Nonequilibrium thermodynamic analysis of the coupling between active sodium transport and oxygen consumption.

Sodium transport and oxygen consumption have been simultaneously studied in the short-circuited toad skin. A constant stoichiometric ratio was observed in each skin under control condition (NaCl-Ringer's solution bathing both sides of the skin) and after block of sodium transport by ouabain. During alterations of sodium transport by removal and addition of K to the internal solution the stoichiometric ratio is constant although having a value higher than that observed in other untreated skins. The coupling between active sodium transport and oxygen consumption was studied after a theoretical nonequilibrium thermodynamic model. Studies were made of the influence of Na chemical potential difference across the skin on the rates of Na transport and oxygen consumption. A linear relationship was observed between the rates of Na transport and oxygen consumption and the Na chemical potential difference. Assuming the Onsager relationship to be valid, the three phenomenological coefficients which describe the system were evaluated. Transient increases in the rate of sodium transport and oxygen consumption were observed after a transitory block of sodium transport by removal of Na from the external solution. Cyanide blocks completely the rate of oxygen consumption in less than 2 min and the short-circuit current measured after that time decays exponentially with time, suggesting a depletion of ATP from a single compartment.

Energetics of sodium transport in frog skin. I. Oxygen consumption in the short-circuited state.

Sodium transport and oxygen consumption were studied simultaneously in the short-circuited frog skin. Sodium transport was evaluated from I(o)/F, where I(o) is the short-circuit current measured with standard Ringer's solution bathing each surface and F is the Faraday constant. Oxygen tension was measured polarographically. Under a variety of circumstances the rate of oxygen consumption from the outer solution exceeded that from the inner solution, the ratio being constant (0.57 +/- 0.09 SD). Both I(o) and the associated rate of oxygen consumption J(ro) declined nonlinearly with time, but the relationship between them was linear, suggesting that the basal oxygen consumption was constant. For each skin numerous experimental points were fitted by the best straight line. The intercept (J(ro))(Io=0) then gave the basal oxygen consumption, and the slope dNa/dO(2) gave an apparent stoichiometric ratio for a given skin. The basal oxygen consumption was about one-half the total oxygen consumption in a representative untreated short-circuited skin. Values of dNa/dO(2) in 10 skins varied significantly, ranging from 7.1 to 30.9 (as compared with Zerahn's and Leaf and Renshaw's values of about 18). KCN abolished both I(o) and J(ro). 2,4-dinitrophenol (DNP) depressed I(o) while increasing J(ro) four- to fivefold. Anti-diuretic hormone stimulated and ouabain depressed both I(o) and J(ro); in both cases apparent stoichiometric ratios were preserved.

Energetics of sodium transport in frog skin. II. The effects of electrical potential on oxygen consumption.

Studies were made of the dependence of the rate of oxygen consumption, J(r), on the electrical potential difference, Deltapsi, across the frog skin. After the abolition of sodium transport by ouabain the basal oxygen consumption was independent of Deltapsi. In fresh skins J(r) was a linear function of Deltapsi over a range of at least +/-70 mv. Treatment with aldosterone stimulated the short-circuit current, I(o), and the associated rate of oxygen consumption, J(ro), and increased their stability; linearity was then demonstrable over a range of +/-160 mv. Brief perturbations of Deltapsi (+/-30-200 mv) did not alter subsequent values of I(o). Perturbations for 10 min or more produced a "memory" effect both with and without aldosterone: accelerating sodium transport by negative clamping lowered the subsequent value of I(o); positive clamping induced the opposite effect. Changes in J(ro) were more readily detectable in the presence of aldosterone; these were in the same direction as the changes in I(o). The linearity of J(r) in Deltapsi indicates the validity of analysis in terms of linear nonequilibrium thermodynamics-brief perturbations of Deltapsi appear to produce no significant effect on either the phenomenological coefficients or the free energy of the metabolic driving reaction. Hence it is possible to evaluate this free energy.

The state of water in human and dog red cell membranes.

The apparent activation energy for the water diffusion permeability coefficient, P(d), across the red cell membrane has been found to be 4.9 +/- 0.3 kcal/mole in the dog and 6.0 +/- 0.2 kcal/mole in the human being over the temperature range, 7 degrees to 37 degrees C. The apparent activation energy for the hydraulic conductivity, L(p), in dog red cells has been found to be 3.7 +/- 0.4 kcal/mole and in human red cells, 3.3 +/- 0.4 kcal/mole over the same temperature range. The product of L(p) and the bulk viscosity of water, eta, was independent of temperature for both dog and man which indicates that the geometry of the red cell membrane is not temperature-sensitive over our experimental temperature range in either species. In the case of the dog, the apparent activation energy for diffusion is the same as that for self-diffusion of water, 4.6-4.8 kcal/mole, which indicates that the process of water diffusion across the dog red cell membrane is the same as that in free solution. The slightly, but significantly, higher activation energy for water diffusion in human red cells is consonant with water-membrane interaction in the narrower equivalent pores characteristic of these cells. The observation that the apparent activation energy for hydraulic conductivity is less than that for water diffusion across the red cell membrane is characteristic of viscous flow and suggests that the flow of water across the membranes of these red cells under an osmotic pressure gradient is a viscous process.

Biological and artificial ion exchangers: electrical measurements with glass microelectrodes.

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.

Transients in toad skin: short circuit current and ionic fluxes related to inner sodium substitution by monovalent cations.

When the Na electrochemical potential difference across the skin (delta muNa) is altered by perturbing the transmembrane electrical potential difference or the external Na concentration, effects on transport and associated oxygen consumption can be described by the formalism of linear nonequilibrium thermodynamics (Vieira, Caplan & Essig, 1972, J. Gen. Physiol. 59:77; Danisi & Lacaz-Vieira, 1974, J. Gen. Physiol. 64:372; Procópio and Lacaz-Vieira, 1977, J. Membrane Biol. 35:219). We now show that with modifications of delta muNa by substitution of Li or choline for Na in the inner bathing solution, this formalism is no longer applicable. Inner Na by K substitution ((Na X K)i) causes profound alterations in short-circuit current (SCC), JinNa, K efflux (JeffK) and PD. SCC drops transiently after (Na X K)i in Cl and in SO4 media, increasing subsequently. In Cl medium, following the initial transient, there is a late decline in SCC toward a steady state. The rate of SCC decline in Cl medium is more pronounced than that observed in SO4 medium. (Na X K)i causes a transient increase in JinNa with a peak synchronous to the minimum in SCC, both in Cl and in SO4 media. This was interpreted as due to depolarization of the inner membrane. In SO4 medium, following the peak observed after (Na X K)i, JimNa drops, to increase again toward a steady state in which SCC and JinNa are not statistically different, resembling the control condition before (Na X K)i. In Cl medium, however, the JinNa steady state is approximately 100% higher than SCC. This difference is due to an important K efflux (JeffK), which builds up progressively after the substitution. The apparent K permeability [JeffK/(Ki)] is of comparable magnitude in Cl and in SO4 media before (Na X K)i and also in SO4 medium after (Na X K)i. However, in Cl medium, after (Na X K)i, the apparent K permeability increases one order of magnitude as compared to the control condition before the ionic substitution. In Cl medium, the high levels of JinNa and of Jeff(K) observed in the steady state after (Na X K)i were interpreted as being a consequence of cell swelling. SCC and PD follow very different temporal patterns after (Na X K)i which are characterized by transients in SCC and a simple fall in PD. Reasons for these differences are discussed.

Negative potential level in the outer layer of the toad skin.

The isolated skin of the toad Bufo marinus ictericus when impaled from the outer surface by glass microelectrodes filled with 3 M 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 mum. Null value is obtained at 19+/-3 mum, with positive values for deeper impalements. Indications of cell impalements (abrupt voltage and resistance jumps) were frequently observed at sites deeper than 25 mum 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 the stratum corneum. PDi measured at a depth of 5 mum 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 on PDi. Acidification of the external solution from pH 9 is accompanied by a reduction in the negative value of PDi. At pH 3 PDi 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 the stratum corneum. Differences in K and Cl mobilities, responsible for the origin of PDi, were attributed to fixed charges in the matrix of the stratum corneum, with density and polarity determined by their degree of proponation, controlled by the hydrogen ion concentration of the external solution. Skin potential, short-circuit current and their relationship to PDI were discussed.

Permeability parameters of the toad isolated stratum corneum.

A technique for isolating the stratum corneum from the subjacent layers of the epithelium was developed which permits studying the stratum corneum as an isolated membrane mounted between half-chambers. The method basically consists of an osmotic shock induced by immersing a piece of skin in distilled water at 50 degrees C for 2 min. When the membrane is bathed on each surface by NaCl-Ringer's solution, its electrical resistance is 14.1 +/- 1.3 omega cm2 (n=10). This value is about 1/100 of the whole skin resistance in the presence of the same solution. The hydraulic filtration coefficient (Lp) measured by a hydrostatic pressure method, with identical solutions on each side of the membrane, is 8.8 X 10(-5) +/- 1.5 X 10(-5) cm sec-1 atm-1 (n=10) in distilled water and 9.2 X 10(-5) +/- 1.4 X 10(-5) cm sec-1 atm-1 (n=10) in NaCl-Ringer's solution. These values are not statistically different and are within the range of 1/80 to 1/120 of the whole skin Lp. The stratum corneum shows an amphoteric character when studied by KCl diffusion potentials at different pH'S. The membrane presents an isoelectric pH of 4.6 +/- 0.3 (n=10). Above the isoelectric pH the potassium transport number is higher than the chloride transport number; below it, the reverse situation is valid. Divalent cations (Ca++ or Cu++) reduce membrane ionic discrimination when the membrane is negatively charged and are ineffective when the membrane fixed charges are protonated at low pH.

Critérios de elegibilidade e plano mínimo de acompanhamento integrado no serviço de assistência domiciliar do Campo Limpo: relato de experiência

Introdução: a avaliação inicial de usuários em situação de dependência funcional é complexa, implicando na avaliação de fatores diversos, de ordens bio-psico-sociais, dificultando a utilização de dados quantitativos e dando margem à interpretação do observador. Entretanto, a conformação de instrumentos de avaliação inicial e o dimensionamento do serviço a partir de escores e dos recursos disponíveis mostram-se úteis às atividades de planejamento e avaliação de serviços de assistência domiciliar. Numa ótica de otimização de recursos, o Serviço de Assistência Domiciliar do Campo Limpo (SAD-CL) criou um instrumento de avaliação inicial pontuada para determinar a elegibilidade do usuário ao serviço e criou uma padronização de plano mínimo de acompanhamento integrado a partir da pontuação obtida na avaliação. Objetivo: o objetivo deste trabalho é apresentar o instrumento de avaliação inicial pontuado utilizado pelo SAD-CL e a criação da padronização do plano mínimo de acompanhamento integrado de cuidados domiciliares.

Critérios de elegibilidade e plano mínimo de acompanhamento integrado no serviço de assistência domiciliar do Campo Limpo: relato de experiência / Eligibility criteria and minimum follow-up plan in integrated home care service Limpo: experience report

Introdução: a avaliação inicial de usuários em situação de dependência funcional é complexa, implicando na avaliação de fatores diversos, de ordens bio-psico-sociais, dificultando a utilização de dados quantitativos e dando margem à interpretação do observador. Entretanto, a conformação de instrumentos de avaliação inicial e o dimensionamento do serviço a partir de escores e dos recursos disponíveis mostram-se úteis às atividades de planejamento e avaliação de serviços de assistência domiciliar. Numa ótica de otimização de recursos, o Serviço de Assistência Domiciliar do Campo Limpo (SAD-CL) criou um instrumento de avaliação inicial pontuada para determinar a elegibilidade do usuário ao serviço e criou uma padronização de plano mínimo de acompanhamento integrado a partir da pontuação obtida na avaliação. Objetivo: o objetivo deste trabalho é apresentar o instrumento de avaliação inicial pontuado utilizado pelo SAD-CL e a criação da padronização do plano mínimo de acompanhamento integrado de cuidados domiciliares.