Experimental realization of a Rydberg optical Feshbach resonance in a quantum many-body system

Feshbach resonances are a powerful tool to tune the interaction in an ultracold atomic gas. The commonly used magnetic Feshbach resonances are specific for each species and are restricted with respect to their temporal and spatial modulation. Optical Feshbach resonances are an alternative which can overcome this limitation. Here, we show that ultra-long-range Rydberg molecules can be used to implement an optical Feshbach resonance. Tuning the on-site interaction of a degenerate Bose gas in a 3D optical lattice, we demonstrate a similar performance compared to recent realizations of optical Feshbach resonances using intercombination transitions. Our results open up a class of optical Feshbach resonances with a plenitude of available lines for many atomic species and the possibility to further increase the performance by carefully selecting the underlying Rydberg state.

The West Pacific diversity hotspot as a source or sink for new species? Population genetic insights from the Indo-Pacific parrotfish Scarus rubroviolaceus

We used a population genetic approach to quantify major population subdivisions and patterns of migration within a broadly distributed Indo-Pacific parrotfish. We genotyped 15 microsatellite loci in Scarus rubroviolaceus collected from 20 localities between Africa and the Americas. A STRUCTURE model indicates the presence of four major populations: Eastern Pacific, Hawaii, Central-West Pacific and a less well-differentiated Indian Ocean. We used the isolation and migration model to estimate splitting times, population sizes and migration patterns between sister population pairs. To eliminate loci under selection, we used BayeScan to select loci for three isolation and migration models: Eastern Pacific and Central-West Pacific, Hawaii and the Central-West Pacific, and Indian Ocean and the Central-West Pacific. To test the assumption of a stepwise mutation model (SMM), we used likelihood to test the SMM against a two-phase model that allowed mutational complexity. A posteriori, minor departures from SMM were estimated to affect ≤2% of the alleles in the data. The data were informative about the contemporary and ancestral population sizes, migration rates and the splitting time in the eastern Pacific/Central-West Pacific comparison. The model revealed a splitting time ∼17,000 BP, a larger contemporary N(e) in the Central-West Pacific than in the eastern Pacific and a strong bias of east to west migration. These characteristics support the Center of Accumulation model of peripatric diversification in low-diversity peripheral sites and perhaps migration from those sites to the western Pacific diversity hotspot.

Why amphibians are more sensitive than mammals to xenobiotics

Dramatic declines in amphibian populations have been described all over the world since the 1980s. The evidence that the sensitivity to environmental threats is greater in amphibians than in mammals has been generally linked to the observation that amphibians are characterized by a rather permeable skin. Nevertheless, a numerical comparison of data of percutaneous (through the skin) passage between amphibians and mammals is lacking. Therefore, in this investigation we have measured the percutaneous passage of two test molecules (mannitol and antipyrine) and three heavily used herbicides (atrazine, paraquat and glyphosate) in the skin of the frog Rana esculenta (amphibians) and of the pig ear (mammals), by using the same experimental protocol and a simple apparatus which minimizes the edge effect, occurring when the tissue is clamped in the usually used experimental device.The percutaneous passage (P) of each substance is much greater in frog than in pig. LogP is linearly related to logKow (logarithm of the octanol-water partition coefficient). The measured P value of atrazine was about 134 times larger than that of glyphosate in frog skin, but only 12 times in pig ear skin. The FoD value (Pfrog/Ppig) was 302 for atrazine, 120 for antipyrine, 66 for mannitol, 29 for paraquat, and 26 for glyphosate.The differences in structure and composition of the skin between amphibians and mammals are discussed.

The adrenergic receptor subtypes present in frog (Rana esculenta) skin

Frog skin transports ions and water under hormonal control. In spite of the fundamental role played by adrenergic stimulation in maintaining the water balance of the organism, the receptor subtype(s) present in the skin have not been identified yet. We measured the increase in short-circuit current (ISC, an estimate of ion transport) induced by cirazoline, clonidine, xamoterol, formoterol, or BRL 37344, in order to verify the presence of alpha1, alpha2, beta1, beta2, or beta3 receptor subtypes, respectively. Only after treatment with formoterol, BRL 37344 and, to a lesser extent, cirazoline was measured a significant increase in ISC (57%, 33.2%, and 4.7%, respectively). The formoterol and BRL 37344 concentrations producing half-maximal effect (EC50) were 1.12 and 70.1 nM, respectively. Moreover, the formoterol effect was inhibited by treatment with ICI 118551 (antagonist of beta2 receptors) while SR 59230A (antagonist of beta3 receptors) had no effect; opposite findings were obtained when the BRL 37344 stimulation was investigated. Finally, by measuring the transepithelial fluxes of 22Na+ and 36Cl-, we demonstrated that Na+ absorption is increased by activation of beta2 and beta3 and is cAMP-sensitive, whereas the Cl- secretion is only increased by activation of beta2 receptors and is cAMP- and calmodulin-sensitive.

Atrazine increases the sodium absorption in frog (Rana esculenta) skin

The presence of atrazine in agricultural sites has been linked to the decline in amphibian populations. The efforts of the scientific community generally are directed toward investigating the long-term effect of atrazine on complex functions (reproduction or respiration), but in the present study, we investigated the short-term effect on the short-circuit current (I(sc)), a quantitative measure of the ion transport operated by frog (Rana esculenta) skin. Treatment with 5 microM atrazine (1.08 mg/L) does not affect the transepithelial outfluxes of [14C]mannitol or [14C]urea; therefore, atrazine does not damage the barrier properties of frog skin. Atrazine causes a dose-dependent increase in the short-circuit current, with a minimum of 4.64 +/- 0.76 microA/cm2 (11.05% +/- 1.22%) and a maximum of 12.7 +/- 0.7 microA/cm2 (35% +/- 2.4%) measured at 10 nM and 5 microM, respectively. An increase in Isc also is caused by 5 microM ametryne, prometryn, simazine, terbuthylazine, or terbutryn (other atrazine derivatives). In particular, atrazine increases the transepithelial 22Na+ influx without affecting the outflux. Finally, stimulation of Isc by atrazine is suppressed by SQ 22536, H89, U73122, 2-aminoethoxydiphenyl borate, and W7 (blockers of adenylate cyclase, protein kinase A, phospholipase C, intracellular Ca2+ increase, and calmodulin, respectively), whereas indomethacin and calphostin C (inhibitors of cyclooxygenase and protein kinase C, respectively) have no effect.

Inositol 1,4,5-trisphosphate and ryanodine receptors mobilize calcium from a common functional pool in human U373 MG cells

This investigation concentrates on the change in Ca(2+) concentration ([Ca(2+)]) caused by ryanodine in U373 MG cells. This cell type from a human astrocytoma is a unique cellular model because it only expresses the type 3 ryanodine receptor (RyR3), which is generally the least abundant isoform. In the presence of physiological [Ca(2+)] in the extracellular medium, U373 MG cells are caffeine-insensitive, even after forskolin treatment, and ryanodine-sensitive only when an unusually high concentration (30 microM) is applied. Xestospongin C behaves like thapsigargin and therefore cannot be used as a selective antagonist of inositol 1,4,5-trisphosphate receptors (InsP(3)Rs). After ryanodine challenge, addition of an analog of Substance P (SP), which should deplete InsP(3)-sensitive stores, has no effect on [Ca(2+)](i). After thapsigargin treatment, which unmasks the calcium leak from intracellular stores, neither ryanodine nor SP change [Ca(2+)](i), suggesting that thapsigargin completely depletes the ryanodine-sensitive and the InsP(3)-sensitive stores of U373 MG cells. Finally, in experiments monitoring the [Ca(2+)] in intracellular stores, InsP(3) stimulation of permeabilized cells causes a decrease in [Ca(2+)] that is not affected by subsequent ryanodine treatment. Our results support the conclusion that U373 MG cells express both InsP(3)Rs and RyRs that can individually or in combination mobilize only one functional Ca(2+) pool.

Eledoisin and Kassinin, but not Enterokassinin, stimulate ion transport in frog skin

In frog skin, tachykinins stimulate the ion transport, estimated by measuring the short-circuit current (SCC) value, by interacting with NK1-like receptors. In this paper we show that Kassinin (NK2 preferring in mammals) increases the SCC, while Enterokassinin has no effect. Therefore, either 2 Pro residues or 1 Pro and 1 basic amino acid must be present in the part exceeding the C-terminal pentapeptide. Eledoisin (NK3 preferring in mammals) stimulation of SCC is reduced by CP99994 and SR48968 (NK1 and NK2 antagonists) and not affected by SB222200 (NK3 antagonist). None of the three antagonists affects Kassinin stimulation of SCC.

Calcium response after stimulation by Substance P of U373 MG cells: inhibition of store-operated calcium entry by protein kinase C

In this paper we investigate the Ca2+ response after Substance P (SP) stimulation of U373 MG cells. SP is a tachykinin and physiologically acts as a neurotransmitter and neuromodulator in the nervous system, but pathologically triggers malignant glial cells, such as U373 MG, to release cytokines and increase proliferation rate. In this paper we show that SP increases the proliferation rate of U373 MG cells and the intracellular Ca2+ concentration by mobilizing Ca2+ only from thapsigargin-sensitive stores. In fact, Ca2+ entry through store-operated calcium entry (SOCE) channels, which was observed after thapsigargin treatment, was not detected after stimulation by SP. The inhibition of SOCE after SP stimulation must be mediated by protein kinase C (PKC), because it was not observed in the presence of calphostin C (an inhibitor of PKC). Moreover, stimulation by SP-induced membrane potential hyperpolarization. Our results are consistent with the following sequence of events: (i) SP interacts with NK(1) receptors; (ii) fast homologous receptor desensitization occurs; (iii) reuptake by endoplasmic reticulum Ca(2+)-ATPase quantitatively overwhelms the extrusion by plasma membrane Ca2+-ATPase. These results have two important consequences. In U373 MG cells the SOCE does not contribute to the Ca2+ response after SP, and is not necessarily involved in promoting cell proliferation.

Pyrethroid stimulation of ion transport across frog skin

Pyrethroids are grouped into two classes (types I and II) because of the absence or presence of an alpha-cyano substituent and the production of a different intoxication syndrome in rodents. In this study, we investigated the effect of pyrethroids on the ion transport across frog skin (Rana esculenta). The short-circuit current value (estimate of ion transport) was increased by each of the eight pyrethroids tested, with the following order of potency: lambda-cyhalothrin > deltamethrin > alpha-cypermethrin = beta-cyfluthrin > bioallethrin > permethrin > bioresmethrin > phenothrin. The first four compounds are type II pyrethroids. Therefore, ion transport is stimulated more by type II pyrethroids than by type I. Experiments performed in the presence of amiloride support the conclusion that pyrethroids mainly increase Na+ absorption and to a lesser extent Cl- secretion. In these experiments, no systematic difference between type I and II pyrethroids was found. Finally, the stimulation by pyrethroids was inhibited by indomethacin and W7 (inhibitors of cyclooxygenases and the Ca2+/calmodulin system, respectively). These observations suggest that pyrethroids do not directly affect the epithelial Na+ channel (ENaC) but indirectly influence an intracellular event involved in ENaC modulation and linked to the Ca2+ signaling cascade.

Differences between ranamargarin and other tachykinins in the stimulation of ion transport in frog skin

In frog skin, tachykinins stimulate ion transport by interaction with NK1-like receptors. The structural requirements of the peptide are the presence of the C-terminal sequence Phe-X-Gly-Leu-Met-NH(2) and at least one Pro residue in the N-terminal sequence. In this paper, we demonstrate that the C-terminal amino acid must be amidated but it can be different from Met, and that the sequence cannot be longer or shorter than 11-12 amino acids. Unexpectedly, Ranamargarin (14 amino acids, no Pro residue) increased the short circuit current value by 48 +/- 0.3%. On the basis of considerable experimental evidence, we suggest that Ranamargarin interacts with a receptor different from those of other tachykinins.

The proliferative response of HT-29 human colon adenocarcinoma cells to bombesin-like peptides

Bombesin-like peptides (BLP) and their receptors are widely distributed throughout the intestine and are potential mitogens for gastrointestinal cancers. In this study we characterized the proliferation induced by BLP in the human adenocarcinoma cell line HT-29. The number of HT-29 cells, partially serum deprived (1% fetal bovine serum) for 48 h, was increased after 24 h of stimulation with bombesin, GRP, neuromedin B (NMB) and neuromedin C (NMC) ranging from 0.1 nM up to 1 microM. Reverse transcription polymerase chain reaction studies, revealed the presence of mRNA for NMB and for the GRP preferring receptor (GRP-R). mRNA for GRP, NMB preferring receptor (NMB-R) and bombesin receptor subtype 3 (BRS-3) were not detected. [D-Phe(6)]bombesin-(6-13)methyl ester (A1) and BIM-23127 (A2), are considered as inhibitors of binding to GRP-R and NMB-R, respectively. Surprisingly, A1 and A2 stimulated the proliferation of HT-29 cells. Moreover, in the simultaneous presence of 1 microM A1 and 0.1 microM GRP or 0.1 nM or 0.1 microM bombesin, inhibition of the proliferation was observed. Our data demonstrate that the proliferation induced by BLP in HT-29 cells is due to interaction with the GRP-R.

Effect of prostaglandin E(2) on the proliferation, Ca(2+) mobilization and cAMP in HT-29 human colon adenocarcinoma cells

Several lines of evidence suggest that non-steroidal antiinflammatory drugs (NSAIDs) have anticarcinogenic effects. The causal relationship linking the preventive effect of NSAIDs on colon cancer and the inhibition of prostaglandin synthesis is questioned by the contrasting results obtained by many laboratories. The experiments reported in this paper demonstrate that prostaglandin E(2) (PGE(2)) did not stimulate the proliferation in HT-29 human colon adenocarcinoma cells under several experimental conditions. Moreover, PGE(2) and 17-phenyl trinor prostaglandin E(2) (a specific agonist of EP1 receptors) did not increase intracellular Ca(2+) concentration. Finally, PGE(2) did not affect the intracellular cAMP and did not reduce the isoproterenol dependent increase in cAMP. These results indicate that in HT-29 cells: (1) proliferation is not directly sensitive to PGE(2); and (2) PGE(2) does not stimulate a signal transduction pathway leading to intracellular increase in cAMP or Ca(2+) mobilization. Therefore, other cell lines should be used to assess the direct role played by prostanoids in promoting cell proliferation in colon cancer.

Lack of effect by prostaglandin F2alpha on the proliferation of the HCT-8 and HT-29 human adenocarcinoma cell lines

A variety of studies have supported the finding that regular intake of aspirin or non-steroidal anti-inflammatory drugs can affect colorectal cancer carcinogenesis by decreasing the synthesis of prostaglandins (PGs). We report that PG F2alpha, in the presence of indomethacin, did not stimulate the proliferation in HCT-8 and HT-29 human colon adenocarcinoma cells. Moreover, in both cell lines fluprostenol, a specific agonist of FP receptors, did not increase intracellular Ca2+ concentration, monitored with the fluorescent dye fura-2. These results indicate that in HCT-8 and HT-29 cells: i) proliferation is not sensitive to PG F2alpha; ii) functional FP receptors are absent. Therefore, either PG F2alpha is not necessarily involved in the proliferation of colorectal mucosa or cell lines other than HCT-8 and HT-29 should be used to assess the role played by PG F2alpha in promoting cell proliferation in colon cancer.

Two B1 and B2 bradykinin receptor antagonists fail to inhibit the Ca2+ response elicited by bradykinin in human skin fibroblasts

The elevation of intracellular [Ca2+] induced by bradykinin (Bk) was monitored with fura-2 fluorescence in human skin fibroblasts. Neither [des-Arg10][Leu9]kallidin nor D-Arg[Hyp3,Thi5,D-Tic7,Oic8]bradykinin (HOE140) inhibited the Ca2+ response stimulated by Bk. Moreover, each behaved as a partial agonist causing the elevation of intracellular [Ca2+].

Action of physalaemin on the ionic transport across the frog skin

The effects of the non-mammalian tachykinin physalaemin were studied on the short circuit current (SCC) and on both influx (Ji) and outflux (Jo) of 36Cl- and 22Na+ across the isolated skin of Rana esculenta. Physalaemin, added to the internal bathing fluid, increased SCC in a dose-dependent manner with a maximal effect at 1 microM. This increase was due to a stimulation of both Na+ absorption and Cl- secretion. Bumetanide (20 microM in the internal fluid), an inhibitor of the Na+/K+/2Cl- cotransporter, reduced the action of physalaemin on SCC by 46%. Furthermore diphenylamine-2-carboxylic acid (DPC, 0.1 mM in the external fluid), an inhibitor of Cl- channels, decreased the effect of the peptide on SCC by 48%. It is concluded that physalaemin activates the Na+/K+/2Cl- cotransporter at the basolateral membrane, accumulating Cl- in the cells and favouring its exit through Cl- channels at the outermost membrane of the epithelium. An inhibitor of cyclooxygenases, i.e. naproxen, strongly inhibited the physalaemin effect on SCC, whereas 5,8,11-eicosatriynoic acid (ETI), an inhibitor of lipooxygenases was without effect. Therefore, it is proposed that prostaglandins (probably PGE2) are the cellular mediators of this action. An antagonist of NK1 receptors for tachykinins, CP 99,994, inhibited the physalaemin action on SCC, whereas challenge with SR 48,968, an antagonist of NK2 receptors, had no effect on physalaemin action. It is concluded that physalaemin effect on SCC in frog skin is mediated by its interaction with NK1 receptors.

Actions of tachykinins on the ion transport across the frog skin

The tachykinin-dependent stimulation of ion transport across frog skin was studied. Tachykinin stimulation was due to interaction with an NK1-like receptor as [Sar9-Met(O2)11]-Substance P (a very selective NK1 agonist) strongly stimulated SCC, whereas [beta-Ala8]-Neurokinin A 4-10 (a very selective NK2 agonist) did not. The rank order of tachykinin potency was: PG-KI > Uperolein > Hylambatin > Kassinin > Phyllomedusin > [Sar9-Met(O2)11]-Substance P > Ranatachykinin A > Physalaemin > Ranakinin > Substance P and Eledoisin >> Neurokinin A. Neurokinin B, Scyliorhinin I, Urechistachykinin I and Urechistachykinin II had no effect. We conclude that the minimal structural requirements for stimulating SCC in the frog skin were the presence of: a) the C-terminal sequence Phe-X-Gly-Leu-Met-NH2; b) at least one Pro residue in the N-terminal sequence.

Cyclosporin A stimulates Na+ transport across the isolated skin of Rana esculenta

Cyclosporin A (Cs A), added to the fluid bathing the internal surface of the isolated skin of Rana esculenta, increased short-circuit current (SCC) with a maximal effect at 5 microM. This effect was completely inhibited by amiloride (0.2 mM in the fluid bathing the external surface). By measuring both transepithelial fluxes of 22Na+ across symmetrical parts of the short circuited skin, Cs A was found to increase the net absorption of Na+. Naproxen (10 microM), a cyclooxygenase inhibitor, decreased the stimulation by Cs A of SCC, suggesting that in this stimulation prostaglandins are involved. The Cs A effect on Na+ transport could be caused by an inhibition of a Ca2+/calmodulin-dependent protein phosphatase, i.e. calcineurin, since: a) it is mimicked by another inhibitor of calcineurin, i.e. fenvalerate: b) the action of Cs A and fenvalerate on SCC are decreased by the calmodulin inhibitor W7.

Bradykinin stimulation does not induce intracellular Ca2+ elevation in cells from desmoid tumors

The intracellular mechanisms controlling cell proliferation in desmoid tumors (DT) are unknown. Bradykinin stimulated an increase in [Ca2+](i), (monitored by the fura-2 fluorescence) in fibroblasts obtained from both the skin of a normal donor and the mesenter of a familial adenomatous polyposis (FAP) patient. Cells from DT of the same patient as well as those from another FAP patient failed to show the elevation of [Ca2+](i) usually caused by bradykinin stimulation.

Effect of calcitonin gene-related peptide on sodium absorption through isolated skin of Rana esculenta

Calcitonin gene-related peptide (CGRP) added to the internal fluid bathing the isolated skin of Rana esculenta strongly stimulates the active sodium absorption. This action is dose-dependent, the dose eliciting the maximal effect being 2 . 10(-7) M; alpha and beta CGRP exhibit the same potency. The CGRP action on sodium transport is mainly due to its interaction with CGRP1 receptors, since it is inhibited by CGRP8-37, its specific antagonist. The second messengers probably involved in the action of CGRP are cAMP and Ca+2, since this action is reduced by SQ22536 and W7, which are inhibitors of adenyl cyclase and calmodulin respectively. On the contrary, inhibitors of protein kinase C (1-O-hexadecyl-2-O-methyl-sn-glycerol) and nitric oxide synthase (L-NAME) do not modify the action on sodium transport. ETYA, an inhibitor of all the metabolic pathways of arachidonic acid, decreases the CGRP action by 38%. In order to search for the arachidonic acid metabolites involved in the CGRP action, the effect of the following inhibitors was tested: aspirin and naproxen (for cyclooxygenases), NDGA (for cyclooxygenases), NDGA (for lipoxygenases) clotrimazole (for epoxygenases). None of these substances is able to inhibit the CGRP action on sodium transport. Moreover, adding arachidonic acid inhibits the CGRP action, but this effect was also obtained by another unsaturated fatty acid, oleic acid. Since unsaturated fatty acids are able to inhibit the protein kinase A, these results indirectly support the role of cAMP as a second messenger of the CGRP action on sodium transport.

Na+ and Cl- net absorption by the isolated skin of Rana esculenta

In the last five years, several measurements of 22Na+ influx (Ji) and outflux (Jo) across symmetrical parts of the isolated skin of Rana esculenta, under permanent short circuitation, were performed in our Institute. The mean value of the 22Na+ net fluxes (Ji-Jo) exceeded the mean value of the short circuit current measurements (1.14 +/- 0.04 versus 0.98 +/- 0.02 microE.cm-2.h-1, 253 experiments). Since this discrepancy could be due to a concomitant Cl- net absorption, 36Cl- unidirectional fluxes were detected under similar experimental conditions. The Cl- net flux mean value was 0.11 +/- 0.02 microE.cm-2.h-1 (316 experiments) which accounts for 70% of the discrepancy between the Na+ net flux and short circuit current. This Cl- net absorption occurred in the absence of electrochemical gradients and was very likely maintained by a Na+/K+/2Cl- cotransport located at the outermost membrane of the epithelium. In fact bumetanide challenge (10(-5) M in the external fluid) strongly inhibited 36Cl- influx and 22Na+ influx across this tissue and cleared off the discrepancy between short circuit current and sodium net flux.

Action of dopamine on the ionic transport across the isolated skin of Rana esculenta

Dopamine addition to the internal fluid bathing the isolated frog skin results in a strong increase of short circuit current (SCC) across this tissue. The effect is dose-dependent, 10(-4) M being the dose resulting in maximal effect. The measure of transepithelial fluxes of both 22Na+ and 36Cl- across symmetrical parts of skin short-circuited in permanence demonstrates that this effect is due to stimulation of Na+ adsorption and Cl- secretion. The former effect, but not the latter one, is mimicked by both SKF89124A and SKF82525J (D1 and D2 agonists, respectively). Moreover the effect of dopamine on SCC and Na+ net flux is wider than that of its synthetic agonists even when both D1 and D2 agonists were added together. It is suggested that the extraeffect of dopamine on SCC is due to a stimulation of Cl- secretion, probably mediated by dopamine interaction with another receptor.

Action of capsaicin and related peptides on the ionic transport across the skin of Rana esculenta

Capsaicin at low concentrations increases the short circuit current (SCC) across frog skin. Simultaneous measurements of both transepithelial fluxes of 22Na or 36Cl demonstrate that the SCC increase is due to stimulation of sodium active absorption. Capsaicin acts through the liberation of several peptides; thus these peptides were tested on the SCC across frog skin. Those more active are, in order of potency: Cyclic Calcitonin Gene Related Peptide (CGRP), Kassinin and Eledoisin, Substance P (SP) and Neurokinin A. Neurokinin B and Vasoactive Intestinal Peptide (VIP) have no effect. Also the actions of SP and CGRP are due mainly to stimulation of Na+ active absorption. A strict parallelism regarding the sensitivity to inhibitors (Naproxen, SQ22536 and CP96345) between SP, CGRP and Capsaicin strengthens the hypothesis that SP and CGRP are liberated by Capsaicin in this tissue.

The nature of Cl- secretion, induced by carbaryl, across the isolated skin of Rana esculenta

1. The pesticide carbaryl induces Cl- secretion through the isolated frog skin. 2. This effect is due to the activation of both processes responsible for this phenomenon: (a) Na+/K+/2Cl- cotransport on the serosal membrane; (b) Cl- selective channels on the external membrane. 3. Cl- outflux is inhibited by bumetanide (10(-5) M) on the serosal side and by diphenylamine-2-carboxylic acid (DPC) (10(-3) M) on the external side. 4. The DPC action is not mimicked by Naproxen, a specific inhibitor of cyclooxygenase. 5. A comparison with isoprenaline, demonstrates that the carbaryl action is, paradoxically, more selective than that of isoprenaline. 6. This selectivity of carbaryl action on Cl- permeability is confirmed by the fact that, unlike isoprenaline, carbaryl does not affect the permeability of Na+ and thiourea.

β2-adrenergic regulation of urea permeability of the Bufo bufo bladder

1. Isoprenaline strongly increases the urea permeability of the bladder of Bufo bufo. This effect is due to its interaction with beta 2-adrenoreceptors, activating, in turn, the adenyl cyclase. 2. In order to ensure the regulation of urea permeability, the isoprenaline effect is present even in pathophysiological conditions, inhibiting the vasopressin action.

Actions of vasopressin and isoprenaline on the ionic transport across the isolated frog skin in the presence and the absence of adenyl cyclase inhibitors MDL12330A and SQ22536

1. The effects of both adenyl cyclase inhibitors (MDL12330A and SQ22536) have been studied on the ionic transport induced by vasopressin and isoprenaline across the frog skin. 2. MDL12330A inhibits the vasopressin action on the short-circuit current (SCC), confirming that this effect is cAMP-mediated. 3. On the other hand, isoprenaline action on the SCC is unaffected by MDL12330A. However, this lack of effect is not a sufficient argument against the role of cAMP in this action; in fact, as MDL12330A is also an inhibitor of cAMP phosphodiesterase, this action could mask the inhibitory effect of the drug on adenyl cyclase. 4. By using the other adenyl cyclase inhibitor (SQ22536), probably deprived of effect on the cAMP phosphodiesterase, we obtained a strong inhibition of isoprenaline action on the SCC. Thus we conclude that the actions of isoprenaline on the ionic transport across the frog skin are also cAMP-mediated.

Permeability properties of the Bufo bufo bladder as affected by isoprenaline and vasopressin

Isoprenaline, a beta adrenergic agonist, strongly increases both transepithelial fluxes across the urinary bladder of Bufo bufo; this effect is dose dependent, 10(-6)M being necessary for the maximal action. This effect is less selective than that of vasopressin: the ratio J urea/J thiourea is 3.8 under isoprenaline and 30.4 under vasopressin treatment. Both hormones differently affect the permeability of a mainly liposoluble molecule, i.e. antipyrine: vasopressin increases antipyrine permeability, while isoprenaline decreases it. Moreover diethylpyrocarbonate treatment of the luminal membrane strongly inhibits vasopressin effect on urea permeability leaving unmodified that of isoprenaline. However, the actions of both hormones are not additive. These results allows to assume that the tissue has a feedback mechanism which inhibits other hormonal action while the bladder is stimulated by a particular hormone.

Diazepam effects on frog skin cyclic nucleotide phosphodiesterase

1. The activities of cAMP phosphodiesterases (cAMP-PDE) have been measured in the homogenate of the skin of Rana esculenta. 2. The tissue possesses two distinct enzymes: a "low" Km PDE (Km = 0.42 x 10(-6) M; Vmax = 16 pmol/mg protein/min) and a "high" Km PDE (Km = 180 x 10(-6) M; Vmax = 2853 pmol/mg prot/min). Only the "high" Km form is stimulated by calcium. 3. Diazepam (1-0.5 mM) significantly inhibits both enzymes, the inhibition being of competitive type.

Action of forskolin on non-electrolyte permeability across the urinary bladder of Bufo bufo as compared to that of various hormones

1. Forskolin, an activator of adenyl-cyclase in a receptor-independent manner, mimics the ADH effect on the urea and thiourea permeabilities across the toad bladder. 2. However, differently from ADH, forskolin increases the erythritol permeability across the tissue and this effect is not reproduced by two substances increasing the urea permeability (8-BrcAMP and isoprenaline). Most probably this effect of forskolin does not involve the cAMP generating system.

Effect of reagents of protein functional groups on the ADH-induced urea facilitated transport across toad urinary bladder

1--The mechanism of the vasopressin-induced, facilitated transport across toad urinary bladder was studied by treating the luminal membrane of the epithelium with the following reagents of protein functional groups: NEM (SH groups), SITS (amino groups), EEDQ (carboxylic groups), DEPC (histidine). 2--Treatment of the luminal side of the epithelium by NEM strongly inhibits the ADH-induced urea transport, leaving unmodified the effect of the hormone on the flux of antipyrine, a lipid soluble molecule. These results confirm the hypothesis that the urea carrier is of proteic nature. 3--Treatment of the luminal side by SITS strongly inhibits ADH action on urea and antipyrine permeability; thus this effect can be considered rather unspecific. 4--On the contrary the EEDQ effect is more specific; in fact treatment of the luminal side by EEDQ strongly inhibits ADH effect on the permeability of urea, slightly increasing the ADH effect on that of antipyrine. 5--Finally, the luminal treatment by diethylpyrocarbonate inhibits almost completely the ADH action on the urea fluxes, slightly increasing the hormone effect on the antipyrine ones. 6--Based on these results we conclude that carboxylic groups and the imidazolic ring are more important than the amino groups in determining the urea transport across toad bladder, in the presence of ADH.

Action of forskolin on non-electrolyte permeability across the frog skin as compared to that of vasopressin and isoprenaline

Forskolin, a natural diterpene activating the adenyl cyclase in a receptor-independent manner, increases symmetrically both transepithelial fluxes of urea and erithrytol through the frog skin. The effect is dose-dependent, being 5 X 10(-6) M the dose necessary to obtain the maximal action. Forskolin-induced permeabilization is inversely proportional to the molecular weight of water soluble molecules (urea greater than erythritol greater than mannitol); also the permeability of a mainly lipid soluble molecule, i.e. antipyrine, is slightly increased by the diterpene. The permeability pattern is more similar to that induced by isoprenaline as compared to that elicited by vasopressin. Differently from what occurs in other tissues, small doses of forskolin (10(-8) M) are unable to potentiate the actions of vasopressin and isoprenaline on urea permeability across the frog skin. Moreover, the maximal action of forskolin is not additive with the maximal ones of isoprenaline and vasopressin.

Effect of vasopressin on the permeability of non electrolytes across the skins of Rana esculenta and Bufo bufo

Maximal doses of vasopressin increase the permeability of the skins of Bufo bufo and Rana esculenta to urea, ethylene glycol, glycerol, erythritol, beta-alanine, leaving virtually unmodified that of mannitol and antipyrine. These results demonstrate that the response to vasopressin is quite different in amphibian skins as compared to the bladders. A careful analysis of the effects of vasopressin on non-electrolyte permeability as a function of their molecular weight demonstrates that hormone elicits the formation of pores with a diameter inferior to 4 A. Under vasopressin treatment the skins exhibit a selectivity for polyhydroxylated molecules as compared to urea and beta-alanine. This selectivity is not due to active of facilitated transport and is not impaired by phloretin or DTNB which selectively blocks the permeability of urea or ethylene glycol in erythrocytes. It is proposed that the site of such selectivity is located in other plasma membranes of the epithelium.

[Effect of N-ethylmaleimide, introduced in to the serous fluid, on the active transport of sodium through the skin of Rana esculenta]

An SH reactive agent, N-ethylmaleimide (NEM), if introduced in the serosal bath (10(-4) M), stimulates the short circuit current (SCC) across the frog skin. This effect is due to an increase of Na active transport, because is inhibited by ouabain (10(-4) M). A stimulatory action on Cl- or HCO3- secretion can be ruled out because the rise in SCC occurs also in the absence of Cl- or HCO3-. It is known that NEM inhibits the ADH action by forming covalent bounds with SH groups of ADH membrane receptors (1). Thus it is possible that this binding should mimic the ADH action on SCC. In order to test this hypothesis, we studied the effect of serosal NEM on SCC both in the absence and in the presence of I midazol (20 mM), an activator of the cyclic AMP phosphodiesterase. Imidazol treatment decreases the effect of NEM on SCC. Thus we conclude that NEM serosal treatment is able to mimic some ADH effects, by using the same ways of the ormone action.

[Effect of N-ethylmaleimide on the active transport of sodium and its permeability in the skin of Rana esculenta]

N-ethyl maleimide (10(-3)M in the external fluid) strongly increases the permeability of urea and phenylalanine. However, the ratio phi 0 urea / phi 0 phenylalanine (a measure of membrane integrity) is not reduced. NEM 10(-4)M elicits a small increase of urea permeability. NEM (10(-3)M or 10(-4)M in the external fluid) stimulates Na active transport across the frog skin. Most probably the activation of Na pump is due to an increase of Na cellular pool, caused by the permeability increase elicited by NEM.

Phloretin sensitive active urea absorption in frog skin

This report presents evidence for urea active absorption by isolated skin of Rana esculenta. One of the supporting factors of such evidence is that at a low concentration the urea influx is five times greater than the outflux, in the absence of a chemical gradient. The transport shows a saturation kinetics with an apparent Km = 1.33 mM and is inhibited by un uncoupling agent (FCCP). 5 x 10(-4) M Phloretin, added to the external side, markedly inhibits inward urea transport, whereas it is ineffective when added to the serosal fluid. This provides evidence for a phloretin-sensitive mechanism located at the external side of the epithelium. Phloretin stimulates the sodium active transport; the possible coupling of urea and sodium movement is analysed.

The nature of urea transport across the luminal membrane of Bufo bufo urinary bladder

By using the washing-out technique, counterflow acceleration for urea was demonstrated on the luminal membrane of Bufo bufo urinary bladder, in the absence of ADH. This phenomenon completely disappears in the presence of phloretin 10-4 M on the luminal side and is consistent with the presence of a mobile carrier mechanism for urea transport across the luminal membrane, in basal conditions. In the presence of ADH, counterflow acceleration is completely absent. This result is in agreement with the presence of urea selective channels, induced by ADH, as proposed by Levine & Worthington (1976).

[The nature of urea transport across the skin of of Rana esculenta]

In several epithelial tissues such as toad bladder, gallbladder and human red cells, it has been established that urea movement implies a phloretin sensitive mediated transport. In the skin of the toad Bufo viridis also it has been described an active transport of urea. Our data, obtained on the frog skin seem to demonstrate the existence of some specific mechanism for urea transport towards the inside solution. In fact, two molecules having the some molecular diameter, such as urea and thiourea, show a large difference in permeability at low concentration. In addition 0.1 mM urea influxes and outfluxes, measured on paired skin halves in the absence of concentration gradient, exhibit an evident asymmetry. Further approaches with phloretin experiments were made in order to characterize the urea transport system. Phloretin (5.10(-4)M) added to the external solution significantly inhibits the urea influx. Little can be said at this time about the composition or kinetics of the carrier involved in the transport.

Polar distribution of sodium-dependent and sodium-independent transport system for L-lactate in the plasma membrane of rat enterocytes

The uptake of L-lactate by rat small intestinal brush-border and basal-lateral plasma membrane vesicles has been studied. L-Lactate uptake by the isolated membrane vesicles is osmotically sensitive and represents predominantly transport into an intravesicular space and not binding to the membranes. The transport of L-lactate across the brush-border membrane is stimulated by sodium, whereas the transport across the basal-lateral plasma membrane is sodium-independent. In both types of membrane vesicles L-lactate is transported faster than D-lactate and L-lactate transport is inhibited by alpha-cyano-cinnamic acid. L-Lactate transport across basal-lateral membranes is inhibited by D-lactate and pyruvate and transstimulated by L-lactate and pyruvate. The polar distribution of transport system for L-lactate in the plasma membrane of rat enterocytes--a Na+/L-lactate cotransport system in the brush-border membrane and a facilitated diffusion system in the basal-lateral membrane--can explain the fact that in the intact epithelium L-lactate produced by cell metabolism is preferentially released on the serosal side and could enable the cell to perform vectorial, secondary active transport of L-lactate from the intestinal lumen to the serosal compartment.

Nonelectrolyte fluxes across gastric mucosa in relation to gastric stimulation. Is gastric juice secreted by osmosis or exocytosis?

The effects of histamine and thiocyanate, added to the serosal bathing solution, on unidirectional fluxes of some nonelectrolytes (thiourea, methylated thiourea derivates, mannitol), and on H+, pepsinogen and mucous secretion were investigated in frog (Rana esculenta) fundic gastric mucosa. Histamine (10(-4) M) increases significantly the outfluxes (serosa to mucosa fluxes) of only thiourea and its derivates (but not mannitol) and the stimulation is the greater the more lipidsoluble the nonelectrolyte is. Influxes (mucosa to serosa fluxes) of the same molecules are not affected. In parallel histamine stimulates H+-secretion but does not modify pepsinogen and mucous secretion. SCN- (10(-2) M) inhibits the histamine effect on thiourea outfluxes and on H+-secretion, while pepsinogen and mucous secretion are not affected. Colchicine (10(-4) M) pretreatment inhibits the histamine effect on outfluxes and H+-secretion. It is concluded that: (1) histamine induces a secretion of nonelectrolytes towards the lumen; (2) such secretion is correlated with the hormone-induced secretion of HCl and fluid; (3) this process is mediated by an exocytotic mechanism.

[Evidence of morphological modifications induced by theophylline in the urinary bladder epithelium of Rana esculenta]

This preliminary work concerns the morpho-functional action induced by Theophylline on bladder epithelium. The epithelium treated with Theophylline shows important structural variations. The whole tissue thickness appears reduced with cell disposed in monostratified layer. They show a light grade of swelling with nucleus and cytoplasm less evident and boundary less marked. It is important to note that the permeability of the epithelium does not appear modified.

[Role of cGMP in the response of frog skin to noradrenaline]

The effects of noradrenaline on cGMP levels of epithelial cells isolated from frog skin are reported. Noradrenaline does not change cGMP levels either in a medium containing Ca++ and Mg++, or without Ca++ or without Mg++.

Effect of cycloheximide on urea facilitated transport through toad gallbladder epithelium

Transepithelial urea outfluxes across toad gallbladder were determined before and after the addition of cycloheximide. The drug inhibits the movement of urea but has no effect on thiourea and antipyrine outfluxes. The inhibition of amide transport is time dependent as also shown in counterflow experiments. These results are consistent with the hypothesis that cycloheximide inhibits the synthesis of membrane proteic sites involved in urea mediated transport.

Colchicine effect on the permeability of the whole epithelium and of isolated cells of frog skin

The effect of 2 X 10(-5) M colchicine on epithelial cells isolated from frog skins was investigated. Three hours of treatment with colchicine did not change either Na+ and K+ content of isolated cells or nonelectrolyte permeability. When ADH (50 mU/ml) was added, thiourea uptake values became greater than without the hormone; the same values were found in the cells previously treated with colchicine. Na+ transepithelial transport, measured by means of short-circuit current, was inhibited by the antimitotic agent both under control conditions and after ADH stimulation. These results support the view that colchicine does not directly affect ADH action on membrane permeability, but influences some mechanism that controls ADH action on transepithelial transport. Intercellular junctions appear to be the location of such a mechanism.

[Uptake of L-(+)lactate by cell membrane (luminal and contraluminal) isolated from rat small intestine microvilli]

L-lactate uptake was measured in vesicles formed by intestinal brush border and baso-lateral membranes, using a rapid filtration technique. In the presence of a Na+ gradient directed into the vesicle, L-lactate can be transiently accumulated in brush border vesicles, but not in baso-lateral ones. The transient L-lactate accumulation does not occur in the presence of a KCl gradient. alpha-cyanocinammic acid strongly inhibits L-lactate uptake in brush border vesicles, but not in baso-lateral ones. These results support the existence of a carrier mediated, Na+ dependent, transport of L-lactate across the brush border membrane.