Biomedical subjects

Daniel Alexander

Publications and source records attributed to Daniel Alexander.

3 recordsLinked to original sources

PubMed2006

Cardiorespiratory fitness and short-term complications after bariatric surgery.

BACKGROUND: Morbid obesity is associated with reduced functional capacity, multiple comorbidities, and higher overall mortality. The relationship between complications after bariatric surgery and preoperative cardiorespiratory fitness has not been previously studied. METHODS: We evaluated cardiorespiratory fitness in 109 patients with morbid obesity prior to laparoscopic Roux-en-Y gastric bypass surgery. Charts were abstracted using a case report form by reviewers blinded to the cardiorespiratory evaluation results. RESULTS: The mean age (+/- SD) was 46.0 +/- 10.4 years, and 82 patients (75.2%) were female. The mean body mass index (BMI) was 48.7 +/- 7.2 (range, 36.0 to 90.0 kg/m(2)). The composite complication rate, defined as death, unstable angina, myocardial infarction, venous thromboembolism, renal failure, or stroke, occurred in 6 of 37 patients (16.6%) and 2 of 72 patients (2.8%) with peak oxygen consumption (Vo(2)) levels < 15.8 mL/kg/min or > 15.8 mL/kg/min (lowest tertile), respectively (p = 0.02). Hospital lengths of stay and 30-day readmission rates were highest in the lowest tertile of peak Vo(2) (p = 0.005). There were no complications in those with BMI < 45 kg/m(2) or peak Vo(2) > or= 15.8 mL/kg/min. Multivariate analysis adjusting for age and gender found peak Vo(2) was a significant predictor of complications: odds ratio, 1.61 (per unit decrease); 95% confidence interval, 1.19 to 2.18 (p = 0.002). CONCLUSIONS: Reduced cardiorespiratory fitness levels were associated with increased, short-term complications after bariatric surgery. Cardiorespiratory fitness should be optimized prior to bariatric surgery to potentially reduce postoperative complications.

Coronary Disease↗

PubMed2005

Self-assembling bipyridinium multilayers.

The identification of strategies to assemble nanostructured films with engineered properties on solid supports can lead to the development of innovative functional materials. In particular, the self-assembly of electroactive multilayers from simple molecular building blocks on metallic electrodes can offer the opportunity to regulate the exchange of electrons between the underlying substrate and solution species. In this context, we designed an experimental protocol to prepare electroactive films from bipyridinium bisthiols. Specifically, we found that a compound incorporating two bipyridinium dications at its core and terminal thiol groups self-assembles into remarkably stable multilayers on polycrystalline gold. The surface coverage of the resulting films can be regulated by adjusting the exposure time of the gold substrate to the bipyridinium solution. Control experiments with appropriate model compounds demonstrate that both bipyridinium dications as well as both thiol groups must be present in the molecular skeleton to encourage multilayer growth. The resulting films transport electrons efficiently from the electrode surface to the film/solution interface. Indeed, they mediate the reduction of Ru(NH(3))(6)(3+) in the electrolyte solution but prevent the back oxidation of the resulting Ru(NH(3))(6)(2+). Furthermore, these polycationic bipyridinium films capture electrostatically Fe(CN)(6)(4-) tetraanions, which can also be exploited to transport electrons across the interfacial assembly. In fact, electrons can travel through the bipyridnium(2+/1+) couples to redox probes in solution and then back to the electrode through the Fe(CN)(6)(4/3-) couples. Thus, our original approach to self-assembling multilayers can produce stable electroactive films with unique electron transport properties, which can be regulated with a careful choice of the anionic components.

Journal Article↗

PubMed2005

Role of angiotensin II in the evolution of diastolic heart failure.

More than half of all persons with heart failure (HF) have diastolic HF. The prevalence of diastolic HF increases from 46% in persons younger than 45 years to 59% in those 85 years and older. The annual mortality rate associated with diastolic HF is >10%. Diagnosis is based on signs and symptoms of HF, elevated plasma B-type natriuretic peptide, preserved left ventricular systolic function, and evidence of diastolic dysfunction by Doppler examination on two-dimensional echocardiography. Approximately 80% of patients with diastolic HF have increased left ventricular mass and a history of hypertension. Neurohormonal activation is a key aspect of this condition. Studies suggest that activation of the renin-angiotensin-aldosterone system, specifically direct cardiac effects of angiotensin II and aldosterone, contributes to the pathogenesis and progression of diastolic dysfunction. Hence, there is a rationale for use of agents that antagonize the renin-angiotensin-aldosterone system, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone antagonists, in patients with heart failure.

Angiotensin II↗