bluuebunny/crossref_metadata_2025_split huggingface dataset:
Division of constricted and urethane‐treated sand dollar eggs: A test of the polar stimulation hypothesis
Authors: Rappaport R. , Rappaport Barbara N. 
Published: June 2005

AbstractIn spherical cells with a central mitotic apparatus, the centers of the asters are closer to the poles than to the equator. This circumstance is basic to several hypothetical explanations of the way in which the mitotic apparatus establishes the division mechanism. This investigation was designed to determine whether that geometrical relationship is necessary for division.Fertilized, mechanically denuded sand dollar eggs were inserted into glass loops, which reduced the diameter in the constriction plane from the normal 142 to 78–80 μm and partly constricted the cell into equal parts. The mitotic apparatus straddled the constriction, and its length was not significantly changed. The manipulation increased the distance from the astral centers to the poles and decreased the distance from the astral centers to the equator to a degree that reversed the normal distance relations. These cells divided normally.Ethyl urethane (0.06 M) reduces the size of the mitotic apparatus and blocks cleavage in spherical cells. When treated cells are confined in 80‐μm i.d. capillaries, they divide. Treated cells also divide when they are constricted by an 80‐μm i.d. glass loop if the mitotic apparatus straddles the constriction. An equal degree of constriction in the subfurrow and subpolar areas did not reverse the effect of urethane.The results demonstrate that cleavage does not depend on the normal distance relation between the mitotic apparatus and the poles, and that the urethane effect can be remedied only by reducing the distance between the mitotic apparatus and the equatorial surface. Both findings are inconsistent with the polar stimulation hypothesis.
Compensatory testicular hypertrophy in the lizard Anolis carolinensis
Authors: Summers Cliff H. 
Published: June 2005

AbstractIn reproductively responsive, male Anolis carolinensis undergoing artificially induced testicular recrudescence, unilateral orchidectomy of the left testis produced compensatory hypertrophy of the remaining testis. Testosterone inhibited this compensatory testicular hypertrophy on a weight basis, but did not reduce the rate of spermatogenic development. These results suggest that there is a mechanism of testosterone feedback in Anolis carolinensis that controls gonadotropin secretion during the recrudescent phase. In reproductively thermorefractory lizards, unilateral orchidectomy had no effect on the remaining testis. Administration of exogenous follicle‐stimulating hormone to refractory animals increased testicular weight and stage of spermatogenic development. Sensitivity to gonadotropin, as well as failure of unilateral orchidectomy to produce compensatory hypertrophy in refractory male anoles, suggests that the control of the refractory period in A. carolinensis results from physiological mechanisms in the pituitary gland or brain rather than in the testis.
The development potential of ethanol‐induced monosomic and trisomic conceptuses in the mouse
Authors: Kaufman M. H. , Bain I. M. 
Published: June 2005

AbstractThe development potential of fertilized embryos isolated from female mice previously given a single dose of either a dilute solution of ethanol or distilled water (controls) by mouth was studied. Exposure to ethanol occurred at various times during the cycle leading to ovulation and shortly after fertilization. The chromosome constitution of all preimplantation embryos isolated from these females was determined either at the first cleavage mitosis or at the morula stage. The incidence of aneuploidy in the ethanol‐exposed groups at these times was approximately 19% and 13.5%, respectively, with a similar number of monosomic and trisomic conceptuses observed at these times. In addition, about 2% of all conceptuses examined were triploid. Further females were autopsied on the 10th or 11th day of gestation, though the chromosome constitution of only the morphologically abnormal or developmentally retarded embryos was determined. Eight embryos out of a total of 16 studied in the ethanol‐exposed group were either aneuploid or triploid, whereas in the control group only one out of 11 examined proved to be aneuploid. The triploids and ethanol‐induced aneuploid conceptuses appeared to be capable of surviving to the morula stage but generally failed to survive to the 10th/11th day. No monosomics were in fact observed in the postimplantation series. The present findings are briefly discussed with reference to the possible pathogenesis of spontaneous abortions in man, which often possess similar types of chromosomal anomalies.
Firing patterns of closer motoneurons during reflex activity in the dimorphic claws of the Lobster Homarus americanus
Authors: Costello Walter J. , Hill Russell H. , Lang Fred 
Published: June 2005

AbstractThe in vivo firing patterns of the fast closer excitor (FCE) and slow closer excitor (SCE) motoneurons to the dimorphic claws of the lobster Homarus americanus were analyzed during reflex closure activity by identifying postsynaptic potentials in muscle fibers with known motor innervation. Three types of claw activity were observed: slow closure, rapid closure, and maintained closure. Slow closure and rapid closure in both claws were mediated by SCE and FCE, respectively. In the cutter, maintained closure was mediated only by SCE; in the crusher, both FCE and SCE could maintain closure. The homologous SCEs displayed no significant differences in activity; in both claws, they fired at medium‐to‐high frequency. The homologous FCEs did display different spike frequencies during claw closure. The crusher FCE fired at high frequencies; the cutter FCE fired at much lower frequencies. Such in vivo differences in axon activity between homologous FCEs are correlated with claw dimorphism and with the population of muscle fiber types.
Injury, nerve, and wound epidermis related electrophoretic and fluorographic protein patterns in forelimbs of adult newts
Authors: Garling David J. , Tassava Roy A. 
Published: June 2005

AbstractPolyacrylamide slab gel electrophoresis and [35S]methionine fluorography were used to examine proteins in regenerating newt limbs, amputated denervated limbs, unamputated denervated limbs, and separated blastema mesodermal core and wound epidermis. A total of 27 protein electrophoretic bands were obtained from amputated limbs and 24 bands from unamputated limbs. Amputation resulted in the appearance of 4 new bands and the loss of 1 band as compared to unamputated limbs. These 5 banding differences were apparent on stained gels 3 days postamputation and were maintained through 10 weeks postamputation (complete regenerate stage).Only one band in unamputated limbs was always detectable on fluorographs, whereas virtually all of the stainable bands of amputated limbs were visible on fluorographs. Amputation clearly stimulated a marked, generalized increase in the synthesis of limb proteins.The 5 amputation induced changes were equally evident in stained gels of both innervated and denervated limbs. Amputated denervated limbs possessed a full set of fluorographic bands (including the 5 differences) through 18 days postamputation. However, denervation without amputation was not sufficient to alter the stainable banding pattern.Wound epidermis and mesodermal core both displayed the 5 banding differences and had identical banding patterns with the exception of one epidermal specific band. This band was also present in whole limb skin but was absent in unamputated mesodermal limb tissue. This was the only band of unamputated limbs that was consistently detectable by fluorography.It is concluded that amputation induces nerve independent changes in protein synthesis that are common to both mesodermal core and wound epidermis. These changes may represent preparation for cellular proliferation.
Electrophysiology of in vitro insulin‐ and progesterone‐induced reinitiation of oocyte meiosis in Rana pipiens
Authors: Lessman C. A. , Marshall W. S. 
Published: June 2005

AbstractInduction of meiosis in Rana pipiens oocytes in vitro was studied using intracellular electrophysiological recordings and a morphological count of nuclear dissolution. In type III (i.e., defolliculated theca‐free, with follicle cells) and type IV (i.e., denuded lacking follicle cells) Rana oocytes (Schuetz and Lessman, '82), Na+‐insulin evoked nuclear or germinal vesicle dissolution (GVD), apparent reinitiation of meiosis, and marked reductions in cellular membrane potential and membrane current. Electrophysiological indications of the reinitiation of oocyte meiosis were most strongly apparent in the marked reduction (ca. 98%) of membrane current. The overall GVD activity of insulin was reduced but not totally absent in type IV oocytes compared to type III cells that received similar hormone treatment, confirming previously published findings that the follicle wall enhances insulin‐induced GVD. Results confirm insulin GVD activity in this system and demonstrate that insulin‐induced reinitiation of meiosis is associated with changes in membrane‐associated parameters that are indistinguishable from those induced by progesterone. These results raise interesting questions concerning the cellular mechanism by which two chemically dissimilar hormones (i.e., steroid vs. protein) have similar or even identical effects on a cell such as the oocyte. The findings presented are consistent with the concept that more than one hormone may be involved in meiotic maturation of the oocyte.
A possible mechanism of chemical induction of conjugation in Paramecium: Importance of cationic exchange on the cell surface
Authors: Kitamura Akio , Hiwatashi Koichi 
Published: June 2005

AbstractThe effect of calcium ions on the chemical induction of conjugation in Paramecium caudatum was examined in the simplest medium that induces conjugation, containing either KCI or MnCl2 in TRIS‐HCI buffer. The concentration of K ions necessary for induction increased with the concentration of Ca ions added. The maximum induction of conjugation took place at a constant ratio of the K+ concentration to the square root of the Ca2+ concentration regardless of their ionic strengths. Similar results were obtained in the induction by Mn2+, where the square root of the Mn2+ concentration is proportional to the square root of the Ca2+ concentration for maximum induction. The results strongly suggest that the activation for conjugation is closely related to removal of Caions bound to the cell surface and that an ion exchange system on the cell surface governed by Gibbs‐Donnan principle has an essential role in the chemical induction of conjugation in Paramecium.
Induced androgenesis in rainbow trout
Authors: Parsons James E. , Thorgaard Gary H. 
Published: June 2005

AbstractAndrogenesis was induced in rainbow trout, Salmo gairdneri, when eggs were irradiated with Co60 gamma‐radiation prior to fertilization. Peak survival of the androgenetic haploids occurred at a radiation dosage of 3 × 104 roentgen (R). The survival of these androgenetic haploid embryos was not significantly lower than that of the gynogenetic haploids. Haploidy and all‐paternal inheritance were confirmed by chromosome counts and by the use of a recessive albino color marker. If androgenetic diploids can be produced, androgenesis should prove useful in the production of inbred lines for genetic studies and breeding programs.
In vitro 11‐ketotestosterone and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one production by testicular fragments and isolated sperm of rainbow trout, Salmo gairdneri
Authors: Ueda Hiroshi , Kambegawa Akira , Nagahama Yoshitaka 
Published: June 2005

AbstractTwo different testicular tissue preparations, testicular fragments and isolated sperm were incubated in the presence or absence of chumsalmon gonadotropin (SGA, lμg/ml), 17μ‐hydroxyprogesterone (17μ‐OHprog, 0.1 μg/ml) and testosterone (T, 0.1 μg/ml). 11‐Ketotestosterone (11‐keto T) and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17α,20β‐diOHprog) in the incubation medium were measured by specific radioimmunoassay. Incubation of testicular fragments with SGA, 17α‐OHprog or T resulted in a highly significant increase in 11‐keto T levels in the incubation medium. Sperm preparations did not produce 11‐keto T under any incubation condition. Both testicular fragments and sperm preparations produced large amounts of 17α,20β‐diOHprog when incubated with 17α‐OHprog. SGA slightly stimulated 17α,20β‐diOHprog by testicular fragments but not by sperm preparations. These results suggest that different testicular elements are the sites of synthesis of 11‐keto T and 17α20β‐diOHprog. Furthermore, it is suggested the involvement of sperm in the production of 17α,2Oβ‐diOHprog in the testis of spermiating rainbow trout.
Changes in mitochondrial distribution and diffusion distances in muscle of goldfish upon acclimation to warm and cold temperatures
Authors: Tyler Seth , Sidell Bruce D. 
Published: June 2005

AbstractTransmission electron microscopy of myotomal muscle from goldfish (Carassius auratus L.) reveals significant differences in distribution and density of mitochondria in animals acclimated to cold temperature (5°C) as compared to those acclimated to warm temperature (25°C). Micrographs of red and white muscle from these animals have been analyzed quantitatively for the stereological parameters Vv (volume density), Sv (surface density), and S/V (specific surface); and diffusion distances between mitochondria have been calculated as the harmonic mean of spacings between clusters of mitochondria (τh). The most dramatic differences occur in Vv, Sv, and τh of red muscle, Vv and Sv being significantly greater in cold‐acclimated animals and τh being smaller. In white muscle, Vv is significantly greater for cold‐acclimated animals than warm‐acclimated animals, but other parameters are not significantly different. Using our values of Sv as estimates of the surface area through which exchange of metabolites occurs and our values of τh as estimates of the distance over which diffusion occurs, we calculate that the diffusivity constant in the one‐dimensional diffusion equation for metabolites may be reduced in cold‐acclimated animals to as low as 0.29 that of warm‐acclimated animals while still maintaining absolute rates of diffusive flux between cytoplasm and mitochondria. It appears reasonable to assume that cold‐induced rises in the concentration of enzymes in fish muscle reflect changes in organellar densities–changes which may serve primarily to ameliorate the effect of temperature on diffusive exchange between mitochondria and cytoplasm rather than solely to overcome catalytic limitation as is widely assumed.
Cellular location and partial characterization of the alanine aminotransferase in ribbed mussel gill tissue
Authors: Paynter Kennedy T. , Ellis Lehman L. , Bishop Stephen H. 
Published: June 2005

AbstractDifferential centrifugation of ribbed mussel gill tissue homogenates and extraction of the mitochondrial fraction demonstrated that most (72%) alanine aminotransferase (AlAT) activity was mitochondrial. Subsequent characterization of the cytosolic activity demonstrated properties identical to those demonstrated by the mitochondrial enzyme. Both enzyme fractions showed little variation in Vmax with pH, had low Km's for ketoacid substrates, and were inhibited by aminooxyacetate (AOA), L‐cycloserine, and β‐chloro‐L‐alanine. It appears that the AlAT in ribbed mussel gill tissue is strictly mitochondrial and that alanine production during hypoxia or hyperosmotic stress must be mitochondrial.
Size regulation and morphogenetic localization in the Dentalium polar lobe
Authors: Render Jo Ann , Guerrier Pierre 
Published: June 2005

AbstractLobe removal experiments show that the Dentalium embryo's first polar lobe is necessary for larval apical tuft and posttrochal region development. The smaller second polar lobe is necessary only for posttrochal region development. When vegetal halves of eggs are isolated before fertilization and then fertilized, they form size‐regulated first polar lobes. These polar lobes are proportional to the isolated halves in size and are necessary for posttrochal region but not apical tuft development. When vegetal halves are isolated after fertilization and then refertilized, they form polar lobes with an average volume that is less than that of normal first polar lobes but greater than that of size‐regulated polar lobes. Like normal first polar lobes, these lobes are necessary for both apical tuft and posttrochal region development. Localization of apical tuft and posttrochal region determinants occurs before fertilization and cannot be altered by the process. Polar lobe size specification occurs at first fertilization but can be somewhat modified by subsequent fertilization events. Size regulation does not affect the localization of apical tuft and posttrochal region determinants but does alter the developmental role of the first polar lobe.
Intracellular chloride activity and pH during polar lobe formation and cytokinesis in eggs and embryos of Ilyanassa obsoleta
Authors: Conrad Gary W. 
Published: June 2005

AbstractThe objectives of this study were to compare membrane potential, intracellular chloride activity, and intracellular pH in unfertilized and fertilized eggs of Ilyanassa obsoleta throughout polar lobe formation and cytokinesis. Membrane potential, ψm, was measured with single‐ and double‐barrel microelectrodes containing 3 M KCl. Chloride activity, (Cl)c, was measured with single‐barrel, chloride‐sensitive microelectrodes. Intracellular pH, pHc, was measured with double‐barrel microelectrodes, utilizing an antimony‐filled barrel to monitor pHc.Unfertilized eggs having a ψm of −13.7 mV displayed an average (Cl)c of 29.9 mM, whereas at electrochemical equilibrium, (Cl)ce, it would be 155.7 mM. This suggests that Cl is pumped out of the cell in eggs that are not fertilized. Fertilized eggs had a ψm of −78.2 mV and a (Cl)c of 18.6 mM. At electrochemical equilibrium, (Cl)ce would be 12.1 mM, thus suggesting that Cl is pumped into the cell in fertilized eggs. Double‐barrel microelectrodes measured a ψm of −69.0 mV and a pHc of 7.3 in fertilized eggs. The ψm, (Cl)c, and pHc remained stable as fertilized eggs underwent the cellular shape changes involved in forming first, second, and third polar lobes and first cleavage.
An acrosome reaction in sperm from the white sturgeon, Acipenser transmontanus
Authors: Cherr Gary N. , Clark Wallis H. 
Published: June 2005

AbstractThe A. transmontanus sperm possesses an elongate main body, a conspicuous acrosome, a midpiece, and a flagellum. Three membrane‐lined nuclear channels that are helically arranged extend from the acrosomal region to the midpiece. Sperm heads contain material that comigrates on sodium dodecyl sulfate (SDS)‐gels with actin. An acrosome reaction can be induced in freshwater with ionophore A23187, high pH, high Ca++, or egg water. This acrosomal reaction is a Ca+‐Mg+‐dependent event. The resulting acrosomal process (10 μm) originates from the subacrosome region and the nuclear channels. Non‐filamentous actin apparently polymerizes and forms the process.
Studies on the localization and activities of Concanavalin‐A‐reactive glycoproteins on the cell surface of sea urchin embryos
Authors: Matsumoto Emiko , Tonegawa Yasuto , Ishihara Katsutoshi 
Published: June 2005

AbstractInhibitory effects of Concanavalin A (con A) on sea urchin development were analyzed. Con A inhibited gastrulation at lower concentrations and disturbed cell association at higher concentrations. This cell‐dissociating effect was due to the binding of con A to specific sugar residues on the cell surface. By autoradiographic study on sectioned embryos, con A binding sites were shown to be mostly localized on cell membranes. The grain number increased during development, especially at the time of hatching, when functional cell association is known to be established. By dissociating embryos with Ca‐,Mg‐deficient artificial seawater (CMF‐SW), con A was shown to react with cell aggregation factor and with surfaces of dissociated cells. These results suggest that con‐A‐reactive materials on the cell surface are directly involved in the cell adhesion mechanism of sea urchin embryos.
Retinoic‐acid‐induced pattern completion in regenerating double anterior limbs of urodeles
Authors: Stocum David L. , Thoms Stephen D. 
Published: June 2005

AbstractThe effects of retinoic acid on the regeneration of double anterior lower arms in the adult newt, Notophthalmus viridescens, were investigated. Normally, double anterior lower arms regenerate a hypomorphic, symmetrical pattern of structures, which are distally complete; and double anterior upper arms regenerate a hypomorphic, symmetrical but distally incomplete pattern of structures. In limbs with a normal anteroposterior axis, the major effect of retinoic acid is to alter the proximodistal (PD) positional value of cells local at the amputation level to a much more proximal value, thereby creating duplications in the regenerate of structures proximal to the amputation plane (Thoms and Stocum, '84). Therefore, we predicted that double anterior lower arms treated with retinoic acid would regenerate like double anterior upper arms. However, in a substantial number of cases, each half of these double anterior lower arms regenerated a limb that was complete in the anteroposterior (AP) axis, with asymmetry corresponding to the half of origin. In addition, these regenerates were serially duplicated in the PD axis. These results indicate that retinoic acid can posteriorize the positional value of midline cells, leading to restoration of normal AP pattern, when the set of posterior‐half positional values is removed from the cross section of the limb.
The effects of Janus Green B on the temporal and spatial pattern of feather germ morphogenesis
Authors: Mayerson Paula L. , Fallon John F. 
Published: June 2005

AbstractThe normal timing and appearance of feather germs was per‐turbed by injecting the dye Janus Green B into the amniotic fluid of chick embryos at late stage 28, prior to the first appearance of feather germs. This treatment prevented feather germ morphogenesis in some regions while else‐where it delayed normal morphological development. The Janus Green B effect lasted for approximately 98 hours. Feather regions, which normally form epidermal placodes during the period of treatment, showed the longest delays in subsequent feather germ formation and were the most likely to remain featherless. These results suggest that the epidermal placode stage is critical for feather germ formation. Janus Green B appears to prevent feather germ morphogenesis by interfering with development prior to this critical stage. Since severely affected regions fail to recover their capacity to form feather germs, even after the period of sensitivity to the dye, a limited period of competence is suggested for feather germ formation.