Calcification-driven CO2emissions exceed blue Carbon sequestration in a carbonate seagrass meadow

Long-term Blue Carbon burial in seagrass meadows is complicated by other carbon and alkalinity exchanges that shape net carbon sequestration. We measured a suite of such processes, including denitrification, sulfur, and inorganic carbon cycling, and assessed their impact on air-water CO2 exchange in a typical seagrass meadow underlain by carbonate sediments. Eddy covariance measurements reveal a consistent source of CO2 to the atmosphere at an average rate of 610 ± 990 μmol m-2 hour-1 during our study and 700 ± 660 μmol m-2 hour-1 (6.1 mol m-2 year-1) over an annual cycle. Net alkalinity consumption by ecosystem calcification explains \u3e95% of the observed CO2 emissions, far exceeding organic carbon burial and anaerobic alkalinity generation. We argue that the net carbon sequestration potential of seagrass meadows may be overestimated if calcification-induced CO2 emissions are not accounted for, especially in regions where calcification rates exceed net primary production and burial

Qualitative and Quantitative Evaluation of Sulfur-Containing Compound Types in Heavy Crude Oil and Its Fractions

Detailed molecular analysis of complex mixtures such as crude oil and its fractions has been successfully covered by a number of groups during the past two decades. On the other side, the most glaring need is some type of method that allows quantitative analysis of a single class, compound species, or even individual compounds. Here, the problem is being complicated by the complexity of the sample and the need for individual response factors necessary for the analysis of single compounds in almost all analytical methods. This can be circumvented by using a method with uniform response like inductively coupled plasma-mass spectrometry. Sulfur is one of the most important heteroelements present in crude oil and its products due to stringent regulations. Quantification of sulfur by means of mass spectrometry has always been a challenging task. Here, we present the combination of a sulfur-selective chromatographic separation of crude oil and its fractions on a Pd-coated stationary phase with two-dimensional detection. Qualitative analysis by ultrahigh-resolution Orbitrap mass spectrometry allows a detailed understanding of individual compositions after chromatographic separation, while the quantitative data from inductively coupled plasma tandem mass spectrometry details the quantities of each part of the chromatogram. The combination of the results from both methods allows assigning three different types of sulfur species and their quantitative determination in extremely complex heavy crude oil fractions

Effects of epidermal growth factor and calcium omission on cholecystokinin-stimulated Cl⁻ conductance in rat pancreatic zymogen granules

Evidence suggests that cholecystokinin-octapeptide (CCK-8)-induced activation of a Cl− conductance in the membrane of zymogen granules (ZG) is closely related to pancreatic enzyme secretion [1,2,3]. Following stimulation of isolated pancreatic acinar cells with increasing concentrations of CCK-8, the Cl− conductance in the ZG from these acini increased, reached a maximum of 40±7 % above basal Cl− conductance at 10−12 M CCK-8, and then decreased at CCK-8 concentrations higher than 10−9 M to a level comparable to the basal Cl− conductance. We had interpreted the inhibitory action of high CCK-8 concentrations to be due to the generation of high concentrations of diacylglycerol and/or its metabolites by an “overstimulation” of phospholipase C at supramaximal CCK-8 concentrations [1]. We now show that EGF abolishes the downstroke of the dose response curve for CCK-8-induced ZG Cl− conductance and shifts the stimulatory response to higher CCK-8 concentrations. Similarly in a nominally “Ca2+-free buffer” (free [Ca2+] ∼0.2 nM), stimulated Cl− conductance at 10−12 M CCK-8 is nearly abolished and the decreased Cl− conductance at 10−8 M CCK-8 is increased to the level of maximal stimulation at 10−12 M CCK-8. We conclude that both EGF and low [Ca2+] affect CCK-8-induced ZG Cl− conductance by decreasing phospholipase C activity

Quantitative and Qualitative Analysis of Three Classes of Sulfur Compounds in Crude Oil

Owing to the environmental hazards arising from sulfur‐containing combustion products, strong legal regulations exist to reduce the sulfur content of transportation fuels down to a few ppm. With the ongoing depletion of low‐sulfur crude oil reservoirs, increased technological efforts are needed for crude oil refining to meet these requirements. The desulfurization step is a critical part of the refining process but partly suffers from the recalcitrance of certain species to sulfur removal and the inability to quantitatively understand the behavior of individual compound classes during the process. We herein present a new and simple approach for the parallel quantification of three different classes of sulfur species present in crude oils by LC separation and on‐line detection and quantification by ICP‐MS/MS. This approach will help to estimate the amount of recalcitrant species and thus facilitate the optimization of desulfurization conditions during fuel production

Bombesin receptors interact with G_i and p21^ras proteins in plasma membranes from rat pancreatic acinar cells

This study investigates interaction of bombesin receptors with heterotrimeric guanosine triphosphate (GTP)-binding proteins (G proteins) and monomeric small molecular weight GTP-binding proteins (smg proteins), respectively, in plasma membranes (PM) of rat pancreatic acinar cells. Addition of bombesin to isolated PM stimulated the incorporation of the photoaffinity analogue [alpha-rasP]GTP-gamma-azidoanilide into Gi proteins of 40-41 kDa and reduced the pertussis toxin-induced ADP ribosylation of three 40-41 kDa proteins, which had been previously identified as Gi1, Gi2, and Gi3 (30). In PM isolated from bombesin-prestimulated acinar cells, binding of [alpha-rasP]-GTP to PM proteins of 21-22 kDa and of a monoclonal antibody against p21ras proteins was increased. Two-dimensional separation of PM proteins revealed the presence of 18 or 19 differently charged smg proteins. The p21ras proteins could be separated into two differently charged proteins with isoelectric points of 5.58 and 5.79. In microsomal membranes (MM), [alpha-32P]GTP binding to yet unidentified 21-22 kDa smg proteins was decreased compared with membranes from unstimulated acinar cells. The data suggest that Gi proteins as well as p21ras proteins are involved in bombesin receptor-mediated signal transduction in the PM. Furthermore, 21-22 kDa smg proteins in MM might play a role in bombesin-induced stimulation of intracellular pathways that lead to enzyme secretion from pancreatic acinar cells

Receptors for insulin interact with G_i-proteins and for epidermal growth factor with G_i- and G_s-proteins in rat pancreatic acinar cells

In rat pancreatic acinar cells epidermal growth factor (EGF) and insulin increase both basal and cholecystokinin (CCK-OP) stimulated amylase release in vitro (1) as a long term function of this tissue. Here we show that preincubation of isolated plasma membranes with EGF or with insulin leads to increased incorporation of the GTP-photoaffinity analogue [alpha-32P]GTP-gamma-azidoanilide into 40/41 kDa proteins and to reduction of pertussis toxin- (PT) catalyzed [alpha-32P]ADP-ribosylation of three 40/41 kDa proteins which had been previously identified as Gi1, Gi2 and Gi3 (2). In the presence of GTP gamma S, EGF- and insulin-induced inhibition of PT-mediated [alpha-32P]ADP-ribosylation of 40/41 kDa proteins is eliminated. EGF enhances cholera toxin- (CT) mediated ADP-ribosylation of all three 40/41 kDa Gi-proteins as well as of five 45 and four 48/50 kDa proteins, which had been previously identified as Gs-proteins (2), whereas insulin has no effect. We conclude from our data that both EGF and insulin interact with the same Gi-proteins as CCK-OP does, whereas EGF additionally interacts with nine Gs-proteins. It is likely that one, two or all three 40/41 kDa Gi-proteins are involved in insulin- and EGF-induced potentiation of CCK-OP-stimulated enzyme secretion. In addition interaction of EGF with Gs-protein could play a role in the potentiation of CCK-OP-induced enzyme secretion from pancreatic acinar cells

Epidermal growth factor inhibits both cholecystokinin octapeptide-induced inositol 1,4,5-trisphosphate production and [Ca²⁺]_i increase in rat pancreatic acinar cells

We have studied the effects of epidermal growth factor (EGF) on both cholecystokinin octapeptide (CCK-OP)-induced inositol-1,4,5 trisphosphate (IP) production and on cytosolic free calcium concentrations [Ca2+]i by fluorescence measurements in fura-2-loaded pancreatic acini. Our data show that EGF inhibits CCK-OP induced IP3 production by 40 ± 9 % and decreases CCK-OP induced rise in cytosolic Ca2+ by 41 ± 9 %. These data indicate that activation of EGF receptors leads to inhibition of CCK-OP induced stimulation of phospholipase C (PLC)