Biomedical subjects

K J Stelzer

Publications and source records attributed to K J Stelzer.

40 records · Page 3Linked to original sources

PubMed1984

Effects of pyrethroids on lymphocyte membrane lipid packing order.

The effects of pyrethroids on the membrane lipid packing order of murine splenic lymphocytes have been investigated by utilizing the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Fluorescence anisotropy and lifetime measurements indicated alterations in the environment of the probe at pyrethroid concentrations near 1 microM. Decreased packing order of membrane lipids was detected for permethrin and cypermethrin by decreased anisotropy values. Permethrin and cypermethrin decreased fluorescence lifetime over a concentration range similar to that causing anisotropy changes. Anisotropy was predominantly increased in the presence of fluvalinate and fenpropathrin, indicating pronounced quenching of fluorescence by these compounds. However, the anisotropy changes in response to fluvalinate and fenpropathrin occurred at concentrations which were similar to effective concentrations of permethrin and cypermethrin. Compared to the other pyrethroids tested, allethrin required approximately 10 fold higher concentrations to alter anisotropy and lifetime values. Effects of pyrethroids on the phase transition of dipalmitoyl phosphatidylcholine liposomes were also studied to give further insight into the membrane interactions of these compounds. Results from the liposomal system indicate that the effects of pyrethroids on membrane order which were observed in the lymphocyte may be generalizable to other cell types.

Allethrins↗

PubMed1984

Effects of pyrethroids on lymphocyte mitogenic responsiveness.

The in vitro effects of pyrethroids on the mitogenic responsiveness of murine splenic lymphocytes to concanavalin A (Con A) and lipopolysaccharide (LPS) have been determined. Mitogenic stimulation was measured by uptake of [6-3H]-thymidine. Permethrin and cypermethrin inhibited the mitogenic response to Con A over a concentration range of 1 X 10(-5) M to 5 X 10(-5) M. Relative to these pyrethroids, slightly lower concentrations of fenpropathrin were required to inhibit mitogenic responsiveness to Con A. Fluvalinate was least effective of the pyrethroids tested, and caused mitogenic inhibition at concentrations of 1.5 X 10(-5) M to 5 X 10(-5) M. Unlike the other pyrethroids, concentrations of fluvalinate as high as 1 X 10(-4) M did not result in complete inhibition of the mitogenic response to Con A. Allethrin, was the most potent inhibitor, with effective concentrations in the range of 1 X 10(-6) M to 1.5 X 10(-5) M. Permethrin (3 X 10(-5) M) inhibited the mitogenic response at each of several concentrations of Con A tested, and did not cause a shift in the lymphocyte mitogenic dose-response to Con A. The mitogenic responsiveness to LPS was found to be inhibited by allethrin and permethrin at the same concentrations which inhibited the mitogenesis induced by Con A. The results support the possibility of immune suppression by pyrethroid exposure.

Allethrins↗

PubMed1983

Cadmium-induced immunotoxicity.

This study assessed the effects of cadmium on functional lymphopoietic precursor cells and cell size in both spleen and bone marrow. Splenic plaque-forming cell (S-PFC) precursors were stimulated by a thymus independent immunogen (TNP-LPS) and by a thymus dependent immunogen (TNP-BSA plus dextran sulfate). Bone marrow plaque-forming cell (M-PFC) precursors were stimulated by TNP-LPS plus dextran sulfate. Male C57Bl/6J mice received either a single ip injection of 5.9 mg/kg CdCl2, and were sacrificed 3 days later (ip group), or 5 daily sc injections of 3.26 mg/kg CdCl2, and were sacrificed either 2 days later (7 day sc group) or 7 days later (12 day sc group). The ip group showed an increase in spleen cellularity which resulted in an enhanced S-PFC (TNP-LPS) response per spleen and compensated for a depressed S-PFC (TNP-BSA) response per 10(6) cells cultured. Bone marrow cellularity was not significantly decreased but the M-PFC response was drastically depressed. Similar results were obtained in the 7 day sc group. However, a significant increase in spleen cellularity was not seen, resulting in a noncompensated decrease in S-PFC (TNP-BSA) response. The S-PFC (TNP-LPS) response per 10(6) cells cultured was increased in this group. Responses were similar to controls in the 12 day sc group, but bone marrow cellularity was decreased. The ip and 7 day sc groups showed substantial cadmium-induced shifts in bone marrow cell size distribution profile to larger diameters. Changes in spleen cell size distribution were not as significant. Partial recovery was evident in the 12 day sc group. This study demonstrated that in vivo exposure to cadmium has a greater effect on the in vitro function of immature B-cells in the bone marrow than on more mature B-cells found in the spleen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Digital radiotherapy simulator.

We describe a prototype digital radiotherapy simulator which consists of a conventional simulator gantry, digital spot imager, and image correction and reconstruction software. The ability of the digital spot imager to acquire a diagnostic quality image directly in digital format during simulation offers unique possibilities in clinical practice. Applications include prescription of multileaf collimator, on-line patient setup verification, remote consultation and treatment planning. In addition, we discuss the possibility of using the digital simulator as a volume-CT scanner capable of obtaining three-dimensional anatomical information in a single scan.

Computer Simulation↗