Tuberculous anal fistulas-prevalence and clinical features in an endemic area

Introduction: The aim of this study was to determine the prevalence of tuberculosis (TB) in anal fistulas at a referral hospital in Cape Town, and to document the clinical features and course of patients with tuberculous anal fistulas. Patients and methods: This was a prospective study of all patients who underwent surgery for anal fistulas at the Colorectal Surgery Unit at Groote Schuur Hospital, Cape Town, from 2004 to 2006. Tissue was submitted for histopathological examination, Ziehl-Neelsen (ZN) staining and TB culture. The patients with proven TB were followed up until January 2008. Results: During the 3-year study period, 117 operations were performed on 96 patients. TB was diagnosed in 7 of the 96 patients (7.3%). In 5 of these 7 cases, the diagnosis of TB could be proven on histological examination and ZN staining, while in 2 cases the diagnosis could only be made on TB culture. None of the 7 patients had systemic features suggestive of TB, and only 1 had evidence of TB on a chest radiograph. Five patients were HIV-negative, and 2 declined testing. After a median follow-up of 2 years, 5 of 7 patients had evidence of recurrent or persistent fistulas, despite having completed 6 months of TB treatment. Conclusion: At a referral hospital in an endemic area, TB was present in 7.3% of anal fistulas. Histopathological examination including ZN staining was inadequate to make the diagnosis in a third of these patients. Tissue from anal fistulas should therefore routinely be sent for TB culture as well as histopathological examination and ZN staining in areas where TB is prevalent

The general relativistic infinite plane

Uniform fields are one of the simplest and most pedagogically useful examples in introductory courses on electrostatics or Newtonian gravity. In general relativity there have been several proposals as to what constitutes a uniform field. In this article we examine two metrics that can be considered the general relativistic version of the infinite plane with finite mass per unit area. The first metric is the 4D version of the 5D "brane" world models which are the starting point for many current research papers. The second case is the cosmological domain wall metric. We examine to what extent these different metrics match or deviate from our Newtonian intuition about the gravitational field of an infinite plane. These solutions provide the beginning student in general relativity both computational practice and conceptual insight into Einstein's field equations. In addition they do this by introducing the student to material that is at the forefront of current research.Comment: Accepted for publication in the American Journal of Physic

Isoform-specific subcellular localization and function of protein kinase A identified by mosaic imaging of mouse brain.

Protein kinase A (PKA) plays critical roles in neuronal function that are mediated by different regulatory (R) subunits. Deficiency in either the RIβ or the RIIβ subunit results in distinct neuronal phenotypes. Although RIβ contributes to synaptic plasticity, it is the least studied isoform. Using isoform-specific antibodies, we generated high-resolution large-scale immunohistochemical mosaic images of mouse brain that provided global views of several brain regions, including the hippocampus and cerebellum. The isoforms concentrate in discrete brain regions, and we were able to zoom-in to show distinct patterns of subcellular localization. RIβ is enriched in dendrites and co-localizes with MAP2, whereas RIIβ is concentrated in axons. Using correlated light and electron microscopy, we confirmed the mitochondrial and nuclear localization of RIβ in cultured neurons. To show the functional significance of nuclear localization, we demonstrated that downregulation of RIβ, but not of RIIβ, decreased CREB phosphorylation. Our study reveals how PKA isoform specificity is defined by precise localization