Experimental Preservation of Muscle Tissue in Quartz Sand and Kaolinite

Siliciclastic sediments of the Ediacaran Period contain exceptionally preserved fossils of macroscopic organisms, including three-dimensional casts and molds commonly found in sandstones and siltstones and some two-dimensional compressions reported in shales. The sporadic and variable associations of these exceptionally preserved macroscopic fossils with pyrite, clay minerals, and microbial fossils and textures complicate our understanding of fossilization processes. This hinders inferences about the evolutionary histories, tissue types, original morphologies, and lifestyles of the enigmatic Ediacara biota. Here, we investigate the delayed decay of scallop muscles buried in quartz sand or kaolinite for 45 days. This process occurs in the presence of microbial activity in mixed redox environments, but in the absence of thick, sealing microbial mats. Microbial processes that mediate organic decay and release the highest concentrations of silica and Fe(II) into the pore fluids are associated with the most extensive tissue decay. Delayed decay and the preservation of thick muscles in sand are associated with less intense microbial iron reduction and the precipitation of iron oxides and iron sulfides that contain Fe(II) or Fe(III). In contrast, muscles buried in kaolinite are coated only by <10 μm-thick clay veneers composed of kaolinite grains and newly formed K- and Fe(II)-rich aluminosilicate phases. Muscles that undergo delayed decay in kaolinite lose more mass relative to the muscles buried in sand and undergo vertical collapse. These findings show that the composition of minerals that coat or precipitate within the tissues and the vertical dimension of the preserved features can depend on the type of sediment that buries the muscles. Similar processes in the zone of oscillating redox likely facilitated the formation of exceptionally preserved macrofossils in Ediacaran siliciclastic sediments

Experimental Preservation of Muscle Tissue in Quartz Sand and Kaolinite

Siliciclastic sediments of the Ediacaran Period contain exceptionally preserved fossils of macroscopic organisms, including three-dimensional casts and molds commonly found in sandstones and siltstones and some two-dimensional compressions reported in shales. The sporadic and variable associations of these exceptionally preserved macroscopic fossils with pyrite, clay minerals, and microbial fossils and textures complicate our understanding of fossilization processes. This hinders inferences about the evolutionary histories, tissue types, original morphologies, and lifestyles of the enigmatic Ediacara biota. Here, we investigate the delayed decay of scallop muscles buried in quartz sand or kaolinite for 45 days. This process occurs in the presence of microbial activity in mixed redox environments, but in the absence of thick, sealing microbial mats. Microbial processes that mediate organic decay and release the highest concentrations of silica and Fe(II) into the pore fluids are associated with the most extensive tissue decay. Delayed decay and the preservation of thick muscles in sand are associated with less intense microbial iron reduction and the precipitation of iron oxides and iron sulfides that contain Fe(II) or Fe(III). In contrast, muscles buried in kaolinite are coated only by <10 μm-thick clay veneers composed of kaolinite grains and newly formed K- and Fe(II)-rich aluminosilicate phases. Muscles that undergo delayed decay in kaolinite lose more mass relative to the muscles buried in sand and undergo vertical collapse. These findings show that the composition of minerals that coat or precipitate within the tissues and the vertical dimension of the preserved features can depend on the type of sediment that buries the muscles. Similar processes in the zone of oscillating redox likely facilitated the formation of exceptionally preserved macrofossils in Ediacaran siliciclastic sediments

The black middle class: middle class Afro-Caribbeans: a racial fraction of the British middle class or a class fraction of a racial group

This research examines the relationship between 'race' and class in Britain. This is achieved by considering how these two concepts articulate in the overall structuring of class relationships in a society which is typified by the incorporatation of black labour into a majority white society, This relationship is examined through an investigation of those black workers who occupy a position in the objectively defined middle class. The basic theme underlying this research is that 'race, in the form of structural racism, plays a significant role at two levels. Firstly, it serves to structure the class position of black labour in Britain. Secondly, it serves to determine the type of race, class and political consciousness generated by black labour. The study was carried out in the London area. Occupation was used as an indicator of 'objective' class position when selecting respondents to be included in the two survey populations required for the research. A 'network' approach was used to actually locate the respondents. In-depth interviews were carried out with all the respondents. The study concludes that the concepts of 'race' and class are not independent of each other in the overall structuring of class relationships between black and white labour. It is argued that the inter-relationship identified between these two concepts serves to highlight the fact that the structural position of black labour, the type of consciousness generated and the type of decisions taken by those who took part in the research are to a large extent a result of the structural constraints deriving from the effects of structural racism in Britain

Experimental Preservation of Muscle Tissue in Quartz Sand and Kaolinite

Siliciclastic sediments of the Ediacaran Period contain exceptionally preserved fossils of macroscopic organisms, including three-dimensional casts and molds commonly found in sandstones and siltstones and some two-dimensional compressions reported in shales. The sporadic and variable associations of these exceptionally preserved macroscopic fossils with pyrite, clay minerals, and microbial fossils and textures complicate our understanding of fossilization processes. This hinders inferences about the evolutionary histories, tissue types, original morphologies, and lifestyles of the enigmatic Ediacara biota. Here, we investigate the delayed decay of scallop muscles buried in quartz sand or kaolinite for 45 days. This process occurs in the presence of microbial activity in mixed redox environments, but in the absence of thick, sealing microbial mats. Microbial processes that mediate organic decay and release the highest concentrations of silica and Fe(II) into the pore fluids are associated with the most extensive tissue decay. Delayed decay and the preservation of thick muscles in sand are associated with less intense microbial iron reduction and the precipitation of iron oxides and iron sulfides that contain Fe(II) or Fe(III). In contrast, muscles buried in kaolinite are coated only by &lt;10 μm-thick clay veneers composed of kaolinite grains and newly formed K- and Fe(II)-rich aluminosilicate phases. Muscles that undergo delayed decay in kaolinite lose more mass relative to the muscles buried in sand and undergo vertical collapse. These findings show that the composition of minerals that coat or precipitate within the tissues and the vertical dimension of the preserved features can depend on the type of sediment that buries the muscles. Similar processes in the zone of oscillating redox likely facilitated the formation of exceptionally preserved macrofossils in Ediacaran siliciclastic sediments.NASA Astrobiology Institute (Grant NNA13AA90A)Simons Foundation (Grants 327126 and 344707)American Chemical Society (Award 54498-ND8

Three asymptomatic animal infection models of hemorrhagic fever with renal syndrome caused by hantaviruses.

Hantaan virus (HTNV) and Puumala virus (PUUV) are rodent-borne hantaviruses that are the primary causes of hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia. The development of well characterized animal models of HTNV and PUUV infection is critical for the evaluation and the potential licensure of HFRS vaccines and therapeutics. In this study we present three animal models of HTNV infection (hamster, ferret and marmoset), and two animal models of PUUV infection (hamster, ferret). Infection of hamsters with a ~3 times the infectious dose 99% (ID99) of HTNV by the intramuscular and ~1 ID99 of HTNV by the intranasal route leads to a persistent asymptomatic infection, characterized by sporadic viremia and high levels of viral genome in the lung, brain and kidney. In contrast, infection of hamsters with ~2 ID99 of PUUV by the intramuscular or ~1 ID99 of PUUV by the intranasal route leads to seroconversion with no detectable viremia, and a transient detection of viral genome. Infection of ferrets with a high dose of either HTNV or PUUV by the intramuscular route leads to seroconversion and gradual weight loss, though kidney function remained unimpaired and serum viremia and viral dissemination to organs was not detected. In marmosets a 1,000 PFU HTNV intramuscular challenge led to robust seroconversion and neutralizing antibody production. Similarly to the ferret model of HTNV infection, no renal impairment, serum viremia or viral dissemination to organs was detected in marmosets. This is the first report of hantavirus infection in ferrets and marmosets

Neuropathogenesis of Zika Virus in a Highly Susceptible Immunocompetent Mouse Model after Antibody Blockade of Type I Interferon

<div><p>Animal models are needed to better understand the pathogenic mechanisms of Zika virus (ZIKV) and to evaluate candidate medical countermeasures. Adult mice infected with ZIKV develop a transient viremia, but do not demonstrate signs of morbidity or mortality. Mice deficient in type I or a combination of type I and type II interferon (IFN) responses are highly susceptible to ZIKV infection; however, the absence of a competent immune system limits their usefulness for studying medical countermeasures. Here we employ a murine model for ZIKV using wild-type C57BL/6 mice treated with an antibody to disrupt type I IFN signaling to study ZIKV pathogenesis. We observed 40% mortality in antibody treated mice exposed to ZIKV subcutaneously whereas mice exposed by intraperitoneal inoculation were highly susceptible incurring 100% mortality. Mice infected by both exposure routes experienced weight loss, high viremia, and severe neuropathologic changes. The most significant histopathological findings occurred in the central nervous system where lesions represent an acute to subacute encephalitis/encephalomyelitis that is characterized by neuronal death, astrogliosis, microgliosis, scattered necrotic cellular debris, and inflammatory cell infiltrates. This model of ZIKV pathogenesis will be valuable for evaluating medical countermeasures and the pathogenic mechanisms of ZIKV because it allows immune responses to be elicited in immunologically competent mice with IFN I blockade only induced at the time of infection.</p></div

Viral titers of ZIKV in Wild-type Mice Treated with an IFNAR1-Blocking MAb.

<p>Five week old wild-type mice were treated with an IFNAR1-blocking MAb or PBS by intraperitoneal (IP) injection and then exposed to 6 log₁₀ of ZIKV strain DAK AR D 41525 subcutaneously (SC) or IP. When mice succumbed or were euthanized, tissues were collected, weighed, homogenized, and analyzed by qRT-PCR. Data are shown as PFU equivalents (PFUe) per gram (g) after normalization to a standard curve. Symbols represent the individual mice, the line represents the geometric mean, and the error bars represent the 95% confidence interval.</p

Wild-type Mice Treated with an IFNAR1-Blocking MAb are Susceptible to ZIKV.

<p>Five week old wild-type mice were treated with an IFNAR1-blocking MAb or PBS by intraperitoneal (IP) injection and then exposed to 6 log₁₀ of ZIKV strain DAK AR D 41525 subcutaneously (SC) or IP. Mice were monitored for survival (A) and weight loss shown as percent change in baseline prior to infection (B). ZIKV RNA in serum was determined on day 4 post-infection (PI) (C) and when the mice were euthanized (D) by qRT-PCR. Data are shown as PFU equivalents (PFUe) per milliliter after normalization to a standard curve. Symbols represent the individual mice, the line represents the geometric mean, and the error bars represent the 95% confidence interval. The dotted line represents the assay limit of detection. Statistically significant differences are denoted by an asterisk (*p < 0.05; *p < 0.0001).</p