A B S T R A C T Porcine intestinal mucosal heparin induced aggregation of platelets in citrated platelet-rich plasma and enhanced platelet aggregation and serotonin secretion induced by other agents. This action ofheparin was blocked by substances that elevate platelet cyclic AMP and by EDTA but not by inhibitors of platelet cyclooxygenase. The effect was not inhibited by apyrase or by N-amylthio-5'-AMP and therefore did not require the action of ADP, nor was there activation of platelet phospholipase. Platelet aggregation by heparin required a plasma cofactor different from the cofactor required for ristocetin.Fractionation of heparin yielded preparations that varied in molecular weight and, within a given molecular weight fraction, in affinity for antithrombin III.Fractions of high molecular weight (average 20,000) were more reactive with platelets than were fractions of low molecular weight (7,000). Anticoagulant activity did not parallel the platelet reactivity of heparin fractions. Among high molecular weight fractions, preparations of high or low antithrombin affinity were equally active in induction of platelet aggregation. In low molecular weight fractions, there was an inverse relationship between platelet reactivity and anticoagulant activity in normal platelet-rich plasma, but, in plateletrich plasma depleted of antithrombin, low molecular weight fractions of high and low antithrombin affinity reacted equally with platelets. These results suggest that formation of an antithrombin-heparin complex protected platelets from aggregation by heparin.Selection of heparin fractions of low molecular weight and high antithrombin affinity may improve anticoagulant therapy and development of thromboresistant heparin-coated artificial materials.
Solutions of sodium carboxymethyl cellulose (CMC), sodium chloride, ethylene glycol, and ethyl alcohol in water were prepared and frozen under controlled conditions. The ice in each case was divided into horizontal sections, melted, and the amount of each impurity measured. The organic liquid and salt concentrations were found from refractive index values using a dipping refractometer, and the CMC content, after treatment with an anthrone solution, was measured with a spectrophotometer. Developments in the anthrone method are described. Qualitative tests were also made by freezing solutions of soluble dyes.In the freezing of aqueous solutions of CMC and the dyes, rejection of the impurity is almost complete. When solutions of salt or alcohol or glycol in water, or of CMC and alcohol or glycol in water, are frozen a surface concentration peak and a second peak about 7 mm below the surface, corresponding to a previously observed discontinuity in the crystal structure of impure ice, are found. The ability of alcohol or glycol to carry CMC or a dye to places in the ice structure not available to them in the absence of the organic liquid is noted.
The effect of RX 72601, neostigmine plus atropine, or saline on neuromuscular blockade with (+)-tubocurarine was studied in a double blind trial in four healthy male volunteers. 2 The methods used to assess neuromuscular function were voluntary grip strength and indirectly evoked muscle twitches. The muscarinic action was assessed by measuring intestinal motility with a pressure sensitive radio pill, and auscultation of the abdomen. Blood pressure and pulse rate were also recorded. The degree of acetylcholinesterase inhibition achieved in whole blood was determined before and at intervals after the administration of the anticholinesterases. 3 Both RX 72601 (0.66-0.83 mg) and neostigmine (2.5 mg) completely reversed the neuromuscular blockade produced by tubocurarine, but the time course of reversal differed. RX 72601 (0.66-0.83 mg) produced similar inhibition of acetylcholinesterase in whole blood to neostigmine (2.5 mg). The doses of RX 72601 used caused minimal stimulation at muscarinic sites as evidenced by the limited effect on pulse rate and intestinal activity. 4 It was concluded that RX 72601 could be safely used to reverse the effects of neuromuscular blockade without the need for premedication with atropine.
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