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Biomedical subjects

A Harrison

Publications and source records attributed to A Harrison.

At least 145 records · Page 8Linked to original sources
PubMed1993

Recurrent ameloblastoma?--An historic case report and a review of the literature.

A case is described in which a patient who was originally treated by radical mandibular surgery including rib grafting, having been told that she had a dentigerous cyst, presented 49 years later with a follicular ameloblastoma. The case is discussed in an attempt to determine whether the initial diagnosis could have been ameloblastoma (if so, this demonstrates a long-term recurrence), whether this is a follicular ameloblastoma arising from remnants of an original dentigerous cyst, or whether this is an ameloblastoma, developing subsequently and coincidentally from adjacent dental lamina. This report is of historical interest, not only because of the long period of time that has elapsed between initial treatment and the present ameloblastoma, but also because of the eminent surgeons involved and the advanced techniques that they so proficiently carried out in 1942-1943.

Aged↗
PubMed1993

A computerized system for morphometric analysis of digitized images of histologically prepared arterial cross sections.

A method is described for computerized, operator-assisted, morphometric measurement of histologically prepared arterial cross sections. The system is composed of an image cytometer equipped with a one power lens and a digitizing camera interfaced with an imaging board residing in a PC computer. Algorithms were developed for automated segmentation of the areas of interest. The method is rapid, objective, accurate and requires minimum operator intervention. It gives reliable and reproducible results in the measurement of all elements of the cross section including circumference, area of the media, circumference of the internal elastic lamina, area of the lumen and percent occlusion of the lumen by the intimal thickening. While manual measurements using computerized planimetric methods give similar results, this method is an order of magnitude faster (1-2 min vs. 10-20 min per cross section) thus facilitating the study of large numbers of specimens. A blinded re-measurement of 284 sections of artery for reproducibility yielded r values of 0.86-0.97.

Adult↗
PubMed1993

A comparison of the dimensional accuracy of microwave and conventionally polymerized denture base materials.

This study compares the dimensional changes of microwave and conventionally polymerized denture bases and also establishes the degree of monomer conversion using gas-liquid chromatography. Dimensional changes of three denture base materials were assessed using an optical comparator and the results showed no significant differences between the materials employed or the curing method used. Efficient monomer conversion was demonstrated with levels of residual monomer of less than 1% for all materials.

Chromatography, Gas↗
PubMed1993

Comparing nurses' and patients' pain evaluations: a study of hospitalized patients in Kuwait.

All eligible patients hospitalized on the general medical, surgical and pediatric wards of a district hospital in Kuwait during the first 2 weeks of April 1990 (N = 199) were interviewed about their pain and the medical care provided. Patients rated their current pain using a 0-10 visual analogue scale (VAS) on which 0 was labelled 'no pain' and 10 'unbearable pain', and also the least and worst levels of pain which they had experienced during the previous 24 hr. Pediatric patients rated their mood at these times using a cartoon faces scale ([1]: McGrath P.A., DeVeber L. L. and Hearn M. T. Advances in Pain Research and Therapy, pp. 387-393. Raven Press, New York, 1985). Patients were asked to describe the most painful procedure which they had experienced whilst hospitalized, to detail their reactions to any uncontrolled pain, and recount the outcome of any requests made for additional analgesics. Whichever nurse on duty had had prime responsibility for caring for the patient was asked to furnish comparable VAS ratings of the patient's pain, and to categorize the patient as providing an accurate picture of, exaggerating, or understating his/her pain. Overall, nurses returned significantly lower pain estimates than their patients. Pediatric patients and patients described by their nurses as 'understating their pain', however, were exceptions. The vast majority of patients approved of the medical care provided and the pain management, and considered that nurses are well able to judge patients' pain and are concerned about what pain patients experience. And yet the VAS reports from patients indicated that uncontrolled pain was common. Also, when specifically questioned, a substantial proportion of patients stated that pain had had a negative impact on their mood and activity. Various explanations for these findings are discussed, and their implications for effective pain management. Some of the special problems facing nurses in Kuwait are considered.

Adolescent↗
PubMed1993

Hepato-biliary and renal excretion in mice of charged and neutral gadolinium complexes of cyclic tetra-aza-phosphinic and carboxylic acids.

Tissue distribution of 21 new 157/153Gd complexes was measured at 5 min and 24 hr after an intravenous injection into mice. A complex was judged to be stable in vivo when the percentage of 153Gd retained in the liver and skeleton at 24 hr was comparable with that of 153Gd(DOTA)-. Complexes varied in net charge and lipophilicity and 20 were phosphinic or carboxylic acid derivatives of tetra-aza-cyclo-dodecane. Three anionic, lipophilic complexes were cleared predominantly by the hepato-biliary pathway and were stable in vivo. The remaining 18 complexes were cleared mainly by the kidneys. Of these 18, 1 anionic, 8 neutral, and 3 cationic complexes were stable in vivo. These findings augur well for the future of hepato-biliary and general purpose Gd contrast enhancing agents for MRI.

Animals↗
PubMed1993

Immunoassay of platelet-derived growth factor in the plasma of patients with scleroderma.

It has been postulated that platelet-derived growth factor (PDGF) is responsible for the abnormal fibroblast proliferation observed in scleroderma. In one previous study, plasma samples from patients with scleroderma caused increased mitogenesis in cultured fibroblasts, suggesting that the pathogenesis of scleroderma is related to increased plasma PDGF concentrations. To test this hypothesis, we used a sensitive, monoclonal antibody-based ELISA to measure PDGF in the plasma of 12 scleroderma patients. A rigorous sampling protocol prevented false elevations in plasma PDGF levels from ex vivo platelet degranulation: beta-thromboglobulin concentrations were measured in each plasma sample to monitor platelet lysis. Plasma PDGF concentrations in the scleroderma patients were not statistically different from those observed in age- and sex-matched normal controls, and patients with RA. While it is possible that changes in PDGF activity at a local level alter fibroblast function, we cannot conclude that elevated plasma concentrations of PDGF play a role in the pathogenesis of scleroderma.

Adolescent↗
PubMed1993

A survey of the dissatisfied denture patient.

A small but important group of complete denture wearers find great difficulty in adjusting to, and wearing, dentures. In the past, efforts have been made to identify a factor or group of factors which typify these patients so that the clinician, having recognised the factors, might modify the management approach accordingly. Most research has concentrated on one form of investigation. In this study a wide range of tests was applied to complete denture wearers attending for treatment at Cardiff or Leeds Dental School, including an exhaustive interview and questionnaire, clinical examination and a personality assessment. In the majority of cases technical errors in denture construction accounted for the presenting complaint. It was not possible to identify a factor or group of factors common to those patients who had suffered chronic denture problems.

Adult↗
PubMed1993

The tooth-denture base bond: stress analysis using the finite element method.

Although acrylic resin teeth are the most popular artificial teeth used for denture construction, a high number fracture away at the tooth-denture base interface. Various causes have been documented for this failure; however, it is logical that eventual fracture occurs due to localised tensile stresses at this interface. Examination of these stresses using the finite element method showed that on load application to the upper incisors, the maximum tensile stresses were concentrated within the body of the tooth and not at the tooth-denture base interface. Stresses encountered at the interface were relatively low and introduction of a crack made no significant difference to their magnitude.

Acrylic Resins↗
PubMed1993

Be prepared.

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Air Pollutants, Occupational↗
PubMed1992

A survey of complete denture prosthetics for the elderly, the handicapped and difficult patients.

A survey was carried out to establish information on the facilities and management of the elderly and the handicapped and to evaluate the treatment of the difficult edentulous patient in general dental practice. A postal questionnaire was sent to a total of 1090 dentists in three regions of England and Wales. There was a 50.4% response. Ninety-nine per cent of practitioners were able to treat the ambulant elderly, whereas only 72% offered treatment if the patient was wheelchair dependent. Ninety-six per cent of all respondents undertook domiciliary visits. All practitioners provided prosthetic treatment (complete and partial dentures) for the elderly, whereas fewer felt able to treat the physically and the mentally handicapped. There was less conservative and periodontal treatment provided than prosthetic treatment. A similar pattern was obtained in all three regions. Forty-seven per cent preferred to treat difficult complete denture patients privately, 44% under the NHS and 6% not at all. There were regional variations in the referral patterns of these difficult denture cases. The majority of respondents considered that there should be more opportunities for postgraduate education in prosthetic dentistry.

Aged↗
PubMed1992

Dimensional accuracy and stability of acrylic resin denture bases.

Proponents of injection molding systems have claimed a number of benefits over conventional press-pack dough molding systems. The aim of this study was to evaluate a recently developed injection (dry heat) procedure of processing compared with press-pack dough molding utilizing three curing cycles. The dimensional accuracy and stability of acrylic resin bases produced by the two molding procedures were compared. Dimensional changes were assessed over a period of 4 months using an optical comparator. The results demonstrate that baseplates produced by the injection molding procedure exhibit less shrinkage than those produced by the conventional press-pack procedures.

Acrylic Resins↗
PubMed1992

Effect of the curing cycle on residual monomer levels of acrylic resin denture base polymers.

It has been shown previously that high levels of residual monomer have a deleterious effect on the properties of denture base polymers. Levels of residual monomer were determined on a homopolymer and a copolymer using gas-liquid chromatography. A wide range of recommended and 'short cut' curing cycles were then investigated which produced values ranging from 0.56 to 18.46%. From the ranges examined an optimum cycle of 7 h at 70 degrees C and 1 h at 100 degrees C was established which was used to polymerize 23 currently available synthetic denture base polymers. Only small differences were found between the materials tested with a range from 0.54 to 1.08% of residual monomer.

Acrylic Resins↗
PubMed1992

Determination of doughing and manipulation times of acrylic resin denture base material and a proposal for a specification for a packing plasticity test.

The doughing and manipulation times of a range of acrylic resin denture base polymers are presented in this study. The methods evaluated were: (i) probing following American Society for testing materials specification, F451-76; (ii) hole penetration following British Standard, 2487: 1989 and International Standard Organisation, 1567: 1988; (iii) probing using a penetrometer employing a 20 g load and 1 mm diameter needle; (iv) oscillating rheometer apparatus used at a fixed frequency of 1 Hz by sweeping through a programmed linear increase in strain. The results indicate that each of the methods is capable of evaluating the doughing and manipulation times of the unprocessed polymers. It is concluded that the Bohlin VOR Oscillating Rheometer is excellent for investigating the flow properties of denture base polymers but it cannot be recommended for a standards specification test because of the high cost. The penetrometer method has been shown to be superior to the current standards specification test and would be ideal for a packing plasticity standards test.

Denture Bases↗
PubMed1992

67Ga-9N3 uptake by xenografts of human melanotic melanoma in mice.

Tumour uptake of the inert, neutral complex 67Ga-9N3 and the tumour:blood concentration ratio (1,4,7,triazacyclononane-1,4,7, triacetic acid) were measured in mice bearing xenografts of the human melanotic melanoma HX118. Between 1 and 4 h after the injection the tumour:blood ratio increased from 3.5 to 21 and the concentration of 67Ga-9N3 in the tumour decreased from 0.43 to 0.13% g-1. During the first 24 h the concentration of 67Ga-9N3 in the tumour exceeded that in all other tissues except the liver and kidneys. The tumour:blood ratio and tissue distribution of 67Ga-9N3 at 4 h were compared with those of four other complexes. The results indicated that of the five complexes 67Ga-9N3 would be the most suitable for tumour imaging at early times after administration. Imaging would not be restricted to gamma emitting 67Ga as there is also the possibility of using the 9N3 ligand to bind 111In for single photon emission computed tomography (SPECT), 68Ga for positron emission tomography (PET) or even stable Ga for direct in vivo nuclear magnetic resonance (NMR) detection.

Animals↗