Glaucoma following congenital cataract surgery – the role of early surgery and posterior capsulotomy

Background  

To determine the rate of glaucoma following congenital cataract surgery at Moorfields Eye Hospital (MEH), and to investigate potential risk factors for glaucoma in our case series.     

PERMEABILITY OF THE DEVELOPING AND MATURE BLOOD-BRAIN BARRIERS TO THEOPHYLLINE IN RATS

1. In the present study, the uptake of theophylline and L-glucose into the adult and neonatal rat brain has been investigated. Steady state cerebrospinal fluid (CSF) and brain concentrations of theophylline were reached within 1 h following a single intraperitoneal (i.p.) injection, whereas steady state CSF and brain concentrations of L-glucose were not approached until after 5 h. 2. Steady state brain:plasma and CSF:plasma concentration ratios for theophylline and L-glucose in neonatal rats were significantly higher than ratios in adult rats. Erythrocyte:plasma ratios for theophylline in neonatal rats were also significantly higher than ratios in adult rats. Steady state ratios for theophylline were significantly higher than those for L-glucose in both neonatal and adult rats. 3. Respiratory acidosis (pH 6.9–7.0) did not affect steady state CSF:plasma or brain.-plasma ratios for theophylline in neonatal or adult rats. In contrast, steady state CSF:plasma and brain:plasma ratios for L-glucose were increased by respiratory acidosis. 4. The lower steady state CSF:plasma, brain:plasma and erythrocyte:plasma ratios for theophylline in adult rats are likely to be due to a higher concentration of plasma proteins in adult blood compared with neonates, with a greater retention of protein-bound (non-exchangeable) theophylline in adult blood, and are unlikely to be due to p-glycoprotein-mediated efflux of theophylline at the adult blood-brain barrier.     

Defecography commode

A mobile wooden commode was designed and built for use in defecography. The commode is made of 1/2-inch-thick plywood with birch veneer and a solid clear pine seat. Water or copper sheets are recommended for radiation filtration. A radiopaque ruler attached to the commode with a spring enables midline measurements. The modifications suggested by the authors have helped with setup and have improved the images acquired.     

In-plane vascular imaging: pulse sequence design and strategy

Magnetic resonance (MR) angiography is a noninvasive method of obtaining images without contrast agents. Recent developments in sequence design have allowed images of moving spins to be obtained without a loss of signal by rephasing the spins with three or four gradient pulses to compensate for constant velocity or acceleration, respectively. At longer echo times (TE), this approach allowed for low readout gradients and high signal-to-noise ratios. Angiograms with a resolution of 300 micron were obtained. With additional sequences that allow some dephasing but minimal signal loss, separate images of arteries and veins were obtained. Phase information was used to estimate flow velocity. Application of the rephasing scheme to gradient-echo sequences allowed for ungated, fast MR angiograms. Acceleration correction was important for long TE sequences, but velocity-corrected, gradient-echo sequences with a very short TE were comparable to velocity- and acceleration-corrected, gradient-echo sequences with slightly longer TEs. With ungated three-dimensional, gradient-echo sequences, susceptibility artifacts were minimized and excellent contrast-to-noise ratios were obtained.     

Tetravinyl-tetramethylcyclo-tetrasiloxane (tetravinyl D4) is a mutagen in Rat2lambda lacI fibroblasts

Small fragments of silicone gels injected intraperitoneally have been used to induce plasmacytomas in genetically susceptible mice. Silicone oils, in contrast to silicone gels, are apparently not tumorigenic in the mouse plasmacytoma system. The reason for this difference as well as the mechanism of silicone gel-induced plasmacytoma development is poorly understood. We chose to examine the possibility that low molecular wt silicone compounds such as siloxanes, leaking from the complex silicone gel matrix into the surrounding tissue, may be mutagenic. We postulate that this mutagenicity may be a critical determinant of the plasmacytoma inducing potency of silicone gels. Six siloxane compounds, either linear or cyclic di-, tri-, or tetrasiloxanes substituted with methyl or vinyl moieties, were selected as model compounds to study mutagenicity in Rat2lambda lacI fibroblasts in vitro. Using phage lambda-derived lacI/lacZ genes as target/reporter genes to quantitate mutagenesis, and gamma-cyclodextrin as vehicle to effectively deliver siloxanes, we found that exposure to 50 microM of tetravinyl-tetramethylcyclo-tetrasiloxane (tetravinyl D4) resulted in a modest 1.7-fold increase of mutant frequencies over controls in Rat2lambda lacI cells. In related toxicity experiments, tetravinyl D4 was shown to perturb lipid membranes leading to a loss of cytosolic glutathione (GSH), which by itself resulted in a 1.5-fold increased mutant rate in Rat2lambda lacI cells. We conclude that certain siloxanes may act as direct mutagens in mammalian cells. In addition, siloxane-induced mutagenicity may be enhanced by the depletion of intracellular GSH caused by the interaction of lipophilic siloxanes with cell membranes.      

Thyroglossal duct cyst or ectopic thyroid gland?

Abstract: We report a 16-year-old boy with an anterior midline neck mass clinically diagnosed as a thyroglossal duct cyst. An ultrasound scan performed prior to surgery suggested a normally located thyroid gland. Following surgical excision of the presumed thyroglossal duct cyst the patient became hypothyroid. A radioisotope scan confirmed no active thyroid tissue. A pitfall in the ultrasonographic identification of the thyroid gland is discussed.