Publications
| Title | Abstract | Year Filter | PMID(sorted ascending) Filter |
|---|
| acetylcholine increases voltage-activated ca2+ current in freshly dissociated smooth muscle cells. | the regulation of voltage-activated ca2+ current by acetylcholine was studied in single freshly dissociated smooth muscle cells from the stomach of the toad bufo marinus by using the tight-seal whole-cell recording technique. ca2+ currents were elicited by positive-going command pulses from a holding level near -80 mv in the presence of internal cs+ to block outward k+ currents. ca2+ current was greatest in magnitude at command potentials near 10 mv. at such command potentials, acetylcholine inc ... | 1987 | 2436224 |
| a method for recording isometric tension development by isolated cardiac myocytes: transducer attachment with fibrin glue. | the purpose of this study was to develop a method for attachment of single isolated cardiac myocytes to a transducer for recording isometric tension development. cardiac myocytes were isolated from the hearts of the toad, bufo marinus or ferrets by enzymatic digestion with collagenase. the method that we used provided a 60-80% yield of ca++-tolerant cells. a suspension of cells was placed into a superfusion chamber coated with bovine thrombin. two glass microtools - each attached to a micromanip ... | 1987 | 2437526 |
| ca2+-movements in muscle modulated by the state of k+-channels in the sarcoplasmic reticulum membranes. | 1. a procedure has been developed to load ca2+ reversibly by the sarcoplasmic reticulum (sr) of mechanically skinned muscle fibres from the toad bufo marinus under controlled conditions and was employed to investigate the effects of conditions known to reduce the k+ conductance located in the sr-membrane during ca2+-loading on the amount of ca2+ releasable by caffeine. 2. the amount of releasable ca2+ was markedly increased compared to controls when 4-aminopyridine (4ap) (6 microm to 2 mm), tetr ... | 1987 | 2442706 |
| beta-adrenergic relaxation of smooth muscle: differences between cells and tissues. | the present studies were carried out in an attempt to resolve the controversy about the na+ dependence of beta-adrenergic relaxation in smooth muscle. previous studies on isolated smooth muscle cells from the toad stomach had suggested that at least some of the actions of beta-adrenergic agents, including a stimulatory effect on 45ca efflux, were dependent on the presence of a normal transmembrane na+ gradient. studies by other investigators using tissues derived from mammalian sources had sugge ... | 1987 | 2443016 |
| pathway-specific connections between peptide-containing preganglionic and postganglionic neurons in the vagus nerve of the toad (bufo marinus). | we have examined immunohistochemically the distribution of postganglionic nerve cell bodies and their preganglionic inputs in the vagus nerve of the toad, bufo marinus. nerve cell bodies containing immunoreactivity (ir) to somatostatin (som) were found at the origin of the oesophago-gastric ramus; these neurons projected to the lung. cell bodies with som-ir also occurred in the intracardiac branches of the vagus, but were absent from the distal segments of the pulmonary and oesophageal rami of t ... | 1987 | 2443548 |
| calcium in dark-adapted toad rods: evidence for pooling and cyclic-guanosine-3'-5'-monophosphate-dependent release. | 1. we have used laser micromass analysis (l.a.m.m.a.) to investigate ca uptake and release in intact 'red' rod photoreceptors in the dark-adapted retina of the toad, bufo marinus. 2. with l.a.m.m.a. it is possible to measure separately the concentrations of each of the ca isotopes. rods normally containing almost exclusively 40ca can be incubated in ringer solution containing the stable isotopes 42ca or 44ca. in this way, the movements of ca into and out of the rod can be separately determined. ... | 1987 | 2445976 |
| ion permeation through single ach-activated channels in denervated adult toad sartorius skeletal muscle fibres: effect of temperature. | the gigaohm seal technique was used to study the effects of temperature on ion permeation through acetylcholine-activated channels. this was done in cell-attached patches of the extrajunctional membrane of chronically-denervated, enzyme-treated cells from sartorius muscle of the toad bufo marinus. the predominant extracellular cation in the pipette solution was na+. single channel current-voltage curves were measured at different temperatures and electrodiffusion and three-site-four-barrier rate ... | 1988 | 2451211 |
| ion permeation through single channels activated by acetylcholine in denervated toad sartorius skeletal muscle fibers: effects of alkali cations. | the gigaohm seal technique was used to study ion permeation through acetylcholine-activated channels in cell-attached patches of the extrajunctional membrane of chronically denervated, enzyme-treated cells from the sartorius muscle of the toad bufo marinus. the most frequently occurring channel type (greater than 95% of channel openings), provisionally classified as 'extrajunctional,' had a chord conductance of approximately 25 ps under normal conditions (-70 mv, 11 degrees c, normal toad ringer ... | 1987 | 2451751 |
| regulation of one type of ca2+ current in smooth muscle cells by diacylglycerol and acetylcholine. | electrophysiological recordings from freshly dissociated smooth muscle cells from the stomach of the toad bufo marinus revealed two types of ca2+ currents. one has a low threshold of activation and inactivates rapidly; the other has a high threshold of activation and inactivates more slowly. acetylcholine (ach) increased the high-threshold current but not the low-threshold current. the synthetic diacylglycerol analog sn-1,2-dioctanoylglycerol, an activator of protein kinase c (pkc), mimicked the ... | 1988 | 2453389 |
| a whole-cell patch clamp study of ionic currents in single atrial cells of the tropical toad bufo marinus. | 1987 | 2455949 | |
| stretch-activated ion channels in smooth muscle: a mechanism for the initiation of stretch-induced contraction. | as in many smooth muscle tissue preparations, single smooth muscle cells freshly dissociated from the stomach of the toad bufo marinus contract when stretched. stretch-activated channels have been identified in these cells using patch-clamp techniques. in both cell-attached and excised inside-out patches, the probability of the channel being open (po) increases when the membrane is stretched by applying negative pressure to the extracellular surface through the patch pipette. the increase in po ... | 1988 | 2459658 |
| metabolic origins of 5-hydroxytryptamine in enteric neurons in a teleostean fish (platycephalus bassensis), a toad (bufo marinus) and the guinea-pig. | 1. 5-hydroxytryptamine (5-ht) content and synthesis in mucosa-free intestine of guinea-pig, the teleost platycephalus bassensis and the amphibian bufo marinus was studied by hplc with electrochemical detection or by tlc. 2. the 5-ht content of small intestine was: guinea-pig 0.58; bufo: 1.23; platycephalus: 26.88 nmol/g. 3. intestine from each species synthesized 5-ht from exogenous 5-htp. 4. platycephalus preparations synthesized labelled 5-ht from 14c-tryptophan, but no labelled 5-ht was detec ... | 1989 | 2468444 |
| extracellular ca2+ controls outward rectification by apical cation channels in toad urinary bladder: patch-clamp and whole-bladder studies. | outward rectifying, cation channels were observed in the epithelial cells of the urinary bladder of the toad. bufo marinus. as studied in isolated cells using the patch-clamp technique, the channel has an average conductance of 24 and 157 ps for pipette potentials between 0 and +60 mv and -60 to -100 mv, respectively, when the major cation in both bath and pipette solutions is k+. the conductance of the channel decreases with increasing dehydration energy of the permeant monovalent cation in the ... | 1989 | 2469799 |
| neuropeptide y-like immunoreactive amacrine cells in the retina of bufo marinus. | neuropeptide y-like immunoreactive (npy-li) amacrine cells of the bufo marinus retina were morphologically characterized, and their retinal distribution was established using immunohistochemistry on retinal wholemount preparations and sectioned material. the somas of npy-li amacrine cells were situated in the innermost part of the inner nuclear layer and their dendrites branched primarily in the scleral sublamina of the inner plexiform layer. a subgroup of the npy-li cells had dendrites in both ... | 1989 | 2475218 |
| morphological characterization of substance p-like immunoreactive amacrine cells in the anuran retina. | using substance p immunohistochemistry it was possible to demonstrate a class of morphologically homogeneous group of neurons in the inner nuclear layer (inl) of the retina of two anuran species: xenopus laevis and bufo marinus. the number of cells with substance p-like immunoreactivity (sp-li) was about 250 and 800 in juvenile and 600 and 2500 in adult xenopus and bufo, respectively, sp-li cells had a small soma with one primary dendrite having up to four slender branches, located in the vitrea ... | 1989 | 2475974 |
| stimulation by aldosterone of a conductive chloride pathway in toad skin. | as a rule, chloride movement (jc1-) across amphibian skin is considered to be passive; this is implied in fact for preparations incubated in ringer's fluid, since short-circuit current (isc) is the quantitative expression of net, active sodium transport (jna+). the nature of the cl- pathway(s) was investigated by incubating amphibian skin (mostly bufo marinus) with cl- present on the epithelial side only, and after blocking jna+ by combined treatment with ouabain and amiloride. in such condition ... | 1989 | 2478240 |
| role of an apical cation-selective channel in function of tight epithelia. | some features of oxytocin stimulation of a cation-selective channel of the apical membrane of amphibian tight epithelia were examined in an attempt to understand the channel's role in the regulation of epithelial transport. we first examined the ability of the channel to pass alkaline-earth cations. we found that oxytocin can stimulate the movement of alkaline-earth ions through the channel. this stimulation became greatly enhanced by treatment with ag+. the stimulation of alkaline-earth movemen ... | 1989 | 2478242 |
| cross-reactivity of an antiserum to the alpha-subunit of the na+, k+-atpase of toad (bufo marinus) kidney with basal and apical membranes of transporting epithelia of the rat. | an antibody to the 96 kd alpha-subunit of the na+, k+-atpase from bufo marinus has been used in immunostaining rat kidney and salivary glands. intense staining was observed on basolateral membranes of distal tubules of the kidney and striated ducts of the three major salivary glands. less intense staining was seen on the basolateral membranes of parotid acinar cells, but no staining was seen on the acinar cells of submandibular or sublingual glands. these sites of staining have been shown, by ot ... | 1989 | 2478290 |
| galanin-like immunoreactivity in sympathetic and parasympathetic neurons of the toad bufo marinus. | immunoreactivity (ir) to galanin (gal) was detected in a wide range of peripheral autonomic neurons in the toad bufo marinus. forty percent of adrenergic nerve cell bodies in paravertebral sympathetic ganglia had gal-ir in addition to neuropeptide y (npy)-ir. some of these neurons projected to systemic arteries. gal-ir was localized in parasympathetic neurons supplying the heart, lung, pulmonary artery, bladder, rectum and tongue. eighty-two percent of intracardiac vagal nerve cell bodies had bo ... | 1989 | 2478927 |
| why are blue visual pigments blue? a resonance raman microprobe study. | a resonance raman microscope has been developed to study the structure of the retinal prosthetic group in the visual pigments of individual photoreceptor cells. raman vibrational spectra are obtained by focusing the probe laser on intact photoreceptors frozen on a 77 k cold stage. to elucidate the mechanism of wavelength regulation in blue visual pigments, we have used this apparatus to study the structure of the chromophore in the 440-nm absorbing pigment found in "green rods" of the toad (bufo ... | 1989 | 2493645 |
| phospholipid changes during adaptation to acidosis in urinary bladder of bufo marinus. | the purpose of this study was to determine whether phospholipids (pl) play a role in the adaptation to metabolic acidosis by toad urinary bladder epithelium. toads were placed in an nh4cl acidosis for 48 hr. quarter bladders were removed and incubated with [32p]orthophosphate or [3h]arachidonic acid for 1 hr at 25 degrees c. pl were detected by thin layer chromatography, autoradiography, and quantitated by liquid scintillation counting or fractional amounts were determined from phosphate content ... | 1989 | 2494669 |
| cardiovascular responses to denervation of pulmocutaneous baroreceptors in toads. | toad pulmocutaneous arterial baroreceptors are connected to afferent fibers carried in the recurrent laryngeal nerves (rlns). bilateral rln denervation in conscious toads (bufo marinus) caused 34 and 78% increases in heart rate (fh) and systemic arterial blood pressure (pa) within 10-15 min, respectively. the variance of pa was significantly increased 2 days after denervation, but pa and fh were not. in additional chronic experiments, 5 of 17 baroreceptor-denervated toads died within the 2-wk re ... | 1989 | 2495740 |
| innervation of the gastrointestinal canal of the toad bufo marinus by neurons containing 5-hydroxytryptamine-like immunoreactivity. | the gut of the toad, bufo marinus, was examined for evidence of enteric neurons containing 5-hydroxytryptamine-like immunoreactivity. such neurons were absent from the stomach. they were present in the small intestine, with processes confined to the myenteric plexus. immunoreactive nerve cell bodies lay on branches of the pelvic nerves supplying the large intestine; fibres were found in the submucosa of the posterior large intestine and in the muscularis external of the anterior large intestine. ... | 1989 | 2495855 |
| the development and the topographic organization of the retinal ganglion cell layer in bufo marinus. | the number and distribution of neurons in the retinal ganglion cell layer were studied from the metamorphic climax to adulthood in the toad bufo marinus. retinal wholemounts stained with cresyl violet showed that total neuron numbers increased from 55,000 at metamorphic climax to about 950,000 in adult animals. during the same time the entire retinal area increased 46-fold from an average 3.4 mm2 to 157 mm2. the morphological character of the neurons and their density across the retina changed d ... | 1989 | 2498114 |
| compartmental and topographical distributions of axons in nerves to the amphibian (bufo marinus) glutaeus muscle. | the present work seeks to determine if axons to an amphibian muscle are segregated in nerve trunks between the spinal cord and muscle according to their primary nerve destination or their topographical projection in the muscle. the distribution of axons to different compartments and subcompartments of the amphibian (bufo marinus) glutaeus muscle has been determined in transverse sections of spinal and limb nerves after retrogradely labelling the axons with horseradish peroxidase. glutaeus axons ... | 1989 | 2502565 |
| 76 and 14 kda polypeptides, two major components released from amphibian urinary bladder epithelium. purification and characterization. | exocytotic processes play a major role in the hormonal control of water permeability in the amphibian urinary bladder. different treatments such as antidiuretic hormone (adh) stimulation, incubation with phorbol ester or mild detergent and mechanical stretch of the bladder, consistently induce a liberation of two major polypeptides of 76 and 14 kda molecular mass into the luminal medium. each of these polypeptides represents 3 to 5% of the total protein of epithelial cell homogenates and 20 to 5 ... | 1989 | 2503379 |
| quinidine blockade of calcium-activated potassium channels in dissociated gastric smooth muscle cells. | the effects of quinidine, an antiarrhythmic alkaloid, on potassium-selective channels in enzymatically dissociated gastric smooth muscle cells from rana pipiens and bufo marinus were investigated using excised patches and the patch-clamp technique. the predominant potassium channel in these cells is the calcium- and voltage-activated maxi-k channel with a single-channel conductance greater than 100 ps. applications of quinidine (100-600 microm) resulted in resolvable rapid flickerings between th ... | 1989 | 2508055 |
| steroid metabolism determines mineralocorticoid specificity in the toad bladder. | edwards et al. (c. r. w. edwards, p. m. stewart, d. burt, l. brett, m. a. mcintyre, w. s. sutanto, e. r. de kloet, and c. monder, lancet 2: 986-989, 1988) proposed that 11 beta-hydroxysteroid-dehydrogenase (11 beta-ohsd) plays a key role in the kidney by converting glucocorticoids (cortisol or corticosterone), which display a high affinity for type 1 mineralocorticoid receptors, into their inactive metabolites (cortisone or 11-dehydroxy-corticosterone), thus preventing their illicit occupation o ... | 1989 | 2508490 |
| synthesis and characterization of a long-acting fluorescent analog of vasotocin. | this study reports the synthesis of l-desamino-7-lysine- (fluorescein)-8-arginine-vasotocin (7-lys(flu) davt), and describes its biological activity in the isolated urinary bladder of the toad bufo marinus. 7-lys(flu)davt was fully active in increasing bladder permeability to water. a half-maximal hydroosmotic response was obtained at a concentration of 3 x 10(-8) m. a unique feature of this analog was that its response was not readily reversed after removal of the analog from the serosal bathin ... | 1989 | 2508970 |
| exocytotic events unrelated to regulation of water permeability in amphibian tight epithelia: effects of oxytocin, pma and insulin on membrane capacitance, water and na+ transport. | we measured the effects of oxytocin on capacitance and hydroosmotic water flow in the urinary bladder of the toad bufo marinus and the skins of rana pipiens and rana temporaria. oxytocin increased capacitance in all these tissues but stimulated hydroosmotic water flow only in the urinary bladder. we also measured the effects of oxytocin and pma on the capacitance and hydroosmotic water flow of the toad urinary bladder. both agents produced increases in membrane capacitance that were additive, ho ... | 1989 | 2508976 |
| interphotoreceptor retinoid-binding protein: role in delivery of retinol to the pigment epithelium. | the ability of interphotoreceptor retinoid-binding protein (irbp) to facilitate the incorporation of retinol into retinyl esters by the retinal pigment epithelium (rpe) was examined in toad (bufo marinus) eyecup preparations devoid of neural retina (rpe-eyecup). solutions containing purified bovine irbp and all-trans[3h]retinol were introduced into the vitreal cavity of the rpe-eyecup. after incubation at 22 degrees c, [3h]retinyl ester was extracted from the rpe cells and isolated by high perfo ... | 1989 | 2509230 |
| retino-retinal projections in three anuran species. | in juvenile and adult xenopus laevis, in adult bufo marinus and rana esculenta frogs retino-retinal projections were traced by filling the central stump of one optic nerve, cut 2-3 mm from the eye, with horse-radish peroxidase (hrp) or cobaltic-lysine complex (clc). the presence of retino-retinal projections was confirmed in all 3 species both in the juvenile and the adult. up to 12 ganglion cells per retina were found to be filled retrogradely with hrp together with optic axons filled anterogra ... | 1989 | 2510094 |
| the development of topographical maps and fibre types in toad (bufo marinus) glutaeus muscle during synapse elimination. | 1. the toad glutaeus muscle consists of two muscle compartments. a study has been made of the topographical distribution of motor units in these compartments, in relation to the fibre types which arise during different stages of development. 2. monoclonal antibodies to myosin allowed the distribution of fibre types to be determined. in mature muscles (from toads of greater than 30 g body weight) clusters of type 5 (tonic) fibres were found exclusively at the dorsal surface of the muscle, surroun ... | 1989 | 2511295 |
| functional similarities in the mechanical design of the aorta in lower vertebrates and mammals. | the mechanical properties of the aorta from the toad bufo marinus, the lizard gekko gecko and the garter snake thamnophis radix were compared to those of the rat, by inflation of vessel segments in vitro. the arteries of the lower vertebrates, like those of mammals, were compliant, highly resilient, and non-linearly elastic. the elastic modulus of the artery wall was similar in the lower vertebrates and mammals, at their respective mean physiological pressures. we conclude that the aorta in each ... | 1989 | 2513219 |
| extracellular ph in the isolated retina of the toad in darkness and during illumination. | 1. extracellular ph (pho) was measured in the isolated retina preparation of the toad, bufo marinus, using h(+)-selective microelectrodes. during superfusion with phosphate-buffered solution (ph 7.8), which had a low buffering capacity, pho in the inner retina was 7.0-7.2 and there was a pho gradient throughout the distal retina and into the bathing solution. 2. the retinal acidity appears to be due in part to the combined reactions of glycolysis and atp hydrolysis, since anoxia greatly increase ... | 1989 | 2516127 |
| intracellular potentials of toad urinary bladder. | short-circuited urinary bladders of bufo marinus were impaled with microelectrodes. intracellular potentials in the order of -80 mv were recorded. on inhibition of apical na entry they hyperpolarized by about 15 mv and the fractional resistance of the apical membrane increased to near 1.0. these patterns are similar to those of other tight na transporting amphibian epithelia. on two occasions, stable recordings from a single cell were obtained before and after oxytocin. intracellular potential a ... | 2007 | 2516305 |
| the effects of vagal stimulation and applied acetylcholine on the sinus venosus of the toad. | 1. the effects of vagal stimulation and applied acetylcholine were compared on the isolated sinus venosus preparation of the toad, bufo marinus. 2. the effects of applied acetylcholine and of low-frequency, or short bursts of high-frequency vagal stimulation were abolished by hyoscine. 3. when intracellular recordings were made from muscle cells of the sinus venosus, it was found that applied acetylcholine caused bradycardia and a cessation of the heart beat which was associated with membrane hy ... | 1989 | 2517987 |
| the morphological characterization and distribution of displaced ganglion cells in the anuran retina. | the number, dendritic morphology, and retinal distribution of displaced ganglion cells were studied in two anuran species, xenopus laevis and bufo marinus. horseradish peroxidase or cobaltic lysine complex was applied to the cut end of the optic nerve, and the size, shape, and retinal position of retrogradely filled ganglion cells displaced into the inner nuclear layer were determined in retinal wholemount and sectioned material. approximately 1% of ganglion cells in xenopus and 0.1% in bufo wer ... | 1989 | 2518634 |
| dissociation of force from myofibrillar mgatpase and stiffness at short sarcomere lengths in rat and toad skeletal muscle. | 1. single fast-twitch fibres from the extensor digitorum longus muscle of the rat, rattus norvegicus, and single twitch fibres from the iliofibularis muscle of the cane toad, bufo marinus, were mechanically skinned and then used to measure maximally ca2+-activated [( ca2+] greater than 0.03 mmol l-1) isometric force production, myofibrillar mgatpase activity and fibre stiffness at different sarcomere lengths. mgatp hydrolysis was linked by an enzyme cascade to the oxidation of nadh (nicotinamide ... | 1989 | 2529371 |
| insulin and igf i receptor-mediated na+ transport in toad urinary bladders. | we compared the concentration dependence of insulin- and insulin-like growth factor i (igf i)-stimulated na+ transport with ligand-receptor affinities in the urinary bladder of the toad bufo marinus. threshold, half-maximal, and maximal natriferic concentrations of both peptides were approximately 0.1, 1, and 10 nm, respectively. amiloride, but not ethyl isopropyl amiloride, (10(-5) m), abolished na+ transport. maximal responses to either peptide rendered the tissue insensitive to challenge with ... | 1989 | 2552816 |
| [stimulation of sodium transport by cobalt ions in the skin of amphibia against a background of aldosterone action]. | sodium transport across toad bufo marinus and frog rana temporaria skin was enhanced by aldosterone added to ringer solution at the basal plasma membrane. cobalt ions applied to the outer surface of amphibian skin have increased sodium transport stimulated by aldosterone. the regulatory sites of the sodium channel macromolecule seem to be located on both surfaces of the channel apical membrane. | 1989 | 2558919 |
| inhibition of voltage-dependent na+ and k+ currents by forskolin in nodes of ranvier. | the effect of forskolin on voltage-activated na+ and k+ currents in nodes of ranvier from the toad, bufo marinus, has been examined using the vaseline-gap voltage-clamp technique. peak na+ currents (ina) were reduced by 35% and the rate of decline of na+ current during continuous depolarization was accelerated following treatment with 450 microm forskolin. however, the voltage-dependence of steady-state inactivation as well as the rate of recovery from fast inactivation remained unchanged. upon ... | 1989 | 2560169 |
| characteristics of toad bladder urinary acidification. | 1. the urinary acification system present in the bladder of the toad bufo marinus ictericus was investigated by means of an improved technique of mounting the membrane that minimizes the edge damage when the bladder is placed as a sheet between lucite half chambers. 2. in ouabain-treated bladders in the absence of exogenous co2, acidification rates were similar to those observed for turtle bladder. 3. the presence of 1% co2 at the serosal gas phase increased proton secretion (jh). stimulation of ... | 1989 | 2561461 |
| the probability of quantal secretion at release sites in different calcium concentrations in toad (bufo marinus) muscle. | 1. the number of quanta secreted from visualized release sites along terminal branches at toad (bufo marinus) neuromuscular junctions in different extracellular concentrations of calcium ions. [ca2+]o, and during facilitation was determined. terminal branches were visualized by prior staining with the fluorescent dye, 3-3 diethyloxardicarbocyanine iodide (dioc2(5)). 2. increasing [ca2+]o between 0.25 and 0.4 mm gave a similar proportional increase in the mean quantal content of the end-plate pot ... | 1989 | 2576063 |
| the probability of quantal secretion at release sites of different length in toad (bufo marinus) muscle. | 1. the evoked quantal secretion recorded with an extracellular microelectrode (me) at selected sites along motor terminal branches visualized with the fluorescent dye 3-3 diethyloxardicarbocyanine iodide (dioc2(5)) was compared with the maximum length of the synaptic contact at these release sites reconstructed from serial sections examined with the electron microscope. in addition the relationship between the binomial probability of secretion at release sites (pe) and the length of the synaptic ... | 1989 | 2576064 |
| an eyecup slice preparation for intracellular recording in vertebrate retinas. | this report describes a new preparation for intracellular recording from the vertebrate retina, the eyecup slice preparation. it consists of a small (2 x 5 mm) strip cut from the posterior wall of the eye and thereby keeps the sclera, pigment epithelium and neural retina in place. initial results are presented here for two vertebrates: the turtle, pseudemys scripta elegans, and the toad, bufo marinus. with conventional microscopy, the histological layers of the retina can be resolved, as well as ... | 1989 | 2755176 |
| immunogold-labeled microtubule crossbridges in platinum-carbon replicas of the marginal band of erythrocyte cytoskeletons. | cytoskeletons of erythrocytes from the toad bufo marinus are composed of a surface-associated cytoskeleton that encapsulates the annular bundle of microtubules known as the marginal band (mb) and the centrally located nucleus. as seen by phase-contrast microscopy, the microtubules (mts) of the mb remain tightly bundled after cell lysis without the need for added stabilizing factors. the integrity of this structure suggested that in addition to mts other components were present in the mb and were ... | 2015 | 2773815 |
| structural organization of alpha-subunit from purified and microsomal toad kidney (na+ + k+)-atpase as assessed by controlled trypsinolysis. | the membrane organization of the alpha-subunit of purified (na+ + k+)-atpase ((na+ + k+)-dependent adenosine triphosphate phosphorylase, ec 3.6.1.3) and of the microsomal enzyme of the kidney of the toad bufo marinus was compared by using controlled trypsinolysis. with both enzyme preparations, digestions performed in the presence of na+ yielded a 73 kda fragment and in the presence of k+ a 56 kda, a 40 kda and small amounts of a 83 kda fragment from the 96 kda alpha-subunit. in contrast to mamm ... | 1987 | 2822121 |
| cellular electrophysiologic effects of vertebrate digitalis-like substances. | substances structurally and functionally similar to digitalis glycosides are produced by several vertebrate species. there also is evidence for a digitalis-like substance of human origin. standard microelectrode techniques were used to study the direct effects on the cellular electrophysiology of canine purkinje fibers of 1) bufalin, an unconjugated cardiotonic steroid molecule that is produced by the toad bufo marinus, and 2) an extract of human bile that showed digitalis-like immunoreactivity ... | 1988 | 2830326 |
| molecular characterization of the bufo marinus mitochondrial genome. | 1988 | 2831506 | |
| insulin-mediated h+ and nh+4 excretion in the urinary bladder of bufo marinus. | this study was done to determine if insulin mediates h+ and nh+4 excretion in the urinary bladder of bufo marinus. acidosis was induced by gavaging with 10 ml of 120 mm nh4cl 3x daily for 2 days. hemibladders were mounted between lucite chambers. insulin (porcine) was added to the serosal solution of the experimental bladder (10(2) mu/ml). after a 15-min equilibration the flux was measured for 2 hr. h+ excretion was measured from change in ph of the mucosal fluid and the nh+4 measured colorimetr ... | 1988 | 2832853 |
| cellular ph and na+-h+ exchange activity in lens epithelium of bufo marinus toad. | incubation of lenses with the acetoxymethyl ester of 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (bcecf-am) led to selective, prolonged entrapment of the deesterified, ph-sensitive, membrane-impermeable form of the dye (bcecf) in the lens epithelial cells allowing, thereby, for the continuous fluorometric monitoring of epithelial intracellular ph (phi) in intact lenses. under anaerobic conditions in physiological solution, the epithelium maintained a phi of 7.36 +/- 0.14 (mean +/- sd, n = 6 lens ... | 1988 | 2847535 |
| light-induced losses and dark recovery rates of guanosine 3',5'-cyclic monophosphate in rod outer segments of intact amphibian photoreceptors. | we used an apparatus in which pieces of dark-adapted amphibian retinas (rana pipiens, bufo marinus) obtained under infrared illumination were exposed to precise intervals of 500-nm illuminations, and then frozen by contact of their outer segment surface with a liquid helium-cooled copper mirror. sections of the frozen outer segment layer were obtained in a cryostat and then assayed for total extractable cyclic 3',5'-guanosine monophosphate (cgmp). significant losses of cgmp with respect to the d ... | 1988 | 2851028 |
| inward rectification in muscle fibres of the toad bufo marinus. | inward rectification of the resting potassium conductance was studied in skeletal muscle fibres of the toad bufo marinus. this conductance was shown to be blocked by ba and cs and located both in the surface membrane and the membranes of the tubular system. some differences were found between the properties of this conductance channel in bufo marinus and those reported for various species of rana. the possible adaptative value of these differences is pointed out. | 1985 | 2863052 |
| gastric acid secretion in the toad bufo marinus with the description of a new technique for in vivo monitoring. | a technique for the implantation of a ph electrode into the stomach of the toad, bufo marinus, is described. the technique permits continuous monitoring of gastric ph for extended periods. results from continuous monitoring and from acute measurements of gastric ph are compared in fasting and fed toads. prostaglandin e, given orally with food, caused a dose-related delay in the fall of gastric ph which followed feeding. | 1985 | 2864175 |
| amino acid transport by corneal epithelial cells from the toad, bufo marinus. | alpha-aminoisobutyric acid is actively accumulated by the epithelium of the cornea of the toad, bufo marinus, resulting in a tissue to medium ratio of 4 to 1 after 40 min of incubation. the accumulation of alpha-aminoisobutyric acid is ouabain-sensitive and dependent upon the presence of extracellular sodium. transport is inhibited by carbon monoxide, 6-aminonicotinamide, arsenite and n-heptyl-3-hydroxy-quinoline-n-oxide and stimulated by diamide. | 1985 | 2864185 |
| independent co-release of acetylcholine and somatostatin from cardiac vagal neurones in toad. | vagal postganglionic neurones in toad (bufo marinus) cause cardio-inhibition by releasing both acetylcholine and somatostatin. in isolated, electrically paced, toad atria, intracardiac neurones were stimulated by short bursts of high-voltage pulses applied during the atrial refractory period. treatment with hemicholinium-3 (5 x 10(-4) m) for 5 h eliminated most of the acetylcholine-mediated cardio-inhibition but did not inhibit somatostatin-mediated transmission. it is concluded that somatostati ... | 1985 | 2865707 |
| osmoregulation of the cane toad, bufo marinus, in salt water. | adult cane toads, b. marinus, survived in salinities up to 40% sea-water (sw). pre-exposure to 30, then 40% sw, increased the survival time of toads in 50% sw. plasma from toads acclimated to salt water is hyperosmotic to the environment--a result of increased plasma sodium, chloride and urea concentrations. when toads were placed in tap-water and 20% sw, all significant changes to plasma sodium, chloride, urea and osmotic pressure occurred within the first 2 days of exposure. when toads were pl ... | 1985 | 2866884 |
| melittin-induced changes in na and cl movements across the skin and cornea (in vitro) of the toad bufo marinus. | melittin, from bee venom, increases short-circuit current (isc) across the skin and cornea of toads. in skin this reflects a rise in the influx of na and is inhibited by meclofenamic acid (inhibits prostaglandin synthetase). in corneas with melittin on the inside the rise in isc is inhibited by bumetanide (inhibits cl transport) and meclofenamic acid. melittin on the tear side of the cornea causes a biphasic change in isc, and a rise in all undirectional fluxes of na and cl. this effect was not ... | 1985 | 2866902 |
| the influence of prostaglandin e2 (pge2) on the acetylcholine-initiated contractions of isolated gastric muscularis muscle of bufo marinus. | acetylcholine (ach) (1.5 x 10(-5) m) elicited three different types of tonic and phasic contraction of muscularis muscle from different parts (cardiac, middle and pyloric) of the stomach of bufo marinus. prostaglandin e2 (pge2) (10(-9)-10(-6) m) induced a concentration-dependent relaxation of tonic contractions elicited by ach (1.5 x 10(-5) m) of strips from the cardiac part while potentiating the phasic contractions from the middle part of the stomach. pge2 (10(-7) m) relaxed tonic contraction ... | 1986 | 2869901 |
| transmitter secretion varies between visualized release sites at amphibian neuromuscular junctions. | living amphibian (bufo marinus) motor-nerve terminals have been stained and electrophysiological techniques have been used to determine the amount of transmitter secreted at selected release sites of the terminals. high secretion occurs at sites laid down near the origin of the terminals; very low or zero secretion occurs at more distal sites. the results indicate that some release sites may fail to secrete transmitter on arrival of a nerve impulse. it is suggested that functionally silent relea ... | 1986 | 2872629 |
| pepsin in the toad bufo marinus. | the macroscopic localization of pepsinogen in the upper gastrointestinal tract of the anuran bufo marinus was studied by means of biochemical assay. the ph optimum of the anuran pepsin was determined to be 1.6. the effect of lowered ambient temperature on stored pepsinogen and proteolytic activity was studied. both parameters were reduced. the results are extrapolated to speculate on the mechanisms of gastric brooding in gastric brooding frogs of the genus rheobatrachus. | 1986 | 2875833 |
| the probability of quantal secretion along visualized terminal branches at amphibian (bufo marinus) neuromuscular synapses. | the number of quanta secreted from selected sites along terminal branches at toad (bufo marinus) neuromuscular junctions was determined. terminal branches were visualized by prior staining with the fluorescent dye, 3-3 diethyloxadicarbocyanine iodide (dioc2(5)); neither impulse conduction nor quantal release were affected by dioc2(5) at concentrations less than 10 microm. the evoked quantal release recorded with an extracellular micro-electrode (me) at different sites along the length of termina ... | 1986 | 2882019 |
| characterization of cholinesterase of muscularis muscle of bufo marinus. | we have characterized the cholinesterase (che) of muscularis muscle of bufo marinus by selectively using specific inhibitors of acetylcholinesterase and pseudocholinesterase and observing susceptibility to inhibition when substrate is present in excess. the che activity in this preparation due to acetylcholinesterase (ache) and pseudocholinesterase (buche) was 90 and 10%, respectively. the optimum temperature and ph for the che were 38 degrees c and 7.4, respectively and the excess substrate inh ... | 1987 | 2885125 |
| calcium in the toad (bufo marinus) cornea: binding by the stroma. | 1. the ca concentration in the toad (bufo marinus) cornea was 2.6 mmol/kg wet wt compared at 1.0 mmol/l in the bathing aqueous humor and 2.8 mmol/kg wet wt in the separated corneal stromal layer. cell ca content was calculated to be about 1.8 mmol/kg wet wt. 2. about 80% of the total ca appears to be sequestered or bound to tissue components most of which (68% of the total) is associated with the stroma (2.2 mmol/kg wet wt stroma). 3. about 85-90% of the ca in the stroma is readily exchangeable ... | 1987 | 2886287 |
| changes in the dimensions of release sites along terminal branches at amphibian neuromuscular synapses. | the probability of transmitter secretion from release sites declines along the length of most long terminal branches (greater than 78 micron) at toad (bufo marinus) neuromuscular junctions; in contrast, few short terminal branches (less than 78 micron) show such a decline. the present study was carried out to see if any of the dimensions of release sites change along the length of terminal branches in a way that can be correlated with the decrease in secretion probability. the size of presynapti ... | 1987 | 2887640 |
| feasibility of continuous glutamate monitoring in perfused retinal tissue with a potentiometric biosensing probe. | a potentiometric biosensing probe for glutamate has been evaluated as a possible tool to measure the release of glutamate from the isolated retina of bufo marinus. this probe is based on carbon dioxide detection, following enzymatic conversion of glutamate to gamma-aminobutyric acid (gaba) via glutamic acid decarboxylase (gad). probe response characteristics of dynamic range, limit of detection, ph dependency, and selectivity are described. probe modifications were required for sensor operation ... | 1988 | 2894485 |
| plasma cathepsin activity and the role of hypovolemic shock in dehydrational death in the toad, bufo marinus. | 1. the ph- and activator-dependence of toad plasma cathepsin activity assayed by hemoglobin digestion was characteristic of cathepsins b1 and d. 2. dehydration, even to the point of death, did not produce a significant elevation of plasma cathepsin activity over controls. 3. toads were remarkably resistant to the effects of splanchnic artery ligation, which also did not produce significantly higher plasma cathepsin levels. 4. cardiac depression via the production of a myocardial depressant facto ... | 1988 | 2900097 |
| quantal secretion at release sites of nerve terminals in toad (bufo marinus) muscle during formation of topographical maps. | 1. the number of quanta secreted from selected sites along terminal branches at suppressed synapses in the developing toad (bufo marinus) gluteus muscle has been determined. the topographical projection from segmental nerves 8 and 9 to the ventral surface of this muscle matures slowly as toads develop in size from 12 to 40 g. terminal branches of nerves 8 and 9 were visualized by prior staining with the fluorescent dye, 3-3-diethyloxardicarbocyanine iodide (dioc2(5]. 2. the evoked quantal releas ... | 1988 | 2902220 |
| influence of prostaglandins on electrical and mechanical activities of gastric muscles of bufo marinus. | 1. study was performed to compare the role of prostaglandins in regulating gastric contractile activity in an amphibian model, bufo marinus, with mammalian models. 2. the prostaglandin synthesis inhibitor, indomethacin, had little effect on spontaneous mechanical activity, but increased the force and frequency of contractions stimulated by acetylcholine. 3. pge2 reversed the effects of indomethacin and reduced the force and frequency of contractions. these effects were concentration-dependent. 4 ... | 2010 | 2902993 |
| detection of poisoning by plant-origin cardiac glycoside with the abbott tdx analyzer. | cardiac glycoside poisoning caused by ingestion of plant material is common in tropical and sub-tropical areas. in evaluating the use of the abbott tdx digoxin ii assay to detect such cases of poisoning, we found it a rapid and convenient method for confirming the ingestion of glycosides from the plants nerium oleander, thevetia peruviana, and adonis microcarpa, and from the toad bufo marinus. here we report some clinical cases illustrating our experience with the use of this assay, and describe ... | 1989 | 2914377 |
| the initial burst of impulses in responses of toad muscle spindles during stretch. | the responses of muscle spindles in the iliofibularis muscle of the cane toad bufo marinus were examined during constant velocity stretch of the passive muscle. spindles were found to show an 'initial burst' of high frequency impulses at the onset of stretch. associated with the initial burst was a steep passive tension rise in the whole muscle, the short-range elastic component (hill, 1968), called here the passive stiffness. the size of the initial burst was found to depend on muscle length in ... | 2010 | 2934546 |
| effects of temperature on contractile properties of skinned muscle fibers from three toad species. | single fast fibers were isolated from the iliofibularis muscles of three species of toad with different thermal minima for active locomotion: 8 degrees c, american toad, bufo americanus; 15 degrees c, rocky mountain toad, bufo woodhousei woodhousei; 22 degrees c, cane toad, bufo marinus. all experiments were carried out during the summer. fibers were chemically skinned and maximum isometric tension and unloaded contraction velocity were determined at a series of temperatures between 0 and 35 deg ... | 1987 | 2949633 |
| ca2+ and mgatp2- dependence of shortening in skinned single smooth muscle cells. | most studies of skinned smooth muscle have been performed in whole tissue preparations. in this study, we report the development of a chemically skinned single smooth muscle cell preparation from the toad, bufo marinus, stomach. isolated smooth muscle cells were skinned using saponin. the effect of various ionic environments (i.e., changing free ca2+ and mgatp2-) on skinned cell contractile response was assessed by measuring cell lengths from populations of cells using a computer-assisted length ... | 1987 | 2952016 |
| response of toad urinary bladder to vasopressin analogs possessing v1 or v2 specificity. | the urinary bladder of the toad bufo marinus has been used to examine the effect on sodium transport, measured by short-circuit current, of natural antidiuretic hormones and several synthetic peptide analogs. in mammals, these synthetic analogs show specificity for different receptors, designated v1 and v2 receptors, whose biological responses are mediated by phosphatidyl inositol breakdown products or adenylate cyclase activity, respectively. all analogs stimulated scc, with relative potencies ... | 1988 | 2967974 |
| electron microscopic cytochemical localization of ca-atpase in the rod outer segments of the toad bufo marinus. | transmission electron microscopy and ultracytochemistry were employed in an attempt to localize the enzyme calcium adenosine triphosphatase (ca-atpase) in the rod outer segments (ros) of the toad retina. utilizing a one-step incubation procedure, ca-atpase was identified as an electron-dense precipitate in the intradiskal spaces of the rod disks (vesicles) of the ros. analytical microscopy identified the reaction product as lead phosphate. the formation of the reaction product was dependent on t ... | 1988 | 2973264 |
| [effect of rhopalurus lauticauda venom on the isolated rectus abdominis muscle of bufo marinus]. | 1988 | 2977999 | |
| receptor occupancy vs. induction of na+-k+-atpase and na+ transport by aldosterone. | in the urinary bladder of the toad bufo marinus aldosterone (between 0.8 and 100 nm) stimulates na+ transport [half-maximal induction concentration (k1/2) = 6.5 nm]. at low hormone concentrations (0.8-8 nm), the increase of na+ transport between 0.75 and 2.5 h is accompanied by a fall in transepithelial resistance (r). higher hormone concentrations (30-800 nm) induce an additional resistance-independent fraction of na+ transport within 2.5-8 h. from 6 h on, aldosterone (between 0.2 and 20 nm) st ... | 2010 | 2981474 |
| specific binding sites for ovine prolactin in three amphibian cell lines. | established cell lines (tb-6c and tb-m) obtained by continuous culture of epithelial cells from toad bufo marinus urinary bladder, which, in culture, maintained a high degree of functional differentiation, exhibited a significant number of high-affinity (ka = 1-2 x 10(10) m-1) binding sites detected both with radioiodinated (125i) ovine prolactin (oprl) and human growth hormone (hgh). binding capacity was higher in the case of tb-6c cells (7,573 +/- 581 sites/cell) than with the tb-m cells (1,16 ... | 1985 | 2981477 |
| effects of bilirubin on transepithelial transport of sodium, water, and urea. | urinary concentrating defects and renal salt wasting have been described in the hyperbilirubinemic gunn strain strain of rat. homozygous animals demonstrate significant reductions in renal medullary urea and sodium ion concentrations. these observations are consistent with possible bilirubin associated disorders in the transepithelial transport of water and solute. to test this hypothesis, measurements of active sodium transport and passive water and urea fluxes were made in hemibladders isolate ... | 1985 | 2984453 |
| forskolin mimics the hydrosmotic action of vasopressin in the urinary bladder of toads bufo marinus. | net water flow jw was measured across the urinary bladder of toads bufo marinus and averaged over periods of 1 min by means of a volumetric, automatic technique. the diterpene forskolin, an activator of adenylate cyclase bypassing the hormonal receptor subunit, induced a rapid, reversible, dose-dependent increase in osmotic water permeability, pf, very similar to that induced by vasopressin. at 1.1 microm, forskolin induced a half-maximal response. at 5 microm forskolin caused a near maximal res ... | 1985 | 2993597 |
| fluctuations in intracellular ph associated with vasopressin stimulation. | intracellular ph (phi) was estimated in paired hemibladders isolated from dominican toads (bufo marinus) by the tissue distribution of [14c]5,5'-dimethyl-2,4-oxazolidinedione and [3h]inulin. tissues were incubated with isotopes for 30 min to correlate changes in phi with the approximate time of peak vasopressin (vp)-induced water flow. at serosal ph 7.1 in the presence of an osmotic gradient, the intracellular hydrogen ion concentration [( h+]i) after 30 min of vp (20 mu/ml) stimulation was 8.29 ... | 1986 | 3022605 |
| cyclic nucleotide levels of the photosensitive irises of bufo marinus and lophius. | the sphincter pupillae muscle of several species contracts autonomously after light directly strikes the iris. the response is initiated by isomerization of rhodopsin in the sarcolemma. light-induced release of ca2+ from internal stores is one step in the transduction process. the levels of cyclic amp and cyclic gmp were measured after irises were stimulated by light. stimulation by light does not produce measurable or consistent changes in the levels of either cyclic amp or cyclic gmp within th ... | 2011 | 3026826 |
| a search for a model tissue for studying effects of thiazide diuretics. | a search was made for a model tissue of nacl absorption which would be sensitive to inhibition by diuretics of the thiazide type. a lack of such a model through the years has hampered the analysis of the cellular mechanism of action of this important class of drugs. using the short-circuit current technique, the urinary bladders of the toads bufo spinosus and bufo marinus, and the frog rana temporaria were investigated regarding the effects of various thiazides. these bladders have nacl absorpti ... | 1987 | 3033994 |
| identification of two isoforms of the catalytic subunit of na,k-atpase in myocytes from adult rat heart. | the present study demonstrates that two forms of the alpha catalytic subunit of the na,k-atpase are present in rat heart and originate from cardiomyocytes. they were resolved on sodium dodecyl sulfate-polyacrylamide gel electrophoresis after reduction and alkylation of the sulfhydryl groups. the two forms were identified on immunoblots using two specific antisera against either the alpha subunit from bufo marinus kidney and the alpha and beta subunits from lamb kidney. comparison of the two form ... | 1987 | 3036837 |
| the gtp-binding protein of rod outer segments. i. role of each subunit in the gtp hydrolytic cycle. | the gtp-binding protein of bufo marinus rod outer segments (ros) is composed of 3 subunits: g alpha, 39,000; g beta, 36,000; and g gamma, approximately 6,500. a stepwise analysis of the gtp hydrolytic cycle (gtp binding, gtp hydrolysis, and gdp release) was facilitated by using purified subunits of the gtp-binding protein. when g alpha and g beta, gamma concentrations were held constant, the initial rate of guanosine-5'-o-(3-thiotriphosphate) (gtp gamma-s) binding to g alpha was dependent upon t ... | 1987 | 3036854 |
| loss of polyneuronal innervation and establishment of a topographical map in the glutaeus muscle of bufo marinus during generation of secondary muscle cells. | the development of synaptic connections to the toad (bufo marinus) glutaeus magnus from segmental nerves 8 (n8) and 9 (n9) was determined in the postmetamorphic period. three different-size toads were studied: small (0.3-2.0 g), medium-size (5-15 g) and large (greater than 20 g). the number of cells in the glutaeus increased about 9-fold during development; this involved the appearance and subsequent maturation of secondary fibres throughout the muscle. the glutaeus in small toads, which consist ... | 1987 | 3040189 |
| characterization of cross-bridge elasticity and kinetics of cross-bridge cycling during force development in single smooth muscle cells. | force development in smooth muscle, as in skeletal muscle, is believed to reflect recruitment of force-generating myosin cross-bridges. however, little is known about the events underlying cross-bridge recruitment as the muscle cell approaches peak isometric force and then enters a period of tension maintenance. in the present studies on single smooth muscle cells isolated from the toad (bufo marinus) stomach muscularis, active muscle stiffness, calculated from the force response to small sinuso ... | 1988 | 3047311 |
| a new method of non-enzymatic dissociation of the bufo retina. | we have formulated a medium in which an electroretinogram (erg) can be elicited from eyecup pieces of bufo marinus up to 2 weeks after dissection. at the same time the retina can be dissociated into healthy, intact photoreceptors and other cells after soaking in the same medium from 4 to 24 h. thus, no enzymes need be used which have deleterious effects on the cells; on the contrary the medium extends cell viability. clearly, this method should be attractive in electrophysiological and biochemic ... | 1986 | 3083159 |
| the ecological genetics of introduced populations of the giant toad, bufo marinus. iv. gene flow estimated from admixture in australian populations. | allele frequency variation is described at nine polymorphic enzyme loci in 21 samples from populations of the introduced giant toad, bufo marinus, in the region of townsville in north queensland, australia. some of these populations appear to have been established through the introgression of other populations that previously had been isolated. comparisons of allele frequencies at three polymorphic loci between the introgressed populations and the original populations are used to obtain admixtur ... | 1986 | 3084402 |
| thyroid hormone antagonizes an aldosterone-induced protein: a candidate mediator for the late mineralocorticoid response. | in the urinary bladder of the toad bufo marinus, the basal rate of synthesis of a number of proteins was modulated in a bidirectional way (i.e., induced or repressed) by aldosterone and by triiodothyronine (t3). each hormone was therefore characterized by a distinct domain of response. when both hormones were added simultaneously, the two domains consistently overlapped at least for one protein, termed aip-1, or aldosterone-induced protein 1 (mr approximately 65 kilodaltons, pi = 6.7, as analyze ... | 1986 | 3084794 |
| calcium transients and resting levels in isolated smooth muscle cells as monitored with quin 2. | the ca2+-sensitive dye quin 2 was used to monitor ca2+ levels and to follow ca2+ transients in suspensions of isolated toad (bufo marinus) smooth muscle cells, whose contractile activity was monitored with a coulter counter. single cells were not utilized to follow ca2+ changes involved with contraction because of problems of rapid dye bleaching and due to photosensitization of smooth muscle cells loaded with quin 2. high levels of quin 2 loading (2-5 mm) severely prolonged (time course increase ... | 1986 | 3085513 |
| naturally occurring cardiac glycosides. | cardiac glycoside poisoning from the ingestion of plants, particularly of oleanders, occurs with reasonable frequency in tropical and subtropical areas. we have assessed a variety of plant specimens for their cardiac glycoside content by means of radioimmunoassays with antibodies that differ in their specificity for cardiac glycosides. significant amounts of immunoreactive cardiac glycoside were found to be present in the ornamental shrubs: yellow oleander (thevetia peruviana); oleander (nerium ... | 1986 | 3086679 |
| fine structure of the photosensitive iris of the toad, bufo marinus. | the iris of the toad bufo marinus is directly photosensitive and will constrict in response to light striking only the iris. this is true even when the iris is isolated from the rest of the eye, and therefore from reflex neuronal influences initiated in the retina. this autonomous response is probably mediated by the sphincter pupillae muscle, since no specialized photoreceptors are present in the iris, nor does the sphincter exhibit any specializations likely to subserve a purely photoreceptive ... | 1986 | 3088285 |
| structure and composition of the cytoskeleton of nucleated erythrocytes: iii. organization of the cytoskeleton of bufo marinus erythrocytes as revealed by freeze-dried platinum-carbon replicas and immunofluorescence microscopy. | platinum-carbon (pt-c) replicas of freeze-dried erythrocyte cytoskeletons of the toad, bufo marinus, were prepared using a modified balzers 300 system. examination in stereo of replicas of the microtubule-containing marginal band revealed filaments projecting from the microtubule walls to form links between adjacent microtubules. these cross-bridging proteins may bundle the microtubules into the configuration of the marginal band (mb) and may also serve to stabilize the structure. the mb appears ... | 1986 | 3093107 |
| a protein factor from bufo marinus erythrocytes cross-bridges microtubules in vitro. | a microtubule cross-bridging factor was isolated from erythrocytes of the toad, bufo marinus. erythrocytes were lysed and their cytoskeletons disassembled by sonication and high salt extraction. the solubilized proteins were recovered and fractionated using sephadex g-200 column chromatography. the protein fractions from the column were analysed by sds-page and pooled into three groups: high molecular weight (hmw) proteins that eluted from the column in the void volume and had a protein composit ... | 1986 | 3095129 |
| light-dependent binding of g-protein to outer segment membranes of toad photoreceptors. | light-dependent changes in the binding of g-protein were analyzed in outer segment disk membranes obtained from photoreceptors of the toad (bufo marinus) retina. isolated, intact retinas, incubated in oxygenated ringer's solution at 23 +/- 1 degree c, were subjected to various conditions of illumination and then incubated in darkness for specified periods. the retinas were then chilled (0-4 degrees c) and the receptor outer segments (ros) were isolated. binding of the alpha- and beta-subunits of ... | 1986 | 3097246 |
| the effects of forced activity on circulating catecholamines and ph and water content of erythrocytes in the toad. | in vivo experiments were carried out to determine the effect of forced activity on circulating catecholamine levels, haematocrit, and the ph and water content of erythrocytes in the toad, bufo marinus. in addition, the effect of the beta-adrenergic agonist isoproterenol on erythrocyte ph and water content was examined in vitro. forced activity caused a significant decrease in both whole blood and erythrocyte ph, while haematocrit and circulating adrenaline and noradrenaline levels increased. ery ... | 1987 | 3104526 |
| background and bleaching equivalence in steady-state adaptation of vertebrate rods. | we have investigated background and bleaching adaptation in vertebrate rods by intracellular recording in the retina of bufo marinus. backgrounds and bleaching produce adaptation in photoreceptors and lead to a shift and a compression of the response operating range. threshold elevation due to backgrounds follows the rose-devries rule at low intensities and the weber-fechner rule at high intensities. threshold elevation due to bleaching is linear almost up to 17% bleached pigment and exponential ... | 1987 | 3106587 |
| a possible mechanism for binocular depth judgements in anurans. | two experiments were performed to analyze how anurans (bufo marinus) use binocular cues to gauge the distance of their prey. in the first, bilateral lesions of the nucleus isthmi eliminated the major source of input from the ipsilateral eye to the tectum. these lesions did not disrupt the animals' ability to use binocular cues to judge distance, suggesting that frogs and toads may not employ binocular disparity-selective cells to assess prey distance. they may instead use a scheme more overtly a ... | 1987 | 3108022 |