LMW heparin fractions obtained from various sources must not be considered as bioequivalent in both the in vitro and in vivo responses. Because of compositional variations, these agents exhibit individual behavior and should be considered as distinct drugs whose safety and efficacy profile must be determined separately. Currently, there is no valid LMW heparin standard available, however, different LMW heparins can be profiled in identical test systems. It is erroneous to assume that most LMW heparins will behave in a similar fashion in terms of safety and efficacy. The need for defined tests to characterized these agents is evident and efforts to profile their actions should be made at both the basic and applied levels. Needless to say, the true efficacy of LMW heparins can only be validated in well-designed randomized clinical trials. Optimization of LMW heparins in preclinical pharmacologic studies, as reported here, is a crucial factor in the development of these agents. The superior clinical efficacy/safety performance of some of the LMW heparins in contrast to other LMW heparins is a result of extensive preclinical pharmacologic investigations undertaken to optimize the therapeutic index of these agents. Such optimization studies have not been conducted during the development of many LMW heparins, resulting in decreased efficacy and undue complications.

The effects of pulsed direct current electrofishing on mortality of and injury to largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, bluegill Lepomis macrochirus, and pumpkinseed L. gibbosus were examined. The pulse frequencies were 30, 60, and 120 Hz, and conductivity categories of 122–214, 456–683, and 752–789 μS/cm were used. Three independent collections were made with nine different combinations of pulse frequency and range of conductivity. Fish were placed in holding pens for 72 h; dead fish were removed and autopsied immediately. Internal hemorrhages were documented by dissection; potential skeletal damage was determined by radiography. After 72 h, one‐fourth of the caged fish were sacrificed and examined for internal hemorrhages. Of 454 largemouth bass collected, 6 died (1.3%) and another suffered external injury. Of 145 smallmouth bass, 1 died (0.7%) and another 5 (3.4%) exhibited external injuries. Of 568 bluegills, 30 died (5.3%). Fifty‐five pumpkinseeds were examined and none died or were injured. Pulsed direct current electrofishing did not cause high mortality; none of the X‐rayed fish exhibited skeletal damage. Mortality appeared to be caused by hemorrhages of the dorsal aorta and other nearby blood vessels in the caudal area.

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