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Biomedical subjects

D J Phillips

Publications and source records attributed to D J Phillips.

At least 127 records · Page 7Linked to original sources
PubMed1982

Evaluation of carotid bifurcation disease: the role of common carotid artery velocity patterns.

We evaluated duplex ultrasonographic velocity patterns from the common carotid artery in 156 patients with arteriographically verified internal carotid artery disease. Flow to zero during diastole in the common carotid was found in three groups of patients: (1) those with flow to zero in both common carotids not related to disease of the carotid bulb; (2) those with a tight (90% to 99%) stenosis in the internal carotid; and (3) those with total occlusion of the internal carotid. Although such flow to zero is commonly observed with total occlusion of the internal carotid artery, it may also be seen with high-grade stenosis. Thus, when found, it is essential to ascertain if flow is indeed present in the internal carotid artery; understanding changes in velocity patterns of the common carotid has improved our overall accuracy in detecting extracranial carotid artery disease.

Arterial Occlusive Diseases↗
PubMed1982

Evaluating Doppler devices using a moving string test target.

Two moving string test targets have been developed and used to characterize ultrasound Doppler instrumentation. The characteristics investigated were sample volume size and location in space, amplitude sensitivity to Doppler shift, and resolution of Doppler direction. The tests were performed on a combined echo/Doppler instrument and on an annular array system. The procedures can be carried out routinely in the clinical laboratory to ensure that the instrument is working properly or as an aid for correct interpretation of acquired data.

Auscultation↗
PubMed1982

Computer based pattern recognition of carotid arterial disease using pulsed Doppler ultrasound.

A minicomputer based system has been developed for studying carotid artery blood flow data obtained for a combined B-mode, pulsed Doppler ultrasound scanner. The goals of this work are to devise and improve techniques for estimating the extent of atherosclerosis at the carotid artery bifurcation. Features are automatically extracted from spectrum analyzed Doppler blood flow data. Five statistical pattern recognition algorithms are compared, with cross validation being used to improve the estimate of classification accuracy. A data collection protocol has been devised in which four sites are studied along each carotid arterial system. Classification of unknowns is done using a hierarchy of three decisions.

Adult↗
PubMed1982

Immunoglobulin M and G antibody response to type- and subtype-specific antigens after primary and secondary exposures of mice to influenza A viruses.

A mouse model of influenza infection was studied to help define parameters that may affect serodiagnosis of human infections by immunoassays. Antibodies to both type- and subtype-specific influenza A antigens were measured by a solid-phase immunofluorometric assay. Dilute mouse sera were added to purified influenza virus that had been covalently bound to polyaminostyrene microbeads, and the bound antibody was detected by fluorescein isothiocyanate-labeled isotype-specific antisera. Results were consistent in that upon exposure of mice by either infection alone or by vaccination after infection, both immunoglobulin M (IgM) and IgG antibodies reactive with newly encountered subtype specific viral antigens were measured. IgG antibody was usually detectable by the solid-phase immunofluorometric assay several days before it could be detected by a hemagglutination inhibition test. Increased levels of antibody of the IgG1, IgGa, IgG2b, and IgG3 subclasses were also measured during influenza infection. Surprisingly, response to type-specific viral antigens was of the IgG class in primary as well as in secondary exposure. The results suggest that for serodiagnosis of influenza infections by detection of specific IgM antibody, the assay should use subtype-specific antigens.

Animals↗
PubMed1982

Evaluation of a solid-phase immunoassay with fluorescein isothiocyanate-conjugated heterogeneous or monoclonal antibodies for identification of virus isolates, with influenza virus as a model.

A solid-phase immunofluorescence assay was evaluated for the identification of viruses isolated in tissue culture, with influenza virus as a model. Purified immunoglobulin G (IgG) from hyperimmune rabbit sera specific for contemporary strains of influenza A or B was covalently attached to microscopic plastic beads to capture virus. Fluorescein isothiocyanate (FITC)-conjugated antibodies of different specificities were then reacted with bound antigen, and the resulting complexes were quantified in a suitable filter fluorometer. The assay, with appropriately absorbed FITC-conjugated second antibody, reliably identified virus present in harvests from cell cultures infected with clinical specimens. For influenza A (H1N1) virus, sensitivity of detecting antigen was about 8- to 32-fold less when an FITC-conjugated monoclonal Igg antibody pool specific for epitopes in three different antigenic sites on influenza hemagglutinin was used as the second antibody as compared to when IgG from hyperimmune sera specific for virus or its components was used as the second antibody. The immunofluorometric assay provides a method for quantitative detection of viral antigen in tissue culture fluids and objective identification of virus type and subtype with FITC-conjugated reagents.

Animals↗
PubMed1981

Effect of test system on the ability of monoclonal antibodies to detect antigenic drift in influenza A(H1N1) virus haemagglutinins.

Results of analysing antigenic variation in the haemagglutinin (HA) molecule of naturally occurring influenza A (H1N1) viruses from 1977 to 1979 with monoclonal antibodies were found to be dependent in some instances on the test system used. In several instances A/USSR/90/77 HA-specific monoclonal antibodies had sharply reduced haemagglutination-inhibition (HI) titres with variant virus although they bound to the variant and A/USSR/90/77 HAs with similar efficiencies as judged by titration in a sensitive and accurate solid-phase immunofluorimetric assay. In another instance, the converse situation was observed: monoclonal antibodies having a reduced efficiency of binding to the HA of a variant virus nevertheless had comparable HI titres with the variant and with A/USSR/90/77. The chemical basis and epidemiological significance of these observations remain to be elucidated. Nevertheless, the finding that the reaction of monoclonal antibodies can, in some cases, be markedly dependent on the test system employed is of significance for the efficient design and correct interpretation of immunochemical studies which employ monoclonal antibodies to investigate the basis for variation in influenza strains.

Antibodies, Monoclonal↗
PubMed1981

Spectral analysis of Doppler velocity patterns in normals and patients with carotid artery stenosis.

A computerized pattern recognition program was utilized to assess the predictive ability of various parameters obtained from the spectra of ultrasonic pulsed Doppler signals from the carotid arteries. The most accurate features selected by linear regression analysis were the natural log (ln) of the ratio of the mean velocity in the internal carotid artery compared to that in the common carotid artery, and the ln of the maximum velocity, the ln of the maximum frequency, and the square of the fractional broadening term, all of which were measured at peak systole in the internal carotid artery. Using the combination of the velocity ratio and the fractional broadening term, the average difference in the estimated percentage stenosis, as compared to that obtained by arteriography, was 12.8%.

Arteriosclerosis↗
PubMed1981

Ultrasonic duplex scanning for disease of the carotid artery.

The duplex ultrasonic scanner combines real-time B-mode imaging with a single-gate, variable-range pulsed Doppler. The detection and categorization of the severity of carotid artery atherosclerosis is achieved by performing spectral analysis of the pulsed Doppler velocity signal obtained from vessels of interest. Using this technique, 750 patients with suspected extracranial carotid artery disease were evaluated between January 1978 and January 1980. One hundred thirty-five of these 750 patients (18%) underwent cerebral arteriography performed with biplanar views of the carotid bifurcation. The degree of stenosis was measured independently in these patients and was available for comparison with the results of duplex scanning and spectral analysis. Duplex scanning correctly detected the presence of disease in 252 of 259 carotid arteries studied (97%). The extent of involvement varied from plaques that produced less than 10% diameter reduction to those that resulted in a total occlusion. The technique was less accurate with lesions that produced less than 10% diameter reduction.

Carotid Artery Diseases↗
PubMed1981

Noninvasive detection of internal carotid artery occlusion.

Flow in the common carotid artery is normally quasisteady with flow never approaching zero during diastole. With total occlusion of the internal carotid artery, flow in the common carotid assumes the pattern observed in the external carotid, which supplies a relatively high-resistance vascular bed. In 34 instances of total internal carotid obstruction, flow went to zero in diastole in 33 cases and also demonstrated flow reversal in 22. In addition, there was a significant reduction in peak systolic velocity when the low-resistance internal carotid was obstructed. These observations, which are simple to determine using an ultrasonic duplex scanner, are of value in suspecting total occlusion of the internal carotid artery, thus obviating the need for arteriography in some cases.

Arterial Occlusive Diseases↗
PubMed1980

Quantitative characterization of specificity and potency of conjugated antibody with solid-phase, antigen bead standards.

An immunofluorescent assay was used to characterize precisely the potency and specificity of fluorescein-conjugated immunoglobulin class-specific and polyvalent anti-sera. Stable antigen standards consisted of highly purified immunoglobulin antigens covalently bound to polyaminostyrene beads. Linear regressions of weighted logit transformations of relative fluorescent intensities versus the logarithm of relative conjugate concentrations were determined. The potency of conjugates was compared using two different methods derived from the logit transformation. Inappropriate specificities were measured in some conjugates described as immunoglobulin 'class-specific'.

Antibodies, Anti-Idiotypic↗
PubMed1980

Detection of monoclonal influenza antibodies synthesized in culture by hybridoma cells with a solid-phase indirect immunofluorometric assay.

A solid-phase indirect immunofluorometric assay for measuring reactions of mouse monoclonal antibodies with antigen has been developed, with influenza virus as a model. Purified IgG from hyperimmune rabbit sera is covalently linked to polyaminostyrene beads, to which influenza viruses are then bound immunologically to make solid-phase antigens. Alternatively, the virus is covalently coupled directly to the beads. Mouse antibodies, produced by hybridoma cells in culture, are reacted with constant amounts of solid-phase antigens, and then indirectly quantitated by adding FITC-labeled antimouse Ig and measuring the fluorescent intensity with a filter-fluorometer. The assay system permits rapid screening for low levels of antibodies synthesized by hybridoma cells in culture. It is about 25- to 150-fold more sensitive than hemagglutination inhibition tests in detecting monoclonal antibodies reactive with influenza virion HA protein.

Animals↗
PubMed1980

Repair of radiation-induced DNA damage in nondividing populations of human diploid fibroblasts.

The occurrence of DNA repair in UV- (254 nm) and X-irradiated normal human diploid fibroblasts maintained in a quiescent, nondividing state using low serum (0.5%) medium was ascertained. Techniques that detect different steps of the excision repair process were used so that the extent of completion of repair at single sites could be determined. These included measuring the disappearance of pyrimidine dimers by chromatography, detecting repair synthesis by density-gradient and autoradiographic methods and detecting the rejoining of repaired regions and repair of x-ray-induced single-strand DNA breaks using alkaline sucrose gradients. Results show that dimer excision occurs and the subsequent steps of repair synthesis and ligation are completed. About 50% of the dimers formed by exposure to 20 J/m2 is excised in the initial 24-h post-UV period. DNA repair (unscheduled DNA synthesis) can be detected through a 5-d post-UV period. The fraction of damaged sites eventually repaired is not known. X-ray-induced single-strand DNA breaks are repaired rapidly.

Cell Line↗
PubMed1979

The significance of carotid bruits in children: transmitted murmur or vascular origin, studies by pulsed Doppler ultrasound.

Forty-four youngsters with precordial murmurs and carotid bruits were evaluated clinically and independently, using pulsed Doppler ultrasound. The precordial murmur was evaluated with M-mode echocardiography combined with Doppler flow evaluation, and the carotid bruit was evaluated with peripheral vascular sector scan with Doppler flow evaluation. These ultrasonic techniques can identify abnormal blood flow at anatomic sites such as the aortic valve and in the carotid arteries. The patients had no symptoms and their condition, except for six, was mild enough that catheterization was not indicated. The clinical diagnosis of aortic stenosis was made in 30 children, and nine were thought to have no heart disease. On the basis of the ultrasonic examinations, 28 patients were diagnosed as having aortic stenosis and seven subjects had no intracardiac turbulence. However, there was disagreement in 14 instances; four of the six clinical "normals" were found to have aortic stenosis by pulsed Doppler echocardiography; six patients diagnosed as having mild aortic stenosis on a clinical basis were found to have no aortic abnormality. The results confirm that aortic stenosis usually presents as a murmur maximal in the aortic area, which is associated with a carotid bruit. Unfortunately, in at least one-fourth of the cases the murmur was not maximal at the aortic area, and a carotid bruit was found in several normal subjects. Since the consequences of over- or under-diagnosis of aortic stenosis are substantial, careful thought should be given to the differential diagnosis, and if possible, pulsed Doppler echocardiography should be utilized for a definitive statement of aortic valve-induced turbulence.

Adolescent↗