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Biomedical subjects

J Clark

Publications and source records attributed to J Clark.

At least 343 records · Page 19Linked to original sources
PubMed1987

Relation between phenotype and banal melanocytic naevi.

In a study of risk factors for the development of melanocytic naevi in relation to the pathogenesis of malignant melanoma 197 white adults were examined by four dermatologists and naevus counts correlated with several other features. Highly significant associations were found between large numbers of banal acquired melanocytic naevi and the ability to tan easily without burning (skin types 3 and 4; relative risk 4.6), brown or hazel eyes (relative risk 3.5), green or grey eyes (relative risk 3.5) and brown or black hair (relative risk 3.7). No significant associations with numbers of naevi were shown for parity or use of oral contraceptives or other steroid hormones. This is the first study to find any relation between melanocytic naevi and phenotypic factors in a white population.

Adolescent↗
PubMed1987

Anatomical interpretation of MR scans of the brain.

A stereotactic method of brain localization is applied to magnetic resonance imaging for the interpretation of brain structures. This proportional grid system developed by Talairach is based on two intracerebral structures, the anterior and posterior commissures. It takes into account individual variations in brain size and shape. In an experimental study on cadavers we demonstrated that his system permitted accurate identification of cortical structures on CT scan. In this paper, we describe its application to MR. It provides, on a routine basis, a simple reliable method of anatomical interpretation. The use of this grid system is made easier by the fact that both commissures are seen on midsagittal MR scans.

Brain↗
PubMed1987

Psychiatric morbidity in acromegaly.

Previous reports on psychiatric morbidity in acromegaly have been unsystematic. This study examined 51 acromegalic patients for psychiatric morbidity using the General Health Questionnaire and a standard psychiatric interview, the Present State Examination. Although psychiatric morbidity was higher in the female than the male acromegalics, the study showed no increase in psychiatric morbidity in general, nor an increased incidence of depression, in comparison with general population and patient samples. No relationship was found between growth hormone levels and psychiatric morbidity. The results raise the question whether acromegalic patients show lower psychiatric morbidity than expected from patients with such an illness. The data suggest that previous reports of depression in acromegalic patients examplify the simple coincidence of a likely and an unlikely condition.

Acromegaly↗
PubMed1987

Stereotactic surgical planning with magnetic resonance imaging, digital subtraction angiography and computed tomography.

Over the past 2 years at the Montreal Neurological Institute and Hospital, we have evolved an integrated environment for the planning of stereotactic procedures, based on images from magnetic resonance imaging, digital subtraction angiography and computed tomography modalities. These procedures rely on fiducial marker sets which are attached to our 'OBT' stereotactic frame, and which may be recognized in the images. The software package is modular and operates in both minicomputer (PDP-11 and VAX) and IBM personal computer environments. In addition to routine tasks for stereotactic planning, the package also supports dosimetry planning for stereotactic radiosurgery.

Brain↗
PubMed1986

Benign melanocytic naevi as a risk factor for malignant melanoma.

Examination of 180 patients with cutaneous malignant melanoma and 197 control patients in a case-control study showed that the risk of melanoma is strongly related to numbers of benign melanocytic naevi (moles). Some unusual features of naevi--a diameter exceeding 7 mm, colour variation, and irregular lateral outline--also showed a strong association with the risk of melanoma, but the relation of numbers of naevi to risk was present even in the group of patients whose naevi had none of these unusual features. Biopsy of clinically atypical naevi from several of the patients at highest risk generally did not show dysplastic histology. Thus a group of people at high risk of melanoma may be identified by using simple clinical assessment of naevi.

Adolescent↗
PubMed1986

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Community Health Nursing↗
PubMed1986

Epidermoid carcinoma of the anal canal.

The charts of 67 patients treated for epidermoid carcinoma of the surgical anal canal were reviewed. The clinical presentation, type of surgical procedure performed, lymph node status of the pararectal and inguinal nodes, time of recurrence, site of recurrence, and median survival from the date of primary surgery and from the date of recurrence were determined. There were 55 patients (82%) who had a minimum of 5 years' follow-up since initial treatment. Optimal surgical treatment requires an abdominoperineal resection with wide dissection of the ischiorectal fossa and perineum in all patients, as well as an en bloc excision of the posterior vaginal wall in women. Although excision of the posterior vaginal wall improves the disease-free interval, median survival is not altered, compared with the group without vaginectomy. The predominant sites of local recurrence in men are the pelvis and perineum, and in women, the pelvis and posterior vaginal wall. The status of the pararectal lymph nodes from the operative specimen can give accurate information about the relative risk of recurrence. The presence of inguinal lymph node metastases represents a poor prognosis because of a close association with systemic metastases.

Adult↗
PubMed1986

Radiation-resistant and repair-proficient human tumor cells may be associated with radiotherapy failure in head- and neck-cancer patients.

Inherent cellular radioresistance and repair of x-ray damage was studied in 19 early-passage squamous cell carcinoma lines derived from head- and neck-cancer patients with known clinical results following radiotherapy. Human tumor cells that were radioresistant and/or proficient in accumulation/repair of x-ray damage were cultured from patients unsuccessfully treated with radiotherapy. Thus, the presence of radiation-resistant and repair-proficient tumor cells was associated with clinical radiation failure, suggesting the possibility of a predictive assay based on in vitro radiobiological parameters.

Carcinoma, Squamous Cell↗
PubMed1986

Preliminary evidence for gut involvement in the pathogenesis of rheumatoid arthritis?

111Indium leucocyte scans were performed on 26 patients with active rheumatoid arthritis. An abnormal localization of radioactivity was observed in the gut of 12 of these patients, generally in the region of the terminal ileum, caecum and ascending colon. No difference was found in the intake of nonsteroidal anti-inflammatory drugs between those with positive and negative scans. Two patients with positive scans were on no medication. These observations suggest the possibility of a primary role for a gastrointestinal lesion in the aetiology of rheumatoid arthritis, although these abnormalities could be secondary or unrelated.

Adult↗
PubMed1986

Speech identification under simulated hearing-aid frequency response characteristics in relation to sensitivity, frequency resolution, and temporal resolution.

Word identification in noise was measured adaptively under flat and rising frequency response conditions to represent basic alternatives for a hearing-aid characteristic. The speech test results were compared with measures of sensitivity, loudness tolerance, frequency resolution, and temporal resolution in 23 hearing-aid users with mild or moderate sensorineural hearing losses. Subjects also rated the two frequency responses for preference and subjective quality. A paradoxical relationship was found whereby superior speech performance under the flat condition was associated with preference for the rising condition, and vice versa. No combinations of psychoacoustic variables satisfactorily explained either relative performance or preference, although high-frequency sensitivity and upward spread of masking were implicated. Absolute speech performance was related to sensitivity at 2 kHz, age, and sex, but not to frequency resolution once other factors were partialed. Temporal resolution was also a factor, but this was due largely to the influence of extreme values in two subjects. It is concluded that, for moderate degrees of hearing loss, speech identification in noise can be predicted from age, sex, and sensitivity with little advantage from recourse to measurement of frequency or temporal resolution.

Adult↗
PubMed1986

Heating RNA before cell-free translation gives no selective increases among the translation products of RNA from rat heart and mammary gland, rabbit reticulocyte membranes, or trout liver.

A recent study has reported that the heating of a population of guanidinium-extracted mRNAs prior to translation causes a selective increase in the translation of certain mRNAs. To determine if this phenomenon is a general property of mRNAs, we carried out a comparison of the translation products obtained when phenol-extracted rat heart and mammary gland RNAs, rabbit reticulocyte membrane RNAs, and trout liver RNAs were translated in the reticulocyte translation system, with and without a prior heat treatment. Our results show that no selective increase in the translation of mRNAs was observed for any of these samples. Among the 14 RNA preparations examined, one total mammary RNA preparation did display a twofold increase in the translation of all mRNAs after heat treatment. It is shown that the heat enhancement of translational activity observed for this sample was due to the reversible formation of intermolecular aggregates with a contaminant that can be removed by chromatography on oligo(dT)-cellulose. Since heat treatment did not selectively enhance the activity of any mRNA in these samples, our results show that the current practice of translating phenol-extracted RNAs without a prior heat treatment should be satisfactory for the translation of most mRNA populations.

Animals↗