Biomedical subjects

M A Dawson

Publications and source records attributed to M A Dawson.

13 recordsLinked to original sources

PubMed1998

Comparison of two flow cytometric methods enumerating CD4 T cells and CD8 T cells.

The enumeration of blood CD4+ (single-positive) T cells by flow cytometry is subject to errors such as counting CD4+ monocytes or CD4+CD8+ (double-positive) T cells as CD4+ T cells. Relatively accurate count can be obtained when CD4+ T cells are defined as CD3+CD4+CD8- mononuclear cells (MNCs), using 3-color flow cytometry. However, using this approach, further classification into CD4+ T cell subsets requires expensive 4-color flow cytometry. In an attempt to enumerate CD4+ T cells using only 2 colors, we have defined CD4+ T cells as MNCs expressing CD4 and not expressing the markers of other MNCs (CD8, CD13, CD14, and CD16) and compared the results to those obtained with the 3-color method in which CD4+ T cells were defined as CD3+CD4+CD8- MNCs. Both methods produced similar results. An analogous approach was undertaken to enumerate CD8+ T cells as MNCs expressing CD8 and not expressing the markers of other MNCs. However, when compared with the percents obtained by the 3-color method in which CD8+ T cells were defmed as CD3+CD4-CD8+ MNCs, the 2-color method overestimated the percent of CD8+ T cells. This was likely due to counting CD8low null cells as CD8+ T cells. When the percentages of CD8high T cells were evaluated, both methods produced similar results. We conclude that the 2-color method is suitable for the enumeration of CD4+ T cells and CD8high T cells and reserves the third color for further enumeration of CD4+ or CD8high T cell subsets.

Adult↗

PubMed1993

Interaction of structurally similar pesticides with organic anion transport by primary cultures of winter flounder renal proximal tubule.

We assessed the interaction of several pesticides with renal organic anion transport based on inhibition of the active transepithelial transport of p-aminohippuric acid ([3H]PAH) by primary cultures of winter flounder proximal tubules. Four structurally similar chlorophenoxy acid herbicides were tested. 2-Methyl-4-chlorophenoxyacetic acid at 0.1 mM had no effect on PAH transport. 2-(2,4-Dichlorophenoxy)propionic acid, 2-(2-methyl,4-chlorophenoxy)propionic acid and 2,4-dichlorophenoxyacetic acid inhibited PAH secretion with IC50 values (median inhibitory concentrations) of 0.09, 0.2 and 0.2 mM, respectively. At 2-(2-methyl,4-chlorophenoxy)propionic acid concentrations of 10(-7) to 10(-6) M, PAH secretion was stimulated to 132 and 139% of controls, respectively, at 2 hr. 2,2-bis-p-Chlorophenylacetic acid was tested at concentrations of 10(-7) to 10(-3) M and inhibited with an IC50 of 0.02 mM. At 10(-7) M 2,2-bis-p-chlorophenylacetic acid, a delayed increase was again seen in which PAH secretion increased to 154% of control at 2 hr. The anticholinesterase insecticide phosphothioic acid O,O-diethyl-O-(3,5,6-trichloro-2-pyridinyl ester), its more active metabolite O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)phosphate and its dimethyl analog, phosphothioic acid O,O-dimethyl-O-(3,5,6-trichloro-2-pyridinyl ester) were tested at 0.1 mM. Phosphothioic acid O,O-diethyl-O-(3,5,6-trichloro-2-pyridinyl ester) increased PAH secretion significantly to 115% of control whereas the O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)phosphate inhibited by 28%.(ABSTRACT TRUNCATED AT 250 WORDS)

2,4-Dichlorophenoxyacetic Acid↗

PubMed1990

Organic anion secretion by winter flounder renal proximal tubule primary monolayer cultures.

Recent models of para-aminohippuric acid (PAH) transport by renal proximal tubule have been deduced from isolated membrane vesicles and stopped flow microperfusion. The flounder proximal tubule primary monlayer cultures mounted in Ussing chambers have provided a means to examine the relationship of these models to transepithelial transport. Unidirectional transepithelial 3H-PAH fluxes were determined in 12-day-old monolayers on floating collagen gels under continuously short-circuited conditions. The kinetic values of PAH secretory flux were complex. Over the range of 0.6 microM to 1.5 mM the K1/2 was 0.4 mM and Vmax was 80 nmol/cm2/h. Reabsorptive flux did not saturate. 1 mM probenecid inhibited 95% of the secretory flux (0.07 +/- 0.18 compared with control of 1.38 +/- 0.34 nmol/cm2/h at 10 microM PAH) and had no significant effect on reabsorptive flux (probenecid, 0.07 +/- 0.04; control, 0.05 +/- 0.01 nmol/cm2/h). 0.1 mM 4-acetamido-4'-isothiocyanalostilbene-2,2'-diasulfonic acid and 1 mM benzoylpropionic acid also significantly inhibited secretory flux (95 and 78%, respectively). These inhibitors appeared to be specific in that no effects on transepithelial potential difference, resistance or phlorizin-sensitive current were seen. Removal of Na during flux measurement reduced net PAH secretion to zero, and 1 mM ouabain reduced PAH secretory flux to 10% of control within 90 min with no effect on reabsorptive (leak) flux. Clamping transepithelial voltage to +/- 10 mV had no significant effect on PAH fluxes. Addition of glutarate to flounder saline significantly inhibited PAH secretory flux starting at 0.1 mM and caused 90% inhibition at 1 mM; no stimulation of transport was noted at any glutarate concentration.

Animals↗

PubMed1975

Field studies on ozone inactivation of a Gymnodinium breve toxin.

Water samples were collected from Boca Ciega Bay (St. Petersburg) during the April, 1974, red tide that occurred on the Florida west coast. The causative agent of this phenomenon was the toxic dinoflagellate, Gymnodinium breve. The toxic red tide samples were treated with ozone gas and rendered nonlethal, as measured by mouse injection.

Animals↗

PubMed1973