bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of shadows in directional training and homing of pigeons, Columba livia
Authors: McDonald Dennis L. 
Published: June 2005

AbstractSome of the hypotheses of how homing pigeons are able to find their way home would require them to make precise measurements of the location of the sun. The purpose of this study was to determine if homing pigeons can measure the altitude and azimuth of a light source accurately enough to use the hypothesized navigational systems. Also the specific cues the pigeons used for the discriminations were analyzed.A psychophysical technique in which the pigeon controls the movement of
the light (or of itself) toward or away from a trained direction was used. The
ability to perform this task gives evidence on how accurately homing pigeons
can measure the location of a light source such as the sun.Five pigeons were trained and tested. They were able to discriminate differences of as little as 3.4° in azimuth of the light source; 8° in altitude. It was
determined that shadow patterns in the apparatus were used in all the discriminations. The role shadows may have played in the directional training
done in the past, and the role shadows may play in the natural homing
process of pigeons are discussed.
Stimulation of limb regeneration in the lizard Xantusia vigilis by means of ependymal implants
Authors: Bryant Susan V. , Wozny Kenneth J. 
Published: June 2005

AbstractThe experiments reported in this paper demonstrate that ependymal cells can stimulate a regenerative outgrowth when implanted into the limb of a lizard. Simple limb amputation, amputation followed by a sham operation, and amputation followed by the implantation of a cartilage tube from a tail regenerate were ineffective in causing the hind limbs of Xantusia vigilis to regenerate. However, amputation followed by the implantation of a cartilage tube containing ependyma caused regenerative outgrowths in 82% of the treated limbs. These results show that ependymal cells, in addition to initiating tail regeneration in their normal location, can when transplanted to the limb, initiate limb regeneration.
Viable amphibian hybrids produced by circumventing a block to cross‐fertilization (Rana clamitans ♀ × Rana catesbeiana ♂)
Authors: Elinson Richard P. 
Published: June 2005

AbstractEggs of Rana clamitans in their own jelly coat are not fertilized by sperm of other species. When the eggs were surrounded by jelly from another species, they were fertilized by R. catesbeiana and R. septentrionalis sperm. The hybrid nature of the resulting embryos was confirmed by detection of paternal enzyme forms. The R. clamitans ♀ × R. septentrionalis ♂ embryos arrested by the tailbud stage. The R. clamitans ♀ × R. catesbeiana ♂ embryos developed into viable tadpoles and subsequently metamorphosed. The hybridization results coupled with the similarity of enzyme patterns indicate that R. clamitans and R. catesbeiana are genetically closely related. R. clamitans is probably not as closely related to R. septentrionalis based on the enzyme patterns. Since cross‐fertilization or early developmental failures of hybrids could be explained by a small number of genes, such failures must be considered with caution in determining species relationships.
An analysis of color change phenomena in the leaf frog, Agalychnis dacnicolor
Authors: Iga Tetsuro , Bagnara Joseph T. 
Published: June 2005

AbstractIn vivo and in vitro studies of integumental color change in the leaf frog, Agalychnis dacnicolor, are reported. A color index is established for the assessment of color change in the absence of melanophore visibility. Green leaf frogs adapt rapidly to background by controlling MSH release. Some members of the population are always brown regardless of background. Naturally brown specimens respond to localized reductions in illumination by becoming green in the affected area. Either skin or chromatophores in these areas are photosensitive. Isolated skins darkened with theophylline are not photosensitive; however, masking of areas of isolated skins prevented darkening of the masked area. Contact between skin and mask may inhibit darkening by physically preventing melanosome dispersion. Neither melanosome aggregation nor dispersion occur in isolated skins incubated in oxygen‐free media. Experiments involving denervation and electrical stimulation both in vivo and in vitro fail to implicate a chromatophore control by innervation.
Prolactin‐thyroxine antagonism and the metamorphosis of visual pigments in Rana catesbeiana tadpoles
Authors: Crim Joe William 
Published: June 2005

AbstractThe relationship between prolactin‐thyroxine antagonism and the metamorphosis of visual pigments in larval amphibians has been investigated using bullfrog (Rana catesbeiana) tadpoles. Although prolactin‐thyroxine antagonism is demonstrable by morphological criteria, ovine prolactin does not appear to antagonize thyroxine‐induced rhodopsin synthesis. The hypothesis is offered that prolactin‐thyroxine antagonism is the result of differential gene activities which are opposite in their physiological effects.
Regeneration of the tail bud in Xenopus embryos
Authors: Deuchar Elizabeth M. 
Published: June 2005

AbstractIn an attempt to solve some aspects of the long‐standing controversy about the regenerative ability of appendages in vertebrate embryos, the tail bud of Xenopus laevis embryos has been amputated at stages ranging from St. 26 to St. 32 and its ability to regenerate during a culture period of 2–3 days has been studied. At amputation stages 26–28, the tail bud consisted only of undifferentiated mesoderm and ectoderm, but at stage 32 it had a fully differentiated neural tube, a vacuolated notochord and segmented somites. A total of 137 amputations at different stages gave consistent results: a tail formed in all the operated larvae and it had normal, well‐developed axial tissues in most cases. The relatively few cases with abnormal tail structure were stunted, oedematous larvae with defects in the trunk region as well. It is concluded from these experiments that cells near the original tail bud are able to differentiate into tailbud tissue and to replace the amputated region, even at these late embryonic stages. The implications of these findings for comparative studies on regeneration in vertebrates are discussed.
Gallium‐67 distribution in pregnant mammals
Authors: Tyndall R. L. , Chaskes S. J. , Carlton J. E. , Nelson Bill , Daniel J. C. 
Published: June 2005

AbstractStudies on the distribution of 67Ga in pregnant rabbits showed a marked concentration of the isotope in uterine tissue and flushings of 5‐day pregnant rabbits 24 hours after isotope injection. The isotope no longer localized throughout the uterine tissues and flushings on injection of 7‐ to 8‐day pregnant rabbits but was specifically associated with the blastocysts and sites of implantation. As the gestation time progressed 67Ga increasingly concentrated in placental and mammary tissue while the concentration in serum and thymus tissue decreased. The marked concentration in placental tissue was readily discernible on total‐body scans of pregnant rabbits.Column chromatography of uterine washings and placental extracts from pregnant rabbits and thymus extracts from estrous rabbits showed most of the isotope associated with moieties ⩾ 200,000 MW whereas the isotope in “milk” and extracts of mammary tissue was bound to components of 25,000–35,000 MW. Extracts of thymus from pregnant rats showed a marked, selective loss of 67Ga binding in two peaks of approximately 50,000 and 120,000 MW compared to the chromatographic profile of extracts from normal rat thymus.
Control of sex differences in the plumage of the house sparrow, Passer domesticus
Authors: Mueller Nancy S. 
Published: June 2005

AbstractIn an experimental study of sexual dimorphism in plumage coloration in the house sparrow, Passer domesticus, skin grafts were exchanged between nestlings on the first to sixth day after hatching. Before fledging, the young birds were moved from the nest to cages and kept for several weeks for observation of the coloration of feathers produced by host and graft skin. The adult feathers that developed on grafted skin at the postjuvenal molt corresponded to those of the donor, regardless of the sex of the host.
Evidence against gene expression after meiosis in the male mouse
Authors: Brock William A. 
Published: June 2005

AbstractIsozyme patterns in homogenates from various testicular cell types from mice were examined in an effort to ascertain whether the haploid genome is expressed during spermiogenesis. Male mice heterozygous for electrophoretic variants of several glycolytic enzymes were analyzed by starch gel electrophoresis. The enzymes examined were isocitrate dehydrogenase, glucose‐6‐phosphate dehydrogenase, and glucosephosphate isomerase. The isozyme patterns produced by these dimeric enzymes reflect the relative activity of genes in each cell type. These patterns reveal the presence or absence of the transcription of specific genes during spermiogenesis. We found that the genes encoding these enzymes continue to increase during spermiogenesis. Synthesis of these enzymes most likely continues in spermatids, but this synthesis must depend upon premeiotically produced mRNA. These data provide biochemical evidence for the hypothesis that the phenotype of the haploid mammalian gamete depends upon the preceding diploid genome and that a mechanism must exist for the long term post‐transcriptional regulation of gene expression during spermiogenesis.
Termination of photorefractoriness in golden hamsters—photoperiodic requirements
Authors: Stetson Milton H. , Watson‐Whitmyre Marcia , Matt Kathleen S. 
Published: June 2005

AbstractThe photorefractory period of golden hamsters is characterized by the failure of short daylengths (<12.5 hours per 24) to induce gonadal regression. Photorefractoriness is terminated by prolonged exposure to long daylengths (>12.5 hours per 24). This study was designed to determine the precise duration of long day (LD 14:10; 14 hours light/24) exposure necessary to terminate refractoriness. The data indicate that 11 weeks of LD 14:10 terminate refractoriness in nearly every hamster. Exposure for fewer than 11 weeks is less effective whereas exposure for more than 11 weeks is no more effective. The data show that hamsters begin measuring long days to terminate photorefractoriness irrespective of the physiological state of the reproductive system, and, therefore, that photorefractoriness is induced some time during the period of testicular regression (during the first 10‐12 weeks of short day exposure).
Frog lysozyme. V. Isolation and some physical and immunochemical properties of lysozyme isozymes of the leopard frog, Rana pipiens
Authors: Snyder John A. , Harrison James H. 
Published: June 2005

AbstractFrog Lysozyme has been purified by sequential application of acid extraction, salt fractionation, CM‐cellulose chromatography, heat treatment, and gel filtration. Eight isozymes of purified lysozyme were found to be stable during prolonged storage. Isozymes were separated by preparative polyacrylamide gel electrophoresis. Ninety percent of the lytic activity of frog ovarian egg was represented by forms 7 and 8, the most highly charged isozymes. Seventy‐eight percent of frog liver lysozyme activity was that of form 4. Forms 7 and 8 differed from form 4 by being larger (apparent molecular weight of 18,000 vs. 16,000), by remaining active in more acidic environment, and by exhibiting a dependency upon NaCl for activity. Antiserum prepared against frog form 4 did not react with frog forms 7 and 8 and antiserum to chicken egg‐white lysozyme did not react with any frog lysozymes. All frog lysozymes showed identical reversible binding to deaminated chitin. Apparent size differences and lack of immunological cross‐reactivity suggest that at least some of the isozymes are nonallelic.
The adjustable “pinhole camera” eye of Nautilus
Authors: Hurley Ann C. , Lange G. David , Hartline Peter H. 
Published: June 2005

AbstractThe “pinhole camera” eye of the chambered nautilus, Nautilus pompilius, contains an adjustable pupil which dilates or constricts in response to changes in light intensity. The dynamics of this pupillary reflex were studied. Closing times for the pupil in response to a sudden increase in light intensity were on the order of ninety seconds. Opening times in response to decreased light intensity were approximately fifty seconds. Stimulation of one eye would cause a constriction of the pupil in the unstimulated eye. The time course of this response was different from that seen in the ipsilateral stimulation experiments.
Water economy of the earthworm Lumbricus terrestris L.: Coping with the terrestrial environment
Authors: Carley Wayne W. 
Published: June 2005

AbstractAlthough it displays many characteristics of a freshwater ani‐mal, the earthworm Lumbricus terrestris survives well in moist terrestrial environments. Earthworms in soil are only partially hydrated and gain weight when transferred to pond water. Worms in air of 70–80% relative humidity (RH) have a much higher dehydration rate than do animals at 100% RH. Compared with animals at 100% RH, the integumental water exchange rate of worms at 70–80% RH is significantly lower than expected based on the amount of water in the atmosphere. Lumbricus may reduce its integumental permeability to re‐strict water loss in terrestrial environments, but cannot regulate the osmotic pressure of its coelomic fluid at relative humidities lower than 100%.
Allopurinol‐induced melanism in the tiger salamander (Ambystoma tigrinum nebulosum)
Authors: Frost Sally K. , Bagnara Joseph T. 
Published: June 2005

AbstractThe enzyme, xanthine dehydrogenase (XDH), has been examined in Ambystoma tigrinum nebulosum with respect to its role in pigmentation. It now seems probable that the melanoid gene (m) either codes directly for XDH or is somehow intimately connected with the normal function of this enzyme. Inhibition of XDH using the drug, allopurinol, results in animals which appear to be phenocopies of melanoid mutants as described for the Mexican axolotl (Ambystoma mexicanum). The effects of allopurinol in terms of specific pigmentary alterations were examined, and a new method for analyzing heterogeneous extracts of skin pigments (e.g., purines and pteridines) is presented. The significance of the link between XDH and melanism is discussed with emphasis on possible mechanisms of pigment induction and general applicability to biological systems.
Parameters for growth of the imaginal wing disk in last instar larvae of Galleria mellonella L
Authors: Meyer Dietrich R. , Sachs Felix N. , Rohner Renate M. 
Published: June 2005

AbstractIn last instar larvae of Galleria mellonella, the observed increase in the number of cells of growing intact imaginal wing disks was completely blocked by ligation of the mesothorax and stimulated again by external applications of low and high doses (2.6 to 130 μg/g) of ecdysterone. However, at no hormonal dose applied has the full extent of normal wing growth been attained. The ecdysteroid dependent cuticle synthesis could be induced in disks of various sizes. The cell number of imaginal disks of young last or supernumerary instar larvae is exponentially correlated with the body weight. The rates of cell division during prepupal development of the wing disk appeared to be about the same in last and supernumerary instar larvae.In normal pupae the borders of the everted wings are fitted precisely to a cuticular demarcation line on the underlying abdomen. X‐ray irradiations of last instar larvae led to a reduction of the pupal wing surface and cell number, but did not affect the position of the demarcation line. The X‐ray experiments confirm the finding that reduced wings are capable of normal pupal cuticle synthesis.
Dissolution of cytoplasmic actin bundles and the induction of nuclear actin bundles by dimethyl sulfoxide
Authors: Sanger J. W. , Gwinn J. , Sanger J. M. 
Published: June 2005

AbstractWithin 30 minutes of exposure to medium containing 10% dimethyl sulfoxide, PtK2 cells begin to round up and lose their cytoplasmic actin bundles. At the same time, bundles of actin filaments appear in the nuclei of the cells. One to 2 hours after the dimethyl sulfoxide is removed from the medium, the cells revert to their flattened shape, losing the nuclear actin bundles and regaining the cytoplasmic bundles.
Micronuclear events during conjugation in nucleo‐cytoplasmic hybrids of Paramecium caudatum
Authors: Fujishima Masahiro 
Published: June 2005

AbstractThe germinal micronucleus in cells of mating type V of P. caudatum, syngen 3 was removed and replaced with a micronucleus of syngen 1 by the microinjection method. The resulting nucleo‐cytoplasmic hybrids were able to grow with mitosis of the transplanted micronucleus. When these cells were mated with cells of complementary mating type VI, the micronucleus was able to perform all the prezygotic nuclear divisions normally occurring in conjugating syngen 3 cells. This technique of intersyngenic micronuclear transplantation may provide a good instrument for genetic analysis between different syngens in cases where conventional cross‐breeding analysis is not easy because of sexual isolation.
Immunochemical characterization and quantification of larval brine shrimp malate dehydrogenase
Authors: Hand S. C. , Conte F. P. 
Published: June 2005

AbstractThe cytosolic malate dehydrogenase (s‐MDH) from larval brine shrimp has been immunochemically characterized by quantitative rocket immunoelectrophoresis (IEP) and antibody catalytic inhibition studies. Monospecific rabbit antiserum produced against purified naupliar s‐MDH was used for rocket IEP as a quantitative assay for the cytoplasmic isozyme. Since cross‐reactivity was not observed against the mitochondrial MDH (m‐MDH), the assay allows specific measurement of the s‐MDH in crude naupliar supernatants in the presence of contaminating m‐MDH. The assay has a sensitivity of approximately 100 nanograms s‐MDH protein using either purified enzyme solutions or crude supernatant preparations. Catalytic inhibition studies using the monospecific antiserum gave 85% inhibition of s‐MDH but did not give significant inhibition of the m‐MDH. Lack of complete s‐MDH inhibition by the antiserum suggests a difference between the enzyme active site and immunological binding site. Although the antiserum was produced against s‐MDH from nauplii of the San Francisco Bay population, the antiserum inhibits equally well the s‐MDH of Great Salt Lake (Utah) nauplii, indicating little if any structural difference in the immunological sites of the s‐MDHs from these two geographical sources. Porcine (s‐ and m‐MDH), bovine (m‐MDH), and pigeon (m‐MDH) were also tried as antigens against the brine shrimp s‐MDH antiserum, but antigen‐antibody reactivity was not observed during rocket IEP or catalytic inhibition experiments.
Larval brine shrimp malate dehydrogenase: Biosynthesis and temporal pattern related to environmental salinity
Authors: Hand S. C. , Conte F. P. 
Published: June 2005

AbstractBrine shrimp nauplii challenged with artificial sea water containing 2.5 M NaCl maintain significantly higher levels of cytoplasmic malate dehydrogenase (s‐MDH) than larvae incubated in sea water having 0.5 M NaCl. Eight to ten hours after emergence, free‐swimming nauplii living in 0.5 M NaCl exhibit a steady decline of s‐MDH for 20–40 hours; the decrease is less and stabilizes earlier — in nauplii incubated in 2.5 M NaCl. The 14C‐labeled amino acids produced by H 14CO3 fixation were rapidly incorporated into newly formed s‐MDH protein as assayed using quantitative rocket immunoelectrophoresis (IEP) with monospecific antiserum prepared against purified brine shrimp s‐MDH. Higher rates of enzyme biosynthesis (>45%) occurred in 2.5 M NaCl together with rapid s‐MDH turnover (half‐life = 17 hours), accounting for the difference observed in enzyme level between different salt regimes. In contrast, incorporation of 14C‐labeled amino acids into total cytoplasmic protein decreases slightly in high salt, suggesting that a preferential synthesis of s‐MDH is taking place. Temporal patterns of s‐MDH during embryonic development were monitored using both catalytic activity and quantitative IEP assays. Levels of s‐MDH seen in encysted gastrulae (0.22 units or 0.57μg s‐MDH protein/100 embryos) remain relatively constant through the E1 and E2 emergent stages until the exhibited decline observed in the naupliar stage. The results are discussed in relation to the bioenergetics and temporal development of water and electrolyte regulation in nauplii.
The culturing of dissociated newt forelimb regenerate cells
Authors: Jabaily Joseph A. , Blue Patricia , Singer Marcus 
Published: June 2005

AbstractA procedure is described for the mechanical dissociation and culturing of early stage newt regenerate blastema cells. The specified growth medium is adjusted to suitable osmolarity and consists of Leibovitz L‐15, water, fetal calf serum, and insulin. This provides a suitable environment in which growth, proliferation, and some differentiation occur with time as evidenced by phase contrast photographs of living cultures.
Properties of the vitelline coat lysin from toad sperm
Authors: Iwao Yasuhiro , Katagiri Chiaki 
Published: June 2005

AbstractThe sperm of the toad, Bufo bufo japonicus, smeared on a gelatin film displays a “halo” reaction around the acrosomal region. The treatment of sperm with 0.5% Triton X‐100 yielded activity which lyses the vitelline coat (VC) of coelomic eggs, but not the fertilization coat of activated eggs. Electronmicroscopy showed that these detergent‐treated sperm had lost the plasma membrane and the acrosomal cap, indicating acrosomal localization of the VC lysin. The VC lysin was able to lyse the VCs of several heterologous anuran species, and this activity correlated well with the occurrence of cross‐fertilization by Bufo sperm. Proteolytic activities of the VC lysin were quantitated employing N,N‐dimethylated VC proteins or casein as substrates. Successive fractionation by NH4 2SO4 precipitation, DEAE‐cellulose chromatography, and Sephadex gel filtration yielded a 100‐fold increase of proteolytic activity compared with that of the original detergent extract. On gel filtration, the VC lysin activity was recovered both in the M.W. 54,000 fractions and the considerably higher (>100,000) M. W. fractions. Part of the latter activity was recoverable in the former after the treatment with urea and rechromatography. The VC lysin was most active at pH 7.4, but its activity was lost by preincubation at temperatures higher than 60°C. The activity was inhibited considerably by serine‐protease and chymotrypsin inhibitors, but not at all by trypsin inhibitors. The lysin was unable to hydrolyze arginine or tyrosine esters, but was able to hydrolyze active site titrants for chymotrypsin more effectively than for trypsin. In all aspects the VC lysin, although sharing some properties with serine‐proteases such as chymotrypsin, is a unique proteinase(s) well adapted to its role in fertilization.