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<jats:p>Photographs are presented of isolated superfluid helium-4 droplets prepared on a cesium surface, the only material known that is not wetted by superfluid helium. Although thermodynamic measurements show that the cesium surface is highly uniform, the contact angle of the droplets is extremely hysteretic and depends on whether the contact line is advancing or receding. Superfluid helium-4 droplets on an inclined surface do not flow downhill but rather are strongly pinned to the surface.</jats:p>

<jats:p>Homologies of digits in the avian hand have been debated for 150 years. Cladistic analysis nests birds with theropod dinosaurs. Theropod hands retain only digits I-II-III, so digits of the modern bird hand are often identified as I-II-III. Study of the developing manus and pes in amniote embryos, including a variety of avian species, shows stereotyped patterns of cartilage condensations. A primary axis of cartilage condensation is visible in all species that runs through the humerus into digit IV. Comparison to serially homologous elements of the hindlimb indicates that the retained digits of the avian hand are II-III-IV.</jats:p>

<jats:p> The <jats:italic>Drosophila</jats:italic> homolog of c-Jun regulates epithelial cell shape changes during the process of dorsal closure in mid-embryogenesis. Here, mutations in the <jats:italic>DFos</jats:italic> gene are described. In dorsal closure, DFos cooperates with DJun by regulating the expression of <jats:italic>dpp</jats:italic> ; Dpp acts as a relay signal that triggers cell shape changes and <jats:italic>DFos</jats:italic> expression in neighboring cells. In addition to the joint requirement of DFos and DJun during dorsal closure, DFos functions independently of DJun during early stages of embryogenesis. These findings demonstrate common and distinct roles of DFos and DJun during embryogenesis and suggest a conserved link between AP-1 (activating protein-1) and TGF-β (transforming growth factor–β) signaling during epithelial cell shape changes. </jats:p>

<jats:p> Leukocytes extravasate from the blood into inflammatory sites through complementary ligand interactions between leukocytes and endothelial cells. Activation of T cells increases their binding to hyaluronate (HA) and enables CD44-mediated primary adhesion (rolling). This rolling could be induced in vivo in murine V <jats:sub>β</jats:sub> 8 <jats:sup>+</jats:sup> T cells in response to specific superantigen stimulation; it was initially found in lymph nodes, then in peripheral blood, and finally within the peritoneum, the original inflamed site. The migration of V <jats:sub>β</jats:sub> 8 <jats:sup>+</jats:sup> cells into the peritoneal cavity was dependent on CD44 and HA, as shown by inhibition studies. Thus, CD44-HA interactions can target lymphocytes to specific extralymphoid effector sites. </jats:p>

<jats:p>A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences. All 12 genes, and six of eight NRY genes or families previously isolated by less systematic means, fell into two classes. Genes in the first group were expressed in many organs; these housekeeping genes have X homologs that escape X inactivation. The second group, consisting of Y-chromosomal gene families expressed specifically in testes, may account for infertility among men with Y deletions. The coherence of the NRY's gene content contrasts with the apparently haphazard content of most eukaryotic chromosomes.</jats:p>

<jats:p> DNA microarrays containing virtually every gene of <jats:italic>Saccharomyces cerevisiae</jats:italic> were used to carry out a comprehensive investigation of the temporal program of gene expression accompanying the metabolic shift from fermentation to respiration. The expression profiles observed for genes with known metabolic functions pointed to features of the metabolic reprogramming that occur during the diauxic shift, and the expression patterns of many previously uncharacterized genes provided clues to their possible functions. The same DNA microarrays were also used to identify genes whose expression was affected by deletion of the transcriptional co-repressor <jats:italic>TUP1</jats:italic> or overexpression of the transcriptional activator <jats:italic>YAP1</jats:italic> . These results demonstrate the feasibility and utility of this approach to genomewide exploration of gene expression patterns. </jats:p>

<jats:p>BAD is a distant member of the Bcl-2 family that promotes cell death. Phosphorylation of BAD prevents this. BAD phosphorylation induced by interleukin-3 (IL-3) was inhibited by specific inhibitors of phosphoinositide 3-kinase (PI 3-kinase). Akt, a survival-promoting serine-threonine protein kinase, was activated by IL-3 in a PI 3-kinase–dependent manner. Active, but not inactive, forms of Akt were found to phosphorylate BAD in vivo and in vitro at the same residues that are phosphorylated in response to IL-3. Thus, the proapoptotic function of BAD is regulated by the PI 3-kinase–Akt pathway.</jats:p>

<jats:p>Genetically distinct populations are an important component of biodiversity. This work estimates the number of populations per area of a sample of species from literature on population differentiation and the average range area of a species from a sample of distribution maps. This yields an estimate of about 220 populations per species, or 1.1 to 6.6 billion populations globally. Assuming that population extinction is a linear function of habitat loss, approximately 1800 populations per hour (16 million annually) are being destroyed in tropical forests alone.</jats:p>

<jats:p> Extinction episodes, such as the anthropogenic one currently under way, result in a pruned tree of life. But what fraction of the underlying evolutionary history survives when <jats:italic>k</jats:italic> of <jats:italic>n</jats:italic> species in a taxon are lost? This is relevant both to how species loss has translated into a loss of evolutionary history and to assigning conservation priorities. Here it is shown that approximately 80 percent of the underlying tree of life can survive even when approximately 95 percent of species are lost, and that algorithms that maximize the amount of evolutionary history preserved are not much better than choosing the survivors at random. Given the political, economic, and social realities constraining conservation biology, these findings may be helpful. </jats:p>

<jats:p> CD8 <jats:sup>+</jats:sup> T lymphocytes from individuals infected with human immunodeficiency virus–type 1 (HIV-1) secrete a soluble activity that suppresses infection by HIV-1. A protein associated with this activity was purified from the culture supernatant of an immortalized CD8 <jats:sup>+</jats:sup> T cell clone and identified as the β-chemokine macrophage-derived chemokine (MDC). MDC suppressed infection of CD8 <jats:sup>+</jats:sup> cell–depleted peripheral blood mononuclear cells by primary non–syncytium-inducing and syncytium-inducing isolates of HIV-1 and the T cell line–adapted isolate HIV-1 <jats:sub>IIIB</jats:sub> . MDC was expressed in activated, but not resting, peripheral blood mononuclear cells and binds a receptor on activated primary T cells. These observations indicate that β-chemokines are responsible for a major proportion of HIV-1–specific suppressor activity produced by primary T cells. </jats:p>