Ultrafiltration as a means to eliminate inhibition of the Limulus Amoebocyte Lysate (LAL) assay.

Inhibition of the Limulus Amoebocyte Lysate (LAL) assay for the detection of endotoxin is often a problem when testing parenteral solutions with actual concentrations of chemical substances. Seven samples of sterile, pyrogen-free solutions widely used in Norwegian hospitals, with inhibiting effect on the LAL test, were spiked with endotoxin, and ultrafiltered with different volumes of diluent. For six of the seven samples the inhibition was reduced or eliminated.

Toxicity testing of medical device materials tested in human tissue cultures.

Rubber and plastic parts of medical devices were applied to human cell monolayers either directly or as aqueous extracts made at different time/temperature conditions. Thirteen rubber and twelve plastic samples were tested. The cultures were observed and photographed by use of a microscope with a camera before and after treatment with the test materials. The toxicity of the specimens was evaluated by comparison of the photographs. Alterations or disappearance of the cells or inhibited growth were interpreted as toxic effects of the materials. Twelve of the rubber and six of the plastic samples were evaluated as toxic in one or more of the systems.

Modified micromethod of the Limulus amoebocyte lysate assay for endotoxin.

A Limulus amoebocyte lysate microtechnique performed in petrolatum wells on a microscope slide is described. Injection of a dye solution in ethanol directly into the wells leads to an unambiguous interpretation of the results. Twelve samples can be tested on a single slide, and compact storing of the samples is possible.

Efficacy of the inactivation of bacterial spores in white petrolatum and a hydrophilic ointment by gamma irradiation.

To evaluate the possibilities of using gamma irradiation for the sterilization of ointments, the effect of irradiation on spores of Bacillus pumilus and Bacillus sphaericus in dry material and in two different kinds of ointments was studied. The results indicate that for sterilization purposes irradiation was less effective in white petrolatum as compared to irradiation in the dry state. No such protective effect was found in a hydrophilic ointment. Accordingly, the sterilization dose needed for the sterilization of an ointment can be decided upon only after inactivation experiments with suitable test organisms in the actual preparation.