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pressure effects on the adh-induced initiation of water flow in toad bladder.earlier studies employed colchicine to demonstrate the need for microtubules in the adh-induced initiation of increased water permeability in toad bladder. we have used colchicine and hydrostatic pressure together to determine whether formed or growing microtubules are required for initiation of the adh response in bufo marinus. when adh and 8,000 psi were administered simultaneously, the adh-induced increase in water flow was inhibited while under pressure by 107 +/- 7% (n = 6). application of ...19836303132
hydrophobic labeling of (na+,k+)-atpase: further evidence that the beta subunit is embedded in the membrane bilayer.o-hexanoyl-3,5-diiodo-n-(4-azido-2-nitro-phenyl)tyramine has been used after photochemical conversion into the reactive nitrene to label (na+,k+)-atpase from bufo marinus toad kidney. immunochemical evidence indicates that the reagent labels both subunits of the enzyme in partially purified form as well as in microsomal membranes. these results support the view that the glycoprotein subunit, like the catalytic subunit, possesses hydrophobic domains by which it is integrated into the plasma membr ...19836305414
the role of the adrenal gland in control of h+ and nh4+ excretion by toad urinary bladder.the urinary bladder of bufo marinus has been shown to excrete h+ and nh4+ and this excretion is increased by metabolic acidosis. the involvement of the adrenal gland and its steroid secretions in the adaptation for increased acid and ammonia excretion by the bladder was tested during the course of this study. groups of toads were adrenalectomized and maintained in chronic nh4cl-induced acidosis. three other groups of toads were adrenalectomized and put in acidosis but repleted with 2.5 mg/day of ...19836405392
high-pass filtering of small signals by retinal rods. ionic studies.the high-pass filtering of small signals by the rod photoreceptor network was studied by intracellular recording in the isolated, perfused retina of the toad, bufo marinus. data were analyzed and interpreted in terms of the network analysis described in the preceding paper. external concentrations of cs+ as high as 10 mm, which blocked the relaxation from peak to plateau of the rod's response to bright light, did not affect the filtering of small signals. the effects of reducing [na+]o were not ...19836404324
high-pass filtering of small signals by the rod network in the retina of the toad, bufo marinus.the electrical spread of excitation in the network of rod photoreceptors was studied by intracellular recording in the isolated, perfused retina of the toad, bufo marinus. experiments with dim, bar-shaped flashes of light revealed that the rod network behaves as a high-pass filter to laterally propagating small signals. such a behavior had been found earlier in the turtle (detwiler et al., 1980). three electrical equivalent circuit models that can explain this behavior were considered and analyt ...19836404323
distribution of alpha-actinin in single isolated smooth muscle cells.in order to probe the organization of the contractile machinery in smooth muscle, we have studied the distribution of alpha-actinin, a protein present in high concentration in dense bodies, structures apparently analogous to the z-disks of striated muscle. localization of alpha-actinin in single isolated smooth muscle cells of the stomach muscularis of bufo marinus was determined by analysis of the pattern of anti-alpha-actinin staining in single fluorescence photomicrographs, stereo pair microg ...19836403554
h-excretion: a program for microcomputers to aid in calculation of acid or base excretion.h-excretion is a program written in basic language for microcomputers and designed to facilitate the calculation of excretion for acid or base from a tissue into the surrounding media. the program is designed in such a way to allow considerable variability in different experimental parameters. five examples of calculation of h+ excretion in the urinary bladder of the toad bufo marinus are presented.20146406137
effects of maintained illumination upon [k+]0 in the subretinal space of the isolated retina of the toad.illumination of the vertebrate retina evokes a transient decrease in extracellular potassium concentration, [k+]0, in the subretinal space. during maintained illumination, [k+]0 recovers toward its dark-adapted level. the mechanisms most likely to contribute to this recovery process were examined by using k+-selective microelectrodes to measure [k+]0 in the isolated retina of the toad. bufo marinus. although both diffusion of k+ and changes in the rod membrane voltage contribute to the recovery ...19836419461
atp causes a structural change in retinal rod outer segments: disc swelling is not involved.mg2+-atp was found to produce a 15 to 30% drop in the turbidity of suspensions of broken retinal rod outer segments from the toad bufo marinus, prepared by washing or flotation in sucrose. this in vitro process has a half-time of about two minutes and appears to be irreversible. it is not affected by the bleaching of rhodopsin. direct measurements show that the drop in turbidity is not due to swelling of the disc internal space measured in outer segments recovered by centrifugation. instead, the ...19836410075
innervation of the renal vasculature of the toad (bufo marinus).the innervation of the dorsal aorta and renal vasculature in the toad (bufo marinus) has been studied with both fluorescence and ultrastructural histochemistry. the innervation consists primarily of a dense plexus of adrenergic nerves associated with all levels of the preglomerular vasculature. non-adrenergic nerves are occasionally found in the renal artery, and even more rarely near the afferent arterioles. many of the adrenergic nerve profiles in the dorsal aorta and renal vasculature are dis ...19836406069
peptide-containing nerves in the urinary bladder of the toad, bufo marinus.the distributions of peptide-containing nerves in the urinary bladder of the toad, bufo marinus, were studied by means of fluorescence immunohistochemistry of whole-mount preparations. the bundles of smooth muscle in the bladder are well supplied by varicose nerve fibres displaying somatostatin-like immunoreactivity; these fibres probably arise from intrinsic perikarya. the urinary bladder also has a well-developed plexus of nerves containing substance p-like immunoreactive material; these eleme ...19836187467
a pharmacological and ultrastructural study of alveolar contractile tissue in toad (bu fo marinus) lung.the structure of the wall of the lung from the toad (bufo marinus) has been examined using scanning and transmission electron microscopy and the presence of smooth muscle cells in the septal-alveolar walls detected. responses of toad isolated lung parenchyma strip to agonists causing relaxation and contraction were measured and the potencies of adrenoceptor and 5-hydroxytryptamine receptor antagonists were determined. results indicated the presence of populations of alpha- and beta-adrenoceptors ...19836138202
cellular and membrane events involved in the k-induced increase in water permeability of toad skin.exposure of the inner surface of toad skin (bufo marinus) to high [k+] resulted in a marked (up to 7-fold) increase in water permeability (pf) that was more marked in kc1-ringer than in k2so4-ringer. although high [k+] did not elicit a maximal increase in pf, it blunted the hydrosmotic responses to vasopressin, isoproterenol and camp. both "post-camp" inhibitors of stimulated water flow, such as diamide and vanadate, and "pre-camp" inhibitors, such as methohexital and propranolol, markedly reduc ...19826817296
surfaces of rod photoreceptor disk membranes: integral membrane components.the membrane surfaces within the rod outer segment of the toad, bufo marinus, were exposed by rapid-freezing followed by freeze-fracture and deep-etching. platinum-carbon replicas of disk membranes prepared in this way demonstrate a distinct sidedness. the membrane surface that faces the lumen of the disk shows a fine granularity; particles of approximately 6 nm are packed at a density of approximately 30,000/micron 2. these dimensions suggest that the particles represent protrusions of the inte ...19826815210
light-dependent ion influx into toad photoreceptors.to measure the influx of na+ and other ions through the light-dependent permeability of photoreceptors, we superfused the isolated retina of the toad, bufo marinus, with a low-ca2+ (10(-8) m), low-cl- ringer's solution containing 0.5 mm ouabain. under these conditions, the membrane potential of the rod is near zero and there is no light-induced potential change either in the rod or in more proximal neurons. the photoreceptors, however, continue to show a light-dependent increase in membrane resi ...19826183392
the effects of sodium replacement on the responses of toad rods.1. we have investigated the effects of na(+) substitution on the membrane potential and light responses of rods in the superfused retina of the toad, bufo marinus.2. when all of the na(+) in the ringer was replaced with li(+), the effects on the rods depended upon the external free ca(2+) concentration ([ca(2+)](o)). at [ca(2+)](o) >/= 10(-6) m, the membrane potential (e(m)) hyperpolarized and light responses were greatly diminished or abolished. at [ca(2+)](o) </= 10(-7) m, li(+) replacement ha ...19826816920
the effects of low calcium and background light on the sensitivity of toad rods.1. we have examined the effects of decreases in extracellular ca(2+) concentration on the intracellularly recorded light responses of rods from the toad, bufo marinus. in agreement with previous results (brown & pinto, 1974; lipton, ostroy & dowling, 1977), ca(2+) concentrations below 10(-6) m produced a depolarization of rod resting membrane potential of approximately 30-40 mv and a corresponding increase in the maximum amplitude of the rod's light responses, so that saturating flashes in norma ...19826816919
pharmacological experiments demonstrate that toad (bufo marinus) atrial beta-adrenoceptors are not identical with mammalian beta 2- or beta 1-adrenoceptors.chronotropic responses to sympathomimetic amines of isolated atrial preparations from toads (bufo marinus) were mediated by beta-adrenoceptors since isoprenaline was more potent than adrenaline and noradrenaline, and propranolol was a potent antagonist (pa2, adrenaline as agonist = 9.33). the beta-adrenoceptors had some of the characteristics of mammalian beta 2-adrenoceptors in that (i) adrenaline was more potent than noradrenaline and (ii) the pa2 values of two selection beta-adrenoceptor anta ...19826127586
how toads breathe: control of air flow to and from the lungs by the nares in bufo marinus.the external nares rarely close completely during positive pressure lung filling in bufo marinus. simultaneous measurement of airflow at the nares and transnarial pressure revealed continuous airflow (out) during lung emptying (nares open) and the subsequent lung filling (nares partially closed). expiratory minute volume (ve) measured at the nares is consistently greater than ve from the lungs because the buccal contents are being simultaneously forced into the lungs and out the partially closed ...19826815751
osmotic water flow across the abdominal skin of the toad bufo marinus: effect of vasopressin and isoprenaline.1. net water flow j(w), was measured across the abdominal skin of the toad bufo marinus with a volumetric, automatic technique that allows for averaging j(w) over time intervals as short as 1 sec.2. basal j(w) was very stable and corresponded to a coefficient of osmotic flow, l(pd), of ca. 15 x 10(-7) cm sec(-1) atm(-1) (or to an osmotic water permeability coefficient, p(f), of 20 mum sec(-1)).3. both vasopressin and the beta-adrenergic agonist, isoprenaline, triggered high hydrosmotic responses ...19826815322
bicarbonate reabsorption and potassium handling in isolated perfused kidneys of bufo marinus.average rates of bicarbonate reabsorption, normalized for glomerular filtration rates, rose linearly with perfusate [hco3-] of 6-21 mm with a constant bicarbonate/creatinine clearance ratio of 0.06, similar to the in vivo value. maximal rates of bicarbonate reabsorption occurred at 20-25 mm hco3- perfusate. at 3 mm perfusate [k+], normalized rates of potassium reabsorption were constant from filtered perfusates mimicking metabolic acidosis, and from control perfusates; during perfusion with alka ...19826807105
renal electrolyte handling, acid-base status, and urinary acidification in bufo marinus.in hydrated toads reabsorption of 92% of filtered bicarbonate produces a urine of ph at 22 degrees c. average blood-to-urine ph gradient is 0.8-0.9 u under these conditions but may reach 3-4 u. net acid excretion rate in hydrated animals is approximately 30 mu eq . h-1 . kg-1. flow-independent acid excretion is a negative nonlinear function of urinary ph and passes from positive to negative values in the range of normal urinary ph due to rapid rise in [hco3-] and slower decline in [nh4+]. [h2po4 ...19826807104
modulation of vasopressin action by reducing agents in bufo marinus.the effects of the reducing agent dithiothreitol (dtt) on vasopressin (avp)-stimulated osmotic water flow and adenylate cyclase activity were studied in the urinary bladder of bufo marinus. dtt produced concentration-dependent inhibition of the hydroosmotic water permeability response to 10 mu/ml avp and 10 mm theophylline but did not inhibit the response to 10 mm adenosine 3',5'-cyclic monophosphate (camp). the inhibitory effects of dtt on avp responsiveness were partially reversed by washing i ...19826283908
the effects of indomethacin and prostaglandin e2 (pge2) on acetylcholine-initiated contractions of gastric muscularis muscle of bufo marinus.we have investigated the effects of indomethacin, a potent prostaglandin synthesis inhibitor, and pge2 on the acetylcholine-initiated contractions of isolated gastric muscularis muscle of bufo marinus. two types of contractions were identified: initial contraction observed on challenging the preparation with acetylcholine (ach) and, spontaneous contractions which persisted after the initial contraction. the challenging dose of ach (2.5 x 10(-5) m) was fixed at the level eliciting optimum contrac ...19826810777
light-dependent effects of a hydrolysis-resistant analog of gtp on rod photoresponses in the toad retina.responses to 100-ms flashes were recorded intracellularly from dark- and light-adapted rod photoreceptors in the isolated retina of the toad, bufo marinus. properties of photoresponses were analyzed under each condition of adaptation when retinas were superfused with 1.0 mm guanosine 5'-[beta, gamma-methylene]triphosphate (p[ch2]ppg), a hydrolysis-resistant analog od gtp. when applied to retinas that previously had been subjected to intense light (approximately 30% bleach), p[ch2]ppg increased b ...19826806815
the effects of hypercapnia on intracellular and extracellular acid-base status in the toad bufo marinus.toads (bufo marinus) were exposed to environmental hypercapnia of 5% co2 in air, and extracellular and intracellular acid-base parameters were determined 1 and 24 h after the onset of hypercapnia. the initial drop in ph was compensated by the elevation of extracellular and intracellular bicarbonate. relating the ph compensation to the ph drop that is expected to occur by increased pco2 at constant bicarbonate concentration, the ph compensation in the extracellular space was 30% and reached the f ...19826806427
functional morphology of lingual protrusion in marine toads (bufo marinus).bufo marinus catches its prey by stiffening the intrinsic muscles of the tongue, rapidly flipping the tongue out of the mouth. high-speed cinematography synchronized with computer-analyzed electromyograms (emgs)shows that during the flip the tongue is supported by the m. genioglossus medialis and that this muscle stiffens into a rod when stimulated. coincident stiffening of the transversely arranged m. genioglossus basalis provides a wedge under the anterior tip of this rod. stiffening of the m. ...19826807077
reversal of copper-induced inhibition of vasopressin responsiveness by reducing agents.copper inhibits the hydro-osmotic response to vasopressin in the urinary bladder of bufo marinus at a site proximal to cyclic amp production. this effect is not reversed by washing in cu2+ -free ringer's solution but is overcome by serosal addition of reducing agents, suggesting that vasopressin responsiveness in this tissue is modulated by either the redox potential or the sulfhydryl content of the serosal membrane.19826277380
[ultrastructural identification of fiber types in the skeletal muscles of the toad bufo marinus]. 19826821293
an investigation of the allosteric functioning of the haemoglobin of the cane toad, bufo marinus.1. cane toad haemoglobin shows co-operative equilibrium co binding at ph 7.0 with n = 2.6. 2. flash photolysis studies show that at high ph the r form of the protein is stabilised whilst low ph and the presence of ihp favours the t form. 3. the combination of stopped-flow and flash photolysis measurements allows estimation of the association and dissociation rates of co binding for the two forms of the protein. 4. the protein functioning can be described by a modified two state model and mathema ...19826817967
behavior of unreduced polymeric and monomdric immunoglobulins in sodium dodecyl sulfate-polyacrylamide gel electrophoresis.investigation of the electrophoretic behavior, in sds-polyacrylamide and sds-polyacrylamide-agarose gels, of igms and low mol. wt. igs from four classes of vertebrates, as well as fragments derived from them, was carried out. a clear but unexpected straight-line relationship was observed for all igs (and fragments) tested when relative mobility was plotted against log mol. wt for the unreduced molecules. aberrant behavior of the low mol. wt ig of bufo marinus was shown to be due to the complete ...19826804792
the influence of verapamil on the amplitude and frequency of cholinergic-initiated contractions of isolated gastric muscularis muscle of bufo marinus.in order to elucidate the role of ca2+ in the acetylcholine-initiated amplitude and frequency of spontaneous contractions of isolated circular muscle strips from bufo marinus stomach, we investigated the effects of omission of ca2+ in the nutrient fluid and also the influence of verapamil, a calcium antagonist, on the amplitude and frequency of the initiated spontaneous contractions. the gastric muscularis muscle strips were prepared and mounted in an organ bath. the control preparation was chal ...19826803261
preparation of individual smooth muscle cells from the stomach of bufo marinus. 19826289042
effect of monensin on osmotic water flow across the toad bladder and its stimulation by vasopressin and cyclic amp.the effects of the sodium ionophore monensin on osmotic water flow across the urinary bladder of the toad bufo marinus were studied. monensin alone did not alter osmotic water flow; however, the ionophore inhibited the hydrosmotic response to vasopressin and cyclic amp in a dose-dependent manner. the inhibitory effects of monensin were apparent when the ionophore was added to th serosal bathing solution but not when it was added to the mucosal bathing solution. the inhibitory effect of serosal m ...19826284944
aldosterone control of the density of sodium channels in the toad urinary bladder.near-instantaneous current-voltage relationships and shot-noise analysis of amiloride-induced current fluctuations were used to estimate apical membrane permeability to na (pna), intraepithelial na activity (nac), single-channel na currents (i) and the number of open (conducting) apical na channels (n0), in the urinary bladder of the toad (bufo marinus). to facilitate voltage-clamping of the apical membrane, the serosal plasma membranes were depolarized by substitution of a high kcl (85 mm) sucr ...19826276550
the role of sodium-channel density in the natriferic response of the toad urinary bladder to an antidiuretic hormone.urinary bladders of bufo marinus were depolarized, by raising the serosal k concentration, to facilitate voltage-clamping of the apical membrane. passive na transport across the apical membrane was then studied with near-instantaneous current-voltage curves obtained before and after eliciting a natriferic response with oxytocin. fitting with the constant-field equation showed that the natriferic effect is accounted for by an increase in the apical na permeability. it is accompanied by a small in ...19826276549
somatostatin is contained in and released from cholinergic nerves in the heart of the toad bufo marinus.the heart of the toad bufo marinus contained a substance with somatostatin-like immunoreactivity which eluted with somatostatin on reverse phase high pressure liquid chromatography. immunoreactivity to somatostatin was localised histochemically to nerve fibers in muscle bundles of the sinus venosus, atria and ventricles and to nerve cell bodies in the sinus venosus and inter-atrial septum. nerve cell bodies were localised both by interference contrast microscopy and immunohistochemistry; all det ...19826128695
immunochemical evidence for a transmembrane orientation of both the (na+, k+)-atpase subunits.antibodies were raised against the large catalytic subunit (apparent mr 96000) and the glycoprotein (apparent mr 60000) of the sodium- and potassium-dependent adenosine triphosphatase [(na+, k+)-atpase] from bufo marinus. the specificity of each antiserum was assessed by two-dimensional immunoelectrophoresis using toad kidney microsomes or the purified holoenzyme as a source of antigen and by indirect immunoprecipitation of detergent-solubilized (na+, k+)-atpase subunits from radioiodinated or b ...19816272846
transient phosphorylation by atp of a 160 000 dalton protein in rod outer segments of bufo marinus.radioactive phosphate was incorporated from (gamma-32p] atp into a 160 000 dalton protein from preparations of highly purified toad retinal rod outer segment membranes. maximal incorporation occurred at 1 microm atp, and turnover in the presence of nonradioactive substrate was rapid, showing that the 160 kdalton protein catalyzes atp hydrolysis. the 160 kdalton intermediate was sensitive to hydroxylamine, suggesting an acyl linkage between the protein and phosphate. ionic requirements for phosph ...19816796119
baroreceptor control of heart rate in the conscious toad bufo marinus.perivascular balloons were used to elicit heart rate (hr) responses to imposed changes in mean arterial pressure (pa) in conscious unrestrained toads (bufo marinus). it is clear that functional baroreceptors lie in the pulmocutaneous arteries of b. marinus, and that these can elicit compensatory heart rate responses to perturbations of blood pressure. functional baroreceptors were not present in the carotid circulation and are probably absent from the lateral aortae and conus arteriosus as well. ...19816795941
alpha-aminoisobutyric acid efflux from the cornea of the toad, bufo marinus.1. amino acids move into and out of the amphibian cornea across its inner aqueous, side only. most alpha-aminoisobutyric acid (aib) accumulation takes place in the corneal epithelium; the endothelium and stroma do not limit exchanges with these cells. the apical, or tear, surface of the epithelium is an impermeable barrier to the transport of amino acids. there are several sites or mechanisms by which aib enters and leaves the cornea. 2. the entry of aib is not na-dependent; however, the exit si ...19816796676
comparisons of the neurotoxic activity of the venom of several species of funnel web spiders (atrax).a bioassay has been developed to allow comparison of the neurotoxic activity of the venom of individuals of the four most common species of funnel web spiders (atrax species). in the absence of purified atrax neurotoxin, the stimulatory action of the venom on skeletal muscle from the cane toad, bufo marinus, was compared with that of known concentrations of acetylcholine. several experiments to validate the assay were performed, then venom samples from both male and female spiders were assayed. ...19816794556
vasopressin-elicited refractoriness of the response to vasopressin in toad urinary bladder.incubation of the urinary bladder of bufo marinus with high concentrations of vasopressin produces refractoriness to subsequent stimulation of water permeability by low concentrations of vasopressin. development of refractoriness is directly dependent on concentration of vasopressin and duration of incubation with the hormone. refractoriness develops in the absence of transepithelial water flow, is evident following a 2-h recovery period of incubation in hormone-free ringer solution, and is reve ...19816264797
interactions among rods in the isolated retina of bufo marinus.1. the existence and extent of interactions among rods were analysed in the isolated retina of bufo marinus. intracellular recordings were made from the outer segments with micropipettes. stimuli of precisely measured geometry were delivered to the outer segments using a compound microscope. 2. to demonstrate the existence of interactions two rods were simultaneously impaled; current injected into one rod resulted in a current-induced potential of like sign in the other rod. 3. when the diameter ...19816796672
inhibition of alpha-aminoisobutyric acid uptake by diisothiocyanostilbenedisulphonic acid in the amphibian cornea.alpha-aminoisobutyric acid accumulation of the toad's (bufo marinus) cornea and lens is inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid. this effect is seen at ph 8.4; at ph 7.4 a small increase in aminoisobutyric acid uptake was observed. efflux of aminoisobutyric acid is unchanged by diisothiocyanostilbenedisulphonic acid at either ph. the inhibitory effect of diisothiocyanostilbenedisulphonic acid on aminoisobutyric acid accumulation appears to reflect a direct action on membran ...19816786350
geographical patterns of genetic variability in introduced australian populations of the marine toad, bufo marinus: sorbitol dehydrogenase, sdh.athe marine toad, bufo marinus, was introduced to australia from hawaii in 1935. from 1935 to 1974, the toad population expanded exponentially to occupy 584,000 km(2), and now has a continuous distribution from cape york to tweed river on the eastern coast of the continent. genetic analysis of the population indicates a difference in allele frequency at the sorbitol dehydrogenase locus. there are two alleles segregating at the locus (nad-sdha and nad-sdhb). the nad-sdhaa homozygote is common in ...19816788038
changes in axonally transported proteins during axon regeneration in toad retinal ganglion cells.in an effort to understand the regulation of the transition of a mature neuron to the growth, or regenerating, state we have analyzed the composition of the axonally transported proteins in the retinal ganglion cells of the toad bufo marinus after inducing axon regeneration by crushing the optic nerve. at increasing intervals after axotomy, we labeled the retinal ganglion cells with [35s]methionine and subsequently analyzed the labeled transported polypeptides in the crushed optic nerve by means ...19816164682
[ultrastructural study of a parasite from bufo marinus called toxoplasma serpai]. 19816821352
fine structure of the gastric mucous and endocrine cells of the toad, bufo marinus.the ultrastructure of the mucous and endocrine cells of the gastric mucosa of the cane toad (bufo marinus) has been examined. surface mucous cells line the entire gastric mucosa and pits. many of their secretory granules contain an electro-dense core that remains unreactive after cytochemical testing for glycoproteins. a second spatially and structurally discrete population of mucous cells is present in the gastric glands. these glandular mucous cells are probably homologous with the antral glan ...19816790174
seasonal changes in testes and thumb pads of the toad, bufo marinus (linn.) and their correlation with fluctuations in the environmental factors.in present studies, the slow rate of spermatogenetic activity and regressed condition of leydig cells have been correlated with declining day length and ambient temperature during winter months (november--february). the gradual enhancement of the spermatogenetic activity and increase in the number and nuclear diameter of leydig cells from march to june have been associated with increasing day length and ambient temperature. during july and august, the process of spermiation has been associated w ...19816789712
structure and function of ciliated peritoneal funnels in the toad kidney (bufo marinus).scanning electron microscopy revealed 600-800 ciliated peritoneal funnels opening onto the ventral surface of each kidney in bufo marinus. the size and configuration of funnel apertures vary greatly, but individuals course beneath the kidney surface before opening into peritubular blood vessels. injections of india ink into the peritoneal cavity demonstrate that cilia lining the peritoneal funnels create a current carrying peritoneal fluid into the renal vasculature. clearance of fluid by the fu ...19816788375
conversion of thyroxine to triiodothyronine in an adult amphibian, bufo marinus. 19816783472
illumination dependent hyperpolarization of the photoreceptor outer segment membrane (role of calcium, cyclic gmp and calmodulin).calmodulin has been isolated from the outer segment of toad (bufo marinus) photoreceptors. bioelectric processes have been recorded from the same preparation during various experimental conditions. the results led to the conclusion that during illumination the rotation of the chemoreceptors opens the ca channels, and free ca is versed into the intermembrane space of the outer segment. changes of this free ca concentrations depend on fast influx and slower removal (mainly dependent on ca binding ...19816273352
current-voltage analysis of apical sodium transport in toad urinary bladder: effects of inhibitors of transport and metabolism.the basal-lateral surface of the epithelium of the urinary bladder of the toad (bufo marinus) was depolarized by exposure of the serosal surface to 85 mm kcl and 50 mm sucrose. the extent of depolarization appeared to be virtually complete, as evaluated by the invariance in the transepithelial electrical potential difference and conductance on addition of nystatin (a monovalent cation ionophore) to the serosal medium. the na-specific current (ina) was defined as the current sensitive to the remo ...19806256553
penetration-induced hyperpolarization as evidence for ca2+ activation of k+ conductance in isolated smooth muscle cells.single smooth muscle cells, freshly isolated by enzymatic digestion of the stomach muscularis of the toad bufo marinus were studied under direct microscopic observation using standard electrophysiological techniques. following penetration with a microelectrode, a hyperpolarization lasting many seconds occurred before the membrane depolarized to a steady-state level. the following lines of evidence indicate that the penetration-induced hyperpolarization results from an increase in k+ conductance ...19806776821
rectifying properties of the membrane of single freshly isolated smooth muscle cells.single smooth muscle cells freshly isolated from the stomach muscularis of the toad bufo marinus were studied under direct microscopic observation using intracellular microelectrodes. the deviation of the membrane potential from rest was recorded when steps of current were injected into the cell. outward-going rectification was consistently observed both in the presence of 1.8 mm and higher external concentrations of ca2+. there was no indication of inward-going rectification even under conditio ...19806776820
calcium action potentials in single freshly isolated smooth muscle cells.the ionic basis of the action potential was investigated using intracellular microelectrodes in single smooth muscle cells freshly isolated from the stomach of the toad bufo marinus. when [ca2+]0 was elevated (> 8mm), action potentials were readily elicited, which had similar characteristics to those found in many tissue preparations of visceral smooth muscle. there was a decrease in membrane resistance at the peak of the action potential and during the undershoot. the following evidence indicat ...19806776819
passive properties of the membrane of single freshly isolated smooth muscle cells.single, smooth muscle cells were isolated from the stomach muscularis of the toad bufo marinus and studied on the same day as isolation using standard electrophysiological techniques and direct microscopic observation at high magnification. following penetration a period of hyperpolarization occurred that appeared to be caused by an increase in k+ conductance activated by ca2+ entering the cell upon penetration. ion substitution studies showed that the stable steady-state resting potential was d ...19806776818
somatostatin: occurrence in urinary bladder epithelium and renal tubules of the toad, bufo marinus.immunohistochemical techniques were used to detect immunoreactive somatostatin-like material in toad urinary bladder epithelium and in kidney distal tubules and collecting ducts. this material has immunological and chromatographic properties identical to those of synthetic cyclic somatostatin. the occurrence of somatostatin-like material in antidiuretic hormone-sensitive portions of the renal urinary system suggests a local regulatory or paracrine role for somatostatin.19806107992
inhibition by amiloride of 22na+ transport into toad bladder microsomes.the diuretic, amiloride, inhibited 22na+ accumulation by microsomes from toad (bufo marinus) bladder by between 40 and 70%. accumulated 22na+ was separated from free isotope by ion-exchange chromatography. the amiloride-sensitive process was directly proportional to the protein concentration and a hyperbolic function of the na+ concentration. the inhibition was competitive. at least 9 times more activity was found in the microsomal fraction than the mitochondrial fraction, and none at all was fo ...19806773576
effects of saline exposure on the response of toad bladder (bufo marinus) to aldosterone.1. the short-circuit current response of toad bladders to high concentrations of aldosterone (2 x 10(-7) m) has been investigated following saline exposure of toads. 2. limited saline exposure appears to enhance the aldosterone-stimulated response. 3. additional saline exposure results in a reduced aldosterone response. 4. overnight pre-incubation of isolated bladders proved a better pretreatment condition for study of an aldosterone short-circuit current response. 5. plasma aldosterone concentr ...19806772236
inhibitory action of dids on chloride transport across the amphibian cornea.1. dids (4,4'-diisothiocyano-2,2'-stilbene disulphonic acid) reduced the ci isc across the toad's (bufo marinus) cornea. it acted on either the aqueous or tear side and these effects were additive. 2. the reduction in the isc was equivalent to the decline in the undirectional flux of cl from the aqueous to the tear side. the cl flux from tear to aqueous was not changed. 3. dids did not change transmural na transport. 4. the action of the diuretic bumetanide, which also inhibits cl transport was ...19806777484
effects of clofibrate on water permeability and short-cicuit current of toad urinary bladder.the effects of the oral antidiuretic drug clofibrate on water permeability of the urinary bladder of the toad, bufo marinus, were studied. clofibrate did not alter control water flow along an osmotic gradient. water flow increases due to vasopressin were reversibly inhibited by 1 to 10 mm clofibrate from the serosal side. clofibrate in the serosal bathing medium inhibited water flow increases due to cyclic amp but not due to theophylline. serosal clofibrate concentrations less than 1 mm or clofi ...19806248630
solubilization of an active opiate receptor from bufo marinus. 19806248353
the effects of tetraethylammonium and cobalt ions on responses to extrinsic current in toad rods.1. double-barrel micropipettes were used to pass pulses of current in darkness into single rods in the isolated, perfused retina of the toad, bufo marinus. 2. in normal ringer solution, current pulses evoked non-linear changes in membrane potential which varied as a function of current amplitude and of time. responses to currents of both polarities showed slow relaxations toward the base line during the pulse, and the steady-state i-v curve exhibited a prominent outward rectification. 3. in ring ...19806776263
calcium spikes in toad rods.1. when the retina of the toad, bufo marinus, was superfused with 6-12 mm-tetraethylammonium chloride (tea), intracellular recordings from rods showed large, depolarizing regenerative potentials. for brief exposures to tea, these potentials occurred during the recovery phase of the light responses; whereas, during longer exposures, they were spontaneous in darkness but suppressed during illumination. similar regenerative potentials were observed during perfusion with 3-10 mm-4-aminopyridine and ...19806776262
structure and function of the undulating membrane in spermatozoan propulsion in the toad bufo marinus.accessory fibers in most sperm surround the axoneme so that their function in propulsion is difficult to assess. in the sperm of the toad bufo marinus, an accessory fiber is displaced from the axoneme, being connected to it by the thin undulating membrane in such a way that the movement of axoneme and accessory fiber can be viewed independently. the axoneme is highly convoluted in whole mounts, and the axial fiber is straight. cinemicrographic analysis shows that it is the longer, flexuous fiber ...19806771299
mechanism of action of aldosterone on active sodium transport across toad skin.epithelium of the abdominal skin of the toad, bufo marinus, has been studied by microelectrode impalement. using an electrical equivalent circuit model, effective emf's and specific conductances of the apical and basolateral membrane could be calculated. the skin was divided into 2 fragments for incubation in the presence, or not, of aldosterone (greater than or equal to 0.1 microm). after incubation overnight, sodium transport by the hormone-treated piece was increased 2.7-fold on average, comp ...19806250128
the relative time course of early changes in mitochondrial function and intracellular ph during hypoxia in the isolated toad ventricle strip.changes in the intracellular h+ ion concentration (phi) and in the oxidation-reduction state of the respiratory chain were measured spectrophotometrically in the isolated ventricle strip from the toad (bufo marinus). the relative time course of the delta phi as indicated by changes in light absorption of the ph dye neutral red, cytochrome c, and peak isometric twitch tension were compared during transient hypoxic episodes. the first detectable change in ph occurred 4.5 minutes after the peak twi ...19806247079
endothelial cells in the oral mucosa of bufo marinus.the oral mucosa of the cane toad (bufo marinus) is lined by a pseudostratified columnar ciliated epithelium containing an intraepithelial network of capillaries, which penetrates it to the bases of the distal layer of cells. the capillaries are lined by fenestrated endothelium lying on a complete basal lamina. a connective tissue sheath, approximately 1 micrometer thick, surrounds the capillaries and separates them from the surrounding epithelial cells. endothelial cells resemble those in lympha ...19806773911
test for effects of visual and position cues on t-maze learning in toads.this research was concerned with the effects of different classes of cues on the ability of toads (bufo marinus) to learn an escape task, discrimination learning, in a t-maze. the cues were either a black or white brightness cue, a right or left position cue, or combinations of brightness and position cues. the toads were given a .6-a shock until they made the correct response. results suggested that toads are capable of learning a discrimination task based on either a position or brightness cue ...19806769097
transneuronal transport in the visual system of the toad, bufo marinus.secondary optic projections were studied in the toad, bufo marinus using the method of transneuronal transport of triated proline and fucose. following a survival of 14 days after eye injection autoradiographic label was transported transneuronally to the contralateral nucleus isthmi, the deeper layers of the contralateral tectum, the pontine region, the ipsilateral tectum and to the contralateral thalamus. toads which survived 21 days or longer exhibited transneuronal transport of isotope to th ...19806820480
the effects of enforced activity on ventilation, circulation and blood acid-base balance in the semi-terrestrial anuran, bufo marinus.strenuous exercise results in a marked blood acid-base disturbance which is accompanied by large increases in ventilation rate, heart rate and mean arterial blood pressure. recovery to normal resting values follows an exponential time course with a half-time of approximately 2 h for all parameters except pa, co2 and ventilation rate. the latter return to normal by 30 min following the exercise period. analysis reveals that there is initially a large discrepancy between the quantity of metabolic ...19806767803
the ultrastructural characteristics of the apical cell in the neuroepithelial bodies of the toad lung (bufo marinus).the cytological features and membrane specialisations of neuroepithelial cells (apical cells) in direct contact with the lumen of the lung were studied with transmission and scanning electron microscopy. the luminal surface of the apical cell is characterised by microvilli, a cilium with an 8 + 1 microtubular pattern and numerous coated vesicles. the cytoplasmic region immediately beneath the luminal plasma membrane contains numerous smooth-walled vesicles, tubules and microtubules, a few microf ...19806773663
decreased sensitivity to amiloride of amphibian epithelia treated with aldosterone. further evidence for an apical hormonal effect.the reversible inhibition of transepithelial sodium transport achieved with amiloride (and triamterene) was evaluated in amphibian preparations stimulated with aldosterone so as to provide further information regarding a possible influence of this hormone on the apical border of target cells. when aldosterone secretion was enhanced by withdrawal of sodium from toad (bufo marinus) habitat, sensitivity of abdominal skin to amiloride decreased; the same occurred in skin and bladder preparations inc ...19806770338
prostacyclin stimulates short circuit current in the isolated toad (bufo marinus) urinary bladder. 19806769307
light adaptation in toad rods: requirement for an internal messenger which is not calcium.1. the mechanism of light adaptation was investigated by recording intracellularly from single rods in the isolated, superfused retina of the toad, bufo marinus. steady background lights produce decreases in rod sensitivity and changes in response wave form similar to those previously observed in the toad eyecup. 2. the sensitivity of a dark-adapted rod is halved by a background light which bleaches about 4 rhodopsins per rod per second. since a toad rod contains over 2000 disks, a rhodopsin ble ...1979119846
effects of the rod receptor potential upon retinal extracellular potassium concentration.it has been hypothesized that the light-evoked rod hyperpolarization (the receptor potential) initiates the light-evoked decrease in extracellular potassium ion concentration, [k+]o, in the distal retina. the hypothesis was tested using the isolated, superfused retina of the toad, bufo marinus; the receptor potential was recorded intracellularly from red rods, and [k+]o was measured in the photoreceptor layer with k+-specific microelectrodes. in support of the hypothesis, variations in stimulus ...1979119827
acid-base relationships in the blood of the toad, bufo marinus. iii. the effects of burrowing.when bufo marinus burrows, the skin becomes intimately surrounded by substrate but the nares always remain exposed to the surface air. upon entering into a state of dormancy the animal hypoventilates and this together with the loss of the skin as a respiratory site results in a rise in arterial blood pco2 despite a probable decline in metabolism. even though lung ventilation falls, the toad regulates blood ph and the respiratory acidosis is progressively compensated for by a progressive increase ...197911799692
acid-base relationships in the blood of the toad, bufo marinus. ii. the effects of dehydration.cutaneous co2 excretion is reduced as the skin dries during dehydration but an increase in breath frequency acts to regulate the arterial blood pco2 and thus pha. moreover, the toad does not urinate and water is reabsorbed from the bladder to replace that lost by evaporation at the skin and lung surfaces. the animal does, however, produce a very acid bladder urine to conserve circulating levels of plasma [hco3-] and this together with an increased ventilation effectively maintains the blood acid ...197911799690
acid-base relationships in the blood of the toad, bufo marinus. i. the effects of environmental co2.an abrupt increase in ambient co2 resulted in a marked respiratory acidosis which took place within 30 min. during this time there was a considerable reduction in the pco2 difference between arterial blood and inspired gas caused by an increase in ventilations. prolonged co2 exposure (24 h) showed that there was some compensation for the acidosis in that plasma bicarbonate concentrations increased substantially. at the same time, however, the pco2 of arterial blood always rose so that the net re ...197911799689
transepithelial current-voltage relationships of toad urinary bladder and colon. estimates of enaa and shunt resistance.studies were done to investigate the transepithelial current-voltage (it-vt) relationships of urinary bladder and colon of the toad bufo marinus. like several other na transporting epithelia, the it-vt plots characteristically showed a break at voltage e1, averaging near 124 mv for urinary bladder and 110 mv for colon. with bladders treated with antidiuretic hormone, estimates of ena and shunt resistance, rs, were obtained according to a method outlined by yonath and civan, 1971 (j membr. biol. ...1979122255
transient potassium fluxes in toad skin.experiments were carried out in the isolated short-circuited skin of the toad bufo marinus ictericus. 42k influx and efflux experiments were carried out with skins bathed on both sides by nacl-ringer's solution. those fluxes showed very similar kinetics of equilibration with time and the results could be fitted by equations of a model of two intraepithelial compartments and the bathing solutions. in the steady state k influx is 3.99 +/- 0.36 nmol cm-2 hr-1 (n = 7) and efflux 3.62 +/- 0.38 nmol c ...1979114665
effects of mk-771 on the isolated amphibian spinal cord: comparison with thyrotropin-releasing hormone.topically applied mk-771 (pyro-2-aminoadipyl-histidyl-thiazolidine-4-carboxamide), a novel thyrotropin-releasing hormone (trh) analog, was found to be equipotent with trh in depolarizing the ventral roots of the isolated, hemisected amphibian (bufo marinus) spinal cord. the 3-methyl-histidyl analog of trh was approximately 10 times more potent than mk-771 and trh. mk-771 is known to be equiactive with trh in their actions on the pituitary gland. taken together these findings suggest that the pre ...1979115561
interaction of acetylcholine and cholecystokinin with dispersed smooth muscle cells.isolated gastric smooth muscle cells were prepared from the stomach of bufo marinus by successive incubation in collagenase without added trypsin. contraction was determined by image-splitting micrometry and expressed as the mean percentage decrease in cell length from control. peak contractile response was attained within 30 s. dose-response curves constructed from peak responses showed that the maximal responses to cck-op (37.2 +/- 3.8%), acetylcholine (35.3 +/- 2.5%), and ca2+ (42.3 +/- 0.9%) ...1979111564
microfilament-rich cells in the toad bladder epithelium.basal cells of the bladder epithelium of bufo marinus have been found heterogenous and consist of microfilament-rich cells (mfr-cell) and undifferentiated cells (un-cell). the mfr-cell, which represents approximately 20% of the epithelial cell population, lies between the epithelial layer lining the urinary space and the basement membrane; it extends under several epithelial cells by processes of varying widths and lengths which contact, via desmosomes, other mfr-cells, as well as cells in the s ...1979113549
isolation and separation of toad bladder epithelial cells.the epithelium of the urinary bladder of bufo marinus is composed of 5 cell types, i.e., granular (gr), mitochondria-rich (mr) and goblet (g) cells which face the urinary lumen, microfilament-rich (mfr) and undifferentiated cells (un) located basally. the epithelium was dissociated by collagenase and egta treatment. fractionation of dispersed cells by isopycnic centrifugation on dense serum albumin solutions yielded 4 fractions: (i) a very light fraction (p approximately equal to 1.025) enriched ...1979113548
the membrane current of single rod outer segments.1. outer segments of individual rods in the retina of the toad, bufo marinus, were drawn into a glass pipette to record the membrane current. 2. light flashes evoked transient outward currents. the peak response amplitude was related to flash intensity by a michaelis equation with half-saturating intensity about 1 photon mum-2. 3. the saturating response amplitude ranged up to 27 pa and corresponded closely to complete suppression of the steady inward current present in darkness. 4. for a given ...1979112242
toad carbonic anhydrase: purification of the enzyme from erythrocytes of bufo marinus and comparison with the enzyme activity in the urinary bladder.1. two forms of carbonic anhydrase, having isoelectric points of 6.1 and 5.8, were purified from erythrocytes of the toad, bufo marinus, and the presence of a third form, pi = 5.4, was demonstrated. 2. each of the two purified isozymes catalyzed the hydration of co2 and the hydrolysis of nitrophenyl acetate esters at rates characteristic of type c (or high-activity) forms of carbonic anhydrase. 3. both forms of the erythrocyte enzyme have similar molecular weights (approx 29,000), amino acid com ...1979122573
assessment of acetylcholine as an optic nerve neurotransmitter in bufo marinus. 1979114871
binding of aldosterone to cytoplasmic and nuclear receptors of the urinary bladder epithelium of bufo marinus.binding of aldosterone to cytoplasmic and nuclear sites in urinary bladder epithelia of bufo marinus (dominican variant) is saturable and dependent upon steroid concentration. scatchard analysis of specific cytoplasmic binding yielded a maximal binding capacity (n) of 14.5 x 10(-14) mol/mg protein and an apparent equilibrium dissociation constant (kd) of 1.4 x 10(-8) m. since scatchard analysis of specific nuclear binding was complex, this binding was resolved by a computer-generated cirve-fitti ...1978211852
evidence for pulmonary vasoconstriction during hypercapnia in the toad bufo marinus. 197899220
renal vascular anatomy of the toad (bufo marinus).the renal vasculature of the toad, bufo marinus, was studied mainly by means of scanning electron microscopy of vascular corrosion casts. all arterial branches terminated in a glomerulus. each glomerulus was supplied by only one afferent arteriole. no shunts between afferent and efferent arterioles were observed. the glomerular channels appeared to be permanent capillaries. no evidence supporting the theory of freely shifting glomerular blood channels was found. efferent arterioles radiated out ...1978418878
lack of protection against oxygen toxicity by in vivo protective agents in the isolated toad bladder.agents which protect against the development of oxygen toxicity in vivo were tested in an in vitro system, the isolated urinary bladder of the toad bufo marinus. none of the agents protected against the inhibition of sodium transport across the bladder by hyperbaric oxygen exposure. two protective agents, disulfiram and diethyldithiocarbamic acid, significantly increased the rate and extent of sodium transport inhibition by 5 ata of oxygen, either when added in vitro or given in vivo. it was con ...1978207261
microviscosity of mucosal cellular membranes in toad urinary bladder: relation to antidiuretic hormone action on water permeability.the microviscosity of cellular membranes (or membrane fluidity) was measured in suspensions of single mucosal cells isolated from the urinary bladder of the toad, bufo marinus, by the technique of polarized fluorescence emission spectroscopy utilizing the hydrophobic fluorescent probe, perylene. at 23 degrees c, 5 mm dibutyryl cyclic 3',5'-amp decreased the apparent microviscosity of the cell membranes from 3.31 to 3.07 p, a minimum decrease of 7.3% (p less than 0.001) with a physiological time ...1978207870
stimulation of urinary acidification by aldosterone and inhibitors of rna and protein synthesis.urinary acidification by the urinary bladder of the toad (bufo marinus) was stimulated, relative to control, by the in vitro addition of aldosterone (10(-7) m), actinomycin d (20 microgram/ml), puromycin (80 microgram/ml) or cycloheximide (5 microgram/ml). the action of the inhibitors of rna or protein synthesis was not additive with that of aldosterone. this is opposite to the situation with na+ transport, where the stimulation by aldosterone is abolished by the same concentrations of these inh ...197883364
the sympathetic innervation of lung muscle in the toad bufo marinus: a revision and an explanation. 197826509
adrenoceptors in the lung of the toad bufo marinus: regional differences in responses to amines and to sympathetic nerve stimulation. 197826500
electrical and adaptive properties of rod photoreceptors in bufo marinus. i. effects of altered extracellular ca2+ levels.the effects of altering extracellular ca(2+) levels on the electrical and adaptive properties of toad rods have been examined. the retina was continually superfused in control (1.6 mm ca(2+)) or test ringer's solutions, and rod electrical activity was recorded intracellularly. low-calcium ringer's (10(-9)m ca(2+)) superfused for up to 6 min caused a substantial depolarization of the resting membrane potential, an increase in light-evoked response amplitudes, and a change in the waveform of the l ...1977412914
electrical and adaptive properties of rod photoreceptors in bufo marinus. ii. effects of cyclic nucleotides and prostaglandins.substances known to alter cyclic nucleotide levels in cells were applied to the isolated toad retina and effects on rod electrical and adaptive behavior were studied. the retina was continually superfused in control ringer's or ringer's containing one or a combination of drugs, and rod activity was recorded intracellularly. superfusion with cgmp, bu(2)gmp, isobutylmethylxanthine (ibmx; a phosphodiesterase inhibitor), or pgf(2alpha) (a prostaglandin) caused effects in rods that closely match thos ...1977201724
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