bluuebunny/crossref_metadata_2025_split huggingface dataset:
The stress response in the abundance of circulating leucocytes in the killifish, Fundulus heteroclitus II. The role of catecholamines
Authors: Pickford Grace E. , Srivastava Anil K. , Slicher Anna M. , Pang Peter K. T. 
Published: June 2005

AbstractIntraperitoneal injections of distilled water at 5 μ1/g, but not at 1 μ1/g, elicit transitory leucopenia at three minutes post‐injection in intact Fundulus heteroclitus. Later phases of the stress sequence (Pickford et al., '71) are not elicited. Intraperitoneal injections of epinephrine (0.025 μg/g in 5 μ1/g H2O) completely simulate the cold‐shock leucocyte sequence. Hypophysectomy abolishes the two hour leucocytic phase, as in the cold‐shock response. Norepinephrine is ineffective at 0.1 μg/g but simulates the epinephrine response at a high dose (1.0 μg/g). Isoprenaline (1.0 or 0.1 μg/g) elicits the leucopenic but not the leucocytic phases.Pretreatment with phenoxybenzamine (2.5 mg/liter aquarium water) abolishes both three minute and 45–60 minute cold‐shock leucopenia; two hour leucocytosis is unimpaired but the 15 minute response is reversed. Pretreatment with propranolol (1 μg/liter aquarium water) has no effect on the two leucopenic phases; two hour leucocytosis is delayed or, at higher doses, abolished; 15 minute leucocytosis is either unaffected, or reversed.It is not possible to interpret these results in terms of classical mammalian alpha‐ and beta‐adrenergic mechanisms.
Cytoplasmic control of nuclear behavior during meiotic maturation of frog oocytes
Authors: Masui Yoshio , Markert Clement L. 
Published: June 2005

AbstractFully grown oocytes of the frog (Rana pipiens) undergo cytoplasmic and nuclear maturation when treated with progesterone after the follicular envelopes have been removed. The mechanism of this maturation was investigated by injection of cytoplasm from progesterone‐treated oocytes at various stages of maturation into fully grown but immature oocytes. The injected cytoplasm becomes effective in inducing maturation by 12 hours after progesterone administration, reaches a maximum effectiveness around 20 hours, and then declines after the donor oocytes complete maturation. However, even cytoplasm from early embryos retains some capacity to induce oocyte maturation. The frequency with which maturation is induced is proportional to the volume of the injected cytoplasm. Progesterone itself is not directly responsible for the maturation‐producing effect of injected cytoplasm since injected progesterone does not promote maturation. However, externally applied progesterone does induce the completion of the first meiotic division, presumably by releasing a cytoplasmic “maturation promoting factor.” The production of this cytoplasmic factor was not affected by removal of the nucleus.After completion of the first meiotic division, oocytes cease further development at the metaphase of the second meiotic division, where they remain until fertilized or activated to develop. Cytoplasm from such secondary oocytes when injected into one of the blastomeres at the two‐cell stage of development suppresses mitosis as well as cleavage. Mitosis is usually arrested at metaphase. No such inhibition was brought about by injection of cytoplasm from cleaving blastomeres. Thus, the arrest of mitosis and cleavage can be attributed to a specific “cytostatic factor” in the cytoplasm of the secondary oocyte. Activation of donor secondary oocytes by insemination or pricking with a glass needle soon destroys the cytostatic factor. Likewise, addition of cortical cytoplasm to endoplasm from the secondary oocyte rapidly destroys the cytostatic capacity. This result implies that cortical material is involved in the process of removing the cytostatic factor at the time of normal activation or fertilization. Enucleation of oocytes demonstrated that production and removal of the cytostatic factor is independent of the nucleus.
Further observations on tail regeneration in Anolis carolinensis (Iguanidae, lacertilia)
Authors: Maderson P. F. A. , Salthe S. N. 
Published: June 2005

AbstractThe rate and extent of tail replacement was followed during two consecutive post‐amputation periods in adult and juvenile male Anolis carolinensis, maintained under three different experimental regimes. Great variation, as indicated by the coefficient of variability, was observed in all experimental groups. These data confirm previous studies and demonstrate that variability is not associated with population or individual genetic make‐up, age, or environment. The general and specific implications of variability in tail regenerative capacity are discussed.
Caste determination in honey bees. I. The significance of moisture in larval food
Authors: Dietz Alfred , Haydak Mykola H. 
Published: June 2005

AbstractHoney bee larval growth is markedly influenced by the moisture content of the larval food. A gradual increase in the moisture content of the larval food (royal jelly) resulted in a large percentage of queens. An apparent linear relationship of royal jelly moisture content to time of larval development was used in the feeding trials. Since the larval food tested was one and one‐half or two and one‐half years old, it is probable that a highly labile queen determining substance, or substances, if present in larval food, is not responsible for caste determination. Results of this study suggest that nurse bees may initiate the mechanism of queen differentiation simply by increasing the moisture content of the food of growing larvae and, thereby, controlling the intake of essential nutrients. The secretions of the mandibular glands are presumably responsible for the change in consistency of the food of either queen or worker larvae.
Superprecipitation of actomyosin extracted from crayfish skeletal muscle: The effect of heavy metal cations, EDTA and drugs
Authors: Huddart Henry 
Published: June 2005

AbstractActomyosin from crayfish skeletal muscle will superprecipitate in the presence of ATP without added Ca++ or Mg++. EDTA totally inhibits Ca++‐induced superprecipitation of actomyosin, but in some cases Mg++ will reverse this effect. It is suggested that Mg++ and not Ca++ is a prerequisite for superprecipitation with ATP alone. EDTA only partly inhibits heavy metal‐induced actomyosin superprecipitation.Heavy metal cations induce far greater actomyosin superprecipitation than Ca++, and they can even enhance previously formed Ca++‐induced precipitates. It is suggested that heavy metal cations may be more strongly bound to crayfish actomyosin than Ca++, and that they may displace Ca++ from existing actomyosin binding sites. Heavy metal potentiation of muscular contraction may thus involve direct action at myofibril binding sites.Caffeine and quinine are without effect either on the rate or extent of development of actomyosin precipitates in the presence of ATP, ATP plus Ca++, and ATP plus Zn++. These observations rule out any direct effect of these drugs at the myofibril level during drug‐induced potentiation of muscular contraction.
Endocrinology of amphibian ultimobranchial glands
Authors: Robertson Douglas R. 
Published: June 2005

AbstractThe historical observations of the amphibian ultimobranchial gland are reviewed and interpreted in light of recent evidence which demonstrates the relationship of this organ to the hypocalcemic hormone, calcitonin. Its discrete anatomical location and separation from other endocrine tissues has made extirpation feasible and has revealed the importance of this gland in preventing excessive mobilization of calcium from the paravertebral lime sacs in larval and adult forms. These glands also appear to prevent hypercalcemia during periods of high dietary calcium ingestion. In view of its phylogenetic development and relationship to the parathyroids, two major functions of the ultimobranchial glands can be ascribed. First, amphibian calcitonin sequesters calcium in storage depots, in pre‐metamorphic and post‐metamorphic forms to insure maximal ossification of adult bone. Such protection in an aquatic environment deficient in calcium ions would be of extreme importance. Second, amphibian calcitonin prevents the rapid influx of calcium across gut epithelium during feeding to protect against acute periods of hypercalcemia. The diversity of aquatic and terrestrial amphibian types provides a broad spectrum of forms in which to develop model systems for calcium homeostasis.
The structure and function of the lateral line system in larval Xenopus laevis
Authors: Shelton Peter M. J. 
Published: June 2005

AbstractEach lateral line organ in Xenopus laevis larvae contains about two dozen receptor cells. These are divided into two classes on the basis of the orientation of the cilia in their sensory‐hair‐bundles. The fine structure of the lateral line organs is similar to the adult pattern and that found in other species of amphibia and fish. However apparently degenerating receptor cells are found in normal tadpoles. Two types of nerve ending, considered to be afferent and efferent, contact the bases of receptor cells. Each organ has two physiologically distinct sensory units which are sensitive to mechanical deflection of the organ's sensory hairs. The organs have a plane of maximum sensitivity to stimulation and respond in a phasic‐tonic manner to vibrational stimuli and water currents. Efferent activity in unmyelinated fibres in the larval lateral line nerves is associated with tadpole movement; heavy efferent activity occurs throughout locomotory tail flexions and periodic bursting activity coincides with branchial respiratory movement. These patterns of activity are modified at metamorphosis when the mode of locomotion and breathing change. The larvae can detect differential stimulation of the system by small jets of water and turn to face the source although the lateral line system is not essential for the orientation of tadpoles in a flowing water mass. Adult toads subjected to a similar stimulus exhibit feeding behaviour.
Origin of calcified tissue in regenerating spines of the sea urchin, Strongylocentrotus purpuratus (Stimpson): A quantitative radioautographic study with tritiated thymidine
Authors: Heatfield Barry M. 
Published: June 2005

AbstractCellular proliferation in the calcified dermis during regeneration of fractured spines of the sea urchin, Strongylocentrotus purpuratus (Stimpson), was studied quantitatively in radioautograms of tissues labeled with tritiated thymidine in vivo or in vitro to establish the origin of regenerated calcified tissue. Non‐fractured, whole spines were included for comparison. In short term experiments, incorporation of tritiated thymidine occurred throughout the length of regenerating and non‐fractured spines, with a peak in the number and proportion of labeled cells in the shaft occurring near the milled ring, declining to low levels in the the base and tip. A localized apical growth zone was absent in these spines. In pulse‐labeling experiments, there was a marked distal shift in the distribution of labeled cells during regeneration of fractured spines and in whole spines presumably due to migration. Significantly, labeled cells appeared in increasing numbers throughout the regenerate during growth. Few migratory coelomocytes within the calcified dermis were observed to incorporate detectable quantities of tritiated thymidine. The results of this study are consistent with the hypothesis that regenerated connective tissue of the calcified dermis originates by distal migration of cells, primarily from proximal regions of relatively high mitotic activity within the shaft near the level of the milled ring.
A study of the intrinsic factors which control the initiation of asexual reproduction in the tunicate Amaroucium constellatum
Authors: Freeman G. 
Published: June 2005

AbstractThe first part of this study describes the normal pattern in terms of which budding takes place as a colony composed of a large number of zooids is generated from an oozooid. During the time interval which elapses from the formation of a zooid until it reproduces asexually by strobilating, size increase is logarithmic. The length of time which elapses until a given zooid strobilates is correlated with the size of its thoracic region and its prior history.The role of zooid size increase in bringing about the conditions which lead to the initiation of strobilization was examined by irradiating small zooids which had been growing for a short period of time with different dosages of gamma radiation. The dosages of irradiation used slowed down the rate of growth or stopped growth; however, these animals strobilated at the same time that the unirradiated controls strobilated, demonstrating that the initiation of strobilization is not tied to the growth cycle of the zooid.The possible role that organ systems situated in different regions of these animals might have in initiating strobilization was studied by removing parts of zooids at different times during their growth cycle. These experiments demonstrated that a population of cells in the dorsal half of the thorax normally function to inhibit strobilization. Studies in which parts of animals were made to regenerate thereby creating a condition in which different regions of the same zooid were of two different chronological ages demonstrated that the activities of cells in the thoracic region of these animals also regulate the time interval which will elapse until strobilization. These experiments were done by compounding “Siamese twin” zooids with two thoracic regions and showing that the youngest thoracic region controls the timing of strobilization.This work is discussed in relation to experimental work which has been done on other ascidian species and to the suggestions that have been made for the purpose of explaining how asexual reproduction is regulated in tunicates.
An evaluation of myotypic respecification in axolotls
Authors: Grimm Leslie M. 
Published: June 2005

AbstractNerves supplying forearm flexor muscles were exchanged (crossed) with those supplying forearm extensors. After complete recovery, the movements of the forelimb were the same as those of normal limbs. Dissections showed that the nerves remained crossed, and electrical stimulation of the crossed nerves close to the muscles they supplied showed that the nerves were functionally connected to the foreign muscles. On the basis of these criteria, it appeared that axolotl nerves could respecify themselves.Stimulation of the crossed nerves further from the muscles they innervated, however, yielded contractions in the muscles that the nerves had originally supplied. Therefore, one of the two crossed nerves was severed at the shoulder and allowed to degenerate so that any movements elicited by subsequent electrical stimulation could be ascribed unambiguously to the remaining, non‐degenerated nerve. Electrical stimulation now showed clearly that the nerve which had originally innervated forearm flexors continued to produce flexion responses after it was crossed, and the nerve which had formerly innervated extensors continued to produce extension. Thus the fibers had somehow recrossed to reinnervate their original muscles.It therefore appears from the present investigation that axolotl nerves do not respecify themselves. Instead, a few fibers find their way back to their original muscles, and this is enough to produce normal movement.
Localization of primordia within the dorsal mesothoracic disc of Drosophila
Authors: Murphy Collin 
Published: June 2005

AbstractDistal regions or “marginal ridge” areas of the dorsal mesothoracic disc of mature Drosophila larvae, not previously included in fate maps, were marked by microcauterization in situ. Structures assumed to have primordia in the distal half of the disc (mesopleura, pteropleura, arch, ventral scutellum, ventral wing hinge and wing proper) are either missing, deficient, or damaged among adults surviving the operation. In contrast, neither the dorsal wing hinge nor mesonotum, which are known to have primordia in the proximal half of the disc, are similarly affected.The pattern of distribution of deformities in surviving adults indicates that (a) the anlage of the mesopleural sclerite is located in the distal edge portion or “marginal ridge” of the disc, (b) anlagen of pteropleura, arch and ventral scutellum may also be tentatively assigned to this location, (c) there are significantly high associations between deformities affecting the pteropleura and the ventral wing hinge, and (d) the anlage of the deep phragma of the postnotum may be more closely related to the first abdominal tergite than to the dorsal mesothoracic disc.The distal localization of pleural, arch, and ventral scutellar anlagen corresponds to the physical separation from mesonotal anlagen predicted from an earlier statistical analysis of genetic mosaics; i.e., these presumptive sclerites are separated from the mesonotal anlagen by the anlagen of the wing in the “pouch” area of the disc.The new information has been incorporated into a hypothetical fate map of the disc, which includes anlagen plans suggested by previous authors.
Growth and differentiation in hydra. II. The effect of temperature on budding in Hydra littoralis
Authors: Park Helen D. , Ortmeyer Anne B. 
Published: June 2005

AbstractHydra littoralis acclimates to 5°, 10°, 15° and 21° C. After acclimation, animals actively initiate and drop buds. The relationship between budding rate of acclimated hydras and temperature in the 5° to 21° range is direct but non‐linear. The temperature coefficient for bud development is much greater than for bud initiation at low temperature. The size (dry weight) of individual buds and adults increases with decreasing temperature; animals acclimated to 5° are more than twice as large as animals acclimated to 21°. Hydras subjected to an abrupt temperature rise show a temporary overshoot in budding rate as compared to controls already acclimated to the higher temperature. The budding rate of hydras subjected to an abrupt temperature drop is temporarily depressed severely as compared to the rate of controls already acclimated to the lower temperature.
The mechanism of puparium formation in flies
Authors: Zdarek Jan , Fraenkel G. 
Published: June 2005

AbstractThe mechanism of puparium formation in the fleshfly Sarcophaga bullata Parker was studied. Several distinct morphological events take place during the hour prior to the completion of the white puparium. 1. The anterior three larval segments are irreversibly retracted. 2. The body contracts by muscular action to about two‐thirds of its original length. 3. Simultaneously a longitudinal shrinkage occurs in the cuticle, giving it a smooth surface. 4. Finally the cuticle becomes stabilized in the sense that it can no longer be stretched, and no longer collapses upon release of internal pressure by bleeding. 5. Tanning starts almost as soon as the smooth barrel shape of the puparium is completed. The following observations demonstrate the largely independent nature of these processes: 1. Paralyzing the musculature, by ligation, tetrodotoxin, or bee venom, leads to tanned puparia in the shape of the larva. 2. Disabling the shrinkage system (e.g., by ryanodine or eserine) leads to puparia with a deeply folded surface. 3. Injecting smaller doses of tetrodotoxin or bee venom leads to elongated puparia with a shrunken (smooth) surface. 4. Injecting a certain ecdysone analogue leads to a puparium which is normal except for the failure of the anterior end to retract. 5. Release of internal pressure by bleeding leads to puparia which are supercontracted and folded. 6. Injection of a tanning inhibitor (α‐MDH) leads to a white puparium of normal shape which fails to tan. The transformation of the larval cuticle into the tanned puparium is accompanied by a spectacular water loss in the cuticle which is particularly rapid during the brief period between completion of the white puparium and start of tanning. This water loss is almost certainly correlated with the above mentioned stabilization of the puparium.
Fine structure of muscles controlling the strike of the mantis shrimp, Hemisquilla
Authors: McNeill Patricia , Burrows Malcolm , Hoyle Graham 
Published: June 2005

AbstractThe ultrastructure of some muscle fibers of the five physiologically different motor units operating the strike of the mantis shrimp were studied by electron microscopy. The distal portion of the lateral flexor was found to have the shortest sarcomere length (4.3 μm), the densest, most complex sarcoplasmic reticulum, the largest number of dyads per unit cross‐sectional area and the smallest filament cluster (“fibril”) size. The proximal portion of the same muscle differs from it mainly in having a less well‐developed reticulum and a large filament cluster size.The remaining muscles have longer sarcomere lengths: 5.3 μm for the medial flexor, 7.8 μm for the lateral extensor, and 6.0–10.2 μm for the medial extensor, as well as a weakly‐developed sarcoplasmic reticulum and fewer dyads per unit cross‐sectional area.These data were compared with contraction and relaxation times of the units and showed that the rates of both contraction and relaxation are lower the greater the A band or true relaxed sarcomere length. For fibers of equal A band length, faster rates were found to be associated with a more extensive sarcoplasmic reticulum, giving reduced filament cluster size, as well as with a larger number of dyads.
The development of avian red cell shape
Authors: Barrett Lucy A. , Scheinberg S. L. 
Published: June 2005

AbstractImmature erythrocytes of pigeons and chickens change from a spherical to a flat form following the final mitotic division during development. In vitro studies provide evidence that initial changes in shape are influenced by conditions that affect availability of oxygen. Transformation to a flat form occurred most rapidly at 37°C, a temperature that results in deoxygenation of hemoglobin in erythrocytes of the bone marrow. The maximum rate of transformation occurred at pH 6.5, a pH which favors deoxygenated hemoglobin. Oxygen inhibited the transformation in shape at 37 °C and resulted in a reversion of shape, from flat to spherical. Flattening and deoxygenation of hemoglobin are highly correlated. Precursor erythrocytes in plasma clot culture were observed microscopically. The cell stages identified in sequence were: (1) the “n‐2” dark cells, apparently lacking hemoglobin. These cells divided to form “n‐1” cells which synthesized hemoglobin as they matured. The “n‐1” cells divided, forming spherical daughter “n” cells which flattened within 60 minutes after mitosis.
Comparative studies on creatine kinase isozymes from skeletal‐muscle and stomach of trout
Authors: Perriard Jean‐Claude , Scholl Adolf , Eppenberger Hans M. 
Published: June 2005

AbstractTissue‐specific heterogeneity of creatine kinase (CPK) isozymes is particularly pronounced in various trout species. Several of the isozymes expressed in stomach and in skeletal muscle appeared to be identical as judged by their electrophoretic behavior, but reversible dissociation studies on single, electrophoretically pure, CPK‐isozymes isolated from these two tissues revealed significant differences between isozymes of similar electrophoretic mobility. Moreover, in contrast to trout skeletal muscle, the native and reassociated stomach CPK isozyme patterns could be accounted for by the association of the polypeptide products of two gene loci into homodimers and heterodimers, providing further evidence that the isozymes of stomach and skeletal muscle are non‐identical and thus presumably the products of distinct genes.