Neutrophil dysfunction among newborn infants, especially those born prematurely, is well recognized, but the mechanism responsible for this phenomenon is yet to be clarified. In this study, we evaluated the stimulus response coupling in neutrophils from 90 healthy newborns and 96 healthy adults in an effort to establish whether defective neonatal neutrophil function is a result of impaired signal perception or immature responsiveness. Measurement of rapid- and slow-light scattering responses (LSR) to 1 microM FMLP stimulation revealed that neonatal neutrophils have about one-half the corresponding responsiveness of adult cells (rapid-LSR: 6.
View Article and Find Full Text PDFBiochim Biophys Acta
February 1995
The ability of neutrophils to carry out chemotaxis in response to low chemoattractant concentrations, but arrest their motility when exposed to higher concentrations of the same substance, has fascinated investigators for years. By analyzing the temporal characteristics of the morphological responses, corresponding to chemotaxis and cell arrest, we have recently discovered that the choice between them is made by transduction of the continuous binding process into either single or multiple stimuli within defined time intervals, initiating chemotaxis or cell arrest, respectively. Both experimental and theoretical lines of evidence are presented to support the validity of this unique mechanism.
View Article and Find Full Text PDFHuman spermatozoa accumulate in vitro in diluted follicular fluids obtained from follicles from which the eggs have been fertilized. Using capillary assays under a variety of experimental conditions (ascending or descending gradients of follicular fluid, or no gradient at all) and microscopic assays in which individual spermatozoa could be followed, we found that the sperm accumulation in follicular fluid was the result of both sperm chemotaxis and chemokinesis and eventually hyperactivation-like motility. We determined the optimal conditions for sperm accumulation, which involved sperm preincubation (possibly to induce sperm capacitation) and proper dilution of follicular fluid.
View Article and Find Full Text PDFHuman polymorphonuclear leukocytes (PMN) hydrolyze the synthetic chemoattractant N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMet-Leu-Phe) at nanomolar concentrations in an autocatalytic-like manner that deviates from classical Michaelis-Menten kinetics [Yuli, I. & Snyderman, R. (1986) J.
View Article and Find Full Text PDFThis study centers on the question of whether the phenomenon of leukocyte aggregation, which is typical to inflammatory conditions, is pathogenic per se. We examined patients and laboratory animals in whom the presence of aggregated leukocytes in the peripheral blood was documented by direct visualization and where, despite the presence of aggregated leukocytes, neither the patients nor the laboratory animals showed clinical or pathological evidence for leukoembolization. Our in vitro findings about the reversibility of the phenomenon of leukocyte aggregation help to explain the above-mentioned observations as well as the well-known daily clinical experience that, despite complement activation and other aggregatory stimuli, there is no clinical or pathological evidence for leukoembolization.
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