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Biomedical subjects

E M Berger

Publications and source records attributed to E M Berger.

At least 55 records · Page 3Linked to original sources
PubMed1985

HEPES may stimulate cultured endothelial cells to make growth-retarding oxygen metabolites.

Zwitterion buffers are often used to modulate the pH of cell culture medium but their effect on cultured cells is controversial. We found that addition of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) caused superoxide dismutase (SOD) inhibitable increases in nitroblue tetrazolium dye reduction and SOD and catalase inhibitable decreases in the growth of cultured bovine pulmonary artery endothelial cells. The findings suggest that HEPES stimulates endothelial cells to make toxic oxygen metabolites that contribute to decreased cell growth.

Animals↗
PubMed1985

Hydrogen peroxide causes dimethylthiourea consumption while hydroxyl radical causes dimethyl sulfoxide consumption in vitro.

Addition of increasing concentrations of hydrogen peroxide (H2O2) caused progressive decreases in dimethylthiourea (DMTU) concentrations which were inhibitable by simultaneous addition of catalase, but not the superoxide anion (O2-.) scavenger, superoxide dismutase (SOD), or hydroxyl radical (.OH) scavengers, such as mannitol, sodium benzoate or dimethyl sulfoxide (DMSO). In parallel, addition of increasing concentrations of H2O2 with FE++/EDTA (but not H2O2 alone) caused decreases in DMSO concentrations which were inhibitable by simultaneous addition of .OH scavengers but not SOD or catalase. Addition of DMTU, but not DMSO, also decreased H2O2 concentrations in vitro. The results indicate the relative scavenging specificities of DMTU and DMSO for H2O2 and .OH, respectively. The findings also suggest that measurement of DMTU or DMSO consumption could help assess the contribution of O2 metabolites in biological systems.

Chromatography, Gas↗
PubMed1985

Transcription of Drosophila small hsp-tk hybrid genes is induced by heat shock and by ecdysterone in transfected Drosophila cells.

Hybrid genes containing the 5' region of Drosophila heat shock protein (hsp) genes, ligated to the herpesvirus thymidine kinase (tk) gene, were transfected into Drosophila line S3 cells. Constructions containing sequences upstream from hsp70, or from any of the small hsp genes, showed heat-inducible tk expression. Ecdysterone-inducible tk expression was seen only in transfections with small hsp-tk hybrid genes. Plasmids containing a synthetic "heat shock consensus sequence" or a deletion of the hsp23 upstream region were totally inactive in transfection studies.

Animals↗
PubMed1985

Effect of superoxide dismutase encapsulated in liposomes or conjugated with polyethylene glycol on neutrophil bactericidal activity in vitro and bacterial clearance in vivo.

Encapsulation in liposomes (LIP) or conjugation with polyethylene glycol (PEG) are methods being used to increase circulating half-life periods and/or improve delivery of antioxidant enzymes that could decrease lung injury induced by O2 metabolites. We found that pretreatment with LIP, with or without the antioxidant enzyme, superoxide dismutase (SOD), decreased killing of Staphylococcus aureus 502A by neutrophils in vitro and clearance of intravenously injected S. aureus in rabbits in vivo. In contrast, pretreatment with PEG (with or without SOD) had no effect on neutrophil bactericidal activity in vitro or bacterial clearance in vivo. Our results suggest that conjugation with PEG may be a better way than encapsulation in liposomes for delivering antioxidant enzymes, especially if one is concerned about preserving host-defense mechanisms.

Animals↗
PubMed1984

Steroid and high-temperature induction of the small heat-shock protein genes in Drosophila.

Transcription of the four small heat-shock protein genes of Drosophila melanogaster can be induced in cultured cells by high-temperature shock, or by physiological doses of the moulting hormone, ecdysterone. We have characterized and compared the two induction events, focusing on hsp22 and hsp23, in terms of rates of heat-shock protein synthesis, transcription rate, messenger RNA abundance and mRNA half-life. The results indicate that relative to hsp22, the rate of hsp23 synthesis is significantly greater during recovery from heat shock and during ecdysterone induction. This difference is not due to differences in transcription rate, but rather reflects differences in mRNA stability and translational efficiency. One intriguing finding is that hsp message stability is temperature-dependent; hsp transcripts are two to three times more stable at 35 degrees C than at 25 degrees C. The possible mechanism and significance of this phenomenon are discussed.

Animals↗
PubMed1984

Stimulation of cytoplasmic actin gene transcription and translation in cultured Drosophila cells by ecdysterone.

When cultured Drosophila line S3 cells are incubated in the presence of the steroid hormone, ecdysterone, they flatten, elongate, and become motile. We show here that accompanying this morphological transformation there is a 5-fold increase in the rate of actin synthesis and a 2-fold increase in actin content. These increases, in turn, are primarily based on a 9-fold increase in the level of mRNA transcribed from the cytoplasmic actin A3 gene. We also find that during hormone treatment the cells go into proliferative arrest, accumulating in the G2 phase of the cell cycle. During this period the level of histone mRNA in the cells decreases significantly.

Actins↗
PubMed1984

Drosophila cells and ecdysterone: a model system for gene regulation.

When Drosophila cell lines are exposed to physiological doses of the steroid molting hormone, ecdysterone, they enter mitotic arrest and differentiate morphologically. These responses are accompanied by specific changes in gene expression. Several enzyme activities (acetylcholinesterase, beta-galactosidase, dopa decarboxylase, and catalase) are induced and the synthesis of a cytoplasmic actin and the four small heat-shock proteins is initiated. Several of these ecdysterone inducible genes have been physically isolated and characterized, in several cases by DNA sequencing. Current studies focus on introducing cloned ecdysterone inducible genes into responsive cells by DNA mediated transfection. Once it is clear that these introduced genes acquire the normal pattern of hormone-regulated gene expression in the cell, in vitro mutagenesis can be used before transfection to modify their structure. Transient expression, then, can become a functional assay to define regions of DNA flanking the coding region of inducible genes that are needed for proper gene expression and regulation in cultured cells.

Acetylcholinesterase↗
PubMed1984

Cyclical abnormalities in the bactericidal function, superoxide production, and lysozyme activity of neutrophils obtained from a healthy woman during menstruation: reversal by pretreatment with aspirin.

Neutrophils obtained from most of 13 healthy young women during menstruation and those obtained from the same women on nonmenstrual days killed comparable numbers of Staphylococcus aureus strain 502A, produced comparable amounts of superoxide anion, and had comparable lysozyme levels. In contrast, neutrophils obtained from a few women during menstruation exhibited decreased function. In particular, neutrophils from one healthy woman developed transient menstrual period-related abnormalities in bactericidal function, superoxide anion production, and lysozyme activity and release; these abnormalities occurred during each of three menstrual periods tested but not during three menstrual periods following the ingestion of aspirin for 14 days. The results suggest that menstrual period-related dysfunction of neutrophils may occur in some healthy women, sometimes rendering them more susceptible to menstrual period-related infections.

Adult↗
PubMed1984

Intact human erythrocytes prevent hydrogen peroxide-mediated damage to isolated perfused rat lungs and cultured bovine pulmonary artery endothelial cells.

Addition of untreated or glutaraldehyde-fixed human erythrocytes decreased hydrogen peroxide (H2O2)-mediated acute edematous injury in isolated rat lungs, H2O2-induced damage to cultured bovine pulmonary artery endothelial cells, and H2O2-dependent oxidation of reduced cytochrome C in vitro. The results suggest that intact erythrocytes can scavenge H2O2, and as a result, protect the lung and possibly other tissues from damage.

Animals↗
PubMed1983

Small heat shock proteins in Drosophila may confer thermal tolerance.

The four small heat shock proteins in Drosophila melanogaster are genetically linked and simultaneously synthesized, both in response to high temperature and, developmentally, during puparium formation. In tissue culture cells their synthesis is inducible by the molting hormone, ecdysterone. We show here that accompanying their induction and accumulation, the cells and animals acquire thermal tolerance.

Animals↗
PubMed1983

Effect of temperature on polymorphonuclear leukocyte function.

The effect of temperature on the function of polymorphonuclear leukocytes (PMN) has been investigated in vitro. Increases in temperature from 37 degrees C to 40 degrees C progressively increased chemiluminescence (CL) responses by PMN after stimulation by Staphylococcus aureus, zymosan or phorbol myristate acetate (PMA) while increases above 40 degrees C decreased these functions. Temperature increases from 37 degrees C to 40 degrees C also produced increased PMN bactericidal activity against S. aureus. In contrast, similar increases in temperature did not change superoxide production by PMN stimulated by PMA. Incubation of PMN at the various temperatures did not cause release of LDH indicating that damage to PMN was not the cause of reduced PMN chemiluminescence and bactericidal activity seen within the temperature range studied. The discrepancy between the influence of temperature on PMN chemiluminescence and bactericidal activity of PMN compared to superoxide anion production by PMN suggests that superoxide anion production may not be solely, or at least directly, responsible for killing of bacteria. Careful temperature control is needed when assaying PMN function. Febrile responses up to 40 degrees C may play a beneficial role in host defense.

Adult↗
PubMed1983

Effect of sodium benzoate on polymorphonuclear leukocyte function.

Sodium benzoate is widely used as a food preservative and reputed to be a scavenger of hydroxyl radical (.OH). The effects of sodium benzoate on the function of polymorphonuclear leukocytes (PMN) stimulated by S. aureus or the chemical agent, phorbol myristate acetate (PMA) were examined in vitro using assays of chemiluminescence (CL), total bactericidal activity, intracellular recovery of bacteria, as well as release of lactate dehydrogenase (LDH), lysozyme and superoxide anion (O2(-)). Sodium benzoate decreased chemiluminescence, superoxide anion and lysozyme release by PMN stimulated with S. aureus but did not similarly affect these responses of PMN to the chemical agent, PMA. The ability of PMN to kill S. aureus was also impaired by sodium benzoate and associated with a reduced number of intracellular bacteria recovered after 90 minutes incubation. LDH release from PMN was not demonstrable at concentrations of sodium benzoate below 100 mM indicating that damage can not account for these findings. The underlying mechanism of the altered bactericidal function of PMN treated with sodium benzoate appears to be a result of decreased uptake of S. aureus.

Adult↗
PubMed1982

Synthesis of low molecular weight heat shock peptides stimulated by ecdysterone in a cultured Drosophila cell line.

Treatment of Schneider's line 3 Drosophila cells with the steroid hormone ecdysterone rapidly stimulated the synthesis and accumulation of the polypeptide previously designated p7 [Berger, E. M., Ireland, R. C. & Wyss, C. (1980) Somatic Cell Genet. 6, 119-129]. In this report, p7 is identified as the 23,000-dalton heat shock polypeptide (hsp23). In addition to hsp23, the synthesis of the low molecular weight heat shock polypeptides hsp22, hsp26, and hsp27 was also stimulated by ecdysterone, although to different extents. Hybridization of a nick-translated genomic clone containing the hsp23 gene to a total RNA blot showed that ecdysterone stimulation of hsp23 synthesis was the result of an increase in the hsp23 RNA content of S3 cells. We detected no effect of the hormone on the synthesis of heat shock polypeptides hsp68, hsp70, and hsp83.

Animals↗
PubMed1981

Hydrogen peroxide kills Staphylococcus aureus by reacting with staphylococcal iron to form hydroxyl radical.

Two lines of investigation supported the premise that killing of Staphylococcus aureus, 502A, by hydrogen peroxide involves formation of the more toxic hydroxyl radical (.OH) through the iron-dependent Fenton reaction. First, growing S. aureus overnight in broth media with increasing concentrations of iron increased their content of iron and dramatically enhanced their subsequent susceptibility to killing by H2O2. Second, in direct relation to their effectiveness as .OH scavengers, thiourea, dimethyl thiourea, sodium benzoate, and dimethyl sulfoxide inhibited H2O2-mediated killing of S. aureus.

Free Radicals↗
PubMed1981

Actin acetylation in Drosophila tissue culture cells.

In a permanent cell line derived from Drosophila embryos, cytoplasmic actin is produced as an unstable precursor, which is subsequently converted to a stable form. This conversion results in a reduction in isoelectric point, with no apparent change in molecular weight. The conversion involves an enzymatic acetylation, and results in an insensitivity to aminopeptidase digestion, suggesting N-terminal blockage. Both the acetylated and unacetylated actins can participate in the assembly of F-actin, but with different efficiencies.

Acetylation↗
PubMed1981

Dimethyl sulfoxide prevents DNA nicking mediated by ionizing radiation or iron/hydrogen peroxide-generated hydroxyl radical.

Eighty percent of the single-strand DNA breaks induced by gamma-irradiation were prevented by the hydroxyl radical (.OH) scavenger dimethyl sulfoxide (Me2SO); CH4 was generated in the process as a product of the interaction of .OH and Me2SO. In contrast, Me2SO completely blocked DNA nicking by an iron/H2O2 system which produces .OH but smaller amounts of CH4 from Me2SO. Because Me2SO prevented DNA breaks from the more efficient iron/H2O2 system but only blocked 80% of irradiation-mediated nicking, the results suggest that .OH is responsible for 80% of the DNA single-strand breaks and the remaining 20% is due to interactions not involving .OH.

DNA, Single-Stranded↗