Endotoxin , lipid component

The biological properties associated with the polysaccharides are those relating to serological specificity, and, at least to some extent, they serve as bacteriophage receptors. The somatic antigens are also referred to as Endotoxins, but their toxic properties and manifold physiological effects are due to the lipide component, and this subject has been adequately reviewed. ... 

Naturally occurring bacterial endotoxins contain the lipid, carbohydrate, and protein makeup of the outer cell membrane of GNB (Fig. 1). However, most of the commercial endotoxin preparations have been purified by various extraction procedures and are generally free of nucleic acids, proteins, phospholipids, and other bacterial cell components. The primary chemical configuration that remains after purification is apolysaccharide structure that is covalently bound to a lipid component called Lipid A. Based on its chemical nature, which is common to various bacterial families, this substance is referred to as lipopolysaccharide (LPS). Although the terms endotoxin and LPS are often used interchangeably, most reference endotoxin standards are purified preparations that are more correctly described as LPS. 

Endotoxins are produced primarily by gramnegative bacteria. They act as antigens, are firmly bound to the bacterial cell wall and are complex in nature. They have protein, poly-saccharide and lipid components. Endotoxins are relatively heat stable and are in general active without a latent period. The toxins causing typhoid and paratyphoid fevers, salmonellosis and bacterial dysentery are in this group. Salmonellosis is very serious. It is an infection by toxins of about 300 different but closely related organisms. The infec-... 

A lipopolysaccharide (LPS) is any compound consisting of covalently linked lipids and polysaccharides. The term is used more frequently to denote a cell wall component from Gram-negative bacteria. LPS has endotoxin activities and is a polyclonal stimulator of B-lymphocytes. 

Contamination with endotoxin is an important and frustrating problem in LEH manufacturing for two reasons. Firstly, hemoglobin has a strong tendency to bind endotoxin, where one hemoglobin molecule binds to four endotoxin molecules (K 3.1 x lO M) (117). Secondly, endotoxin has amphiphilicity that enables its stable insertion into lipid bilayer. Such an interaction not only presents contamination and stability problems, but also hampers accurate quantitation of endotoxin. The best possible way to prevent endotoxin contamination is to use aseptic precautions with utmost care. All the machinery, filters, and water should be endotoxin-free. Glass and metallic components may be dry-heat sterilized at about 200° C for three... 

One of the most serious consequences of (Gram-negative) bacterial infection is the possible development of septic shock. This is caused by the release of lipopolysaccharide (LPS endotoxin) from the bacterial cell surface. Various anti-LPS monoclonals (mainly targeted at its lipid A component Chapter 3) have been developed. It is hoped that administration of such monoclonals to affected individuals would effectively mop up free LPS, hence ameliorating the severity of the condition. Most trial results to date have proved disappointing in this regard. 

Lipid A. All R form lipopolysaccharides as well as free lipid A (obtained by mild acid cleavage of the KDO linkage) represent potent endotoxins, comparable in activity to complete lipopolysaccharides. This shows that lipid A represents the component of lipopolysaccharides which is responsible for its endotoxic properties. 

Use of Endotoxin in Cancer Immunotherapy and Characterization of Its Nontoxic but Active Lipid A Components... 

We showed the existence of a toxic and a nontoxic lipid A fraction in the acid hydrolyzed endotoxin preparation (23). These two fractions were separated and the composition was determined on the purified components so that we could relate specific structural features of lipid A to both toxicity and tumor regression activity (23). 

Suda, Y., Kim, Y.M., Ogawa, T., Yasui, N., Hasegawa, Y., Kashihara, W., Shimoyama, T., Aoyama, K., Nagata, K., Tamura, T., Kusumoto, S. Chemical structure and biological activity of a lipid A component from Helicobacter pylori strain 206. J Endotoxin Res 7 (2001) 95-104. 

Abstract Lipopolysaccharides are the major components on the surface of most Gram-negative bacteria, and recognized by immune cells as a pathogen-associated molecule. They can cause severe diseases like sepsis and therefore known as endotoxins. Lipopolysaccharide consists of lipid A, core oligosaccharide and O-antigen repeats. Lipid A is responsible for the major bioactivity of endotoxin. Because of their specific structure and amphipathic property, purification and analysis of lipopolysaccharides are difficult. In this chapter, we summarize the available approaches for extraction, purification and analysis of lipopolysaccharides. 

Although H. pylori induces chronic infection whereas C. jejuni induces an acute infection (and to which the structural characteristics and biological properties of endotoxin, particularly their lipid A components contribute), both bacteria induce pathogenic autoimmune responses in which molecular mimicry in the... 

Human lactoferrin (HL) is a component of innate immunity. Human lactoferrin is an iron-binding protein found in milk, granulocytes and exocrine secretions. It is released during inflammation, has bactericidal effects and reduces cytokine production by binding to the lipid A portion of endotoxin (Appelmelk et al., 1994). 

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