bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma hormones (arginine vasotocin, prolactin, aldosterone, and corticosterone) in relation to hydration state, NaCl intake, and egg laying in fowls
Authors: Arad Zeev , Skadhauge Erik
Published: June 2005

This review surveys our latest research dealing with the involvement of arginine vasotocin (AVT), the avian antidiuretic hormone, and other hormones in the regulation of water and salt balance in fowl. We examined the effect of dehydration, salt loading, high‐ and low‐salt diets, and oviposition on plasma hormone levels and analyzed them in light of our knowledge of avian osmoregulatory responses to changes in water and salt balance. Gradual dehydration and hyperosmotic loading in domestic fowl revealed consistent differences in the AVT response between groups adapted to low‐ and high‐NaCl diets. In birds on a low‐NaCl diet the sensitivity of the AVT release was significantly higher than in birds on a high‐NaCl diet. These results support the concept that the link between osmotic and volume regulation is established via varying sensitivity of the AVT release. We determined the half‐life of the AVT in fowls (6.3 min), a value similar to that of ADH in mammals. We found that during oviposition, plasma AVT increases by a factor of four over the normal level, a magnitude consistent with the maximal responses revealed in osmotic stimulations. We have shown that as long as drinking water is available, heat exposure has no effect on the plasma osmotic constituents and the regulatory hormones. However, combined dehydration and heat exposure resulted in pronounced osmoregulatory responses integrated with the thermoregulatory responses to maintain water and salt balance without jeopardizing the birds' ability to cope with the thermoregulatory demands. We now have ample evidence that AVT does not release prolactin from the pituitary and that probably hyperosmolality (or high sodium) as such releases prolactin.
Endocrine regulation of avian renal function
Authors: Braun Eldon J. , Dantzler William H.
Published: June 2005

The avian kidney contains reptilian‐type (RT) nephrons that do not function in concert and mammalian‐type (MT) nephrons that do function in concert to permit production of concentrated urine. Significant data on endocrine regulation of renal function are available only for antidiuretic hormone (arginine vasotocin, AVT) and parathyroid hormone (PTH). Plasma AVT increases and number of filtering RT nephrons decrease when plasma osmolality increases. Small doses of AVT reduce the number of filtering RT nephrons, and all RT nephrons filter following acute neurohypophysectomy. In addition to changing tubule permeability to water, AVT affects the concentrating mechanism by reducing the number of filtering RT nephrons and flow through collecting ducts. Both net tubular reabsorption and net tubular secretion of PO4 occur. Parathyroidectomy (PTX) stimulates PO4 reabsorption, and PTH replacement decreases reabsorption and stimulates secretion, apparently in proximal tubules of RT nephrons. PTX stimulates and PTH replacement inhibits Na‐dependent PO4 transport by renal brush border membrane vesicles. PTH also stimulates Ca2+ reabsorption but apparently not along the proximal tubule of RT nephrons.
Antidiuretic effect of [Sar1, Val5, Ala8] angiotensin II in Lophius americanus
Authors: Churchill Paul , Malvin Richard , Churchill Monique , Beasley Debbie , Shier David
Published: June 2005

We have reported previously that angiotensin II increases urine flow and Na and K excretion rates in the aglomerular goosefish Lophius americanus. The present experiments were undertaken to determine if antagonism of endogenous angiotensin has the opposite renal effects. Arterial blood pressure, urine flow, and plasma and urine electrolytes were measured during two consecutive clearance periods in two groups of goosefish. The control group (n = 7) received saline intravenously during both periods; the experimental group (n = 8) received saline during the first period and a competitive antagonist of angiotensin II (saralasin, or [Sar1, Val5, Ala8] angiotension II) dissolved in saline during the second period. The control group exhibited no significant change over time in any of the measured variables: arterial blood pressure; plasma [Na], [K], [Mg], [Ca]; osmolality; urine flow; and excretion rates of Na, K, Ca, and Mg. Arterial blood pressure and plasma electrolytes and osmolality were stable over time in the experimental group also. However, during saralasin infusion there were significant decreases in urine flow and in excretion rates of K, Mg, and Ca. Taken together with our previous results, these observations suggest that endogenous levels of angiotensin in goosefish are sufficient to have direct renal effects. The mechanisms of action of angiotensin are not clear, but involve neither changes in systemic blood pressure nor filtration but might involve inhibitory effects of angiotensin on tubular reabsorptive processes.
Temporal variations in gonadal and body fat responses to daily injections of 5‐hydroxytryptophan (5‐HTP) and dihydroxyphenylalanine (DOPA) in the gulf killifish, Fundulus grandis
Authors: Emata Arnil C. , Meier Albert H. , Spieler Richard E.
Published: June 2005

Daily injections of dihydroxyphenylalanine (DOPA), a dopamine precursor, stimulate large increases in reproductive and body fat indices in gulf killifish, Fundulus grandis, when given 20 hours after daily injections of 5‐hydroxytryptophan (5‐HTP), a serotonin precursor. However, DOPA injections are inhibitory when given 8 hours after 5‐HTP. The drug effects persist for at least 3 weeks following drug treatment indicating a possible resetting of an endogenous mechanism involved in seasonality.
Structural and functional development of cricket wing muscles
Authors: Ready Neal E. , Najm Ramzi E.
Published: June 2005

The sizes of the unifunctional dorsal longitudinal (DLM) and bifunctional subalar (Sa) metathoracic flight muscles of the cricket Teleogryllus oceanicus increase by more than an order of magnitude between the second instar before the terminal molt and the tenth day of adult life. During the same developmental period isometric twitch duration (onset to 50% relaxation, 25°C) varies little, while muscle mitochondrial content increased by a factor of ten as measured by stereological analysis of electron micrographs and citrate synthase activity (μmoles citrate·min−1· gm protein−1, 25°C). The wing muscles of adults have abundant sarcoplasmic reticulum (SR), narrow myofibrils, and a high volume density of mitochondria. At two molts from adulthood muscles that will later be used in flight behavior also have narrow myofibrils and abundant SR, but unlike muscles at later stages, nymphal muscles have a low volume density of mitochondria. At the terminal molt muscles have at least as much SR as is seen in muscles at the tenth day of adult life, and the myofibrils are also more narrow at the earlier stage. Since there is significant variation in muscle structure and little change in twitch duration during late development, the efficacy of the SR in releasing and resequestering CA2+ is seemingly lower in muscles at the terminal molt, a time of rapid muscle growth.
Functional connections are established between giant nerve fibers in grafted earthworms
Authors: Vining Elizabeth P. , Drewes Charles D.
Published: June 2005

Giant fiber interconnections were examined in successful grafts between two posterior portions of earthworms (Eisenia foetida). Electrophysiological and histological results indicated that cell‐specific interanimal connections were formed between the medial giant fibers (MGF) in these preparations. Similar interconnections were formed between the paired lateral giant fibers (LGF), except that these involved the apposed left and right LGFs. Establishment of reliable and bidirectional conduction of LGF and MGF spikes across the graft occurred 2–4 days and 7–14 days after grafting, respectively. Subsequently, conduction across the graft remained effective for at least 6 weeks. These results are consistent with a hypothesis that grafted giant fibers are joined by a direct electrical connection, involving either fusion or an electrical synapse.
Pregnancy diagnosis by vaginal lavage in deer mice, Peromyscus maniculatus
Authors: Paull Judith A. , Fairbrother Anne
Published: June 2005

We developed a method for diagnosing pregnancy in the deer mouse (Peromyscus maniculatus) using vaginal lavage. We first clearly defined stages of the estrous cycle by using the ratio of the cell types observed. The distribution of cells found in vaginal smears prepared from visibly pregnant females matched the cell ratio of the metestrous stage. Two females were monitored through consecutive pregnancies; no significant variation of the cell types from the metestrous cell ratio was observed. We tested the accuracy of this predictive method using 67 breeding females. Because the vaginal smear of a pregnant mouse is indistinguishable from the smear of a mouse in cyclic metestrus, we lavaged mice twice at a 2‐day interval to eliminate false positives (mice in cyclic metestrus). We obtained an 86.6% accuracy rate and concluded that the method can predict pregnancy in deer mice.
Respiratory properties of the haemolymph of the intertidal prawn Palaemon elegans (Rathke)
Authors: Morris S. , Taylor A. C. , Bridges C. R. , Grieshaber M. K.
Published: June 2005

The properties of the haemolymph of Palaemon elegans for oxygen and carbon dioxide transport were studied with respect to the considerable fluctuation in the environmental conditions normally experienced by this prawn in intertidal rock pools. The haemolymph was found to have a high oxygen affinity (P50 = 3.6 Torr, 15°C, pH 8.0) and a large oxygen carrying capacity (1.17 mmol.L−1), as well as a marked Bohr shift (φ = ‐ 1.7). Under some conditions, the affinity appeared to be independent of temperature as did the n50 value (n50 = 2.8). Experiments in which the pH of the haemolymph was varied using fixed acid together with two different CO2 tensions demonstrated a specific CO2 effect on O2 affinity, which did not affect the Bohr factor. The nonbicarbonate buffer value of the haemolymph was found to be high (16.02 mmol.L−1.pH unit−1). The in vivo postbranchial haemolymph pH at 15°C was 7.89 with a calculated Pco2 of 1.26 Torr. A large functional Haldane coefficient was observed (1.25), which was only moderately temperature dependent. The haemolymph exhibited an extremely high capacitance for CO2 at low Pco2 values (βCO2 = 8.4 mmol.L−1.Torr−1). Some functional implications of linkage between the large Bohr and Haldane effects are discussed in light of present knowledge.
Salinity‐induced changes in gill Na, K‐ATPase activity in the mud fiddler crab, Uca pugnax
Authors: Holliday Charles W.
Published: June 2005

Male mud fiddler crabs (Uca pugnax) were shown to hyperosmoregulate in 10% and 50% seawater (SW) and to hypoosmoregulate in 150% and 200% SW. Crabs fully immersed in the media did not osmoregulate as well as those that were free to enter or leave the medium at will (“natural” environment). Gill sodium‐plus‐potassium ATPase (Na,K‐ATPase) enzyme specific activity was characterized in crude homogenates. After acclimation (21 days) in 10% SW, all six gill pairs in immersed crabs showed significantly higher enzyme specific activity (ESA) than 100% SW controls; crabs in 50% SW had significantly higher ESA in gills 3 through 6. With one exception, a decrease, acclimation to 150% or 200% SW did not significantly change gill ESA in immersed crabs. In all media, gills 5 and 6 had approximately 75% of the total ESA in the crabs' gills. Crabs in the “natural” environment showed a similar pattern of changes in gill ESA. Thus, changes in gill ESA appear to be important only in hyperosmotic regulation and in active sodium uptake by the gills from dilute media. The time‐course of changes in crude homogenate ESA in gills 5 and 6, after transfer of 100% SW crabs to 10% SW, was relatively rapid (significantly increased after 1 day) and correlated well with changes in hemolymph osmolality. Three different microsomal preparations from gills 5 and 6 did not show significantly increased ESA until between 3 and 7 days after transfer. Therefore, gill Na,K‐ATPase activity may be altered both by rapid modulation of existing enzyme and by longer term synthesis of new enzyme.
Commitment to sexual and asexual phases in Paramecium multimicronucleatum
Authors: Shimomura Fumiyo , Takagi Yoshiomi
Published: June 2005

Sexually mature cells of Paramecium multimicronucleatum, syngen 2, which have been starved 1 day, can be artificially controlled to select either the sexual phase or the asexual phase by putting them either in autogamy‐inducing medium (AIM) or in culture medium (CM). Simultaneous treatment with AIM and CM was found to bring the cells into the sexual phase. When cells were first treated with AIM for T hr and then with CM, they all reverted to the asexual phase if T ≦ 1.5 hr; they were increasingly determined to undergo nuclear activation with the increase of T; and virtually all of them were determined if T ≧ 2.5 hr. Cells lost their capacity to feed and divide with the same kinetics. It was demonstrated by using the same single cells that there was a complete correspondence between the final loss of capacity to feed and nuclear activation, and between nuclear activation and the loss of capacity to divide. When cells were first treated with CM for t hr and then with AIM, they could be pulled back to the sexual phase if t < 2 hr, with decreasing possibility with time. Within this time interval, longer pretreatment of CM required longer posttreatment of AIM to set the competent cells back to the sexual phase. Incubation in CM for t ≧ 2 hr made all of the cells insensitive to AIM, while incubation in CM for at least 4 hr was necessary to let them actually pass through the asexual phase.
Cross‐phyletic bioactivity of arthropod neurohormones and molluscan ganglion extracts: Evidence of an extended peptide family
Authors: Greenberg M. J. , Rao K. R. , Lehman H. K. , Price D. A. , Doble K. E.
Published: June 2005

Two structurally related arthropod neuropeptides, red pigment concentrating hormone (RPCH) and adipokinetic hormone (AKH), are potent excitors of the heart of the clam Mercenaria mercenaria. The response is bimodal: whereas the threshold for affected hearts is 1–3 × 10−9 M, about 40% of the preparations are virtually unresponsive. Aqueous extracts of Mercenaria ganglia contain a substance which concentrates the red pigment in the erythrophores of intact destalked Uca pugilator and even of its isolated legs. This substance is retained on Sephadex G‐15 and co‐elutes with synthetic shrimp RPCH. The active fractions also concentrate the erythrophores and the leucophores of destalked shrimp (Penaeus). Neither dopamine nor the molluscan neuropeptide FMRFamide had any chromatophorotropic effect in these assays. The activity of the ganglion extracts was abolished by digestion with chymotrypsin. In conclusion, molluscan ganglion extracts contain a peptide factor, possibly an analog of RPCH, that concentrates the pigments of crustacean chromatophores by a direct action on the cells.
Growth and aging in the rat: Changes in total protein, cellularity, and polyploidy in various organs
Authors: Bohman R. , Tamura C. T. , Doolittle M. H. , Cascarano J.
Published: June 2005

The objectives of this study were to determine the influence of growth and aging on ploidy, cell number, and protein content of various organs. Tissue homogenates were prepared at 3, 8, 25, 50, and 100 weeks of age. Samples were analyzed for DNA per nucleus (by flow cytofluorometry), nuclei number, and protein content. Livers of 8‐ and 100‐week‐old animals were also perfused with collagenase and the released cells separated into parenchymal and nonparenchymal populations by unit gravity sedimentation. Nuclei of these cells were also analyzed for DNA. In all four zones of the kidney and in thyroid, 4n nuclei diminished in percentage between 3 and 50 weeks and increased at 100 weeks. In the growth phase these probably are cycling cells and after 50 weeks represent an increasing population of nuclei arrested after synthesis of DNA. Constant levels of ploidy were found in brain, heart, rectus abdominis, and adrenal throughout the 3–100 weeks. A dramatic increase in 4n nuclei occurred between 3 and 8 weeks in liver with little change occurring thereafter. Ploidy is a property of only parenchymal cells in liver and this probably is also true in other organs. The 4n nuclei that remain in constant proportion to the total population are established early in life and are not related to aging. They are probably tetraploid and replicate into 4n daughter cells during growth. Cerebrum shows no changes in nuclei number but exhibits a 70% increase in protein between 3 and 100 weeks. Although kidney, liver and adrenal show large increases in number of nuclei (≈ fourfold) with growth, these are not as great as increases in body weight (≈ 11‐fold). With regard to organ protein, only liver shows increases approximating those in body weight. Increases in organ nuclei appear to occur in concert for adrenal, kidney, and liver whereas increases in organ protein bear no relationship to each other. Protein content remains at stable levels in organs of 100‐week‐old animals and little (adrenal, liver) or no (brain, kidney) diminution occurs in nuclei numbers.
Isolation of intact sperm asters from fertilized sea urchin eggs
Authors: Hinkley Robert E. , Wright Brent D.
Published: June 2005

We have developed a procedure for isolating intact sperm asters in quantity from fertilized sea urchin eggs. This procedure is based on detergent‐extraction methods developed previously for the bulk isolation of mitotic apparatuses. Using this protocol it is possible to isolate sperm asters as soon as they appear in the fertilized egg or at any subsequent point in their brief existence.
Lack of renal effects of DOCA, ACTH, spironolactone, and angiotensin II in Squalus acanthias
Authors: Churchill Paul C. , Malvin Richard L. , Churchill Monique C.
Published: June 2005

Angiotensin II was infused intravenously in spiny dogfish sharks (Squalus acanthias). There were no significant effects on arterial blood pressure, glomerular filtration rate, urine flow, or Na excretion either in comparison with pre‐ and postinfusion values or in comparison with values measured in a control group of fish given elasmobranch saline intravenously. In other dogfish, glomerular filtration rate, urine flow, and Na and K excretory rates were measured for 3 days following implantation of desoxycorticosterone (DOCA), adrenocorticotropin (ACTH), or spironolactone; a control group was given no drug. There were no significant differences between these four groups of fish with respect to any of the measured parameters. These results suggest that the dogfish kidney is not a target organ for several substances known to affect renal function, either directly or indirectly, in other animals.
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

Previous 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

Double‐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

Salinity 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

Representative 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

The 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

Seasonal 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

In 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

We 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

This 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

In 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

The 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

Uric 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

Under 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

We 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

Radioactively‐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

The 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.
The effects of diet on growth and reproduction in gray short‐tailed opossums (Monodelphis domestica)
Authors: Cothran E. Gus , Aivaliotis M. J. , Vandeberg J. L.
Published: June 2005

In order to develop standard conditions for rearing the gray short‐tailed opossum, Monodelphis domestica, as a potentially useful experimental laboratory animal, the effects of four different diets on growth and reproduction were assessed. One diet was a meat‐based diet prepared in the laboratory. The other three diets were commercially produced fox foods designated Reproduction diet, Lactation diet, and Growing and Furring diet. All pairs of M. domestica fed the Reproduction diet produced at least one litter, but only two‐thirds or fewer of the pairs fed any of the other three diets reproduced. There were no significant differences in the number of young born per litter or the number of young weaned per litter among the diets. Weight at weaning was significantly lower for individuals on the meat‐based diet compared to those on the fox food diets. Young on the meat‐based diet suffered 50% mortality within 6 weeks after weaning, whereas none of the animals fed the fox food diets died within the same 6‐week period.

Age‐weight data were described using the Bertalanffy growth function. In terms of growth and overall reproductive performance, the fox food diets were clearly superior to the meat‐based diet, and the Reproduction diet was judged to be the best of the fox food diets tested. Growth curves, from birth to 550 days of age, of individuals fed the Reproduction diet were developed and can be used as standards for the species under laboratory conditions. The maximal weights attained by animals fed the fox food diets were similar to the weights of the wild‐caught founders of the laboratory population, indicating that the fox food diets provide adequate nutrition for normal growth. An additional observation was that females housed singly past the normal age of sexual maturity attained significantly lower adult weights than did females that were paired with males at 6 months of age.
Effects of environmental salinity on intercellular organization and junctional structure of chloride cells in early stages of teleost development
Authors: Hwang Pung Pung , Hirano Reijiro
Published: June 2005

Morphology of chloride cells was studied in embryos, larvae and juveniles of ayu (Plecoglossus altivelis), carp (Cyprinus carpio) and flounder (Kareius bicoloratus). Chloride cells of seawater‐adapted fishes interdigitated to neighboring cells and linked each other with leaky junctions. No such interdigitation or a leaky junction was found in those of freshwater fishes. Larval ayu were able to tolerate direct transfer from fresh water to seawater even immediately after hatching. Juvenile flounder reared in seawater for 60 days were able to adapt to fresh water. Their chloride cells started developing or degenerating interdigitations and leaky junctions within 3 h after the transfer. Juvenile ayu of landlocked form caught in Lake Biwa survived in seawater for no longer than 6 h. Juvenile carp died within 12 h after transfer to 15%. seawater. Newly hatched flounder did not survive in fresh water for longer than 48 h. Their chloride cells did not show any morphological change, although the epithelial cells were severely damaged. Thus, the ability of chloride cells to modify their intercellular organization and junctional structure appears to play a critical role in salinity adaptation.
Action of polyvalent cations on sodium transport across skin of larval and adult Rana catesbeiana
Authors: Alvarado Ronald H. , Cox Thomas C.
Published: June 2005

The actions of alkaline earth (AE) and transition element (TE) cations on Na+ transport across skin of larval and adult Rana catesbeiana were compared. Bathed on the outside by Ca+2‐free Ringer's, both larval and adult skins maintained a stable short‐circuit current (3–4 μAmps cm−2 for larval skin and 20–30 μAmps cm−2 for adult skin). Addition of Ca+2 to the external bath reduced the SCC; maximal inhibition was about 36% for larval skin and 22% for adult skin. Other AE divalent cations were also inhibitory. The order of effectiveness was: Ba+2 = Ca+2 > Sr+2 > Mg+2 for larval skin and Ba+2 > Ca+2 = Mg+2 for adult skin. Sodium influx was markedly elevated when Ca+2 was removed from the external medium. Current‐voltage analysis indicated that Ca+2 increases the resistance of the active pathway without affecting the shunt resistance or the electromotive force of Na+ transport (ENa) in larval and adult skins.

The SCC across adult skin was stimulated by TE cations (Co+2, Cd+2, La+3). These ions were inhibitory on larval skin. The transition in the response occurred at stage XXI. The inhibitory effect of TE on larvel skin resembles that seen in response to AE cations and we postulate a common mechanism. Since larval skin lacks the selective Na+ channels found in apical membranes of adult skin, we infer that the mechanism of inhibition by AE cations is not on these channels. A more general phenomenon such as change in surface charge at the apical membrane seems more reasonable. The stimulatory action of TE cations in adult skin is discussed in terms of interference with the Na+‐self‐inhibition response. Apparently, larval skin lacks some component of the molecular mechanism underlying this response.
The Limulus sperm motility‐initiating peptide initiates acrosome reactions in sea water lacking potassium
Authors: Clapper David L. , Epel David
Published: June 2005

During fertilization in Limulus, the spermatozoa first attach to the egg and then undergo an acrosomal reaction. In this reaction, the acrosomal vesicle exocytoses, and a long, preformed acrosomal filament is extruded (and subsequently penetrates the egg chorion). The egg surface component that triggers the acrosome reaction has not yet been solubilized; therefore, previous studies have examined either spontaneous acrosome reactions or acrosome reactions that were triggered by eggs (or insoluble egg fragments), elevated extracellular Ca2+, or Ca2+ ionophores. In this study, we report a new method for initiating acrosome reactions in Limulus sperm. When the Limulus sperm motility‐initiating peptide (SMI) is added to sperm in K+‐free sea water, greater than 90% acrosome reactions are initiated within 5 min. However, less than 5% acrosome reactions occur either in K+‐free sea water lacking SMI or when SMI is added to sperm in either normal sea water or K+‐and Ca2+‐free sea water. Experiments with K+ ionophores (nigericin and valinomycin), a K+ channel blocking agent (tetraethyl ammonium), an Na+ ionophore (monensin), and reagents that increase the intracellular pH (monensin, nigericin, and NH4Cl) indicate that changes in intracellular K+, Na+, or H+ do not mediate SMI‐initiated acrosome reactions. The K+/Ca2+ ratio determines whether or not SMI will initiate acrosome reactions, with > 50% acrosome reactions being initiated when this ratio is below 0.3. In that K+ movement does not appear to be the critical event, possibly the K+/Ca2+ ratio either determines the rate of Ca2+ entry or controls the conformation of sperm surface molecules to allow SMI to initiate acrosome reactions in low K+.