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Biomedical subjects

R W Young

Publications and source records attributed to R W Young.

At least 19 recordsLinked to original sources
PubMed1992

Estimation of median human lethal radiation dose computed from data on occupants of reinforced concrete structures in Nagasaki, Japan.

This paper presents an estimate of the median lethal dose for humans exposed to total-body irradiation and not subsequently treated for radiation sickness. The median lethal dose was estimated from calculated doses to young adults who were inside two reinforced concrete buildings that remained standing in Nagasaki after the atomic detonation. The individuals in this study, none of whom have previously had calculated doses, were identified from a detailed survey done previously. Radiation dose to the bone marrow, which was taken as the critical radiation site, was calculated for each individual by the Engineering Physics and Mathematics Division of the Oak Ridge National Laboratory using a new three-dimensional discrete-ordinates radiation transport code that was developed and validated for this study using the latest site geometry, radiation yield, and spectra data. The study cohort consisted of 75 individuals who either survived > 60 d or died between the second and 60th d postirradiation due to radiation injury, without burns or other serious injury. Median lethal dose estimates were calculated using both logarithmic (2.9 Gy) and linear (3.4 Gy) dose scales. Both calculations, which met statistical validity tests, support previous estimates of the median lethal dose based solely on human data, which cluster around 3 Gy.

Adult↗
PubMed1992

Sunlight and age-related eye disease.

Within 50 years, if current trends continue, 50 million elderly Americans will suffer visual impairment from macular degeneration or cataract. However, available evidence indicates that this impending crisis of visual health can be minimized by a simple, safe, inexpensive, and practical means of prevention. Cataract and macular degeneration are the ultimate consequences of normal aging, a lifelong process of deterioration. Three major causes of ocular deterioration have been identified: oxygen, heat, and solar radiation. Among these, the radiation hazard is readily accessible to human intervention. The lens is damaged by ultraviolet radiation in sunlight, whereas the retina can be harmed by high-energy visible radiation (the "violet and blue"). Use of sunglasses that block all ultraviolet radiation and severely attenuate high-energy visible radiation will slow the pace of ocular deterioration and delay the onset of age-related disease, thereby reducing its prevalence. A 20-year delay would practically eliminate these diseases as significant causes of visual impairment in the United States.

Age Factors↗
PubMed1992

Vitreoretinal surgical technique for transplanting retinal pigment epithelium in rabbit retina.

Transplantation of retinal pigment epithelial (RPE) cells has been proposed as a potential remedial procedure for previously untreatable retinal diseases. In this study, a vitreoretinal surgical technique was used to transplant pigmented RPE cells obtained from pigmented rabbits into the subretinal space of New Zealand White rabbits. At the time the animals were sacrificed, the retina was re-attached in all but 4 of the 24 experimental eyes. Histologically, by one week the transplanted RPE cells had formed a monolayer in patchy areas beneath the attached retina. By electron microscopy, RPE cells with prominent melanin granules were found attached to Bruch's membrane. Three weeks after transplantation, grafted RPE cells had formed apical microvilli and tight junctions with adjacent cells. The nucleus of the cells containing pigment had become oval, and their contact with Bruch's membrane appeared to be composed of bsal infoldings that were well formed. Our findings demonstrated the functional appearance of the transplanted RPE cells.

Animals↗
PubMed1991

Cellular retinoic acid-binding protein in rat lacrimal gland.

We employed a monoclonal antibody to cellular retinoic acid-binding protein (CRABP) to assess the presence and localization of this retinoid-binding protein in the lacrimal gland of the rat. Immunoblots of extracts of rat lacrimal gland showed specific immunostaining of lacrimal CRABP in the region 14-16 kDa. Sections of rat lacrimal glands that were stained with anti-CRABP antibodies showed reaction product in the cytoplasm of the acinar cells. Retinoic acid may play a role in maintaining the proper function of lacrimal gland cells.

Animals↗
PubMed1991

A mathematical model for radiation-induced myelopoiesis.

A model for damage, repair, killing, and repopulation of myelopoietic marrow is presented. Evaluation produces time and dose-rate profiles during and following any complex irradiation. Equations model variable dose rates, multiple exposures, different sources, and arbitrary intervals between treatments. If factors which dominate the control of biological processes can be demonstrated, an option is to set biological rate constants to experimentally determined values. Previously, knowledge did not permit identification of dominating biological processes and their temporal rates. But a unique feature of this study is that unspecified lesions for killing and injury of cells are evaluated from mortality data on the animal species of choice. "Unspecified" is used to indicate a condition of assumption-free modeling of molecular processes, whereby rate constants for cellular effects are simply computed directly from animal mortality data. Coefficients (estimated by maximum-likelihood methods for nonspecific processes) are compared with experimental values for specific processes. The model has many uses, including modeling of the myelopoietic potential as a function of time. Another option is to calculate the whole-body survival curve for cells that control myelopoiesis as a result of the treatment schedule. Also through simple extensions of the model, an extremely complex protocol can be identified with an equivalent prompt dose value--even for partial-body, fractionated exposures.

Animals↗
PubMed1991

Estimation of coefficients in a model of radiation-induced myelopoiesis from mortality data for mice following X-ray exposure.

The rate coefficients in the model of cell kinetics and mortality introduced by Jones et al. (Radiat. Res. 128, 258-266 (1991)) are estimated using mortality data from several mouse experiments. The evaluated model fits data from a large variety of prompt, protracted, and fractionated irradiations with 250-k Vp X rays with good fidelity. Although the maximum-likelihood estimates are not unique, all estimates lead to greater cell survival than that observed in in vitro experiments on nonterminally differentiated reproducing cells from the marrow.

Animals↗
PubMed1989

Symptomatology of acute radiation effects in humans after exposure to doses of 0.5-30 Gy.

This article distills from available data descriptions of typical human symptoms in reaction to prompt total-body ionizing radiation in the dose range 0.5 to 30 Gy midline body tissue. The symptoms are correlated with dose and time over the acute postexposure period of 6 wk. The purpose is to provide a symptomatology basis for assessing early functional impairment of individuals who may be involved in civil defense, emergency medical care and various military activities in the event of a nuclear attack. The dose range is divided into eight subranges associated with important pathophysiological events. For each subrange, signs and symptoms are designated including estimates of symptom onset, severity, duration and incidence.

Accidents↗
PubMed1988

Protectiveness of Gore-Tex and PVC spray suits in orchard pesticide spraying.

An experimental Gore-Tex spray suit and a commercial polyvinylchloride suit were equally protective in orchard spraying with a fungicide. No pesticide was detected on patches inside the suits at six upper body sites, though outside deposition was substantial and variable. Body sites and spray replications were significant sources of variation in depositions. Contrasts between certain body sites indicated that more deposition occurred on the chest than on the back and that more occurred on the shoulders than on the upper arms.

Agriculture↗
PubMed1987

Determination of norgestimate and ethinyl estradiol in tablets by high-performance liquid chromatography.

A rapid, simple, stability-indicating assay procedure for norgestimate [(+)-13-ethyl-17-hydroxy-18,19-dinor-17 alpha-pregn-4-en-20-yn-3-one oxime acetate], a new progestational agent, and ethinyl estradiol (19-nor-17 alpha-pregna-1,3,5(10)-trien-20-yne-3,17-diol) in single- and composite-tablet analyses was developed using high-performance liquid chromatography. Norgestimate and ethinyl estradiol were extracted from the tablet matrix with methanol containing an internal standard. An aliquot was chromatographed on a 5-microns, reversed-phase column using water:tetrahydrofuran:methanol solution (65:25:10 v/v/v) as the mobile phase. The selectivity of the chromatographic system for intact norgestimate and ethinyl estradiol was demonstrated by resolving both compounds from various potential degradation products of each compound. An essential property of the chromatographic system was its ability to separate norgestimate as its syn and anti isomers. The method is linear, quantitative, and reproducible.

Drug Stability↗
PubMed1987

Comparisons of histones in retinal and brain nuclei from newborn and adult mice.

Histone proteins from purified nuclei of neonatal and adult mouse retinas were analyzed and compared utilizing SDS-polyacrylamide gel electrophoresis. Identical procedures were applied to examine the histones extracted from the brains of the same animals. In the newborn and mature retina and brain, 8 histone fractions have been separated, identified and quantified by scanning densitometry. These are the linker histone (H1), consisting of 3 subfractions (H1a, H1b, H1(0); the semi-histone uH2A (A24); and the 4 nucleosome core histones (H2A, H2B, H3, H4). Developmental differences are exhibited by the linker histone in both brain and retinal cells. The greatest differences between the histone patterns of retina and brain are also in the H1 group. Because the linker histone is subject to the greatest variability. H1 was selectively extracted with 5% perchloric acid from both neonatal and adult brain. This procedure established that the observed differences are a developmental phenomenon and are not due to interactions of the linker histones with other nuclear proteins. The ratio of the non-histone chromosomal proteins to total histone was found to be significantly greater in both adult and neonatal brain compared to retina at either age.

Aging↗
PubMed1987

Histone proteins in fetal and adult human retinas.

The DNA-binding histone proteins from the human retina are described for the first time. Retinas were obtained from male and female donors ranging in age from 11 to 72 years old. Retinas from two human fetuses at approximately four months of gestation were also examined for their histone content. Histones extracted from purified nuclei were separated and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Eight histone fractions were identified in all retinal samples, and were quantified by scanning transmittance densitometry. These fractions included three subfractions of linker histones (H1a, H1b, H1(0)), four nucleosomal core histones (H2A, H2B, H3, H4), and the modified core histone, A24 (uH2A), comprised of H2A covalently bound to the non-histone protein, ubiquitin. When fetal and adult retinal histones were compared, the relative amounts of the linker histone subfractions proved to be different. In the adult retinas, H1a diminished in amount whereas H1b and H1(0) were increased. No alterations were detected in the core histones. The developmental changes in linker histones may be related to modifications of chromatin compaction which accompany cell differentiation. Species differences in the pattern of linker histones were detected when the nuclear proteins of human and mouse retinas were compared. Non-histone nuclear proteins are more abundant in the adult human retina than in the mouse retina or the fetal human retina.

Adult↗
PubMed1986

Acute toxicity of petroleum- and shale-derived distillate fuel, marine: light microscopic, hematologic, and serum chemistry studies.

Rats were gavaged with 60, 48, 38, 30, or 24 ml/kg of either petroleum (P) or shale (S)-derived distillate fuel, marine (DFM). Surviving rats were killed 14 days after dosing. There was a slight difference in toxicity of the two fuels but neither fuel was very toxic. The LD50/14 was 43 ml/kg for P-DFM and 50 ml/kg for S-DFM. Lesions in rats that died indicated hepatic and renal toxicity. In another study, rats were gavaged with 24 ml/kg of either P- or S-DFM and killed at 1, 2, or 3 days after dosing. Prominent clinicopathologic findings included loss of body weight, hematologic evidence of dehydration, transient leukopenia, and serum chemistry and histopathologic alterations indicative of mild hepatic and renal toxicity.

Animals↗
PubMed1986

Lead in tissues of woodchucks fed crown vetch growing adjacent to a highway.

Woodchucks (Marmota monax) were fed crown vetch (Coronilla varia) growing along a major highway that was harvested in 1979, before unleaded gas was widely used, and again in 1985. Crown vetch, harvested 300 m from the nearest road, was fed as the control. The crops were fed as 50% dry weight of the diet for 58 d. The concentrations of lead in the control, 1979 crop, and 1985 crop were, respectively, 0.74, 50.65, and 6.78 ppm dry weight. The average +/- SE) concentrations (ppm, dry weight) of lead found in the tissues of the control, 1979, and 1985 dietary-treatment animals were, respectively, kidney, 0.36 +/- 0.05, 5.78 +/- 0.72, and 0.79 +/- 0.09; liver, 0.09 +/- 0.01, 4.71 +/- 0.17, and 0.46 +/- 0.06; muscle, 0.07 +/- 0.01, 0.14 +/- 0.02, and 0.07 +/- 0.00; blood, 0.09 +/- 0.02, 2.17 +/- 0.13, and 0.31 +/- 0.05; and bone, 1.27 +/- 0.25, 47.52 +/- 7.05, and 3.71 +/- 0.65. No significant differences (p greater than 0.05) between dietary treatments were found in the general hematological analyses of the woodchucks. The ecological significance of these findings is discussed.

Animals↗