bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field experiments on sexuality in the freshwater sponge Spongilla lacustris. The control of oocyte production and the fate of unfertilized oocytes
Authors: Gilbert John J. 
Published: June 2005

AbstractGemmulated, female sponge was collected from nature on 10 November 1971 and then stored in the laboratory at 3°C in the dark. Pieces of this sponge were set out in the pond of origin on 29 May, 6 July, 10 August, and 14 September 1972 and on 16 May 1973. Oocyte production was observed in all sponges developing from the hatched gemmules about one week after implantation. The production of young oocytes ceased three or four weeks following implantation except in the sponges implanted on 14 September 1972, which continued to produce oocytes up to 6 November. This extended period of oocyte production was associated with and may be due to low water temperatures.The study shows that oocyte production does not require an environmental stimulus specific to a particular time of year, for oocytes differentiated under conditions of increasing as well as decreasing water temperatures and day lengths. The control of oocyte production is probably endogenous and associated with gemmule hatching. The possible nature and the adaptive significance of this control mechanism are discussed.Oocytes produced in sponges implanted after the normal sexual period in the pond were not fertilized. Such oocytes go through the normal growth sequence up to the end of the “grand accroissement” phase. Then they degenerate, ultimately releasing their stored yolk bodies into the mesenchyme.All evidence indicates that this population of the species is dioecious.
Calls of different individual hens and the parental control of feeding behavior in young Gallus gallus
Authors: Cowan P. J. , Evans Roger M. 
Published: June 2005

AbstractSelective food pecking by young domestic chiks to parental calls from different individual hens was demonstrated. Previous experience with a parental call paired with visual movement can decrease the number of food pecks to novel calls in testing as compared to the responses of chicks which have received either the parental call or visual movement alone in training. Selective food pecking to parental calls appears to assist in the maintenance of the family unit.
Effects of grouping on sexual receptivity in female hamsters
Authors: Lisk Robert D. , Reuter Lawrence A. , Raub Jeffrey A. 
Published: June 2005

AbstractFemale hamsters maintained in groups of 4 to 12 animals continue to show four‐day ovulatory cycles. However, when placed with males on the evening of proestrus, only 40% of these grouped females mate. Ninety‐five per cent of females caged singly or in groups of two, mate in less than ten minutes when placed with males on the evening of proestrus. Thus, grouping of female hamsters blocks reproduction in some individuals through a behavioral mechanism which does not apparently affect the ovulatory cycle. Receptivity cannot be reinitiated in such animals by administration of exogenous progesterone on the afternoon of proestrus.
Establishment of cleavage furrows by the mitotic spindle
Authors: Rappaport R. , Rappaport B. N. 
Published: June 2005

AbstractThe purpose of this investigation was to determine the capacity for furrow establishment of the mitotic spindle in several kinds of dividing animal cells. To this end the cell shape was altered so that equatorial surface was brought in contact with the spindle and its normal geometrical relation with the asters changed. In flattened Tripneustes gratilla eggs, furrows formed at the tips of deeply cut notches that impinged upon the spindle area. In Echinarachnius parma eggs, furrows formed at the tips of deeply cut notches and also at the margins of perforations that straddled the spindle. The distance separating the perforations was less than the normal spindle diameter. In flattened, dividing cultured newt (Diemictylus viridescens) kidney cells furrows formed in equatorial surface that was pushed inward far enough to displace the metaphase chromosomes. These results appear to indicate that the mitotic spindle of animal cells can establish furrows. We speculate that the actual role played by the spindle in normal cytokinesis depends upon the relative sizes of the asters and the spindle and upon the normal distance between the spindle and the equatorial surface.
Mayer waves in the circulation of a teleost fish
Authors: Wood Chris M. 
Published: June 2005

AbstractRegular oscillation in arterial blood pressures identical to mammalian Mayer waves were recorded in unanaestetized trout (Salmo gairdneri). The waves were associated with hemorrhage, were caused by fluctuations in systemic vascular resistance, and were sometimes accompanied by fluctuations in cardiac output of opposite phase. Alpha‐adrenergic blockade eliminated the phenomena; muscarinic cholinergic blockade was ineffective. The existence of Mayer waves provides evidence for a nervous control of vasomotor tone in teleosts.
Sound and sound emission apparatus in puerulus and postpuerulus of the western rock lobster (Panulirus longipes)
Authors: Meyer‐Rochow V. Benno , Penrose John D. 
Published: June 2005

AbstractSounds and sound emitting structures of larval rock lobsters are compared with those of juvenile and adult. The rasping sound, typical of disturbed juveniles and adults, is not produced by the puerulus, although file and plectrum are developed. The sound is, however, heard in the postpuerulus. Sound characteristics vary with age, individual and species, and therefore are of little value to spiny lobster taxonomy.
Avian scale development. III. Ultrastructure of the keratinizing cells of the outer and inner epidermal surfaces of the scale ridge
Authors: Sawyer Roger H. , Abbott Ursula K. , Fry Greta N. 
Published: June 2005

AbstractUltrastructural features of keratinization differ for the inner and outer epidermal surfaces of developing avian scales. Only the alpha stratum develops along the inner scale surface, and it is retained after hatching and is still present in adult birds. The cells of the alpha stratum are characterized by lipid droplets, multigranular bodies, and peripherally located keratohyalin granules. In contrast, the epidermis of the outer scale surface develops both alpha and beta strata. The alpha stratum is lost soon after hatching and only the beta stratum is found in the mature bird. Bundles of 30 Å filaments fill the cells of the beta stratum and keratohyalin granules are not present. The outermost peridermal and subperidermal cell layers develop along both epidermal surfaces of the scale. These two cell layers are characteristic of the embryonic period and are lost at the time of hatching.
Avian scale development. IV. Ultrastructure of the anterior shank skin of the scaleless mutant
Authors: Sawyer Roger H. , Abbott Ursula K. , Fry Greta N. 
Published: June 2005

AbstractScales do not form on the legs and feet of the scaleless mutant chicken, and consequently, the skin in these regions remains soft and pliable, similar to that covering the rest of the body. By 17 days of embryonic development, both the peridermal and subperidermal cell layers have developed along the surface of the anterior shank epidermis. Subsequently, the scaleless epidermis cornifies, producing an alpha stratum characteristic of the inner epidermal surface of normal scales. The cells of the alpha stratum elaborate lipid droplets, multigranular bodies, and peripherally located keratohyalin granules. The beta stratum found along the outer epidermal surface of normal scales never develops.
Regeneration of the forelimb in adult hypophysectomized Notophthalmus (Diemictylus) viridescens given embryonic or adult chicken anterior pituitary extract
Authors: Liversage Richard A. , Fisher Kenneth R. S. 
Published: June 2005

AbstractIn absence of the anterior pituitary gland, limb and tail regeneration does not occur in the adult newt Notophthalmus (Diemictylus) viridescens. Sixty‐five adult newts were included in this work which was designed to test to what degree a hypophysectomized newt can regenerate its forelimb when given daily injections of fresh adult or stored (−20° C)‐thawed embryonic or adult chicken anterior pituitary gland extract. Injections were begun seven days after hypophysectomy (to minimize further the titres of residual circulatory hormones) and concomitant amputation. The results are based on three experimental, one control and one sham series.In 40 out of 45 cases in Experiments C, D, and E, limb regeneration ensued for 25–30 days post‐amputation (until fixation). However, in the Experiment E newts, which were given embryonic chick pituitary extract, the regenerates were less advanced than those seen in the animals of Experiments C and D, given adult chicken pituitary extracts. Possible explanations for the differences in results are discussed.The results show that forelimb regeneration and survival in our hypophysectomized animals were due to extracts of embryonic or adult chicken anterior pituitary glands; presumably, these extracts contained the essential hormones. On the basis of our newt bio‐test system, 15–18 day chick embryo and adult chicken anterior pituitary extracts (hormones) are not species specific. Freezing and storage of extracts at −20° C for up to three months before thawing and use apparently does not appreciably affect their hormonal activity.
Neuromuscular analysis of closing in the dimorphic claws of the lobster Homarus americanus
Authors: Govind C. K. , Lang Fred 
Published: June 2005

AbstractThe mechanical and electrical activity of the closer muscle is compared in the cutter and crusher claws of the lobster Homarus americanus. Two excitor axons innervate the closer muscle. In the cutter the fast axon produces twitch contractions in response to single stimuli while its counterpart in the crusher gives twitches only to paired stimuli. The twitches fatigue more rapidly in the cutter than in the crusher. The slow axon in both claws produces tonic contractions which are fatigue resistant. The electrical events in the muscle fibers correlate closely with the mechanical activity. Thus the cutter fast EPSPs show poor facilitation and fatigue rapidly while the slow EPSPs have high facilitation values and are less prone to fatigue. The slow and fast axon EPSPs in the crusher are qualitatively similar to their counterparts in the cutter. In both claws the postsynaptic response was considerably enhanced by paired stimuli.
Intracellular actions of 5‐hydroxytryptamine on the bivalve myocardium. II. Cyclic nucleotide‐dependent protein kinases and microsomal calcium uptake
Authors: Higgins William J. , Greenberg Michael J. 
Published: June 2005

AbstractThe effects of cyclic AMP, cyclic AMP‐induced phosphorylation, and 5‐hydroxytryptamine (5HT) on calcium uptake by bivalve heart microsomes were investigated. Cyclic AMP‐dependent and cyclic GMP‐dependent protein kinases were purified from Macrocallista nimbosa ventricles. The cyclic AMP‐dependent preparation readily phosphorylates myocardial cell proteins in both the soluble and microsomal fractions. The cyclic AMP‐mediated phosphorylation of microsomal protein augments microsomal calcium uptake; but 5HT and cyclic AMP also induce a similar increase directly. The protein kinase activity indigenous to the microsomal preparation was not increased by cyclic AMP.In many molluscan ventricles, 5HT increases intracellular cyclic AMP and simultaneously enhances muscle contractility by altering the amount of intracellular calcium available for contraction. Therefore, if cyclic AMP acts as a second messenger and mediates the effects of 5HT, the nucleotide should augment, directly or indirectly, the amount of membrane associated calcium. This study suggests that cyclic AMP can mediate 5HT action either by the activation of a cyclic AMP‐dependent protein kinase, or by a direct modification of the amount of membrane associated calcium.
The caecilian ear
Authors: Wever Ernest Glen 
Published: June 2005

AbstractA study of the ear and its responses to acoustic stimuli was carried out in two caecilian species, Geotrypetes seraphini and Dermophis mexicanus. There is no external ear opening or tympanic membrane. The middle ear mechanism consists of a single element, the stapes, with its footplate in the oval window and a headpiece extending anterolaterally to the quadrate. The inner ear contains a single auditory endorgan, the amphibian papilla, somewhat similar to this organ in anurans. The mode of stimulation by sounds, however, involves a reentrant fluid circuit as in certain of the reptiles.In terms of the electrical potentials this ear is rather uniformly sensitive, though in low degree, to tones over the low‐frequency range.
Autoradiographic study of mouse spermatozoan arginine‐rich nuclear protein in fertilization
Authors: Kopečný Vaclav , Pavlok Antonín 
Published: June 2005

AbstractGeneral labeling of ripe mouse spermatozoa was obtained two weeks after six injections of L‐arginine‐5‐3H monohydrochloride, administered within two days. Besides tail labeling a very intensive nuclear labeling was obtained. It is presumed that this nuclear labeling represents almost exclusively tritiated arginine incorporation into basic nuclear protein.Mouse oocytes were fertilized in vitro with such labeled spermatozoa. It was found that the nuclear label is lost very early during male pronucleus formation, probably concomitantly with sperm chromatin decondensation. This might indicate total loss of the basic spermatozoal nuclear protein before male genome activation.
Influence of season, photoperiod and thermal acclimation on the panting threshold of Amphibolurus muricatus
Authors: Heatwole Harold , Firth Bruce T. , Stoddart Helen 
Published: June 2005

AbstractThe panting threshold of Amphibolurus muricatus progressively elevates with increasing acclimation temperature. It is also elevated by long (16L:8D) photoperiod in comparison to values obtained under constant photic conditions or short photoperiods. There is a seasonal cycle (higher thresholds in the austral summer than in other seasons) which is independent of shortterm thermal acclimation or photoperiod. A fluctuating temperature regimen of eight hours at 6°C and 16 hours at 26°C under constant light resulted in a panting threshold intermediate between values for animals acclimated at constant 5°C and those acclimated at constant 26°C.
Sperm release evoked by electrical stimulation of the fish brain: A functional‐anatomical study
Authors: Demski Leo S. , Bauer Diana H. , Gerald Jerry W. 
Published: June 2005

AbstractAcute brain stimulation experiments were carried out in anesthetized male green sunfish, Lepomis cyanellus. Semen discharge was evoked consistently by low level electrical stimulation (100 μA or less) in the following areas: the preoptic region, dorsal hypothalamus, thalamus, midbrain tegmentum and the basolateral midbrain and medulla. Areas which were stimulated repeatedly at 100 μA and were always negative for sperm release included: the telencephalon with the exception of the preoptic region, the optic tectum, the cerebellum, the inferior lobe of the hypothalamus, the nucleus rotundus and the dorsal medulla. Removal of most of the optic tectum and cerebellum failed to block responses evoked from the preoptic area; however, they were usually eliminated by transecting the rostral spinal cord. Electrical stimulation of an isolated 4 mm segment of spinal cord located at the third vertebral level resulted in sperm release, indicating that adequate mechanisms for semen discharge are present within the upper spinal cord. The results of this study suggest that a sperm release system in the green sunfish extends from the preoptic area to the spinal cord passing through the hypothalamus, midbrain tegmentum and basal midbrain and medulla.
An analysis of nuclear numbers in individual muscle fibers during differentiation and growth: A satellite cell‐muscle fiber growth unit
Authors: Cardasis Constance A. , Cooper George W. 
Published: June 2005

AbstractA numerical analysis of changes in the populations of nuclei in individual, intact muscle fibers was made to study how multinucleation arises during normal differentiation and growth. Gastrocnemius muscle fibers from pre‐ and post‐natal mice were isolated with guanidine (Cardasis and Cooper, '75) and examined.Satellite cells associated with muscle fibers were first observed at 19 days of gestation. The number of nuclei per muscle fiber (muscle + satellite cell nuclei) averages 83 at this age, 157 at birth and continues to increase to 354 by 63 days of age. However, the rate of increase during growth is not constant. Estimates of satellite cell and muscle nuclei in histological cross sections indicate that there is a decrease in the percentage of satellite cells from 32% at birth to 6% in the adult. However, the numbers of satellite cells associated with individual muscle fibers, calculated from these percentages and the nuclear counts on whole fibers, decreases only between 2 and 4 weeks of age.Cytosine arabinoside was injected subcutaneously during the first two weeks of age. Pairs of satellite cells, abnormal nuclei and elevated percentages of satellite cells were observed. This evidence as well as the numerical analysis of nuclear populations in whole fibers lends further support to the hypothesis that satellite cells account for the increase in muscle nuclei from birth to maturity.
Hybrid desmosomes in aggregated chick and mouse cells
Authors: Overton Jane , Kapmarski Rita 
Published: June 2005

AbstractMouse embryo skin epidermis has been examined during maturation, and stages have been found when desmosomes are first scarce, then increasing in frequency and finally numerous. Cells of skin epithelium from these stages have been combined in reaggregates with cells of the 15‐day chick corneal epithelium which also form desmosomes readily. When these two cell types are reaggregated in the presence of cytochalasin B which inhibits cell sorting, they form numerous junctions with each other. Desmosomes in mouse and chick appear similar morphologically except for certain cytoplasmic components. Mouse skin epidermis cells combined with cardiac muscle or intestinal epithelium formed imperfect or no specialized contacts. The possible role of junctions in cell sorting in reaggregates is discussed.
Urea excretion in the hibernating columbian ground squirrel (Spermophilus columbianus)
Authors: Passmore J. C. , Pfeiffer E. W. , Templeton J. R. 
Published: June 2005

AbstractHibernation was induced in Columbian ground squirrels by placing them in refrigerated cages equipped with urine‐collection pans. On arousal, urine and blood were collected from each animal, which was then allowed to reenter hibernation. After several days the animal was sacrificed and bladder urine and another blood sample were taken. In addition, four active non‐hibernating ground squirrels were placed in a cage at room temperature with neither food nor water. Urine was collected at 9 and 26 hours and blood was collected at 0 and 26 hours. Although only seven of ten hibernating squirrels had a higher blood‐urea level when sacrificed than during the previous arousal, the other three had very high levels in the arousal period and probably further excreted urea before entering hibernation. When total body urea was calculated on a body weight basis, all except one animal showed a greater level of urea during hibernation than in the previous arousal. During their period of dehydration, the non‐hibernating summer squirrels showed a marked decrease in blood urea. The osmotic concentration of the urine from these squirrels was due less to urea than that excreted during arousal by hibernating squirrels. Thus, it appears that urea accumulates in the blood during hibernation and is excreted in the urine during arousal.
Ultrastructural analysis of artificially activated rabbit eggs
Authors: Longo Frank J. 
Published: June 2005

AbstractUltrastructural investigations have been carried out on parthenogenetic rabbit eggs in an effort to elucidate events occurring during artificial activation and their similarity to processes of fertilization and embryogenesis. Rabbit eggs were artificially activated by culturing at 10°C for 24 hours followed by incubation at 37°C for 2 to 24 hours. Examination of eggs immediately after incubation at 10°C for 24 hours indicates that activation is initiated when the chromosomes coalesce to form a reticulum which is either surrounded completely by two parallel membranes or incompletely by cisternae of smooth endoplasmic reticulum. Aggregation of the chromosomes occurs as a result of a reduction in the number of microtubules making up the meiotic spindle. When cold treated ova are subsequently incubated at 37°C a nucleus is formed which moves centrad where it may participate in the cleavage of the egg. Formation of a second polar body and release of the contents of the cortical granules as reported for inseminated eggs was not found to be a part of activation of the egg by cold treatment. Approximately 95% of the ova cultured at 10°C for 24 hours followed by 37°C for 12 hours were activated, i.e., they possessed a nucleus or they had cleaved. Many of the activated eggs cultured for short periods at 37°C were structurally similar to fertilized ova, with further incubation fragmented eggs and abnormal multicellular stages predominated.
Mitosis in presumptive primordial germ cells in post‐blastula embryos of Xenopus laevis
Authors: Dziadek M. , Dixon K. E. 
Published: June 2005

AbstractIn X. laevis embryos injected with (3H) thymidine between early gastrula and late neurula, the presumptive primordial germ cell nuclei were labelled and some were observed in mitosis, confirming that division occurs throughout this developmental period. In all labelled and mitotic cells, the germ plasm adjoined the nucleus, an observation which invalidates the hypothesis that germ plasm inhibits mitosis in presumptive primordial germ cells after gastrula. In embryos which had been irradiated with UV at the vegetal pole at the 2‐cell stage, the presumptive primordial germ cells also incorporated (3H) thymidine and divided during the same developmental period.
Considerations of symmetry in the cortical integration of Tetrahymena doublets
Authors: Nanney D. L. , Chow Margaret , Wozencraft Barbara 
Published: June 2005

AbstractHomopolar doublets of syngen 1, T. pyriformis, may be induced by treatment of conjugating pairs with immobilizing antiserum. These doublets have geometric properties and basal body populations generally indicative of separate autonomous integrative systems in the two halves. The duplex system, though metastable, is transformed through a process of “simplification” back to the simplex state. The transformation is not a single event, but a series involving changes at different times for different structures and processes; for the micronuclei and the macronuclei; for the capacity to generate two oral apparatuses through stomatogenesis and the capacity to develop them through oral replacement; for the structures at the anterior and posterior ends of the cell; for the numbers of ciliary rows and for the numbers of basal bodies which make up the rows.Although the two semicells composing a doublet are in important respects independent of each other, they are coordinated in significant ways. The positions of the contractile vacuole pores and their numbers depend not only on the number of ciliary rows in a semicell, but also on the number of ciliary rows in the opposing twin. Most notably, the probability for dual stomatogenesis, and hence the perpetuation of the doubled oral apparatus, depends on the symmetry of the semicells. The cell as a whole is maintained as an integrated unit over a prolonged interval as various aspects of duplex structure and function are progressively consolidated.