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Even though platelets are known to play a critical role in hemostasis, mediated in part by their uptake, storage, and release of serotonin, there are many unexplored aspects of this process. Herein, single-cell amperometry is employed to characterize the dynamic secretion of serotonin from platelet dense-body granules. On the basis of a three-dimensional random walk simulation that estimates detection efficiency with varied spacing between the carbon-fiber microelectrode and the platelet, it is clear that the detected charge likely represents complete oxidation of the released granule contents and, thus, is a good method to calculate the serotonin concentration in each granule. Using the measured charge and volume estimates based on transmission electron microscopy (TEM) data, the granular concentration of serotonin is approximately 0.5 M. The simulated spike widths are significantly narrower than most of the measured amperometric spikes, clearly indicating that the stored serotonin is highly associated with an aggregate rather than freely diffusible within the dense-body granule. Additionally, by varying extracellular buffer temperature and pH to adjust the driving forces for serotonin delivery from the dense-body granules to the extracellular space, it is clear that, although platelet chemical messenger storage and secretion is similar to that of other secretory cells, there are some important distinctions.

The deconvolution method and the combined model were used to estimate the kinetic parameters of the C-peptide and the insulin secretion rate in pancreas-kidney transplant patients during periods of slow and fast changes in insulin secretion. The estimation of individual kinetic parameters is a useful method of evaluating the insulin secretion in transplant patients. Further, insulin secretion in the test subjects were still defective even after transplantation.

In this paper, the deconvolution of infrequently and nonuniformly sampled data is addressed. A nonparametric technique is worked out that provides a smooth estimate of the unknown input signal and takes into account nonnegativity constraints. In spite of the size of the problem, efficient algorithms for solving the constrained optimization problem and computing confidence intervals are proposed. The new technique is used to estimate growth hormone (GH) secretion after repeated GH-releasing hormone (GHRH) administration from samples of blood concentration.

The cysts present in autosomal dominant polycystic kidney disease seem capable of secreting fluid. This secretion can be increased by as yet unidentified substances in the cyst fluid. Polycystic kidney disease is characterized by enlarged kidneys and the presence of cysts. The term autosomal dominant refers to the genetic mode of disease transmission. Eighteen cysts were removed from three kidneys taken from women with polycystic kidney disease. Tests were performed to determine secretion rates of both natural cyst fluid and a laboratory-made fluid inserted into the cysts. Cysts containing cyst fluid secreted more fluid than cysts containing artificial fluid. Cyst fluid also stimulated fluid secretion in canine and human kidney cells. Drug therapy may eventually provide a means of controlling the size of cysts.

We describe an optical method to quantify single-gland secretion. Isolated tracheal mucosa were mounted at the air-Krebs interface and coated with oil. Gland secretions formed spherical bubbles that were digitally imaged at intervals, allowing rates of secretion to be calculated. We monitored 340 glands in 54 experiments with 12 sheep. Glands secreted basally at low rates (0.57 [+ or -] 0.04 nl [multiplied by] [min.sup.-1] [multiplied by] [gland.sup.-1], 123 glands) in tissues up to 9 h postharvest and at lower rates for up to 3 days. Carbachol (10 [micro]M) stimulated secretion with an early transient and a sustained or oscillating phase. Peak secretion was 15.7 [+ or -] 1.2 nl [multiplied by] [min.sup.-1] [multiplied by] [gland.sup.-1](60 glands); sustained secretion was 4.5 [+ or -] 0.5 nl [multiplied by] [min.sup.-1] [multiplied by] [gland.sup.-1] (10 glands). Isoproterenol and phenylephrine (10 [micro]M each) stimulated only small, transient responses. We confirmed that cats have a large secretory response to phenylephrine (11.6 [+ or -] 3.7 nl [multiplied by] [min.sup.-1] [multiplied by] [gland.sup.-1], 12 glands), but pigs, sheep, and humans all have small responses ([is less than] 2 nl [multiplied by] [min.sup.-1] [multiplied by] [gland.sup.1]). Carbachol-stimulated peak secretion was inhibited 56% by bumetanide, 67% by [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] replacement with HEPES, and 92% by both. The distribution of secretion rates was nonnormal, suggesting the existence of subpopulations of glands. carbachol; phenylephrine; cystic fibrosis transmembrane conductance regulator; lung disease; mucociliary clearance