Modelling alterations in the partition coefficient in in vitro biological systems using headspace gas chromatography

Headspace gas chromatography was used to determine the physiological media–air partition coefficient (K) of four volatile organic solvents of industrial importance. The experimental conditions were those likely to be used in in vitro metabolic and toxicological studies on volatile compounds. The addition of solvent to the liquid phase from a stock solution in ethanol, or the presence of organic material at concentrations normally seen in in vitro studies, did not significantly alter the K value. Binary solvent addition resulted in a dose-dependent decrease in K for each solvent that was also influenced by the solvent solubility and the constituents of the liquid matrix. The aromatic solvents exerted the greatest effect and showed the greatest change in K value.     

PARTICLE SIZE OF INSECTICIDAL SUSPENSIONS AND THEIR CONTACT TOXICITY III. TEMPERATURE COEFFICIENTS AND TESTS BY INJECTION

Aqueous DDT suspensions containing particles of different sizes gave different temperature coefficients of mortality in dipping tests against adult Oryzaephilus surinamensis and Tribolium castaneum. In the range 12–30°C., colloidal DDT showed a large negative coefficient, but the coefficient for a suspension of DDT crystals of 400μ was smaller ( T. castaneum ) or negligible ( O. surinamensis ). Thus, although a suspension of crystalline DDT was more toxic than colloidal DDT to warm insects, it was less toxic than the colloid to cool insects.
A test was made of rotenone suspensions against adult milkweed bugs ( Oncopeltus fasciatus Dall.) by application of measured droplets under the wings. Colloidal rotenone was more toxic than a crystalline suspension. Milkweed bugs could not be killed in this way by DDT suspensions.
Tests were also made by injecting suspensions of rotenone, DDT and its fluorine analogue (DFDT) into milkweed bugs. A suspension of rotenone crystals was equitoxic with colloidal rotenone against insects kept for 3 days at 27°C. after treatment. The same was true of crystalline and colloidal DDT suspensions. If the bugs were kept at 10°C., colloidal rotenone was much more toxic than crystalline rotenone 2 days after treatment. But if the insects were kept for about 3 weeks and inspected at intervals, the first apparent difference in toxicity grew smaller, and in the end it nearly disappeared. With DDT the time for this to occur was about 10 days; and suspensions of colloidal and crystalline DFDT were equitoxic after only 2 days, even at 10°C.
In the application test, the difference between colloidal and crystalline rotenone was a real difference in toxicity. It did not disappear with the lapse of time; but in the injection tests the two forms of each poison differed only in speed of action, and not in ultimate toxicity.     

Temporal characteristics of cortisol metabolism in adrenalectomized primates

The rhythmicities observed in the plasmatic levels of cortisol are generally attributed to rhythms of production and release of the hormone. Since the plasmatic concentration of any given substance is a function of its production and its removal from the circulation, it is conceivable that the metabolism of cortisol also occurs in an oscillating fashion. To test this hypothesis Rhesus monkeys were submitted to bilateral adrenalectomy; cortisol was replaced at a constant infusion rate while blood was sampled at hourly intervals for the measurement of cortisol plasma levels. Rhythmic oscillations in the cortisol levels were observed. These rhythms exhibited two major components: a circadian and an ultradian component. The authors suggest that these rhythms be considered whenever normal or pathologic hormone rhythmicities are analyzed.     

Further studies on cold insoluble circulating immune complexes in rabbits immunized with bovine albumin.

Cold insoluble circulating immune complexes of BSA and anti-BSA antibody are formed in vivo while immune catabolism of antigen is occurring. The effects of temperature, rate of precipitation and redissolvability of the cold insoluble antigen were studied in this model. Circulating BSA is soluble at 37 degrees, but may precipitate when the temperature is reduced. The solubility of antigen decreases at 24 degrees and below. Complete precipitation occurs in 5-7 days. The antigen in the cryoprecipitate is difficult to redissolve unless low pH citrate or glycine buffers are used.