RESUMEN
The placenta functions to nourish and protect the fetus. Imaging of the placenta can have a profound impact on patient management, owing to the morbidity and mortality associated with various placental conditions. To fully appreciate placental pathology, its physiology, anatomy, and variant anatomy will be outlined. Placental conditions affecting the mother and fetus include molar pregnancies, placental hematoma, abruption, previa, accreta, vasa previa, choriocarcinoma, and retained products of conception. Ultrasonography remains the definitive modality in diagnosing most of these conditions, with magnetic resonance imaging remaining an adjunctive measure. Computed tomography is occasionally used in cases of trauma and tumor staging.
Asunto(s)
Enfermedades Placentarias/diagnóstico , Complicaciones del Embarazo/diagnóstico , Diagnóstico Prenatal/métodos , Tomografía Computarizada por Rayos X/métodos , Ultrasonografía/métodos , Femenino , Humanos , Embarazo , Estadística como AsuntoRESUMEN
We have investigated the conditions required for polar localization of the CheZ phosphatase by using a CheZ-green fluorescent protein fusion protein that, when expressed from a single gene in the chromosome, restored chemotaxis to a DeltacheZ strain. Localization was observed in wild-type, DeltacheZ, DeltacheYZ, and DeltacheRB cells but not in cells with cheA, cheW, or all chemoreceptor genes except aer deleted. Cells making only CheA-short (CheA(S)) or CheA lacking the P2 domain also retained normal localization, whereas cells producing only CheA-long or CheA missing the P1 and P2 domains did not. We conclude that CheZ localization requires the truncated C-terminal portion of the P1 domain present in CheA(S). Missense mutations targeting residues 83 through 120 of CheZ also abolished localization. Two of these mutations do not disrupt chemotaxis, indicating that they specifically prevent interaction with CheA(S) while leaving other activities of CheZ intact.