bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency response of the ear of the Tokay gecko
Authors: Manley Geoffrey A. 
Published: June 2005

AbstractA comparative analysis of the frequency response of the inner and middle ear of Gekko gecko is described. Tungsten microelectrodes were used to isolate single auditory neurons in the cochlear nucleus in order to study their frequency selectivity and sensitivity.Neurons were detected with characteristic frequencies up to 5 kHz, and tuning curves were similar to those of mammalian systems. The single neuron responses were strongly frequency selective, as was expected from the presence of a well‐differentiated basilar membrane. The sensitivity of this hearing system compares favorably with that of birds and mammals and is the most sensitive of those reptiles yet studied with neurophysiological techniques.The middle‐ear response was studied with the Mössbauer system and shows a typical non‐mammalian response. Amplitude of the drum or columella is constant up to 1 kHz, then falls off rapidly at higher frequencies. A lever action between drum and columella presumably aids impedance matching. The overall ear sensitivity function was corrected for middle ear response and reveals a true inner‐ear sensitivity curve. Analysis of the single‐unit data is aided by a knowledge of the middle‐ear response, and somewhat different conclusions are reached after correction of the data to constant columella amplitude.
Physiological studies on supercooled killifish (Fundulus heteroclitus). IV. Carbohydrate metabolism in hypophysectomized killifish at subzero temperatures
Authors: Umminger Bruce L. 
Published: June 2005

AbstractIntact Fundulus heteroclitus, acclimated to −1.5°C in sea water, showed increased levels of serum glucose, decreased levels of hepatic glycogen and unchanged levels of serum non‐glucose free carbohydrates and muscle glycogen when compared with controls at 20°C. In hypophysectomized killifish, acclimation to subzero temperatures was accompanied by hyperglycemia, increased concentrations of muscle glycogen and increased levels of serum non‐glucose free carbohydrates. Hepatic glycogen concentration as mg/g of liver was unchanged in cold‐acclimated hypophysectomized fish, but liver size increased so that total hepatic glycogen (mg/g of fish) was markedly elevated. The pituitary gland was not involved in eliciting the cold‐induced hyperglycemia but was important in regulating other aspects of carbohydrate metabolism.
Action of intrinsic laryngeal muscles during release calling in leopard frog
Authors: Schmidt Robert S. 
Published: June 2005

AbstractCinematographic, gross anatomical, muscle contraction, histological, and electromyographic data were used to determine the actions of the intrinsic laryngeal muscles of the leopard frog (Rana pipiens pipiens) during release calling. The dilator muscles act as glottal openers, the posterior constrictors as vocal cord opposers, and the external and anterior constrictors as glottal closers. The posterior constrictors do not “tense” the vocal cords, but merely bring them into opposition at the midline by pulling on the vocal pulvinaria, which act as levers. The anterior constrictors probably are not involved in vocal cord changes. Most of the release call trills (glottal trills) are produced by a brief opening of the glottis (which is quickly terminated by contraction of the glottal closers) during which there is a brief vocal cord opposition. The final trills of the call (vocal cord trills) occur during a continuous, prolonged opening of the glottis and are produced by the relaxation oscillations of the vocal cords.
The requirement for RNA synthesis in the differentiation of cultured chick embryo chondrocytes
Authors: Solursh Michael , Meier Stephen 
Published: June 2005

AbstractSecondary chick embryo sternal chondrocyte colonies, derived from differentiated clones, were treated with 0.005 μg/ml of actinomycin D for 18 hours. While RNA synthesis was inhibited by 70%, both growth and matrix accumulation were inhibited. The incorporation of 3H‐uridine into acid precipitable‐base hydrolyzable material, 35SO4 into hyaluronidase‐sensitive material, and of 3H‐proline into collagenase sensitive and insensitive material was measured in high density cultures treated with various doses of actinomycin D for 18 hours. The inhibition of sulfate incorporation was highly correlated with RNA synthesis and was observable within the first six hours after drug addition. Ethidium bromide and lucanthasone had no effect on sulfate incorporation. On the other hand, collagen synthesis was more resistant to actinomycin D treatment and was not inhibited until non‐collagenous protein synthesis was also inhibited. The results are discussed in terms of the independent regulation of the synthesis of two specialized cell products made by the same cell.
Hypothalamic control of the hypophyseal gonadotropic function in the adult male green frog, Rana esculenta L.
Authors: Rastogi Rakesh K. , Chieffi G. 
Published: June 2005

AbstractRemoval of the pars distalis, homoiotopic and ectopic autografting of the pars distalis, and transection of the hypothalamo‐hypophyseal link was done and their effect upon the cytology of the pars distalis and its gonadotropic functions was studied in the male green frog, Rana esculenta. Removal of pars distalis led to the regression of gonads and secondary sex organs. The gonadotropic activity of the pars distalis regrafted under the median eminence was comparable to that of the sham‐operated control except that in the gland oriented at an angle of 180° the thumb pads were involuted. The normal functional activity of the regrafted gland can be explained by the contact re‐established between the grafted gland and the portal vessels at the level of the median eminence as ascertained by injections of India ink. The ectopic pars distalis graft showed a general cytological disorganization and regression of the various cell types and its gonadotropic function appeared to be extremely poor. Transection of the hypothalamo‐hypophyseal connections diminished the gonadotropic effectiveness of the pars distalis.
Further studies on the maternal effect of the o gene in the Mexican axolotl
Authors: Briggs Robert 
Published: June 2005

AbstractAxolotl females homozygous for o produce eggs which are fertilizable and cleave normally, but are invariably arrested during gastrulation. This block can be corrected by injecting the eggs with nuclear sap from normal (o+/o+ or o+/o) ovarian oocytes. The factor responsible for the correction is designated o+ substance. In this paper we show the following: 1. The o+ substance is not species specific. Oocyte nuclear sap from a variety of amphibians is about as effective as that of the axolotl itself in correcting the maternal effect of o. The cytoplasm of ovarian oocytes is inactive or very weakly active. That of some species (e.g., Xenopus laevis) exerts no discernable effect. That of others (e.g., Rana pipiens) is highly toxic, killing axolotl eggs shortly after it is injected into them. 2. The o+ substance is synthesized during most of the growth of the oocytes. Oocytes assayed just at the beginning of yolk deposition or at intermediate stages contain o+ substance of about the same activity, volume for volume, as that of fully grown oocytes. 3. Uncorrected o+/o and o/o offspring of o/o females are indistinguishable — all stop at gastrulation. When corrected by injections of o+ substance they respond equally at first and develop to an advanced embryonic stage (St. 37). At this time 50% of the embryos (o/o) stop, the other 50% (o+/o) continue to develop. These results indicate that the o+ gene does not function in early development, but can begin to do so in advanced embryos.
Seasonal variation of newt forelimb regeneration under controlled environmental conditions
Authors: Schauble Muriel K. 
Published: June 2005

AbstractForelimb regeneration studies using the newt, Notophthalmus viridescens, were done under constant environmental conditions at 20°C. A series of three‐month regenerative studies were done during a two and one‐half year period. Under conditions which eliminated factors known to affect regeneration, such as temperature and variation in light‐dark cycle, a significant seasonal variation in the regenerative process was found. The rate and amount of regenerative new growth during the summer was enhanced over that in winter. A series of repetitive regenerations in the same group of animals demonstrated that this variation was cyclic under controlled environmental conditions for long periods of time. It is suggested that a cyclic biologic rhythm, probably endocrine in nature, is responsible for the phenomenon.
Protein incorporation by isolated amphibian oocytes. II. A survey of inhibitors
Authors: Wallace Robin A. , Ho Ti 
Published: June 2005

AbstractA variety of some of the more commonly used metabolic inhibitors and several substances previously found to influence protein incorporation by other types of cells were tested for their effects on protein incorporation by growing oocytes in vitro. With the exception of the uncouplers and the sulfhydryl reagent iodoacetate, the metabolic inhibitors at concentrations of 10 −3 M or less had little influence on sequestering activity. Cycloheximide, at concentrations which essentially abolished all protein synthesis, reduced protein incorporation by only 40–50%. The most pronounced inhibition of protein uptake without apparent cytotoxic side effects was provided by vinblastine and sulfhydryl reagents (especially trivalent arsenicals). The sulfhydryl reagents appeared to exert their effect primarily on the oocyte rather than the proteins of the medium. The results are evaluated both in terms of their relevance to previous studies with other cell systems and their significance towards understanding the mechanisms involved in the incorporation of macromolecules by cells. Finally, a preliminary model of protein incorporation by the oocyte is presented for further testing.
Migration of follicle cells through the zona pellucida and their sequestration by human oocytes in vitro
Authors: Zamboni L. , Smith D. Moore , Thompson R. S. 
Published: June 2005

AbstractThis study describes the fine morphologic features of follicle cell penetration through the zonae pellucidae of cultured human oocytes and the subsequent sequestration of the cells into the ooplasm. The observations made in this study would indicate that follicle cells progress through the zona pellucida because of their motility and that their sequestration by the oocytes occurs by phagocytosis. These phenomena are discussed on the basis of the knowledge of the process of sperm progression toward and into the egg at fertilization.
Regeneration in the African lungfish, Protopterus. II. Branching structures
Authors: Conant Elizabeth Babbott 
Published: June 2005

AbstractIt is possible to elicit the growth of a lateral branch from either the pectoral or the pelvic fin of the African lungfish Protopterus by excising a wedge of tissue, including cartilage, from the original limb. In pectoral limbs, 18 notches produced four bifids, but in pelvic limbs only one out of 14 cuts resulted in a branching element. Although cuts were distributed along the length of the limbs and along both anterior and posterior faces, accessory structures were elicited only from the posterior and posterior‐dorsal faces of the pectoral limb and from the anterior edge of the pelvic. The new branch was always of a size, proportion, and function nearly identical with that of the original, and to date none has grown longer than the equivalent branch of the primary limb. One broken pectoral limb gave rise spontaneously to a bifid growth.Fully developed horizontal branches effect changes in the long axis of the limb from which they have grown. Although the new filament first grows out perpendicular to the long axis of the primary element, it later assumes a shallower angle. Subsequent skewing of the axis of the primary limb results in a “Y” configuration. However, one vertically directed branch on the posteriordorsal surface of a pectoral limb, after ten months, still retains its original orientation, there having been no change in either its orientation or that of the original limb. One caudal anomaly is figured.
Studies of water uptake in the euryhaline crab, Rhithropanopeus harrisi
Authors: Capen Ronald L. 
Published: June 2005

AbstractWater uptake in the crab, Rhithropanopeus harrisi, was studied using D2O (deuterium oxide) as a label. Results were expressed as per cent saturation, or the D2O concentration in the blood, attained in a 30‐minute exposure to D2O at 20°C, expressed as a percentage of the D2O concentration in the bathing medium. Crabs acclimated to 75% sea water (SW), to which the blood is about isosmotic, had a mean per cent saturation of 51.8, and in 10% SW‐acclimated crabs (blood hyperosmotic by about 40% SW) the mean per cent saturation was 33.9. Thus, water uptake, or exchange, is slower when the osmotic gradient favors net water uptake than when no osmotic gradient exists. In gill chamber perfusion experiments at least 87% of the total water influx in 10% SW and 92% of the total in 75% SW are taken up in the gill chambers, the gills probably being responsible for most, if not all, of the uptake. The time course of acclimation between 10% SW and 75% SW was followed in both directions. Measurable changes in water uptake occurred in 30 minutes; half the change from 75% SW to 10% SW occurred in two hours (seven hours for the transfer from 10% SW to 75% SW), and over 90% of full acclimation was reached in two days.Gill chamber perfusion experiments showed that the receptor or receptors which perceive the change between 10% and 75% SW and mediate the change in water uptake are not in the gill chamber. Thus the system responsible for the change in water uptake is composed of at least a receptor with some means of communication (presumably nervous or hormonal) with the effectors (probably the gills).The use of Na+‐free and Cl−‐free D2O media showed that the absence of these ions did not affect water uptake, and that the change in water uptake was not caused by a change in influx of these ions.
The effects of cytochalasin B on the events of fertilization in the surf clam, Spisula solidissima. I. Polar body formation
Authors: Longo Frank J. 
Published: June 2005

AbstractInvestigations, employing the drug cytochalasin B (CB), have been carried out in an effort to determine the mechanisms underlying the processes involved in polar body formation and their possible relation to cytokinesis of mitosis. Fertilized eggs of the surf clam, Spisula were treated with 1 or 10 μg/ml CB and prepared for light and electron microscopy. Germinal vesicle breakdown and formation of the first meiotic spindle are similar in CB treated zygotes and in controls. At anaphase I a cytoplasmic protrusion develops at the site of the peripheral aster and contains dyad chromosomes. Although the inner aspect of the plasma membrane of this projection in CB treated zygotes is lined with a discontinuous layer of fine textured material, a cleavage furrow fails to form and the cytoplasmic bleb gradually regresses in size. The failure of the presumptive first polar body to cleave results in the presence of two groups of dyads within the zygote. These become aligned on separate or shared meiotic spindles in preparation for the second meiotic division. At anaphase II a protrusion, structurally similar to the first, is formed which also fails to separate from the zygote via a cleavage furrow. Due to the absence of polar body formation, four groups of maternally derived chromatin may be observed at the animal hemisphere of the zygote. These groups are organized into female pronuclei (usually 4) which may not be of equal ploidy. Failure of the cleavage furrow to develop during polar body formation in CB treated zygotes suggests that the filamentous material associated with the leading edge of the furrow of control specimens may function in a manner proposed for the contractile ring of mitotic cells.
The influence of ammonia on the transition to ureotelism in Xenopus laevis
Authors: Janssens P. A. 
Published: June 2005

AbstractToads of the species Xenopus laevis were immersed in 5 mM NH4Cl or 5 mM NaCl for periods of up to 28 days. In stronger solutions of NH4Cl, toads died within one hour. The rate of excretion of ammonia and urea and the activities of carbamyl phosphate synthetase, ornithine transcarbamylase, arginase and glutamate dehydrogenase in liver and kidney were measured. In toads in 5 mM NH4Cl, the excretion of urea was increased about ten‐fold, and there were increases in the activities of carbamyl phosphate synthetase and glutamate dehydrogenase in the liver. The activities of ornithine transcarbamylase and arginase in the liver, and of glutamate dehydrogenase in the kidney, were unaffected. In toads in 5 mM NaCl, there was no change in the rate of urea excretion or in the activities of any of the enzymes assayed. It was concluded that a rise in tissue ammonia levels is followed by alterations in the metabolic pathways of the toads which result in a decrease in those levels. Thus, the transition to ureotelism in X. laevis is triggered by an increase in tissue ammonia levels. Because there was no response to immersion in 5 mM NaCl, it is concluded that a slight increase in the osmotic pressure of the external medium has no effect, and that urea is of little significance in osmotic regulation in this toad.
Purification and site of synthesis of Aedes aegypti yolk proteins
Authors: Hagedorn H. H. , Judson C. L. 
Published: June 2005

AbstractThe identity and site of synthesis of the yolk proteins of the mosquito Aedes aegypti were studied. Disc gel electrophoresis of freshly prepared egg yolk revealed a predominant protein (YP‐1) which stained for bound lipid and carbohydrate. The molecular weight of the protein complex was estimated to be 2.7 × 105. It was present in vitellogenic females and absent in males and unfed females.Yolk Protein‐1 was purified by Sepharose and DEAE column chromatography and represented 75% of the protein extractable from the egg. The lipids conjugated to YP‐1 were identified as phosphatidyl choline, phosphatidyl ethanolamine and several steroids. The carbohydrate content was estimated as 10.5% with a phenol‐sulfuric acid method, and 5.8% with an orcinol method.The site of yolk protein synthesis was determined using antibody to purified yolk to precipitate labeled yolk proteins from organ culture media. Only the fat body synthesized antibody precipitable material. Synthesis began five to six hours after the blood meal, reached a peak of activity by 20 hours and declined to low levels of synthesis by 72 hours. These data correlate well with endocrino‐logical evidence indicating that egg development requires a hormonal factor from the head from four to eight hours after the blood meal.
Nickel uptake by sea urchin embryos and their subsequent development
Authors: Timourian Hector , Watchmaker George 
Published: June 2005

AbstractThere is active uptake of radioactive nickel by fertilized eggs and embryos of the sea urchin Lytechinus pictus. The nickel taken into the cells is free and can be released by the addition of exogenous, non‐radioactive nickel. The morphological development of embryos raised in sea water containing 10−2 to 10−6 M NiCl2 was investigated. Nickel uptake is initiated right after fertilization, but its effect on development does not appear until much later. Embryos grown in 10−2 and 10−3 M NiCl2 cleaved at a normal rate and formed blastulae but did not gastrulate. Embryos grown in 10 −4 to 10−6 M NiCl2 were able to gastrulate but failed to develop dorsoventral symmetry and formed radialized larvae.
On the neuroendocrine control of ovarian development in the Monarch butterfly
Authors: Barker John F. , Herman William S. 
Published: June 2005

AbstractSeveral methods have been used to examine the role of the neuroendocrine system in the regulation of ovarian development in the Monarch butterfly, Danaus plexippus. Ovarian development ceases after neck ligature, removal of the retrocerebral complex, disconnection of the retrocerebral complex from the brain, and after removal of the neurosecretory cells and associated neurons of the medial pars intercerebralis. Removal of the retrocerebral complex causes oocyte resorption in mature females. Normal ovarian development was obtained by injecting material with high juvenile hormone activity into animals lacking the retrocerebral complex, but normal ovarian development was not obtained in neck‐ligatured animals injected with the same material. The results suggest that the brain and corpora allata both act to regulate ovarian growth in this species. The brain apparently stimulates posteclosion corpora allata activity. The medial neurosecretory cells of the pars intercerebralis, or some other cephalic center, may produce a hormone requisite for quantitatively normal öogenesis. The corpora allata apparently stimulate vitellogenin synthesis.
Oxidative phosphorylation in mitochondria during, embryonic development
Authors: Henson Miriam M. 
Published: June 2005

AbstractP:O ratios have been determined in mitochondria from the liver and skeletal muscle of chicks ranging in age from eight days of incubation through hatching. The values obtained remain constant throughout development and are the same as those of mitochondria from corresponding tissues of the adult. Developmental changes in respiratory control (RC) show variations depending on the tissue and the substrate oxidized. RC is constant in liver mitochondria with all substrates; in muscle mitochondria, RC increases with glutamate and αketoglutarate, while with malate, RC shows a marked decrease prior to hatching. Similarly, changes in specific activity of oxidation and phosphorylation in mitochondria vary with tissue and developmental stage. In liver mitochondria, specific activities of oxidation and phosphorylation with glutamate and αketoglutarate decrease during development; in muscle mitochondria, specific activities with these substrates increase. With malate, specific activities increase in liver, but decrease in muscle mitochondria; in the latter tissue this occurs at about the time of hatching. Added cytochrome c increases oxidation rate of muscle mitochondria, the increase being progressively greater the older the animals from which the mitochondria are derived.