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Biomedical subjects

E C Gregg

Publications and source records attributed to E C Gregg.

36 records · Page 2Linked to original sources
PubMed1969

Kinetics of cell volume changes of murine lymphoma cells subjected to different agents in vitro.

Cell volume distributions obtained with an electronic particle analyzer were used to study the changes in volume of individual cells in the absence of cell division. Cultures of murine lymphoma (strain L5178-Y) cells in suspension were used in these studies. During a division delay following ionizing radiation, individual cells increased exponentially in volume with equal rate constants; these rate constants were indistinguishable from that describing the increase in cell number of an unirradiated population. When an originally log phase population of cells was prevented from increasing in number by inhibitors of DNA synthesis, individual cells increased exponentially in volume for about one generation time with the same rate constant as observed after exposure to ionizing radiation; thereafter, only the cells defining the upper half of the volume distribution continued to increase in volume, and they apparently did so with a first order rate constant proportional to their amount of DNA exceeding that present in one diploid complement of chromosomes in G(1). Cells arrested in mitosis with colchicine increased in volume for approximately 4 hr after which they remained constant in volume for almost one generation time; eventually these cells again increased in size. Inhibitors of protein and RNA synthesis inhibited the cell volume growth of irradiated cells.

Animals↗
PubMed1965

Electrical counting and sizing of mammalian cells in suspension.

A recently developed method of determining the number and size of particles suspended in a conducting solution is to pump the suspension through a small orifice having an immersed electrode on each side to supply electrical current. The current changes due to the passage of particles of resistivity different from that of the solution. Theoretical expressions are developed which relate the current change caused by such particles to their volume and shape. It is found that most biological cells may be treated as dielectric particles whose capacitive effects are negligible. Electrolytic tank measurements on models confirm the theoretical development, and electric field plots of model orifices are used to predict the observed pulse shapes. An equivalent circuit of the orifice-electrode system is analyzed and shows that the current pulse may be made conductivity-independent when observed with a zero input impedance amplifier.

Animals↗
PubMedDate not supplied

An analysis of the value of additional diagnostic procedures.

When several diagnostic procedures are performed on a patient, the probability of his having or not having a specific ailment will change as the result of each procedure is known. This paper describes how such a change is readily calculated using Bayes' theorem. Information theory is also used to find the increment in information from each successive test. Numerical estimates are made using data pertinent to lung X-ray examinations. Finally, some implications for diagnostic examinations in general are drawn.

Bayes Theorem↗
PubMedDate not supplied

A revised estimate of the risk of carcinogenesis from x-rays to scoliosis patients.

A considerable amount of concern has been felt recently for the risk of carcinogenesis from x-rays to scoliosis patients. This paper re-evaluates risk in quantitative terms by using some data measured by us and other data recently published in the literature. The risks are considerably smaller than had been estimated earlier. Compared with the natural incidence of cancer in the general population, the cumulative additional risk for scoliosis patients varies from 0.2% for breast carcinoma to 5% for leukemia.

Adolescent↗
PubMedDate not supplied

Designing a wax phantom to simulate a flat tumor with diffuse edges.

A suitable was phantom was designed for evaluating various film techniques used in subtraction radiography. Holes are drilled in a slab of wax and filled with various concentrations of iodinated wax, producing disk-shaped regions with diffuse borders. The technical details of construction and a representative application are described.

Models, Structural↗
PubMedDate not supplied

Radiographic quality, tube potential, and patient dose.

Measurements were made to determine if there was an optimal kVp that would maximize radiographic contrast for various materials while minimizing average patient dose. Radiographs were made of a 17-cm-thick plexiglass phantom (to simulate a typical abdomen) with added regions of plexiglass, hydroxyapatite, and iodine with peak kilovoltages from 40 to 150 kVp and 2 mm A1 added filtration. Radiographs were also made of a 4-cm-thick plexiglass phantom to simulate a typical breast, with added regions of plexiglass, hydroxyapatite, and fat at a peak kilovoltage from 35 to 100 kVp and with 1 mm added filtration. For the thicker phantom it was found that the contrast per average absorbed dose for the added plexiglass, hydroxyapatite, and iodine increased by about 3, 2, and 0.4, respectively, when going from 50 to 150 kVp. Contrast was measured relative to a reference region on the phantom. Similar data for the thinner phantom showed an increase of about 35% in contrast per average absorbed dose for plexiglass and fat but a decrease by about 30% for hydroxyapatite as the kVp changes from 35 to 100 kVp.

Humans↗