Search Results - (Author, Cooperation:F. Vieira)

2018-01-26

BMJ Publishing

2044-6055

Medicine

Open access, Intensive care

2015-03-07

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; *Aquatic Organisms ; Brazil ; *Conservation of Natural Resources ; *Extinction, Biological ; *Fisheries

2015-11-28

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Budgets ; Research Personnel/*economics ; *Research Support as Topic ; *Science

2018-05-17

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

0011-2240

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

0005-2736

Angiotensin ; Bradykinin ; Cellophane membrane ; Diffusion potential ; Kinetics ; Peptide diffusion

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Medicine

Physics

Electronic Resource

1432-1203

Springer Online Journal Archives 1860-2000

Biology

Medicine

Summary A family with four 46,XX siblings affected by the pure gonadal dysgenesis syndrome is described. Inheritance is by an autosomal recessive gene limited to the female sex.

Electronic Resource

1432-2013

Toad skin ; Cl channels ; Cl transport ; Transport regulation ; Activation ; Inactivation

Springer Online Journal Archives 1860-2000

Medicine

Abstract (1) Combined use of external Cl concentration pulses and apical membrane depolarization permitted to compare the roles of apical voltage and Cl ions upon the activation of a skin Cl conductance,G Cl, which is assumed to reflect activation of the permeability of a Cl pathway. (2) Apical membrane depolarization induced by skin hyperpolarization, or by short-circuiting skins with high K Ringer's on the inner side, failed to activateG Cl in the absence of external Cl,G Cl remaining negligible. Under apical membrane depolarization, a step elevation of [Cl]0 slowly activatedG Cl as characterized by a sigmoidal current response of slow onset concomitant to a slow conductance increase. External Cl removal had the reverse effect, showly inactivatingG Cl. (3) With the apical membrane in the normal polarized state, a step increase of [Cl]0 slowly activatedG Cl to submaximal values. This indicates that the interaction of Cl ions with the apical membrane partially activatesG Cl in the absence of apical membrane depolarization. (4) Activation ofG Cl was interpreted on the basis of a direct effect of Cl ions upon the apical membrane, having been attributed to the apical membrane voltage an indirect role. Voltage would affect the Cl distribution across the apical membrane, and, as a result, the Cl concentration at a proposed regulatory site which modulates the apical membrane permeability to Cl ions.

Electronic Resource

1432-2072

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1432-2072

Behaviour Induction ; Brain Extract ; Skinner Box

Springer Online Journal Archives 1860-2000

Medicine

Abstract Results indicate successful attempts to induce modification of behaviour by intravenous injection of brain extract from trained rats into naive recipients. Experimental recipients exhibited higher performances as compared with appropriate controls in testing sessions continuously reinforced by a drop of water in a Skinner box. The observed effect may be correlated with reinforcement contingencies received by the donor animal; however, further work is required to determine whether the phenomenon is situationally specific. Under the conditions used the optimum dosage to produce the effect is equivalent to 40% of a brain. Results also indicate that dose and route of injection are conditions that must be carefully controlled in behaviour induction experiments.

Electronic Resource

1432-2013

Vanadate ; Ouabain ; Active Na transport ; Toad skin ; Paracellular path ; Electrical resistance

Springer Online Journal Archives 1860-2000

Medicine

Abstract In this study we compare the effects of two inhibitors of the Na,K-ATPase, ouabain and vanadate, upon transport properties of the isolated short-circuited toad skin: The main conclusions are: 1. Both inhibitors induce a similar decline in shortcircuit current (SCC). 2. They differ regarding skin electrical resistance (R). Ouabain induces an increase in resistance that, after some delay, builds up slowly after its addition to the preparation, while vanadate causes a fast increase in resistance that remains constant for most of the experimental period. 3. Vanadate, but not ouabain, promotes an unspecific increase in skin permeability characterized by a delayed and progressive rise of42K (J eff K ) and14C sucrose (J eff suc ) effluxes. 4. Vandate effect upon skin permeability, as measured by J eff K , is not affected by pre-treating the skin with DIDS, a stilbene derivative, indicating that anion-exchange is not an important step for the entrance of vanadate into the epithelial cells to trigger its effect. 5. Vanadate effect upon J eff K is also not affected by previous ouabain inhibition of the Na,K-ATPase, showing that this effect is not mediated by the inhibition of this enzyme. Vanadate action in toad skin seems to occur at junctional structures opening paracellular routes. A possible mechanism for the effect of vanadate is discussed in terms of cytosolic Ca2+ balance, cytoskeleton and their interplay with the sealing of tight junctions.

Electronic Resource

1432-2013

Furosemid ; Chloride Transport ; Micropuncture ; Water Reabsorption ; Chloridtransport ; Mikropunktion ; Wasserresorption

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Die Chloridausscheidung wurde in Kontrollratten und in solchen mit 1 mg/kg · min Furosemid- oder 0,1 ml/min 4% NaCl-Infusion mittels Bestimmung der proximalen und distalen Cl TF/P Quotienten untersucht. Proximal waren diese Werte durchwegs höher als 1, und zwar 1,29 in Kontrollen, 1,23 während NaCl- und 1,29 bei Furosemidinfusion. Distal fanden sich Werte under 1 bei Kontrollen (0,30) und bei 4% NaCl Infusion (0,51), während Furosemidinfundierte Ratten einen Mittelwert von 1,27 aufwiesen, was auf die Abwesenheit des normalen frühdistalen Osmolaritätsgradienten hinweist. Die mittels Inulin gemessene Nettowasserresorption wurde im proximalen Tubulus signifikant durch 4% NaCl-Infusion verringert, nicht aber durch Furosemid. Nach Gabe dieses Diureticums wurde eine signifikante Verlängerung der Resorptionshalbwertszeiten im gespaltenen Tropfen (t/2=16,3 sec) beobachtet. Dies wurde jedoch durch erhöhte Farbstoffpassagezeiten kompensiert. Die geringe Veränderung von Chlorid und Inulinkonzentrationen zwischen distalem Tubulus und Endharn zeigt die beinahe vollkommene Ausschaltung der Harnkonzentrierung längs des Sammelrohres in der Furosemidgruppe. Dieser Befund deutet auf den aufsteigenden Ast der Henleschen Schleife als Angriffspunkt dieses Diureticums, d. h. auf die Ausschaltung des Einzeleffektes des medullären Gegenstromsystems. Distale transtubuläre Potentialdifferenzen wurden nicht durch Furosemid verändert, was eine Veränderung der Permeabilität dieser Strukturen auszuschließen scheint.

Summary Chloride excretion was studied in control rats, and in rats receiving an infusion of 1 mg/kg x min of Furosemid or 0.1 ml/min of 4% NaCl, through measurement of Cl TF/P concentration ratios in proximal and distal tubular fluid. Fluid reabsorption was evaluated by measurement of inulin TF/P ratios. In proximal tubule, chloride TF/P's were always higher than 1, respectively 1.29 in controls, 1.23 during NaCl infusion, and 1.29 after Furosemid. In distal tubules both control (mean TF/P=0.30) and 4% NaCl infused rats (mean TF/P=0.51) had ratios below unity, whereas Furosemid infused rats showed a value of 1.27, indicating the absence of the normal osmolar gradient in early distal tubule. Net fluid reabsorption across the proximal tubule showed no significant reduction with Furosemid, and some reduction with 4% NaCl. With Furosemid, however, the transepithelial transport rate as measured with the split-drop method was significantly reduced (t/2=16.3 sec) in comparison with controls. This reduction, however, was offset by increased transit times, measured with Lissamine green, leading to somewhat increased overall reabsorption. The variation in chloride and inulin concentrations between distal tubule and final urine showed almost complete absence of urinary concentration along the collecting duct in the Furosemid group. These data suggest that this substance may act, under the present experimental conditions, mainly on the ascending limb of Henle's loops, and therefore on the “single effect” of the medullary countercurrent system. Distal electrical PD measurements did not show any significant change with respect to controls in the Furosemid group, indicating no, alteration of the permeability of the tubular membranes.

Electronic Resource

1432-2013

Key words Biotechnology ; Chamber ; Controller ; Epithelium ; Temperature ; Thermostat

Springer Online Journal Archives 1860-2000

Medicine

Abstract  We describe a temperature-control system for solutions in free flow, suitable for electrophysiological or optical studies of isolated cells, natural epithelia or cell culture monolayers. The system is small enough to be located close to the preparation and was designed specifically to be coupled to the inlets of a modified, continuous-flow Ussing chamber, allowing rapid change of the solutions bathing tissue surfaces. The system consists of a highly compact monoblock heating unit and a control circuit. Solutions from different reservoirs, kept at room temperature or lower (from an ice bath), can be rapidly switched at the inlet of the heating unit by manually or electrically actuated microvalves without affecting the temperature of the fluid leaving the heating unit. The control unit consists of a bead thermistor firmly placed close to the heating unit outlet and an electronic circuit which is basically a proportional controller. This unit continuously regulates the electric current through the Ni-Cr heater, keeping the temperature of the fluid leaving the heating unit constant at a preset value. The system allows control of fluid temperature (normally 37°C) for flow rates in the range of 1.0 ml/min to 12 ml/min. However, the temperature can be set at any value above that of the incoming fluid.

Electronic Resource

1573-2568

antacids ; cimetidine ; H2 blockers ; duodenal ulcers

Springer Online Journal Archives 1860-2000

Medicine

Abstract Antacid (AA) in a very low dose (88 mmol/day) was compared to the standard 800-mg dose of cimetidine in healing duodenal ulcers. The influence of sex, age, symptom duration at entry, night pain, smoking, coffee consumption, and alcohol on ulcer healing was studied. The antacid was given in two different schedules: group I-20 ml 1 hr after breakfast and at bedtime; group II-10 ml 1 hr after breakfast and lunch and 20 ml at bedtime. Cimetidine (group III) was given in two divided doses: 400 mg 1 hr after breakfast and 400 mg at bedtime. Endoscopic control was performed after four weeks and, if necessary, after eight weeks of treatment. The healing rate after four weeks of treatment was, respectively, for groups I, II, and III, 45.5%, 55.8%, and 69.4% (group I=group II, and group III different from groups I and II). After eight weeks of treatment the healing rate was 61.5%, 80.8%, and 88.0% for groups I, II, and III, respectively (group II=group III, and group I different from groups II and III). Except for group I, smoking did not influence healing rate. Age, sex, symptoms at entry, night pain, and coffee consumption did not influence the treatment results. The authors concluded that the very low dose of magaldrate (88 mmol/day), when administered in three divided doses (10 ml after breakfast and lunch and 20 ml at bedtime) for eight weeks was as effective as 800 mg of cimetidine (400 mg twice a day) in healing duodenal ulcer.

Electronic Resource

1432-1424

Toad skin ; pH ; Ion conductance ; Voltage dependence ; Chloride conductance

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract The present study focuses on two closely related topics on ion conductance in toad skins: (i) the interaction of apical protons with the apical voltage-dependent Cl−-activated channels of the mitochondriarich cells, and (ii) the description and characterization of a novel subject, a voltage-dependent H+-activated conductance. The Cl− conductance (G Cl) is activated by tissue hyperpolarization (which leads to apical membrane depolarization) and the presence of Cl− ions in the apical solution. Increasing apical proton concentration (from pH 8 to pH 4) impairs the process of activation of the Cl− conductive pathway, slowing the kinetics of I t activation and reducing the steady-stage values of G t and I t . This effect is markedly voltage-dependent since no effect is seen at V t =−100 mv and is fully present at −50 mV. The voltage-dependence of the pH effect suggests that the critical protonation sites of the apical Cl− channels are not freely exposed to the apical solution but dwell within the membrane electric field. An also coherent interpretation is that titration of apical proton binding sites affects the gating of the voltage-dependent Cl− channels, shifting the conductance-vs.-voltage curve to more negative clamping potentials. Tissue conductance in the absence of apical Cl− ions can be importantly affected by the pH of the apical solution (pH a ), the effect being markedly dependent on the clamping potential. Generally speaking, the effect of rising apical proton concentration can be conspicuous at negative clamping potentials, while at positive potentials changes in tissue conductance were never observed. For a clamping potential of −100 mV, a turning point somewhere between pH a =4 and pH a =3 was observed. Apical acidification to pH 4 has no effect upon tissue conductance while apical acidification to pH 3 leads to a marked, slow and reversible increase of tissue conductance. A striking similitude exists between the voltage-dependent Cl−-gated conductance and the voltage-dependent proton-gated conductance regarding: (i) slow time courses of activation and deactivation, (ii) requirement for a negative clamping potential and the presence of a specific ion species in the apical solution for activation to take place, (iv) instantaneous ohmic behavior, and (v) steady-state rectification. However, so far the results do not permit one to conclude definitely that the voltage-dependent Cl−-gated conductance and the voltage-dependent proton-gated conductance share a common pathway.

Electronic Resource

1432-1424

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Summary The isolated skin of the toadBufo marinus ictericus when impaled from the outer surface by glass microelectrodes filled with 3m KCl shows a voltage profile which is a continuous function of the depth of impalement. The superficial intraepithelial potential difference measured with reference to the external solution (PDi) is negative with NaCl-Ringer's solution on both sides of the skin, displaying a minimum of −26.7±3.6 mV at 6±2 μm. Null value is obtained at 19±3 μm, with positive values for deeper impalements. Indications of cell impalements (abrupt voltage and resistance jumps) were frequently observed at sites deeper than 25 μm from the outer surface. Measurements of the electrical resistance between the microelectrode and the external solution, made with single- and double-barreled microelectrodes, showed great discrepancies, which may be attributed to distinct pathways of different resistances in thestratum corneum. PDi measured at a depth of 5 μm was a logarithmic function of Na2SO4 or K2SO4 concentration in the external solution, increasing in negativity with a reduction in concentration. Substitution of Na by K in the external solution had only minor effects onPDi. Acidification of the external solution from pH 9 is accompanied by a reduction in the negative value ofPDi. At pH 3PDi was positive.PDi was interpreted as a diffusion potential at the tip of the microelectrode due to KCl diffusion from the electrode into the matrix of thestratum corneum. Differences in K and Cl mobilities, responsible for the origin ofPDi, were attributed to fixed charges in the matrix of thestratum corneum, with density and polarity determined by their degree of protonation, controlled by the hydrogen ion concentration of the external solution. Skin potential, short-circuit current and their relationship toPDi were discussed.

Electronic Resource

1432-1424

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Summary Net influxes of Na and Cl and effluxes of K and H (J Na,J Cl,J K andJ H) and volume flowJ v across isolated open-circuited toad skins were measured using rotating chambers and a small volume of external solution, the ion fluxes being determined by chemical analysis of the external solution, in the range of 0.2 to 5.0mm external Na concentration. In this concentration range, with skin potential varying with (Na) e ,J Na is a linear function of the Na electrochemical potential difference across the skin, as expected on irreversible thermodynamic grounds. TheL Na coefficient calculated asΔJ Na/Δμ Na is equal to 5.5×10−12 mole2 joule−1 cm−2 min−1, which is similar to values obtained for the same species in the short-circuited state and in higher ranges of (Na) e . A positive correlation is observed betweenJ Na andJ K whenJ Na varied with (Na) e and also whenJ Na varies in randomly selected skins. Antidiuretic hormone stimulatesJ Na,J K andJ v in the range of 0.2 to 5.0mm (Na) e and lowers the Na concentration in the equivalent solution absorbed by the skin (calculated asJ Na/J v ). Substitution of external Cl by SO4 has no effect onJ Na,J K andJ H and also in the skin potential in the range of (Na) e studied. Substitution of external Na by K abolishesJ Cl and reverses the skin polarity, the external solution now being positive to the internal one. Na removal from the external solution also reducesJ K almost to zero.J H is significantly reduced in this condition; however, a basal secretion still persists with (Na) e equal to zero. The results of these experiments can be tentatively interpreted in terms of electrical coupling between ion fluxes, since only the procedures that result in alterations of skin potential are followed by changes in the rates of ion transport. The existence of other coupling mechanisms cannot be ruled out.

Electronic Resource

1432-1424

toad skin ; sodium permeability ; permeability regulation ; ouabain ; amiloride ; sodium channels

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Summary The24Na efflux (J eff Na ) (i.e., the rate of appearance of24Na in the outer compartment) in the isolated short-circuited toad skin bathed by NaCl-Ringer's solution on both sides is composed of para- and transcellular components of almost equal magnitudes. This relies on the assumption that amiloride acts on the transcellular component only and could block it completely. Ouabain induces a large transient increase of the transcellular component. This increase, which starts within a few minutes after the addition of ouabain, is due to electrical depolarization of the outer barrier, rather than a consequence of blocking Na recirculation across the inner barrier. The subsequent decline ofJ eff Na , which takes place after the ouabain-inducedJ eff Na peak, is due to a progressive block of outer barrier Na channels with time, which can eventually be complete, depending on the duration of action of ouabain. As the external Na concentration was always kept high and constant in these experiments, the results indicate that a rise in cell Na concentration, and not in the outer bathing solution, is the signal that triggers the reduction of outer barrier Na permeability (P 0 Na ). Ouabain has no effect uponJ eff Na with Na-free solution bathing the outer and NaCl-Ringer's solution the inner skin surface, showing the importance of Na penetration across the outer barrier, and not across the inner barrier due to its low Na permeability, in the process of closing the Na channels of this structure. Step changes from Na 115mm to Na-free external solution, or vice-versa, may affect both the outer barrier electrical potential difference (PD0) and cell Na concentration (Na) c . Therefore, the behavior ofJ eff Na depends on which variable (if PD0 or (Na) c regulated outer barrier Na permeability) is most affected by step changes in outer bathing solution Na concentration. Amiloride in the control condition blocks the transcellular component ofJ eff Na . However, in the condition of approximate short-circuiting of the outer barrier and high cellular Na concentration induced by long term effects of ouabain, when the Na channels of the outer barrier are already blocked by elevated cell Na concentration, amiloride may induce the opposite effect, increasing Na permeability of the outer barrier. With outer barrier Na channels completely blocked by high cell Na concentration, PCMB in the outer bathing medium induces a large increase ofJ eff Na , rendering these channels again amiloride sensitive. The results are consistent with the notion that Na efflux from cell compartment to the outer bathing solution goes through the amiloride-sensitive Na channels of the apical border of the superficial cell layer of toad skin, with an apparent Na permeability modulated by cell ionic environment, most probably the cell Na concentration. The ensemble of the present results are consistent with Na permeability regulation taking place at the outer barrier level. However, this precise location could only be made unambiguously by measurements across the individual outer cell membranes.

Electronic Resource

1432-1424

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Summary Biological (stratum corneum) and artificial (cation-exchange resin beads, Bio-Rad AG 50W-X2) ion exchangers were impaled by glass microelectrodes filled with KCl solution. The electrical potential difference recorded in these structures in reference to the external bathing medium was shown to be dependent on the KCl concentration of both the external and the microelectrode filling solutions. The potentials were interpreted on the grounds of the fixed charge theory of membrane potentials as a consequence of two phase boundary potentials (Donnan potentials), one at the matrix-external solution interface and the other at the matrix-microelectrode solution interface. The contribution of a diffusion component for the recorded potential was considered.

Electronic Resource

1432-1424

Key words: Tight junction — Occludin — ZO-1 — Transepithelial resistance

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract. This study shows that resealing of opened tight junctions (TJs) is impaired by interaction with oligopeptides homologous to the external domain of chick occludin. The experiments were carried out with confluent A6 cell monolayers grown on collagen supports under stable transepithelial electrical resistance (TER). The monolayers were bathed on the apical side with a 75 mm KCl solution and on the basolateral side by NaCl-Ringer's solution. TJ opening was induced by basolateral Ca2+ removal and was characterized by a marked drop of TER. The reintroduction of Ca2+ triggered junction resealing as indicated by an elevation of TER to control values. Custom-made peptides SNYYGSGLSY (corresponding to the residues 100 to 109) and SNYYGSGLS (residues 100 to 108), homologous to segments of the first external loop of chick occludin molecule, impaired junction resealing when the peptides were included in the apical bathing fluid (concentrations in the range of 0.5 to 1.5 mg/ml). Peptide removal from the apical solution usually triggered a slow recovery of TER, indicating a slow recovery of the TJ seal. Changes in localization of ZO-1, a cytoplasmic protein that underlies the membrane at the TJs, were evaluated immunocytochemically following Ca2+ removal and reintroduction. The presence or absence of the oligopeptides showed no influence on the pattern of change of ZO-1 localization. These observations support the hypothesis that the TJ seal results from the interaction of specific homologous segments of occludin on the surface of adjacent cells. Additionally, our results show that small peptides homologous to segments of the occludin first external loop can be used as specific reagents to manipulate the permeability of tight junctions.

Electronic Resource