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Biomedical subjects

E Cumming

Publications and source records attributed to E Cumming.

15 recordsLinked to original sources
PubMed1983

Intake and subsequent fate of a ceramic particle containing 2.85 microCi 241Am: a case study.

Intake of 241Am was reported in a young female technologist. External monitoring, whole body counting, urinalysis and fecal analysis were performed to determine the subsequent fate of the contaminant. Five days later, more than 99.5% of the radioactivity was voided in a fecal sample. A single particle, containing 2.85 microCi of 241AmO2 incorporated in a ceramic matrix, was isolated from the fecal sample. Brief descriptions of the radioanalytical results and dosimetry implications are presented. A shadow shield whole body counter was conveniently used to make an early estimate of the intake. This initial estimate enabled staff to decide that it was not necessary to artifically remove the contaminant. It was estimated that the lower large intestine was the organ which received the highest dose due to the passage of the ceramic particle. Systemic uptake of 241Am was indicated by urinalysis. The fractional transfer of 241Am from the GI tract to the blood was estimated to be less than 6 X 10(-5). This maximum estimate is limited by the MDA of the analytical procedures used. The fractional transfer of the 241Am from the GI tract to blood in this case is about an order of magnitude less than recent ICRP recommendations for "all compounds of americium".

Accidents, Occupational↗
PubMed1975

Engagement with an old theory.

The co-author of Disengagement Theory restates the central propositions, suggests new studies that might test its usefulness, and examines some of the controversy that has been generated over the years either by the theory itself or the context in which it was set forth. The four key propositions focus upon decreasing life space with advancing age, the individual's own anticipation and participation in this process, a change in style of interaction, and the momentum of the disengagement process once it has begun. Although some useful research has been done, the theory remains poorly operationalized and largely untested. A measure of life space variety is proposed, and attention also directed to neuro-physiological findings. Several misunderstandings and misapplications of Disengagement Theory are discussed, including the erroneous idea that disengaged people necessarily are either higher or lower in morale than others, and the unenlightening controversy over "activity versus disengagement."

Aged↗
PubMedDate not supplied

[Effects of adenosine on automaticity and post-potential oscillations in Purkinje fibers of mammals].

The aim of the present paper was to study the effects of adenosine (ADO) on automaticity and after potential oscillations on canine cardiac Purkinje fibers. ADO concentrations from 10(-8) to 10(-5) M were used. The intracellular electrical activity was recorded with conventional microelectrodes. ADO increased during the first two minutes the basic cycle length (BLC) with concentrations higher than 10(-8) M, to a value 50% above control, later there is a progression to a steady state. The dose-response curve in the steady state is sigmoidal and resembles those of receptor occupation. The slopes of pacemaker potentials have a tendency to decrease along with the increase in BLC length. After potential oscillations decrease with 10(-8) M of ADO but not with larger concentrations. There results supports the hypothesis that ADO produces an increase in the time independent potassium current similar to the one described for atrial and ventricular myocytes. This effect probably depends on specific receptor stimulation. The biphasic time course suggests the existence of subtypes of A1 receptor with different dissociation constants and affinities but with similar actions. The idea that the ADO effects depend mainly on the potassium currents and not on I(f) is supported by the absence of a dose-dependent effects in the oscillatory after potentials.

Adenosine↗
PubMedDate not supplied

[Barium ion blockade on an inward rectifying potassium current in oocytes of the frog Xenopus laevis].

The effect of barium (Ba2+) on inward rectifier K+ current endogenous (IRK-endo) was characterized in Xenopus laevis oocytes with two microelectrodes voltage clamp technique. Varying [K+]o caused a shift in the reversal potential and a change in the straight pert of the slope as expected for K+ current. External Ba2+ blocked IRK-endo displayed lower affinity in the channel in two different forms. The blockade of the peak current was voltage independent, and had a Kd of 0.9 +/- 0.1 mM. In contrast, a second effect on the late current (80 ms). Was both time and voltage dependent, with a Kd that display monoexponential voltage dependence (tau = 50 +/- mV.) These observations suggest the presence of two different binding sites for Ba2+, one in the external vestibule of the channel and another lying within the channel. Our results demonstrate the existence of an endogenous K+ current in Xenopus laevis oocytes with characteristics that resemble other inward rectifier K+ channels found in other species.

Animals↗