Polymorphonuclear neutrophilic leukocytes (PMNs) take up opsonized microorganisms into phagosomes that fuse with secretory granules in the PMN cytoplasm to form phagolysosomes. Killing and digestion of microorganisms take place within phagolysosomes. Antimicrobial activities in phagolysosomes are divided into two classes. Oxygen (O2)-dependent mechanisms are expressed when PMNs undergo the "respiratory burst." An NADPH oxidase in the phagolysosome membrane is activated and reduces O2 to superoxide (O2-). O2 reduction is the first step in a series of reactions that produce toxic oxidants. For example, .O2- dismutases to hydrogen peroxide (H2O2), and the azurophil granule enzyme myeloperoxidase catalyzes the oxidation of Cl- by H2O2 to yield hypochlorous acid (HOCl). The reaction of HOCl with ammonia and amines modulates the toxicity of this oxidant. O2-independent antimicrobial mechanisms include the activities of lysosomal proteases, other hydrolytic enzymes, and proteins and peptides that bind to microorganisms and disrupt essential processes or structural components. For example, the bactericidal/permeability-increasing protein, cathepsin G, and the defensins are released into phagolysosomes from the azurophil granules. Proposed mechanisms of action of neutrophil antimicrobial agents, their range of microbial targets, and their possible interactions within phagolysosomes are discussed.

Humans↗

PubMedDate not supplied

Histopathology and ultrastructure of krypton and argon laser lesions in a human retina-choroid.

The authors studied a normal eye 24 hours after retinal treatment with argon and krypton photocoagulation. The findings indicate the relative sparing of the inner retina and greater choroidal effects of krypton when compared with argon photocoagulation. Bruch's membrane was not completely ruptured as long as the energy densities of burns were kept low. Krypton wavelengths are transmitted more effectively to the pigment epithelium and choroid. Therefore, the use of relatively lower and therefore safer power densities compared with the argon laser should suffice for the treatment of diseases at this level.

Argon↗

PubMedDate not supplied

On the differentiation of "Brucella Abortus" biotypes 3 and 6.

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Brucella abortus↗