Ecological Aspects of Amphibian Metamorphosis: Nonnormal distributions of competitive ability reflect selection for facultative metamorphosis     

Wilbur HM  Collins JP 《Science (New York, N.Y.)》1973,182(4119):1305-1314

A synthetic theory of the ecology of amphibian metamorphosis is founded on the observation that the large variation in length of larval period and body size at metamorphosis typical of a particular species of amphibian cannot be directly explained by differences in dates of hatching or egg sizes. It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes. The degree of skewing increases and the median of the distribution decreases with increasing initial densities of populations. The relative advantages of the largest members of a cohort may arise from a variety of mechanisms including the production of growth inhibitors, interference competition, and size-selective feeding behavior. These mechanisms result in a nonnormal distribution of competitive ability, a possible source of the density-dependent competition coefficient found in systems with many species (1). In our model the ranges of body sizes and dates of metamorphosis are determined by a minimum body size that must be obtained and a maximum body size that will not be exceeded at metamorphosis. Between these two size thresholds the endocrinological initiation of metamorphosis is expected to be related to the recent growth history of the individual larva. Species that exploit uncertain environments will have a wide range of possible sizes at metamorphosis. Species exploiting relatively certain environments will have a narrower range. The evolution of neoteny and direct development logically follow from the application of these ideas to the ecological context of the evolution of amphibian life histories. Species that live in constant aquatic habitats surrounded by hostile environments (desert ponds, caves, high-altitude lakes) may evolve permanent larvae genetically incapable of metamorphosis. Other populations may evolve a facultative metamorphosis such that populations are a mixture of neotenes and terrestrial adults. Direct development results from selection to escape the competition, predation, and environmental uncertainty characteristic of some aquatic habitats and is usually accompanied by parental care. The relation between our ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested and it remains an open problem for developmental biologists.  相似文献   

Protein uptake in multivesicular bodies in the molt-intermolt cycle of an insect   总被引：5，自引：0，他引：5  

M Locke  J V Collins 《Science (New York, N.Y.)》1967,155(761):467-469

Plant peroxidase injected into the hemocoel is taken up in granules by almost all tissues. These granules may become multivesicular bodies or isolation bodies which later breakdown. There is most uptake and breakdown at times in the molt-intermolt cycle when cells are engaged in active syntheses.  相似文献   

Whole-genome shotgun sequencing of mitochondria from ancient hair shafts     

Gilbert MT  Tomsho LP  Rendulic S  Packard M  Drautz DI  Sher A  Tikhonov A  Dalén L  Kuznetsova T  Kosintsev P  Campos PF  Higham T  Collins MJ  Wilson AS  Shidlovskiy F  Buigues B  Ericson PG  Germonpré M  Götherström A  Iacumin P  Nikolaev V  Nowak-Kemp M  Willerslev E  Knight JR  Irzyk GP  Perbost CS  Fredrikson KM  Harkins TT  Sheridan S  Miller W  Schuster SC 《Science (New York, N.Y.)》2007,317(5846):1927-1930

Although the application of sequencing-by-synthesis techniques to DNA extracted from bones has revolutionized the study of ancient DNA, it has been plagued by large fractions of contaminating environmental DNA. The genetic analyses of hair shafts could be a solution: We present 10 previously unexamined Siberian mammoth (Mammuthus primigenius) mitochondrial genomes, sequenced with up to 48-fold coverage. The observed levels of damage-derived sequencing errors were lower than those observed in previously published frozen bone samples, even though one of the specimens was >50,000 14C years old and another had been stored for 200 years at room temperature. The method therefore sets the stage for molecular-genetic analysis of museum collections.  相似文献   

Synthetic biology moving into the clinic     

Ruder WC  Lu T  Collins JJ 《Science (New York, N.Y.)》2011,333(6047):1248-1252

Synthetic biology is an emerging field focused on engineering biomolecular systems and cellular capabilities for a variety of applications. Substantial progress began a little over a decade ago with the creation of synthetic gene networks inspired by electrical engineering. Since then, the field has designed and built increasingly complex circuits and constructs and begun to use these systems in a variety of settings, including the clinic. These efforts include the development of synthetic biology therapies for the treatment of infectious diseases and cancer, as well as approaches in vaccine development, microbiome engineering, cell therapy, and regenerative medicine. Here, we highlight advances in the biomedical application of synthetic biology and discuss the field's clinical potential.  相似文献   

Chronic mucocutaneous candidiasis in humans with inborn errors of interleukin-17 immunity   总被引：1，自引：0，他引：1  

Puel A  Cypowyj S  Bustamante J  Wright JF  Liu L  Lim HK  Migaud M  Israel L  Chrabieh M  Audry M  Gumbleton M  Toulon A  Bodemer C  El-Baghdadi J  Whitters M  Paradis T  Brooks J  Collins M  Wolfman NM  Al-Muhsen S  Galicchio M  Abel L  Picard C  Casanova JL 《Science (New York, N.Y.)》2011,332(6025):65-68

Chronic mucocutaneous candidiasis disease (CMCD) is characterized by recurrent or persistent infections of the skin, nails, and oral and genital mucosae caused by Candida albicans and, to a lesser extent, Staphylococcus aureus, in patients with no other infectious or autoimmune manifestations. We report two genetic etiologies of CMCD: autosomal recessive deficiency in the cytokine receptor, interleukin-17 receptor A (IL-17RA), and autosomal dominant deficiency of the cytokine interleukin-17F (IL-17F). IL-17RA deficiency is complete, abolishing cellular responses to IL-17A and IL-17F homo- and heterodimers. By contrast, IL-17F deficiency is partial, with mutant IL-17F-containing homo- and heterodimers displaying impaired, but not abolished, activity. These experiments of nature indicate that human IL-17A and IL-17F are essential for mucocutaneous immunity against C. albicans, but otherwise largely redundant.  相似文献   

Direct isolation of satellite cells for skeletal muscle regeneration   总被引：6，自引：0，他引：6  

Montarras D  Morgan J  Collins C  Relaix F  Zaffran S  Cumano A  Partridge T  Buckingham M 《Science (New York, N.Y.)》2005,309(5743):2064-2067

Muscle satellite cells contribute to muscle regeneration. We have used a Pax3(GFP/+) mouse line to directly isolate (Pax3)(green fluorescent protein)-expressing muscle satellite cells, by flow cytometry from adult skeletal muscles, as a homogeneous population of small, nongranular, Pax7+, CD34+, CD45-, Sca1- cells. The flow cytometry parameters thus established enabled us to isolate satellite cells from wild-type muscles. Such cells, grafted into muscles of mdx nu/nu mice, contributed both to fiber repair and to the muscle satellite cell compartment. Expansion of these cells in culture before engraftment reduced their regenerative capacity.  相似文献   

G protein-coupled receptors in Anopheles gambiae   总被引：3，自引：0，他引：3  

Hill CA  Fox AN  Pitts RJ  Kent LB  Tan PL  Chrystal MA  Cravchik A  Collins FH  Robertson HM  Zwiebel LJ 《Science (New York, N.Y.)》2002,298(5591):176-178

We used bioinformatic approaches to identify a total of 276 G protein-coupled receptors (GPCRs) from the Anopheles gambiae genome. These include GPCRs that are likely to play roles in pathways affecting almost every aspect of the mosquito's life cycle. Seventy-nine candidate odorant receptors were characterized for tissue expression and, along with 76 putative gustatory receptors, for their molecular evolution relative to Drosophila melanogaster. Examples of lineage-specific gene expansions were observed as well as a single instance of unusually high sequence conservation.  相似文献   

The Human Genome Project: lessons from large-scale biology   总被引：1，自引：0，他引：1  

Collins FS  Morgan M  Patrinos A 《Science (New York, N.Y.)》2003,300(5617):286-290

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Peroxisomal defects in neonatal-onset and X-linked adrenoleukodystrophies   总被引：13，自引：0，他引：13  

S Goldfischer  J Collins  I Rapin  B Coltoff-Schiller  C H Chang  M Nigro  V H Black  N B Javitt  H W Moser  P B Lazarow 《Science (New York, N.Y.)》1985,227(4682):67-70

Accumulation of very long chain fatty acids in X-linked and neonatal forms of adrenoleukodystrophy (ALD) appears to be a consequence of deficient peroxisomal oxidation of very long chain fatty acids. Peroxisomes were readily identified in liver biopsies taken from a patient having the X-linked disorder. However, in liver biopsies from a patient having neonatal-onset ALD, hepatocellular peroxisomes were greatly reduced in size and number, and sedimentable catalase was markedly diminished. The presence of increased concentrations of serum pipecolic acid and the bile acid intermediate, trihydroxycoprostanic acid, in the neonatal ALD patient are associated with a generalized diminution of peroxisomal activities that was not observed in the patient with X-linked ALD.  相似文献   

Control of embryonic motoneuron survival in vivo by ciliary neurotrophic factor   总被引：22，自引：0，他引：22  

R W Oppenheim  D Prevette  Q W Yin  F Collins  J MacDonald 《Science (New York, N.Y.)》1991,251(5001):1616-1618

During development of the nervous system, neurons in many regions are overproduced by proliferation, after which the excess cells are eliminated by cell death. The survival of only a proportion of neurons during normal development is thought to be regulated by the limited availability of neurotrophic agents. One such putative trophic agent is ciliary neurotrophic factor (CNTF), a polypeptide that promotes the survival of ciliary, sensory, and sympathetic neurons in vitro. In contrast to the results of in vitro studies, however, the daily treatment of chick embryos in vivo with purified human recombinant CNTF failed to rescue any of these cell populations from cell death, whereas CNTF did promote the in vivo survival of spinal motoneurons. Thus, CNTF may not act as a neurotrophic agent in vivo for those embryonic neurons (especially ciliary neurons) on which it acts in vitro. Rather, CNTF may be required for in vivo survival of motoneurons.  相似文献