The number of alleles in electrophoretic experiments

We examine the rate of divergence of the number of distinguishable alleles in a large sample. Our calculations are based on the Ohta-Kimura model for electrophoretic experiments, in which types can only take discrete values, and mutations are selectively neutral.     

Comparison of human lung tissue mass measurements from Ex Vivo lungs and high resolution CT software analysis

ABSTRACT: BACKGROUND: Quantification of lung tissue via analysis of computed tomography (CT) scans is increasingly common for monitoring disease progression and for planning of therapeutic interventions. The current study evaluates the quantification of human lung tissue mass by software analysis of a CT to physical tissue mass measurements. METHODS: Twenty-two ex vivo lungs were scanned by CT and analyzed by commercially available software. The lungs were then dissected into lobes and sublobar segments and weighed. Because sublobar boundaries are not visually apparent, a novel technique of defining sublobar segments in ex vivo tissue was developed. The tissue masses were then compared to measurements by the software analysis. RESULTS: Both emphysematous (n = 14) and non-emphysematous (n = 8) bilateral lungs were evaluated. Masses (Mean +/- SD) as measured by dissection were 651 +/- 171 g for en bloc lungs, 126 +/- 60 g for lobar segments, and 46 +/- 23 g for sublobar segments. Masses as measured by software analysis were 598 +/- 159 g for en bloc lungs, 120 +/- 58 g for lobar segments, and 45 +/- 23 g for sublobar segments. Correlations between measurement methods was above 0.9 for each segmentation level. The Bland-Altman analysis found limits of agreement at the lung, lobe and sublobar levels to be 13.11% to 4.22%, -13.59% to 4.24%, and -45.85% to 44.56%. CONCLUSION: The degree of concordance between the software mass quantification to physical mass measurements provides substantial evidence that the software method represents an appropriate non-invasive means to determine lung tissue mass.     

An investigation of the reaction kinetics of luciferase and the effect of ionizing radiation on the reaction rate

The bioluminescence produced by luciferase, a firefly enzyme, requires three substrates: luciferin, ATP and oxygen. We find that ionizing radiation, in the form of a proton beam from a cyclotron, will eliminate dissolved oxygen prior to any damage to other substrates or to the protein. The dose constant for removal of oxygen is 70 ± 20 Gy, a much smaller dose than required to cause damage to protein. Removal of oxygen, which is initially in excess, leads to a sigmoidal response of bioluminescence to radiation dose, consistent with a Michaelis–Menten relationship to substrate concentration. When excess oxygen is exhausted, the response becomes exponential. Following the irradiation, bioluminescence recovers due to a slow leak of oxygen into the solution. This may also explain previous observations on the response of bioluminescent bacteria to radiation. We have studied the dependence of the reaction rate on enzyme and substrate concentration and propose a model for the reaction pathway consistent with this data. The light output from unirradiated samples decreases significantly with time due to product inhibition. We observe that this inhibition rate changes dramatically immediately after a sample is exposed to the beam. This sudden change of the inhibition rate is unexplained but shows that enzyme regulatory function responds to ionizing radiation at a dose level less than 0.6 Gy.     

Tissue expression of the vesicle protein pantophysin

The cell-type restricted expression of cytoplasmic microvesicle membrane protein isoforms may be a consequence of the functional adaptation of these vesicles to the execution of specialized processes in cells of different specialization. To characterize the expression of the vesicle protein pantophysin, an isoform of the synaptic vesicle proteins synaptophysin and synaptoporin, we have prepared and characterized antibodies useful for the immunological detection of pantophysin in vitro and in situ. Using these reagents, we show by immunoblot analyses that pantophysin expression is not homogeneous but differs significantly between various bovine tissues. Furthermore, these differences are not exactly paralleled by the expression of other vesicle proteins of the SCAMP (secretory carrier-associated membrane protein) and VAMP (vesicle-associated membrane protein) types that have previously been localized to pantophysin vesicles in cultured cells. By immunofluorescence microscopy, pantophysin expression is seen predominantly in non-neuroendocrine cells with pronounced membrane traffic. Pantophysin staining codistributes with SCAMP and VAMP immunoreactivities in most instances but differs in some. Remarkably, pantophysin staining in liver is restricted to cells surrounding sinusoids and is not detectable in hepatocytes, similar to that of the SCAMP and VAMP isoforms as detected by our reagents in tissue sections.