6-Endotoxin susceptibility

B. thurigiensis is a common Gram-positive, spore-forming soil bacterium that produces inclusion bodies, microcrystalline clusters of many different proteins. These crystalline proteins, called 5-endotoxins, are the ion channel toxins that are sold commercially for pest control. Most such endotoxins are protoxins, which are inactive until cleaved to smaller, active proteins by proteases in the gut of a susceptible insect. One such crystalline protoxin. 

The crystal formed by any given strain of crystalliferous bacterium is a constant and a strain function. Constancy of insect susceptibility spectra for given bacillus strains tells us this, and differences between strains indicate uniqueness. Krywienczyk and Angus (22) demonstrated that dissolved endotoxins of strains of B. thurin-... 

Roth, R. A. et al. Is exposure to bacterial endotoxin a determinant of susceptibility to intoxication from xenobiotic agents Toxicol. Appl. Pharmacol. 147, 300, 1997. 

Koh, J. Y., and Choi, D. W. (1988). Vulnerability of cultured cortical neurons to damage by endotoxins Differential susceptibility of neurons containing NADPH-diaphorase. J. Neurosci. 8, 2153-2163. 

Smith, J.R., Hart, P.H., Coster, D.J., Williams, K.A. Mice deficient in tumor necrosis factor receptors p55 and p75, interleukin-4, or inducible nitric oxide synthase are susceptible to endotoxin-induced uveitis, Invest. Ophthalmol. Vis. Sci. 1998, 39, 658-661. 

Heppner G, Weiss DW. High susceptibility of strain A mice to endotoxin and endotoxin-red blood cell mixtures. J Bacteriology 1965 90(3) 696-703. 

The data of Gudding (1982) suggest that the elevation of FFAs may depend on the cause of mastitis, as relatively higher levels of FFAs were observed in milk from quarters infected with Staphylococcus aureus. When mastitis is induced experimentally by intramammary infusion of endotoxins or bacteria, the increases in FFAs correspond closely with the increases in SCC and other indices of mastitis (Salih and Anderson, 1979 Fitz-Gerald et al., 1981 Ma et al., 2000). Murphy et al. (1989) concluded that the increased lipolysis in mastitic milk is due to increased susceptibility of the milk fat. 

Another method of neurotoxicant entry into the CNS is by exploitation of a compromised blood-brain barrier. Aluminum itself compromises the blood-brain barrier and reactive species, both directly and indirectly, can open the barrier. Blood-borne inflammation, possibly through the release of reactive oxygen species, is widely known to create a leaky blood-brain barrier. This allows inflammatory cells, endotoxins, and neurotoxicants to enter the CNS. Inflammation within the brain itself also affects blood-brain barrier permeability, an aspect that potentially links psychological stress to increased susceptibility to neurotoxicants. It has been shown that inflammatory responses are induced in animals under stressful conditions, such as electrical shock, restraint, or adverse social interactions. 

SakaoY,Takeda K,Tsutsui H, KaishoT, Nomura F, Okamura H, Nakanishi K, Akira S IL-18-deficient mice are resistant to endotoxin-induced liver injury but highly susceptible to endotoxin shock. Int Immunol. 11 471-480,1999... 

Wang W, Mitra A, Poole B, Falk S, Lucia MS,Tayal S, Schrier R Endothelial nitric oxide synthase-deficient mice exhibit increased susceptibility to endotoxin-induced acute renal failure. American Journal of Physiology - Renal Fluid Electrolyte Physiology 287 F1044-F1048, 2004... 

Mode of Action. Despite the wide spectrum of insect host range activities displayed by Bt varieties, the mode of action of the insecticidal delta endotoxins is similar. When susceptible insects ingest Bt protein crystals, the first gross symptom observed is feeding inhibition due to paralysis of the digestive tract, including mouth parts. This usually occurs within one hour of ingestion ( ). 

Unique Mode of Action. As described above, the Bt delta endotoxin is a stomach poison which acts on the midgut epithelial cells of susceptible insects. This is in contrast to the typical mode of action for synthetic chemical insecticides, which act as nerve poisons. Because the Bt site of action is so different from that of synthetic insecticides, Bt has been successfully utilized for control of otherwise resistant insects such as mosquitoes, the diamondback moth and the Colorado potato beetle. 

Kim Y, Watson D A purified group A streptococcal pyrogenic exotoxin. Physiochemical and biological properties, including the enhancement of susceptibility to endotoxin lethal shock. J Exp Med 1970 131 611-622. 

SEs and TSST-1 share common biological properties. These include induction of high fever similar to bacterial endotoxin induction [37], lethal shock in animals resulting from excessive intravenous doses [38], enhanced host susceptibility to endotoxin lethality [39], cytokine production [40], and polyclonal T-lymphocyte proliferation as seen with superantigens (SAgs) [41],... 

Schlievert PM Enhancement of host susceptibility to lethal endotoxin shock by staphylococcal pyrogenic exotoxin type C. Infect Immun 1982 36 123-128. 

The 8-endotoxins and the other Bt toxins function only as stomach poisons. A susceptible insect must eat them, and the crystals dissolve in the midgut. This solubilization is sometimes dependent on chymotrypsin-like enzymes. The protoxin is further attacked by proteolytic enzymes present in the gut that convert it to the active toxin. An interesting and unexpected finding is that DNA is intimately associated with the toxin crystal and appears to play a role in the proteolytic processing. 

Selye H, Tuchweber B, Bertok L (1966) Effect of lead acetate on the susceptibility of rats to bacterial endotoxins. J Bacteriol 91 884-890 Seyberth HW, Schmidt-Gayk H, Hackental E (1972) Toxicity, clearance and distribution of endotoxin in mice as influenced by actinomycin D, cycloheximide, a-amanitin and lead acetate. Toxicon 10 491-500... 

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