PubMed Health⌕ Search

Biomedical subjects

S A Nelson

Publications and source records attributed to S A Nelson.

15 recordsLinked to original sources
PubMed2000

Isolation and characterization of a novel PDGF-induced human gene.

Using a differential display RT-PCR strategy to identify novel growth-factor-induced transcripts, we cloned and characterized the human homolog of yeast NOP5/NOP58, whose gene product has been implicated in the execution of early pre-rRNA processing steps. Human NOP5 cDNA was isolated from an M426 fibroblast cDNA library. Determination of the cDNA nucleotide sequence revealed an open reading frame of 1587 nucleotides encoding a predicted gene product of 529 amino acids and mass of 59554Da. The yeast and human NOP5 gene products were found to share 63% homology and 46% identity. NOP5 mRNA was induced within 2h of platelet-derived growth factor (PDGF) treatment of human M426 fibroblasts. Pretreatment with cycloheximide enhanced, while actinomycin blocked induction of the NOP5 transcript. In vitro translational analysis of the cDNA revealed a 60kDa species, consistent with the predicted molecular weight of the gene product. Ubiquitous, but differential NOP5 mRNA expression was revealed after Northern blot analysis of total RNA from several human tissues. Moreover, NOP5 mRNA expression was also demonstrated in cell lines of fibroblast, epithelial, and myeloid origin. A highly charged carboxy terminal domain and consensus phosphorylation sites were identified. The presence of potential regulatory elements, together with growth factor induction and widespread expression is consistent with the hypothesis that the NOP5 gene product may play a role in fundamental cellular growth processes.

Amino Acid Sequence↗
PubMed2000

Multiple growth factor induction of a murine early response gene that complements a lethal defect in yeast ribosome biogenesis.

Identification of the transcriptionally activated targets of receptor tyrosine kinases is critical to understanding biologic programs directing both normal and neoplastic growth. To elucidate these molecular processes, we identified genes induced by a potent mesenchymal mitogen, platelet-derived growth factor (PDGF). Using differential display reverse transcription-polymerase chain reaction technology, we isolated a novel growth factor-induced cDNA, San5. San5 transcript induction occurred within 60 min in NIH 3T3 fibroblasts and proceeded in the presence of cycloheximide. Maximal induction of the San5 transcript occurred between 8 and 16 h, concurrent with passage of fibroblasts through G(1). San5 message was potently induced by PDGF AA and BB and acidic and basic fibroblast growth factors, all strong activators of fibroblast proliferation, but not by epidermal growth factor and interleukin-4. In a murine hematopoietic progenitor cell line, San5 transcript induction strictly correlated with [(3)H]thymidine uptake. Isolation and sequencing of the murine San5 cDNA revealed amino acid sequence homology to yeast Nop5p, a nucleolar protein required for pre-rRNA processing and ribosome assembly. Strikingly, SAN5 was able to rescue a nop5 null mutant, implicating SAN5 in the process of ribosome biogenesis. Consistent with this result, SAN5 was localized to the nucleolus in both yeast and mouse. Thus, San5 may provide a link between growth factor receptor activation and the cellular translational machinery.

3T3 Cells↗
PubMed2000

Avidin- or streptavidin-biotin as a highly sensitive method to stain total protein on membranes.

A sensitive method for staining proteins after transfer from polyacrylamide gels to nitrocellulose paper is described. Transferred proteins are first derivatized by reaction of the nitrocellulose replica with sulfosuccinimidobiotin and are then reacted sequentially with streptavidin, rabbit anti-streptavidin, and horseradish peroxidase-conjugated goat anti-rabbit IgG antibody. Incubation with the enzyme substrate alpha-chloronaphthol, produces dark protein bands against a white background. The binding of streptavidin to the proteins is dependent on biotin derivatization as demonstrated by competition with biotinylated bovine serum albumin or 10 nM biotin. The procedure detects less than 5 ng of transferred protein in a single band and is thus 5-10 times more sensitive than horseradish peroxidase-conjugated avidin alone. For bovine serum albumin, the method is comparable in sensitivity to silver staining of protein in polyacrylamide gels.

Animals↗
PubMed1999

Consequences of Stat6 deletion on Sis/PDGF- and IL-4-induced proliferation and transcriptional activation in murine fibroblasts.

Aberrant communication among growth factors and cytokines that regulate tissue homeostasis often results in malignancy. Among the many cell types that participate in this process, stromal fibroblasts communicate in a paracrine and juxtracrine manner with cells of epithelial, endothelial, and hematopoietic origin. For fibroblasts, platelet-derived growth factor (PDGF) is a major proliferative and differentiation agent. Interleukin-4 (IL-4), however, possesses only modulating functions in this cell type. Here, we investigated the consequences of deleting Stat6 on PDGF and IL-4 signaling, proliferation, and transcriptional activation by establishing and characterizing early passage fibroblasts from wild-type and Stat6 null mice. Both wild-type and Stat6-/- fibroblasts showed nearly identical PDGFR and IL-4R activation, gross substrate tyrosine phosphorylation, PI 3-kinase activation, as well as Stat1, 3 and 5 DNA binding activities. Unexpectedly, IL-4's enhancement of PDGF-induced [3H]thymidine incorporation was greatly diminished in Stat6-/-, but not wild-type fibroblasts. PDGF-induced [3H]thymidine uptake was largely unaffected. Strikingly, IL-4, but not PDGF induction of the proinflammatory gene products, IL-6 and MCP-1 was markedly reduced in Stat6-/- fibroblasts. Thus, Stat6 is an important and specific mediator of IL-4-enhanced PDGF-induced proliferation as well as IL-4's transcriptional activation of IL-6 and MCP-1.

Animals↗
PubMed1999

Maturation of cochlear glutathione-S-transferases correlates with the end of the sensitive period for ototoxicity.

The developing mammalian cochlea is especially sensitive to chemical toxins. In rats, the period of increased sensitivity falls roughly between postnatal days (P) 8 and 28. One unexplored hypothesis for this 'sensitive period' is that young cochleas may have immature complements of detoxification enzymes. Glutathione-S-transferases (GSTs) are a family of detoxification enzymes which catalyze the conjugation of many xenobiotics to glutathione. Using high performance liquid chromatography (HPLC), we measured the concentrations of soluble GST isoforms in cochleas of developing Fischer 344 rats. At P1, the concentration of isoform rGSTP1 was 9 pmol/mg protein. That of the remaining isoforms studied was low, <2 pmol/mg protein, and, except for rGSTA3, remained so throughout the period of study. At P2, immunolabelling visualized rGSTP1 in the stria vascularis, Reissner's membrane, spiral limbus and organ of Corti. From P1 to P28, rGSTP1 increased to 15 pmol/mg protein and was detected additionally in satellite cells of the spiral ganglion and in the spiral ligament. From P7 to P28, rGSTA3 increased 8-fold (3-24 pmol/mg protein), became the predominant isoform in the adult organ and localized to pillar cells, the limbus and the spiral ligament. In the vestibule, rGSTP1 predominated, although rGSTA3 increased slightly over time. These observations suggest that biochemical immaturity in detoxification enzymes in the cochlea may contribute to the increased sensitivity to ototoxins during development and that differences in detoxification enzymes between cells in the cochlea and between inner ear organs may underlie differences in susceptibility to ototoxins.

Animals↗
PubMed1998

Effects of lead on rat kidney and liver: GST expression and oxidative stress.

The effect of acute exposure to lead acetate on the expression of glutathione S-transferase (GST) subunits and the levels of reduced and oxidized glutathione (GSH) and malondialdehyde (MDA) in rat kidney and liver was determined. The purpose of this study was to determine if GSH depletion and/or oxidative stress were responsible for changes in the expression of some or all GSTs that followed lead exposure. In kidney, all GST subunits increased following injection of lead. The level of kidney GSH was not changed at either 0.5 or 1 h after lead exposure, but increased 3, 6, 12 and 24 h after a single injection of lead. MDA levels (a marker of lipid peroxidation) did not change in kidney following lead injection. Immunohistochemical markers of oxidative stress and nitric oxide production were also unchanged by lead administration. Therefore. we conclude that the increases in GST levels in kidney following lead exposure were not dependent on oxidative stress. In liver, lead injection caused GSH depletion (61% of control 12 h after lead treatment) and increased MDA production (2.5-fold increase 6 h after lead exposure), while GSTA1, GSTA2, GSTM1 and GSTM2 did not increase. Analysis of the effects of lead on GST mRNA and GST cellular localization were performed by Northern blot and immunohistochemical techniques. Immunoperoxidase light microscopy and immunogold electron microscopy revealed that the increase in kidney GSTM1 and GSTP1 occurred in nuclei, cytoplasm and microvilli of proximal tubules. Northern blot analysis of GSTA2 and GSTP1 mRNAs showed that their increase following lead exposure was inhibited by actinomycin D, suggesting transcriptional induction. This study demonstrates that acute lead exposure causes dramatic changes in the subcellular distribution and expression of rat kidney GSTs, and that these changes are not a result of oxidative stress.

Animals↗
PubMed1998

Glutathione S-transferases: two-dimensional electrophoretic protein markers of lead exposure.

Glutathione S-transferases (GST) are a family of detoxification isoenzymes that catalyze the conjugation of xenobiotics and their metabolites with reduced glutathione. Lead exposure in rats is known to induce GST isoenzymes in the liver and kidney. These changes in expression have potential use as biomarkers of lead exposure. Because two-dimensional electrophoresis (2-DE) enables one to analyze both protein abundance changes and chemical changes in protein structure, 2-DE was used to determine the effect of in vivo lead exposure on GST isoform expression in rat kidney cytosols. Male Sprague-Dawley rats were exposed to inorganic lead, and proteins were separated by conventional ISO-DALT and NEPHGE-DALT techniques and blotted for immunological identification. Lead exposure caused detectable inductions in both GSTP1 and GSTM1 and quantifiable charge modification in GSTP1. These preliminary data confirm the utility of 2-D electrophoretic GST analysis as indicative of lead exposure and toxicity and support its use for further elaboration of lead's effects on renal protein expression.

Animals↗
PubMed1997

Regulatory capacity of an androgen-specific enhancer of the mouse Slp gene in transgenic mice.

Different steroid hormone receptors can activate transcription from the same hormone response element (HRE) in vitro, but in vivo the effects of each hormone on gene activity are distinct. To determine sequences mediating androgen-specific response in a physiological setting, we placed the androgen-responsive mouse sex-limited protein gene (Slp) enhancer before a tkCAT reporter in transgenic mice. The enhancer contains a consensus HRE plus accessory factor binding sites that act in concert to direct transcription in response to androgen. A 160 bp fragment, C'delta2, is responsive to several steroids in transfection; in transgenic mice, this enhancer was active in several tissues of male and female mice, in four of six transgenic lines. In striking contrast, C'delta9, a 120 bp sub-fragment of C'delta2 that responds only to androgen in transfection, showed activity in testes, prostate and kidney, where it was strongly androgen-inducible in females. However, expression was obtained in only one transgenic line. Multimerization of the C'delta9 enhancer conferred expression in prostate, but again in only one line. The greater penetrance of C'delta2 expression was not driven by glucocorticoids, as adrenalectomy had little effect, but may be dependent on the NF-kappaB-like element absent from the C'delta9 fragment. That two transgenic lines showed expression in androgen target sites driven by enhancers that are androgen-specific in vitro suggested that activation of this enhancer, when it could occur, was in response to androgen. The dramatically different behavior of the two related enhancer sequences underscores the importance of chromosomal context to the activity and specificity of regulatory elements.

Adrenal Glands↗
PubMed1997

Effects of triethyl lead administration on the expression of glutathione S-transferase isoenzymes and quinone reductase in rat kidney and liver.

The effects of triethyl lead chloride (TEL) on the expression of two detoxication enzyme families, glutathione S-transferases (GSTs) and NAD(P)H:quinone oxidoreductase (QR) were determined in rat liver and kidney. Fischer 344 rats were given one intraperitoneal (i.p.) injection of TEL. GST activity, GST isoenzyme levels, mRNA levels of alpha class GST isoenzymes Ya1, Ya2, and Yc1 and activity of QR were determined. Treatment of rats with TEL caused a significant increase in GST activity in kidney. In kidney, the levels of all GST subunits were significantly elevated; the largest increase was a 3.2-fold increase in GST Yb1. The levels of GST Ya1, Ya2, and Yc1 mRNA also increased after injection of TEL. In liver, TEL injection resulted in decreased GST activity and lower levels of hepatic GSTs Yb2, Yb3, Ya1, and Ya2. The largest decrease was a 40% reduction of GST Ya1. In contrast, the level of liver GST Yc1 increased from day 4 through day 14 after injection of 10 mg/kg TEL and Yp was increased 1.4-fold 4 days after injection of 12 mg/kg TEL. The levels of liver mRNAs coding for alpha class GSTs Ya1, Ya2, and Yc1 were reduced 12 h after injection of TEL. The mRNA levels of GST Ya1 and Ya2 returned to basal level while Yc1 message increased to a level higher than controls 24 h after TEL injection. The increase in Yc1 protein between days 4 and 14 is consistent with the increase in the corresponding mRNA. The activity of QR was elevated 1.5-fold in kidney and 2.7-fold in liver 14 days after the injection of TEL. This report demonstrates that administration of organic lead significantly affects GST expression and QR activity in a tissue-specific and isoenzyme-specific manner. These results indicate that GST expression and QR activity are not co-regulated.

Animals↗
PubMed1997

Two distinct mechanisms elicit androgen-dependent expression of the mouse sex-limited protein gene.

The mouse sex-limited protein (Slp) gene is expressed in liver and kidney of adult males and is testosterone-inducible in females, indicative of androgen dependence. Analysis of mRNA levels and chromatin configuration reveals that this androgen regulation is achieved by distinct means in the two tissues. In the liver, Slp expression requires pituitary function, and specifically, as shown by others, a pulsatile pattern of GH secretion that is itself determined by androgen. After hypophysectomy, Slp synthesis cannot be reestablished in liver by testosterone, although mRNA decline can be slowed. In contrast, in the kidney Slp mRNA is directly induced by androgen in hypophysectomized mice. In vivo footprinting was used to examine the role of the Slp enhancer, which directs androgen-specific transcription in transfection and contains a factor-binding site, FPIV, whose protection in vivo has been correlated with Slp expression. In kidney, FPIV was protected in intact males and hypophysectomized mice supplemented with testosterone, but not in females or untreated hypophysectomized mice, corroborating FPIV's association with androgen-driven transcription. Surprisingly, protection of FPIV also occurred in liver of hypophysectomized males treated with testosterone, despite the lack of Slp expression. Thus androgen directly affects the Slp enhancer in kidney, where steroid is sufficient for gene activation, as well as in liver, where chromatin remodeling occurs in response to androgen, although GH is clearly required for expression. This may indicate that both GH and androgen signal transduction pathways target the Slp enhancer to elicit precise gene regulation.

Animals↗
PubMed1992

The physician and employee judgment system: reliability and validity of a hospital quality measurement method.

Hospitals engaged in quality improvement must measure and assess customer perceptions of hospital services. Hospital customers are either "external"--patients, their families, and payers--or "internal"--physicians and hospital employees. This article describes two measurement systems designed to gather information from internal customers about the quality of hospital services. One system targets physicians, the other hospital employees. This article describes how these systems were developed and pilot-tested, and how the results were analyzed. Analysis of results showed the systems to be reliable, valid, and representative. The article also addresses limitations of the research (focus on general acute-care hospitals), interesting findings and implications (the correlation between physicians' and employees' ratings of hospital quality), and uses of these measures in corporate-level and hospital-level quality improvement (measuring trends and identifying specific opportunities for improvement).

Attitude of Health Personnel↗
PubMed1980

Determination of clindamycin in pharmaceuticals by high-performance liquid chromatography using ion-pair formation.

A reversed-phase ion-pairing high-performance liquid chromatographic procedure with refractive index or UV 214 nm detection was developed for the separation of clindamycin, clindamycin B, and 7-epiclindamycin. The chromatographic retention behavior of these compounds on an octadecylsilane column was investigated as a function of pairing-ion, mobile phase composition, and pH. The method was applied to the determination of clindamycin in bulk drug and in a number of pharmaceutical formulations. The relative standard deviations for all assays was in the 0.5-2% range.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

School-age parents.

Explore the source record for details and available documents.

Adolescent↗