Abordaje submaseterino ampliado para la resección de lipoma del espacio masticatorio: nota anatomoquirúrgica y reporte de un caso

ResumenIntroducciónLos lipomas del espacio masticatorio son lesiones benignas de origen mesenquimal localizadas en los espacios profundos de la cara dentro de los límites de lo que anatómicamente es denominado «espacio masticatorio».Reporte de casoReportamos el caso de un niño de 5años con hiperplasia en la región parotídea donde se sospechaba un tumor de glándula salival. Los estudios de imagen revelaron una lesión de aspecto lipomatoso en el espacio masticatorio que provocaba abombamiento de la región parotídea. El abordaje quirúrgico de este paciente pediátrico se realizó por la vía submaseterina, técnica ampliamente utilizada para resolver infecciones submaseterinas de origen dentario pero que, ligeramente más extendida en su magnitud, sirvió para resecar el tumor de manera íntegra y lograr el control de la lesión a largo plazo.DiscusiónSe examina la probable utilidad de la técnica para el abordaje de tumores benignos en esta área anatómica, así como detalles anatomoquirúrgicos y radiológicos del espacio masticatorio. No encontramos reportes en la literatura sobre el uso previo de esta técnica en la resección de tumores.ConclusionesEl abordaje submaseterino ampliado es una opción más en el manejo de tumores benignos del espacio masticatorio en casos seleccionados.AbstractIntroductionMasticator space lipomas are benign lesions of mesenchymal origin emerging in deep facial spaces within the limits of what anatomically is known as the masticator space.Case reportThe case is presented on a 5-year-old child with a swelling in the parotid region, suspected to be a salivary gland tumour. Imaging studies revealed an apparently lipomatous lesion in the masticator space causing swelling of the parotid region. The surgical approach for this paediatric patient was submasseteric, a technique widely used for odontogenic infections invading the submasseteric space, but that with a slightly larger incision to allow the tumour to be completely removed and to achieve long-term control of the lesion.DiscussionThe probable usefulness of this surgical approach for benign lesions, as well as radiological and surgical anatomy details are discussed. No previous reports on the use of this technique in tumours were found in medical literature.ConclusionsExtended submasseteric approach is one more choice in the management of masticator space benign tumours in selected cases

Distribution of hammerhead and hammerhead-like RNA motifs through the GenBank

Hammerhead ribozymes previously were found in satellite RNAs from plant viroids and in repetitive DNA from certain species of newts and schistosomes. To determine if this catalytic RNA motif has a wider distribution, we decided to scrutinize the GenBank database for RNAs that contain hammerhead or hammerhead-like motifs. The search shows a widespread distribution of this kind of RNA motif in different sequences suggesting that they might have a more general role in RNA biology. The frequency of the hammerhead motif is half of that expected from a random distribution, but this fact comes From the low CpG representation in vertebrate sequences and the bias of the GenBank for those sequences. Intriguing motifs include those found in several families of repetitive sequences, in the satellite RNA from the carrot red leaf luteovirus, in plant viruses like the spinach latent virus and the elm mottle virus, in animal viruses like the hepatitis E virus and the caprine encephalitis virus, and in mRNAs such as those coding for cytochrome P450 oxidoreductase in the rat and the hamster

NKG2D ligands mediate immunosurveillance of senescent cells

Cellular senescence is a stress response mechanism that limits tumorigenesis and tissue damage. Induction of cellular senescence commonly coincides with an immunogenic phenotype that promotes self-elimination by components of the immune system, thereby facilitating tumor suppression and limiting excess fibrosis during wound repair. The mechanisms by which senescent cells regulate their immune surveillance are not completely understood. Here we show that ligands of an activating Natural Killer (NK) cell receptor (NKG2D), MICA and ULBP2 are consistently up-regulated following induction of replicative senescence, oncogene-induced senescence and DNA damage - induced senescence. MICA and ULBP2 proteins are necessary for efficient NK-mediated cytotoxicity towards senescent fibroblasts. The mechanisms regulating the initial expression of NKG2D ligands in senescent cells are dependent on a DNA damage response, whilst continuous expression of these ligands is regulated by the ERK signaling pathway. In liver fibrosis, the accumulation of senescent activated stellate cells is increased in mice lacking NKG2D receptor leading to increased fibrosis. Overall, our results provide new insights into the mechanisms regulating the expression of immune ligands in senescent cells and reveal the importance of NKG2D receptor-ligand interaction in protecting against liver fibrosis

Urodele p53 tolerates amino acid changes found in p53 variants linked to human cancer

<p>Abstract</p> <p>Background</p> <p>Urodele amphibians like the axolotl are unique among vertebrates in their ability to regenerate and their resistance to develop cancers. It is unknown whether these traits are linked at the molecular level.</p> <p>Results</p> <p>Blocking p53 signaling in axolotls using the p53 inhibitor, pifithrin-α, inhibited limb regeneration and the expression of p53 target genes such as Mdm2 and Gadd45, suggesting a link between tumor suppression and regeneration. To understand this relationship we cloned the p53 gene from axolotl. When comparing its sequence with p53 from other organisms, and more specifically human we observed multiple amino acids changes found in human tumors. Phylogenetic analysis of p53 protein sequences from various species is in general agreement with standard vertebrate phylogeny; however, both mice-like rodents and teleost fishes are fast evolving. This leads to long branch attraction resulting in an artefactual basal emergence of these groups in the phylogenetic tree. It is tempting to assume a correlation between certain life style traits (e.g. lifespan) and the evolutionary rate of the corresponding p53 sequences. Functional assays of the axolotl p53 in human or axolotl cells using p53 promoter reporters demonstrated a temperature sensitivity (ts), which was further confirmed by performing colony assays at 37°C. In addition, axolotl p53 was capable of efficient transactivation at the Hmd2 promoter but has moderate activity at the p21 promoter. Endogenous axolotl p53 was activated following UV irradiation (100 j/m²) or treatment with an alkylating agent as measured using serine 15 phosphorylation and the expression of the endogenous p53 target Gadd45.</p> <p>Conclusion</p> <p>Urodele p53 may play a role in regeneration and has evolved to contain multiple amino acid changes predicted to render the human protein defective in tumor suppression. Some of these mutations were probably selected to maintain p53 activity at low temperature. However, other significant changes in the axolotl proteins may play more subtle roles on p53 functions, including DNA binding and promoter specificity and could represent useful adaptations to ensure p53 activity and tumor suppression in animals able to regenerate or subject to large variations in oxygen levels or temperature.</p

Senescence gives insights into the morphogenetic evolution of anamniotes

Senescence represents a mechanism to avoid undesired cell proliferation that plays a role in tumor suppression, wound healing and embryonic development. In order to gain insight on the evolution of senescence, we looked at its presence in developing axolotls (urodele amphibians) and in zebrafish (teleost fish), which are both anamniotes. Our data indicate that cellular senescence is present in various developing structures in axolotls (pronephros, olfactory epithelium of nerve fascicles, lateral organs, gums) and in zebrafish (epithelium of the yolk sac and in the lower part of the gut). Senescence was particularly associated with transient structures (pronephros in axolotls and yolk sac in zebrafish) suggesting that it may play a role in the elimination of these tissues. Our data supports the notion that cellular senescence evolved early in vertebrate evolution to influence embryonic development

Capturing Hammerhead Ribozyme Structures in Action by Modulating General Base Catalysis

We have obtained precatalytic (enzyme–substrate complex) and postcatalytic (enzyme–product complex) crystal structures of an active full-length hammerhead RNA that cleaves in the crystal. Using the natural satellite tobacco ringspot virus hammerhead RNA sequence, the self-cleavage reaction was modulated by substituting the general base of the ribozyme, G12, with A12, a purine variant with a much lower pKa that does not significantly perturb the ribozyme's atomic structure. The active, but slowly cleaving, ribozyme thus permitted isolation of enzyme–substrate and enzyme–product complexes without modifying the nucleophile or leaving group of the cleavage reaction, nor any other aspect of the substrate. The predissociation enzyme-product complex structure reveals RNA and metal ion interactions potentially relevant to transition-state stabilization that are absent in precatalytic structures

A screen for genes involved in respiration control and longevity in Schizosaccharomyces pombe

We present results showing that glucose signaling has proaging effects in the yeast Schizosaccharomyces pombe. Deletion of the receptor that senses extracellular glucose (Git3) increases the life span of S. pombe, while constitutive activation of the Gα subunit acting downstream of this receptor (Gpa2) shortens its life span. The latter mutant is also impaired for growth under respiration conditions. We have used this phenotype in a selection strategy to identify genes that when overexpressed can rescue the respiratory defect of constitutively active Gα subunit mutants. Here, we report an extended version of the work we presented at the IABG meeting and the results of this screen. This strategy allowed us to isolate four genes: psp1 + /moc1 + , cka1 + , adh1 + , and rpb10 + . Interestingly, the overexpression of these genes was also capable of increasing the chronological life span of wild-type yeast cells