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Biomedical subjects

J E Simons

Publications and source records attributed to J E Simons.

3 recordsLinked to original sources

Steam sterilization of laparoscopic instruments.

Because of the intricate internal parts of laparoscopic instruments, questions have been raised about the efficacy of cleaning and sterilization techniques. To assess these risks, hamburger meat was inoculated with high concentrations of vegetative pathogens and packed into laparoscopic cannulas. All openings of the cannulas were sealed during steam sterilization cycles ranging from 3 to 10 min in different experiments; cultures were obtained after cooling. Experiments were then performed using heat-resistant spore forms. Our studies showed that both the standard 10-min cycle and the 3-min "flash" were uniformly successful in killing all pathogenic microorganisms. A 7-min steam sterilization was necessary to kill spores within sealed cannulas. We conclude that a standard 10-min cycle within the steam autoclave provides complete sterilization of laparoscopic instruments; the 3-min "flash" sterilization is appropriate and safe for instruments that have been inadvertently contaminated or dropped during a surgical procedure.

Equipment Contamination↗

Volumetric sampling strategies for heterogeneous brainstem nuclei.

Many brainstem nuclei are heterogeneous structures in which neuronal and glial populations are unevenly distributed, and focal normal or pathologic deviations in cell density, so-called "features," are found. Examples of features include subnuclei, focal neuronal loss, and focal gliosis. We present a statistical test that justifies an investigator's claim that a feature is present in a nucleus at a selected level of confidence after completion of a cell counting experiment. The computer program developed for the test also indicates the most probable location of the feature within the nucleus, and its most probable density and length, and potentially allows one to make comparisons of feature characteristics among cases. We also present quantitative guidelines for the selection of a sampling periodicity in a heterogeneous nucleus before a cell counting experiment. Sampling periodicity is based upon analysis of computer-generated simulations of the nucleus with features of different sizes; for each feature the probability of Type I (false positives) and Type II (false negatives) errors are examined against one another. Type II error rate is dependent upon feature length and density, acceptable Type I error rate, and sampling periodicity. Feature detection is important for devising sampling strategies in brainstem nuclei.

Astrocytes↗

Vascularized versus nonvascularized nerve grafts: an experimental structural comparison.

This study compared the success of nerve regeneration through conventional nonvascularized and vascularized nerve grafts in the sciatic nerve of rats. The number or size of regenerated axons between the two grafts was not significantly different. In addition, the ratio of axonal diameter to total diameter of the nerve, a measurement linearly related to conduction velocity, was not significantly different in the two groups. Thicker myelin sheaths were found around axons in the nonvascularized nerve grafts.

Animals↗