Livestock ingest numerous potentially toxic compounds, including natural plant and fungal metabolites, insect chemical defenses, human-made environmental pollutants, and therapeutic drugs. In turn, animals evolved physiological mechanisms to protect themselves from these ingested toxins. Enzymes have been described that first activate toxins cytochrome P-450 and then conjugate the compounds (gl...

Plants have evolved complex biochemical mechanisms to counter threats from insect herbivory. Recent research has revealed an important role of roots in plant responses to above ground herbivory (AGH). The involvement of roots is integral to plant resistance and tolerance mechanisms. Roots not only play an active role in plant defenses by acting as sites for biosynthesis of various toxins and bu...

After weaning, groups of rats were fed a semi-purified diet containing fiddlehead greens (the unfuried frond of the ostrich fern Matteuccia struthiopteris), mature bracken fern (Pteridium aquilinum), or cycad meal (Cycas circinalis), or this diet plus aflatoxin B1. The groups fed 1-10% fiddlehead greens for 70-73 weeks developed no tumors, whereas those fed mature bracken fern for 67 weeks deve...

Host-specific toxins from Helminthosporium victoriae (HV) and Periconia circinata (PC) caused gradual decreases in the negative electropotentials of single cells of susceptible but not of resistant plants. When tissues were held in a standard nutrient solution, the decrease (depolarization) induced by HV toxin was approximately 50 mv/hr; the decrease induced by PC toxin was even more gradual. C...

The intoxication of livestock from ingested feed contaminated with naturally occurring toxicants is of great economic importance. Certain toxicants require enzymatic bioactivation before harmful effects are exhibited. In the liver, the cytochrome P-450 dependent mixed function oxidase (MFO) system normally metabolizes foreign compounds (xenobiotics) into more polar, more excretable and less tox...

Introduction Various herbivorous insects prefer toxic plants as their hosts, although this may appear paradoxical. They have evolved specific adaptations (called counter-defenses) against the toxins. For example, two-component chemical defense system of Brassicaceae family herbivores consists glucosinolates (GLSs) and activating enzyme myrosinase. GLS hydrolysis by myrosinase leads to isothiocy...

Lepidopteran types of podborer and homopteran aphid insects are damaging pests of chickpea. CryIAc toxins are established control agents for podborers but do not or only slightly affect homopteran (sucking) insects. However, certain plant lectins are known for their power of killing aphids. Bioassay experiments carried out in our laboratory with lectins isolated from garlic leaves have already ...

Herbivores regularly ingest natural toxins produced by plants as a defence against herbivory. Recent work suggests that compound toxicity is exacerbated at higher ambient temperatures. This phenomenon, known as temperature-dependent toxicity (TDT), is the likely result of decreased liver function at warmer temperatures; however, the underlying cause of TDT remains speculative. In the present st...

Under continual exposure to naturally occurring plant toxins and synthetic insecticides, insects have evolved cytochrome P450 monooxygenases (P450s) capable of metabolizing a wide range of structurally different compounds. Two such P450s, CYP6B8 and CYP321A1, expressed in Helicoverpa zea (a lepidopteran) in response to plant allelochemicals and plant signaling molecules metabolize these compoun...

Insect resistance to plant toxins is widely assumed to have evolved in response to using defended plants as a dietary resource. We tested this hypothesis in the milkweed butterflies (Danaini) which have progressively evolved higher levels of resistance to cardenolide toxins based on amino acid substitutions of their cellular sodium-potassium pump (Na(+)/K(+)-ATPase). Using chemical, physiologic...