PubMed · 13461033
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J MATES. 1957-07-12. [Kidney function in nephrolithiasis].. https://pubmed.ncbi.nlm.nih.gov/13461033/
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The pancreatic stones (Pancreatic calculi) collected from patients suffering from chronic calcific pancreatitis were studied in a view to explore the constituents involved in the calcification. The calcified stones were characterized by XRD, EPR and IR spectroscopic techniques. The detailed studies indicate that these stones consist of calcium carbonate as a major component, besides phosphates and other protein content. The presence of aragonite phases in the biomineralized stones is also discussed. The EPR spectra gave an evidence of the presence of traces of manganese in different oxidation states, which is used as one of the EPR probes in the present work. The samples were sintered at different temperatures to remove all the organic matter, and their EPR spectra have been studied to obtain detailed information regarding the changes in the symmetry of these stone samples. The X-irradiated sample was also characterized by EPR and the resonance signals are attributed to freely rotating CO(2)(-) radicals. The infrared spectrum reveals the presence of many organic bands corresponding to the protein amides.
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Benign paroxysmal positional vertigo (BPPV) is a mechanical disorder of the vestibular system in which calcite particles called otoconia interfere with the mechanical functioning of the fluid-filled semicircular canals normally used to sense rotation. Using hydrodynamic models, we examine the two mechanisms proposed by the medical community for BPPV: cupulolithiasis, in which otoconia attach directly to the cupula (a sensory membrane), and canalithiasis, in which otoconia settle through the canals and exert a fluid pressure across the cupula. We utilize known hydrodynamic calculations and make reasonable geometric and physical approximations to derive an expression for the transcupular pressure DeltaPc exerted by a settling solid particle in canalithiasis. By tracking settling otoconia in a two-dimensional model geometry, the cupular volume displacement and associated eye response (nystagmus) can be calculated quantitatively. Several important features emerge: (1) a pressure amplification occurs as otoconia enter a narrowing duct; (2) an average-sized otoconium requires approximately 5 s to settle through the wide ampulla, where DeltaPc is not amplified, which suggests a mechanism for the observed latency of BPPV; and (3) an average-sized otoconium beginning below the center of the cupula can cause a volumetric cupular displacement on the order of 30 pL, with nystagmus of order 2 degrees/s, which is approximately the threshold for sensation. Larger cupular volume displacement and nystagmus could result from larger and/or multiple otoconia.