Healthy adult dogs were subjected to stepwise reduction of nephron population so as to create the transition from normal renal function to advanced renal insufficiency. Studies were performed at each level of renal function. Glomerular filtration rate (GFR), renal phosphate clearance, and serum radioimmunoassayable parathyroid hormone (PTH) levels were measured. Two groups of animals were studied. In one, phosphorous intake was maintained at 1200 mg/day. As GFR declined, fractional phosphate excretion rose reciprocally, and PTH levels increased over 20-fold. In the second group, phosphorous intake was maintained at less than 100 mg/day. As GFR fell, fractional phosphate excretion changed little, and no increment in PTH levels occurred. The data suggest that the control system regulating phosphate excretion contributes importantly to the pathogenesis of secondary hyperparathyroidism in advancing renal insufficiency.

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IntroductionAutologous Matrix-Induced Chondrogenesis (AMIC) is an innovative treatment for localized full-thickness cartilage defects combining the well-known microfracturing with collagen I/III scaffold. The purpose of this analysis was to evaluate the medium-term results of this enhanced microfracture technique for the treatment of chondral lesions of the knee.Methods and materialsPatients treated with AMIC (Chondro-Gide®, Geistlich Pharma, Switzerland) were followed using the AMIC Registry, an internet-based tool to longitudinally track changes in function and symptoms by the Lysholm score and VAS.ResultsA series of 57 patients was enrolled. The average age of patients (19 females, 38 males) was 37.3 years (range 17–61 years). The mean defect size of the chondral lesions was 3.4 cm2 (range 1.0–12.0 cm2). All defects were classified as grade III (n = 20) or IV (n = 37) according to the Outerbridge classification. Defects were localized at the medial (n = 32) or lateral (n = 6) condyle, at the trochlea (n = 4) and at the patella (n = 15). The follow-up period was 2 years. The majority of patients were satisfied with the postoperative outcome, reporting a significant decrease of pain (mean VAS preop = 7.0; 1 year postop = 2.7; 2 years postop = 2.0). Significant improvement of the mean Lysholm score was observed as early as 1 year after AMIC and further increased values were noted up to 2 years postoperatively (preop. 50.1, 1 year postop. 79.9, 2 year postop. 85.2).ConclusionsAMIC is an effective and safe method of treating symptomatic chondral defects of the knee. However, further studies with long-term follow-up are needed to determine if the grafted area will maintain structural and functional integrity over time.Level of evidencePrognostic study, Level IV.

A B S T R A C T Circulating levels of immunoreactive

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