Ionic materials in solution do not penetrate the skin following local (topical) application. Such a low permeability can, however, be altered by iontophoresis. Utilization of transmission and scanning electron microscopy and cryostat techniques has made it possible to demonstrate the penetration and site of deposition of ionic tracers in the skin of the rat. It has been found that the penetration of cationic dyes and metal cations is facilitated by positive iontophoresis while the penetration of anionic dyes is facilitated by negative iontophoresis. The extent of penetration is determined by the current density, the concentration of the tracer in the vehicle, the physico-chemical properties of the tracers and the type of vehicle used. The removal of surface lipid is regarded as insignificant in terms of enhancing the penetration of tracers by iontophoresis. It has been found that the penetration of ionic tracers into the skin is preferentially transfollicular. However, the penetration of electron-dense tracers into the stratum corneum of the epidermis and the follicular infundibula is preferentially intercellular, while that into the sebaceous glands is transcellular. It is considered that the whole of the stratum corneum of the epidermis is the major barrier to cutaneous penetration by electrolytes. In addition, a barrier function is suggested for sebum situated in the follicular infundibula.

Bean plants were grown in a phosphate-free nutrient solution to the early trifoliate stage. At this time, they were transferred to a minus phosphate nutrient solution containing 100 p.p.m. 3-amino-1,2,4-triazole for 48 hours, and then placed into a labelled phosphate nutrient solution for another hour. The plants were then returned to a phosphate-free nutrient solution and harvested one, 24, 48, and 96 hours after the period of initial phosphate uptake. AT-treatment did not affect uptake of P³² but did decrease loss of P³² to the phosphate-free nutrient solutions after it had been absorbed by the plants. The proportion of absorbed phosphate found in the stems and leaves of AT-treated plants was higher than in these organs in the control plants. This phosphate represented an increase in both acid-soluble activity and acid-insoluble activity. The accumulation of acid-soluble activity in the shoots of AT-treated plants was an accumulation of inorganic phosphates, sugar phosphates, and nucleotides. AT appeared to inhibit downward translocation of acid-soluble and acid-insoluble activity. The incorporation of P³² into esterified compounds (i.e., nucleotides and sugar phosphates) was unaffected by AT indicating that AT does not interfere with oxidative phosphorylation nor with glycolysis. However, AT did inhibit transfer of P³² from the acid-soluble fraction to the acid-insoluble fraction. Therefore, the principal effect of AT is to inhibit the incorporation of phosphate into one or more of the nucleic acid, phospholipid, or phosphoprotein fractions. / Science, Faculty of / Botany, Department of / Graduate

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis supervisor: Alan R. Kay. Includes bibliographic references (p. 157-173).

Thesis (Ph.D.) -- University of Western Sydney, 2004. / Includes bibliography.

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

A thesis submitted to the faculty of Engineering, University of the Witwatersrand, Johannesburg , in fulfillment of the requirements for the degree of Doctor of Philosophy. Johannesburg, November 1994 / Organ function is often characterised using imaging techniques. In particular a tracer is often used which does not react with tissue, is low in concentration, follows body fluid flows and is distinguishable from the observed system and thus measurable. These requirements ensure linear characteristics of the tracer. In this thesis, these linear characteristics are used to develop a generalised mathematical theory to determine organ function from imaged tracer experiments. The theory is based on anatomical and physiological information for single and multiple input organs. [Abbreviated Abstract. Open document to view full version] / MT2018