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Geophysical and air photo studies at the Twin Cities Army Ammunition Plant (TCAAP), Minnesota, were conducted to establish a chronology of dumping and waste disposal. This study was undertaken to aid in the assessment of the amount of remediation needed to reclaim a wetland area. An integrated analysis of electromagnetic, magnetic and ground-penetrating RADAR (GPR) measurements over a 25-acre site, provided the information necessary to define waste disposal events. These events are observed on a sequence of aerial photos taken between 1940 and 1993. The former southwestern embayment of the lake, filled in during the original construction of the base, has been clearly defined. Two burn cages and their surrounding debris have been delineated. The areal extent of another waste site has been defined along the northern shoreline. Depth estimates determined from EM-61 analysis, and depths to original lake bottom, derived from GPR, have yielded volumetric estimates of the amount of material that would need removal if excavation is required. Magnetic and electromagnetic data have pinpointed the locations of mounds, observed from historical air photos. Except for these areas along the Northwestern shore, there is no evidence of waste disposal along the shoreline or within the present-day lake margins. Themore » ability to date the anomalous regions is significant, in that different production demands upon TCAAP, during the time periods of WWII, The Korean War, and The Vietnam Conflict, have resulted in different types of waste. The ability to categorize areas with distinct time periods of operation and waste disposal can greatly aid the environmental cleanup effort with regard to the type of contaminants that might be expected at these poorly documented disposal sites.« less

Geophysical studies at Site H of Twin Cities Army Ammunition Plant have delineated specific areas of dumping and waste disposal. Anomalous areas noted in the geophysical data sets have been correlated with features visible in a chronological sequence of aerial photos. The photos aid in dating the anthropogenic changes and in interpreting the geophysical anomalies observed at Site H and across Sunfish Lake. Specifically, two burn cages and what has been interpreted as their surrounding debris have been delineated. The areal extent of another waste site has been defined in the southwest corner of Area H-1. Depth estimates to the top of the Area H-1 anomalies show that the anomalies lie below lake level, indicative of dumping directly into Sunfish Lake. Except for these areas along the northwestern shore, there is no evidence of waste disposal along the shoreline or within the present-day lake margins. Magnetic, electromagnetic, and ground-penetrating-radar data have pinpointed the locations of mounds, observable in aerial photos, around the first burn cage. The second burn cage and its surrounding area have also been clearly defined from aerial photos, with support from further geophysical data. Additional analysis of the data has yielded volumetric estimates of the amount of material that would need removal in the event of excavation of the anomalous areas. Magnetic and electromagnetic profiles were also run across Marsden Lake. On the basis of these data, it has been concluded that no large-scale dumping has occurred in or around Marsden Lake.

At a time when the columns of Trends in NeuroSciences have been humming with controversy over the question whether or not exocytosis plays any part in the release of acetylcholine —and by inference perhaps other transmitter substances —it may seem surprising to find an article devoted specifically to the mechanism of neurosecretion by exocytosis. Some explanation is obviously required.

Exposure of ‘leaky’ adrenal medullary cells to GTP-γ-S inhibits Ca-dependent exocytosis in bovine cells, but stimulates exocytosis in chicken cells. The inhibitory action on bovine cells persists in the presence of TPA suggesting that in this tissue an inhibitory GTP-binding protein may modulate the action of protein kinase C on exocytosis.

The past few years have witnessed important advances in our understanding. of the mechanism and control of catecholamine release, largely through the application to adrenal medullary cells of a number of powerful new techniques. Fluorescent dyes have revealed that intracellular Ca 2+ rises during secretion, the patch clamp has permitted the ion channels that control these changes in Ca 2+ to be characterized, and high-voltage permeabilization has made possible a direct attack on the problem of how a rise in Ca 2+ initiates the exocytotic event.

Exposure of washed human platelets to a high voltage electric field renders these cells permeable to small molecules such as Ca EGTA. Such accessed platelets secrete 5-hydroxytryptamine (5HT) when challenged with 10- 5 M Ca 2+ but do not release lactate dehydrogenase under these conditions. The secretion of 5HT induced by Ca 2+ requires MgATP but is independent of synthesis of prostaglandin endoperoxides. Half maximal secretion of 5HT is observed in the presence of 1.9μM Ca 2+ . These data suggest a direct involvement of Ca 2+ in platelet amine granule secretion.

The daily averages of the dawn and dusk observed exospheric temperatures (deduced from solar EUV attenuation measurements between 250 and 400 km) are presented for 280 days from day 227, 1969. They are compared with the empirical model of the US Standard Atmosphere Supplements 1966 and the Jacchia 35 H model. Although consistently lower temperatures than either model were found, a better fit to the latter rather than the former was observed. The exospheric response to solar and geomagnetic activity is investigated, and refinements to the models are suggested.

Anextreme ultraviolet spectrometer experiment by University College London for observation of whole-Sun spectrum -line fluxes, and flown on Orbiting Solar Observatory-6, is described. Results for the four lines with absolute calibration, are show n for the first 6 months of flight, from August 1969 to February 1970. The mean fluxes for the 30.4, 53.7, 58.4 and 121.6 nm lines are 8.1 x 10 9 ± 35 % ph cm-2 s-1 , 3.2 x 10 8 + 40% ph cm -2 s-1 , 2 .5 x 10 9 + 40% ph cm -2 s-1 , and 3 x 10 11 ± 50% ph cm -2 s -1 respectively. Relations between these fluxes and the 10.7 cm radio flux and Zurich sunspot number are presented.

Relative absorption cross-sections between 180 A and 304 A, and between 584 A and 304 A are obtained for atomic oxygen in the upper atmosphere, by observing the attentuation of solar radiation using a satellite instrument.

Enhancement by thrombin of Ca2+ -dependent 5HT secretion in the absence of added GTP decreases as the time between electropermeabilisation and addition of thrombin is increased. No decrease occurs if thrombin is added with GTP. Observation of apparent GTP-independent receptor/phospholipase C coupling may result from the presence of bound GTP in the preparation. Enhancement by GTP of Ca2+ -dependent 5HT secretion occurs with a significant lag indicating an agonist-independent effect. Cyclic 3′,5′-AMP inhibits enhancement by GTP of Ca2+ -dependent 5HT secretion while having no effect on enhancement induced by GTPγS. Hence cyclic AMP may impair receptor/phospholipase C coupling by enhancing Np GTPase activity.

Exposure of ‘leaky’ bovine adrenal medullary cells to the phorbol ester TPA causes a shift in the calcium-activation curve to lower calcium concentrations without altering the levels of secretion at the extremes of the activation curve. These results are consistent with a role for protein kinase C in exocytosis.

Cells were isolated by collagenase digestion of chicken adrenal glands. Catecholamine secretion could be stimulated by acetylcholine, carbamylcholine, potassium or veratridine. Methacholine, muscarine and oxotremorine were also effective secretagogues whereas nicotine was not. Secretion evoked by acetylcholine was blocked by low concentrations of atropine but was relatively insensitive to hexamethonium. Atropine-sensitive secretion required both external sodium and calcium, was unaffected by tetrodotoxin, blocked by methoxy verapamil and nifedipine, and potentiated by BAY-K-8644. These data suggest that muscarinic activation of these cells facilitates tetrodotoxin insensitive depolarization, thereby opening conventional voltage-sensitive calcium channels. The mechanism by which calcium activates catecholamine secretion was investigated in cells that had been made permeable by exposure to brief intense electric fields. Catecholamine release required Mg-adenosine 5′ triphosphate, was half-maximally activated by 1 μM Ca 2+ and could be inhibited by high concentrations of Mg 2+ . At low Ca 2+ concentrations, release was potentiated by 12-O-tetradecanoyl-phorbol 13-acetate, dioctanoylglycerol, guanosine 5′-O-(3-thiotriphosphate) and 5′-guanylylimidodi-phosphate, all of which increased the apparent affinity of exocytosis for Ca 2+ .

Publisher Summary This chapter describes the main features of the high-voltage technique and its application in particular to the problem of membrane turnover by exocytosis and endocytosis. Exposure to brief, intense electric fields provides a simple, rapid, and chemically clean method for gaining access to the interior of cells. Under certain conditions high-voltage techniques can be used to render the plasma membrane transiently permeable, whereas under other conditions the plasma membrane remains permeable for prolonged periods. Two methods have been used routinely to subject isolated cells to electric fields: (1) passing cells through a Coulter counter, and (2) discharging a capacitor through a cell suspension. The main disadvantage of using the Coulter-counter method is the length of time taken to harvest a worthwhile number of “leaky” cells. The two main disadvantages of the high-voltage technique are that accessibility is largely restricted to small molecules and that even for these molecules the rate of change in intracellular solute composition is dependent on the diameter of the cell and the number and size of the pores that have been created by exposure to the electric field.

Addition of GTP markedly enhances the ability of thrombin to cause a leftward shift in the Ca 2+ dose/ response curve for 5-hydroxytryptamine secretion from permeabilised human platelets. Little effect is observed on addition of GTP in the absence of thrombin. Neither ADP nor adrenaline, in the presence or absence of GTP, causes such a shift, whereas 5-hydroxytryptamine does so to a small extent but only in the presence of GTP. The leftward shift in the Ca 2+ dose/response curve induced by 12- O -tetradecanoyl-phorbol-13-acetate or 1-oleyl-2-acetylglycerol is not enhanced by addition of GTP. The thrombin concentration required for half-maximal enhancement of the responce to Ca 2+ is markedly reduced by addition of GTP. The results support the postulate that the effects of excitatory agonists in this system correlate with their ability to activate phospholipase C and provide further evidence for a role for GTP in signal transduction between the receptor and phospholipase C.

Enzyme digestion of rat pancreatic tissue yielded a preparation of isolated acinar cells, over 90% of which excluded trypan blue. These isolated cells responded to a variety of secretagogues, the responses being sensitive to the removal of extracellular calcium, increasing extracellular magnesium, and by trifluoperazine, an antagonist of Ca-dependent processes. When exposed to intense electric fields, isolated acinar cells became permeable to CaEGTA and MgATP, these markers gaining access to over 60% of the intracellular mileu within minutes. The accessability to these markers seemed independent of the ionised Ca2+ level. Less than 0.5% of the cellular amylase was released when cells were rendered leaky in a medium containing about 10−9 M Ca2+, but typically 4% was released when the Ca2+ level was subsequently raised to 10−5M levels, the EC50 for Ca2+ being 2 μM. This amount of amylase released was comparable to the amounts secreted from intact cells in response to a variety of agonists. The cytosolic marker lactate dehydrogenase was also released from leaky cells, but the extent was independent of Ca2+ concentration. No amylase was released at 10−7M Ca2+ when permeable cells were exposed to cyclic 3′,5′-AMP or cyclic 3′,5′-GMP. The calcium activation curve for amylase release seemed to be independent of cyclic nucleotides, but was markedly increased in both the extent of release and apparent affinity for Ca2+ in the presence of the phorbol ester 12-O-tetradecanoyl phorbol 13 acetate. These results suggest that when “functionally normal” isolated acinar cells are rendered permeable, Ca2+ — but not cyclic nucleotides — acts as a second messenger for amylase secretion, and furthermore that protein kinase C may be involved in the secretory process.