bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyspermic fertilization in pigs during the luteal phase of the estrous cycle
Authors: Hunter R. H. F. 
Published: June 2005

AbstractMammalian eggs ovulated during the luteal phase of the estrous cycle or after progesterone injections rarely become fertilized, but the reasons for this low incidence of fertilization are not clear. Mature gilts were injected subcutaneously with 1,500 i.u. pregnant mare's serum gonadotrophin on Day 5 (second day of estrus designated as Day 1), followed by 500 i.u. human chorionic gonadotrophin intramuscularly on Day 9; ovulation occurred 40 to 42 hours later. Eggs recovered from the oviducts of slaughtered animals at specific intervals after ovulation were fixed, stained, and examined by phase‐contrast microscopy.None of the injected animals showed estrous symptoms. Of 165 eggs examined on Days 11 or 12 from 14 noninseminated animals, 160 (96.9%) were secondary oocytes and five (3.1%) were primary oocytes. Eggs penetrated by spermatozoa were recovered from 14 of 26 animals inseminated 4 to 18 hours before ovulation with 120 ml of fresh, undiluted semen; spermatozoa were recovered from the oviducts of a further three animals. Fifty‐one (31.9%) of 160 penetrated eggs from these 14 animals were normally fertilized, three eggs (1.9%) were fragmenting, nine (5.6%) were primary oocytes, and 97 (60.6%) were polyspermic. The polyspermic eggs contained varying numbers of accessory male pronuclei (2‐7) as well as from 2 to > 50 swollen and unswollen sperm heads. The high incidence of polyspermic eggs found during the luteal phase was considered to be due to an effect of the oviducal environment under the influence of ovarian progesterone on the mechanism controlling the block to polyspermy.
The role of cell migration in the development of the embryonic chick limb bud
Authors: Searls Robert L. 
Published: June 2005

AbstractExperiments were done to determine if cell migration is involved in cartilage differentiation in the embryonic chick limb bud. Blocks of tissue labeled with tritiated thymidine or with S‐35 sulfate were isolated surgically from early stage 22 limb buds or from the chondrogenic areas of stage 23 or stage 24 limb buds and implanted in unlabeled limb buds of embryos growing in ovo. The host embryos were allowed to develop, the limbs containing the labeled implants were fixed, and the effect of the development of the host on the implanted tissue and the effect of the implant on the development of the host was examined by autoradiography. The implanted blocks appeared to be integrated into the host limbs and to develop harmoniously with the host tissue. No evidence was obtained for any of the following events: (1) movement of cells out of the implanted block of tissue, (2) movement of host cells through the implanted block, or (3) interference by the implanted block with the normal development of the host. It is concluded that cell migration is not involved in the differentiation of cartilage in the embryonic chick limb bud.
Skin grafting in the bisexual teiid lizard Cnemidophorus sexlineatus and in the unisexual C. tesselatus
Authors: Maslin T. Paul 
Published: June 2005

AbstractSatisfactory procedures for skin transplants have been worked out in Cnemidophorus using C. s. viridis as a pilot species. The homograft reaction occurs in this form, the first clear signs of rejection appearing on about the twelfth day after surgery. Homografts, however, are not rejected in transplants between individuals of the same populations of C. tesselatus; but skin from two of three populations in eastern Colorado are rejected when transplanted to C. tesselatus of north central New Mexico. The reciprocal transplants, in contrast, are accepted by the Colorado forms. This evidence supports the hypothesis that C. tesselatus is parthenogenetic; but it is suggested that the disparity in the behavior of the grafts between the two Colorado populations and the New Mexico population is correlated with the triploid condition of the former and the diploid condition of the latter.
Action of hormones on germinal vesicle breakdown in frog (Rana pipiens) oocytes
Authors: Schuetz Allen W. 
Published: June 2005

AbstractThe mechanism of pituitary gland and progesterone induced germinal vesicle breakdown (GVBD) was investigated in isolated ovarian follicles or oocytes of Rana pipiens. The effects of removing follicular tissue and the metabolic inhibitors, puromycin and actinomycin D, on oocyte responsiveness to the hormones were of Rana pipiens. The effects of removing follicular tissue and the metabolic inhib of protein synthesis, blocked both pituitary and steroid induced GVBD. Timed inhibition studies indicated that protein synthesis was completed at a time approximately midway between the time of progesterone addition and the initiation of GVBD. Only a short exposure of oocytes (5–15 minutes) to progesterone was sufficient to initiate GVBD. Puromycin did not act by preventing the uptake of steroids by the ovarian follicles; however, it caused irreversible effects to oocytes when present in the incubation medium for more than 4 hours. Removal of the follicular tissue from oocytes did not impair oocyte GVBD following exposure to progesterone; however, pituitary induced GVB was inhibited in approximately 50% of the animals utilized. Addition of actinomycin D (100 μg/15 ml) prevented pituitary, but not steroid induced GVBD when added to the incubation medium at the time of hormone administration. Actinomycin D was increasingly ineffective in preventing GVBD when its addition to oocytes was delayed following exposure to pituitary tissue.These data suggest that pituitary and steroid induced GVBD are mediated by a common mechanism concerned with protein synthesis. The differential inhibition of pituitary induced GVBD with actinomycin D suggests the presence of a pituritary stimulated intermediary process prior to the initiation of protein synthesis. The ovarian follicular tissue appears to be partially responsible for mediating the action of the pituitary gland.
Relative roles of the pituitary, follicle cells, and progesterone in the induction of oocyte maturation in Rana pipiens
Authors: Masui Yoshio 
Published: June 2005

AbstractThe responses of ovarian oocytes obtained from mature frogs (Rana pipiens) to pituitary hormone were examined after removal of the follicular envelope. When the follicular envelope was removed manually or after treatment with collagenase, the apparently naked oocyte can still respond to pituitary hormone by germinal vesicle breakdown and by polar body formation. However, when the follicular envelope was removed after treatment with EDTA or Ca‐Mg‐free solution, the responsiveness of the oocyte was completely lost. Microscopic examination revealed that removal of the follicular cells was incomplete unless Ca‐Mg‐free solutions or EDTA were used. Complete removal of follicle cells prevents the oocyte from responding to pituitary hormone.Moreover, the naked oocytes packed together with previously separated follicular envelopes showed maturation responses when treated with pituitary hormone solution in the presence of large amounts of ovarian tissue. Naked oocytes which are unable to respond to pituitary hormone can nevertheless full respond to progesterone to undergo maturation reactions. In fact, germinal vesicle berakdown and polar body formation were brought about within intact ovarian tissue by treatment with progesterone alone. Oocytes responding to progesterone alone always remained within the follicular envelope.The degree of maturation of the oocytes after progesterone treatment was tested by means of nuclear transplantation. When nuclei obtained from blastula or early gastrula cells were implanted into treated oocytes, still within the follicular envelope, normal cleavage occurred. These results indicate that pituitary gonadotropin acts on the follicle cells to stimulate them to release a hormone that directly acts on the oocyte to induce maturation.
A test of the capacity of chick embryo cells to home after vascular dissemination
Authors: Burdick Morton L. 
Published: June 2005

AbstractExperiments were carried out to determine whether chick embryonic cells have the capacity to lodge preferentially in their homologous organ after intravascular dissemination in host embryos. Chick embryos incubated for five and one‐fourth days were used as donor and hosts. Donors were labeled with tritiated thymidine and selected organs were dissociated into single cells with trypsin. In separate experiments, labeled cells of mesonephros, limb, or heart ventricle were injected into hosts via a large chorioallantoic vein. The hosts were sacrificed 6 and 24 hours later. In each experiment, autoradiographs were prepared from serial sections of these three organs and the labeled cells in each organ were counted.The distribution of cells among the three organs was found to be almost identical for the three types of cells and at both time periods. Approximately 65–78% of the cells found in the three organs were in the mesonephros; about 21–31% were in the limbs; and about 1–4% were in the ventricle. Thus the cells failed to show a tendency to home; their distribution was completely independent of their organ source. These results suggest that homing is not a general property of embryonic cells, and their lodging properties offer no support for the hypothesis that embryonic cells of different types have highly type‐specific adhesive preferences.
Stability of chondrocyte differentiation and contribution of muscle to cartilage during limb regeneration in the axolotl (Siredon mexicanum)
Authors: Steen Trygve P. 
Published: June 2005

AbstractIn order to determine whether chondrocytes are stable as to type during limb regeneration and whether any cells from limb muscle become chondrocytes in the regenerate, labeled cartilage and muscle were transplanted into limbs which were then allowed to regenerate. Transplanted cells were identified after redifferentiation in the regenerate by three kinds of label: H3‐thymidine detected by radioautography; triploidy as judged by the presence of three nucleoli per nucleus; or a combination of the two.The results of this investigation indicate that limb chondrocytes are intrinsically stable with respect to cell type, for grafts of both triploid and H3‐thymidine labeled chondrocytes gave rise to morphologically dedifferentiated blastema cells which almost exclusively differentiated into chondrocytes. The small percentage of labeled noncartilage cells observed could have been the result of metaplasia, although it is more likely that all or most of them arose as spontaneous polyploids or as contaminants of the original grafts. Isotope dilution in H3‐thymidine labeled chondrocytes indicated that they had usually divided at least five times. Hence, the basis for the intrinsic stability of chondrocytes must be heritable.Chondrocytes from the coracoid, scapula, and visceral arch cartilages also contributed cells to cartilage of limb regenerates, and the available evidence indicates that cells released from these cartilages are similarly stable as to type. These cartilages did not dedifferentiate and participate in limb regeneration to the same extent as did limb cartilage.Results from transplanted limb muscle, labeled by all three methods used in this study, indicate that certain cells of muscle can become chondrocytes during limb regeneration. The exact cellular origin of these chondrocytes, however, is uncertain, for muscle is a mixture of cell types.
Heart induction in salamanders
Authors: Jacobson Antone G. , Duncan James T. 
Published: June 2005

AbstractHeart determination is a gradual, cumulative process involving inductive and suppressive interactions between the heart mesoderm and nearby embryonic tissues. Our analysis of heart determination in the California newt, Taricha torosa, includes defect and other in vivo experiments, and explants in epidermal vesicles and into hanging drops.Explants of presumptive heart mesoderm from neurulae into hanging drops of a completely defined salt solution (Niu‐Twitty solution) produce beating hearts only infrequently. The addition of various other tissues and fractions of tissue homogenates changes the frequency and the rate of differentiation. These two parameters were used to assess the stimulatory and suppressive effects of tissues and tissue fractions on the differentiation of the presumptive heart mesoderm.At least three different factors are active in eliciting and regulating heart differentiation. A specific heart inductor in anterior endoderm increases the rate and the freqency of heart differentiation. A general stimulatory factor in epidermis and other embryonic tissues increases the frequency, but not the rate, of heart differentiation. An inhibitory agent in cranial fold and neural plate tissues delays or prevents heart differentiation. These three factors operate from intact tissues in the embryo or when explanted in vesicles or hanging drops, and are effectively present in a fraction (from sephadex column chromatography) of homogenates of the appropriate tissues.
Partial characterization of the component from normal eggs which corrects the maternal effect of gene o in the Mexican axolotl (Ambystoma mexicanum)
Authors: Briggs Robert , Justus J. T. 
Published: June 2005

AbstractAxolotl females homozygous for o produce eggs which cleave normally, but never develop beyond gastrulation. This cessation of development is due to a cytoplasmic deficiency which can be corrected by injecting eggs of o/o females with cytoplasm from normal eggs. When so injected, the recipient eggs develop beyond gastrulation and may attain larval stages. The corrective component of normal cytoplasm has the following characteristics: 1. It remains in the supernatant of normal egg homogenates after two hours of centrifugation at 105 g, but is gradually sedimented thereafter. 2. The corrective activity persists for at least eight days when preparations are stored at O°C. It is abolished on heating for one hour at 50° to 55°, and on incubation with crystalline trypsin. 3. The active material is customarily extracted from egg homogenates in 0.1 M or 0.2 M KCl, with 0.01 M Tris, pH. 7.6. It can be precipitated by 2M to 3M ammonium sulfate and retains its corrective activity. It is also precipitated by distilled water, but is then irreversibly denatured. 4. The corrective component is found mainly within the germinal vesicle of large oocytes; then in the egg cytoplasm or extracts thereof following germinal vesicle breakdown. Comparable extracts of blastulae show a reduced corrective activity. Attempts to extract the active material from older embryos and from organs of adults have so far failed. These results suggest that the corrective material, presumably a product of the normal allele of o, depends upon a protein or proteins for its activity. It is produced during oogenesis and later plays an indispensible role in early organogenesis.
Limb regeneration in Ambystoma larvae during and after treatment with adult pituitary hormones
Authors: Tassava R. A. , Chlapowski F. J. , Thornton C. S. 
Published: June 2005

AbstractIntact and hypophysectomized larvae of Ambystoma maculatum, A. opacum, A. laterale and A. mexicanum were subjected to the influence of adult newt (Notophthalmus viridescens) pituitary hormones by means either (1) of adenohypophyseal implants to the lower jaw or, (2) daily intraperitoneal injections of ACTH. After a 10–21 day treatment period, the ecotopic newt pituitary was removed or the ACTH injections were terminated. Neither procedure had any consequence for limb regeneration, whether limbs were amputated during, or from two to five days following cessation of, hormone treatment. The positive regenerative response suggests that limb tissues of larval Ambystoma do not respond either directly, or indirectly via the adrenal cortex, to the ectopic adult newt pituitary or to ACTH injection. Implanted adult newt pituitaries were found to cause precocious metamorphosis in A. maculatum, A. opacum, and A. laterale but not in A. mexicanum.
Electroencephalographic studies of survival following hypothermic hypoxia in developing chicks
Authors: Peters Joseph J. , Bright Thomas P. , Vonderahe Alphonse R. 
Published: June 2005

AbstractIn chicks between the day of hatching and ten days after hatching the body temperature was lowered from normal to either 34°C or 24°C. Oxygen was then replaced by nitrogen until breathing ceased and the electroencephalograms of the cerebral lobes were reduced to no difference of potential. When this zero potential had endured for a period four times as long as that which yielded about 50% recovery in one to ten day chicks at normal body temperature, artificial ventilation was applied for a maximum of eight minutes or until the onset of spontaneous breathing. This four fold duration of zero potential was: 12 minutes for newly hatched and one day chicks, six minutes for five day chicks, and four minutes for ten day chicks. A withholding of artificial respiration for these prolonged periods of zero potential resulted in the following percentages of recovery: at normal body temperatures, 0%; at 34°C and 24°C respectively, newly hatched chicks 23% and 90%, one day chicks 10% and 40%, five day chicks 40% and 70%, ten day chicks 80% and 90%. Prior to artificial resuscitation birds had electrocardiograms indicating irregular beats, various degrees of heart block, and cardiac arrest for as long as seven minutes; some of these recovered. The transition of the electroencephalogram from zero potential to normal EEG patterns was characterized by a gradual increase in amplitude of both slow and fast waves in the younger chicks and a kind of steplike recovery in the older birds. During recovery about 50% of the younger chicks showed seizures resembling “petit mal”. After a recovery period of 4 to 24 hours the surviving chicks showed no behavioral abnormalities.
Tissue culture analysis of immunological capacity of snapping turtles
Authors: Sidky Younan A. , Auerbach Robert 
Published: June 2005

AbstractSpleens obtained from the common snapping turtle, Chelydra serpentina (Linné), have been analyzed for immunological competence in several in vitro systems. Spleen fragments can be maintained in tissue culture for several weeks under conditions permitting antibody formation. Such fragments can produce specific agglutinins to sheep or mouse red blood cells when presented with these antigens in vitro. Cells obtained from adult turtle spleens can elicit splenomegaly or hepatomegaly in vitro in a manner suggestive of a graft‐versus‐host reaction. Using these in vitro procedures, it has been observed that maturation of the immunological system of the turtle occurs several months after hatching, and that hibernating turtles are defective in immunological capacity. Histological studies indicate that the snapping turtle has cloaca‐associated lymphoid tissues similar to the bursa of Fabricius.
Inheritance of frog lactate dehydrogenase patterns and the persistence of maternal isozymes during development
Authors: Wright David A. , Moyer Frank H. 
Published: June 2005

AbstractA female Rana pipiens sphenocephala suspected of being heterozygous at a locus specifying the B or most negatively charged, subunit of the lactate dehydrogenase isozymes was back‐crossed to a R. p. sphenocephala male and outcrossed to a R. p. pipiens male. The results of these crosses show that: (1) the structure of the B subunit of frog LDH is controlled by at least three allelic genes (LDBa, LDBb, and LDBc; (2) LDH of the offsprings' phenotype appears before hatching; (3) maternal‐type enzyme, probably synthesized during oogenesis, persists until at least the eleventh day after the tadpoles begin to feed.
On the role of metal cations in cellular adhesion: Cation specificity
Authors: Armstrong Peter B. , Jones Daniel P. 
Published: June 2005

AbstractOf the four common alkaline earth cations, only Ca++ is able to protect Rana pipiens embryos from dissociation of the epidermis into isolated cells by EDTA. Presumably this is because only Ca++ is able to satisfy the divalent cation requirement for cellular adhesion in this tissue. Although early stage embryos are completely dissociable by EDTA, the axial musculature, brain and spinal cord become resistant to dissociation by stage 17. Tetraphenyl boron is also effective in disaggregating amphibian embryo tissues.
Induction of conjugation by chemical agents in Paramecium
Authors: Miyake Akio 
Published: June 2005

AbstractInduction of conjugation by chemical agents was studied in nine species of Paramecium. KCl + acriflavine + Ca‐poor conditions were effective in inducing conjugation in P. caudatum, P. multimicronucleatum, P. aurelia, P. jenningsi and probably in P. trichium. KCL + Ca‐poor conditions were effective in P. caudatum, P. traunsteineri and probably in P. trichium. KCl + acriflavine + Ca‐poor conditions were also effective in inducing interspecific conjugation. Interaction between complementary mating types is not involved in the chemical induction of conjugation, but otherwise chemically‐induced conjugation is, in at least some pairs, essentially identical to normal conjugation induced by the interaction between complementary mating types. The mechanism of induction of conjugation and applications of chemical induction of conjugation to genetic studies are discussed.
The effect of experimental cryptorchism on the isozymes of lactate dehydrogenase in mouse testes
Authors: Goldberg Erwin , Hawtrey Christopher 
Published: June 2005

AbstractUnilateral cryptorchism produced by experimental retention of one testis in the abdomen of the mouse results in a rapid decrease in the weight of that testis. At the same time the specific activity of lactate dehydrogenase (LDH) decreases to 70% of the normal value. The sperm‐specific isozyme, LDH‐X, declines from 41% of the total activity to only 16% after eleven days in the abdomen. All LDH‐X activity is lost by post‐operative day 24. The relative proportion of the other isozymes of LDH increase following the operation. LDH‐5, absent from the mature testis, is detectable in the cryptorchid testis at post‐operative day 28 and represents 15% of the total LDH activity. These observations provide further support of the suggestion that LDH‐X is only found in the testes when meiosis is occurring.
Synthesis of RNA and protein in relation to oral regeneration in the ciliate Stentor coeruleus
Authors: Burchill Brower R. 
Published: June 2005

AbstractThe effects of actinomycin D, puromycin, and cycloheximide on oral regeneration and macromolecular syntheses in the ciliate Stentor coeruleus were investigated. At concentrations which significantly reduced the rate of RNA synthesis (actinomycin D) and protein synthesis (puromycin and cycloheximide), these inhibitors prevented the completion of development of most cells treated prior to stage “late 4” of regeneration. Cells exposed to the inhibitors in stages “late 4” or 5 were, for the most part, delayed or not affected. Cells treated after stage 5 were unaffected. The oral primordia of many cells arrested in stages “2–3” through 4 were subsequently resorbed, whereas cells blocked in stage 5 retained their oral organelles for the period of the block. The results suggest that both RNA and protein syntheses are essential to regeneration and that the final synthesis of essential macromolecules occurs during stage 5.