bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of denervation on grafted hindlimb regeneration of larval Xenopus laevis
Authors: Filoni Sergio , Bernardini Sergio , Cannata Stefano M. 
Published: June 2005

AbstractThe aim of the present research is to ascertain whether in larval Xenopus laevis nerve‐independence for the regeneration of early stage limbs and nerve‐dependence of late stage limbs observed in a previous work (Filoni and Paglialunga, '90) is related to extrinsic (systemic) factors or to intrinsic changes taking place in the limb cells themselves during development. In this paper the regenerative capacity of early and late stage hindlimbs under the same extrinsic conditions, insofar as both are grafted onto the denervated hindlimbs of host larvae at the same developmental stage, is studied. All the grafted limbs are amputated after the host larvae have reached stage 57–58 (according to Nieuwkoop and Faber, '56).In experiment I, the grafted limb is amputated at stage 52, at the thigh level; in experiment II, the grafted limb is amputated at stage 54–55, at the tarsalia level; in experiment III the grafted limb is amputated at stage 57, at the tarsalia level. In all three experiments, together with the grafted limb, also the host limb is amputated at the tarsalia level.The results show that while grafted limbs amputated at stages 52 and 54–55 regenerate in the absence of nerves, grafted limbs amputated at stage 57 cannot. The failure of late stage grafted limbs to regenerate cannot be explained in terms of an immune‐type inhibiting reaction since it has been observed also in denervated autografted limbs and in the host limbs.Since all the grafted limbs are in the same environmental conditions, the results show that in larval Xenopus laevis nerve‐independence for regeneration of early stage limbs and nerve‐dependence of late stage limbs are not related to factors extrinsic to the limb but to intrinsic changes taking place in the limb cells themselves during development.
Region‐specific expression of scutate scale type beta keratins in the developing chick beak
Authors: Shames Rose B. , Knapp Loren W. , Carver Wayne E. , Sawyer Roger H. 
Published: June 2005

AbstractThis study shows that different patterns of scutate scale type beta keratins are accumulated in the three adjacent structures of the embryonic chick beak: periderm, egg tooth, and cornified beak. The cornified beak accumulates all of the beta keratins of scutate scale except pp2,3. The periderm, which is the outermost, multilayered covering of the whole embryonic beak, accumulates only beta keratins 2,3, and p2,3 of the scutate scale pattern. The egg tooth, which is the rounded elevation on the dorsal surface of the upper beak, and the embryonic claw accumulate greatly reduced levels of 2,3 and p2,3 compared to scutate scale. Like cornified beak, the claw does not accumulate pp2,3, but both tissues express a potentially new beta keratin, beta keratin 8. Neither the histidine rich “fast” proteins (HRPs), which are expressed in embryonic scutate scales and feathers, nor the avian cytokeratin associated proteins (cap‐1 and cap‐2), which are expressed in scutate and reticulate scales, are expressed in any of the embryonic beak structures or in the claw. The implications of these findings with regard to regulation of terminal differentiation of avian skin are discussed.
Morphological basis of “growling” in the king cobra, Ophiophagus hannah
Authors: Young Bruce A. 
Published: June 2005

AbstractA bioacoustic analysis is conducted on the defensive sounds produced by 21 species of snakes. The “typical” snake hiss is described as having a broad‐frequency span (from roughly 3,000 to 13,000 Hertz) and a dominant frequency near 7,500 Hertz. The “growl” of the king cobra (Ophiophagus hannah) differs from the “typical” snake hiss in consisting solely of frequencies below 2,500 Hertz, with a dominant frequency near 600 Hertz. Structural analysis of the upper respiratory tract of O. hannah suggests that the “growl” is produced by tracheal diverticula functioning as low‐frequency resonating chambers. This hypothesis is supported in several ways. An acoustic analysis of a mechanical model of the trachea demonstrates the potential for these diverticula to produce resonance effects. A “growl” also occurs in the mangrove ratsnake (Gonyosoma oxycephalum), a species that also has tracheal diverticula. Flushing the respiratory tract of G. oxycephalum with helium produces a shift of over 1,000 Hertz in the “growl,” a shift that is indicative of a resonance effect.
Anaerobic glycolysis in the dental plate retractor muscles of the New Zealand hagfish Eptatretus cirrhatus during feeding
Authors: Baldwin J. , Davison W. , Forster M. E. 
Published: June 2005

AbstractHagfish lack jaws, and the teeth are carried on a cartilagenous dental plate associated with the large longitudinal and tubular retractor muscles. Previous studies had shown that the retractors had intracellular pH buffering capacities among the highest reported for vertebrate muscle, and as these animals indulge in bursts of feeding within the hypoxic body cavity of dead fish it was of interest to examine the role of anaerobic glycolysis in powering the dental plate retractor muscles. Both retractors of the New Zealand hagfish Eptatretus cirrhatus contain only large diameter white muscle fibres (X = 200μm), and show low capillary:fibre ratios relative to the red and pink fibres of the general body musculature. These white fibres are characterized by sparsely distributed small mitochondria with poorly developed inner membranes, low activities of enzymes unique to aerobic ATP production, and moderate activities of glycolytic enzymes. During bursts of continuous feeding for periods of from 1.5 to 6.45 min there was a linear increase in lactate concentration at rates of 19.6 and 17.4 μmol lactate min−1 g−1 wet wt muscle, respectively, for the longitudinal and tubular retractors, reaching a maximum of 132 μmol lactate g−1 wet wt muscle. While the glycolytic flux in the hagfish retractors during feeding may not reach levels encountered in white muscle of burst swimming tuna, the actual lactate concentrations achieved are among the highest ever reported for normal muscle work by unrestrained animals.
Chronology and morphology of temperature‐dependent sex determination
Authors: Wibbels Thane , Bull James J. , Crews David 
Published: June 2005

AbstractTemperature sensitivity and gonadal differentiation were studied in a turtle, Trachemys scripta, with temperature‐dependent sex determination. Sex determination was sensitive to both the duration and magnitude of incubation temperature. Temperature exerted an “all or none” effect on the ovarian or testicular nature of most gonads, but affected the length of ovaries in a graded fashion. Collectively, the results indicate that sex determination is controlled by the quantitative effect of temperature during a period beginning prior to (histologically detectable) sexual differentiation and extending to a time when initial sex specific changes are evident in the gonads.
Homeoboxes in cnidarians
Authors: Schierwater Bernd , Murtha Michael , Dick Matthew , Ruddle Frank H. , Buss Leo W. 
Published: June 2005

AbstractHomeoboxes have previously been documented from various phyla of triploblastic, coelomate and pseudocoelomate, animals. We report here the first homeoboxes from cnidarians, a phylum of diploblastic organisms thought to occupy a near‐basal position in metazoan phylogeny. We have sequenced three partial (77 bp) fragments of Antennapedia (Antp) class homeoboxes from the hydroids Hydractinia symbiolongicarpus and Eleutheria dichotoma. A pair of fragments, Cnox‐2‐Hs and Cnox‐2‐Ed, from the two species differ in nucleotide sequences but have identical derived amino acid sequences. A gene tree produced by parsimony analysis shows that these two fragments cluster within the Antp homeobox lineage. The third fragment, Cnox‐1, clusters as a sister group of the other Antp class homeoboxes.
Acid‐base balance and ion transfers in the spiny dogfish (Squalus acanthias) during hypercapnia: A role for ammonia excretion
Authors: Claiborne J. B. , Evans David H. 
Published: June 2005

AbstractThe effect of hypercapnia on the acid‐base balance and acid‐equivalent transfers has been measured in the dogfish Squalus acanthias. Previous reports on Squalus are not in agreement as to the role played by compensatory acid‐base transfers between the animal and the water during hypercapnia.Cannulated animals were maintained in a closed circuit, seawater recirculation system. Plasma pH, Cco2 (from which Pco2 and [HCO3−] were calculated), and transfers of NH4+ and HCO3−‐equivalent ions between the fish and the water, were measured during 24 hours of hypercapnic exposure (Pco2: 8–10 torr) and a subsequent 8–24 hour normocapnic recovery period.Respiratory acidosis resulted in a plasma pH depression, which was then almost completely compensated (within ˜ 0.1 pH unit) over 24 hours by a ˜ 20 mM increase in plasma [HCO3 ]. In contrast to previous studies on elasmobranch acid‐base regulation, hypercapnia induced a rapid 3 × increase in not only HCO3−‐equivalent uptake but also branchial ammonia (NH4+) excretion. These transfers combined for a net Δ H+ loss to the water of 5.5 mmol kg−1. During the normocapnic period, net Δ H+ was reversed to −6.9 mmol kg−1, nearly completely due to HCO3‐efflux.Several lines of evidence point to the contribution of gill Na+/NH4+ exchange to the total ammonia excreted during hypercapnia, whereas NH3 diffusion predominates during the recovery period. Likewise, Cl−/HCO3− or Cl−/OH− exchange may enhance the uptake of HCO3− during hypercapnia.
Embryonic retinal ablation and post‐metamorphic optic nerve crush: Effects upon the pattern of regenerated retinotectal connections
Authors: Underwood Lauren Wunsh , Nelson Paula , Noelke Elizabeth , Ide Charles F. 
Published: June 2005

AbstractWe examined relationships between healing observed during embryonic Xenopus retinal and optic nerve regeneration and resultant visuotectal pattern formation. Dorsal (D) and nasoventral (NV) 1/3 sized eye fragments were surgically created in stage 32 Xenopus laevis embryos. Gross anatomical healing modes of these fragments were examined 2 days post‐surgery (stage 43). Healing was categorized according to the degree of cell movements observed. Animals were reared through metamorphosis and electrophysiologic mapping techniques were employed on those animals whose eyes regenerated. All D 1/3 fragments showed normal (non‐duplicated) projections to the tectum; most (80%) of the healing observed showed little cell movements (the remaining 20% showed substantial cell movements, yet failed to show duplicated projections). Most NV 1/3 fragments (73%) formed two mirror image projections to the contralateral midbrain optic tectum (pattern duplication). Most (88%) of the healing observed among these animals showed massive cell movements in the ventral retinal region (the remaining 12% showed moderate cell movements). The remaining NV 1/3 fragments (27%) showed moderate cell displacement and failed to show duplicated projections). These data are compatible with a cell‐movement:intercalary cell division hypothesis in which duplication is dependent upon specific positional confrontation and subsequent cell division.In additional studies, in adult animals, the optic nerves of eyes with duplicated projections were crushed and allowed to regenerate for 1 year. Duplicated projections were restored, indicating that developmental and maturational factors are probably not responsible for duplicative pattern formation; rather, information intrinsic to the eye, possibly created during healing interactions and/or fiber ingrowth to the tectum, underlies duplicate innervation of the tectum.
Prolactin‐dependent seasonal changes in pelage: Role of the pineal gland and dopamine
Authors: Badura Lori L. , Goldman Bruce D. 
Published: June 2005

AbstractThe Siberian hamster displays seasonal changes in pelage that are dependent upon fluctuations in circulating prolactin levels. Pinealectomy prevented the decrease in serum prolactin and molt to the winter pelage displayed by castrated males housed under a short‐day photoperiod. A dopaminergic antagonist, pimozide, enhanced prolactin levels in both pinealectomized and shamoperated animals under both long and short photoperiods. In the short‐day animals, this effect of pimozide was associated with a prevention of the development of winter pelage. These results indicate that seasonal prolactin levels and related pelage changes are dependent upon the integrity of the pineal gland. However, basal prolactin levels under different photoperiod conditions appear to be only partly regulated by the actions of the dopaminergic system.
Eyestalk ablation in female crabs: Effects on egg characteristics
Authors: Lachaise Fabienne , Goudeau Marie , Carpentier Gilles , Saidi Bassima , Goudeau Henri 
Published: June 2005

AbstractEyestalk ablation in Crustacea eliminates the inhibitory hormonal effects exerted by the eyestalk neuroendocrine center on ovarian growth. Planning to use crab eggs throughout the year as a model for physiological cell research, we performed a preliminary study to examine the characteristics of eggs that originated from eyestalk‐ablated females. Here we discuss the data that deal with the characteristics of eggs at fertilization and during the first 40 h of embryonic development. We found that eyestalk ablation in female crabs did not modify the resumption of egg meiosis that is stimulated by sea water, nor did it affect the electrical and cortical responses of eggs to fertilization. We also found that eyestalk ablation in females did not result in any changes in the nature of the two major ecdysteroids that are usually found in crabs' eggs (ponasterone A and 20‐hydroxyecdysone) or in their respective precursors (25‐deoxyecdysone and ecdysone) in eggs tested from 0 to 40 h post‐spawning. The respective variations in the concentrations of the four ecdysteroids were the same during this period as in control eggs. However, eyestalk ablation in females induced a striking decrease in the concentration of ponasterone A (60%) in eggs 30 to 40 h post‐spawning. Furthermore, eyestalk ablation in females promoted an increase in the titer of ponasterone A in the ovaries of about 2‐ and 20‐fold, at egg‐laying and 40 hours afterwards. This difference is discussed in terms of possible perturbations in either the synthesis of ponasterone A at the ovarian level, or its metabolism in spawned eggs.
Autocrine and paracrine role of steroids during spermatogenesis: Studies in Squalus acanthias and Necturus maculosus
Authors: Callard Gloria V. 
Published: June 2005

AbstractDue to a cystic mode of spermatogenesis and zonal testes, the spiny dogfish shark (Squalus acanthias) and salamander (Necturus maculosus) are advantageous for studying the relationship between steroidogenesis and germ cell development. Direct analysis of steroidogenic enzymes and steroid receptors in staged tissue samples, together with light and electron microscopic observation, suggests that androgens and estrogens produced by Sertoli cells or Leydig cells immediately before or after spermiation serve as intratesticular regulators of events specific to premeiotic stages of spermatogenesis. These correlative data are consistent with limited observations in mammalian testis and provide a conceptual framework for direct testing of functional interactions between spermatogenesis and steroidogenesis in future studies.
In vivo and in vitro evidence for the role of hormones in fish spermatogenesis
Authors: Cochran Roger C. 
Published: June 2005

AbstractIn an attempt to discern general mechanisms by which specific hormones control certain aspects of fish spermatogenesis, we focus on a single fish species (Fundulus heteroclitus), and, by analogy, generalize to other fishes. At least three androgenic steroids (testosterone, 11‐ketotestosterone, 11β‐hydroxytestosterone) are present in the serum of Fundulus heteroclitus, but only testosterone appears to be associated with spermatogenesis in vitro as well as in vivo. 11‐Ketotestosterone appears to be associated with spermiation in vivo, but has not yet been tested for its ability to cause spermiation in vitro. The preponderant androgen present in the serum, 11β‐hydroxytestosterone, does not appear to be directly associated with spermatogenic process either in vitro or in vivo.In F. heteroclitus, in vivo studies indicate that at least two different gonadotropins are produced, on that primarily causes steroid production and a second that causes testicular growth. Indirect evidence suggests that production of these gonadotropins is seasonal in terms of both their amounts and their relative proportions.
Early innervation of abdominal swimmeret muscles in developing lobsters
Authors: Kirk Mark D. , Govind C. K. 
Published: June 2005

AbstractThe swimmerets in the abdomen of the lobster Homarus americanus are paired external appendages whose back and forth propulsive movements are brought about largely by a group of power and return stroke muscles located in the lateral abdominal cavity. We find functional innervation of these muscles by several excitatory axons and a single inhibitor in embryonic and stage 1 larval lobsters before the external appendages are even formed. This early innervation is via a few nerve bundles in which branches of the motor axons are intertwined in a complex manner. As the swimmerets develop to maturity in later larval and juvenile stages, the innervation consisting usually of several excitor and a single inhibitor synaptic terminals becomes localized to individual muscles. Patterned synaptic activity in these muscles was not seen in the embryonic and larval stages but has been shown in early juvenile stages, when it coincides with the onset of rhythmic movement of the swimmerets. Consequently, such early innervation of the swimmeret muscles may be influential in establishing the central circuitry for the generation of patterned activity, a possibility that was discounted in a previous study (Proc. Natl. Acad. Sci. USA, 70:954–958).
The role of hormones in the acquisition of sperm motility in salmonid fish
Authors: Miura Takeshi , Yamauchi Kohei , Takahashi Hiroya , Nagahama Yoshitaka 
Published: June 2005

AbstractIn salmonid fish, spermatozoa taken from the testes are immotile, but acquire motility during their passage through the sperm duct. Using male masu salmon (Oncorhynchus masou), we found that gonadotropin‐induced testicular production of 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17α,20β‐DP), the oocyte maturation‐inducing hormone of salmonid fish, is responsible for the acquisition of sperm motility. However, neither testosterone (T) nor 11‐ketotestosterone (11‐KT), the two major androgens in teleost fish, were effective. We also present evidence that 17α,20β‐DP action is mediated through an increase in sperm duct pH, which in turn increases the cAMP content of sperm allowing the acquisition of motility.
Sulfation is required for mobility of veliger larvae of Concholepas concholepas (Mollusca; Gastropoda; Muricidae)
Authors: Urrea Rodrigo , González Mauricio , Inestrosa Nibaldo C. , Brandan Enrique 
Published: June 2005

AbstractThe sulfation reaction seems to be a critical biochemical process during early steps of development. We have evaluated the effect of sulfation on the mobility of veliger larvae of the gastropod Concholepas concholepas. It was found that incubation of larvae in low‐sulfate artificial sea water had strong inhibitory effect on mobility. The use of sodium chlorate, a specific inhibitor of sulfation, also resulted in a strong inhibition of larval mobility. At the biochemical level, the synthesis of proteoglycans (PGs) and detergent‐soluble sulfoproteins and sulfolipids was specifically inhibited by chlorate, without affecting either total protein synthesis or phosphorylation. Intracellular levels of the sulfate donor 3′‐phosphoadenosine 5′‐phosphosulfate (PAPS) were decreased to 4% by chlorate treatment, indicating that this molecule is also involved in sulfation of marine invertebrates. Both effects of chlorate, the inhibition of sulfation and the larval mobility, were reversible. It is therefore concluded that sulfation is required for larval mobility in the mollusc C. concholepas. © 1992 Wiley‐Liss, Inc.
Cooling rate influences cryoprotectant distribution and organ dehydration in freezing wood frogs
Authors: Costanzo Jon P. , Lee Richard E. , Wright Michael F. 
Published: June 2005

AbstractIce formation in the freeze‐tolerant wood frog (Rana sylvatica) induces the production and distribution of the cryoprotectant, glucose. Concomitantly, organs undergo a beneficial dehydration which likely inhibits mechanical injury during freezing. Together, these physiological responses promote freezing survival when frogs are frozen under slow cooling regimes. Rapid cooling, however, is lethal. We tested the hypothesis that the injurious effects of rapid cooling stem from an inadequate distribution of glucose to tissues and an insufficient removal of water from tissues during freezing. Accordingly, we compared glucose and water contents of five organs (liver, heart, skeletal muscle, eye, brain) from wood frogs cooled slowly or rapidly during freezing to — 2.5°C. Glucose concentrations in organs from slowly cooled frogs were significantly elevated over unfrozen controls, but no significant increases occurred in rapidly cooled frogs. Organs from slowly cooled frogs contained significantly less water than did those from controls, whereas water contents from rapidly cooled frogs generally were unchanged. Rapid cooling therefore inhibited the production and distribution of cryoprotectant and organ dehydration during freezing. This inhibition may result from an accelerated, premature failure of the cardiovascular system. © 1992 Wiley‐Liss, Inc. © 1992 Wiley‐Liss, Inc.
The zona pellucida binds the mature form of an oviductal glycoprotein (oviductin)
Authors: St‐Jacques Sylvie , Malette Brigitte , Chevalier Simone , Roberts Kenneth D. , Bleau Gilles 
Published: June 2005

AbstractThe use of a monoclonal antibody (MAb) specific for the oviductal zona pellucida (ZP) of the hamster has demonstrated that a new antigen (oviductin) is acquired by the ZP during transit of the oocyte in the oviduct. The epitope that is recognized by the MAb bears a terminal N‐acetyl‐D‐galactosamine residue. We conducted a study in order to determine whether this immunoreactivity of the oviductal ZP results from the addition of the terminal sugar residue to a preformed ZP protein or from the transfer of the mature glycoprotein produced by oviductal secretory cells. We measured the incorporation of [35S]methionine into proteins using four different incubation systems: cumulus oophorus (CO) alone, CO in the presence of oviductal fluid, CO co‐incubated with empty oviducts, and CO within intact oviducts. At the end of the incubation period, the ZP, vitelli, dispersed cumulus without oocyte, oviducts, and culture medium were isolated and analyzed for their protein content by sodiumdodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), autoradiography, and immunodetection. The cumulus cells synthesized several proteins, independently of the oviductal environment; however, none of these proteins corresponded to oviductin. The ZP and the vitelli of cumulus oophorus that were incubated either alone or in the presence of oviductal fluid did not contain radioactive oviductin. When the oviduct (empty or intact) was present in the incubation system, radiolabeled oviductin was synthesized and secreted into the incubation medium. The ZP picked up a detectable amount of radioactive antigen only in the system in which intact oviducts were incubated. These results demonstrate that the entire molecule of oviductin (including its antigenic determinant) is produced by the oviduct and subsequently becomes associated with the ZP of the oocyte. © 1992 Wiley‐Liss, Inc.