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Biomedical subjects

B Murray

Publications and source records attributed to B Murray.

At least 73 records · Page 4Linked to original sources
PubMed1991

Reduction of the Bremsstrahlung component of clinical electron beams: implications for electron arc therapy and total skin electron irradiation.

The dose due to Bremsstrahlung in stationary electron beams of nominal energies in the range 6-20 MeV is typically between 1-7% of the maximum dose and is usually not clinically significant. However, in treatments using rotational or multiple electron beams where the x-ray dose from several beams is added the x-ray dose will reach much higher proportions and will be of clinical significance. Moreover, this dose often is located in normal tissue beyond the target volume. Reduction of this x-ray dose is therefore desirable. In the present study a reduction of the x-ray component of electron beams produced by a Clinac 2100C accelerator by a change of the transmission ion chamber and scattering foils is reported. A reduction in Bremsstrahlung of up to 50% can be achieved.

Electrons↗
PubMed1991

An experimental study in electrical impedance tomography using backprojection reconstruction.

This paper reports on experiments designed to evaluate the performance of the equipotentials backprojection method under conditions modeling those of proposed applications of electrical impedance tomography. Small spherical targets were placed inside a saline-filled tank with dimensions similar to a human torso. Data were acquired with a computer-based instrument that applies current to pairs of electrodes located on two horizontal planes and records potential differences between electrodes of a third plane. The relative contrast produced by nonconducting spheres in a uniform saline background was measured on the reconstructed images and used to determine system sensitivity to target volume and to the radial and vertical positions of single spheres. Results show that for radial positions within a critical radius sensitivity is always maximum when the spheres center is on the recording plane and decreases gradually when the target is moved outside this plane. Localization of simple targets in 3-D, with data acquired from multiple recording planes, appears feasible. The results provide guidelines for the interpretation of images with complex 3-D conductivity distributions.

Electric Conductivity↗
PubMed1991

The use of a low molecular weight heparinoid (Org 10172) for extracorporeal procedures in patients with heparin dependent thrombocytopenia and thrombosis.

We report two cases of heparin induced thrombocytopenia (HIT), in patients who required anticoagulation for extracorporeal procedures (haemodialysis and cardiopulmonary bypass) one associated with recurrent thrombosis of the artificial circuits. Resolution of thrombocytopenia and successful anticoagulation were achieved using a low molecular weight heparinoid (LMWH) Org 10172. Anticoagulation was monitored using estimations of plasma anti-factor Xa activity. These cases demonstrate that LMWH provides safe and effective anticoagulation in patients in whom unfractionated heparin has caused HIT.

Aged↗
PubMed1990

Chemical characterization of the parasitophorous vacuole membrane antigen QF 116 from Plasmodium falciparum.

On the basis of amino acid sequencing and immunological cross-reactivity, the Plasmodium falciparum parasitophorous vacuole antigens QF116 and exp-1/CRA are apparently identical. The epitope recognized by an inhibitory monoclonal antibody directed against QF116 is located proximal to the C-terminus of the protein. The QF116 protein is processed during maturation by the cleavage of a 22-amino-acid signal peptide and acylated as measured by labeling with myristic acid.

Acylation↗
PubMed1990

Experimental dissociation of behavioral and cardiovascular outcome in the borderline hypertensive rat.

F1 Offspring of hypertensive and normotensive rats (BHR) were reared with either hypertensive (SHR) or normotensive (WKY) cagemates, and observations were conducted at two developmental periods to assess the effects of rearing condition on the social environment and the behavior of BHR subjects. SHR displayed significantly more agonistic behavior during development than WKY, and BHR subjects reared with SHR were the targets of significantly more agonistic behavior than BHR subjects reared with WKY cagemates. BHR reared with SHR initiated twice as much agonistic behavior as BHR reared with WKY. When heart rate and blood pressure were assessed at 75-80 days of age, however, neither the alterations in developmental social environment nor the alterations in the behavioral characteristics of BHR were associated with differences in cardiovascular variables. The results do not support a causal connection between behavioral characteristics and cardiovascular outcome.

Agonistic Behavior↗
PubMed1990

Telework as an employment option for people with disabilities.

This feasibility study, based on intensive casework, examined the potential of home-based teleworking arrangements for people with severe physical disabilities. Eleven teleworking arrangements, each involving a unique combination of work, working conditions and worker characteristics, were set up in different parts of Ireland and monitored over periods ranging from 6 to 18 months. Eight were still operational at the end of the project and, with one exception, were set to continue as longer-term arrangements. Outcomes from this action-research project suggest that teleworking is a feasible form of employment for such persons--provided care is taken over selection of workers, identification of work that is suited to the telework format and management of telework units by employers. They also suggest that teleworking arrangements can be quite flexible, ranging from examples in which work is performed mainly from home to those which combine home-based activity with varying degrees of conventional office-based activity. It is concluded that telework will create new opportunities for people with severe disabilities, as well as enabling others who become disabled during employment to retain their jobs. However, it is important that workers are appropriately trained in the use of computers and advanced telecommunications and, in many cases, home-delivered training is required.

Adult↗
PubMed1989

Crohn's disease (regional enteritis) in association with Hodgkin's disease.

It has long been known that Crohn's disease may occur in association with certain forms of malignancy, specifically adenocarcinoma and lymphoma of the bowel and carcinoma of the vulva and perianal area. Here, the authors report the rare occurrence of extraintestinal Hodgkin's disease in a patient with documented regional enteritis of five years' duration. They propose explanations for this unusual combination of disease, reported in the literature only once previously, and review the pathophysiology of lymphoma and regional enteritis.

Adult↗
PubMed1987

Pharmacodynamics of warfarin at steady state.

We studied the pharmacodynamics of warfarin in chronically treated patients. Two methods were used to estimate the pharmacodynamic parameters M/Kd and Cmax (mg/L). In Method 1 the prothrombin time response was modeled directly without use of warfarin concentrations and Method 2 used warfarin concentrations and prothrombin time response to estimate M/Kd and Cmax. The mean Cmax and M/Kd for Method 1 (n = 88) were 5.5 +/- 2.3 mg/L and 51 +/- 46 and for Method 2 (n = 27) 6.3 +/- 2.8 mg/L and 35.4 +/- 13. When Method 1 was applied to the same 27 patients in Method 2, the mean Cmax and M/Kd were 5.7 +/- 3.3 mg/L and 36.1 +/- 14.9. These differences were not significant. Multiple regression analysis revealed that the value of Cmax and M/Kd varied between medical centers. No other patient characteristics were found to be significant. We conclude that modeling steady-state prothrombin time response directly adequately describes pharmacodynamic response to warfarin.

Humans↗
PubMed1986

A mammalian cell variant in which 3-aminobenzamide does not potentiate the cytotoxicity of dimethyl sulphate.

Variants of mouse leukaemia L1210 cells have been isolated in which cytotoxicity to dimethyl sulphate is not fully potentiated by ADP-ribosyl transferase inhibitor 3-aminobenzamide, as occurs in normal L1210 cells. These variants were selected after mutagenesis by growing the cells in dimethyl sulphate and 3-aminobenzamide. The characterisation of one of these variants is described. Variant 3 cells repair low doses of DNA damage in the presence of ADP-ribosyl transferase inhibitors. The Vmax of the ADP-ribosyl transferase enzyme in these cells is only increased 35% compared to normal wild-type L1210 cells. The basal DNA ligase I activity is increased 66% above wild-type whereas DNA ligase II activity appears to be unchanged. The most striking observation, however, is that the DNA ligase II activity is not increased after dimethyl sulphate treatment as occurs in wild-type L1210 cells. It seems that by increasing DNA ligase I levels these cells can survive DNA damage in the presence of 3-aminobenzamide. This variant (mutant) provides genetic evidence for our previously published hypothesis that (ADP-ribose)n biosynthesis is required for efficient DNA repair after DNA damage by monofunctional alkylating agents, because ADP-ribosyl transferase activity regulates DNA ligase activity. This variant is the first mammalian cell reported in which DNA ligase activity is altered, as far as we are aware. In yeast, a DNA ligase mutant has a cell division cycle (cdc) phenotype. Presumably, DNA ligase is essential for DNA synthesis, repair and recombination. The present variant provides further evidence that in mammalian cells, DNA ligase II activity is related to ADP-ribosyl transferase activity.

Animals↗
PubMed1984

Hepatic dysfunction due to intravenous abuse of methylphenidate hydrochloride.

Methylphenidate-induced hepatic injury was documented by abnormal liver function tests including a markedly elevated serum bilirubin, serum glutamic oxaloacetic transaminase, and serum glutamic pyruvic transaminase. Liver biopsy confirmed portal inflammation and hepatocellular disarray. Enzyme changes were reproducible with rechallenge of the drug (Ritalin). The drug is capable of producing hepatic injury, particularly when given in nonstandard doses intravenously.

Adult↗