Background The stability of parathyroid hormone (PTH) in blood ex vivo is a significant practical problem for laboratories and clinicians. Several studies have suggested that PTH is more stable in blood collected into a potassium edetate (EDTA) preservative.

No abstract

The relationship between macrovascular disease and serum lipids, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL), and subfraction cholesterol, and apolipoproteins has been examined in 53 female and 95 male patients with non-insulin-dependent diabetes mellitus (NIDDM). In males, those with macrovascular disease had higher serum and LDL cholesterol concentrations than those without. In females, those with macrovascular disease had higher levels of serum triglyceride, cholesterol, LDL cholesterol, as well as lower HDL, HDL2, and HDL3 cholesterol and apoprotein A-1, than those without. On multivariate analysis, LDL cholesterol was the most important association with macrovascular disease in males and apoprotein A-1 in females. In a subgroup of 36 patients, a double-blind placebo controlled study using bezafibrate or placebo, in addition to conventional oral hypoglycaemic therapy over 4 months, showed falls in serum and LDL cholesterol and in serum triglyceride and a rise in HDL cholesterol in the treated group. These changes should reduce the incidence of macrovascular disease in NIDDM and we suggest further prospective studies of such therapy in addition to conventional oral hypoglycaemic agents.

The separation and properties of heat-stable phosphatase effectors from muscle and liver were studied using phosphoprotein phosphatases with molecular weights of 250000, 65 000 and 30000. Muscle inhibitors that were only active when phosphorylated were eluted from DEAE-cellulose by 20 mM NaCl (inhibitor 1) and 65 mM NaCl (inhibitor 1 '). Available evidence suggests that these are different forms of the same protein and that inhibitor 1' more closely resembles the native inhibitor. Liver extracts contained only the form eluted by 20 mM NaC1. These inhibitors did not affect the activity of the smallest enzyme. Both tissues also contained a non-phosphorylatable inhibitor of phosphorylase phosphatase activity (inhibitor 2) and an activator of phosphohistone phosphatase activity that affected all three enzymes. There was no evidence for the presence of effectors that were specific for only one of the phosphatases employed. The ratio of phosphorylatable to non-phosphorylatable inhibitor was much lower in liver than in muscle. Corresponding effectors from muscle and liver had similar physical properties and similar effects upon the activities of the three enzymes. Phosphorylase phosphatase activity was not affected by the activator. The 250000-Mr enzyme was relatively less sensitive than the 65000-M, enzyme to inhibitor 2, and more sensitive to inhibitor 1'. With phosphohistone as substrate, only the largest enzyme was inhibited by inhibitor 1 and no enzyme was inhibited by inhibitor 1' or inhibitor 2. There was no apparent competition between effectors. The presence of one effector did not modify the action of any of the others.Although it is now established that the reversible phosphorylation of enzymes and proteins can play a significant part in the control of a wide variety of cellular functions, the role of phosphoprotein phosphatases in the process is still poorly understood.