Coupling hydrocarbon degradation to anaerobic respiration and mineral diagenesis: theoretical constraints

The diagenetic mineral assemblages in petroleum reservoirs control the formation fluid pH and pCO₂. Anaerobic biodegradation of petroleum is controlled by the transfer of electrons from reduced organic species to inorganic, redox sensitive, aqueous and mineral species in many cases through intermediates such as H₂ and CH₃COO^?. The terminal electron accepting reactions induce the dissolution or precipitation of the same minerals that control the ambient pH and pCO₂ in petroleum reservoirs. In this study, we develop a model for anaerobic biodegradation of petroleum that couples the production of acetate and H₂ to ‘late stage’ diagenetic reactions. The model reveals that the principal terminal electron accepting process and electron donor control the type of diagenetic reaction, and that the petroleum biodegradation rate is controlled through thermodynamic restriction by the minimum ΔG required to support a specific microbial metabolism, the fluid flux and the mineral assemblage. These relationships are illustrated by modeling coupled microbial diagenesis and biodegradation of the Gullfaks oil reservoir. The results indicate that the complete dissolution of albite by acids generated during oil biodegradation and the corresponding elevated pCO₂ seen in the Gullfaks field are best explained by methanogenic respiration coupled to hydrocarbon degradation and that the biodegradation rate is likely controlled by the pCH₄. Biodegradation of Gullfaks oil by a consortium that includes either Fe³⁺‐reducing or ‐reducing bacteria cannot explain the observed diagenetic mineral assemblage or pCO₂. For octane, biodegradation, not water washing, was the principal agent for removal at fluid velocities <20 m Myr^?1.     

RNA and Protein Synthesis in Germinating Pine Pollen

The results of autoradiographic experiments demonstrate that,as with the pollen of most other species, both the generativeand vegetative nuclei of Loblolly Pine (Pinus taeda) activelyengage in RNA synthesis from the very early stages of pollengermination. Unlike most other species, however, this newlysynthesized RNA includes rRNA. Evidence is provided for theimportance of this newly synthesized RNA in the process of continuedpollen tube growth. One and two-dimensional gel electrophoretic analysis revealsa number of both qualitative and quantitative differences amongthe proteins synthesized during the early stages of germinationand the later stages of pollen tube growth. One of the mostnotable of these is a 36 kD protein, the synthesis of whichpredominates during the later stages of pollen germination.A similar pattern of 36 kD protein synthesis is observed whenmRNA extracted from pollen at each of these stages is translatedin vitro. Key words: Pinus, pollen tube growth     

Is bigger better? Water balance in the polymorphic desert harvester ant Messor pergandei

Abstract. Foraging activity of ants in xeric areas may be limited by desiccation stresses. To assess the extent of such stresses on a polymorphic ant species [Messor pergandei (Mayr), body mass range 1-12mg], we measured body water reserves, absolute rates of water loss, and cuticular permeability over the species' foraging temperature range (15–45C). Cuticular permeability of M. pergandei was typical of xeric arthropods (17μgcm^-2h^-1mmHg^-1). However, the effect of polymorphism on both absolute and relative rates of water loss was unexpected. Large workers lost water more slowly than small workers, even after adjusting for cuticular surface area. In addition, the body water reserves of large workers were larger, even after adjusting for body mass. Small workers of this ant species are therefore disproportionately prone to dehydration, yet, in spite of this, constitute a large and important component of the foraging force. To assess the practical relevance of desiccation to polymorphic ants, we developed a 'worst-case' model of desiccation-limited foraging parameters (time to complete loss of locomotor coordination in 5% of the foraging force). In this model, average actual foraging duration was substantially less than would be required to incapacitate the ants by dehydration. We discuss direct and indirect evidence suggesting that desiccation may, nevertheless, impose limitations on the foraging activity of ants.     

Ecteinascidia turbinata Extract Activates Components of Inflammatory Responses Throughout the Phylogenetic Spectrum

The tunicate Ecteinascidia turbinata contains a substance orsubstances capable of exerting a number of biological effects.Extracts of tunicate tissues have been shown to kill tumorcells in vitro and arrest tumor growth in vivo. The extractsalso suppress allograft rejection, graft-US.-host reactionsand lymphocyte proliferative responses as well as humoral responsesto immunization. By modifying the conditions, the extracts couldpotentiate antibody responses. In addition, they augment functionsof monocyte-macrophages as evidenced by in vitro phagocytosis,in vivo clearance, and cytotoxic activity against target cells.After studies in mice, we were able to demonstrate that theextracts could activate the phagocytic systems of shrimp, bluecrab, and fish (the American eel). In fish, the intraperitonealroute was superior to the intravenous route for promotion ofphagocytosis, increase in percent presentation of granulocytesand for enhancement of resistance to bacterial infection. Intrarriuscularand intraperitoneal injection led to local inflammation withaccumulation of granulocytes and macrophages.     

Hypoxic Quiescence in Alligatorweed

Propagules (stem cuttings) of alligatorweed [Alternanthera philoxeroides (Mart.) Griseb.] were subjected to various treatments of submergence, emergence, light, dark, and oxygen to relate hypoxia to the suppression of alligatorweed growth by dark submergence. In the dark, submergence completely inhibited alligatorweed growth. A nitrogen atmosphere inhibited growth from emersed propagules in the dark. The suspension of growth by dark submergence was relieved by light (40 μ einsteins/m²× s photo-synthetically active radiation), emergence (whereby air is transported to underwater nodes via the aerenchyma), or exposure to 100 mg · l^-1 of hydrogen peroxide solution renewed at 48-h intervals. Suspension of growth by a nitrogen atmosphere was relieved by inclusion of 16% oxygen in the ambient atmosphere. Dark to light transfers showed that the suspension of growth was immediately relieved if the requisite conditions were restored; this phenomenon, as described, thus appears to be hypoxic quiescence. The suppression of growth of two other amphibious species, mild smartweed (Polygonum hydropiperoides Michx.) and creeping water-primrose (Jussiaea repens L. var. glabrescens Ktze.), by dark submergence suggests that hypoxic quiescence may be a factor in the life history of amphibious species other than alligatorweed.     

Contributions to the Life Cycle of Peneroplis planatus (Fichtel and Moll) Montfort

Direct observations of schizonts and agamonts releasing megalospheres clarified the asexual phase of the life cycle of Peneroplis planatus and made it most probable that this species has a paratrimorphic life cycle. Specimens with maximum lengths between 837 and 3,503 μm released about 500 to 1,500 megalospheric juveniles, which possessed two chambers (proloculi and flexostyles) prior to emergence from the parental shell. The presence of gamonts was not shown and was only implied by the occurrence of the agamonts. Since agamonts and schizonts have been found from December to May and since asexual reproduction occurs in spring in Elat, sexual reproduction probably occurs at another time of year (June to December). More detailed studies of this species need to be conducted throughout the year to improve our knowledge of the life cycle of this species.     

The Control of Vascular Branching in Coleus 1. The Side Bundle

Xylary branching at the proximal end of a differentiating sidebundle was modified by surgical alteration of the surroundingleaf traces and manipulation of their auxin fluxes. Incisionsthrough one corner trace, with the other pre-existing traceintact, resulting in xylem differentiation in the branch ofthe newly formed side bundle toward only the severed trace.Application of IAA to the cut trace allowed xylem branchingof the new strand in both directions. With sufficient auxinimbalance created by increasing the concentration of the appliedIAA, the new xylem strand branched away from the higher auxinsource. Auxin relations were thus able to regulate the courseof differentiation of vascular strands, but their role in regulatingbranching patterns in intact plants may be questioned. Xylembranched exclusively toward an incised trace only when the auxinflux of the incised trace was virtually eliminated. Phloem andprocambium of the differentiating strand were unaffected bythis treatment. Coleus, vascular differentiation, vascular anatomy, vascular branching, vascular patterns, auxin, auxin balance, node     

Dose response of hepatic and renal DNA synthetic rates to continuous exposure of bromodeoxyuridine (BrdU) via slow-release pellets or osmotic minipumps in male B6C3F1 mice

We studied the use of acute and chronic 5-bromo-2'-deoxyuridine (BrdU) administration for detection of DNA-synthesizing cells in the liver and kidney of B6C3F1 male mice. Six-week-old mice were exposed to BrdU either acutely with a single-pulse (IP) injection 1 hr before sacrifice or chronically with the use of slow-release pellets or osmotic minipumps at one of four BrdU dose rates. Pellets (2.5, 10, 25, and 50 mg) and minipumps (2.5 and 10 mg equivalents) were implanted subcutaneously on the backs of the animals 4 or 7 days before sacrifice). BrdU incorporation into DNA was determined by immunohistochemistry using an anti-BrdU antibody. Mice chronically exposed to BrdU demonstrated increased levels of nuclear labeling compared with those receiving a single-pulse injection. No time-related increases in nuclear labeling were detected in hepatocytes or renal tubule cells of mice exposed to BrdU pellets and in the kidneys of mice receiving BrdU minipumps at the 7-day compared with the 4-day time point. In some cases, the labeling indices at 7 days were significantly decreased compared with those at 4 days. In contrast, a time-related increase in nuclear labeling was seen in hepatocytes and Kupffer cells of mice exposed to BrdU minipumps. Therefore, the method used to administer BrdU chronically to the animal appears to play an important role in presenting the true proliferative scenario in cell kinetic studies. Our findings also provide evidence for an effect of BrdU on normal proliferation rates in these tissues.