bluuebunny/crossref_metadata_2025_split huggingface dataset:
Keratogenic metaplasia of the avian chorionic epithelium: Absence of the Beta stratum which characterizes the epidermis of the avian scutellate scale
Authors: Sawyer Roger H. 
Published: June 2005

AbstractUpon exposure to air, the avian chorionic epithelium (CE) transforms into a keratinizing, stratified squamous epithelium. The overall morphology of this keratogenic CE is unlike any keratinized epidermis of the normal embryo. The basal cells are squamous, not like those of normal avian epidermis which are cuboidal or columnar, and the basal lamina is poorly developed. Although desmosomes are present throughout this keratogenic epithelium, hemidesmosomes do not form in the basal cells. Peridermal and subperidermal layers likewise were not observed. This ultrastructural study does show, however, that the cells of the intermediate layers and stratum corneum resemble very closely those observed in the Alpha Stratum of normal avian epidermis. Yet, in no case does a Beta Stratum characteristic of the normal avian scutellate scale epidermis ever form. Evidently, a rather non‐specific cue can bring about the formation of an Alpha Stratum, whereas induction of a Beta Stratum requires a more specific cue. The hypothesis that the formation of the Beta Stratum of scutellate scales does require a specific dermis and that the dermis itself requires a prior association with an “epidermal placode” is discussed.
Wound healing in tadpole tailfin pieces in vitro
Authors: Derby Albert 
Published: June 2005

AbstractExplants of tail fins from R. catesbeiana tadpoles undergo reepithelialization of their cut surfaces (healing) when cultured in vitro in Hanks' balanced salt solution at 22°C. Healing is initiated early and closure of the wound is complete by 12 to 24 hours. Morphogenesis continues for several days as further reorganization and migration of epidermal cells from the regions adjacent to the wound margins take place. The addition of serum to the culture media improves the general appearance of these tissues and promotes healing. The rate of healing is affected by temperature. Tail fins maintained at 10°C do not heal while fins maintained at 30° and 37°, although healing more rapidly than at 22°, undergo progressive degeneration in culture.Epidermal cell movements were also studied in explants consisting of a combination of intact tail fin plus tail fin deprived of its epithelium. Rapid and extensive migration of epidermal cells from the intact tail fin across the collagen lamella of the stripped fin is observed.
Nuclear transplantation in Bombina orientalis and utilization of the Pale mutation as a nuclear marker
Authors: Ellinger Mark S. , Carlson John T. 
Published: June 2005

AbstractThe discoglossid frog, Bombina orientalis, displays many characteristics that make it desirable as a laboratory animal. We report here the first successful transplantation of embryonic nuclei into enucleated eggs of this organism. The participation of the grafted nucleus in the development of the transplant embryos was confirmed with the use of a genetic marker, the Pale mutation. Frogs homozygous for this recessive gene are much lighter in appearance than the wild‐type animals. The use of this trait in appropriate experiments demonstrated that nuclear tansplantation in B. orientalis provides embryos whose nuclei may be reliably interpreted as being derived from the injected nucleus.
Acid base changes during recovery from disturbance and during long term hypoxic exposure in the lobster Homarus vulgaris
Authors: McMahon B. R. , Butler P. J. , Taylor E. W. 
Published: June 2005

AbstractHemolymph O2 and CO2 levels and pH were measured in lobsters (H. vulgaris) as they settled in normoxic conditions and during prolonged exposure to moderately hypoxic seawater. Initial handling and transfer to the experimental conditions resulted in a marked acidosis. Complete recovery took from 24 to 48 hours. Samples of hemolymph taken after 48 hours yielded “settled” normoxic levels for O2 CO2 and pH. Subsequent exposure to moderately hypoxic water caused an initial respiratory alkalosis associated with pronounced hyperventilation. The induced pH change was sufficient to cause a marked increase in the oxygen affinity of the hemocyanin, allowing almost complete saturation of post‐branchial (arterial) hemolymph despite a 3‐fold decrease in hemolymph oxygen tension. Prolonged exposure to hypoxia resulted in an attenuation of the hyperventilation response but hemolymph bicarbonate levels rose substantially and may have maintained pH high and thus kept oxygen affinity above the normoxic level. On return to normoxic water both ventilation volume and hemolymph carbon dioxide decreased and pH and oxygen affinity returned to normoxic levels.
Ontogenetic studies of cyclic AMP‐dependent protein kinase enzymes from Mouse Heart and Other Tissues
Authors: Malkinson Alvin M. , Hogy Lora , Gharrett Anthony J. , Gunderson Thomas J. 
Published: June 2005

AbstractCyclic AMP is one of the factors which regulate cell differentiation. In animals the apparent mechanism of action of cyclic AMP is the activation of protein kinase enzymes. Postnatal changes in cyclic AMP‐dependent protein kinase enzymes were therefore examined. Determinations were made of the protein kinase and cyclic AMP‐binding specific activities and of the isozyme content (as analyzed by DEAE‐cellulose chromatography) for cytosol fractions from different neonatal and adult mouse tissues. Slight or negligible differences in enzymatic activity and isozyme distribution were observed in comparisons between neonatal and adult samples obtained from brain, liver and lung. In contrast to these tissues, however, major ontogenetic changes were observed with heart. The protein kinase and cyclic AMP‐binding I activities were constant from birth until the end of postnatal week 2. Protein kinase activity decreased 40% between days 12 and 21, and cyclic AMP‐binding activity decreased 30% between days 17 and 25. Both activities then decreased gradually with age. By ten months the kinase activity had decreased 75%, and the cyclic AMP‐binding activity 60%, from the perinatal levels. In addition to these changes in specific activity there were also age‐dependent changes in the heart isozyme distribution. The apparent amounts of the Type I and Type II isozymes decreased 75% and 25%, respectively, with age. Thus, while neonatal heart cytosol contained two to three times more Type I activity than Type II, the relative activities of the two isozymes in adults were nearly equal. The fact that the most dramatic changes in the protein kinase and cyclic AMP‐binding specific activities occur at that time period when cardiac growth shifts from a mainly hyperplastic to a predominantly hypertrophic process suggests that this enzyme may have a regulatory role in heart development.
Inhibition of early events of sexual processes in Paramecium by concanavalin A
Authors: Tsukii Yuuji , Hiwatashi K. 
Published: June 2005

AbstractThe lectin concanavalin A (ConA) inhibited specifically an early step of sexual reproduction (conjugation or autogamy) in Paramecium caudatum. ConA (50 μg/ml) did not prevent the initial agglutinative mating reaction in natural conjugation or a specific swimming behavior observed prior to the induction of conjugation by chemicals, but inhibited pair formation which usually occurs about one hour later. Cells pretreated by protease, ficin or papain increased in their sensitivity to the inhibitory effect of ConA. Conjugating pairs once formed were not separated by the treatment with ConA and underwent nuclear changes normally. The sensitive period to ConA was proximately the first 30 minutes from the onset of mating reaction or of the chemical treatment for induction of conjugation.The same kind of inhibition by ConA was observed in two other species, Paramecium trichium and Paramecium bursaria, but could not be demonstrated in Paramecium multimicronucleatum.ConA (4 μg/ml) completely prevented chemical induction of autogamy in an early step but did not if applied 60 minutes after initiation of the induction. The inhibition of conjugation and autogamy was completely released by α‐methyl‐D‐mannoside or mannose, competitive inhibitors of ConA. PHA had no effect on these sexual processes.
Effect of light and dark adaptation upon the rhabdom in the compound eye of the mosquito
Authors: Brammer J. D. , Stein Peter J. , Anderson Ronald A. 
Published: June 2005

AbstractDuring the first two hours of light adaptation rhabdom volume in compound eyes of adult mosquitoes is strikingly reduced. In females this involves a net loss of photoreceptor membrane of 500–700 μ2/cell/hour. Concurrently, numerous coated vesicles and multivesicular bodies appear in the cytoplasm adjacent the rhabdom. After longer illumination times (up to 5 hours) membrane loss averages considerably less, 220 μ2/cell/hour. Furthermore, puromycin experiments suggest that it is counter‐balanced by the formation of an equal amount of new membrane. Thus, despite substantial membrane turnover no net change in rhabdom volume takes place.When light‐adapted mosquitoes are dark adapted for 12 to 36 hours there occurs a net increase of rhabdom membrane averaging 75 μ2/cell/hour, and a corresponding increase in rhabdom volume.
Genetic control of enzyme expression in Drosophila: A locus influencing tissue specificity of aldehyde oxidase
Authors: Dickinson W. J. 
Published: June 2005

AbstractA natural genetic variant in Drosophila melanogaster with a highly tissue specific effect on the level of an enzyme (aldehyde oxidase) is described. This variant causes overproduction of the enzyme by a factor of 2‐ to 3‐ fold in paragonia (male accessory sex glands) while having no significant effect on the enzyme level in other tissues. This difference is controlled by a single genetic element in the vicinity of the aldehyde oxidase structural gene that operates in a strictly cis‐active mode. It is not associated with any change in enzyme primary structure detectable by a variety of physical, chemical and immunochemical tests. The most likely explanation for all of these observations is that the variant defines a cis‐active regulatory element adjacent to the structural site.
Lactate dehydrogenase C4 in male sex accessory glands of normal mice and in testes of sex‐reversed mice
Authors: Holmes Roger S. , Jones Janet T. 
Published: June 2005

AbstractLactate dehydrogenase (LDH) C4 activity was observed in testis extracts of sex‐reversed mice (Sxr) and in male sex accessory gland (seminal vesicle and prostate) extracts from C3H/He and C57BL/Go mice. These results reflect either (1) the presence of low concentrations of germinal cells in these tissues; or (2) the synthesis of LDH‐C4 by somatic cells in Sxr testes and normal male sex accessory glands.
The effect of a single epilation on successive hair eruptions in normal and hormone‐treated rats
Authors: Hale Patricia A. , Ebling F. J. 
Published: June 2005

AbstractIn intact female rats and in one receiving hormonal treatments which alter spontaneous follicular cycles, hairs were plucked before, during or after the spontaneous growth of G2 hairs. Several successive hair eruptions on the epilated and the contra‐lateral intact flank were then observed.Epilation always advanced the next eruption, except that if performed during the last few days before spontaneous eruption was expected, it had no effect.Eruption after a fixed interval characteristic of the region epilated followed the plucking of club hairs from resting follicles. After growing hairs were plucked, the interval to eruption was longer, and varied with the stage of anagen reached at epilation. Nevertheless the advance of eruption was even greater than after the epilation of resting follicles. The interval from epilation to eruption was increased by estradiol or propylthiouracil, which prolong both spontaneous and induced follicular cycles, and reduced by spaying or thyroxine, which shorten them.Under all treatments, epilation also advanced subsequent eruptions, the second usually even more than the first. Comparison of cycle lengths of epilated and normal follicles, and correlation with observations on pulse‐labelled hairs, showed that while the first post‐epilation anagen was unaltered, the resting phase which followed it was shortened. Subsequent cycles tended to be prolonged.Some evidence was found for a slow‐acting systemic control tending to resynchronize the cycles of epilated follicles with those of symmetrically‐placed nonapilated ones, although complete synchrony was not achieved within three or four cycles of a single epilation.
Investigations into the degree of cell mixing that occurs between the 8‐cell stage and the blastocyst stage of mouse development
Authors: Kelly Susan J. 
Published: June 2005

AbstractThis study was designed to assess the degree of cell mixing that occurs during the early development of the mouse embryo, and thus provide information which is important in relation to the current theories of differentiation. Previous studies of this nature have involved either chimeric composites, or have only followed a very limited number of cells in the embryo. Here the products of one of the 4‐cell stage blastomeres have been labeled with tritiated thymidine, at a level which allows their descendants to be identified three or four cell divisions later, and recombined with the remaining blastomeres of the same embryo. After fixing and sectioning of the embryos at the blastocyst stage the locations of the labelled cells have been analyzed to assess the degree of clumping that they display. A significant tendency for the products of this one 4‐cell stage blastomere to be confined to a single area in the blastocyst is demonstrated. This indicates that there is little marked cell movement during the observation period. The relevance of these results to current knowledge of blastocyst development is discussed.
Changes in internal pressure during puparium formation in flies
Authors: Zdarek Jan , Slama Karel , Fraenkel Gottfried 
Published: June 2005

AbstractChanges in the internal pressure of fly larvae during puparium formation were measured by a method previously described. Two different types of pressure changes were recorded: (1) Reversible pulsations of various types corresponding to different kinds of muscular contractions, and (2) an irreversible increase of the pressure baseline caused by dimensional shrinkage and loss of elasticity of the cuticle, association with ultrastructural reorganization and sclerotization. The pressure pulses potentiated by neuromuscular activity are association with the initial stages of pupariation, immobilization, retraction of the anterior segments, and longitudinal body contraction, and can generate pressure peaks of up to 300 mm Hg. By contrast, the steady rise of the basic pressure during the final stages of pupariation is generated independently of muscular activity and is also independent of phenolic tanning. The basic pressure can reach levels of 100 mm Hg and is indispensable for the final rounding and smoothening of the ovoid puparium. Morphogenesis of the puparium thus can be understood as a result of a delicate concert between neuromuscular activity and structural changes in the integument.
Experimental analysis of lens regeneration in Xenopus laevis and Rana esculenta tadpoles by means of xenoplastic grafts
Authors: Filoni Sergio , Bosco Luigi , Cioni Carla 
Published: June 2005

AbstractLens forming capacities of the eye of Xenopus laevis and Rana esculenta tadpoles were studied by means of xenoplastic grafts. The results obtained demonstrated that the lentectomized eye of larval Rana esculenta transplanted under the outer cornea of larval Xenopus laevis was able to support lens regeneration in the outer cornea of Xenopus. This observation was confirmed by implanting the outer cornea of Xenopus into the eye cup of Rana and noting lens transformation in the implanted cornea. On the contrary, the lentectomized eye of larval Xenopus laevis transplanted under the outer cornea of Rana esculenta, was not able to allow the lens regeneration from the cornea.These results indicate that the absence of lens regeneration in lentectomized eyes of larval Rana esculenta, demonstrated in previous researches, is due to the absence of lens forming capacity in the outer cornea of Rana.
Ultrastructure of the eggshell of two species of anoline lizards
Authors: Sexton Owen J. , Veith George M. , Phillips David M. 
Published: June 2005

AbstractThe role of the eggshell of two species of lizard (Anolis limifrons and A. sagrei, lguanidae, Squamata) in water transport is discussed. Levels of soil moisture in habitats of A. limifrons in Panama vary seasonally in two locales; the lowest values are attained during the dry season months of February–April. The transfer of water from the soil to the egg must be mediated by the biologically passive eggshell. The eggshells of these two species consist of five concentrically arranged zones of fibrils peripheral to the shell and egg membranes. The fibrils are covered by a granular layer containing CaCO3. This layer bounds irregular channels passing from the exterior to the interior of the eggshell. It is proposed that water moves from the soil through the eggshell by capillary.
Ultrastructure of normals and castrates and the effects of testosterone and ultraviolet (UVL‐B) irradiation on scrotal skin of rats
Authors: Glimcher Mark Edward , Flynn Evelyn A. , Szabo George 
Published: June 2005

AbstractThe ultrastructure of the testosterone dependent epidermal melanocyte system of the scrotal skin of normals and castrates, with and without testosterone replacement therapy, and UVL‐B (280–315 nm) radiation in black Long Evans rats is reported. UVL‐B increases melanocyte activity, melanosome forming apparatus, (size of Golgi zone and RER, and quantity of cytoplasmic vesicles, dendrites, and stages of melanosomes) in normals and in castrates. Testosterone replacement therapy to castrates is not a prerequisite for stimulation by UVL‐B, but it enhances the effects of UVL‐B without restoring normalcy as melanosome packaging into complexes predominates. After UVL‐B stimulation of normals or castrates, melanocyte dendrites are observed more often. Melanocyte dendrites of skin of castrated rats are observed less often than in normals, but with testosterone replacement therapy, the dendrites become more numerous. Melanosomes donated to keratinocytes are mostly located as singles in normals and as complexes in castrates. After UVL‐B, castration, or testosterone replacement therapy, the melanosomes are packaged in keratinocytes in complexes larger than in normals. In the epidermis of long term castrates (9–109 days), non‐specific clear cells are observed and Langerhans cells containing melanosomes; we did not observe them in normals. Melanocytes of castrates have a reduced melanosome forming apparatus. The dermis of castrates contains many dermal melanocytes in the superficial dermis with melanosomes in several stages of formation. These cells are not apparent in normals at this location in the dermis.Testosterone replacement therapy and/or UVL‐B administered to castrates does not restore the epidermal melanocyte system nor the dermis to precastration ultrastructural appearance; castration has a permanent altering effect as melanosomes are packaged into complexes.
Influence of 3,3′,5′‐triiodo‐L‐thyronine on the involution of the cement gland of Xenopus laevis (Daudin) in vivo and in vitro
Authors: Weets J. , Picard J. J. 
Published: June 2005

AbstractThe cement gland of Xenopus laevis appears at stage 15. It increases rapidly in volume and reaches its maximum size five days after fertilization at 18° The growth is followed by involution and the gland eventually disappears at stage 50. The evolution of explanted glands cultured in vitro is similar to the evolution observed in vivo. The involution of explanted glands cultured in Barth solution suggests that the initiation of the involution is independent of hormonal control. However, 3,3′,5′‐triiodo‐L‐thronine increases the rate of the involution in vivo as well as in vitro and this rate is a function of the concentration of the hormone.
Xenopus oocyte cAMP‐dependent protein kinases before and during progesterone‐induced maturation
Authors: O'Connor Clare M. , Smith L. Dennis 
Published: June 2005

AbstractTwo cAMP‐dependent kinase activities, corresponding to the Type I and Type II isozymes characterized in other tissues, have been partially purified from Xenopus laevis oocytes both before and during progesteroneinduced maturation in vitro. The two activities are present in approximately equimolar concentrations in ovarian oocytes and the total kinase concentration has been estimated at 0.2–0.4 μM minimally. The relative activities of the two isozymes do not change during oocyte maturation.
Intrafollicular cumulus cell transformations associated with oocyte maturation following gonadotrophic hormone stimulation of adult mice
Authors: Schuetz Allen W. , Swartz William J. 
Published: June 2005

AbstractEffects of gonadotrophic hormones on the intrafollicular morphological transformation of cumulus cells were examined in adult mice. Formation of transformed cumulus masses was examined during both the pre‐ and post‐ovulatory course of gonadotrophic (PMS or PMS + HCG) induction of follicular synchronization and ovulation. Within nine hours of PMS injection and prior to ovulation, transformed cumulus cell masses were present within ovaries. Injection of HCG within 48 hours of the PMS injection stimulated the formation of additional and increased numbers of pre‐ovulatory transformed cumulus cell masses. Ovulation occurred within 24 hours of both the PMS injection and the HCG injection when given to animals previously stimulated with PMS. Oocytes isolated from transformed cumulus cell masses following PMS or HCG injection had invariably undergone meiotic maturation. Transformed cumulus masses were also recovered from ovaries following induced ovulation; however, their numbers were decreased. Follicles stimulated by PMS remained sensitive to HCG (underwent ovulation) for approximately four days following a single injection of PMS. Results indicate that identifiable morphological and physiological changes in cumulus cells precede ovulation and are strongly correlated with the induction of the meiotic maturation process in the enclosed oocytes. The presence of mature oocytes in transformed cumulus masses following ovulation furthermore indicates that asynchrony of the oocyte maturation and ovulatory events are induced by the gonadotrophic hormones. Intrafollicular cumulus cell transformations are discussed in relation to dissociation of the somatic and germ cells, the mechanisms of meiotic induction and the process of atresia. Results suggest that the simple morphological changes described provide a quantitative and selective indicator of gonadotrophic action within the ovary.
The influence of inorganic ions and pH on oxygenation properties of the blood in the gastropod mollusc Busycon canaliculatum
Authors: Mangum C. P. , Lykkeboe G. 
Published: June 2005

AbstractThe oxygen affinity of Busycon canaliculatum blood decreases with increasing pH in the range 6.6–7.9, and increases from 7.9–8.5, which encompasses the physiological range under normoxic conditions. When inorganic ions are removed from the blood, the oxygen affinity of the hemocyanin increases, the reverse Bohr shift diminishes and the normal Bohr shift cannot be detected. The addition of physiological levels of NaCl restores much, but not all, of the oxygen affinity and the Bohr shifts remain reduced or absent. The addition of physiological levels of Ca+2 and Mg+2 to the NaCl solution restores virtually all of the oxygen equilibrium properties that characterize native blood.When the samples are buffered with CO2 instead of Tris Maleate, the salt and pH effects change above pH 7.9, which may be due to either an indirect effect of carbon anions on divalent cation activity or a heterotropic effect of CO2 on the hemocyanin molecule.The pH dependence of oxygen affinity changes at low temperature.