bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidative metabolism in thermogenic tissues of the swordfish and mako shark
Authors: Ballantyne J. S. , Chamberlin M. E. , Singer T. D. 
Published: June 2005

AbstractMitochondria isolated from the heater organ of the swordfish Xiphias gladius and the warm lateral red muscle of the mako shark Isurus oxyrinchus display respiratory control, indicating that uncoupling of oxidative phosphorylation is not important in heat production. The mitochondria of the swordfish heater organ resemble those of mammalian brown adipose tissue in their substrate preferences, oxidizing pyruvate plus malate, palmitoyl carnitine, and α‐glycerophosphate at high rates. The high hexokinase levels in the heater organ indicate exogenous glucose is an important energy source. The high activity of cytosolic α‐glycerophosphate dehydrogenase and the high rates of mitochondrial oxidation of α‐glycerophosphate indicate that cytosolic redox is balanced via the α‐glycerophosphate cycle. Calcium stimulates mitochondrial α‐glycerophosphate oxidation, and it is proposed that calcium released from the sarcoplasmic reticulum may act as the signal coupling enhanced rates of substrate oxidation with calcium transport. Based on mitochondrial respiration rates, heat generation by the intact heater organ was calculated. Complete oxidation of glucose produces heat at a greater rate than oxidation of lipids. Nevertheless, oxidation of either substrate could produce sufficient heat to maintain tissue temperature 10°C above ambient at 20°C.The mitochondria from the red muscle of the mako shark oxidize pyruvate plus malate, glutamine, glutamate, proline, and β‐hydroxybutyrate at high rates. Palmitoyl carnitine was not oxidized. The respiration rates are similar to those described for mitochondria isolated from “cold” muscle of other elasmobranchs. Therefore, it does not appear that mako shark red muscle mitochondria are specialized for thermogenesis.
Leydig cell renewal in testes of seasonally breeding animals
Authors: Hardy Matthew P. , Sprando Robert L. , Ewing Larry L. 
Published: June 2005

AbstractAnnual variations of androgen secretion and Leydig cell number occur in seasonally breeding animals: herein we review comparative observations on two widely divergent species, the salamander and hamster. Based on our laboratory studies in the hamster, we conclude that Leydig cell numbers increase during testicular recrudescence through a combination of differentiation of mesenchymal cell precursors and Leydig cell division. Secretion of androstane‐3α, 17β‐diol, a 5α‐reduced androgen, occurs transiently during the seasonal cycle and may be a characteristic of differentiating Leydig cells.
Environmental predictability and control of gonadal cycles in birds
Authors: Wingfield John C. , Hahn Thomas P. , Levin Rachel , Honey Pulmu 
Published: June 2005

AbstractIn most vertebrates, information from the external environment is used to regulate secretion of gonadotropins and thus time gonadal maturation in anticipation of the breeding season. These environmental factors provide “predictive” information in both the long term (initial predictive) and short term (supplementary), are integrated by the central nervous system, and are then transduced into neuroendocrine and endocrine control components. We apply the constancy/contingency model of predictability to breeding data from several avian species to derive a potential unifying hypothesis to explain how these environmental factors are integrated to regulate gonadal maturation. Predictability (Pr) is a function of varying degrees of constancy (C, the habitat is predictable because it is always the same) or contingency (M, the habitat is predictable in the degree of change from season to season). Thus, although variations in Pr provide useful information for timing gonadal maturation and regression, changes in the contributions of C and M to Pr (i. e., the ratio, M/C) provide even more useful information. It is proposed that the degree to which individuals integrate initial predictive and supplementary information to regulate secretion of gonadotropins, and thus time gonadal maturation and onset of breeding, is a function of the ratio of M to C for any given Pr value. When Pr is not significant (i. e., the environment is unpredictable), then only supplementary factors may be useful for timing breeding. Hypotheses generated by this approach are easily testable. Furthermore, this method could be applied to all vertebrates, and perhaps other organisms, and may provide a unifying framework to investigate the mechanisms by which proximate environmental factors regulate reproductive function in general.
Developmental regulation of ecdysteroid receptors in the nervous system of Manduca sexta
Authors: Fahrbach Susan E. 
Published: June 2005

AbstractThe technique of steroid hormone autoradiography has been used to study the cellular distribution of ecdysteroid binding sites in the ventral nervous system of the tobacco hornworm moth, Manduca sexta. The ligand was 26‐[125I]iodoponasterone. Tissue was examined from the subesophageal ganglia, thoracic ganglia, and abdominal ganglia of larvae at two times during the larval‐pupal transition: the 2nd day of wandering and the prepupal stage. The patterns of neuronal binding seen were compared with those found in earlier autoradiographic studies of hormone binding in tissue sampled on the 1st day of wandering, in the pharate adult, and in the 4‐day‐old moth (Fahrbach and Truman, '89). The pattern of binding was reproducible but dependent upon developmental stage: whereas only a subset of neurons exhibited nuclear accumulation of radiolabeled ecdysteroids on the 1st day of wandering, less than 24 hours later nearly every neuron in the ventral nervous system was labeled. A limited pattern of binding, however, was seen again in the prepupal nervous system. Thus, the insect nervous system is able to use a single hormone both as a general cue for metamorphic development and as a signal targeted to stage‐specific subsets of neurons by alternating periods of ubiquitous expression of receptor with periods during which the capacity to bind the steroid hormone is highly restricted.
Development of spinal motor networks in the chick embryo
Authors: O'Donovan Michael , Sernagor Evelyne , Sholomenko Gerald , Ho Stephen , Antal Miklos , Yee Wayne 
Published: June 2005

AbstractWe have examined the cellular and synaptic mechanisms underlying the genesis of alternating motor activity in the developing spinal cord of the chick embryo. Experiments were performed on the isolated lumbosacral cord maintained in vitro. Intracellular and whole cell patch clamp recordings obtained from sartorius (primarily a hip flexor) and femorotibialis (a knee extensor) motoneurons showed that both classes of cell are depolarized simultaneously during each cycle of motor activity. Sartorius motoneurons generally fire two bursts/cycle, whereas femorotibialis motoneurons discharge throughout their depolarization, with peak activity between the sartorius bursts. Voltage clamp recordings revealed that inhibitory and excitatory synaptic currents are responsible for the depolarization of sartorius motoneurons, whereas femorotibialis motoneurons are activated principally by excitatory currents. Early in development, the dominant synaptic currents in rhythmically active sartorius motoneurons appear to be inhibitory so that firing is restricted to a single, brief burst at the beginning of each cycle.In E7‐E13 embryos, lumbosacral motor activity could be evoked following stimulation in the brainstem, even when the brachial and cervical cord was bathed in a reduced calcium solution to block chemical synaptic transmission. These findings suggest that functional descending connections from the brainstem to the lumbar cord are present by E7, although activation of ascending axons or electrical synapses cannot be eliminated.Ablation, optical, and immunocytochemical experiments were performed to characterize the interneuronal network responsible for the synaptic activation of motoneurons. Ablation experiments were used to show that the essential interneuronal elements required for the rhythmic alternation are in the ventral part of the cord. This observation was supported by real‐time Fura‐2 imaging of the neuronal calcium transients accompanying motor activity, which revealed that a high proportion of rhythmically active cells are located in the ventrolateral part of the cord and that activity could begin in this region. The fluorescence transients in the majority of neurons, including motoneurons, occurred in phase with ventral root or muscle nerve activity, implying synchronized neuronal action in the rhythm generating network.Immunocytochemical experiments were performed in E14‐E16 embryos to localize putative inhibitory interneurons that might be involved in the genesis or patterning of motor activity. The results revealed a pattern similar to that seen in other vertebrates with the dorsal horn containing neurons with γ‐aminobutyric acid (GABA)‐like immunoreactivity and the ventral and intermediate regions containing neurons with glycine‐like immunoreactivity.
Changes in monoamine transmitter concentration in freshwater mussel tissues
Authors: Dietz Thomas H. , Wilson John M. , Silverman Harold 
Published: June 2005

AbstractFreshwater mussels were analyzed for biogenic amine transmitter substances in gill tissue, suprabranchial nerve and blood. Gill tissue from normal pondwater‐acclimated mussels contained significant amounts of monoamine neurotransmitter substances. In comparison with the suprabranchial nerve the gill tissue contained 42% of the dopamine, 7% of the serotonin and 490% of norepinephrine. Exposing the animals to deionized water (salt‐depleted) resulted in a loss of transmitter substances from gill tissue, but serotonin reduction was modest. The mussel gill tissue content of serotonin and the precursor tryptophan was regulated at nearly constant levels. Serotonin is an important transmitter substance in mussels and the many functions it controls, including sodium transport regulation, would depend on its continued presence.
External CO2 levels influence energy yielding metabolic pathways under hypoxia in the leech, Hirudo medicinalis
Authors: Hildebrandt Jan‐Peter 
Published: June 2005

AbstractMedicinal leeches, Hirudo medicinalis L., were exposed to hypocapnic (nominal pCO2 0.0 kPa) or hypercapnic (pCO2 1.3 kPa) hypoxia (pO2 2.0 kPa) for up to 4 days. Changes in blood concentrations and tissue content of organic acids were measured.In the early phase of hypercapnic hypoxia leeches accumulated mainly succinate, and the normally high malate concentrations in blood and tissue were reduced concomitantly. Between 2 and 24 h of hypoxia the animals started to produce propionate which is the major end‐product of this type of hypoxia. Only low concentrations of lactate were found in blood and tissue. During the initial phase of hypocapnic hypoxia an accumulation of succinate was also observed, but at a higher rate than during hypercapnic hypoxia. Subsequently, propionate was also produced. Between 24 and 48 h of hypocapnic hypoxia the concentrations of succinate in blood and tissue decreased rapidly and lactate appeared as an end‐product of anaerobic metabolism.The results indicate that, in leeches under “environmental” hypoxia, the external concentration of carbon dioxide affects the pathway of carbohydrate metabolism resulting in either succinate/propionate production or in lactate accumulation. © 1992 Wiley‐Liss, Inc.
Purification and characterization of acidic alpha‐D‐mannosidase from the hepatopancreas of the shrimp Penaeus monodon (Crustacea: Decapoda)
Authors: Chuang Nin‐Nin , Yang Bei‐Chia , Lin Kung‐Shih 
Published: June 2005

AbstractAcidic alpha‐D‐mannosidase purified from the hepatopancreas of Penaeus monodon is pentameric, with a Mr 251,000 as estimated by size‐exclusion FPLC on a SuperoseTM 12, and retains a hydrophobic domain, being stable to heating at 65°C for 1 h. The specific activity of the purified enzyme is 1,923 units/mg of protein. After polyacrylamide gel electrophoresis under denaturing conditions, the purified acidic alpha‐D‐mannosidase from shrimp was found to consist of a single homogeneous type of monomer of Mr 51,000. The purified enzyme has an isoelectric point of 4.4 ± 0.1 and becomes more alkaline after the removal of either sialic acid or phosphate groups. The apparent Km value of alpha‐D‐mannosidase from shrimp hepatopancreas with 4‐methylumbelliferylalpha‐D‐mannopyranoside as substrate is 243 μM. © 1992 Wiley‐Liss, Inc.
Intracellular free magnesium in the muscle of an osmoconforming marine invertebrate: Measurement and effect of metabolic and acid‐base perturbations
Authors: Doumen C. , Ellington W. R. 
Published: June 2005

AbstractDissociation constants for MgATP [Kd(MgATP)] were measured with the combined techniques of spectrophotometry using the metallochromic dye, Antipyrylazo III, and phosphorus nuclear magnetic resonance (31P‐NMR) spectroscopy. Values of the Kd(MgATP) were dependent on pH, ionic strength, and the relative concentrations of competing and noncompeting ions. A model solution was constructed simulating the cytoplasm of the muscle of the horseshoe crab, Limulus polyphemus. Using this model solution, Kd(MgATP) values were determined. In addition, the acid dissociation constants (Ka's) for inorganic phosphate, ATP and MgATP were determined by 31P‐NMR. Free Mg+2 concentrations ([Mg+2]i) were estimated from 31P‐NMR spectra of superfused bundles of L. polyphemus muscle fibers based on the difference in chemical shift of the γ and β‐ATP resonances using Kd(MgATP) values corrected for prevailing intracellular pH (also estimated from spectra). The [Mg+2]i in L. polyphemus muscle was around 1,200 μM. Metabolic perturbations (anoxia, metabolic poisons) and experimental acidosis (hypercapnia) had no significant effect on [Mg+2]i but did alter the fraction of the total ATP pool complexed with Mg+2. Free magnesium is not in thermodynamic equilibrium, and thus it appears that [Mg+2]i is stringently regulated in L. polyphemus muscle. © 1992 Wiley‐Liss, Inc.
Histochemical identification and behavior of quail primordial germ cells injected into chick embryos by the intravascular route
Authors: Nakamura Masao , Yoshinaga Kazuya , Fujimoto Toyoaki 
Published: June 2005

AbstractThe behavior of quail primordial germ cells (PGC) after injection into chick embryos by the intravascular route was examined. The quail (donor) PGC, taken from the bloodstream of quail embryos (recipient) at stage 13–14, were injected into the vitelline vessels of chick embryos (recipient) at stage 15. In the recipient embryos, the PGC of the quail and the chick were histochemically distinguished by a double‐staining technique involving a lectin, from Wistaria floribunda (WFA) and the PAS reaction. One day after injection, quail PGC appeared in the prospective gonadal region of recipient chick embryos, being localized among the recipient chick PGC. This result indicates that a staining technique specific for WFA lectin is useful for identification of quail PGC and that quail PGC can be transferred by a vascular route for the production of germline chimeras. © 1992 Wiley‐Liss, Inc.
The pupillary system of noctuid moth eyes: Dynamic changes in relation to control of pupil size
Authors: Nordtug Trond , Melø Thor Bernt 
Published: June 2005

AbstractEye pupil‐size changes, in response to repetitive ON‐OFF light stimulation, of 3 species of noctuid moths have been observed by infrared reflection photometry. For moderate ON stimulus intensities (2.5·109 quanta·cm−2·s−1), eye reflectance changed exponentially with time, in both the ON and OFF phases. For low ON stimuli (2.5·108 quanta·cm−2·s−1), however, the dark adaptation response in the OFF phase was composed of an initial exponential and a subsequent linear term. For repetitive low‐intensity ON‐OFF stimuli, the response amplitude changed in a diurnal way. The shape of the response to each ON‐OFF stimulus was, however, independent of diurnal time. Finally, in eyes that were spontaneously entering a light‐adapted state, pure exponential dark adaptation was elicited by intense light pulses. It is suggested that the substances controlling light and dark adaptation are interrelated. The substances constitute a chemical cycle running at constant speed, in the absence of light, and the substance causing pigment dispersion (light adaptation) is a photoproduct of the other substance. The concentration of the substance causing pigment contraction (dark adaptation) is controlled by the rate of the back reaction, which is composed of an exponential term, related to accumulation of the photoproduct during light stimulation, and a constant term, due to the speed of the cycle. The cycle speed is subject to diurnal changes. © 1992 Wiley‐Liss, Inc.
Intra‐ and extra‐cellular sources of T3 binding to putative thyroid hormone receptors in liver, kidney, and gill nuclei of immature rainbow trout, Oncorhynchus mykiss
Authors: MacLatchy D. L. , Eales J. G. 
Published: June 2005

AbstractThe sources of extracellular and intracellular 3,5,3′ ‐triiodo‐L‐thyronine (T3) binding to putative thyroid hormone receptors in liver, kidney, and gill nuclei were determined in vivo for immature rainbow trout at 12°C. Both [131I]T3 and [125I]T4 were injected intraperitoneally, the plasma and tissues were examined at isotopic equilibrium at 20 h, and the proportions of intracellular [125I]T3 and extracellular [131I]T3 saturably bound in the nucleus were determined. Comparable total amounts of T3 were saturably bound in the nuclei of liver (7.2), kidney (8.0), and gill (9.7 moles × 10−13 .mg DNA−1), but the percentage of nuclear T3 generated within the target cell was greater for gill (76%) than for liver (50%) and kidney (28%). Both gill and liver possess a low Km T4 5′monodeiodinase which could be responsible for the high proportion of the nuclear T3 generated within those tissues. © 1992 Wiley‐Liss, Inc.
Ganglia implantation as a means of supplying neurotrophic stimulation to the newt regeneration blastema: Cell‐cycle effects in innervated and denervated limbs
Authors: Goldhamer David J. , Tomlinson Bruce L. , Tassava Roy A. 
Published: June 2005

AbstractRegulation of blastema cell proliferation during amphibian limb regeneration is poorly understood. One unexplained phenomenon is the relatively low level of active cell cycling in the adult newt blastema compared to that of larval axolotls. In the present study, we used ganglia implantation as a means of “superinnervating” normally innervated adult newt blastemas to test whether blastema cell subpopulations are responsive to nerve augmentation. The effectiveness of implanted ganglia to provide neurotrophic stimulation was demonstrated in denervated blastemas. Blastemas implanted with 2 dorsal root ganglia and simultaneously denervated 14 days after amputation exhibited control levels of cell cycle activity 6 days later, as measured by 3H‐thymidine pulse labeling. Denervated blastemas that were sham‐operated or implanted with pituitary glands exhibited cell‐cycle declines similar to those of denervated blastemas without implanted ganglia. Thus, 2 implanted ganglia provide neurotrophic stimulation equivalent to that of the normal nerve supply. Dorsal root ganglia implanted into normally innervated blastemas, which should effectively double neurotrophic activity to the blastema, had no effect on cell‐cycle activity; innervated blastemas implanted with ganglia for 6 days exhibited pulse labeling indices similar to those of normally innervated blastemas. These data indicate that neurotrophic stimulation is not normally limiting in inner‐vated limbs, and that some other factor, whether extrinsic or intrinsic to blastema cells, accounts for the relatively low level of active cell cycling in the adult newt blastema. © 1992 Wiley‐Liss, Inc.
Partial purification and some chemical properties of the sperm chemoattractant from the forcipulate starfish Pycnopodia helianthoides (Brandt, 1835)
Authors: Punnett Thomas , Miller Richard L. , Yoo Bong‐Hee 
Published: June 2005

AbstractThe sperm attractant of the forcipulate starfish Pycnopodia helianthoides has been isolated by sea water extraction from ripe ovaries. After concentration and purification by adsorption and desorption using an Amberlite resin followed by gel filtration chromatography, the most active fractions have been further purified by reverse‐phase and hydrophobic‐interaction chromatography. A relative purification of 2 × 105 was obtained. Exposure of the partially purified attractant to temperature extremes and enzymes reveals that the molecule is heat and freeze‐thaw stable and that it is degraded by the proteases trypsin, chymotrypsin, and pronase. Four different procedures used to determine molecular size produce the same estimate of about 12 kD. The attractant is retarded during Sephadex G‐25 chromatography and does not run as a tight band on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). These results suggest that the sperm attractant of this starfish is a small protein. © 1992 Wiley‐Liss, Inc.
Hormonal control of sulfate uptake by branchial cartilage of coho salmon: Role of IGF‐I
Authors: McCormick Stephen D. , Tsai Peter I. , Kelley Kevin M. , Nishioka Richard S. , Bern Howard A. 
Published: June 2005

AbstractThe direct hormonal control of sulfate uptake by cartilage matrix of coho salmon was examined by exposing branchial cartilage to 1 μCi · ml−1 35SO4 for 48 hours at 15°C in a defined medium. Sulfate uptake occurred primarily in cartilage (rather than bone) and the amount of specific uptake was similar in epibranchial and ceratobranchial cartilages. Intact and hypophysectomized coho salmon starved for 22 days had equivalent in vitro sulfate uptake, which in both cases were 30% of the uptake seen in branchial cartilage of fed, intact controls. In branchial cartilage from starved coho salmon, in vitro exposure to recombinant bovine insulin‐like growth factor I (rbIGF‐I) at 1, 10, 100, and 1,000 ng · ml−1 caused a dose‐dependent increase in sulfate uptake, with a maximum 3‐fold increase over control at 1,000 ng · ml−1 rbIGF‐I. Coho salmon insulin (1, 10, 100, and 1,000 ng · ml−1) resulted in a maximum 30% increase in sulfate uptake at the highest dose. Growth hormone and triiodo‐L‐thyronine had no direct effect on in vitro sulfate uptake. The results indicate that IGF‐I has direct effects on coho salmon cartilage and may be an important regulator of growth in salmon and other teleosts. © 1992 Wiley‐Liss, Inc.
Effects of human insulin‐like growth factor‐I on release of growth hormone by rainbow trout (Oncorhynchus mykiss) pituitary cells
Authors: Pérez‐Sánchez J. , Weil C. , Le Bail P.‐Y. 
Published: June 2005

AbstractA recombinant human IGF‐I (rhIGF‐I) was applied to primary cultures of rainbow trout pituitary cells. In wells containing 3 × 104 and 6 × 104 cells/well, rhIGF‐I inhibited basal GH release both in short (6 h) and long (12 and 24 h) exposures. The decline in GH release was dose‐dependent over the range of 0.01 and 100 mM. The combination of rhIGF‐I and low concentrations of synthetic somatostatin14 (SRIF) enhanced the inhibitory effect of rhIGF‐I in an additive manner. Any appreciable effect of rhIGF‐I on PRL release was not evidenced. To our knowledge, this report demonstrates for the first time the participation of IGFs on the inhibitory component of fish GH regulation. © 1992 Wiley‐Liss, Inc.