A gene on chromosome 11q23 coding for a putative glucose- 6-phosphate translocase is mutated in glycogen-storage disease types Ib and Ic

Glycogen-storage diseases type I (GSD type I) are due to a deficiency in glucose-6-phosphatase, an enzymatic system present in the endoplasmic reticulum that plays a crucial role in blood glucose homeostasis. Unlike GSD type Ia, types Ib and Ic are not due to mutations in the phosphohydrolase gene and are clinically characterized by the presence of associated neutropenia and neutrophil dysfunction. Biochemical evidence indicates the presence of a defect in glucose-6-phosphate (GSD type Ib) or inorganic phosphate (Pi) (GSD type Ic) transport in the microsomes. We have recently cloned a cDNA encoding a putative glucose-6-phosphate translocase. We have now localized the corresponding gene on chromosome 11q23, the region where GSD types Ib and Ic have been mapped. Using SSCP analysis and sequencing, we have screened this gene, for mutations in genomic DNA, from patients from 22 different families who have GSD types Ib and Ic. Of 20 mutations found, 11 result in truncated proteins that are probably nonfunctional. Most other mutations result in substitutions of conserved or semiconserved residues. The two most common mutations (Gly339Cys and 1211-1212 delCT) together constitute approximately 40% of the disease alleles. The fact that the same mutations are found in GSD types Ib and Ic could indicate either that Pi and glucose-6-phosphate are transported in microsomes by the same transporter or that the biochemical assays used to differentiate Pi and glucose-6-phosphate transport defects are not reliable.     

Solution structure of murine macrophage inflammatory protein-2

The solution structure of murine macrophage inflammatory protein-2 (MIP-2), a heparin-binding chemokine that is secreted in response to inflammatory stimuli, has been determined using two-dimensional homonuclear and heteronuclear NMR spectroscopy. Structure calculations were carried out by means of torsion-angle molecular dynamics using the program X-PLOR. The structure is based on a total of 2390 experimental restraints, comprising 2246 NOE-derived distance restraints, 44 distance restraints for 22 hydrogen bonds, and 100 torsion angle restraints. The structure is well-defined, with the backbone (N, Calpha, C) and heavy atom atomic rms distribution about the mean coordinates for residues 9-69 of the dimer being 0.57 +/- 0.16 A and 0.96 +/- 0.12 A, respectively. The N- and C-terminal residues (1-8 and 70-73, respectively) are disordered. The overall structure of the MIP-2 dimer is similar to that reported previously for the NMR structures of MGSA and IL-8 and consists of a six-stranded antiparallel beta-sheet (residue 25-29, 39-44, and 48-52) packed against two C-terminal antiparallel alpha-helices. A best fit superposition of the NMR structure of MIP-2 on the structures of MGSA, NAP-2, and the NMR and X-ray structures of IL-8 are 1.11, 1.02, 1.27, and 1.19 A, respectively, for the monomers, and 1.28, 1.10, 1.55, and 1.36 A, respectively, for the dimers (IL-8 residues 7-14 and 16-67, NAP-2 residues 25-84). At the tertiary level, the main differences between the MIP-2 solution structure and the IL-8, MGSA, and NAP-2 structures involve the N-terminal loop between residues 9-23 and the loops formed by residues 30-38 and residues 53-58. At the quaternary level, the difference between MIP-2 and IL-8, MGSA, or NAP-2 results from differing interhelical angles and separations.     

Assigning buses to schedules in a metropolitan area

The problem of scheduling a fleet of buses to a given set of trips is encountered by large bus companies performing thousands of trips per day. The time-tables for those trips are planned separately and reflect the passengers demand for transportation. These time-tables are inputs for the bus scheduling procedures. The scheduling problem is difficult due to its size and due to many operational constraints which are imposed. A mathematical formulation of the problem is presented and an efficient algorithm is developed. This paper presents results and computational experience that were obtained from implementing the model in a large bus company.     

Occam algorithms for computing visual motion

The standard approach to computing motion relies on pixel correspondence. Computational schemes impose additional constraints, such as smoothness and continuity of the motion vector even though these are not directly related to pixel correspondence. This paper proposes an alternative to the multiple constraints approach. By drawing analogy with machine learning, motion is computed as a function that accurately predicts frames. The Occam-Razor principle suggests that among all functions that accurately predict the second frame from the first frame, the best predictor is the “simplest,” and simplicity can be rigorously defined in terms of encoding length. An implementation of a practical algorithm is described. Experiments with real video sequences verify the algorithm assumptions by showing that motion in typical sequences can be accurately described in terms of a few parameters. Our particular choice of predictors produces results that compare very favorably with other image flow algorithms in terms of accuracy and compactness. It may, however, be too constrained to enable accurate recovery of 3D motion and structure     

Adhesion of mature polyploid megakaryocytes to fibronectin is mediated by beta 1 integrins and leads to cell damage

Human CD34+ bone marrow cells were committed to the megakaryocytic lineage in serum-free liquid cultures by the following cytokines: thrombopoietin, erythropoietin, and IL-6. Megakaryocyte maturation has been described as being regulated by the extracellular matrix. These cells express receptors for laminin, collagen, and vitronectin, but they selectively adhere to and spread on fibronectin, a major component of the bone marrow environment. Function-perturbing antibodies against beta 1 integrins totally abolished the adhesion of megakaryocytes on fibronectin, whereas antibodies to beta 3 did not, suggesting that beta 1 integrins were responsible for the adhesive phenotype of these polyploid cells. beta 1-positive clusters were visualized in close contact with the extremities of stress fibers at the cell surface. In the course of cell spreading, we observed morphological modifications such as the disorganization of the compact nuclei structure and the appearance of holes in the cytoplasm leading to the release of alpha IIb beta 3-positive cellular fragments. This process appeared to be a specific feature of megakaryocytes and is correlated neither to apoptosis nor to integrin signaling.     

Treatment of progressive cervical spinal instability secondary to hydatid disease. A case report

STUDY DESIGN: A case report of a patient with progressive cervical spinal instability secondary to hydatid disease and the operative therapy. OBJECTIVE: To document how the combination of contemporary imaging, medical, and operative methods has obviated severe neurologic sequelae in a patient's cervical spine ravaged by hydatidosis. SUMMARY OF BACKGROUND DATA: The incidence of hydatid disease in the vertebral column is unusual and rare in the cervical spine. Until recently, patients with spinal hydatid disease have had guarded prognoses, because the various medical and surgical therapies could not effect curative or even palliative results. METHODS: The use of contemporary imaging methods, including computed tomography and magnetic resonance imaging, is described, in conjunction with current anthelminthic therapy and operative spinal instrumentation in this patient with recurrent quadriparesis from progressive hydatid spinal erosion. RESULTS: With the operative and medical therapies described in this case report, the patient has had six successful operative results in 6 years for cervical spinal hydatidosis and remains neurologically normal, with a stable cervical spine. CONCLUSIONS: It is hoped that this case presentation will justify a spirit of guarded optimism in the patient whose spine has been rendered unstable by hydatid disease and that, though a cure is still not likely, at least the past inexorable prognosis of paralysis and death is ameliorated.