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Biomedical subjects

L R Epps

Publications and source records attributed to L R Epps.

8 recordsLinked to original sources
PubMed1987

Cocaine: long-term administration depletes cardiac enzymes in the rat.

Arterioles and myocytes of the cardiac ventricle were examined histochemically to determine their metabolic profiles in normal rats and in rats treated either acutely or chronically with cocaine. Following long-term, but not acute, cocaine administration, enzymes involved in both aerobic and anaerobic metabolism as well as in hexosemonophosphate shunt were greatly decreased. These data suggest that long-term usage of cocaine leads to severely impaired coronary metabolism.

Adenosine Triphosphatases↗
PubMed1985

Zinc and Chlamydia trachomatis.

Zinc was noted to have significant effects upon the infection of McCoy cells by each of two strains of Chlamydia trachomatis. With a high or low Chlamydia inoculant, the number of infected cells increased up to 200% utilizing supplemental zinc (up to 1 X 10(-4) M) in the inoculation media compared with standard Chlamydia cultivation media (8 X 10(-6) M zinc). Ferric chloride and calcium chloride did not effect any such changes. Higher concentrations of zinc, after 2 hr of incubation with Chlamydia, significantly decreased the number of inclusions. This direct effect of zinc on the Chlamydia remained constant after further repassage of the Chlamydia without supplemental zinc, suggesting a lethal effect of the zinc. Supplemental zinc (up to 10(-4)M) may prove to be a useful addition to inoculation media to increase the yield of culturing for Chlamydia trachomatis. Similarly, topical or oral zinc preparations used by people may alter their susceptivity to Chlamydia trachomatis infections.

Calcium Chloride↗
PubMed1984

Zinc and the heat-labile enterotoxin of Escherichia coli.

Enterotoxigenic Escherichia coli is a major cause of diarrhoea in man. When zinc in concentrations of 10(-6) M or 10(-5) M was added to the growth medium, there was a significant increase in heat-labile enterotoxin production by each of six toxigenic strains. Zinc in these concentrations did not alter bacterial growth or the activity of preformed toxin. Other heavy metals did not enhance toxin production and o-phenanthroline, a relatively specific zinc-chelating compound, blocked the enhancing effect. The significance of these findings is discussed in relation to the use of supplemental dietary zinc.

Bacterial Toxins↗
PubMed1983

Antibiotic and nonantibiotic ionophores can alter bacterial adherence to mammalian cells.

Epithelioid (HeLa) and fibroblastic (L) cells in culture incubated for 18 hr with the ionophores amphotericin B and amiloride were noted to bind significantly more and less bacteria, respectively, than control cells incubated without ionophores. These effects were related to dose and incubation length and were present at concentrations approximating those in vivo after administration of maximal doses of these drugs given to humans therapeutically. Electron microscopy of both receptor cell lines revealed increased length and number of cellular projections in the amphotericin-treated cells and flattening and loss of membrane individuality in the amiloride-treated cells. These findings could explain the differences in subsequent bacterial binding. The ionophores nifedipine and verapamil which block calcium transport in cells which have calcium channels did not alter bacterial binding to these receptor cells or bacterial binding to calcium channel-containing myoblasts (in culture). These data suggest that certain ionophores could alter bacterial colonization and infection in the host indirectly by altering bacterial binding; however, the clinical significance of these findings remains to be determined.

Adhesiveness↗
PubMed1982

Effect of estrogens on bacterial adherence to HeLa cells.

Incubating confluent cell culture HeLa cells for 18 h with increasing concentrations of estrogens progressively enhanced the subsequent attachment of a variety of radiolabeled bacteria to the HeLa cells. This effect was not caused by other hormones and was not produced by 1-h incubations of HeLa cells or bacteria with hormones. Estrogens did not similarly affect two other receptor cell lines studied. The addition of metabolic inhibitors showed that this effect of estrogens on HeLa cells was energy dependent and involved protein synthesis. Concurrent incubation of the HeLa cells and estrogens with the antiestrogen nafoxidine blocked the subsequent increase in adherence. These data suggest that estrogen receptors are present in HeLa cells and that hormonally-induced alterations in the synthesis of bacterial receptor sites may modify the capacity of certain cells to bind bacteria.

Adhesiveness↗
PubMed1982

Zinc and bacterial adherence.

Zinc significantly enhances the ability of piliated Gram-negative and Gram-positive bacteria to attach to HeLa cells. This effect is related to the concentration of zinc and degree of bacterial piliation, and is not present with unpiliated organisms. Bacterial viability is not necessary for this effect, and sulfhydryl blockers decrease the response. These data suggest that zinc can bind to bacterial pili and augment bacterial adherence; in this manner, zinc may act as a virulence factor.

Adhesiveness↗
PubMedDate not supplied

Nutrient chemotactic agents and the in vitro selective control of bacterial colonization.

Certain nutrient chemotactic agents after 3-18 hours of incubation with viable mammalian cells in culture can cause significant alterations in subsequent attachment of Escherichia coli to the mammalian (receptor) cells. Results were amongst the most significant with an essentially non-oxidizable amino acid analogue. Differences obtained were dependent upon the number of washings of the receptor cells after incubation with the chemotactic agents and the incubation concentrations. All E. coli isolates tested readily displayed chemotaxis, yet significant differences in adherence were observed with the minority of 16 chemotactic agents, two receptor cell lines, six E. coli and one Salmonella typhi studied. This is most likely due to poor localization of these agents in the outer layers of viable mammalian receptor cells, metabolism of the agents, or both. Some nutrient chemotactic agents may facilitate the selective control of bacterial colonization or infection.

Adhesiveness↗