bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphogenetic factors in hydroids: I. Stolon tip activation and inhibition
Authors: Müller Werner A. , Hauch Alexander , Plickert Günter 
Published: June 2005

AbstractColonial hydroids expand by means of vascular tubings, termed stolons, which elongate, generate new polyps, and branch at regular intervals. The pattern of the resulting network is controlled by specialized distal organs, the stolon tips. Two factors are described which activate or inhibit, respectively, stolon tip formation. Both factors emanate from existing tips. The activating factor is released into the medium and stimulates, in adjacent stolons, lateral tip formation and, hence, branching. A transplanted tip not only induces tip formation over distances of up to 140 μm but also attracts the induced tip by guiding the direction of its movement. Upon contact both tips fuse, provided the encounter occurs between isogeneic or histocompatible stolons, and an anastomosis is formed. The inhibitory principle appears to be transmitted within the stolon and is used to control branching distances. However, measurable traces of inhibitory activity leak into the medium. The factor is of low molecular weight. The activating and the inhibiting factors are both found in two distantly related colonial species—Hydractinia echinata (Athecata) and Eirene viridula (Thecata).
Retrovirus‐like particles in embryonic kidney tissue of the platyfish, Xiphophorus maculatus
Authors: Perlmutter Alfred , Potter Hugh 
Published: June 2005

AbstractUltrastructural studies were performed on embryos of an inbred strain (163A) of the platyfish Xiphophorus maculatus, and a pooled stock of the Rio Sarabia strain of the swordtail, X. helleri. Viral‐like particles were found in the kidney tissue of platyfish embryos. Exposure of pregnant platyfish to 5‐bromodeoxyuridine during the time of differentiation of embryonic melanocytes enhanced the production of viral‐like particles in platyfish embryos. Viral‐like particles were not found in untreated or drug‐treated swordtail embryos. The morphology of these particles corresponds to type C retroviruses.
Response of male brown bullhead catfish, Ictalurus nebulosus lesueur, to gonadotropin‐releasing hormone and gonadotropin
Authors: Rosenblum Paul M. , Callard Ian P. 
Published: June 2005

AbstractThese studies were performed in order to investigate the roles of GnRH and GtH in the regulation of reproductive function in male brown bullhead catfish, Ictalurus nebulosus. Adult catfish were given intravenous injections of salmon GtH (SG‐G100) or salmon GnRH (sGnRH), and plasma testosterone, 11‐ketotestosterone, and estradiol‐17β levels were measured. SGG100 elicited parallel increases in testosterone and 11‐ketotestosterone, with peak levels between 8–12 hr after treatment. The effects of SG‐G100 on plasma testosterone were dose‐dependent, whereas increased 11‐ketotestosterone was only seen with the two highest doses. Treatment with sGnRH elicited increased testosterone at 4 hr, and 11‐ketotestosterone between 4–24 hr posttreatment. No clear dose‐response to sGnRH was observed. The effects of SG‐G100 and sGnRH varied with the annual reproductive cycle. During early testicular recrudescence in May, both the pituitary and testis were sensitive to trophic stimulation, with 2‐ to 4‐fold increases in plasma androgens following sGnRH and SG‐G100. Neither treatment was effective in mature animals trapped in July. In November, despite low basal androgen levels, SG‐G100 and sGnRH elicited 2‐fold increases in plasma androgen levels. The stimulatory effects of sGnRH, but not SG‐G100, were abolished in hypophysectomized fish. These results indicate a functional hypothalamic‐pituitary‐testicular axis in this species, the components of which vary in sensitivity during the annual reproductive cycle in a manner consistent with the observed cycle of plasma steroids of this species.
Mechanical properties of mineralized and sclerotized puparial cuticles of the flies Musca autumnalis and M. domestica
Authors: Grodowitz Michael J. , Roseland Craig R. , Hu Kuo Kuang , Broce Alberto B. , Kramer Karl J. 
Published: June 2005

AbstractMechanical properties of mineralized and sclerotized puparial cuticles of the face fly, Musca autumnalis, and the house fly, M. domestica, respectively, were determined. The thickness of mineralized cuticle is 55% greater than that of sclerotized cuticle (thickness = 41.7 and 26.8 μm, respectively) from puparia of similar diameter (2.4 to 2.8 mm). Nonetheless, breaking forces for both types of puparial cuticle are similar (load ultimate strength = 9.3–10.9 g). However, the mineralized puparia are considerably stiffer than sclerotized puparia (elastic modulus = 346.4 kg mm−1 and 711.5 kg mm−1, respectively) and exhibit fracture at relatively lower load values (percentage total deformation at fracture = 3.5% and 11.0%, respectively). Differences in mechanical properties of puparial cuticle are probably due to the kinds and quantities of cuticular components: The mineralized puparia contain appreciably more inorganic components such as calcium, phosphorus and magnesium, while the sclerotized puparia consist of relatively more organic components such as proteins and phenolics. The evolutionary and functional significance of mineralization and sclerotization as mechanisms for puparial cuticle stabilization is discussed.
Monohydroxyeicosatetraenoic acid and leukotriene production by the inflammatory cells of Xenopus laevis
Authors: Green Floyd A. , Herman Ceil A. , Herman R. Peter , Claesson Hans‐Erik , Hamberg Mats 
Published: June 2005

AbstractTen frogs (Xenopus laevis) were injected with mixed bacteria to produce a septic peritonitis. Peritoneal inflammatory cells of eight animals were studied for monohydroxyeicosanoid and leukotriene production from exogenous arachidonic acid. Large amounts of 12‐hydroxyeicosatetraenoic acid were produced; smaller amounts of 5‐ and 15‐hydroxyeicosatetraenoic and leukotriene B4 were produced. Identifications were confirmed by retention times on HPLC, ultraviolet spectroscopy on all products, and gas chromatograph/mass spectrometry in the case of 12‐hydroxyeicosatetraenoic acid.
Influence of chromatographic fractions of extracts derived from bovine neural retina on newt (Notophthalmus viridescens) lens regeneration in vitro
Authors: Connelly Thomas G. , Green M. Sean 
Published: June 2005

AbstractRemoval of the ocular lens in adult newts (Notophthalmus viridescens) is followed by a series of cellular events leading to regeneration of a new lens by cell type conversion of pigmented iris epithelial cells at the dorsal pupillary margin (Yamada, Curr. Top. Dev. Biol. 2:247–283, 1967). Following depigmentation and five to seven cell divisions, iris epithelial cells redifferentiate into lens fiber cells and synthesize crystallin proteins (Yamada, Curr. Top. Dev. Biol. 2:247–283, 1967). This process is dependent upon neural retina in vivo (Stone, Anat. Rec. 131:151–172, 1958; Reyer, Dev. Biol. 14:214–225, 1966) and in vitro (Yamada et al., Differentiation 1:65–82, 1973). Acting on the hypothesis that the role of the neural retina is to promote passage of iris epithelial cells through the requisite number of cell cycles which will then allow them to redifferentiate as lens fiber cells (Yamada, in: Cell Biology of the Eye. Academic Press, New York, 1982), we undertook testing of the effects of eye‐derived mitogenic substances, as well as other mitogens, on regeneration of lens from iris in organ culture. We have previously defined a critical period for the retinal influence in vivo and in vitro, and have shown that crude extracts of retina can enhance regeneration of lenses in culture (Connelly et al., J. Exp. Zool., 240:343–351, 1986). In this paper, we report on the lens regeneration enhancing activity (LRA) of more highly purified fractions of the retinal extracts. Heparin‐sepharose chromatography of the crude retinal extract yields three fractions (Courty et al., Biochemie 67:265–269, 1985) called EDGF I, II, and III. EDGF I and II have affinity for heparin, while EDGF III does not. In our bioassay, LRA appears only in the EDGF III fraction. Dialysis of EDGF III against 0.1 N acetic acid yields a fraction which has affinity for cibacron blue sepharose (eluting at 2.15 M salt) and also has significant LRA. Because insulin at high doses has a marginal effect on lens regeneration in culture (Williams and McGlinn, Am. Zool. 19:923, 1979; Connelly, Differentiation 16:85–91, 1980), we tested IGF‐I. Because of the putative neurotrophic effects of transferrin (Tf) (Mescher and Munaim, J. Exp. Zool., 230:485–490, 1986), we tested Tf for its ability to enhance regeneration of the lens in culture. IGF‐I seems to have an enhancing effect on lens regeneration; Tf does not.
Rates of male pronuclear enlargement in sea urchin zygotes
Authors: Luttmer Shirley J. , Longo Frank J. 
Published: June 2005

AbstractRates of male pronuclear enlargement were determined using synchronous populations of fertilized sea urchin eggs (Arbacia punctulata and Lytechinus variegatus), fixed at regular intervals following insemination and stained with Hoechst 33342. The rate of male pronuclear expansion in both Arbacia and Lytechinus zygotes was linear and significantly affected by polyspermy, temperature, metabolic inhibitors (dinitrophenol, potassium cyanide, sodium azide, antimycin A, and oligomycin), and blockage of cytoplasmic alkalinization. Inhibitors of protein synthesis (emetine and puromycin) and disrupters of cytoskeletal elements (colchicine, nocodazole and cytochalasin B) had no effect on the rate of male pronuclear enlargement.
Light and electron microscopic observations of sperm entry in the chum salmon egg
Authors: Kobayashi Wataru , Yamamoto Tadashi S. 
Published: June 2005

AbstractSperm entry into the egg of the chum salmon, Oncorhynchus keta, was observed in living material as well as by electron microscopy. When the egg was inseminated in tap water, actively moving spermatozoa entered the micropylar canal and filled its lumen. When a narrow perivitelline space appeared in the egg (about 150 seconds after insemination), supernumerary spermatozoa were invariably discharged from the canal lumen. A similar discharge was observed in a few batches of eggs that were inseminated in Salmon‐Ringer solution. In response to the penetration of a fertilizing spermatozoon into the ooplasm, a narrow perivitelline space was formed in a restricted area of the animal pole. We suggest that the discharge is induced by the spouting of perivitelline material through the micropylar canal.A fertilizing spermatozoon was observed in contact with the apex of the ooplasmic papilla in the micropylar canal and was seen to enter the ooplasm. When a fertilizing spermatozoon entered the egg, contractile activity was seen in the ooplasm, and a “protrusion” at the animal pole was formed. The papilla extending from the upper surface of the “protrusion” increased in length. These changes did not occur in unfertilized eggs stimulated by tap water in the absence of participation by the spermatozoon. It is, therefore, clear that the “protrusion” and the elongated papilla are analogous to the fertilization cone of invertebrate eggs.The presence of the fertilization cone delayed the separation of the egg envelope from the ooplasm at the animal pole of the egg and inhibited penetration of any supernumerary spermatozoa into the perivitelline space. When the fertilization cone disappeared from the animal pole, 300 seconds after insemination, the micropylar canal decreased in diameter near the lower end. Super‐numerary spermatozoa were, thus, unable to pass through the thick egg envelope. Meanwhile, a transparent structure was seen to form at the micropylar vestibule and to serve as a barrier to entry by spermatozoa into the micropylar canal. We conclude that the formation of the fertilization cone and the spouting of perivitelline material through the micropylar canal play an important role in the prevention of polyspermy of the chum salmon egg.
ATP and the contractile vacuole in Amoeba proteus: Mechanism of action of exogenous ATP and related nucleotides
Authors: Pothier F. , Forget J. , Sullivan R. , Couillard P. 
Published: June 2005

AbstractThe mode of action of external ATP on the contractile vacuole of Amoeba proteus has been examined. ATP and, to a lesser extent, some other polyphosphates, interact with calcium at nonhydrolyzing membrane sites. This induces an increase of output of the contractile vacuole provided sodium is present in the medium. A long‐lasting reversible membrane depolarization occurs in the presence of ATP. Results are discussed in the light of theories describing the contractile vacuole as the principal sodium‐excreting organelle in freshwater Protozoa.
Characterization of enzymes that degrade crab exoskeleton: I. Two alkaline cysteine proteinase activities
Authors: O'brien Jack J. , Skinner Dorothy M. 
Published: June 2005

AbstractExtracts from integumentary tissues of the Bermuda land crab, Gecarcinus lateralis, degraded proteins extracted from the membranous layer (ML), the innermost layer of the exoskeleton that serves as the interface between epidermal cells and calcified exoskeleton. Separation of the extracts by HPLC hydrophobic chromatography and characterization using 125I‐casein as substrate identified two peaks of degradative activity. The activities showed pH optima of 7 to 8, were sensitive to inhibitors of cysteine proteinases, and required the reducing agent, dithiothreitol, for activity, indicating that they are alkaline cysteine proteinases (ACPs). The pH optima of ACPs I and II indicated that they could function in the slightly alkaline extracellular environment of the proecdysial animal when the old exoskeleton is broken down. Although ACPs I and II are distinctly different from other crustacean cysteine proteinases (CP) they are similar to a CP activity present in extracts from the ML. A 23‐kDa protein from the ML was particularly susceptible to degradation by these enzymes. Activity of these enzymes in the extracellular environment might be controlled by the concentration of reducing agents as they are inactive unless in a reduced state.
Relation between interastral distance, time of furrow initiation, and rate of furrow progress in cylindrical sand dollar eggs
Authors: Rappaport R. , Rappaport Barbara N. 
Published: June 2005

AbstractThe purpose of this investigation was to determine whether measurable characteristics of furrow activity were affected when the distance between the asters was manipulated. The mitotic apparatus of cleaving Echinarachnius parma eggs was broken by passing the egg several times through a constricting pipet nozzle. Manipulated eggs were then confined in 80 μm i.d. silicone rubber capillaries. When the astral pairs developed before second cleavage, the distances between the pairs often differed. When the difference between interastral distances was 8.6 μm or less, furrows developed in the normal relation to both astral pairs within 1 minute in 31 of 35 cases. When the difference of interastral distances was greater than 8.6 μm, the furrow appeared first in association with the smaller distance in 53 of 54 cases. In all (24) cases in which the rates of progress of each astral pair were measured, the furrow formed between the closer astral pair progressed more rapidly when the distance was greater than 8.6 μm. No significant correlation between the rates of furrow progress and the magnitude of interastral distances measured 4 minutes before the beginning of furrowing could be demonstrated.
Serum immunoreactive insulin levels in intact and regenerating postmetamorphic xenopus laevis
Authors: Liversage Richard A. , Foty Ramsey A. , Miles Philip D. G. 
Published: June 2005

AbstractIn order to confirm the presence of immunoreactive insulin (IRI) in the serum of postmetamorphic Xenopus laevis, radioimmunoassay (RIA) methods were used. The concentration of hormone found in samples of blood serum taken from nonanaesthetized intact male and female animals by the guillotine method was 10.46 ± 0.76 μU/ml. Significantly higher IRI concentrations were found in our intact animals anaesthetized in MS 222 at pH 3.5 (21.9 μU/ml) compared with intact controls anaesthetized in MS 222 adjusted to pH 7.0, (14.4 μU/ml). During the wound‐healing stage subsequent to forelimb amputation in the experimental cases (0 hours to 3 days) anaesthetized in MS 222 pH 7.0, there were intervals of significantly elevated serum IRI followed by a period of decreased IRI concentration compared with the levels in anaesthetized (MS 222 pH 7.0) and nonanaesthetized intact controls. These fluctuations were due, presumably, to stress caused by amputational injury and/or anaesthetic. Serum IRI increased steadily from 3 to 14 days postamputation then remained stable for the balance of the regeneration period (28 days) compared with nonanesthetized intact controls. A positive correlation was found between immunoreactive insulin and glucose levels in the serum of our animals. However, no correlation exists between serum IRI levels and serum osmolality in the data.
The metabolic potential of hepatocytes and kidney tissue in the little skate, Raja erinacea
Authors: Mommsen Thomas P. , Moon Thomas W. 
Published: June 2005

AbstractIsolated hepatocytes from the little skate (Raja erinacea) are characterized by a general low metabolic activity, which can be explained by the benthic lifestyle of the animal. Of the substrates tested, alanine, serine, and leucine are equally good oxidative substrates, and the highest rates of gluconeogenesis are achieved with alanine and glycerol as carbon sources. In both respects, lactate is a relatively poor substrate, and this probably reflects the low abundance of this potential energy source in the skate, even after bouts of anaerobic exercise. The long chain fatty acid oleate and glycerol are poor oxidative substrates for the hepatocytes, Experiments with 3‐mercaptopicolinate, an inhibitor for phosphoenolypyruvate carboxykinase (PEP CK), reveal that serine is funneled into gluconeogenesis through the serinetransaminase pathway, and PEP CK is bypassed. In vitro, the skate liver cells display the potential to synthesis and export ketone bodies from precursors sush as leucine or oleate, whereas added β‐hydroxybutyrate is poorly oxidized. The skate liver appears to be geared towards export of ketone podies while at the same time conserving glycerol carbon for lipid synthesis. Supplied with precursors such as bicarbonate, blutamine, and aspartate, the cells synthesize urea at a rate 0.85 μmol/g/hr at 10°C. β‐Hydroxybutyrate can acelerate the rate of urea synthesis, probably by increasing the intramitochondrial availability of ATP. Unlike any other vertebrate kidney, the tissue of the little skate appears to play no role in glucose synthesis. Skate kidney is characterized by an active oxidative metabolism and a broad substrate preference, with lactate, serine, alanine, and β‐hydroxybutyrate serving as equally good oxidative fuels.
Enzymes of intermediary metabolism in tissue of the little skate, Raja erinacea
Authors: Moon Thomas W. , Mommsen Thomas P. 
Published: June 2005

AbstractEnzymes of intermediary metabolism were assayed in seven tissues (liver, kidney rectal gland, white muscle, red muscle, heart and brain) of the little skate, Raja erinacea, to assess the general metabolic desing of these tissues. Judged by the activities of enzymes linked to oxidative processes, the kidney, red and heart muscles, and rectal gland are the most metabolically active tissues, with ketone bodies potentially supplying the bulk of the required energy. The brain is only tissue with substantial potential to utilize exogenous glucose as an oxidative substrate; it also has the capacity to synthesize and degrade glycogen. The rectal gland may also use exogenous glucose, although its glycolytic potential is minor compared to that of other tissues. Amino acids, in addition to ketone bodies, may play significant metabolic role in these oxidative tissues based on the tissue activities of the amino transferases and the plasma content of amono acids. Enzyme activities in white skeletal muscle reflect the benthic, sluggish lifestyle of this species with low oxidative potential and rather limited anaerobic capacity. Hepatic tissue appears to be designed for the export of ketone bodies and to display a high potential for amino acid metbolism. The potential for gluconeogenesis, albeit at a low level, is realized only in the liver. Other pathways, especially fatty acid oxidation and pentose shunt, appear to play only monor roles in the intermediary metabolism of this elasmobranch.
Response of sipunculid hemerythrins to inorganic ions and CO2
Authors: Mangum C. P. , Burnett L. E. 
Published: June 2005

AbstractThe O2 equilibrium properties of sipunculid hemerythrins (Hr) are influenced by intracellular effectors. O2 affinity rises and cooperativity decreases when the tentacular O2 carrier is extracted into incorrect ratios of inorganic ions. The effectors include Ca2+ and Cl−, which raise the O2 affinity and lower cooperativity and which are present within the cell in either low levels or an inaccessible form. In the presence of salines approximating the inorganic ion conditions within the cell, tentacular hemerythrin‐O2 affinity decreases and cooperativity increases. Another effector of O2 bindng is CO2, which lowers O2 affinity and enhances cooperativity. While the inorganic ion and CO2 effects on coelomic hemerythrin are either absent or very small, the actions of at least the inorganic ions on tentacular Hr clearly have respiratory significance. Physiological variations in intracellular ions are very small, but the low levels of free Ca2+ and Cl− in the cell exaggerate the intrinsically lower O2 affinity of tentacular than coelomic Hr and thus enhance the routing of O2 from the ambient source to the tentacular compartment and from there to the coelomic compartment and then to metabolizing tissue.
Regulation of goby intestinal ion absorption by the calcium messenger system
Authors: Loretz Christopher A. 
Published: June 2005

AbstractThe role of the calcium messenger system in the regulation of ion absorption across the teleost intestine was studied using pharmacological intervention. Radiochloride transport was independent of external Ca2+ over the range 10 μM to 2.5 mM. Treatment with the Ca2+ ionophore A23187 (to elevate intracellular Ca2+) reduced Cl− absorption and produced hyperpolarization of the apical membrane potential of intestinal epithelial cells. The Ca2+‐calmodulin antagonists trifluoperazine (TFP) and calmidazolium (R24571) produced opposite effects, i.e., stimulation of Cl− absorption and cellular depolarization. Treatment with TFP or R24571 will block or override the inhibitory action of A23187. These data suggest a regulatory role for Ca2+ in the control of intestinal NaCl absorption and mediation via calmodulin.
Induction of deer antlers by transplanted periosteum: II. Regional competence for velvet transformation in ectopic skin
Authors: Goss Richard J. 
Published: June 2005

AbstractThe fallow deer develops its first set of antlers at about 1 year of age, but by 6 months the pedicles can be felt protruding from the frontal bones. If the thickened periosteum covering these locations is transplanted beneath the skin elsewhere on the body, it differentiates into a subcutaneous bony nodule which induces the overlying skin to transform into velvet as a small ectopic antler is produced. A survey of different graft sites has shown that skin on the fore and hind legs, hip, forehead, and outer and inner ears can participate in antler induction by undergoing velvet transformation. Tail, back, and nose skins fail to do so.