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At least 433 records · Page 24Linked to original sources
PubMed2003

Video-logging for examining biogenic structures in deep heterogeneous subsurface sediments.

Video-logging through a transparent tube is described as an alternative method for examining in situ the distribution of biogenic structures within the deep layers of heterogeneous sediments in which undisturbed cores are hard to be obtained. The method comprises four successive phases: the installation of transparent tubes into the sediment, the lowering of a video-camera for scanning sediments through the tube walls, the numerical treatment of images for correcting deformations and obtaining panoramic views of discrete sediment layers, and the mapping of biogenic structures. The method was used successfully to determine the density and depth distribution of galleries made by the oligochaetae Tubifex tubifex (Müller, 1874) within the infiltration bed of a stormwater basin.

Ecosystem↗
PubMed2000

On-line characterization of organic aerosols formed from biogenic precursors using atmospheric pressure chemical ionization mass spectrometry.

A method to investigate the chemical composition of organic aerosols formed from biogenic hydrocarbon oxidation using atmospheric pressure chemical ionization mass spectrometry (APCI/MS) is described. The method involves the direct introduction of aerosol particles into the ion source of the mass spectrometer. Using this technique, reaction monitoring experiments of alpha-pinene ozonolysis show the formation of hetero- and homomolecular cluster anions (dimers) of the primary oxidation products (multifunctional carboxylic acids). Since the formation of dimers plays a profound role in new particle formation processes by homogeneous nucleation in the atmosphere and, at the same time, is an intrinsic feature of APCI, it is essential to differentiate between both processes when on-line APCI/MS is applied. In this paper, we compare the results from the investigations of organic aerosols and artificially generated dimer cluster ions of the same compounds using identical ionization conditions. The clusters and their formation processes are characterized by varying the analyte concentration, investigating the thermal stability of dimers, and studying collisional activation properties of both ion species. The investigations show a significant difference in ion stability: dimer anions measured on-line have an estimated stability that is 20 kJ mol(-1) higher than that of the corresponding artificially generated cluster ions. Hence, the technique provides the possibility to accurately characterize dimers as ionized reaction products from biogenic hydrocarbon oxidation and allows an insight into the process of new-particle formation by homogeneous nucleation.

Aerosols↗
PubMed2002

Effect of oxide formation mechanisms on lead adsorption by biogenic manganese (hydr)oxides, iron (hydr)oxides, and their mixtures.

The effects of iron and manganese (hydr)oxide formation processes on the trace metal adsorption properties of these metal (hydr)oxides and their mixtures was investigated by measuring lead adsorption by iron and manganese (hydr)oxides prepared by a variety of methods. Amorphous iron (hydr)oxide formed by fast precipitation at pH 7.5 exhibited greater Pb adsorption (gamma(max) = 50 mmol of Pb/mol of Fe at pH 6.0) than iron (hydr)oxide formed by slow, diffusion-controlled oxidation of Fe(II) at pH 4.5-7.0 or goethite. Biogenic manganese(III/IV) (hydr)oxide prepared by enzymatic oxidation of Mn(II) by the bacterium Leptothrix discophora SS-1 adsorbed five times more Pb (per mole of Mn) than an abiotic manganese (hydr)oxide prepared by oxidation of Mn(II) with permanganate, and 500-5000 times more Pb than pyrolusite oxides (betaMnO2). X-ray crystallography indicated that biogenic manganese (hydr)oxide and iron (hydr)oxide were predominantly amorphous or poorly crystalline and their X-ray diffraction patterns were not significantly affected by the presence of the other (hydr)oxide during formation. When iron and manganese (hydr)oxides were mixed after formation, or for Mn biologically oxidized with iron(III) (hydr)oxide present, observed Pb adsorption was similar to that expected for the mixture based on Langmuir parameters for the individual (hydr)oxides. These results indicate that interactions in iron/manganese (hydr)oxide mixtures related to the formation process and sequence of formation such as site masking, alterations in specific surface area, or changes in crystalline structure either did not occur or had a negligible effect on Pb adsorption by the mixtures.

Adsorption↗
PubMed2005

Sediment depth attenuation of biogenic phosphorus compounds measured by 31P NMR.

Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.

Environmental Monitoring↗
PubMed2006

Contribution of first- versus second-generation products to secondary organic aerosols formed in the oxidation of biogenic hydrocarbons.

Biogenic hydrocarbons emitted by vegetation are important contributors to secondary organic aerosol (SOA), but the aerosol formation mechanisms are incompletely understood. In this study, the formation of aerosols and gas-phase products from the ozonolysis and photooxidation of a series of biogenic hydrocarbons (isoprene, 8 monoterpenes, 4 sesquiterpenes, and 3 oxygenated terpenes) are examined. By comparing aerosol growth (measured by Differential Mobility Analyzers, DMAs) and gas-phase concentrations (monitored by a Proton Transfer Reaction Mass Spectrometer, PTR-MS), we study the general mechanisms of SOA formation. Aerosol growth data are presented in terms of a "growth curve", a plot of aerosol mass formed versus the amount of hydrocarbon reacted. From the shapes of the growth curves, it is found that all the hydrocarbons studied can be classified into two groups based entirely on the number of double bonds of the hydrocarbon, regardless of the reaction systems (ozonolysis or photooxidation) and the types of hydrocarbons studied: compounds with only one double bond and compounds with more than one double bond. For compounds with only one double bond, the first oxidation step is rate-limiting, and aerosols are formed mainly from low volatility first-generation oxidation products; whereas for compounds with more than one double bond, the second oxidation step may also be rate-limiting and second-generation products contribute substantially to SOA growth. This behavior is characterized by a vertical section in the growth curve, in which continued aerosol growth is observed even after all the parent hydrocarbon is consumed.

Aerosols↗
PubMed2001

Structural and morphological anomalies in magnetosomes: possible biogenic origin for magnetite in ALH84001.

We report biogenic magnetite whiskers, with axial ratios of 6 : 1, elongated in the [1 1 1], [1 1 2] and [1 0 0] directions, resembling the magnetite whiskers detected in the Martian meteorite ALH84001 by Bradley et al., and interpreted by those authors as evidence of vapour-phase (abiogenic) growth. Magnetosomal whiskers with extended defects consistent with screw dislocations and magnetosomes resembling flattened twinned platelets, as well as other twinning phenomena and other structural defects, are also reported here. Magnetosomes with teardrop-shaped, cuboidal, irregular and jagged structures similar to those detected in ALH84001 by McKay et al., coprecipitation of magnetite possibly with amorphous calcium carbonate, coprecipitation of magnetite possibly with amorphous silica, the incorporation of titanium in volutin inclusions and disoriented arrays of magnetosomes are also described. These observations demonstrate that the structures of the magnetite particles in ALH84001, their spatial arrangement and coprecipitation with carbonates and proximity to silicates are consistent with being biogenic. Electron-beam-induced flash-melting of magnetosomes produced numerous screw dislocations in the [1 1 1], [1 0 0], and [1 1 0] lattice planes and induced fusion of platelets. From this, the lack of screw dislocations reported in the magnetite particles in ALH84001 (McKay et al., and Bradley et al.) indicates that they have a low-temperature origin.

Bacteria↗
PubMed2003

Dimethyl sulphide and methanethiol formation in microbial mats: potential pathways for biogenic signatures.

Mechanisms of dimethyl sulphide (DMS) and methanethiol (MT) production and consumption were determined in moderately hypersaline mats, Guerrero Negro, Mexico. Biological pathways regulated the net flux of DMS and MT as revealed by increases in flux resulting from decreased salinity, increased temperature and the removal of oxygen. Dimethylsulphoniopropionate (DMSP) was not present in these microbial mats and DMS and MT are probably formed by the reaction of photosynthetically produced low-molecular weight organic carbon and biogenic hydrogen sulphide derived from sulphate reduction. These observations provide an alternative to the notion that DMSP or S-containing amino acids are the dominant precursors of DMS in intertidal sediment systems. The major sink for DMS in the microbial mats was biological consumption, whereas photochemical oxidation to dimethylsulphoxide was the major sink for DMS in the overlying water column. Diel flux measurements demonstrated that significantly more DMS is released from the system during the night than during the day. The major consumers of DMS in the presence of oxygen were monooxygenase-utilizing bacteria, whereas under anoxic conditions, DMS was predominantly consumed by sulphate-reducing bacteria and methanethiol was consumed by methanogenic bacteria. Aerobic and anaerobic consumption rates of DMS were nearly identical. Mass balance estimates suggest that the consumption in the water column is likely to be smaller than net the flux from the mats. Volatile organic sulphur compounds are thus indicators of high rates of carbon fixation and sulphate reduction in these laminated sediment ecosystems, and atmospheric sulphur can be generated as a biogenic signature of the microbial mat community.

Bacteria↗
PubMedDate not supplied

Quantitative exposure assessment for confinement of maize biogenic systems.

The development of transgenic crops as production platforms for biogenic agents will largely depend on the success of efforts to confine the genes and their expressed proteins in field environments. We have used quantitative exposure assessment to evaluate how management practices affect materials escape due to outcrossing by pollen flow or grain loss during harvest operations. Specifically, we study the use of maize to produce biogenic agents within field-confined systems. Decision trees representing simplified schemes of fully conforming (designed to comply with current regulatory standards for field confined trials), partially conforming, and non-conforming management practices were developed. Exemplifying assumptions and published data for conformance and material fate probabilities were used in Monte Carlo simulations to forecast materials escape by pollen outcrossing and harvest operations from a 1 ha source field. Deterministic analyses showed fully conforming confinement management restricted materials loss to low levels (for this example, outcrossing produced <1 in 10(6) kernels in receptor fields). The corresponding high-end (90th percentile) probabilistic result was 16- and 4333-fold higher (relative to deterministic outcrossing = 1) for outcrossing and harvest loss, respectively. For partially conforming practice, high-end outcrossing ranged from 100- to >15000-fold over the base result in receptor fields, and harvest loss was >10000-fold over the base result. For non-conforming practice, high-end outcrossing produced >15000-fold greater kernels in receptor fields and high-end harvest loss was at least 19000-fold greater. Deterministic estimates of off-field loss by machine transfer are as much as 30000-fold higher for non-conforming operations relative to the base case of pollen outcrossing. Better knowledge of failure frequencies for confinement management practices, improved physical models of materials flows, refined analysis of confinement loss probabilities using quantitative tools, and decision analysis to improve and audit management system performance are all needed to extend understanding of confinement integrity beyond the exemplifying case used here.

Agriculture↗
PubMed1986

Insulin dependence of the actions of growth hormone and somatostatin on splanchnic biogenic amines of the dog.

It is known from studies previously conducted in this laboratory that an iv injection of ovine growth hormone (GH, 100 micrograms/kg BW) or an equimolar amount of somatostatin (SRIF, 7.5 micrograms/kg BW), given to normal conscious dogs into a saphenous vein, leads to a significant increase in hepatic portal plasma serotonin and a simultaneous decrease in the concentrations of dopamine, norepinephrine and epinephrine. The changes take place within 12 minutes after the injection and are observed only in the portal circulation. The purpose of the present experiment was to investigate whether or not similar results could be obtained in diabetic animals. Mongrel dogs were rendered diabetic by surgical pancreatectomy and fitted with an indwelling hepatic portal catheter. Radioenzymatic methods were employed for quantitative measurements of plasma free serotonin and catecholamines. No response was noted when the same type of experiments as those conducted in normal dogs were now carried out in trained, fully conscious totally pancreatectomized dogs deprived of exogenous insulin supply. When the same animals were given an injection into a peripheral vein of 50 mU/kg BW regular crystalline insulin (a small dose that affected neither plasma glucose nor biogenic amine levels) 10 minutes prior to the administration of the other hormones, the usual response to both GH and SRIF was restored, i.e. the data were comparable to those of normal dogs. It is concluded that the GH/SRIF effect on gut biogenic amines is insulin dependent.

Animals↗
PubMed1970

Stimulated formation of adenosine 3',5'-cyclic phosphate in cerebral cortex: synergism between electrical activity and biogenic amines.

When cortical slices are incubated with adenine-(14)C, adenine nucleotides are labeled in a small and relatively stable pool. The ATP-(14)C of this pool is readily converted to cAMP-(14)C during incubations with depolarizing agents, such as K(+), ouabain, veratridine, or batrachotoxin. During incubations with these agents, release of acetylcholine and of adenosine into the medium is enhanced. The increase in release of adenosine parallels the enhanced formation of cAMP-(14)C elicited by depolarizing agents, providing further evidence that adenosine may serve to couple electrical activity in the central nervous system with formation of cAMP. When adenosine or a depolarizing agent are incubated, together with a biogenic amine, such as histamine, serotonin, or norepinephrine, the combined effect on cAMP-(14)C formation in cortical slices is much more than additive. Extracellular levels of biogenic amines could in this manner modulate cAMP formation and biochemical responses in nervous tissue during electrical activity.

Acetylcholine↗
PubMed1977

Biogenic amine-ionophore interactions: Structure and dynamics of lasalocid (X537A) complexes with phenethylamines and catecholamines in nonpolar solution.

The ionophore lasalocid A forms 1:1 complexes with phenethylamines (1-amino-1-phenylethane and 1-amino-2-phenylethane) and catecholamines (dopamine and norepinephrine) in nonpolar solution. We have undertaken high-resolution proton nuclear magnetic resonance studies to deduce structural and kinetic information on the ionophore-biogenic amine complexes in chloroform solution. The coupling constant, chemical shift, and relaxation time data demonstrate that the lasalocid backbone conformation and the primary amine binding sites in the complexes are similar to those determined earlier for the alkali and alkaline earth complexes of this ionophore in solution. The exchange of lasalocid between the free acid (HX) and the primary amine complexes (RNH(3)X) in chloroform solution have been evaluated from the temperature-dependent line shapes at superconducting fields. The kinetic parameters associated with the unimolecular dissociation [Formula: see text] and the bimolecular exchange [Formula: see text] reactions have been deduced from an analysis of the lifetime of the complex as a function of the reactant concentrations. The relative stability of the complex decreases in the order phenyl > n-pentyl for substituents on the carbon alpha to the amino group (1-amino-1-phenylethane and 2-aminoheptane) and phenyl > 3,4-dihydroxyphenyl for substituents on the carbon beta to the amino group (1-amino-2-phenylethane and dopamine). These results suggest that nonpolar interactions between the biogenic amine side chain and the lasalocid molecule contribute to the stability of the complex in solution.

Journal Article↗
PubMed1999

The paraventricular organ of mormyrid fish: uptake or release of intraventricular biogenic amines?

The paraventricular organ of Gnathonemus petersii was investigated with light and electronmicroscopical techniques. It contains high concentrations of dopamine, noradrenaline and serotonin, but the synthesizing enzymes are not or hardly present. Consequently, the cerebrospinal fluid-contacting neurons might pick up their biogenic amines from the ventricular fluid. Dense subependymal axonal plexuses in the everted telencephalon probably release these substances into the ventricle. However, electronmicroscopical observations suggest release rather than uptake by the paraventricular organ. The possible significance of intraventricular release, transport and uptake of biogenic amines is discussed.

Animals↗
PubMed1992

Regulation of the natural killer cell response to interferon-alpha by biogenic amines.

Monocytes, recovered from human peripheral blood by counter-current centrifugal elutriation (CCE), suppressed baseline natural killer (NK) cell cytotoxicity (NKCC) and rendered NK cells resistant to activation of cytotoxicity by human recombinant interferon-alpha (IFN-alpha) by a cell contact-dependent mechanism. Monocyte-induced suppression of resting and IFN-activated NK cells was abrogated by the biogenic amines histamine [via H2-type receptors (H2R)] and serotonin [via 5-HT1A-type receptors (5-HT1AR)]. Our data are suggestive of a monocyte/NK cell interaction that is subject to regulation by biogenic amines.

Cell Adhesion↗
PubMedDate not supplied

Circadian and circatrigintan rhythms of biogenic amines in premenstrual syndrome (PMS).

Circadian and circatrigintan (menstrual) rhythms in biogenic amines were studied in premenstrual syndrome (PMS). Selection of patients and controls was based on assessment of Menstrual Distress Questionnaires (MDQs). Patients showed a clear increase in menstral tension symptoms in the week before menstruation, both during selection and during the study. In the group of control subjects, there was hardly any increase in average MDQ symptoms during the late luteal phase. Diurnal urine and nocturnal urine were collected on days 5, 11, 17, 21, and 25 of the cycle. Blood was sampled from subjects in supine position through an intravenous (iv) catheter the morning after urine collection. Patients showed a higher tryptophan (Trp) and epinephrine (Epi) level in plasma, higher excretion of 3-methoxy-4-hydroxyphenylglycol (MHPG) in urine and a larger volume of 24-hr urine. Excretion of norepinephrine (NE) in 24-hr urine showed a linear increase during the cycle, while excretion of dopamine (DA) showed a quadratic pattern, being lowest at day 17. Homovanillic acid (HVA) and MHPG gave cubic patterns, i.e., an increase during the follicular phase, followed by a decrease after ovulation and a subsequent increase in the late luteal phase. Plasma Epi showed a linear decline during the cycle in patients, but not in control subjects. Excretion of NE, Epi, vanilmandelic acid (VMA), and HVA in urine was higher during the day than at night. The results of this study suggest that the metabolism of biogenic amines in patients suffering from PMS differs from that in control subjects, but that, except for plasma Epi, changes do not parallel the actual presence of PMS symptoms.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2003

Preliminary evaluation of nanoscale biogenic magnetite-based ferromagnetic transduction mechanisms for mobile phone bioeffects.

Ferromagnetic transduction models have been proposed as a potential mechanism for mobile phone bioeffects. These models are based on the coupling of RF and pulsed electromagnetic emissions to biogenic magnetite (Fe3O4) present in the human brain via either ferromagnetic resonance or mechanical activation of cellular ion channels. We have tested these models experimentally for the first time using a bacterial analogue (Magnetospirillum magnetotacticum) which produces intracellular biogenic magnetite similar to that present in the human brain. Experimental evaluation revealed that exposure to mobile phone emissions resulted in a consistent and significantly higher proportion of cell death in exposed cultures versus sham exposure (p = 0.037). Though there appears to be a repeatable trend toward higher cell mortality in magnetite-producing bacteria exposed to mobile phone emissions, it is not yet clear that this would extrapolate to a deleterious health effect in humans.

Apoptosis↗
PubMed1986

Human aldehyde dehydrogenase: kinetic identification of the isozyme for which biogenic aldehydes and acetaldehyde compete.

Michaelis constants and maximal velocities for phenylacetaldehyde (a metabolite of phenylethylamine), 3,4-dihydroxyphenylacetaldehyde (a metabolite of dopamine), 5-hydroxyindole acetaldehyde (a metabolite of serotonin), and 3,4-dihydroxyphenylglycolaldehyde (a metabolite of epinephrine and norepinephrine) have been determined for both cytoplasmic (E1) and mitochondrial (E2) isozymes of human liver aldehyde dehydrogenase (EC 1.2.1.3). Kinetic constants with biogenic aldehydes have never been previously determined for individual homogeneous isozymes of aldehyde dehydrogenase from any species. Mathematical treatment of these constants suggests that competition with acetaldehyde during alcohol metabolism would severely inhibit dehydrogenation of biogenic aldehydes with the mitochondrial and not the cytoplasmic isozyme of human liver aldehyde dehydrogenase.

Acetaldehyde↗
PubMed1986

Effect of nitrate on biogenic sulfide production.

The addition of 59 mM nitrate inhibited biogenic sulfide production in dilute sewage sludge (10% [vol/vol]) amended with 20 mM sulfate and either acetate, glucose, or hydrogen as electron donors. Similar results were found when pond sediment or oil field brines served as the inoculum. Sulfide production was inhibited for periods of at least 6 months and was accompanied by the oxidation of resazurin from its colorless reduced state to its pink oxidized state. Lower amounts of nitrate (6 or 20 mM) and increased amounts of sewage sludge resulted in only transient inhibition of sulfide production. The addition of 156 mM sulfate to bottles with 59 mM nitrate and 10% (vol/vol) sewage sludge or pond sediment resulted in sulfide production. Nitrate, nitrite, and nitrous oxide were detected during periods where sulfide production was inhibited, whereas nitrate, nitrite, and nitrous oxide were below detectable levels at the time sulfide production began. The oxidation of resazurin was attributed to an increase in nitrous oxide which persisted in concentration of about 1.0 mM for up to 5 months. The numbers of sulfate-reducing organisms decreased from 10 CFU ml sludge to less than detectable levels after prolonged incubation of oxidized bottles. The addition of 10 mM glucose to oxidized bottles after 14.5 weeks of incubation resulted in rereduction of the resazurin and subsequent sulfide production. The prolonged inhibition of sulfide production was attributed to an increase in oxidation-reduction potential due to biogenic production of nitrous oxide, which appeared to have a cytotoxic effect on sulfate-reducing populations.

Journal Article↗
PubMed1977

Impact of centrally applied biogenic amines upon the energy balance of fowl.

The impact of intraventricular injections of 100 microng of the biogenic amines, norepinephrine or dopamine, upon the energy balance of white leghorn hens Gallus domesticus was examined. Both drugs reduce metabolic heat production (about 35% at 9 and 20 degrees C, and about 15% at 35 degrees C) by inhibiting shivering or by reducing activity or both. Also the drugs inhibit the opposing thermal response, evaporative heat loss (about 3% at 9 and 20 degrees C, and about 20% at 35 degrees C) by reducing respiration rate. The relative balance of inhibiting these opposing responses by the drugs results in hypothermia at 9 and 20 degrees C, and hyperthermia or no change in body temperature at 35 degrees C. Both drugs usually caused an initial vasodilation of the feet and comb at all temperatures tested but did not persist long enough to have much of an impact on body temperature. It was concluded that differing ambient temperatures do not alter the action of the biogenic amines upon the modes of physical thermoregulation in chickens even though the direction of body temperature change is reversed at different ambient temperatures.

Animals↗