Bufo Arenarum Hensel Research Articles

Growth Hormone Inhibits the Hypophysectomy-Induced Expression of Galanin in Hypothalamic Neurons of the Toad (Bufo arenarumHensel)

The expression of the neuropeptide galanin was analyzed by immunohistochemistry in magnocellular and preoptic hypothalamic neurons of toads following hypophysectomy (HPX) and pars distalectomy (PDX). There was a marked increase in the galanin-like immunoreactive expression in magnocellular hypothalamic cells 3 days after HPX, followed by a decrease to normal levels after 7 days. No changes in the expression of galanin were detected after PDX in these neurons when compared to controls. Moreover, 7 days after HPX or PDX the number of cells expressing galanin was significantly increased in the preoptic area, where numerous intraependymal cells were intensely immunoreactive. The hypophysis grafts into the hind limb in HPX or PDX animals prevented increased galanin-like immunoreactivity in preoptic cells but not in magnocellular neurons. Similarly, PDX toads given growth hormone showed no GAL-LI in the intraependymal preoptic cells. These results suggest the presence of a regional regulation of galanin expression in the preoptic area by hypophyseal hormones, in particular growth hormone.

Identification of immunoreactive mammalian gonadotropin-releasing hormone in the brain of metamorphic larvae of Bufo arenarum hensel (Amphibia: Anura)

Gonadotropin-releasing hormone (GnRH) immunoreactivity in brain extracts of Bufo arenarum tadpoles were investigated by high-performance liquid chromatography, followed by radioimmunoassay analysis using two different antisera raised against different GnRH variants. Only one immunoreactive peak was identified, eluting in the same position as synthetic mammalian GnRH. This result was further confirmed by serial dilution studies using more specific mammalian GnRH antisera. Our results suggest that mammalian GnRH is most likely an endogenous peptide in the brain of the developing larvae and froglets of Bufo arenarum and quite likely it is the only GnRH variant present during those development stages. The distribution and density of cell bodies and fibers were analysed by immunocytochemical procedures. Immunoreactive cell bodies appeared in the olfactory epithelium and across the olfactory nerve at late prometamorphic larval stages. Near the metamorphic climax and in froglets, perikarya and fibers were detected in basal forebrain, preoptic and hypothalamic areas. No immunoreaction was observed at midbrain, hindbrain and spinal cord levels. This study suggests that mammalian GnRH is most likely an endogenous peptide and is probably the only GnRH variant in the brain of the developing larvae and froglets of Bufo arenarum.

Effect of malathion on Bufo arenarum hensel development—I : Esterase inhibition and recovery

Newly fertilized Bufo arenarum Hensel embryos were exposed continuously or for a brief period (72–120 hr) to malathion (44 ppm) and then resuspended in amphibian Ringer's solution. Continuous exposure depressed acetylcholinesterase (EC 3.1.1.7), butyrylcholinesterase (EC 3.1.1.8) and carboxylesterase (EC 3.1.1.1) activities. The activities of the three enzymes in embryos treated for 72 hr recovered after a delay of 24 hr, but these enzymes showed different rates of recovery in embryos treated for 120 hr. Acrylamide disc electrophoresis showed several bands of esterase activity in control embryos. Continuous exposure to malathion abolished all esterase activity within 48 hr, but if the exposure continued new bands of esterase activity appeared at 120 hr of exposure. The zymograms of embryos exposed for 72 or 120 hr to malathion and then transferred to uncontaminated medium for 120 hr were similar to that of control embryos.

Effects of temperature and general anesthesia on the water gain and the inulin space of the brain of the toad, Bufo arenarum Hensel.

1. The water gain in vitro and the inulin space of the brain of the toad were measured under different experimental conditions. 2. There exists a highly positive correlation between water uptake by the brain and the acclimation-incubation temperature, 7 degrees-37 degrees C. 3. Regional differences in the water gain and inulin space were also demonstrated when measured at 20 degrees C. Higher gains were observed in hemispheres, mesodiencephalon and rhombencephalon. 4. The water gain was higher for whole brains obtained under deep anesthesia with ether or urethane but not under nembutal. The inulin space was also higher under ether but lower under urethane. Nembutal had no effect in this case either. 5. A hypothesis about the possible role of water and electrolyte movements in the mechanism of action of some general anesthetics is advanced.

Fine structure of the testis in the toad (Bufo arenarum hensel): a freeze-fracture study.

The present work reports novel findings in the toad testis using freeze-fracture techniques. Tight and gap junctions are observed in the nonfenestrated endothelial cells. Numerous gap junctions are present between interstitial cells. Sertoli-Sertoli junctional specializations in the toad are similar to those described in mammals although they appear to be less elaborate. The appearance of nuclear pores, in the seminiferous epithelium, ranges from a uniformly and apparently random distribution in Sertoli cells to large aggregations of closely spaced pores separated by free areas in the nuclear envelope of spermatocytes. Inasmuch as these features have also been described in mammals, the fact that they are present in amphibia might indicate that they represent a widespread pattern. Concomitantly with increasing chromatin condensation, nuclear pores diminish in round spermatids and seem to disappear in the more mature germ cells. The en face freeze-fracture views of annulate lamellae in the postnuclear cytoplasm and membranous features of the acrosome formation, flagellum, and undulating membrane of elongating spermatids are also described.

The different origins of the neurosecretory hypothalamo-hypophysial tracts of the toad Bufo arenarum hensel

In one group of toads, the external region of the median eminence containing the nerve fibres ending on the portal capillaries was severed by electrocoagulation whereas most or all the fibres going to the neural lobe were left intact. In a second group of animals, the whole median eminence was electrocoagulated, and therefore, all the fibres entering the median eminence and the neural lobe were interrupted. Four and 7 days after the operation, the animals with a partial destruction of the median eminence showed an increase in neurosecretory material in the axons leading from the dorsal group of neurons of the preoptic nucleus (DPO). After 14 days, these neurons became hypertrophied, vacuolated and very deeply stained by the aldehyde fuchsin. After a complete destruction of the median eminence, the changes after 4, 7 and 14 days appeared not only in the DPO but also in the ventral group of neurons of the preoptic nucleus (VPO). It is concluded that in the toad, the preoptic nucleus gives origin to two different aldehyde-fuchsin positive tracts; the VPO → neural lobe tract, and the DPO → median eminence tract.

The innervation of the pars intermedia of the pituitary gland in the toad.

The pars intermedia of the pituitary in Bufo arenarumHensel is innervated by two types of fibers, both coming from the adjacent neurohypophysis: 1. The neurosecretory nerve endings, originating in the neurohypophysis and found along the limit of the pars intermedia with the neurohypophysis. 2. The common nerve endings, which penetrate the pars intermedia as a single bundle from the neurohypophysis and distribute throughout the gland.

Ultrastructure of the peptidergic and monoaminergic neurons in the hypothalamic neurosecretory system of anuran batracians.

In the toad Bufo arenarumHensel the following regions of the hypothalamic — neurohypophyseal system were studied under the electronmicroscope: preoptic and paraventricular nuclei, median eminence and infundibular process of the neurohypophysis.

Seasonal variations of brain epinephrine, norepinephrine and 5-hydroxytryptamine associated with changes in the EEG of the toad, Bufo arenarum hensel

1. 1. Observations concerning the concentrations of epinephrine (E), norepinephrine (NE) and 5-hydroxytryptamine (serotonin, 5-HT) in the brain of the toad and the EEG pattern according to the seasons of the year were simultaneously performed. 2. 2. Brain E showed marked seasonal changes, with its lowest value near the onset of the mating period. From this moment it began to increase, reaching its maximum at the middle of estivation. Thereafter a progressive and significant lowering was noted. 3. 3. Conversely, 5-HT brain content showed its highest during hibernation, whereas a marked fall coinciding with mating was evident. 4. 4. Accordingly, the 5-HT/E ratio varied in the course of the year from a maximum of 18 during hibernation to 1·3 in the middle of the estivating period. 5. 5. Our results concerning these seasonal and opposite displacements of brain levels in E and 5-HT in toads are discussed in relation to simultaneously occuring changes in the EEG and to the hibernation-estivation cycle in amphibians.

Glycogen in the neurohypophysis of toads.

Studies with the electron microscope revealed the presence of glycogen granules in the neurohypophysis of toads (Bufo arenarum Hensel). The glycogen appeared as scattered particles or as clusters formed by these particles within the nerve fibers. The scattered granules were intermingled with the neurosecretory granules and with the microvesicles. Chemical assays showed the presence of glycogen in the neurointermediate lobe of the toad's hypophysis.

Neurosecretory system of the toad Bufo arenarum hensel and its changes during inanition

Studies have been carried out on the neurosecretory system of the toad Bufo arenarum Hensel in normal conditions and in different states of inanition. Extreme inanition produces an increase in neurosecretory material (NSM) which can be due to a decreased demand of the hypofunctioning adenohypophysis, or to a blockage of liberation of NSM. Furthermore, this accumulation of NSM in the hypothalamus could indicate that inanition does not stop its production. In normal conditions and especially in cases of extreme inanition the axons that form the hypothalamus-hypophysial tract show three different images of the NSM. This suggests the possibility that we are dealing with different secretory materials. At the same time the parallel increase of the NSM in the neuronal processes which go toward the third ventricle and of the Gomori-positive granules of the choroid plexus leads us to believe that other extrahypophysial pathways exist for the elimination of the NSM. A description is given, both in the controls and in the experimentals, of a group of neurosecretory axons which leave from the tract and run ventrally toward the optic chiasma.

Appearance of granules in the Purkinje cells of dehydrated toads (Bufo arenarum Hensel).

Seven days of dehydration produce alterations in the Purkinje cells of the toad, Bufo arenarumHensel. Aldehyde-fuchsin-positive granules appear in the cytoplasm of the cells and at the same time modifications take place in cytoplasmatic and nuclear ribonucleoproteins. These modifications consist of an increase in nucleolar volume and appearance of a nuclear cap, polarized towards the granules.

ECOLOGICAL AND PHYSIOLOGICAL OBSERVATIONS ON POLYMORPHIC POPULATIONS OF THE TOADBUFO ARENARUMHENSEL, FROM ARGENTINE

Journal Article ECOLOGICAL AND PHYSIOLOGICAL OBSERVATIONS ON POLYMORPHIC POPULATIONS OF THE TOAD BUFO ARENARUM HENSEL, FROM ARGENTINE Get access J. M. Cei J. M. Cei Instituto de Biologia Universidad Nacional de Cuyo Mendoza ArgentineCentro de Investigaciones Zoologicas Universidad de Chile Santiago de Chile Search for other works by this author on: Oxford Academic Google Scholar Evolution, Volume 13, Issue 4, 1 December 1959, Pages 532–536, https://doi.org/10.1111/j.1558-5646.1959.tb03041.x Published: 01 December 1959 Article history Received: 04 February 1959 Published: 01 December 1959