==================================BSR31================================== 31. Platelet aggregation induced by decompression. Decompression activation of platelets. Reduced pressure- induced platelet aggregation. Decompression due to Bernoullis Principle. Hyperbaric decompression induced platelet aggregation (simulation of diver surfacing). 1 UI - 87056109 AU - Jauchem JR ; Waligora JM ; Taylor GR ; Horrigan DJ Jr ; Johnson PC Jr TI - Hematological changes following repetitive decompressions during simulated extravehicular activity. AB - A study was performed to evaluate decompression procedures suggested for use prior to Space Shuttle extravehicular activity. Hematological parameters were measured in 12 male human subjects before and after exposure in an altitude chamber to a 3-day staged decompression schedule, with simulated extravehicular activity. Following the exposure, significant increases occurred in white blood cell count and activated partial thromboplastin time, and platelet aggregate ratio was significantly decreased. Pre-exposure samples from subjects who were susceptible to formation of venous gas emboli (VGE) exhibited a significantly lower degree of ADP-induced platelet aggregation and a significantly higher amount of lymphocyte blastogenic transformation in response to the mitogen phytohemagglutinin than samples from VGE-resistant subjects. The results indicate that, following this decompression profile, small but significant changes occur in several hematological parameters, and that levels of certain parameters may be related to susceptibility to VGE formation during decompression. MH - Adult ; *Decompression ; Embolism, Air/ETIOLOGY ; *Hematologic Tests ; Human ; Leukocyte Count ; Lymphocyte Transformation ; Male ; Partial Thromboplastin Time ; Platelet Aggregation ; *Space Flight ; Support, U.S. Gov't, Non-P.H.S. SO - Int Arch Occup Environ Health 1986;58(4):277-85 2 UI - 87043819 AU - Thorsen T ; Ovstedal T ; Vereide A ; Holmsen H TI - Effects of platelet antagonists on the reduction in platelet density caused by microbubbles in vitro. AB - Platelet-rich plasma (PRP) was stirred and incubated at 37 degrees C with N2 microbubbles in vitro in the presence and absence of platelet antagonists. The N2 microbubbles acted as a platelet agonist, like "classical: agonists such as ADP, collagen, and thrombin, causing an agonist-induced aggregation requiring extracellular Ca2+. This aggregation is abolished by 2-ethylamineglycolether (N',N',N',N') tetraacetate (chelator of extracellular Ca2+), and 2-deoxy-D-glucose plus antimycin A (inhibitors of glycolysis and electron transport, and thereby of ATP production). Furthermore, this aggregation could be depressed pharmacologically by several antagonists of the aggregation induced by "classical: platelet agonists. The greatest inhibition of microbubble-induced aggregation was obtained by substances that increase the intracellular levels of cyclic AMP. Medications that are in common clinical use, such as theophylline, seem promising in this respect. The prostaglandin-thromboxane pathway did not seem to be involved in the N2 microbubble-induced platelet aggregation in vitro, since acetylsalicylic acid and indomethacin were without effect, nor did the 3',5'-cyclic guanosine monophosphate pathway seem to be linked to this aggregation mechanism. MH - Adenosine Diphosphate/PHARMACODYNAMICS ; Adenosine Triphosphate/ METABOLISM ; Adenyl Cyclase/PHYSIOLOGY ; Alprostadil/PHARMACODYNAMICS ; Antimycin A/ANALOGS & DERIVATIVES/PHARMACODYNAMICS ; Blood Platelets/ *DRUG EFFECTS/PHYSIOLOGY ; Calcium/PHYSIOLOGY ; Decompression Sickness/ BLOOD ; Deoxyglucose/PHARMACODYNAMICS ; Gases/*PHARMACODYNAMICS ; Human ; Nitrogen/*PHARMACODYNAMICS ; Platelet Aggregation/DRUG EFFECTS ; Prostaglandin Synthase/ANTAGONISTS & INHIBITORS ; Receptors, Adrenergic/ DRUG EFFECTS ; 3',5'-Cyclic AMP Phosphodiesterase/ANTAGONISTS & INHIBITORS SO - Undersea Biomed Res 1986 Sep;13(3):289-303 3 UI - 87043818 AU - Thorsen T ; Brubakk A ; Ovstedal T ; Farstad M ; Holmsen H TI - A method for production of N2 microbubbles in platelet-rich plasma in an aggregometer-like apparatus, and effect on the platelet density in vitro. AB - The mechanisms involved in the interactions between microgasbubbles and platelets are not clear. The platelet aggregatory response to agonist-induced, receptor-mediated stimuli has been studied extensively. As a direct in vitro approach to elucidate the interaction between gas bubbles and platelets, N2 microbubbles were used as a platelet agonist in an experimental apparatus similar to an ordinary aggregometer. N2 microbubbles of varying number and size were produced in platelet-rich plasma (PRP) and incubated at 37 degrees C. The gas-liquid interface of the gas bubbles consists of plasma proteins and lipids. In stirred PRP a considerable decrease occurred in the platelet density, which could not be attributed to formation of citrate complexes with calcium and/or the corresponding reduction in the concentration of free calcium. Gas bubbles with a diameter in the range of 40-120 micron caused the greatest reduction in the platelet density. The platelet movements in PRP and the curvature of the N2 microbubble surface seemed more important for the interaction than the total gas bubble surface available for contact. MH - Analysis of Variance ; Blood Platelets/*DRUG EFFECTS/PHYSIOLOGY ; Decompression Sickness/BLOOD ; Gases/*PHARMACODYNAMICS ; Hematology/ INSTRUMENTATION ; Human ; Nitrogen/*PHARMACODYNAMICS ; Platelet Aggregation/DRUG EFFECTS ; Platelet Count ; Vibration SO - Undersea Biomed Res 1986 Sep;13(3):271-88 4 UI - 86236256 AU - Murayama M ; Kumaroo KK TI - Inhibitors of ex vivo aggregation of human platelets induced by decompression, during reduced barometric pressure. AB - It has been shown experimentally ex vivo that human platelet aggregation is induced by decompression (reduced pressure) produced by various means, i.e., reduced barometric pressure, reduced hydrostatic pressure, and reduced hydrodynamic pressure due to Bernoulli's principle. We report here that the spontaneous platelet aggregation induced by reduced barometric pressure (253 torr for three hours) is inhibited by 1:10(7) diluted Japanese herbal plant oil (JHP) and also by two of its major constituents, menthone and menthol with the median inhibitory concentration (IC50) in the millimolar range. These drugs gave essentially similar results when collagen and ADP were used as aggregating agents. Inhibitor concentrations were determined by microscopic examination of platelets in wet preparations when the aggregating stimulus was reduced pressure and by optical aggregometry when collagen and ADP were the aggregating agents. Potential usefulness of these compounds in the prevention of decompression syndrome (DCS) and acute mountain sickness (AMS) are discussed. MH - Atmospheric Pressure ; *Decompression ; Dose-Response Relationship, Drug ; Human ; Hydrostatic Pressure ; Japan ; Menthol/PHARMACODYNAMICS ; Plants, Medicinal/*PHYSIOLOGY ; Platelet Aggregation/*DRUG EFFECTS ; Thymol/PHARMACODYNAMICS SO - Thromb Res 1986 May 15;42(4):511-6 5 UI - 86209574 AU - Price RA ; Ogston D ; Macdonald AG TI - Effects of high pressure on platelet aggregation in vitro. AB - An apparatus which enables aggregating agents to be added to a stirred suspension of platelets subjected to a pressure of up to 600 ATA is described. The ensuing aggregation reaction is monitored optically. The pressure is applied with helium; data are presented that indicate the effects are mainly attributable to hydrostatic pressure. The aggregation of human platelets induced by ADP was reversibly inhibited by pressure in the 1-270 ATA range. The second phase of aggregation was blocked by 65 ATA; the rate of first phase aggregation was reduced but the time to respond to ADP was not affected. Comparable pressures also affected collagen and arachidonate-induced aggregation. The time to respond to these aggregating agents was prolonged and both the rate and the degree of aggregation were reduced by pressure. MH - Adenosine Diphosphate/PHARMACODYNAMICS ; Arachidonic Acids/ PHARMACODYNAMICS ; Collagen/PHARMACODYNAMICS ; Decompression ; Human ; Hydrogen-Ion Concentration ; *Hydrostatic Pressure ; *Platelet Aggregation/DRUG EFFECTS ; *Pressure SO - Undersea Biomed Res 1986 Mar;13(1):63-75