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At least 847 records · Page 47Linked to original sources
PubMed1973

A saturable, vasopressin-sensitive carrier for urea and acetamide in the toad bladder epithelial cell.

The permeability of the toad bladder to a series of isotopically labeled nonelectrolytes was determined in the presence of 150 mM unlabeled acetamide. Under these conditions, overall bladder function was unimpaired, as shown by a normal response to vasopressin of short-circuit current and permeability coefficient of [(3)H]water,[(14)C]ethanol, and [(14)C]propionamide. The permeability of the bladder to isotopic acetamide and urea, however, was significantly depressed by unlabeled acetamide, in both the absence and presence of vasopressin. These experiments indicate a competition between unlabeled and isotopic species for binding sites, and show the existence of a saturable, vasopressin-sensitive carrier for urea and acetamide in the epithelial cell membrane.

Acetamides↗
PubMed1999

TCE treatment pasta-bilities.

Monsanto's "Lasagna" process uses layers of treatment zones spaced between buried electrodes to remove trichloroethylene (TCE) from contaminated soil and groundwater. TCE is used primarily as a metal degreaser as well as in products such as dyes, printing ink, and paint. TCE can eventually make its way into the environment and is prevalent in the water and soil of industrialized nations. Although TCE breaks down in a few days when released into the atmosphere, it degrades much more slowly in soil, taking months or years. Moreover, it is often broken down by microbes into toxic substances such as vinylidene chloride (a suspected human carcinogen) and vinyl chloride (a known human carcinogen). The Lasagna process is based on the principle of electro-osmosis, in which an electric current draws water from low--permeability soils such as clays, silts, and fine sands. To remove TCE from contaminated soils, Monsanto scientists added layers of filtering media, which attack the contaminant as it is pulled from electrode to electrode. The technology has been tested at the Paducah Gaseous Diffusion Plant in western Kentucky, where it removed over 98% of TCE from contaminated soil.

Humans↗
PubMed2005

Oral pulsatile drug delivery systems.

In the field of modified release, there has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable lag phase from the time of administration. In particular, the recent literature reports on a variety of pulsatile release systems intended for the oral route, which have been recognised as potentially beneficial to the chronotherapy of widespread diseases, such as bronchial asthma or angina pectoris, with mainly night or early morning symptoms. In addition, time-dependent colon delivery may also represent an appealing related application. The delayed liberation of orally administered drugs has been achieved through a range of formulation approaches, including single- or multiple-unit systems provided with release-controlling coatings, capsular devices and osmotic pumps. Based on these premises, the aim of this review is to outline the rational and prominent design strategies behind oral pulsatile delivery.

Administration, Oral↗
PubMed1984

Cerebrovascular permeability and delivery of gentamicin to normal brain and experimental brain abscess in rats.

Antibiotics vary widely in their ability to penetrate the blood-brain barrier. In studies of 70 rats, the permeability of the normal blood-brain barrier to gentamicin was shown to be poor. In experimental brain abscesses, during the cerebritic stage of development, the penetration of intravenous antibiotics was increased compared to normal brain but was very inconsistent. Antibiotic delivery to brain abscess was not significantly altered with the administration of high-dose steroids, but the macrophage and glial response was markedly decreased with high-dose steroid therapy. Reversible osmotic blood-brain barrier modification with mannitol increased the delivery of gentamicin both to brain abscess and to the surrounding brain. It also resulted in more consistent tissue drug levels. The clinical implications of these studies suggest that, because of the inconsistent delivery of gentamicin to brain abscess, the therapeutic efficacy of medical management alone may be quite variable. This mode of therapy could possibly increase the efficacy of medical management of brain abscesses, especially in patients with multiple or surgically inaccessible brain abscesses.

Animals↗
PubMed1979

[A fast osmotic transition method for the study of pulmonary transcapillary exchange: theoretical model].

A theoretical model allowed the simultaneous determination of the reflexion coefficients of capillary membrane to small hydrophilic molecules and of the ratios of their permeability to filtration coefficient. This was applied to dilution curves obtained after injection of a hypertonic solution containing a vascular tracer. The calculated variables did not depend on the capillary exchange surface area.

Capillaries↗
PubMed2005

Efficiency of membrane processes for taste and odor removal.

The occurrence of tastes and odors (T&O) in drinking water is considered as one of the main problems by the drinking water companies. Thus, several treatment processes were developed over the years to control T&O including air stripping, activated carbon and oxidation using ozone. However, little information is available in the literature on the use of membranes for T&O removal. Therefore, the objectives of this paper are to present potential of membrane processes for removal of taste and odor causing compounds. Several membranes were tested including ultrafiltration (UF), UF combined with powdered activated carbon (PAC), nanofiltration (NF) and low pressure reverse osmosis (LP RO) membranes. The results of this study indicate that the combination of UF with PAC is effective for T&O control whereas the benefit of NF and LP RO remains unclear for T&O control.

Adsorption↗
PubMedDate not supplied

[Decreased sensitivity of frog bladder cells to the antidiuretic hormone in the presence of D20].

Antidiuretic hormone (ADH) does not enhance the bladder wall permeability for the water, when 50% of the water is substituted for D2O in Ringer's solution. ADH reaction is partially reduced in the inhibition of phosphodiesterase activity by theophylline. In D2O presence cAMP-theophylline combination stimulates the water penetration, growing in proportion to an increase in Ringer's solution osmolarity under polyethylene glycol 400 action. It is suggested that D2O affects ADH-membrane receptor interaction or intensifies cAMP destruction, but the effectiveness of the subsequent intracellular reactions, stipulating augmentation of osmotic permeability, persists.

Animals↗
PubMed1993

[Spontaneous and induced permeability of the tight junctions in the bladder epithelium of the frog Rana temporaria].

The spontaneous and induced alterations in paracellular permeability of the isolated frog urinary bladder were studied. For estimation of the tight junction (TJ) permeability, a fluorescent dye uranine was used. No morphological or functional evidences for the TJ opening were found in the autumn-winter period, both in the control and after the osmotic flow stimulation by 25 mg/ml pituitrine (P) or serosal mannitol (200 mM). In the spring, a spontaneous uranine efflux through the bladder wall from the mucosal solution was found in parallel with an increase in the basal water flow and a decrease in the responses of the bladder to P and serosal hypertonicity. At the same time, the intercellular substance remained to be a barrier for water. In the autumn-winter the TJ opening could be induced by adding sulfhydryl reagents, p-chloromercury-phenyl-sulfonic acid (PCMPS) or N-ethylmaleimide (NEM), to the serosal solution. However, NEM was effective only when added to the mucosal solution. The uranine efflux induced by sulfhydryl reagents was accompanied with a marked hydroosmotic flow in parallel with a diminished sensitivity to P, the barrier properties of intercellular substances were lost. As evidenced by electron microscopy, PCMPS induced a gradual destruction of TJ structures, while certain cytoplasmic structures were not affected. The uranine efflux in the autumn-winter frogs could be induced by an artificial osmotic gradient after preincubation of the bladders in the isotonic solution with P. Some possible intracellular mechanisms causing both spontaneous and induced alterations in the TJ permeability are discussed.

Animals↗
PubMedDate not supplied

[Effect of water pollution by oil and oil products on barrier functions of bacterial cell cytoplasmic membranes].

The effects of oil, diesel fuel, and kerosene on the electroorientational spectra and osmo-optical characteristics of bacterial cells were studied. Electroorientational spectra were found to be affected over the entire frequency range studied; changes in low-frequency (< 100 kHz) electroorientation were related to alterations in the cell surface, and those in high-frequency electroorientation, to the impairment of the barrier function of the plasma membrane. The membranotropic activity of petroleum products was also demonstrated by the osmo-optical method. Of nine bacterial species studied, Pseudomonas fluorescens VKM B-894, P. oleovorans VKM B-1522, and P. stutzeri VKM B-903 were most susceptible to the membranotropic action of kerosene; P. putida VKM B-1292 was the most resistant. Other bacterial strains studied were moderately sensitive.

Cell Membrane Permeability↗
PubMed1965

THE CONTROL OF THE MEMBRANE POTENTIAL OF MUSCLE FIBERS BY THE SODIUM PUMP.

Frog sartorius muscles were made Na-rich by immersion in K-free sulfate Ringer's solution in the cold. The muscles were then loaded with Na(24) and the extracellular space cleared of radioactivity. When such Na-rich muscles were transferred to lithium sulfate Ringer's solution at 20 degrees C, Na efflux was observed to increase with time, to reach a maximum about 15 minutes after the transfer of the muscles to Li(2)SO(4), and then to decline. The decline in efflux from these muscles was proportional to ([Na](i))(8) over a considerable range of [Na](i). The membrane potential of Na-rich muscles was about -48 mv in K-free sulfate Ringer's at 4 degrees C but changed to -76 mv in the same solution at 20 degrees C and to -98 mv in Li(2)SO(4) Ringer's at 20 degrees C. By contrast, muscles with a normal [Na](i) showed a fall in membrane potential when transferred from K-free sulfate Ringer's to Li(2)SO(4) Ringer's solution. The general conclusions from this study are (a) that Na extrusion is capable of generating an electrical potential, and (b) that increases in [Na](i) lead to reversible increases in P(Na) of muscle fibers.

Animals↗