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Biomedical subjects

C M Ballantyne

Publications and source records attributed to C M Ballantyne.

106 records · Page 6Linked to original sources
PubMed1991

Insensitivity of noninvasive tests to detect coronary artery vasculopathy after heart transplant.

Obstructive coronary artery vasculopathy can be a major problem after cardiac transplant. The use of noninvasive tests to detect coronary artery vasculopathy was studied in 73 consecutive patients after heart transplant. Angiographically or autopsy-proved coronary artery disease was noted in 19 consecutive patients (26%) followed prospectively for 2.5 +/- 1.3 years (mean +/- standard deviation). Patients underwent yearly surveillance echocardiographic, rest/exercise-gated wall motion, oral dipyridamole thallium, ambulatory electrocardiographic monitor and angiographic studies. Positive test results were defined by decrease in ejection fraction, wall motion abnormality, failure to increase ejection fraction, lack of systolic blood pressure increase, and ischemic ST changes at maximal exercise (or on ambulatory monitor). Wall motion abnormalities and depressed ejection fraction on echocardiography were also abnormal studies as were fixed or reversible perfusion defects on thallium scan. Angiograms were considered positive when 50% luminal narrowing was observed and autopsy coronary artery vasculopathy was defined as cross-sectional coronary obstruction greater than or equal to 70%. No procedure that was examined proved to be a sensitive noninvasive detector of heart transplant coronary artery vasculopathy. All except ambulatory electrocardiographic monitoring had positive predictive values less than 50%. Interestingly, of the techniques evaluated, echocardiography was most sensitive (53%). The poor predictive ability of noninvasive testing in this population may be due to the fact that these tests are designed to detect effects of ischemia rather than coronary obstruction alone. Use of these particular noninvasive modalities routinely after heart transplant to detect coronary artery vasculopathy should be reconsidered because of their low sensitivity and predictive value when used as a surveillance screen.

Adult↗
PubMed1991

Lipoprotein(a) and apolipoprotein changes after cardiac transplantation.

Although lipoprotein changes after cardiac transplantation have been documented, the effects of transplantation and subsequent immunosuppressive therapy (particularly the combination of prednisone, azathioprine and cyclosporine) on apolipoprotein levels and lipoprotein(a) have not been reported. Fasting cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, apolipoprotein A-1 and B-100 and lipoprotein(a) were evaluated in 69 consecutive patients during the waiting period before cardiac transplantation. There were 28 deaths before donor organ identification and 41 patients received a cardiac allograft. The lipoprotein levels of transplant recipients were again assayed 3 months postoperatively. Mean (+/- SEM) values increased for total plasma cholesterol (from 180 +/- 8 to 228 +/- 8 mg/dl, p less than or equal to 0.001), triglycerides (from 126 +/- 11 to 207 +/- 14 mg/dl; p less than or equal to 0.001), HDL cholesterol (from 39 +/- 2 to 49 +/- 3 mg/dl; p less than or equal to 0.002) and LDL cholesterol (from 119 +/- 7 to 138 +/- 7 mg/dl; p less than 0.02). Apolipoprotein A-1 and B-100 also increased, but lipoprotein(a) decreased from 11.7 +/- 1.7 to 6.8 +/- 1.1 mg/dl; p less than or equal to 0.0001) after transplantation. Although total cholesterol, triglycerides, LDL cholesterol, apolipoprotein A-1 and B-100 increased dramatically after cardiac transplantation, so did HDL cholesterol, thereby keeping the LDL/HDL cholesterol ratio constant. The surprising decrease in lipoprotein(a) after cardiac transplantation suggests that metabolism of lipoprotein(a) is independent of LDL cholesterol and that immunosuppressive drugs either decrease the synthesis or increase catabolism of lipoprotein(a).

Apolipoproteins↗
PubMed1991

Assignment of the gene for intercellular adhesion molecule-1 (Icam-1) to proximal mouse chromosome 9.

Intercellular adhesion molecule-1 (ICAM-1) is an integral membrane protein, a member of the immunoglobulin superfamily, and a ligand for LFA-1, a beta 2 leukocyte integrin. ICAM-1 has a tissue distribution similar to that of the major histocompatibility complex class II antigens and is likely to play a role in inflammatory responses. We have mapped this gene to proximal mouse chromosome 9 by using mouse-hamster somatic cell hybrids and an interspecies backcross. Since human ICAM-1 maps to chromosome 19, it joins the LDL receptor to establish a new conserved syntenic segment between human chromosome 19 and proximal mouse chromosome 9. Murine Icam-1 maps between Cbl-2 and the centromere in the same region as one of the susceptibility genes for insulin-dependent diabetes mellitus (Idd-2) that is postulated to play a role in immune function and inflammation leading to insulitis. The mapping of Icam-1 to the region known to contain the Idd-2 gene raises the question of whether the phenotypic differences attributed to the Idd-2 locus might be due to genetic variation in Icam-1.

Animals↗
PubMed1990

Deletion and linkage mapping of eight markers from the proximal short arm of chromosome 6.

Eight chromosome 6p markers (MUT, D6S4, D6S5, D6S19, D6S29, PIM, HLA, and F13A) were regionally mapped using somatic cell hybrid deletion cell lines that retained different regions of chromosome 6p. New restriction fragment length polymorphisms were identified at the D6S5 and PIM loci using newly isolated genomic clones at these loci. Genetic linkage among the eight loci was determined using the 40 CEPH reference families. Linkage analyses showed that these loci are in one linkage group spanning 48 cM in males and 128 cM in females. Using both the deletion mapping data and multipoint linkage analyses, chromosomal order for these loci was determined as centromere-(MUT, D6S4)-(D6S5, D6S19)-(D6S29, PIM)-HLA-F13-A-telomere. Analyses of sex-specific recombination frequencies revealed a higher rate of recombination in females in the region between D6S4 and D6S29, while the recombination rate in males was higher for the interval between D6S29 and the HLA loci.

Chromosome Deletion↗
PubMed1989

Effects of cyclosporine therapy on plasma lipoprotein levels.

Accelerated atherosclerosis is a leading cause of death in long-term survivors of heart and renal transplantation and may be exacerbated by the frequent occurrence of posttransplant hyperlipidemia. Attempts to define the mechanism for hyperlipidemia in transplant recipients are confounded by dramatic changes in metabolism and nutritional status after transplantation, as well as by treatment with multiple immunosuppressive and antihypertensive drugs. To avoid these pitfalls and to determine if cyclosporine alone adversely affects lipid levels, we measured lipoprotein levels in a prospective, double-blind, randomized, placebo-controlled trial of cyclosporine in 36 men with amyotrophic lateral sclerosis. Plasma total cholesterol, triglyceride, high-density lipoprotein cholesterol, and apolipoprotein B levels were measured at baseline, 2 weeks, 1 month, and 2 months. Significant increases of 21% in total cholesterol, 31% in low-density lipoprotein cholesterol, and 12% in apolipoprotein B levels occurred only in the cyclosporine group. Cyclosporine therapy alone adversely affects plasma lipoprotein levels by increasing total cholesterol levels, primarily due to an increase in low-density lipoprotein cholesterol level.

Adult↗
PubMed1987

Low-density lipoprotein metabolism in cerebrotendinous xanthomatosis.

Cerebrotendinous xanthomatosis (CTX) is a rare disorder characterized by a defect in conversion of cholesterol into bile acids, increased plasma levels of cholestanol, and accumulations of sterols in tendons, brain, and coronary arteries. Despite the presence of tendon xanthomas, patients with CTX frequently have low levels of plasma cholesterol and low density lipoproteins (LDL). The mechanisms for a low LDL are not understood. The present study, therefore, was carried out to examine the metabolism of LDL in a 58-year-old black man with CTX. This particular patient had an LDL-cholesterol in the mid-normal range (149 +/- 6 mg/dL). Nonetheless, his fractional catabolic rate (FCR) for LDL-apolipoprotein (apo-LDL) was 0.45 pools/d, which was increased compared to 15 aged-matched men (FCR, 0.30 +/- 0.01 pools/d). His production rate for apo-LDL (18.5 mg/kg-d) also was increased compared to those of middle-aged men (13.5 +/- 2.5 mg/kg-d). Since the underlying defect in CTX can be reversed by administration of chenodeoxycholic acid (chenodiol), the patient was treated with chenodiol (250 mg 4X daily), and measurements of LDL kinetics were repeated. During chenodiol therapy, his LDL-cholesterol concentration rose significantly to 165 +/- 12 mg/dL; his FCR for apo-LDL fell to 0.29 pools/d; and his production rate of apo-LDL declined to 14.4 mg/kg-d. We postulate that chenodiol suppressed the excessive synthesis of cholesterol and bile acids, which had two effects. It curtailed both the overproduction of LDL and the excessive synthesis of LDL receptors, the latter being responsible for the high FCR of apo-LDL in the untreated state.

Apolipoproteins↗
PubMed1987

Delayed recovery of severely "stunned" myocardium with the support of a left ventricular assist device after coronary artery bypass graft surgery.

A 53 year old man underwent repeat coronary artery bypass graft surgery after presenting with unstable angina. Because of intraoperative ischemia, the patient developed profound left ventricular dysfunction requiring placement of a left ventricular assist device and intraaortic balloon pump and catecholamine infusion. Serial radionuclide ventriculograms documented delayed recovery of the severely stunned myocardium with mechanical and pharmacologic support.

Angiography↗
PubMedDate not supplied

Role of early reperfusion in the induction of adhesion molecules and cytokines in previously ischemic myocardium.

Our studies in vitro demonstrate that neutrophil mediated injury of isolated cardiac myocytes requires the presence of ICAM-1 on the surface of the myocyte and CD11b/CD18 activation on the neutrophil. In post-ischemic cardiac lymph, there is rapid appearance of C5a activity during the first hours of reperfusion. Interleukin-6 activity is present throughout the first 72 h of reperfusion and is sufficient to induce ICAM-1 on the surface of the cardiac myocyte. In situ hybridization studies suggest that ICAM-1 mRNA is found in viable myocardial cells on the edge of the myocardial infarction within 1 h of reperfusion. ICAM-1 protein expression on cardiac myocytes is seen after 6 h of reperfusion, and increases thereafter. Non-ischemic tissue demonstrates no early induction of ICAM-1 mRNA or ICAM-1 protein on myocardial cells. In our most recent experiments, we have determined that reperfusion is an absolute requirement for the early induction of myocardial ICAM-1 mRNA in previously ischemic myocardial cells. To further assess this, we have cloned and sequenced a canine interleukin-6 (IL-6) cDNA. The data suggest that early induction of IL-6 mRNA is also reperfusion dependent as it could be demonstrated in the same ischemic and reperfused segments in which ICAM-1 mRNA was found. Peak expression of IL-6 mRNA occurred much earlier than that for ICAM-1 mRNA. Similar experiments were then performed with a molecular probe for interleukin-8 (IL-8). This chemokine is a potent neutrophil stimulant and has a higher degree of specificity for neutrophils than classic chemoattractants such as C5a.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMedDate not supplied

Defining specific goals of therapy in treating dyslipidemia in the patient with low high-density lipoprotein cholesterol.

Because patients with low high-density lipoprotein (HDL) cholesterol (HDL-C) are at high risk for clinical coronary artery disease (CAD) events, these patients require aggressive treatment with lifestyle modifications-increased exercise, smoking cessation, and weight loss in overweight patients-and available pharmacological agents. Drugs that raise HDL-C include nicotinic acid, fibric acid derivatives, estrogens, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), alpha-blockers, and alcohol. However, all agents that increase HDL-C may not have the same clinical benefit, just as, as shown in genetic studies in humans and mice, genetic causes of high HDL-C do not always protect against CAD, nor do genetic causes of low HDL-C always increase risk for CAD. Better understanding of the complexities of HDL metabolism and the mechanisms by which HDL protects against CAD is needed to enable the development of new therapeutic strategies--novel drugs or gene delivery systems--to increase HDL-C and reduce CAD events. The statins are the agents with the greatest evidence for slowing progression of CAD and reducing clinical events in patients with low HDL-C, but additional research is needed to determine the potential benefits of additional interventions that increase HDL-C, including combination therapy, which may provide greater improvements in the entire lipid profile.

Animals↗
PubMedDate not supplied

Relationship of increased levels of circulating intercellular adhesion molecule 1 after heart transplantation to rejection: human leukocyte antigen mismatch and survival.

Noninvasive methods to assess immune activation would be helpful in optimizing therapy after heart transplantation to reduce rejection (acute and chronic) and complications caused by excessive immunosuppressive therapy. Intercellular adhesion molecule 1 has been shown to play an important role in T-cell activation and allograft rejection. A soluble form of intercellular adhesion molecule 1 has been discovered to be circulating in plasma. To test the hypothesis that increased levels of circulating intercellular adhesion molecule 1 may have prognostic value as a marker of immune activation, we examined whether levels of circulating intercellular adhesion molecule 1 during the early postoperative period correlated with endomyocardial biopsy scores, soluble interleukin-2 receptor levels, human leukocyte antigen mismatch, and survival. For the first 3 weeks after surgery, serum was obtained once weekly on the same day as endomyocardial biopsy samples from 52 patients who survived more than 30 days after heart transplantation. A sandwich enzyme-linked immunosorbent assay was used to measure circulating intercellular adhesion molecule 1 and soluble interleukin-2 receptor. Increased circulating intercellular adhesion molecule 1 levels did not correlate with endomyocardial biopsy scores but were associated with greater mismatch at the human leukocyte antigen-B and -DR loci (p = 0.02). A significant correlation was found (p = 0.002) between circulating intercellular adhesion molecule 1 levels and soluble interleukin-2 receptor, albeit with a low r value of 0.27. Survival was reduced in patients with high levels of circulating intercellular adhesion molecule 1 (p = 0.006) or soluble interleukin-2 receptor (p = 0.001) with the greatest reduction in survival when both were elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗