THE EFFECTS OF EUGLVCEMIC INSULIN CLAMP ON THE METABOLISM OF 3-HYDROXVBUTYRATE AND PLASMA FREE FAHY ACIDS BY THE HIND LIMB OF LACRATING SHEEP

The effects of exogenous insulin, with euglycemia, on the concentration differences, extraction ratio and uptake of 3- hydroxybutyrate and plasma free fatty acids by the lactating sheep hind limb were studied. Generally, the results showed that with increasing plasma insulin levels, while maintaining euglycemia, the concentrations, arterio-venous concentration differences, extraction ratio and uptake of 3-hydrubutyrate and free fatty acids Were significantly (P<0.05) reduced, but Significant correlation was established between arterial concentration of 3-hydtoxvbutyrate and plasma free fatty acids and their uptake. A similar relationship was also obtained between the arterial concentrations of 3-hydroxybutyrate plasma free fatty acids.

Plasma radio-metabolite analysis of PET tracers for dynamic PET imaging: TLC and autoradiography

Background In molecular imaging with dynamic PET, the binding and dissociation of a targeted tracer is characterized by kinetics modeling which requires the arterial concentration of the tracer to be measured accurately. Once in the body the radiolabeled parent tracer may be subjected to hydrolysis, demethylation/dealkylation and other biochemical processes, resulting in the production and accumulation of different metabolites in blood which can be labeled with the same PET radionuclide as the parent. Since these radio-metabolites cannot be distinguished by PET scanning from the parent tracer, their contribution to the arterial concentration curve has to be removed for the accurate estimation of kinetic parameters from kinetic analysis of dynamic PET. High-performance liquid chromatography has been used to separate and measure radio-metabolites in blood plasma; however, the method is labor intensive and remains a challenge to implement for each individual patient. The purpose of this study is to develop an alternate technique based on thin layer chromatography (TLC) and a sensitive commercial autoradiography system (Beaver, Ai4R, Nantes, France) to measure radio-metabolites in blood plasma of two targeted tracers—[18F]FAZA and [18F]FEPPA, for imaging hypoxia and inflammation, respectively. Results Radioactivity as low as 17 Bq in 2 µL of pig’s plasma can be detected on the TLC plate using autoradiography. Peaks corresponding to the parent tracer and radio-metabolites could be distinguished in the line profile through each sample (n = 8) in the autoradiographic image. Significant intersubject and intra-subject variability in radio-metabolites production could be observed with both tracers. For [18F]FEPPA, 50% of plasma activity was from radio-metabolites as early as 5-min post injection, while for [18F]FAZA, significant metabolites did not appear until 50-min post. Simulation study investigating the effect of radio-metabolite in the estimation of kinetic parameters indicated that 32–400% parameter error can result without radio-metabolites correction. Conclusion TLC coupled with autoradiography is a good alternative to high-performance liquid chromatography for radio-metabolite correction. The advantages of requiring only small blood samples (~ 100 μL) and of analyzing multiple samples simultaneously, make the method suitable for individual dynamic PET studies.

Plasma radio–metabolite analysis of PET tracers for dynamic PET imaging: TLC and autoradiography

Background In molecular imaging with dynamic PET, the binding and dissociation of a targeted tracer is characterized by kinetics modeling which requires the arterial concentration of the tracer to be measured accurately. Once in the body the radiolabeled parent tracer may be subjected to hydrolysis, demethylation/dealkylation and other biochemical processes, resulting in the production and accumulation of different metabolites in blood which can be labeled with the same PET radionuclide as the parent. Since these radio-metabolites cannot be distinguished by PET scanning from the parent tracer, their contribution to the arterial concentration curve has to be removed for the accurate estimation of kinetic parameters from kinetic analysis of dynamic PET. High performance liquid chromatography has been used to separate and measure radio-metabolites in blood plasma, however, the method is labor intensive and remains a challenge to implement for each individual patient. The purpose of this study is to develop an alternate technique based on thin layer chromatography (TLC) and a sensitive commercial autoradiography system (Beaver, Ai4R, Nantes, France) to measure radio-metabolites in blood plasma of two targeted tracers - [ 18 F]FAZA and [ 18 F]FEPPA , for imaging hypoxia and inflammation respectively. Results Radioactivity as low as 17Bq in 2µL of pig’s plasma can be detected on the TLC plate using autoradiography. Peaks corresponding to the parent tracer and radio-metabolites could be distinguished in the line profile through each sample (n=8) in the autoradiographic image. Significant inter-subject and intra-subject variability in radio-metabolites production could be observed with both tracers. For [ 18 F]FEPPA, 50% of plasma activity was from radio-metabolites as early as 5 min post injection while for [ 18 F]FAZA, significant metabolites did not appear until 50 min post. Simulation study investigating the effect of radio-metabolite in the estimation of kinetic parameters indicated that 32-400% parameter error can result without radio-metabolites correction. Conclusion TLC coupled with autoradiography is a good alternative to high performance liquid chromatography for radio-metabolite correction. The advantages of requiring only small blood samples (~ 100 μL) and of analyzing multiple samples simultaneously, make the method suitable for individual dynamic PET studies.

Plasma radio–metabolite analysis of PET tracers for dynamic PET imaging: TLC and autoradiography

Background In molecular imaging with dynamic PET, the binding and dissociation of a targeted tracer is characterized by kinetics modeling which requires the arterial concentration of the tracer to be measured accurately. Once in the body the radiolabeled parent tracer may be subjected to hydrolysis, demethylation/dealkylation and other biochemical processes, resulting in the production and accumulation of different metabolites in blood which can be labeled with the same PET radionuclide as the parent. Since these radio-metabolites cannot be distinguished by PET scanning from the parent tracer, their contribution to the arterial concentration curve has to be removed for the accurate estimation of kinetic parameters from kinetic analysis of dynamic PET. High performance liquid chromatography has been used to separate and measure radio-metabolites in blood plasma, however, the method is labor intensive and remains a challenge to implement for each individual patient. The purpose of this study is to develop an alternate technique based on thin layer chromatography (TLC) and a sensitive commercial autoradiography system (Beaver, Ai4R, Nantes, France) to measure radio-metabolites in blood plasma of two targeted tracers - [18F]FAZA and [18F]FEPPA , for imaging hypoxia and inflammation respectively. Results Radioactivity as low as 17Bq in 2µL of pig’s plasma can be detected on the TLC plate using autoradiography. Peaks corresponding to the parent tracer and radio-metabolites could be distinguished in the line profile through each sample (n=8) in the autoradiographic image. Significant inter-subject and intra-subject variability in radio-metabolites production could be observed with both tracers. For [18F]FEPPA, 50% of plasma activity was from radio-metabolites as early as 5 min post injection while for [18F]FAZA, significant metabolites did not appear until 50 min post. Simulation study investigating the effect of radio-metabolite in the estimation of kinetic parameters indicated that 32-400% parameter error can result without radio-metabolites correction.Conclusion TLC coupled with autoradiography is a good alternative to high performance liquid chromatography for radio-metabolite correction. The advantages of requiring only small blood samples (~ 100 mL) and of analyzing multiple samples simultaneously, make the method suitable for individual dynamic PET studies.

Plasma Radio–Metabolite Analysis of PET Tracers for Dynamic PET Imaging: TLC and Autoradiography

Background In molecular imaging with dynamic PET, the binding and dissociation of a targeted tracer is characterized by kinetics modeling which requires the arterial concentration of the tracer to be measured accurately. Metabolism of the radiolabeled parent tracer in the body due to hydrolysis, methylation and other biochemical processes, results in the production and accumulation of different metabolites in blood which can be labeled with the same PET radionuclide as the parent. Since these radio-metabolites cannot be distinguished by PET scanning from the parent tracer, their contribution to the arterial concentration curve has to be removed for the accurate estimation of kinetic parameters from kinetic analysis of dynamic PET. High performance liquid chromatography has been used to separate and measure radio-metabolites in blood plasma, however, the method is labor intensive and remains a challenge to implement for each individual patient. The purpose of this study is to develop an alternate technique based on thin layer chromatography (TLC) and a sensitive commercial autoradiography system (Beaver, Ai4R, Nantes, France) to measure radio-metabolites in blood plasma of two targeted tracers  [18F]FAZA and [18F]FEPPA , for imaging hypoxia and inflammation respectively. Results Radioactivity as low as 17Bq in 2µL of plasma can be detected on the TLC plate using autoradiography. Peaks corresponding to the parent tracer and radio-metabolites could be distinguished in the line profile through each sample (n=8) in the autoradiographic image. Significant inter-subject and intra-subject variability in radio-metabolites production could be observed with both tracers. For [18F]FEPPA, 50% of plasma activity was from radio-metabolites as early as 5 min post injection while for [18F]FAZA, significant metabolites did not appear until 50 min post. Simulation study investigating the effect of radio-metabolite in the estimation of kinetic parameters indicated that 32-400% parameter error can result without radio-metabolites correction.Conclusion TLC coupled with autoradiography is a good alternative to high performance liquid chromatography for radio-metabolite correction. The advantages of requiring only small blood samples (~ 100 L) and of analyzing multiple samples simultaneously, make the method suitable for individual dynamic PET studies.

Enhanced cardiac production of matrix metalloproteinase-2 and -9 and its attenuation associated with pravastatin treatment in patients with acute myocardial infarction

Previous experimental studies have demonstrated that MMPs (matrix metalloproteinases) contribute to LV (left ventricular) remodelling. We hypothesized that cardiac MMPs are activated in patients with AMI (acute myocardial infarction) and, if so, MMP production may be attenuated by statins (3-hydroxy-3-methylglutaryl-CoA reductase inhibitors) through their cardiovascular protective actions. We studied 30 patients, ten control patients with stable angina pectoris and 20 patients with AMI, in whom LV catheterization at the chronic stage was performed 22±12 days (value is mean±S.D.) after the onset of AMI. Blood samples were collected from the CS (coronary sinus) and a peripheral artery. In patients with AMI, the levels of MMP-2 and MMP-9 were significantly (P<0.05) higher in the CS than the peripheral artery (MMP-2, 853±199 compared with 716±127 ng/ml; MMP-9, 165±129 compared with 98±82 ng/ml), whereas no significant differences were observed in the patients with angina pectoris. The CS–arterial concentration gradients of MMP-2 and MMP-9 correlated positively with BNP (brain natriuretic peptide) levels (MMP-2, R=0.68, P<0.01; MMP-9, R=0.59, P<0.05) and LV end-diastolic volume index (MMP-2, R=0.70, P<0.01; MMP-9, R=0.70, P<0.01). When patients with AMI treated with 10 mg of pravastatin or without (n=10 in each group) were compared, this statin therapy significantly (P<0.05) decreased the CS–arterial concentration gradients of MMP-2 (69±43 compared with 213±185 ng/ml) and MMP-9 (14±27 compared with 119±84 ng/ml). In conclusion, the enhanced production of cardiac MMP-2 and MMP-9 is associated with LV enlargement and elevated BNP levels in patients with AMI. A pleiotropic effect of statins appears to be associated with the modulation of cardiac MMP activation, which may be potentially beneficial in the attenuation of post-infarction LV remodelling.

Pyruvate improves redox status and decreases indicators of hepatic apoptosis during hemorrhagic shock in swine

Previous studies have shown that the liver is the first organ to display signs of injury during hemorrhagic shock. We examined the mechanism by which pyruvate can prevent liver damage during hemorrhagic shock in swine anesthetized with halothane. Thirty minutes after the induction of a 240-min controlled arterial hemorrhage targeted at 40 mmHg, hypertonic sodium pyruvate (0.5 g · kg−1 · h−1) was infused to achieve an arterial concentration of 5 mM. The volume and osmolality effects of pyruvate were matched with 10% saline (HTS) and 0.9% saline (NS). Although the peak hemorrhage volume increased significantly in both the pyruvate and HTS group, only the pyruvate treatment was effective in delaying cardiovascular decompensation. In addition, pyruvate effectively maintained the NADH/NAD redox state, as evidenced by increased microdialysate pyruvate levels and a significantly lower lactate-to-pyruvate ratio. Pyruvate also prevented the loss of intracellular antioxidants (GSH) and a reduction in the GSH-to-GSSG ratio. These beneficial effects on the redox environment decreased hepatic cellular death by apoptosis. Pyruvate significantly increased the ratio of Bcl-Xl (antiapoptotic molecule)/Bax (proapoptotic molecule), prevented the release of cytochrome c from mitochondria, and decreased the fragmentation of caspase 3 and poly(ADP ribose) polymerase (DNA repair enzyme). These beneficial findings indicate that pyruvate infused 30 min after the onset of severe hemorrhagic shock is effective in maintaining the redox environment, preventing the loss of the key antioxidant GSH, and decreasing early apoptosis indicators.