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Biomedical subjects

T Anderson

Publications and source records attributed to T Anderson.

At least 73 records · Page 4Linked to original sources
PubMed1999

Merger, they wrote.

When senior executives at Grant and Riverside Methodist Hospitals in Columbus, OH, decided to merge their institutions into one healthcare system, the two security forces suddenly were faced with the need for major changes. The directors of the two security departments decided to work together to plot a successful integration strategy and to protect the security staff in the bargain. By involving staff in organization decisions, they made integration easier.

Decision Making, Organizational↗
PubMed1999

Millennium midwife.

Explore the source record for details and available documents.

Anecdotes as Topic↗
PubMed1998

Axonal swellings and degeneration in mice lacking the major proteolipid of myelin.

Glial cells produce myelin and contribute to axonal morphology in the nervous system. Two myelin membrane proteolipids, PLP and DM20, were shown to be essential for the integrity of myelinated axons. In the absence of PLP-DM20, mice assembled compact myelin sheaths but subsequently developed widespread axonal swellings and degeneration, associated predominantly with small-caliber nerve fibers. Similar swellings were absent in dysmyelinated shiverer mice, which lack myelin basic protein (MBP), but recurred in MBP*PLP double mutants. Thus, fiber degeneration, which was probably secondary to impaired axonal transport, could indicate that myelinated axons require local oligodendroglial support.

Animals↗
PubMed1998

Current concepts of PLP and its role in the nervous system.

Proteolipid protein (PLP) and its smaller isoform DM20 constitute the major myelin proteins of the CNS. Mutations of the X-linked Plp gene cause the heterogeneous syndromes of Pelizaeus-Merzbacher disease (PMD) and spastic paraplegia (SPG) in man and similar dysmyelinating disorders in a range of animal species. A variety of mutations including missense mutations, deletions, and duplications are responsible. Missense mutations cause a predicted alteration in primary structure of the encoded protein(s) and are generally associated with early onset of signs and generalised dysmyelination. The severity of the phenotype varies according to the particular codon involved and the influence of uncharacterised modifying genes. There is some evidence that the dysmyelination results from the altered protein acquiring a novel function deleterious to the oligodendrocyte's function. Transgenic mice carrying extra copies of the Plp gene provide a valid model of PMD/SPG due to gene duplication. Depending on the gene dosage, the phenotype can vary from early onset of severe and lethal dysmyelination through to a very late onset of a tract-specific demyelination and axonal degeneration. Mice with a null mutation of the Plp gene assemble and maintain normal amounts of myelin but develop a progressive axonopathy, again demonstrating tract specificity. The results indicate that the functions of PLP are far from clear. There is good evidence that it is involved in the formation of the intraperiod line of myelin, and the results from the knockout and transgenic mice suggest a role in the interaction of oligodendrocyte and axon.

Animals↗
PubMed1998

Three-dimensional echocardiographic evaluation of left ventricular volume: comparison of Doppler myocardial imaging and standard gray-scale imaging with cineventriculography--an in vitro and in vivo study.

BACKGROUND: Standard gray-scale imaging (GSI), three-dimensional (3D) echocardiography has been shown to be superior to two-dimensional echocardiography in measuring left ventricular volume. However, the often relatively poor quality of transthoracic gray-scale data can limit the potential application of this technique. Doppler myocardial imaging (DMI) is a new ultrasound technique that potentially offers higher-quality 3D images with a transthoracic approach than the 3D GSI technique. This study was designed to compare the accuracy of standard GSI and DMI 3D left ventricular volume measurements in vitro and in vivo. METHODS AND RESULTS: In vitro, the minimum and maximum volume of the contracting single-chamber, tissue-mimicking phantom was calculated by using both techniques. In vivo, GSI and DMI 3D left ventricular volume measurements were performed in 16 patients. End-diastolic and end-systolic left ventricular volumes were computed for both techniques and compared with those calculated by cineventriculography. In vitro, both methods tended to underestimate the true phantom volume, but the systematic error was smaller for DMI than for GSI (-1.2% +/- 1.5% vs. -4.3% +/- 3%; p < 0.01) and was more constant in the case of DMI over the range of different sizes of true volume. In vivo, for GSI the end-diastolic volume mean difference was -12.6 ml and the limits of agreement were +/-18 ml, and for DMI the corresponding values were -4.2 and +/- 10.6 ml, respectively. The difference for end-systole was -6.5 +/- 10.6 ml and -1.5 +/- 10 ml for GSI and DMI, respectively. The magnitude of the difference in volume measurement between 3D echocardiography and cineventriculography was significantly smaller when using the Doppler technique. CONCLUSIONS: The results of this in vitro and in vivo study indicate that DMI is superior to GSI as a transthoracic acquisition technique for 3 D volume computation.

Echocardiography, Three-Dimensional↗
PubMed1998

An acoustic injection test object for colour flow imaging systems.

There are few test objects suitable for colour-flow ultrasound scanners. An acoustic injection device is described that enables the production of a 2-D region of colour on a colour-flow image. The device involves detection of the transmitted ultrasound pulse from the scanner, followed by the emission of a synthesized echo that consists of a radiofrequency burst modulated by an audiofrequency signal in such a way that, on reception by the ultrasound scanner, it is interpreted as a signal arising from a region of flow. The depth of the colour region may be controlled by adjustment of the length of the synthesised echo. The audiofrequency content may be altered as desired, enabling examination of the relationship between the displayed colour and the signal spectral content.

Acoustics↗
PubMed1998

Quantification of the enhanced backscatter phenomenon from an intravenous and an intra-arterial contrast agent.

The phenomenon of enhanced backscatter from myocardial contrast agents was studied using two examples, a robust thicker-walled, intra-arterial agent (AIP 201) and a smaller thinner-walled, intravenous agent (Quantison). Both agents are composed of albumin-encapsulated microbubbles. Samples of the agents were inserted into an in vitro phantom and insonated under different scanning regimes. Upon insonation, Quantison exhibited a pronounced increase in mean backscatter at medium and low concentrations, which decreased dramatically with increasing number of frames of insonation. At high concentrations, no dramatic decrease or increase in mean backscatter was observed over the period of the experiment. AIP 201 exhibited an overall decrease in mean backscatter with increasing number of frames of insonation. These results suggest that the difference in size and wall thickness of the contrast microcapsules can significantly affect the behaviour of the contrast agents in an ultrasound field.

Contrast Media↗