Biomedical subjects

Juan J Hicks

Publications and source records attributed to Juan J Hicks.

3 recordsLinked to original sources

PubMed2007

Antioxidants decrease reperfusion induced arrhythmias in myocardial infarction with ST-elevation.

In myocardial infarctions with ST-segment elevation, ischemia followed by reperfusion (IR) leads to arrhythmia, myocardial stunning and endothelial dysfunction injury by reactive oxygen species (ROS). To determine the impact of ROS, we examined the effect of antioxidant vitamins on biochemical changes and arrhythmias induced by reperfusion before and after therapeutic thrombolysis (Actilyse). As compared with those receiving placebo, in individuals who received antioxidants, there was a significant decrease in premature ventricular beats (100% vs 38%), atrial fibrillation (44% vs 6%), ventricular tachycardia (31% vs 0%), first-degree atrial-ventricular block (44% vs 6%), plasma malondialdehyde at the first hour after initiation of thrombolysis (1.07 +/- 0.10 vs 0.53 +/- 0.10 nmols plasma malondialdehyde/mg protein) and circulating neutrophils after 24 hr after reperfusion. The antioxidant capacity of plasma was increased from 1.89 +/- 0.15 to 3.00 +/- 0.31 units/mg protein and paraoxonase-1 rose from 0.77 +/- 0.08 to 1.27 +/- 0.11 nmol/min/mg protein. These findings suggest that antioxidants might be useful as adjuvants in controlling reperfusion induced arrhythmias following therapeutic alteplase thrombolysis.

Antioxidants↗

PubMed2005

Oxidation by reactive oxygen species (ROS) alters the structure of human insulin and decreases the insulin-dependent D-glucose-C14 utilization by human adipose tissue.

The formation of dityrosine of human insulin oxidized by metal-catalyzed oxidation system (H2O2/Cu) was estimated by fluorescent methods. The oxidation of tyrosine and phenylalanine residues present on the insulin molecule was evident after 2 minutes of in vitro oxidation due to the formation of protein-bound dityrosine. The success of oxidative protein modification was followed until available aromatic residues were consumed (60 minutes), measured by their emission at 405 nm. The structural and chemical changes on insulin molecule are related to the loss of biological activity as assessed by measuring the increase of U-14C-glucose utilization by human adipose tissue in a radiorespirometry system. The oxidation of glucose (14CO2 production) of the adipose cells was increased 35 % (301 +/- 119 to 407 +/- 182 cpm/mg in dry weight. P < 0.05) in presence of 0.1 IU and 69 % (301 +/- 119 to 510 +/- 266 cpm/dry weight. P < 0.05) for 1.0 IU of insulin. The recombinant human insulin oxidized for 5 minutes only increased the glucose oxidation by 25 %. In conclusion, these observations show that dityrosine formation and other oxidative chemical changes of insulin due to its in vitro oxidation decrease and can abolish its biological activity.

Adipose Tissue↗

PubMed2005

Reactive oxygen species (ROS) induce chemical and structural changes on human insulin in vitro, including alterations in its immunoreactivity.

Oxidative stress occurs when the production of reactive oxygen species (ROS) exceeds the endogenous antioxidant defense. Peroxidations induced by ROS are the key of chemical and structural modifications of biomolecules including circulating proteins. To elucidate the effect of ROS on circulating proteins and considering the presence of oxidative stress in Diabetes Mellitus, the effects of ROS, in vitro, on human insulin were studied. We utilized the Fenton reaction for free hydroxyl radical (HO*) generation in presence of human recombinant insulin measuring chemical changes on its molecular structure. The induced changes in insulin were: a) significant increase on absorbance (280 nm) due to phenylalanine hydroxylation (0.023 +/- 0.007 to 0.13 +/- 0.07). b) Peroxidation products formed on amino acids side branches (peroxyl and alcohoxyl group); measured as increased capacity of reduce nitroblue of tetrazolium (NBT) to formazan (0.007 +/- 0.007 to 0.06 +/- 0.02). c) Increased concentration of free carbonyl groups (8.8 +/- 8.7 to 45.6 +/- 20.2 pmoles dinitrophenylhidrazones/nmol insulin) with lost of secondary structure, and d) Modification of epithopes decreasing the insulin antigen-antibody reactivity measured as a decrease in insulin concentration by RIA. In conclusion, the radical hydroxyl in vitro is able to induce molecular modifications on insulin.

Carbon↗