Reticulo-endothelial system

The introduction of an antigen into the tissues of a susceptible animal results initially in increased proliferation of lymphocytes in the tissues of the reticulo-endothelial system particularly the lymph nodes and the spleen (Figure 7.1). An animal will show different responses if the antigen is completely new to it (a primary response) or if the antigen has been encountered... 

The use of the reticulo-endothelial system (RES) was the first approach to liver contrast agents. As an adjunct, spleen imaging would also be possible with a contrast agent that is taken up by the RES. The Kupffer cells of the liver, which represent 10% of all hepatic cells, constitute the major portion (80-90%) of all fixed macrophages and they are extremely effective in the phagocytosis of all types of particles. The downside of the use of this mechanism, however, is the concomitant release of toxic mediators that might and - as a matter of fact - often has made this approach non-feasible. Adverse events provoked by the mediators are changes in blood pressure (most often hypotension) and fever. 

Correct answer = B. The cyclic heme molecule is oxidatively cleaved to form biliverdin. The catabolism occurs in the cells of the reticulo endothelial system, particularly the spleen, and results in the liberation of carbon monoxide. Protoporphyrinogen is an intermediate in the synthesis, not degradation, of heme. Hemo globin and tissue cytochromes are precursors of bilirubin. 

Martland HS, Conlon P, Knef JP. 1925. Some unrecognized dangers in the use and handling of radioactive substances with especial reference to the storage of insoluble products of radium and mesothorium in the reticulo-endothelial system. JAMA 85 1769-1775. 

If the drug is insoluble in water, suspensions have to be administered. In such cases vehicles like sesame oil, hydroxy-methyl-cellulose or hydroxy-ethyl-cellulose can be used. The selection of the vehicle is a critical issue because of inherent toxicity of the vehicle used frequently for kinetic and metabolism studies (e.g. vehicles which form metabolically oxalic acid). Natural oils such as sesame or com oil can be used. However, it should be checked whether the use of oily vehicles alters the gastrointestinal absorption due to their laxative properties and whether oily vehicles can cause oil granulomas (reaction to oily vehicles in the reticulo-endothelial system) in case of parenteral administration. 

Depending on their size and surface charge, parenter-ally administered liposomes interact with the reticulo endothelial system (RES) and provoke an immunological response. After being marked by the adsorption of certain serum proteins, called opsonins, they are identified as an invader and destroyed by specific immune cells mainly in the liver, spleen, and bone marrow. 

The uptake of MoAb-based delivery systems by the reticulo-endothelial system (RES) is another drawback to these systems. It has been suggested that only 0.1-1% of the administered dose of antibody-based systems reaches non-RES sites, with 8 /o dose reaching... 

Fig. 5. Biodistribution of DOPE CHEMs liposomal formulations 48 h after an intravenous injection in rats (20 gmol total lipid/kg body weight) noncoated liposomes, liposomes containing 5 mol% of PEG(2000)-DSPE and (DDGG)4(E0) 4. Each data point represents the arithmetic mean standard deviation (n=3). The liposomal formulation sterically stabilized with 5 mol% (DDGG)4(E0) 4 is obviously able to avoid the reticulo-endothelial system, localized in the liver and spleen, to a larger extent as compared to nonstabilized and liposomes stabilized by conventional PEG-lipid...

Restriction fragment length polymorphism (RFLP) 84 Retavase 11, 462 Reteplase 11, 462 Reticulo endothelial system 1366... 

The appearance of clofazimine in the plasma following absorption is short lived (Banerjee et al., 1974), it rapidly passed out of the circulation and is deposited in various tissues and organs, particularly the fatty tissue, the spleen, lymph nodes, and the cells of the reticulo - endothelial system. Concentrations of 2.1-... 

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