title: The corneal stroma: an inhomogeneous structure.
abstract: OBJECTIVE
  This study was conducted to determine the elemental composition of the human cornea. Special attention was paid to corneal stroma inhomogeneity.
  
  
  METHODS
  Seventy human corneas were examined by means of energy-dispersive X-ray analysis. Epithelium, subepithelium, middle stroma, sub-Descemet layer, Descemet's membrane and endothelium were subjected to repeated measurements.
  
  
  RESULTS
  In the cellular layers the phosphorus concentrations were high [0.35 mol/kg dry weight (dw) in the epithelium and 0.403 mol/kg dw in the endothelium]. Similar concentrations were found for sulphur (0.38 mol/kg dw in the epithelium). Stromal layers showed high contents of sulphur: 0.26 mol/kg dw. The phosphorus concentration was found to be higher in the subepithelium than in the middle stroma. Sulphur concentrations were highest in Descemet's membrane, followed by the subepithelium and the middle stroma.
  
  
  CONCLUSIONS
  Nucleic acids and energy-containing phosphates explain the high levels of phosphorus in the cellular layers. The high sulphur concentrations may be related to the phosphoadenosinphosphosulfate and protein turnover in the epithelium. We interpret the inhomogeneous distribution of phosphorus in the stroma as a function of the density of keratocytes. An evaluation of all known sulphur-containing biochemical components of the stroma (0.217 mol sulphur/kg dw) corresponds to our measurements. In contrast to former results we find the corneal stroma to be an inhomogeneous structure.
authors.affiliation: Universitätsaugenklinik der RWTH Aachen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Langefeld
authors.forename: M
authors.initials: M
authors.lastname: Reim
authors.forename: C
authors.initials: C
authors.lastname: Redbrake
authors.forename: N F
authors.initials: NF
authors.lastname: Schrage
mesh_terms: D000368:Aged; D003319:Corneal Stroma / Q000737:chemistry* / Q000166:cytology; D003886:Descemet Membrane / Q000737:chemistry; D004577:Electron Probe Microanalysis; D004728:Endothelium, Corneal / Q000737:chemistry; D006801:Humans; D010758:Phosphorus / Q000032:analysis*; D012016:Reference Values; D013455:Sulfur / Q000032:analysis*
chemical_list: D010758:Phosphorus; D013455:Sulfur