The Relationship Between Arachidonic Acid Release and Catecholamine Secretion from Cultured Bovine Adrenal Chromaffin Cells

Increased arachidonic acid release occurred during activation of catecholamine secretion from cul- tured bovine adrenal medullary chromaffin cells. The nicotinic agonist l,l-dimethyl-4-phenylpiperazinium (DMPP) caused an increased release of prcincubated [ 3 H]arachidonic acid over a time course which corre- sponded to the stimulation of catecholamine secretion. Like catecholamine secretion, the DMPP-induced [ 3 H]arachidonic acid release was calcium-dependent and was blocked by the nicotinic antagonist mecamylamine. Depolarization by elevated K + , which induced catechol amine secretion, also stimulated arachidonic acid release. Because arachidonic acid release from cells probably re- sults from phospholipase A 2 activity, our findings indicate that phospholipase A 2 may be activated in chromaffin cells during secretion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66068/1/j.1471-4159.1984.tb06690.x.pd

Arachidonic Acid Release and Catecholamine Secretion from Digitonin-Treated Chromaffin Cells: Effects of Micromolar Calcium, Phorbol Ester, and Protein Alkylating Agents

The relationship between catecholamine secretion and arachidonic acid release from digitonin-treated chromaffin cells was investigated. Digitonin renders permeable the plasma membranes of bovine adrenal chromaffin cells to Ca 2+ , ATP, and proteins. Digitonin-treated cells undergo exocytosis of catecholamine in response to micromolar Ca 2+ in the medium. The addition of micromolar Ca 2+ to digitonin-treated chromaffin cells that had been prelabeled with [ 3 H]arachidonic acid caused a marked increase in the release of [ 3 H]arachidonic acid. The time course of [ 3 H]arachidonic acid release paralleled catecholamine secretion. Although [ 3 H]arachidonic acid release and exocytosis were both activated by free Ca 2+ in the micromolar range, the activation of [ 3 H]arachidonic acid release occurred at Ca 2+ concentrations slightly lower than those required to activate exocytosis. Pretreatment of the chromaffin cells with N -ethylmaleimide (NEM) or p -bromophenacyl bromide (BPB) resulted in dose-dependent inhibition of 10 Μ M Ca 2+ -stimulated [ 3 H]arachidonic acid release and exocytosis. The IC 50 of NEM for both [ 3 H]arachidonic acid release and exocytosis was 40 Μ M. The IC 50 of BPB for both events was 25 Μ M. High concentrations (5–20 m M ) of Mg 2+ caused inhibition of catecholamine secretion without altering [ 3 H]arachidonic acid release. A phorbol ester that activates protein kinase C, 12- O -tetradecanoylphorbol-13-acetate (TPA), caused enhancement of both [ 3 H]arachidonic acid release and exocytosis. The findings demonstrate that [ 3 H]arachidonic acid release is stimulated during catecholamine secretion from digitonin-treated chromaffin cells and they are consistent with a role for phospholipase A 2 in exocytosis from chromaffin cells. Furthermore the data suggest that protein kinase C can modulate both arachidonic acid release and exocytosis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65534/1/j.1471-4159.1985.tb07140.x.pd

An Audible Demonstration Of The Speed Of Sound In Bubbly Liquids

The speed of sound in a bubbly liquid is strongly dependent upon the volume fraction of the gas phase, the bubble size distribution, and the frequency of the acoustic excitation. At sufficiently low frequencies, the speed of sound depends primarily on the gas volume fraction. This effect can be audibly demonstrated using a one-dimensional acoustic waveguide, in which the flow rate of air bubbles injected into a water-filled tube is varied by the user. The normal modes of the waveguide are excited by the sound of the bubbles being injected into the tube. As the flow rate is varied, the speed of sound varies as well, and hence, the resonance frequencies shift. This can be clearly heard through the use of an amplified hydrophone and the user can create aesthetically pleasing and even musical sounds. In addition, the apparatus can be used to verify a simple mathematical model known as Wood's equation that relates the speed of sound of a bubbly liquid to its void fraction. (c) 2008 American Association of Physics Teachers.Mechanical Engineerin

Predicting the Focus of Cryogenicaly-Cooled Optical Systems

Results of an experimental study to ascertain how well the focal -plane location of cryogenically -cooled optical systems can be predicted are reported. These results indicate that if the required low- temperature thermal expansion and index -of- refraction data are available, the focal shift caused by cooling to cryogenic temperatures can be accurately predicted by simply computing the shift in the paraxial focus. In this study, the differences between the measured focal shifts and the computed shift in the paraxial focus were less than the diffraction -limited depth -of -focus tolerance. The results of this study also indicate that for off - the -shelf optical systems ray- tracing analysis may not adequately predict the absolute location of the focal plane. Thus, the following method of predicting the focal -plane location of a cryogenically- cooled optical system is suggested: first measure the focal -plane location with the optics at room temperature, and then add the computed paraxial focal shift to the measured location

Relationship Between Ca 2+ Uptake and Catecholamine Secretion in Primary Dissociated Cultures of Adrenal Medulla

Carbachol or elevated K + stimulated 45 Ca 2+ uptake into chromaffin cells two- to fourfold. The uptake was stimulated by cholinergic drugs with nicotinic activity, but not by those with only muscarinic activity. Ca 2+ uptake and catecholamine secretion induced by the mixed nicotinic-muscarinic agonist carbachol were inhibited by the nicotinic antagonist mecamylamine, but not by the muscarinic antagonist atropine. Significant Ca 2+ uptake occurred within 15 s of stimulation by carbachol or elevated K + at a time before catecholamine secretion was readily detected. At later times the time course of secretion induced by carbachol or elevated K + was similar to that of Ca 2+ uptake. There was a close correlation between Ca 2+ uptake and catecholamine secretion at various concentrations of Ca 2+ . The concentration dependencies for inhibition of both processes by Mg 2+ or Cd 2+ were similar. Ca 2+ uptake saturated with increasing Ca 2+ concentrations, with an apparent K m for both carbachol-induced and elevated K + -induced Ca 2+ uptake of approximately 2 m M . The Ca 2+ dependency, however, was different for the two stimuli. The studies provide strong support for the notion that Ca 2+ entry and a presumed increase in cytosolic Ca 2+ concentration respectively initiates and maintains secretion. They also provide evidence for the existence of saturable, intracellular, Ca 2+ - dependent processes associated with catecholamine secretion. Ca 2+ entry may, in addition, enhance nicotinic receptor desensitization and may cause inactivation of voltage-sensitive Ca 2+ channels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66166/1/j.1471-4159.1982.tb07940.x.pd

Selective Modulation Interferometric Spectrometer (SIMS) Technique Applied to Background Suppression

A method of using the SIMS (the Selective Modulation Interferometric Spectrometer) to measure the difference between the spectral content of two optical beams is given. The differ - encing is done optically; that is, the modulated detector signal is directly proportional to the difference between the two spectra being compared. This optical differencing minimizes the dynamic -range requirements of the electronics and requires only a simple modification of the basic cyclic SIMS spectrometer. This technique can be used to suppress background radiation for the enhancement of target detection and tracking. Laboratory measurements demonstrating the application of this technique are reported

Estimating The Economic Impact Of Local Cultural Organizations: The Charlotte Arts & Science Council Example

This paper details the impact of the 58 affiliated members of the Charlotte Arts & Science Council on the economy of Mecklenburg County, North Carolina. We find that the affiliated members of the Arts & Science Council had a sizable impact on the Mecklenburg economy.  Output was expanded by $129,171,622; earnings were increased by$50,589,999; and employment was increased by 2,132 full-time equivalent jobs.  These economic impacts were an important addition to the rich and varied cultural offerings provided by the Arts & Science Council affiliates

Soft Tissue Changes of the Lower Lip Following Isolated Mandibular Advancement Osteotomies

The purpose of this study was to evaluate the soft tissue changes that occur following isolated mandibular advancement surgery. A sample of 70 non-growing patients were examined by tracing pre and post-operative radiographs. Then various landmarks were chosen and hand measured to determine hard and soft tissue changes. Significant correlations were found for many of the horizontal and vertical tissue landmarks and weaker correlations for all other landmarks. The decrease in the interlabial gap and the angular changes in the lower lip reflect the direction of surgical movement. The data from this study supports previous studies of smaller sample sizes and suggests a 1:1 soft to hard tissue ratio for rough clinical prediction in the chin and sublabial area. Reliability tests demonstrate the measurement technique to be accurate

Bubble dynamics and size distributions during focused ultrasound insonation

This is the published version. Copyright © 2004 Acoustical Society of AmericaThe deposition of ultrasonic energy in tissue can cause tissue damage due to local heating. For pressures above a critical threshold, cavitation will occur, inducing a much larger thermal energy deposition in a local region. The present work develops a nonlinear bubble dynamicsmodel to numerically investigate bubble oscillations and bubble-enhanced heating during focused ultrasound (HIFU) insonation. The model is applied to calculate two threshold-dependent phenomena occurring for nonlinearly oscillating bubbles: Shape instability and growth by rectified diffusion. These instabilities in turn are shown to place physical boundaries on the time-dependent bubble size distribution, and thus the thermal energy deposition