Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Permeability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed1993

Arterial permeability dynamics and vascular disease.

There is a growing consensus that regional susceptibility to atherosclerosis correlates topographically with an increased endothelial permeability to macromolecules such as low-density lipoprotein. Earlier research suggested that increases in arterial macromolecular permeability accompany the adaptation of the endothelial lining to changes in fluid dynamic shear stress, and that permeability might therefore be chronically increased where the endothelium is exposed to a shear stress environment that changes throughout the day. Thus the temporal variability of hemodynamic stresses at the vessel wall, with time constants of many minutes or a few hours, may affect local susceptibility to disease. Changes in the hemodynamic stresses on the endothelial surface ('local' stress) result from the normal variations in more 'global' hemodynamic variables such as blood flow rate, heart rate, and flow partition at branches, that occur throughout the day in response to changes in peripheral metabolic demand. Thus, at any given time, the permeability at a site is determined by: (1) the steady-state relationship between the local permeability and local shear stress; (2) the dynamics of the permeability change induced by changes in local shear; and (3) the extent to which the shear stress at the site is affected by changes in the global variables. Regional variations in any or all of these three factors can lead to corresponding variations in endothelial permeability, macromolecular uptake and, apparently, atherosclerotic risk. Among the three factors, the first may be relatively unimportant if most transport takes place while the endothelium is responding to hemodynamic changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Atherogenic levels of low density lipoprotein alter the permeability and composition of the endothelial barrier.

In the present study we investigated the influence of elevated low density lipoprotein (LDL) concentration on endothelial permeability. Endothelial cells were cultured on microporous membranes until confluence and albumin, dextran and LDL transfer across endothelial monolayers was determined to assess macromolecular permeability. Exposure of proliferating aortic endothelial cells to LDL levels of more than 1 mg/ml LDL-cholesterol induced a concentration-dependent exponential increase in the permeability of confluent endothelial monolayers. Acute addition of high LDL concentration did not alter macromolecular permeability. Once elevated permeability was induced, it persisted. It was not readily reversible after addition of normal LDL levels. Change in permeability was accompanied by a selective decrease in basement membrane associated heparan sulfate proteoglycan (HSPG) content. The apparent parallel between the loss in endothelial barrier function and HSPG decrease implicates a connection between the two events. Prolonged, but not acute, incubation with antiserum directed against the core-protein of HSPG also led to increased permeability, suggesting a causal role of HSPG for the proper function of endothelium. The fact that non-atherogenic LDL-cholesterol levels had no effect indicates that a 'threshold' concentration for LDL-cholesterol may exist, leading to nondenuding injury in the endothelial barrier as an early event in development of atherosclerosis.

Animals↗
PubMed1992

Increased mucosal permeability after intestinal ischemia-reperfusion injury is mediated by local tissue factors.

Subclinical intestinal ischemia-reperfusion injury (IRI) causes an increase in mucosal permeability and may represent an early event in the pathogenesis of necrotizing enterocolitis. The present study was undertaken to determine whether these changes are mediated by local or systemic factors. In 6-week-old weanling rats, the ileum was divided into two isolated loops with separate vascular supplies. The mesentery of the proximal loop was occluded for 30 minutes, following which the bowel was reperfused; permeability to 51Cr EDTA was then assessed in the distal loop 30 minutes after reperfusion. In control groups, the distal loop was subjected to 30-minute IRI ("positive" control) or 30-minute sham operation ("negative" control). Permeability in the distal loop was increased only with IRI to the distal bowel (15.4 +/- 3 counts/min/standard), and not with IRI to the proximal bowel (5.1 +/- 1) or with sham operation (8.5 +/- 2). To determine whether a mild "priming" injury might be necessary for systemic factors to have an effect, the distal loop was subjected to 2-minute IRI and the proximal to 30-minute IRI or sham. Permeability was not increased in the distal loop in either of these groups (5.7 +/- 1 and 7.8 +/- 2, respectively). Thirty-minute IRI in the proximal loop did not increase permeability in the distal loop, with or without a priming injury. Only direct IRI in the distal loop resulted in a significant increase in permeability. We conclude that the permeability changes in this model are mediated through local tissue effects, rather than by systemic factors.

Animals↗
PubMed1975

Permeability and porosity of dental casting investments.

Permeability of various gypsum- and phosphate-bonded investments was measured during conventional burn-out procedures. Porosity determinations were made on specimens cooled to room temperature after burn-out. As a group, the gypsum-bonded investments were found to be more permeable than the phosphate-bonded investments. Two phosphate-bonded investments were determined to be relatively impermeable to gas flow, while another exhibited permeability comparable to that of the gypsum-bonded investments. In spite of differences in permeability, the porosity of each type of investment was nearly constant. The porosity of the phosphate-bonded investment was approximately three-fourths that of the gypsum investments. These investments were modified by the addition of varying amounts of acrylic polymer for the purpose of altering permeability. The addition of acrylic polymer increased porosity and permeability of all of the materials included in this investigation. The acrylic additives, however, had no effect on the permeability of relatively impermeable investments unless used in high concentration. The results of this investigation would tend to substantiate the need for special spruing and venting procedures.

Acrylic Resins↗
PubMed1986

Segmental differences of microvascular permeability for FITC-dextrans measured in the hamster cheek pouch.

An intravital microscopic method for quantitative measurement of interstitial concentrations of fluorescent tracers has been applied to the investigation of microvascular permeability in the hamster cheek pouch. Some nanoliters of FITC-dextran mean mol wt (Mw) 20,000, 3000, or sodium fluorescein (Mw 376) were injected into an arteriole of the exposed cheek pouch via micropipet. The extravasation of fluorochromes was measured by a photodensitometric method including two sets of calibration procedures (in vitro and in vivo). Postcapillary and collecting venules exhibited the highest absolute increase of fluorochrome concentration in the tissue for all tracer molecules tested when compared to arterioles or capillaries. The permeability of the vascular wall was quantified, assuming that diffusion processes play the main role for the transport of the investigated molecules under the experimental conditions of a high concentration gradient across the membrane. Permeability coefficients P (cm/sec) and apparent diffusion coefficients D' (cm2/sec) of the microvascular wall were calculated using a mathematical model for one-dimensional diffusion in composite media. The analysis is based on measured data of interstitial diffusion coefficients of the tracers used. For all tracer molecules tested, the wall of the capillaries and postcapillary venules was significantly more permeable than the arteriolar wall. For the largest test molecule (FITC-dextran Mw 20,000), the permeability coefficient of the vessel wall showed a maximum in the postcapillary venules. These findings support the concept of a "gradient of permeability" with a nonuniform distribution of exchange capacity only for the precapillary microvessels. A marked preponderance of venular over capillary permeability could, if at all, only be detected for FITC-dextran Mw 20,000. The present study characterizes the vessel wall by apparent diffusion coefficients which are, for FITC-dextran Mw 3000, and free fluorescein, roughly three orders of magnitude lower than the apparent diffusion coefficients in connective tissue.

Animals↗
PubMed1992

Possible mechanism(s) for permeability recovery of venules during histamine application.

Histamine is known to cause a substantial increase in the permeability of venules to both water and proteins. However, this increase is transient, i.e., the initially elevated permeability returns toward control levels, or "recovers," even during continuous histamine stimulation. In this investigation, we attempted to identify the possible chemical signal(s) initiating the permeability recovery process in single venules of rat mesentery. Specifically, we tested whether histamine's binding to H2 receptors and/or the production of prostacyclin by endothelial cells was involved in this process. To achieve this aim, the time course of endothelial cells was involved in this process. To achieve this aim, the time course of histamine-induced changes in permeability to alpha-lactalbumin was measured in the presence of H2 receptor antagonist (cimetidine) or of prostacyclin synthetase inhibitor (tranylcypromine), respectively. Permeability of individually perfused microvessels was measured using fluorescence microscopy. The results demonstrated that permeability recovery was not affected by the H2 receptor antagonist but was suppressed or even abolished by the prostacyclin synthesis inhibitor. Therefore, these results suggest that the production of prostacyclin by endothelial cells might serve as one chemical signal to initiate the permeability recovery process, whereas histamine's binding to H2 receptors is not involved in this phenomenon.

Animals↗
PubMed1987

A comparison of intestinal permeability between humans and three common laboratory animals.

Intestinal permeability of humans and three species of experimental animals was assessed by the oral administration of the three non-metabolizable sugars: lactulose, rhamnose and mannitol and collecting all the urine produced in a specified time. The total percentage recovery of the permeability markers was determined by high performance liquid chromatographic assays of urinary aliquots. The permeability of the human gut to mannitol was substantially greater than that of rats, guinea pigs, or hamsters (18-, 6- and 29-fold increases, respectively). The permeability to lactulose in humans was somewhat less than that found in guinea pigs (P less than 0.05), but three times greater than that found in rats or hamsters (P less than 0.001). Human rhamnose permeability was substantially greater than that of rats, guinea pigs or hamsters (6-, 2.5-, and 7-fold increases, respectively). The results suggest that the permeability of the human gut to probe molecules is considerably different from that of three common laboratory rodents, but is closest to that of guinea pigs. Possible species differences in the physiological factors which control permeability are discussed.

Adult↗
PubMed1987

The effect of exposure to elevated temperatures on membrane permeability to adriamycin in Chinese hamster ovary cells in vitro.

The effect of environmental temperature on plasma membrane permeability to Adriamycin was studied in Chinese hamster ovary (CHO) cells in vitro using flow cytometry. Initial rates of uptake increased steadily between 23 degrees C and 47 degrees C and there was a greater than 2-fold increase in permeability between 37 degrees C and 47 degrees C. The increase in permeability with increasing temperature was greater than expected based on the model of passive drug influx. Adriamycin uptake was also measured at 37 degrees C following previous exposure of the cells to elevated temperatures. Twenty-minute preexposures to temperatures above 41 degrees C caused a significant decrease in membrane permeability, which fell to approximately 60% of control levels after exposure to 45 degrees C. Longer periods of pre-exposure to temperatures as low as 40 degrees C were also shown to decrease membrane permeability to Adriamycin subsequently measured at 37 degrees C. The state of decreased permeability to Adriamycin induced by hyperthermia persisted for at least 2 h. The thermally induced decrease in membrane permeability to Adriamycin is of potential importance to the design of optimal schedules for thermochemotherapy.

Animals↗
PubMed1990

Calcium-dependent regulation of potassium permeability in the glial perineurium (blood-brain barrier) of the crayfish.

The physiological basis of the high selective potassium permeability of the crayfish glial perineurium was studied. The transient spike-like perineurial potential generated in high external [K+] was used as a measure of barrier K+ permeability. The medial giant axon membrane potential was used to monitor interstitial [K+]. Perineurial current-voltage relations of the perineurium were used to measure electrical resistance and to determine changes in K+ conductance of the perineurial barrier. Of a range of cations studied only Rb+, in addition to K+ generated a large transient sheath potential. In some experiments "regenerative" multiple spikes were observed during the continued exposure of the perineurium to high [Rb+]0. This degree of ion selectivity is typical of glial cell membranes and K channels. Barrier conductance increased only very briefly in Rb+; the potential falling rapidly to a steady 5-10 mV. The PCl/PRb and the PCl/PK ratios at the peak transient potential were similar suggesting the permeability site for these cations was the same. The permeability of Rb+ in the plateau phase was significantly lower than K+ suggesting that high [Rb+]0 may act to block K+ channels. The K(+)-selective permeability was reversibly blocked by extracellular Ba2+ at both the peak and the plateau phase, in a concentration-dependent manner. Other K-channel blocking agents, tetraethylammonium ions (10 mM), caesium ions (20 mM), and 3,4-diaminopyridine (0.5 mM) were ineffective. The effect of Ba2+ on the peak potential was similar to the removal of external Ca2+ or exposure to the Ca2(+)-channel blockers, verapamil (10(-4) M) or La3+ (5 mM). The time- and concentration-dependent reversible block of the K+ permeability of the perineurium was consistent with the known action of these agents on voltage-gated Ca2+ channels in nerve and glia. La3+ caused an irreversible decrease in perineurial conductance and K+ influx. Lanthanum titration of the negative charges of glial membranes and mucopolysaccharide matrix of the intercellular space suggest they may be important factors in determining the magnitude of the perineurial leak and paracellular K+ permeability. Electron microscopic examination of La3+ distribution demonstrated a diffusion barrier at the outer layer of perineurial glia. The binding of La3+ at the basolateral membranes of the glial barrier suggested this was the site at which La3+ had its physiological actions. The results suggest that the increase in glial membrane K+ conductance in high [K+]0 was most likely due to voltage-gated Ca2+ and K+ channels and Ca2(+)-activated K+ channels of the membranes of perineurial glia.

Animals↗
PubMed1992

Divalent ion permeability of AMPA receptor channels is dominated by the edited form of a single subunit.

Functionally diverse GluR channels of the AMPA subtype are generated by the assembly of GluR-A, -B, -C, and -D subunits into homo- and heteromeric channels. The GluR-B subunit is dominant in determining functional properties of heteromeric AMPA receptors. This subunit exists in developmentally distinct edited and unedited forms, GluR-B(R) and GluR-B(Q), which differ in a single amino acid in transmembrane segment TM2 (Q/R site). Homomeric GluR-B(R) channels expressed in 293 cells display a low divalent permeability, whereas homomeric GluR-B(Q) and GluR-D channels exhibit a high divalent permeability. Mutational analysis revealed that both the positive charge and the size of the amino acid side chain located at the Q/R site control the divalent permeability of homomeric channels. Coexpression of Q/R site arginine- and glutamine-containing subunits generates cells with varying divalent permeabilities depending on the amounts of expression vectors used for cell transfection. Intermediate divalent permeabilities were traced to the presence of both divalent permeant homomeric and impermeant heteromeric channels. It is suggested that the positive charge contributed by the arginine of the edited GluR-B(R) subunit determines low divalent permeability in heteromeric GluR channels and that changes in GluR-B(R) expression regulate the AMPA receptor-dependent divalent permeability of a cell.

Base Sequence↗
PubMed1995

Influence of metabolic inhibitors on mitochondrial permeability transition and glutathione status.

Treatment of isolated mitochondria with Ca2+ and inorganic phosphate (Pi) induces an inner membrane permeability that appears to be mediated through a cyclosporin A (CsA)-inhibitable Ca(2+)-dependent pore. Isolated mitochondria during inner membrane permeability undergo rapid efflux of matrix solutes such as glutathione as GSH and Ca2+, loss of coupled functions, and large amplitude swelling. Permeability transition without large amplitude swelling, a parameter often used to assess inner membrane permeability, has been observed. The addition of either oligomycin, antimycin, or sulfide to incubation buffer containing Ca2+ and Pi abolished large amplitude swelling of mitochondria. The GSH status during a Ca(2+)- and Pi-dependent mechanism of mitochondrial GSH release in isolated mitochondria was influenced significantly by metabolic inhibitors of the respiratory chain but did not prevent inner membrane permeability as demonstrated by the release of mitochondrial GSH and Ca2+. The release of GSH was inhibited by the addition of CsA, a potent inhibitor of permeability transition. Under these conditions we did not find GSSG; however, rapid oxidation of pyridine nucleotides and depletion of ATP and ADP with conversion to AMP occurred. The addition of CsA, prevented the oxidation of pyridine nucleotides and depletion of ATP and ADP. Since NADH and NADPH were extensively oxidized, protection against oxidative stress is reflected in maintenance of GSH and not observable lipid peroxidation. Evidence from transmission electron microscopy analysis, combined with the GSH release data, indicate that permeability transition can be observed in the absence of large amplitude swelling.

Adenine Nucleotides↗
PubMed1996

Protection against oxidative injury and permeability alteration in cultured alveolar epithelium by transferrin-catalase conjugate.

The successful prevention of hydrogen peroxide-induced alveolar permeability alterations and cell injury by transferrin-catalase conjugate is described in this study. Permeability alterations and cell injury were induced in cultured alveolar epithelial monolayers by hydrogen peroxide. Transepithelial transport of a permeability marker, [14C] mannitol, and cellular nuclear fluorescence of a membrane integrity indicator, propidium iodide, were used to quantitate epithelial permeability and damage respectively. Hydrogen peroxide (0.1 - 10 mM) induced a dose-dependent increase in both alveolar permeability and cellular damage; however, the oxidant effect on monolayer permeability did not require prior cell damage. Electron spin resonance measurements using the spin trap 5,5-dimethyl-l-pyrroline-N-oxide indicated the formation of hydroxyl radicals in hydrogen peroxide-treated cells. Chelation of the cellular pool of iron by deferoxamine inhibited radical formation and helped protect the cells from oxidative changes. Prior treatment of the cells with catalase (0.1 U-10 U/ml) had minimal protective effects on cell injury and permeability alterations. In contrast, transferrin-catalase conjugate, at the same concentration range, exhibited much improved protective effects on the cells in response to oxidant stress. This enhanced protection was found to correlate well with an increase in cellular uptake of the enzyme conjugate via the transferrin receptor endocytosis pathway. Effective protection by the enzyme conjugate was shown to require both the antioxidant enzyme moiety and the cognate moiety for the cell surface receptor. These findings indicate the potential therapeutic merit of transferrin-catalase conjugate for the treatment of pathological processes in the lung, whenever oxidative stress is involved.

Animals↗
PubMed2005

Water- and cryoprotectant-permeability of mature and immature oocytes in the medaka (Oryzias latipes).

The permeability of the plasma membrane plays a crucial role in the successful cryopreservation of oocytes/embryos. To identify a stage feasible for the cryopreservation of teleost oocytes, we investigated the permeability to water and various cryoprotectants of medaka (Oryzias latipes) oocytes at the germinal vesicle (GV) and metaphase II (MII) stages. In sucrose solutions, the volume changes were greater in GV oocytes than MII oocytes. Estimated values for osmotically inactive volume were 0.41 for GV oocytes and 0.74 for MII oocytes. Water-permeability (microm/min/atm) at 25 degrees C was higher in GV oocytes (0.13+/-0.01) than MII oocytes (0.06+/-0.01). The permeability of MII oocytes to various cryoprotectants (glycerol, propylene glycol, ethylene glycol, and DMSO) was quite low because the oocytes remained shrunken during 2 h of exposure in the cryoprotectant solutions at 25 degrees C. When the chorion of MII oocytes was removed, the volume change was not affected, except in DMSO solution, where dechorionated oocytes shrunk and then regained their volume slowly; the P(DMSO) value was estimated to be 0.14+/-0.01x10(-3) cm/min. On the other hand, the permeability of GV oocytes to cryoprotectants were markedly high, the P(s) values (x10(-3) cm/min) for propylene glycol, ethylene glycol, and DMSO being 2.21+/-0.29, 1.36+/-0.18, and 1.19+/-0.01, respectively. However, the permeability to glycerol was too low to be estimated, because GV oocytes remained shrunken after 2 h of exposure in glycerol solution. These results suggest that, during maturation, medaka oocytes become less permeable to water and to small neutral solutes, probably by acquiring resistance to hypotonic conditions before being spawned in fresh water. Since such changes would make it difficult to cryopreserve mature oocytes, immature oocytes would be more suitable for the cryopreservation of teleosts.

Animals↗
PubMedDate not supplied

Reciprocal regulation of permeability through a cultured keratinocyte sheet by IFN-gamma and IL-4.

The T cell cytokines profoundly modify the phenotypic and functional characteristics of keratinocytes. Until now, no study has focused on the effect of Th1 and Th2 cytokines on keratinocyte permeability. Using a two-layer well culturing system, permeability was assessed through cultured keratinocyte sheet in the presence or absence of various concentrations of IFN-gamma and IL-4. Transepithelial electrical resistance (TER) and the flux of 40 kDa FITC-dextrans were measured across the cultured keratinocyte sheet. IFN-gamma significantly increased the TER in a dose- and time-dependent manner, suggesting that IFN-gamma profoundly inhibited the permeability of ions through the keratinocyte sheet. In contrast, IL-4 did not affect the TER. When compared to medium control, the flux of FITC-dextran of the IFN-gamma group was significantly decreased in a dose-dependent fashion. In sharp contrast, the flux of FITC-dextran was significantly and dose-dependently increased in the presence of IL-4. A significant increase in TER and a significant decrease in the flux of dextran suggested that IFN-gamma clearly reduced the permeability of both ions and high molecular weight material through the keratinocyte sheet. Although IL-4 did not affect the permeability of the ions, it significantly enhanced the permeability of high molecular weight material. A flow cytometric assay revealed that the expression of desmoglein-3 was suppressed by IL-4, but was enhanced by IFN-gamma. The reciprocal regulation of permeability of the cultured keratinocyte sheet by IFN-gamma and IL-4 may be partly related to the modification of intercellular adhesion molecules.

Cell Line↗
PubMed2006

Site of drug absorption after oral administration: assessment of membrane permeability and luminal concentration of drugs in each segment of gastrointestinal tract.

This study was conducted to assess the site of drug absorption in the gastrointestinal (GI) tract after oral administration. Drug permeability to different regions of rat intestine, jejunum, ileum and colon, was measured by in situ single-pass perfusion method. It was revealed that the epithelial surface area should not be a determinant of the regional difference in the intestinal permeability of highly permeable drugs. Effects of the mucus layer at the surface of the epithelium and the fluidity of the epithelial cell membrane on the drug permeability were investigated. These factors are demonstrated to contribute to the regional differences in intestinal drug permeability. The luminal drug concentration in each segment of the GI tract after oral administration was measured directly in fasted rats. Water ingested orally was absorbed quickly in the jejunum and the luminal fluid volume was diminished in the middle to lower part of the small intestine. According to the absorption of water luminal concentration of atenolol, a drug with low permeability, was elevated and exceeded the initial dose concentration. In contrast, the concentration of highly permeable drugs, antipyrine and metoprolol, decreased quickly in the upper part of the intestine and a significant amount of drugs was not detected in the lower jejunum and the ileum. From the time-profiles of luminal drug concentration, fraction of dose absorbed from each segment of the GI tract was calculated. Both antipyrine and metoprolol were found to be absorbed quickly at the upper part of the small intestine. In addition, the possible contribution of gastric absorption was demonstrated for these drugs. The pattern of site-dependent absorption of atenolol showed the higher absorbability in the middle and lower portion of the jejunum. These informations on site-dependent absorption of drugs are considered to be important for effective oral delivery systems.

Administration, Oral↗
PubMed2006

In vivo human buccal permeability of nicotine.

The aim was to examine the in vivo buccal pH-dependent permeability of nicotine in humans and furthermore compare the in vivo permeability of nicotine to previous in vitro permeability data. The buccal permeability of nicotine was examined in a three-way cross-over study in eight healthy non-smokers using a buccal perfusion cell. The disappearance of nicotine from perfusion solutions with pH 6.0, 7.4, and 8.1 was studied for 3h. The apparent permeability of nicotine (P(app)) was determined at each pH value. Parotid saliva was collected in an attempt to assess systemic levels of nicotine. The disappearance rate of nicotine increased significantly as the pH increased, which resulted in P(app) values of 0.57+/-0.55 x 10(-4), 2.10+/-0.23 x 10(-4), and 3.96+/-0.54 x 10(-4)cms(-1) (mean+/-S.D.) at pH 6.0, 7.4, and 8.1, respectively. A linear relationship (R(2)=0.993) was obtained between the P(app) values and non-ionised nicotine, which indicates that the nicotine transfer occurred by means of passive diffusion. P(app) values of 0.60 x 10(-4) and 6.18 x 10(-4)cms(-1) were obtained for the mono-protonated and non-ionised species of nicotine, respectively. The analysis of the parotid saliva samples indicated that these samples might be useful in the assessment of systemic absorption of nicotine. Previous buccal in vitro models underestimated the in vivo human permeability of nicotine. However, the in vitro models were capable of predicting the effect of pH on the nicotine permeability.

Administration, Buccal↗
PubMed2005

Estimation of bone permeability using accurate microstructural measurements.

While interstitial fluid flow is necessary for the viability of osteocytes, it is also believed to play a role in bone's mechanosensory system by shearing bone cell membranes or causing cytoskeleton deformation and thus activating biochemical responses that lead to the process of bone adaptation. However, the fluid flow properties that regulate bone's adaptive response are poorly understood. In this paper, we present an analytical approach to determine the degree of anisotropy of the permeability of the lacunar-canalicular porosity in bone. First, we estimate the total number of canaliculi emanating from each osteocyte lacuna based on published measurements from parallel-fibered shaft bones of several species (chick, rabbit, bovine, horse, dog, and human). Next, we determine the local three-dimensional permeability of the lacunar-canalicular porosity for these species using recent microstructural measurements and adapting a previously developed model. Results demonstrated that the number of canaliculi per osteocyte lacuna ranged from 41 for human to 115 for horse. Permeability coefficients were found to be different in three local principal directions, indicating local orthotropic symmetry of bone permeability in parallel-fibered cortical bone for all species examined. For the range of parameters investigated, the local lacunar-canalicular permeability varied more than three orders of magnitude, with the osteocyte lacunar shape and size along with the 3-D canalicular distribution determining the degree of anisotropy of the local permeability. This two-step theoretical approach to determine the degree of anisotropy of the permeability of the lacunar-canalicular porosity will be useful for accurate quantification of interstitial fluid movement in bone.

Animals↗
PubMed2004

Analysis of PEG 400 and 4000 in urine for gut permeability assessment using solid phase extraction and gel permeation chromatography with refractometric detection.

We developed a treatment of urine samples allowing the analysis of two intestinal permeability markers: polyethylene glycol (PEG) 400 (highly diffusible; basal permeability indicator) and PEG 4000 (poorly diffusible; indicator of an abnormal increase of permeability) by a unique gel permeation chromatography (GPC) with refractometric detection. Urinary PEG were extracted using a mixed-bed resin composed of C2 and C18 layers. Permeability mean values determined in 11 human healthy subjects were 24.20 +/- 9.30% and 0.12 +/- 0.08% for, respectively, PEG 400 and 4000. The percentage of the PEG 4000 permeability value to the one of PEG 400 corresponded to an intestinal permeability index (IPI) of 0.52 +/- 0.35 expressing a low diffusion of this poorly permeability marker.

Adult↗