Precambrian animal life: Taphonomy of phosphatized metazoan embryos from southwest China

Phosphatized fossils from the Neoproterozoic Doushantuo Formation have provided valuable insight into the early evolution of metazoans, but the preservation of these spectacular fossils is not yet fully understood. This research begins to address this issue by performing a detailed specimen-based taphonomic analysis of the Doushantuo Formation phosphatized metazoan embryos. A total of 206 embryos in 65 thin sections from the Weng'an Phosphorite Member of the Doushantuo Formation were examined and their levels of pre-phosphatization decay estimated. The data produced from this examination reveal a strong taphonomic bias toward earlier (2-cell and 4-cell) cleavage stages, which tend to be well-preserved, and away from later (8-cell and 16-cell) cleavage stages, which tend to exhibit evidence for slight to intense levels of organic decay. In addition, the natural abundances of these embryos tend to decrease with advancement in cleavage stage, and no evidence of more advanced (beyond 16-cell) cleavage stages or eventual adult forms were found in this study. One possible explanation for this taphonomic bias toward early cleavage stages is that later cleavage stages and adult forms were more physically delicate, allowing them to be more easily damaged during burial and reworking, allowing for more rapid decay. The spectacular preservation of these embryos was probably aided by their likely internal enrichment in phosphate-rich yolk, which would have caused their internal dissolved phosphate levels to reach critical levels with only miniscule organic decay, thereby hastening phosphatization. If internal sources of phosphate did indeed play a role in the phosphatization of these embryos, it may explain their prolific abundance in these rocks compared to other phosphatized fossils as well as indicating that metazoans lacking such internal phosphate sources were likely much more difficult to preserve. The phosphatic fossils of the Doushantuo Formation, therefore, provide an indispensable, yet restricted, window into Neoproterozoic life and metazoan origins.     

Precambrian animal life: probable developmental and adult cnidarian forms from Southwest China

We have previously described the affinity of a pig sperm surface protein, P68, to mammalian zonae pellucidae (ZP). In this report, we identified P68 as arylsulfatase A (AS-A) based on the presence of P68 tryptic peptide sequences in the pig testis AS-A cDNA sequence. Our objective was to demonstrate the presence of AS-A on the sperm surface and to elucidate its role in ZP binding. Immunogold electron microscopy revealed the presence of AS-A on the sperm surface. Furthermore, live pig sperm and the extract of peripheral sperm plasma membrane proteins exhibited AS-A's desulfation activity. Significantly, the role of pig sperm surface AS-A in ZP binding was demonstrated by dose-dependent decreases of sperm-ZP binding upon sperm pretreatment with anti-AS-A IgG/Fab, and by the binding of Alexa-430-conjugated sperm surface AS-A to homologous ZP. ZP pretreatment with anti-pig-ZP3 antibody abolished AS-A binding, suggesting that ZP3, recognized as the pig sperm receptor, was AS-A's binding ligand. This was further confirmed by the ability of exogenous ZP3 to competitively inhibit AS-A-ZP binding. Similarly, purified ZP3alpha, a major sperm receptor component of ZP3, exhibited great inhibitory effect on AS-A-ZP binding. All of these results designated a new function of AS-A in gamete interaction.     

The evolution and distribution of life in the Precambrian eon-Global perspective and the Indian record

The discovery of Precambrian microfossils in 1954 opened a new vista of investigations in the field of evolution of life. Although the Precambrian encompasses 87% of the earth’s history, the pace of organismal evolution was quite slow. The life forms as categorised today in the three principal domains viz. the Bacteria, the Archaea and the Eucarya evolved during this period. In this paper, we review the advancements made in the Precambrian palaeontology and its contribution in understanding the evolution of life forms on earth. These studies have enriched the data base on the Precambrian life. Most of the direct evidence includes fossil prokaryotes, protists, advanced algal fossils, acritarchs, and the indirect evidence is represented by the stromatolites, trace fossils and geochemical fossils signatures. The Precambrian fossils are preserved in the form of compressions, impressions, and permineralized and biomineralized remains.     

The ethics of animal research: a UK perspective

The Nuffield Council on Bioethics, an independent body in the United Kingdom, has published a 2005 report titled The Ethics of Research Involving Animals. The Report, produced by a Working Party that represented a wide range of views, seeks to clarify the debate that surrounds this topic and aims to help people identify and analyze the relevant scientific and ethical issues. The Working Party considered the arguments surrounding whether animal research yields useful results, and recommends that its predictability and transferability should be evaluated more fully, particularly in controversial areas. Commonly encountered ethical questions and arguments were considered in order to understand what lies behind disagreement on the moral justification of animal research. Four possible ethical positions on animal research, which represent points on a continuum, are described. Despite the range of views that exist among members of the Working Party, the Report presents a "Consensus Statement" that identifies agreement on several important issues. Building on this statement, recommendations are made for improving the quality of the debate and promoting the 3Rs (refinement, reduction, and replacement).     

The development and diversification of Precambrian life

During the past decade, important strides have been made toward deciphering the paleobiology of the Precambrian Eon, the earliest seven-eighths of Earth history. This progress has accured chiefly from micropaleontological and organic geochemical studies of fine-grained, ancient cherts. Although understanding of the early biota—of its composition, diversity, paleocology and evolution—still remains far from adequate, three particularly significant generalizations have emerged: (i) Living systems were extant earlier than about 3000 m.y. ago; (ii) between about 3000 and 1000 m.y. ago, the Earth's biota was dominated by prokaryotic blue-green algae; and (iii) the development of the nucleated, eukaryotic cell type somewhat earlier than 1000 m.y. ago led to a stage of rapid diversification that culminated with the appearance of megascopic life near the close of the Precambrian. Consideration of these generalizations, and of the evidence bearing on them provides a ‘state-of-the-art’ assessment of the current status of Precambrian paleobiology.     

The animal enterprise protection act: a scientist's perspective

The Animal Enterprise Protection Act gives courts latitude in sentencing animal rights terrorists, but remains largely unused by prosecutors. The author, himself a victim of animal rights terrorism, comments on the Act's strengths and weaknesses, and challenges the lab animal community to unify in its response.     

The emergence of life on Earth

Combined top-down and bottom-up research strategies and the principle of biological continuity were employed in an attempt to reconstruct a comprehensive origin of life theory, which is an extension of the coevolution theory (Lahav and Nir, Origins of Life Evol. Biosphere (1997) 27, 377-395). The resulting theory of emergence of templated-information and functionality (ETIF) addresses the emergence of living entities from inanimate matter, and that of the central mechanisms of their further evolution. It proposes the emergence of short organic catalysts (peptides and proto-ribozymes) and feedback-loop systems, plus their template-and-sequence-directed (TSD) reactions, encompassing catalyzed replication and translation of populations of molecules organized as chemical-informational feedback loop entities, in a fluctuating (wetting-drying) environment, functioning as simplified extant molecular-biological systems. The feedback loops with their TSD systems are chemically and functionally continuous with extant living organisms and their emergence in an inanimate environment may be defined as the beginning of life. The ETIF theory considers the emergence of bio-homochirality, a primordial genetic code, information and the incorporation of primordial metabolic cycles and compartmentation into the emerging living entities. This theory helps to establish a novel measure of biological information, which focuses on its physical effects rather than on the structure of the message, and makes it possible to estimate the time needed for the transition from the inanimate state to the closure of the first feedback-loop systems. Moreover, it forms the basis for novel laboratory experiments and computer modeling, encompassing catalytic activity of short peptides and proto-RNAs and the emergence of bio-homochirality and feedback-loop systems.     

Companion animal parasitology: a clinical perspective

In recent years there have been many changes to the ways that clinical veterinary science is conducted and nowhere is this more evident than in companion animal practice. Veterinarians working with pet dogs and cats are facing new challenges associated with the emergence and re-emergence of parasitic diseases. Some, such as Neospora caninum, have been recently recognised; others like Giardia and Cryptosporidium have been reported with increasing frequency, in part as a result of laboratory tests with improved sensitivity and specificity. In many regions, the emergence of parasitic diseases has been a consequence of pet travel and exotic diseases pose a unique diagnostic challenge for the veterinarian, as the index of suspicion for these conditions may be absent. The ranges of certain vector-borne diseases such as babesiosis, hepatozoonosis, ehrlichiosis, leishmaniasis and dirofilariasis are extending due to ecological and climatic changes and enhanced by animals with subclinical infection returning home from endemic areas. In companion animal practice, veterinarians have the additional responsibility of providing accurate information about the zoonotic transmission of parasite infections from pets, especially to those most vulnerable such as children, the elderly and the immunocompromised. Effective education is vital to allay public concerns and promote responsible pet ownership.     

The value of juvenile animal studies: a Japanese industry perspective

Pharmaceuticals have been used on adults and children; however, they were previously investigated only by adult human clinical studies and adult animal nonclinical studies. The US FDA finalized the guidance of juvenile animal toxicity studies in 2006, and EMEA was finalized in 2008. At that point, juvenile animal toxicity studies were encouraged to investigate the safety of the pediatric population. In Japan, the awareness of the development of pediatric drugs is increasing, and many scientific meetings about juvenile animal studies are being held. A Japanese guideline for juvenile animal toxicity studies has been long awaited by many Japanese pharmaceutical companies because concrete directionality has not been available in Japan thus far. The Ministry of Health, Labour, and Welfare started to prepare the guideline for nonclinical safety studies in juvenile animals since October 2010. After completion of the Japanese guideline, guidelines would exist in the three regions: Japan, US, and Europe. Then, global development of pediatric pharmaceuticals would be accelerated effectively.     

The value of juvenile animal studies: a pediatric clinical perspective

With the emphasis of US American and European legislators on consideration of children in the drug development process regulatory authorities ask increasingly for additional non-clinical data to elucidate the safety of a given drug in development in future pediatric use. Juvenile animal studies are increasingly requested. These requests should never be tick box requests. Companies, academic toxicologists, clinicians, and regulatory authorities need a dialogue to differentiate between the perceived need to do "something" and the request for studies that have clinically meaningful results.     

The geobiological nitrogen cycle: From microbes to the mantle

Nitrogen forms an integral part of the main building blocks of life, including DNA, RNA, and proteins. N₂ is the dominant gas in Earth's atmosphere, and nitrogen is stored in all of Earth's geological reservoirs, including the crust, the mantle, and the core. As such, nitrogen geochemistry is fundamental to the evolution of planet Earth and the life it supports. Despite the importance of nitrogen in the Earth system, large gaps remain in our knowledge of how the surface and deep nitrogen cycles have evolved over geologic time. Here, we discuss the current understanding (or lack thereof) for how the unique interaction of biological innovation, geodynamics, and mantle petrology has acted to regulate Earth's nitrogen cycle over geologic timescales. In particular, we explore how temporal variations in the external (biosphere and atmosphere) and internal (crust and mantle) nitrogen cycles could have regulated atmospheric pN₂. We consider three potential scenarios for the evolution of the geobiological nitrogen cycle over Earth's history: two in which atmospheric pN₂ has changed unidirectionally (increased or decreased) over geologic time and one in which pN₂ could have taken a dramatic deflection following the Great Oxidation Event. It is impossible to discriminate between these scenarios with the currently available models and datasets. However, we are optimistic that this problem can be solved, following a sustained, open‐minded, and multidisciplinary effort between surface and deep Earth communities.     

The evolution of the early precambrian geobiological systems

Bacterial paleontology provides vast opportunities for the study of all types of sedimentary and volcanic-sedimentary rocks, at any stage of metamorphism and of any age. Bacteria are shown to play an important role in weathering, transfer, sedimentation, and diagenesis of the sediments and in the formation of many minerals that have previously been thought to be abiogenic.     

The earth and its life: Systems perspective

From the planetary point of view, the Earth can be imagined as a system comprised of interwined natural populations propagated through time via recycling. This recycling, or birth/death process, imposes age patterns on natural populations of the solid earth, hydrosphere, atmosphere and living entities. Mathematically, the concept is analogous to that of population dynamics in living systems. The populations of the Earth system form a hierarchical structure. The hierarchy of geological tectonic realms contains populations of 10²⁴–10²⁶ gr in size, with half-lives in the 10⁷–10⁹ yr time range. The approximate parameters for the oceans are 10²⁴ gr and 10²–10⁷ yr, for the atmosphere 10²¹ gr and 10^–2–10⁷ yr, and for living systems 10¹⁴–10¹⁹ gr and 10^–3–10² yr, respectively. In this perspective, and in departure from the GAIA hypothesis, the subordinate populations, such as those of living systems, are constrained to operate within limits imposed by the larger, and slower, hierarchies. They can overstep the imposed limits only on time scales shorter than the response time of the dominant populations. Isotopic record of past sea water shows that on time scales of 10⁷ yr the solid earth, hydrosphere, atmosphere and life act as a unified system controlled by tectonics, that is by the hierarchy of the solid earth.     

Laboratory animal allergy: a British perspective on a global problem

In the United Kingdom, laboratory animal allergy (LAA) has been recognized as an important occupational disease for nearly 25 years. However, introduction of health and safety legislation (e.g., the Control of Substances Hazardous to Health Regulations of 1988) and an increasing knowledge of the factors that contribute to the etiology of this disease have had surprisingly little impact on the prevalence and incidence of LAA over the last 10 to 20 yr. Studies of the relation between exposure to animal allergens and the development of LAA reveal that the risk of disease increases with increasing intensity of exposure. Current evidence suggests that animal allergens are very potent, and substantial decreases in allergen exposure are therefore necessary before a reduction in symptoms will be observed. In the United Kingdom, it is unlikely that an Occupational Exposure Limit will be set for animal allergens in the near future, partly because an adequately standardized assay for quantifying exposure is not yet available. Prevention of LAA in the future will probably be driven by the needs of the industry and will most likely rely on the adoption of guidelines describing " best practise" which incorporate sophisticated engineering methods of controlling exposure to animal allergens.