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Biomedical subjects

D M Levine

Publications and source records attributed to D M Levine.

At least 37 records · Page 2Linked to original sources
PubMed1997

Automated measurement of mouse apolipoprotein B: convenient screening tool for mouse models of atherosclerosis.

Although mice are commonly used for studies of atherosclerosis, investigators have had no convenient way to quantify apolipoprotein (apo) B, the major protein of atherogenic lipoproteins, in this model. We now report an automated immunoturbidimetric assay for mouse apo B with an NCCLS imprecision study CV < 5%. Added hemoglobin up to 50 g/L did not interfere with the assay, nor did one freeze-thaw cycle of serum samples. Assay linearity extends to apo B concentrations of 325 mg/L. We have used the assay to determine serum apo B concentrations under several atherogenic conditions, including the apo E "knock-out" genotype and treatment with a high-cholesterol diet. Our assay can be used to survey inbred mouse strains for variants in apo B concentrations or regulation. Moreover, the mouse can now be used as a convenient small-animal model to screen compounds that may lower apo B concentrations.

Animals↗
PubMed1996

Low lipid concentrations in critical illness: implications for preventing and treating endotoxemia.

OBJECTIVES: To determine the prevalence and clinical significance of hypolipidemia found in critically ill patients, and whether the addition of a reconstituted lipoprotein preparation could inhibit the generation of tumor necrosis factor-alpha (TNF-alpha) in acute-phase blood taken from these patients. SETTING: Surgical intensive care unit (ICU) of a large urban university hospital. DESIGN: Prospective case series. PATIENTS: A total of 32 patients with a variety of critical illnesses had lipid and lipoprotein concentrations determined. Six patients and six age- and gender-matched control subjects had whole blood in vitro studies of the effect of lipoprotein on lipopolysaccharide mediated TNF-alpha production. INTERVENTIONS: Blood samples were drawn on admission to the ICU and over a subsequent 8-day period. MEASUREMENTS AND MAIN RESULTS: Mean serum lipid and lipoprotein values obtained from patients within 24 hrs of transfer to the surgical ICU were extremely low: mean total cholesterol was 117 mg/dL (3.03 mmol/L), low-density lipoprotein cholesterol 71 mg/dL (1.84 mmol/L), and high-density lipoprotein cholesterol 25 mg/dL (0.65 mmol/L). Only the mean triglyceride concentration of 105 mg/dL (1.19 mmol/L), and the mean lipoprotein(a) concentration of 25 mg/dL (0.25 g/L) were within the normal range. During the first 8 days following surgical ICU admission, there were trends toward increasing lipid and lipoprotein concentrations that were significant for triglycerides and apolipoprotein B. Survival did not correlate with the lipid or lipoprotein concentrations, but patients with infections had significantly lower (p = .008) high-density lipoprotein cholesterol concentrations compared with noninfected patients. Lipopolysaccharide-stimulated production of TNF-alpha in patient and control blood samples was completely suppressed by the addition of 2 mg/mL of a reconstituted high-density lipoprotein preparation. CONCLUSIONS: Patients who are critically ill from a variety of causes have extremely low cholesterol and lipoprotein concentrations. Correction of the hypolipidemia by a reconstituted high-density lipoprotein preparation offers a new strategy for the prevention and treatment of endotoxemia.

Adult↗
PubMed1996

Visualization of hepatitis C virions and putative defective interfering particles isolated from low-density lipoproteins.

Hepatitis C virus (HCV) in highly infectious sera has been shown to be predominantly associated with low-density lipoproteins. To determine whether the association is specific to low-density lipoproteins (LDL) or very low-density lipoproteins (VLDL), we fractionated HCV-containing plasma by a column chromatographic procedure known to separate these classes. Hepatitis C virus RNA detected by polymerase chain reaction (PCR) was associated primarily with the very low-density (VLDL) fraction. However, it could not be ruled out that virus-associated LDL may have eluted with this fraction. Hepatitis C virus virions isolated from sera having sufficient titre for visualization by electron microscopy are generally coated with antiviral antibodies, therefore we utilized the lipid association to isolate antibody-free virions. Very low-density lipoproteins were isolated by ultracentrifugal flotation and then treated with deoxycholate to release the virions. These were then isolated in a highly purified form by centrifugation in a sucrose gradient. The 1.10-1.11 g ml-1 region of the gradients contained 60-70 nm particles. Particles with similar surface structure but having a diameter of only 30-40 nm constituted about 30% of the total. The latter may represent defective interfering particles. The identity of both small and large particles with HCV virions and associated particles was confirmed by their trapping on grids by an anti-HCV E2 monoclonal antibody, and by their aggregation by rabbit antiserum to an amino-terminal peptide of E1. Thus, both E1 and E2 epitopes are displayed on the surface of intact HCV virions.

Blood↗
PubMed1995

Racial differences in the incidence of gout. The role of hypertension.

OBJECTIVE: To estimate the incidence of and examine risk factors for the development of gout in black and white male physicians. METHODS: Data from 2 cohorts of former medical students, 352 black men in the Meharry Cohort Study and 571 white men in the Johns Hopkins Precursors Study, were analyzed. Cases of gout were identified by self-report. Baseline variables and incident hypertension were examined as risk factors for the development of gout in both cohorts. RESULTS: The incidence of gout was 3.11 and 1.82 per 1,000 person-years in the black men and the white men, respectively (P < 0.05); the cumulative incidence was 10.9% and 5.8%, respectively (P = 0.04). The relative risk (RR) for gout among the black men was 1.69 (95% confidence interval [95% CI] 1.02-2.80). This excess risk persisted after adjustment for baseline systolic blood pressure (adjusted RR = 1.96 [95% CI 1.14-3.38]). Incident hypertension was independently associated with the development of gout in univariate analysis (RR = 3.78 [95% CI 2.18-6.58]); when this variable was included as a time-dependent covariate in a Cox model, the excess risk for gout in black men was reduced and no longer significant (adjusted RR = 1.30 [95% CI 0.77-2.19]). CONCLUSION: The approximately 2-fold excess risk for gout among black men is explained, in part, by a greater risk of incident hypertension.

Adult↗
PubMed1995

Lipoprotein(a) levels in patients receiving renal replacement therapy: methodologic issues and clinical implications.

Lipoprotein(a) [Lp(a)] is a genetically determined risk factor for vascular disease and a potential link between coagulation, lipoproteins, and the development of atherosclerosis. Its role in the vascular complications of patients with chronic renal disease is unclear. We review methodologic issues involved in measuring Lp(a), particularly as they relate to studies of patients with chronic renal disease. The accurate measurement of Lp(a) is difficult because all the commercially available assays are sensitive to apolipoprotein(a) isoform size, Lp(a) behaves like an acute phase reactant, and levels vary markedly among ethnic groups. The results of 12 studies that included data on median Lp(a) levels in controls and patients receiving renal replacement therapy were analyzed. Although there was variation among studies, most found elevated levels of Lp(a) in patients receiving hemodialysis (range of medians, 9.0 to 38.4 mg/dL) compared with controls (range of medians, 4.7 to 19.7 mg/dL). With the exception of one study, Lp(a) levels also were elevated in patients receiving continuous ambulatory peritoneal dialysis compared with controls and patients receiving hemodialysis. In one study, an elevated Lp(a) level in patients receiving hemodialysis correlated with subsequent development of vascular events. A separate study associated the occurrence of vascular access occlusion with Lp(a) level. Following renal transplantation, Lp(a) levels decreased in all four studies, which included data before and after transplantation. Although variability in results were seen, Lp(a) levels appear to be elevated in patients receiving renal replacement therapy. Renal transplantation at least partially reverses this effect. The variability in results is probably related to methodologic difficulties in measuring Lp(a) and failure to segregate ethnic groups in study design and analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme-Linked Immunosorbent Assay↗
PubMed1995

Reconstituted high-density lipoprotein neutralizes gram-negative bacterial lipopolysaccharides in human whole blood.

We have tested hypotheses relating lipoprotein structure to function as measured by the relative ability to neutralize endotoxin by comparing natural human lipoproteins, a chemically defined form of reconstituted high-density lipoprotein (R-HDL), and a lipid emulsion (Intralipid). The human whole-blood system was used as an in vitro model of lipopolysaccharide (LPS) binding protein and CD14-dependent activation of cytokine production. When lipoproteins were compared on the basis of protein content, R-HDL was most effective in reducing tumor necrosis factor alpha (TNF-alpha) production followed in order by very low density lipoprotein, low-density lipoprotein, Intralipid, and natural HDL. However, when these particles were compared by protein, phospholipid, cholesterol, or triglyceride content by stepwise linear regression analysis, only phospholipid was correlated to effectiveness (r2 = 0.873; P < 0.0001). Anti-CD14 monoclonal antibodies MY4 and 3C10 inhibited LPS binding protein and CD14-dependent activation of TNF-alpha production by LPS at LPS concentrations up to approximately 1.0 ng/ml. R-HDL (2 mg of protein per ml) blocked TNF-alpha production by LPS from both smooth- and rough-type gram-negative bacteria at concentrations up to 100 ng of LPS per ml but had little effect on heat-killed gram-positive Staphylococcus aureus and no effect on other LPS-independent stimuli tested. These results support our hypothesis that LPS is neutralized by binding to phospholipid on the surface of R-HDL and demonstrate that R-HDL is a potent inhibitor of the induction of TNF-alpha by LPS from both rough- and smooth-form gram-negative bacteria in whole human blood.

Antigens, CD↗
PubMed1995

Therapeutic trial of reconstituted human high-density lipoprotein in a canine model of gram-negative septic shock.

In a controlled, randomized trial, the authors investigated the effects of reconstituted human high-density lipoprotein (R-HDL) on survival, endotoxemia, cytokine production and pathophysiologic and metabolic events in an animal model of gram-negative septic shock. At 0.5, 8 and 16 hr after implantation of a clot infected with Escherichia coli, canines received intravenous R-HDL (n = 13), control lipid (n = 7) or human serum albumin (HSA, n = 7) divided into three doses (0.3, 0.1 and 0.1 g/kg, respectively) at an hourly rate of 0.1 g/kg. All animals were treated with antibiotics and fluids. Animals treated with R-HDL had lower levels of circulating endotoxin and tumor necrosis factor and a smaller decrease in white blood cell counts than did animals treated with lipids and HSA (all P < .05). The survival times of lipid- and HSA-treated animals were similar (P = .3) and were significantly greater than those of R-HDL-treated animals (P = .02). During the first 6 hr after clot implantation, R-HDL-treated animals had significantly greater abnormalities in liver function test findings compared with lipid- and HSA-treated animals (all P < .05). For the first 24 hr, R-HDL-treated animals had significant increases in HDL levels; however, there were no significant relationships between these levels and the constituents of HDL (apolipoprotein AI and phosphatidylcholine) or liver function abnormalities and survival times (all r < .2, P > .3). In normal animals, administration of R-HDL (in similar doses) caused transient elevation of liver enzymes; in animals given sterile clot i.p., R-HDL caused seizures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The psychosocial work environment of physicians. The impact of demands and resources on job dissatisfaction and psychiatric distress in a longitudinal study of Johns Hopkins Medical School graduates.

This study examines the relationship between the psychosocial work environment and cross-sectional job dissatisfaction and prospective psychiatric distress in a cohort of Hopkins Medical School graduates in midcareer. An instrument was constructed consisting of five scales: psychological job demands, patient demands, work control, physician resources, and coworker support. The results of scale reliability and factor analysis are presented. Higher job demands were found to be associated with increases in job dissatisfaction and psychiatric distress and greater resources were associated with decreased levels of dissatisfaction and distress. In multiple-regression analysis, only work control and social support were found to be independently associated with dissatisfaction and distress. These results suggest that the presence of control and social support at work protects physicians from developing job dissatisfaction and psychiatric distress.

Adult↗
PubMed1994

Long-term effects of ethics education on the quality of care for patients who have do-not-resuscitate orders.

OBJECTIVE: To assess the long-term clinical impact of a broad-based ethics education program for medical houseofficers with specific emphasis on appropriate care for patients who have do-not-resuscitate (DNR) orders. DESIGN: Prospective, with an initial randomized phase. SETTING: The medical service of a university teaching hospital. PARTICIPANTS: Medical houseofficers and their inpatients. INTERVENTIONS: A pilot program in 1988, and a full program with a two-year curricular cycle from 1989 to 1991. MEASUREMENTS AND MAIN RESULTS: The authors measured compliance with specific standards of care by reviewing charts of patients who had DNR orders at baseline (n = 39, 1988), after the pilot phase (n = 57, 1989), and at the end of the first curricular cycle (n = 56, 1991), noticing who wrote the DNR order, whether the reasons for the order and appropriate consent were documented, and whether there was documented attention to any of 11 concurrent care concerns (CCCs), such as spiritual needs, the appropriateness of tube feedings or pressors, and adjustment of analgesic dose. The percentage of DNR orders written by houseofficers increased from 26% in 1988 to 67% in 1991 (p < 0.01). The percentage of charts documenting the rationale and consent for the DNR order was consistently high. The percentage of charts documenting attention to any CCC increased from 68% in 1988 to 86% in 1991 (p < 0.01). The mean number of CCCs addressed per DNA order increased from 1.34 in 1988 to 2.14 in 1991. The mean number of CCCs addressed per DNR order for patients who had AIDS increased from 0.89 in 1988 to 2.25 in 1991 (p = 0.03). CONCLUSIONS: The quality of care for patients who had DNR orders, both overall and for those who had AIDS, improved over long-term observation in the setting of an ethics education program for medical houseofficers. The results suggest that ethics education may alter physician practices and improve patient care.

Baltimore↗
PubMed1994

Coffee intake and coronary heart disease.

We examined the risk of coronary heart disease (CHD) associated with coffee intake in 1040 male medical students followed for 28 to 44 years. During the follow-up, CHD developed in 111 men. The relative risks (95% confidence interval) associated with drinking 5 cups of coffee/d were 2.94 (1.27, 6.81) for baseline, 5.52 (1.31, 23.18) for average, and 1.95 (0.86, 4.40) for most recent intake after adjustment for baseline age, serum cholesterol levels, calendar time, and the time-dependent covariates number of cigarettes, body mass index, and incident hypertension and diabetes. Risks were elevated in both smokers and nonsmokers and were stronger for myocardial infarction. Most of the excess risk was associated with coffee drinking prior to 1975. The diagnosis of hypertension was associated with a subsequent reduction in coffee intake. Negative results in some studies may be due to the assessment of coffee intake later in life or to differences in methods of coffee preparation between study populations or over calendar time.

Adult↗
PubMed1993

In vivo protection against endotoxin by plasma high density lipoprotein.

Overwhelming bacterial infection is accompanied by fever, hypotension, disseminated intravascular coagulation, and multiple organ failure leading to death in 30-80% of cases. These classical symptoms of septic shock are caused by potent cytokines that are produced in response to endotoxin released from Gram-negative bacteria. Treatments with antibodies and receptor antagonists to block endotoxin or cytokine mediators have given mixed results in clinical trials. High density lipoprotein (HDL) is a natural component of plasma that is known to neutralize endotoxin in vitro. We report here that raising the plasma HDL concentration protects mice against endotoxin in vivo. Transgenic mice with 2-fold-elevated plasma HDL levels had more endotoxin bound to HDL, lower plasma cytokine levels, and improved survival rates compared with low-HDL mice. Intravenous infusion of HDL also protected mice, but only when given as reconstituted HDL prepared from phospholipid and either HDL apoprotein or an 18-amino acid peptide synthesized to mimic the structure of apolipoprotein A-I of HDL. Intact plasma HDL was mildly toxic, and HDL apoprotein was ineffective. The effectiveness of the reconstituted peptide renders very unlikely any significant contribution to protection by trace proteins in apo-HDL. These data suggest a simple leaflet insertion model for binding and neutralization of lipopolysaccharide by phospholipid on the surface of HDL. Plasma HDL may normally act to protect against endotoxin; this protection may be augmented by administration of reconstituted HDL or reconstituted peptides.

Amino Acid Sequence↗
PubMed1993

Haemin enhancement of glucose transport in human lymphocytes: stimulation of protein tyrosine phosphatase and activation of p56lck tyrosine kinase.

Following our previous observation that haemin is mitogenic for human lymphocytes, we investigated the ability of haemin to enhance glucose uptake in these cells. We found that preincubation of human peripheral-blood mononuclear cells (PBMC) with haemin for 60 min increased up to 5-fold the rate of 2-deoxy-D-[1-3H]glucose uptake by the cells. Actinomycin D and cycloheximide did not inhibit the effect, and cytochalasin B completely blocked it. Among the metalloporphyrins tested (Fe-, Ni-, Co-, Zn- and Sn-protoporphyrin), only haemin (Fe-protoporphyrin) induced a marked increase in glucose uptake. Thiourea, a scavenger of oxygen free radicals, and 3-amino-1,2,4-triazole inhibited haemin-induced glucose uptake. Oxidants such as H2O2 and phenylarsine oxide were previously reported to stimulate protein tyrosine phosphorylation and to enhance glucose uptake. We found that incubation of PBMC with haemin resulted in an increase in protein tyrosine phosphatase (PTPase) activity, probably that identified as CD45. Similarly to haemin, we found that phytohaemagglutinin also enhanced PTPase activity. Haemin also activated the tyrosine kinase p56lck, which is negatively controlled by phosphorylation of Tyr-505 at the C-terminus, and increased protein tyrosine phosphorylation in these cells. Tyrphostins, specific inhibitors of tyrosine kinases, at low concentrations markedly enhanced glucose uptake and synergized with haemin in enhancing glucose uptake. At high doses, tyrphostins inhibited the effect of haemin. Taken together, we postulate that haemin enhancement of glucose uptake in human lymphocytes results from its stimulation of PTPase, followed by activation of tyrosine kinase p56lck, leading to an increase in protein tyrosine phosphorylation.

Animals↗
PubMed1993

Activation of human peripheral blood mononuclear cells by nitric oxide-generating compounds.

Recent work in this laboratory has identified immune-stimulatory properties of the oxidant hemin. In this study, we examined whether the nitrogen-based oxidant nitric oxide (NO) had inductive effects on human lymphocytes. We found that the NO-generating compounds sodium nitroprusside and S-nitroso-N-acetylpenicillamine rapidly enhanced the rate of glucose transport in resting human PBMC. In addition, NF-kappa B binding activity was induced by these agents as was the secretion of TNF-alpha. The data suggest that a cGMP-independent mechanism is involved as the cell permeant cGMP analogue, 8-Br-cGMP, had no effect in eliciting these inductive events. Activation of lymphocytes by these NO-generating compounds may be mediated through the protein tyrosine phosphorylation signal transduction pathway. We found that membrane-associated protein tyrosine phosphatase activity was enhanced in PBMC treated with sodium nitroprusside or S-nitroso-N-acetylpenicillamine and that the src family protein tyrosine kinase p56lck was activated in these cells. Inasmuch as p56lck activity is negatively controlled by tyrosine phosphorylation, its activation may be related to the enhancement of protein tyrosine phosphatase activity. 8-Br-cGMP had no effect on these enzymes. Taken together, these data suggest that NO may have immune-stimulatory properties and may signal through a hitherto undescribed cGMP-independent pathway.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Serum cholesterol in young men and subsequent cardiovascular disease.

BACKGROUND: The increased risk of cardiovascular disease associated with higher serum cholesterol levels in middle-aged persons has been clearly established, but there have been few opportunities to examine a potential link between serum cholesterol levels measured in young men and clinically evident premature cardiovascular disease later in life. METHODS: We performed a prospective study of 1017 young men (mean age, 22 years) followed for 27 to 42 years to quantify the risk of cardiovascular disease and total mortality associated with serum cholesterol levels during early adult life. The mean serum cholesterol level at entry was 192 mg per deciliter (5.0 mmol per liter). RESULTS: During a median follow-up of 30.5 years, there were 125 cardiovascular-disease events, 97 of which were due to coronary heart disease. The serum cholesterol level at base line was strongly associated with the incidence of events related to coronary heart disease and cardiovascular disease, as well as to total mortality and mortality due to cardiovascular disease. The risks were similar whether the events occurred before or after the age of 50. In a proportional-hazards analysis adjusted for age, body-mass index (the weight in kilograms divided by the square of the height in meters), the level of physical activity, coffee intake, change in smoking status, and the incidence of diabetes and hypertension during follow-up, a difference in the serum cholesterol level at base line of 36 mg per deciliter (0.9 mmol per liter)--the difference between the 25th and 75th percentiles of cholesterol level in the study population at base line--was associated with an increased risk of cardiovascular disease (relative risk, 1.72; 95 percent confidence interval, 1.39 to 2.14), coronary heart disease (relative risk, 2.01; 95 percent confidence interval, 1.59 to 2.53), and mortality due to cardiovascular disease (relative risk, 2.02; 95 percent confidence interval, 1.23 to 3.32). A difference in the base-line serum cholesterol level of 36 mg per deciliter was significantly associated with an increased risk of death before the age of 50 (relative risk, 1.64; 95 percent confidence interval, 1.03 to 2.61), but not with the overall risk of death (relative risk, 1.21; 95 percent confidence interval, 0.93 to 1.58). CONCLUSIONS: These findings indicate a strong association between the serum cholesterol level measured early in adult life in men and cardiovascular disease in midlife.

Adult↗
PubMed1993

Heart, body, and soul: a church-based smoking-cessation program for Urban African Americans.

BACKGROUND: This article provides a descriptive overview of the implementation process of the Heart, Body, and Soul program. The program objective was to test strategies to reduce the prevalence of cigarette smoking among urban African Americans in East Baltimore. METHOD: This study constitutes a prospective randomized trial among inner-city African Americans designed to improve quit rates among church attenders. A random-digit-dialing survey was conducted to establish baseline levels of self-reported cigarette smoking, examine attendant attitudes, and determine the presence of known cardiovascular risk factors among community residents of the catchment area. A similar survey was conducted among churchgoers to establish a baseline. Twenty-two churches were recruited and randomly assigned to either intensive or minimal (self-help) intervention strategies. Baseline health screenings were held in all participating churches. Innovative culturally specific smoking cessation strategies mediated through lay volunteers from participating churches were implemented in the intensive intervention churches. RESULTS: Pastors of all churches were directly involved in all aspects of the planning and implementation process. A total of 29 volunteer lay smoking-cessation specialists were trained and successfully implemented the intensive interventions in churches. An additional 272 church members were trained to conduct their church's health screenings. CONCLUSION: The essential component of this successful implementation process were building trust and acceptance and providing the technical support to encourage smoking-cessation strategies. This description of the project is presented to assist others involved in church-based trials in urban African American communities.

Adult↗