Computed tomography and plain radiography in experimental fracture healing

We evaluated the relative contribution of plain radiographs and computed tomography to the assessment of fracture healing under experimental circumstances. In 15 sheep, we performed midshaft femoral osteotomies and internal fixation of the resultant segmental fractures. Radiographs were obtained preoperatively and immediately postoperatively. Animals were sacrificed at 3 weeks, 6 weeks, 12 weeks, 24 weeks, and 36 weeks after surgery, and the femoral specimens radiographed. After removal of the internal fixation devices, computed tomographic scans of the specimens were performed.By 3 weeks, callus was visible, but at 6 weeks, a trabecular pattern in the callus was seen on plain films but not on computed tomography. There was progressive organization of the callus on both studies. At 24 weeks, computed tomography demonstrated fracture lines not seen due to overlying callus on plain films and also more accurately showed incomplete union. By 36 weeks, healing was essentially complete according to both modalities, although there still were small gaps in the callus detectable on computed tomography but not on plain films.Computed tomography may be of value in the evaluation of fractures of long bones in those cases in which clinical examination and plain radiographs fail to give adequate information as to the status of healing.     

Food allergy as a risk factor for asthma morbidity in adults.

BACKGROUND: The objective of this study was to evaluate the relationship between food allergy and asthma morbidity in adults. METHODS: We interviewed a cohort of persistent asthmatics from an inner-city clinic. Allergies to food were assessed by patient report of convincing symptoms of acute allergic reactions. Outcome variables included health resource utilization and medication use. RESULTS: The prevalence of allergy to fish, peanut, tree-nut, shellfish, and seed allergies were 3%, 3%, 3%, 13%, and 1%. Patients with allergies to > 1 food had increased asthma hospitalizations, ED visits, and use of oral steroids (p < 0.05 for all comparisons). Specifically, allergy to fish was associated with a greater risk of health resource utilization and increased frequency of oral steroid use (p < or = 0.03 for all comparisons). CONCLUSIONS: Self-reported allergy to foods was associated with worse outcomes, suggesting that food allergy may be a risk factor for increased asthma morbidity in adults.     

Calorie restriction extends yeast life span by lowering the level of NADH

Calorie restriction (CR) extends life span in a wide variety of species. Previously, we showed that calorie restriction increases the replicative life span in yeast by activating Sir2, a highly conserved NAD-dependent deacetylase. Here we test whether CR activates Sir2 by increasing the NAD/NADH ratio or by regulating the level of nicotinamide, a known inhibitor of Sir2. We show that CR decreases NADH levels, and that NADH is a competitive inhibitor of Sir2. A genetic intervention that specifically decreases NADH levels increases life span, validating the model that NADH regulates yeast longevity in response to CR.     

Craniosynostosis in Twist heterozygous mice: A model for Saethre‐Chotzen syndrome

Saethre‐Chotzen syndrome is a common autosomal dominant form of craniosynostosis, the premature fusion of the sutures of the calvarial bones of the skull. Most Saethre‐Chotzen syndrome cases are caused by haploinsufficiency for the TWIST gene. Mice heterozygous for a null mutation of the Twist gene replicate certain features of Saethre‐Chotzen syndrome, but have not been reported to exhibit craniosynostosis. We demonstrate that Twist heterozygous mice exhibit fusions of the coronal suture and other cranial suture abnormalities, indicating that Twist heterozygous mice constitute a better animal model for Saethre‐Chotzen syndrome than was previously appreciated. Anat Rec 268:90–92, 2002. © 2002 Wiley‐Liss, Inc.     

Control of T-cell activation by CD4+ CD25+ suppressor T cells

Summary: Depletion of the minor (∼10%) subpopulation of CD4⁺ T cells that co-expresses CD25 (interleukin (IL)-2 receptor α-chain) by thymectomy of neonates on the third day of life or by treatment of adult CD4⁺ T cells with anti-CD25 and complement results in the development of organ-specific autoimmunity. Autoimmune disease can be prevented by reconstitution of the animals with CD4⁺ CD25⁺ cells. CD4⁺ CD25⁺-mediated protection of autoimmune gastritis does not require the suppressor cytokines IL-4, IL-10, or transforming growth factor (TGF)-β. Mice that express a transgenic T-cell receptor (TCR) derived from a thymectomized newborn that recognizes the gastric parietal cell antigen H/K ATPase all develop severe autoimmune gastritis very early in life. CD4⁺ CD25⁺ T cells are also powerful suppressors of the activation of both CD4⁺ and CD8⁺ T cells in vitro . Suppression is mediated by a cell contact-dependent, cytokine-independent T–T interaction. Activation of CD4⁺ CD25⁺ via their TCR generates suppressor effector cells that are capable of non-specifically suppressing the activation of any CD4⁺ or CD8⁺ T cell. Activation of suppressor effector function is independent of co-stimulation mediated by CD28/CTLA-4 interactions with CD80/CD86. We propose that CD4⁺ CD25⁺ T cells recognize organ-specific antigens, are recruited to sites of autoimmune damage where they are activated by their target antigen, and then physically interact with autoreactive CD4⁺ or CD8⁺ effector cells to suppress the development of autoimmune disease.     

Magnetic resonance imaging of femoral head development in roentgenographically normal patients

Magnetic resonance images (MRI) of 22 patients with roentgenographically normal hips were reviewed retrospectively and the findings categorized according to age. With increasing maturity, the MR intensity of the femoral heads on spin echo images increased, as marrow fat became a dominant tissue in the head. The femoral head pattern was relatively inhomogeneous, with a broad band of diminished intensity extending in a posteromedial to anterolateral direction, corresponding to the pattern of trabecular bone. The femoral capital epiphyses were visible in younger patients as structures of bright intensity which remained evident through early adulthood. The articular cartilage of the hip joint was noted as a distinctive halo around the femoral head. An understanding of the MR pattern of the normal hip will aid in the early recognition of pathologic conditions, such as osteonecrosis.