Scanning electron microscopy (SEM) has occasionally been used by anthropologists and forensic scientists to look at morphological characteristics that certain implements leave on bone. However, few studies have addressed techniques or protocols for assessing quantitative differences between tool marks on bone made by different bladed implements. In this study, the statistical variation in cut mark width was examined between control and test samples on bone using a scalpel blade, paring knife, and kitchen utility knife. Statistically significant differences (p < .0005) were found between cut marks made by the same knife under control and test conditions for all three knife types used in the study. When the control sample and test samples were examined individually for differences in mean variation between knife types, significant differences were also found (p < .0005). While significant differences in cut mark width were found, caution should be used in trying to classify individual cut marks as being inflicted by a particular implement, due to the overlap in cut mark width that exists between different knife types. When combined, both quantitative and qualitative analyses of cut marks should prove to be more useful in trying to identify a suspect weapon. Furthermore, the application of SEM can be particularly useful for assessing many of these features.

Abstract.A protocol for routine 4-hour microwave tissue processing of clinical or other samples for electron microscopy was developed. Specimens are processed by using a temperature-restrictive probe that can be set to automatically cycle the magnetron to maintain any designated temperature restriction (temperature maximum). In addition, specimen processing during fixation is performed in 1.7-ml microcentrifuge tubes followed by subsequent processing in flow-through baskets. Quality control is made possible during each step through the addition of an RS232 port to the microwave, allowing direct connection of the microwave oven to any personal computer. The software provided with the temperature probe enables the user to monitor time and temperature on a real-time basis. Tissue specimens, goat placenta, mouse liver, mouse kidney, and deer esophagus were processed by conventional and microwave techniques in this study. In all instances, the results for the microwave-processed samples were equal to or better than those achieved by routine processing techniques.Microwave irradiation is an excellent method for tent reproducibility and high-quality tissue preparathe preservation of cell structure and immunogenicity tion using microwave technology.3,1 In addition, a newfor electron microscopy (EM) 1,13,14 and for light mi-ly modified 800-watt safety-exhausted microwave a decroscopy (1988, Histochem J 20:311-404; 1990, His-veloped for EM includes features such as programtochem J 22:311-393).9 In addition, the reduction in mability, magnetron prewarming, built-in water feedprocessing time offered by microwave technology pro-throughs for a recirculating water load cooling system, vides an enormous advantage for diagnostic patholo-a 1.6-mm-diameter internal temperature restrictive gy. 4,5,11,12 The rather extensive literature compiled on microwave tissue processing has been recently reprobe, and computer monitoring of temperature and time data (Fig. 1). Coupled with these equipment adviewed. 15 Much work has gone into the understanding vances and a unique tissue processing protocol, miof how microwave energy reacts with various buffers crowave-assisted sample processing makes same-day and fluids employed in the fixation process and how results and reliable control of tissue processing parammicrowaves behave inside the oven itself. 10,15 There eters (time and temperature) possible. are instances where the microwave has been used as a Using the above mentioned protocols and processing substitute for chemical fixation in tissue processing for equipment, we compared transmission EM results ob-EM.2 The use of microwave technology to achieve rap-tained by 4-hour microwave tissue processing versus id tissue processing has received only limited accep-conventional 56-72-hour tissue processing methods. tance in the EM community, probably because of both Duplicate samples of normal goat placenta, mouse livthe lack of a unified protocol offering consistent re-er, and mouse kidney and a postmortem sample of producible results and th...

The use of microwave irradiation for rapid chemical fixation of tissues in electron microscopy is a subject of current interest. The effects of water load size and location, sample placement in the oven cavity (hot or cold spots), and time on tissue preservation were examined. The use of a microwave container (4 dram vial) encased in 60 ml of ice in a 100 ml polyethylene beaker and a 0% power setting between two 100% power settings (time interval) provided reliable control of temperature during microwave irradiation. High brightness neon lights provided a quick and easy method to identify and map hot and cold spots within the oven cavity. Using microwave irradiation for rapid glutaraldehyde and osmium tetroxide fixation of tissues (Pacific yew needle and mouse kidney and liver) for electron microscopy yielded preservation equal or better than routine immersion fixation when a time interval, a cold spot (as the sample location), and an ice-encased vial were used during microwave fixation. These adaptations provided reliable control of fixation conditions in an 800 watt laboratory microwave oven.

One unit (500 ml) of 10% Intralipid (an intravenous soy bean oil-egg yolk lecithin preparation) was infused into 20 normal subjects over 4 hr. Serum triglyceride concentration and plasma optic density (at 700 nm) increased to maximal levels of 339 +/- 102 mg/100 ml and 1.14 +/- 0.41, respectively, at the completion of the infusion, and returned to basal levels in most subjects within 4 hr. Pulmonary membrane diffusion was decreased in six subjects at rest and with exercise at 25 and 50% maximum oxygen uptake. Only one subject showed a minor change in PO2 and none showed clinical signs of ischemia. The changes in pulmonary diffusion reverted to basal levels when serum lipids were cleared. Heparin (60 IU/kg) prevented the marked increase in serum lipids and, as a consequence, the changes in pulmonary function. Changes in pulmonary function from Intralipid-induced lipemia are similar to those known to result from diet-induced lipemia. The findings suggest that in the presence of normal vasculature and pulmonary function, Intralipid-induced lipemia should cause no clinical consequences. However, patients with preexisting pulmonary or vascular disease may be at greater risk after Intralipid-induced lipemia.

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