A B S T R A C T The development of hyperphospholipidemia and hypercholesterolemia was studied in infants that required total parenteral nutrition and given a continuous infusion of Intralipid, (1)(2)(3)(4) g/kg body wt per 24 h. Detailed studies were carried out on infusion periods lasting 1-10 d. After 24 h there was a marked increase in plasma free cholesterol (68%) and phospholipid (77%) concentrations. Based on the amount of cholesterol in Intralipid, and the rate of infusion, it was estimated that at least 50% of the plasma cholesterol increment during 64-h infusions was derived from endogenous sources. By contrast, the hyperphospholipidemia could be attributed to the Intralipid as the rise in plasma was calculated to be equivalent to only 16% of the exogenous phospholipid infused. Approximately 10% of the phospholipid in Intralipid was in a triglyceride-free mesophase form with a free cholesterol:phospholipid molar ratio of 0.063. There were no systematic changes in plasma concentrations of cholesterol ester or triglyceride during Intralipid infusions. The increase in free cholesterol and phospholipid was localized in the low density lipoproteins (d = 1.006-1.063 g/ml). The presence of lipoprotein X (Lp-X) 2 Detailed analyses of Intralipid (three preparations) revealed the presence of free cholesterol (4 mg/g Intralipid triglyceride) as well as plant sterols (2 mg/g Intralipid triglyceride). Two Intralipid preparations were subjected to ultracentrifugation at saline density (1.6 x 106 g min). Analysis of the supematant and infranatant fractions obtained after tube slicing revealed that 8-12% of the total phospholipid and free cholesterol was associated with the infranatant fraction as a triglyceride-free micelle. The molar ratio of free cholesterol:phospholipid in the triglyceride-rich supernatant and the infranatant mesophase was 0.063.3Griffin, E. A., M. H. Bryan, and A. Angel. Intralipid tolerance tests and continuous infusion in neonates. Manuscript submitted for publication. cellulose nitrate centrifuge tubes. Plasma (0.6-1.0 ml) was overlayered with saline, pH 7.4 (d = 1.006 g/ml) and centrifuged at 106,000 g for 18 h. A supematant fraction (0.8 ml) and an infranatant fraction (1.2 ml) were quantitatively collected by tube slicing. The infranatant fraction was adjusted to d 1.063 and centrifuged at 106,000 g for 24 h to obtain low density lipoproteins (LDL) in the supernatant fraction. For studies involving protein analyses, LDL was washed once. The infranatant was adjusted to d = 1.21 g/ml and centrifuged for 42 h at 106,000 g to obtain high density lipoproteins (HDL).The lipoproteins ofd 1.006-1.063 were further resolved by hydroxylapatite column chromatography as described by Kostner et al. (14) for the isolation of lipoprotein X (Lp-X) from cholestatic patients. In these studies, columns were eluted at 0.1 M phosphate buffer (pH 6.8) to obtain Lp-X and at 0.65 M phosphate (pH 6.8) to obtain "residual LDL." Because initial studies demonstrated that the elution profiles monitored by optical den...

A B S T R A C T To determine the influence of cardiac ischemia on the activity and subcellular localization of lysosomal cathepsin D, anesthetized rabbits were subjected to ligation of the circumflex coronary artery. Total enzyme activity remained unchanged throughout the 2-h ischemic period, but the subcellular distribution of cathepsin D, as analyzed by biochemical and immunohistochemical techniques, was altered dramatically. A marked increase in nonsedimentable (i.e., 40,000-g supernate) activity developed by 30-45 min and increased further by 2 h. Simultaneously, the immunofluorescent localization of cathepsin D was also changed significantly.Within 30-60 min after occlusion, the fine, particulate staining observed in control myocytes was replaced by bright fluorescent patches composed of large granules. Many of these structures displayed prominent halos of diffuse fluorescent staining in the neighboring myocytic cytoplasm, apparently outside lysosomes per se. After 2 h, when nonsedimentable activity was maximally elevated, most of the fluorescent particles had disappeared completely. During this same interim there was no detectable change in the distribution of lysosomal cathepsin D within interstitial cells. These results are consistent with the hypothesis that an early feature of cardiac ischemia is the release of cathepsin D from myocytic lysosomes into the cytosol of damaged cells.

SUMMARY Cardiac hypertrophy was induced in rats by daily injections of L-thyroxine (1.0 mg/kg).Regression from hypertrophy was studied 4 days after discontinuing thyroxine. Isolated, Langendorffperfused hearts were perfused with Krebs-Henseleit buffer, glucose, insulin, and amino acids. To measure protein synthesis, left ventricular tissue was assayed for incorporation of tritiated phenylalanine into protein. Indices of rates of protein degradation were obtained by measuring the release of cold phenylalanine after blocking protein synthesis with cycloheximide. After 3 days of thyroxine (when cardiac growth was maximally increased), the rate of protein synthesis increased by 22% (P < 0.001). After 1 week, synthesis was 8% greater than control (P < 0.05), and by 2 weeks (when hypertrophy was stable and the rate of cardiac growth was similar to controls), synthesis had returned to control levels. In hearts regressing from hypertrophy, synthesis was reduced to 68% of control (P < 0.001). The rate of protein degradation was decreased by 12% ( P < 0.05) after 3 days of thyroxine, but was not different from control at 1 or 2 weeks. During regression, degradation was 12% below control (P < 0.05). Changes in the release of several amino acids that are synthesized or metabolized in heart (e.g., alanine, glycine, serine) were different from changes in phenylalanine release. In conclusion thyroxine-induced cardiac hypertrophy and regression are accompanied by changes in protein synthesis and degradation, and amino acid metabolism. The predominant change in hypertrophy is increased protein synthesis with a minor contribution from reduced degradation. Regression of hypertrophy is accompanied by decreased synthesis, not increased degradation.THEORETICALLY, cardiac hypertrophy may occur as a consequence of increased protein synthesis, reduced protein degradation, or both. Similarly, a decrease in heart size, as in regression of hypertrophy, might be brought about by accelerated protein degradation, a decreased rate of synthesis, or both.The relative importance of these factors is defined imprecisely. There is a general agreement that protein synthesis is accelerated during the development of hypertrophy, 1 " 5 but reports differ regarding whether rates of degradation are retarded 5 or not. 23 The type and magnitude of changes that occur may depend on the nature, intensity, and duration of the stress imposed on the heart, and on whether or not the hypertrophic process is accompanied by cellular damage and/or repair.To clarify the roles of altered synthesis and degradation of cardiac protein in one experimental model of hypertrophy and regression, we have measured their rates in vitro following induction and Received January 13, 1978; accepted for publication July 12, 1978. cessation of a well-defined stimulus to hypertrophy-daily injections of L-thyroxine in rats. The regimen employed produces rapid growth of the heart (over and above that observed in age-matched controls), predominantly involving myocardial cells and without...

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