The role of anoxia in the decay and mineralization of proteinaceous macro-fossils

Actualistic experiments have quantified rate of anaerobic decay and associated mineralization around proteinaceous macro-organisms. Carcasses of the polychaete wormNereisand the eumalacostracansNephropsandPalaemonwere buried in airtight glass jars filled with sediment and water from marine, brackish, and lacustrine environments. Over a period of 25 weeks the contents were examined to determine the state of decay and were chemically analyzed to monitor early diagenetic mineralization (two methods for such analysis are reviewed). Decay processes were active in the experimental conditions despite anoxia and had virtually destroyed the carcasses within 25 weeks. However, decay-rate in the sulfate-reducing marine system was greater than in the methanogenic freshwater environments. Petrological and geochemical analyses of the organic remains identified discrete layers of authigenic iron monosulfide (a pyrite precursor) on the surface of the decayingNephropscuticle within weeks of initiating the experiment. Chemical analysis of decomposing flesh showed a marked increase in pore-water calcium content with time.The results clearly show that anoxia is ineffective as a long-term conservation medium in the preservation of soft-bodied fossils. However, decay-induced mineralization can be very rapid so that even a slight reduction in decay rate can lead to improved levels of fossil preservation. Traditionally, stagnation and rapid burial are considered to be the main prerequisites for the preservation of soft-bodied fossils and the formation ofKonservat-Lagerstätten. Clearly these factors are only important in that they promote early diagenetic mineralization. This is the only way to halt information loss through decay.

Download Full-text

Assessing the Role of Iron Sulfides in the Long Term Sequestration of U by Sulfate Reducing Bacteria

10.2172/1149699 ◽

2013 ◽

Author(s):

Bruce Rittman ◽

◽

Chen Zhou ◽

Raveender Vannela

Keyword(s):

Sulfate Reducing Bacteria ◽

Iron Sulfides ◽

Sulfate Reducing ◽

Reducing Bacteria

Download Full-text

Integrated carbon-nitrogen-phosphorus cycling for sustainable agriculture – a knowledge gap and investigation of the role of phosphatase enzymes

10.5194/egusphere-egu21-3037 ◽

2021 ◽

Author(s):

Victoria Janes-Bassett ◽

Phil Haygarth ◽

Martin Blackwell ◽

Malika Mezeli ◽

Gavin Stewart ◽

...

Keyword(s):

Enzyme Activity ◽

Crop Yields ◽

Organic P ◽

Experimental Conditions ◽

P Deficiency ◽

Soil C ◽

P Addition ◽

Phosphatase Enzyme

<p>Phosphorus is closely linked to other nutrient cycles, notably carbon and nitrogen, therefore, to understand potential risks to food production models are required that simulate integrated nutrient cycling over long timescales. The soil-plant system model N14CP meets these requirements and simulates both semi-natural and agricultural environments. N14CP has been validated both spatially and temporally across a range of long-term agricultural experimental sites comparing soil C, N and P, and crop yields, and in most instances performs well. However, under experimental conditions where N is applied in the absence of P, the model indicates exhaustion of P reserves and a decline in yields that is not observed at these sites, highlighting a gap in the model process representation. Potential sources of this &#8216;missing P&#8217; such as enhanced atmospheric deposition, weathering and flexible plant stoichiometries were explored yet cannot account for this deficit. We hypothesise that access of organic P through other mechanisms not fully represented within the model, such as phosphatase enzymes, could be part of this explanation.</p><p>In order to test this, we conducted a meta-analysis of phosphatase enzyme activity in agricultural settings, comparing response to P sufficient and deficient conditions. Results suggest phosphatase enzyme activity is higher in P deficient conditions compared to inorganic P addition, yet lower compared to organic P addition. Meta-regression analysis indicates magnitude of P addition and pH of substrate are significant factors influencing enzyme response. However, due to numerous additional processes and adaption strategies in response to P deficiency and the difficulty isolating the role of phosphatase enzymes it is not possible to determine the degree to which this mechanism alone accounts for the missing P. We discuss the continuing need for additional empirical evidence to understand the cycling of organic P, and the development of models to include these processes to inform sustainable land management and ensure long-term food security.</p>

Download Full-text

The Influence of Stimulus Deviance on Electrophysiologic and Behavioral Responses to Novel Events

Journal of Cognitive Neuroscience ◽

10.1162/089892900562219 ◽

2000 ◽

Vol 12 (3) ◽

pp. 393-406 ◽

Cited By ~ 48

Author(s):

Kirk R. Daffner ◽

Leonard F.M. Scinto ◽

Vivian Calvo ◽

Robert Faust ◽

M. Marsel Mesulam ◽

...

Keyword(s):

Cognitive Processing ◽

Behavioral Responses ◽

Event Related Potential ◽

Button Press ◽

Experimental Conditions ◽

Background Stimulus ◽

Preceding Context ◽

Within Subjects

This study investigated the role of stimulus deviance in determining electrophysiologic and behavioral responses to “novelty.” Stimulus deviance was defined in terms of differences either from the immediately preceding context or from long-term experience. Subjects participated in a visual event-related potential (ERP) experiment, in which they controlled the duration of stimulus viewing with a button press, which served as a measure of exploratory behavior. Each of the three experimental conditions included a frequent repetitive background stimulus and infrequent stimuli that deviated from the background stimulus. In one condition, both background and deviant stimuli were simple, easily recognizable geometric figures. In another condition, both background and deviant stimuli were unusual/unfamiliar figures, and in a third condition, the background stimulus was a highly unusual figure, and the deviant stimuli were simple, geometric shapes. Deviant stimuli elicited larger N2-P3 amplitudes and longer viewing durations than the repetitive background stimulus, even when the deviant stimuli were simple, familiar shapes and the background stimulus was a highly unusual figure. Compared to simple, familiar deviant stimuli, unusual deviant stimuli elicited larger N2-P3 amplitudes and longer viewing times. Within subjects, the deviant stimuli that evoked the largest N2-P3 responses also elicited the longest viewing durations. We conclude that deviance from both immediate context and long-term prior experience contribute to the response to novelty, with the combination generating the largest N2-P3 amplitude and the most sustained attention. The amplitude of the N2-P3 may reflect how much “uncertainty” is evoked by a novel visual stimulus and signal the need for further exploration and cognitive processing.

Download Full-text

Assessing the Role of Iron Sulfides in the Long Term Sequestration of Uranium by Sulfate-Reducing Bacteria

10.2172/1121431 ◽

2013 ◽

Author(s):

Kim F. Hayes ◽

Yuqiang Bi ◽

Julian Carpenter ◽

Sung Pil Hyng ◽

Bruce E. Rittmann ◽

...

Keyword(s):

Sulfate Reducing Bacteria ◽

Iron Sulfides ◽

Sulfate Reducing ◽

Reducing Bacteria

Download Full-text

Consequences of assisted reproductive technologies for offspring function in cattle

Reproduction Fertility and Development ◽

10.1071/rd19278 ◽

2020 ◽

Vol 32 (2) ◽

pp. 82 ◽

Cited By ~ 1

Author(s):

Luiz G. Siqueira ◽

Marcos V. G. Silva ◽

João C. Panetto ◽

João H. Viana

Keyword(s):

Assisted Reproductive Technologies ◽

Neonatal Morbidity ◽

Reproductive Technologies ◽

Postnatal Life ◽

Slight Reduction ◽

Long Term Effects ◽

Epigenetic Effects ◽

Postnatal Mortality

Abnormal fetuses, neonates and adult offspring derived by assisted reproductive technologies (ART) have been reported in humans, rodents and domestic animals. The use of ART has also been associated with an increased likelihood of certain adult diseases. These abnormalities may arise as a result of an excess of or missing maternally derived molecules during invitro culture, because the invitro environment is artificial and suboptimal for embryo development. Nonetheless, the success of ART in overcoming infertility or improving livestock genetics is undeniable. Limitations of invitro embryo production (IVEP) in cattle include lower rates of the establishment and maintenance of pregnancy and an increased incidence of neonatal morbidity and mortality. Moreover, recent studies demonstrated long-term effects of IVEP in cattle, including increased postnatal mortality, altered growth and a slight reduction in the performance of adult dairy cows. This review addresses the effects of an altered preimplantation environment on embryo and fetal programming and offspring development. We discuss cellular and molecular responses of the embryo to the maternal environment, how ART may disturb programming, the possible role of epigenetic effects as a mechanism for altered phenotypes and long-term effects of ART that manifest in postnatal life.

Download Full-text

Thrombocytopenia Induced in Mice by Thromboplastin Infusion – Essential Role of the Third Complement Component

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646750 ◽

1978 ◽

Vol 39 (03) ◽

pp. 733-742

Author(s):

Luis A Giraudo ◽

Agustin P Dalmasso

Keyword(s):

Blood Platelet ◽

Total Serum ◽

Minor Role ◽

Slight Reduction ◽

Experimental Conditions ◽

Slow Infusion ◽

A Minor ◽

Deficient Mice

SummaryStudies were performed in mice to investigate the effects of the slow infusion of brain thromboplastin (tissue factor) on blood platelet levels. Thromboplastin caused pronounced thrombocytopenia in all strains of mice tested without histological evidence of intravascular coagulation. The role of the complement system in the thrombocytopenic response to thromboplastin administration was evaluated by using complement-deficient animals. Depending on experimental conditions, the degree of platelet reduction in C5-deficient mice was similar to or significantly lower than in normocomplementemic animals. C5-deficient mice reconstituted with mouse plasma or purified human C5 had a thrombocytopenic reaction identical to that of normocomplementemic controls. The thrombocytopenic response of B10.D2/new and old line mice could be abrogated by inactivating C3 with cobra venom factor prior to the administration of thromboplastin. We conclude that in mice C3 plays a central role in the thrombocytopenia induced by thromboplastin infusion, while C5 (and/or other late acting components) plays only a minor role. In vivo activation of complement by thromboplastin was indicated by the finding that thromboplastin infusion in B10.D2/new mice caused a significant reduction in total serum hemolytic complement and a slight reduction in C3 measured immunochemically. The platelet counts of uninjected B10.D2/new mice were slightly but significantly higher than in B10.D2/old mice.

Download Full-text

The Role of Long-Term Head-Down Bed Rest in Understanding Inter-Individual Variation in Response to the Spaceflight Environment: A Perspective Review

Frontiers in Physiology ◽

10.3389/fphys.2021.614619 ◽

2021 ◽

Vol 12 ◽

Author(s):

Jonathan P. R. Scott ◽

Andreas Kramer ◽

Nora Petersen ◽

David A. Green

Keyword(s):

Bed Rest ◽

Individual Variability ◽

Control Group ◽

Statistical Concept ◽

Gravitational Unloading ◽

Experimental Conditions ◽

Mechanical Unloading ◽

Musculoskeletal Systems

Exposure to the spaceflight environment results in profound multi-system physiological adaptations in which there appears to be substantial inter-individual variability (IV) between crewmembers. However, performance of countermeasure exercise renders it impossible to separate the effects of the spaceflight environment alone from those associated with exercise, whilst differences in exercise programs, spaceflight operations constraints, and environmental factors further complicate the interpretation of IV. In contrast, long-term head-down bed rest (HDBR) studies isolate (by means of a control group) the effects of mechanical unloading from those associated with countermeasures and control many of the factors that may contribute to IV. In this perspective, we review the available evidence of IV in response to the spaceflight environment and discuss factors that complicate its interpretation. We present individual data from two 60-d HDBR studies that demonstrate that, despite the highly standardized experimental conditions, marked quantitative differences still exist in the response of the cardiorespiratory and musculoskeletal systems between individuals. We also discuss the statistical concept of “true” and “false” individual differences and its potential application to HDBR data. We contend that it is currently not possible to evaluate IV in response to the spaceflight environment and countermeasure exercise. However, with highly standardized experimental conditions and the presence of a control group, HDBR is suitable for the investigation of IV in the physiological responses to gravitational unloading and countermeasures. Such investigations may provide valuable insights into the potential role of IV in adaptations to the spaceflight environment and the effectiveness of current and future countermeasures.

Download Full-text

Site of Lysosome Production During Hepatic Injury

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100063652 ◽

1969 ◽

Vol 27 ◽

pp. 348-349

Author(s):

Nalin J. Unakar

Keyword(s):

Electron Microscopy ◽

Golgi Apparatus ◽

Mouse Liver ◽

Hepatic Injury ◽

Close Approximation ◽

Experimental Conditions ◽

Toxic Injury

The increased number of lysosomes as well as the close approximation of lysosomes to the Golgi apparatus in tissue under variety of experimental conditions is commonly observed. These observations suggest Golgi involvement in lysosomal production. The role of the Golgi apparatus in the production of lysosomes in mouse liver was studied by electron microscopy of liver following toxic injury by CCI4.

Download Full-text