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Biomedical subjects

L G Bush

Publications and source records attributed to L G Bush.

24 records · Page 2Linked to original sources
PubMed1981

A quantitative regional analysis of protein synthesis inhibition in the rat brain following localized injection of cycloheximide.

Previous work has shown that bilateral injection of as little as 10 microgram of cycloheximide (CHX) into the amygdala, but not into the internal capsule, caused a time-dependent disruption of long-term retention of passive avoidance training. Under these conditions, protein synthesis in the entire brain was inhibited by less than 10%. The present study was undertaken to quantify the resulting inhibition of protein synthesis in various brain regions (amygdala, internal capsule, caudate, cortex, hippocampus, thalamus, hypothalamus and the entire half brain). Rats were subcutaneously injected with L-[14C-methyl]methionine following unilateral administration of CHX via a cannula implanted in either the amygdala or the internal capsule. Regional inhibition of protein synthesis was determined by analysis of autoradiograms from different brain levels using an image analyzing computer to measure the optical densities of microscopic areas corresponding to discrete neuroanatomical structures. Regional patterns of inhibition were assessed: (a) after injection of different doses of CHX (10 or 20 microgram) into the amygdala; (b) after injection of 20 microgram of CHX into the amygdala or internal capsule; and (c) at different times (0.5, 3, 6 and 24 h) after injection of 20 microgram of CHX into the amygdala. Quantitative results are presented for the temporal and spatial patterns of protein synthesis inhibition caused by CHX injection. Since injection of CHX into the amygdala resulted in a profound inhibition of protein synthesis in both the amygdala and internal capsule while injection into the thermal capsule only caused a marked inhibition in the capsule itself, these results provide a possible explanation for our earlier observation that injection of CHX into the amygdala produced a retention deficit while injection into the adjacent internal capsule had no effect on memory function. These observations on protein synthesis inhibition support our earlier hypothesis that CHX injected into the amygdala might impair memory by virtue of its action on amygdaloid function rather than as a result of its effect on the brain as a whole.

Amygdala↗
PubMed1981

Effects of millimeter-wave radiation on monolayer cell cultures. II. Scanning and transmission electron microscopy.

Both thermal and athermal effects of millimeter-wave radiation of BHK-21/C13 cells were sought using scanning and transmission electron microscopy in conjunction with an in vitro technique that allows direct exposure of monolayer cultures to high average power densities. Culture dishes were irradiated by placing them on the open end of an E- or U-band wave guide. This technique exposes different regions of the cell monolayer lying along the longer axis of the wave guide aperture to varying power densities ranging from zero at each edge to twice the average power density at the center. Cell ultrastructure was unaffected by microwave radiation for 1 hour (41.8 or 74.0 GHz, average power densities = 320 or 450 mW/cm2, respectively) with or without cooling by rapid recirculation of the culture medium. Temperature in recirculated cultures was held at 37.2 degrees C, and that in noncooled cultures never exceeded 42 degrees C during irradiation at either power density. In contrast, cell morphology was affected by microwave exposure whenever irradiation conditions were altered so that the temperature of the monolayer reached or exceeded 44.5 degrees C. Ultrastructural alterations included breakage of cell processes, progressive detachment of cells from the substrate, increased clumping of heterochromatin in the nuclei, and the appearance of large empty vesicles in the cytoplasm. Such morphological changes resulted from either application of higher average power densities or irradiation at the power densities described above at a higher ambient temperature (greater than or equal to 38.5 degrees C).

Animals↗
PubMed1981

Effects of millimeter-wave radiation on monolayer cell cultures. III. A search for frequency-specific athermal biological effects on protein synthesis.

A method recently developed in this laboratory has been used to directly expose BHK-21/C13 cells to high levels of microwave radiation without significant microwave-induced heating (less than or equal to 0.1 degrees C). Monolayer cultures were grown on microwave-transparent polystyrene coverslips, placed on the open end of a wave guide, and maintained at 37.2 degrees C during irradiation at frequencies in both the E- and U-bands (average power densities 292 and 177 mW/cm2, respectively). Effects of microwave radiation were assessed at 0.1 GHz increments in the ranges of 38-48 GHz and 65-75 GHz. Protein synthesis was measured in quadruplicate cultures that were allowed to incorporate labeled methionine during the 15-minute period of microwave irradiation. Autoradiographs of each monolayer culture were scanned along the region corresponding to the longer axis of the wave guide aperture using a microdensitometer to quantify incorporation. Since microwave power incident on the cells was previously shown to vary along this axis according to a cosine2 relationship from zero at each edge of the wave guide to twice the average power density at the center of the wave guide, this technique should reveal biological effects that might only be manifested in narrow amplitude domains or "power windows." Observations of protein synthesis in monolayer cultures irradiated at 202 closely spaced frequencies in the E- and U-bands failed to reveal changes associated with microwave exposure. Thus no evidence was obtained in support of the existence of frequency-specific athermal biological effects of microwaves. In addition, no support was found for the existence of amplitude-specific "power windows."

Animals↗
PubMed1981

A novel technique for quantitative autoradiography of labeled histological specimens.

A novel quantitative method is described that makes it possible to routinely and accurately quantify contact autoradiographs of tissue sections in terms of actual amounts of radioactivity per square millimeter. Such determinations can either be made on the entire specimen or on any selected area of arbitrary shape that might correspond to a particular histological structure. This method utilizes the tissue specimens themselves as internal standards and requires the availability of a computerized image analyzer.

Animals↗