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PubMed1991

Increased blood-brain barrier permeability following acute short-term swimming exercise in conscious normotensive young rats.

The status of the blood-brain barrier (BBB) was examined following short-term forced swimming (FS) exercise in younger rats (age 8-9 wks, 80-90 g). Subjection of animals to continuous FS for 30 min duration increased the permeability of the BBB to Evans blue albumin (EBA) and 131I-sodium in 5 and 8 brain regions, respectively. Extravasation of the tracers was markedly pronounced in the cerebellum followed by the cerebral cortex. EBA staining was confined mainly to the posterior cingulate cortex, parietal and occipital cortices, whole cerebellar vermis and the mediolateral cerebellar cortices as well as the dorsal surface of the hippocampus. In addition to the above brain regions. BBB permeability to 131I-sodium extended to the caudate nucleus, thalamus and hypothalamus. At this time period, the serotonin (5-hydroxytryptamine, 5-HT) content showed a profound increase in plasma and brain of about 150% and 250% respectively from the control value. Pretreatment with p-CPA (p-chlorophenylalanine, a serotonin synthesis inhibitor) prevented both the increased permeability of the BBB and the rise in plasma and brain 5-HT level. However, prior treatment with cyproheptadine (a 5-HT2 receptor antagonist) prevented the increased permeability alone. The 5-HT level continued to remain high. These results suggest that short-term FS increases BBB permeability in specific brain regions. This increased permeability appears to be mediated through serotonin via 5-HT2 receptors.

Animals↗
PubMed1993

Prolonged contact with blood alters surgical gown permeability.

INTRODUCTION: Surgical gowns are designed to prevent or minimize transmission of blood and pathogens between patients and hospital personnel. During prolonged procedures, a gown will probably be presented with repeated challenges of blood and other liquids. These multiple insults may alter the fabric's permeability to subsequent blood contact. METHODS: In this study, a pressing-leaning simulator was used to quantify changes in fabric permeability to blood after surgical gowns were prewetted with anticoagulated or coagulating blood. RESULTS: Of the five commercially available gowns tested, contact with blood for 1 hr before application of an external pressure increased permeability for two gowns, decreased permeability for two gowns, and did not alter the permeability of one gown (as compared with test conditions in which the fabrics were not prewetted with blood). These data indicate that at least in some cases prolonged contact with blood increases the amount of blood penetration on application of an external pressure, such as may occur during a pressing or leaning motion. CONCLUSION: Because increased fabric permeability results in an increased risk of skin contact with liquid-borne pathogens for gown users, a major criterion in the design and selection of a gown should be its ability to resist blood penetration for prolonged periods.

Blood-Borne Pathogens↗
PubMed1994

What is the clinical relevance of in vitro dentine permeability tests?

This paper reviews the effect of dentine permeability on the bond strength of dentinal bonding systems and its relationship with the morphology of dentine. Deep dentine is more permeable than superficial dentine. Demineralization of dentine surfaces with acidic conditioners significantly increases permeability with respect to dentine covered by a smear layer. Several primers apparently leave intact smear layers as seen by scanning electron microscopy, but greatly increase the fluid filtration towards the dentine suggesting several modifications in the smear layer. Previous generations of dentinal bonding systems have been shown to be extremely sensitive to dentine humidity and permeability. By contrast, contemporary dentine bonding systems are not influenced by wet dentine. According to the Poiseuille-Hagen equation, small changes in the functional diameter of dentinal tubules can greatly modify permeability. Restorative materials are able to reduce the permeability of prepared dentine subject to location.

Dental Bonding↗
PubMed1995

21-aminosteroid and 2-(aminomethyl)chromans inhibition of arachidonic acid-induced lipid peroxidation and permeability enhancement in bovine brain microvessel endothelial cell monolayers.

Selected 21-aminosteroids (U74500A, U74006F, and U74389G) and a 2-(aminomethyl)chromans (U78517F) were tested for their efficacy in preventing arachidonate-induced lipid peroxidation and permeability alterations in brain microvessel endothelial cells (BMECs). The 21-aminosteroids and 2-(aminomethyl)chromans were effective in varying degrees in inhibiting (U74500A = U78517F > U74006F = U74389G) concentration- and time-dependent arachidonate-induced thiobarbituric acid reactive substances (TBARS) production by BMECs. Arachidonate produced a corresponding concentration-dependent increase in BMEC monolayer permeability to the membrane impermeant marker, sucrose. Pretreatment of BMEC monolayers with either the 21-aminosteroids or the 2-(aminomethyl)chromans completely blocked the arachidonate-induced increase in permeability to sucrose. Our results demonstrated that these membrane-associating antioxidants were particularly effective in preventing both arachidonic acid-induced lipid peroxidation and permeability changes in BMEC monolayers. However, concentrations of some antioxidants that only partially inhibited TBARS production, completely inhibited the arachidonic acid-induced enhancement in BMEC monolayer permeability. Therefore, arachidonic acid-induced effects on BMEC permeability were likely due in part to both lipid peroxidation and direct or indirect effects of the fatty acid on membrane integrity. This study provides further support for the application of primary cultures of BMECs as a useful in vitro system to evaluate mechanisms through which mediators of disease or injury states compromise blood-brain barrier integrity.

Animals↗
PubMed1991

Effects of platelet-activating factor on lung epithelial permeability in the guinea-pig.

We examined the effects of platelet-activating factor (PAF) on lung epithelial permeability by measuring the clearance of intratracheally administered 99m-technetium-labeled diethylene triamine penta-acetic acid (99mTc-DTPA) in guinea-pigs which were anaesthetised, paralysed and mechanically ventilated. The clearance of the radiolabeled tracer molecule 99mTc-DTPA from airways to the blood was expressed as changes in counts/min corrected for background. For each guinea-pig, 99mTc-DTPA clearance was assessed before and after i.v. PAF administration, when tracheal pressure had returned to near control values. Doses of 10, 50 and 100 ng/kg of PAF caused dose-dependent increases in 99mTc-DTPA clearance of 7 +/- 3%, 38 +/- 7% and 65 +/- 11% respectively. The respective effects of 0.5 mg/kg of the beta 2-adrenergic agonist salbutamol and 0.3 mg/kg of the alpha 1-adrenergic agonist methoxamine on the increase in lung epithelial permeability induced by 50 ng/kg PAF were also studied. Salbutamol significantly reduced the acute bronchoconstrictor effects of PAF, but did not affect the increase in lung epithelial permeability, which was 58 +/- 10%. Conversely, methoxamine significantly enhanced the bronchoconstrictor effects of PAF but inhibited the lung epithelial permeability increase, which was only 10 +/- 13%. In the absence of PAF, salbutamol significantly increased this permeability by 49 +/- 11%, whereas methoxamine alone slightly reduced, it by -11 +/- 4%. These results demonstrate that PAF increases lung epithelial permeability and suggest that vascular surface area recruitment may explain this increase.

Albuterol↗
PubMed2004

Permeability behaviour of lipid vesicles prepared from plant plasma membranes--impact of compositional changes.

Exposure of oat seedlings to repeated moderate water deficit stress causes a drought acclimation of the seedlings. This acclimation is associated with changes in the lipid composition of the plasma membrane of root cells. Here, plasma membranes from root cells of acclimated and control plants were isolated using the two-phase partitioning method. Membrane vesicles were prepared of total lipids extracted from the plasma membranes. In a series of tests the vesicle permeability for glucose and for protons were analysed and compared with the permeability of model vesicles. Further, the importance of critical components for the permeability properties was analysed by modifying the lipid composition of the vesicles from acclimated and from control plants. The purpose was to add specific lipids to vesicles from acclimated plants to mimic the composition of the vesicles from control plants and vice versa. The plasma membrane lipid vesicles from acclimated plants had a significantly increased permeability for glucose and decreased permeability for protons as compared to control vesicles. The results point to the importance of the ratio phosphatidylcholine (PC)/phosphatidylethanolamine (PE), the levels of cerebrosides and free sterols and the possible interaction of these components for the plasma membrane as a permeability barrier.

Avena↗
PubMed2005

Lysolipid incorporation in dipalmitoylphosphatidylcholine bilayer membranes enhances the ion permeability and drug release rates at the membrane phase transition.

The enhanced permeability of lipid bilayer membranes at their gel-to-liquid phase transition has been explained using a "bilayer lipid heterogeneity" model, postulating leaky interfacial regions between still solid and melting liquid phases. The addition of lysolipid to dipalmitoylphosphatidylcholine bilayers dramatically enhances the amount of, and speed at which, encapsulated markers or drugs are released at this, already leaky, phase transition through these interfacial regions. To characterize and attempt to determine the mechanism behind lysolipid-generated permeability enhancement, dithionite permeability and doxorubicin release were measured for lysolipid and non-lysolipid, containing membranes. Rapid release of contents from lysolipid-containing membranes appears to occur through lysolipid-stabilized pores rather than a simple enhancement due to increased drug solubility in the bilayer. A dramatic enhancement in the permeability rate constant begins about two degrees below the calorimetric peak of the thermal transition, and extends several degrees past it. The maximum permeability rate constant coincides exactly with this calorimetric peak. Although some lysolipid desorption from liquid state membranes cannot be dismissed, dialyzation above T(m) and mass spectrometry analysis indicate lysolipid must, and can, remain in the membrane for the permeability enhancement, presumably as lysolipid stabilized pores in the grain boundary regions of the partially melted solid phase.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2005

HIV protease inhibitor ritonavir increases endothelial monolayer permeability.

HIV protease inhibitors (PIs) are often associated with metabolic and cardiovascular complications although they are effective anti-HIV drugs. In this study, we determined whether HIV PI ritonavir could increase endothelial permeability, one of the important mechanisms of vascular lesion formation. Human dermal microvascular endothelial cells (HMECs) treated with ritonavir showed a significant increase of endothelial permeability in a dose- and time-dependent manner assayed with a transwell system. Ritonavir significantly reduced the mRNA levels of tight junction proteins zonula occluden-1, occludin, and claudin-1 by 40-60% as compared to controls (P<0.05) by real-time PCR analysis. Protein levels of these tight junction molecules were also substantially reduced in the ritonavir-treated cells. In addition, HMECs treated with ritonavir (7.5, 15, and 30microM) showed a substantial increase of superoxide anion production by 10%, 32%, and 65%, respectively, as compared to controls. Antioxidants (EGCG and SeMet) effectively reduced ritonavir-induced endothelial permeability. Furthermore, ritonavir activated ERK1/2 (phosphorylation), but not P38 and JNK. Specific ERK1/2 inhibitor, PD89059, significantly abolished ritonavir-induced endothelial permeability by 92%. Thus, HIV PI ritonavir increases endothelial permeability, decreases levels of tight junction proteins, and increases superoxide anion production. ERK1/2 activation is involved in the signal transduction pathway of ritonavir-induced endothelial permeability.

Antigens, CD↗
PubMed2004

Mannitol opening of the blood-brain barrier: regional variation in the permeability of sucrose, but not 86Rb+ or albumin.

Clinically, infusion of hyperosmolar solutions is used to enhance chemotherapeutic drug penetration of the blood-brain barrier (BBB) in patients with malignant brain tumors or metastases. We examined the effect of hyperosmolar BBB disruption on brain permeability of three compounds, 86Rb+, a marker for K+ permeability and transport, [14C]sucrose and Evans blue albumin, using a rat in situ perfusion model. 86Rb+ and [14C]sucrose had increased permeability 20 min after BBB disruption with 1.6 M mannitol. There was no change in Evans blue albumin permeability. Only [14C]sucrose showed regional variation in permeability after mannitol-induced BBB disruption, with the cortex and midbrain having higher sucrose permeability then either the cerebellum or brainstem. These data suggest that the clinical efficacy of hyperosmolar disruption therapy in conjunction with chemotherapeutic agents, of a similar molecular weight to sucrose, may be affected by the location of the tumor within the brain.

Albumins↗
PubMed2006

Intestinal permeability and oxidative stress in patients with alcoholic pellagra.

BACKGROUND & AIMS: Increased intestinal permeability is one of the grastointestinal changes observed in alcoholic patients. However, there are no objective definitions as yet of how alcohol induces pathological changes in the various organs. The action of oxygen-free radicals during ethanol metabolism has been considered a determinant factor of these alterations. The present study was undertaken to determine the effect of niacin supplementation on intestinal permeability and oxidative stress in patients with alcoholic pellagra. METHODS: The study was divided into two phases: in Phase 1 we studied ten patients with pellagra before treatment with niacin, and in Phase 2 we studied the same patients after 27 days of treatment with niacin. Intestinal permeability was assessed by the (51)CrEDTA test and the antioxidant action of niacin supplementation was assessed by the determination of lipid peroxidation (plasma malondialdehyde, MDA), protein oxidation (plasma carbonyl group) and of the antioxidants plasma vitamin E and erythrocyte glutathione peroxidase. RESULTS: Comparison of intestinal permeability by the (51)CrEDTA test before and after niacin treatment showed a significant decrease in permeability from 4.29+/-1.92% to 1.90+/-1.19% (P<0.05). Assessment of oxidative stress showed a significant decrease (P<0.05) in lipid and protein peroxidation (MDA: 1.19+/-0.40-0.89+/-0.27 micromol/l; carbonyl groups: 2.22+/-0.36-1.84+/-0.40 nmol/mg protein). CONCLUSIONS: The results suggest that niacin and vitamin E deficiency in patients with pellagra could be important factors in increased intestinal permeability and decreased antioxidant conditions, recovering to normal values after treatment with niacin, associated to alcohol abstinence and a balanced diet.

Alcoholism↗
PubMed2005

Studies on membrane permeability of zebrafish (Danio rerio) oocytes in the presence of different cryoprotectants.

Investigation into fish oocyte membrane permeability is essential for developing successful protocols for their cryopreservation. The aim of the present work was to study the permeability of the zebrafish (Danio rerio) oocyte membrane to water and cryoprotectants before cryopreservation protocol design. The study was conducted on stage III and stage V zebrafish oocytes. Volumetric changes of stage III oocytes in different concentrations of sucrose were measured after 20 min exposure at 22 degrees C and the osmotically inactive volume of the oocytes (Vb) was determined using the Boyle-van't Hoff relationship. Volumetric changes of oocytes during exposure to different cryoprotectant solutions were also measured. Oocytes were exposed to 2 M dimethyl sulphoxide (DMSO), propylene glycol (PG), and methanol for 40 min at 22 degrees C. Stage III oocytes were also exposed to 2 M DMSO at 0 degrees C. Oocyte images were captured on an Olympus BX51 cryomicroscope using Linkham software for image recording. Scion Image was used for image analysis and diameter measurement. The experimental data were fitted to a two-parameter model using Berkeley Madonna 8.0.1 software. Hydraulic conductivity (L(p)) and solute (cryoprotectant) permeability (Ps) were estimated using the model. The osmotically inactive volume of stage III zebrafish oocytes was found to be 69.5%. The mean values+/-SE of Lp were found to be 0.169+/-0.02 and 0.196+/-0.01 microm/min/atm in the presence of DMSO and PG, respectively, at 22 degrees C, assuming an internal isosmotic value for the oocyte of 272 mOsm. The Ps values were 0.000948+/-0.00015 and 0.000933+/-0.00005 cm/min for DMSO and PG, respectively. It was also shown that the membrane permeability of stage III oocytes decreased significantly with temperature. No significant changes in cell volume during methanol treatment were observed. Fish oocyte membrane permeability parameters are reported here for the first time. The Lp and Ps values obtained for stage III zebrafish oocytes are generally lower than those obtained from successfully cryopreserved mammalian oocytes and higher than those obtained with fish embryos and sea urchin eggs. It was not possible to estimate membrane permeability parameters for stage V oocytes using the methods employed in this study because stage V oocytes experienced the separation of outer oolemma membrane from inner vitelline during exposure to cryoprotectants.

Animals↗
PubMed2006

Cryoprotectant permeability of aquaporin-3 expressed in Xenopus oocytes.

It has been shown that aquaporin-3, a water channel, is expressed in mouse embryos. This type of aquaporin transports not only water but also neutral solutes, including cell-permeating cryoprotectants. Therefore, the expression of this channel may have significant influence on the survival of cryopreserved embryos. However, permeability coefficients of aquaporin-3 to cryoprotectants have not been determined except for glycerol. In addition, permeability coefficients under concentration gradients are important for developing and improving cryopreservation protocols. In this study, we examined the permeability of aquaporin-3 to various cryoprotectants using Xenopus oocytes. The permeability of aquaporin-3 to cryoprotectants was measured by the volume change of aquaporin-3 cRNA-injected oocytes in modified Barth's solution containing either 10% glycerol, 8% ethylene glycol, 10% propylene glycol, 1.5 M acetamide, or 9.5% DMSO (1.51-1.83 Osm/kg) at 25 degrees C. Permeability coefficients of aquaporin-3 for ethylene glycol and propylene glycol were 33.50 and 31.45 x 10(-3) cm/min, respectively, which were as high as the value for glycerol (36.13 x 10(-3) cm/min). These values were much higher than those for water-injected control oocytes (0.04-0.11 x 10(-3) cm/min). On the other hand, the coefficients for acetamide and DMSO were not well determined because the volume data were poorly fitted by the two parameter model, possibly because of membrane damage. To avoid this, the permeability for these cryoprotectants was measured under a low concentration gradient by suspending oocytes in aqueous solutions containing low concentrations of acetamide or DMSO dissolved in water (0.20 Osm/kg). The coefficient for acetamide (24.60 x 10(-3) cm/min) was as high as the coefficients for glycerol, ethylene glycol, and propylene glycol, and was significantly higher than the value for control (6.50 x 10(-3) cm/min). The value for DMSO (6.33 x 10(-3) cm/min) was relatively low, although higher than the value for control (0.79 x 10(-3) cm/min). This is the first reported observation of DMSO transport by aquaporin-3.

Animals↗
PubMed2006

Effect of simulated pulpal pressure on dentin permeability and adhesion of self-etch adhesives.

OBJECTIVES: Dentin bonds made with one-bottle etch-and-rinse and self-etch adhesives are affected by the formation of interfacial blisters, porosities and deterioration. The first objective of this study was to evaluate the fluid flow through resin-dentin interfaces created by self-etching adhesives applied to deep dentin using a replica technique and by directly measuring dentin permeability (P). The second objective was to examine the effect of intrapulpal pressure on the microtensile bond strength of these adhesives. METHODS: A fluid-transport model was used to measure the fluid permeability (%P) through different adhesives. Impressions of bonded dentin were taken with a polyvinylsiloxane impression material to monitor fluid transudation from the surface of the adhesive. Positive replicas were fabricated for SEM examination. Two groups of resin-bonded specimens (pulpal pressure versus no pulpal pressure) were created for microtensile bond strength evaluation. Adhesive application was performed under 0 cm H(2)O. Pulpal pressure group was submitted to 20 cm H(2)O of pulpal pressure during build-up procedures. RESULTS: Clearfil Protect Bond exhibited the lowest permeability and fewest numbers of fluid droplets over the surface of the bonded dentin. G-Bond and Clearfil-S3 Bond were more permeable than Clearfil Protect Bond. One Up Bond F was the most permeable adhesive. A highly significant correlation was observed between the relative permeability of these adhesives (%P) and the number of fluid droplets on the adhesive surfaces. The application of pulpal pressure significantly reduced bond strength. SIGNIFICANCE: Resin-dentin bonds created by contemporary self-etch adhesives are susceptible to fluid permeation induced by pulpal pressure. HEMA-based adhesives showed the largest reductions in bond strengths after pulpal pressure application.

Acid Etching, Dental↗
PubMed2006

Intestinal permeability in patients with adverse reactions to food.

BACKGROUND: An abnormal intestinal permeability could contribute to establish an altered sensitivity to food-allergen. AIM: To evaluate the intestinal permeability in subjects with adverse reactions to food on allergen-free diet. SUBJECTS: Twenty-one patients with food allergy and 20 with food hypersensitivity on allergen-free diet were enrolled and divided in four groups according to the seriousness of their referred clinical symptoms when they were on a free diet. METHODS: Intestinal permeability was evaluated by Lactulose/Mannitol ratio urinary detection determined by anion-exchange chromatography. RESULTS: Statistically significant different Lactulose/Mannitol ratio was evidenced in subjects with food allergy (p=0.003) or hypersensitivity (p=0.0008) compared to control patients. The correlation between Lactulose/Mannitol ratio and the seriousness of clinical symptoms, by using Spearman test, was statistically significant for food allergy (p=0.0195) and hypersensitivity (p=0.005) patients. CONCLUSIONS: The present data demonstrate that impaired intestinal permeability, measured in our conditions, is present in all subjects with adverse reactions to food. In addition, for the first time, we report a statistically significant association between the severity of referred clinical symptoms and the increasing of Intestinal Permeability Index. These data reveal that intestinal permeability is not strictly dependent on IgE-mediated processes but could better be related to other mechanisms involved in early food sensitisation, as breast-feeding, or microbial environment that influence the development of oral tolerance in early infancy.

Adolescent↗
PubMed2006

Effect of nanoparticulate polybutylcyanoacrylate and methylmethacrylate-sulfopropylmethacrylate on the permeability of zidovudine and lamivudine across the in vitro blood-brain barrier.

Effect of size of nanoscaled polybutylcyanoacrylate (PBCA) and methylmethacrylate-sulfopropylmethacrylate (MMA-SPM) on the permeability of zidovudine (AZT) and lamivudine (3TC) across the blood-brain barrier (BBB) was investigated. Also, influence of alcohol on the permeability of AZT and 3TC incorporated with the two polymeric nanoparticles (NPs) was examined. The loading efficiency and the permeability of AZT and 3TC decreased with an increase in the particle size of the two carriers. By employing PBCA NPs, the BBB permeability of AZT and that of 3TC became, respectively, 8-20 and 10-18 folds. Application of MMA-SPM NPs leaded to about 100% increase in the BBB permeability of the two drugs. In the presence of 0.5% ethanol, 4-12% enhancement in the BBB permeability of the two drugs was obtained in the current carrier-mediated system.

Animals↗
PubMed2006

Effects of fractionated radiation on the brain vasculature in a murine model: blood-brain barrier permeability, astrocyte proliferation, and ultrastructural changes.

PURPOSE: Radiation therapy of CNS tumors damages the blood-brain barrier (BBB) and normal brain tissue. Our aims were to characterize the short- and long-term effects of fractionated radiotherapy (FRT) on cerebral microvasculature in mice and to investigate the mechanism of change in BBB permeability in mice. METHODS AND MATERIALS: Intravital microscopy and a cranial window technique were used to measure BBB permeability to fluorescein isothiocyanate (FITC)-dextran and leukocyte endothelial interactions before and after cranial irradiation. Daily doses of 2 Gy were delivered 5 days/week (total, 40 Gy). We immunostained the molecules to detect the expression of glial fibrillary acidic protein and to demonstrate astrocyte activity in brain parenchyma. To relate the permeability changes to endothelial ultrastructural changes, we used electron microscopy. RESULTS: Blood-brain barrier permeability did not increase significantly until 90 days after FRT, at which point it increased continuously until 180 days post-FRT. The number of adherent leukocytes did not increase during the study. The number of astrocytes in the cerebral cortex increased significantly; vesicular activity in endothelial cells increased beginning 90 days after irradiation, and most tight junctions stayed intact, although some were shorter and less dense at 120 and 180 days. CONCLUSIONS: The cellular and microvasculature response of the brain to FRT is mediated through astrogliosis and ultrastructural changes, accompanied by an increase in BBB permeability. The response to FRT is delayed as compared with single-dose irradiation treatment, and does not involve leukocyte adhesion. However, FRT induces an increase in the BBB permeability, as in the case of single-dose irradiation.

Animals↗
PubMed2006

Permeability predictions for sand-clogged Portland cement pervious concrete pavement systems.

Pervious concrete is an alternative paving surface that can be used to reduce the nonpoint source pollution effects of stormwater runoff from paved surfaces such as roadways and parking lots by allowing some of the rainfall to permeate into the ground below. This infiltration rate may be adversely affected by clogging of the system, particularly clogging or covering by sand in coastal areas. A theoretical relation was developed between the effective permeability of a sand-clogged pervious concrete block, the permeability of sand, and the porosity of the unclogged block. Permeabilities were then measured for Portland cement pervious concrete systems fully covered with extra fine sand in a flume using simulated rainfalls. The experimental results correlated well with the theoretical calculated permeability of the pervious concrete system for pervious concrete systems fully covered on the surface with sand. Two different slopes (2% and 10%) were used. Rainfall rates were simulated for the combination of direct rainfall (passive runoff) and for additional stormwater runoff from adjacent areas (active runoff). A typical pervious concrete block will allow water to pass through at flow rates greater than 0.2 cm/s and a typical extra fine sand will have a permeability of approximately 0.02 cm/s. The limit of the system with complete sand coverage resulted in an effective system permeability of approximately 0.004 cm/s which is similar to the rainfall intensity of a 30 min duration, 100-year frequency event in the southeastern United States. The results obtained are important in designing and evaluating pervious concrete as a paving surface within watershed management systems for controlling the quantity of runoff.

Facility Design and Construction↗
PubMed2004

The importance of cuticular permeability, osmolyte production and body size for the desiccation resistance of nine species of Collembola.

Euedaphic collembolans have recently been shown to actively regulate internal osmotic pressure by means of sugars and polyols in response to desiccation. In contrast, studies of cuticular permeability have shown that some, especially epedaphic, species of collembolans may primarily rely on a low cuticular permeability to survive desiccation. To elucidate to what extent these strategies are important for desiccation resistance, the survival of 7-day acute desiccation stress (LRH(50)), the cuticular water conductance constant and osmolyte production were investigated in nine species of collembolans, covering euedaphic, hemiedaphic and epedaphic species. The LRH(50) values ranging from 98.8% to 95.2% RH showed no correlation with the vertical distribution of species, since both the highest and lowest values were found in epedaphic species. The water conductance varied from 698+/-141 to 41+/-13 microg h(-1) cm(-2) mmHg(-1) and showed good agreement with the vertical distribution of species in their natural habitats. Modelling the drying curves showed that, in addition to cuticular permeability and osmolyte production, body size also plays an important role in the survival of short-term severe desiccation stress. Furthermore, the model pointed to the need for behavioural responses to desiccation, particularly in epedaphic species. Thus, in keeping with expected humidity regimes in their respective microhabitats, euedaphic species rely on small body size, high cuticular permeability and the ability to actively regulate the osmotic pressure of their body fluids, hemiedaphic species have similar strategies but with reduced cuticular permeability, whereas in epedaphic species, active regulation of osmotic pressure is replaced by combinations of greatly reduced cuticular permeability or greatly reduced surface area to volume ratio combined with behavioural responses to desiccation.

Adaptation, Physiological↗