No abstract

No abstract

Tegumental membranes of Schistosoma mansoni were disrupted by 0.2% Triton X-100 in Tris-maleate buffered/Kreb-Ringer's solution. Subsequent differential centrifugation of the disruption solution at 2,500 g and 30,000 g produced two pellets which contained membrane components. Examination of the carcass by scanning electron microscopy revealed that most of the exposed tegument of both male and female worms was removed, while surface membrane protected by close apposition of another surface (i.e., in the gynecophoral canal) remained intact. The parenchymal tissue (e.g., subtegumental muscle and tegumental perikarya), excretory and gut epithelia, and the tegument's basement membrane also remained intact. The selectivity of the disruption suggests that membrane in both pellets originated almost exclusively from the tegument. Although larger morphological features (i.e., surface crypts) present in the intact tegument did not maintain their form in the 2,500 g pellet, the high specific activity of 3H-concanavalin A retained by this fraction, and the presence of numerous spines and large pieces of membrane, suggest that the 2,500 g pellet contained most of the worm's disrupted surface membrane. Transmission electron microscopy demonstrated the presence of dense spinelike material and vesicles of various sizes and densities, as well as some mitochondria in the 30,000 g pellet. Low specific activity of 3H-concanavalin A in the post-30,000 g supernatant suggests that relatively few externally oriented, saccharide-containing molecules were solubilized from tegumental membranes by Triton X-100.

The mechanisms by which mediators and cytokines stimulate neutrophils to migrate across the lung epithelium are still unclear. We hypothesized that neutrophil transepithelial migration depends upon polarity of the epithelium. We therefore compared neutrophil migration through human lung Type II-like alveolar epithelial cell line (A549) monolayers grown on the upper versus lower surface of permeable filters to simulate apical-to-basal and basal-to-apical movement of neutrophils, respectively. The classic chemoattractants formyl-methionylleucylphenylalanine (FMLP), leukotriene B4 (LTB4), and interleukin-8 (IL-8) induced equivalent neutrophil transepithelial migration in the apical-to-basal and basal-to-apical directions. However, the degree of neutrophil transepithelial migration was significantly greater in the basal-to-apical direction in response to either IL-1beta or tumor necrosis factor-alpha (TNF-alpha). Enhanced TNF-alpha-induced neutrophil migration through A549 monolayers in the basal-to-apical direction occurred regardless of whether the TNF-alpha was above or below the filter/monolayer complex. Actinomycin D pretreatment of A549 monolayers had no effect on FMLP-induced neutrophil transepithelial migration, but markedly (about 75%) inhibited both TNF-alpha- and IL-1beta-induced neutrophil transepithelial migration, regardless of monolayer orientation. Thus, in contrast to classic chemoattractants, IL-1beta and TNF-alpha induced greater neutrophil transepithelial migration in a basal-to-apical direction, and this occurred independently of the cytokine location, but depended upon intact metabolic capacity of the A549 cells. These data suggest that the mechanisms important for neutrophil transepithelial migration in response to classic chemoattractants differ from those important for migration in response to inflammatory cytokines.

We studied the proximal tibial growth plates of 15-day-old mice to determine if matrix vesicle concentration varies among growth plate zones or between the pericellular and territorial matrix compartment and the interterritorial matrix compartment. Growth plates were examined by electron microscopy and divided into five zones: reserve zone (RZ), upper proliferative zone (UPZ), lower proliferative zone (LPZ), upper hypertrophic zone (UHZ), and lower hypertrophic zone (LHZ) which included the calcifying zone. We measured the diameter and volume fraction of matrix vesicles and calculated their numerical density and volume per cell and number per cell in the pericellular and territorial matrix and in the interterritorial matrix of each zone. In the pericellular and territorial matrix compartment, the matrix vesicle concentration progressively decreased from the RZ to the LHZ. Changes in matrix vesicle concentration in the interterritorial matrix followed a different pattern. Between the RZ and the UPZ, matrix vesicle numerical density declined slightly and then increased to peak values in the LPZ and UHZ, followed by a decline between the UHZ and the LHZ. These changes in matrix vesicle concentration paralleled previously reported changes in intramitochondrial calcium content, suggesting that matrix vesicle production in growth plate may be related to intracellular calcium concentration. The existence of the maximum concentration of matrix vesicles in the LPZ and UHZ longitudinal septa which do not mineralize followed by a decline in matrix vesicle concentration in the LHZ longitudinal septa which mineralize suggests that a high concentration of matrix vesicles may be needed to prepare the matrix for mineralization or to initiate mineralization and that matrix vesicles are depleted during mineralization.