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A new in vitro model has been developed for studying migration of human polymorphonuclear leukocytes (PMN) through living native cellular and matrix barriers. Human amnion membrane consists of a single layer of epithelium bound to a continuous basement membrane interfacing an avascular collagenous stroma. Living amnion was placed in plastic chambers with separate compartments on each side of the membrane. PMN were introduced on the epithelial side of the amnion, and a Millipore filter (Millipore Corp., Bedford, Mass.) was placed against the stromal side. In response to N-formylmethionyl-leucyl- phenylanlanine (FMLP) chemoattractant, PMN penetrated the full thickness of the amnion and were collected and counted on the filter. The rate of PMN traversal of the amnion was dependent on the concentration of FMLP (optimal at 10(-8)M) as well as the slope of the FMLP gradient across the amnion. The route of PMN migration was studied by transmission electron microscopy. PMN first attached to the epithelial surface, then infiltrated between intercellular junctions. PMN migrated around or through tight junction and hemidesmosome attachments. The PMN then penetrated the basement membrane and migrated through the dense collagenous stroma. The present amnion migration system has characteristics of the in vivo inflammatory state not described in any previous method for monitoring PMN migration in vitro. Prior methods have not used native epithelium, whole basement membrane, or collagenous stroma. PMN penetration of these barriers occurs in the normal inflammatory response and probably involves biochemical mechanisms not required for simple migration through the pores of an artificial filter. The amnion system can be useful for future biochemical and morphological studies of PMN penetration of these barriers and possible repair processes that may follow. 相似文献
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Saturated and unsaturated fatty acids independently regulate low density lipoprotein receptor activity and production rate. 总被引:5,自引:0,他引:5
These studies examine the regulation of plasma low density lipoprotein (LDL)-cholesterol levels by varying quantities of dietary saturated and polyunsaturated triacylglycerols. At a constant load of 0.12% cholesterol and 20% triacylglycerol, substitution of polyunsaturated for saturated triacylglycerols caused LDL receptor activity to increase from 25% to 80% of control and reduced the LDL-cholesterol production rate from nearly 200% to 155%. These changes caused the plasma LDL-cholesterol concentration to decrease from nearly 190 to 50 mg/dl. When the dietary content of each triacylglycerol alone was incrementally increased, the saturated lipid suppressed receptor activity while the polyunsaturated triacylglycerol increased receptor-dependent LDL transport. The magnitude of these effects was quantitatively similar, although oppositely directed. However, the saturated triacylglycerol also caused a dose-dependent increase in the LDL-cholesterol production rate and markedly increased the plasma LDL-cholesterol level while the polyunsaturated lipid did not affect either of these. These independent effects were also evident in experiments where it was found that substituting polyunsaturated triacylglycerol for saturated lipid increased receptor activity significantly more than did simply reducing the dietary content of saturated triacylglycerol. Thus, these studies show that triacylglycerols containing saturated or polyunsaturated fatty acids have effects on the major processes that regulate the plasma LDL-cholesterol level that are qualitatively and quantitatively distinct. 相似文献
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