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Current views on membrane construction are presented as a basis for discussing certain modifications of structure that may render membranes leaky, allowing solutes to diffuse from them. Biophysical experiments on dehydrated membranes indicate that, when their water content is reduced below 20%, they no longer adopt the lipid bilayer conformation. When dry seeds, spores or lichens are placed in water, soluble cell constituents leak from them for a few seconds or minutes until membrane integrity is re-established; the same may apply also to the liberation of solutes from pollen grains. Moreover, there are indications that 'dry' in this context means having less than about 20% water. Some plants are sensitive to chilling, their tissues becoming leaky when exposed to temperatures between o and 10 °C. This chilling-induced leakage, attributed to a phase change in all the phospholipids of which the membrane is composed occurs at a slightly lower temperature than the change in the activation energy of membrane-bound enzymes. At senescence, leaf tissues become leaky and may eventually dry out. So much phospholipid disappears from senescing cotyledons of cucumber that there is no longer sufficient to fabricate complete and intact membranes around the cells. Treating cucumber cotyledons with iodoacetate also causes a loss of phospholipids, allowing solutes to leak out of the cells. It is possible that exposing seeds or mature plant tissues to oxygen at pressures of I or more atm renders them leaky because of lipid peroxidation. [ABSTRACT FROM AUTHOR]

The importance of the stratum corneum as the rate-limiting barrier to perceutaneous penetration has been well documented in the literature. Data have also been reported which suggest that the barrier function of this zone varies among different regions of the body. However, little attention has been given to regional variation of two morphologic parameters know to affect permeability--thickness and number of cell layers. In the present study, significant regional variation in both the mean thickness and the mean number of cell layers has been documented for four selected , sample regions of the body of a population of six adult volunteers, and for two more homogeneous subgroups separated by sex and age. While the pooled data from the total population and the pooled data from the male and female subgroups are in general agreement. It has been shown that there is also marked individual variation within a region that is characteristic and specific for each individual. The number of cell layers appears to account for the variation in thickness. [ABSTRACT FROM AUTHOR]

Under normal conditions the stratum corneum in vivo is very much less hydrated than the excised tissue routinely used in laboratory permeability experiments. As a consequence, certain quantitative predictions of skin permeability based on laboratory experiments are not applicable to many cases of clinical and practical interest. In this study a modified in vitro permeability technique was used which permitted the hydration of the stratum corneum to be maintained very close to its natural state. Penetrant molecules were applied by adding a few microliters of acetone solution to the stratum corneum surface. The acetone quickly evaporated leaving a residue of solid penetrant. The time course of penetration of the solid material through the epidermis was observed as a function of applied dose, mild hydration, and solvent contact time. Remarkably steady, uniform penetration persisting over several weeks was observed. Generally, the penetration rates were similar to those observed in vivo and increased in a similar manner upon occlusion. Diffusion through the stratum corneum rather than sorption of the solid at the surface appears to be rate limiting. [ABSTRACT FROM AUTHOR]

The effect of Alanap, N‐1‐naphthylphthalamic acid (NPA), on the permeability of onion (Allium cepa) epidermal cells was studied by means of a plasmometric method. Urea, 1,3‐dimethylurea, and water were used for the test of permeability. It was found that the treatment of onion epidermis with NPA at various concentration (5 × 10–3 to 5 × 10–6M) altered the deplasmolysis rates and the absolute permeability constants. However, NPA did not alter the osmotic value of the treated cells. It was suggested that NPA treatment altered the permeability of onion epidermal cells due to the effect of this herbicide on the plasma membrane. [ABSTRACT FROM AUTHOR]

Water uptake of root systems of Phaseolus vulgaris was measured in a Scholander pressure cylinder at a constant pressure. Water uptake rises gradually till a steady state is reached after 15 to 60 minutes. This time course can be described as a transport process with the property of a self-induction. The latter was not affected by temperature. It is concluded that the property of self-induction is located in the cytoplasm or at the interface between cytoplasm and plasmalemma of the endodermal cells. It is suggested that cytoplasmic streaming controls the time course of water transport. [ABSTRACT FROM AUTHOR]

The permeability of four dental lining materials has been tested by water vapor penetration in vitro. Films of Dycal® and Copalite® were found to have low permeability values while rather great permeability was found for test specimens of Dropsln® and Tubulitec®. [ABSTRACT FROM AUTHOR]

Forty-eight dental students were screened regarding the rate of plaque formation. The four most rapid (RPF-group) and the four slowest (SPF-group) plaque formers were selected and compared as to: (1) the development of gingivitis during a 14-day period without oral hygiene, (2) the chemotactic activity elaborated by (a) gingival crevicular material (GCM) sampled 24 h after withdrawal of oral hygiene measures and (b) 4- and 8- day-old plaques, and (3) permeability-inducing factors in 4- and 8-day-old plaques. The Gingival Index, Plaque Index and flow of gingival fluid were used for assessing plaque formation and gingivitis development. The chemotactic activity was estimated with the use of Boyden's in vitro model, and subcutaneously implanted wound chambers were used for demonstrating change in vascular permeability. It was found that: (1) individuals vary considerably with regard to the rate of formation of dental plaque, (2) gingivitis developed faster in the RPF group than in the SPF group, (3) GCM sampled already 24 h after cessation of oral hygiene yielded higher chemotactic activity in the RPF group than in the SPF group, and (4) the RPF and SPF groups did not differ from one another regarding chemotactic activity or permeability-inducing activity of equal amounts (wet weight) of plaque. [ABSTRACT FROM AUTHOR]

Hamster brown-adipose-tissue mitochondria, swollen in the chloride, bromide or nitrate salts of sodium, or potassium in the presence of nigericin, do not contract on the addition of oxidizable substrate. If albumin is added to the swollen mitochondria a rapid and complete contraction occurs on substrate addition; however no contraction was observed of mitochondria swollen in KCl or potassium phosphate plus valinomycin or in sodium phosphate. Contraction is interpreted as being a consequence of ion expulsion linked to respiration-dependent proton translocation. GDP inhibits respiration-independent chloride permeation but does not prevent chloride efflux from the matrix during respiration in the presence of albumin; respiratory control is retained in this condition after completion of contraction. The stoichiometry of chloride extrusion is approximately 2 Cl-/O with succinate as substrate in the presence of albumin, and is unchanged if GDP is additionally present. In the presence of albumin the chloride conductance of the inner membrane is approximately 8 nequiv. Cl- × min-1 × mg-1 × mV-1. The farther addition of GDP decreases the conductance, and no chloride efflux is observed if the membrane potential is below 40 mV. The effectiveness of purine nucleotides in inhibiting chloride permeation in non-respiring systems is attributed to the low membrane potentials generated by diffusion. The possibility that the sites of electrical anion permeation and purine-nucleotide-sensitive proton (or hydroxyl ion) permeation are identical is discussed. [ABSTRACT FROM AUTHOR]

In this paper we demonstrate that two compounds which are known to enhance the permeability of membranes to potassium, valinomycin, a cyclic dodecapeptide and dicyclohexyl-18-crown-6, a macrocyclic polyether, inhibit protein synthesis in reticulocytes and that this inhibition is not primarily due to changes in the intracellular potassium concentration. No effect is obtained by adding the drugs to a cell free system and the inhibition observed is likely to be membrane mediated. Dicyclohexyl-18-crown-6 and low concentration of valinomycin (10 nM) act reversibly probably by interacting with the lipid phase of the membrane. This interaction in turn affects the protein synthesizing apparatus by affecting ribosomal functions. Ribosomes once isolated from treated cells are perfectly normal in structural and functional respects. High concentrations of valinomycin, which change the K+ gradient between the inside and the outside of the cell, affect the protein synthesizing apparatus of reticulocytes irreversibly by blocking incorporation of amino acids at the level of elongation or termination. Ribosomes isolated from cells treated with high valinomycin concentrations are mostly in the form of polysomes which are inactive in cell free protein synthesis. The high valinomycin block on the ribosomal fraction can be relieved either by washing ribosomes with high salt or with puromycin. It is believed that with high concentrations of valinomycin an inhibitor is released (probably from the membrane) and attached to the ribosomes. This high valinomycin effect is believed to by a supplementary phenomenon which when added to the effect of low valinomycin renders the inactivation of ribosomal functions irreversible.

An Escherichia coli ‘permeabilized’ cell system obtained by treatment in high sucrose concentration, because of its depletion from endogenous metabolites, its low nuclease, phosphatase and phosphokinase content, catalyzes a very efficient polymerisation of the common ribonucleoside diphosphates (UDP, CDP, ADP and GDP) presumably through the polynucleotide phosphorylase retained within the cells after osmotic shock. Accordingly incorporation of nucleotides into polymers is insensitive to actinomycin D and does not take place in the presence of Mg2+ ions with E. coli Q13 a strain in which the polynucleotide phosphorylase is a Mn-dependent enzyme. Polymers containing U, C, G, or A as the only constituting nucleosides have been found to accumulate for several hours at a linear rate, in the supernatant phase from osmotically shocked E, coli D10. If, following the arrest of polymer formation the amino acid coded for by the corresponding triplet is added to the incubation medium together with an energy-yielding system, a very efficient incorporation of this amino acid (and of this amino acid only) into an acid-precipitable material takes place. The resulting product (presumably an homopolypeptide) is associated with the cell bodies. Translation of the preformed poly-ribonucleotide is concomitant with its nucleolytic cleavage by a K-dependent nuclease. [ABSTRACT FROM AUTHOR]

Total haemolytic complement was reduced in blister fluids of four pemphigus vulgaris patients when compared to serum complement levels and other serum and blister fluid proteins. Complement levels in most control blister fluids, on the other hand, more closely approached their corresponding serum levels. Haemolytic C1, C4, C2, C3 and C5, measured in two pemphigus sera and blister fluids, were not measurable in one blister fluid and were extremely low in the second patient. C3 proactivator (C3PA) was absent from both of these blister fluids. Three of the blister fluids exhibited anti-complementary activity when tested with normal human serum. By adding one blister fluid to normal human serum, inhibition of haemolytic C1, C2. C3 and C5 with conversion of C3 and C3PA occurred. Activation of complement locally in pemphigus blister fluids would suggest a pathogenetic role for complement in this disease. [ABSTRACT FROM AUTHOR]

The permeability to water of whole detopped root systems of five herbaceous species, all grown under the same conditions, was determined by the solution-change method of Arisz, fielder and van Nie (1951). Measurements of root dimensions allowed permeability to be expressed per unit of (a) root surface area, (b) endodermis area, (c) root volume, and (d) root length. By any of these four methods of calculation there were large differences in permeability between the species. Per unit surface area the permeabilities were: broad bean, 0.54; dwarf bean, 0.56; sunflower, 0.71; maize, 2.2; tomato, 6.1 nm second[SUP-1] bar[SUP-1]. These differences cannot be explained by any obvious difference in root morphology. The permeability values fit with two previously proposed theories; (1) that much of the root resistance lies in the endodermis; and (2) that the resistance of the soil in the rhizosphere is small compared with that of the plant until the soil has dried to near or beyond the permanent wilting point. [ABSTRACT FROM AUTHOR]

A method is described for the assay of nitrate-reductase activity in frozen and thawed cells of Chlorella. The method depends on coupling nitrate reductase with malic dehydrogenase, both enzymes and the necessary coenzyme being retained within frozen/thawed cells. Other ways than destroying permeability by freezing arc considered and a short treatment of fresh cells with 1.5 M glycerol is shown to be effective. The method has been used to follow the induction of nitrate-reductase activity in Chlorella. Other enzyme activities that can be measured by similar methods, i.e. by enzymic coupling within damaged cells, are nitrite reductase and urea amido-lyase. [ABSTRACT FROM AUTHOR]

Concentrations of the major component ions (K., Na and Cl) of sea water and cells of Enteromorpha intestinalis(L. ) Link were determined, Measurements of the electric potential difference across the plasmalemma and the influx and efflux of each ion indicate that K and Cl are actively imported and Na actively exported Estimates of membrane permeability to the passive diffusive fluxes of these three ions alone have been used to explain the origin of the cell membrane potential. Tracer ion exchange kinetics are taken as showing that the tonoplast is more permeable than the plasmalemma to each ion. [ABSTRACT FROM AUTHOR]

The effect of changes in the vacuole of the amounts of solute and of water and of the turgor pressure, on the apparent weight of a cell and of a piece of tissue is considered. The permeability of cells in the root of carrot is estimated from the change in apparent weight of discs suspended in a solution of KNO[SUB3]. The permeability to urea is estimated from the change in apparent weight in water after discs had equilibrated with a solution of urea. The dimensions of permeability to water and solute and the effect of flow of water on the apparent permeability to solute, are considered. The change in apparent weight is used to measure the relatively slow uptake of cane sugar from dilute solutions of this substance. The uptake is not due to passive diffusion and the sugar absorbed appears to be osmotically active. From measurements of carbon dioxide produced and chloride ions absorbed from o.az M KCI the change in apparent weight in water and change in osmotic pressure of the vacuolar sap are estimated. These are compared with the observed changes in apparent weight and changes in osmotic pressure deduced from the change in the relation between the vacuolar volume and the concentration of KCI with which it is in equilibrium. [ABSTRACT FROM AUTHOR]

The effect of aspermy virus infection the water status of tomato leaves was studied. Infected leaves had a higher relative water content than controls, the increase being related to inoculum concentration. This was shown to be caused by an inability to take up water rather than a truly higher water content. It is suggested that this may be the result of a reduction in the permeability of cell membranes. [ABSTRACT FROM AUTHOR]

Most quantitative permeability data on human skin are based on studies in which water was used as the vehicle. Very little is known of the permeability of normal stratum corneum as it exists in vivo where it is considerably less hydrated. Similarly very little is known of the effect of nonaqueous solvents on the skin although they are common vehicles in topical therapy. In this study the permeation rates of a homologous series of primary alcohols (C1-C10) through skin were measured. The alcohols were applied from aqueous solutions and also as the pure liquids. The permeation behavior in the two cases is compared in terms of (1) the transport rates of the alcohols, (2) the distribution equilibrium between the tissue and vehicle, and (3) the damage to the tissue produced by the vehicle. Fick's law was found to hold as an approximation for both the aqueous and the liquid alcohol systems. Using the measured data, which include permeability and diffusion constants and tissue:vehicle partition coefficients, the diffusional resistance offered by epidermis and dermis is accurately apportioned. The overwhelming role of the stratum corneum in both the aqueous and the pure liquid systems is quantitatively confirmed. The effect of the solubility characteristics of different vehicles on skin permeability is discussed. It is shown that with the aid of a few simple principles and a knowledge of the solubility character of the vehicle, the permeation of different substances can be qualitatively predicted. [ABSTRACT FROM AUTHOR]

A comparative study was undertaken in rats, rabbits, miniature swine and man, in which the percutaneous absorption of the following compounds, labeled with 14C or 35S, were studied: haloprogin, N-acetylcysteine, cortisone, testosterone, caffeine and butter yellow. The amount of radioactivity excreted in urine for 5 days following application of the test compound to the skin was employed as the index for quantifying skin penetration. A special nonocclusive foam pad device for rabbits and miniature swine was developed to prevent artifacts resulting from transfer of drug to the urine by any route other than percutaneous absorption. The dose was 4 μg/cm² of skin surface. The excretion data obtained from the topical studies were adjusted for recovery of radioactivity following intravenous administration of the radioactive drug. The results obtained in this study indicated that skin permeability decreases in the following order: rabbit, rat, pig and man. Overall, skin of miniature swine has the closest permeability characteristics to that of human skin with this series of compounds. [ABSTRACT FROM AUTHOR]

A permeability factor extracted from guinea pig skin was partially purified by Sephadex G-50, hydroxylapatite and CM-Sephadex C-50; and its properties were studied. The factor is a heat labile protein (m.w. ca. 31,000) which gave a prolonged increase in vascular permeability after intradermal injection and its activity was slightly inhibited by soybean trypsin inhibitor (24%) and diisopropyl fluorophosphate (10%) but not by Trasylol. A heat inactivation study indicated that the increase in permeability was not due to a proteinase which was present in vasoactive fractions from CM-Sephadex C-50 eluate. Separation of the permeability factor from any esterolytic activity (α-n-Benzoyl-L-Arginine Ethyl Ester as substrate) was achieved. All available evidence indicated that the permeability factor was different from previously described endogenous vasoactive substances. [ABSTRACT FROM AUTHOR]

Compounds which are known to labilize biological membranes have been demonstrated to increase tyrosinase activity in the B-16 melanoma and newborn mouse skin. Detergents, bile acids, chlorpromazin (CPZ), neutral steroids and proteases all increase melanosomal tyrosinase activity. Digitonin (0.5%) produced approximately a five fold increase in tyrosinase activity and released 50% of the enzyme from the melanosome. CPZ (10-5M) produced a 2.7 fold increase in tyrosinase activity without releasing the enzyme from the melanosome. The CPZ-induced activition of tyrosinase was decreased by the membrane stabilizer, chloroquine and abolished by prior treatment of the melanosomes with digitonin. Alteration of the outer melanosomal membrane by digitonin and CPZ was confirmed by electron microscopy. The results suggest that the membrane surrounding the melanosome regulates the accessibility of eh substrate tyrosine to the tyrosinase molecule inside the organelle. A change in membrane permeability may be the mechanism by which certain physio-logical and pharmacological compounds control or alter pigmentation. [ABSTRACT FROM AUTHOR]

Model roots of known length and internal porosity were assayed for ROL (radial oxygen loss) by the cylindrical Pt electrode technique and a series of curves were obtained which express the inter-relationships between ROL and diffusion path length over a wide range of internal porosity levels. The results indicate that internal porosity can exert considerable control on the amount of oxygen lost from roots, the more so the narrower the root. Because radial oxygen loss is necessary for survival and competitiveness, doubt is therefore cast on the currently held view that aerenchyma formation furnishes the wetland plant with an oxygen diffusion pathway excessive to its requirements. The results also suggest that cellular partitions and diaphragms in wetland species may impede gas transport far less than has hitherto been thought. [ABSTRACT FROM AUTHOR]

The relative anion permeability of chloroplasts was measured by u utilizing three techniques: (a) measurement of light induced NH4+ movements, (b) measurement of the light induced osmotic swelling in the presence of NH4+ salts and (c) measurements of valinomycin incuded dark swelling in the presence of K+ salts. All were found to be dependent on the nature of the anion in the solution. Impermeant anions have been found specially in the group of zwitterions (tricine, glycine, ε-amino-caproate and aspartate) or polyvalent ions (citrate, succinate, AMP, ADP, and ATP). The permeant anions could be placed in the following order: I- > NO3- > Cl- > SO4-. The uncoupling by ammonium salts was independent of the nature of the anion in solution. Thus, in chloroplasts, uncoupling by ammonium salts was not necessarily accompanied by massive ammonium uptake or dependent on the presence of a permeant anion. The relevance of these studies to the chemioasmotic hypothesis is discussed, and it is suggested that a membrane potential by itself is not sufficient in chloroplasts to provide the driving force for ATP synthesis. [ABSTRACT FROM AUTHOR]

Active cutaneous anaphylaxis was studied in guinea-pigs sensitized by inhalation of egg albumen powder and producing high titre IgGγl and low titre IgE homocytotropic antibodies. On cutaneous antigen challenge an immediate increase in venular permeability occurred which declined rapidly over the next hour, normal permeability being restored by 2 hours. This was followed by a biphasic tissue eosinophilia with peaks at 3–6 hours and 14–16 hours. Tissue neutrophilia was also maximal at 14–16 hours with a preceding ‘shoulder’ between 6 and 12 hours. Injection of antigen into non-sensitized animals produced only the early peak of leucocytosis. Fluorescent protein tracing demonstrated that little antigen persisted in lesions older than 7 hours. Neutrophil phagocytosis of antigen was maximal between 1 and 3 hours; eosinophil phagocytosis of antigen was not observed. IgGγ1 and IgGγ2 were localized to granulocytes during the 3–6 hour peak of leucocytosis, but not in older lesions. IgGγ1 was detected in cosinophils, but which granulocytes contained IgGγ2 antibodies remained uncertain. Binding of IgGγ1 antibodies to mast cells was not observed and C3 was not detected in any lesion. It is concluded that antigen induced the first peak of tissue leucocytosis; possible mediators of the second leucocytic peak include cosinophil chemotactic factor of anaphylaxis, mast cell products and leucoegresin. [ABSTRACT FROM AUTHOR]

Cerebral vascular permeability was measured in guinea-pigs developing experimental allergic encephalomyelitis (EAE). A sensitive double radioisotope method was used which allowed the permeability changes to be measured independently of alterations in cerebral blood volume. The onset of the disease was accompanied by a striking increase in vascular permeability, but there was no evidence that this change preceded the entry of inflammatory cells into the brain and cord. Injection of serum from rabbits with EAE into normal guinea-pigs had no measurable effect on the cerebral vessels. These findings are consistent with the view that EAE is a cell-mediated lesion and provide no support for the suggestion that the initial damage is due to circulating antibody. [ABSTRACT FROM AUTHOR]

The vascular permeability factor present in extracts of lymph node cells (LNPF) has been examined as a possible mediator of the cutaneous inflammation associated with the delayed hypersensitivity produced by painting the skin of guinea-pigs with 2:4-dinitrochlorobenzene. It has been found that during the development of the DNCB reaction it becomes possible to extract from the reaction site a substance indistinguishable from LNPF, the results being similar to those obtained previously in tuberculin sensitivity. Precipitating antibody to guinea-pig LNPF has been produced in rabbits. Pretreatment of animals with the antibody serum caused a marked diminution of the erythema and cellular infiltration seen after application of the challenging dose of DNCB. It is suggested that in the tuberculin and DNCB reactions, sensitized mononuclear cells may reach the reaction site as a result of non-specific stimuli, react with antigen and release LNPF which might bring about a major inflammatory response. [ABSTRACT FROM AUTHOR]

A soluble extract from guinea-pig lymph node cells (LPF) has been found to increase vascular permeability in the skin of the rat. The active substance has been differentiated from histamine, 5-hydroxytryptamine, bradykinin, substance P, kallikrein and the globulin permeability factors from rat and guinea-pig serum by means of parallel quantitative assays. LPF was present in both sensitized guinea-pig lymph node cells and in lymph node cells from rats and mice. LPF also increased vascular permeability in the skin of guinea-pigs, mice and rabbits. The possible importance of this factor in the mechanism of the delayed reactions is discussed. [ABSTRACT FROM AUTHOR]

Gamma globulins, isolated from guinea-pig serum by five different methods, increased capillary permeability when injected intradermally into guinea pigs. None of the methods of isolation caused aggregation of the globulins as judged by ultracentrifugal analysis. The γ-globulin activity was not altered by heat (56° for 3° minutes) but was inhibited by albumin, soya-bean trypsin inhibitor and di-isopropylphosphofluoridate. All preparations inhibited serum complement but only when they had been freeze-dried. [ABSTRACT FROM AUTHOR]

The basic proteins of rat neutrophils possessing the capacity to induce vascular Permeability were analysed. Evidence indicating the presence of four such permeability proteins was presented. One of these induced the release of' histamine from rat mast cells. [ABSTRACT FROM AUTHOR]

A capsule is described which can be used for the measurement of the water vapor loss of the nail with the aid of the same instrumentation that has been used for the measurement of the water vapor loss of skin. The effective area of the described capsule has been determined applying an electric analog. The specific water permeability of the nail plate appeared to be independent of nail thickness in the finger nails of a healthy volunteer. [ABSTRACT FROM AUTHOR]