Factors influencing interocular blur suppression

An Important feauture of monovision correction is the ability of the binocular system to suppress blur from the defocused eye (interocular blur suppression). We conducted a study with three subjects and found that interocular blur suppression improved with higher levels of monocular defocus (addition powers in monovision) but was not affected by the eye defocused (sighting dominant or non-domninant) or by pupil size. The selection and management of monovision patients may be assisted by an understading of the understanding of the underlying suppression preocesses.     

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.     

Passive hepatic congestion in heart failure: CT abnormalities

Using bolus-enhanced CT, we encountered an unusual constellation of findings in seven patients with clinical evidence of right heart failure. These included retrograde hepatic venous opacification on the early bolus scans and a diffusely mottled pattern of hepatic enhancement seen only during the vascular phase of contrast administration. Ancillary CT findings include cardiomegaly, pleural effusions, ascites, and intrahepatic perivascular radiolucency. We believe that these CT abnormalities are caused by passive hepatic congestion. This pattern of abnormal hepatic enhancement represents a potential pitfall in the use of dynamic bolus-enhanced CT for the detection of focal hepatic masses. Recognition of passive hepatic congestion as a possible cause of mottled hepatic enhancement on CT may help explain clinical abnormalities of liver function in patients with heart failure and prevent confusion with other disease processes that produce abnormalities of hepatic attenuation.     

Breast cancer: PET imaging of estrogen receptors

Thirteen patients with primary breast masses were studied with positron emission tomography (PET) and 16 alpha-[fluorine-18]-fluoroestradiol-17 beta. PET images demonstrated uptake of the labeled estrogen analog at sites of primary carcinomas and in several foci of axillary lymph node metastases, as well as in one distant metastatic site. There was excellent correlation between uptake within the primary tumor measured on the PET images and the tumor estrogen-receptor concentration measured in vitro after excision (r = .96). This technique may provide an in vivo method of assessing estrogen receptors in primary and metastatic breast cancers and thus guide management of this disease with antiestrogen chemotherapy.     

Endemic institutional salmonellosis due to lactose-fermenting Salmonella newport in Nova Scotia.

We report two outbreaks of salmonellosis due to lactose-fermenting Salmonella newport in a Halifax nursing home in August 1983 and July 1986 that we believe were related. The relative rarity of this serotype and other epidemiologic evidence suggest that the organism was endemic in the institution for at least 3 years. Persistent carriers as well as ill and convalescing patients presumably were responsible for propagation of the outbreak. We recommend adequate microbiologic follow-up of infected residents and implementation of surveillance and infection control measures for nursing homes and special care institutions.