurnal changes in stress responsivity in this species?; and (4) how do levels of glucocorticoids in P. hypomelanus compare with those found in other species of Chiroptera (both micro and megachiropteran species)? Of five species examined, P. hypomelanus had slightly higher total glucocorticoid levels than P. pumulis, but ∼‐fold higher levels than in three species of Microchiroptera (Artibeus jamaicensis, Carollia perspicillata, and Myotis lucifigus). There was a pronounced diurnal rhythm in glucocorticoid levels in one species (M. lucifigus) for which this was determined. A 1‐h period of restraint stress increased glucose and glucocorticoid levels in P. pumulis, and also increased ACTH and glucocorticoids in P. hypomelanus. Fifteen minutes of routine handling (weighing, measuring, etc.) elicited a significant rise in plasma glucocorticoids in P. hypomelanus to combined peak (cortisol plus corticosterone) levels of over 1,000 ng/ml (100 μg%). There was no significant difference in the response to handling in bats tested in the morning or evening. Basal ACTH levels as detected by radioimmunoassay were low in P. hypomelanus, in spite of high steroid levels. Displacement of labeled ACTH by plasma of P. hypomelanus was roughly parallel to that produced by synthetic human ACTH. The identity of immunoreactive ACTH was confirmed by subjecting separate aliquots of plasma to an immunoradiometric assay (IRMA), which operates on a different principle from the RIA and necessitates an intact molecule closely resembling human ACTH. We conclude that bats possess a “stress response” similar in some ways to that seen in other mammals. The extremely high constitutive and stress‐induced levels of glucocorticoids in the Megachiroptera are nearly unique among mammals. Although high circulating levels of ACTH were detected by IRMA, but not by RIA, it is possible that the Chiropteran adrenal gland is hypersensitive to ACTH or possesses exceptionally active intracellular steroidogenic mechanisms. Finally, the routine daily procedures associated with measuring, weighing, and monitoring bats in captivity constitutes a significant stress to the animal as revealed by pronounced activation of the HPA axis. © 1994 Wiley‐Liss, Inc.
Developmental expression and modulation of the vitellogenin receptor in ovarian follicles of the rainbow trout, Oncorhynchus mykiss
Authors: Lancaster Petrina M. , Tyler Charles R. 
Published: June 2005

AbstractOvarian uptake of vitellogenin (VTG) accounts for a considerable proportion of oocyte growth in many oviparous species. The mechanisms controlling the expression and modulation of the VTG receptor, therefore, will be key determinants in effecting oocyte growth. This study documents the expression and modulation of the VTG receptor in follicles of the rainbow trout (Oncorhynchus mykiss) during ovarian development.SDS‐PAGE and ligand blotting with 125I‐VTG demonstrated the presence of the VTG receptor in rainbow trout follicles throughout the period of ovarian development, known as vitellogenesis. The vitellogenin receptor was also shown to be present in very small follicles (those measuring 0.3 mm or less in diameter) and in ovulated eggs. Filter binding assays followed by Scatchard analyses revealed developmental changes in both the receptor equilibrium dissociation constant, Kd, and the maximum number of binding sites, Bmax. The binding affinity of the VTG receptor for VTG in follicles was highest in the smallest follicles examined (0.4 mm in diameter, Kd = 1.3 × 10−9 M) and in those approaching ovulation (1.8 × 10−9 M). Ovulated eggs also had a high binding affinity for VTG (1.2 × 10−9 M). The Bmax increased almost 4‐fold during early development from 70.8 fmol/mg protein in 0.4 mm follicles to 260.5 fmol/mg protein in 0.6 mm follicles, but subsequent to this there was little change in the Bmax throughout follicle growth. Ovulated eggs had a relatively low binding capacity for VTG. The number of VTG receptors per follicle increased 100‐fold with increasing follicle size, but dropped dramatically at ovulation. The data presented also suggests that the density of VTG receptors (numbers per mm2 follicle surface) changed significantly during follicular development. © 1994 Wiley‐Liss, Inc.
Analysis of lung surfactant in the metamorphosing bullfrog (Rana catesbeiana)
Authors: Oguchi Atsuko , Mita Masatoshi , Ohkawa Muneyoshi , Kawamura Kosuke , Kikuyama Sakaé 
Published: June 2005

AbstractIn bullfrog (Rana catesbeiana) tadpoles, the lung begins to function at an advanced stage of metamorphosis. As a preliminary step for investigation of the mechanisms involved in lung maturation, pulmonary surfactant was prepared from tadpoles at advanced stages of metamorphosis and its biochemical properties were analyzed. Surfactant phospholipid analysis revealed that the major constituent was phosphatidylcholine (PC), as examined in the animals at late climax (stage 24). Other detectable phospholipids were phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and phosphatidylglycerol, a marker lipid in mammalian surfactant. As in mammals, PC in the surfactant was rich in saturated fatty acids, about 50% of fatty acid moieties being palmitic acid. The content of surfactant PC in the lung increased moderately around mid‐climax and markedly at the end of climax. The effect of antiserum against bullfrog prolactin (PRL) on the pulmonary surfactant was studied in climactic tadpoles. The content of surfactant PC in the lung of the antiserum‐treated larvae was lower than that in the lung of the normal rabbit serum‐injected larvae, whereas the content of PC in the whole lung did not differ between the antiserum‐treated and control groups. The results suggest that synthesis of surfactant in the amphibian lung is enhanced as metamorphosis progresses and that PRL is involved in lung maturation. © 1994 Wiley‐Liss, Inc.
Patterns of temperature‐dependent sex determination in turtles
Authors: Ewert Michael A. , Jackson Dale R. , Nelson Craig E. 
Published: June 2005

AbstractAmong reptiles that show temperature‐dependent sex determination, sex ratios vary across constant incubation temperatures in ways sufficiently predictable to allow classification into patterns. One common pattern shows low temperatures yielding only males and high temperatures yielding only females. Another common pattern has low as well as high temperatures yielding only or mostly females and some intermediate temperatures yielding mostly males. Patterns tend to be associated with the direction of sexual dimorphism in adult size, especially for species with strong dimorphism.Pivotal temperatures (those yielding 1:1 sex ratios) within the best‐documented species and genera tend to increase with both latitude and longitude across central and southern North America. These geographic trends probably reflect factors that affect nest temperatures (duration of growing season, insolation, and prevailing amounts of shading by vegetation).Data from a population of the alligator snapping turtle (Macroclemys temminckii) suggest that some embryos are temperature‐independent females because these individuals become females even when they are shifted among male‐producing temperatures during development. These individuals are also more frequent in clutches of small eggs. In this and several other species, no constant incubation temperatures yield more than 75% males. © 1994 Wiley‐Liss, Inc.
Temperature‐dependent sex determination in crocodilians
Authors: Lang Jeffrey W. , Andrews Harry V. 
Published: June 2005

AbstractHalf of the 22 extant crocodilians show evidence of temperature‐dependent sex determination (TSD). We examine evidence for TSD in 11 species by reviewing reports on five and presenting new data for six. The female‐male pattern (FM; females at low temperature, males at high temperature) attributed to Alligator mississippiensis and Caiman crocodilus are here revised to be female‐male‐female (FMF; males at intermediate temperature, females at low and high temperatures). A similar pattern characterizes Crocodylus palustris, C. moreletii, C. siamensis, and Gavialis gangeticus based on new data; published accounts establish a FMF pattern in Crocodylus porosus, C. johnstoni, and C. niloticus. TSD apparently occurs in Paleosuchus trigonatus and Alligator sinensis, but patterns are not yet documented. In the well‐studied species, the incubation temperatures for FM transitions are congruent, but MF transition temperatures differ among species. In A. mississippiensis, 100% males are produced over a range of constant incubation temperatures, whereas in C. johnstoni, only low proportions of males are produced at any constant temperature.The thermosensitive period (TSP) for A. mississippiensis occurs during stages 21 to 24 (days 30–45 at intermediate temperatures) and coincides with gonadal differentiation. A similar scenario is suggested in other species. The TSP in A. mississippiensis (and possibly other crocodilians) encompasses the third quarter of development and occurs later than in turtles and a lizard. In A. mississippiensis as in turtles, the duration (cumulative effect) and/or the magnitude (potency effect) of incubation temperatures during the TSP predictably alter sex ratios. TSP chronologies and features which are shared among TSD reptiles suggest common, underlying mechanisms; A. mississippiensis is an appropriate model for further study. In crocodilians, clutch effects are a significant source of variation in TSD response. Hatchling sex ratios previously reported for A. mississippiensis are reconsidered in light of our new data. © 1994 Wiley‐Liss, Inc.
Temperature sensitivity of sexual differentiation of gonads in the European pond turtle: Hormonal involvement
Authors: Pieau Claude , Girondot Marc , Richard‐Mercier Noëlle , Desvages Gisèle , Dorizzi Mireille , Zaborski Patrick 
Published: June 2005

AbstractIn the European pond turtle, the incubation of eggs below 28°C yields 100% phenotypic males, whereas above 29.5°C 100% phenotypic females are obtained. Many data argue in favor of the involvement of steroid hormones in this phenomenon. During the thermosensitive period for sex determination, gonads are able to metabolize different steroid precursors, such as pregnenolone, progesterone, androstenedione, and dehydroepiandrosterone. Gonadal œstrogen content is higher at 30°C than at 25°C. When œstradiol benzoate (5 to 50 μg) or œstrone (100 μg) are injected into eggs incubated at 25°C before or at the beginning of the thermosensitive period, gonads differentiate into ovaries instead of testes: an ovarian‐cortex develops whereas medullary testicular cords are inhibited. Conversely, when tamoxifen (an antiœstrogen) is injected into eggs incubated at 30°C, medullary testicular cords (or tubes) differentiate. Gonadal aromatase activity during the thermosensitive period increases in an exponential fashion at 30°C, and remains very low at 25°C. When eggs are first incubated at 25°C up to a stage within this period, and then shifted to 35°C (a highly feminizing temperature) for different times, the response is also exponential, showing an amplification of aromatase synthesis. Temperature could act, directly or indirectly, on the regulation of the expression of the aromatase gene. The anti‐üullerian hormone (AMH) exerts an inhibitory effect on aromatase activity. The termination of the thermosensitive period could result in testes from an active synthesis of AMH, and in ovaries from high levels of œstrogens. © 1994 Wiley‐Liss, Inc.