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Biomedical subjects

D Herrington

Publications and source records attributed to D Herrington.

At least 19 recordsLinked to original sources
PubMed2006

Plasma hemostatic factors and endothelial markers in four racial/ethnic groups: the MESA study.

BACKGROUND: Hemostatic factors and endothelial markers may play some role in racial/ethnic differences in cardiovascular disease (CVD) rates. However, little information exists on hemostatic factors and endothelial markers across racial/ethnic groups. OBJECTIVES: To describe, in four American racial/ethnic groups (Caucasian, Black, Hispanic, and Chinese), mean levels of selected hemostatic factors and endothelial markers. PATIENTS AND METHODS: Multi-ethnic Study of Atherosclerosis baseline data were used (participant age: 45-84 years). Sex-specific analysis of covariance models, and t-tests for pairwise comparisons, were used to compare means of factors and markers. Adjustments were made for demographics and traditional CVD risk factors. Differences were significant at P < 0.05. RESULTS: Blacks had the highest levels of factor VIII, D-Dimer, plasmin-antiplasmin (PAP), and von Willebrand factor, among the highest levels of fibrinogen and E-selectin (women only), but among the lowest levels of intercellular adhesion molecule 1 (ICAM-1), and, in men, the lowest levels of plasminogen activator inhibitor-1 (PAI-1). Whites and Hispanics tended to have intermediate levels of factors and markers, although they had the highest levels of ICAM-1, and Hispanics had the highest mean levels of fibrinogen and E-selectin (women only). Chinese participants had among the highest levels of PAI-1, but the lowest, or among the lowest, of all other factors and markers. No soluble thrombomodulin differences were observed. CONCLUSIONS: In this large cohort, hemostatic factor and endothelial marker mean levels varied by race/ethnicity, even after adjustment for traditional CVD risk factors.

Aged↗
PubMed2006

Association analysis of genes in the renin-angiotensin system with subclinical cardiovascular disease in families with Type 2 diabetes mellitus: the Diabetes Heart Study.

AIMS: Cardiovascular disease (CVD) is a major complication of Type 2 diabetes mellitus. The renin-angiotensin system (RAS) and nitric oxide production are both important regulators of vascular function and blood pressure. Genes encoding proteins involved in these pathways are candidates for a contribution to CVD in diabetic patients. We have investigated variants of the angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin type 1 receptor (AT1R) and endothelial nitric oxide synthase (NOS3) genes for association with subclinical measures of CVD in families with Type 2 diabetes mellitus (T2DM). METHODS: Atherosclerosis was measured by carotid intima-media thickness and calcification of the carotid and coronary arteries in 620 European Americans and 117 African Americans in the Diabetes Heart Study. Because of the role of these systems in blood pressure regulation, blood pressure was also investigated. RESULTS: Compelling evidence of association was not detected with any of the SNPs with any outcome measures after adjustments for covariates despite sufficient power to detect relatively small differences in traits for specific genotype combinations. CONCLUSIONS: Genetic variation of the RAS and NOS3 genes do not appear to strongly influence subclinical cardiovascular disease or blood pressure in this diabetic population.

Adult↗
PubMed2005

Association of genes of lipid metabolism with measures of subclinical cardiovascular disease in the Diabetes Heart Study.

BACKGROUND: Dyslipidaemia is a well known risk factor for cardiovascular disease (CVD). Lipid metabolism is affected by a range of genes and proteins. This study investigated whether some of these genes are associated with measures of subclinical CVD. METHODS: Polymorphisms of paraoxonase 1 and 2, cholesteryl ester transfer protein, hepatic lipase, and lipoprotein lipase were tested for associations with measures of subclinical CVD including carotid intima-media thickness measured by B-mode ultrasound and carotid and coronary arterial calcification measured by computed tomography. Analysis was performed in 620 European American participants in the Diabetes Heart Study, 83% of whom had type 2 diabetes mellitus. Associations of genotypes with subclinical CVD were tested by computing a series of generalised estimating equations. RESULTS: The Q192R variant of paraoxonase 1 and rs285 of lipoprotein lipase were associated with carotid artery calcium (p values = 0.002 and 0.005, respectively). Paraoxonase 2 S311C was associated with coronary artery calcium (p value = 0.037). CONCLUSIONS: There is evidence for modest, but significant, association of multiple single nucleotide polymorphisms in lipid genes with measures of subclinical CVD.

Aged↗
PubMed2001

Recruitment of participants for the Estrogen Replacement and Atherosclerosis (ERA) trial. a comparison of costs, yields, and participant characteristics from community- and hospital-based recruitment strategies.

This paper documents recruitment for the Estrogen Replacement and Atherosclerosis trial, a multicenter, placebo-controlled, double-blind angiographic trial of the effects of opposed and unopposed estrogen on coronary atherosclerosis in postmenopausal women (average scheduled duration of follow-up 3.2 years). We compare costs, yields, and participant characteristics between community-based and hospital-based recruitment strategies. We further compare community-based enriched sources (i.e., those that allowed self-selection or targeted women with known health characteristics) and nonenriched sources. Data gathered on potential participants include method of contact, clinical site, eligibility, completion of screening visits, and randomization rates. Demographic data on participants include age, race, education, marital status, and income. Self-reported health status, smoking status, lipid level, ejection fraction as well as history of chest pain, hypertension, and diabetes were recorded at baseline. Recruitment costs were estimated from employee salaries and costs of screening tests and procedures. Yields were compared by clinical site and by method of contact. Enriched sources of recruitment yielded higher percentages of enrolled participants than nonenriched sources. Both types of source resulted in demographically similar participants. Costs of community-based recruitment were less than hospital-based recruitment; however, screening costs were higher. Overall, screening and recruitment averaged $2508 per randomized participant. Control Clin Trials 2001;22:13-25

Aged↗
PubMed2000

Postmenopausal hormone therapy increases risk for venous thromboembolic disease. The Heart and Estrogen/progestin Replacement Study.

BACKGROUND: Oral contraceptive use increases risk for venous thromboembolism, but data on the effect of postmenopausal hormone therapy are limited. OBJECTIVE: To determine the effect of therapy with estrogen plus progestin on risk for venous thromboembolic events in postmenopausal women. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: 20 clinical centers in the United States. PARTICIPANTS: 2763 postmenopausal women younger than 80 years of age (mean age, 67 years) who had coronary heart disease but no previous venous thromboembolism and had not had a hysterectomy. INTERVENTION: Conjugated equine estrogens, 0.625 mg, plus medroxyprogesterone acetate, 2.5 mg, in one tablet (n = 1380) or placebo that was identical in appearance (n = 1383). MEASUREMENTS: Documented deep venous thrombosis or pulmonary embolism. RESULTS: During an average of 4.1 years of follow-up, 34 women in the hormone therapy group and 13 in the placebo group experienced venous thromboembolic events (relative hazard, 2.7 [95% CI, 1.4 to 5.0] [P = 0.003]; excess risk, 3.9 per 1000 woman-years [CI, 1.4 to 6.4 per 1000 woman-years]; number needed to treat for harm, 256 [CI, 157 to 692]). In multivariate analysis, the risk for venous thromboembolism was increased among women who had lower-extremity fractures (relative hazard, 18.1 [CI, 5.4 to 60.4]) or cancer (relative hazard, 3.9 [CI, 1.6 to 9.4]) and for 90 days after inpatient surgery (relative hazard, 4.9 [CI, 2.4 to 9.8]) or nonsurgical hospitalization (relative hazard, 5.7 [CI, 3.0 to 10.8]). Risk was decreased with aspirin (relative hazard, 0.5 [CI, 0.2 to 0.8]) or statin use (relative hazard, 0.5 [CI, 0.2 to 0.9]). CONCLUSIONS: Postmenopausal therapy with estrogen plus progestin increases risk for venous thromboembolism in women with coronary heart disease. This risk should be considered when the risks and benefits of therapy are being weighed.

Aged↗
PubMed2000

Role of estrogens, selective estrogen receptor modulators and phytoestrogens in cardiovascular protection.

A large body of evidence suggests that estrogen may be of benefit in reducing the risk of heart disease in postmenopausal women. The mechanism by which this benefit is conferred has been the subject of numerous investigations. In addition to the well known effects of estrogen on lipids, estrogen exerts a number of endothelium-dependent effects related to both vasodilation and nitric oxide metabolism that may have a favourable impact on vascular health. However, this benefit has not yet been confirmed in randomized clinical trials. Indeed, the only large trial published to date failed to document a benefit in women with established heart disease. Recent studies have shown that estrogen may also have some prothrombotic or proinflammatory effects that may offset other benefits. The extent to which selective estrogen receptor modulators and phytoestrogens share in the beneficial and potentially harmful effects of estrogen is not yet established.

Cardiovascular Diseases↗
PubMed1998

Randomized trial of estrogen plus progestin for secondary prevention of coronary heart disease in postmenopausal women. Heart and Estrogen/progestin Replacement Study (HERS) Research Group.

CONTEXT: Observational studies have found lower rates of coronary heart disease (CHD) in postmenopausal women who take estrogen than in women who do not, but this potential benefit has not been confirmed in clinical trials. OBJECTIVE: To determine if estrogen plus progestin therapy alters the risk for CHD events in postmenopausal women with established coronary disease. DESIGN: Randomized, blinded, placebo-controlled secondary prevention trial. SETTING: Outpatient and community settings at 20 US clinical centers. PARTICIPANTS: A total of 2763 women with coronary disease, younger than 80 years, and postmenopausal with an intact uterus. Mean age was 66.7 years. INTERVENTION: Either 0.625 mg of conjugated equine estrogens plus 2.5 mg of medroxyprogesterone acetate in 1 tablet daily (n = 1380) or a placebo of identical appearance (n = 1383). Follow-up averaged 4.1 years; 82% of those assigned to hormone treatment were taking it at the end of 1 year, and 75% at the end of 3 years. MAIN OUTCOME MEASURES: The primary outcome was the occurrence of nonfatal myocardial infarction (MI) or CHD death. Secondary cardiovascular outcomes included coronary revascularization, unstable angina, congestive heart failure, resuscitated cardiac arrest, stroke or transient ischemic attack, and peripheral arterial disease. All-cause mortality was also considered. RESULTS: Overall, there were no significant differences between groups in the primary outcome or in any of the secondary cardiovascular outcomes: 172 women in the hormone group and 176 women in the placebo group had MI or CHD death (relative hazard [RH], 0.99; 95% confidence interval [CI], 0.80-1.22). The lack of an overall effect occurred despite a net 11% lower low-density lipoprotein cholesterol level and 10% higher high-density lipoprotein cholesterol level in the hormone group compared with the placebo group (each P<.001). Within the overall null effect, there was a statistically significant time trend, with more CHD events in the hormone group than in the placebo group in year 1 and fewer in years 4 and 5. More women in the hormone group than in the placebo group experienced venous thromboembolic events (34 vs 12; RH, 2.89; 95% CI, 1.50-5.58) and gallbladder disease (84 vs 62; RH, 1.38; 95% CI, 1.00-1.92). There were no significant differences in several other end points for which power was limited, including fracture, cancer, and total mortality (131 vs 123 deaths; RH, 1.08; 95% CI, 0.84-1.38). CONCLUSIONS: During an average follow-up of 4.1 years, treatment with oral conjugated equine estrogen plus medroxyprogesterone acetate did not reduce the overall rate of CHD events in postmenopausal women with established coronary disease. The treatment did increase the rate of thromboembolic events and gallbladder disease. Based on the finding of no overall cardiovascular benefit and a pattern of early increase in risk of CHD events, we do not recommend starting this treatment for the purpose of secondary prevention of CHD. However, given the favorable pattern of CHD events after several years of therapy, it could be appropriate for women already receiving this treatment to continue.

Aged↗
PubMed1997

Rationale, design, and baseline characteristics of the Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial (PREVENT).

The Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial is the first angiographic clinical trial to be designed to test whether an agent can slow or even reverse the progression of early coronary atherosclerosis in patients with documented disease. In addition, a subset of patients are undergoing carotid ultrasound examinations, providing a unique opportunity to assess and correlate disease progression in 2 arterial beds.

Aged↗
PubMed1992

T cell responses to repeat and non-repeat regions of the circumsporozoite protein detected in volunteers immunized with Plasmodium falciparum sporozoites.

The design of a malarial vaccine based on the circumsporozoite (CS) protein, a major surface antigen of the sporozoite stage of the malaria parasite, requires the identification of T and B cell epitopes for inclusion in recombinant or synthetic vaccine candidates. We have investigated the specificity and function of a series of T cell clones, derived from volunteers immunized with Plasmodium falciparum sporozoites, in an effort to identify relevant epitopes in the immune response to the pre-erythrocytic stages of the parasite. CD4+ T cell clones were obtained which specifically recognized a repetitive epitope located in the 5' repeat region of the CS protein. This epitope, when conjugated to the 3' repeat region in a synthetic MAPs construct, induced high titers of antisporozoite antibodies in C57BL mice. A second T cell epitope, which mapped to aa 326-345 of the carboxy terminal, was recognized by lytic, as well as non-lytic, CD4+ T cells derived from the sporozoite-immunized volunteers. The demonstration of CD4+ CTL in the human volunteers, and the recent studies in the rodent model (Renia et al., 1991; Tsuji et al., 1990), suggest that CS-specific CD4+ T cells, in addition to their indirect role as helper cells in the induction of antibody and CD8+ effector cells, may also play a direct role in protection against sporozoite challenge by targeting EEF within the liver.

Amino Acid Sequence↗
PubMed1991

Cytotoxic CD4+ T cells from a sporozoite-immunized volunteer recognize the Plasmodium falciparum CS protein.

The present data provide the first evidence that a protozoan parasite, Plasmodium falciparum, can induce CD4+ cytotoxic T cells in man. The CD4+ cytotoxic T lymphocytes (CTL) were derived from a sporozoite-immunized volunteer who was protected against challenge with P. falciparum sporozoites. These T cells recognize an epitope within the circumsporozoite (CS) protein, an immunodominant sporozoite surface antigen, present also in liver stages of the parasite, which has been investigated as a vaccine candidate. The class II restricted T cell clones specifically lyse autologous B cells pulsed with a synthetic peptide representing a C-terminal sequence of the P. falciparum CS protein. The same peptide, as well as recombinant or native CS protein, also stimulates proliferation and gamma-interferon production by the CD4+ CTL. The CTL epitope, KIQNSLSTEW, is recognized in the context of HLA-DR7 and overlaps both a highly conserved, as well as a polymorphic, region of the P. falciparum CS protein.

Adult↗
PubMed1991

Successful immunization of humans with irradiated malaria sporozoites: humoral and cellular responses of the protected individuals.

Two groups of volunteers were vaccinated by repeated exposure to the bites of Plasmodium falciparum-infected, x-irradiated mosquitoes in order to characterize the humoral and cellular immune responses of sporozoite-immunized, protected individuals. One of the two volunteers in the first immunization trial, when challenged by the bite of P. falciparum-infected mosquitoes, developed an infection only after a prolonged prepatent period. A second group of three volunteers who were exposed more frequently to larger numbers of infected mosquitoes irradiated with a lower x-ray dose was completely protected against sporozoite challenge. These individuals and the volunteer with delayed infection had high levels of antibodies to sporozoites and to the repeat region of the circumsporozoite (CS) protein. The CS-specific cellular immune responses of these volunteers were also stimulated by sporozoite immunization, as determined by proliferation of peripheral blood mononuclear cells (PBMC) and mitogen or antigen-expanded PBMC, in response to in vitro challenge with a recombinant P. falciparum CS protein. Based upon the assays used in this study, it is not possible to reach conclusions regarding specific immunologic responses and protection from sporozoite challenge.

Adult↗
PubMed1990

Cellular and humoral immune responses to a recombinant P. falciparum CS protein in sporozoite-immunized rodents and human volunteers.

The immune responses of sporozoite-immunized rodents and of human volunteers exposed to multiple bites of irradiated Plasmodium falciparum infected mosquitos have been investigated using a yeast-derived recombinant P. falciparum circumsporozoite (rPfCS) protein. The murine immune response to immunization with rPfCS was not genetically restricted. Nine different murine haplotypes, when immunized with rPfCS, developed high levels of antisporozoite antibodies detectable by IFA and RIA. In addition, injection of rPfCS induced a secondary antibody response in P. falciparum sporozoite-primed mice. Murine T-cell epitopes were mapped in the C terminus of the rPfCS protein using overlapping synthetic peptides. The human T-cell response was investigated using T-cell clones derived from peripheral blood lymphocytes (PBL) of a P. falciparum sporozoite-immunized volunteer. A total of 40 CD4+ T-cell clones were obtained. Stimulation indices ranged from 2.5 to 103.4 following challenge with rPfCS in the presence, but not in the absence, of antigen-presenting cells. The clones were specific for rPfCs and did not proliferate or secrete lymphokines when challenged with yeast-derived recombinant P. vivax or P. berghei CS protein or with a yeast-extract control. The clones also recognized the native CS protein in extracts of P. falciparum, but not P. berghei or P. cynomolgi, sporozoites.

Animals↗
PubMed1988

Safety, immunogenicity, and efficacy of recombinant live oral cholera vaccines, CVD 103 and CVD 103-HgR.

The genes encoding the A (toxic) subunit of cholera toxin were deleted from pathogenic Vibrio cholerae O1 strain 569B by recombinant techniques, leaving intact production of immunogenic, non-toxic B subunit. The resultant strain, CVD 103, evaluated for safety, immunogenicity, and efficacy as a live oral vaccine, was highly attenuated and elicited strong antibacterial and antitoxic immune responses; a single dose significantly protected volunteers against challenge with pathogenic V cholerae O1 of either serotype or biotype. A further derivative, CVD 103-HgR, which has an Hg++-resistance gene to differentiate it from wild-type vibrios, was also well-tolerated, immunogenic, and protective; moreover, faecal excretion of this derivative was significantly lower than that of CVD 103, which should minimise environmental spread of the vaccine. CVD 103-HgR is a candidate for expanded clinical trials in endemic areas.

Administration, Oral↗
PubMed1988

Volunteer studies of deletion mutants of Vibrio cholerae O1 prepared by recombinant techniques.

Vibrio cholerae O1 A-B- vaccine strain JBK 70 and A-B+ CVD 101 prepared by recombinant DNA techniques from pathogenic EI Tor Inaba N16961 and classical Ogawa 395, respectively, were fed to 38 volunteers in single doses of 10(4) to 10(10). Although severe diarrhea did not occur in any vaccine, more than one-half developed mild diarrhea. These attenuated strains colonized well and elicited prominent vibriocidal and antitoxic (CVD 101) antibody responses. Recipients of a single dose of JBK 70 were significantly protected when challenged with 10(6) wild-type N16961. Diarrhea occurred in 7 of 8 controls but in only 1 of 10 vaccines (P less than 0.003, 89% vaccine efficacy), demonstrating the potency of immune mechanisms that do not involve cholera antitoxin. Further derivatives were prepared to explore the pathogenesis of the residual diarrhea, considering that either intestinal colonization by the vaccine itself or accessory toxins might be responsible. CVD 102, an auxotrophic mutant of CVD 101, did not cause diarrhea but colonized poorly and elicited feeble immune responses. Derivatives of JBK 70 and CVD 101 (CVD 104 and 105) deleted of genes encoding the EI Tor hemolysin still caused mild diarrhea. Genetically engineered strains can be colonizing, highly immunogenic, and protective single-dose oral vaccines, but they must be further attenuated before they can be considered for use as public health tools.

ABO Blood-Group System↗