The effect of sex on central histaminergic responses and corticosterone bioperiodicity in Sprague-Dawley rats.

Male and female rats demonstrate a difference in the relationship between food intake and H(1) receptor binding, which may be due to hormonal differences that exist. The relationship between the endocrine and histaminergic regulation and synchronization of food intake needs to be elucidated. Male and female rats fed 25% protein displayed bioperiodicity in mean corticosterone levels of 148.95+/-33.71 and 288.48+/-47.84 ng/ml, respectively. Accompanying bioperiodic times were of 22.43+/-1.35 h (males) and a period of 21.42+/-1.96 h (females). Central H(1) receptors in male rats had a mean bioperiodic value of 102.37+/-1.95 pmol/g protein with a period of 21.66+/-1.85 h, while that for females was 97.42+/-4.19 pmol/g protein with a period of 10.23+/-0.95 h. Central histaminergic activity affects feeding in rats with distinct gender variation that is bioperiodic in nature and functions as a major regulatory mechanism.

Human iodine requirements determined by the saturation kinetics model.

Iodine plays a decisive role in metabolism and the process of early growth and development of most organs, especially of the brain. Effects of iodine deficiency include goiter, stillbirth and miscarriage, neonatal and juvenile thyroid deficiency, dwarfism, mental defects, deaf mutism, spastic weakness and paralysis. In this study, the application of a mathematical model (derived from Machaelis-Menten enzyme kinetics) to iodine measured in urine samples from a randomly selected group derived from the Egyptian village of West El-Mawhoub in the Dakhlah Oasis resulted in the conclusion that iodine excretion parameters can be used to characterize iodine utilization and accurately predict the level of salt iodination required to maintain proper physiological functions. The four parameter saturation kinetics model analysis indicated that a salt iodination level of 63 mg/kg reduced the severity of IDD, with 83% of the studied subjects having urinary excretion levels of 1.18 micromol/L. This gives a convenient mechanism for providing adequate dietary iodine with a non-invasive index for the avoidance of IDD. Commercially available salt was analyzed using standard iodiometric titration methods to determine iodination levels. Analysis revealed that only 20% of the commercially available salt complied with the manufacturer's label and revealed the presence of large individual variability between batches amounting to -95 to +150% of the claimed iodine level. Therefore, salt iodination requires careful supervision to ensure that promised iodine levels are being delivered and consumed.