A simple method for the determination of serum free insulin levels in insulin-treated patients

A method for the determination of free, active insulin in the sera of insulin-treated diabetics is described. This involved radioimmunoassay after extraction of free insulin with polyethylene glycol. Recovery tests with cold insulin showed 73 per cent recovery of free insulin and no recovery of bound insulin.

The fasting free insulin levels were slightly lower in the patients than in normal persons; exceptions were some patients with complications expected to cause insulin resistance at the peripheral tissue level. Free insulin levels did not correlate with total insulin levels, antibody titers, insulin requirements or conditions of insulin treatment.

A very slight increase of insulin was observed after glucose loading in insulin-treated patients, but a marked increase of the free insulin level followed by an exaggerated increase in the total insulin level was observed in a patient with the insulin autoimmune syndrome.

The diurnal changes of the free insulin suggested the dynamic states of this fraction and its usefulness for determining control of diabetes with insulin.

Adenine Nucleotide Metabolism of Human Platelets during Collagen-Induced Aggregation

Changes in platelet adenine nucleotides during collagen-induced aggregation were estimated. Averaged values of ATP and ADP in intact platelets were 56.3 and 28.9 attomoles per platelet, respectively. After collagen-induced aggregation, intracellular ATP plus ADP was depleted to about half of that in intact platelets. The released ADP accounted for 13% of that in intact platelets.

Behavior of platelet adenine nucleotides during aggregation was divided into the following phases. At first, platelet ATP decreased without the release of nucleotides. The release of ADP occurred at the stage of rapid change of light transmission. Subsequently, the released ADP decomposed in parallel with the degradation of intracellular ADP. The radioactive ATP in platelets decreased during exposure to collagen, without appreciable release of radioactive nucleotides. The ATP released from disrupted platelets was rapidly metabolized in plasma.

Effect of Complement Upon Viral Neutralization

Viral neutralization tests are usually performed without paying attention to the effect of complement upon viral neutralization. An exceptional case was the use of unheated normal human serum for the potentiation of human anti-dengue antibody. Several workers indicated that the use of unheated sera may enhance virus-neutralizing action of antibody to some extent, but the degree of enhancement was in general too small to necessitate the change of the neutralization test procedure. We found in 1964 that early immune sera of rabbits infected or immunized with herpes simplex virus contained a neutralizing antibody (CRN antibody) that could be detected only in the presence of complement. The same phenomenon was also found in cases of human infections with herpes virus. Other workers found a similar effect in the case of rabbits immunized with vaccina virus. We also found that neutralization of virus by CRN antibody required C′1, C′2, C′3 complex, and C′4.