Long-term trends in alkalinity in large rivers of the conterminous US in relation to acidification, agriculture, and hydrologic modification.

Alkalinity increases in large rivers of the conterminous US are well known, but less is understood about the processes leading to these trends as compared with headwater systems more intensively examined in conjunction with acid deposition studies. Nevertheless, large rivers are important conduits of inorganic carbon and other solutes to coastal areas and may have substantial influence on coastal calcium carbonate saturation dynamics. We examined long-term (mid-20th to early 21st century) trends in alkalinity and other weathering products in 23 rivers of the conterminous US. We used a rigorous flow-weighting technique which allowed greater focus on solute trends occurring independently of changes in flow. Increasing alkalinity concentrations and yield were widespread, occurring at 14 and 13 stations, respectively. Analysis of trends in other weathering products suggested that the causes of alkalinity trends were diverse, but at many stations alkalinity increases coincided with decreasing nitrate+sulfate and decreasing cation:alkalinity ratios, which is consistent with recovery from acidification. A positive correlation between the Sen-Thiel slopes of alkalinity increases and agricultural lime usage indicated that agricultural lime contributed to increasing solute concentration in some areas. However, several stations including the Altamaha, Upper Mississippi, and San Joaquin Rivers exhibited solute trends, such as increasing cation:alkalinity ratios and increasing nitrate+sulfate, more consistent with increasing acidity, emphasizing that multiple processes affect alkalinity trends in large rivers. This study was unique in its examination of alkalinity trends in large rivers covering a wide range of climate and land use types, but more detailed analyses will help to better elucidate temporal changes to river solutes and especially the effects they may have on coastal calcium carbonate saturation state.

A comparison of selected diversity, similarity, and biotic indices for detecting changes in benthic-invertebrate community structure and stream quality.

Implementation of advanced wastewater treatment at the two municipal wastewater-treatment plants for Indianapolis, Indiana, resulted in substantial improvement in the quality of the receiving stream and significant changes in the benthic-invertebrate community. Diversity, similarity, and biotic indices were compared to determine which indices best reflected changes in the composition of the biota in the river. None of the indices perfectly reflected the changes in river quality or community structure. Similarity indices, especially percentage similarity, exhibit the most promise of the three classes of indices. Diversity indices were least useful, wrongly indicating that water quality deteriorated after the upgrade of the wastewater-treatment plants. The most descriptive tool in analyzing the data was the percentage of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa present. Using a mixture of indices and other analytical tools, such as EPT, in the analysis of biological data will ensure the most effective investigations of water quality.

Comparison of gas chromatography/mass spectrometry and immunoassay techniques on concentrations of atrazine in storm runoff.

Gas chromatography/mass spectrometry (GC/MS) and enzyme-linked immunosorbent assay (ELISA) techniques were used to measure concentrations of dissolved atrazine in 149 surface-water samples. Samples were collected during May 1992-September 1993 near the mouth of the White River (Indiana) and in two small tributaries of the river. GC/MS was performed on a Hewlett-Packard 5971A with electron impact ionization and selected ion monitoring of filtered water samples extracted by C-18 solid phase extraction; ELISA was performed with a magnetic-particle-based assay with photometric analysis. ELISA results compared reasonably well to GC/MS measurements at concentrations below the Maximum Contaminant Level for drinking water set by the U.S. Environmental Protection Agency (3.0 microg/L), but a systematic negative bias was observed at higher concentrations. When higher concentration samples were diluted into the linear range of calibration, the relation improved. A slight positive bias was seen in all of the ELISA data compared to the GC/MS results, and the bias could be partially explained by correcting the ELISA data for cross reactivity with other triazine herbicides. The highest concentrations of atrazine were found during the first major runoff event after the atrazine was applied. Concentrations decreased throughout the rest of the sampling period even though large runoff events occurred during this time, indicating that most atrazine loading to surface waters in the study area occurs within a few weeks after application.

Enzyme-linked immunomagnetic electrochemical detection of Salmonella typhimurium.

There is a need for rapid methods to detect pathogenic bacteria in food products as alternatives to the current laborious and time-consuming culture procedures. We report a microbial detection technique that combines the selectivity of antibody-coated superparamagnetic beads with the rapidity and sensitivity of electrochemical detection in a format termed enzyme-linked immunomagnetic electrochemistry. In it, Salmonella typhimurium were sandwiched between antibody-coated magnetic beads and an enzyme-conjugated antibody. With the aid of a magnet, the beads (with or without bound bacteria) were localized onto the surface of disposable graphite ink electrodes in a multi-well plate format. Enzyme substrate was added and conversion of substrate to an electroactive product was measured using electrochemical detection. The electrochemical response was directly proportional to the number of captured bacteria. Using this technique, a minimum detectable level of 8 x 10(3) cells/ml of Salmonella typhimurium in buffer was achieved in ca. 80 min.

Sugar Uptake and Metabolism in the Developing Endosperm of Tassel-seed Tunicate (Ts-5 Tu) Maize.

Factors regulating assimilate transport into developing maize (Zea mays L.) kernels have been difficult to determine because of the structural complexity of basal kernel tissues and the damage that results from tissue dissection. The sensitivity of maize kernels to experimental manipulation is such that substantial maternal tissue is required to support kernel growth in vitro. Consequently, sugar transport experiments with isolated seed tissues or detached kernels have not unequivocally demonstrated how sugar transport occurs. In the present study, Tassel-seed Tunicate (Ts-5 Tu) maize kernels were investigated as a model system for introducing test solutions into the pedicel apoplast with minimal wounding. Transpiration in leafy glumes drew (14)C-sugar solutions up the 8- to 10-millimeter-long pedicel stalks into the basal endosperm transfer cell region. (14)C from fructose was incorporated into starch for 8 days. Sugar uptake into endosperm and embryo tissue showed specificity and inhibitor sensitivity. In particular, p-chloromercuribenzene sulfonate partially inhibited fructose uptake into the endosperm but had no effect on the metabolic conversion of that fructose that entered the endosperm. These results are consistent with active, carrier-mediated sugar transport, but a definitive determination would require more detailed tissue analysis. We propose that further refinement of the incubation solution may allow long-term kernel growth without cob tissue and thus provide a more precise determination of which maternal factors influence seed development.

Purification and characterization of galactinol synthase from mature zucchini squash leaves.

Galactinol synthase catalyzes the first committed step in the biosynthesis of raffinose sugars. Previous attempts to purify the enzyme have proven difficult and have resulted in low quantities of unpurified enzyme. Galactinol synthase was purified 752-fold from mature zucchini (Cucurbita pepo L. cv Burpee Hybrid) leaves using sequential liquid chromatography on DE 52, Octyl-Sepharose CL-4B, and Sephacryl S-200. This isolation scheme resulted in an 18.6% recovery of the initial activity. The purified enzyme had a specific activity of 23.3 micromoles per minute per milligram protein, a pH optimum of 7.5, and the activity was enhanced by dithiothreitol and MnCl(2). The enzyme was only half as active with MgCl(2) as with MnCl(2). Na(+), K(+), and Ca(2+) cations had little effect on the enzyme activity, while Co(2+), Zn(2+), Cu(2+), and Fe(3+) cations were strongly inhibitory at 10 millimolar concentrations. Purified galactinol synthase bound specifically to the substrates myo-inositol and UDP-galactose (K(m) = 6.5 and 1.8 millimolar, respectively), while exhibiting little affinity for an alternative glycosyl donor (UDP-glucose) or inositol epimers (epi- and scyllo-). Ten millimolar concentrations of UMP, UDP, UTP, AMP, ADP, ATP, NAD(+), NADH, NADP(+), UDP-xylose, and UDP-mannose, or 20 millimolar sucrose, talose, galactose, glucose, xylose, and melibiose exhibited various degrees of inhibitory effects. Twenty millimolar stachyose, raffinose, fructose, and mannose, and 10 millimolar UDP-glucuronic acid and UDP-galacturonic acid had little or no effect on the enzyme activity. The purified galactinal synthase is a monomer of M(r) 42,000 with an isoelectric point of 4.1.

Sugar metabolism in germinating soybean seeds: evidence for the sorbitol pathway in soybean axes.

Characterization of sugar content and enzyme activity in germinating soybean (Glycine max L. Merrell) seeds led to the discovery of sorbitol accumulating in the axes during germination. The identity of sorbitol was confirmed by relative retention times on high-performance liquid chromatography and gas liquid chromatography and by mass spectra identical with authentic sorbitol. Accumulation of sorbitol in the axes started on day 1 of germination as sucrose decreased and glucose and fructose increased. Sucrose also decreased in the cotyledons, but there was no accumulation of sorbitol, glucose, or fructose. Accumulation of sorbitol and hexoses was highly correlated with increased invertase activity in the axes, but not with sucrose synthase and sucrose phosphate synthase activities. Sucrose synthase activity was relatively high in the axes, whereas the activity of sucrose phosphate synthase was relatively high in the cotyledons. Ketose reductase and aldose reductase were detected in germinating soybean axes, but not in cotyledons. Fructokinase and glucokinase were present in both axes and cotyledons. The data suggest a sorbitol pathway functioning in germinating soybean axes, which allows for the interconversion of glucose and fructose with sorbitol as an intermediate.

Phospholipid molecular species quantitation from mass spectra of underivatized lipids.

Isobutane chemical ionization of 0.05 to 5 micrograms of phospholipid volatilized from a direct exposure probe provides, in less than a minute, mass spectra from which the component molecular species can be quantitated. Molecular response factors are determined from a stable external standard mixture containing saturated molecular species; a simple series of linear equations is used to correct for isotope effect and hydrogen abstraction. An internal standard allows absolute quantitation of the sample. In cases where different molecular species have the same molecular weight, the species can be quantified by tandem mass spectrometry daughter ion analysis.

Negative Ames tests of epoxide fatty methyl esters derived from hemolysis of linoleic acid hydroperoxides.

Five isomeric epoxyhydroxyene and epoxyoxoene fatty esters derived from hemolytic decomposition of linoleic acid hydroperoxide were tested for mutagenicity by the "Ames' top-agar incorporation method using S-9 mix derived from livers of male rats pretreated with Aroclor 1254. The epoxide fatty esters tested--methyl trans-12,13-epoxy-erythro-11-hydroxy-cis(trans)-9-octadecenoate and methyl trans-12,13-epoxy-threo-11-hydroxy-cis(trans)-9-octadecenoate (each composed of approximately 80% cis-9-ene and 20% trans-9-ene), methyl trans-12,13-epoxy-9-oxo-(trans-10-octadecenoate, methyl trans-12,13-epoxy-9-hydroxy-trans-10-octadecenoate and methyl cis-12,13-epoxy-9-oxo-trans-10-octadecenoate--had structural characteristics similar to certain potent mutagens. However, these esters were not mutagenic in Salmonella typhimurium strains TA100, TA98 or TA1537 at concentrations up to 2000 micrograms/test plate. Under the same test conditions, the methyl ester of hydroperoxy linoleic acid, from which these epoxides were derived, was weakly mutagenic in strain TA100 and possibly also in strain TA98.

Ammonia chemical ionization mass spectrometry of intact diacyl phosphatidylcholine.

Mass spectra have been obtained on molecular species of intact diacyl phosphatidylcholine by means of ammonia gas-induced chemical ionization. MH(+) ions were observed with all species, and other prominent ions in the spectra identified the fatty acid composition. Spectra of phosphatidylcholine containing deuterated methyl groups and spectra obtained using [(15)N]ammonia have allowed identification of fragments containing choline methyl groups and ammonium adducts.-Crawford, C. G., and R. D. Plattner. Ammonia chemical ionization mass spectrometry of intact diacyl phosphatidylcholine.

Rickettsial infection of the pulmonary microcirculation: the basis for interstitial pneumonitis in Rocky Mountain spotted fever.

Pulmonary tissue from 10 patients with fatal Rocky Mountain spotted fever was examined by brightfield microscopy for histopathologic lesions and by immunofluorescence for Rickettsia rickettsii. The distribution of rickettsiae and the vasculitis of the pulmonary microcirculation coincided. The lungs demonstrated the consequent interstitial pneumonia--alveolar septal congestion and interstitial edema; alveolar edema, fibrin, macrophages, and hemorrhage; and interlobular septal edema. The effects of the rickettsial damage to the pulmonary microcirculation are an important component of the pathophysiology of severe Rocky Mountain spotted fever. The distribution of rickettsial organisms within the lung indicates that person to person aerosol transmission is extremely unlikely.

Coronary vasodilator activity of 13,14-dehydroprostacyclin methyl ester: comparison with prostacyclin and other prostanoids.

The effects of a recently synthesized, stable prostacyclin (PGI2) analog, 13,14-dehydro-PGI2 methyl ester, and authentic PGI2 and several other prostanoids on the coronary circulation were investigated in the intact dog by using a new technique to measure coronary sinus blood flow. The PGI2 analog, PGI2, and prostaglandin (PG) E2 and D2 each increased coronary sinus blood flow in a dose-related fashion when injected into the left coronary artery. The analog and PGE2 had similar vasodilator activity while PGI2 was slightly more potent. PGD2 was a moderately active coronary vasodilator whereas PGF2alpha was inactive. The coronary vasodilator effects of PGI2, its analog, PGE2, and PGD2 occurred at doses that had little effect on aortic pressure, left ventricular pressure and its first derivative, or on cardiac output and heart rate. The prostaglandin precursor arachidonic acid and the endoperoxide intermediate PGH2 both increased coronary sinus blood flow in a dose-dependent manner. The effects of arachidonic acid were inhibited by indomethacin. These data show that PGE2, PGI2, and a stable PGI2 analog are potent vasodilators in the canine coronary vascular bed and suggest that the vasodilator effects of arachidonic acid and PGH2 may be due to the formation of PGE2, PGD2, or PGI2 in the dog heart.

Lipoxygenation activity of purified prostaglandin-forming cyclooxygenase.

Purified cyclooxygenase, a single enzyme which catalyzes the formation of endoperoxide from arachidonic acid (20:4) in a bis(dioxygenase) reaction, is capable of oxygenating eicosadienoic acid (20:2) at C-11 in a single dioxygenase reaction. The partial oxygenation of 20:2 resembles the formation of prostaglandin from 20:4, with both oxygenation reactions exhibiting similar pH optima, substrate Km values, and cofactor effects including a need for peroxide and an absolute requirement for heme. In addition, those processes known to destroy 20:4 oxygenase activity, such as heat inactivation, inactivation with anti-inflammatory drugs, and turnover-mediated inactivation, have equally destructive effects on 20:2 oxygenase activity. Thus, both oxygenations are catalyzed by one enzyme. All of the above similarities for 20:2 and 20:4 oxygenation demonstrate that C-11 oxygenation is an integral rate-limiting step of cyclooxygenase action rather than a separate reaction resembling that of plant lipoxygenase.

Unusual pulmonary vasodilator activity of 13,14-dehydroprostacyclin methyl ester: comparison with endoperoxides and other prostanoids.

Microsomes from stomach fundus and blood vessels transform the endoperoxide, PGH2, into a newly discovered unstable substance, PGI2, that relaxes arterial strips and inhibits platelet aggregation. 13,14-Dehydro-PGI2 methyl ester, a newly synthesized, stable PGI2 analog, was found to have potent vasodilator activity in the feline and simian pulmonary vascular bed. The PGI2 analog decreased lobar arterial perfusion pressure in the intact cat and monkey. Because pulmonary blood flow was held constant and left atrial pressure was unchanged, the decrease in perfusion pressure reflects a decrease in pulmonary vascular resistance. The dilator response was unusual in that it persisted for 10-12 min, whereas the response to PGE1, the only other vasodilator prostaglandin in the mature animal, persisted for only 1-2 min. The dilator response to the PGI2 analog was enhanced when pulmonary vascular resistance was increased. This substance had less effect on cardiac output and aortic pressure than PGE1, whereas it was a more potent pulmonary vasodilator. These data demonstrate that prostacyclin-like substances possess novel vasodilator activity in the pulmonary circulation and suggest a therapeutic use in the treatment of pulmonary hypertensive diseases.