bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and differentiation of the cultured secretory cells of the cow oviduct on reconstituted basement membrane
Authors: Joshi M. S. 
Published: June 2005

AbstractIsolated bovine oviduct epithelial cells were cultured on plastic precoated with matrigel. The epithelial cells seeded on 10 mg/ml matrigel often organized themselves into hollow tubes or spheres with microvilli directed towards the lumen. This is the first report of describing the spontaneous tube formation of oviduct epithelial cells in vitro. The epithelial cells growing on this substratum became fully differentiated with the formation of junctional complexes and the production of secretory vesicles which migrated to apical plasmalemma. Epithelial cells seeded on 2 mg/ml matrigel (dry film) formed a subconfluent monolayer in 15–20 days after seeding. The histoarchitecture of the secretory cells growing on the matrigel dry film closely resembled that of intact epithelial cells. Occasional ciliated cells containing large numbers of mitochondria were observed in cell colonies growing on 2 mg/ml matrigel but they possessed very few intact cilia. The monolayer linearly incorporated 35S‐methionine into proteins up to 8 hr in presence of estradiol or progesterone. The fluorography of the newly synthesized proteins indicated that the cell extracts of estradiol‐stimulated cells contained an additional protein of approximate molecular weight of 60 kd as compared to the extracts of cells incubated without steroids or incubated with progesterone.
Sites of melatonin action in the brain of the house sparrow, Passer domesticus
Authors: Cassone Vincent M. , Brooks David S. 
Published: June 2005

AbstractThe pineal gland and its hormone melatonin are important for the generation of circadian rhythms by passerine birds such as the house sparrow, Passer domesticus. The sites of melatonin action within the brain of this species were determined by employing two techniques. First, the distribution of 2[125I]iodomelatonin (IMEL) binding was determined by in vitro incubation in IMEL, autoradiography, and computer image analysis. Data from these experiments indicated reversible IMEL binding in a wide array of cerebral structures primarily associated with vision. Second, the effects of exogenous melatonin on cerebral uptake of the metabolic marker 2‐deoxy[14C]glucose (2DG) were determined. Many of the same structures that bind IMEL also exhibited decreased 2DG uptake in response to melatonin administration, whereas structures that did not bind IMEL were unaffected by the hormone. The data suggest that much of the house sparrow's visual world is modulated on a circadian basis via the circadian secretion of melatonin. These observations are discussed in the context of avian circadian organization and the role it may play in the behavioral physiology of the bird.
The effects of orchidectomy and gonadotropins on steroidogenesis and oogenesis in Bidder's organs of the toad Bufo woodhousii
Authors: Pancak‐Roessler Martha K. , Norris David O. 
Published: June 2005

AbstractIn the family Bufonidae, male toads possess rudimentary ovaries, called Bidder's organs, which are attached to the testes. The mechanisms involved in the inhibition of oogenesis in these structures were investigated in male Bufo woodhousii. Orchidectomized and sham‐operated animals were injected with gonadotropins (pregnant mare serum gonadotropin [PMSG] + human chorionic gonadotropin [hCG]) for 26 days and the effects of these hormones on oogenesis and steroidogenic activity (3β‐hydroxysteroid dehydrogenase [3β‐HSD] and 17β‐HSD) in the Bidder's organ were quantified. Bilateral orchidectomy alone resulted in the growth of bidderian oocytes and a shift towards later stages of oogenesis. Gonadotropins enhanced this effect and stimulated the proliferation of new germ cells. In the presence of testes, however, bidderian oogenesis remained inhibited despite high levels of circulating gonadotropins. In both ooplasm and follicular layers of the bidderian oocytes of all toads, 3β‐HSD and 17β‐HSD activities were detected by histochemistry. Follicular enzymatic activity increased in orchidectomized toads treated with PMSG + hCG but decreased in sham‐operated toads treated with gonadotropins. Testis weights, rudimentary oviduct weights, and plasma steroid levels increased in intact toads injected with hCG + PMSG. Gonadotropins had no effect on plasma steroid levels in orchidectomized toads, however. These results suggest that the testes play a major role in the inhibition of oogenesis in Bidder's organs of B. woodhousii and are a major source of androgens. High circulating levels of gonadotropins do not overcome the inhibitory effects of the testes.
Early innervation of skeletal muscle during tail regeneration in urodele amphibians
Authors: Thouveny Yves R. , Komorowski Thomas E. , Arsanto Jean‐Pierre , Carlson Bruce M. 
Published: June 2005

AbstractThe innervation pattern of skeletal muscles was studied in the normal and regenerating tail of Notophthalmus viridescens. Silver staining for nerve endings and histochemical localization of acetylcholinesterase (AChE) were used for light microscopy. In normal musculature, AChE positive reactions were localized at the ends of the muscle fibers where they are anchored on connective tissue septa by myotendinous junctions. At this level, silver staining shows nerve terminals forming endplates. During regeneration, positive reactions for AChE appear de novo as dense plates localized at the ends of the newly formed myotubes. The mechanisms involved in the localization of AChE on this surface seem to operate before previous local contacts by nerve terminals. From the ultrastructural data and immunohistochemical results with anti‐laminin antibody, these observations suggest that regenerating muscle fibers determine a region of post‐synaptic specialization in close relation with the organization of myotendinous regions and basement membrane formation. Nerve‐muscle contacts appear at these levels at stage IV (15–20 days after amputation) in the stump and in the rostral part of the regenerate (transition zone). These nerve terminals are provided by the disorganized peripheral nervous system of the injured segment. In the regenerate a similar pattern of AChE reaction can be seen in every myotube, differentiating according to a rostro‐caudal gradient. Innervation at the ends of the muscle fibers is in spatiotemporal relation with the exits of the ventral roots from the regenerating nerve cord as the regenerate continues to grow in length.
An increase of intracellular free Ca2+ is essential for spontaneous meiotic resumption by mouse oocytes
Authors: De Felici Massimo , Dolci Susanna , Siracusa Gregorio 
Published: June 2005

AbstractThe involvement of calcium ions in the mechanism of meiotic resumption has been studied in mouse oocytes made resistant to the lethal effects of calcium‐free medium (CFM) by zona pellucida removal (De Felici et al., '89). We show here that such oocytes undergo meiotic resumption in CFM (as evaluated by germinal vesicle breakdown, GVBD) at a rate comparable to that shown by oocytes cultured in medium containing 1.7 mM Ca2+. The addition to CFM of 50 uM Quin2/AM (a membrane permeable, high affinity Ca2+ chelator) totally prevents GVBD, while purported antagonists of Ca2+ release from intracellular stores, such as 150 uM 8‐(N, N‐diethylamino)octyl‐3‐4‐5 trimethoxybenzoate (TMB‐8) or 300 uM chlortetracycline, only cause a slight meiotic delay. On the other hand, if the oocytes are pre‐incubated for 30 min in CFM supplemented with 100 uM TBM‐8 plus 0.2 mM dibutyryl‐cyclic AMP (dbcAMP, a reversible inhibitor of GVBD), and then cultured in the same medium, without dbcAMP, a sustained inhibition of meiotic maturation is obtained.Our observations suggest that an increase in intracellular free Ca2+ is essential for meiotic resumption by mouse oocytes; in the experimental absence of external Ca2+, release of the cation from internal stores is sufficient to allow meiotic resumption.
Some problems related to the assessment of sperm motility in freshwater fish
Authors: Billard Roland , Cosson Marie Paule 
Published: June 2005

AbstractThe motility of the spermatozoa of freshwater fish is usually of short duration, but a precise description has rarely been provided. Motility requires a high dilution (more than 1,000‐fold) for initiation of synchronous motility in 100% of spermatozoa; a two‐step procedure is necessary, with an initial dilution of 1 to 100 in a medium that keeps the spermatozoa immotile and allows good mixing of the viscous semen. The second dilution (1 to 20) in the activating solution can be made directly under the microscope. Studies of carp sperm indicate that movement of live sperm is influenced by the ionic environment. The inhibition of motility in semen is mainly due to K+ ions in trout and osmotic pressure in carp, but other ions such as Na+, H+, and Mg2+ also interfere. Initiation of motility in trout requires external divalent cations. Immediately after dilution at 20°C, spermatozoa exhibit large circular trajectories (>400 μm in diameter), high beat frequencies (60 Hz), and velocities of 250 μm/sec. These values decrease rapidly. Within 20 sec after dilution, most spermatozoa stop moving, although some of them show some agitation with low beat frequency (< 10 Hz) and with very limited displacement during the next few minutes. A similar pattern is observed in carp, with active motility lasting 40 sec. Under certain ionic conditions, intratesticular spermatozoa are motile and have some fertilizing capacity.
Seasonal changes in shark testicular structure and spermatogenesis
Authors: Parsons Glenn R. , Grier Harry J. 
Published: June 2005

AbstractIn this report, seasonal changes in testicular structure and spermatogenesis in several shark species are reviewed, and new information concerning the bonnethead shark, Sphyrna tiburo, is presented. Shark species are separated into four categories based on the relationship between testicular GSI and mating season: 1) species that have a defined seasonal cycle in GSI and a defined mating season, 2) species that have a defined seasonal cycle in GSI and that mate year‐round, 3) species that show no seasonal change in GSI but that have a defined mating season, and 4) species that show no seasonal change in GSI but that mate year‐round. The testis of S. tiburo differs from the few species that have been examined in that 1) not all spermatogenic stages are present at all times of the year, 2) an annual zone of degeneration that progresses through the testis is not present, and 3) there appears to be complete testicular regression and recrudescence.
The mechanism of suckling in two species of infant mammal: Miniature pigs and long‐tailed macaques
Authors: German R. Z. , Crompton A. W. , Levitch L. C. , Thexton A. J. 
Published: June 2005

AbstractSuckling is the form of feeding unique to infant mammals. The mechanism used by infant mammals to withdraw liquid from the nipple is the subject of considerable debate. Suckling has been examined in two species of infant mammals: miniature pigs and long‐tailed macaques. In both species radio‐opaque markers were inserted into the tongue and jaws; the movements of the jaw and tongue (and also of specific regions within the tongue) plus the movement of milk containing barium were studied by high‐speed cineradiography (100 and 150 frames/sec). In the case of macaques, simultaneous pressure transducer recordings were also made. In both species, liquid moved out of the nipple as the intraoral space was expanded by a combination of tongue movement (negative pressure pumping) coupled with jaw opening. There was no evidence for expression (positive pressure on the nipple) in either species, strongly supporting the view that a suction mechanism is responsible for acquisition of milk from the nipple. Subsequent intraoral transport was different in the two species. The pigs used a second pump mechanism at the base of the tongue to transport liquid through the pillars of the fauces into the valleculae. The monkeys used a “squeeze‐back” mechanism similar to the transport mechanism documented for adult macaques. Further work with other species can test our tentative hypothesis that all mammals use a negative pressure suction for acquisition, but, as is true for adult mammals, infants may use different transport mechanisms to form and move the bolus.
Expansion of surface epithelium provides the major extrinsic force for bending of the neural plate
Authors: Alvarez Ignacio S. , Schoenwolf Gary C. 
Published: June 2005

AbstractNeurulation, formation of the neural tube, requires both intrinsic forces (i.e., those generated within the neural plate) and extrinsic forces (i.e., those generated outside the neural plate in adjacent tissues), but the precise origin of these forces is unclear. In this study, we addressed the question of which tissue produces the major extrinsic force driving bending of the neural plate. We have previously shown that 1) extrinsic forces are required for bending and 2) such forces are generated lateral to the neural plate. Three tissues flank the neural plate prior to its bending: surface epithelium, mesoderm, and endoderm. In the present study, we removed two of these layers, namely, the endoderm and mesoderm, underlying and lateral to the neural plate; bending still occurred, often with complete formation of a neural tube, although the latter usually rotated toward the side of tissue depletion. These results suggest that the surface epithelium, the only tissue remaining after microsurgery, provides the major extrinsic force for bending of the neural plate and that the mesoderm (and perhaps endoderm) stablizes the neuraxis, maintaining its proper orientation and position on the midline.
Inhibition of neural crest cell differentiation by embryo ectodermal extract
Authors: Thibaudeau Giselle , Frost‐Mason Sally K. 
Published: June 2005

AbstractThe white mutation in Mexican axolotls has long been thought to be a defect associated with the embryonic extracellular environment, but not with embryonic neural crest cells. Thus it was believed that pigment cells in white axolotls disappear from the skin during early development, not because they are intrinsically defective but because they have no choice but to move into an unfavorable environment. We present evidence to suggest that: (1) white neural crest cells are in fact intrinsically different from dark (wild‐type) cells, and (2) an inhibitor is produced in white embryonic ectoderm that actively suppresses the migration, differentiation, and survival of pigment cells in this animal. How these observations fit into the existing body of literature on the white mutant and a model for how the white phenotype might develop are discussed. © 1992 Wiley‐Liss, Inc.
Epimorphic vs. tissue regeneration in Xenopus forelimbs
Authors: Goss Richard J. , Holt Roger 
Published: June 2005

AbstractPostmetamorphic froglets of Xenopus laevis regenerate hypomorphic unbranched spikes from amputated arm stumps. These are composed primarily of cartilage, produced from blastemalike structures sparsely populated with cells and rich in connective tissue. Some consider these outgrowths to be an example of epimorphic regeneration produced from blastemas, albeit deficient ones. Others interpret them as a case of tissue regeneration derived from fibroblastemas augmented by chondrocytes and periosteal and perichondrial fibroblasts.To resolve these alternatives, forelimbs were amputated proximal to the wrist, skinned, and inserted through the body wall into the abdominal cavity. In the absence of skin, epidermal wound healing failed to occur and blastemas could not develop. After 2 months, by which time controls had regenerated spikes averaging 3.38 mm long, the denuded stumps had not given rise to outgrowths. They typically developed cartilaginous caps on the severed ends of the radius‐ulna, and in rare cases formed amorphous growths of cartilage. If blastema formation is considered diagnostic of epimorphic regeneration and tissue regeneration can proceed in the absence of epidermal wound healing and blastema formation, these findings lead to the conclusion that Xenopus limb regeneration is epimorphic. © 1992 Wiley‐Liss, Inc.
Patterns of sperm‐specific histone variation in sea stars and sea urchins: Primary structural homologies in the N‐terminal region of spermatogenic H1
Authors: Massey Carl B. , Watts Stephen A. 
Published: June 2005

AbstractAn electrophoretic characterization of histones from pyloric caeca, testes, and sperm of Asterias vulgaris revealed a sperm/testes‐specific variant of histone H1 significantly larger than its somatic counterpart from pyloric caeca. Additional proteins were observed in H1 regions of acetic acid‐urea polyacrylamide gels in testicular extracts. Sperm or testis‐specific variants of H2B observed in sea urchins were not found in the sea star. Evidence presented suggests that sperm‐ or testes‐specific H1 species of intermediate mobility may arise from a single, slow‐migrating H1 species (SpH1). Although an increase in nonspecific DNA binding by nuclear proteins must occur during the process of spermatogenesis, different organisms exhibit various patterns of sperm‐specific protein mediating differential binding during the process. Sperm‐specific variants of both H1 and H2B histones are observed in sea urchins, while the only variant observed in sea stars during spermatogenesis is SpH1. Sequencing of the N‐terminus of SpH1 from A. vulgaris revealed a repeating tetrapeptide in residues 3–6 and 8–11 (Ser‐Pro‐Arg‐Lys and Ser‐Pro‐Lys‐Lys, respectively), homologous to repeats in the N‐termini of sperm‐specific H1s from sea urchins. Primary structure within critical, variable regions of molecules responsible for nonspecific DNA binding appear conserved in many organisms. The occurrence of repeating tetrapeptides in SpH1 and other DNA binding proteins suggests that such domains may function similarly in various chromatins undergoing regulated or reversible condensation. © 1992 Wiley‐Liss, Inc.
The marginal zone of the 32‐cell amphibian embryo contains all the information required for chordamesoderm development
Authors: Pierce Kenneth E. , Brothers Ann Janice 
Published: June 2005

AbstractThe formation of the amphibian organizer is evidenced by the ability of cells of the dorsal marginal zone (DMZ) to self‐differentiate to form notochord and to induce the formation of other axial structures from neighboring regions of the embryo. We have attempted to determine when these abilities are acquired in the urodele, Ambystoma mexicanum (axolotl), and in the anuran, Xenopus laevis, by removing the mesodermalizing influence of the vegetal hemisphere at different stages of development and culturing the animal hemisphere isolate. This was possible, even at the 32 and 64‐cell stage, through the use of embryos with rare cleavage patterns. Cultured isolates were analyzed for morphological differentiation of mesodermal and neural structures, and for biochemical differentiation of the tissue‐specific enzyme, acetylcholinesterase (AChE). Large amounts of mesodermal and neural structures, and normal expression of AChE were found in isolates made as early as the 32‐cell stage in both species. Only a small increase in the percentage of isolates developing mesoderm was detected when isolations were made at later cleavage or blastula stages. The amount of mesoderm formed did not depend on the stage of isolation. Mesoderm differentiation was usually limited to the notocord and muscle. The isolates rarely formed pronephros, mesothelium, or mesenchyme, derivatives of ventral mesoderm, during normal development. The results indicate that the marginal zone of the cleavage‐stage embryo contains all of the information needed for the formation of the organizer. The formation of dorsal mesoderm does not require subsequent interaction with the cells of the vegetal hemisphere, although the presence of those cells is likely to play a role in normal pattern formation. © 1992 Wiley‐Liss, Inc.
Secondary mesenchyme of the sea urchin embryo: Ontogeny of blastocoelar cells
Authors: Tamboline Colin R. , Burke Robert D. 
Published: June 2005

AbstractSecondary mesenchyme in sea urchin embryos is released into the blastocoel after primary mesenchyme, and although these cells have been recognized for some time, we lack knowledge about many fundamental aspects of their origin and fate. Here we documented the ontogeny of one of the principal, and least well‐known, types of cells derived from secondary mesenchyme. The blastocoelar cells arise from mesenchyme released from the tip of the archenteron following the initial phase of gastrulation. The cells migrate with their cell bodies suspended in the blastocoel, rather than being apposed to the basal lamina like primary mesenchyme. The cells extend numerous fine filopodia to form a network of cytoplasmic processes around the gut, along the skeletal rods, and within the larval arms. Once the network is formed, the cells maintain their positions, although they actively translocate vesicles and cytoplasm along their filopodia. Cell counts indicate there is an initial recruitment of cells during gastrulation, followed by a more gradual increase in cell number after the larva begins to feed. Lineage studies in which 16‐cell‐stage macromeres were injected with horseradish peroxidase indicate that almost all of the macromere‐derived mesenchyme forms pigment cells and blastocoelar cells. We propose that blastocoelar cells are a distinct subset of secondary mesenchyme that forms fibroblast‐like cells in the blastocoel of sea urchin embryos. © 1992 Wiley‐Liss, Inc.
Asymmetric metabolism of hypothalamic catecholamines alternates with side of ovulation in a lizard (Anolis carolinensis)
Authors: Desan Paul H. , Lopez Kristin H. , Austin Harriet B. , Jones Richard E. 
Published: June 2005

AbstractWe determined levels of monoamines and their metabolites in 2 hypothalami dissected from the right and left hemibrains of 15 females during the right‐left alternating ovulatory cycle of Anolis carolinensis. Tissue contents of the following were measured using HPLC and electrochemical (coulometric) detection: dopamine (DA) and its metabolite 2,4‐dihydroxyphenylacetic acid (DOPAC), norepinephrine (NE) and its metabolites 3‐methoxy‐4‐hydroxyphenylglycol (MHPG) and 3,4‐dihydroxyphenylglycol (DHPG), and serotonin (5‐HT) and its metabolite 5‐hydroxyindoleacetic acid (5‐HIAA). An asymmetry ratio (AR) was determined by subtracting hypothalamic content (pM/mg) on the larger ovary (LO) side from that on the smaller ovary (SO) side, divided by the sum of the 2 sides (AR = SO − LO/SO + LO). The AR of MHPG and DHPG both decreased as the largest follicle in the LO grew during the cycle, from >0 (content higher on the SO side) at the beginning of the cycle to <0 (content higher on the LO side). The average content of MHPG in the 2 sides significantly increased during the cycle. There were no significant asymmetric changes in hypothalamic DA or DOPAC. The average content of DA increased during the cycle, whereas the content of DOPAC, as well as DOPAC/DA, did not change. The average content of 5‐HT increased, and the average metabolite ratio of 5‐HIAA/5‐HT decreased during the cycle without significant asymmetries. The metabolite ratios of NE and DA, but not 5‐HT, were asymmetric on the same side in a given female. These results suggest, that catecholamine metabolism shifts from being greater on the SO side of the hypothalamus to being greater on the LO side of the hypothalamus. This shift occurs when a follicle has reached 4.7–5.2 mm in diameter, with ovulation occurring at 8 mm. The asymmetric changes in catecholamine metabolism in synchrony with asymmetric ovarian growth indicate the presence of neural communication, in one direction or the other or both, between the ovaries and hypothalamus. © 1992 Wiley‐Liss, Inc.