bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative studies of fish, amphibian, and reptilian vitellogenins
Authors: Carnevali Oliana , Belvedere Paola
Published: June 2005

Plasma vitellogenins (VTGs) from estrogen‐treated males of the common carp Cyprinus carpio, common frog Rana esculenta, crested newt Triturus carnifex, and lizard Podarcis sicula were purified by MgCl2‐EDTA precipitation, DEAE cellulose chromatography, and ionexhange FPLC. VTG isoelectric points and molecular weights of VTG subunits were determined by chromatofocusing and SDS‐PAGE, respectively.

Immune cross‐reactivity was examined by ELISA with homologous and heterologous anti‐VTG sera which were tested before and after purification by affinity chromatography with Sepharose‐bound heterologous VTGs.

Amphibian and reptilian VTGs contained both common and species specific antigenic determinant, whereas carp VTG was immunologically distinct and formed by subunits with smaller mass as compared to the monomeric VTGs of the other three species.

The three‐dimensional structure of VTG does not appear to be conserved during vertebrate evolution, probably because of differences in post‐translational processing.
A mechanism for the action of pregnant mare serum gonadotropin on aromatase activity in the ovarian follicle of the medaka, Oryzias latipes
Authors: Nagahama Yoshitaka , Matsuhisa Arito , Iwamatsu Takashi , Sakai Noriyoshi , Fukada Sachiko
Published: June 2005

Our recent studies (Sakai et al., '88) have shown that there is a progressive increase in aromatase activity, assessed indirectly by the conversion of exogenous testosterone to estradiol‐17β, in medaka (Oryzias latipes) vitellogenic follicles isolated between 28 and 20 hr before spawning. The present study was designed to determine if pregnant mare serum gonadotropin (PMS) and cAMP are able to induce aromatase activity in early vitellogenic follicles isolated at 32 hr before spawning. Both 100 IU/ml PMS and 100 ng/ml testosterone alone significantly stimulated estradiol‐17β production by follicles at this stage. PMS also enhanced testosterone‐induced estradiol‐17β production. This enhancing effect of PMS on aromatization of exogenous testosterone to estradiol‐17β was completely inhibited by 10 μg/ml actinomycin D and 10 μ/ml cycloheximide. Both 5 mM dibutyryl cAMP (dbcAMP) and 10 μM forskolin, an adenylate cyclase activator, alone significantly stimulated estradiol‐17β production. A 1 μg/ml dose of cyanoketone, a potent inhibitor of 3β‐hydroxysteroid dehydrogenase, completely suppressed PMS‐ and forskolin‐induced estradiol‐17β production in the absence of testosterone, but did not influence the enhancing effect of either PMS or forskolin on the conversion of exogenous testosterone to estradiol‐17β. These results indicate that PMS induces aromatase activity in medaka vitellogenic follicles via an adenylate cyclase‐cAMP system, and further suggest that this action of PMS is dependent upon both transcriptional and translational processes.
Neither retinal nor pineal photoreceptors mediate photoperiodic control of seasonal reproduction in American tree sparrows (Spizella arborea)
Authors: Wilson Fred E.
Published: June 2005

Using sighted (SIG) and bilaterally enucleated (BOE) female tree sparrows, SIG, BOE, pinealectomized (SIG‐PX), and bilaterally enucleated‐pinealectomized (BOE‐PX) male tree sparrows, and intact and castrated male tree sparrows implanted epicranially with continuously emitting light sources or nonemitting blanks, I tested the hypothesis that extraretinal, extrapineal encephalic photoreceptors mediate photoperiodic control of seasonal reproduction in American tree sparrows (Spizella arborea). SIG females and BOE females displayed similar patterns of plasma luteinizing hormone (LH) responses to a photoregimen designed to induce LH secretion and later photorefractoriness, to restore photosensitivity, and to reinitiate the photosexual reflex. The testicular length profiles for SIG males, BOE males, SIG‐PX males, and BOE‐PX males likewise revealed similar patterns of responses (i.e., testicular growth, regression, photorefractoriness, and recovery of photosensitivity) to an essentially identical photoregimen. These data show, for the first time in an obligately photoperiodic species, that a simulated annual reproductive cycle can be generated in the absence of both the eyes and the pineal gland and argue that neither retinal nor pineal photoreceptors are obligatorily linked to the neuroendocrine mechanism that controls seasonal reproduction. When evaluated within the context of the failure of bilateral ocular enucleation and pinealectomy to disrupt seasonal reproduction, the observations that continuously emitting light sources implanted atop the skull induced testicular growth and later photorefractoriness in intact males, induced LH secretion and later photorefractoriness in castrated males, and blocked recovery of photosensitivity in photorefractory males make a compelling case for extraretinal, extrapineal encephalic photoreception in the mechanism that controls seasonal reproduction in tree sparrows.
Neuropeptide schistosomin inhibits hormonally‐induced ovulation in the freshwater snail Lymnaea stagnalis
Authors: Hordijk Peter L. , van Loenhout Harry , Ebberink Rob H. M. , de Jong‐Brink Marijke , Joosse Joos
Published: June 2005

This study examines the interaction between the caudodorsal cell hormone (CDCH) and schistosomin, a peptide secreted by the central nervous system of the snail (Lymnaea stagnalis) infected with the avain schistosome Trichobilharzia ocellata. Non‐infected snails were injected with synthetic as well as native CDCH in the absence or presence of purified schistosomin. The response to 2 pmol of synthetic CDCH was blocked for 90% by coinjection with 3.5 pmol of schistosomin. The ovulation‐inducing activity of extracts of cerebral commissures (the storage area of native CDCH) was also blocked by schistosomin. The degree of inhibition (65%), however, was less than that observed with synthetic CDCH. These results show that schistosomin inhibits ovulation and egg laying in Lymnaea. This explains the decrease or absence of egg laying in schistosome‐infected freshwater snails.
Concentration of gonadotropin‐releasing hormone in the brain during metamorphosis in the lamprey, Petromyzon marinus
Authors: Youson John H. , Sower Stacia A.
Published: June 2005

The concentration of lamprey gonadotropin‐releasing hormone (lamprey GnRH) and relative amounts of a second GnRH‐like form from brains of larvae (ammocoetes) and individuals during the seven stages of lamprey metamorphosis were measured using a lamprey GnRH radioimmunoassay following elution on a reverse‐phase high performance liquid chromatography (HPLC) system. Lamprey GnRH was not detectable in ammocoetes and was present in small quantities in only a few samples of metamorphosing individuals in stages 1–5 (0.475–0.667 ng/brain) but was more conspicuous at stage 6 (0.873 ± 0.308) and had increased significantly (7.8 ± 0.371) by the final stage (7). The second, GnRH‐like hormone eluted at a different time on HPLC compared to lamprey GnRH and was detected by the lamprey GnRH antiserum. This second GnRH‐like hormone appeared at stage 4 and was present, at a progressively increased relative concentration, in almost all samples to the end of metamorphosis where the level of 5.15 ± 0.625 ng/brain was significantly lower than that of lamprey GnRH. The brain weight increased by the final two stages but concentration of the two hormones/brain sample weight revealed, for both hormones, a trend of increased levels as metamorphosis progressed and significant differences in concentration between stages 6 and 7. The timing of increased concentration of GnRH in the brain of metamorphosing lampreys is discussed with reference to the acceleration of gonad maturation during and immediately after metamorphosis.
Oocyte and zygote zona pellucida lectin binding in BALB/cBy and C57BL/6By mice and their F1 hybrids
Authors: Legge Michael
Published: June 2005

Zona pellucida intact oocytes and zygotes from two inbred strains of mice (BALB/cByEss and C57BL/6ByEss) and their F1 hybrids were reacted with a lectin panel (ConA, WGA, sWGA, PNA, UEA I, LTA, BSB4, DBA, PHA‐P, LPA, and LFA). No major differences were observed between groups of mice for the majority of the lectin binding patterns. However, oocytes from BALB/cByEss and the F1 (C57BL/6ByxBALB/cBy) gave identical binding patterns for PNA. Following fertilization BALB/cByEss and the F1 (C57BL/6ByxBALB/cBy) bound UEAI and LTA more strongly, but the other two groups of mice demonstrated identical weaker binding of UEAI and LTA. These results indicate the possible influence of the paternal genotype on zona pellucida formation.
Oxygen consumption in relation to sustained exercise and social stress in Arctic charr (Salvelinus alpinus L.)
Authors: Christiansen Jørgen Schou , Jørgensen Even H. , Jobling Malcolm
Published: June 2005

Rates of oxygen consumption were measured repeatedly in feeding groups of Arctic charr (Salvelinus alpinus L.) subjected to moderate sustained exercise or allowed to perform routine swimming activity (control). Oxygen consumption did not differ significantly between treatments. Agonistic activity, assessed in terms of bite mark frequencies, were significantly reduced in exercising fish. Consequently, high levels of spontaneous activity displayed by the control fish in performing agonistic interactions may have led to substantial increases in energetic costs resulting in energy expenditures equivalent to those shown by fish performing forced swimming at moderate speeds.

Plasma cortisol levels measured at the end of the experiment suggested that both control and exercising fish were subjected to chronic stress with cortisol levels of exercising fish being significantly higher than those of controls. The validity of using plasma cortisol levels as an indicator of stress per se is discussed.
Reorganization of escape reflexes during asexual fission in an aquatic oligochaete, Dero digitata
Authors: Drewes Charles D. , Fourtner Charles R.
Published: June 2005

Asexual reproduction in the aquatic oligochaete Dero digitata involves 1) formation of a mid‐body fission zone and transverse fission plane separating the worm into anterior and posterior zooids; 2) development of four new head segments in the posterior zooid, just behind the fission plane; and 3) development of new tail segments in the anterior zooid, just anterior to the fission plane. Electrophysiological recordings from normal (i.e., non‐fissioning) and prefission worms indicate similar proportioning of giant nerve fiber sensory fields; the medial (MGF) and lateral (LGF) giant fiber fields encompass the anterior‐most 30% and posterior‐most 70%, respectively, of the worm's length. Throughout prefission stages both MGF and LGF spikes were reliably through‐conducted, though at reduced velocity, across the fission zone. This agrees with anatomical results showing continuity and reduced diameter of MGF and LGF in the fission zone. Within seconds after fissioning, sensory fields in the rostral segments of posterior zooids (= 18% of zooid length) switch from LGF to MGF sensitivity. Further changes in giant fiber sensory fields and conduction velocities in the posterior zooid, during the next 7 days, lead to a functional organization of escape reflex pathways comparable to that in normal worms. Our results suggest that an escape reflex switching mechanism, along with strong modulatory influences, ensures appropriate and adaptively significant escape reflex functioning in posterior zooids both before and after fissioning.
Growth and differentiation of the cultured secretory cells of the cow oviduct on reconstituted basement membrane
Authors: Joshi M. S.
Published: June 2005

Isolated 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

The 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

In 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

The 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

The 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

The 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

In 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

Suckling 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

Neurulation, 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

The 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

Postmetamorphic 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

An 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

The 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

Secondary 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

We 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.
In vitro and in vivo characterization of blastemal cells from regenerating newt limbs
Authors: Maier C. Eberhardt , Miller Robert H.
Published: June 2005

To better characterize the cells involved in newt limb regeneration, blastemal cells from accumulation and differentiation phase blastemas were grown in dissociated cell culture, and their morphology and antigenic phenotype determined using a variety of antibodies directed against intermediate filaments, cell adhesion molecules, and extracellular matrix molecules. In addition to previously described blastemal cell morphologies, many of the cells in these cultures had a round cell body, with an eccentrically placed nucleus and a cytoplasm filled with autofluorescent granules. The majority of accumulation phase blastemal cells labeled with antibodies against GFAP, vimentin, 22/18 as well as with antibodies against NCAM, L‐1, laminin, and fibronectin. The majority of differentiation phase blastemal cells had a similar phenotype but lacked expression of vimentin and fibronectin.

Comparison of the blastemal phenotype in vitro and in vivo showed similar expression characteristics. However, in differentiation phase blastemas, laminin immunoreactivity was concentrated in specific locations. In addition, the proliferation of cultured blastemal cells is stimulated by the addition of a crude brain extract, consistent with previous studies in vivo and in vitro. Taken together, these observations suggest that dissociated cultures of newt limb blastemal cells provide a suitable model for the analysis of the cell and molecular mechanisms involved in limb regeneration. © 1992 Wiley‐Liss, Inc.
Biocalcification mechanism in gorgonians: 45Ca uptake and deposition by the mediterranean red coral Corallium rubrum
Authors: Allemand Denis , Grillo Marie‐Christine
Published: June 2005

The biocalcification of Mediterranean red coral Corallium rubrum (Anthozoa, Octocorallia) was investigated by using 45Ca as a tracer to follow calcium transport and deposition. Kinetic experiments were performed by tracing the appearance of radioisotope in the three studied compartments of the apical part of the red coral: tissue fraction, spicules, and axial skeleton. The results demonstrate that calcium is absorbed by tissue before being deposited in the skeletal structures. The interval of time required by calcium to reach the site of calcification is about 1 hour. The spicule fraction represents the most important site of 45Ca deposition in comparison with the other two compartments.

By using different kinds of inhibitors, we demonstrate that calcium enters the cell along its electrochemical gradient via verapamil‐sensitive calcium channels and is concentrated in spicule‐forming vesicles or exported to the site of axis formation by an energetic process whose activation energy is 12 Kcal/mol for both skeletal structures.

Modifications of the CO2/HCO3− buffering system were used to examine the possible origins of inorganic carbon for CaCO3 formation. Our results suggest that metabolic CO2 may serve as a main source. The carbonic anhydrase enzyme appears to be involved in the hydratation of CO2 to HCO3, this latter ion being subsequently transported to the calcification site by a Cl−/HCO3− exchanger. © 1992 Wiley‐Liss, Inc.
Role of thyroid hormone in intermediary metabolism of propranolol or alloxan‐treated Calotes versicolor
Authors: Jacob Valsa , Oommen Oommen V.
Published: June 2005

Administration of L‐thyroxine (T4) to thyroidectomized Calotes versicolor significantly increased the activity of glucose‐6‐phosphatase (G‐6‐Pase) (liver and kidney), the concentrations of blood glucose and total protein (liver and kidney), and decreased hepatic cholesterol when compared to thyroidectomized lizards. Propranolol injections in thyroidectomized lizards increased the cholesterol concentration and did not change the other parameters. The activity of G‐6‐Pase and blood glucose content was stimulated, whereas the total protein and cholesterol contents were decreased after alloxan treatment. Administration of T4 to thyroidectomized animals pretreated with propranolol or alloxan significantly elevated the activity of G‐6‐Pase, the concentrations of blood glucose, and total protein, and reduced hepatic cholesterol level when compared to drug‐treated lizards. From the results, it is evident that thyroid hormone has an independent stimulatory influence on intermediary metabolism in C. versicolor irrespective of the involvement of adrenaline or insulin. © 1992 Wiley‐Liss, Inc.
Calcitonin‐like immunoreactivity in the blue crab: Tissue distribution, variations in the molt cycle, and partial characterization
Authors: Cameron James N. , Thomas Peter
Published: June 2005

Calcitonin‐like immunoreactivity has been found in blood and tissues of the marine blue crab, Callinectes sapidus Rathbun. The activity in blood rises significantly during the immediate premolt (D4) stage, but tissue immunoreactivity does not vary significantly with molt stage. The immunoreactivity to antisalmon calcitonin serum is due to a 27.2 kDa protein that shows strong similarities in amino acid composition to a similar protein in a lobster and to human calcitonin precursor. The protein is most abundant in the midgut glands (hepatopancreas), but is also found in significant quantities in several other tissues. Immunoreactivity in the blood appears to be primarily due to the same molecular weight fraction, with secondary contributions from smaller molecules, closer in size to vertebrate calcitonin. A physiological function of the calcitonin‐like substance in calcium transport during or after molt has yet to be demonstrated. © 1992 Wiley‐Liss, Inc.
Specificity and early ontogeny of historecognition in the hydroid Hydractinia
Authors: Lange R. G. , Dick M. H. , Müller W. A.
Published: June 2005

The marine hydroid Hydractinia is a model system for study of historecognition in invertebrates. Present knowledge of this system comes from fusibility studies involving intraspecific (i.e., isogeneic and allogeneic) encounters of adult‐stage stolonal tissues. Little is known about the ability of Hydractinia to recognize and respond to xenogeneic tissue, about allorecognition by tissues other than stolonal, and about the ontogeny of historecognition. We have investigated these questions with stolonal‐encounter and grafting experiments, using the species H. echinata and H. symbiolongicarpus. We find that (a) Hydractinia employs the nematocyst effector system against the closely related hydroid Podocoryne and the more distantly related Eirene; (b) unlike intraspecific encounters, these interspecific encounters elicit nematocyst discharge by Hydractinia over a distance of up to 50 μm prior to stolonal contact; (c) the capability for historecognition is not restricted to stolonal tissues; (d) the capacity to display incompatibility, or rejection, arises between the late larval stage and early post‐metamorphosis; and (e) embryo grafts of H. symbiolongicarpus, but not those of H. echinata, appeared to show limited tolerization. © 1992 Wiley‐Liss, Inc.
Activity patterns of the wing muscles of the pigeon (Columba livia) during different modes of flight
Authors: Dial Kenneth P.
Published: June 2005

The temporal sequence of activity patterns and intensities (voltage per wingbeat) of electromyograms (EMGs) from 17 muscles in the shoulder and forelimb of the pigeon (Columba livia) were measured during five modes of flight (level flapping, takeoff, landing, vertical ascending, and near vertical descending flight). EMG signals were referenced to wing position using high‐speed movie film. Most muscles exhibited EMG activity during phases within a wingbeat cycle not expected a priori. All muscles exhibited some level of activity within each wingbeat cycle and during all modes of flight. Intensity of EMG activity varied significantly between different modes of flight. Most shifts in temporal patterns were minor with the exception of the humerotriceps. © 1992 Wiley‐Liss, Inc.
Effects of the nonsteroidal ecdysone mimic RH 5849 on larval crustaceans
Authors: Clare Anthony S. , Rittschof Daniel , Costlow John D.
Published: June 2005

The effects of the nonsteroidal ecdysone mimic RH 5849 on larvae of a crab (Rhithropanopeus harrisii) and the cypris larva of a barnacle (Balanus amphitrite) have been investigated. Larvae were exposed to exogenous RH 5849 in the concentration range of 0.1–10.0 mg/L. The two lowest concentrations tested (0.1 and 1.0 mg/L) accelerated molting of crab zoeae. RH 5849 did not induce premature apolysis. A concentration of 10 mg/L RH 5849 was toxic to zoeae: these larvae underwent apolysis but not ecdysis and subsequently died. Attachment and metamorphosis of barnacle cyprids was enhanced by 10.0 mg/L RH 5849. Increased attachment may be a result of physiological aging of larvae by the ecdysone mimic. Increased metamorphosis is consistent with the stimulatory effect of 20‐hydroxyecdysone on this process. RH 5849 was first demonstrated as an ecdysone mimic in insects (Wing, Science, 241:467–469, '88). The present study provides preliminary evidence for a similar action in crustaceans. © 1992 Wiley‐Liss, Inc.
Steroid hormone‐induced male sex determination in an amniotic vertebrate
Authors: Wibbels Thane , Bull James J. , Crews David
Published: June 2005

In many reptiles, sex is determined by the temperature at which the eggs are incubated (i.e., temperature‐dependent sex determination, or TSD). Past studies have shown that exogenous steroid hormones can override the effects of temperature and induce female sex determination. However, past attempts to induce male sex determination have consistently failed. In the present study, sex determination was studied in a turtle with TSD. By utilizing an incubation temperature regimen that resulted in approximately a 1:1 sex ratio in the control group, sex determination was shown to be sensitive to both exogenous androgen and estrogen treatments: androgen induced the production of male hatchlings, whereas estrogen induced the production of female hatchlings. This is the first report of an amniotic vertebrate in which an exogenous steroid hormone induces male sex determination. © 1992 Wiley‐Liss, Inc.
Immunoglobulin‐containing cells in chick embryo urogenital tissues: A new site for early B lineage cells in endothermic vertebrates
Authors: Zettergren Leslie D. , Cutlan Robert T.
Published: June 2005

We have employed histological and immunofluorescent staining procedures in order to characterize the distribution of μ+ B lineage cells in tissue sections prepared from developing chicken embryo urogenital tissues (UGTs) between 14 and 21 days of incubation. B lineage cells were observed in tissue sections prepared from developing UGTs, especially the mesonephros and its associated tissue, throughout the sample period. The highest densities of μ+ B lineage cells were observed in tissue sections prepared from 18 day embryos. The μ+ UGT cells were distributed singly and in clusters in subcapsular regions and within the peritubular interstitium of the mesonephros. These observations (1) are consistent with those which suggest nonbursal site(s) for origin of cells in B lineage, (2) may help account for the varying effects of embryonic caudectomy performed between the second and third days of incubation and surgical bursectomy performed close to hatching, (3) may help provide new insights on the effects of sex hormones on B cell development, and (4) suggest fundamental ontogenetic and phylogenetic similarities between developing vertebrate immune systems. © 1992 Wiley‐Liss, Inc.
Environmental factors affecting ventilation in the ascidian, Pyura praeputialis
Authors: Evans B. K. , Huntington R.
Published: June 2005

Ventilatory behaviour in the Australian cunjevoi Pyura praeputialis is described in terms of the rate of ciliary pumping and the frequency of the squirting reflex. These two behaviours were examined during conditions of low pO2, high pCO2, high and low pH, and low salinity. Ciliary pumping was impaired during hypoxic, low pH, and hyposaline conditions, and was enhanced by conditions of high pH. Squirting behaviour was increased during hypoxic and hyposaline conditions. While the results for ciliary pumping may be due to direct effects on the cilia themselves, the experiments on squirting behaviour show that Pyura is able to detect and produce a coordinated response to hypoxia and hyposalinity. The adaptive significance of these responses is discussed. © 1992 Wiley‐Liss, Inc.