bluuebunny/crossref_metadata_2025_split huggingface dataset:
The developmental genetics of polymorphism in the rotifer Asplanchna. III. Quantitative modification of developmental responses to vitamin E, by the genome, physiological state, and population density of responding females
Authors: Birky C. W. 
Published: June 2005

AbstractAn increase in the level of vitamin E in the diet of amictic female Asplanchna fed paramecia and reproducing by parthenogenesis elicits three responses: (1) the mixis response: a proportion of their offspring develop into mictic females, which reproduce bisexually; (2) the BWO response: the offspring develop regular body‐wall outgrowths and (3) a reduction in fecundity of amictic females. The quantitative control of these responses has been studied. Genotypic modification of the BWO response has been demonstrated by showing consistent quantitative differences in the response of different clones from the same or different natural populations. Variation in the BWO response has also been demonstrated among the progeny of different females from a clone, and among the individual progeny of single females. The age of a female proved to be a significant physiological factor affecting both the BWO and mixis responses as measured in her offspring. The composition of the culture fluid may also modify the BWO response. An environmental variable of special interest is population density. The BWO, mixis and fecundity responses are all enhanced at high densities, and this effect is seen at natural population levels. It is suggested that this effect may help explain the observation that mixis generally coincides with peaks of population density in nature; this variable, rather than levels of dietary vitamin E per se, may be the most significant factor controlling polymorphism in nature. The density effect has been shown to be due to one or more conditioning factors, possibly pheromones, liberated by the female rotifers.
Testis growth and regression in starlings (Sturnus vulgaris) as a function of the presence of females
Authors: Schwab Robert G. , Lott Dale F. 
Published: June 2005

AbstractFour groups of male starlings were exposed to stimulatory photoperiods. Two groups had 14 hours of light per day, the other two groups, 12 hours. One of the two groups treated with each photoperiod was in a cage including both male and female starlings; the other group was in a cage including only male starlings. Testis widths were measured via laporotomy every 15 days through a growth and regression cycle.Neither the rate of testis development, nor the maximum size reached, was significantly changed by the presence of the females in either photoperiod. Likewise, the chronology of testis involution in those treated with a 14 hour light per day photoperiod was not changed by the presence of females. But maintenance of spermatogenesis in birds treated with 12 hours of light daily was significantly longer in the group caged with females.
Modification of excitation‐contraction coupling in locust skeletal muscle induced by caffeine
Authors: Huddart Henry , Abram Roland G. 
Published: June 2005

AbstractPotassium contractures were recorded isometrically in locust extensor tibialis muscles. The graphs relating contracture tension to external potassium, and contractute tension to depolarization were of sigmoid shape. In normal circumstances, peak contracture tension was obtained with 100 mM/1 potassium saline at a depolarization level of about −10 mV. At a concentration of 2 mM/1, caffeine considerably lowered the mechanical threshold of the muscle fibres such that peak contracture tension was obtained with 40 mM/1 potassium saline, at a depolarization level of only −30 mV. Withdrawal of calcium ions from caffeine containing salines resulted in a loss of the contractile response to depolarization, and the lowering of the mechanical threshold was abolished. These results are consistent with the view that caffeine may activate muscle in vivo by accelerating calcium release from the sarcoplasmic reticulum and by suppressing active calcium binding by the reticular calcium pump. Since caffeine can activate depolarized muscle it is suggested that caffeine short‐circuits the normal excitation‐contraction coupling channels to initiate a direct release of calcium ions from the sarcoplasmic reticulum without transient depolarization.
Lactate dehydrogenase isozymes of the flatfish, Pleuronectiformes: Kinetic, molecular and immunochemical analysis
Authors: Markert Clement L. , Holmes Roger S. 
Published: June 2005

AbstractAt least two genes are responsible for lactate dehydrogenase (LDH) synthesis in the tissues of eighteen species of flatfish (Pleuronectiformes). The relative activity of these genes is markedly skewed with LDH‐A4 being present in much larger amounts and in a wider variety of tissues than LDH‐B4. Certain flatfish exhibit a single LDH‐A4 while others have five forms of this tetramer. Molecular hybridization experiments demonstrate that these five tetramers have two distinguishable subunits. These subunits were purified and subjected to amino acid analysis, peptide mapping, kinetic and immunochemical analysis and shown to be very similar, perhaps identical, in primary structure. Treatment with reducing reagents failed to interconvert them. LDH‐B4 was partially purified and shown to be kinetically and immunochemically distinct from LDH‐A4. As is true for many other fish, additional LDH isozymes are obseved in eye and brian tissues. These results show that the flatfish genetic information for LDH synthesis is similar to that of other fish, and flatfish LDH A and B subunits are homologous to those of other vertebrates.
The effect of teratogenic doses of trypan blue on the yolk sac placenta of the mouse. A histological and histochemical study
Authors: Greenhouse Gerald , Pesetsky Irwin , Hamburgh Max 
Published: June 2005

AbstractInjection of teratogenic doses of trypan blue into pregnant mice resulted in depression of acid phosphatase activity in embryonic visceral yolk sac endoderm. In addition, the apical localization of this enzyme was lost, and enzyme active loci were dispersed throughout the cytoplasm. Perinuclear Golgi structures were prominent in yolk sac cells of control mice incubated for thiamine pyrophosphatase activity. In trypan blue treated animals the Golgi apparatus was attenuated and disrupted. Whereas yolk sacs of most trypan blue treated embryos showed depression of acid phosphatase activity and morphological alteration in Golgi, only 25% of such embryos exhibited gross malformations. Trypan blue treatment may cause malformations by altering nutritive and transport functions of the yolk sac placenta or the dye may exert a direct effect upon the cells of the embryo.
Hormone‐stimulated amino acid incorporation by Rana catesbeiana tadpole hindleg muscle in vitro
Authors: Hosick Howard L. , Strohman Richard C. , Bern Howard A. 
Published: June 2005

AbstractTreatment of isolated tadpole (Rana catesbeiana) gastrocnemius muscles with either insulin or thyroxine, in a rich nutritive medium, results in an approximate doubling of incorporation of 3H‐leucine into perchloric acid‐precipitable material. We have not observed parallel increases in the amount of acid‐soluble label appearing in hormone‐treated muscles. Various combinations of insulin and/or thyroxine with growth hormone give responses similar to those occurring with insulin or thyroxine alone. The greatest rates of incorporation, relative to control muscles receiving no hormone treatment, were observed in muscles exposed briefly to thyroxine, insulin and growth hormone simultaneously. The interaction of prolactin with thyroxine in this quasi‐adult system remains equivocal.
Survival and limb regeneration of hypophysectomized newts with pituitary xenografts from larval axolotls, Ambystoma mexicanum
Authors: Tassava Roy A. 
Published: June 2005

AbstractTen of 15 hypophysectomized newts with pituitary xenografts from larval axolotls, Ambystoma mexicanum, survived for over 140 days, regenerated amputated limbs and underwent occasional molts. Newts from which the larval pituitary graft was removed underwent typical hypophysectomy symptoms: sluggishness, lack of molting and death within 30 days. The results suggest that the pituitary of the larval axolotl, when implanted into the adult newt, secretes the hormones which are essential for survival and limb regeneration of the adult newt. Furthermore, pituitary xenografts to newts survive as long as pituitary homografts.
A histological study of the regenerative response in a lizard, Anolis carolinensis
Authors: Zika Jocelyn M. 
Published: June 2005

AbstractAmputated hyperinnervated Anolis carolinensis limbs were studied histologically at various times from early stages of post‐amputational wound healing to formation of mature mounds. Comparable stages of normally innervated amputated limbs were also studied. The sequence of events involved in tissue repair was found to be similar in both groups. The mounded adigital outgrowths which were produced on the hyperinnervated limbs were composed, in 80% of the cases, of large amounts of connective tissue or bone, whereas the other 20% contained primarily nerve fascicles and adipose tissue. The mounds were formed as the result of extensive regeneration of individual tissues without the interposition of a mesenchymatous cell blastema. It was concluded that the regenerative response shown by the hyperinnervated Anolis limb differs from the de novo regeneration seen in urodele amphibians. Whether this hyperinnervation procedure accurately tests the influence of nerve tissue on reptilian limb regeneration is discussed.
Cytological aspects of fertilization in the lamellibranch, Mytilus edulis I. Polar body formation and development of the female pronucleus
Authors: Longo Frank J. , Anderson Everett 
Published: June 2005

AbstractAspects of fertilization encompassing the meiotic events of the maternal chromatin, the formation of the polar bodies, and the development of the female pronucleus have been investigated in the lamellibranch, Mytilus edulis.The cromosomes of the mature egg of Mytilus edulis at the time of fertilization are organized on the first metaphase plate of meiosis. The first meiotic metaphase figure, oriented normal to the egg's cortex, consists of two asters, each of which contains paired centrioles, microtubules, and some smooth endoplasmic reticulum. Subsequent to sperm incorporation, the first polar body is produced by a process akin to cytokinesis following the movement of the chromosomes at anaphase. Later, the metaphase plate of the second meiotic apparatus is formed. Morphologically, the second metaphase figure is similar to the first; however, each aster appears to contain only one centriole. The second polar body, produced in the same manner as the first, remains associated with the zygote via a cytoplasmic bridge which persists up to the time of the first cleavage. Both polar bodies contain the same cellular inclusions as the zygote; however, only the second polar body has its chromatin delimited by a perforated nuclear envelope. After the formation of the second polar body, the maternal chromatin is organized into chromosomal vesicles. The chromosomal vesicles later fuse to form the female pronucleus.
The relationship between the intensity of light pulses and the extent of phase shifts of the circadian rhythm in the eclosion rate of Drosophila pseudoobscura
Authors: Chandrashekaran M. K. , Loher Werner 
Published: June 2005

AbstractThe advance as well as the dealy phases of the circadian system of Drosophila pseudoobscura respond in a similar manner to exposure to light signals of 15‐minute duration and different intensities. The response, measured by the extent of phase shifts four to five days after the signals, is complete at an intensity of 10 lux; light signals of higher intensities such as 3000 and 10000 lux effect phase shifts of similar time course and magnitude as light signals of 10 lux. Light pulses of intensities below 10 but above 1 lux induce phase shifts of a lesser degree. The response of the system to light signals in this range appears to be a graded one. Low light intensity signals of 0.1, 0.3 and 1.0 lux induce “reversing transients,” i.e., transients having a direction opposite to that seen in the subsequent steady state, whereas light pulses of higher intensities do not induce reversing transients.
Clonal distribution of melanocytes in piebald‐spotted and variegated mice
Authors: Schaible Robert H. 
Published: June 2005

AbstractExperimental observations of mice support the hypothesis that the complete pigmentation of most normal mammals and birds develops by the expansion and merger of clones of pigment cells from the same centers that appear as pigmented spots against a white background in piebald‐spotted mutants. Specific piebald‐spotted mutants, bt and s, having nearly normal pigment coverge in certain parts of their bodies were selected for progressive restriction of those areas until the center of each area was located. Repeated reversion of the same pigment areas in variegated Miwh, Wa, and Va heterozygotes indicated that each of the areas was a clone of cells derived from a single primordial melanoblast that migrated from the neural crest to the location of the center during embryogenesis. White regions completely separated cells of different clones into differently pigmented spots when piebald‐spotting mutants, bt or s, were combined with variegated Miwh/+. Because the separation of clones was so complete, it appears that no pigment cells exist in the intervening white regions at any stage of development. Additional evidence also indicates that restricted proliferation of pigment cells is a common end effect in all piebald‐spotting mutants, even though more direct effects may be on the pigment cell, the neural crest or the tissue environment of the skin.
Studies on the relationship between uterine fluid components and the diapausing state of blastocysts from mammals having delayed implantation
Authors: Daniel Joseph C. , Krishnan R. S. 
Published: June 2005

AbstractIn the uterine secretions of certain mammals, gross qualitative and quantitative differences in their protein content were observed depending on whether or not the animals exhibited delayed implantation. Diapause blastocysts of the animals representative of those with obligate delayed implantation were stimulated to grow (as measured by total expansion and increased mitotic index) when maintained in vitro in medium containing rabbit “blastokinin” but not in serum‐containing medium. Diapause rat blastocysts taken from animals where a facultative delayed implantation has been produced by heavy lactation, expanded in F10 medium alone or containing serum or the macromolecular components of uterine secretions taken from a 5‐day pregnant animal, but not in rabbit “blastokinin.” The mitotic index, however, was the same under all three conditions and higher than in uncultured controls. Growth of active 5‐day rat blastocysts was stimulated by medium containing the proper concentration of uterine macromolecular components; mitotic activity increased three to four‐fold.We conclude that delayed implantation results from the failure of the mother to provide sufficient protein and/or certain specific proteins as needed for active growth of the blastocysts. In facultative delayed implantation, as exemplified by the lactating rat, there is evidence that, in addition to the protein deficiency, some substance or condition exists in the uterus which inhibits growth of the blastocysts.
Physiological studies on supercooled killifish (Fundulus heteroclitus) II. Serum organic constituents and the problem of supercooling
Authors: Umminger Bruce L. 
Published: June 2005

AbstractTo gain insight into the mechanism permitting Fundulus heteroclitus to survive subzero temperatures in a supercooled state, previously published data on inorganic components of the serum were complemented by studies on serum organic constituents in parallel groups of adult male killifish acclimated to various temperatures (30°C, 20°C, 10°C, 4°C, 2°C, −1°C and −1.5°C) in salt water under otherwise constant laboratory conditions. When the acclimation temperature was lowered from 20°C to −1.5°C, there was little or no change in levels of serum total non‐protein nitrogen, total amino acids, urea and non‐glucose free carbohydrates. Total serum protein levels were usually unaffected by the cold, but occasionally showed a decrease. Serum total cholesterol levels increased by 69% in the subzero cold, presumably due to an increased lipid metabolism. Whereas most serum constituents (organic and inorganic) showed only minor changes in supercooled F. heteroclitus, serum glucose levels increased from three‐ to sixfold. Serum glucose levels of 68 mg% in fish at 20°C increased to 460 mg% in sexually regressed fish at −1.5°C but to only 280 mg% in supercooled mature fish. It was suggested that the elevation of serum glucose in the subzero cold permitted survival in a supercooled state, presumably by retarding ice crystal growth on any ice nuclei that might form spontaneously in the blood.
Deletion‐transplantation experiments on embryos of Fundulus heteroclitus. II. The anterior embryonic shield
Authors: Brummett Anna Ruth 
Published: June 2005

AbstractExperiments are described in which the differentiative capacity of the anterior embryonic shield of the teleost. Fundulus heteroclitus, was investigated by means of deletion‐transplantation techniques.The anterior embryonic shield, deleted from gastrula stages and transplanted into the pericardial chamber of an older embryo, exhibits growth and differentiates structures appropriate only to anterior head. All germ layers are involved in both the operation and subsequent differentiation. The donor embryos, in general, develop normally except for striking deficiencies in forebrain and eyes. Both donors and grafts indicate increasing specificity of determination in the cells of the anterior shield as development proceeds from early to late gastrula.The experiments are discussed from the standpoint of their elucidation of localization of developmental potencies in the anterior embryonic shield.Two unexpected effects of graft on host are described and briefly discussed: (1) the differentiation of glandular cells in the host pericardial epithelium in the immediate vicinity of the graft, tentatively labeled an “induction,” and (2) a deleterious systemic effect of the graft on the host embryo. Both of these effects occurred in a significant number of cases but appear to be unrelated to each other and are, as yet, unexplained.
Ultrastructure of the germinal epithelium during oogenesis in the rabbit
Authors: Gondos Bernard 
Published: June 2005

AbstractElectron microscopic examination of newborn New Zealand white rabbit ovaries revealed numerous germ cells within the germinal epithelium during the early stages of oogenesis. The germ cells were found at all levels of the germinal epithelium, as well as in bridges connecting with the underlying sex cords. Germ cell nuclei were large and round with smooth, regular double membranes, reticular nucleoli and evenly distributed chromatin. Mitochondria were characteristically spherical with slightly eccentric cristae. The number of germ cells within the germinal epithelium gradually diminished until they were completely absent by the time oogenesis was complete.The germinal epithelial cells were characterized by irregular, elongated nuclei with eccentric nucleoli and peripherally marginated chromatin. Cytoplasm was rich in ribosomes, rough‐surfaced endoplasmic reticulum and elongated mitochondria. Junctional complexes, cytoplasmic projections and occasional cilia were present on the cell surfaces. At the junctions of germ cells and germinal epithelial cells, cell membranes were closely apposed and small interdigitating cytoplasmic projections were present.During the early stages of oogenesis, the germinal epithelium was multilayered and connected to the cortical sex cords in many places. Bridges joining the germinal epithelium to the sex cords contained both germ cells and germinal epithelial cells. Occasionally, germinal epithelial cells could be seen extending partially into the sex cords. With increase in the thickness and extent of the tunica albuginea, contact between the germinal epithelium and the sex cords was gradually diminished. As oogenesis reached completion, the germinal epithelium was reduced to a single layer of epithelial cells separated from the developing follicles below by a dense band of fibroblasts, collagen and capillaries.
The control of DNA synthesis in macronuclei and micronuclei of a hypotrich ciliate: A comparison of normal and regenerating cells
Authors: Jerka‐Dziadosz Maria , Frankel Joseph 
Published: June 2005

AbstractUrostyla weissei, a hypotrichous ciliate possessing two macronuclei and four or more micronuclei, has an inter‐division interval of about 12 hours. Macronuclear DNA replication occurs between five and ten hours after cell division, while micronuclear DNA replication takes place a short time prior to mitosis. Synchronous populations of dividing cells were isolated, provided with H3‐thymidine labelled Tetrahymena, and then were equatorially transected during either G1 or macronuclear S. Regeneration was completed, with attendant micronuclear and macronuclear division, four to five hours after transection. No macronuclear DNA synthesis took place during the regeneration interval. In cells transected during macronuclear S, the replication band generally disappeared and DNA synthesis was arrested. The macronucleus then divided without mixing of replicated and un‐replicated portions, so that the replicated material generally passed to only one of the macronuclear division products, which was larger than the other. Following the completion of regeneration, a new wave of DNA synthesis commenced immediately in macronuclei of cells transected during G1, and with some delay in cells transected during S. The completion of this replication wave was not followed by cell division; instead a second replication was initiated a few hours later, and then the cells divided.Micronuclei initiated DNA synthesis prior to mitosis, which occurred whenever regeneration was completed, and regardless of the time of transection or the concurrent state of the macronucleus. Thus, in cells transected during G1, micronuclei replicated considerably earlier than in the unoperated controls.In cells subjected to repeated transection at four to five hour intervals, macronuclei became progressively smaller while micronuclei remained the same size, which is expected if macronuclear replication is suppressed due to the regeneration‐stimulus, while micronuclear replication occurs automatically prior to every mitosis.
Target discrimination by the echolocating bat Vampyrum spectrum
Authors: Bradbury Jack W. 
Published: June 2005

AbstractFive specimens of Vampyrum spectrum were trained to discriminate between solid targets differing in shape or size using echolocation alone. A pair of lucite targets, one a sphere, the other a prolate spheroid, were then designed so as to produce echoes of approximately equal overall amplitude at the distance of choice by the bats, but of different frequency composition. This discrimination was successfully performed by four of the animals and the two best performers were studied in detail by photographic analysis to ascertain whether frequency or amplitude cues were actually being utilized. By manipulating the degree of frequency dependence in the echoes, it was shown that one animal seemed to rely on the availability of frequency‐dependent cues for successful discrimination while the other did not. Examination of the structure of the pulses used on these flights indicated a consistent pattern of changes as the targets were approached. Some of these changes could be correlated with the kinds of cues the two bats seemed to be using in making the discriminations.