Atypical white matter volume development in children following craniospinal irradiation

Most children with medulloblastoma (MB), the second most common pediatric brain tumor, have a 70% probability of survival. However, survivors who receive aggressive therapy are at significant risk of cognitive deficits that have been associated with lower volumes of normal-appearing white matter (NAWM). We hypothesized that cranial irradiation inhibited normal brain volume development in these survivors. We retrospectively analyzed 324 MRI studies of 52 patients with histologically proven MB treated with surgery and 35 to 40 Gy craniospinal irradiation, with or without chemotherapy. The volume of NAWM and that of cerebrospinal fluid were quantified from a single index section and compared with those of healthy, age-similar control subjects. A quadratic random coefficient model was used to identify trends in brain volume with increasing age. Patients treated for MB at younger ages demonstrated substantially less development of NAWM volume than did their healthy peers. Younger age at the time of irradiation and the need for a ventricular shunt were significantly associated with reduced NAWM volume. NAWM and craniospinal fluid volume differences between patients who had shunts and those without resolved over a period of four to five years. NAWM volume is known to be associated with neurocognitive test performance, which shows deficiencies after cranial irradiation early in life. Therefore, volumetric monitoring of brain development can be used to guide the care of survivors, assess the toxicity of previous and current clinical trials, and aid in the design of therapies that minimize toxicity.     

Multispectral analysis of magnetic resonance images

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.     

A multi-disciplinary professional practice model: supporting autonomy and accountability in program-based structure

This article addresses the challenge of maintaining high quality patient care in a large, diverse health care organization as it merged and moved from a functional to a program-based management structure. The article describes the Professional Practice Model (PPM) which was developed to address the professional issues inherent in a program-based management structure. The operationalization of the PPM, including the committee structures which were put in place to support it, are discussed. The final section of the article highlights the strengths and challenges which have arisen through the development and implementation of the Professional Practice Model.     

Effect of retroviral transduction of canine microvascular endothelial cells on beta(1) integrin subunit expression and cell retention to PTFE grafts

This study evaluated the effect of retroviral transduction on canine microvascular endothelial cell (CMVEC) detachment from fibrin glue coated expanded polytetrafluoroethylene (ePTFE) graft material. CMVEC were isolated from adipose tissue by fluorescent activated cell sorting (FACS). Three treatment groups were evaluated: G-I, transduced CMVEC, selected in antibiotic G418 for 10 days (n=5); G-II, CMVEC selected in G418 and recovered from selection for 4 days (n=5); and G-III, control group of naive CMVEC (n=6). (3)H-thymidine labeled endothelial cells were seeded on fibrin glue coated four-mm diameter PTFE. Grafts were exposed to physiologic shear stresses of 16 dyn/cm(2). Cell detachment was determined by (3)H-thymidine counts in the circuit effluent. beta(1) integrin subunit expression was measured by flow cytometry. After 2 hours of flow exposure, G-I and G-II demonstrated significantly greater cell detachment rates compared with the control seeded grafts. Median peak channel beta(1) integrin subunit value for G-III CMVEC was 2311+/-481.7 vs. 31.5+/-4.51 and 26.3+/-2.0 in the transduced cell groups (p=0.00043). Low beta(1) integrin expression correlated with flow induced high detachment rates of retrovirally-transduced CMVEC.     

Rapid method for isolation of normal human peripheral blood eosinophils on discontinuous Percoll gradients and comparison with neutrophils

Previous studies on human eosinophils often have used cells from patients with hypereosinophilia syndrome or parasitosis owing to the difficulty in isolating pure populations of eosinophils from normal individuals. In the present study, human eosinophils were isolated with a purity of 97%, with 70% recovery from normal individuals with blood eosinophil counts of less than 3%. Human eosinophils are denser than neutrophils, but the range of densities of the two cell types overlap, making purification of eosinophils by density-gradient centrifugation difficult. However, if neutrophils were exposed to the chemotactic peptide (f-Met-Leu-Phe), which did not stimulate eosinophils, the neutrophils' density decreased, shifting them away from the density of eosinophils. Whole normal blood anticoagulated with EDTA was incubated at 37 degrees C for 15 minutes with 10(-6) mol/L f-Met-Leu-Phe and then layered over a discontinuous Percoll gradient (65% and 75% in diluted phosphate-buffered saline) and centrifuged at 400 g for 25 minutes at 22 degrees C. The cell layer between the 65% and 75% Percoll was collected and washed, and hypotonic lysis was used to remove erythrocytes. This cell layer contained 97.3 +/- 0.7% eosinophils (N = 8) with a yield of 4.9 X 10(4) eosinophils per milliliter of whole blood, or 70% of the total eosinophil count. The isolated eosinophils were in a quiescent state but responded to Escherichia coli endotoxin- activated serum with shape change and chemotaxis, membrane depolarization, and reduced nitroblue tetrazolium (96.0 +/- 1.0%), when stimulated with phorbol myristate acetate. In phagocytic assays, 89.3 +/- 1.3% of the eosinophils ingested Candida albicans v 96.0% +/- 1.0% of neutrophils. In contrast, the eosinophils did not respond chemotactically, alter membrane potential, or reduce nitroblue tetrazolium when treated with f-Met-Leu-Phe, and studies with f-Met-Leu- [3H]Phe showed that normal eosinophils lacked expression of receptors for f-Met-Leu-Phe. In control studies, normal eosinophils that were not exposed to f-Met-Leu-Phe during purification also failed to respond to f-Met-Leu-Phe, indicating intrinsic differences between normal eosinophils and neutrophils. Thus, exposure of whole blood to f-Met-Leu- Phe, followed by separation on Percoll is a simple method for rapid isolation of normal human eosinophils.