Biomedical subjects

J M Shackleford

Publications and source records attributed to J M Shackleford.

At least 19 recordsLinked to original sources

PubMed1987

Application of the fiber-optic perfusion fluorometer to absorption and exsorption studies in hairless mouse skin.

This study was undertaken to test the fiber-optic perfusion fluorometer as a direct means of evaluating skin absorption and exsorption in hairless mice. Skin-barrier compromise was accomplished in the absorption experiments by application of dimethyl sulfoxide to the skin surface or by partial removal of the stratum corneum with sticky tape. Absorbed fluorescein was measured easily in unanesthetized control (skin-barrier intact) and experimental mice. Unabsorbed chemical did not fluoresce 15 minutes after application, although it was present on the surface of the skin as a dry powder. The time course of fluorescein elimination from the skin was related to a rapid phase (vascular removal) and a slow phase (reservoir entrapment). In the exsorption experiments the fluorescein was injected intraperitoneally. Back skin on the right side was swabbed with either dimethyl sulfoxide or 1% capsaicin in alcohol prior to the injections, and differences in skin fluorescence on the left (control) and right sides were recorded. One application of dimethyl sulfoxide or capsaicin increased the level of skin exsorption. Three applications of dimethyl sulfoxide almost doubled the amount of exsorbed dye, whereas three applications of the capsaicin inhibited the exsorption process. It was concluded that the fiber-optic perfusion fluorometer provides an excellent technique in support of other methods of investigating the skin.

Absorption↗

PubMed1984

Observations on epidermal exsorption in mice following injections of procion dyes and ethidium bromide and topically applied dimethyl sulfoxide.

Back skin of hairless mice and external ears of CD-1 white mice were used to study the details of epidermal exsorption . Ethidium bromide, a DNA ligand, and two dichlorotriazinyl (procion) dyes were injected, i.v. or i.p. Migration patterns from the skin vasculature into the epidermis were observed by fluorescence microscopy and microspectrofluorometry . Topically applied DMSO greatly enhanced the exsorption process and produced intensely labeled epidermis. Ethidium bromide reacted primarily with nuclear DNA of living cells while the procion dyes tended to migrate intercellularly to label the stratum corneum. External ears of white mice treated topically with DMSO showed a pattern of labeling which included intense fluorescence of the cartilage and perichondrium as well as the ear epidermis.

Administration, Topical↗

PubMed1984

Ultrastructural studies of barrier restoration in epidermis of hairless mice following dimethyl sulfoxide application.

Sixteen hairless mice were studied by transmission electron microscopy to determine the ultrastructural changes in epidermal barrier restoration following topical applications of dimethyl sulfoxide (DMSO) to back skin. Samples of experimental skin were examined at 30 min, 1 h, 2 h and 3 h after the initial DMSO treatment and compared with that of control animals. At earlier time periods (30 min-1 h) the DMSO treated epidermis showed greatly expanded intercellular spaces, disrupted desmosomal attachments, and desmosomal remnants lying free within the intercellular space. Mitochondria contained droplets of lipoid material which reached maximum size in the spinous and granular layers. Cytoplasmic vacuoles were particularly prominent in the 30-min samples. Large numbers of membrane coating granules (MCG) emerged in the 1 h specimens. The MCG were laden with numerous electron-dense inner membranes which crisscrossed at various angles. Many of the MCG were observed in the process of fusion with plasma membranes of granular cells adjacent to the stratum corneum. At 2 h a process of recovery from the effects of DMSO was evident and at 3 h there was little or no difference between experimental and control epidermis.

Animals↗

PubMed1983

Facilities.

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Alabama↗

PubMed1982

Histochemical applications of two phenanthridinium compounds.

The fluorescent compounds ethidium monoazide and ethidium bromide were found to react intensely with nucleic acids of fixed, paraffin embedded tissues of rat and mouse. For routine staining, 10(-5) M solutions of ethidium bromide and its monoazide analogue were virtually identical in their reactions. Fresh frozen sections of the tissues reacted in the same manner as fixed, paraffin embedded samples. Fluorescence of DNA and RNA in rat pancreas could be selectively abolished by taking advantage of the greater sensitivity of RNA to acid hydrolysis. Hydrolysis in aqueous solutions (1 N HCl at 55-60 C) abolished RNA fluorescence in 5 min, whereas 20 min or longer were required to destroy DNA fluorescence. DNA fluorescence was selectively abolished by 3 hr in 0.1 N HCl in anhydrous methanol while the RNA remained unaffected. Rat pancreas stained with the 10(-5) M ethidium compounds below pH 5.0 showed reduced RNA fluorescence, but the DNA continued to fluoresce brightly at pH 0.6. Reducing the pH of the staining solution to pH 1.0, therefore, was an additional method of selectively abolishing RNA fluorescence. Ethidium solutions in 5.0 M NaCl at pH 5.0 had little effect on DNA or RNA fluorescence. This new method of examining nucleic acids in fixed tissue samples opens new approaches to the histochemistry of these substances. The method also offers new possibilities for the study of mutagenic drug-DNA interactions.

Animals↗

PubMed1978

Sexual differences among duodenal glands of hamster.

This histochemical study was undertaken to determine whether sexual differences existed in the duodenal glands of hamster. Alcian blue staining and atomic absorption spectrophotometry (for copper content of the bound Alcian blue) showed the duodenal glands of males to contain about double the acid mucosubstance of the female glands. Periodic acid Schiff staining was stronger in the females over a larger portion of the gland than in males. It was concluded that sexual differences were evident in duodenal glands of hamster.

Animals↗

PubMed1973