Magnetic resonance imaging of occult vascular malformations of the brain stem.

A characteristic appearance of occult cerebrovascular malformations (OCVMs) on high-field spin-echo magnetic resonance imaging (MRI) has been described previously. The authors report a series of 21 of these lesions located in the brain stem and examine the clinical and MRI characteristics. Most of these lesions display a prolonged, fluctuating clinical course, which suggests multiple sclerosis or brain-stem glioma. Although the possibility of hemorrhagic neoplasms mimicking the MRI appearance of OCVMs has been emphasized recently, distinguishing between these two groups of lesions should be possible in most cases. MRI should allow the diagnosis to be made with sufficient certainty to avoid unnecessary intervention for OCVMs in this delicate location.

Effect of hypoxic hypoxia on taurine concentrations in ventricles of mouse hearts.

The effects of hypoxic hypoxia on the concentration of taurine in right ventricles was studied in the hearts of male CF1 mice caged individually and maintained for 16 hr per day in a hypobaric chamber evacuated to an air pressure of 307 mm Hg. After 23 days hearts were excised and right and left ventricles were separated and lyophilized. Hematocrits in chamber animals were 77-82%, compared to 45-49% for control mice. Mean weights of right ventricles of animals from the chamber were 11.2 +/- 0.9, compared to control values of 7.0 +/- 0.4, mg dry weight. The mean dry weights of left ventricles in both groups of animals were the same. There were no significant differences in the nmoles taurine per mg day tissue in either heart chamber, with mean values +/- S.E.M. of 124.0 +/- 4.6 and 135.0 +/- 4.5 in right ventricles and 128.0 +/- 4.3 and 110.9 +/- 15.3 in left ventricles of experimental and control animals respectively. Thus, hypertrophy which results from hypoxia is not accompanied by increased concentrations of taurine in right ventricles.