Three-dimensional visualization as a tool for interpreting locomotion strategies in ophiuroids from the Devonian Hunsrück Slate.

Living brittle stars (Echinodermata: Ophiuroidea) employ a very different locomotion strategy to that of any other metazoan: five or more arms coordinate powerful strides for rapid movement across the ocean floor. This mode of locomotion is reliant on the unique morphology and arrangement of multifaceted skeletal elements and associated muscles and other soft tissues. The skeleton of many Palaeozoic ophiuroids differs markedly from that in living forms, making it difficult to infer their mode of locomotion and, therefore, to resolve the evolutionary history of locomotion in the group. Here, we present three-dimensional digital renderings of specimens of six ophiuroid taxa from the Lower Devonian Hunsrück Slate: four displaying the arm structure typical of Palaeozoic taxa (Encrinaster roemeri, Euzonosoma tischbeinianum, Loriolaster mirabilis, Cheiropteraster giganteus) and two (Furcaster palaeozoicus, Ophiurina lymani) with morphologies more similar to those in living forms. The use of three-dimensional digital visualization allows the structure of the arms of specimens of these taxa to be visualized in situ in the round, to our knowledge for the first time. The lack of joint interfaces necessary for musculoskeletally-driven locomotion supports the interpretation that taxa with offset ambulacrals would not be able to conduct this form of locomotion, and probably used podial walking. This approach promises new insights into the phylogeny, functional morphology and ecological role of Palaeozoic brittle stars.

A Field Guide to Finding Fossils on Mars.

The Martian surface is cold, dry, exposed to biologically harmful radiation and apparently barren today. Nevertheless, there is clear geological evidence for warmer, wetter intervals in the past that could have supported life at or near the surface. This evidence has motivated National Aeronautics and Space Administration and European Space Agency to prioritize the search for any remains or traces of organisms from early Mars in forthcoming missions. Informed by (1) stratigraphic, mineralogical and geochemical data collected by previous and current missions, (2) Earth's fossil record, and (3) experimental studies of organic decay and preservation, we here consider whether, how, and where fossils and isotopic biosignatures could have been preserved in the depositional environments and mineralizing media thought to have been present in habitable settings on early Mars. We conclude that Noachian-Hesperian Fe-bearing clay-rich fluvio-lacustrine siliciclastic deposits, especially where enriched in silica, currently represent the most promising and best understood astropaleontological targets. Siliceous sinters would also be an excellent target, but their presence on Mars awaits confirmation. More work is needed to improve our understanding of fossil preservation in the context of other environments specific to Mars, particularly within evaporative salts and pore/fracture-filling subsurface minerals.

A soft-bodied lophophorate from the Silurian of England.

Soft-bodied taxa comprise an important component of the extant lophophorate fauna, but convincing fossils of soft-bodied lophophorates are extremely rare. A small fossil lophophorate, attached to a brachiopod dorsal valve, is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of England. This unmineralized organism was bilaterally symmetrical and comprised a subconical body attached basally to the host and partially enclosed by a broad 'hood'; the body bore a small, coiled lophophore. Where the hood attached laterally, there is a series of transverse ridges and furrows. The affinities of this organism probably lie with Brachiopoda; the hood is interpreted as the homologue of a dorsal valve/mantle lobe, and the attachment as the homologue of the ventral valve and/or pedicle. The ridges are arranged in a manner that suggests constructional serial repetition, indicating that they are unlikely to represent mantle canals. Extant brachiopods are not serially structured, but morphological and molecular evidence suggests that their ancestors were. The new organism may belong to the brachiopod stem group, and might also represent a significant element of the Palaeozoic lophophorate fauna.

Fossilized soft tissues in a Silurian platyceratid gastropod.

Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknown, and have not been reported previously from the Palaeozoic. Here, we describe a Silurian (approx. 425 Myr) platyceratid gastropod from the Herefordshire Lagerstätte that preserves the oldest soft tissues yet reported from an undoubted crown-group mollusc. The digestive system is preserved in detail, and morphological data on the gonads, digestive gland, pedal muscle, radula, mouth and foot are also available. The specimen is preserved three-dimensionally, and has been reconstructed digitally following serial grinding. Platyceratids are often found attached to echinoderms, and have been interpreted as either commensal coprophages or kleptoparasites. The new data provide support for an attached mode of life, and are suggestive of a coprophagous feeding strategy. The affinities of the platyceratids are uncertain; they have been compared to both the patellogastropods and the neritopsines. Analysis of the new material suggests that a patellogastropod affinity is the more plausible of these hypotheses.

A starfish with three-dimensionally preserved soft parts from the Silurian of England.

Palaeozoic asteroids represent a stem-group to the monophyletic post-Palaeozoic Neoasteroidea, but many aspects of their anatomy are poorly known. Using serial grinding and computer reconstruction, we describe fully articulated Silurian (ca 425 Myr) specimens from the Herefordshire Lagerstätte, preserved in three dimensions complete with soft tissues. The material belongs to a species of Bdellacoma, a genus previously assigned to the ophiuroids, but has characters that suggest an asteroid affinity. These include a pyloric system in the gut, and the presence of large bivalved pedicellariae, the latter originally described under the name Bursulella from isolated valves. Ampullae are external and occur within podial basins; the radial canal is also external. Podia are elongate and lack terminal suckers. The peristome is large relative to the mouth. Aspects of the morphology are comparable to that of the extant Paxillosida, supporting phylogenetic schemes that place this order at the base of the asteroid crown group.

A three-dimensionally preserved fossil polychaete worm from the Silurian of Herefordshire, England.

Polychaete body fossils are rare, and are almost invariably compressed and too poorly preserved for meaningful comparison with extant forms. We here describe Kenostrychus clementsi gen. et sp. nov. from the Silurian Herefordshire Konservat-Lagerstätte of England, in which three-dimensional external morphology is preserved with a fidelity unprecedented among fossil polychaetes. The fossils, which are preserved in calcite, were serially ground and photographed at 30 microm intervals to produce computer-generated reconstructions of the original external surface. The new genus has a generalized polychaete morphology with large biramous parapodia, unspecialized anterior segments and a small prostomium with median and lateral antennae and ventral prostomial palps. Cirriform branchiae arise from the ventral surface of each notopodium, and may be homologous with the inter-ramal branchiae of the extant nephtyids. Through cladistic analysis, Kenostrychus is interpreted as a member of a stem group of either the Phyllodocida or the Aciculata (Phyllodocida + Eunicida). Direct comparison with other fossil forms is difficult, but hints that inter-ramal respiratory structures may be primitive within the Phyllodocida and/or the Aciculata.

Should mild or moderate stroke patients be admitted to an intensive care unit?

BACKGROUND AND PURPOSE: Inhospital placement of patients with mild (National Institutes of Health Stroke Scale [NIHSS] score <8) or moderate (NIHSS 8 through 16) acute strokes is variable. We assessed the outcome of such patients based on intensive care unit (ICU) versus general ward placement. METHODS: We reviewed 138 consecutive patients admitted within 24 hours of stroke onset to 2 physically adjacent hospitals with different admitting practices. Outcome measures included complication rates, discharge Rankin scale score, hospital discharge placement, costs, and length of stay (LOS). RESULTS: Hospital A, a 626-bed university-affiliated hospital, admitted 43% of mild and moderate strokes (MMS) to an ICU (26% of mild, 74% of moderate), whereas hospital B, a 618-bed community facility, admitted 18% of MMS to an ICU (3% of mild, 45% of moderate; P<0.004). There were no significant differences in outcomes between the 2 hospitals. Analysis of only patients admitted to hospital A, and of all patients, demonstrated that mild stroke patients admitted to the general ward had fewer complications and more favorable discharge Rankin scale scores than similar patients admitted to an ICU. There was no statistically significant difference in LOS, but total room costs for a patient admitted first to the ICU averaged $15 270 versus $3638 for admission directly to the ward. CONCLUSIONS: While limited by the retrospective nature of our study, routinely admitting acute MMS patients to an ICU provides no cost or outcomes benefits.

An exceptionally preserved vermiform mollusc from the Silurian of England.

Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding their nearest relatives, phylogeny and ancestral characters. The Polyplacophora (chitons) and the Aplacophora are widely interpreted as the most primitive extant molluscs, but Lower Palaeozoic fossils of the former lack soft parts, and the latter were hitherto unrecognized as fossils. The Herefordshire Lagerstätte is a Silurian (about 425 Myr bp) deposit that preserves a marine biota in remarkable three-dimensional detail. The external surface of even non-biomineralized cuticle was preserved by entombment in volcanic ash, subsequent incorporation into concretions, and infilling of the fossils with sparry calcite. Here we describe, from this deposit, a complete vermiform mollusc, which we interpret as a plated aplacophoran. Serial grinding at intervals of tens of micrometres, combined with computer-based reconstruction methods, renders the fossils in the round.

A new arthropod from the Silurian Konservat-Lagerstätte of Herefordshire, UK.

A small, non-biomineralized, macrophagous arthropod with chelicerate affinities, Offacolus kingi gen. et sp. nov., from the Silurian (Wenlock Series) of Herefordshire, UK, is described. The dorsal exoskeleton comprises an arch-like cephalic shield, a thorax of three free tergites and a triangular posterior tagma of five fused tergites, the last with a stout postero-dorsally directed medial spine. Seven pairs of appendages beneath the cephalic shield surround a postero-medially sited oral cavity on the ventral surface of the head. Appendages I and, probably II are uniramous and project antero-ventrally; I was sensory and II sensory and/or ambulatory. Appendages III-VI are biramous, each with an antero-ventrally projecting ramus and a robust, highly geniculate, horizontally oriented ramus that projects through an anterior gape. The former rami were ambulatory and the latter have spinose terminal podomeres and functioned as a unit for trapping food and transferring it towards the oral cavity. Appendage VII, which is probably uniramous, is posteroventrally directed and flap like. Each tergite of the thorax and posterior tagma covers at least a pair (probably two pairs) of probably biramous appendages with each ramus flap like and setose.

Assessment of bog-body tissue preservation by pyrolysis-gas chromatography/mass spectrometry.

Flash pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) was used to assess the quality and mechanism of protein preservation in the tissue of Iron Age bog bodies from Lindow, UK, and south-eastern Drenthe, The Netherlands. Abundant pyrolysis products of the fresh skin tissue, including 2,5-diketopiperazines of Pro-Gly, Pro-Ala, Pro-Val, Pro-Pro and Hyp, were readily assigned to specific amino acid or dipeptide moieties. Comparison of the pyrolysates of the bog-body tissues with that of modern samples revealed qualitative similarities suggesting good preservation of the collagen and non-collagenous proteins in the ancient tissues. Examination of the pyrolysates of samples of fresh calf skin, which had been treated with various vegetable tanning agents, clearly revealed markers of non-hydrolysable tannins including 1,2-benzenediol, 1,3-benzenediol and 1,2,3-benzenetriol, although chromatographic quality inevitably diminished with increasing functionalization of the compounds. Such markers were not detected in the pyrolysates of the bog-body tissues. Instead 4-isopropenylphenol, a characteristic pyrolysis product of Sphagnum moss, was detected in both solvent-extracted and base-treated samples of tissue. The presence of 4-isopropenylphenol in the pyrolysates of the bog-body tissues provides evidence that their preservation involves reactions of amino acids with sphagnum acid, and possibly other agents derived from the peat. The study constitutes the first chemical characterization of the pyrolysis products of modern and ancient collagen.

Technetium-99m-MAG3 renal studies in spinal cord injury patients: normal range, reproducibility, and change as a function of duration and level of injury.

UNLABELLED: The normal range, reproducibility, and change as a function of duration and level of injury for Tc-99m-MAG3 renal studies were quantitated in spinal cord injury (SCI) patients. METHODS: Five SCI patients without evidence of renal disease in each of four groups: less than 2 months, 2-12 months, 1-2 years, and greater than 2 years from time of injury, were each studied twice. There were at least two patients with paraplegia and two with tetraplegia in each group. Renal clearance (camera based method), percent function in each kidney, time of peak renal parenchymal activity, and half time of parenchymal activity following the peak were evaluated. The peak and half times were determined with regions of interest (ROIs) over the entire kidney and over just the cortex. All results were compared to normal ranges previously established in normal subjects of the same age range using the same methodology. RESULTS: Renal clearance in the less than 2 month SCI patients was not significantly different from normal subjects in either paraplegic or in tetraplegic individuals. However, clearance in tetraplegics was increased by 28.5% at 2-12 month, increased by 50.6% at 1-2 years, and decreased by 25.9% at greater than 2 years compared to normal subjects (all P < 0.02). Clearance in those with paraplegia showed a similar, but less marked, trend (P = NS). The time of peak parenchymal activity when measured with cortical ROIs did not vary among patient groups or level of injury, but was increased compared to normal subjects (P < 0.05). The percent function in each kidney and half time following the peak were symmetrical, did not differ among patient groups or with level of injury, and did not differ from normal subjects. The parenchymal peak time was significantly shorter with cortical rather than renal ROIs in all patient groups (P < 0.05). In serial studies in the same patient the percent standard deviation in total renal clearance was less than between single studies in different patients, but the decrease was significant for only the right kidney (P < 0.03), and the decrease was not as great as in normal subjects. In addition, the percent standard deviation for percent function in each kidney was significantly less than the percent standard deviations in single studies (P < 0.02). There were no significant differences between intra- and interpatient studies for any other parameter. CONCLUSION: We conclude that: (1) renal clearance measured with Tc-99m-MAG3 in tetraplegic patients increases significantly during the first 2 years following injury and decreases significantly thereafter; there is a similar, but much less marked, trend in paraplegics, (2) parenchymal peak times with cortical ROIs occur later for SCI patients than for normal subjects, and (3) there is more intrapatient variation in total renal clearance and percent renal clearance on a side in SCI patients than in normal subjects suggesting that it may be harder to study SCI patients reproducibly. These findings should be taken into account when performing and interpreting Tc-99m-MAG3 renal studies in SCI patients.

Recognition of chitin and proteins in invertebrate cuticles using analytical pyrolysis/gas chromatography and pyrolysis/gas chromatography/mass spectrometry.

Flash pyrolysis/gas chromatography (py/GC) and py/GC/mass spectrometry (MS) have been utilized to characterize the cuticles of invertebrates chemically. Pyrolysis products have been identified and assigned to specific cuticular components. Acetylpyridones, acetamidofuran, 3-acetamido-5-methylfuran and 3-acetamido-(2 and 4)-pyrones are proposed as characteristic pyrolysis markers for chitin. Pyrolysis products displaying ions of m/z 70, 154, 168, 194 are thought to derive from diketopiperazine structures and provide potential markers for proteins and peptides in which proline, alanine, valine, arginine and glycine are the dominant amino acids. These products, constituting specific pyrolysis markers for invertebrate cuticles, may reflect the amino acid composition of their constituent structural proteins. The source of the various pyrolysis products of proteins has been verified by pyrolysis of reference proteins, peptides and amino acid mixtures. The presence of additional pyrolysis products related directly to histidine and catechol moieties is consistent with the chemical structure and composition proposed for arthropod cuticles based on recent work utilizing solid state 13C and 15N nuclear magnetic resonance. This study constitutes the first comprehensive chemical characterization of the pyrolysis products of invertebrate cuticles and provides the basis for future investigations requiring qualitative screening for cross-linked chitin and proteins in modern and fossil cuticles and in materials, e.g. geopolymers, that may be derived from them.

Technetium-99m-MAG3 renal studies: normal range and reproducibility of physiologic parameters as a function of age and sex.

UNLABELLED: The normal range and reproducibility of common physiologic parameters for 99mTc-MAG3 renal studies were quantitated in normal subjects. METHODS: Six females and six males in each of three age groups, 21-40, 41-60 and 61-80 yr, were each studied twice. Renal clearance (camera based method), percent function in each kidney, time of peak renal parenchymal activity and half time of parenchymal activity following the peak were evaluated. The peak and half times were determined with regions of interest (ROIs) over the entire kidney and over the cortex only. RESULTS: There were no significant differences between sexes for any parameter. The only significant difference among age groups was a decrease in renal clearance, normalized for body surface area, with increasing age (p < 0.01). The percent function in each kidney, time of peak parenchymal activity and half time following the peak were symmetrical and did not vary with age or sex. The peak times were always less with cortical ROIs (p < 0.05). In serial studies in the same subject the percent s.d. for clearance and percent function in each kidney was less than half of the percent s.d. in single studies, suggesting that at least one half of the error is due to intersubject variation (p < 0.05). CONCLUSIONS: We conclude that: (1) renal clearance decreases with age in normal subjects, (2) cortical ROIs are superior to renal ROIs in measuring peak parenchymal activity, and (3) variation in clearance and percent function per kidney in serial studies is approximately one half the variation in single studies.

Fossilization of soft tissue in the laboratory.

Some of the most remarkable fossils preserve cellular details of soft tissues. In many of these, the tissues have been replaced by calcium phosphate. This process has been assumed to require elevated concentrations of phosphate in sediment pore waters. In decay experiments modern shrimps became partially mineralized in amorphous calcium phosphate, preserving cellular details of muscle tissue, particularly in a system closed to oxygen. The source for the formation of calcium phosphate was the shrimp itself. Mineralization, which was accompanied by a drop in pH, commenced within 2 weeks and increased in extent for at least 4 to 8 weeks. This mechanism halts the normal loss of detail of soft-tissue morphology before fossilization. Similar closed conditions would prevail where organisms are rapidly overgrown by microbial mats.

Morphological disparity in the cambrian.

An analysis of the range of morphology among arthropods demonstrates that disparity among living arthropods is similar to that in Cambrian arthropods. The range of morphological design resulting from the Cambrian "explosion" has been overestimated, reflecting a tendency to separate as "problematic" taxa that cannot be accommodated in the classification on the basis of the living biota. Problematic taxa are largely an artifact of an inadequate taxonomy. Special evolutionary processes may not be necessary to explain the early radiation of the metazoans.

The early radiation and relationships of the major arthropod groups.

Cambrian arthropods are now well known, but there has been little agreement on how they contribute to an understanding of arthropod phylogeny. Fossils have either been lumped together as "trilobitomorphs" or, more recently, have been the subject of speculation invoking a multiple polyphyletic origin of arthropods. Cladistic analysis of characters of Cambrian and living representatives (excluding Uniramia) shows that trilobites and chelicerates are relatively advanced compared with "crustaceans," and there are doubts whether the latter constitute a national group. An undue emphasis on singular autapomorphies of problematic fossils has obscured these relationships in the past. "Trilobitomorphs" were simply an artificial taxon based on shared primitive characters. The arthropods that evolved during the Cambrian radiation show no more apparent morphological diversity than do the living groups. The evidence of wellpreserved problematica is critical to understanding the nature of this radiation and the affinities of the groups that remain today.

A silurian soft-bodied biota.

A new Silurian (Llandoverian) biota from Wisconsin with a significant soft-bodied and lightly sclerotized component is dominated by arthropods and worms. The fauna includes the earliest well-preserved xiphosure, a possible marine uniramian, three new arthropods of uncertain affinity, and possibly the first Paleozoic leech. This may be only the second locality to yield a conodont animal. Lack of a normal shelly fauna suggests an unusual environment. The discovery adds significantly to the few such exceptionally preserved faunas known from Lower Paleozoic rocks.