WILBERT

Wildauer Bücher+E-Medien Recherche-Tool

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 38 (1982), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Changes in cellular [K] and [Na] in the choroidal epithelium (as a reflection of Na-K pump activity) were analyzed in Sprague-Dawley rats subjected to acute systemic acidosis. In the lateral and 4th ventricle choroid plexus (CP) of adult rats in which metabolic acidosis was induced for 1 h, cell [K] and [Na] increased and decreased by 35 and 15 mm/kg water, respectively, indicating marked stimulation of the Na-K exchange pump in the CSF-facing membrane; in contrast, this striking response of the CP to acidosis could not be elicited in immature animals (1 week old). Since the effects of respiratory acidosis on CP cell [K] and [Na] were similar to those of metabolic acidosis, the reduction in plasma pH (rather than in [HCO3]) is likely the mechanism underlying the enhanced turnover of Na and K across the CP in adults. The concentration of Na and K in the cerebral cortex, medulla, and CSF was generally not altered during acute acid-base distortions in both mature and immature animals. The striking difference in the response of CNS tissue protected by the blood-CSF barrier (i.e., CP) and the blood-brain barrier (BBB) to systemic acidosis emphasizes a unique role, presumably homeostatic, for the plexus. Since propranolol substantially attenuated the acidosis-induced changes in choroidal cell [K] and [Na], it is possible that there is β-receptor modulation of the Na,K-ATPase (Na-K pump) in the CP. We postulate that the generally observed enhanced electropositivity in the CSF in systemic acidosis is brought about, at least in part, by facilitation of Na-K pumping in the CP, although induced changes in membrane permeability may also be a factor.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 10 (1993), S. 1745-1750 
    ISSN: 1573-904X
    Keywords: transdermal ; human ; in vitro ; in vivo ; estradiol ; oleic acid ; fatty acid ; permeation enhancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The permeation enhancing property of 5% oleic acid in ethanol on β-estradiol was investigated in vitro and in vivo using symmetrical and asymmetrical side-by-side diffusion cells and the human skin sandwich flap, respectively. β-Estradiol permeability in vitro and in vivo was similar in 75% ethanol (ETOH). Oleic acid (5%) did not alter β-estradiol permeability in vivo but increased permeability sixfold in vitro in symmetrical diffusion cells. β-Estradiol permeability in oleic acid was not different from that in ETOH, however, using asymmetrical diffusion cells. Stratum corneum-to-vehicle partition coefficients of β-estradiol in the vehicles were similar, yet fourfold more steroid was detected in skin biopsies from the in vitro symmetrical diffusion cells. Thus, oleic acid increased β-estradiol permeability in vitro only when skin was equilibrated with fatty acid. Attention to in vitro diffusion cell design and its relevance in vivo is critical to defining the mechanisms of enhanced solute permeation.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 7 (1990), S. 352-358 
    ISSN: 1573-904X
    Keywords: percutaneous absorption ; mathematical modeling ; human skin sandwich flap ; in vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The possibility of predicting the behavior of in vivo systems based on physical and chemical parameters determined by in vitro experiments is examined using benzoic acid. The physical and chemical parameters governing percutaneous absorption of benzoic acid—permeability, partition coefficient, and skin thickness—were determined by in vitro experiments as described in Ref. 1. These parameters were used, in combination with benzoic acid elimination kinetics, to predict the results of in vivo experiments using a comprehensive mathematical model. The in vivo system consists of a congenitally athymic (nude) rat with a surgically constructed human skin sandwich (HSSF) flap on which a donor cell is placed. To apply the in vitro parameters to an in vivo system requires a suitable pharmacokinetic model describing distribution and elimination for benzoic acid in the nude rat. Blood concentrations of benzoic acid following a bolus intravenous injection are closely described by a two-compartment open pharmacokinetic model with elimination occurring from only one compartment. The mathematical model of the rat-donor cell system combines this two-compartment model of the rat with a percutaneous absorption model to provide useful estimates of the measured in vivo blood levels. Comparisons of predicted and measured results suggest that the parameters determined by in vitro experimentation can be used to predict the behavior of complex in vivo systems, if a suitable mathematical model is available.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 15 (1998), S. 167-171 
    ISSN: 1573-904X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 7 (1990), S. 170-175 
    ISSN: 1573-904X
    Keywords: human ; skin ; estradiol ; ethanol ; percutaneous absorption ; permeation enhancers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of ethanol on the permeation of 17β-estradiol (estradiol) across viable human skin in vivo was investigated with the human skin sandwich flap model. Maintaining continuous delivery of a constant concentration of the solute in phosphate-buffered saline, pH 7.4 (PBS), or mixtures of ethanol in PBS to the skin surface revealed that steady-state flux of estradiol was achieved within 30–60 min and maintained throughout 4 hr. The 10-fold decrease in in vivo flux and permeability coefficient (K p) of tracer estradiol solutions in ethanol or ethanol solutions compared with PBS vehicle reflected the 10-fold difference in the apparent partition coefficients (K m) of estradiol from the respective vehicles into isolated human stratum corneum. Neither the stratum corneum thickness nor the diffusion coefficient of estradiol was significantly different among the vehicles tested. In vivo flux of estradiol in ethanol or ethanol solutions across viable human skin was increased with saturated solutions of estradiol. Further, in vivo flux of estradiol from vehicles such as PBS, ethanol, and ethanol mixtures, which minimally alter the rate-limiting barrier, can be successfully predicted with knowledge of only two physicochemical parameters, the estradiol concentration in the vehicle and the K m of estradiol from the vehicle into isolated human stratum corneum.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 7 (1990), S. 230-236 
    ISSN: 1573-904X
    Keywords: percutaneous absorption ; mathematical model ; human skin ; partition coefficient ; in vitro ; benzoic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The percutaneous absorption of benzole acid across human skin in vitro was experimentally and mathematically modeled. Skin partition coefficients were measured over a range of benzoic acid concentrations in both saline and distilled water. The permeation of benzoic acid was measured across isolated stratum corneum, stratum corneum and epidermis, and split-thickness skin. These experiments demonstrated that the stratum corneum was the rate-limiting barrier and that the flux is proportional to the concentration of the undissociated species. The permeation data were analyzed with a comprehensive non-steady-state mathematical model of diffusion across skin. Two adjustable parameters, the effective skin thickness and diffusivity, were fit to the permeation data by nonlinear regression.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 9 (1992), S. 45-51 
    ISSN: 1573-904X
    Keywords: bioavailability ; skin blanching ; vasoconstriction ; topical corticosteroids ; betamethasone dipropionate ; tape-stripping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An in vivo technique has been developed which simultaneously compares a skin blanching bioassay with drug content in human stratum corneum following topical application of four 0.05% beta-methasone dipropionate formulations. Bioavailability of drug from commercial cream and ointment formulations was assessed by quantification of drug content in tape-stripped stratum corneum and skin blanching in the treated skin site under occluded conditions. Tape-stripping removed stratum corneum to a varying degree between individuals but was consistent (35%) within an individual with all formulations, day to day. A correlation (r = 0.9935) between the amount of drug in the treated stratum corneum normalized for surface area and the corresponding skin blanching score was observed with four 0.05% betamethasone dipropionate formulations. Increasing the amount of drug in the tape-stripped stratum corneum correlated with an increased skin blanching score. Ointment formulations delivered more drug to the skin and produced greater blanching scores than the cream formulations. Topical corticosteroid content in the treated skin site can therefore be quantified and correlates well with the resulting pharmacodynamic activity.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-4632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: An ideal method for measuring the bioavailability of topical corticosteroids should be simple, accurate, and adaptable to a variety of settings and should not require extensive special training to perform. Drug uptake into the stratum corneum, measured by tapestripping, is correlated with the pharmacodynamic response of skin blanching, observed in the vasoconstrictor assay. Differences in stratum corneum drug uptake can be objectively quantitated as a function of time, occlusion, dose applied, and vehicle. Tapestripping measurements are reproducible within individual subjects, but large interindividual variabilities may exist. The chromameter, a new technology, objectively quantitates color numerically and can be used to measure skin blanching as part of the pharmacodynamic response to topical corticosteroids. The chromameter offers an easy, objective method with which to quantitate the pharmacodynamic response of topical corticosteroids. Both methods allow a more mechanistic approach than currently used methods to investigate topical drug pharmacokinetics and pharmacodynamics.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...