Showing papers on "Toad published in 1971"

Role of skin and neurohypophyseal hormones in the adaptation of the toad Bufo viridis to high salinities.

Abstract: MANY people maintain that ADH is important in the control of water and salt metabolism of amphibia1. The toad Bufo viridis is one of the species most resistant to dehydration and high ambient salinity, in which situations it has a high plasma salt concentration. In toads adapted to high salinity, the urine sodium chloride concentration increases to about plasma level, whereas active sodium transport, as measured by short circuit current, is almost completely reduced (ref. 2 and our measurements). The animals apparently do not drink and water is passively transferred along the osmotic gradient from the ambient solution into the body. We found that the sensitivity to added hormone was lost from the skins of animals that were adapted to saline solutions above 400 mosm.

Effect of prostaglandin e1 on osmotic water flow and sodium transport in the toad bladder

Abstract: The pros tag landins ,which are n a t u r a l l y occurr ing p ros t ano ic a c i d d e r i v a t i v e s , a r e widely d i s t r i b u t e d i n t i s s u e s and e x h i b i t a wide v a r i e t y of e f f e c t s . They imi t a t e , modify o r an tagonize t h e a c t i o n of s e v e r a l hormones which are thought t o be mediated by adenyl cyc la se and adenosine 3',5'-monophosphate(cyclic AMP). These a spec t s a r e covered comprehensively i n a series of recent reviews,and i n t h e proceedings of t h i s conference (Bergstr6m e t al, 1968; E l i a s son , 1959;von Euler & Eliasson,1967;Hortonl1969;Ramwell & Shaw,1970). Seve ra l e f f e c t s of p ros t ag land ins have been r epor t ed on t h e r e n a l handl ing of w a t e r and e l e c t r o l y t e s ( J o h n s t o n e t a l , 1967;Vander,1968) ,on osmotic water flow i n t h e i s o l a t e d c o l l e c t i n g duct(Or1off & GranthamIl967;Grantham & O r l o f f , 1968) ,and on both water flow and sodium t r a n s p o r t a c r o s s t h e toad b ladder (Or lof f e t a1,1965)and f rog sk in (Bar ry & H a l l , 1969; Fass ina e t a l , 1 9 6 9 ; Ramwell & Shaw, 1 9 7 0 ) . The s t u d i e s r epor t ed he re are p a r t of an a t t empt t o understand t h e a c t i o n s of PGEl( l la , 15( S ) -dihydroxy-9-keto-13-transp ros t ano ic a c i d ) on osmotic water flow and sodium t r a n s p o r t i n t he toad b ladder , t o i n v e s t i g a t e t h e r e l a t i o n s h i p of P G E l w i th vasopress in and t o determine t h e probable mechanism of a c t i o n of PGEl .

The effect of osmotic flow on the distribution of horseradish peroxidase within the intercellular spaces of toad bladder epithelium.

Abstract: Numerous studies have suggested that the lateral intercellular spaces can serve as part of the pathway for water movement across epithelia (2, 3, 5, 6, 11, 14, 15, 20, 22, 23, 24) . The primary evidence for this view has been the frequent observation in several tissues that increases in net fluid transport is accompanied by marked widening of intercellular spaces. However, recent work has demonstrated that widened intercellular spaces can occur without net water transfer, possibly due to contractile activity of smooth muscle (8, 9) . It has also been observed that the degree of stretch imposed on tissue can markedly affect the width of intercellular spaces (9) . Thus, it would be useful to follow water movement through intercellular spaces by a technique other than size changes .

Direct observation of toad bladder response to vasopressin.

Abstract: It has been suggested that the lateral intercellular space is a pathway for transepithelial water flow in several tissues. Fundamental to this postulate is the observation that coincident with accelerated net fluid transport, either coupled to active electrolyte transport as in the gallbladder (1, 2), or due to passive water flow along osmotic gradients as in the collecting tubule (3, 4) and anuran membranes (5, 6), the lateral intercellular spaces widen . To correlate morphologic changes with fluid transport the epithelium is usually fixed with aldehydes or osmium tetroxide in preparation for electron microscopy. There has been no uniformity in the manner of applying the different fixative solutions to the different tissues . Water translocations may occur during the period of primary fixation, resulting in distortions of the lateral intercellular spaces unrelated to the physiologic function of the viable tissue (7) . The problem of fixation artifacts, specifically with regard to changes in the size of the intercellular channels, can be obviated by observing the effect of hormone on the living tissue directly (3, 4) . In the present report we describe a simple method to observe directly the effect of accelerated hydrosmotic flow on the size of intercellular spaces in the isolated bladder of the toad, Bufo marinur.

Kinetics of RNA synthesis in toad bladder epithelium: action of aldosterone during the latent period

Abstract: Processing of RNA in the toad bladder was analyzed by polyacrylamide-gel electrophoresis to determine whether aldosterone causes any changes in the 1 hr before it potentiates transport of sodium ion. No change was found in the quantity or in the specific activity of bulk RNA labeled with uridine-5-3H. In vivo and in vitro with either uridine-5-3H or with methionine-(methyl)-3H as precursors, processing of RNA was extremely slow. Heterodisperse RNA was obvious after 30 min of continuous labeling, but labeling of the 40S precursor of ribosomal RNA was not apparent for 60 min. Labeling of mature 28S and 18S RNA first became apparent after 8 hr. ~7S RNA was the principal fastmigrating species labeled at 30 min, and 4S RNA was not heavily labeled until 1 hr. Aldosterone (5 × 10-7 mole/liter) produced no changes. If care were not taken to inhibit metabolism of native bacteria colonizing the bladder, bacterial RNA of high specific activity predominated. We conclude that RNA metabolism in the toad bladder is extraordinarily slow, that a major acceleration of de novo synthesis in response to physiologic doses of aldosterone was not demonstrable, and that some reports to the contrary may have been influenced by artifacts from bacterial RNA metabolism. Earlier evidence for obligatory alterations in RNA metabolism during the latent period is not strong.

Primary and secondary immune responses of the marine toad (Bufo marinus) to bacteriophage f2.

Abstract: The primary and secondary immune responses of toads (Bufo marinus) were studied using the bacteriophage f2 as antigen. Antibodies were identified in the serum 2 weeks after primary immunization and peak antibody levels were reached at 6 weeks. Although both IgM and IgG antibodies can be found in toad serum, most of the antibody activity in our animals persisted in the IgM fraction until 8 weeks after immunization. When a second injection of antigen was given 4 weeks after primary immunization, there was a marked increase in the total serum antibody activity and IgG antibodies were found as early as 4 weeks after the second injection of antigen. These observations suggest that the toad, B. marinus, is capable of a true secondary response to the bacteriophage f2.

Assessment of the Mineralocorticoid Activity of 18-Hydroxy-ll-deoxycorticosterone (18-OH-DOC) in the Isolated Toad Bladder

Abstract: 1. The stimulatory effect of 18- hydroxy-11-deoxycorticosterone (18-OH-DOC) on active sodium transport was assessed by measuring the short-circuit current (sec) of the isolated urinary bladder of the toad. The sec pattern recorded with 18-OH-DOC administration was identical with that of other mineralocorticoids such as aldosterone, deoxycorticosterone (DOC) and 9α-fluorocortisol although the magnitude of response was not as great. 2. The affinity of 18-OH-DOC for the mineralocorticoid receptor of the toad bladder was estimated by its dissociation constant to be 1/7 that of either aldosterone or 9a-fluorocortisol and approximately equal to cortisol. 3. Substitutions at either the C-18 and/or C-21 position of the corticosteroid molecule can modify or eliminate stimulatory effect on active sodium transport. (Endocrinology 89: 353, 1971)

Chohlinergic transmission in the recurrent facilitatory pathway of the spinal motoneuron of the toad

Abstract: 1. The VR-EPSP of the spinal motoneuron of the toad was investigated by intracellular recording. Concerning the size, time course, and effect of membrane potential displacements, no essential difference was found between the VR-EPSP in the toad and that in the frog. A remarkable facilitatory effect of the DR-EPSP on the VR-EPSP was observed.2. The effects of various pharmacological agents on the VR-EPSP were tested by topical application using a double- or triple-barrel microelectrode, or by application to the perfusion fluid through the vascular system.3. The VR-EPSP was increased in size and the decaying phase was prolonged by topical application of physostigmine. Acetylcholine was effective in increasing the size of the VR-EPSP when applied topically or through the vascular system.4. A transient depolarization, which may be called acetylcholine potential, was recorded intracellulary when acetylcholine was applied extracellularly by a brief outward current from the microelectrode filled with acetylcholine.5. Curare was found to have no effect on the VR-EPSP, while nicotine and atropine were effective in depressing the VR-EPSP.6. Cholinergic trasmission at the synapse between motor axon collaterals and motoneurons in the toad was demonstrated. It was, furthermore, pointed out that the present investigation did not exclude the possibility of electrical interaction between motoneurons.

Factors involved in the action of cyclic AMP on the permeability of mammalian kidney and toad urinary bladder.

Abstract: This discussion will be concerned with the role of cyclic AMP in the effects of antidiuretic hormone on the mammalian kidney and toad urinary bladder. The second messenger role of cyclic AMP has been established for the action of vasopressin by studies demonstrating that ADH stimulates adenyl cyclase activity in preparations of mammalian kidney 1. and of toad urinary bladder,3 that ADH increases the concentration of cyclic AMP in toad urinary bladder,4 and that cyclic AMP or theophylline has an effect on the permeability of renal collecting tubules 5 , and on the toad urinary bladder resembling that of vasopressin. Some factors affecting adenyl cyclase activity and the response to ADH have just been considered.R We are now trying to delineate the steps involved in the response to cyclic AMP. Before discussing this, it is of importance to point out that although cyclic AMP is generated presumably at the cell membrane at the basal or blood surface of the cell, the major permeability change occurs at the apical or urinary surface of these polar cells. There is excellent evidence that in the toad bladder and in the mammalian renal collecting tubule the major permeability barrier to water movement across the tissue is located at the apical or urinary surface and that vasopressin increases the permeability of this barrier.9~ 10, l 1 The locus of the major rate-limiting step in sodium transport affected by vasopressin in toad bladder has not been clearly delineated. There is no evidence that vasopressin directly affects sodium transport in the mammalian kidney. The usual working model for sodium transport across the toad bladder epithelial cell includes a passive entry step from the urine into the cell across the apical cell membrane and an active extrusion step across the basal cell membrane. A number of laboratories have provided evidence indicating that the hormone affects the passive mucosal entry step l2 and the active serosal extrusion step.l3, l4 Experiments now in progress in our laboratory indicate that the major effect of the hormone is on the mucosal entry step. In these studies sheets of epithelial cells are scraped off the intact bladder after treatment with collagenase and incubated with or without vasopressin. These cells are viable in that their rate of oxidation of 14C-labeled substrate is stimulated by vasopressin and depressed by ouabain as expected. After 15 minutes, the time at which hormonal stimulation of sodium transport in the intact bladder reaches a peak, the paired cell preparations are harvested and their water and electrolyte content measured by standard techniques. Within the framework of the model of mucosal entry in series with active serosal extrusion of sodium, one would predict that if the major effect of the hormone is to enhance mucosal entry, there will be an increase in the cell sodium content. If the major effect is stimulation of the serosal extrusion step, we would expect a fall in cell sodium. The results are summarized in TABLE 1. There is a rise in cell sodium and water content and a fall in cell potassium.

Fluorescent histochemical studies on the effects of 6-hydroxydopamine on adrenaline-containing nerves in the toad

Abstract: Fluorescence histochemistry has been used to study the effects of 6-hydroxydopamine (6-OHDA) (100 mg/kg injected into the dorsal lymph sac) on adrenaline-containing nerves in the large intestine, mesentery, lung, bladder and heart atria of the toad Bufo marinus. A gradual decrease both in fluorescence intensity and in number of detectable fibres during the first 4 hours after 6-OHDA was accompanied by a build-up of fluorescence in the nonterminal regions. These phenomena have been discussed in relation to the time course of the degeneration produced by 6-OHDA in noradrenergic nerves of higher vertebrates. Almost complete “chemical sympathectomy” was seen after one day, and it was not till 13 days that regenerating nerve fibres were seen in any organ. In the large intestine, however, re-innervation was slower, being first noted after 39 days. The time course of regeneration has been compared with that following sympathectomy in various mammalian organs.