Avian, biological effects

The relationship between incidence of lead shot in waterfowl gizzards and biological effects varies widely and is probably a function of shot availability caused by differences in shooting intensity, size of pellets, availability of grit, firmness of soil and sediments, and depth of surface water (Street 1983). Also, lead accumulations and the frequency of avian lead toxicosis following... 

Fig. 6.2 Biological effects of IPG from different sources on otic vesicle and cochleovestib-ular ganglion. (A) Purified IPG mimicked the effects of IGF-I on Jun expression and could be involved in the mechanism that triggers proliferation in response to insulin and IGF-I during early organogenesis of the avian inner ear. C3, synthetic analogue of IPG a-IPG, anti-IPG antibody. Scale bar, 125 pm. Reprinted with permission from Ref. [11] ...

Several lab studies have examined effects from single metal exposure to birds. Eggs from adults dosed with arsenic have been examined for accumulation and effects 109). Eggs have been dosed with lead followed by embryo examination for effects 101). Although Beyer et al. 42) did not examine multiple metals, they did examine the uptake and biological effects of six avian species dosed with lead. The dose dependent distributions and effects of lead, selenium and cadmium have been examined in several species 72, 98, 110). Scheiihammer 83) reviews numerous studies examining chronic toxicity of several metals. 

The biological targets of paralytic conotoxins are presumably ion channels and receptors in the fish neuromuscular system. Amphibian, avian, and mammalian systems may also be affected by a -, a-, and x-conotoxins. However, specific conotoxins vary in their phylogenetic spectrum and detailed physiological effects in vivo. 

The ubiquitous nature of metals from both natural and anthropogenic sources combined with their necessity in biological processes produce a complex system for study. Metal distributions in abiotic and biotic systems must be examined to accurately assess impact on ecosystems. Wildlife studies of exposure and effect can be challenging, but the results are more complete than evaluation of only metal concentrations. Birds are good sentinel species because they visible, sensitive to toxins, and occupy different trophic positions. Therefore, studies to assess avian population status, reproductive success, and toxicological significance of metal exposures can be extrapolated to other wildlife and possibly humans. 

Several workers have tried to ascertain the effects of mammalian sialidase action on endogenous substrates. Studies of the effects of soluble microbial sialidases on cell-surface properties and on the activities of sialocompounds have been performed in order to try to determine, by analogy, the role of mammalian sialidase. This part of the chapter will summarize what is known about mammalian, and where possible, avian sialidase and will suggest biological roles for the enzyme. 

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