RESUMEN
As an essential feature of development, robustness ensures that embryos attain a consistent phenotype despite genetic and environmental variation. The growing number of examples demonstrating that embryos can mount a compensatory response to germline mutations in key developmental genes has heightened interest in the phenomenon of embryonic robustness. While considerable progress has been made in elucidating genetic compensation in response to germline mutations, the diversity, mechanisms, and limitations of embryonic robustness remain unclear. In this work, we have examined whether Xenopus laevis embryos are able to compensate for perturbations of the Notch signaling pathway induced by RNA injection constructs that either upregulate or inhibit this signaling pathway. Consistent with earlier studies, we found that at neurula stages, hyperactivation of the Notch pathway inhibited neural differentiation while inhibition of Notch signaling increases premature differentiation as assayed by neural beta tubulin expression. However, surprisingly, by hatching stages, embryos begin to compensate for these perturbations, and by swimming tadpole stages most embryos exhibited normal neuronal gene expression. Using cell proliferation and TUNEL assays, we show that the compensatory response is, in part, mediated by modulating levels of cell proliferation and apoptosis. This work provides an additional model for addressing the mechanisms of embryonic robustness and of genetic compensation.
Asunto(s)
Diferenciación Celular , Embrión no Mamífero/embriología , Regulación del Desarrollo de la Expresión Génica , Neurulación , Receptores Notch/metabolismo , Transducción de Señal , Animales , Xenopus laevisRESUMEN
Lung cancer is one of the most common cancers in America. Frequent sites of metastasis include the Hilar lymph nodes, adrenal glands, liver, brain, and bone. The following case report is of a primary lung cancer with metastases to the breast and skin. Case. A 48-year-old African American male with a past medical history of poorly differentiated left breast cancer status after modified radical mastectomy (MRM), chronic obstructive pulmonary disease, and smoking (20 pack-years) presents to the ER with progressive shortness of breath on exertion, upper back pain, and weight loss for 2 months in duration. On physical examination he is found to have a MRM scar on his left breast and a left periumbilical cutaneous mass. Chest X-ray and chest CT reveal a right upper lobe mass and biopsies from the breast, lung, and the periumbilical mass indicate a poorly differentiated carcinoma of unclear etiology; all tumor markers are negative. The patient is male and a chronic smoker; therefore the diagnosis is made as lung carcinoma with metastases to the breast and skin. Conclusion. A high index of suspicion for cutaneous metastases should be cast when investigating cutaneous pathologies in patients at risk for primary lung malignancy.
RESUMEN
Effective disease monitoring and prevention is critical to the success of captive amphibian care. Nematodes, including the genera Rhabdias and Strongyloides, are known to contribute to mortality in captive amphibians and have been identified in the Houston Zoo's endangered Houston toad (Bufo [Anaxyrus] houstonensis) captive assurance colony. Five years of fecal data for the toad colony were compiled and analyzed in order to investigate the efficacy of two anthelminthic medications, fenbendazole (FBZ) and levamisole (LMS), which were used to control nematode infections. Both FBZ (dusted onto food items) and topical LMS (6.5 to 13.5 mg/kg) significantly reduced the number of nematode eggs, larvae, and adults observed by fecal parasitologic examination. There were no significant differences between treatments, and egg reappearance periods were difficult to compare as a result of low sample size. No adverse effects from either anthelminthic treatment were observed. Both topical LMS and oral FBZ appear to be safe and efficacious treatments for the reduction of the internal nematode burden in captive Houston toads.