PubMed Health⌕ Search

Biomedical subjects

S A Edwards

Publications and source records attributed to S A Edwards.

18 recordsLinked to original sources
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↗
PubMed1979

gag-Related polyproteins of Moloney murine leukemia virus: evidence for independent synthesis of glycosylated and unglycosylated forms.

Immunoprecipitation of labeled extracts from murine leukemia virus-infected cells with antisera specific for internal structural (gag) proteins yields three major gag-related polyproteins with molecular weights of 180,000 (Pr180gag-pol), 80,000, and 65,000 (Pr65gag). It has been shown by others that Pr65gag is the immediate precursor of the internal structural (gag) protein, and that Pr180gag-pol is the precursor to reverse transcriptase. In studies reported here, the 80,000-dalton gag-related polyprotein from Moloney strain murine leukemia virus (M-MuLV)-infected cells was found to be glycosylated by the following criteria: (i) incorporation of [3H]mannose, (ii) a change in electrophoretic mobility upon digestion with endoglycosidase H, and (iii) a change in electrophoretic mobility when glycosylation was inhibited by treatment of the cells with tunicamycin during labeling. The 80,000-dalton gag polyprotein has therefore been designated GpP80gag. The unglycosylated form of GpP80gag was a polypeptide of 75,000 daltons. A comparison of [3H]mannose and [3H]galactose labeling experiments suggested that GpP80gag is further glycosylated to yield a glycopolypeptide of 95,000 daltons. This 95,000-dalton polypeptide is relatively rapidly cleaved to yield two glycopeptides of 55,000 and 40,000 daltons which are released into the cell culture fluid, as soluble proteins. Cell-free translation of M-MuLV genomic RNA resulted in two major gag-related products of 75,000 and 65,000 daltons. The 65,000-dalton gag-related cell-free translation product comigrated with Pr65gag, and the 75,000-dalton cell-free product comigrated with the unglycosylated form of GpP80gag. Both of the gag-related cell-free translation products could be labeled with [35S]formyl methionine, which is incorporated only as the N-terminal amino acid during translation. Other investigators have shown that GpP80gag and Pr65gag differ at their N-termini, and these results combined with those reported here suggest that GpP80gag and Pr65gag are translated from two separate initiation sites in M-MuLV RNA.

Cell Line↗
PubMed1979

The period between birth and first suckling in dairy calves.

The period between birth and first suckling was recorded for 82 dairy calves. 11 per cent of heifers' calves and 46 per cent of cows' calves had not suckled by 6 h after birth. All calves, whether suckling spontaneously or put to the teat at 6 hr, had adequate 48 h total serum immunoglobulin levels.

Animals↗
PubMed1978

Comprehensive self-medication program for epileptic patients.

The establishment and operation of a comprehensive self-medication program for hospitalized epileptic patients are described. The patients in the program are required to meet established behavioral criteria during each of four stages of self-medication before progressing to the next stage. The patient has increasing responsibility in each successive phase of the program. The areas of patient involvement for the pharmacist are: (1) obtaining a medication history, (2) teaching patients about seizure medications, (3) conducting patient consultations during the self-medication program and (4) counseling the patient at discharge.

Counseling↗
PubMedDate not supplied

Behaviour of groups of weaner pigs in three different housing systems.

Behavioural observations were made on 150 3-week weaned pigs housed in pens with fully perforated floors, or a solid-floored lying area with or without straw. Observations were made during a period of high ambient temperatures and during cool weather. At high ambient temperatures pigs with part-solid floors defaecated and urinated in the lying area and showed a higher (P less than 0.01) incidence of rooting behaviour associated with wallowing. Pigs on fully perforated floors showed reduced levels of activity in hot conditions (P less than 0.01). Pigs given straw were more active (P less than 0.01) and spent 25% of active behaviour in straw directed behaviour. There was a higher incidence (P less than 0.01) of oral behaviour directed at penmates and pen fittings amongst pigs housed on fully perforated floors.

Animals↗
PubMedDate not supplied

The transcriptional factor Egr-1 is synthesized by baculovirus-infected insect cells in an active, DNA-binding form.

The Egr-1 (zfp-6) gene encodes a zinc-finger-containing nuclear protein that is rapidly and transiently induced in quiescent cells treated with mitogens. We have constructed baculovirus vectors that synthesize mouse Egr-1 protein initiating at two putative ATG start sites. The ATG site producing the larger protein (Mr, 80,000) is similar, if not identical, to Egr-1 synthesized by serum-stimulated quiescent mouse fibroblasts, thus identifying the likely site for translation. The protein synthesized by the insect cells is active as assayed by its ability to bind to a specific DNA sequence that has been identified as an Egr-1 binding site. The insect cell system will allow further studies of the structure and function of the Egr-1 product, a protein that appears to be an important "master switch" for other genes.

Animals↗