Effects of growth hormone (GH) replacement therapy on very low density lipoprotein apolipoprotein B100 kinetics in patients with adult GH deficiency: a stable isotope study

Patients with adult GH deficiency are often dyslipidemic and may have an increased risk of cardiovascular disease. The secretion and clearance of very low density lipoprotein apolipoprotein B 100 (VLDL apoB) are important determinants of plasma lipid concentrations. This study examined the effect of GH replacement therapy on VLDL apoB metabolism using a stable isotope turnover technique. VLDL apoB kinetics were determined in 14 adult patients with GH deficiency before and after 3 months GH or placebo treatment in a randomized double blind, placebo-controlled study using a primed constant [1-(13)C]leucine infusion. VLDL apoB enrichment was determined by gas chromatography-mass spectrometry. GH replacement therapy increased plasma insulin-like growth factor I concentrations 2.9 +/- 0.5-fold (P < 0.001), fasting insulin concentrations 1.8 +/- 0.6-fold (P < 0.04), and hemoglobin A1C from 5.0 +/- 0.2% to 5.3 +/- 0.2% (mean +/- SEM; P < 0.001). It decreased fat mass by 3.4 +/- 1.3 kg (P < 0.05) and increased lean body mass by 3.5 +/- 0.8 kg (P < 0.01). The total cholesterol concentration (P < 0.02), the low density lipoprotein cholesterol concentration (P < 0.02), and the VLDL cholesterol/VLDL apoB ratio (P < 0.005) decreased. GH therapy did not significantly change the VLDL apoB pool size, but increased the VLDL apoB secretion rate from 9.2 +/- 2.0 to 25.9 +/- 10.3 mg/kg x day (P < 0.01) and the MCR from 11.5 +/- 2.7 to 20.3 +/- 3.2 mL/min (P < 0.03). No significant changes were observed in the placebo group. This study suggests that GH replacement therapy improves lipid profile by increasing the removal of VLDL apoB. Although GH therapy stimulates VLDL apoB secretion, this is offset by the increase in the VLDL apoB clearance rate, which we postulate is due to its effects in up-regulating low density lipoprotein receptors and modifying VLDL composition.

The use of stable isotopes to unravel the hyperlipidemia of adult growth hormone deficiency

Using stable isotope techniques to establish turnover rates for very low density lipoprotein (VLDL), a group of eight adult patients with growth hormone deficiency (GHD) exhibited an increased VLDL apoprotein B (apo B) secretion and decreased VLDL apoB metabolic clearance rate compared to controls. Such increased secretion is seen in some dyslipidemic states, including GHD, which are associated with atherosclerosis. The study of VLDL metabolism may provide a clue to the lipid metabolism disorder associated with GHD.

Stable expression of Escherichia coli beta-glucuronidase A (GusA) in Giardia lamblia: application to high-throughput drug susceptibility testing

OBJECTIVES: In order to create a suitable model for high-throughput drug screening, a Giardia lamblia WB C6 strain expressing Escherichia coli glucuronidase A (GusA) was created and tested with respect to susceptibility to the anti-giardial drugs nitazoxanide and metronidazole. METHODS: GusA, a well-established reporter gene in other systems, was cloned into the vector pPacVInteg allowing stable expression in G. lamblia under control of the promoter from the glutamate dehydrogenase (gdh) gene. The resulting transgenic strain was compared with the wild-type strain in a vitality assay, characterized with respect to susceptibility to nitazoxanide, metronidazole and -- as assessed in a 96-well plate format -- to a panel of 15 other compounds to be tested for anti-giardial activity. RESULTS: GusA was stably expressed in G. lamblia. Using a simple glucuronidase assay protocol, drug efficacy tests yielded results similar to those from cell counting. CONCLUSIONS: G. lamblia WB C6 GusA is a suitable tool for high-throughput anti-giardial drug screening.

Cost-effectiveness of percutaneous coronary intervention in patients with stable coronary artery disease and abnormal fractional flow reserve

BACKGROUND The Fractional Flow Reserve Versus Angiography for Multivessel Evaluation (FAME) 2 trial demonstrated a significant reduction in subsequent coronary revascularization among patients with stable angina and at least 1 coronary lesion with a fractional flow reserve ≤0.80 who were randomized to percutaneous coronary intervention (PCI) compared with best medical therapy. The economic and quality-of-life implications of PCI in the setting of an abnormal fractional flow reserve are unknown. METHODS AND RESULTS We calculated the cost of the index hospitalization based on initial resource use and follow-up costs based on Medicare reimbursements. We assessed patient utility using the EQ-5D health survey with US weights at baseline and 1 month and projected quality-adjusted life-years assuming a linear decline over 3 years in the 1-month utility improvements. We calculated the incremental cost-effectiveness ratio based on cumulative costs over 12 months. Initial costs were significantly higher for PCI in the setting of an abnormal fractional flow reserve than with medical therapy ($9927 versus $3900, P<0.001), but the $6027 difference narrowed over 1-year follow-up to $2883 (P<0.001), mostly because of the cost of subsequent revascularization procedures. Patient utility was improved more at 1 month with PCI than with medical therapy (0.054 versus 0.001 units, P<0.001). The incremental cost-effectiveness ratio of PCI was $36 000 per quality-adjusted life-year, which was robust in bootstrap replications and in sensitivity analyses. CONCLUSIONS PCI of coronary lesions with reduced fractional flow reserve improves outcomes and appears economically attractive compared with best medical therapy among patients with stable angina.

Optimized Demineralization Technique for the Measurement of Stable Isotope Ratios of Nonexchangeable H in Soil Organic Matter

To make use of the isotope ratio of nonexchangeable hydrogen (δ2Hn (nonexchangeable)) of bulk soil organic matter (SOM), the mineral matrix (containing structural water of clay minerals) must be separated from SOM and samples need to be analyzed after H isotope equilibration. We present a novel technique for demineralization of soil samples with HF and dilute HCl and recovery of the SOM fraction solubilized in the HF demineralization solution via solid-phase extraction. Compared with existing techniques, organic C (Corg) and organic N (Norg) recovery of demineralized SOM concentrates was significantly increased (Corg recovery using existing techniques vs new demineralization method: 58% vs 78%; Norg recovery: 60% vs 78%). Chemicals used for the demineralization treatment did not affect δ2Hn values as revealed by spiking with deuterated water. The new demineralization method minimized organic matter losses and thus artificial H isotope fractionation, opening up the opportunity to use δ2Hn analyses of SOM as a new tool in paleoclimatology or geospatial forensics.

Enhancement of excess electron transfer efficiency in DNA containing a phenothiazine donor and multiple stable phenanthrenyl base pairs

EET grown ohm: Excess electron transfer (EET) was observed within a DNA duplex containing π-stacked phenothiazine as an electron donor, phenanthrenes as electron carriers and 5-bromouracil as an electron trap. Increasing the number of phenanthrenyl base pairs increased EET efficiency.

Long-term outcomes of patients receiving zotarolimus-eluting stents in ST elevation myocardial infarction, non-ST elevation acute coronary syndrome, and stable angina: data from the Resolute program

BACKGROUND Outcome data are limited in patients with ST-segment elevation acute myocardial infarction (STEMI) or other acute coronary syndromes (ACSs) who receive a drug-eluting stent (DES). Data suggest that first generation DES is associated with an increased risk of stent thrombosis when used in STEMI. Whether this observation persists with newer generation DES is unknown. The study objective was to analyze the two-year safety and effectiveness of Resolute™ zotarolimus-eluting stents (R-ZESs) implanted for STEMI, ACS without ST segment elevation (non-STEACS), and stable angina (SA). METHODS Data from the Resolute program (Resolute All Comers and Resolute International) were pooled and patients with R-ZES implantation were categorized by indication: STEMI (n=335), non-STEACS (n=1416), and SA (n=1260). RESULTS Mean age was 59.8±11.3 years (STEMI), 63.8±11.6 (non-STEACS), and 64.9±10.1 (SA). Fewer STEMI patients had diabetes (19.1% vs. 28.5% vs. 29.2%; P<0.001), prior MI (11.3% vs. 27.2% vs. 29.4%; P<0.001), or previous revascularization (11.3% vs. 27.9% vs. 37.6%; P<0.001). Two-year definite/probable stent thrombosis occurred in 2.4% (STEMI), 1.2% (non-STEACS) and 1.1% (SA) of patients with late/very late stent thrombosis (days 31-720) rates of 0.6% (STEMI and non-STEACS) and 0.4% (SA) (P=NS). The two-year mortality rate was 2.1% (STEMI), 4.8% (non-STEACS) and 3.7% (SA) (P=NS). Death or target vessel re-infarction occurred in 3.9% (STEMI), 8.7% (non-STEACS) and 7.3% (SA) (P=0.012). CONCLUSION R-ZES in STEMI and in other clinical presentations is effective and safe. Long term outcomes are favorable with an extremely rare incidence of late and very late stent thrombosis following R-ZES implantation across indications.

Stable secondary arrhythmias late after intraoperative radiofrequency ablation of atrial fibrillation: incidence, mechanism, and treatment.

INTRODUCTION Intraoperative radiofrequency (RF) ablation is an effective treatment of atrial fibrillation (AF). However, secondary arrhythmias late after ablation may complicate the patient's course. We report on the incidence, mechanisms, and treatment of gap-related atrial flutter and other secondary arrhythmias during long-term follow-up. METHODS AND RESULTS In 129 patients who underwent intraoperative RF ablation with placement of left atrial linear lesions using minimally invasive surgical techniques, secondary arrhythmias were analyzed during long-term follow-up (20 +/- 6 months). Transient atrial arrhythmias during the first 3 postoperative months were excluded. In 8 (6.2%) of 129 patients, sustained stable secondary arrhythmias were documented. Left atrial, gap-related atrial flutter was observed in 4 patients (3.1%). The flutter was treated by percutaneous RF ablation in 3 patients (2.3%) and with drugs in 1 patient (0.8%). In 2 patients (1.6%), right atrial isthmus-dependent atrial flutter occurred and was treated successfully by percutaneous RF ablation. In 2 patients (1.6%), ectopic right atrial tachycardias occurred and were treated with percutaneous RF ablation. CONCLUSION Late after intraoperative RF ablation of atrial fibrillation, three types of stable secondary arrhythmias were observed in 6% of patients: left atrial gap-related atrial flutter, right atrial isthmus-dependent atrial flutter, and ectopic atrial tachycardia. Gaps after intraoperative RF ablation due to noncontinuous or nontransmural linear lesions may lead to stable left atrial macroreentrant tachycardias, requiring new interventional therapy.

The effect of heart rate reduction by ivabradine on collateral function in patients with chronic stable coronary artery disease

Objective To evaluate the effect of heart rate reduction by ivabradine on coronary collateral function in patients with chronic stable coronary artery disease (CAD). Methods This was a prospective randomised placebo-controlled monocentre trial in a university hospital setting. 46 patients with chronic stable CAD received placebo (n=23) or ivabradine (n=23) for the duration of 6 months. The main outcome measure was collateral flow index (CFI) as obtained during a 1 min coronary artery balloon occlusion at study inclusion (baseline) and at the 6-month follow-up examination. CFI is the ratio between simultaneously recorded mean coronary occlusive pressure divided by mean aortic pressure both subtracted by mean central venous pressure. Results During follow-up, heart rate changed by +0.2±7.8 beats/min in the placebo group, and by –8.1±11.6 beats/min in the ivabradine group (p=0.0089). In the placebo group, CFI decreased from 0.140±0.097 at baseline to 0.109±0.067 at follow-up (p=0.12); it increased from 0.107±0.077 at baseline to 0.152±0.090 at follow-up in the ivabradine group (p=0.0461). The difference in CFI between the 6-month follow-up and baseline examination amounted to −0.031±0.090 in the placebo group and to +0.040±0.094 in the ivabradine group (p=0.0113). Conclusions Heart rate reduction by ivabradine appears to have a positive effect on coronary collateral function in patients with chronic stable CAD.

Late Quaternary palaeoenvironmental reconstruction from Lakes Ohrid and Prespa (Macedonia/Albania border) using stable isotopes

Abstract. Here we present stable isotope data from three sediment records from lakes that lie along the Macedonian- Albanian border (Lake Prespa: 1 core, and Lake Ohrid: 2 cores). The records only overlap for the last 40 kyr, although the longest record contains the MIS 5/6 transition (Lake Ohrid). The sedimentary characteristics of both lakes differ significantly between the glacial and interglacial phases. At the end of MIS 6 Lake Ohrid’s water level was low (high �18Ocalcite) and, although productivity was increasing (high calcite content), the carbon supply was mainly from inorganic catchment rock sources (high �13Ccarb). During the last interglacial, calcite and TOC production and preservation increased, progressively lower �18Ocalcite suggest increase in humidity and lake levels until around 115 ka. During ca. 80 ka to 11 ka the lake records suggest cold conditions as indicated by negligible calcite precipitation and low organic matter content. In Lake Ohrid, �13Corg are complacent; in contrast, Lake Prespa shows consistently higher �13Corg suggesting a low oxidation of 13C-depleted organic matter in agreement with a general deterioration of climate conditions during the glacial. From 15 ka to the onset of the Holocene, calcite and TOC begin to increase, suggesting lake levels were probably low (high �18Ocalcite). In the Holocene (11 ka to present) enhanced productivity is manifested by high calcite and organic matter content. All three cores show an early Holocene characterised by low �18Ocalcite, apart from the very early Holocene phase in Prespa where the lowest �18Ocalcite occurs at ca. 7.5 ka, suggesting a phase of higher lake level only in (the more sensitive) Lake Prespa. From 6 ka, �18Ocalcite suggest progressive aridification, in agreement with many other records in the Mediterranean, although the uppermost sediments in one core records low �18Ocalcite which we interpret as a result of human activity. Overall, the isotope data present here confirm that these two big lakes have captured the large scale, low frequency palaeoclimate variation that is seen in Mediterranean lakes, although in detail there is much palaeoclimate information that could be gained, especially small scale, high frequency differences between this region and the Mediterranean.

Whole Proteome Analysis of the Protozoan Parasite Trypanosoma brucei using Stable Isotope Labeling by Amino Acids in Cell Culture and Mass Spectrometry

The single-celled protozoan Trypanosoma brucei spp. is the causative agent of human African trypanosomiasis and nagana in cattle. Quantitative proteomics for the first time allowed for the characterization of the proteome from several different life stages of the parasite (1-3). To achieve this, stable isotope labeling by amino acids in cell culture (SILAC; (4)) was adapted to T. brucei spp. cultures. T. brucei cells grown in standard media with dialyzed fetal calf serum containing heavy isotope-labeled amino acids (arginine and lysine) show efficient incorporation of the labeled amino acids into the whole cell proteome (8-12 divisions) and no detectable amino acid conversions. The method can be applied to both of the major life stages of the parasite and in combination with RNAi or gene knock-out approaches.