Biomedical subjects

C Cullander

Publications and source records attributed to C Cullander.

24 records · Page 2Linked to original sources

PubMed1994

Diffusion rates and transport pathways of fluorescein isothiocyanate (FITC)-labeled model compounds through buccal epithelium.

The aim of this study was to characterize transport of FITC-labeled dextrans of different molecular weights as model compounds for peptides and proteins through buccal mucosa. The penetration of these dextrans through porcine buccal mucosa (a nonkeratinized epithelium, comparable to human buccal mucosa) was investigated by measuring transbuccal fluxes and by analyzing the distribution of the fluorescent probe in the epithelium, using confocal laser scanning microscopy for visualizing permeation pathways. The results revealed that passage of porcine buccal epithelium by hydrophilic compounds such as the FITC-dextrans is restricted to permeants with a molecular weight lower than 20 kDa. The permeabilities of buccal mucosa for the 4- and 10-kDa FITC-dextran (of the order of 10(-8) cm/sec) were not significantly different from each other or from the much smaller compound FITC. The confocal images of the distribution pattern of FITC-dextrans showed that the paracellular route is the major pathway through buccal epithelium.

Animals↗

PubMed1994

Imaging in the far-red with electronic light microscopy: requirements and limitations.

The acquisition of simultaneous dual confocal images with red and far-red light has both advantages (e.g. lower autofluorescence) and limitations. An understanding of these requisites is necessary to acquire high-quality images and to avoid the misinterpretation of experimental data. The poor detection of far-red light mandates a high optical transfer efficiency for the system, thus the transmittance of the objective lens and its axial and lateral chromatic aberration in the far-red are important factors for consideration. This technical note is an attempt to 'demystify' the process of filter set design for confocal microscopy by discussing the considerations that went into the construction of a filter set for use with the reagents cyanine 3.18 (Cy3) and cyanine 5.18 (Cy5), and thus to encourage users to look beyond the multi-purpose designs available commercially. The 568-nm laser line exciting Cy3 is at its emission maximum, which limits the collectable Cy3 fluorescence. High-transmission optical filters with sharp band pass cutoffs are thus desirable for maximum light throughout. Light path mirror efficiency rapidly degrades above 700 nm, but the loss of this portion of the Cy5 emission spectrum is acceptable since the fluorophore is very bright, and these very long wavelengths are also likely to introduce aberration. While resolution is decreased with far-red light, there is also greater penetration and less scattering, and it is thus possible to obtain high-quality images from deeper within the specimen.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbocyanines↗

PubMed1991

Iontophoretic delivery of amino acids and amino acid derivatives across the skin in vitro.

The effects of penetrant properties (lipophilicity and charge) and of vehicle pH on the iontophoretically enhanced delivery of amino acids and their N-acetylated derivatives have been examined in vitro. The penetrants were nine amino acids (five were zwitterionic, two positively charged, and two negatively charged) and four N-acetylated amino acids, which carry a net negative charge at pH 7.4. Iontophoresis at constant current (0.36 mA/cm2), using Ag/AgCl electrodes, was conducted across freshly excised hairless mouse skin. Iontophoretic flux of the zwitterions was significantly greater than passive transport. Delivery from the anode was greater than from the cathode for all zwitterions. The level of enhancement was inversely proportional to permeant octanol/pH 7.4 buffer distribution coefficient. Cathodal iontophoresis of the negatively charged amino acids and of the N-acetylated derivatives produced degrees of enhancement which were significantly greater than those measured for the "neutral" zwitterions. Furthermore, the enhanced flux reached a steady-state level within a few hours for the negatively charged species, whereas the transport of the zwitterions continued to increase with time. Anodal iontophoresis of histidine and lysine, the two positively charged amino acids studied, induced substantial enhancement which was sensitive to the pH of the delivery vehicle. For example, the flux of histidine from an applied solution at pH 4 (where the amino acid carries a net positive charge) was significantly greater than that from a vehicle at pH 7.4 (where histidine is essentially neutral). The behavior of lysine was more complex and suggested a certain degree of neutralization of the skin's net negative charge.

Administration, Cutaneous↗

PubMed1991

Sites of iontophoretic current flow into the skin: identification and characterization with the vibrating probe electrode.

The routes taken by charged substances (e.g., peptides) through the skin during iontophoretic drug delivery are not well characterized. We have used a vibrating probe electrode to reproducibly identify and vectorize site-specific (spatial resolution = 20 microns) ionic flows as they were occurring in hairless mouse skin clamped at clinically relevant current densities. These iontophoretic currents were primarily appendageal, and certain appendages (e.g., small hairs) appeared to carry most of the current. This finding may have important ramifications with respect to irritation, allergic reaction, and electrical current damage in iontophoretic drug delivery. The size and direction of the current vectors could change under certain conditions (e.g., in an unbuffered preparation, where pH changes occurred during the experiment). The vibrating probe can operate in (and is not adversely affected by) the ranges of pH, tonicity, and current required for the study of iontophoretic currents.

Administration, Cutaneous↗

PubMed1990

Rapid detection of spatial pattern by Fourier analysis.

Fast Fourier transform analysis can be used to accurately and rapidly detect pattern in large two-dimensional arrangements of points, such as the locations of cells in culture or plants in a unit square. We present here a sample study of pattern in spatial random point processes. This is evidently the first time that Fourier transform-based cross-correlation techniques have been applied to the analysis of point processes of biological origin. Radial profiles of the power spectra and autocorrelation estimates revealed a nearly constant interpore distance of 0.49 +/- 0.04 mm in the locations of eccrine gland pores on the surface of human skin. Additionally, gland-free areas may exist near hair follicles.

Algorithms↗

PubMed1988

A new system for in vitro studies of iontophoresis.

This report describes a new iontophoretic diffusion cell that allows both electrodes to be applied to the same side of the same piece of skin. The cell permits a better approximation of the in vivo situation than do conventional side-by-side cells. The unique construction of the cell allows nonliquid material to be applied to the skin surface and makes it possible to investigate horizontal transport paths. Preliminary results utilizing the cell are described. Iontophoretic enhancement of morphine and clonidine delivery across full-thickness hairless mouse skin has been achieved. The importance of pH control in these experiments is apparent. Further experiments with morphine indicate that, for this drug at least, iontophoretically driven lateral transport within the skin is unimportant. Because the cell design allows significant parallels to the use of iontophoresis in vivo, we suggest that it will prove to be a useful tool in the determination of fundamental structure/transport relationships under the influence of an externally applied current.

Animals↗