Clinical utility of intraoperative frozen section diagnosis in head and neck surgery: a quality assurance perspective

The technical and professional issues that affect the clinical utility of intraoperative frozen section diagnosis in head and neck surgery are addressed from a quality assurance perspective. The most common reasons for sampling errors and interpretive errors are discussed. We offer several recommendations for head and neck surgeons and pathologists which will optimize the clinical utility of intraoperative frozen section consultation.     

Influence of carrier-specific, thymus-derived cells on the immunologlobulin M antibody response to staphylococcal lipoteichoic acid

The immunoglobulin M antibody response to the lipoteichoic acid (LTA) of Staphylococcus aureus ATCC 6538P was examined by a procedure in which erythrocytes sensitized with periodate-activated LTA were used for the detection of immunoglobulin M-producing plaque-forming cells LTA-specific plaque-forming cells were first detected 2 days after immunization with heat-killed bacterial cells, and maximal numbers of plaque-forming cells, mostly of the immunoglobulin M class rather than the immunoblogulin G or immunoglobulin A class, were attained by day 4; specificity for LTA was affirmed by plaque inhibition tests. No plaque-forming cells were found in mice given isolated LTA over a 10,000-fold range of immunizing doses. Mice pretreated with a carrier known to activate thymus-derived helper lymphocytes produced a plaque-forming cell response to LTA only when immunized with LTA bound to the same carrier. This suggests that carrier-specific thymus-derived cells are needed to initiate an antibody response to poorly immunogenic LTA. Since an antibody response can be elicited in mice given heat-killed cells, other cell wall and/or cell membrane constituents may play an important role as immunologically active carriers for this antigen.     

The Analysis of a Class of Non-Series Parallel Redundant Systems

Two analysis techniques for use in the study of a class of non-series parallel, dual channel systems are presented. The first technique is a method for obtaining an approximate solution for the system. It is based on a systematic analysis of first- and second-order failure modes and involves the use of matrix algebra. The second technique is a method for generating the exact solution from the approximate solution. This method involves a transformation which converts the system into a logically equivalent system. An exact solution for the transformed system is derived and is shown to be the exact solution for the original system.