MR imaging of thoracic disk herniations

Magnetic resonance (MR) is of value in imaging intervertebral disk disease. We present the MR findings in two patients with thoracic disk herniations who required surgical intervention. The advantages of MR over CT myelography are ease of obtaining sagittal sections, rapid assessment of the entire thoracic spine, and a high rate of patient acceptance related to the noninvasive nature of MR and lack of morbidity and complications. For these reasons, we currently rely, almost exclusively, on MR for evaluating thoracic disk disease.

Intrinsic differences of insulin receptor kinase activity in red and white muscle

The sensitivity and responsiveness of glucose uptake and glycogen synthesis to insulin are 3-4-fold greater in red than in white skeletal muscle (James, D. E., Jenkins, A. B., and Kraegen, E. W. (1985) Am. J. Physiol. 248, E567-E574). In the present study, the insulin receptor tyrosine kinase activity has been examined in red and white muscle of rats. Partially purified insulin receptors were obtained from muscle following solubilization in detergent, ultracentrifugation, and lectin affinity chromatography. Total insulin receptor number per gram of tissue was slightly higher in red (30%) than in white muscle. In contrast, basal and insulin-stimulated autophosphorylation, normalized for receptor number, were 2.3-fold higher in red muscle. A similar difference was observed in the ability of partially purified receptors to phosphorylate the exogenous substrate polyglutamate/tyrosine. The integrity of the insulin receptor preparation in the two fiber types was identical as determined by affinity cross-linking of [125I-TyrB26]insulin to the receptor. Mixing partially purified receptors from red and white muscle resulted in an additive response for exogenous substrate phosphorylation, suggesting that the difference in tyrosine kinase activity was not due to the presence of an inhibitor or activator. The results suggest that there are differences in the insulin receptors of red and white muscles that lead to discordance in their basal and insulin-stimulated intrinsic tyrosine kinase activity. The correlation between these differences and insulin action in red and white muscle supports the concept that the insulin receptor tyrosine kinase activity is involved in the initiation of insulin action.

Glucose intolerance due to insulin resistance in patients with spinal cord injuries

Glucose intolerance occurs frequently in patients with spinal cord injury (SCI). To characterize this better, 45 patients with spinal cord injuries received oral glucose tolerance tests (OGTT). The subjects with glucose intolerance had significantly higher insulin levels than either the glucose-tolerant or normal control subjects. Since hyperinsulinism in the presence of glucose intolerance suggests insulin resistance, the peripheral insulin activity (A) was calculated from the OGTT data. The glucose-intolerant SCI patients had significantly lower A values than the other groups. The most resistant SCI subjects (A < 0.3) also had resistance to exogenous insulin. In 18 subjects receiving insulin tolerance tests, the A value calculated from the OGTT was 100% accurate in predicting the presence of sensitivity or resistance to exogenous insulin. In spite of the presence of insulin resistance, however, 125I-insulin binding to SCI patients' circulating monocytes was not significantly different from that in control subjects.

Intestinal absorption of immune complexes by neonatal rats: a route of antigen transfer from mother to young

Horseradish peroxidase (HRP) in the presence of specific immunoglobulin G antibody to HRP is selectively absorbed from the gut lumen and transferred by intestinal epithelial cells to the lamina propria in newborn rats. The HRP is not transferred in detectable amounts in the absence of the antibody. Transport of maternally derived antigen via antigen-antibody complexes may have important influences on the developing immune system in young mammals.