bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pineal melatonin: Circadian rhythm and variations during the hibernation cycle in the ground squirrel, Spermophilus lateralis
Authors: Stanton Toni L. , Craft Cheryl M. , Reiter Russel J. 
Published: June 2005

AbstractVariations in pineal melatonin content throughout a 24‐hour period and during different phases of the hibernation bout cycle were studied in the golden‐mantled ground squirrel (Spermophilus lateralis). In addition to pineal melatonin, the circadian variation in the activities of pineal N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) were also investigated in summer animals maintained at 22 ± 2°C, on a light:dark (L:D) schedule of 12:12 hr for 1 month (lights on at 08.00 hr). Pineal glands were collected from six animals in each group at 1200, 1600, 2000, 2400, 0200, 0400, and 0800 hr. Changes in pineal melatonin content during the hiberation bout cycle were investigated in ground squirrels housed at 4 ± .05°C in relative darkness (1.9–3.4 lux; 10:14 LD). Pineal glands were obtained between 12:00 and 18:00 hr from 30 animals during one of three phases of the cycle (deep hibernation, euthermic interbout, and entrance into hibernation). Pineal melatonin was also measured for comparison in six winter euthermic animals that were housed at 22 ± 2°C, on a L:D schedule of 10:14 hr. Melatonin was measured in individual pineal glands by radioimmunoassay. The daily melatonin rhythm in S. lateralis was characterized by a marked increase in pineal melatonin during the dark phase, in which peak nighttime values were nearly 20‐fold greater than daytime basal levels. The daily rhythm for NAT activity paralleled the changes in melatonin, showing a peak activity at 0200 hr that was 45 times greater than mean daytime values. No significant variation was observed in HIOMT activity. Pineal melatonin levels in winter animals were lowest during the state of deep hibernation. Melatonin content was increased significantly in the interbout phase within 1 hr postarousal (p < .01). A significant decline was evident in interbout animals that were sacrificed 6–8 hr postarousal and in animals that were in the entrance phase of hibernation (p < .01), although these values remained significantly higher compared to hibernation.
Myofiber death plays a role in determining fiber type composition in the claw closer muscles of the snapping shrimp, Alpheus heterochelis
Authors: Quigley Michael M. , Mellon Deforest 
Published: June 2005

AbstractMarine shrimp of the genus Alpheus exhibit a remarkable reversal of asymmetry in their great claws. This unique phenomenon includes transition of the closer muscle in one claw from a muscle of mixed fiber type into a homogenous slow muscle. We have developed monoclonal antibodies that specifically recognize fast and slow myosin heavy chain (MHC), and have used these as immunohistochemical markers to follow the fate of different myofiber types during this transformation. This analysis reveals a strikingly specific necrosis of the fast fibers. The onset of fiber degeneration appears linked to the molt cycle and occurs rapidly once started. This represents the first example of programmed myofiber death as a mechanism used in crustacean muscle development.
Solute effects on mitochondria from an elasmobranch (Raja erinacea) and a teleost (Pseudopleuronectes americanus)
Authors: Ballantyne J. S. , Moon T. W. 
Published: June 2005

AbstractVarying osmolarity with sucrose/KCI media resulted in similar effects on the oxidation of glutamate by mitochondria isolated from the livers of an elasmobranch, Raja erinacea, and a teleost, Pseudopleuronectes americanus. In both species trimethylamine oxide (TMAO) inhibited mitochondrial oxidation of glutamate. Urea penetrated the inner mitochondrial membrane of both species and equilibrated with a ratio ureai/ureao of unity. Urea had little effect on the oxidation of glutamate in both species at concentrations as high as 760 mM. Addition of urea (urea/TMAO, 2:1) did not overcome the detrimental effects of TMAO in the mitochondria of either species. In the case of the elasmobranch, the osmolarity of the urea/TMAO media giving the optimal rate of respiration was hypoosmotic with respect to the intracellular osmolarity. The rate of glutamate oxidation steadily declined as osmolarity increased above this value. Assuming the osmotic profile obtained with the urea/TMAO (2:1) medium resembled most closely the in vivo situation, higher rates of oxidation or organic solutes at low osmolarity would help deplete the cell of these solutes and could contribute to cell volume regulation during hypoosmotic stress.It is suggested that two broad classes of intracellular solutes can be defined based on their effects on mitochondrial respiration. Solutes such as K+, C1−, and TMAO penetrate the inner mitochondrial membrane slowly or not at all. Increasing concentrations of these solutes result in lower rates of oxidation. This capacity may be important in regulating intracellular levels of organic solutes during osmotic stress. Solutes such as urea rapidly penetrate the cell and inner mitochondrial membrane reducing the mitochondrial volume changes associated with osmotic stress. The known detrimental effects of urea on protein structure may prevent its exclusive use as an intracellular osmotic effector.
Organisation of Xenopus egg cytoplasm: Response to simulated microgravity
Authors: Smith Rosamund C. , Neff Anton W. 
Published: June 2005

AbstractThe cytoplasm of Xenopus fertilised eggs appears to be organised into three major compartments based primarily on the uneven distribution of yolk platelets. There is a shift of these yolk compartments during the first cell cycle that is thought to be involved in the dorsal/ventral morphogenesis of the embryo. The involvement of gravity in Xenopus cytoplasmic organisation and in compartment shifts was addressed by examining, cytologically, the yolk compartments in embryos that developed under the simulated microgravity conditions of the horizontal clinostat. The cytoplasmic organisation into yolk compartments was found to be maintained, and the asymmetric movements of compartments still occurred in eggs that developed on the clinostat. It is suggested that the organisation of Xenopus egg cytoplasm into discrete compartments relies on forces other than those involving gravity (i.e., not density differences), and that the compartment shifts that take place during the first cell cycle are active movements.The variation in compartment size and composition observed from batch to batch of eggs, and to a lesser extent from egg to egg, during this study was addressed.
Cyclic AMP stimulation of Cl− secretion by the opercular epithelium: The basolateral chloride uptake mechanism
Authors: Degnan Kevin J. 
Published: June 2005

AbstractThe isolated, short‐circuited opercular epithelium of Fundulus heteroclitus, secretes Cl− by a mechanism dependent on the presence of serosal Na+ and inhibited by bumetanide and furosemide. Under serosal Na+‐free conditions the active Cl− secretion is abolished. However, subsequent elevations of intracellular cyclic AMP (cAMP) levels with isoproterenol or forskolin stimulated Cl− secretion markedly. This stimulation was unaffected by SITS, DIDS, methazolamide, and HCO−3‐free solutions, but was blocked by furosemide and bumetanide. Determinations of relative intracellular 36Cl− levels showed a Na+ dependence of intracellular 36Cl− in epithelia not stimulated by isoproterenol and a Na+ independence of intracellular 36Cl− in isoproterenol stimulated epithelia. In both conditions, the intracellular 36Cl− was bumetanide sensitive. The results indicate that cAMP stimulation of Cl− secretion can occur by a Na+‐independent, loop diuretic‐inhibitable mechanism, which may be operative even in the presence of Na+. Whether this is a separate Cl− uptake mechanism or a cAMP‐induced alteration in the normal Na+‐dependent mechanism could not be determined. In either instance, an alternative to the Na+ gradient as a source of energy for Cl− uptake into the cell across the basolateral membrane is required.
Neoplastic transformation in the planarian: I. Cocarcinogenesis and histopathology
Authors: Hall Frederick , Morita Michio , Best Jay Boyd 
Published: June 2005

AbstractAlthough several investigators have reported that exposure to mammalian carcinogens induces abnormal tumorlike growths and teratogenic remodeling in planarians, there is no general agreement that these, or comparable responses in any other invertebrates, model mammalian carcinogenesis. To investigate this question, freshwater planarians of the species Dugesia dorotocephala were exposed to culture water containing an initiator and a promoter, either alone or in combination. Cadmium, a potent carcinogen, was used as an initiator in the protocol. Treatment with sublethal concentrations of cadmium sulfate produced a benign, but persistent, tumor in a small percentage of the planarians. The addition of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), a phrobol ester and well‐known promoter, to the cadmiumcontaining solutions resulted in the induction of a progressive, potentially lethal, transplantable tumor in a large proportion of the treated flatworms. Light and electron microscopy revealed this particular tumor to be composed both of immature cells and of a single mature cell type: newly differentiated, but transformed, reticular cells. Further examination of the infiltrating tissue formations elucidated the profile of differentiation, from a population of mitotically active transformed stem cells through the transitional stages in the associated reticuloma. These results suggest that (1) the freshwater planarian displays the major phenomenology of mammalian cocarcinogenesis and that (2) the planarian reticuloma models several important features of a neoplastic stem cell disease.
The effect of the presence of adult fishes, gonad homogenates, and embryo homogenates on the dispersion‐reaggregation phase during early embryonic development of the annual fish Nothobranchius korthausae
Authors: Levels P. J. , van Tits L. J. H. , Denucé J. M. 
Published: June 2005

AbstractThe effect of the presence of adults of the annual fish Nothobranchius korthausae on development of eggs of this species was investigated. If the eggs were incubated in glass tanks together with adult females, embryonic development was prolonged during the dispersion‐reaggregation phase. Furthermore, gonadal homogenates as well as homogenates of oocytes and fertilized eggs or embryos (until the prehatching stage) also caused prolongation of the dispersion‐reaggregation phase. This prolongation was attributed to a longer lasting reaggregation, although the occurrence of a brief diapause I could not be ruled out.We suggest that gonads of adult annual fishes, especially females, contain one or more pheromonelike agents that are released into the water and induce a prolongation of the dispersion‐reaggregation phase of the deposited eggs. By increasing or decreasing the amount of agent released, the adults would be able to affect embryonic development. The fact that homogenates of oocytes and fertilized eggs had the same effect on egg development indicates that also the eggs may be a source of this agent. Therefore, it probably plays a function during (normal) embryonic development.
Integumentary uptake of acetate and propionate (VFA) by Tubifex sp, a freshwater oligochaete. II. Role of VFA as nutritional resources and effects of anaerobiosis
Authors: Hipp Erich , Bickel Ursula , Mustafa Tariq , Hoffmann Klaus H. 
Published: June 2005

AbstractThe freshwater oligochaete Tubifex tubifex is able to absorb 14C‐labeled short‐chain carboxylic acids (VFA) from ambient water (Hipp et al., '86). In this paper evidence is given that VFA are transported across the body surface (autoradiography) and not taken up to any significant extent by bacteria or accumulated on the surface layer. Absorbed carboxylic acids are metabolized, as shown by the appearance of label in respiratory Co2 as well as in glycogen content. Rates of uptake are determined by the metabolic state of the worms. Under anoxic conditions, uptake is rapidly reduced. However, only 30 to 60 minutes of aerobic recovery were needed to regain aerobic control levels of uptake. Comparison of potential rates of VFA accumulation to rates of oxidative metabolism suggest that acetate and propionate might serve as an important nutritional supplement to these benthic freshwater animals.
Serotonin regulation of gill cAMP production, Na, and water uptake in freshwater mussels
Authors: Scheide John I. , Dietz Thomas H. 
Published: June 2005

AbstractActive Na transport in freshwater mussels was stimulated by addition of 10−4 M serotonin (5‐HT) in the bath. Carrier kinetics apply to serotonin‐stimulated Na uptake with no effect on the affinity (Km 10−4 M). The Jmaxi was increased 350% over controls to 5.83 μeq (g dry tissue · h)−1. Amiloride reversibly inhibited the 5‐HT‐stimulated Na influx. Serotonin also caused a net water uptake of 0.36 ml H2O (g dry tissue · h) −1, due, in part, to a reduction in renal filtration. When mussel gill tissue was incubated in pondwater containing 10−4 M 5‐HT, cAMP content increased 2.5 times control levels within the first minute and then declined toward control values by 20 minutes. Theophylline (10−3 M) in the incubation medium prevented this decline. Dopamine, epinephrine, or norepinephrine (10−4 M in pondwater) increased gill cAMP concentrations; L‐dopa did not. Both 5‐HT and dopamine significantly increased gill cAMP concentration at 10−5 M.
Role of the neural retina in newt (Notophthalmus viridescens) lens regeneration in vitro
Authors: Connelly Thomas G. , Green M. Sean , Sahijdak Walter M. , Loyd Robert M. 
Published: June 2005

AbstractRemoval of the lens from the eye of an adult newt (Notophthalmus viridescens) is followed by regeneration of a new lens from the dorsal iris epithelial cells at the pupillary margin. This process is dependent upon the neural retina for its normal completion in vivo and in vitro. To examine the relationship between the retina and lens regeneration, we have conducted experiments that delimit the time period during which the retinal presence is critical (in vivo) and have investigated the influence of extracts of the retina on the progress of regeneration (in vitro).In vivo, removal of the retina at day 11 seriously retards further progression of regeneration while removal of the retina at day 15 does not retard regeneration significantly. This defines a “critical period” in regeneration of the lens during which the retina is required.Explantation of regenerates 11 or 12 days after lentectomy to organ culture medium enriched with either crude retinal homogenate or extracts prepared from chick or bovine retinas according to Courty et al. ('85, Biochimie, 67:265–269) reveals that the progress of regeneration can be supported in culture by the crude extract. This is the first demonstration of complete iris‐lens trnsformation in culture in the presence of retinal extract.It is possible that the retina acts indirectly by promoting passage of the iris epithelial cells through the critical number of mitoses required before redifferentiation into lens cells can occur (as proposed by Yamada, '77, Monogr. Dev. Biol., 13:126). It is also possible that the retina acts by directly instructing the iris cells to redifferentiate. Our experiments provide some indirect support for the first possibility but do not distinguish between them at this time.
The cellular basis of the calcium dependence of GnRH‐stimulated gonadotropin release from frog, Rana pipiens, pituitaries
Authors: Porter David A. , Licht Paul 
Published: June 2005

AbstractAn in vitro superfusion system was used in an attempt to identify the cellular systems involved in the Ca2+ dependence of gonadotropin‐releasing hormone (GnRH) actions in the frog, Rana pipiens. Superfusion with 5 μM A23187 (a calcium ionophore) or phorbol myristate acetate (an analog of diacylglycerides) caused marked increases in luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) secretion. Exclusion of Ca2+ from the medium prevented the stimulatory effects of PMA. The potent stimulator of adenylate cyclase, forskolin, caused only slight stimulation of LH and FSH secretion, which was also prevented by removal of Ca2+. The cytoskeletal disruptive agents colchicine, nocodazole, and cytochalasin B, and the calmodulin inhibitors, trifluoperazine and pimozide, had no significant effects on the action of GnRH. Overall, these results indicate that the major mechanisms of Ca2+ involvement in the response to GnRH by the frog pituitary are similar to that of mammals, with the possible exceptions of lesser roles for calmodulin and the cytoskeleton in the frog. The study suggests that polyphosphatidyl‐inositol‐diacylglyceride metabolism may be critical in understanding the mechanism of GnRH action in frogs.
Effect of ouabain on the meiotic maturation of stage IV–V Xenopus laevis oocytes
Authors: Penna Mary Jo , Wasserman William J. 
Published: June 2005

AbstractFull‐grown stage VI Xenopus laevis oocytes (1,200 to 1,300μm) respond to progesterone stimulation by undergoing a series of physiological and morphological changes that are referred to as meiotic maturation. Oocytes in earlier stages of oogenesis (I through V) do not undergo these changes and remain in prophase arrest when exposed to this steroid. We have found that oocytes ranging from 850 μm (stage IV) to 1,000 μm (stage V) are capable of responding to progesterone under the appropriate conditions. Oocytes ≥ 850 μm in diameter underwent germinal vesicle breakdown (GVBD) after 10–12 hr of exposure to progesterone when ouabain was added to the medium at a concentration > 2.5 × 10−6M. Under this culture condition, progesterone was now able to induce a 0.3‐ to 0.4‐unit increase in the intracellular pH of stage IV–V oocytes, a 4‐ to 5‐fold increase in 40s ribosomal protein S‐6 phosphorylation, and a 2.3‐fold increase in their rate of protein synthesis. All of these physiological changes are characteristic of full‐grown stage VI oocytes undergoing meiotic maturation. In addition, we have found that oocytes ≥ 750 μm are capable of amplifying maturation promoting factor (MPF) in their cytoplasm leading to GVBD. Therefore, stage IV–V Xenopus oocytes have the potential for undergoing meiotic maturation, but they are blocked at a point in prophase that appears to be alleviated by the combination of progesterone and ouabain.
Circadian and circannual rhythms of melatonin in plasma of male white‐tailed deer and the effect of oral administration of melatonin
Authors: Bubenik G. A. , Smith P. S. 
Published: June 2005

AbstractCircadian levels of melatonin (M) were determined in plasma of four male white‐tailed deer sampled hourly in September for 24 h via indwelling jugular catheter. Concentrations of M, detected by the radioimmunoassay rise with the onset of darkness, peak at 1.00 h (265 pg/ml) and then quickly decline to baseline levels (60 to 70 pg/ml) maintained during the scotophase. Orally administered M (5 mg, given at 13:00 h) induced a rapid elevation of plasma M (peak 980 pg/ml at 15:00 h) followed by a decline to baseline (100 pg/ml) reached at 22:00 h. The usual midscotophase peak was abolished by exogenous M administration. Seasonal midscotophase levels of M (determined in three samples taken 45 min apart between 23:00 and 1:00 h reach maximum in December (1530 pg/ml) followed by decline to minimum (69 to 90 pg/ml) observed between May and July. The data indicate that: 1) similarly to other mammals, deer exhibit peak level of M during the dark phase; 2) 5 mg of M given orally caused a rapid elevation of M levels in blood followed by a depression of the normally present night‐time peak; and 3) midscotophase levels of M exhibit very pronounced seasonal fluctuations which might be related to yearly cycles, such as the reproduction, hair molt, and antler growth.
Effect of mammalian gonadotropins on testosterone secretion in male alligators
Authors: Lance Valentine A. , Vliet Kent A. 
Published: June 2005

AbstractMale farm‐reared alligators were injected with mammalian FSH, LH, hCG, prolactin, or saline. A blood sample was taken immediately prior to injection of hormone and at 24 h postinjection. Testosterone concentrations in the plasma were then determined by radioimmunoassay. Only the alligators injected with FSH showed a significant increase in plasma testosterone. In a second series of experiments male alligators were injected with ovine LH, ovine FSH, or saline and bled at 0, 2, 4, 16, and 24 h postinjection. Again, only the alligators injected with FSH showed significant increases in plasma testosterone at 16 and 24 h postinjection. Mammalian LH does not appear to stimulate testosterone secretion in male alligators.
Utilization of aspartate transcarbamylase activity in the study of neuroendocrinal control of gametogenesis in Mytilus edulis
Authors: Mathieu Michel 
Published: June 2005

AbstractStudies on the endocrine control exerted upon cellular multiplication in mussel mantle tissue (the site of the gonad in this species) are rendered difficult by its extremely heterogeneous nature and require the use of a quantifiable bioassay. Measurement of specific ATCase activity gives a good estimation of pyrimidine biosynthesis; in mussels, the specific activity of this enzyme is highest in the mantle tissue and is closely correlated to the gonadosomatic index. Stimulatory action of cerebral ganglia in organ culture experiments are associated with increases of specific ATCase activity. Antimitotic substances, such as 5 fluorouracile or arabinocytosine on the other hand, induce a decrease of ATCase activity in mantle explants. The utilization of ATCase activity measurements, in the study of gametogenic controls, is proposed in species in which the gonad is not a differentiated organ.
Isolation and characterization of a polarized isolated hepatocyte preparation in the skate Raja erinacea
Authors: Smith D. J. , Grossbard M. , Gordon E. R. , Boyer J. L. 
Published: June 2005

AbstractHepatocytes of the small skate (Raja erinacea) were isolated by collagenase perfusion and evaluated by a variety of functional and morphologic criteria. Cell yield was 1.45 × 108 ± 1.3 × 107 cells per isolation, and as long as 8 h after isolation 98% of the hepatocytes excluded Trypan blue and no leakage of lactate dehydrogenase (LDH) or cell associated potassium could be detected. Oxygen consumption averaged 1.6 ± 0.5 nmol/min/mg cell protein, was not stimulated by 1 mM succinate, and also remained stable for up to 8 h following isolation. However, 2,4,‐dinitrophenol (5 × 10−5 M) produced a 55% increase in oxygen utilization while ouabain, (1 mM) or sodium removal decreased oxygen consumption by 31 ± 6 and 33 ± 7%, respectively, indicating that a significant portion of the cells energy utilization is coupled to the activity of plasma membrane Na+, K+‐ATPase.Light microscopic studies showed that the individual hepatocytes had diameters of 28 ± 5 μm and contained large lipid droplets. Electron microscopy revealed groups of three to five cells with normal ultrastructure and tight junctions and desmosomes surrounding a single bile canaliculus.These studies indicate that skate hepatocytes can be isolated in high yield that retain their structural polarity in the form of clusters of cells formed around a single bile canaliculus. These hepatocytes remain morphologically intact and metabolically stable for a prolonged period of time. Isolated skate hepatocyte preparations should be a useful experimental model to study hepatic metabolism in marine species, not only because of their viability but also because they retain their apical and basolateral membrane polarity, a feature that is usually lost in other isolated hepatocyte preparations.