bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rana ridibunda varies geographically in inducing clonal gametogenesis in interspecies hybrids
Authors: Hotz Hansjürg , Mancino Giorgio , Bucciinnocenti Stefania , Ragghianti Matilde , Berger Leszek , Uzzell Thomas 
Published: June 2005

AbstractDiploid F1 hybrids between Rana ridibunda from Adriatic SW Yugoslavia and Polish R. lessonae, and between Polish R. ridibunda and an unnamed species from SW Yugoslavia are shown by electrophoresis and examination of lampbrush chromosomes to contain both parental genomes in their diploid oocytes I. In contrast, central European R. ridibunda genomes in diploid hybrids, whether F1s or from natural hemiclonal lineages, induce exclusion of the lessonae genome in the germ line, only ridibunda translation products and endoreduplicated ridibunda chromosomes being detected in their diploid oocytes I. The data demonstrate geographic variation of R. ridibunda in the ability of its genomes to induce clonal gametogenesis in interspecies hybrids. They also suggest that genomes of the unnamed Yugoslavian species may be resistant to such exclusion.
Dichotomous effects of forskolin on somatic and germ cell components of the ovarian follicle: Evidence of cAMP involvement in steroid production and action
Authors: Kwon Hyuk B. , Schuetz A. W. 
Published: June 2005

AbstractThe role of cyclic AMP (cAMP) in ovarian follicular functions in Rana pipiens was investigated with the use of the adenylate cyclase stimulator, forskolin, which is thought to elevate intracellular level of cAMP. Effects offorskolin on oocyte germinal vesicle breakdown (GVBD) and on progesterone production by the follicles were assessed during the course of in vitro culture. Addition of forskolin to culture medium suppressed both progesterone‐and frog pituitary homogenate (FPH)‐induced meiotic maturation of the oocytes. Inhibitory effects of forskolin were essentially reversible and forskolin completely inhibited GVBD when added during the first four hours of incubation following exposure to progesterone. Forskolin alone stimulated a low level progesterone production by isolated follicles, but markedly stimulated progesterone production when it was supplemented with a low dose of FPH (0.005 pituitary equivalent/ml). Thus, forskolin acts synergistically with FPH on follicle cells to stimulate progesterone production. A higher dose of FPH (0.05 pitui. eq./ml) produced no additional synergistic effect of forskolin. Therefore, forskolin appears to have two contradictory functions in ovarian follicles: it augments FPH induced follicle secretion of meiosis initiator, progesterone, and simultaneously suppresses the maturation of the oocytes triggered by exogenous progesterone or FPH.The data presented indicate that there are two independent adenylate cyclase systems in the ovarian follicles which have separate functions: one in the follicle cells and the other in the oocyte. The two enzyme systems are thus compartmentalized and regulate different biological functions using the same messenger, cAMP. The data provide evidence that in amphibians, as in mammals, pituitary hormones regulate steroid hormone production by follicle cells via a cyclic AMP system. Thus, control of oocyte maturation induction appears to be determined by the relative levels of cAMP present in the follicle cells and oocytes.
Luminal and basolateral surface membranes of secretory acinar cells: Electrophysiological comparison of cationic sensitivities
Authors: Senseman D. M. , Horwitz I. S. , Cleemann L. , Orkand P. M. 
Published: June 2005

AbstractCation sensitivities (K+, Na+, and Ca2+) of luminal and basolateral membrane surfaces of secretory acinar cells were compared using a luminally perfused and externally superfused salivary gland from the aquatic snail, Helisoma trivolvis. Tight junctions delimiting the two membrane surfaces were observed near the acinar lumen suggesting that the total membrane area exposed to the superfusion solution exceeded that in contact with the luminal perfusion solution.The resting membrane potential of acinar cells was found to be dependent upon the K+ concentration in both the external superfusion and the luminal perfusion solutions. Unilateral K+ elevation at either membrane surface produced a rapid and sustained depolarization of the acinar cell. For a given K+ concentration, the level of depolarization produced by K+ elevation at the basolateral surface was significantly higher than at the luminal surface. The highest level of membrane depolarization was observed following simultaneous K+ elevation at both membrane surfaces.The ability of acinar cells to generate overshooting action potentials in response to electrical field stimulation was dependent upon both Na+ and Ca2+. Complete blockade invariably occurred following bilateral removal of either cation. The effects of unilateral removal of either Na+ or Ca2+ proved to be somewhat variable. In general, unilateral removal of Na+ was more effective in reducing the regenerative response than Ca2+ while removal of either cation from the basolateral surface was more effective in reducing the regenerative response than its removal from the luminal surface.Electrically evoked action potentials in acinar cells could also be blocked with unilateral application of the Ca2+ antagonist, cadmium (Cd2+), at either membrane surface. However, higher Cd2+ concentrations were required to achieve complete blockade when applied to the luminal than to the basolateral gland surface. This result fails to support a hypothesis of voltage‐sensitive Ca2+ channels being spatially restricted to the luminal cell surface in this preparation.
Changes in the rate of translation with reactivation of delayed implanting mouse embryos
Authors: Weitlauf H. M. 
Published: June 2005

AbstractThe transient embryonic diapause associated with delayed implantation in mice is characterized by decreases in the rates of synthesis of RNA and protein as well as a cessation of development. The present experiments were undertaken to examine the possibility that controls on protein synthesis at the level of translation of mRNA provide a regulatory mechanism in this situation. Rates of peptide chain elongation were determined in dormant embryos as well as in embryos that were reactivated either in vivo by estradiol‐17β or by incubation in vitro. In dormant embryos the rate of peptide elongation was found to be approximately half that in active embryos. Although this change in translational efficiency appears to be sufficient to account for previously observed differences in overall rates of protein synthesis in dormant and reactivated embryos, the possibility that some changes also occur at the level of transcription during reactivation is not ruled out.
Unusual responses of cultured Fundulus heteroclitus melanophores to epinephrine and lons, paradox of K+ versus Na+
Authors: Clark Carl R. , Taylor John D. , Tchen T. T. 
Published: June 2005

AbstractFundulus heteroclitus melanophores were successfully cultured and maintained in culture for up to 2 months. Compared to other teleost melanophores in the fin, scale, or split fin preparation, the cultured melanophores show unusual responses to both epinephrine and ion solutions. First, they aggregated their melanosomes in response to concentrations of epinephrine as low as 10−12M. Second, the melanophores in a 6‐day, or older, culture aggregated their melanosomes in response to both sodium and potassium ion solutions. This is in contrast to 4‐day‐old cultures (and reports of noncultured melanophores) where melanosomes are aggregated in response to potassium but dispersed in sodium ion solutions.
Anaerobic aspartate metabolism and the formation of alanine in molluscan cardiac muscle: A 13C Nmr study
Authors: Graham R. A. , Ellington W. R. 
Published: June 2005

AbstractCarbon nuclear magnetic resonance (13C‐NMR) spectroscopic techniques were used to investigate the metabolism of (13C‐3>)‐aspartate and (13C‐4>)‐aspartate by in vitro preparations of the ventricle of the whelk Busycon contrarium. Under anoxic conditions, there was substantial conversion of (13C‐4>)‐aspartate to C‐1,4 succinate with no detectable enrichment of other compounds. When (13C‐3>)‐aspartate was the substrate, there was substantial enrichment of C‐2,3 succinate. However, there was no detectable enrichment of the C‐2 or C‐3 positions of alanine. This finding suggests that the direct transfer of carbon from aspartate to alanine is minimal under anoxic conditions in whelk ventricle. Thus, the malic enzyme may not be functional in the decarboxylating direction under these conditions.
Modification of cardiac activity in response to dehydration in the terrestrial slug, Limax maximus
Authors: Grega Debra S. , Prior David J. 
Published: June 2005

AbstractThe level of body hydration in the terrestrial slug Limax maximus modifies several aspects of behavior such as pneumostome activity, feeding responsiveness, huddling, and contact‐rehydration. The relationship between water balance and pneumostome activity and respiratory function suggested that cardiac activity might also be affected. To pursue this possibility, intact slugs and isolated heart‐central nervous system (CNS) preparations were used to investigate cardiac responses to the increase in hemolymph osmolality which occurs during dehydration. In intact animals, heart rate increased in response to progressive air‐dehydration and to increases in hemolymph osmolality resulting from injections of hyperosmotic solutions of mannitol or NaCl. In isolated preparations, the heart or CNS were separately exposed to hyperosmotic saline. Exposure of the heart alone to hyperosmotic saline resulted in decreased heart rate while exposure of only the CNS resulted in an increase in heart rate. These observations suggest that the increase in heart rate that is observed in intact air‐dehydrated slugs is primarily mediated by the CNS.
Bidirectional folding of an insect epithelial monolayer
Authors: Nardi James B. , Reynolds Ingrid 
Published: June 2005

AbstractMoth wing epithelium has a well‐defined apicobasal polarity expressed in the positioning of specialized junctions and microfilament bundles. This cytoarchitecture predisposes epithelial monolayers to fold with their basal surfaces outermost. However, a given epithelial population appears not to be constrained by its cytoarchitecture to fold in a particular direction. Direction of folding—either with basal surfaces or apical surfaces outermost—is determined by environmental factors and is correlated with changes in lateral cell contacts as well as dimensions of the apicalmost epithelial junctions (belt desmosomes). These configurational changes of epithelial sheets are accomplished without altering the intrinsic polarity of individual epithelial cells.
Electron microscopic observations on the process of polar body formation in artificially activated eggs of the rose bitterling
Authors: Ohta Tadayuki 
Published: June 2005

AbstractMature eggs were obtained from adult female rose bitterling, Rhodeus ocellatus ocellatus. Both intact and dechorionated eggs were activated by immersion in freshwater. The formation of the second polar body after egg activation was examined ultrastructurally by both scanning and transmission electron microscopy. The second polar body was extruded from a specialized site identified by an aggregation of thick leaf‐like projections of the egg cytoplasm, a short distance from the sperm entry site about 15 min postactivation. After extrusion, formation of a cleavage furrow was completed at the base of the polar body protuberance about 30 min postactivation. The nucleus of the extruded second polar body had a nuclear envelope. The formation of the second polar body in activated eggs are discussed.
The cylindrical or tubiliform glands of Nephila clavipes
Authors: Candelas Graciela C. , Ortiz Anselmo , Molina Carlos 
Published: June 2005

AbstractThe cylindrical or tubiliform glands of the spider Nephila clavipes have been studied and compared to the large ampullates on which we have previously reported. The three pairs of cylindrical or tubiliform glands secrete the fibroin for the organism's egg case. Their solubilized luminar contents migrate as a homogeneous band in Sodium dodecyl sulfate polyacrylamide gel electrophoresis and turn out to be a larger protein than that produced by the large ampullates. The excised cylindrical glands remain metabolically active for several hours in a simple culture medium, where fibroin synthesis can be monitored through the incorporation of 14C alanine. The glands' response to a fibroin production stimulus does not reach the magnitude displayed by the large ampullates, but this is to be expected since their products supply different functions in this organism. This fibroin also seems to be elongated discontinuously. Translational pauses have been detected in the secretory epithelium of cylindrical and large ampullate glands of Nephila as well as in the silk glands of Bombyx mori. Since these glands produce the fibroin for the females egg case, they should prove to be an interesting model system.
Partial characterization of the mating‐inducing factors (gamones) produced by mating type VI cells in the ciliate Euplotes patella syngen 2
Authors: Akada Rinji 
Published: June 2005

AbstractThe mating‐inducing factors (gamones) secreted from the mating type VI (strain 10) cells in the ciliate Euplotes patella syngen 2 have been characterized. The gamone activity was sensitive to pronase and was resistant to trypsin, chymotrypsin, heating, and periodate oxidation. DEAE‐Sepharose column chromatography of the cell‐free fluid has revealed that cells of heterozygous mating type VI (mt2/mt4) secrete two different gamones, gamones 2 and 4. These results strongly suggest that the two gamones of type VI cells are proteins that contain little or no carbohydrate moiety and are controlled by their own mating type genes.
Presence of sucrase in the yolk sac of the chick
Authors: Matsushita Susumu 
Published: June 2005

AbstractThe presence of sucrase in the yolk sac of the chick was studied biochemically and immunologically. The sucrase was partially purified from the yolk sac of hatched chicks and was compared with the sucrase purified from the small intestine. Immunodiffusion with antiserum against intestinal sucrase and characterization of the activity revealed that the two enzymes were almost identical. However, the size of the yolk sac sucrase was found to be slightly smaller than that of the intestinal enzyme by chromatography on Sephadex G‐200 and polyacrylamide gel electrophoresis. Immunocytochemical studies showed that the sucrase was located on the free surface of yolk sac endodermal cells, but the sucrase may also be present in the cytoplasm.
Reprograming of murine blastocoele formation
Authors: Prather Randall S. , First Neal L. 
Published: June 2005

AbstractThe present study shows that there is communication between reaggregated asynchronous cleavage stage blastomeres that regulates blastocoele formation. Individual blastomeres from eight‐cell murine embryos were transferred to empty zonae pellucidae, intact two‐cell embryos, or enucleated two‐cell embryos, and were examined over a period of 75 hours for development of cavitation. It was found that the isolated blastomeres cavitated concurrently with intact control eight‐cell embryos, while intact control two‐cell embryos cavitated 24 hours later. However, the embryos resulting from combining a two‐cell embryo and a blastomere from an eight‐cell embryo cavitated at a time in between the eight‐ and two‐cell controls.
Capacitated, acrosome reacted but immotile sperm, when microinjected under the mouse zona pellucida, will not fertilize the oocyte
Authors: Barg Patricia E. , Wahrman Miryam Z. , Talansky Beth E. , Gordon Jon W. 
Published: June 2005

AbstractWe have devised a procedure for mechanically inserting intact, acrosome reacted spermatozoa under the mouse zona pellucida, and have examined the ability of sperm so inserted to fertilize the mouse oocyte. Sperm immobilized by a variety of different methods are unable to fertilize the egg, despite the fact that electron microscopy confirms that they are acrosome reacted. Control experiments show that the oocytes are capable of being fertilized by motile sperm after the microinjection procedure, and that the immobilized sperm are able to form male pronuclei after injection directly into the ctyoplasm. These results indicate that in addition to its importance for penetration of egg investments, sperm motility is required for fusion of the gametes. Alternatively, the findings suggest that the enzymatic machinery required for sperm motility is very similar to that utilized for gamete fusion, and that destruction of one is likely to lead to inactivation of the other.
The effect of melatonin administration and short exposures to cold on body temperature of the blind subterranean mole rat (rodentia, Spalax ehrenberghi, Nehring)
Authors: Heth G. , Pevet P. , Nevo E. , Beiles A. 
Published: June 2005

AbstractImprovement of the cold resistance capacity of the mole rat (Spalax ehrenbergi, Nehring), a blind subterranean rodent, was achieved following subcutaneous melatonin administration. Melatonin‐treated mole rats exhibited reduction both in initial body temperature (Tbo) and in the decrease of body temperature (ΔTb) after 6 hours of exposure to cold. The tested mole rats were acclimated to and kept during the experiment, under long (16L/8D) photoperiod schedule while the effects of melatonin administration on body temperature simulated the effects of short photoperiod conditions. These results suggest that in mole rats, melatonin biochemically mediates photoperiodic information into body temperature physiological response. As a byproduct of the original experiment, it was found that frequently repeated short (6 hours) exposure to cold (Ta = 5 ± 1°C) can in itself initiate an improvement of cold resistance capacity similar to the effect of melatonin administration. This supports the idea that mole rats may improve their cold resistance in response to either photoperiodic or climatic changes.
Development of fast singing muscles in a katydid
Authors: Ready Neal E. 
Published: June 2005

AbstractIn males of the katydid Neoconocephalus robustus, mesothoracic wings are used in flight (wing stroke frequence = 20 Hz) and stridulation (200 Hz), while the metathoracic wings are used in flight alone. Most mesothoracic wing muscles produce much briefer isometric twitches than metathoracic counterparts. The mesothoracic first tergocoxal muscle (TCX1) has a twitch duration (onset to 50% relaxation, 35°C) of 6–8 ms and the metathoracic TXC1 a twitch duration of 12–15 ms. The TCX1 muscles from animals one and two instars from adulthood produce twitches similar in duration to those of the adult metathoracic TCX1. The twitch duration of the mesothoracic TCX1 acquires its adult brevity gradually over the first 5 days of adult life. Both TCX1 muscles increase greatly in size and mitochondrial content around the time of the terminal molt. During this period the mesothoracic TCX1 develops narrower myofibrils and a smaller ratio of fibril volume to sarcoplasmic reticulum volume than is characteristic of the metathoracic TCX1. Changes in the ultrastructure of the mesothoracic TCX1 precede changes in contraction kinetics around the time of the terminal molt so that there is not a strict correlation between muscle structure and performance during the period of rapid growth.
Stimulation of genital eversion in the land snail Helix aspersa by extracts of the glands of the dart apparatus
Authors: Chung Daniel J. D. 
Published: June 2005

AbstractThe dart apparatus, used during courtship in some groups of hermaphroditic land snails, has long been assumed to have a “stimulatory” effect on the mating partner, though how stimulation occurs and exactly what function it serves has never been determined. In this study, extracts of the mucous glands of the dart apparatus of the land snail Helix aspersa were injected into conspecifics and into a related snail, Cepaea nemoralis, in order to test the hypothesis that the dart is used to achieve inflow of bioactive mucous gland secretions into the darted snail. Helix aspersa injected with the extract responded by everting their terminal genitals; eversion normally takes place during courtship and mating. Boiling the extract increased the bioactivity. Pronase‐treated extract lost bioactivity, and gel filtration of the boiled extract indicated that the active substance has a molecular weight of about 5,000. The active substance may be a polypeptide. Cepaea nemoralis also everted their genitals when injected with the boiled Helix extract. The active substance appears to be a contact sex pheromone, the second such pheromone in a pulmonate land snail for which experimental evidence has been obtained.
Thyroid and gonadal hormones in feather regeneration of the redheaded bunting, Emberiza bruniceps
Authors: Pati Atanu Kumar , Pathak Vishnu Kant 
Published: June 2005

AbstractThe time lag in the appearance of the first feather papillae (rate of feather regeneration) was studied after monthly depluming of the redheaded bunting (Emberiza bruniceps). Results indicate that the rate of feather regeneration varies over an annual time scale. When a comparison was made between monthly changes in levels of plasma thyroid hormones (thyroxine‐T4 and triiodothyronine‐T3) in redheaded buntings (Pathak and Chandola, '82a) and the rate of feather regeneration, the rate of regeneration showed a distinct correlation with levels of circulating T4. The rate of feather regeneration was faster during December and June when endogenous T4 levels were high and slower during July/August and March/April when levels of circulating T4 were relatively low. Such a relationship was, however, not observed with T3. Results of administration of T4 and T3 separately, in normal as well as in thyroidectomized birds; in different doses; and during different phases of the annual cycle, indicate a strikingly greater influence of T4 on the rate of feather regeneration and on the number of regenerated papillae than T3. Injection of propylthiouracil (PTU—an effective inhibitor of peripheral conversion of T4 to T3 in the redheaded bunting) in thyroidectomized birds that were also receiving T4, resulted in even faster rates of feather regeneration. Thyroidectomized birds receiving saline had no feather regeneration. Castration led to a slow rate of feather regeneration during May/June only. During this period thyroid activity of the redheaded bunting is known to be significantly influenced by gonadal hormones; this influence is not apparent during January/February or August. Injections of testosterone neutralized the effects of castration. It is concluded that T4 is more important than T3 for feather regeneration in redheaded buntings and that the effects of castration are due to alterations in thyroid function.
CNPase activity in the vertebrate retina, retinal pigmented epithelium, and choroid
Authors: Heath Ashley R. , Hindman Heather M. 
Published: June 2005

AbstractThe activity of the enzyme 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (CNPase, E.C.3.1.4.37) has been studied in the retina of three vertebrate species. Activity was highest in the goldfish, followed by Xenopus laevis and Rana pipiens. Also, high activity levels were found in goldfish retinal pigment epithelium and choroid, but not in the other two species. When added to in vitro culture systems, 2′,3′‐cyclic nucleotides were found to have no effect on goldfish cone retinomotor movement, but caused a marked inhibition of Rana pipiens rod outer segment disc membrane shedding. It is suggested that CNPase may play a role in cellular processes requiring membrane structural reorganization.