Juan González

Cardiovascular Deterioration in STZ-Diabetic Rats: Possible Role of Vascular RAS

The precise mechanisms involved in the etiology of cardiovascular complications in diabetes are undefined. Recent evidence suggests that the renin-angiotensin system plays a predominant role in the genesis of these complications. The temporal evolution of vascular angiotensin-converting enzyme (ACE) activity was evaluated in streptozotocin-diabetic rats 2 and 4 weeks following the induction of diabetes. Vascular ACE activity was correlated with acetylcholine-induced relaxation, systolic blood pressure, and cardiac output index, establishing a possible link between these variables. Age-matched Sprague-Dawley rats were used as controls. ACE activity in aortic homogenates doubled in rats after 2 weeks of diabetes as compared with controls (0.46 ± 0.06 vs. 0.19 ± 0.02 nmol/mg × min, n = 8, p < 0.05). In contrast, no difference was observed between rats 4 weeks following diabetes onset (0.20 ± 0.05 nmol/mg × min) and controls (n = 8, p > 0.05). Impaired endothelial function was also observed in the aorta of diabetic animals. The maximal aortic relaxation with 10 µmol/l acetylcholine was reduced by 40% in diabetic rats 2 weeks after onset and by 41% after 4 weeks when compared to controls (n = 8, p < 0.05). Two weeks following diabetes induction, the cardiac output index decreased by 16% and after 4 weeks by 30% (n = 4, p < 0.05). Systolic blood pressure increased from 116 ± 12 mm Hg before diabetes to 158 ± 4 mm Hg (p < 0.05) after 2 weeks and to 182 ± 5 mm Hg after 4 weeks (p < 0.05). Together, these results suggest that a local renin-angiotensin system plays an important role in the genesis of vascular dysfunction and cardiac deterioration within the first stages of diabetes. A high vascular ACE activity may promote progressive deterioration of the cardiovascular system in streptozotocin-diabetic rats from the earliest stages by increasing peripheral resistance, blood pressure, preload, afterload, and cardiac work.

Structural evolution during chemical vapor deposition of diamond thin films

In situ phase-modulated ellipsometry was employed to monitor the nucleation and growth processes of diamond thin films fabricated by chemical vapor deposition. The effective extinction coefficient (k) at 1.96 eV was used as a basis for dividing the deposition process into intervals. The film growth was aborted at various k values yielding diamond film samples that represent snapshots of the growth process at different stages. Ex situ characterization of the films was performed using Raman spectroscopy, scanning electron microscopy, and x-ray diffraction. The results indicate that the diamond film deposition process consists of various stages in which the crystalline quality, the net compressive stress, and the relative amount of non-sp3 carbon follow different trends. A correlation between the effective k value measured in situ and the film microstructure characterized ex situ was established which enables the monitoring of the diamond film growth process in real time.

Burden of stroke in Puerto Rico

Stroke is the fifth leading cause of death and the first cause of long-term disability in Puerto Rico. Trained staff reviewed and independently validated the medical records of patients who had been hospitalized with possible stroke at any of the 20 largest hospitals located in Puerto Rico during 2007, 2009, and 2011. The mean age of the 5005 newly diagnosed stroke patients (51·2% female) was 70 years. At the time of hospitalization, women were 41/2 years older, were less likely to be married (60·2% vs. 39·9%, P < 0·001), smoked less (5·8% vs. 13·4%, P < 0·001), and had significantly higher proportion of diabetes (56·0% vs. 54·8%), hypertension (89·1% vs. 85·0%), and low density lipoprotein-cholesterol (LDL-Chol) > 100 mg/dL (65·7% vs. 57·5%) P < 0·05. Ischemic stroke represented 75% of all types of strokes. Atrial fibrillation was mentioned in 7·9% of the medical records. The risk for dying before discharge was similar for both genders, but was 40% higher for women than for men at one-year follow-up: age-adjusted odds ratio = 1·4 (95% confidence interval = 1·2–1·5).