One year comparison of costs of coronary surgery versus percutaneous coronary intervention in the stent or surgery trial.

OBJECTIVES: To compare initial and one year costs of coronary artery bypass grafting (CABG) versus percutaneous coronary intervention (PCI) in the stent or surgery trial. DESIGN: Prospective, unblinded, randomised trial. SETTING: Multicentre study. PATIENTS: 988 patients with multivessel disease. INTERVENTIONS: CABG and stent assisted PCI. MAIN OUTCOME MEASURES: Initial hospitalisation and one year follow up costs. RESULTS: At one year mortality was 2.5% in the PCI arm and 0.8% in the CABG arm (p = 0.05). There was no difference in the composite of death or Q wave myocardial infarction (6.9% for PCI v 8.1% for CABG, p = 0.49). There were more repeat revascularisations with PCI (17.2% v 4.2% for CABG). There was no significant difference in utility between arms at six months or at one year. Quality adjusted life years were similar 0.6938 for PCI v 0.6954 for PCI, Delta = 0.00154, 95% confidence interval (CI) -0.0242 to 0.0273). Initial length of stay was longer with CABG (12.2 v 5.4 days with PCI, p < 0.0001) and initial hospitalisation costs were higher (7321 pounds sterling v 3884 pounds sterling for PCI, Delta = 3437 pounds sterling, 95% CI 3040 pounds sterling to 3848 pounds sterling). At one year the cost difference narrowed but costs remained higher for CABG (8905 pounds sterling v 6296 pounds sterling for PCI, Delta = 2609 pounds sterling, 95% CI 1769 pounds sterling to 3314 pounds sterling). CONCLUSIONS: Over one year, CABG was more expensive and offered greater survival than PCI but little added benefit in terms of quality adjusted life years. The additional cost of CABG can be justified only if it offers continuing benefit at no further increase in cost relative to PCI over several years.

Off-pump coronary artery bypass grafting provides complete revascularization with reduced myocardial injury, transfusion requirements, and length of stay: a prospective randomized comparison of two hundred unselected patients undergoing off-pump versus conventional coronary artery bypass grafting.

OBJECTIVE: Retrospective comparisons of selected patients undergoing off-pump versus conventional on-pump coronary artery bypass grafting have yielded inconsistent results and raised concerns about completeness of revascularization in off-pump coronary artery bypass grafting. METHODS: Two hundred unselected patients referred for elective primary coronary artery bypass grafting were randomly assigned to undergo off-pump coronary artery bypass grafting with an Octopus tissue stabilizer (Medtronic, Inc, Minneapolis, Minn) or conventional coronary artery bypass grafting with cardiopulmonary bypass by a single surgeon. Revascularization intent determined before random assignment was compared with the revascularization performed. All management followed strict, unbiased, criteria-driven protocols. Patients and nonoperative care providers were blinded to surgical group. RESULTS: Baseline characteristics were similar. The number of grafts performed per patient (mean +/- SD 3.39 +/- 1.04 for off-pump coronary artery bypass grafting, 3.40 +/- 1.08 for conventional coronary artery bypass grafting) and the index of completeness of revascularization (number of grafts performed/number of grafts intended, 1.00 +/- 0.18 for off-pump coronary artery bypass grafting, 1.01 +/- 0.09 for conventional coronary artery bypass grafting) were similar. Likewise, the index of completeness of revascularization was similar between groups for the lateral wall. Combined hospital and 30-day mortalities and stroke rates were similar. Postoperative myocardial serum enzyme measures were significantly lower after off-pump coronary artery bypass grafting, suggesting less myocardial injury. Adjusted postoperative thromboelastogram indices, fibrinogen, international normalized ratio, and platelet levels all showed significantly less coagulopathy after off-pump coronary artery bypass grafting. Patients undergoing off-pump coronary artery bypass grafting received fewer units of blood, were more likely to avoid transfusion altogether, and had a higher hematocrit at discharge. Cardiopulmonary bypass was an independent predictor of transfusion (odds ratio 2.42, P =.0073) by multivariate analysis. More patients undergoing off-pump coronary artery bypass grafting were extubated in the operating room and within 4 hours. Postoperative length of stay (in days) was shorter for off-pump coronary artery bypass grafting (5.1 +/- 6.5 for off-pump coronary artery bypass grafting, 6.1 +/- 8.2 for conventional coronary artery bypass grafting, P =.005 by Wilcoxon test). One patient (in the conventional coronary artery bypass grafting group) required angioplasty for graft closure within 30 days. CONCLUSIONS: When compared with conventional coronary artery bypass grafting with cardiopulmonary bypass, off-pump coronary artery bypass grafting achieved similar completeness of revascularization, similar in-hospital and 30-day outcomes, shorter length of stay, reduced transfusion requirement, and less myocardial injury.

Impact of the Duett sealing device on quality of life and hospitalization costs for coronary diagnostic and interventional procedures: Results from the Study of Economic and Quality of Life substudy of the SEAL trial.

BACKGROUND: The Simple and Effective Arterial Closure (SEAL) trial examined the safety and effectiveness of the Duett vascular sealing device (Vascular Solutions, Minneapolis, Minn) versus manual compression after diagnostic and interventional coronary procedures. We compared quality of life and initial hospitalization costs among patients treated with the Duett device versus manual compression. METHODS: Functional status was assessed with the Duke Activity Status Index (DASI) at 7 and 30 days after intervention. General health status was assessed with the Short Form (SF-36) at 30 days after intervention. Hospitalization costs were derived from the UB92 formulation of the hospital bill. RESULTS: There was a strong trend toward higher functional status in patients receiving treatment with the Duett device at 7 days both before (P =.04) and after (P =.08) adjustment for significant covariates. This difference was significant in the diagnostic group but not in the interventional group. No significant differences in quality of life between the Duett device and manual compression at 30 days were found. There was no significant difference in total hospitalization costs between treatment arms (P =.91). For interventional patients, mean total in-hospital costs were $10,167 in the Duett group and $10,225 in the manual compression group (P =.82). For diagnostic patients, mean hospitalization costs were $7784 and $7996 for the Duett device and manual compression groups, respectively (P =.72). Trends toward reduced recovery/observation room costs with the Duett device (P =.06) were found; this difference was significant in the diagnostic group ($198 vs $279, P =.02). CONCLUSIONS: The Duett sealing device was associated with significantly higher functional status at 7 days after the procedure in addition to shortened time to hemostasis and ambulation, with no associated increase in cost.

Trends in outcome and costs of coronary intervention in the 1990s.

Our objective was to examine trends in outcome and cost of percutaneous coronary intervention (PCI) between 1990 and 1999. PCI has become the most common form of myocardial revascularization in recent years, rivaling the more established coronary artery bypass surgery. There has been increasing interest in improving outcome of PCI while also seeking to minimize cost. A total of 21,755 patients undergoing PCI were evaluated. Clinical data were gathered from the Emory Cardiovascular Database and financial data from the UB92 formulation of the hospital bill. Charges were reduced to cost using departmental cost-to-charge ratios. Costs were inflated to 1999 dollars using medical care inflation rates. Mortality varied without a significant trend from 0.63% to 0.44% (p = 0.64). The Q-wave myocardial infarction rate decreased from 0.68% to 0.40% (p = 0.0003). Emergent coronary surgery decreased from 3.50% to 1.25% (p <0.0001). Mean hospital inflation-adjusted cost decreased from $10,478 to $8,367 (p <0.0001). Length of stay after the procedure decreased from 2.8 to 1.8 days (p <0.0001). Outcome of PCI continues to improve, with a decrease in coronary surgery and Q-wave myocardial infarction but with no significant change in mortality. This was accomplished while also decreasing costs and length of stay. Whether these favorable trends will continue remains to be seen.

Response to measles, mumps, and rubella revaccination among HIV-positive and HIV-negative children and adolescents with hemophilia. Hemophilia Growth and Development Study.

The effect of human immunodeficiency virus (HIV) infection on response to measles, mumps, and rubella revaccination in children and adolescents with hemophilia was evaluated. Antibody levels of measles, mumps, and rubella were assayed at baseline and two annual examinations in 207 HIV-positive and 126 HIV-negative hemophiliacs participating in the Hemophilia Growth and Development Study (HGDS). Response to revaccination was analyzed for participants whose antibody levels were below the cut-off at the start of a year-long observation period. Among HIV-positive participants, antibody levels were below cut-off in 52 subjects for measles, in 71 for mumps, and in 96 for rubella. Among HIV-negative participants, antibody levels were low in 23 subjects for measles, in 23 for mumps, and in 31 for rubella. For measles and mumps antigens, revaccination was associated with a significant increase in redraw antibody levels for HIV-negative participants. Although there was an increase in the mean measles titers for revaccinated HIV-positive participants, it was not significant. Revaccination was associated with an increase in rubella antibodies in HIV-positive and HIV-negative participants. Revaccination with measles and mumps was associated with an increase in antibody levels in HIV-negative participants but not in HIV-positive participants. Both HIV-positive and HIV-negative participants responded to rubella revaccination with an increase in antibody levels.

HIV-associated changes in adaptive, emotional, and behavioral functioning in children and adolescents with hemophilia: results from the Hemophilia Growth and Development Study.

OBJECTIVE: To assess changes in adaptive, emotional, and behavioral functioning over four years in children and adolescents with hemophilia and with or without HIV infection and to evaluate the relationship of these changes to immune status. METHODS: Participants were 277 HIV-seropositive and 126 HIV-seronegative boys with hemophilia. Participants with HIV infection were divided into three groups based on trajectory of immune functioning (CD4+ cell counts) over the course of the study. Caregivers completed the Vineland Adaptive Behavior Scales and Pediatric Behavior Scale (PBS). RESULTS: Results showed declining Vineland Communication scores for participants with consistently poor immune functioning. These participants also started with more PBS Attention Deficit and Deviation symptoms, which then decreased more sharply than for other groups. Low CD4+ counts were consistently associated with more Health and Depression-Anxiety symptoms on the PBS. However, with few exceptions, group means remained within normal limits. CONCLUSIONS: According to their caregivers, boys with hemophilia and HIV infection showed considerable resilience with regard to adaptive behavior and emotional and behavioral problems. However, over time changes occurred in these areas that appear to be related to immune functioning.

Ten-year trends in heart valve replacement operations.

BACKGROUND: There has been increasing concern in recent years about the quality and cost of heart valvular replacement procedures. The purpose of this study is to examine the profile of patients undergoing valvular operations during the past decade, and to look at trends in outcome and resource utilization over that period. METHODS: Clinical and procedural data of 2,972 patients undergoing heart valve replacement at Emory University Hospitals between 1988 and 1997 were recorded prospectively on standardized forms by trained medical personnel and entered into a computerized database. RESULTS: There were 1,802 patients undergoing aortic valve replacement (AVR), 966 undergoing mitral valve replacement (MVR), and 204 undergoing combined aortic and mitral valve procedures (AVR + MVR). No patients were excluded. There was a statistically significant trend for patients undergoing AVR, MVR, or AVR + MVR over time to be older and sicker by multiple criteria. Nonetheless, procedural outcome and inhospital mortality for patients undergoing AVR remained unchanged. Cost and length of stay increased from 1988 to 1992 when a concerted effort to decrease resource utilization began. Between 1992 and 1997 for AVR, length of stay decreased from 13.4 to 8.0 days and cost from $37,047 to $21,856. Similarly, between 1992 and 1997 for MVR, length of stay decreased from 15.6 to 8.1 days and cost from $45,072 to $21,747. The net result over the time period from 1988 to 1997 was an average decline in the cost of operation of $785 a year, adjusted for other factors. CONCLUSIONS: This study reveals that outcome of valvular replacement during the period from 1988 to 1997 has remained constant despite the patients becoming older and sicker during the same period. This constant outcome has been accomplished, but length of stay has decreased significantly. Hospital costs increased during the first years of the study period, but then decreased to levels in 1997 that were equal to or significantly less than 1988 levels.

Declining immune function in children and adolescents with hemophilia and HIV infection: effects on neuropsychological performance. Hemophilia Growth and Development Study.

OBJECTIVE: To determine whether declines in immune functioning are associated with changes in neuropsychological performance in children and adolescents with hemophilia who are infected with the human immunodeficiency virus (HIV). METHODS: Participants were 333 males with hemophilia, ages 6-19 years at entry. A baseline and four annual neuropsychological evaluations were given. A longitudinal growth curves analysis of data was performed to detect changes associated with declining immune function. The cohort was stratified into four groups: (1) HIV- (n = 126); (2) HIV+, average of first two and last two CD4 counts > or = 200, (n = 106; High CD4 group); (3) HIV+, average first two counts > or = 200, average last two counts < 200 (n = 41; CD4 Drop group); and (4) HIV+, average first two and last two counts < 200 (n = 60; Low CD4 group). RESULTS: There were significant differences among the four groups over time in nonverbal intelligence, perceptual/performance skills, nonverbal memory, academic achievement, and language. The Low CD4 group consistently showed the greatest decrement in performance. On measures showing a practice effect for repeated measurements, the Low CD4 group participants' scores remained stable over time, suggesting opposing effects of practice and HIV-related declines. Lowered academic performance relative to IQ was found in all groups. CONCLUSIONS: Declines in neuropsychological functioning are directly related to declines in immune functioning in HIV+ children, adolescents, and young adults with hemophilia. Hemophilia itself may be a risk factor for academic underachievement.

Changes in hepatitis B serologic titers in HIV+ and HIV- children with haemophilia.

This longitudinal study examines differences in hepatitis B immune titres in children and adolescents with haemophilia to determine if they are dependent on how immunity was acquired (vaccination or natural infection), and whether they are related to the child's HIV status and/or are influenced by HIV disease progression. Serologic titres (HBcAb, HBsAb) and HBsAg were measured prospectively at baseline, and at years 1, 2 and 3 of follow-up in 126 HIV- and 207 HIV+ children and adolescents with haemophilia. Analyses were performed to assess the impact of HIV status on the measured titres, and for HIV+ subjects to examine the association with CD4+ lymphocyte counts and p24 antigen status. The results show that HIV+ children were more likely than HIV- children to lose vaccine-induced immunity as indicated by the loss of HBsAb. There was an increased risk of losing HBsAb with higher CD4+ counts and younger age. Re-immunization was not successful in seven of eight HIV+ children. Two subjects (one HIV+, one HIV-) entered the study HBsAg- but became HBsAg+ over the course of follow-up. Seven HIV+ subjects lost natural immunity as indicated by the loss of HBcAb. The loss of either HBsAb or HBcAb in HIV--subjects was negligible to absent. In conclusion, because of the loss of immunity in HIV+ children the viral safety of factor replacement concentrates for these children is an important consideration. HIV- children rarely lose immunity, therefore frequent measures of HBsAb are not necessary.

HIV-associated immune dysfunction and delayed pubertal development in a cohort of young hemophiliacs. Hemophilia Growth and Development Study.

As part of the Hemophilia Growth and Development Study (HGDS), we investigated the relationship between HIV-associated immune dysfunction and delayed pubertal development in a cohort of 333 boys and adolescents with moderate or severe hemophilia who were between the ages of 6 and 19 years at study entry in 1989. Sixty-two percent of the cohort was infected with HIV in the late 1970s and early 1980s through exposure to contaminated clotting factor concentrates. The cohort was observed during follow-up at 6-month intervals; measurements taken at each follow-up visit included Tanner stage and CD4+ cell count. This analysis of data from the first 4 years of follow-up revealed statistically significant delays in pubertal development associated with increasing levels of immune dysfunction. Our results emphasize the importance of following pubertal development in HIV-infected adolescent boys since delays in maturation may reflect underlying disease progression.

Mucoepidermoid carcinoma of the trachea in a child.

Primary tracheal neoplasms in children, especially malignant lesions, are extremely rare. We report a unique case of low-grade mucoepidermoid carcinoma of the trachea in a 4-year old child, presenting as new-onset asthma. Using the ventilating resectoscope, endoscopic excision was accomplished without complications. The case is presented with documentation including airway films, endoscopic photographs, and histopathology. The diagnosis of tracheal masses depends upon maintaining a high index of suspicion, complemented by imaging and timely diagnostic endoscopy. A review of the literature is included.

Comparability of absolute/percent CD4+ T-lymphocytes completed locally and centrally. Hemophilia Growth and Development Study.

The Hemophilia Growth and Development Study (HGDS) is a multicenter longitudinal study of 333 male children and adolescents with moderate or severe hemophilia, ranging in age from 6 to 19 at entry. Sixty-two percent of the cohort was infected with human immunodeficiency virus (HIV) in the late 1970s and early 1980s through exposure to contaminated clotting factor concentrates. The HGDS has followed this cohort since 1989. HGDS subjects have blood drawn twice each year for t-lymphocyte subsets, with fresh blood shipped overnight to a central laboratory. T-lymphocyte subsets from the same blood draw are often determined locally as well. To evaluate interlaboratory variation, we examined the comparability of pairs of local and central results for CD4+ absolute counts and percents. Ninety-four pairs of absolute counts and 73 pairs of percent CD4 + results were available. We calculated concordance correlation coefficients, which evaluate the agreement between two readings from the sample by measuring the variation from the 45 degrees line through the origin. Absolute counts were square root transformed. Comparability of the pairs was high for both absolute counts and percents (0.93 and 0.92, respectively). Agreement was high whether we determined the CD4+ counts and percents centrally, using fresh samples received the day after the examination (0.95, 0.95), or from specimens that were frozen upon receipt and batched for later testing (0.90, 0.87). We conclude that when a centrally processed CD4+ result is unavailable because of shipping problems or loss of specimens, a study may reasonably accept a CD4+ result completed locally, if validity checks indicate good comparability. In the HGDS, the data provided by the local laboratories were of comparable quality to those provided by the central laboratories.

Sodium ipodate (oragrafin) in the preoperative preparation of Graves' hyperthyroidism.

Fourteen Graves' hyperthyroid patients who had been prepared for surgery with sodium ipodate (SI) 500 mg orally twice daily for 3 days were retrospectively studied. SI was administered in combination with propylthiouracil (10 cases) and beta blockers (all cases), which had been previously initiated. Free serum thyroxine (T4) and total triiodothyronine (T3) concentrations were measured before and after SI therapy on the morning of surgery. SI treatment significantly reduced total T3 concentration from 445.9 to 193.4 ng/dL (P < 0.0001) and free T4 concentration from 3.874 to 2.800 ng/dL (P = 0.0003). Preoperatively, only one patient had persistent tachycardia, and intraoperatively this same patient required beta blockers. Blood loss was unremarkable or reduced (average blood loss, 121 mL). On clinical examination glands were firm with normal or somewhat decreased vascularity. On histologic study all glands demonstrated changes consistent with treated Graves' disease. Preoperative treatment with SI appears to be a safe and efficacious method of preparing hyperthyroid patients for surgery.

Cutaneous ureterostomy in adults.

In the patient with metastatic carcinoma, urinary diversion is usually achieved with indwelling ureteral stents or placement of a percutaneous nephrostomy tube. Most forms of surgical diversion carry an unacceptable morbidity rate, especially in the debilitated patient. Over a fifteen-year period (1974-1989), 29 adult patients with pelvic malignancy (32 ureters) underwent palliative cutaneous ureterostomy. This previously reported technique involves transverse nephropexy and construction of a stoma using a small skin flap. Indications included ureteral obstruction or severe urinary tract symptoms. Hydroureter, often considered a precondition for this procedure, was not present in several patients and was not a prerequisite to success. Complications related to the procedure included one postoperative death due to stroke, one death due to uremia and sepsis, and one instance of severe renal arterial stenosis resulting in renal failure. Preservation of renal function was possible in the 10 patients known to have survived from one to thirteen years postoperatively; only 3 patients eventually required stomal revision. By adherence to the surgical techniques described, the usually high incidence of stomal stenosis was avoided. Our experience reveals that although the indications for cutaneous ureterostomy are limited, this procedure can provide an alternative to permanent nephrostomy drainage or to a higher risk intestinal urinary diversion in carefully selected patients with a reasonable life expectancy.

Relative lipophilicities, solubilities, and structure-pharmacological considerations of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors pravastatin, lovastatin, mevastatin, and simvastatin.

The apparent octanol-water partition coefficients (Po/w) and aqueous solubilities for four 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors [pravastatin, lovastatin (mevinolin), mevastatin (compactin), and simvastatin (synvinolin)] were compared. Pravastatin is highly hydrophilic compared with lovastatin, mevastatin, or simvastatin. Pravastatin is clinically used as the active hydroxy acid, while the other three compounds are administered as prodrug lactones which, over a period of time, convert in vivo to their respective active hydroxy acid forms. The order of the Po/w values of the hydroxy acid forms was pravastatin much less than mevastatin less than lovastatin less than simvastatin at each pH evaluated, with approximate ratios of 1:25:75:200, respectively. The relative order and the ratios of partition coefficients for the lactone forms were similar to those for the hydroxy acid forms. In addition, lovastatin, mevastatin, and simvastatin are virtually insoluble in water, with solubility values ranging from 0.0013 to 0.0015 mg/mL at 23 degrees C. In comparison, pravastatin is hydrophilic, as demonstrated by the greater than 100-fold greater solubility of its lactone form (0.18 mg/mL). The greater hydrophilicity of pravastatin may explain its reported lower permeation into nonhepatic cells and the selectivity with respect to inhibition of cholesterol synthesis.

Clonazepam versus alprazolam in the treatment of panic disorder: interim analysis of data from a prospective, double-blind, placebo-controlled trial.

The authors present interim results of a prospective, random assignment, double-blind, placebo-controlled trial conducted to determine whether clonazepam is as effective as alprazolam in reducing the frequency of panic attacks and whether both agents are superior to placebo. Analysis on 44 of 60 randomized subjects showed no statistically significant differences between the clonazepam and alprazolam groups on the following clinically meaningful outcome measures: total number of panic attacks and percent of time subjects experienced anticipatory anxiety, extent of phobic avoidance, and fear. Statistically significant differences did exist among the drug and placebo groups on these measures. The authors conclude that this interim analysis of the data supports the inclusion of clonazepam in the treatment of panic disorder.

Cytotoxicity and mutagenicity of aflatoxin dichloride in normal and repair deficient diploid human fibroblasts.

The cytotoxic and mutagenic effect of aflatoxin B1-dichloride (AFB1-Cl2), a direct-acting carcinogen which is a model for the proposed ultimate reactive metabolite of AFB1 (the 2,3-epoxide), was compared in normal, repair-proficient, diploid human fibroblasts and in complementation Group A xeroderma pigmentosum cells (XP12BE) which are virtually incapable of excision repair of DNA damage induced by ultraviolet radiation, the 7,8-diol-9,10-epoxide of benzo[alpha]pyrene, and several reactive aromatic amide derivatives. The XP cells were significantly more sensitive than normal to the cytotoxic and mutagenic effects of AFB1-Cl2, not only as a function of concentration administered but also of the number of AFB1-Cl2 residues initially bound to DNA. Cytotoxicity was determined from survival of colony-forming ability; resistance to 6-thioguanine was the genetic marker used for mutagenicity. We compared the rate of loss of AFB1-Cl2-DNA adducts from cells treated and held in the non-dividing state (confluent) over several days, as well as their ability to recover from the potentially mutagenic and/or cytotoxic effects of the agent. AFB1-Cl2 residues were lost from both strains of cells and both exhibited a gradual increase in survival. However, the rate of loss of adducts from the DNA in the normal cells was more rapid than in XP cells and they exhibited recovery from higher doses of AFB1-Cl2 than XP cells. The major primary DNA adduct formed in the human cells and in isolated DNA was a chemically unstable guanine derivative which could undergo a change in structure with time posttreatment to form a more stable secondary adduct. The cytotoxic effect of AFB1-Cl2 was highly correlated with the presence of either of these guanine adducts. Evidence suggests that the primary adduct is an N7-guanine adduct. The kinetics of the loss of this guanine and its transformation into the more stable secondary adduct resembled that reported recently for the major primary DNA adduct formed by the reaction of AFB1 at the N-7 position of guanine in the DNA of normal and XP cells and its transformation into the putative AFB1-ring opened triamino pyrimidyl structure.

Neutral triglyceride lipase in macrophages.

High levels of neutral triglyceride lipase activity have been demonstrated in several types of macrophages (J774 cells, human monocyte/macrophages, rabbit alveolar macrophages, and resident mouse peritoneal macrophages). The pH optima ranged from 6.5 to 7.4 depending upon the buffer and the conditions of incubation. The addition of bovine serum albumin stimulated activity at low concentrations, as expected for a fatty acid-releasing reaction, but strongly inhibited at higher concentrations; maximal activity was observed in the presence of 0.625 mg/ml of bovine serum albumin. The enzyme was remarkably thermostable, showing no apparent loss of activity at 50 degrees C for as long as 6 hours. The lipase was inhibited 80% by 0.1 M NaCl. Assayed under optimal conditions, the specific activity of the neutral triglyceride lipase from J774 cells was more than 100-fold greater than the activity of lipoprotein lipase or neutral cholesterol esterase from those cells; this activity was 10-fold greater than the levels of hormone-sensitive lipase from 3T3-L1 adipocytes. This neutral triglyceride lipase may play an important role in the degradation and mobilization of cytosolic triglyceride in macrophage-derived foam cells.

Enhanced macrophage degradation of biologically modified low density lipoprotein.

Low density lipoprotein (LDL) conditioned by incubation in the presence of rabbit aortic or human umbilical vein endothelial cells (endothelial cell-modified LDL) was degraded by macrophages three to five times more rapidly than LDL incubated in the absence of cells (control LDL). This enhanced degradation occurred mostly via a high affinity, saturable pathway related to the pathway for macrophage uptake of acetylated LDL. Conditioning LDL with cultured aortic smooth muscle cells had a qualitatively similar but smaller effect; conditioning with fibroblasts had no effect. Conditioning very low density lipoproteins or high density lipoproteins with endothelial cells did not affect subsequent metabolism of these lipoproteins by macrophages. Endothelial cell-modified LDL, while degraded more rapidly than control LDL by macrophages, was degraded more slowly by cultured smooth muscle cells and by human skin fibroblasts. Degradation of endothelial cell-modified LDL by macrophages was accompanied by stimulation of cholesterol esterification, inhibition of cholesterol synthesis, and a net increment in total cellular cholesterol content. Thus, a biologically generated modification of LDL is described that markedly alters cholesterol metabolism of macrophages and, consequently, may play a role in foam cell formation during atherogenesis.