A novel method for dynamic ventilation imaging of the full respiratory cycle from four-dimensional computed tomography (4D CT) acquired without added contrast is presented. Three cases with 4D CT images obtained with respiratory gated acquisition for radiotherapy treatment planning were selected. Each of the 4D CT data sets was acquired during resting tidal breathing. A deformable image registration algorithm mapped each (voxel) corresponding tissue element across the 4D CT data set. From local average CT values, the change in fraction of air per voxel (i.e. local ventilation) was calculated. A 4D ventilation image set was calculated using pairs formed with the maximum expiration image volume, first the exhalation then the inhalation phases representing a complete breath cycle. A preliminary validation using manually determined lung volumes was performed. The calculated total ventilation was compared to the change in contoured lung volumes between the CT pairs (measured volume). A linear regression resulted in a slope of 1.01 and a correlation coefficient of 0.984 for the ventilation images. The spatial distribution of ventilation was found to be case specific and a 30% difference in mass-specific ventilation between the lower and upper lung halves was found. These images may be useful in radiotherapy planning.

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Four variants of human beta globin in which the Trp at position 37 has been replaced with a Tyr, Ala, Gly, or Glu have been expressed in Escherichia coli. These globins have been combined with normal human alpha chains and heme to form tetrameric hemoglobin molecules. A technique for the preparation of alpha chain dimers, which are cross-linked between their alpha99 lysine residues, has been developed, and these alpha dimers were combined with two of the beta globins, betaW37G and betaW37E, to form the corresponding cross-linked variants. The kinetics of CO binding to the deoxygenated derivatives following rapid mixing and of CO rebinding following flash photolysis have been examined as functions of pH in the presence and absence of the organic phosphate inositol hexaphosphate, IHP. The kinetic measurements indicate that replacement of the tryptophan with other residues destabilizes the hemoglobin tetramer, resulting in considerable dissociation of even the deoxygenated hemoglobins into alphabeta dimers at micromolar protein concentrations. Substitutions at beta37 also alter the properties of the deoxygenated hemoglobin tetramer. The alteration of the functional properties of the T states of these variants as well as the tendency of the deoxygenated derivatives to dissociate into alphabeta dimers increases in the order HbA < betaW37Y < betaW37A < betaW37G < betaW37E. Stabilizing the betaW37G or betaW37E tetramers by addition of IHP or by cross-linking does not restore the normal functional properties of the T state. Measurements of the geminate rebinding of CO establish a kinetic difference between the normal R state tetramer and the alphabeta dimer consistent with quaternary enhancement, the greater affinity of oxygen for the R state tetramer than for the alphabeta dimer. Kinetics of geminate rebinding also suggest that quaternary enhancement may be altered by substitutions at the beta37 position.

BACKGROUNDAlthough central nervous system (CNS) prophylaxis in patients with leukemia has reduced the incidence of CNS disease recurrence, it still is reported to occur in approximately 5–10% of cases, resulting in a median survival of 6 months. Craniospinal irradiation (CSI) has been shown to improve survival in children who develop a CNS recurrence of acute lymphocytic leukemia (ALL). However, to the authors' knowledge, the role of CSI in adults with a CNS recurrence of leukemia is unknown.METHODSA retrospective review of adult patients treated with CSI for a CNS recurrence of leukemia identified 16 patients treated between 1986 and 2001. The median age of the patients was 34 years (range, 16–58 years). The diagnoses included seven patients with acute myelogenous leukemia (AML), eight patients with ALL, and one patient with chronic myelogenous leukemia in blast crisis. All patients had achieved a complete disease remission prior to the CNS recurrence. Eleven patients had an isolated CNS recurrence and 5 patients had concurrent disease identified in the blood/bone marrow. The median dose of radiation was 24 grays (Gy) (range, 18–34.5 Gy) to the cranium and 18 Gy (range, 15–30 Gy) to the spine. The median fraction size was 1.8 Gy (range, 1.5–2.0 Gy) to the cranium and 1.5 Gy (range, 1.5–2.0 Gy) to the spine. Fifteen patients were also treated with intrathecal chemotherapy.RESULTSOne patient failed to complete radiation treatment because of disease progression. Thirteen patients achieved a complete response in the cerebrospinal fluid (CSF). The median time to disease progression was 3 months from the first day of CSI and 7 months from CNS recurrence. The median survival was 4 months and 9 months, respectively. No CNS recurrences occurred, but there were 11 bone marrow failures, 2 patients without recurrence at > 5 years, and 3 deaths without a documented site of failure. Thirteen patients had no evidence of disease in the CSF until their death or the time of last follow‐up.CONCLUSIONSCSI with or without intrathecal chemotherapy appears to be effective at eliminating leukemia in the craniospinal axis. However, the eradication of disease in the CNS was not found to be effective at preventing disease recurrence in the bone marrow, and despite improved control of disease in the CNS, adult patients with a CNS recurrence still had a poor prognosis. Furthermore, the rapidly fatal course of disease prevented an assessment of the durability of CNS response to irradiation. Cancer 2004. © 2004 American Cancer Society.

Our goal was to develop a method for generating high-resolution three-dimensional pulmonary compliance images in rodents from computed tomography (CT) images acquired at a series of constant pressures in ventilated animals. One rat and one mouse were used to demonstrate this technique. A pre-clinical GE flat panel CT scanner (maximum 31 line-pairs cm(-1) resolution) was utilized for image acquisition. The thorax of each animal was imaged with breath-holds at 2, 6, 10, 14 and 18 cm H2O pressure in triplicate. A deformable image registration algorithm was applied to each pair of CT images to map corresponding tissue elements. Pulmonary compliance was calculated on a voxel by voxel basis using adjacent pairs of CT images. Triplicate imaging was used to estimate the measurement error of this technique. The 3D pulmonary compliance images revealed regional heterogeneity of compliance. The maximum total lung compliance measured 0.080 (+/-0.007) ml air per cm H2O per ml of lung and 0.039 (+/-0.004) ml air per cm H2O per ml of lung for the rat and mouse, respectively. In this study, we have demonstrated a unique method of quantifying regional lung compliance from 4 to 16 cm H2O pressure with sub-millimetre spatial resolution in rodents.

Metal nanoparticles have significant interaction cross-sections with electromagnetic waves due to their large surface area-to-volume ratio, which can be exploited in cancer radiotherapy to locally enhance the radiation dose deposition in tumors. We developed a new type of silver nanoparticle composite, PEGylated graphene quantum dot (GQD)-decorated Silver Nanoprisms (pGAgNPs), that show excellent in vitro intracellular uptake and radiosensitization in radiation-sensitive HCT116 and relatively radiation-resistant HT29 colorectal cancer cells. Furthermore, following biodistribution analysis of intravenously injected nanoparticles in nude mice bearing HCT116 tumors radiosensitization was evaluated. Treatment with nanoparticles and a single radiation dose of 10 Gy significantly reduces the growth of colorectal tumors and increases the survival time as compared to treatment with radiation only. Our findings suggest that these novel nanoparticles offer a promising paradigm for enhancing colorectal cancer radiation therapy efficacy.

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For many years, human hemoglobin (Hb) isolated from erythrocytes has been investigated as a potential oxygen delivery therapeutic. Advantages with respect to the need for blood typing were balanced with various undesirable properties of cell-free Hb, including cost, overall oxygen affinity, alterations in cooperativity, and ready dissociation into toxic dimeric species. The use of total gene synthesis has resulted in very high levels of functional human Hb expression in Escherichia coli, but there remains a desire for effecting the crosslinking of the hemoglobin tetramer and providing for ready means for increasing the globular molecular weight. In this communication, we report a novel method for linking alpha chains. By circularly permuting one alpha sequence, the second alpha chain in the Hb tetramer can be linked with glycine residues to form 2 bridges across the central cavity. The second alpha chain thus presents its amino and carboxyl termini on a solvent exposed surface, providing for additional polymerization of oxygen-carrying subunits or attachment of any other peptide-based therapeutic. IntroductionA mechanistic and predictive understanding of how a primary sequence can fold to a single tertiary structure remains undefined. Since a thorough understanding of this process will enable the rational design of unique protein structures, this remains an area of active research. One theory suggests that short continuous regions within a protein develop local interactions early in the folding process to minimize the number of accessible structures and catalyze the formation of a functional protein. Radical perturbations of protein structure by circular permutation is one technique being used in an attempt to explore this issue. In addition, utilization of circular permutation itself can be exploited in the design of new protein structures.A circularly permuted protein is created in 2 steps. First, the original termini are linked to form a circular polypeptide. New termini are then created by cleavage of a peptide bond at a location distant from the original termini. Goldenberg and Creighton engineered the first circularly permuted sequence by chemically condensing the termini of bovine pancreatic trypsin inhibitor (BPTI) and generating new termini by limited proteolysis. 1 This circularly permuted variant was shown to refold, in vitro, to a native functional conformation. This seminal experiment suggested that the location of the termini has little effect on the final 3-dimensional structure of the protein. Luger and coworkers genetically circularly permuted phosphoribosyl anthranilate isomerase. 2 The Escherichia coli translated variant was structurally and functionally similar to the wild-type protein. Several other monomeric proteins have since been circularly permuted through genetic manipulations, all of which maintain a nativelike function. [3][4][5][6][7][8][9][10][11] Single subunits of multimeric proteins can also withstand circularly permuted sequences. For example, circularly permuted catalytic cha...