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R G Stafford

Publications and source records attributed to R G Stafford.

11 recordsLinked to original sources
PubMed1994

Method for the identification of saxitoxin in rat urine.

Saxitoxin (STX) is one of several related toxins that cause paralytic shellfish poisoning. We used solid-phase extraction (SPE) and prechromatographic oxidation/HPLC with fluorescence detection to isolate, identify, and quantify STX in rat urine. STX recovery from urine with the SPE procedure was approximately 76 +/- 6.5%. The standard curve was linear between 2 and 50 ng/ml. The lower limit of quantification with the method was 2 ng STX/ml of rat urine. Preliminary results with i.v. administration of STX to rats demonstrated that this method can detect and quantify STX in urine.

Animals↗
PubMed1992

Comparison of the partition coefficient and skin penetration of a marine algal toxin (lyngbyatoxin A).

Lyngbyatoxin A is produced by marine algae, and causes local cutaneous toxicity in swimmers. The purpose of this research was (1) to determine the partition coefficient of lyngbyatoxin A in octanol/water and (2) to use methods in vitro to measure the penetration and distribution of lyngbyatoxin A in guinea pig and human skin. Discs of excised guinea pig and human skin were mounted in diffusion chambers that exposed the epidermal surface to air and bathed the dermis with HEPES-buffered Hanks' balanced salt solution with gentamicin sulphate. The epidermal surfaces were dosed with 26 micrograms lyngbyatoxin A/cm2 dissolved in 13 microliters dimethyl sulphoxide/cm2. The diffusion chambers were incubated at 36 degrees C for varying periods (1.0-24 hr). HPLC was used to quantify lyngbyatoxin A. Skin penetration was calculated by summing the amount of lyngbyatoxin A recovered from the dermis and receptor fluid. The mean partition coefficient for lyngbyatoxin A was 1.53. Penetration of lyngbyatoxin A (expressed as a percentage of dose, n = 3) in guinea pig and human skin was 23 and 6.2 (respectively) after 1 hr of topical exposure. The amount of lyngbyatoxin A in the dermis and receptor fluid did not change significantly over time.

Animals↗
PubMed1991

Methods for in vitro skin absorption studies of a lipophilic toxin produced by red tide.

The penetration and distribution of [3H]PbTx-3 into pig skin was determined using in vivo and in vitro methods. The dose used in each topical study was 0.3-0.4 micrograms/cm2 skin, with dimethylsulfoxide as the vehicle. In the in vivo study, mean cutaneous absorption after 48 h (expressed as percentage of the dose) was 11.5% (n = 3). In the in vitro study, mean cutaneous absorption after 48 h was 1.6% (n = 12), when based on accumulation of radioactivity in receptor fluid, or 9.9% when based on receptor fluid and dermis. [3H]PbTx-3 readily penetrated through the epidermis into the dermis, reaching maximal dermal accumulation at 4 h (9.1% in vivo and 18% in vitro). At 24 h, the amount in the dermis decreased to 2.3% and 15% in vivo and in vitro, respectively and at 48 h the amount in the dermis decreased to 8.2% in vitro. These results demonstrate the important role of the dermis as a reservoir for a lipophilic compound in both in vivo and in vitro percutaneous absorption studies.

Administration, Topical↗
PubMed1991

In vitro penetration of tritium-labelled water (THO) and [3H]PbTx-3 (a red tide toxin) through monkey buccal mucosa and skin.

The permeability coefficients (Kp) for tritium-labelled water (THO) were determined in human and monkey skin, and monkey buccal mucosa. Kp of human skin (0.47 x 10(-3) cm/h) correlated favorably with previous reports. Kp of hydrated monkey skin for THO (0.77 x 10(-3) cm/h) was not significantly different (P greater than 0.05) from Kp of hydrated human skin (0.88 x 10(-3) cm/h). Kp of monkey buccal mucosa for THO (6.15 x 10(-3) cm/h) was significantly greater than that for monkey skin. Penetration and disposition of [3H]PbTx-3 into layers of monkey buccal mucosa and skin was determined. [3H]PbTx-3 (5-7 microCi) dissolved in 2 ml of water was applied to epithelial/epidermal surface (2.8 cm2) at zero time. The relative percent dose recovered from the upper layers of buccal mucosa (epithelium) and skin (epidermis) varied, but at each time interval was less than 2.5% of the dose. At most of the time intervals (2-24 h), a larger percent of the dose was recovered from the inner layer of the buccal mucosa (lamina propria) than from the inner layer of skin (dermis). After 24 h, as much as 34 or 13% of the dose was recovered from lamina propria or dermis, respectively. At each time interval studied, less than 2% of dose of [3H]PbTx-3 penetrated into the receptor fluid which bathed the inner surfaces of the lamina propria or dermis. The results of this study demonstrate that monkey buccal mucosa is more permeable than skin to THO and PbTx-3.

Administration, Topical↗
PubMed1972

Photoelectron microscopy: a new approach to mapping organic and biological surfaces.

A general method of imaging organic and biological surfaces based on the photoelectric effect is reported. For the experiments, a photoelectron emission microscope was constructed. It is an ultrahigh vacuum instrument using electrostatic electron lenses, microchannel plate image intensifier, cold stage, hydrogen excitation source, and magnesium fluoride optics. The organic surfaces examined were grid patterns of acridine orange, fluorescein, and benzo(a)pyrene on a Butvar surface. A biological sample, sectioned rat epididymis, was also imaged by the new photoelectron microscope. Good contrast was obtained in these initial low magnification experiments. These data demonstrate the feasibility of mapping biological surfaces according to differences in ionization potentials of exposed molecules. A number of technical difficulties, such as the intensity of the excitation source, must be solved before high resolution experiments are practical. However, it is probable that this approach can be useful, even at low magnifications, in determination of the properties of organic and biological surfaces.

Acridines↗