Despite some early doubts concerning its presence in plasma and its physiological function (1-4), the thyroxine-binding prealbumin of human serum (TBPA) is now known to play a significant role in the transport of thyroxine (T4) (5-8). Normally, as assessed by in vitro techniques, TBPA appears to bind at least 25 to 35%o of T4 in serum (5,6). In the serum of many patients with severe acute or chronic illness, however, the proportion of endogenous T4 in serum bound by TBPA and the T4-binding capacity of TBPA decline (8,9). The recent availability of substantial quantities of a highly purified preparation of TBPA has made possible an investigation of the in vivo metabolism of this protein in normal patients and in patients with a variety of disorders that lead to decreased binding of T4 by TBPA in serum. In addition, the cause of this decrease in T4 binding in the serum of such "sick" patients has been evaluated. A portion of the findings has been presented in abstract form (10). While these studies were in progress, Oppenheimer, Surks, Bernstein, and Smith reported similar studies in abstract form (11,12). MethodsHighly purified TBPA was prepared from plasma Fraction IV-6 (method 6) of Cohn and colleagues (13).* Submitted for publication April 9, 1965; accepted June 16, 1965. This The method of purification of the protein and details of its characterization will be described in detail elsewhere (14). Additional characterization of the specific batch of protein employed in the present studies was carried out. Solutions of TBPA (2.0 g per 100 ml), enriched with I'-labeled T4,1 were subjected to electrophoresis in acrylamide gel in a Tris-maleate buffer system,2 pH 9.2. Gel concentrations of 5.0, 7.0, and 8.0 g per 100 ml were employed, and, in some instances, two dimensional gel electrophoretic studies were conducted (15). After electrophoresis, gels were radioautographed and then stained with amido black 10 B.Iodination of TBPA. To minimize the possibility of denaturing the TBPA during the iodination process, a technique was developed for iodinating protein by a microdiffusion process. The technique, an adaptation of that described by Banerjee and Ekins (16), was first employed in tests with human serum albumin (HSA) or with purified TBPA for relatively low specific activity labeling. When the method had been standardized, it was employed for higher specific activity labeling of the TBPA used in the present studies. This was performed as follows. All glassware and buffer media employed were autoclaved before use. A 2.0 g per 100 ml solution of TBPA was prepared in 0.01 M phosphate buffer, pH 7.5, and 200 Al was pipetted into the center well of a single side-armed Warburg flask of 5.0 ml capacity. NaI' (10 to 15 mc, free of carrier iodide and reducing agent),8 together with 60 Ag of unlabeled NaI, was introduced into the main compartment of the vessel in approximately 1 ml of phosphate buffer. Five hundred Al of fresh 3% H202 4 was added to the side arm, and the vessel was closed with a greased ground-glass stopp...

It has long been known that fat accumulates in old injured cells both in tissue culture and in many mammalian disease states. The use of L cells grown in suspension tissue culture permitted the opportunity to study conditions in which lipide accumulation could be retarded or accelerated.These cultures exhibit a three-phase growth curve which is similar to that previously found with bacteria and consists of a lag period, logarithmic growth period, and stationary period. Daily aliquots were removed from cultures going through these phases and protein and cholesterol content correlated with celt division.It was found that L cells gradually accumulated lipide in the cell concurrent with retardation of cell division and protein synthesis. Conversely old lipide-laden cells, placed in fresh media and encouraged to active division with net protein synthesis progressed from a high to a low lipide/cell ratio over a period of 2 to 4 days. An amino acid analogue p-fluorophenylalanine and a mitotic inhibitor, colchicine, also markedly increased the lipide/cell ratio. Similar results were found in in vitro experiments with Ehrlich ascites cells.

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Strain L cells accumulate lipid, concurrent with cessation of protein synthesis, in the stationary phase of growth from the extracellular medium and as a result of de novo synthesis. Cells which have been more severely damaged with an amino acid analogue also accumulate lipid from the extracellular medium, but synthesize very little lipid from labeled acetate. The possible roles which lipid accumulation may play in the cell are discussed.