Biomedical subjects

W A Fletcher

Publications and source records attributed to W A Fletcher.

7 recordsLinked to original sources

PubMed1992

Eye position signals in human saccadic processing.

1. We studied saccades to briefly flashed targets in 8 human subjects. The target flash occurred (i) during smooth pursuit ("ramp-flash"), (ii) just before a saccade to another target ("step-flash"), or (iii) during steady fixation ("flash only"). All lights were extinguished after the target flash so that smooth pursuit or saccadic eye movements occurred during the interval of complete darkness between the target flash and the saccade to it. We compared these saccades to those made without intervening eye movement (flash only), and quantified the extent to which the saccadic system compensated for the change in eye position that occurred during the dark interval. 2. Saccades to control flashes were reasonably accurate (mean gain 0.87) and consistent. Compensation for the intervening eye movement in the ramp-flash and step-flash paradigms was highly variable from trial to trial. On average, subjects compensated for 27% of the intervening pursuit eye movement on ramp-flash trials and for 58% of intervening saccadic movement on step-flash trials. 3. Multiple regression analysis showed that the variability did not depend on factors such as variations in underlying saccadic gain, response latency, timing of stimuli or size of the required response. We conclude that this variability is intrinsic to saccadic responses that require the use of an eye position signal. 4. These results show that an eye position signal is available to the saccadic system but that this signal has low fidelity.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗

PubMed1992

Immunohistochemical reaction to human milk fat globule antibodies and breast cancer differentiation.

Immunohistochemical studies of human breast cancers using human milk fat globule (HMFG) antibodies are divergent regarding the association with histologic differentiation. To clarify this association 392 tumors were assessed using two antibodies, HMFG-1 and HMFG-2. In half the tumors studied the tissue reaction to both antibodies was the same and in 63% the site of reaction was identical. Using both univariate and multivariate statistics, a highly significant association was recorded between membrane staining and well differentiated cancers and cytoplasmic staining and poor differentiation. Well differentiated tumors contained significantly more reactive cells. Complementing these findings was the association between age at diagnosis, tumor stage, and estrogen receptor status and differentiation. It is possible that immunohistochemical analysis with HMFG antibodies will provide better characterization of tumor differentiation than morphologic interpretation.

Antibodies↗

PubMed1992

Prognostic significance of the immunohistochemical reaction to human milk fat globule antibodies in node-negative and node-positive breast cancer.

The status of axillary lymph nodes in patients with breast cancer is important prognostically but does not identify all patients who will have long or short survival. To determine if the immunohistochemical reaction of tumor cells to human milk fat globule (HMFG) antibodies will define prognosis more specifically, we examined patients with node-negative disease and patients with more than three positive nodes, the extremes of the prognostic spectrum. In both node-negative and node-positive groups, patients who relapsed were matched by age at diagnosis, tumor size, histologic type, and receptor status, with patients who remained disease-free for a minimum of 48 months. Patients with poor survival had a higher proportion of poorly differentiated cancers. The ability to generate antigens recognized by HMFG antibodies was decreased in patients with recurrent disease, but this was significant only in patients with node-positive tumors. Tumors of patients who remained disease-free were more likely to have a pattern of membrane staining, while cytoplasmic staining was more frequent in those who relapsed. The results suggest that immunohistologic response to HMFG antibodies may assist in identifying cancers with poor prognosis, supplementing the prediction derived from node status.

Adult↗

PubMed1992

Immunohistochemical characteristics of human milk-fat globule antibodies in predicting chest wall and distant metastasis after mastectomy for localized cancer of the breast.

Because postoperative radiation reduces chest wall metastasis after mastectomy, it is important to identify patients in whom it might develop. Pathologic and immunohistochemical features in 59 patients with chest wall metastasis were compared with characteristics in disease-free patients and patients with systemic metastases without chest wall metastasis. Immunohistochemical studies with human milk-fat globule (HMFG)-2 were not predictive, but a membrane reaction with HMFG-1 was associated with fewer systemic metastases and tumors, in which most of the cells reacted with the antibody had significantly decreased likelihood of chest wall metastasis. Antigenic concordance between the primary breast cancer and the chest wall metastasis was demonstrated. Neither tumor size nor axillary node metastasis predicted development of chest wall metastasis, but systemic metastases were less common when fewer than four nodes were involved, the primary tumor was well differentiated, and estrogen receptors were positive.

Antigens, Neoplasm↗

PubMed1991

Further studies on ultraviolet-absorbing hydrogels for intraocular lenses: relationship between concentration of a polymerizable benzophenone, absorption, and extractability.

A tendency to reduce the use of benzophenone absorbers is currently evident in the manufacture of the UV-absorbing IOLs, mainly because the cutoff wavelengths are inferior to those provided by benzotriazoles. In principle, by incorporating large amounts of benzophenones it may be possible to achieve high cutoff wavelengths. A covalently bondable benzophenone UV absorber, Cyasorb UV-2098, was incorporated in poly(2-hydroxyethyl methacrylate) (PHEMA) in increasing concentrations, and certain associated phenomena were investigated. At 4% w/w absorber content, the nonhydrated polymers turned partially opaque. In water-swollen hydrogels, opacification occurred at a lower absorber content (2% w/w). By using extraction techniques and gas chromatography, we also found that up to 8% w/w of the absorber remained unpolymerized and could leach out from any material containing less than 5% w/w absorber. In samples with higher initial content of absorber, the amount of unreacted, leachable absorber was significantly higher (25% to 30%). Based on this study model (hydrogel/Cyasorb UV-2098), we concluded that benzophenone absorbers cannot provide cutoff wavelengths higher than those provided by benzotriazoles.

Acrylates↗

PubMed1991

Bilateral cancer of the breast: a review of clinical, histologic, and immunohistologic characteristics.

The clinical, histologic, and immunohistologic characteristics of 19 synchronous and 47 metachronous bilateral breast cancers was compared. Patients with metachronous tumors were 5 years younger and more likely to have a family history of breast cancer than those patients with synchronous cancers. The nondominant synchronous cancer was usually discovered mammographically accounting for small, node-negative tumors, and high prevalence of in situ lesions. The same was true of the second metachronous tumor when discovered mammographically. Patients with metachronous cancers who were not in a follow-up program had second cancers with characteristics similar to incidentally diagnosed unilateral cancer. The mean interval between metachronous cancers was 101 months. Significantly more first metachronous tumors were invasive lobular cancers. Histologic type of the first and second tumor was the same in only 68% of synchronous and 61% of metachronous cancers. Combined histologic evidence and differentiation was concordant in only 13% and 22% of tumors, respectively. Immunoperoxidase studies were performed with two human milk fat globule antibodies. Each antibody reacted similarly in the first and second tumor in less than 50% of tumors and concordance was less than 25% when both antibody reactions were assessed. Differences in histologic evidence, differentiation, and immunohistologic reaction suggest that both synchronous and metachronous cancers are morphologically and functionally dissimilar.

Adult↗

PubMed1979

Pulmonary epithelial-mesenchymal interactions: beyond organogenesis.

Epithelial-mesenchymal interactions are important regulators of lung growth and organogenesis, but later functional maturation of the fetal lung is though to be primarily under hormonal control. Recent evidence, however, suggests that hormonal effects on pulmonary cellular and biochemical maturation continue to involve intercellular interactions. Communication between cells may have wider importance than has hitherto been appreciated. It should be noted that in addition to organogenesis and biochemical development, mature lung requires an extensive capillary network in close proximity to areas of gas exchange. Recent attempts to isolate and culture pumonary endothelium may be expected to provide new insights into this neglected aspect of lung maturation. The possibility of hormonal or intercellular mediation of the differentiation of airway epithelium might also merit investigation.

Animals↗