Effects of variations in thyroid hormone serum concentrations on serum ACE-activity

Serum angiotensin converting enzyme activities were significantly increased in 26 untreated hyperthyroid patients (20.3 +/- 5.4 U/ml; P less than 0.001) compared with healthy control subjects (13.1 +/- 2.3 U/ml). In 12 patients a significant fall in enzyme activities was observed after treatment compared with pretreatment serum ACE levels (P less than 0.001). Eight patients with hypothyroidism (15.7 +/- 5.1 U/ml) and 11 athyreotic patients, totally thyroidectomized for well-differentiated thyroid cancer, showed no significant differences in serum ACE activities (14.3 +/- 2.2 U/ml) compared with control subjects. After thyroid hormone supplementation a significant increase in serum ACE activity (P less than 0.05) was found in the athyreotic patients. Addition of increasing amounts of L-thyroxine to a serum sample of an athyreotic patient showed no significant effect on ACE activity in vitro. We suggest that the elevated serum ACE activity in hyperthyroidism is not from the thyroid gland, but represents a direct effect of thyroid hormone on ACE synthesis and/or release from endothelial cells.     

Delipidated serum abolishes the inhibitory effect of serum on in vitro liposome-mediated transfection

All the standard in vitro lipofection has been routinely performed in serum-free medium as the transfection activity of liposome/DNA complexes is sensitive to the presence of serum. In this study, we have demonstrated that lipid-rich serum lipoprotein included in the transfection medium strongly inhibited the transfection activity of DC-chol liposome/DNA complexes in five different cell types (CHO, 293, A2780CP, A431 and SKBR3). The levels of inhibition by serum lipoprotein were rather greater than those by serum and varied with cell types. However, this inhibition was completely abolished by delipidation of serum. Thus, delipidated serum can be included in the transfection medium. The complexes formed in the presence of serum (zeta=-18.2+/-1.07 mV), delipidated serum (zeta=-19.6+/-0.54 mV), IgG (zeta=-21.6+/-1.92 mV) or serum lipoprotein (zeta=-10.5+/-2.33 mV) were as much negatively charged as those in serum-free medium (zeta=-21.3+/-1.60 mV). The results suggest that the inhibition of liposome-mediated transfection by serum was not associated with charges of serum proteins but with lipids or lipid-associated proteins present in serum.     

The effect of thymus extracts on phosphorus compounds in muscle and serum, and on serum calcium

1. Thymectomy in young rabbits decreased the ATP content and increased the inorganic phosphate content of skeletal muscle. The serum calcium content was decreased, whereas the inorganic phosphate content was increased. 2. The administration of a lipid fraction (TL) or protein fractions (CIF and TP) of thymus extracts to thymectomized rabbits in short-term experiments increased the ATP content of muscle and decreased the inorganic phosphate contents of muscle and serum. Serum calcium content was increased. 3. The action of the thymus extract TP was specific only on the phosphate compounds, since the increase in serum calcium concentration was also caused by the control extract from muscle. The action of the extract TL is not specific, being paralleled by the action of a control extract from muscle.