Birds/bird species metabolism

A distinguishing element of avian physiology is ho-moiothermy, or metabolic activity that maintains the body temperature within a narrow, warm range optimized for muscular functions and enzyme efficiency. (Mammals and some other vertebrates are also warmblooded.) Homoiothermy is a crucial physiological trait that allows almost all bird species to have an extremely active lifestyle. It also allows some species to live year-round in cold environments. 

Methoxychlor is slightly toxic to bird species. Met-hoxychlor is highly toxic to fish and aquatic invertebrates. Methoxychlor accumulates in aquatic organisms because these organisms metabolize methoxychlor very slowly. The compound is relatively nontoxic to bees. 

Only circumstantial evidence is available that supports the supposition that wildlife species are exposed to explosive compounds. Studies conducted at U.S. Army ammunition plants and other areas of known soil contamination have failed to detect body burdens of suspected explosive compounds in mice, deer, and some bird species [4-7] (see Chapter 10 in this book for a more complete review). Given the relatively rapid metabolic potential of many explosives in vivo, the heterogeneous distribution of these substances in the environment, and the potential for bioaccumulation of some nitramines in plants, body burden analysis may not adequately describe exposure potential. Therefore, the data reviewed in this chapter will focus on controlled laboratory toxicity studies conducted to evaluate the effects in wildlife species, many of which were designed for specific risk assessment applications. 

Except for the mouse tissue, in every other case the data showed that the accepted scheme for the metabolic organization and hormonal regulation of the young rat s fat cell had to be revised in one or more major respects. Certain novel features are shared by the fat cells of insects of different species other characteristics are exhibited by fat cells of different bird species and even within the rodent order, taxonomical-ly-correlated metabolic characteristics are emerging. 

The organophosphorons insecticides dimethoate and diazinon are mnch more toxic to insects (e.g., housefly) than they are to the rat or other mammals. A major factor responsible for this is rapid detoxication of the active oxon forms of these insecticides by A-esterases of mammals. Insects in general appear to have no A-esterase activity or, at best, low A-esterase activity (some earlier stndies confnsed A-esterase activity with B-esterase activity) (Walker 1994b). Diazinon also shows marked selectivity between birds and mammals, which has been explained on the gronnds of rapid detoxication by A-esterase in mammals, an activity that is absent from the blood of most species of birds (see Section 23.23). The related OP insecticides pirimiphos methyl and pirimiphos ethyl show similar selectivity between birds and mammals. Pyrethroid insecticides are highly selective between insects and mammals, and this has been attributed to faster metabolic detoxication by mammals and greater sensitivity of target (Na+ channel) in insects. 

Nickel is considered essential to animals because it is present in the fetus or newborn, is homeostatically regulated, the metabolic pool of nickel is specifically influenced by hormonal substances or pathologic processes, certain metalloproteins contain nickel, and because nickel deficiency has been induced experimentally in certain species of birds and animals (NAS 1975 USPHS 1977 Kirchgessner and Schnegg 1980). In general, the nickel deficiency syndrome can be cured or prevented by trace amounts of nickel (NAS 1975). However, nickel administration may not be successful in reversing all abnormalities produced by nickel deprivation (USPHS 1977). 

Pentachlorophenol was most toxic and most rapidly metabolized in aquatic environments at elevated temperatures and reduced pH. Adverse effects on growth, survival, and reproduction of representative sensitive species of aquatic organisms occurred at PCP concentrations of about 8 to 80 pg/L for algae and macrophytes, about 3 to 100 pg/L for invertebrates (especially molluscs), and <1 to 68 pg/L for fishes, especially salmonids. Fatal PCP doses for birds were 380 to 504 mg/kg BW (acute oral), >3850 mg/kg in diets, and >285 mg/kg in nesting materials. Adverse sublethal effects were noted at dietary levels as low as 1.0 mg/kg ration. Residues (mg/kg fresh weight) in birds found dead from PCP poisoning were >11 in brain, >20 in kidney, >46 in liver, and 50 to 100 in egg. 

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