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PubMed1988

Very low osmotic water permeability and membrane fluidity in isolated toad bladder granules.

Osmotic water permeability of the apical membrane of toad urinary epithelium is increased greatly by vasopressin (VP) and is associated with exocytic addition of granules and aggrephores at the apical surface. To determine the physiological role of granule exocytosis, we measured the osmotic water permeability and membrane fluidity of isolated granules, surface membranes and microsomes prepared from toad bladder in the presence and absence of VP. Pf was measured by stopped-flow light scattering and membrane fluidity was examined by diphenylhexatriene (DPH) fluorescence anisotropy. In response to a 75 mM inward sucrose gradient, granule size decreased with a single exponential time constant of 2.3 +/- 0.1 sec (SEM, seven preparations, 23 degrees C), corresponding to a Pf of 5 x 10(-4) cm/sec; the activation energy (Ea) for Pf was 17.6 +/- 0.8 kcal/mole. Under the same conditions, the volume of surface membrane vesicles decreased biexponentially with time constants of 0.13 and 1.9 sec; the fast component comprised approximately 70% of the signal. Granule, surface membrane and microsome time constants were unaffected by VP. However, in surface membranes, there was a small decrease (6 +/- 2%) in the fraction of surface membranes with fast time constant. DPH anisotropies were 0.253 (granules), 0.224 (surface membranes) and 0.190 (microsomes), and were unaffected by VP. We conclude: (1) granules have among the lowest water permeabilities of biological membranes, (2) granule water permeability is not altered by bladder pretreatment with VP, (3) granule membrane fluidity is remarkably lower than that of surface and microsomal membranes, and (4) rapid water transport occurs in surface membrane vesicles. The unique physical properties of the granule suggests that apical exocytic addition of granule membrane may be responsible for the low water permeability of the unstimulated apical membrane.

Animals↗
PubMed1984

Sodium and potassium permeability of membrane vesicles in a sarcolemma-enriched preparation from canine ventricle.

Vesicles in a highly enriched sarcolemma preparation from canine ventricle were found to develop membrane potentials in response to outwardly directed potassium and inwardly directed sodium concentration gradients. The magnitude of the potential measured by the fluorescent dye diS-C3-(5) suggested a sodium-to-potassium permeability ratio between 0.2 and 1.0 which is one to two orders of magnitude greater than values obtained for the myocardial cell. Radiotracer techniques were employed to evaluate the permeability coefficients of the isolated cardiac sarcolemma membrane for sodium and potassium under equilibrium conditions (i.e., equal salt concentrations in the intravesicular and extravesicular spaces). The uptake of sodium and potassium was best described by two exponential processes which followed an increment of uptake that occurred prior to the earliest assay time (i.e., 17 sec). The compartment sizes were linear, nonsaturable functions of the cation activity. Evaluation of the rate coefficients of cation uptake by the two exponential processes versus cation activity revealed that sodium influx via the slow process and potassium influx via the fast process varied linearly with cation activity, suggesting that the permeability coefficients were concentration independent for these compartments. Conversely, sodium influx via the fast process exhibited a nonlinear increase with increasing sodium activity, and potassium influx via the slow process appeared to saturate with increasing potassium activity. In general, the permeabilities of the sarcolemma-enriched preparation for sodium and potassium were of equal magnitude. The permeability coefficients were lower than that for the potassium coefficient reported for cardiac cells but are in the range of that reported for sodium.

Animals↗
PubMed1984

Studies on cutaneous vascular permeability in the rat: increases caused by histamine and histamine-like agents.

The pharmacology of histamine-induced increases in microvascular permeability has been studied in rat skin. Histamine caused dose-dependent increases in microvascular permeability, assessed as increases in extravascular albumin accumulation. The responses to histamine were inhibited in a dose-dependent manner by pretreatment with mepyramine and were not changed by cimetidine. 2-(2-Aminoethyl)pyridine also increased microvascular permeability whereas impromidine did not. These results suggest that H1-receptors and not H2-receptors are involved in the permeability response to histamine in rat skin. In contrast, dimaprit increased microvascular permeability and responses to dimaprit exceeded the maximum response to histamine. The response to dimaprit proved to be independent of H2 receptors and was consistent with an indirect response due to mast cell degranulation.

Animals↗
PubMed1981

Cell junction and cyclic AMP: 1. Upregulation of junctional membrane permeability and junctional membrane particles by administration of cyclic nucleotide or phosphodiesterase inhibitor.

Mammalian cells in culture were exposed to cyclic AMP, dibutyryl cyclic AMP, the phosphodiesterase inhibitor caffeine, or a combination of the last two, while junctional molecular transfer was probed with the series of microinjected, fluorescent-labelled linear molecules Glu, Glu-Glu, Glu-Glu-Glu, and Leu-Leu-Leu-Glu-Glu. The junctional permeability for these molecules increased with each of the agents, most markedly with the dibutyryl cyclic AMP-caffeine combination, as the intracellular cyclic nucleotide concentration rose. The junctional permeability effect developed over several hours. When probed with molecules close to the limit of cell-to-cell channel permeation (the most sensitive setting), the effect was detectable both, as an increase in the (relative) junctional transit rate and as an increase in the number of transferring cell interfaces in the test populations. The number of transferring cell interfaces reached a maximum by 4 hr, when the junctional transit rate, hence the junctional permeability, was still rising. Nonjunctional membrane permeability for the probe molecules, as determined by intracellular fluorescence loss, was not significantly changed (nor was there significant nonjunctional cell-to-cell transfer of molecules before or after the treatments). The rise in junctional permeability was associated with an increase in the number of gap junctional membrane particles, as determined by freeze-fracture electron microscopy: the average size of the particle clusters increased, and the frequency of the clusters increased, particularly that of the smaller (and presumably newer) clusters. This effect was blocked by treatments with the protein synthesis inhibitors cycloheximide or puromycin. These agents caused particle diminution (diminution of cluster frequency but not of average cluster size), with or without cyclic nucleotide. The junctional effects may represent a cyclic AMP-promoted proliferation of cell-to-cell channels. Some physiological implications, in particular, implications for hormone-regulated tissues, are discussed.

Animals↗
PubMed1993

Alteration in intestinal permeability after ileal pouch-anal anastomosis.

PURPOSE: The physiologic changes that occur when the small bowel is used as a reservoir, as in the ileal pouch-anal anastomosis, are poorly understood. Alterations in bowel permeability, which may lead to bacterial translocation that could result in illness or dysfunction of the pouch, may be one such consequence of the pouch procedure. METHODS: Whole-bowel permeability was evaluated in patients with and without the pouch through the use of an orally consumed nonmetabolizable sugar clearance technique. Patients in whom the ileal pouch-anal anastomosis was performed for ulcerative colitis (17 patients) and patients with familial polyposis (7 patients) were compared with normal healthy volunteers (10 patients) and patients with ulcerative colitis with and without curative colectomy and ileostomy (6 and 5 patients, respectively). RESULTS: Measured by this technique, no differences were noted in bowel permeability between the volunteers and patients with ulcerative colitis, even after colectomy and ileostomy (1.7 +/- 0.4 in normal healthy volunteers, 1.8 +/- 0.5 in patients with ulcerative colitis without stoma, and 1.4 +/- 0.2 in patients with ulcerative colitis with ileostomy). The group of patients with an ileal reservoir, however, had a significantly increased index of measured bowel permeability (3.5 +/- 0.5 in patients with ulcerative colitis and 5.1 +/- 0.7 in patients with familial polyposis; P < 0.05 by analysis of variance compared with normal healthy volunteers and patients with ulcerative colitis with or without ileostomy). CONCLUSION: The exact site, cause, and consequence of this possible alteration of bowel permeability are unclear but appear to be related to the presence of the pouch and are not caused by the underlying pathologic diagnosis.

Adenomatous Polyposis Coli↗
PubMed1996

Increased permeability occurs in rat ileum following induction of pan-colitis.

Acetic acid-induced pan colitis in rats leads not only to colonic injury but also to a bystander ileal injury, characterized by decreased fluid and electrolyte absorption without associated histological injury or infiltration of inflammatory cells. To examine the nature of this decreased ileal fluid and electrolyte absorption, we measured effect of acetic acid-induced pancolitis on ileal transmural sodium and chloride transport, as well as on ileal permeability to mannitol and inulin on mucosal sheets mounted in Ussing chambers. In addition, ileal tight junctional morphology was assessed by electron microscopy. In colitic animals, ileal serosal-to-mucosal sodium and chloride transmural fluxes were increased (P<0.05); compatible with the observed decrease in net fluid absorption. Mannitol and inulin ileal serosal-to-mucosal and mucosal-to-serosal ileal fluxes were similarly increased (P<0.05), suggesting that an increase in ileal permeability occurred during acetic acid-induced pancolitis. This increase in ileal permeability was not accompanied by changes in tight junctional ultrastructure. These results suggest that: (1) the decrease in ileal fluid and electrolyte absorption seen during acetic acid-induced rat pancolitis occurred in parallel with a rise in both transcellular and paracellular permeability, and (2) the ileal permeability changes were not accompanied by structural changes.

Animals↗
PubMed1996

Multiple sclerosis patients have peripheral blood CD45RO+ B cells and increased intestinal permeability.

Increased intestinal permeability and the CD45RO isoform expression of the leukocyte common antigen on peripheral blood CD20+ B cells are found in Crohn's disease. Others have observed that multiple sclerosis (MS) patients may have an increased risk of coacquisition of Crohn's disease. The aim of this study was to identify an association between these diseases using peripheral blood CD45 isoform expression and intestinal permeability in MS. Lactulose/mannitol permeability and peripheral blood CD20+ B cell CD45RO expression were defined in healthy controls, MS patients, and patients coincidentally affected by MS and Crohn's or MS and ulcerative colitis (UC). Five of 20 MS patients had increased intestinal permeability, a finding not previously reported. High levels of CD45RO were found on circulating CD20+ B cells from patients with MS. This has not been reported previously in MS and is found in very few other conditions. Eight patients with coincident MS and Crohn's disease or MS and UC were studied. Coincident MS and UC patients expressed CD45RO on CD20+ B cells, a finding not identified in UC patients alone. A subgroup of MS patients has increased intestinal permeability. These patients express CD45RO CD20+ B cells, also found in Crohn's disease.

Antigens, CD20↗
PubMed1986

Blood-retinal barrier permeability to carboxyfluorescein and fluorescein in monkeys.

Lipid solubility is a major determinant of permeability across the blood-brain barrier, to which the blood-retinal barrier (BRB) has many similarities. Carboxyfluorescein is a dye with about 1/1000 the lipid solubility of fluorescein, but their molecular sizes and spectral characteristics are similar. We studied the importance of lipid solubility in BRB permeability by comparing the BRB permeabilities to these two dyes. Dye in the vitreous and plasma of four monkeys was measured by fluorophotometry. The estimated inward permeability coefficients (Pin) were 11 +/- 7.4 X 10(-6) cm/min (mean and SD) for carboxyfluorescein and 21 +/- 5.9 X 10(-6) cm/min for fluorescein. The ratio of the means was 1/1.9, far from the expected 1/1000. This finding suggests that the BRB does not function as a continuous lipid membrane and that other factors are more important determinants of permeability for these dyes than lipid solubility.

Animals↗
PubMed1995

Phorbol myristate acetate ex vivo model of enhanced colonic epithelial permeability. Reactive oxygen metabolite and protease independence.

The initiating mechanisms involved in colonic injury are currently unknown. The goal of the current study was to examine the role of the inflammatory mediators reactive oxygen metabolites and proteases in an ex vivo model of selective epithelial permeability. Rats were prepared with exteriorized colonic chambers to which the protein kinase C (PKC) activator phorbol myristate acetate (PMA) was added in doses ranging from 5 to 800 micrograms. PMA caused a dose-dependent transient increase in epithelial permeability, but had no significant effect on microvascular permeability. There was no accumulation of neutrophils and no apparent histological changes. PMA acts via a PKC-dependent mechanism, as assessed using the PKC-inactive phorbol analog 4 alpha-phorbol didecanoate, and the response is tachyphylactic. The mechanism is independent of reactive oxygen metabolites and proteases, as shown by the lack of effect of the free radical scavengers superoxide dismutase and catalase and the general serine protease inhibitor soybean trypsin inhibitor. The classic inflammatory process does not appear to be involved in the PMA-induced epithelial permeability changes. This finding suggests that noninflammatory mechanisms may regulate the increased epithelial permeability induced by PMA. Further study to elucidate these mechanisms is of importance for understanding both normal gastrointestinal physiology and initiation of pathology.

Acute Disease↗
PubMed1996

Inward and outward permeability of the blood-retinal barrier in experimental myopia.

BACKGROUND: To investigate the pathophysiology of the retina in myopia, vitreous fluorophotometry was used to evaluate the permeability of the blood-retinal barrier (BRB) in experimentally induced myopia in cynomolgus monkeys. METHODS: Five animals underwent unilateral eyelid suturing. The suture was removed temporarily at 3, 10, 16, 28 and 36 months, and the dioptric power and axial length were measured in both eyes. Vitreous fluorophotometry was performed before and 60 min after intravenous injection of fluorescein-Na. BRB inward permeability (P(in)) was determined by a computer simulation method. At 36 months, fluorescein-Na was injected into the vitreous cavity, and the intraocular fluorescence was measured. BRB outward permeability (P(out)) was determined by the computer simulation method. RESULTS: Significant myopia developed by 10 months after suturing and progressed thereafter. Starting at 10 months, the P(in) of sutured eyes increased significantly compared with control fellow eyes, and the increase continued throughout the observation period. At 36 months, the BRB P(out) was significantly lower (P < 0.05) in the myopic than in the emmetropic fellow eyes, suggesting decreased active transport mechanisms at the BRB in myopia. CONCLUSION: Our study demonstrated, for the first time, abnormal permeability of the BRB in myopic monkey eyes. Such abnormal permeability may play an important role in the development in human myopes of retinal and vitreous changes such as retinal detachment. Thus, simply correcting refractive errors surgically may not represent a cure for myopia. Patients who have had refractive surgery to correct myopia should also be closely followed up by vitreo-retinal specialists to manage vitreo-retinal disorders in originally myopic eyes.

Animals↗
PubMed1978

The permeability coefficient of the wall of a villous membrane.

The equations hitherto used to correct the permeability coefficient for the unstirred layer influence are valid only for flat membranes. Therefore, appropriate equations for membranes with a villous surface (e.g., small intestine) have been derived. They take into account the non-linear concentration gradient in the intervillous part of the unstirred layer. Quantitative information about the geometry of the villous surface and the unstirred layer thickness are needed to calculate the permeability coefficient of the membrane wall (e.g., intestinal epithelium). The concentration of highly permeable substances drops sharply already in the upper part of intervillous space, so that the tips of the villi function as effective absorbing area. The intervillous concentration gradient of a substance with a low permeability coefficient is so small, that such a substance is absorbed by the total surface area of the villous membrane. The effective absorbing area of substances with intermediate permeability coefficient lies between the described limits.

Cell Membrane↗
PubMed1980

Permeability of the cell-to-cell membrane channel and its regulation in an insect cell junction.

Cells of organs and tissues commonly communicate directly with one another via permeable membrane junctions. Cell-to-cell channels, spanning the width of both membranes of a junction, are thought to provide the pathways between the cytoplasms of adjacent cells for the immediate exchange of ions and small molecules. We study these cell-to-cell channels in a cell model system, the salivary gland of Chironomus. Using intracellularly injected fluorescent labelled peptides and oligosaccharides of various molecular dimensions as channel permeability probes we find the channels to have a bore of about 2 nm. The channel permeability can be modulated and, in the extreme, the channels can be closed under various experimental conditions. With the aid of the Ca2+-sensitive photoprotein aequorin as monitor of cytoplasmic free Ca2+ concentration, we show that a determining factor in this modulation of channel permeability is the cytoplasmic free Ca2+ concentration. Moreover, results obtained by injection of different-sized and different-labelled channel permeability probes together with Ca2+ indicate that closure of the individual channels may occur in more than one step, i.e., by a graded reduction of channel bore.

Animals↗
PubMedDate not supplied

An acute stressor enhances sensitivity to a chemical irritant and increases 51CrEDTA permeability of the colon in adult rats.

We investigated the effect of prior acute stress on colonic permeability induced by a chemical irritant known to induce symptoms similar to inflammatory bowel disease in rodents. Adult male rats (n = 12) were stressed by a single session of ten unpredictable, uncontrollable foot shocks, and half were home cage controls (n = 12). Twenty-nine days later, half of each treatment group was exposed to 4% DSS (dextran sulphate sodium) solution in their drinking water for 48 hours while half received pure water over two periods separated by 17 days. After food deprivation overnight and light isoflurane anaesthesia the following morning, the animals were given a colonic infusion of 2000 nCi (nanocurie) 51CrEDTA (51Cr-labelled ethylenediaminetetraacetic acid) and then placed individually in metabolic cages for a six hours continuous urine collection. Radioactivity in urine was measured by a gamma counter and percentage recovery of 51CrEDTA calculated as an indicator of colonic mucosal permeability. Results concluded that pre-shocked animals exposed to DSS showed significantly higher mucosal permeability than the pre-shocked animals given water, and the non-shocked animals given either DSS or water. Pre-shock in combination with two exposures to a chemical irritant separated by 17 days had a pronounced effect on colonic permeability, indicating that stress should be considered a possible initiating or contributory factor to increased intestinal permeability related to a mucosal challenge.

Animals↗
PubMed1998

The effect of selenium and vitamin E on microvascular permeability of rat organs.

The effects of dietary sodium selenite and vitamin E on the microvascular permeability of rat organs such as heart, brain, kidney, liver and eye were investigated by using the Evans blue leakage method. Combined deficiency of selenium and vitamin E caused an increase in the permeability of the heart and eye with respect to their controls while it had no considerable effect on the permeability of other organs. On the other hand, toxic levels of selenium (4.2 mg/kg) in diet decreased the permeabilities in kidney, liver, and eye whereas this parameter of brain increased in the same animal group. These results suggested that low or high sodium selenite and vitamin E contents in diet could alter the microvascular permeability of different organs in different manners. It might be important to give reasonable explanations for the pathophysiology of some diseases that are characterized with organ damage and/or disfunction originated from selenium deficiency or toxicity.

Animals↗
PubMed2002

The effect of storage conditions on the permeability of porcine buccal mucosa.

The impact of storage conditions on the permeability of porcine buccal mucosa to [3H]water and [14C]mannitol was assessed. The fresh porcine buccal tissue (fresh tissue) was obtained by utilizing pig heads within 24 hours of slaughter. The stored and frozen porcine buccal tissues (stored tissue and frozen tissue) were obtained after the storage of the tissue intact in the pig heads at 4 degrees C or -20 degrees C, respectively, for 24 h. The results demonstrated that the barrier properties of the porcine buccal mucosa were maintained with regard to [3H]water permeability when stored at 4 degrees C for 24 h. However, freezing the tissue resulted in tissue damage illustrated by a significant increase in [3H]water permeability. [14C]Mannitol does not appear to be a suitable model solute to assess the ex vivo permeability of porcine buccal mucosa due to its extremely low permeability.

Algorithms↗
PubMed2005

Evaluation of alveolo-capillary permeability in thyrotoxicosis using Tc-99m DTPA aerosol scintigraphy.

Surfactant secreted from type II pneumocytes plays an important role in alveolo-capillary permeability. In thyrotoxicosis, high levels of T3 receptors detected at these cells might affect the alveolo-capillary permeability due to increased serum thyroid hormone levels. The results by CO-diffusion capacity measurement in thyrotoxicosis are conflicting. Changes in alveolo-capillary membrane permeability resulting from thyrotoxicosis are not well established yet. This prompted us to investigate the alveolo-capillary permeability in thyrotoxic patients in comparison with CO-diffusing capacity. For this aim twenty-two non-smoking thyrotoxic patients (before treatment) and fifteen healthy voluntary controls underwent 99mTc-DTPA aerosol scintigraphy. CO-diffusing and pulmonary function tests were performed in all subjects. After ventilation of radiotracer through a nebulizer for 15 minutes, 30 dynamic images (1 frame/minute) were taken from both lungs. ROI's were drawn over both lung areas, and the time-activity curves were generated. Then clearance half time (CT1/2) for radioaerosol was obtained. CT1/2 of thyrotoxic patients did not differ from that of the controls: 77.9 +/- 25.9 min vs. 79.4 +/- 22.3 min; p > 0.05. Similar result was found for CO-diffusion parameters. Also there was no significant correlation between CT1/2 and CO-diffusion parameters. We concluded that in patients with thyrotoxicosis, the alveolo-capillary permeability is unaffected. Further experimental research is needed to establish the possible effects of thyroid hormones on alveolo-capillary membrane.

Adolescent↗
PubMed1993

In vitro determination of human dura mater permeability to opioids and local anaesthetics.

The permeability of human thoracic and lumbar dura mater to various compounds in clinical use was determined in vitro. Sections of dura mater, 3 to 4 cm in diameter, obtained at post-mortem were placed between the ports (area = 3 cm2) of two glass chambers (A and B) which fitted tightly together to form a two-chamber apparatus for measuring permeability through the dura. Each chamber contained 5 ml of artificial cerebrospinal fluid. A sample of test drug solution was introduced into one chamber (A) and 50 microliters aliquots were withdrawn from the other chamber (B) at predetermined intervals. Permeability was determined by calculating the rate of diffusion (slope) from the plot of mean drug concentration (chamber B) versus time. Dura mater permeability was shown to be a simple diffusion process and to be independent of lipid-solubility and molecular weight. Permeability appeared to increase with age and may have a linear relationship to the initial concentration.

Adult↗
PubMed1998

Development of a new method for simultaneously evaluating mucociliary clearance and pulmonary epithelial permeability in rabbit experiments by means of 18FDG, three-dimensional positron emission tomography and rectilinear scan.

We tried to simultaneously obtain the elimination constant of mucociliary clearance and the pulmonary epithelial permeability constant after inhalation of 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) solution by carrying out whole lung positron emission tomography and a rectilinear scan in rabbit experiments. The elimination constant of pulmonary epithelial permeability was obtained from the decrease in the amount of the radioactivity with time in the region of interest (ROI) confined to the lungs, trachea and tracheal cannula in the rectilinear scan. The total elimination constant of the radioactivity in the lungs was obtained from the ROI confined to the lungs in the tomography. The mucociliary clearance rate constant in the lungs was then obtained after subtracting the elimination constant of the pulmonary epithelial permeability from the total elimination constant of the 18FDG in the lungs. The mucociliary clearance constant in the trachea was calculated from the residual radioactivity in the trachea and the mucociliary clearance constant in the lungs. The mean pulmonary epithelial permeability constant was 0.0020% min(-1) obtained from the rectilinear scan. The mean mucociliary clearance constants of the lungs and the trachea were 0.0006 and 0.025% min(-1), respectively. These results indicated that the pulmonary epithelial permeability and mucociliary clearance could be evaluated simultaneously with 18FDG by using three-dimensional positron emission tomography and a rectilinear scan.

Administration, Inhalation↗