Showing papers on "Toad published in 1976"

Membrane structural specialization of the toad urinary bladder revealed by the freeze-fracture technique. II. The mitochondria-rich cell.

Abstract: Examination of the toad urinary bladder by freeze-fracture electron microscopy reveals that the mitochondria-rich cells of the epithelium possess distinctive and characteristic membrane structural specialization. Unique rod-shaped intramembrane particles are found in luminal and basal membranes as well as certain intracellular vesicles of this cell type. The consistent finding of two discrete patterns of luminal membrane structural organization supports the possibility that two morphological forms of mitochondria-rich cell exist within the toad bladder epithelium.

Membrane structural and functional responses to vasopressin in toad bladder

Abstract: Freeze-fracture electronmicroscopy demonstrates that vasopressin stimulation of isolated toad bladder results in a striking morphologic alteration of epithelial membrane structure. This alteration is characterized by the aggregation of intramembranous particles in orderly linear arrays at multiple sites in the luminal membranes of granular cells specifically. The size of these aggregates varies considerably, in terms of area, over a range from 0.5 to 70×10−3 μm2. The median aggregate size is about 10.5×10−3 μm2. Since the extent of vasopressin-associated particle aggregation, in terms of frequency of sites per area of membrane or cumulative area of membrane occupied by them, closely correlates with induced changes in transport function, as measured by osmotic water flow, the aggregates themselves appear to be of physiologic significance in the mechanism of action of vasopressin. This hypothesis is supported by the observations that sites of aggregation occur (a) in response to serosal exposure to hormone specifically, (b) independently of an osmotic gradient, and (c) following stimulation with cyclic adenosine monophosphate.

Color discrimination mechanisms in the retina of the toad ( Bufo bufo )

Abstract: In many class 2 ganglion cells in the toad (Bufo bufo) retina the blue-sensitive green rods contribute only to the “on” responses, while the yellow-sensitive cones contribute to both “on” and “off”. Thus the spectral sensitivities of the on and off responses deviate in the blue and violet parts of the spectrum (Fig. 1). This correlates with Dietz's (1972) finding that toads detect a moving blue prey-dummy irrespective of the intensity of the grey background.

Phospholipid composition and [14C]glycerol incorporation into glycerolipids of toad retina and brain.

Abstract: — The phospholipid composition as well as the in vivo [14C]glycerol uptake in lipids was found to be similar in the toad brain and retina. The choroid lipid labeling was markedly different. An in vitro time-course study of [14C]glycerol incorporation in toad retina lipids disclosed that under the conditions of these experiments: (1) retina is able to rapidly synthetize phosphatidic acid from the radioactive precursor; (2) the sequence phosphatidic acid-diacylglycerol-triacylglycerol operates; (3) a high rate of phosphatidylinositol de novo biosynthesis takes place; (4) phosphoglycerides of choline and of ethanolamine are also heavily labeled after a lag period; (5) in vivo labeling profiles resembled those obtained in vitro mainly regarding phosphatidylinositol biosynthesis; and (6) the presence of glycerol kinase in the CNS is suggested.

Insulin stimulates active sodium transport in toad bladder by two mechanisms.

Abstract: INSULIN has been shown to increase sodium and potassium fluxes in a series of tissues including muscle1, and colon2 and the isolated perfused kidney3. Attempts to define the exact mechanisms by which insulin stimulates ion transport in these tissues have been hindered by their anatomical complexity and heterogeneous cell populations. Tracer flux studies, using 22Na, in frog muscle1 and toad bladder4 have suggested a direct stimulatory action of insulin on the sodium pump. Preincubation of intact frog muscle with insulin for 1 h has been shown to increase the amount of ouabain binding by this tissue suggesting that insulin unmasks latent sodium pumps in this structure5. The urinary bladder of the toad (Bufo marinus) has been shown to transport sodium actively from the urinary (mucosal) side to the blood (serosal) side and has been used extensively to study cation transport and the effects and mode of action of numerous hormones and drugs6–8. We have now examined the mechanisms by which insulin increases short circuit current (a measure of active sodium transport) in the toad bladder.

The passive permeability of the skin of anuran amphibia: a comparison of frogs (Rana pipiens) and toads (Bufo marinus).

Abstract: 1. Efflux of Na across dorsal skin, in vitro (bathed on both sides with Ringer solution), of frogs and toads were similar, but it was greater in ventral skin from the latter. 2. The efflux of Na declined, in both species, when the external surface of ventral, but not dorsal, skin was exposed to hyposmotic solutions with a low Na concentration. This change in Na permeability was influenced by the low osmotic concentration as well as the low Na concentration. 3. Efflux of Cl was similar in both the dorsal and ventral skin preparations (Ringer on both sides) from frogs and toads. 4. Chloride efflux declined in all skin preparations exposed on the external surface to dilute Ringer solution. Solute replacement with sucrose or choline or Na2SO4 showed that the decreased Cl efflux was principally due to the low Cl concentration, though Na may also contribute. This observation suggests the presence of Cl-/Cl- exchange diffusion mechanism. 5. Cutaneous urea permeability was less in toads than frogs and the dorsal and ventral skin was similar with respect to this solute in each species. 6. The presence of external hyposmotic solutions reduced the efflux, but not the influx, of urea across frog, but not toad, skin and it appeared that solvent 'drag' may contribute to this change. 7. Diffusion permeability to water was greater in frogs than toads and in the latter the ventral skin was more permeable than the dorsal. 8. The passive permeability of amphibian skin shows considerable interspecific and regional differences to various molecules which do not necessarily parallel each other. The control of passive cutaneous permeability appears to involve a variety of specific mechanisms, the distribution of which may have evolved during their adaptation to different environments.

Study of enzymes regulating vasopressin-stimulated cyclic AMP metabolism in separated mitochondria-rich and granular epithelial cells of toad urinary bladder.

Abstract: The epithelial cells of the toad urinary bladder are morphologically heterogeneous. In order to relate the effect of vasopressin on cyclic AMP metabolism to cell type, the epithelial cells were separated by the density gradient technique of Scott, Sapirstein and Yoder (Science 184: 797, 1974). The separation was verified by electron-microscopy and by observing that the band of cells enriched in mitochondria-rich cells was enriched in carbonic anhydrase activity compared to the band of granular cells. A large portion of the cells collected from the gradient was considered to be nonviable, precluding further study of their function as intact cells. Vasopressin-stimulated adenylate cyclase activity in homogenates of granular cells was similar to that in homogenates of mitochondria-rich cells. Cyclic nucleotide phosphodiesterase activity was also similar in the two types of cell. Thus, the enzymes known to be involved in cyclic AMP metabolism in response to vasopressin appear to be located in both major cell types.

The innervation of the cutaneous artery in the toad Bufo marinus

Abstract: 1. 1. The autonomic innervation of the cutaneous artery of a toad (Bufo marinus) was investigated by techniques of vascular perfusion and by the fluorescence histochemical technique for the demonstration of adrenergic neurons. 2. 2. The cutaneous artery was innervated by excitatory adrenergic nerve fibres originating in the cervical sympathetic connective and running in the pulmonary vago-sympathetic supply. The initial segment of the cutaneous artery was circumscribed by a moderately-dense plexus of catecholamine-containing fibres lying at the outer border of the tunica media. 3. 3. In jointly-perfused pulmonary and cutaneous artery preparations, injected acetylcholine, which caused a marked pulmonary arterial constriction, caused an increase in the proportion of total flow leaving via the initial segment of the cutaneous artery. 4. 4. It was concluded that, since the pulmonary and cutaneous arteries in the toad are to some extent reciprocally innervated, the toad has the capacity to selectively perfuse either the lungs or the skin.

Actions of aldosterone on polyadenylated ribonucleic acid and Na+ transport in the toad bladder.

Abstract: Polyadenylated ribonucleic acid [poly(A)(+)-RNA] has been isolated from the cytoplasm of the epithelium of the urinary bladder of the toad (Bufo marinus) by oligo-(deoxythymidylate)cellulose chromatography. Aldosterone increased the incorporation of [3H]uridine, and of [3H]uridine and [3H]adenosine (given in combination) into 7S, 12S, and 18S poly(A)(+)-RNA during the first 30 min of the action of the hormone, as defined by either a pulse or pulse-chase sequence. The quantity of cytoplasmic poly(A)(+)-RNA that hybridized to [3H]poly(uridine) was also increased by aldosterone. These results are consistent with the inference of induction of messenger RNA synthesis. This effect was most marked during the first 30 min of the action of the hormone.

Motor innervation of the toad iris (Bufo marinus).

Abstract: The sphincter pupillae muscle cells in the iris of Bufo marinus contract autonomously in response to bright light, causing a rapid constriction of the pupil. A strong sympathetic beta-adrenergic inhibition of the sphincter pupillae is apparent in this species. The inhibitory fibers can originate in the second, third, or fourth ventral spinal roots. No strong, consistent excitatory innervation of the toad iris was detected, even by transmural stimulation of the isolated iris. Pupilloconstriction occasionally resulted from stimulation of the 3rd or 5th cranial nerves, but the effect was small (10-20% of the magnitude of the light response) and inconsistent. It therefore appears that the toad must regulate pupillary diameter by balancing myogenic contraction, in direct response to light, against neurogenic (sympathetic) relaxation of the sphincter pupillae.

Actions of aldosterone on rRNA and Na+ transport in the toad bladder.

Abstract: Aldosterone increased methylation by [methyl-3H]methionine of nuclear ribosomal ribonucleic acid (rRNA) sedimenting at 18S, 28S, and 40S within 90 min and of 28S cytoplasmic RNA within 240 min of continuous exposure to the precursor and the hormone, in the toad bladder. In addition, incorporation of [14C]uridine into cytoplasmic 4S transfer RNA, and 18S and 28S rRNA was enhanced after 240 min of continuous exposure to the precursor and the hormone. Aldosterone had minimal effects on the 3H or 14C-labeled, acid-soluble pools. These results suggest that aldosterone augments the synthesis of rRNA at the transcriptional level. Ribosomes isolated 240 min after treatment of the toad bladder with aldosterone showed increased incorporation of [3H]-phenylalanine into peptides with both endogenous messenger RNA (mRNA) and exogenous mRNA (i.e., poly(uridylic acid) in an in vitro assay. Inhibition of reinitiation with NaF or poly (AUG) reduced the rate of amino acid polymerization by 45% but the aldosterone to control ratio remained significantly high. These results imply an increase in active ribosomes and perhaps in endogenous mRNA content. Our findings, however, do not distinguish between a steroid-dependent increase in the total number of active ribosomes and an increase in translational activity per ribosome.

The natural heterohaemagglutinin in the serum of the toad Bufo regularis, and its relationship to lower vertebrate immunoglobulins.

Abstract: The serum of the toad Bufo regularis contains a natural heterohaemagglutinin for human erythrocytes, Which appears to have anti-(B + HP) specificity. Results of inhibition and absorption experiments indicate that only one agglutinin is present. The biochemical specificity of the agglutinin may be provisionally described as involving alpha-D-galactose residues linked (1-3) in the B determinant, of red cells possessing the H ANTIGEN. Unlike amphibian IgM, the agglutinin was insensitive to 2-mercaptoethanol treatment; moreover, it could be eluted from the alpha1 globulin region on cellulose acetate electrophoresis. These results suggest that this naturally occurring heterohaemagglutinin has a structure similar to that of plant and animal lectins. The relationship of this observation to the phylogenetic evolution of immunity is discussed.

Immunochemical investigations on toad (Bufo) eggs: comparative studies on three species (B. bufo, B. viridis, B. calamita).

Abstract: Eggs of three Bufo species (B. bufo, B. viridis and B. calamita) were examined for blood group activity. B. bufo showed distinct A activity, whereas in B. viridis and B. calamita a marked H-activity was observed. These results correspond with the zoological systematic classification of the three toad species tested.

Effect of cadmium on spermatogenesis in toad (Bufo melanostictus).

Abstract: A quantitative study of seminiferous tubules in toad treated with a single subcutaneous injection of cadmium chloride, showed that 7 days after cadmium injection some stages of spermatogenesis consisting of secondary spermatogonia and primary spermatocytes were decreased significantly.

Facilitated transport of urea across the toad gallbladder.

Abstract: The toad gallbladder epithelium is much more selective than that of the rabbit expecially as to the permeability of two molecules like urea and thiourea.

Effects of ethanol on the permeability of toad urinary bladder epithelium.

Abstract: Ethanol (9%) decreases the potential difference across the toad bladder when present at the mucosal surface, the short-circuit current was unchanged. The electrical resistance decreased indicating a change in ion movements across the bladder. Unidirectional 22Na and 36Cl flux measurements showed an increase in the movement of Cl, but no change in Na. The vasopressin-induced increase in Na transport (natriferic response) was also unaffected by the presence of ethanol. It is suggested that ethanol may be altering the apical tight junctions and affecting an anion selective pathway. The hydro-osmotic response of the toad bladder to vasopressin was decreased by 70% in the presence of 3% ethanol. The hydro-osmotic action of cyclic adenosine monophosphate was also inhibited by ethanol, indicating an action subsequent to the endogenous formation of this nucleotide. Tritiated water fluxes (in the absence of an osmotic gradient) were reduced by 30% in the presence of 3% ethanol. The vasopressin-induced increase in diffusional water flow was similarly reduced. Osmotic water movements across glutaraldehyde and N-ethylmaleimide-"fixed" vasopressin-stimulated bladders were also decreased in the presence of ethanol. However, 3% ethanol had no effect on osmotic water transfer across artificial collodion membranes. Ethanol, therefore, probably interacts with the bladder membrane. The Ktrans (permeability coefficient) of ethanol and water is increased by vasopressin. suggesting that their movement is through similar pathways. It is suggested that ethanol empedes the flow of water across the toad bladder by facilitating a physicochemical interaction between the membrane "pore" and the water molecules.

Effect of rapid cooling on toad and guinea pig cardiac muscles.

Abstract: When bathing solution temperature was lowered rapidly to below 5 degrees C, contracture was observed in toad and guinea pig cardiac muscles (Rapid Cooling Contracture, RCC). RCC in toad cardiac muscle was observed even in the presence of TTX and Mn, and enhanced by reducing [Na]o and caffeine. RCC in guinea pig cardiac muscle showed two components; phasic component was dependent on stimulation frequency before cooling, stimulation period, [Ca]o, and [Na]o; tonic component was not dependent on these factors, but was enhanced by reducing [Na]o and in high [K]o solution. From these results, the possible role of Ca ion accumulated at intracellular sequestered sites in cardiac muscle was discussed in relation to excitation-contraction (E-C) coupling.

A simple approach to the toad's ( Bufo melanostictus ) nerver muscle preparation

Abstract: A simple and modified dorsal approach method has been made in the toad's (Bufo melanostictus) sciatic gastrocnemius nerve-muscle preparation. This method incurs less blood loss, time consumption, nerve damage and visceral spoil compared to conventional ventral approach method.

Effect of ethanol on the water permeability and short-circuit current of the urinary bladder of the toad and the response to vasopressin, adenosine-3',5'-monophosphate and theophylline.

Abstract: The effects of ethanol on the water permeability and short-circuit current of the isolated urinary bladder of the toad, Bufo marinus, were investigated. Ethanol alone did not alter the flow of water along an osmotic gradient. The increase in osmotic water flow caused by vasopressin, theophylline or cyclic adenosine-3',5'-monophosphate was inhibited by 4 to 40 mg per ml of ethanol in the mucosal or serosal bathing medium. The inhibition was more marked when ethanol was added to the serosal bathing medium, in spite of the increase in the osmotic gradient across the toad bladder caused by the ethanol. Ethanol had no effect on the increase in sodium transport (short-circuit current) due to vasopressin, although there was a significant inhibition of base-line short-circuit current. It is possible that the water diuresis due to ethanol may result in part from an inhibition of the effect of vasopressin on the collecting duct.

Effect of ascorbic acid on pigmentation of toad (Bufo melanostictus).

Abstract: Administration of ascorbic acid in toad during breeding season results an increase in melanin pigments in skin, liver and vocal sac.