Effect of detergents on the critical shear of detachment of cultured animal cells.
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Animals↗
Biomedical subjects
S Webb
Publications and source records attributed to S Webb.
Three-dimensional x-ray microtomography for medical and biological applications.
Three-dimensional (3D) x-ray microtomography is a technique for obtaining the 3D distribution of x-ray attenuation coefficients within small objects. To obtain microtomographic images apparatus has been developed which consists of a microfocal x-ray source, a computer-controlled stage for rotating the object, a 2D multi-wire gas proportional x-ray counter and a microcomputer to control image acquisition. Projection data were generated by rotating the object to discrete orientations around a single axis until of the order of 100 2D projection images of the object were collected. The projection images were transferred to a VAX 11/750 computer for subsequent 3D reconstruction using a convolution and back-projection algorithm in cone-beam geometry. The reconstructed data, comprising cubic voxels, may be displayed as sets of sequential transaxial, sagittal and coronal planes through the object. Alternatively, perspective displays of individual orthogonal sections may be formed with either intersecting planes or with these planes projected onto the surfaces of a box-like structure. The technique provides for the investigation of small-scale structures in biological specimens and we show some illustrative images of dead insects.
Animals↗
Analysis of HLA-DQB and HLA-DPB alleles in Graves' disease by oligonucleotide probing of enzymatically amplified DNA.
We have tested the possible association of HLA-DQB and HLA-DPB alleles with Graves' thyrotoxicosis, with or without severe ophthalmopathy, by polymerase chain amplification of genomic DNA and allele-specific oligonucleotide probing. There was no significantly abnormal distribution of DQB alleles compared to 50 control subjects except for a reduced prevalence of DQw 3.1 in the Graves' patients with severe ophthalmopathy (X2 = 6.23, P less than 0.02). HLA-DPB 2.1/8 was found in only 1 of 40 of these patients compared with 15 of the controls (X2 = 11.49, P less than 0.001). Ten of 48 patients with Graves' disease but without clinically significant eye involvement were HLA-DPB 2.1/8 positive, not significantly different from controls, but significantly different from the ophthalmopathy group (X2 = 6.70, P less than 0.01). The other DPB alleles in both groups of Graves' disease patients were the same as controls. These results suggest that HLA-DPB 2.1/8 may confer a protective effect in Graves' disease with respect to ophthalmopathy.
Alleles↗
Postimplantation development of tetraploid mouse embryos produced by electrofusion.
Despite the fact that a variety of experimental techniques have been devised over the years to induce tetraploid mammalian embryonic development, success rates to date have been limited. Apart from the early study by Snow, who obtained development to term of a limited number of cytochalasin B-induced tetraploid mouse embryos, no other researchers have achieved development of tetraploid embryos beyond the early postimplantation period. We now report advanced postimplantation development of tetraploid mouse embryos following electrofusion of blastomeres at the 2-cell stage, and subsequent transfer of these 1-cell 'fused' embryos to appropriate recipients. Cytogenetic analysis of the extraembryonic membranes of all of the postimplantation embryos encountered in the present study has provided an unequivocal means of confirming their tetraploid chromosome constitution. A preliminary morphological and histological analysis of the tetraploid embryos obtained by this technique has revealed that characteristic craniofacial abnormalities particularly involving the forebrain and eyes were consistently observed, and these features were often associated with abnormalities of the vertebral axis and heart. The most advanced viable embryo in this series was recovered on the 15th day of gestation, and its morphological features suggest that it was developmentally equivalent to a normal embryo of about 13.5-14 days p.c.
Animals↗
Proficiency testing for creatine kinase isoenzyme CK-2 (CK-MB) in Ontario.
Three surveys of the measurement and interpretation of creatine kinase (CK; EC 2.7.3.2) isoenzyme 2 (CK-MB) were conducted in Ontario, Canada, in 1989. Of the clinical laboratories participating, 66% used immunological methods and 24% used electrophoretic methods. Although reference ranges and interpretative routines varied widely, 95% of the laboratories reported correct interpretations for 10 of the 15 vials tested. The only major problems occurred with samples with very low total CK activity. Within-survey duplicate results compared well, and 89% of the laboratories had consistent between-survey results, even for specimens with low total CK activity. Errors were proportional to the frequency of use of the different analytical methods. The lyophilized testing material gave higher results with methods for measuring the mass of CK-2, suggesting that the material contained inactive but immunologically intact CK-2. The surveys indicate that laboratories should review their protocols for measuring CK-2 when only a single sample from the patient is available.
Creatine Kinase↗
Vitamin A and bone formation. Different responses to retinol and retinoic acid of chick bone cells in organ culture.
The response of bone cells in organ culture to retinol and retinoic acid was studied. Both stimulated incorporation of [3H]thymidine into DNA by 16-day embryonic chick calvaria, but the time-course of the responses differed; the peak responses to retinol and retinoic acid occurred at about 18 h and 48 h, respectively. Although retinol inhibited chick bone collagen synthesis retinoic acid had no effect, but it did stimulate non-collagenous protein synthesis, whereas the effect on the latter of retinol was, if anything, inhibitory. When present with retinol, retinoic acid was able to attenuate the inhibitory effect of the former on chick bone collagen synthesis, but preincubation with retinoic acid had no such effect. In neonatal murine calvarial cultures, retinoic acid inhibited collagen synthesis selectively in the same manner as did retinol. The ability of chick osteoblasts to respond differently to retinol and retinoic acid suggests that both forms of the vitamin may have a role in bone formation and that their intracellular models of action may differ although the attenuation response indicates there may be some interaction between the two.
Animals↗
Image quantification with a large area multiwire proportional chamber positron camera (MUP-PET).
A large area multi wire proportional chamber positron camera system is under evaluation for clinical Nuclear Medicine investigation using isotopes both from the house generators (68Ga) and from remote cyclotrons (18F, 124I, 64Cu and 81Rb). Images are reconstructed using a fully three dimensional (3D) algorithm and exhibit equal resolution in all three orthogonal directions. The axial field of view of 15 cm is large enough to allow coverage of the whole brain. This paper discusses the performance of the MUP-PET system with particular emphasis on quantification and the development of an attenuation correction scheme for a large area detector system. The distribution of scattered and accidental events is investigated and observed to contribute a fairly uniform background to the image. Dead time correction factors are calculated from an analytical expression obtained by considering the various sources of dead time present in the system. Following correction for attenuation, accidentals, scattered events and dead time, reconstructed phantom images show a strong linear correlation (r = 0.998) between count density and regional isotope concentration. The extension of the methods to clinical studies is discussed.
Image Processing, Computer-Assisted↗
Optimisation of conformal radiotherapy dose distributions by simulated annealing.
A method of computing the beam profiles for multi-element multiple-beam radiotherapy treatment is presented. This is applicable to the treatment planning of conformal radiotherapy using an isocentric rotation technique. The method begins with the treatment dose prescription and calculates the beam profiles rather than the reverse 'conventional' planning technique. The method is the iterative optimisation method of simulated annealing. It is shown using published 'difficult' clinical treatment planning problems that the high-dose region can be very precisely tailored to the tumour volume even when this has a re-entrant (concave) periphery. Simultaneously the dose can be constrained in other sensitive regions. The mathematics of the method is explained together with this implementation. The analogy of this optimisation with certain reconstruction problems in medical imaging is drawn and by way of experiment dose distributions are presented in image form and beam profiles as sinograms.
Computer Simulation↗
Quantitation of blood-brain barrier permeability by positron emission tomography.
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Blood-Brain Barrier↗
SPECT reconstruction by simulated annealing.
The technique of simulated annealing has been introduced for reconstruction in single photon emission computed tomography (SPECT) of data from rotating gamma camera systems. This is a much used technique in fields other than medical imaging but has only been used for one previous medical imaging application by Barrett et al (1983). It is shown that for noiseless data, the method can give perfect quantitative results, even when photon attenuation is included in the problem. This is true whatever the object distribution. With noisy data, mean level quantitation is still achievable although image mottle is worse. This paper describes simulated annealing in the language of SPECT, paying particular attention to the computational tricks which are central to a practicable implementation. The results of many computer simulations are presented to show the potential power of the method. A short comparison with other reconstruction techniques is made.
Brain Neoplasms↗
The performance of a multiwire proportional chamber positron camera for clinical use.
The Rutherford Appleton Laboratory clinical positron camera consists of two opposed multiwire proportional chambers (MWPCS) mounted on a rotating gantry capable of performing routine nuclear medicine studies. The system has operated since the end of 1986 with complete reliability. It has a sensitivity of 37 kcps MBq-1 cm3 per axial cm for a 20 cm diameter uniformly filled cylinder of activity. The best spatial resolution obtainable is about 6 mm, although in practice images are smoothed in order to reduce statistical noise with a corresponding decrease in resolution. Cross-plane rays are utilised during image reconstruction and the resulting three-dimensional images exhibit the same spatial resolution in three orthogonal directions over a large cylindrical field of view 15 cm high by 30 cm in diameter. The maximum data-taking rate is limited to 1.5 to 2 kcps at present due to deadtime in the read-out system. The performance of the system is described with particular reference to the problems of imaging with the large fractions of random and scattered events which are a consequence of using large-area detectors. Images of phantoms and patients are presented and proposed modifications to the camera are described.
Algorithms↗
Legibility of health warnings on billboards that advertise cigarettes.
At present only subjective criteria exist to determine the legibility of health warnings on billboards that display advertisements for cigarettes. We constructed a set of objective standards and used them to assess the legibility of warnings on a sample of 37 billboards in Perth, Western Australia. The three features that were analysed were the apparent size of the letters, the colour contrast between the letters and their background, and the obliqueness of the message. We also compared the size and legibility of the health warning with that of the brand name. Health warnings were not legible to passing motorists in 51% of cases and not legible to motorists who were stopped at nearby intersections in 74% of cases, whereas almost all the brand names could be read easily. These results indicate that the present system of voluntary regulation of advertisements for cigarettes has failed to ensure that health warnings on billboards are legible. For health warnings on advertisements to have any useful effect it is essential that they are legible. The only way to ensure legibility is to adopt objective requirements for it.
Advertising↗
Human immunodeficiency virus infection in Papua New Guinea.
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Acquired Immunodeficiency Syndrome↗
Stimulatory effect of prolactin on the mitotic activity of the adrenal cortex in snell mice with hereditary dwarfism.
Effects of thyrotropin (TSH), growth hormone (GH), prolactin (Prl), and ACTH on the proliferation of adrenocortical cells in male Snell dwarf mice and in phenotypically normal male mice from the same strain were examined by means of the colchicine metaphase-arrest technique. After 6 days of treatment, ACTH increased significantly the mean mitotic activity rate (MMAR) of adrenocortical cells in both the normal (nondwarf) and dwarf mice as compared to the corresponding control groups receiving physiologic saline. None of the remaining examined pituitary hormones did exert a mitogenic action on the adrenal cortex of normal mice. It was, however, recorded the significant elevation of the MMAR of the adrenocortical cells in Prl-treated Snell dwarf mice, while TSH and GH did not stimulate mitogenesis. The acquired data corroborates a well-known proliferogenic effect of ACTH on the adrenal cortex in vivo. The increase of the MMAR of the adrenal cortex of Snell dwarfs following Prl-treatment is in agreement with earlier reports.
Adrenal Cortex↗
Brain blotting: a method to detect multiple DNA copies in specific brain regions.
We developed a method to detect multiple DNA copies (both cellular and viral) in specific brain regions by blotting thick frozen sections onto nylon membranes. This was achieved by "printing" the frozen sections on standard blotting paper immediately after cryotome sectioning and performing blotting according to the standard Southern technique. A "replica" of the blotted section was obtained by keeping on the glass slide the next frozen section cut, which was then stained for conventional histopathological analysis and the cell nuclei counted to give an estimate of the total amount of DNA present in each section. The blotted membranes were then denatured and hybridized with a nick-translated Alu probe either at 42 degrees C with 50% formamide or at 68 degrees C without formamide. Brain sections from mice infected with Herpes simplex virus 1 (HSV1), blotted and hybridized with a nick-translated HSV1 probe, clearly showed the focal nature of the Herpes simplex infection, which was also demonstrated immunohistologically using a virus specific antiserum. This method of DNA detection, conveniently modified, might also be used to detect nuclear and cytoplasmic RNAs in specific coronal sections of whole brain before localization at high power by standard in situ techniques.
Animals↗
Deconvolution of emission tomographic data: a clinical evaluation.
A method of improving the quality of images in single photon emission computed tomography (SPECT) is demonstrated using transaxial images of the liver and brain. Deconvolution of the nuclear medicine data by a point source response function (PSRF) acquired previously in a scattering medium attempts to compensate for scattered radiation within the patient. The average geometric response of the collimator of the gamma camera is also compensated for with this technique. Three patients with known metastatic lesions in the liver and three with primary lesions in the brain were imaged. Clinical assessment of reconstructed slices both before and after deconvolution demonstrates that compensating for the effects of scatter and of collimator blurring leads to enhanced detail of pathological lesions. In all cases, cold lesions seen prior to deconvolution were enhanced in detail and, in addition, new lesions were seen with this technique.
Adult↗
Three-dimensional shaded-surface images from positron tomography using MUP-PET.
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Goiter, Nodular↗
Comparison of the effects of nebulized terbutaline with intravenous enprofylline in patients with acute asthma.
We compared the bronchodilating effects of intravenously administered enprofylline (2 mg/kg) with nebulized terbutaline (10 mg) in patients presenting to hospital with acute asthma in a multicenter double-blind parallel study. One hundred twenty three patients were randomized into the study, and 69 of these fulfilled the inclusion criteria and a retrospective time to study entry criterion; 34 received enprofylline and 35 received terbutaline. There was no significant difference in maximum increase in forced expired volume in 1 second (FEV1) between the enprofylline group (0.24 +/- 0.33 L) and the terbutaline group (0.25 +/- 0.28 L) (p greater than 0.05), nor for the increase in FEV1 over the 1-hour study period. Tremor was reported more in the group receiving terbutaline, and nausea was reported more in the group receiving enprofylline. Two patients experienced hypotension and one patient had a vasovagal episode with enprofylline treatment. Both agents acted as bronchodilators with similar efficacy in patients with acute asthma in this study.
Acute Disease↗