bluuebunny/crossref_metadata_2025_split huggingface dataset:
Release of hyaluronidase and β‐N‐acetylhexosaminidase during in vitro incubation of hamster sperm
Authors: Zao Peter Z. R. , Meizel Stanley , Talbot Prudence 
Published: June 2005

AbstractPrevious studies have shown that hamster sperm release a significant amount of hyaluronidase before and independently of the normal acrosome reaction. In this study, we have used improved methods for in vitro incubation to investigate the time course of the release of hyaluronidase and hexosaminidase from hamster sperm. When hamster sperm are incubated in medium which allows capacitation, 34 to 47% of the total mechanically extractable hyaluronidase and 34 to 51% of β‐N‐acetylhexosaminidase are released into solution prior to and independently of the normal acrosome reaction (ARx). An additional 40 to 50% of the hyaluronidase and 34 to 51% of the hexosaminidase are released at the time of the normal ARx. Control experiments indicate that the early release is not due to the presence of dead sperm in culture and that the normal ARx is required for the second release. Increasing amounts of TCA‐precipitated bovine serum albumin in the culture medium stimulated the early (1 hr) release of both enzymes. The data are consistent with the ideas that a significant amount of both enzymes is released from the sperm surface by 1 hr of incubation and that about the same amount of each enzyme is released during the normal ARx. Hyaluronidase and hexosaminidase release at the time of the acrosome reaction was measured for the first time using hamster sperm. The biphasic release of these enzymes may indicate that they have a dual function in fertilization and may help explain how sperm can penetrate the cumulus and corona radiata without undergoing an acrosome reaction.
Immunocytochemistry of luteinizing hormone‐releasing hormone during spontaneous and thyroxine‐induced metamorphosis of bullfrogs
Authors: Whalen Richard , Crim Joe William 
Published: June 2005

AbstractDouble‐bridge peroxidase‐antiperoxidase immunocytochemistry was used to compare the developmental appearance of immunoreactive LH‐RH (ir‐LH‐RH) in brains of bullfrog (Rana catesbeiana) tadpoles during either spontaneous or thyroxine‐induced metamorphosis. During spontaneous metamorphosis, ir‐LH‐RH was localized in fibers of the external layer of the median eminence (ME) of stage XIII–XXV animals, while immunoreactive perikarya and other immunostained brain structures were absent. The extent and intensity of ME immunostaining increased concomitantly with measured ME morphological development. Tadpoles induced with thyroxine to metamorphic stages XIX–XXI exhibited ME structural development and neurohypo‐physial neurosecretory staining similar to spontaneously metamorphosed individuals of equal stages. However, comparable ME ir‐LH‐RH immunostaining and gonadal size were both less developed in thyroxine‐treated animals, although increased relative to non‐metamorphic vehicle‐injected controls. These results indicate that the hypothalamic LH‐RH system changes concurrently with ME structural development during spontaneous metamorphosis. Reduced ME ir‐LH‐RH staining and gonadal size in thyroxine‐treated animals suggest that during prometamorphosis, factors other than thyroxine alone may coordinate the normal maturation of the hypothalamo‐pituitary‐gonadal axis of the bullfrog.
Hypoosmoregulation in an anadromous teleost: Influence of sex and maturation
Authors: McCormick Stephen D. , Naiman Robert J. 
Published: June 2005

AbstractSalinity tolerance and hypoosmoregulatory ability of anadromous brook trout (Salvelinus fontinalis) were investigated in relation to sex and state of maturation. Seawater survival of mature males was significantly poorer than that of females or immature males. Lowered salinity tolerance of adult males became acute during the autumn photoperiod (normal spawning period) when the gonadosomatic index was high. Plasma [Cl−], [Mg2+], osmolarity and hematocrit were significantly higher in mature males after transfer to seawater, relative to mature females. It is postulated that reduced adult male hypoosmoregulatory ability explains skewed sex ratios in anadromous brook trout populations and may limit the extent of brook trout anadromy.
Distribution and characterization of mineral‐binding phosphoprotein particles in bivalvia
Authors: Marsh M. E. , Sass R. L. 
Published: June 2005

AbstractRepresentative species of four bivalve subclasses were examined for the presence of mineral‐binding phosphoprotein particles in the physiological fluids. The particles were identified in Heterodont bivalves only, and particles from nine different Heterodont species were isolated and characterized. All phosphoprotein particles are internally cross‐linked via histidinoalanine residues. In all species over 80% of the amino acid residues in the particles are aspartic acid, phosphoserine (and/or phosphothreonine), and histidine. These amino acids are probably the only residues directly related to mineral ion binding, since all phosphoprotein particles bind mineral irrespective of the minor amino acid content, which is species dependent. In their native state the phosphoprotein particles contain large amounts of calcium, magnesium, and inorganic phosphate ions (up to 45 metal ions and 8 phosphate ions per 100 amino acid residues) and trace amounts of transition elements. Evidence for the presence of calcium phosphate complexes in the native phosphoprotein particles was obtained by observing a concomitant increase in the inorganic phosphate and calcium ion content of the particles with pH in vivo.
Antagonistic actions of estradiol and tamoxifen upon forskolin‐dependent meiotic arrest, intercellular coupling, and the cyclic AMP content of hamster oocyte‐cumulus complexes
Authors: Racowsky Catherine 
Published: June 2005

AbstractThe effects of estradiol (E2) and the anti‐E2 tamoxifen (tam) on forskolin (F)‐dependent meiotic arrest in hamster oocytes were investigated. The hypotheses tested were that (1) the arresting action of F is enhanced by E2 and suppressed by tam and (2) the extent of heterologous metabolic coupling and the concomitant transfer of cumulus cell cAMP into the oocyte is increased and decreased by E2 and tam, respectively. E2 was tested with the ID25 F (where ID25 is the dose of F previously shown to arrest the meiosis of 25% cultured oocytes; intact, 3 μM; denuded, 10 μM) and tam was tested with the ID75 F (intact, 10 μM; denuded, 100 μM).E2 induced reversible dose‐dependent increases in the percent germinal vesicle (%GV; determined cytogenetically) of both intact and denuded oocytes in the presence of ID25F (intact: ID50 E2 = 18.0 μM; denuded: ID50 E2 = 17.2 μM) but, in contrast to intact oocytes, E2 also exerted a dose‐dependent action on denuded oocytes in the absence of F (ID50 = 26.1 μM). E2 induced dose‐dependent increases in the cAMP content (determined by RIA) of intact oocytes (cAMP‐oo) and of cumulus masses (cAMP‐cm) and in the ratio of cAMP‐oo:cAMP‐cm but failed to elevate F‐stimulated cAMP in denuded oocytes. Heterologous metabolic coupling, as assessed by determination of the fraction of radiolabeled uridine marker that was transferred from the cumulus cells to the oocyte, was not significantly enhanced by E2. In contrast to denuded oocytes, tam induced dose‐dependent decreases in the %GV and cAMP content of intact oocytes in the presence of ID75 F and significantly depressed heterologous metabolic coupling. While tam failed to antagonize the E2 action on denuded oocytes in the presence of ID25 F, in intact oocytes cultured with E2 and the ID25 F, the anti‐E2 significantly decreased the %GV, the cAMP‐oo and cAMP‐cm, and the extent of heterologous metabolic coupling.These data show that while E2 can directly arrest the maturation of denuded hamster oocytes with no associated elevation of cAMP‐oo, E2‐enhancement of arrest in intact oocytes is correlated with both elevation of cAMP within the oocyte‐cumulus complex and maintenance of heterologous metabolic coupling and is accompanied by an increase in cAMP‐oo.
Seasonal changes in the concentrations of plasma gonadotropins and prolactin in wild mallard drakes
Authors: Haase Eberhard , Sharp Peter J. , Paulke Edgar 
Published: June 2005

AbstractSeasonal changes in the concentrations of plasma luteinizing hormone (LH), follicle‐stimulating hormone (FSH), and prolactin were measured in serial samples taken from seven captive wild mallard drakes exposed to natural lighting and temperature in Kiel, West Germany (54° N), for 20 months. The seasonal pattern of plasma LH levels was characterized by high titers during the reproductive phase in the spring, a steep decrease toward the end of this phase (May/June), low levels during the summer, and a second annual peak in the fall. Plasma FSH levels increased during February and March, the period of rapid testicular growth, and reached the highest values at the end of March/beginning of April. Later in the spring FSH levels decreased and remained low for the rest of the year. The concentrations of plasma prolactin increased progressively during April and May, reaching their highest values at the end of the breeding season, coinciding with the steep fall in the levels of plasma gonadotropins. Prolactin concentrations fell during July and August and were at their lowest level in the autumn. It is concluded that the development of photorefractoriness is associated with an increase in the concentrations of plasma prolactin.
Stress reduces hemolymph ecdysteroid levels in the crab: Mediation by the eyestalks
Authors: Mattson Mark P. , Spaziani Eugene 
Published: June 2005

AbstractIn decapod crustaceans, molt hormone (ecdysone) production by Y‐organs is suppressed by an eyestalk neurosecretory product, molt‐inhibiting hormone (MIH). Environmental stressors are known to delay or prevent molting in crabs. The present study assesses the function of the MIH–Y–organ neuroendocrine system in the crab Cancer antennarius under conditions of daily handling stress. After three days, stressed crabs showed significant suppression of hemolymph ecdysteroid levels, which continued to fall to 20% of controls by day 14. Ecdysteroid titers of stressed crabs returned to prestress levels seven days after stress termination. Ecdysteroid levels in de‐eyestalked (DES) crabs rose 160% within 48 hr post‐DES. Stressing DES crabs over 16 subsequent days did not significantly alter ecdysteroid levels compared with unstressed DES controls. Handling stress thus depresses hemolymph ecdysteroid levels in the crab, a response that is mediated by eyestalks and appears to result from stress‐induced MIH release.
Changes in polyamine synthesis and concentrations during chick embryo development
Authors: Löwkvist Bertil , Emanuelsson Hadar , Heby Olle 
Published: June 2005

AbstractWe have measured the activities of the two rate controlling enzymes in polyamine synthesis, L‐ornithine decarboxylase (ODC) and S‐adenosyl‐L‐methionine decarboxylase (SAMDC), and the concentrations of the polyamines, putrescine, spermidine and spermine, in the developing chick embryo from laying to hatching. The embryo exhibited major peaks in the ODC and SAMDC activities as well as in the concentrations of all three polyamines at 15 h (gastrulation), 23–30 h (early organogenesis), days 4–5 (mid‐organogenesis), and days 12–17 (organ growth and maturation). In the 4 1/2‐day‐old embryo, ODC activity and polyamine concentrations were about twice as high in the head region as compared to the trunk region. In the 14‐day‐old embryo, the highest ODC and SAMDC activities were found in lung, intestine and kidney, and there was a positive correlation between the enzyme activities and the growth rates of most organs/tissues.
Later stages of sperm penetration and second polar body and blastodisc formation in the egg of Fundulus heteroclitus
Authors: Brummett Anna Ruth , Dumont James N. , Richter Carole S. 
Published: June 2005

AbstractThis study represents a follow‐up to earlier papers in which the initial stages of sperm penetration and cortical vesicle breakdown in activated eggs of Fundulus heteroclitus were described. Light and electron microscopy were used to examine later events of fertilization, second polar body formation, and changes in animal pole cytoplasm as the embryonic blastodisc forms. Fusion of sperm and egg plasmalemmae is quickly followed by the formation of a distinctive fertilization cone which persists for only 3 to 5 minutes. The protruding sperm flagellum disappears to the inside of the egg within 10 to 15 minutes. Inside the egg cytoplasm the sperm nucleus begins to undergo chromatin decondensation and nuclear envelope fragmentation as early as 20 seconds post‐insemination. In the egg the second meiotic spindle underlies the first polar body and the second polar body begins to form within about 3 minutes post‐insemination. The animal pole cytoplasm triples or quadruples in thickness within 3 minutes after insemination. It continues to thicken to form the definitive blastodisc by 1 to 1.75 hours after insemination. Details of changes in the surface topography of the egg which accompany these events are presented.
Experimental analysis of polar body formation in starfish eggs
Authors: Rappaport R. , Rappaport Barbara N. 
Published: June 2005

AbstractIn polar body formation, a protuberance develops on the oocyte surface and subsequently separates from it by a process resembling normal cytokinesis. Protuberance formation has usually been attributed to controlled cytoplasmic outflow associated with local surface weakening. This investigation was designed to ascertain by physical manipulation more information concerning the physical mechanisms that accomplish the form changes. In unoperated Pisaster giganteus and Asterias vulgaris oocytes, unsymmetrical polar body formation was associated with failure of the mitotic apparatus to assume its normal orientation perpendicular to the oocyte surface. Needles inserted perpendicular to the plane of division straddling the mitotic apparatus can block separation of the polar body depending on the distance between them. Consequences of moving the mitotic apparatus with a needle were consistent with those in oocytes in which the mitotic apparatus was spontaneously maloriented. Shifting all or part of the mitotic apparatus resulted in polar body formation activity if the apparatus was close enough to the surface. Shifting at interphase did not affect the surface until the next meiotic cycle. Shifting during meiotic activity resulted in rapid local protuberance formation at the new site (av. 1.74 min, n=21). Increasing internal hydrostatic pressure by flattening the oocyte did not enhance cytoplasmic flow into the normal protuberance and usually caused it to recede rapidly. When oocytes were immersed in 50% seawater, the osmotic swelling did not enhance the flow of cytoplasm into the protuberance and the point of rupture showed no tendency to be localized in the polar body area. There did not appear to be a cytochalasin B resistant form change during starfish polar body formation. Extensive tears in the oocyte surface, which prompted massive cytoplasmic outflow, had no effect on the form of the nearby protuberance. Experiments indicated clear differences in response to hydrostatic pressure between normal early stages of polar body formation and similarly sized excrescences formed on the oocyte by mechanical or chemical weakening of a restricted part of the surface. They suggest that the protuberance of normal polar body formation may not result from local surface weakening.
Unusual features of sperm ultrastructure in the Musk shrew Suncus murinus
Authors: Phillips David M. , Michael Bedford J. 
Published: June 2005

AbstractThe spermatozoon of the Musk shrew Suncus murinus displays unusual fine anatomical features. In the head, the equatorial segment of the acrosome is recessed within a waist in the sperm nucleus in a way that could afford some protection for this fusogenic region, perhaps during penetration of the egg vestments. The perinuclear material has distinctive inner and outer regions, the latter being arranged as a series of coxcomblike spikes. These structures in Suncus could serve to anchor its characteristically giant acrosome to the sperm nucleus. In the tail, small aggregations of electron dense material appear against some centriolar triplets and also, proximally, against some axonemal doublets. In the midpiece, prominent satellite material aggregates proximally over the inner border of the dense fibers. More distally, the material maintains a close relationship with and primarily lies between the corresponding axonemal doublets and dense fibers 5 and 6, the latter being positioned asymmetrically in relation to the remaining dense fibers.
A new role for uric acid: Modulator of haemocyanin oxygen affinity in crustaceans
Authors: Morris S. , Bridges C. R. , Grieshaber M. K. 
Published: June 2005

AbstractUric acid enhances the oxygen affinity of some crustacean haemocyanins and can account for some of the potentiating effects due to unidentified factors in the haemolymph of the freshwater crayfish Austropotamobius pallipes. A similar effect can be elicited by an analogous purine, caffeine, which demonstrates a low specificity of haemocyanin for urate. This suggests that other haemolymph purines might produce a cumulative effect on haemocyanin oxygen affinity.
Water economy of the honeybee: A stoichiometric accounting
Authors: Louw Gideon N. , Hadley Neil F. 
Published: June 2005

AbstractUnder simulated moderate‐desert conditions (30°C, < 5% RH), isolated honeybee workers lose more water through evaporation (18.95 mg g−1 h−1) than they produce metabolically (2.39 mg g−1 h−1). At high ambient temperatures they ferry water to the hive for thermoregulatory purposes, and, in so doing, they airlift 52 mg of water, or 65% of their body mass. The extremely high metabolic demand for flight when water‐loaded (92.54 ml CO2 g−1 h−1) produces almost sufficient metabolic water (74.36 mg g−1 h−1) to balance the simultaneous evaporative water loss (79.72 mg g−1 h−1). Metabolic rate and evaporative water loss are generally positively related but remarkably independent under certain conditions of activity and high ambient temperature.
Epinephrine decreases the potassium requirements of hamster sperm capacitation: Furosemide blocks the effect of epinephrine
Authors: Bize Isabel , Santander Gabriel 
Published: June 2005

AbstractWe have investigated the possibility of an interaction between epinephrine and external potassium in the stimulation of the hamster sperm acrosome reaction and in vitro fertilizing ability. We have found that: 1) K+ is required late in capacitation and/or the acrosome reaction, but is not required for penetration of the zona pellucidae, 2) the presence of epinephrine (50 μM) in the capacitation medium lowers the K+ requirements of these processes and 3) furosemide, a cotransport inhibitor, blocks the acrosome reaction, in vitro fertilization, and inhibits the stimulation by epinephrine. These results support the idea that there is an interaction between epinephrine as a stimulus to the secretion of the acrosomal content, and K+ as a mediator of the stimulus signal. They further suggest that K+ influx through the cotransport mechanism occurs during capacitation, that this mechanism is activated late during the process, and that it probably mediates the stimulatory effects of epinephrine. We would like to propose that the activation of passive cation transport mechanisms is a general phenomenon in biological signal transduction.
Hemodynamic adjustments to head‐up posture in the partly arboreal snake, Elaphe obsoleta
Authors: Lillywhite Harvey B. , Gallagher Kim P. 
Published: June 2005

AbstractRadioactively‐labeled microspheres were used to quantify adjustments of regional blood flows in 15 snakes (Elaphe obsoleta) subjected to 45° head‐up tilt. Heart rate and peripheral vascular resistance increased during tilt to compensate for the passive drop of pressure at the head. Two snakes failed to regulate blood pressure, but in 13 others arterial pressure increased at midbody (where passive changes in pressure are unexpected due to tilt alone) and arterial pressure at the head averaged 67% of the pretilt value. Tissue blood flow was reduced significantly in visceral organs, posterior skin and posterior skeletal muscle, but was maintained at pretilt levels in brain, heart, lung and anterior tissues. Ventricular systemic output averaged 24 ml/min·kg in horizontal posture and 9.4 ml/min·kg during tilt. Comparable values for pulmonary output were 4 and 6.5 ml/min·kg. Patterns of intraventricular shunting of blood acted to maintain pulmonary flow during tilt. A large right‐to‐left shunt (mean 76%) was present in horizontal snakes, but the shunted fraction declined during tilt (mean 54%). Left‐to‐right shunt increased during tilt from 7% to 14%.
Steroid and thyroid hormone profiles following a single injection of partly purified salmon gonadotropin or GnRH analogues in male and female sea lamprey
Authors: Sower Stacia A. , Plisetskaya Erika , Gorbman Aubrey 
Published: June 2005

AbstractThe effects of exogenous administration of gonadotropin‐releasing hormone (GnRH) analogues or of a partly purified salmon gonadotropin extract (GTH) on the duration of steroid and thyroid hormone levels were determined in female and male sea lampreys, Petromyzon marinus, tested under differing temperature and reproductive status. Plasma estradiol levels, but not androgens, were significantly elevated in response to the GnRH analogues or GTH injection compared to controls in female and male lampreys. Higher temperature and/or advance in time of maturation appeared to be inversely related to plasma estradiol levels. These data provide further evidence of hypothalamic control over reproductive function in lampreys.Plasma thyroxine was significantly elevated after female lampreys were treated with GTH, GnRHa (10 μg/lamprey) or GnRHa (1 μg/lamprey) compared to controls. The present study is the first to demonstrate that the GnRH analogue stimulated in some way the pituitary‐thyroid axis. These data suggest that a GnRH activity may activate both gonado‐ and thyrotropic secretion or that the endogenous hormone may itself have both functions in one of the most primitive vertebrates, the sea lamprey.