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β-Catenin is essential for patterning the maternally specified animal-vegetal axis in the sea urchin embryo

Wikramanayake, Athula H.; Huang, Ling; Klein, William H.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 04/08/1998 Português
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In sea urchin embryos, the animal-vegetal axis is specified during oogenesis. After fertilization, this axis is patterned to produce five distinct territories by the 60-cell stage. Territorial specification is thought to occur by a signal transduction cascade that is initiated by the large micromeres located at the vegetal pole. The molecular mechanisms that mediate the specification events along the animal–vegetal axis in sea urchin embryos are largely unknown. Nuclear β-catenin is seen in vegetal cells of the early embryo, suggesting that this protein plays a role in specifying vegetal cell fates. Here, we test this hypothesis and show that β-catenin is necessary for vegetal plate specification and is also sufficient for endoderm formation. In addition, we show that β-catenin has pronounced effects on animal blastomeres and is critical for specification of aboral ectoderm and for ectoderm patterning, presumably via a noncell-autonomous mechanism. These results support a model in which a Wnt-like signal released by vegetal cells patterns the early embryo along the animal–vegetal axis. Our results also reveal similarities between the sea urchin animal–vegetal axis and the vertebrate dorsal–ventral axis, suggesting that these axes share a common evolutionary origin.

Influence of drinking water and diet on the stable-hydrogen isotope ratios of animal tissues

Hobson, Keith A.; Atwell, Lisa; Wassenaar, Leonard I.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 06/07/1999 Português
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Despite considerable interest in using stable-hydrogen isotope ratio (δD) measurements in ecological research, it was previously unknown whether hydrogen derived from drinking water, in addition to that derived from diet, contributed to the nonexchangeable hydrogen in animal tissues. We raised four experimental groups of quail (Coturnix coturnix japonica) from hatch on two isotopically distinct diets (mean nonexchangeable δD: −146 and −60‰, Vienna Standard Mean Ocean Water Standard) and drinking waters (mean δD: −130 and +196‰, Vienna Standard Mean Ocean Water Standard). Here we show that both dietary and drinking water hydrogen are incorporated into nonexchangeable hydrogen in both metabolically active (i.e., muscle, liver, blood, fat) and inactive (i.e., feather, nail) tissues. Approximately 20% of hydrogen in metabolically active quail tissues and 26–32% of feathers and nail was derived from drinking water. Our findings suggest environmental interpretations of δD values from modern and fossil animal tissues may need to account for potentially large isotopic differences between drinking water and food and require a good understanding of the physiological ecology of study organisms.

Hepatocyte gene therapy in a large animal: A neonatal bovine model of citrullinemia

Lee, Brendan; Dennis, Julie A.; Healy, Peter J.; Mull, Benjamin; Pastore, Lucio; Yu, Hung; Aguilar-Cordova, Estuardo; O’Brien, William; Reeds, Peter; Beaudet, Arthur L.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 30/03/1999 Português
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The development of gene-replacement therapy for inborn errors of metabolism has been hindered by the limited number of suitable large-animal models of these diseases and by inadequate methods of assessing the efficacy of treatment. Such methods should provide sensitive detection of expression in vivo and should be unaffected by concurrent pharmacologic and dietary regimens. We present the results of studies in a neonatal bovine model of citrullinemia, an inborn error of urea-cycle metabolism characterized by deficiency of argininosuccinate synthetase and consequent life-threatening hyperammonemia. Measurements of the flux of nitrogen from orally administered 15NH4 to [15N]urea were used to determine urea-cycle activity in vivo. In control animals, these isotopic measurements proved to be unaffected by pharmacologic treatments. Systemic administration of a first-generation E1-deleted adenoviral vector expressing human argininosuccinate synthetase resulted in transduction of hepatocytes and partial correction of the enzyme defect. The isotopic method showed significant restoration of urea synthesis. Moreover, the calves showed clinical improvement and normalization of plasma glutamine levels after treatment. The results show the clinical efficacy of treating a large-animal model of an inborn error of hepatocyte metabolism in conjunction with a method for sensitively measuring correction in vivo. These studies will be applicable to human trials of the treatment of this disorder and other related urea-cycle disorders.

Abrogation of disease development in plants expressing animal antiapoptotic genes

Dickman, M. B.; Park, Y. K.; Oltersdorf, T.; Li, W.; Clemente, T.; French, R.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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An emerging topic in plant biology is whether plants display analogous elements of mammalian programmed cell death during development and defense against pathogen attack. In many plant–pathogen interactions, plant cell death occurs in both susceptible and resistant host responses. For example, specific recognition responses in plants trigger formation of the hypersensitive response and activation of host defense mechanisms, resulting in restriction of pathogen growth and disease development. Several studies indicate that cell death during hypersensitive response involves activation of a plant-encoded pathway for cell death. Many susceptible interactions also result in host cell death, although it is not clear how or if the host participates in this response. We have generated transgenic tobacco plants to express animal genes that negatively regulate apoptosis. Plants expressing human Bcl-2 and Bcl-xl, nematode CED-9, or baculovirus Op-IAP transgenes conferred heritable resistance to several necrotrophic fungal pathogens, suggesting that disease development required host–cell death pathways. In addition, the transgenic tobacco plants displayed resistance to a necrogenic virus. Transgenic tobacco harboring Bcl-xl with a loss-of-function mutation did not protect against pathogen challenge. We also show that discrete DNA fragmentation (laddering) occurred in susceptible tobacco during fungal infection...

Receptor-like kinases from Arabidopsis form a monophyletic gene family related to animal receptor kinases

Shiu, Shin-Han; Bleecker, Anthony B.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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Plant receptor-like kinases (RLKs) are proteins with a predicted signal sequence, single transmembrane region, and cytoplasmic kinase domain. Receptor-like kinases belong to a large gene family with at least 610 members that represent nearly 2.5% of Arabidopsis protein coding genes. We have categorized members of this family into subfamilies based on both the identity of the extracellular domains and the phylogenetic relationships between the kinase domains of subfamily members. Surprisingly, this structurally defined group of genes is monophyletic with respect to kinase domains when compared with the other eukaryotic kinase families. In an extended analysis, animal receptor kinases, Raf kinases, plant RLKs, and animal receptor tyrosine kinases form a well supported group sharing a common origin within the superfamily of serine/threonine/tyrosine kinases. Among animal kinase sequences, Drosophila Pelle and related cytoplasmic kinases fall within the plant RLK clade, which we now define as the RLK/Pelle family. A survey of expressed sequence tag records for land plants reveals that mosses, ferns, conifers, and flowering plants have similar percentages of expressed sequence tags representing RLK/Pelle homologs, suggesting that the size of this gene family may have been close to the present-day level before the diversification of land plant lineages. The distribution pattern of four RLK subfamilies on Arabidopsis chromosomes indicates that the expansion of this gene family is partly a consequence of duplication and reshuffling of the Arabidopsis genome and of the generation of tandem repeats.

Cost and conflict in animal signals and human language

Lachmann, Michael; Számadó, Szabolcs; Bergstrom, Carl T.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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The “costly signaling” hypothesis proposes that animal signals are kept honest by appropriate signal costs. We show that to the contrary, signal cost is unnecessary for honest signaling even when interests conflict. We illustrate this principle by constructing examples of cost-free signaling equilibria for the two paradigmatic signaling games of Grafen (1990) and Godfray (1991). Our findings may explain why some animal signals use cost to ensure honesty whereas others do not and suggest that empirical tests of the signaling hypothesis should focus not on equilibrium cost but, rather, on the cost of deviation from equilibrium. We use these results to apply costly signaling theory to the low-cost signals that make up human language. Recent game theoretic models have shown that several key features of language could plausibly arise and be maintained by natural selection when individuals have coincident interests. In real societies, however, individuals do not have fully coincident interests. We show that coincident interests are not a prerequisite for linguistic communication, and find that many of the results derived previously can be expected also under more realistic models of society.

Functional correction of established central nervous system deficits in an animal model of lysosomal storage disease with feline immunodeficiency virus-based vectors

Brooks, Andrew I.; Stein, Colleen S.; Hughes, Stephanie M.; Heth, Jason; McCray, Paul M.; Sauter, Sybille L.; Johnston, Julie C.; Cory-Slechta, Deborah A.; Federoff, Howard J.; Davidson, Beverly L.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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Gene transfer vectors based on lentiviruses can transduce terminally differentiated cells in the brain; however, their ability to reverse established behavioral deficits in animal models of neurodegeneration has not previously been tested. When recombinant feline immunodeficiency virus (FIV)-based vectors expressing β-glucuronidase were unilaterally injected into the striatum of adult β-glucuronidase deficient [mucopolysaccharidosis type VII (MPS VII)] mice, an animal model of lysosomal storage disease, there was bihemispheric correction of the characteristic cellular pathology. Moreover, after the injection of FIV-based vectors expressing β-glucuronidase into brains of β-glucuronidase-deficient mice with established impairments in spatial learning and memory, there was dramatic recovery of behavioral function. Cognitive improvement resulting from expression of β-glucuronidase was associated with alteration in expression of genes associated with neuronal plasticity. These data suggest that enzyme replacement to the MPS VII central nervous system goes beyond restoration of β-glucuronidase activity in the lysosome, and imparts improvements in plasticity and spatial learning.

Animal antibiotic use has an early but important impact on the emergence of antibiotic resistance in human commensal bacteria

Smith, David L.; Harris, Anthony D.; Johnson, Judith A.; Silbergeld, Ellen K.; Morris, J. Glenn
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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Antibiotic use is known to promote the development of antibiotic resistance, but substantial controversy exists about the impact of agricultural antibiotic use (AAU) on the subsequent emergence of antibiotic-resistant bacteria among humans. AAU for animal growth promotion or for treatment or control of animal diseases generates reservoirs of antibiotic-resistant (AR) bacteria that contaminate animal food products. Mathematical models are an important tool for understanding the potential medical consequences of this increased exposure. We have developed a mathematical model to evaluate factors affecting the prevalence of human commensal AR bacteria that cause opportunistic infections (e.g., enterococci). Our analysis suggests that AAU hastens the appearance of AR bacteria in humans. Our model indicates that the greatest impact occurs very early in the emergence of resistance, when AR bacteria are rare, possibly below the detection limits of current surveillance methods.

Large-scale comparison of intron positions among animal, plant, and fungal genes

Fedorov, Alexei; Merican, Amir Feisal; Gilbert, Walter
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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We purge large databases of animal, plant, and fungal intron-containing genes to a 20% similarity level and then identify the most similar animal–plant, animal–fungal, and plant–fungal protein pairs. We identify the introns in each BLAST 2.0 alignment and score matched intron positions and slid (near-matched, within six nucleotides) intron positions automatically. Overall we find that 10% of the animal introns match plant positions, and a further 7% are “slides.” Fifteen percent of fungal introns match animal positions, and 13% match plant positions. Furthermore, the number of alignments with high numbers of matches deviates greatly from the Poisson expectation. The 30 animal–plant alignments with the highest matches (for which 44% of animal introns match plant positions) when aligned with fungal genes are also highly enriched for triple matches: 39% of the fungal introns match both animal and plant positions. This is strong evidence for ancestral introns predating the animal–plant–fungal divergence, and in complete opposition to any expectations based on random insertion. In examining the slid introns, we show that at least half are caused by imperfections in the alignments, and are most likely to be actual matches at common positions. Thus...

Hexadecyloxypropyl-cidofovir, CMX001, prevents adenovirus-induced mortality in a permissive, immunosuppressed animal model

Toth, Karoly; Spencer, Jacqueline F.; Dhar, Debanjan; Sagartz, John E.; Buller, R. Mark L.; Painter, George R.; Wold, William S. M.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Adenoviruses (Ads) cause a wide array of end-organ and disseminated diseases in severely immunosuppressed patients. For example, ≈20% of pediatric allogeneic hematopoietic stem cell transplant recipients develop disseminated Ad infection, and the disease proves fatal in as many as 50–80% of these patients. Ad infections are a serious problem for solid-organ transplant recipients and AIDS patients as well. Unfortunately, there are no antiviral drugs approved specifically to treat these infections. A suitable animal model that is permissive for Ad replication would help in the discovery process. Here we identify an animal model to study Ad pathogenesis and the efficacy of antiviral compounds. We show that human serotype 5 Ad (Ad5) causes severe systemic disease in immunosuppressed Syrian hamsters that is similar to that seen in immunocompromised patients. We also demonstrate that hexadecyloxypropyl-cidofovir (CMX001) rescues the hamsters from a lethal challenge with Ad5. The antiviral drug provided protection both prophylactically and when given up to 2 days after i.v. exposure to Ad5. CMX001 acts by reducing Ad replication in key target organs. Thus, the immunosuppressed Syrian hamster is a powerful model to evaluate anti-Ad drugs...

Structure-based discovery and description of plant and animal Helitrons

Yang, Lixing; Bennetzen, Jeffrey L.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Helitrons are recently discovered eukaryotic transposons that are predicted to amplify by a rolling-circle mechanism. They are present in most plant and animal species investigated, but were previously overlooked partly because they lack terminal repeats and do not create target site duplications. Helitrons are particularly abundant in flowering plants, where they frequently acquire, and sometimes express, 1 or more gene fragments. A structure-based search protocol was developed to find Helitrons and was used to analyze several plant and animal genomes, leading to the discovery of hundreds of new Helitrons. Analysis of these Helitrons has uncovered mechanisms of element evolution, including end creation and sequence acquisition. Preferential accumulation in gene-poor regions and target site specificities were also identified. Overall, these studies provide insights into the transposition and evolution of Helitrons and their contributions to evolved gene content and genome structure.

Hydrodynamic gene delivery of baboon trypanosome lytic factor eliminates both animal and human-infective African trypanosomes

Thomson, Russell; Molina-Portela, Pilar; Mott, Helen; Carrington, Mark; Raper, Jayne
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Several species of African trypanosomes cause fatal disease in livestock, but most cannot infect humans due to innate trypanosome lytic factors (TLFs). Human TLFs are pore forming high-density lipoprotein (HDL) particles that contain apolipoprotein L-I (apoL-I) the trypanolytic component, and haptoglobin-related protein (Hpr), which binds free hemoglobin (Hb) in blood and facilitates the uptake of TLF via a trypanosome haptoglobin-hemoglobin receptor. The human-infective Trypanosoma brucei rhodesiense escapes lysis by TLF by expression of serum resistance-associated (SRA) protein, which binds and neutralizes apoL-I. Unlike humans, baboons are not susceptible to infection by T. b. rhodesiense due to previously unidentified serum factors. Here, we show that baboons have a TLF complex that contains orthologs of Hpr and apoL-I and that full-length baboon apoL-I confers trypanolytic activity to mice and when expressed together with baboon Hpr and human apoA-I, provides protection against both animal infective and the human-infective T. brucei rhodesiense in vivo. We further define two critical lysines near the C terminus of baboon apoL-1 that are necessary and sufficient to prevent binding to SRA and thereby confer resistance to human-infective trypanosomes. These findings form the basis for the creation of TLF transgenic livestock that would be resistant to animal and human-infective trypanosomes...

Chimpanzees as an animal model for human norovirus infection and vaccine development

Bok, Karin; Parra, Gabriel I.; Mitra, Tanaji; Abente, Eugenio; Shaver, Charlene K.; Boon, Denali; Engle, Ronald; Yu, Claro; Kapikian, Albert Z.; Sosnovtsev, Stanislav V.; Purcell, Robert H.; Green, Kim Y.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Noroviruses are global agents of acute gastroenteritis, but the development of control strategies has been hampered by the absence of a robust animal model. Studies in chimpanzees have played a key role in the characterization of several fastidious hepatitis viruses, and we investigated the feasibility of such studies for the noroviruses. Seronegative chimpanzees inoculated i.v. with the human norovirus strain Norwalk virus (NV) did not show clinical signs of gastroenteritis, but the onset and duration of virus shedding in stool and serum antibody responses were similar to that observed in humans. NV RNA was detected in intestinal and liver biopsies concurrent with the detection of viral shedding in stool, and NV antigen expression was observed in cells of the small intestinal lamina propria. Two infected chimpanzees rechallenged 4, 10, or 24 mo later with NV were resistant to reinfection, and the presence of NV-specific serum antibodies correlated with protection. We evaluated the immunogenicity and efficacy of virus-like particles (VLPs) derived from NV (genogroup I, GI) and MD145 (genogroup II, GII) noroviruses as vaccines. Chimpanzees vaccinated intramuscularly with GI VLPs were protected from NV infection when challenged 2 and 18 mo after vaccination...

Superoxide dismutase is dispensable for normal animal lifespan

Van Raamsdonk, Jeremy Michael; Hekimi, Siegfried
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Reactive oxygen species (ROS) are toxic oxygen-containing molecules that can damage multiple components of the cell and have been proposed to be the primary cause of aging. The antioxidant enzyme superoxide dismutase (SOD) is the only eukaryotic enzyme capable of detoxifying superoxide, one type of ROS. The fact that SOD is present in all aerobic organisms raises the question as to whether SOD is absolutely required for animal life and whether the loss of SOD activity will result in decreased lifespan. Here we use the genetic model organism Caenorhabditis elegans to generate an animal that completely lacks SOD activity (sod-12345 worms). We show that sod-12345 worms are viable and exhibit a normal lifespan, despite markedly increased sensitivity to multiple stresses. This is in stark contrast to what is observed in other genetic model organisms where the loss of a single sod gene can result in severely decreased survival. Investigating the mechanism underlying the normal lifespan of sod-12345 worms reveals that their longevity results from a balance between the prosurvival signaling and the toxicity of superoxide. Overall, our results demonstrate that SOD activity is dispensable for normal animal lifespan but is required to survive acute stresses. Moreover...

A small animal Raman instrument for rapid, wide-area, spectroscopic imaging

Bohndiek, Sarah E.; Wagadarikar, Ashwin; Zavaleta, Cristina L.; Van de Sompel, Dominique; Garai, Ellis; Jokerst, Jesse V.; Yazdanfar, Siavash; Gambhir, Sanjiv S.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Raman spectroscopy, amplified by surface enhanced Raman scattering (SERS) nanoparticles, is a molecular imaging modality with ultra-high sensitivity and the unique ability to multiplex readouts from different molecular targets using a single wavelength of excitation. This approach holds exciting prospects for a range of applications in medicine, including identification and characterization of malignancy during endoscopy and intraoperative image guidance of surgical resection. The development of Raman molecular imaging with SERS nanoparticles is presently limited by long acquisition times, poor spatial resolution, small field of view, and difficulty in animal handling with existing Raman spectroscopy instruments. Our goal is to overcome these limitations by designing a bespoke instrument for Raman molecular imaging in small animals. Here, we present a unique and dedicated small-animal Raman imaging instrument that enables rapid, high-spatial resolution, spectroscopic imaging over a wide field of view (> 6 cm2), with simplified animal handling. Imaging of SERS nanoparticles in small animals demonstrated that this small animal Raman imaging system can detect multiplexed SERS signals in both superficial and deep tissue locations at least an order of magnitude faster than existing systems without compromising sensitivity.

Correlating preclinical animal studies and human clinical trials of a multifunctional, polymeric nanoparticle

Eliasof, Scott; Lazarus, Douglas; Peters, Christian G.; Case, Roy I.; Cole, Roderic O.; Hwang, Jungyeon; Schluep, Thomas; Chao, Joseph; Lin, James; Yen, Yun; Han, Han; Wiley, Devin T.; Zuckerman, Jonathan E.; Davis, Mark E.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Nanoparticles are currently being investigated in a number of human clinical trials. As information on how nanoparticles function in humans is difficult to obtain, animal studies that can be correlative to human behavior are needed to provide guidance for human clinical trials. Here, we report correlative studies on animals and humans for CRLX101, a 20- to 30-nm-diameter, multifunctional, polymeric nanoparticle containing camptothecin (CPT). CRLX101 is currently in phase 2 clinical trials, and human data from several of the clinical investigations are compared with results from multispecies animal studies. The pharmacokinetics of polymer-conjugated CPT (indicative of the CRLX101 nanoparticles) in mice, rats, dogs, and humans reveal that the area under the curve scales linearly with milligrams of CPT per square meter for all species. Plasma concentrations of unconjugated CPT released from CRLX101 in animals and humans are consistent with each other after accounting for differences in serum albumin binding of CPT. Urinary excretion of polymer-conjugated CPT occurs primarily within the initial 24 h after dosing in animals and humans. The urinary excretion dynamics of polymer-conjugated and unconjugated CPT appear similar between animals and humans. CRLX101 accumulates into solid tumors and releases CPT over a period of several days to give inhibition of its target in animal xenograft models of cancer and in the tumors of humans. Taken in total...

Animal personality aligns task specialization and task proficiency in a spider society

Wright, Colin M.; Holbrook, C. Tate; Pruitt, Jonathan N.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Here we demonstrate strong links among task specialization, task proficiency, and animal personality in a nonpolymorphic spider, reminiscent of the associations observed among task specialization, task aptitude, and castes in the social insects. Such links previously have been demonstrated only for single tasks, and some studies failed to find any links whatsoever. In contrast, the present study demonstrates such links in four different tasks important for proper colony function. Unlike morphological castes, individual differences in personality have been detected in almost every animal system imaginable. Thus, we argue that the classic canon of theories and predictions developed in the context of castes could be adaptively retrofitted and redeployed in the personality literature to a much broader swath of animal diversity.

An animal-to-human scaling law for blast-induced traumatic brain injury risk assessment

Jean, Aurélie; Nyein, Michelle K.; Zheng, James Q.; Moore, David F.; Joannopoulos, John D.; Radovitzky, Raúl
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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A physics-based animal-to-human scaling law for the effects of a blast wave on brain tissue is proposed. This scaling law, or transfer function, enables the translation of animal-based assessments of injury to the human, thus effectively enabling the derivation of human injury criteria based on animal tests. This is critical both in the diagnosis of traumatic brain injury as well as in the design of blast-protective helmets.

Animals in a Bacterial World, A New Imperative for the Life Sciences

McFall-Ngai, M.; Hadfield, M. G.; Bosch, T. C. G.; Carey, H. V.; Domazet-Loso, T.; Douglas, A. E.; Dubilier, N.; Eberl, G.; Fukami, T.; Gilbert, S. F.; Hentschel, U.; King, N.; Kjelleberg, S.; Knoll, Andrew Herbert; Kremer, N.; Mazmanian, S. K.; Metcalf,
Fonte: Proceedings of the National Academy of Sciences Publicador: Proceedings of the National Academy of Sciences
Tipo: Artigo de Revista Científica
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In the last two decades, the widespread application of genetic and genomic approaches has revealed a bacterial world astonishing in its ubiquity and diversity. This review examines how a growing knowledge of the vast range of animal–bacterial interactions, whether in shared ecosystems or intimate symbioses, is fundamentally altering our understanding of animal biology. Specifically, we highlight recent technological and intellectual advances that have changed our thinking about five questions: how have bacteria facilitated the origin and evolution of animals; how do animals and bacteria affect each other’s genomes; how does normal animal development depend on bacterial partners; how is homeostasis maintained between animals and their symbionts; and how can ecological approaches deepen our understanding of the multiple levels of animal–bacterial interaction. As answers to these fundamental questions emerge, all biologists will be challenged to broaden their appreciation of these interactions and to include investigations of the relationships between and among bacteria and their animal partners as we seek a better understanding of the natural world.; Earth and Planetary Sciences; Organismic and Evolutionary Biology

A receptor tyrosine kinase from choanoflagellates: Molecular insights into early animal evolution

King, Nicole; Carroll, Sean B.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 18/12/2001 Português
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The evolution of the Metazoa from protozoans is one of the major milestones in life's history. The genetic and developmental events involved in this evolutionary transition are unknown but may have involved the evolution of genes required for signaling and gene regulation in metazoans. The genome of animal ancestors may be reconstructed by identification of animal genes that are shared with related eukaryotes, particularly those that share a more recent ancestry and cell biology with animals. The choanoflagellates have long been suspected to be closer relatives of animals than are fungi, the closest outgroup of animals for which comparative genomic information is available. Phylogenetic analyses of choanoflagellate and animal relationships based on small subunit rDNA sequence, however, have yielded ambiguous and conflicting results. We find that analyses of four conserved proteins from a unicellular choanoflagellate, Monosiga brevicollis, provide robust support for a close relationship between choanoflagellates and Metazoa, suggesting that comparison of the complement of expressed genes from choanoflagellates and animals may be informative concerning the early evolution of metazoan genomes. We have discovered in M. brevicollis the first receptor tyrosine kinase (RTK)...