Biomedical subjects

Thomas A Hughes

Publications and source records attributed to Thomas A Hughes.

10 recordsLinked to original sources

PubMed2006

Regulation of axin2 expression at the levels of transcription, translation and protein stability in lung and colon cancer.

Axin2 is a negative regulator of Wnt/beta-catenin signalling with a role in tumour suppression. Its expression can be up-regulated by E2F1 allowing cross-talk between the pRb/E2F and Wnt/beta-catenin pathways, which both have critical roles in the development of many cancers. Thereby, axin2 may have a crucial role in carcinogenesis and here we examine the regulation of its expression. Axin2 mRNAs contain one of three different 5' untranslated regions that can have profound effects on the efficiency of axin2 translation. We show that axin2 mRNA expression is altered in tumours at levels of both total mRNA and relative proportions of alternative 5' untranslated regions. Moreover, the translational efficiencies defined by these 5' untranslated regions are modulated considerably. Additionally, we show that stability of axin2 protein provides a further level of expression regulation. We discuss this complex regulation in terms of axin2's function in carcinogenesis.

5' Untranslated Regions↗

PubMed2006

Regulation of gene expression by alternative untranslated regions.

The untranslated regions of mRNAs can determine gene expression by influencing mRNA stability and translational efficiency. Recent reports show that gene expression can be regulated by the differential use of alternative untranslated regions. Tissue-specific expression of transcripts that have different untranslated regions (UTRs) can control protein expression enabling developmental, physiological and pathological regulation. Several examples of alternative UTRs have been characterized, including those found in AXIN2, FGF1 and BRCA1. Results from bioinformatics studies indicate that this mechanism is more common than previously appreciated.

3' Untranslated Regions↗

PubMed2006

Combining beta-adrenergic and peroxisome proliferator-activated receptor gamma stimulation improves lipoprotein composition in healthy moderately obese subjects.

Current pharmacological regimens for hypertriglyceridemia and low high-density lipoprotein (HDL) are limited to the peroxisome proliferator-activated receptor (PPAR) alpha activating fibrates, niacin, and statins. This pilot study examined the impact of simultaneous stimulation of cyclic adenosine monophosphate with a beta-adrenergic agonist and PPARgamma with pioglitazone (PIO) on lipoprotein composition in moderately obese, healthy subjects. Subjects were treated with PIO (45 mg) to stimulate PPARgamma or a combination of ephedrine (25 mg TID), a beta-agonist, with caffeine (200 mg TID), a phosphodiesterase inhibitor (ephedrine plus caffeine), or both for 16 weeks. Lipoproteins were separated by gradient ultracentrifugation into very low-density lipoprotein (VLDL), intermediate-density lipoprotein, low-density lipoprotein (LDL), and 3 HDL (L, M, and D) subfractions. Apolipoproteins were measured by high-performance liquid chromatography. PIO alone reduced the core triglyceride (TG) content relative to cholesterol ester (CE) in VLDL (-40%), IDL (-25%), and HDL-M (-38%). Ephedrine plus caffeine alone reduced LDL CE (-13%), phospholipids (-9%), and apolipoprotein (apo) B (-13%); increased HDL-M LpA-I (HDL containing apoA-I without apoA-II, 28%), CE/TG (23%), and CE/apoA-I (8%) while reducing apoA-II (-10%); and increased HDL-L LpA-I (29%). Combination therapy reduced total plasma TG (-28%), LDL cholesterol (LDL-C, -10%), apoB (-16%), apoB/apoA-I ratio (-21%) while increasing HDL cholesterol (HDL-C, 21%), total plasma apoA-I (12%), LpA-I (43%), and apoC-I (26%). It also reduced VLDL total mass (-34%) and apoC-III (-39%), LDL CE (-13%), apoB (-13%), and total mass (-11%). Combination therapy increased HDL-L CE/TG (32%), apoC-I (30%), apoA-I (56%), and LpA-I (70%), as well as HDL-M CE (35%), phospholipids (24%), total mass (19%), apoC-I (25%), apoA-I (18%), and LpA-I (56%). In conclusion, simultaneous beta-adrenergic and PPARgamma activation produced beneficial effects on VLDL, LDL, HDL-L, and HDL-M. Perhaps the most important impact of combination therapy was dramatic increases in LpA-I and apoC-I in HDL-L and HDL-M, which were much greater than the sum of the monotherapies. Because LpA-I appears to be the most efficient mediator of reverse-cholesterol transport and a major negative risk factor for cardiovascular disease, this combination therapy may provide very effective treatment of atherosclerosis.

Adolescent↗

PubMed2005

E2F1 up-regulates the expression of the tumour suppressor axin2 both by activation of transcription and by mRNA stabilisation.

Axin2 is a negative regulator of Wnt/beta-catenin signalling with roles in early development and tumour suppression. Axin2 is induced by E2F1 and therefore acts as a point of cross-talk between the pRb/E2F and Wnt/beta-catenin pathways: two of the most frequently deregulated pathways in human cancers. In this study, we show that E2F1 up-regulates axin2 by two independent mechanisms. The human axin2 gene allows transcription of messages with three different 5' untranslated regions and in the first mechanism E2F1 directly activates the transcription of only one of these species by acting at canonical E2F binding sites. Second, E2F1 induces stabilisation of axin2 mRNAs. We discuss this regulation with respect to other known E2F targets.

5' Untranslated Regions↗

PubMed2005

Cross-talk between pRb/E2F and Wnt/beta-catenin pathways: E2F1 induces axin2 leading to repression of Wnt signalling and to increased cell death.

The pRb/E2F and Wnt/beta-catenin pathways are two of the most frequently deregulated pathways in human cancers. In this study, we show that E2F1 up-regulates the expression of axin2. Further, we show that axin2 can repress Wnt signalling leading to reduced cell growth and increased cell death. This represents cross-talk between major pathways involved in the formation of tumours. We use our data to suggest a novel mechanism for tumour suppression.

Animals↗

PubMed2004

Expression of axin2 is regulated by the alternative 5'-untranslated regions of its mRNA.

Axin2 is a negative regulator of Wnt/beta-catenin signaling with roles in early development and tumor suppression. We find that axin2 expression is regulated at both transcriptional and translational levels. The gene allows transcription of mRNAs with three alternative 5'-untranslated regions, and these are differentially expressed in various human cell types. These untranslated regions can differentially determine protein expression from messages by influencing mRNA stability and translational efficiency. We identify short upstream reading frames and structural motifs that are responsible for modulation of mRNA translational efficiencies. We show that the proportions of axin2 message expressing each 5'-untranslated region influence the amount of Axin2 protein expressed within cells. We discuss this complex regulation in the context of the function of Axin2 as a tumor suppressor.

5' Untranslated Regions↗

PubMed2002

Typing and subtyping of 83 clinical isolates purified from surgically implanted silicone feeding tubes by random amplified polymorphic DNA amplification.

In this study, 83 clinical isolates purified from biofilms colonizing 18 silicone gastrostomy devices (12 "buttons" and six tubes converted to skin level devices) were selected for subtype characterization utilizing genetic analysis. The tubes, previously used for feeding, remained in place for 3 to 47 months (mean, 20.0 months) in children ranging in age from 6 months to 17 years. Classification of specific microbes using random amplified polymorphic DNA (RAPD) analysis revealed genetic similarities and differences among isolates belonging to the same genus. Both gram-positive and -negative bacteria were investigated, including 2 isolates of Bacillus brevis, 4 isolates of Bacillus licheniformis, 2 isolates of Bacillus pumilus, 3 isolates of Enterococcus durans, 19 isolates of Enterococcus faecalis, 8 isolates of Enterococcus faecium, 2 isolates of Enterococcus hirae, 7 isolates of Escherichia coli, 8 isolates of Lactobacillus plantarum, 19 isolates of Staphylococcus aureus, 2 isolates of Staphylococcus epidermidis, and 7 isolates of Staphylococcus saprophyticus. Amplified DNA fragments (amplicons) provided species-specific fingerprints for comparison by agarose gel electrophoresis. A total of 62 distinct RAPD types were categorized from the five genera studied. Typing analysis suggested cross acquisition of E. coli, E. faecalis, and S. aureus in three patient pairs. Genomic polymorphism detection proved efficient and reliable for classifying bacterial subtypes isolated from biofilms adhering to various portions of commonly employed enteral access tubes.

Adolescent↗

PubMed2002

Use of intercostal bupivacaine with epinephrine after surgery to decrease use of narcotics and duration of intubation.

BACKGROUND: Postoperative pain plays a significant part in the recovery of patients after open heart surgery. OBJECTIVE: To determine if the use of intercostal bupivacaine with epinephrine is associated with decreases in use of narcotics and intubation times after open heart surgery. METHODS: A randomly selected experimental group of 25 patients received injections of bupivacaine with epinephrine in the intercostal tissues before chest closure in open heart surgery. A control group of 22 patients received no bupivacaine, only standard care. Postoperative use of narcotics and intubation times were determined for both groups. RESULTS: Compared with the control group, the group given bupivacaine with epinephrine used significantly less narcotics (P=.008) and had significantly shorter intubation times (P=.003). CONCLUSION: Injection of intercostal bupivacaine with epinephrine before chest closure in open heart surgery decreases use of narcotics and length of intubation postoperatively, thus speeding up recovery times.

Adult↗

PubMed1996

The fructokinase from Rhizobium leguminosarum biovar trifolii belongs to group I fructokinase enzymes and is encoded separately from other carbohydrate metabolism enzymes.

The Rhizobium leguminosarum bv. trifolii BAL fructokinase (frk) gene was isolated on a 2 center dot 4 kb BamHI fragment from the cosmid pLA72 by complementation analysis of the Tn5-induced frk mutant BAL79, and confirmed by hybridization analysis. The nucleotide sequence of the frk gene was found to contain an open reading frame consisting of 978 bp encoding 326 amino acids, which was then compared to known fructokinase sequences. The fructokinase gene was not contained in an operon and is encoded separately from other enzymes of carbohydrate metabolism. Its product is therefore assigned to the group I fructokinases. A putative promoter (TTGACA-N16-GTTGAT), ribosome-binding site and termination sequence were identified. The Frk protein contained several motifs conserved in other known fructokinase sequences, including an ATP-binding and a substrate-binding motif. The hydropathy plot derived from the frk gene sequence data revealed the fructokinase as a hydrophilic protein. The fructokinase protein was purified to electrophoretic homogeneity by a three-step method using chromatofocusing, affinity chromatography and gel filtration. Its purity was confirmed by SDS-PAGE and it was visualized as a single band by silver staining. The N-terminal amino acid sequence of the purified fructokinase confirmed the proposed open reading frame of the frk gene. The purified fructokinase had a molecular mass of 36 center dot 5 kDa, pl of 4 center dot 65, pH activity range of 6 center dot 0-9 center dot 0 (maximum activity at pH 8 center dot 0) and a Mg2+ requirement. It had a Km of 0 center dot 31 mM and a Vmax of 31 mumol fructose 6-phosphate (mg protein)-1 min-1 with fructose as substrate. The R. leguminosarum bv. trifolii BAL fructokinase was biochemically and molecularly similar to other bacterial fructokinases.

Amino Acid Sequence↗

PubMedDate not supplied

Lipoprotein compositional changes with combination hormone therapy (conjugated estrogen and medroxyprogesterone) in African American women.

OBJECTIVE: To determine whether combination hormone therapy (HT) significantly alters lipoprotein composition in healthy African American women. METHODS: Postmenopausal African American women, 45 to 65 years old, were randomly assigned to receive daily HT (conjugated equine estrogen, 0.625 mg, and medroxyprogesterone, 2.5 mg) or placebo (treated, 44; placebo, 16) for 12 weeks. Lipoproteins were separated by gradient ultracentrifugation into very-low-density, intermediate-density, and low-density lipoproteins (VLDL, IDL, and LDL) and 3 high-density lipoprotein (HDL) subfractions (light, medium, and dense--L, M, and D). Apolipoprotein (apo) A-I, A-II, C-III, C-II, and C-I were measured by high-performance liquid chromatography. Apo B, phospholipids, triglycerides, cholesterol, and free cholesterol were measured by standard assays. RESULTS: Total plasma cholesterol, triglycerides, LDL apo B, and total apo B did not change during HT. A small, transient reduction occurred in LDL cholesterol, and a persistent reduction was noted in VLDL apo B, apo C-II, and apo C-III. Total HDL phospholipids, cholesterol, apo A-I, and apo A-II increased, whereas the LDL/HDL ratio and the apo B/apo A-I ratio decreased. Cholesterol ester increased in both HDL-L and HDL-M, but only a transient increase occurred in HDL-L phospholipids. Apo A-I increased in HDL-L, HDL-M, and HDL-D; however, a similar increase occurred in HDL-D apo A-I in the control subjects. Moreover, an increase occurred in apo A-II in HDL-M. A reduction in the apo A-II:A-I ratio in HDL-L but not in HDL-M indicated an increase in HDL-L LpA-I particles. The increase in HDL particles in HDL-M was entirely due to an increase in LpA-I:A-II particles. Apo C-III increased in both HDL-L and HDL-M. The absence of changes in the HDL lipid ratios indicated an unaltered lipid composition of these particles. No changes were found in IDL compositional measurements. In 12 treated patients and 4 control subjects, Lp(a) was detected by ultracentrifugation; no changes were noted in Lp(a) composition or quantity with HT. Total Lp(a) measured by enzyme immunosorbent assay showed a trend toward an increase in treated patients after 12 weeks of HT. CONCLUSION: African American women had a beneficial response to HT by increasing the number of LpA-I particles in HDL-L and LpA-I:A-II particles in HDL-M as well as cholesterol esters in both. There was a small reduction in VLDL apo B (and thus particle number) but only a transient reduction in LDL cholesterol. A shift of apo C-III from VLDL to HDL was noted. No detrimental changes occurred in any lipoprotein subfraction (specifically, no increase in triglycerides).

Black or African American↗