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D W Sawyer

Publications and source records attributed to D W Sawyer.

6 recordsLinked to original sources
PubMed1987

Influence of type and opsonization of ingested particle on intracellular free calcium distribution and superoxide production by human neutrophils.

Intracellular free calcium concentration [( Ca2+]i) was measured with the fluorescent Ca2+ indicator Fura 2 within individual human neutrophils during the phagocytosis of several types of particles, including serum-treated zymosan (STZ), immunoglobulin G (IgG)-coated zymosan (IGZ), C3b-coated zymosan (C3Z), nontreated zymosan (Z), and serum-treated similarly sized latex particles (STL). STZ was coated with both IgG and C3b. IGZ was coated with only IgG, and C3Z was coated with only C3b. STL was coated with only C3b but to a lesser extent than C3Z. The ingestion of particles was greatest for STZ and somewhat lower for C3Z. Ingestion of IGZ and STL was much less than ingestion of C3Z. The relative efficiencies of the particles for inducing superoxide production were as follows: STZ greater than IGZ = C3Z greater than Z = STL. [Ca2+]i significantly increased from the resting level of approximately 70 to greater than 240 nM (P less than 0.01) during phagocytosis of the particles. The increment in [Ca2+]i was greater in the paraphagosomal region than in the cell body after the ingestion of STZ or IGZ. The mean peak [Ca2+]i values in the paraphagosomal cytoplasm of neutrophils ingesting one particle of STZ, IGZ, C3Z, Z and STL were 536.1 +/- 57.6, 424.7 +/- 55.8, 373.8 +/- 62.7, 272.3 +/- 31.5, and 270.8 +/- 38.0 nM, respectively, which showed good correlation (r = 0.97) with the efficiency of the particles for inducing superoxide production. Depletion of extracellular Ca2+ by EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N'N'-tetraacetic acid] attenuated both [Ca2+]i increase and superoxide production induced by particles. Thus [Ca2+]i increased after ingestion of several types of particles, and the subcellular pattern of [Ca2+]i was different depending on the type of particle ingested. Greater increases in paraphagosomal [Ca2+]i were closely associated with greater increases in superoxide production by neutrophils.

Benzofurans↗
PubMed1985

Intracellular free calcium localization in neutrophils during phagocytosis.

Intracellular free calcium (Ca2+ i) is thought to be an important second messenger for phagocyte functions. The fluorescent indicator Quin2 was used to measure and visualize [Ca2+]i in human neutrophils during chemotaxis toward, and phagocytosis of, opsonized zymosan. In neutrophils migrating toward zymosan, [Ca2+]i was highest in the lamellipodium. Neutrophils ingesting opsonized zymosan had the highest [Ca2+]i in the pseudopods and periphagosomal cytoplasm. Most of the increase in [Ca2+]i was from extracellular sources. Regional increments in [Ca2+]i are strategically located to modulate such cellular functions as chemotaxis, oxidative activity, and degranulation.

Aminoquinolines↗
PubMedDate not supplied

Polymorphonuclear neutrophils: an effective antimicrobial force.

The production and deployment of polymorphonuclear neutrophils (PMNs) are under close regulation. PMNs interact through cytokines with a number of cell types, including macrophages, lymphocytes, and endothelial cells. PMNs are guided by bacterial products and cytokines to target sites, where microbes are recognized and killed. Killing occurs through oxygen-dependent and oxygen-independent mechanisms. The frequent and severe infections seen in patients with defects (either congenital or acquired) in PMN function demonstrate the importance of PMNs in host defense against infection. PMNs are potent inflammatory cells and can exacerbate disease states such as myocardial ischemia, gram-negative bacterial sepsis, and the adult respiratory distress syndrome.

Cell Adhesion↗