Azide function and polyaddition: reaction of 2-azido-2,4,4-trimethylpentane and monoazidopoly(2-methylpropene) with some dienophiles

The 1,3-dipolar addition of 2-azido-2,4,4-trimethylpentane ( 1 ) to acetylene and ethylene derivatives such as phenylacetylene (2), acrylonitrile, diphenyl fumarate ( 4 ) and N,N′-methylenebis(1,4-phenylene)dimaleimide ( 8 ) leads to the corresponding triazole and triazoline derivatives. This study demonstrates that tertiary azides are able to react with dienophiles, and the application of this reaction for the synthesis of block copolymers was investigated with monoazido-telechelic poly(2-methylpropene) (PMP). It was shown that the azido group is stable under the severe conditions of the polycondensation reaction without decomposition (170°C, 24 h), and the monoadduct PMP- 8 is produced with acceptable yield.     

Clinical characteristics of patients with exercise-induced ST-segment elevation without prior myocardial infarction.

BACKGROUND: Exercise-induced ST-segment elevation is a relatively uncommon problem and occurs more frequently in patients who have had a myocardial infarction. Data is limited on the characteristics of Taiwanese patients without prior myocardial infarction who develop exercise-induced ST-segment elevation. METHODS AND RESULTS: Exercise-induced ST-segment elevation developed in 9 of 6,147 consecutive patients without myocardial infarction who underwent treadmill exercise testing at out institution over a 4-year period. The clinical and angiographic characteristics of these patients were studied. Angiographically normal coronary arteries with coronary vasospasm were found in 5 patients, hemodynamically significant coronary stenosis was found in 3 patients, and coexisting spasm in angiographically normal coronary arteries combined with hemodynamically significant coronary stenosis in the different vessel was found in 1 patient. During a median follow-up of 71 months, 2 patients with coronary vasospasm developed recurrent angina after self-discontinuation of calcium antagonists and 2 patients (1 with coronary vasospasm and 1 with hemodynamically significant coronary stenosis) died of cardiac causes before arrival at the emergency department. CONCLUSION: Coronary vasospasm was a more common underlying pathology of exercise-induced ST-segment elevation in this Taiwanese cohort. Coronary angiography +/- intracoronary ergonovine provocation testing is necessary in these patients to identify the underlying pathology and appropriate treatment.     

Magnetic nanoparticle labeling of mesenchymal stem cells without transfection agent: cellular behavior and capability of detection with clinical 1.5 T magnetic resonance at the single cell level.

The purpose of this work was to evaluate the efficacy of labeling human mesenchymal stem cells (hMSCs) by ionic superparamagnetic iron oxide (SPIO) without a transfection agent and verifying its capability to be detected with clinical 1.5 T magnetic resonance (MR) at the single-cell level. Human hMSCs were incubated for 24 h with an ionic SPIO, Ferucarbotran. The labeling efficiency of hMSCs was determined by iron content measurement spectrophotometrically, and the influence of labeling on cell behavior was ascertained by examination of cell viability using the trypan blue exclusion method, cell proliferation analysis using MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, mitochondrial membrane potential (MMP) change, differentiation capacity, and reactive oxygen species (ROS) production measured by dichlorofluorescein diacetate (DCFDA) fluorescent probe. Labeled hMSCs were scanned under 1.5 T MRI with three-dimensional (3D) and two-dimensional (2D) T(2)-weighted gradient echo (GRE) pulse sequences. Human hMSC labeling without transfection agent was efficient. The iron content in hMSCs was 23.4 pg Fe/cell. No significant change was found in viability, proliferation, MMP change, ROS production, or differentiation capacity. About 45.2% of the hMSCs could be detected using 1.5 T MRI at the single cell level with 3D GRE and four repetitions.     

Effects of continuous distraction on cartilage in a moving joint: An investigation on adult rabbits

An animal model, using distraction force on adult rabbits, was developed to study the effects of nonweight-bearing on articular cartilage in a moving joint. Histologic evaluation was used to compare the morphology of chondrocytes, safranin O intensity, cartilage thickness, and structural changes between the test and contralateral joints. At 3 and 6 weeks, the chondrocytes in superficial and intermediate zones were round, with an increase in cellular volume density and mean cell volume and with less metachromasia; the safranin O intensity and cartilage thickness were the same as in the controls. In cartilage of the 9-week group, mean cell volume decreased with cell cloning in the superficial zone, while numerical density increased and mean matrix volume per cell decreased in the superficial and intermediate zones. The cartilage, with a 34% reduction in thickness and a 53–72% decrease in safranin O intensity from the superficial to the deep zone, had superficial fibrotic proliferation, suface erosion or depression, ard tidemark irregularity. Continuous distraction in a moving joint caused morphological changes in chondrocytes prior to degeneration of cartilage. These results support the hypothesis that the forces perceived by cells may dictate their shape and then stimulate alterations in cellular biochemistry and matrix metabolism.     

L-arginine reverses the antinatriuretic effect of cyclosporin in renal transplant patients

BACKGROUND: Cyclosporin has been shown to facilitate renal vasoconstriction and to have an antinatriuretic effect. The existence of an interference of cyclosporin with the vasodilating properties of endothelium mediated by nitric oxide production could mediate these effects. On the other hand, the infusion of the nitric oxide precursor L-arginine has been shown to induce renal vasodilatation and to facilitate natriuresis in normal volunteers. We have investigated the renal effects of the administration of an infusion of L-arginine in renal transplant patients chronically treated with cyclosporin. To facilitate the analysis of the data the effects of the administration of a similar dose of cyclosporin on renal function during the infusion of a vehicle were also investigated during the administration of a vehicle of L-arginine. DESIGN: Ten male renal transplant patients, chronically treated with cyclosporin and with a stable renal function were studied during 2 consecutive days after the administration of the usual morning dose of cyclosporin. The first day they received an intravenous infusion of vehicle and the second the infusion of graded doses of L-arginine (50, 100, 150 mg/kg/h) during 3 consecutive h. RESULTS: The first day, after cyclosporin administration a significant fall (P < 0.01) was observed in natriuresis and kaliuresis in the absence of changes in renal plasma flow and glomerular filtration rate. After the administration of L-arginine significant (P < 0.01) increases of renal plasma flow, glomerular filtration rate, and natriuresis were seen. The increase in blood levels of cyclosporin after its administration did not differ between days 1 and 2. CONCLUSION: These results indicate that L-arginine facilitates renal vasodilatation and natriuresis in renal transplant patients. Furthermore, the observed increase in sodium excretion could indicate that L-arginine counteracts the antinatriuretic effect of cyclosporin.