SummaryADP-induced platelet aggregation and shape change were monitored optically in citrated rabbit platelet-rich plasma (PRP) diluted with isotonic salt solutions. Lithium (Li) produced a concentration-dependent reduction in the rate of platelet aggregation but had no discernible effect on the shape change which precedes aggregation. When PRP was pre-incubated with Li, the inhibitory effect of the ion was independent of the duration and temperature of the treatment. The inhibitory effect of Li also was observed in heparinized PRP or when 5-HT was used as the aggregation-inducing agent. When Li was combined with aggregation inhibitors which enhance platelet cyclic AMP content either by activating adenylate cyclase or by inhibiting phosphodiesterase, only additive effects were observed. The inhibitory effect of Li was opposed by added calcium. Kinetic evaluation of the interaction between Li and Ca indicated that their antagonism was competitive. Added calcium also displayed competitive antagonism toward the aggregation inhibiting effect of increased hydrogen ion concentration in the pH range between 6 and 8.
SummaryLocal anaesthetics and antiarrhythmic agents produced changes in responses of rabbit platelets to ADP and thrombin that varied with the agent and its concentration. In high concentrations all local anaesthetics decreased aggregation rates. At lower concentrations several local anaesthetics increased aggregation rates. Depending on the agonist and local anaesthetic, increases were produced at all or only at low or high agonist concentrations. Local anaesthetics failed to influence shape change except at concentrations much greater than those which inhibited aggregation. Inhibition of aggregation by procaine was potentiated by small organic anions suggesting effects at different sites on the platelet membrane. The inhibitory effect of local anaesthetics was decreased by increasing Ca. Kinetic analysis indicated different mechanisms for this Ca effect, i. e., predominantly competitive for procaine or lidocaine and predominantly non-competitive for tetracaine or ethyl lidocaine. Local anaesthetics may affect aggregation by modifying the participation of Ca in this process.
Conducting ethnographic fieldwork “at home” is often undermined by the colonial foundations of anthropology, which still permeate understandings of value and legitimacy in academic research. Scholars often present hometown ethnography as providing automatic insider status or as a threat to objectivity. In this paper, I offer a self‐reflexive account of my fieldwork with working holidaymakers in the small rural Australian town where I spent my teenage years. Adjusting to conflicting roles of researcher and returning resident revealed feelings of discomfort and a heightened, uncertain sense of self at odds with the familiarity and belonging associated with localness. I argue that conducting ethnography in familiar research sites is an exercise in understanding the uncomfortable complexities of shifting researcher positionality. By sharing some internal conflicts and crises, I examine the process of conducting research in a familiar space and consider the broader methodological implications and transformative potential of doing ethnography at home.
SummarySufficient concentrations of small organic anions inhibited ADP- or 5-HT-induced shape change and aggregation in rabbit PRP diluted with isotonic salt solutions. Both effects were concentration-dependent and varied with the size of the hydrocarbon chain. Carboxylate and sulfonate anions of corresponding size produced a similar degree of interference with aggregation but carboxylates were somewhat more effective than sulfonates in impairing shape change. The inhibitory effect of these anions was not potentiated by a phosphodiesterase inhibitor and therefore was not attributable to adenylate cyclase activation.The inhibition of shape change by both series of anions was enhanced at acid pH, an effect which was greater with carboxylates than with alkyl sulfonates. The pH dependence of shape change on the alkaline side of the optimum range was unaffected by either type of anion. These results show that organic anions exert their inhibitory effects on platelets at least in part at the external platelet surface, and that their effects can be influenced by the degree of dissociations of protonatable membrane groups. Hence, surface negative charge and hydrophobic interactions both play an important role in platelet functional responses and their modification by organic anions. The inhibition of aggregation by these anions was opposed by the addition of calcium. Kinetic analysis indicated that both activation of aggregation by Ca++ and inhibition of aggregation by organic anions involved more than one site or mechanism of action. The more sensitive inhibitory effect was surmounted by increased Ca++ concentrations without apparent alteration in the affinity of Ca++ binding sites and competitive antagonism was evident only at high concentrations of organic anions. A simple model to account for these effects is proposed.
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