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Biomedical subjects

P Simpson

Publications and source records attributed to P Simpson.

At least 127 records · Page 7Linked to original sources
PubMed1982

The effects of clofibrate ingestion on alveolar macrophage peroxisome content and oxygen metabolism.

Respiratory burst activity in alveolar macrophages in response to particulate and soluble challenges, such as zymosan particles and phorbol myristate acetate (PMA), is not nearly as dependent upon membrane stimulation as in neutrophils. Microperoxisomes are subcellular organelles containing catalase and are present in lung macrophages and cells of other organs. Evidence from liver cells indicates that peroxisomes are intimately involved with hydrogen peroxide and lipid metabolism. Clofibrate (2-(p-chlorophenoxy)-2-methylpropionic acid ethyl, Atromid-S-), a hypolipidemic drug known to cause peroxisomal proliferation in liver cells, was studied with respect to its ability to cause increases in the microperoxisome content and to alter the cellular metabolism of alveolar macrophages. Liver weight increased over a 2-week drug treatment period while lung weight remained unchanged. Plasma triglyceride levels were decreased by the treatment, indicating the effectiveness of the drug. Unlike the effect on liver cells, however, clofibrate did not cause a proliferation of microperoxisomes, as determined by morphometric analysis. Oxygen consumption and hydrogen peroxide generation by alveolar macrophages in response to either stimulant (zymosan or PMA) was no greater in clofibrate-treated rats than in controls. Superoxide release, when expressed as the change in response to PMA, appeared elevated in the drug group; statistical significance, however, was not demonstrated. The hexose monophosphate shunt (HMP), which produces reducing equivalents for lipid biosynthesis, was elevated in macrophages from clofibrate-treated rats when expressed similarly. The significance of these results in relation to the known effects of the drug on liver cells.

Animals↗
PubMed1982

Myocyte hypertrophy in neonatal rat heart cultures and its regulation by serum and by catecholamines.

The role of hormones and other humoral factors in the regulation of myocardial hypertrophy has been difficult to evaluate. We asked whether myocardial cell hypertrophy could be demonstrated in cultures from the day-old rat ventricle and evaluated the effect of serum concentration and catecholamines on the growth process. Two single-cell preparations were used: serum-supplemented, bromodeoxyuridine-treated cultures and serum-free cultures with transferrin and insulin. Both preparations were characterized by myocardial cell predominance (about 75--80% of total cells) and constant cell numbers. Myocardial cell size was documented by photomicroscopy and quantified by volume (microscopic diameter of suspended cells), surface area (planimetry of attached cells), and total cell protein concentration (Lowry method and cell counts). Growth was also evaluated in pure nonmyocardial cell cultures. In cultures with 5% (vol/vol) serum, myocardial cell size increased 2- to 3-fold over 11 days in culture. Final volume, surface area, and protein concentration were about 3000 micrometer3/cell, 5000 micrometer2/cell, and 1500 pg/cell, respectively. Serum had a dose-related effect on myocardial cell hypertrophy; myocardial cell size increased about 4-fold when serum concentration was increased from 0% to 5% or 10%. Cells maintained in serum-free medium with transferrin and insulin (each 10 microgram/ml) did not hypertrophy, but did remain responsive to the growth-promoting activity of serum. Chronic exposure to isoproterenol or norepinephrine (1 microM) significantly stimulated myocardial cell hypertrophy. This stimulation was dose-related, was not blocked by equimolar propranolol, was not associated with a sustained chronotropic effect, and was more pronounced in the serum-free preparation. In pure cultures of nonproliferating (bromodeoxyuridine-treated) nonmyocardial cells, cell size also increased with time in culture, but variation in serum concentration and addition of norepinephrine had no significant effect on cell size. Myocardial cell hypertrophy occurs in culture and is regulated by variations in the culture medium, including serum, with its contained hormones and growth factors, and catecholamines. The culture preparation can be used to explore the regulation of myocardial cell hypertrophy by nonhemodynamic factors.

Animals↗
PubMed1981

The influence of bone on temperature patterns produced by 434-MHz electromagnetic radiation.

The temperature pattern produced in phantoms containing simulated bone and muscle components was determined for 434-MHz electromagnetic radiation. A parallelepiped phantom was employed in this study and heating was conducted for 15 minutes using a commercially available diathermy unit. Both slab and cylindrical bone geometries were investigated, as well as the influence of depth in muscle of the bone component on the resulting temperature pattern. The temperature perturbation produced by bone irradiated by 434-MHz radiation was found to vary drastically with the bone geometry, as well as with the depth of the bone in muscle.

Body Temperature↗
PubMed1980

The initiation of pupariation in Drosophila: dependence on growth of the imaginal discs.

Regeneration was induced in the imaginal discs in situ following lesions caused by heat-sensitive cell-lethal mutations. A clonal analysis of this event demonstrated that the subsequent delay in pupariation was correlated with the amount of extra growth that occurred during the regeneration. Pupariation of heat-treated gynandromorphs bearing the mutations was also retarded, and the duration of larval development increased with greater amounts of mutant tissue, it was therefore correlated with the extent of the lesions in the imaginal discs. Elimination of entire imaginal discs, or the presence of very small amounts of lethal tissue, did not result in prolonged larval life.

Animals↗
PubMed1979

Regeneration and compartments in Drosophila.

A clonal analysis was performed in order to study the process of regeneration in wounded wing discs of Drosophila. Regeneration was induced either by cutting the disc in situ, or by shifting gynandromorphic larvae whose male tissue was hemizygous for a temperature-sensitive cell lethal to the restrictive temperature. Fast growing M+ clones, labelled with y and/or mwh, were produced by X-irradiation of the following genotypes: y; scJ4(y+)M(3)i55/mwh jv M+ (series I), and l(1)ts 504 sn3 l(1)ts 5697/ In(1)wvC; M(3)i55/mwh M+ (series II). The clones were induced either before or after the experimental lesion. Clones initiated one day prior to the lesion were able to cross compartment boundaries whereas clones initiated one day after the lesion did not do so. It is concluded that cells involved in the process of regeneration lose their compartmental commitment, but that later on the growing population of cells again becomes subdivided into the same compartments.

Animals↗
PubMed1978

Regulation of acetylcholine release from neuroblastoma x glioma hybrid cells.

Neuroblastoma x glioma NG108-15 hybrid cells exposed to N6, O2'-dibutyryladenosine 3':5'-cyclic monophosphate for several days release [3H]acetylcholine in response to serotonin, prostaglandin F2alpha, KCl, or veratridine. NG108-15 cells grown in the absence of dibutyrul cyclic AMP do not respond to an excitatory stimulus by releasing [3H]acetylcholine but can be shifted to a responsive state by treatment with dibutyryl cyclic AMP. Thus, the reactions that are required for acetylcholine release can be regulated in NG108-15 cells, thereby regulating the ability of cells to form synapses and the efficiency of synaptic communication.

Acetylcholine↗