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Biomedical subjects

R E Snyder

Publications and source records attributed to R E Snyder.

At least 55 records · Page 3Linked to original sources
PubMed1980

Mammography in 1980: an historical perspective and present state of the art.

Continued improvement in mammographic techniques, with marked reduction in radiation exposure, now makes mammography an essential part of the workup of any breast problem in women over age 30-35. Breast patterns alone cannot be used as the basis for determining high or low risk patients, but they can guide the clinician in deciding what are the proper intervals between mammograms. With increasing use of mammography, emphasis has now changed from the diagnosis of obvious cancers to the evaluation of minimal or questionable mammographic findings. Such occult masses or calcifications require needle localization, with or without specimen radiography, to ensure removal of the proper areas for histologic study.

Adult↗
PubMed1979

A multiwire proportional chamber study of axoplasmic transport in frog sciatic nerve involving interruption of somatic supply.

A multiwire proportional chamber was used to detect axoplasmic transport in isolated spinal-cord-sciatic nerve preparations in which the nerve cell bodies were exposed to L-[35S]methionine. The detector collected radiation from a series of 6-mm segments of sciatic nerve for consecutive periods of 30 min for the duration of experiments lasting 16--23 h. The radioactivity of each segment showed an initial plateau at background level followed by a rise which was approximately linear through time. Plots of the time at which the rise in radioactivity took place against the position of each segment of the nerve yielded transport velocities for the most rapidly moving label; at room temperature (21--23 degrees C) these were typically 150 mm/24 h. Approximately 1.5 h after the addition of 5 mM colchicine to the bathing solution the slope of the radioactivity-time curve decreased for all segments of the nerve; this indicated that the method satisfactorily detected impaired axoplasmic transport. If the sciatic nerve were severed at the proximal end of the preparation at about 9 h after the radioactive front had been established, the slope of the radioactivity-time curve for each nerve segment subsequently changed abruptly. Plots of the time at which the transition occurred against position in the nerve yielded transport velocities which did not differ statistically from those of the radioactive front. This transition time is thought to indicate the time at which the fastest labelled material left each segment of nerve. In some experiments, an additional change in slope occurred, possibly indicating the departure of the slowest material from each segment.

Animals↗
PubMed1977

Prospective study of non-infiltrating carcinoma of the breast.

A long-term prospective study of non-infiltrating breast carcinoma is being carried out in order to study the natural history and proper management of such lesions with particular interest in patients treated solely by local excision. During an 11-year period, 175 patients with lobular Ca in situ and intraductal Ca have been followed. None has developed recurrent disease including 18 undergoing wide local excision only. Histologic examination revealed that 36% of mastectomy specimens showed multifocal lesions, whereas only one of the patients treated by wide local excision had more than one microscopic focus. For these reasons total mastectomy is recommended as the treatment of non-infiltrating breast carcinoma. Subsequent development of contralateral cancer has occurred in ten patients.

Adult↗
PubMed1976

Application of a multiwire proportional chamber to the detection of axoplasmic transport.

A new technique for the detection of the axoplasmic transport of beta-radioactively labelled materials is described wherein a multiwire proportional chamber is used to measure the distribution of activity along peripheral nerve fibers which are maintained in vitro. The operating principles of the chamber are described and basic construction parameters given. Potential radiolabels are discussed. Two types of studies were performed at room temperature in vitro using sciatic nerves of the amphibian Xenopus laevis: static and dynamic. In the static study the nerve ganglion was incubated for a suitable period of time in either L-(U-14C) leucine or L-(35S) methionine after which the ganglion was removed and the activity in the remaining nerve assayed with the chamber. In the dynamic study the nerve activity was assayed by the chamber while incubation proceeded so that a dynamic picture of transport could be observed. Using the second approach, transport rates were observed which are in agreement with others which have been reported in the literature. Some advantages and limitations of the technique are discussed.

Animals↗
PubMed1976

An automatic bolus injector for use in radiotracer studies of blood flow: design and evaluation.

An electromechanical device is described which automatically injects the radiotracer bolus used in the measurement of cerebral blood flow. It consists of two electronically controlled, solenoid operated syringes, one containing the radiotracer solution and the other heparinized saline. Results are presented which show that use of the automatic bolus injector in place of hand injection leads to an improvement in the precision of measured flow values. Additional advantages of the device are discussed.

Animals↗
PubMed1975

Patient exposures from film and xeroradiographic mammographic techniques.

Radiation exposures of several mammographic imaging systems, including (a) industrial film, xeroradiographic plates, the Du Pont Lo-Dose vacuum-cassette screen-film combination exposed with a molybdenum target tube and (b) xeroradiographic plates exposed with a tungsten target, were investigated with a thin-window ionization chamber and a range of exposures for different breast sizes was determined for each technique. The Lo-Dose system was found to provide high-quality diagnostic images with minimal patient exposure.

Health Physics↗