PubMed Health⌕ Search

Biomedical subjects

C R Crawford

Publications and source records attributed to C R Crawford.

32 records · Page 2Linked to original sources
PubMed1984

Use of a zwitterionic detergent for the preparation of an influenza virus vaccine: 2. Immunogenicity of Empigen-treated virus in animals.

The immunogenicity of zwitterionic detergent-disrupted influenza virus vaccine preparations, intact virus vaccine and vaccine preparations obtained by treatment of the intact virus with Triton-X 100 or cetyl trimethyl ammonium bromide (CTAB) was studied in hamsters and mice. In all experiments the intact, inactivated virus vaccine induced greater serum haemagglutination-inhibiting (HI) and neuraminidase-inhibiting (NI) antibody titres than the detergent-disrupted preparations. The serum HI antibody responses induced in hamsters and mice by Empigen-, Triton-, or CTAB-disrupted vaccines were similar, although more highly purified Empigen-disrupted preparations elicited marginally lower immune responses. In both animal species, all vaccine preparations afforded a similar degree of protection against homologous virus challenge.

Animals↗
PubMed1982

Depletion and recovery of ATP in V79 cells with exposure to inhibitors of glycolysis and oxidative phosphorylation.

Cells of the cultured hamster cell line V79 were labeled with tritiated adenosine and incubated for up to 30 min in the presence of inhibitors of glycolysis and oxidative phosphorylation. These inhibitors were (a) 5 mM KCN plus 5 mM iodoacetate, (b) 5 mM KCN plus 5 mM KF, and (c) 15 mM KCN plus 15 mM KF. The fate of the tritium label was examined during incubation with inhibitors and also during subsequent incubation in growth medium in the absence of inhibitors. The tritiated ATP pool was found to decrease in cells incubated in the presence of any of the inhibitor combinations, but only in the presence of 15 mM KCN plus 15 mM KF was this pool decreased below the level of detection. After cells were incubated with KCN plus KF, a high level of ATP was recovered when the inhibitors were removed. Cells incubated with KCN plus iodoacetate retained depletion levels of ATP. Plating efficiency and trypan blue staining showed that KCN-KF treated cells retained viability, whereas KCN-iodoacetate treated cells did not. Cells were examined for ability to take up tritiated uridine before, during, and after depletion of ATP by incubation in the presence of 15 mM KCN plus 15 mM KF. These cells were found to have a variation in uridine uptake that was related directly to intracellular ATP level. Cells in which the ATP was very low exhibited little or no uridine uptake, whereas cells in which the ATP level was near normal exhibited normal uridine uptake.

Adenosine Triphosphate↗
PubMed1982

Isolation of a Chinese hamster cell mutant with low intracellular phosphoribosylpyrophosphate concentration.

A tritium-adenine suicide procedure was used to select for mutants with reduced uptake of adenine from a population of Chinese hamster V79 cells mutagenized with ethyl methane sulfonate. In one of the mutant lines isolated, designated KC62, the uptake of adenine, hypoxanthine, and guanine was reduced by approximately 70%. The specific activities, Km values, and Vmax values of adenine phosphoribosyltransferase and of hypoxanthine phosphoribosyltransferase were the same in extracts from KC62 and from the parental cell line. Metabolic fate studies of incorporated [3H]adenine and 3[H]hypoxanthine revealed a metabolic block at the level of phosphoribosylation. Determination of phosphoribosylpyrophosphate pool size showed that the mutant contained only 25% of the phosphoribosylpyrophosphate found in the parent. Its reduced availability in KC62 appears to result in a decreased ability to salvage adenine, hypoxanthine, and guaninine via phosphoribosylation. Phosphoribosylpyrophosphate synthetase from KC62 was shown to have an increased sensitivity to inhibition by a variety of nucleotides.

Adenine↗
PubMed1982

The effect of bacterial peptidoglycans on the immune response of hamsters to influenza virus vaccines.

The immune response of hamsters to influenza virus vaccine incorporating peptidoglycans derived from Streptomyces griseus was investigated. The results showed that although inoculation of a subunit influenza virus vaccine together with a peptidoglycan elicited a markedly increased serum HI antibody response compared to that induced by the subunit vaccine alone, pre-treatment of animals with peptidoglycans resulted in a suppression of the antibody response to the vaccine haemagglutinin antigen. The immunosuppressive effect was dose-related, and could be shown by adoptive transfer experiments to be transferred by spleen cell preparations from peptidoglycan-treated hamsters. The reasons for these findings, and their implication for the use of peptidoglycans as 'carriers' in influenza virus subunit vaccines, are discussed.

Animals↗
PubMedDate not supplied

Reprojection using a parallel backprojector.

Reprojection is the process by which projections are produced from an image, such that if these projections are filtered and backprojected, they yield the original image. In computed tomography, applications of reprojection include its use in algorithms for iterative beam hardening correction, metal artifact removal, and streak suppression. However, because of the computational expense of reprojection, algorithms that employ this process have never been widely used. A method will be presented that enables an unmodified backprojector to be used as a reprojector. Because backprojectors are designed to exploit the parallelism in the backprojection algorithm, the time required to obtain reprojections is significantly reduced.

Humans↗
PubMedDate not supplied

Reconstruction for fan beam with an angular-dependent displaced center-of-rotation.

A convolutional backprojection algorithm is derived for a fan beam geometry that has an angular-dependent displacement in its center-of-rotation from the midline of the fan beam. In both x-ray computed tomography and single photon emission computed tomography, misalignment can occur when the mechanical center-of-rotation is not colinear with midline of the fan beam. In some cases the shift in the center-of-rotation is constant for every angle, whereas, in other cases it varies with angular position. Standard reconstruction algorithms, which directly filter and backproject the fan beam data without rebinning into parallel beam geometry, have been derived for a geometry having its center-of-rotation at the midline of the fan beam. However, in the case of any misalignment of the center-of-rotation, if these conventional reconstruction algorithms are used to reconstruct the fan beam projections, structured artifacts and a loss of resolution will result. Simulations are performed that illustrate these artifacts and demonstrate how the new algorithm corrects for this misalignment. A method for estimating the parameters of the fan beam geometry, including the angular-dependent shift in the center-of-rotation, is also described.

Algorithms↗
PubMedDate not supplied

Two algorithms for the three-dimensional reconstruction of tomograms.

Three-dimensional (3-D) surface reconstructions provide a method to view complex anatomy contained in a set of computed tomography (CT), magnetic resonance imaging (MRI), or single photon emission computed tomography tomograms. Existing methods of 3-D display generate images based on the distance from an imaginary observation point to a patch on the surface and on the surface normal of the patch. We believe that the normalized gradient of the original values in the CT or MRI tomograms provides a better estimate for the surface normal and hence results in higher quality 3-D images. Then two algorithms that generate 3-D surface models are presented. The new methods use polygon and point primitives to interface with computer-aided design equipment. Finally, several 3-D images of both bony and soft tissue show the skull, spine, internal air cavities of the head and abdomen, and the abdominal aorta in detail.

Algorithms↗
PubMedDate not supplied

Computed tomography scanning with simultaneous patient translation.

This paper deals with methods of reducing the total time required to acquire the projection data for a set of contiguous computed tomography (CT) images. Normally during the acquisition of a set of slices, the patient is held stationary during data collection and translated to the next axial location during an interscan delay. We demonstrate using computer simulations and scans of volunteers on a modified scanner how acceptable image quality is achieved if the patient translation time is overlapped with data acquisition. If the concurrent patient translation is ignored, structured artifacts significantly degrade resulting reconstructions. We present a number of weighting schemes for use with the conventional convolution/backprojection algorithm to reduce the structured artifacts through the use of projection modulation using the data from individual and multiple slices. We compare the methods with respect to structured artifacts, noise, resolution and to patient motion. Review of preliminary results by a panel of radiologists indicates that the residual image degradation is tolerable for selected applications when it is critical to acquire more slices in a patient breathing cycle than is possible with conventional scanning.

Algorithms↗
PubMedDate not supplied

Estimation of geometrical parameters and collimator evaluation for cone beam tomography.

A method is presented for estimating the geometrical parameters for a cone beam detector geometry from the coordinates of the centroid of a projected point source sampled over 360 degrees. Nonlinear expressions are derived for the coordinates of the centroids in terms of the geometrical parameters which include: the two-dimensional coordinates of the projection of the center of rotation onto the detector image plane; the focal length; the distance from the focal point to the center of rotation; and the spatial coordinates of the point source itself. Experimental data were obtained using a rotating gamma camera with a symmetrically converging collimator. The Marquardt algorithm was used to estimate the parameters for this particular cone beam geometry. The method was able to estimate the geometrical parameters and evaluate the accuracy of the collimator construction.

Evaluation Studies as Topic↗