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Showing papers on "Toad published in 1993"



Journal ArticleDOI
TL;DR: The primary sequence and functional expression of a novel β subunit (βbladder=βbl) isolated from a toad bladder epithelial cell cDNA library is reported, indicating that, in addition to the known β1 and β3 isoforms, a third distinct isoform of theβ subunit is present in the bladder epithelium.
Abstract: The cortical collecting tubule (CCT) of the mammalian kidney reabsorbs sodium and potassium, processes that are mediated by Na/K-ATPase and H/K-ATPase. CCT is also an important site for proton secretion, which is driven, in part, by H/K-ATPase. Na/K-ATPase and H/K-ATPase are members of the ion-motive P-ATPase gene family. They are closely related plasma membrane proteins which consist of αβ heterodimers. The urinary bladder of the toad Bufo marinus is the amphibian counterpart of mammalian CCT. We have previously characterized a ouabain-resistant Na/K-ATPase [see ref. 17], from TBM cells, a clonal cell line derived from the toad bladder, which expresses transepithelial sodium transport. In the present study, we report the primary sequence and functional expression of a novel β subunit (βbladder=βbl) isolated from a toad bladder epithelial cell cDNA library. The deduced polypeptide is 299 amino acids in length and has a predicted molecular mass of 33 kDa. The βbl protein exhibits 35% amino acid identity to the previously characterized β1 of B. marinus Na/K-ATPase and 39% identity with β3 of B. marinus Na/K-ATPase. It shares 38% identity with the mammalian β gastric H/K-ATPase and 52% with the mammalian β2 Na/K-ATPase. Northern blot analysis shows that a 1.4×103-base mRNA is expressed at a high level in bladder epithelial cells and eye and at a trace level in kidney; it is not detectable in significant amounts in the stomach, colon and small intestine. The βbl subunit can associate with the α1 subunit of B. marinus Na/K-ATPase to form a functional sodium pump in the Xenopus laevis oocyte. Our data indicate that, in addition to the known β1 and β3 isoforms, a third distinct isoform of the β subunit is present in the bladder epithelium. This new isoform could be functionally associated with α subunits of either Na/K- or H/K-ATPase.

28 citations


Journal ArticleDOI
TL;DR: It is indicated that bladder volume participates in the regulation of Jv in the ventral pelvic patch and angiotensin II and circulation as the regulatory mechanism.
Abstract: This report examines the importance of bladder volume in regulating cutaneous water uptake (Jv, cm3.cm-2.s-1 x 10(-7)) across the ventral pelvic patch and examines the role of angiotensin II (ANG II) and circulation as the regulatory mechanism. Jv in empty-bladder Bufo marinus (bladder volume 3.89 +/- 1.49%, n = 7) was 1,671 +/- 68 (n = 7). Injection of Ringer solution into the bladder (12.8 +/- 2.2%, n = 7) decreased Jv to 1,025 +/- 202 (n = 7). ANG II injected into toads with filled bladders increased Jv in a dose-dependent manner. At 5 micrograms/100 g toad Jv increased by 136 +/- 63 (n = 6), at 50 micrograms/100 g toad by 432 +/- 82 (n = 7), and at 200 micrograms/100 g toad by 620 +/- 142 (n = 5). Saralasin (200 micrograms/100 g toad) completely inhibited the response to ANG II (50 micrograms/100 g toad) and at 1 mg/100 g toad decreased Jv in empty-bladder toads. These experiments indicate that 1) bladder volume participates in the regulation of Jv in the ventral pelvic patch; 2) ANG II increases the Jv in toads with full bladders; 3) saralasin inhibits the high Jv in empty bladder toads; 4) the high Jv, associated with an empty bladder, requires an intact circulation to be maintained; 5) without an intact circulation, the high water flow associated with an empty bladder causes the Na+ content of the tissue in the ventral patch to be reduced; and 6) ANG II causes only a minimal increases in water permeability in the isolated pelvic patch skin.

23 citations


Journal ArticleDOI
TL;DR: The results obtained suggest that the major toad liver GST is distinct from any known GST, including microbial, plant and mammalian GSTs.
Abstract: Five forms of glutathione transferase (GST) were resolved from the cytosol of adult common toad (Bufo bufo) liver by GSH-affinity chromatography followed by isoelectric focusing. The major enzyme (GST-7.64; 55% of total activity bound to the column) has a pI value of 7.64, is composed of two subunits each with a molecular mass of 23 kDa, and has the N-terminal amino acid residue blocked. GST-7.64 has also been characterized with respect to amino acid composition, substrate specificity, inhibition characteristics, c.d. spectra and immunological reactivity. The N-terminal sequence of some peptides obtained after tryptic digestion has also been determined. All together the results obtained suggest that the major toad liver GST is distinct from any known GST, including microbial, plant and mammalian GSTs.

19 citations


Journal ArticleDOI
TL;DR: It is concluded that amphibian tachykinins cause depressor effects via an NK-1-like receptor which differs substantially from its mammalian counterpart.

15 citations


Journal ArticleDOI
TL;DR: Digitalis-like compounds (DLC), normal constituents of animal tissues, are possible regulators of the Na + ,K + -ATPase implicated in water and salt homeostasis and are present in toad (Buffo viridis) tissues.
Abstract: Digitalis-like compounds (DLC), normal constituents of animal tissues, are possible regulators of the Na+,K(+)-ATPase implicated in water and salt homeostasis. DLC are present in toad (Bufo viridis) tissues. Although DLC highest levels were found in toad skin, it was also detected in plasma and many internal organs. The abundant distribution and the different levels of DLC in various tissues exclude the possibility that toxicity is the only function of these compounds in the toad. The concentration of DLC in toad plasma is 30 microM, out of which 25-30% is bound to plasma proteins. Fractionation of toad plasma proteins on a G-100 Sephadex column followed by the extraction of DLC from the plasma proteins revealed that DLC are bound primarily to proteins of 48,000-53,000 Da. These results establish the existence of bufodienolide-binding protein(s) in animal plasma.

14 citations


Journal Article
TL;DR: In one case, an EKG showed bradycardia, and a first and second degree A-V block; this patient died of ventricular fibrillation, and the prognosis in two cases was good.

14 citations


Journal ArticleDOI
TL;DR: It is concluded that, up to stage 22, no significant changes in the expression of glutathione transferases isoenzymes occurred during Bufo bufo embryo development.

13 citations


Journal Article
TL;DR: The studies suggest that some of the metabolites of corticosterone found in toad bladder are the same as those identified in mammalian tissues, and some of them may be important modulators of sodium and water transport in the distal nephron.
Abstract: The mammalian kidney metabolizes virtually all of the steroid hormones. Corticosterone receptors have been found in the cortical collecting tubule, and at least four metabolites of the hormone have been identified in rat renal tissue and urine. The biologic activity of these metabolites is not completely known. In this study, we examined the functional effects of three of the metabolites of corticosterone on membrane transport in toad and turtle bladders; we also analyzed the oxidoreductase pathways for corticosterone metabolism. In the toad bladder, maximal water flow (vasopressin- and cyclic AMP-stimulated) was unaffected by corticosterone, 11-dehydro-20-dihydrocorticosterone (metabolite I) and 11-dehydrocorticosterone (metabolite IV); maximal water flow was significantly inhibited by 20-dihydrocorticosterone (metabolite II). Sodium transport in the toad bladder was stimulated by corticosterone, 11-dehydrocorticosterone and 20-dihydrocorticosterone. Analysis of the oxidoreductase pathways in this tissue revealed that most of the corticosterone was oxidized to 11-dehydrocorticosterone, a biologically active compound; 11-dehydrocorticosterone was further metabolized to 11-dehydro-20-dihydrocorticosterone, a biologically inactive compound. Only 6% of the parent compound was converted to 20-dihydrocorticosterone. In the turtle bladder, none of the metabolites tested altered hydrogen ion secretion over the time period studied; no significant biotransformation of corticosterone occurred in this tissue. As the metabolites of corticosterone found in toad bladder are the same as those identified in mammalian tissues, our studies suggest that some of them may be important modulators of sodium and water transport in the distal nephron. Our data further suggest that these compounds are likely not involved in the regulation of urinary acidification.

9 citations


Journal ArticleDOI
TL;DR: Microinjection of L-glutamic acid into the basal midbrain of the toad Bufo paracnemis induced a series of responses linked to antipredator behavior such as flight, backward locomotion and defensive postures, a behavior which is probably important for the animal to achieve the above responses.
Abstract: Microinjection of L-glutamic acid into the basal midbrain of the toad Bufo paracnemis induced a series of responses linked to antipredator behavior such as flight, backward locomoti

9 citations


Journal ArticleDOI
TL;DR: Data from this study and available studies in the literature suggest that adenosine monophosphate deaminase in land vertebrates is quite high in white skeletal muscle, usually somewhat lower in red muscle, and 15-to 500-fold lower in cardiac muscle, whereas the common North American toad, Bufo americanus, provides a striking exception to the rule.
Abstract: The specific activity of three characteristic enzymes, adenylate deaminase, adenylate kinase, and creatine kinase, in the skeletal muscles and heart of a variety of vertebrate land animals, including the human, are surveyed. Data from this study and available studies in the literature suggest that adenosine monophosphate deaminase in land vertebrates is quite high in white skeletal muscle, usually somewhat lower in red muscle, and 15- to 500-fold lower in cardiac muscle. Adenosine monophosphate deaminase is active primarily under ischemic or hypoxic conditions which occur frequently in white muscle, only occasionally in red muscle, and ought never occur in heart muscle, and this may therefore account for observed enzyme levels. The common North American toad, Bufo americanus, provides a striking exception to the rule with cardiac adenosine monophosphate deaminase as high as in mammalian skeletal muscle, whereas its skeletal muscle level of adenosine monophosphate deaminase is several times lower. The exceptional levels in the toad are not due to a change in substrate binding and are not accompanied by comparable change in the level of adenylate or creatine kinase. Nor do they signal any major change in isozyme composition, since a human muscle adenosine monophosphate deaminase-specific antiserum reacts with toad muscle adenosine monophosphate deaminase, but not with toad heart adenosine monophosphate deaminase. They do not represent any general anuran evolutionary strategy, since the bullfrog (Rana catesbeiana) and the giant tropic toad (Bufo marinus) have the usual vertebrate pattern of adenosine monophosphate deaminase distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Journal ArticleDOI
TL;DR: This finding suggests that the increases in plasma and pituitary prolactin levels in larvae at metamorphic climax and in adults that remain in or migrate into water, as reported previously, accompany the increase in Prolactin synthesis.
Abstract: A toad (Bufo japonicus) prolactin cDNA was specifically amplified from cDNAs constructed from the total RNA of adenohypophyses, employing the DNA polymerase chain reaction. Sequencing analysis revealed that the cDNA clone thus obtained was 602 bp in length, and encoded the C-terminal 134 amino acid residues of the toad prolactin molecule. The length of the toad prolactin mRNA was estimated to be about 1.0 kb by Northern blot analysis. The partial amino acid sequence deduced from the nucleotide sequence showed the following homologies between toad prolactin and the prolactins of other vertebrates: 69% with man, 80% with chicken, 81% with sea turtle, 91% with bullfrog and 38% with salmon. Using the cDNA as a probe, developmental and seasonal changes in prolactin mRNA levels in the pituitaries of toads were studied. Prolactin mRNA in the pituitary rose as metamorphosis progressed and declined at the end of metamorphosis. During the breeding season the pituitary content of prolactin mRNA was relatively high. This finding suggests that the increases in plasma and pituitary prolactin levels in larvae at metamorphic climax and in adults that remain in or migrate into water, as reported previously, accompany the increase in prolactin synthesis.

Journal ArticleDOI
TL;DR: Dose‐dependent tension curves were recorded from the in vitro toad aortas by administration of endothelin‐1 and sarafotoxin‐S6b and the maximal contractile tensions by both drugs were evoked at a 10−8 M concentration.
Abstract: Dose-dependent tension curves were recorded from the in vitro toad aortas by administration of endothelin-1 and sarafotoxin-S6b. The maximal contractile tensions by both drugs were evoked at a 10(-8) M concentration. By a single dose application (10(-8) M) of endothelin-1 and sarafotoxin-S6b to both endothelium-preserved and denuded vessels, the induction of the endothelium-dependent vasocontraction occurs after 2 min of administration. Ultrastructural changes of Weibel-Palade bodies such as decrease in electron density, swelling with a wide peripheral halo, and expulsion of their contents in a manner of exocytosis become evident within 2 min after administration of these drugs. These findings indicate that some vasocontractile substances in Weibel-Palade bodies are extracellularly discharged by endothelin-1 and sarafotoxin-S6b.

Journal ArticleDOI
TL;DR: Measurements of osmotic water permeability (Pf) have shown that the plasma membranes of human red cells and certain epithelial cells possess specialized water channels that form functional water channels in Xenopus oocytes and when reconstituted into proteoliposomes.
Abstract: Measurements of osmotic water permeability (Pf) have shown that the plasma membranes of human red cells and certain epithelial cells possess specialized water channels. Although these water channels have been characterized extensively using biophysical techniques, the proteins that compose these unique channels have only recently been identified. Antidiuretic hormone (ADH) stimulation rapidly increases collecting duct epithelial cell Pf by fusion of water channel-containing vesicles (WCV) with their apical membranes. The proteins of WCV from toad bladder and rodent kidney have been characterized. The principal proteins in toad bladder WCV are 55,000 daltons (55 kDa) and 53 kDa and span the lipid bilayer of these vesicles. Polyclonal antisera raised against the 55-kDa and 53-kDa proteins inhibit ADH-stimulated toad bladder Pf by 80% and recognize protein bands of 46, 38 and 30 kDa in mouse kidney. Purification of WCV from rat kidney reveals enrichment of the 46-kDa protein. Recently, a 28-kDa integral membrane protein (called CHIP-28) has been isolated from human red cells. It forms functional water channels inXenopus oocytes and when reconstituted into proteoliposomes. Large amounts of CHIP-28 protein are present in epithelial cells of the proximal tubule and descending thin limb of Henle's loop. Molecular cloning efforts are underway to elucidate the structure and function of these candidate water channel proteins.

Journal ArticleDOI
TL;DR: The data point to the presence of a Hg(2+)‐sensitive apical water pathway in stimulated epithelia, very probably constituted by water channels similar to those reported in red blood cells, amphibian bladder and mammalian kidney tubules.
Abstract: 1. Net water flow (Jw) was continuously monitored across the abdominal skin of the toad Bufo marinus by means of a volumetric, automatic technique. Jw was either averaged over periods of 2 min or taken cumulatively (10 or 30 min periods). 2. The state of high water permeability induced by vasopressin or isoprenaline was reversed (88-89% inhibition of delta Jw after 1 h) by the addition of 10(-3) M HgCl2 (or CH3ClHg) to the external bathing medium. Similarly, pre-exposure of the skins to Hg2+, totally blocked the induction of the hydrosmotic response to the same agents. By itself, Hg2+ exerted only a minor (26%) stimulation of basal Jw. 3. There was a sigmoidal dose-response relationship between the reduction of the hydrosmotic effect of vasopressin (VP) and the concentration of Hg2+ in the external medium, with a half-maximal effect at 1.2 x 10(-4) M HgCl2. 4. Total replacement of Na+ by K+, Rb+ or Cs+ in the Ringer solution, caused a VP-like, hydrosmotic effect that was reversed, or prevented, by exposure to Hg2+ in a manner indistinguishable from that previously seen with vasopressin or isoprenaline. 5. The data point to the presence of a Hg(2+)-sensitive apical water pathway in stimulated epithelia, very probably constituted by water channels similar to those reported in red blood cells, amphibian bladder and mammalian kidney tubules.

Journal ArticleDOI
TL;DR: The levels of IGF-I have been simultaneously measured by radioimmunoassay in samples of the toad Bufo arenarum and of normal male Wistar rats and their binding properties have been identified by ligand blot and Scatchard analysis in the serum of both species.

Journal ArticleDOI
TL;DR: The Hg-induced apical water pathway in toad skin appears to be a unique model for studying the interplay between cell volume, cell ionic composition and water permeability.
Abstract: Hg compounds block membrane transport units behaving as water channels. Here we show that Hg induces an apical water pathway in toad skins pretreated with 10(-3) M CH3ClHg or HgCl2, added to the outer bathing medium. Washing with SO4-Ringer caused a several-fold increase in net water flow (Jw) and osmotic permeability coefficient (Pf) that was reversed by re-exposure to Cl- or NO3-Ringer and mimicked by gluconate-Ringer. These Pf changes could be elicited repeatedly and were present if, and only if, anion replacements took place in the inner bathing solution. Such inner polarity was related to the anion permeability of the epidermal basolateral membrane: impermeant anions (SO4, gluconate) increased Pf; permeant anions (Cl, NO3) did not change basal Pf but reversed the high Pf induced by impermeant anions. Hg induced the appearance of aggregates that persisted despite repeated washings of the skins during 4-5 h, and whether Pf was high (SO4-Ringer) or low (Cl-Ringer) before skin fixation. The Hg-induced apical water pathway in toad skin appears to be a unique model for studying the interplay between cell volume, cell ionic composition and water permeability.

Journal ArticleDOI
01 Sep 1993
TL;DR: A new species of toad is described from the Nile Delta that appears to be mostly aquatic and closely related to Afro-tropical bufonids.
Abstract: A new species of toad is described from the Nile Delta. It appears to be mostly aquatic and closely related to Afro-tropical bufonids. The species has previously been misidentified as Bufo vittatus Boulenger, 1906.

Journal ArticleDOI
TL;DR: A modified protocol for the immunocytochemical identification of 5-bromo-2'-deoxyuridine (BrdU) as an indicator of cell replication in different tissues of the toad, Bufo arenarum Hensel, can be used safely for the study ofcell replication in toads and other Anura amphibia.
Abstract: We present a modified protocol for the immunocytochemical identification of 5–bromo-2′4eoxyuridine (BrdU) as an indicator of cell replication in different tissues of the toad, Bufo arenarum Hensel. Animals were sacrificed 60 min after BrdU (5 mg/100 g body weight) was injected into the dorsal lymph sac. The tissues were fixed in Carnoy's fluid and stained by the immunoperoxidase method using an anti-BrdU monoclonal antibody. This protocol can be used safely for the study of cell replication in toads and other Anura amphibia.

Journal ArticleDOI
TL;DR: The effectiveness of the sulfidopeptide leukotrienes in eliciting hypotension at low doses (1 ng/kg body wt) suggests that these compounds may be important cardiovascular regulators in the toad.

Journal Article
TL;DR: The results suggested that GABA_A and GABA_B receptors coexist on the so-matic membrane of toad dorsal root ganglion neurons and mediate the changes respec-tively in membrane potential and shortening of ApD.
Abstract: Intracellular recordings were made from neurons in toad dorsal root ganglion in vitro. Bath application of GABA (10(-4)-10(-3) mol/L) elicited either depolarization or depolarization followed by hyperpolarization respectively in 79% and 10% of the neurons. The remaining 11% did not show any response. The GABA-induced depolarization, which was accompanied by an increase of membrane conductance and usually a shortening of action potential duration (ApD), could be blocked by bicuculline. The GABA-depolarization was enhanced by low Cl- Ringer or reduced by high Cl- Ringer The membrane potential was not affected by 10(-4) mol/L baclofen. On the other hand, shortening of ApD could be produced by baclofen, but not blocked by bicuculline. Our results suggested that GABAA and GABAB receptors coexist on the somatic membrane of toad dorsal root ganglion neurons and mediate the changes respectively in membrane potential and shortening of ApD. The mechanism underlying presynaptic inhibition in the terminals of the primary afferents was discussed.

Journal Article
TL;DR: It is concluded that morphine down-regulates the sensitivity of alpha 1-adrenoceptor in toad SG neuron mediated by opioid receptor and the variation in Ca2+ activity may be involved in this effect.
Abstract: Intracellular recordings were performed on 35 neurons from 35 isolated toad spinal ganglia (SG) and the extracellular free calcium ion activities were measured in another 26 isolated toad SG by Ca(2+)-selective microelectrodes. The effects of morphine on the sensitivities of alpha-adrenoceptors were observed. It was found that depolarization of membrane potential induced by norepinephrine (NE 10-100 mumol.L-1) or alpha 1-adrenoceptor agonist phenylephrine (100 mumol.L-1) was depressed by morphine (27 mumol.L-1). Superfusing SG with opioid receptor antagonist naloxone (100 mumol.L-1) blocked the depressing effect of morphine on NE-induced depolarization. The depressing effect of morphine on NE-induced depolarization was not affected by superfusing SG with alpha 2-adrenoceptor antagonist yohimbine (5 mumol.L-1). NE (100 mumol.L-1) reduced the extracellular free calcium ion activity while morphine (27 mumol.L-1) increased the extracellular free calcium ion activity in SG. It is concluded that morphine down-regulates the sensitivity of alpha 1-adrenoceptor in toad SG neuron mediated by opioid receptor and the variation in Ca2+ activity may be involved in this effect.


Journal ArticleDOI
TL;DR: Results indicate that this homologue AT I would act in amphibian tissues by conversion to AT II, and it is suggested that toad skin and aorta contractility would be affected by this conversion.

Journal ArticleDOI
TL;DR: It is concluded that MA, IN, PGE2, CO2, and ↑CO2 stimulate IP formation in cells of toad urinary bladder and inositol triphosphate may be an important second messenger in mediating the response of MA.
Abstract: The urinary bladder of Bufo marinus excretes H+ and this excretion is increased by metabolic acidosis (MA), insulin (IN), prostaglandin E2 (PGE2), increases CO2, and aldosterone. The purpose of this experiment was to determine whether MA, IN, PGE2, CO2, and aldosterone stimulate inositol phosphate's (IP) formation in isolated cells of toad urinary bladder. Cells were prepared by treating bladder sacs with collagenase. Cells were obtained from 10 toads in MA and 10 normal toads, suspended in 2 ml of Ringer's solution containing LiCl (10 mM), myo-inositol (5 mM), and [3H]myo-inositol (10 microCi), and then incubated for 2 hr at 25 degrees C. Cells were homogenized and the IP fractions quantitated by column chromatography and liquid scintillation counting. The results were expressed as dpm (mu MPO4)-1 (hr)-1. The IP in MA cells was 44,202 +/- 4,646 and in normal toad cells it was 31,637 +/- 3,613 (P < 0.05). In a separate experiment, cells from 10 paired hemibladders were isolated from normal toads. The cells were treated exactly as above except there were no LiCl in the bath. LiCl was added to all baths after 2 hr and the experimental cells were challenged with IN, PGE2, increases CO2, and aldosterone for 20 min. The IP were quantitated as above. IN treatment stimulated inositol bisphosphate and inositol triphosphate (P < 0.01). PGE2 and increases CO2 also stimulated inositol triphosphate (P < 0.05). Aldosterone did not alter formation of any of the IP fractions. We conclude that MA, IN, PGE2, and increases CO2 stimulate IP formation in cells of toad urinary bladder and inositol triphosphate may be an important second messenger in mediating the response of MA, IN, PGE2, and increases CO2.

Journal Article
TL;DR: Digitalis-like compounds (DLC), normal constituents of animal tissues, are possible regulators of the Na+,K+-ATPase implicated in water and salt homeostasis and establish the existence of bufodienolide-binding protein(s) in animal plasma.
Abstract: Summary: Digitalis-like compounds (DLC), normal constituents of animal tissues, are possible regulators of the Na+,K+-ATPase implicated in water and salt homeostasis. DLC are present in toad (Bufo viridis) tissues. Although DLC highest levels were found in toad skin, it was also detected in plasma and many internal organs. The abundant distribution and the different levels of DLC in various tissues exclude the possibility that toxicity is the only function of these compounds in the toad. The concentration of DLC in toad plasma is 30 μM, out of which 25–30% is bound to plasma proteins. Fractionation of toad plasma proteins on a G-100 Sephadex column followed by the extraction of DLC from the plasma proteins revealed that DLC are bound primarily to proteins of 48,000–53,000 Da. These results establish the existence of bufodienolide-binding protein(s) in animal plasma.


01 Jan 1993
TL;DR: In this article, the proteins of WCV from toad bladder and rodent kidney have been characterized and the principal proteins in WCV are 55,000 daltons (55 kDa) and 53 kDa and span the lipid bilayer of these vesicles.
Abstract: Measurements of osmotic water permeability (Pf) have shown that the plasma membranes of human red cells and certain epithelial cells possess specialized water channels. Although these water channels have been charac- terized extensively using biophysical techniques, the pro- teins that compose these unique channels have only re- cently been identified. Antidiuretic hormone (ADH) stim- ulation rapidly increases collecting duct epithelial cell Pf by fusion of water channel-containing vesicles (WCV) with their apical membranes. The proteins of WCV from toad bladder and rodent kidney have been characterized. The principal proteins in toad bladder WCV are 55,000 daltons (55 kDa) and 53 kDa and span the lipid bilayer of these vesicles. Polyclonal antisera raised against the 55- kDa and 53-kDa proteins inhibit ADH-stimulated toad bladder Pf by 80% and recognize protein bands of 46, 38 and 30 kDa in mouse kidney. Purification of WCV from rat kidney reveals enrichment of the 46-kDa protein. Recently, a 28-kDa integral membrane protein (called CHIP-28) has been isolated from human red cells. It forms functional water channels in Xenopus oocytes and when reconstituted into proteoliposomes. Large amounts of CHIP-28 protein are present in epithelial cells of the proximal tubule and descending thin limb of Henle's loop. Molecular cloning efforts are underway to elucidate the structure and function of these candidate water channel proteins.

Journal ArticleDOI
TL;DR: An acid extract of 12 intermediate pituitaries from adult B .
Abstract: FIGURE 1. An acid extract of 12 intermediate pituitaries from adult B . marinus was fractionated on a Sephadex G-25 column, equilibrated in 10% formic acid. Aliquots of column fractions were screened with a N-acetyl-specific @-endorphin RIA (filled circles) and a C-terminal-specific @-endorphin RIA (open circles). The C-terminal-specific P-endorphin RIA detected a broad peak of immunoreactivity that corresponds to a molecular weight ranging between 3200-2500 Da. The N-acetyl-specific @-endorphin RIA detected a major peak of immunoreactivity (Kav 0.66) that had an apparent molecular weight of 1.2 kDa. The fractions from the lower molecular weight peak were pooled for further analyses by reversedphase HPLC.

Journal ArticleDOI
TL;DR: It is concluded that the inhibition of CA release by muscarine in the toad probably occurs at a level other than the membrane, and the participation of both Na+ and Ca2+ currents in the genesis of spikes is suggested.