bluuebunny/crossref_metadata_2025_split huggingface dataset:
The lack of an effect of magnesium on the uptake of amino acids by the sea urchin Strongylocentrotus purpuratus
Authors: Bellis Susan , Davis James P. , Stephens Grover C. 
Published: June 2005

AbstractThe effects of magnesium on the influx, net entry, and efflux of amino acids by larvae of the sea urchin Strongylocentrotus purpuratus were investigated. Kinetic studies revealed that the influx of alanine is not dependent on external magnesium. In addition, influx and net entry are equivalent, as determined by high performance liquid chromatography (HPLC), and are independent of ambient magnesium concentrations.
Effects of eyestalk ablation upon water relations in the American lobster, Homarus americanus
Authors: Jackson Susan A. , Bruce Marilyn J. , Chang Ernest S. , Clegg James S. 
Published: June 2005

AbstractA study of tissue and cell water content was carried out on eyestalk‐ablated (EA) and intact control juvenile lobsters (Homarus americanus). Both parameters were significantly higher in abdominal muscle and hepatopancreas from EA lobsters compared to controls. Similarly, the extracellular spaces of these tissues were larger in EA animals as were estimates of total hemolymph volume. The density and dry solids content of hemolymph from EA lobsters were less than controls, although hemolymph osmotic pressures of both groups were indistinguishable. The results are discussed in relation to other relevant studies on the effects of eyestalk ablation. Possible osmoregulatory and endocrine consequences are also considered.
Sex‐change linked growth acceleration in a coral‐reef fish, Thalassoma duperrey
Authors: Ross Robert M. 
Published: June 2005

AbstractEnvironmental factors are known to affect the growth rates of fishes through most of their adult life. In the hermaphroditic saddleback wrasse (Thalassoma duperrey), the effects of social factors on growth were studied experimentally by subjecting individuals in submerged enclosures to various social environments that induce sex change. The results showed that social factors may either stimulate or inhibit the growth of adult fish. Individuals with one or more pen mates grew better than isolated individuals. Conspecifics stimulated more growth than heterospecifics. In paired fish, larger individuals inhibited the growth of smaller individuals. Growth rates were independent of both the sex and color phase of associates. Placing a tactile barrier between fish did not alter growth rates, but a tactile—visual barrier did. Increasing the space available to a fish did not increase the growth rate. Dominance relationships based on relative size and visual stimuli best explain the results obtained. Since all fish that showed growth acceleration also changed sex, a unitary, hypothalamically mediated, causal system is suggested. From an evolutionary perspective, sex‐change linked growth acceleration may reduce the cost of changing sex by shortening the nonreproductive interim in species in which males must be large to compete successfully for multiple matings.
Subcellular distribution of carbonic anhydrase activity in the gills of the blue crab, Callinectes sapidus
Authors: Henry Raymond P. 
Published: June 2005

AbstractDifferential centrifugation and density gradient ultracentrifugation were used to separate a basal–lateral membrane fraction from the cytoplasm in the gills of the blue crab, Callinectes sapidus. For both anterior and posterior gills of animals acclimated to 35 or 12 parts per thousand salinity the basal–lateral membrane fraction of the gill possessed significant levels of carbonic anhydrase activity. Membrane‐associated carbonic anhydrase (CA) activity was uniformly distributed between anterior and posterior gills, and it was only slightly sensitive to changes in salinity. This activity was not significantly altered by freeze‐thawing or sonication, but it was virtually eliminated after treatment with detergent. Stability of CA activity stored in vitro was not influenced by the presence of reducing agents. Protein‐specific CA activity in the membrane fraction was equal to or greater than that in the cytoplasmic fraction in all cases. Cytoplasmic CA activity in the posterior gills was highly sensitive to environmental salinity, increasing over 10‐fold. These data show that, in addition to a large cytoplasmic pool of CA activity, there is also a significant amount of CA activity associated with the basal–lateral membrane. The membrane associated CA is potentially available to catalyse the dehydration of hemolymph HCO3− to CO2 and thus facilitate CO2 excretion, while the role of cytoplasmic CA in ion regulation is confirmed.
Effects of stimulants of electrogenic ion transport on cyclic AMP and cyclic GMP levels in locust rectum
Authors: Chamberlin M. E. , Phillips J. E. 
Published: June 2005

AbstractA variety of agents stimulate the chloride‐dependent short‐circuit current (Isc) across isolated locust recta. In this study, the role of cyclic nucleotides in mediating this stimulation was examined by measuring levels of cyclic AMP and cyclic GMP in tissues exposed to these agents. After bathing recta in saline, there is a decline in Isc, and this is accompanied by a fall in cellular levels of cyclic AMP and cyclic GMP. Stimulants of Isc across locust recta, corpus cardiacum (CC) extracts containing chloride transport‐stimulating hormone (CTSH) and forskolin, also elevate cellular levels of cyclic AMP. Between 5 and 10 min after addition of CC extract, there is an increase in cyclic AMP levels. During this same time period, the Isc rises at its maximal rate. The Isc remains elevated for at least another 20 min, even though tissue cyclic‐AMP levels decline rapidly by 15 min. These results suggest that stimulation of Isc is induced by a rise in cyclic AMP, but the cessation of stimulated active ion transport is controlled by other biochemical processes. In contrast to the relatively rapid rise in cyclic‐AMP levels, a 60‐min exposure to CC extract was required to elicit a rise in cyclic GMP, and therefore it may not be involved in the early stages of Isc stimulation.
Electrical responses to amputation of the eye in the mystery snail
Authors: Bever Michele Miller , Borgens Richard B. 
Published: June 2005

AbstractImmediately following amputation through the eyestalk of the mystery snail (Pomacea), a persistent ionic current enters the apical amputation surface of the eyestalk stump. The circuit is completed by current driven from undamaged integument of the eyestalk stump and other body regions. The current is relatively steady during the first 10 hours following amputation. Currents subsequently begin a slow decline to base line levels by 60 hours postamputation—a time coincident with wound healing processes. The “battery” driving this ionic current is the internally negative transepidermal potential existing across the snail integument—perhaps the result of a net inward pumping of chloride across the skin. This system is compared to other regeneration models such as the amphibian limb, bone fracture repair, and skin wound healing. We suggest that ionic current may be a control of eye regeneration in the snail.
Comparison of heterospermic and homospermic inseminations as measures of male fertility
Authors: Robl J. M. , Dziuk P. J. 
Published: June 2005

AbstractThis study attempted to determine a basis for the previously observed greater sensitivity of heterospermic tests when compared to homospermic tests for detecting differences in fertility between males. In theory, the results of heterospermic tests are an indication of the proportion of eggs fertilized per unit time whereas results of homospermic inseminations measure only the cumulative or final proportion of eggs fertilized. The fertilizing ability of sperm from males of CF1 and C57BL/6N strains of mice was compared homospermically using both relatively high and low concentrations of sperm and by measuring the proportion of eggs penetrated per unit of time. The fertilizing ability of sperm from these strains was also compared using heterospermic inseminations. When females were inseminated with a high concentration of sperm, males of both strains fertilized a high and indistinguishable percentage of eggs when examined after 30 hr. When females were inseminated with either a low concentration of sperm or when the proportion of eggs penetrated was measured at 5 hr, differences between strains of mice were distinguishable. Heterospermic insemination further magnified the observed difference between strains. The results of this study confirm that measuring the percentage of eggs fertilized per unit of time can enhance the magnitude of differences between males in fertility as compared to measuring only the final percentage of eggs fertilized. Measuring the percentage of eggs fertilized per unit of time does not, however, entirely account for the large differences observed between fertility of males when they are compared using heterospermic inseminations.
Directional cell movement during early development of the teleost Blennius pholis: I. Formation of epithelial cell clusters and their pattern and mechanism of movement
Authors: Trinkaus J. P. 
Published: June 2005

AbstractEmbryos of the teleost Blennius pholis provide exceptional material for observation of the formation and movement of cell clusters in vivo because the clusters are packed with melano‐somes and migrate beneath the transparent enveloping layer. These clusters arise from two pigmented cell masses (PCM) which appear precociously on either side of the embryonic axis at 3/5 epiboly, at the future level of somites 1 and 2. As development proceeds, each PCM enlarges and spreads on its lateral margins to form an epithelial sheet. As spreading continues, the sheet fragments, forming small cell clusters that move in a distad direction in the yolk sac. The highly motile lateral marginal cells of the spreading PCM, as well as those of the marginal cells of each moving cluster, invariably protrude highly flattened lamellipodia, which terminate in long, fine, often branched filopodia. As cell clusters leave the PCM, they form long, taut retraction fibers. The rate of spreading of both the lateral edge of the PCM and the initial phase of cluster movement, is higher (1.0 μm/min or greater) than the later rate of cluster movement, apparently because at this phase, motile activity is confined to the distal borders of each. This directional migration ceases in 24 h at 16°–18°C, when the farthest clusters have reached the ventral region of the yolk sac. By then, all clusters are spaced more or less evenly, apparently due to cessation of all cluster movement at about the same time. Once movement ceases, the clusters remain immobile for 2–4 days, depending on the temperature.
Endogenous opioid peptide system in male brown bullhead catfish, Ictalurus nebulosus lesueur: Characterization of naloxone binding and the response to naloxone during the annual reproductive cycle
Authors: Rosenblum Paul M. , Callard Ian P. 
Published: June 2005

AbstractThe endogenous opioid peptide system was investigated in male brown bullhead catfish. 3H‐naloxone binding was assessed in 20,000g membrane preparations from catfish brains. 3H‐naloxone bound to a high‐affinity, low‐capacity receptor (Kd = 0.27nM; Bmax = 119.52 fmol/mg protein) and a low‐affinity, high‐capacity receptor (Kd = 5.77 nM; Bmax = 323.06 fmol/mg protein). Binding was ligand and tissue specific. 3H‐naloxone binding was regionally distributed, with highest levels in telencephalon:preoptic area, and lower levels in remaining diencephalon, mesencephalon, and cerebellum:brain stem. A seasonal cycle in receptor number was observed, with highest numbers occurring during testicular recrudescence in association with elevated plasma androgens. In vivo naloxone treatment resulted in decreased levels of testosterone and 11‐ketotestosterone during testicular recrudescence but had no effect during the resting phase. These data indicate the presence of an endogenous opioid peptide system in brown bullhead catfish which is involved in the regulation of reproductive function in this species.
Identification of Xenopus laevis sperm and egg envelope binding components on nitrocellulose membranes
Authors: Lindsay Leann L. , Hedrick Jerry L. 
Published: June 2005

AbstractInteracting egg envelope and sperm surface components were identified for Xenopus laevis using blotting methods. Sperm were extracted with sodium dodecyl sulfate (SDS), the extracted proteins separated by gel electrophoresis and blotted, and the blots treated with 125I‐labeled heat solubilized envelopes. The converse experiment was also performed where envelope components were separated by gel electrophoresis, blotted, and the blots treated with 125I‐labeled sperm components. Blotted sperm components with apparent molecular weights of 14K, 19K, 25K, and 35K selectively bound the solubilized envelopes. All of the envelope binding components were found to be localized on the sperm surface by radioiodinating intact sperm using lodo‐Gen. The blotted egg envelope component with an apparent molecular weight of 37K selectively bound to solubilized sperm components, and this binding was due to the protein moiety of the glycoprotein. 125I‐labeled heat solubilized envelopes from unfertilized and fertilized eggs showed the same pattern of binding to blotted sperm components. Selected sulfated carbohydrates (fucoidan, dextran sulfate, and heparin, but not chon‐ droitin sulfate) inhibited fertilization and binding of 125I‐labeled heat solubilized envelopes to blotted sperm extract. Thus, the binding of heat solubilized envelopes to electrophoretically separated and blotted sperm proteins may reflect cellular interactions.
Oogenesis in Fundulus heteroclitus. V. The relationship of yolk vesicles and cortical alveoli
Authors: Selman Kelly , Wallace Robin A. , Barr Valarie 
Published: June 2005

AbstractYolk vesicles, which first appear in small oocytes, are morphologically indistinguishable from cortical alveoli, which are present in eggs. Both types of membrane‐limited vesicles show identical staining properties with both classical dyes for acidic glycoproteins and with fluorescein‐labeled lectins for specific carbohydrate moieties. Lectin (Dolichos biflorus agglutinin)‐affinity chromatography was used to isolate from yolk vesicle‐stage follicles a > 200‐kilodalton (kDa) glycoconjugate that had been shown previously to be synthesized within the oocyte and to reside within yolk vesicles. Antiserum was prepared against the > 200‐kDa glycoconjugate and was used on immunoblots to demonstrate the presence of a substance both in yolk vesicle‐stage follicles and eggs that was immunoreactive. Indirect immunolabeling of plastic sections of various size follicles and eggs demonstrated that the antibody reacted with a substance found only in yolk vesicles and cortical alveoli. Thus, a combination of approaches (morphological, biochemical, and immunological) have been used to confirm the earlier cytological observations that suggested that yolk vesicles of small oocytes give rise to cortical alveoli of eggs. We suggest, therefore, that the term “yolk vesicle” is a misnomer since these structures, when mature, ultimately release their contents into the perivitelline space at fertilization, rather than serve as a source of nutrients for the embryo.
In vitro differentiation of male germ line cells from sea urchin testis
Authors: Poccia Dominic 
Published: June 2005

AbstractFragments of sea urchin testicular tissue were cultured at 15°C in serum‐supplemented seawater for 5 weeks. Cells whose DNA had been pulse‐labelled with 3H‐thymidine at the beginning of the experiment were followed by autoradiography, and counts were made of the proportions of each male germ‐line cell type from sections of tissue at several time points. Differentiation of spermatogonia to mid‐spermatids occurred within the first 10 days, with a decline of about 40% in the total number of spermatogonia and an increase of 250% in the number of mid‐spermatids. Thereafter, no changes occurred in the proportions of germ‐line cells, although tissue integrity was maintained throughout. The results indicate that sea urchin male germ‐line cells can complete meiosis and the first stages of spermiogenesis including nuclear condensation and cytoplasmic reduction in culture with kinetics similar to those in vivo. The system should permit analysis of factors responsible for male germ‐cell differentiation.
In vitro effects of calmodulin antagonists on macrophage function in the posterior necrotic zone of the chick wing
Authors: Brewton Randolph G. , MacCabe Jeffrey A. 
Published: June 2005

AbstractExcised tissues from the prospective posterior necrotic zone (pPNZ) of the stage 21 chick wing were cultured in the presence of the calmodulin antagonists/protein kinase C inhibitors trifluoperazine (TFP) or chlorpromazine (CPZ). The appearance of cell death in vitro was not affected by the drugs. Macrophages differentiated normally and were competent to engulf debris. Lysosomal fusion with phagosomes and the digestion of most debris also occured in the presence of the drugs. However, the macrophages were unable to process internalized cell membranes properly and continued accumulating membrane until they were grossly distended. The effect was reversible upon removal of the drugs. The results suggest a role for calmodulin and/or protein kinase C in the proper recycling of internalized membrane in embryonic macrophages.
Do ascidians possess the ancestral subunit type of vertebrate lactate dehydrogenase?
Authors: Baldwin J. , Mortimer K. , Patak A. 
Published: June 2005

AbstractThe tetrameric lactate dehydrogenases (LDH) of vertebrates contain three major subunit types, A, B, and C, that are assumed to have arisen by gene duplication. Ammo acid sequence comparisons imply that the A‐B duplication occurred among the lower chordates and that the duplication separating the C subunit from the A and B subunits is even older. In this evolutionary scheme, which conflicts with earlier interpretations, the C subunit of modern vertebrates resembles most closely the ancestral subunit type of vertebrate LDH.Lactate dehydrogenase was purified from the ascidian Pyura stolonifera, subphylum Urochordata. The enzyme occurs as a single L‐lactate specific homotetramer with a molecular weight of about 39,000, and with kinetic properties that resemble the LDHA4 isozymes of higher vertebrates. Amino acid compositional analysis and immunochemical titration of LDH activity provide strong evidence that the single ascidian LDH subunit is more closely related to the teleost C than to the teleost A or B subunits. In addition, immunochemical comparisons demonstrate affinities with hagfish LDHB4. It is suggested that the ascidian and teleost C subunits represent the ancestral subunit type of vertebrate LDH and that the lamprey subunit and the hagfish B subunit may be related more closely to this ancestral subunit than to the A and B subunits of gnathostomes.
Sources of calcium and phosphorus during embryogenesis in bullsnakes (Pituophis melanoleucus)
Authors: Packard Mary J. , Packard Gary C. 
Published: June 2005

AbstractThe yolk of eggs of bullsnakes (Pituophis melanoleucus) contains an average of 88 mg of calcium and 23 mg of phosphorus at oviposition. Calcium and phosphorus in yolk decline dramatically during the growth phase of development, and residual yolk removed from hatchlings contains only 3 mg of calcium and 1 mg of phosphorus. Thus, bullsnake embryos deplete the yolk of virtually all of its calcium and phosphorus, and residual yolk does not contain sufficient quantities of these ions to support significant posthatching growth. Calcium and phosphorus in embryos increase during incubation, and carcasses of hatchlings contain an average of 113 mg of calcium and 21 mg of phosphorus. Total calcium content (calcium in yolk plus calcium in carcass) of eggs increases significantly from 88 mg at oviposition to 116 mg at the end of incubation, but total phosphorus content of eggs does not vary significantly. Embryonic bullsnakes obtain about 24% of their calcium from the eggshell but rely on the yolk for all of their phosphorus. Bullsnake embryos seemingly mobilize considerably more calcium than is required for skeletogenesis. This excess calcium may be stored in endolymphatic sacs, but the functional significance of such deposits is unknown.
Stability of the glandular morphogenesis produced by retinoids in the newborn hamster cheek pouch in vitro
Authors: Covant H. A. , Hardy Margaret H. 
Published: June 2005

AbstractRetinoids can induce alterations in differentiation and morphogenesis in the hamster cheek pouch. In order to determine the stability of these changes, explants of neonatal pouch were exposed to 6 μg/ml of either retinyl acetate (RAc: 1.8 × 10−5 M) or all‐trans retinoic acid (RA: 2.0 × 10−5 M) for an initial 3 of 7 days, out of a total of 21 days in organ culture. Three days of RAc or RA caused a delay in the differentiation and keratinization of the epithelium at least up to day 7 of culture. Additionally, two out often explants exposed to RA showed small downgrowths of epithelium into the stroma at 7 or 14 days. Seven days of exposure to either retinoid led to inhibition of epithelial keratinization, and produced a mucous metaplasia which was still seen at the end of the 21‐day culture period. Periodic acid‐Schiff (PAS)–positive, diastase‐resistant material was present in the metaplastic epithelium, in intercellular, and in some instances, intracellular locations. An excess of either RAc or RA, for 7 days, induced persistent glandlike downgrowths of epithelium, suggesting that a stable alteration in the developmental program of the epithelium may have occurred. Many of these downgrowths possessed a lumen which was lined by cuboidal epithelium and contained PAS‐ positive, diastase‐resistant secretory material. RA appeared more potent than RAc in inhibiting keratinization, in producing a mucous metaplasia, and in initiating glandlike downgrowths. The persistence of glandular downgrowths suggests that retinoids, either directly or indirectly, act in a manner similar to that of an embryonic inductor.