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Biomedical subjects

S A Edwards

Publications and source records attributed to S A Edwards.

At least 37 records · Page 2Linked to original sources
PubMed1995

Controlled exposures of young asthmatics to mixed oxidant gases and acid aerosol.

To help assess short-term respiratory responses to summertime air pollution, we exposed 24 asthmatic volunteers aged 11-18 in a chamber to respirable acid aerosol (mass median aerodynamic diameter 0.66 micron) plus 0.3 ppm nitrogen dioxide (NO2) plus 0.2 ppm ozone (O3). The aerosol contained available hydrogen ions (H-) at an average concentration of 2.6 mumol/m-, equivalent to 127 micrograms/m3 sulfuric acid (H2SO4); some H+ probably was in NH4HSO4 rather than H2SO4. The volunteers were exposed separately to O3/NO2 without acid and to clean air. Exposures lasted 90 min, including three 15-min exercise sessions with ventilation averaging 32 L/min, at 21 degrees C and 50% relative humidity. Asthma medications were withheld before and during exposures. Subjects gargled lemonade to minimize acid neutralization by oral ammonia (NH3). Exercise-induced bronchospasm was evident in all exposures. Differences in group mean lung function response among H2SO4/O3/NO2, O3/NO2, and clean-air exposures were not statistically significant. Individuals' measured oral NH3 concentrations or estimated inhaled doses of H2SO4 did not significantly predict their lung function changes. A few subjects showed unfavorable function changes during pollutant exposures, which might be chance occurrences or might indicate the existence of an acid-pollution-susceptible subgroup among young asthmatic subjects.

Adolescent↗
PubMed1994

An analysis of the causes of piglet mortality in a breeding herd kept outdoors.

The 229 piglets which died on an outdoor unit during a period of eight months were examined post mortem to determine the cause of death. The majority of the deaths (72 per cent) had occurred by the time that the litter was first inspected and of these 27 per cent had uninflated lungs and 53 per cent of the piglets born alive had no food in the stomach. Seventeen per cent of the stillborn pigs were of type I and 83 per cent were of type II. It was impossible to identify stillborn piglets reliably from their external appearance alone. At all ages, crushing was the most common cause of death (72 per cent of liveborn piglets). Six per cent of the corpses of the piglets had been damaged by birds, and attacks on live piglets occurred in the later stages of the study.

Animal Husbandry↗
PubMed1993

Anaesthesia for gynaecological laparoscopy--a comparison between the laryngeal mask airway and tracheal intubation.

In a single-blind, randomised, controlled study, we compared two anaesthetic techniques in 60 patients undergoing gynaecological laparoscopy. In the first group, ventilation was controlled, after paralysis and tracheal intubation. In the second group, a laryngeal mask airway was inserted and spontaneous or assisted ventilation allowed. There were no clinically significant differences in the intra-operative conditions of the two groups, although the procedure was quicker in the second group. The only significant difference in morbidity was a greater incidence of nausea and vomiting in the second group in the first 4 h after operation. We conclude that use of the laryngeal mask airway is an acceptable technique for elective gynaecological laparoscopy, in patients who are at low risk of regurgitation.

Adolescent↗
PubMed1992

Controlled exposures of volunteers to respirable carbon and sulfuric acid aerosols.

Respirable carbon or fly ash particles are suspected to increase the respiratory toxicity of coexisting acidic air pollutants, by concentrating acid on their surfaces and so delivering it efficiently to the lower respiratory tract. To investigate this issue, we exposed 15 healthy and 15 asthmatic volunteers in a controlled-environment chamber (21 degrees C, 50 percent relative humidity) to four test atmospheres: (i) clean air; (ii) 0.5-microns H2SO4 aerosol at approximately 100 micrograms/m3, generated from water solution; (iii) 0.5-microns carbon aerosol at approximately 250 micrograms/m3, generated from highly pure carbon black with specific surface area comparable to ambient pollution particles; and (iv) carbon as in (iii) plus approximately 100 micrograms/m3 of ultrafine H2SO4 aerosol generated from fuming sulfuric acid. Electron microscopy showed that nearly all acid in (iv) became attached to carbon particle surfaces, and that most particles remained in the sub-micron size range. Exposures were performed double-blind, 1 week apart. They lasted 1 hr each, with alternate 10-min periods of heavy exercise (ventilation approximately 50 L/min) and rest. Subjects gargled citrus juice before exposure to suppress airway ammonia. Lung function and symptoms were measured pre-exposure, after initial exercise, and at end-exposure. Bronchial reactivity to methacholine was measured after exposure. Statistical analyses tested for effects of H2SO4 or carbon, separate or interactive, on health measures. Group data showed no more than small equivocal effects of any exposure on any health measure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Overexpression of uvomorulin in a compaction-negative F9 mutant cell line.

The mutant F9 cell line F9att-5.51 synthesizes reduced amounts of uvomorulin (UM) protein and we hypothesized earlier (Adamson, Baribault, and Kemler, Dev. Biol. (1990), 138, 338) that this may account for its inability to compact into tightly aggregated balls of cells. Subsequently, when 5.51 cells are treated with retinoic acid to stimulate their differentiation, they are unable to form embryoid bodies as do wild-type cells which form an outer epithelial layer of visceral endoderm cells. We have now examined the possibility that the UM protein made in the mutant line is defective, but find that it is normal in structure and stability. The gene coding for UM appears to be normal as does the mRNA which is synthesized at a normal rate but is severely reduced in steady-state measurements of mutant cells. A rescue experiment was performed by increasing levels of UM in mutant cells by means of transfection with a UM expression vector. The resulting cells expressed abundant UM mRNA and protein but were still unable to form compacted aggregates and did not differentiate into embryoid bodies. Interestingly, the stability of endogenous UM mRNA was improved in the presence of exogenous UM; therefore, a positive feedback mechanism contributes to low mRNA levels in mutant cells. The accumulated data suggest that UM in 5.51 cells is unable to mount a compaction activity because a distal connecting link in the multicomponent process initiated by UM is missing or or aberrant. The missing component is likely to connect UM to actin and the cytoskeleton of the cell.

Animals↗
PubMed1991

The transcription factor, Egr-1, is rapidly modulated in response to retinoic acid in P19 embryonal carcinoma cells.

The pluripotent murine embryonal carcinoma cell line, P19, differentiates along at least three main pathways under the inductive influence of retinoic acid (RA). The events most critical to the establishment of a particular differentiation pathway must occur early since P19 cells are committed to differentiation pathways after 30 min of exposure to RA (M. W. McBurney, personal communication and our unpublished results). We have, therefore, looked for genes that are induced (or repressed) within 30 min of RA addition and find that Egr-1 is one of these genes. Egr-1 is a transcription factor of the zinc-finger class and is known to transactivate genes after binding to specific oligonucleotide sequences. We describe here the extremely rapid and transient increase of Egr-1 transcript and protein levels in P19 cells after RA addition. Stable induction of Egr-1 transcripts occurred in the presence of protein synthesis inhibitors. Simultaneous addition of RA and cycloheximide did not result in an additive effect. The mechanism of induction with either drug appears to involve relief of a block to transcriptional elongation. The response was more rapid at high RA concentrations and this suggests that the Egr-1 transcription factor could play a role in initiation of differentiation pathways of P19 EC cells.

Animals↗
PubMed1991

Regulation of Egr-1 (Zfp-6) and c-fos expression in differentiating embryonal carcinoma cells.

The Egr-1 gene (zfp-6) encodes a 'zinc finger'-type transcription factor that is one of the early growth response genes induced, together with c-fos proto-oncogene, in many cell types. Our earlier work indicated that Egr-1 and c-fos may also play roles in differentiation and we now present data to show some features of their regulation. Transcriptional regulation accounts at least partly for the increased steady-state levels of Egr-1 mRNA in differentiating teratocarcinoma cells; this rate increases threefold over the 7-10 days of differentiation of P19 embryonal carcinoma cells with both 0.5% DMSO (to give predominantly cardiac muscle) and 1 microM retinoic acid (to give nerve and glial cells). The stability of Egr-1 transcripts remains the same (T1/2 = 90 min) in undifferentiated EC and differentiated cell products. In contrast, transcripts for c-fos are barely detectable in EC cells and increase 20-fold during differentiation. The basis for this is a marked increase in stability of c-fos mRNA after differentiation. The protein products of both genes parallel the steady-state levels of their mRNAs, but both proteins become more stable in differentiated cells. This is particularly marked for c-Fos protein, which appears as a distinct 58 kDa species in terminally differentiated P19 cells. Both Egr-1 and c-Fos proteins remain at high constitutive levels in differentiated cells indicating a distinct role for these transcription factors, For instance, it appears that this form of Fos protein may not repress the synthesis of the Egr-1 gene as it does during transient expression of serum-stimulated genes.

Animals↗
PubMed1988

Analysis of a transformed cell line using antisense c-fos RNA.

Simian sarcoma virus (SSV)-infected NIH-3T3 cells (SSV-NIH-3T3), express a homologue of platelet-derived growth factor, (PDGF) a powerful inducer of the c-fos gene. We have used these cells to test the hypothesis that autocrine stimulation by PDGF-like molecules leads to c-fos expression which is functional in the transformed phenotype. We have transfected SSV-NIH-3T3 cells with a c-fos antisense-RNA expression vector, pSVsof, or control plasmids. pSVsof-transfected cells exhibit markedly decreased c-fos mRNA and protein levels, restored density-dependent growth arrest and reduced (three of five clones) tumorigenicity compared to control lines. The results confirm that c-fos cooperates in the transformed phenotype of SSV-NIH-3T3 cells.

Animals↗
PubMed1988

A zinc finger-encoding gene coregulated with c-fos during growth and differentiation, and after cellular depolarization.

Egr-1 is an early growth response gene that displays fos-like induction kinetics in fibroblasts, epithelial cells, and lymphocytes following mitogenic stimulation. Sequence analysis of murine Egr-1 cDNA predicts a protein with three DNA binding zinc fingers. The human EGR1 gene maps to chromosome 5 (bands 5q23-31). Egr-1 mRNA increases dramatically during cardiac and neural cell differentiation, and following membrane depolarization both in vitro and in vivo. Thus, Egr-1 and c-fos are often coregulated with strikingly similar kinetics. These results, in conjunction with the Egr-1 primary structure, suggest that Egr-1 may function as a transcriptional regulator in diverse biological processes.

Amino Acid Sequence↗
PubMed1988

Expression of c-fos antisense RNA inhibits the differentiation of F9 cells to parietal endoderm.

To test the putative role of c-fos in F9 differentiation, we have attempted to inhibit c-fos expression in these cells using an SV40-based expression vector (pSVneo-sof) that programs expression of c-fos antisense (sof) sequences as a 3' extension of a neo mRNA transcript. Of six G418-resistant clones isolated in transfection experiments, five expressed neo-sof transcripts. Two clones synthesized polyadenylated mRNA of the expected size (3.8 kb), two were smaller than expected, and one was larger. Two clones that expressed reduced levels of c-fos protein were inhibited in the induction of laminin, type IV collagen, and proteoglycan-19 RNA transcripts measured after 4 days of differentiation induction with RA and dibutyryl cyclic AMP. Also inhibited was the induction of the differentiation markers, TROMA-1 and TROMA-3. Antisense-expressing cells were not inhibited in the differentiation pathway to visceral endoderm since the alpha-fetoprotein gene was activated normally. We conclude that c-fos antisense expression inhibits some aspects of differentiation in F9 cells.

Bucladesine↗
PubMed1987

Isolation of a clone of F9 teratocarcinoma cells "naturally" resistant to G418.

Resistance to the neomycin analogue G418 forms the basis of a dominant marker selection system for mammalian (and other) cells transfected with the bacterial neo gene. This system has been particularly effective because of the low incidence of spontaneous conversion to G418 resistance in mammalian cells; no case of resistance to the drug in the absence of the bacterial genes has yet been reported to our knowledge. During the course of transfection experiments, we recently isolated a clone of F9 teratocarcinoma cells which is drug resistant yet has no detectable integrated plasmid sequences, neo RNA transcripts, or aminoglycoside phosphotransferase activity. The G418-resistant clone (F9nr7) did not display enhanced resistance to other cytotoxic drugs tested: colchicine, actinomycin D, cycloheximide, and hygromycin B. Therefore, nr7 cells differ from multidrug-resistant phenotypes previously described. However, this clone is inhibited, relative to control cells, in its response to the differentiation-inducing drugs retinoic acid and dibutyryl cAMP, which suggests that some aspects of general drug metabolism may be altered in these cells.

Animals↗
PubMed1987

Proteoglycan-19, laminin and collagen type IV production is correlated with the levels of mRNA in F9 cell aggregates differentiating in the presence or absence of cyclic AMP.

F9 embryonal carcinoma cells differentiate to embryoid bodies containing an outer epithelial layer of visceral endoderm cells when cultured as aggregates in medium containing retinoic acid (RA). Another pathway of differentiation to parietal endoderm is followed when dibutyryl cyclic AMP (cAMP) is added to the medium. We have measured the accumulated levels of RNA transcripts from a chondroitin sulfate proteoglycan gene (PG-19), the type IV collagen alpha 1, alpha 2 subunit genes, and laminin B1, B2 subunit genes during these differentiation processes. Laminin B2 gene is uniquely regulated among the extracellular matrix component genes studied. The level of laminin B2 RNA remains almost invariant during RA induction of differentiation but is induced 11-fold by cAMP with RA. In contrast, laminin B1, collagen IV alpha 1, and alpha 2 genes are induced in two stages with six- to sevenfold accumulation of RNA induced by RA and fourfold greater levels by cAMP (19- to 28-fold overall). All of these matrix-encoding genes except proteoglycan are expressed at low levels in unstimulated F9 cells, whereas PG-19 is completely undetectable and is observed only after 2 days of stimulation with RA. Its increased expression with RA and cAMP induction is at least 100-fold during F9 differentiation. Extracellular matrix transcripts are relatively stable and this accounts in part for high accumulated levels during differentiation. We conclude that several kinds of gene regulation occur among the matrix components and other differentiation markers, and this makes the F9 model system useful to study the differential effects of hormone treatments on cellular events leading to differentiation and loss of tumorigenicity.

Bucladesine↗
PubMed1986

Induction of c-fos and AFP expression in a differentiating teratocarcinoma cell line.

The introduction of a c-fos expression vector has been shown to potentiate spontaneous differentiation in teratocarcinoma cells. We have studied a teratocarcinoma stem cell line which can be induced to differentiate with dimethylsulfoxide (DMSO) to determine endogenous c-fos expression during the process of differentiation. c-Fos expression increases dramatically as P19S1801A1 embryonal carcinoma cells are induced to differentiate into a variety of cell types. Expression peaks 12 days after the start of aggregate culture about the same time as alphafetoprotein (AFP), a characteristic of visceral endoderm differentiation, as demonstrated by RNA hybridization to specific probes, ELISA, and immunofluorescent staining with specific antibodies. However, most differentiated cells expressed c-fos, while AFP was expressed in a minor fraction (less than 5%). The data suggest that c-fos is correlated with differentiation of teratocarcinoma cells but not specifically to visceral endoderm formation.

Animals↗
PubMed1985

Product of the cellular oncogene, c-fos, observed in mouse and human tissues using an antibody to a synthetic peptide.

The transforming gene of the osteosarcoma-producing FBJ murine sarcoma virus, v-fos, is homologous to a normal cellular gene, c-fos, in vertebrate species. Transcripts from the c-fos proto-oncogene accumulate to very high levels in late gestational mouse and human extra-embryonic tissues. We now report that these RNA transcripts are translated in these tissues. Rabbits were immunized with a synthetic peptide whose sequence is common to both c-fos and v-fos. After affinity purification on an immunosorbent containing the fos peptide (a nonapeptide), the antibody reacted with a component(s) in nuclei in sections of human and murine tissues and immunoprecipitated the v-fos gene product (p55) and a cellular protein of 39 kd (p39, complexed with fos) from lysates of metabolically-labelled virally transformed cells. Crude extracts of normal tissues contained major anti-fos-reactive proteins in the range of 55-60 kd as shown by protein blot analysis. Indirect immunofluorescence and immunoperoxidase staining showed that in addition to strong immunoreactive component(s) in the nuclei of extra-embryonic tissues of human and mouse, weaker reactions are detectable in all normal fetal and adult tissues tested. This demonstrates that fos-reactive protein is expressed in a wide variety of cells and tissues.

Amino Acid Sequence↗
PubMed1985

Lymphangiography, ultrasonography, and computed tomography in Hodgkin's disease and non-Hodgkin's lymphoma.

Findings from histologic analysis, lymphangiography, ultrasonography, and computed tomography were reviewed for 54 cases of Hodgkin's disease and 18 cases of non-Hodgkin's lymphoma. All patients were classified as clinical stage 1 or 2 disease at the time of the imaging studies. The ultrasound and computed tomography studies identified only 30 to 40% of the truly positive patients. This low sensitivity contrasts with lymphangiography, which identified 95% of the truly positive Hodgkin's disease patients and 70% of the patients with abdominal spread of non-Hodgkin's lymphoma. Many errors in interpretation were attributable to location and distribution of disease in these patients and the differing patterns of spread in Hodgkin's disease and non-Hodgkin's lymphoma. The evidence indicates that when findings are positive on computed tomography or ultrasound, no other study is necessary. In stage 1 or 2 lymphoma, non-Hodgkin's patients with negative noninvasive findings and all Hodgkin's patients, regardless of their noninvasive findings, should undergo lymphangiography.

Abdomen↗
PubMed1983

Flow cytometric separation of gonadotrophs from dispersed rat pituitaries using a fluorescent GnRH antagonist.

A gonadotropin-releasing hormone (GnRH) antagonist, [Ac-delta 3 Pro1,pFDPhe2,DTrp3,DLys6[-GnRH, was synthesized, conjugated to tetramethyl rhodamine, and found to retain GnRH antagonist activity. The fluorescent compound was used to label dispersed pituitary cells from 14-17 day-old Sprague-Dawley female rats. A subset comprising approximately 10% of the pituitary population was specifically labeled with a mean intensity of fluorescence 4.9-fold higher than the unlabeled population. The labeled cells were larger on average than the general population as inferred by forward narrow angle light scatter intensity measurements, and more granular as inferred by right angle light scatter intensity. Cells were sorted on the basis of fluorescent intensity: gonadotrophs were found to be concentrated in the rhodamine-positive fraction 5- or 6-fold relative to unfractionated cells, and 21- or 28-fold relative to rhodamine-negative fraction cells based on LH or FSH content, respectively. Gonadotrophs comprised 73 +/- 3.9% of the rhodamine-positive fraction by immunocytochemical staining. Sorted rhodamine-positive cells were cultured and found to be fully functional with respect to subsequent challenge with 30 nM GnRH. We conclude that the use of the fluorescent GnRH antagonist in conjunction with a multi-parameter cell sorter allows the purification of gonadotrophs, indicating, as expected, that these cells have a significantly higher level of GnRH binding sites than the general pituitary population. This technology should prove generally valuable in endocrine research.

Animals↗