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Biomedical subjects

S M Wright

Publications and source records attributed to S M Wright.

At least 19 recordsLinked to original sources
PubMed1992

Interspecies transmission and reassortment of influenza A viruses in pigs and turkeys in the United States.

Genetic reassortment between influenza A viruses in humans and in animals and birds has been implicated in the appearance of new pandemics of human influenza. To determine whether such reassortment has occurred in the United States, the authors compared the genetic origins of gene segments of 73 swine influenza virus isolates (1976-1990), representing 11 states, and 11 turkey virus isolates (1980-1989), representing eight states. The host origin of gene segments encoding the internal proteins of H1N1 swine and turkey influenza viruses was identified by developing a dot-blot assay. All gene segments of swine influenza viruses were characteristic of influenza virus genes from that species, indicating that pigs may not be frequent participants in interspecies genetic exchange and reassortment of influenza viruses in the United States. In contrast, 73% of the turkey influenza virus isolates contained genes of swine origin. One turkey isolate was a reassortant having three genes characteristic of avian influenza virus and three of swine origin. These findings document a high degree of genetic exchange and reassortment of influenza A viruses in domestic turkeys in the United States. The molecular biologic techniques used by the authors should aid future epidemiologic studies of influenza pandemics.

Animals↗
PubMed1992

Prosthetic assessment in the treatment of denture hyperplasia.

The removal of denture-induced trauma is important in the treatment of denture hyperplasia and in the prevention of its redevelopment in susceptible patients. A simple approach to the assessment of dentures is described, which highlights potentially damaging areas of the borders and the fitting surface.

Dental Occlusion↗
PubMed1991

Reproductive health: knowledge, attitudes and needs of adolescents.

OBJECTIVE: To determine the knowledge and attitudes of adolescents with respect to reproductive health, with particular emphasis on their knowledge of the symptoms and transmission of sexually transmitted diseases (STDs), preventive strategies and sources of information. DESIGN: Questionnaire survey of a stratified random sample of Year 10 students followed by group interviews with volunteers from the sample. SETTING: The study was carried out in 33 Victorian secondary schools. PARTICIPANTS: The questionnaire was administered to a stratified random sample of 1351 Year 10 students. Group interviews were conducted with 533 volunteers from the sample. MEASUREMENTS AND MAIN RESULTS: Considerable gaps were identified in knowledge of STDs and their short-term and long-term effects on reproductive health. An STD Knowledge Score was constructed based on responses to 46 items. The mean score for the full sample was 22.7 (49.3% correct) with a standard deviation of 6.4. As a group, country students scored better than city students (mean, 23.8 v. 22.2, t = 3.97, P less than 0.001) and females better than males (mean, 23.5 v. 21.9, t = 4.21, P less than 0.001). Medical practitioners were rarely identified as a source of preventive advice. CONCLUSION: The deficiencies identified in knowledge about reproductive health suggest that young people need better access to health information. Schools and the medical profession need to work together both to provide information and to help young people develop the confidence to use available information sources.

Adolescent↗
PubMed1991

Arrays of mutually coupled receiver coils: theory and application.

Specialized receiver coils having a small sensitive region can provide an improvement in SNR for MR imaging and spectroscopy, at the expense of limiting the usable field of view. This work presents a technique for designing coil arrays that allows the size and location of the sensitive region to be selected remotely. Only one element of the coil array is directly connected to the receiver, allowing flexibility in system design and implementation. A method is presented for the analysis and design of mutually coupled coil arrays of any number of elements of arbitrary shape. The analysis includes mutual coupling effects between primary coils, to allow multiple primary coils to be used simultaneously. A controller system allows remote selection of the sensitive region and automatically matches the impedance of the array to the preamplifier. Results obtained using a mutually coupled coil array designed for spine imaging are shown.

Equipment Design↗
PubMed1991

Dextran magnetite as a liver contrast agent.

The superparamagnetic particle dextran magnetite was studied as a liver tumor contrast agent for magnetic resonance imaging (MRI). The effects of dextran magnetite on the longitudinal (T1) and transverse (T2) relaxation times in liver, spleen, and an implanted rat liver tumor were measured at 0.47 T (IBM/Bruker PC-20 relaxometer) over the dose range of 23 to 69 mumol Fe/kg. Dextran magnetite substantially reduced the T2 of the liver and spleen, but not of the tumor, thereby providing a basis for improved tumor imaging. The T1 of the tumor was not affected following injection of dextran magnetite in the dose range studied, while the spleen T1 was reduced substantially more than the T1 of the liver. Histological studies using the iron reaction for Prussian blue clearly showed dextran magnetite in the liver and spleen, but not in the tumor. While dextran magnetite was sequestered in macrophages in both liver and spleen, the distribution in the liver was more diffuse (70 microns average particle separation) than that in the spleen (25 microns separation). The lack of a T1 effect in the liver is consistent with the fact that a majority of the water in the tissue cannot diffuse to the relaxational centers on the time scale of the liver's intrinsic T1 (280 ms). In the spleen, however, the dextran magnetite is more densely packed in the red pulp allowing a significant fraction of the water to be relaxed by a T1 mechanism. Spin-echo images of the implanted tumor (mammary adenocarcinoma. R3230AC) in the livers of Fischer 344 rats were obtained at 0.50 T (Siemens Magnetom). The tumor-to-liver contrast was improved for both T1 and T2-weighted spin-echo images after intravenous injection of the dextran magnetite contrast agent. The contrast determined from these images agreed with that predicted by the measured T1 and the T2 (Hahn spin-echo) values. In addition, gradient-echo T2-weighted images with good contrast were obtained in a much shorter imaging time than was needed for T2-weighted spin-echo images. These results demonstrate that the MRI contrast enhancement observed with dextran magnetite is based on its selective uptake and distribution in the macrophages in the liver and spleen and that this agent has substantial potential as a superparamagnetic MR contrast agent.

Adenocarcinoma↗
PubMed1991

Quality assessment in support services: do practitioners concur with expert consensus?

The purpose of this study was to examine the degree of concordance between experts and practitioners as to the importance of quality assessment measures (elements and indicators) in therapeutic recreation (TR) services. Results from a survey of TR practitioners as to actual uses of these quality assessment measures within Veterans Affairs Recreation Services nationwide were compared to expert opinions used in a previous study that identified quality assessment measures for TR. Agreement between expert ratings of importance and frequency of use by practitioners were greatest for the experts' most important elements and indicators and least for the least important. Findings suggest that a select few "important" elements and indicators might be universally required of all quality assessment programs; others might be optional or can be modified to meet the needs of individual settings. Results also demonstrate the need for further study of optimal quality assessment approaches using both expert knowledge and practitioner experience.

Ancillary Services, Hospital↗
PubMed1991

A programmable data acquisition and control system for magnetic resonance imaging: application to mutually coupled surface coil arrays and temperature monitoring.

A programmable data acquisition and control system was developed for use in conjunction with magnetic resonance imaging (MRI). The controller consists of two functional blocks: a host system and a remote system. The remote system resides inside the shielded room housing the magnet. The host, an IBM compatible personal computer, is located at the technician's console. Communication between these devices is implemented over a fiber optic RS-232 data link. This configuration allows experiments to be performed remotely by using a series of keyboard typed commands, by programming the host to send a series of commands, or by directly programming the remote system. As an example of its capabilities, the controller was used to tune and match arrays of receiver coils for localized imaging and to record the rectal temperature of a sedated rat during image acquisition.

Algorithms↗
PubMed1990

Liposome encapsulated MnCl2 as a liver specific contrast agent for magnetic resonance imaging.

We examined the usefulness of MnCl2 entrapped in liposomes as a liver specific contrast agent for magnetic resonance imaging. Toxicity experiments showed that the effective dose for imaging experiments was 7 to 11 times lower than the LD50 of free MnCl2. In rats with implanted liver tumors, liposome encapsulated MnCl2 caused a two- to three-fold increase in the relaxation rate of the liver while having little effect on the relaxation rate of tumor tissue. T1 weighted, magnetic resonance images obtained at 0.5 T of an R3230 adenocarcinoma implanted in the liver showed an increase in the signal intensity of both normal liver and tumor tissue after the injection of free MnCl2 (25 mumole/kg). However, after the injection of liposome encapsulated MnCl2 (40 mumole/kg) the liver exhibited a marked increase in signal intensity with little change in the signal intensity of the tumor tissue. These results suggest that liposome encapsulated MnCl2 has excellent potential as a liver specific contrast agent for the improved detection of liver metastases.

Animals↗
PubMed1990

Pathophysiology of congestive heart failure.

Although the mortality rate for cardiovascular disease is declining, the incidence of congestive heart failure (CHF) is escalating. This article reviews normal cardiovascular physiology and cellular anatomy; defines CHF; explores the etiologies, pathophysiology and clinical presentation of CHF; and briefly discusses diagnostic modalities and prognostic indices.

Heart Failure↗
PubMed1989

Fundamentals of prosthetic practice. Part II--The surgery.

It is important for the smooth running of appointments that everyone, patient, receptionist, dental surgery assistant (DSA), the laboratory and, of course, the dental surgeon should know what is happening. Obviously, they do not all require the same information, but certain points will be essential to each of them for maximum efficiency of treatment.

Consumer Behavior↗
PubMed1989

Fundamentals of prosthetic practice. Part I--The laboratory.

Prosthetic dentistry in general practice produces many challenges for both the newly qualified trainee and the long-standing practitioner. If these challenges are not appreciated, met and dealt with effectively, the dentist may be left disillusioned with his skills and expertise, and stressed at the thought of treating patients requiring dentures. The economic need for rapid treatment while maintaining good standards of work, can result in pressure, and the temptation to 'cut corners' can prove costly. These articles, far from being a definitive text, seek to illuminate some potential problems and to lead the clinician to establish his own solutions in the areas of the laboratory, the prescription, communication and some alternative clinical techniques.

Communication↗
PubMed1989

Bilateral MR imaging with switched mutually coupled receiver coils.

The authors describe a system of bilateral mutually coupled receiver coils and its initial clinical use in magnetic resonance imaging of the knees and temporomandibular joints. Switched mutually coupled coils allow bilateral simultaneous imaging of paired structures without a penalty in signal-to-noise ratio because the coils can be alternated with each section acquisition. With this coil system, there is no restriction on placement or design of coils to prevent interaction. When combined with three-dimensional imaging techniques, switched coils allow simultaneous bilateral acquisition of multiple, contiguous sections through paired anatomic structures in a reasonable amount of imaging time.

Adult↗
PubMed1988

Host immune responsiveness to the chigger, Eutrombicula cinnabaris.

Chigger infestation is often associated with severe cutaneous reactions. Mice were given four infestations with the pest chigger Eutrombicula cinnabaris, and each exposure was separated by a 14-day mite-free period. Mean duration of engorgement was nine to ten days for a first exposure and four to five days for a fourth exposure. An initial exposure did not elicit macroscopic changes at chigger attachment sites, while all third and fourth exposure animals had marked reactions consisting of erythema, epidermal thickening and serous exudation. Approximately 20% of second exposure animals had macroscopic changes at chigger feeding sites, but these reactions were much less intense than the responses of third and fourth infestation hosts. Third and fourth exposure animals had infiltrates of lymphocytes, eosinophils, basophils and neutrophils at attachment sites, with eosinophil influx the most intense. Cutaneous reactivity to chigger feeding was adoptively transferred with lymphocytes from fourth exposure animals. Passive transfer of serum from fourth infestation donors resulted in heightened reactivity to a challenge infestation. Skin testing, after a fourth infestation, with an extract of whole E. cinnabaris larvae provided evidence for Arthus and delayed type hypersensitivity responses to chigger antigens. Chigger-reactive homocytotropic antibody was not detected by skin testing and active cutaneous anaphylaxis.

Anaphylaxis↗
PubMed1987

Biomedical research in the nursing home: methodological issues and subject recruitment results.

Although nursing homes are potentially important sites for geriatric research, previous reports have identified impediments to subject recruitment in this setting. We are conducting five simultaneous clinical studies in a 725-bed nursing home. Utilizing a systematic subject recruitment methodology designed to minimize patient and staff burden, we have recruited over 100 subjects. The average recruitment rate over two years from nursing home residents meeting study entry criteria was 43%. The rate was highest (81%) for a study of urinary incontinence offering direct benefit to participants, and lowest (28% and 14% respectively) for physiologic studies of vasopressin regulation and dermal vitamin D production, offering no direct benefit. Studies of syncope and dementia which benefitted groups affected by these problems but not controls, had intermediate recruitment rates (46 and 44%, respectively, P less than .002 compared to incontinence). Thus, clinically relevant projects, sensitive to the needs of the patient and institution, can recruit subjects from the nursing home.

Aged↗