Results are presented on the rate of thiamin cleavage by sulphite in aqueous solutions as affected by temperature (20-70 degrees ), pH(2.5-7.0), and variation of the concentration of either thiamin (1-20mum) or sulphite (10-5000mum as sulphur dioxide). Plots of the logarithm of percentage of residual thiamin against time were found to be linear and cleavage thus was first-order with respect to thiamin. At pH5 the rate was also found to be proportional to the sulphite concentration. In the pH region 2.5-7.0 at 25 degrees the rate constant was 50m(-1)hr.(-1) at pH5.5-6.0, and decreased at higher or lower pH values. The rate of reaction increased between 20 degrees and 70 degrees , indicating a heat of activation of 13.6kcal./mole.

Chemical Phenomena↗

PubMedDate not supplied

Decreased birth weight and attainment of postnatal catch-up growth in offspring of rats exposed to cigarette smoke during gestation.

Pregnant rats were exposed to cigarette smoke daily for a 2-hour period throughout gestation and the body weights of offspring were monitored for 5 weeks postnatally. The average birth weight of the cigarette smoke exposed pups was significantly smaller compared to both pair-fed and ad libitum control groups. However, the body weights of the pups exposed to smoke were no longer significantly different from those in the pair-fed and ad libitum control groups at weeks 1 and 2 after birth, respectively. This study indicates that fetal growth retardation caused by exposure to cigarette smoke during pregnancy does not persist after birth.

Animals↗