ABSTRACT
A cross section of the vagrant soil lichen Xanthoparmelia chlorochroa was analyzed using proton microprobe PIXE. Data were used to generate quantitative, two-dimensional element distribution maps for Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, and Sr. Element maps show differential element partitioning between the stratified layers of the thallus. These data document transfer of inorganic nutrients across the thallus to the algal layer. Inorganic particle entrapment was also evident in the element maps. Dense accumulations of calcium oxalate at the junction of the medulla and the algal layer on the order of 10% by dry mass were discovered. Scanning electron microscopy and thermogravimetric analyses were used to characterize the calcium oxalate region. These data provide evidence for possible functional roles of the calcium oxalate layer, including regulation of water and light. Data also provide support for a mutualistic interpretation of the lichen association.
ABSTRACT
The total amount of phosphorus and sulfur inside the nuclei of individual bull, stallion, hamster, human, and mouse sperm from fertile subjects has been measured using Particle Induced X-ray Emission (PIXE). Using the sulfur masses, we determined the total protamine (protamine 1 plus protamine 2) mass within the sperm nuclei of each species. Using the phosphorus masses, we determined the DNA mass present within the sperm nuclei of each species. The results reveal that although the relative proportion of protamine 1 to protamine 2 varies among the species examined, the total protamine mass to DNA mass ratio is similar in bull, stallion, hamster, and mouse sperm nuclei. In contrast, mature human sperm nuclei were found to contain significantly less protamine. This observation is consistent with other studies, which suggest that as much as 15% of the DNA in human sperm remain packaged by histones. Using the data obtained for bull sperm, the length of DNA that could be covered by each protamine 1 molecule in bull sperm has been estimated. Making the assumption that the size of the protamine 1 binding site on DNA is similar in the sperm of these species, the length of DNA covered by a single protamine 2 molecule also has been estimated.
