ABSTRACT
Bioinsecticides from Bacillus thuringiensis (Bt) are widely used around the world in biological control against larval stages of many insect species. Bt has been considered a biopesticide that is highly specific to different orders of insects, non-polluting and harmless to humans and other vertebrates, thus becoming a viable alternative for combating agricultural pests and insect vectors of diseases. The family of Bt δ-endotoxins are crystal-protein inclusions showing toxicity to insects' midgut, causing cell lysis leading to starvation, septicemia and death. The aim of this study is to evaluate the genotoxic potential of recombinant Bt spore-crystals expressing Cry1Ia, Cry10Aa and Cry1Ba6 on peripheral erythrocyte cells of Oreochromis niloticus, through comet assay, micronucleus (MN) test and nuclear abnormalities (NA) analysis. Fish (n = 10/group) were exposed for 96 h at 10(7) spores 30 l(-1), 10(8) spores 30 l(-1) or 10(9) spores 30 l(-1) of Bt spore-crystals. Cry1Ia showed a significant increase in comet cells at levels 1 and 2, but not at levels 3 and 4, so it was not mutagenic nor did it induce MN or NA. These three spore-crystals showed some fish toxicity at only the highest exposure level, which normally does not occur in the field.
Subject(s)
Bacterial Proteins/toxicity , Cichlids , DNA Damage , Endotoxins/toxicity , Hemolysin Proteins/toxicity , Animals , Bacillus thuringiensis/chemistry , Bacillus thuringiensis Toxins , Cloning, Molecular , Comet Assay , Larva/drug effects , Larva/growth & development , Pest Control, Biological/methods , Pesticides/toxicity , Recombinant Proteins/toxicity , Spores, BacterialABSTRACT
The experiments were performed on dogs with isolated pouches (according to Pavlov, Heidenhain and Gregory) to study the action of antidiuretic hormone (ADH) on gastric secretion produced by a food irritant (100 g of meat) and by administration of histamine and pentagastrin. ADH was shown to exert an inhibitory action on gastric secretion induced by food or humoral irritants in dogs with isolated pouches according to Pavlov and Heidenhain. In dogs with completely denervated isolated pouches, food irritant-induced gastric secretion was suppressed for 2 1/2--3 1/2 h. Then it exceeded the control level. During ADH administration the total acidity and the content of free hydrochloric acid noticeably decreased as compared to control. There was also a clear-cut tendency to a reduction in the concentration of common proteinases in gastric juice. Adrenoblockers abolished the inhibitor action of ADH on gastric secretion produced by food or humoral irritants, while the inhibitory action of fat was not reversed by phentolamine or obsidan. The data obtained indicate a different mechanism of the inhibitory effect of fat and ADH on gastric secretion.
Subject(s)
Dietary Fats/pharmacology , Gastric Mucosa/metabolism , Vasopressins/pharmacology , Animals , Depression, Chemical , Dogs , Dose-Response Relationship, Drug , Gastric Acidity Determination , Gastric Juice/metabolism , Gastric Mucosa/drug effectsABSTRACT
On the ground of an investigation on dogs with different types of isolated stomachs a characteristics of peculiarities of the action on the gastric secretion by three dissimilar fats is given, viz. butter, sunflower and corn oils. The investigated fats differ considerably by the lengthy inhibition of the gastric secretion produced by meat, and to a still greater degree by the intensity of the 2nd phase of secretion (after inhibition). It is also shown that with a complete extramural denervation of the isolated stomach (after Gregory) the inhibitory action of fats remains to be strongly marked. However, in this case after the period of inhibition, in the 2nd phase a significantly reduced secretion of the gastric juice is observed.