Catálogo de publicaciones - revistas

<jats:title>Size distributions of tropical trees</jats:title> <jats:p> The distribution of tree size in tropical forests follows a power-law regardless of location. This pattern has largely eluded mechanistic explanation. Using 30 years of tree demography and growth data from a forest plot in Panama, Farrior <jats:italic>et al.</jats:italic> show that the power-law size structure emerges after natural local disturbances such as the gaps formed by falling trees. A model of forest dynamics identifies the structural parameter governing the power-law distribution. A mechanistic understanding of tropical forest structural dynamics will benefit forest carbon cycling studies. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="155" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad0592">155</jats:related-article> </jats:p>

<jats:title>Decomposition spawns a microbial zoo</jats:title> <jats:p> The death of a large animal represents a food bonanza for microorganisms. Metcalf <jats:italic>et al.</jats:italic> monitored microbial activity during the decomposition of mouse and human cadavers. Regardless of soil type, season, or species, the microbial succession during decomposition was a predictable measure of time since death. An overlying corpse leaches nutrients that allow soil- and insect-associated fungi and bacteria to grow. These microorganisms are metabolic specialists that convert proteins and lipids into foul-smelling compounds such as cadaverine, putrescine, and ammonia, whose signature may persist in the soil long after a corpse has been removed. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="158" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad2646">158</jats:related-article> </jats:p>

<jats:title>Stomach ache for a European mummy</jats:title> <jats:p> Five thousand years ago in the European Alps, a man was shot by an arrow, then clubbed to death. His body was subsequently mummified by ice until glacier retreat exhumed him in 1991. Subsequently, this ancient corpse has provided a trove of intriguing information about copper-age Europeans. Now, Maixner <jats:italic>et al.</jats:italic> have identified the human pathogen <jats:italic>Helicobacter pylori</jats:italic> within the mummy's stomach contents. The strain the “Iceman” hosted appears to most closely resemble pathogenic Asian strains found today in Central and Southern Asia. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="162" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad2545">162</jats:related-article> </jats:p>

<jats:title>The difference is all in the water</jats:title> <jats:p> Glacial cycles are in part controlled by the pattern of incident solar energy determined by the geometry of Earth's orbit around the Sun. The classic record of the penultimate deglaciation from Devils Hole, Nevada, did not reconcile the presumption of so-called orbital forcing, however, suggesting that deglaciation began ~10,000 years too early. Moseley <jats:italic>et al.</jats:italic> present analyses of a new set of data from Devils Hole that show that the deglaciation indeed occurred at the time expected on the basis of orbital forcing. The age offset displayed by the older samples apparently was caused by interaction with groundwater, which preferentially affected the deeper original samples but not the new shallower samples. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="165" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad4132">165</jats:related-article> </jats:p>

<jats:title>Mitochondria migration during mitosis</jats:title> <jats:p> Every time a cell divides, it is faced with the problem of ensuring adequate distribution of all components to the daughter cells. This includes components that are present in relatively small numbers, like the mitochondria and their DNA-containing nucleoids. Jajoo <jats:italic>et al.</jats:italic> used quantitative time-lapse fluorescence microscopy of single yeast cells to explore how this works. Unlike chromosomes or macromolecules, mitochondria and nucleoids are distributed in proportion to the volume of cytoplasm received by each daughter cell. Partitioning errors are kept low by even distribution of the mitochondrial volume and roughly equal spacing of the nucleoids before they are distributed. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="169" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aaa8714">169</jats:related-article> </jats:p>

<jats:title>Location, location, location</jats:title> <jats:p> Aggregates of certain disease-associated proteins are involved in neurodegeneration. Woerner <jats:italic>et al.</jats:italic> now show that the exact location of these aggregates in the cell may be the key to their pathology (see the Perspective by Da Cruz and Cleveland). An artificial aggregate-prone protein caused problems when expressed in the cytoplasm but not when expressed in the nucleus. Cytoplasmic aggregates interfered with nucleocytoplasmic import and export. Perhaps if we can shunt pathological aggregates to the nucleus in the future, we will be able to ameliorate some forms of degenerative disease. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="173" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad2033">173</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="125" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad9872">125</jats:related-article> </jats:p>

<jats:title>How HSCs populate the fetal liver</jats:title> <jats:p> Hematopoietic stem cells (HSCs) undergo dramatic expansion in the fetal liver before migrating to their definitive site in the bone marrow. Khan <jats:italic>et al.</jats:italic> identify portal vessel–associated Nestin <jats:sup>+</jats:sup> NG2 <jats:sup>+</jats:sup> pericytes as critical HSC niche components (see the Perspective by Cabezas-Wallscheid and Trumpp). The portal vessel niche and HSCs expand according to fractal geometries, suggesting that niche cells—rather than factors expressed by the niche—drive HSC proliferation. After birth, arterial portal vessels transform into portal veins, and lose Nestin <jats:sup>+</jats:sup> NG2 <jats:sup>+</jats:sup> pericytes. When this happens, the niche is lost and HSCs migrate away from the neonatal liver. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="176" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad0084">176</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="126" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aae0325">126</jats:related-article> </jats:p>

<jats:title>Going in with a BAM</jats:title> <jats:p> Integral membrane proteins in bacterial outer membranes play roles in nutrient import and infectivity. These proteins are folded into a barrel shape composed of β-strands and inserted into the outer membrane by the β-barrel assembly machinery (BAM) complex. Bakelar <jats:italic>et al.</jats:italic> determined the crystal structure of a four-component BAM subcomplex. The structure of a central β barrel in BAM changes in the presence of the accessory components to create a lateral opening that may be involved in how BAM inserts proteins into the outer membrane. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="180" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad3460">180</jats:related-article> </jats:p>

<jats:title>A chemokine's sugary release</jats:title> <jats:p> As immune cells survey the body for pathogens, they circulate through the blood and migrate through the lymphatic system. The latter route allows for tissues and lymph nodes—the central hubs of the immune system—to communicate. Kiermaier <jats:italic>et al.</jats:italic> reveal the importance of the monosaccharide sialic acid in keeping immune cells in motion. Multiple sialic acids decorate the surface CCR7 on immune cells. CCR7 recognizes proteins called chemokines, which direct where cells move in the body. Sialic acids on CCR7 release one such chemokine present on lymph node endothelial cells from an inhibited state, allowing immune cells to enter lymph nodes. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6269" page="186" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad0512">186</jats:related-article> </jats:p>

<jats:p>On this week's show: Mitigating migraines, clocking corpse decomposition, and a news roundup.</jats:p>