Strontium, a Tracer to Study the Transport of Calcium in Mineralizing Tissues by Electron Probe Microanalysis

In growth plate cartilage the mineralization starts extracellularly in the lower hypertrophic zone. The mineral formed is the calcium phosphate apatite. Enough calcium and phosphate must be available at the mineralization front as well as in regions with proceeding mineralization. There must be a transport of Ca (and phosphate) to these sites. Electron probe X-ray microanalysis is a well established method to analyze element concentrations in small volumes, but it cannot discriminate isotopes. Strontium is similar to Ca in its chemical and biological behaviour and is therefore a suitable tracer to investigate the transport of Ca. Small amounts of Sr (0.1 g per kg body weight) were administered intraperitoneally to young rats. After definite intervals of time ranging from 10 to 120 min, 2-4 rats were killed. On freeze dried cryosections the Sr/Ca ratio of the serum and of the intra- and extracellular space of the growth plate were measured. The Sr/Ca ratio reaches its maximum after about 10 min in the serum and after 20 min in the extracellular space of growth plate cartilage. The intracellular Sr/Ca ratio shows large variations because of the low intracellular Ca and Sr concentration, and is lower than the extracellular ratio for times shorter than 30 min. No significant differences were found between the different cell zones of the unmineralized growth plate cartilage. The results demonstrate that the transport of Ca to the growth plate cartilage is relatively fast and that in growth plate cartilage, Ca is transported extracellularly, not intracellularly

Stents With Torsional Strength for Superficial Femoral Artery Disease:: The Prospective Q3-Registry

Purpose: This postmarketing surveillance study aimed to assess effectiveness and safety of a peripheral self-expanding stent with high torsional strength (POLARIS stent) for the treatment of de novo superficial femoral artery (SFA) lesions in the routine clinical practice. Materials and Methods: Consecutive patients with symptomatic de novo SFA occlusive disease who underwent POLARIS stent implantation were enrolled into the prospective, multicenter, observational postmarket surveillance study. Primary outcome measure was freedom from clinically driven target lesion revascularization (cdTLR) at 12 months. Main secondary outcomes were procedural success, primary clinical improvement, and freedom from major adverse cardiovascular and limb events (MACLE) throughout 24 months. Results: A total of 199 participants (70±11 years, 70.4% men) were included in the study at 9 German sites from December 2014 to August 2018. Half of them (52.6%) were current smokers, 37.6% had diabetes, and 25.0% were obese. Most participants suffered from intermittent claudication (88.4%). Mean lesion length was 98±83 mm, 43.5% of lesions were occluded, and 27.3% were severely calcified. Freedom from 12 months cdTLR was 94.4% (95% confidence interval [CI], 90.6–98.2). At 24 months, freedom from cdTLR was 88.7% (95% CI, 83.0–94.4). Procedural success was achieved in 96.2% of participants. Primary clinical improvement occurred in 87.5% and 85.4% of participants at 12 and 24 months, respectively. Freedom from MACLE was 94.8% (95% CI, 91.4–98.1) and 93.8% (95% CI, 89.9–97.6) at 12 and 24 months, respectively. Conclusions: Treatment of SFA occlusive disease in a real-world setting using the POLARIS stent with high bidirectional torsional strength is efficacious and does not raise any safety concern in the medium term. The study is registered with ClinicalTrials.gov (Identifier: NCT02307292)