The Effect of Chromium on Platelet Function In Vitro

Sodium chromate inhibits platelet function in vitro. The primary effect is inhibition of connective tissue-induced aggregation. In addition, the primarywave of epinephrine-induced aggregation is moderately inhibited andadenosine diphosphate-induced aggregation is mildly inhibited. The effect onconnective tissue-induced aggregation is due to inhibition of the platelet "release reaction"; chromate inhibited the release of adenine nucleotides, ¹⁴Clabeled serotonin and the activation of platelet factor III normally caused byconnective tissue. The amount of chromium which must be bound to plateletsto inhibit aggregation is 10-100 times the amount of radioactive chromiumbound to platelets under the usual conditions of labeling for survival studies.However, this does not imply that chromium labeled platelets functionnormally.

     

Inability of haptoglobin to bind myoglobin

1. The old and the current concepts of the renal handling of extracorpuscular plasma Hgb are briefly reviewed.

2. Studies are presented on the starch gel electrophoretic behavior of Mbalone and Mb in serum.

3. It is suggested that Mb is not bound by Hp, known to bind Hgb, andthat this constitutes the reason for the "low renal threshold" of Mb as compared to that of Hgb.

Submitted on August 4, 1958 Accepted on October 12, 1958     

Pathways to Blood Coagulation Product I Formation

The basic reagent used was an eluate obtained from barium sulfate usedto adsorb various sera. When this eluate was prepared from normal rabbitserum, it responded to treatment with coagulants from adsorbed plasma,with Stypven, or with 25 per cent sodium citrate to give products withsimilar if not identical properties. With each preparation a stable complexformed with cephalin which withstood washing, was relatively heat-stable,was inactivated by adsorbed serum, and which required factor V for optimalprothrombin conversion. In eluates prepared from human serum, normalactivation occurred in the absence of factor IX, but was defective in theabsence of factor X. A preparation of factor X purified by DEAE cellulosechromatography was activated by 25 per cent sodium citrate. It is suggestedthat product I, the product of Stypven activation, and autoprothrombin Crepresent similar or identical reagents; it is further suggested that factor Xis their common precursor.

Submitted on November 7, 1962 Accepted on January 23, 1963