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Biomedical subjects

R W Young

Publications and source records attributed to R W Young.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1985

Cell differentiation in the retina of the mouse.

Cell differentiation in the retina of the mouse during the postnatal period was studied by autoradiography. Animals were injected with 3H-thymidine at ages extending from the day of birth through postnatal day 11. Six weeks later the distribution of labeled nuclei in the cells of the mature neural retina was analyzed to determine when these cells completed their final mitosis prior to differentiating. Central and peripheral zones were analyzed separately. Cell division ceases by 5-6 days in the center of the retina and by 11 days in the periphery. Among cells produced postnatally, 73% differentiate as rods, 20% as bipolar cells, 6% as Müller cells, and 1% as amacrine and ganglion cells. At all stages of embryogenesis, the differentiation of at least three and as many as six distinct types of specialized cells is initiated simultaneously within the ventricular cell population.

Animals↗
PubMed1985

Cell proliferation during postnatal development of the retina in the mouse.

Cell proliferation was studied in the developing mouse retina by autoradiography following injection of [3H]thymidine. In 1-day-old mice, the duration of the phases of the cell-division cycle was investigated in ventricular cells, the mitotically active precursors of postmitotic cells that comprise the neural retina. In the center of the retina, the generation time (T) was 30 h, consisting of 8.5 h G1 phase, 16.0 h S phase, 2.6 h (minimum) G2 phase, and 2.5 h mitosis. In the periphery, T was 28.5 h; G1, 7.5 h; S, 16.0 h; minimum G2, 2.6 h; and mitosis, 2 h. As embryogenesis proceeds, the mitotic cycle decelerates. In contrast with postembryonic cell populations (in which G2, S and M tend to be invariable), all phases of the cycle increase in duration, and most become longer than is commonly observed in mature animals. Approx. 18 generations of ventricular cells are produced. However, throughout the stage of multiplication, some cells cease dividing and differentiate. In 1-day-old mice, 23% of ventricular cells in the center of the retina and 37% in the periphery remain mitotically active. DNA synthesis ceases on the 6th day in the center and the 11th day in the periphery.

Animals↗
PubMed1984

Cell death during differentiation of the retina in the mouse.

A reproducible pattern of cell death associated with differentiation of the retina in mice was analyzed quantitatively by microscopy. Cell death occurs primarily during the first 2 weeks after birth and is essentially complete by the end of the third week. Death of individual cells involves nuclear condensation and pyknosis (apoptosis), followed by phagocytosis of the cellular remains by adjacent cells or motile phagocytes. From birth through 4 days, an increasing incidence of cell death is observed among ventricular cells. Ganglion cell degeneration is prominent during the first 11 days, peaking on days 2-5. Many presumptive amacrine cells die within the inner plexiform and inner nuclear layers, particularly between 3 and 8 days. Among adjoining bipolar and Müller cells, degeneration reaches a peak at 8-11 days. On day 5, formation of the outer plexiform layer separates the rods into two groups. Rod nuclei situated on the inner side of that layer immediately move across it to enter the outer nuclear layer, but numerous cells die during nuclear migration. Sporadic death of rods continues during the following 2 weeks. Cell death associated with cell differentiation (histogenetic death) is considered to represent a normal developmental process. Possible mechanisms resulting in cell degeneration are discussed. It is suggested that genetically regulated cell death serves to fine-tune neuronal networks during the terminal stages of development.

Aging↗