Localisation of pseudohypoaldosteronism genes to chromosome 16p12.2- 13.11 and 12p13.1-pter by homozygosity mapping

Pseudohypoaldosteronism type 1 (PHA1, OMIM 264350) is a rare Mendelian disorder characterised by end-organ unresponsiveness to mineralocorticoids. Most steroid hormone insensitivity syndromes arise from mutations in the corresponding receptor, but available genetic evidence is against involvement of the mineralocorticoid receptor gene, MLR, in PHA1. A complete genome scan for PHA1 genes was undertaken using homozygosity mapping in 11 consanguineous families. Conclusive evidence of linkage with heterogeneity was obtained with a maximum two- locus admixture lod score of 9.9. The disease locus mapped to chromosome 16p12.2-13.11 in six families and to 12p13.1-pter in the other five families. The two chromosomal regions harbour genes for subunits of the amiloride-sensitive epithelial sodium channel: SCNN1B and SCNN1G on 16p and SCNN1A on 12p. Liddle's syndrome of hypertension and pseudoaldosteronism has been shown to arise from mutations in SCNN1B and SCNN1G. These results strongly suggest that PHA1 and Liddle's syndrome are allelic variants caused by mutations in genes encoding subunits of this sodium channel. These genes are of broad biological interest both in relation to sodium and water homeostasis in mammals and by virtue of their homology to the mec genes of Caenorhabditis elegans involved in mechanosensitivity and neuronal degeneration.      

Syrinx-like artifacts on MR images of the spinal cord

Magnetic resonance (MR) imaging of the spinal cord frequently demonstrates, especially on sagittal sections, a central stripe that mimics a true syrinx. This syrinx-like manifestation of a truncation artifact occurs in objects having a width of only a few pixels and was demonstrated by calculations verified with phantom MR images. Healthy volunteers and two patients with a syrinx and cervical spondylosis, respectively, underwent MR imaging. By increasing the number of phase-encoding steps, decreasing the field of view, and switching phase- and frequency-encoding axes, the syrinx-like artifact can be eliminated.     

Foundational studies in nursing

The essential nature of foundational studies in nursing, which are usually called meta-theories or conceptual frameworks, is explored. There are three approaches to this type of study, namely foundationalism, language critique and philosophical analysis. The work of Orem, King and Rogers is briefly analysed as an example of each of these approaches.     

Ocular melanoma: total dose and dose rate effects with Co-60 plaque therapy

From 1968 to 1987, 123 consecutive patients with nonmetastatic choroidal melanoma were treated with cobalt-60 plaques. One hundred sixteen patients were followed up for a mean of 3.8 years. Twenty patients had local failure, and 14 patients had distant failure. Complications included 32 cataracts, and seven enucleations were required. Local recurrence did not correlate with tumor height, tumor volume, dose, or dose rate. Increased volume (P = .004) and height (P = .01) correlated with increased rates of distant metastases. Dose adjusted for volume did not correlate with the rate of metastases.