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Biomedical subjects

D McLean

Publications and source records attributed to D McLean.

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

Sensitometric evaluation of some mammographic film-screen combinations.

The rapid expansion of screening and assessment mammography is due in part to recent advances in film and processing technology. This has been facilitated by the achievement of high contrast images at lower radiation dose levels. One of the recognised keys for this advancement has been the adoption of extended processing times when compared to regular radiographic processing. The role of other factors, including film types and development chemistry, have received less attention to the present, but is becoming increasingly important as mammographic film technology progresses. This paper reports on four locally available mammographic films that have been exposed through film screen systems to ascertain sensitometric parameters for a variety of processing conditions. Three development times were used (23, 32 and 42 seconds) in combination with four development temperature (32, 34, 36 and 38 degrees) for each of four different chemistries. The results indicate that, as expected, development temperature and time play a major role in film contrast and speed. They also show, however, that different film types respond very differently to extended development times and that development chemistries can be critical to optimal film performance.

Evaluation Studies as Topic↗
PubMed1990

The development and functioning of the sense of shame.

An extensive literature on shame has not yet sufficiently addressed the nature and functioning of this affect from the psychoanalytic, developmental point of view. This paper tries to lay the ground for such a task.

Child↗
PubMed1990

Detection of early lung cancer using low dose Photofrin II.

Fluorescence imaging using hematoporphyrin derivative (HpD) or Photofrin II as a tumor marker has been used for localization of early bronchogenic carcinoma. Wider clinical application of HpD or Photofrin II as a cancer imaging agent has been hampered by the potentially serious and prolonged skin photosensitivity. Using a sensitive fluorescence bronchoscope system with a ratio fluorometer probe, carcinoma in situ was detected in four patients with low dose Photofrin II (0.25 mg/kg) with no apparent skin phototoxicity to 30 J/cm2 visible light on skin photosensitivity test.

Aged↗
PubMed1989

Cardiovascular disease in Canada.

Since the first national mortality statistics were published in 1921, cardiovascular disease (CVD) has been the leading cause of death in Canada, accounting for almost half of all deaths each year. In 1987, more than 77,000 Canadians died from CVD, almost 60% more than cancer, the second leading cause of death. The costs of CVD are high in economic as well as human terms. CVD accounts for 21% of all hospital days and is responsible for 25% of all disability pensions paid by the Canadian Pension Plan before age 65. CVD hospital costs alone, excluding doctors' fees and costs of surgery, exceed $3 billion annually. Not all the news about CVD is bad, however. Overall CVD incidence has been steadily declining since the early 1950s, and since 1979 the total number of CVD deaths has actually been decreasing, despite a growing and aging population. Improved survival rates are probably the result from more widespread use of advanced surgical technology during the acute phases of heart attacks, and better medical care for people who survive heart attacks. As this paper shows, CVD incidence varies by sex, age, region, and socio-economic status, as does the prevalence of controllable factors that increase the risk of CVD. These risk factors include smoking, high blood pressure, overweight, lack of physical activity, high levels of dietary fat, and elevated cholesterol levels. Lowering CVD rates to those of nations such as Japan and France, both with less than half the Canadian rate, requires increased public awareness of the dangers of the 'typical' Canadian lifestyle. At the same time, lower-income Canadians, the group with the highest CVD rates, must be given increased opportunities to make healthy lifestyle choices.

Adolescent↗
PubMed1989

Diagnostic x-ray spectra simulation, verification and application to the clinical environment.

A set of computer programs to simulate diagnostic x-ray spectra has been developed according to the method of Birch and Marshall, with good agreement to published HPA data. These programs have been extended to simulate spectra generated with capacitor discharge x-ray units. The application of these programs has proved useful clinically having been applied to filtration problems in chest radiography, and mobile x-ray units amongst others.

Computer Simulation↗
PubMed1987

Immunohistochemical localization of melanoma-associated antigen p94 kd200 with the use of a modified avidin-biotin-complex lectin method.

The immunohistochemical localization of melanoma-associated antigen p94 kd200 was investigated in frozen sections of 3 congenital nevi, 4 benign intradermal nevi, 1 regressing nevus, 1 blue nevus, 1 dysplastic nevus, 1 lentigo maligna, 1 superficial spreading melanoma and 2 metastatic melanomas. The original avidin-biotin complex lectin method (Hsu SM, Raine L, Fanger H: Am. J. Clin. Pathol., 75: 734-738, 1981) was modified to detect the antigen. The sections were exposed to the monoclonal antibody to p94 kd200 (Hybritech Inc.), the linking biotin-labelled anti-mouse IgG, the avidin-biotin peroxidase complex and the 3-amino-9-ethylcarbazole solution in an incubator at 37 degrees C and 100% humidity. We found that the percentage of cells expressing p94 kd200 varied between 0 and 100% in congenital nevi, between 80 and 100% in benign intradermal nevi, between 0 and 20% in the regressing, blue and dysplastic nevi, and in the lentigo maligna, 80 to 100% in the superficial spreading melanoma, and between 0 and 40% in the metastatic melanomas. Positive cells were found to be hypomelanotic (did not have heavy melanin content). The intensity of labelling or the degree of antigen expression on benign and malignant hypomelanotic cells was also found to vary. These findings 1) reinforce the concept of quantitative rather than qualitative antigenic differences in benign and malignant cells 2) suggest that kd200 is lost with increasing pigment production 3) offer a potentially significant tool to investigate the antigenic changes during cell differentiation.

Antigens, Neoplasm↗
PubMed1986

An holistic approach to recovery from an overuse injury in a games player.

The management of a chronic injury to an international squash player is described. By good physiotherapeutic management and the involvement of an interdisciplinary team it was possible to make gains in the non-playing period. The rehabilitation period included physiological assessment on the basis of which a training programme was devised with target goals set throughout the period. Mental rehearsal of skills was included at all stages. As a result, the player's confidence was maintained and fitness levels improved. The long term prognosis has been good. The model could be applied to any sports injury.

Athletic Injuries↗
PubMed1984

Sexual offenders, violence and testosterone: a clinical study.

Sexual assault has increased steadily over the last decade. Attempts at a more accurate evaluation of the violent sexual offender have included studies looking for correlation between plasma testosterone and high levels of sexual violence. The present study failed to replicate these findings, however, it confirmed the known association between violence and alcoholism. The significant association between a psychiatric diagnosis of depressive neurosis and low plasma testosterone levels was an associated finding.

Adolescent↗
PubMed1982

Local modulation of progesterone production in human fetal membranes.

We have studied the ability of human fetal membranes (amnion, chorion, and decidua) to produce progesterone. Membranes were obtained from women at 38-41 weeks pregnancy following spontaneous onset of labor. The tissues were dispersed into single cell preparations using 0.05% collagenase in a Krebs-Ringer buffer system. Progesterone was measured by specific RIA. All 3 tissues produced progesterone in a significant dose-response relationship with added pregnenolone but chorion was significantly more active than the other membranes. Equimolar concentrations of dehydroepiandrosterone, estrone or estradiol cause significant inhibition (to 50%) of this activity but dehydroepiandrosterone sulfate and estriol did not. We conclude that human fetal membranes at term can produce progesterone and this production may be modulated by other steroids of fetal or maternal origin. Local regulation of progesterone production, without significant changes in circulating levels of progesterone, may have an important influence on local prostaglandin generation and hence on myometrial contractility.

Dehydroepiandrosterone↗
PubMed1972

Initial intensive care in an accident and emergency department.

The work in the resuscitation room is initial intensive care. This must be always available independent of inpatient resources. This demands investment in adequate equipment and staffing. Much of the work is medical rather than surgical and appropriate for physicians to treat. Our experience might help others to plan for the future.

Accidents, Traffic↗
PubMedDate not supplied

A cranio-cervical malformation presenting as acute respiratory failure.

An 18-year-old, previously healthy male presented with bilateral pneumonia and acute respiratory failure with severe carbon dioxide retention. The presence of mild brainstem signs and hypoventilation led to the discovery of a platybasia, basilar invagination, and kinking of the medulla oblongata with early syrinx. He was operated upon but postoperatively was noted to have a mixed type of sleep apnea. This case illustrates the diagnostic challenge in acute respiratory failure in a previously healthy young person and the possible pathogenic mechanisms underlying it.

Adolescent↗
PubMedDate not supplied

Computer simulation of broad-beam and narrow-beam attenuation in lead for diagnostic x-ray energies.

Significant differences between broad- and narrow-beam transmission measurements for lead protective barriers have been noted for x-ray beams in the diagnostic energy range. Work reported in this paper indicates that these differences in transmitted exposure between broad- and narrow-beam geometry measurements are primarily the result of two independent interaction processes; the transmission of K-characteristic photons produced in the barrier, and coherently scattered photons. The magnitude of these effects was studied for x-ray spectra between 70 and 150 kVp. The K-characteristic component was found to be maximal at 150 kVp, while the coherently scattered contribution was found to be maximal for thick barriers and at lower energies. The effect of beam field size on relative transmitted intensities was also studied and found to increase with increasing field size up to 30 cm. A detector-to-barrier distance of 10 cm was found to maximize the K-characteristic component. For a typical diagnostic x-ray potential of 100 kVp, the K-characteristic component was found to be less than 7% of the total transmitted beam. Voltage wave form considerations were found to be significant as has been previously reported. The contribution of K-characteristic photons has been mathematically modeled and a computer program written to allow the rapid computation of broad beam transmission exposures for lead barriers, once the appropriate beam specifications have been entered.

Biophysical Phenomena↗