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At least 181 records · Page 10Linked to original sources
PubMed1984

Kinetic considerations in monitoring exposure to chemicals.

The aim of biological exposure monitoring is to estimate the amount of the chemical absorbed in the body of each individual worker. As the concentration of any foreign chemical in body fluids is not constant, but shows an exposure-related fluctuation, this estimation may be successful only when based on knowledge of the behaviour of the chemical in the body, i.e., its kinetics. Skin absorption is one of the reasons for performing biological monitoring of exposure. However, when the absorbed chemical is being monitored in the blood, skin absorption may be a source of considerable error since the concentration of the chemical in the blood specimen collected from the cubital vein does not represent the whole body but only the arm. It should be borne in mind that the errors caused by kinetic variations are similar, independent of the type of measurement performed; thus, they pertain equally to the measurements of chemicals by traditional chemical analytical means and to measurements of the character of the chemical, e.g., mutagenicity.

Animals↗
PubMed2003

In vitro percutaneous absorption of cobalt.

OBJECTIVES: To evaluate skin absorption of cobalt powder in an in vitro system. Experiments with volunteers show that cobalt powder can permeate through the skin, but there are no data with regard to the mechanism or the amount of permeation. METHODS: Skin permeation was calculated by the Franz diffusion cell method with human skin. A physiological solution was used as receiving phase and the cobalt powder was dispersed in synthetic sweat. The amount of metal passing through the skin was analysed by electro-thermal atomic absorption spectrometry (ETAAS). Parallel polarographic analysis (differential pulse polarography-DPP) allowed evaluation of cobalt present as ions (Co(2+)) in donor and receiving phases. Measurements of cobalt skin content were also performed. RESULTS: Evaluation of metal in the receiving phase allowed us to demonstrate the permeation of cobalt through the skin. Steady-state flow of percutaneous cobalt permeation was calculated as 0.0123+/-0.0054 microg cm(-2) h(-1), with a lag time of 1.55+/-0.71 h. CONCLUSIONS: The experiments show that cobalt powder can pass through the skin when applied as a dispersion in synthetic sweat, oxidising metallic cobalt into ions, which permeate the skin. These experiments show for the first time how cobalt can permeate the skin.

Cobalt↗
PubMedDate not supplied

Receptor microscopic autoradiography for the study of percutaneous absorption, in vivo skin penetration, and cellular-intercellular deposition.

INTRODUCTION: Microscopic autoradiography with cellular resolution and preservation of in vivo conditions is potentially the method of choice to gain detailed information about sites of deposition and retention in the epidermis and of penetration to the dermis after topical application of drugs. We tested this using (3)H-Maxacalcitol. METHODS: Dorsal skin of adult rats was treated in vivo with ointment containing 1 or 40 microg/kg body weight of the vitamin D analogue (3)H-Maxacalcitol for periods of 0.5, 2, 8, 24, 48, or 168 h. Samples of skin exposed to the ointment and control samples remote from the treatment site were excised and freeze-mounted, and 4-microm frozen sections were exposed to nuclear emulsion. RESULTS: Two penetration routes to the dermis could be distinguished: one via epidermal cell layers and the other via hair follicles. Highest uptake and retention of radiolabeled steroid was observed in stratum corneum and in intercellular spaces of stratum granulosum. By contrast, cell boundaries and intercellular spaces in the stratum spinosum and basale contained low levels of radioactivity. Keratinocytes in these layers showed high concentration in the cytoplasm at early time intervals, when surrounding radioactivity levels were high, but high nuclear and low or no cytoplasmic concentration at late time intervals, when surrounding radioactivity levels were low. DISCUSSION: The autoradiographic method provides detailed information on time- and dose-related distribution of radiolabeled compound at the cellular level that is not obtainable with common radioassays and biochemical procedures. A sustained concentration and retention of radiolabeled steroid in the stratum corneum and intercellular space of the stratum granulosum indicate a selective deposition in components of secreted-membrane-coating granules and suggest a temporary barrier and depot for slow release. The differential cytoplasmic-nuclear distribution in the stratum Malpighi suggests functional correlation to a toxic-hormetic reversal of action on cell proliferation, from high-dose inhibitory effects associated with high extranuclear concentration as utilized in the treatment of psoriasis, to low-dose stimulatory effects associated with high nuclear and low cytoplasmic concentration as applicable in wound healing.

Administration, Topical↗
PubMed1993

Disparity of in vitro and in vivo oleic acid-enhanced beta-estradiol percutaneous absorption across human skin.

The permeation enhancing property of 5% oleic acid in ethanol on beta-estradiol was investigated in vitro and in vivo using symmetrical and asymmetrical side-by-side diffusion cells and the human skin sandwich flap, respectively. beta-Estradiol permeability in vitro and in vivo was similar in 75% ethanol (ETOH). Oleic acid (5%) did not alter beta-estradiol permeability in vivo but increased permeability six-fold in vitro in symmetrical diffusion cells. beta-Estradiol permeability in oleic acid was not different from that in ETOH, however, using asymmetrical diffusion cells. Stratum corneum-to-vehicle partition coefficients of beta-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 beta-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.

Administration, Cutaneous↗
PubMed1980

Estrogenic absorption through the skin: an experimental study.

Our results show in an unquestionable way that both the steroid (ethinylestradiol) and non-steroid (Ralone) estrogens studied by us were absorbed percutaneously by the rat. They also demonstrate that both estrogens affected target organs in a quite similar way being proportionally dependent upon the 1-to-1,000 ratio existing between them, as established on the basis of a known activity parameter. When one of the two estrogens is given for therapeutical purposes its systemic effects are of a dose-related type.

Animals↗
PubMed1995

[Toxicity dynamics of anionic dyes in the air of a work place and long-term effects after absorption through the skin].

The study covered 10 types of anion dyes for leather: Crimson 4RT, Gray M, Solid Blue, Red 8S, Black N, Brown 46, 673, 911, 551, 557. According to LD50 criterion they all were assigned to IV jeopardy class. It instilled per os 30 times, the chemicals induced mild hemotoxic effect similar to that of methemoglobin-formers, in half of the cases affected gonads. Allergic and local irritating skin effects were unusual. Solid Blue and Crimson 4RT dyes were subjected to inhalation trials. Limcf for those two equal 51.8 and 38.0 mg/m3 respectively Limch--8.3 and 7.1 mg/m3, measured through changes in red blood parameters, behavioral response and other reactions. With consideration of Limch, toxicity for gonads and embryos, mutagenicity, the authors justified the MAC for Crimson 4RT dye in the air of workplace--1 mg/m3 (II jeopardy class), for Solid Blue dye--5 mg/m3 (III jeopardy class).

Air Pollutants, Occupational↗
PubMed2006

Unexpected cause of raised benzene absorption in coke oven by-product workers.

BACKGROUND: Urinary biological monitoring for benzene (by measuring benzene metabolites) in coke oven by-product workers produced the unexpected result that 2 out of 10 employees had significantly raised urinary S-phenylmercapturic acid (S-PMA). However, simultaneous personal air sampling showed no excessive airborne exposure. METHODS: Possible causes for this finding were investigated having excluded inhalation as the route of uptake. It was suspected that skin absorption via contaminated overalls was the possible mechanism and a standard frequency for overall change was introduced. RESULTS: Changing overalls after every four shifts reduced uptake levels to less than the equivalent of 1 ppm inhaled dose for all employees. CONCLUSION: Skin absorption of benzene in coke oven by-product workers from contaminated overalls can be significant and therefore overalls should be changed on a regular and frequent basis.

Acetylcysteine↗
PubMed1989

Percutaneous absorption of 4 organic solvents in the guinea pig (II). Effect of surfactants.

Percutaneous absorption of 4 organic solvents (1,1,1-trichloroethane, 1,1,2-trichloroethane, toluene and butanol) from various colloidal preparations in a surfactant-water-organic solvent system was studied in vivo in guinea pigs. The preparations examined were binary solutions of organic solvents and surfactants, o/w emulsions and microemulsions. Phase diagram, birefringence microscopy and droplet size distribution analysis were used for characterization of the preparations. It was found that skin absorption of the solvents depends on the type of surfactant, type of preparation and also on phase equilibria in the systems studied. The presence of nonionic surfactants in the solvents and in a microemulsion with butanol caused skin absorption to decrease. A reduced uptake of solvents from o/w emulsions was observed. The absorption of butanol from a microemulsion with anionic surfactant was greater than from the pure solvent.

Animals↗