PubMed Health⌕ Search

Biomedical subjects

A Travis

Publications and source records attributed to A Travis.

15 recordsLinked to original sources
PubMed2001

Validation in the canine model of a new non-invasive method of measuring coronary blood flow reserve: split dose thallium-201 rest/stress imaging.

Diffusely impaired coronary blood flow reserve is difficult to measure non-invasively. We developed and tested a quantitative non-invasive method of measuring coronary blood flow reserve using thallium-201 perfusion imaging. Ten anesthetized dogs were injected simultaneously at rest with thallium-201 and either Ru-103 or Sn-113 microspheres. SPECT images were obtained followed by varying doses of intravenous adenosine, and a second thallium-201 dose was injected simultaneously with either Nb-95 or Sc-46 microspheres. SPECT images were then repeated. The heart was removed, sectioned and counted, along with arterial blood samples. Blood flow was calculated at rest and stress. Peak resting counts in four regions in each of three SPECT slices were subtracted from stress values and stress/rest thallium-201 count ratios (coronary flow reserve (CFR)) were calculated and correlated with the corresponding microsphere flow ratios. Overall correlation of the imaging and microsphere flow ratios was 0.77 (p = 0.0001). Regional correlation coefficients ranged from 0.65-0.86 (p = 0.0001). Coronary blood flow reserve ratios by the microsphere method ranged from 0.7 to 5.3, and by thallium-201 imaging from 0.33-2.45. The non-invasively measured coronary blood flow reserve with thallium-201 imaging and adenosine stress correlates well with microsphere-measured coronary blood flow reserve over a wide range of coronary flows, and should be useful in clinical studies of CFR impairment.

Adenosine↗
PubMed1999

Effect of long-term eprosartan versus enalapril antihypertensive therapy on left ventricular mass and coronary flow reserve in stage I-II hypertension. Eprosartan Study Group.

A double-blind comparator study was performed in 528 hypertensive patients [baseline sitting diastolic blood pressure (SitDBP) 95-114 mmHg]. The primary objective was to compare the incidence of drug-related cough in patients treated with enalapril and eprosartan. This paper reports the results of 27 asymptomatic patients who were recruited into a single centre substudy of the multicentre trial and randomised to receive either eprosartan (200-300 mg b.i.d.) or enalapril (5-20 mg o.d.). Blood pressure (BP) reduction, left ventricular (LV) mass regression and change in coronary flow reserve (CFR) after 6 months' treatment with either eprosartan or enalapril were compared. At the end of the study, eprosartan and enalapril were found to have caused similar reductions in BP. There was an increase in CFR in the eprosartan group to 1.6 +/- 0.3 and a decrease in CFR in the enalapril group to 1.3 +/- 0.3. Neither value was significantly different from baseline although the difference between the two groups was significant (p = 0.05). By study endpoint, there was a significant reduction in LV mass in the enalapril group (p = 0.05), but not the eprosartan (p = ns) group. Further investigation of the effects of angiotensin receptor blockers on CFR and LV mass regression appear warranted.

Acrylates↗
PubMed1996

C-erbB-3 in human breast carcinoma: expression and relation to prognosis and established prognostic indicators.

A series of 346 patients with primary operable breast cancer and a series of 145 patients with advanced breast cancer were investigated for c-erbB-3 protein expression using the monoclonal antibody RTJ1. Formalin-fixed, paraffin-embedded tumour samples were stained using a standard immunochemical method and staining was assessed on a four-point scale. The study aimed to observe the expression of the c-erbB-3 protein and investigate any relationship between expression and established prognostic indicators and prognosis. In both the primary and advanced series breast tumour tissue was found to stain heterogeneously for c-erbB-3. The staining was observed to be predominantly cytoplasmic and the majority of tumours exhibited moderate positivity. However, 15% and 35% of cases in the primary operable and advanced series respectively displayed strong positive staining. No significant difference was found between the staining in the primary and advanced series. In the primary operable breast cancers, no significant associations were demonstrated with overall survival, disease-free interval, regional recurrence, the presence of distant metastases, age, menopausal status, oestrogen receptor status, histological grade, lymph node stage, vascular invasion and c-erbB-2 protein expression. However, a significant association was seen between the degree of c-erbB-3 immunoreactivity and both tumour size (P < 0.01) and tumour type prognostic group (P = 0.05). No overall association with local recurrence was seen when the four groups of c-erbB-3 expression were analysed (P = 0.12), but when those tumours showing no or weak staining were compared with those showing moderate and strong immunoreactivity it was seen that the latter were significantly more likely to develop local recurrence (P = 0.03). In the series of patients with advanced disease, no significant associations were demonstrated with survival, UICC criteria, age, menopausal status, oestrogen receptor status, histological grade, c-erbB-2 status or the presence of vascular invasion. In conclusion this study found variable expression of c-erbB-3 protein in human breast carcinoma and an association with some recognised prognostic factors in those patients with primary operable breast carcinoma. It seems, however, unlikely that c-erbB-3 protein expression will emerge as a powerful enough prognostic factor to be of value in clinical practice.

Adult↗
PubMed1993

Cloning and functional characterization of early B-cell factor, a regulator of lymphocyte-specific gene expression.

Early B-cell factor (EBF) was identified previously as a tissue-specific and differentiation stage-specific DNA-binding protein that participates in the regulation of the pre-B and B lymphocyte-specific mb-1 gene. Partial amino acid sequences obtained from purified EBF were used to isolate cDNA clones, which by multiple criteria encode EBF. The recombinant polypeptide formed sequence-specific complexes with the EBF-binding site in the mb-1 promoter. The cDNA hybridized to multiple transcripts in pre-B and B-cell lines, but transcripts were not detected at significant levels in plasmacytoma, T-cell, and nonlymphoid cell lines. Expression of recombinant EBF in transfected nonlymphoid cells strongly activated transcription from reporter plasmids containing functional EBF-binding sites. Analysis of DNA binding by deletion mutants of EBF identified an amino-terminal cysteine-rich DNA-binding domain lacking obvious sequence similarity to known transcription factors. DNA-binding assays with cotranslated wild-type and truncated forms of EBF indicated that the protein interacts with its site as a homodimer. Deletions delineated a carboxy-terminal dimerization region containing two repeats of 15 amino acids that show similarity with the dimerization domains of basic-helix-loop-helix proteins. Together, these data suggest that EBF represents a novel regulator of B lymphocyte-specific gene expression.

Amino Acid Sequence↗
PubMed1993

Purification of early-B-cell factor and characterization of its DNA-binding specificity.

Early-B-cell factor (EBF) is a nuclear protein that recognizes a functionally important sequence in the promoter of the mb-1 gene. Like the mb-1 gene, which encodes an immunoglobulin-associated protein, EBF is specifically expressed in the early stages of B-lymphocyte differentiation. We purified EBF by sequence-specific DNA affinity chromatography and examined its biochemical properties and DNA-binding specificity. Crude nuclear extract and affinity-purified EBF generated protein-DNA complexes with the mb-1 promoter that were indistinguishable in electrophoretic mobility shift and DNase I footprint assays. Fractionation of affinity-purified EBF by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and renaturation of isolated polypeptides indicated that EBF DNA-binding activity could be reconstituted from polypeptides with molecular masses of 62 to 65 kDa. Gel filtration chromatography suggested that native EBF has a molecular mass of 140 kDa, if a globular shape of the protein is assumed. Thus, EBF appears to be a dimer with subunits of 62 to 65 kDa. To characterize the DNA-binding specificity of purified EBF, we performed two sets of experiments. First, we examined various mutant EBF-binding sites for interaction with purified EBF in an electrophoretic mobility shift assay. Second, we used oligonucleotides containing pairs of randomized bases in a binding-site selection and amplification experiments to determine a preferred sequence for DNA binding by EBF. Taken together, the results of these experiments indicated that EBF recognizes variations on the palindromic sequence 5'-ATTCCCNNGGGAAT, with an optimal spacer of 2 bp between the half-sites.

Animals↗
PubMed1992

The membrane IgM-associated proteins MB-1 and Ig-beta are sufficient to promote surface expression of a partially functional B-cell antigen receptor in a nonlymphoid cell line.

The B-cell antigen receptors consist of membrane immunoglobulins (mIgs) noncovalently associated with two accessory proteins, MB-1 and Ig-beta. We used transfection into a nonlymphoid cell line to test whether MB-1 and Ig-beta were sufficient to promote cell surface expression of mIgM capable of signal transduction. Expression of MB-1 and Ig-beta, but not MB-1 alone, allowed high-level surface expression of mIgM in the AtT20 endocrine cell line, which presumably lacks other B-cell-specific components. The reconstituted antigen receptor was capable of mediating some of the signaling reactions characteristic of mIgM in B lymphocytes. Crosslinking mIgM on transfected AtT20 cells stimulated tyrosine phosphorylation of MB-1 and Ig-beta and also increased the amount of phosphatidylinositol 3-kinase activity that could be precipitated with anti-phosphotyrosine antibodies. When total cell lysates were analyzed by anti-phosphotyrosine immunoblotting, however, no induced phosphorylation of more abundant proteins was detected. Moreover, crosslinking of the receptor in AtT20 cells did not stimulate inositol phospholipid breakdown. Thus, the transfected B-cell antigen receptor could initiate some signal transduction events but AtT20 cells may lack components required for other signaling events associated with mIgM.

Animals↗
PubMed1991

A novel lineage-specific nuclear factor regulates mb-1 gene transcription at the early stages of B cell differentiation.

The mb-1 gene, which encodes a protein associated with membrane-bound antibody, is expressed only at the early stages of B cell differentiation. To gain insight into the mechanisms that underlie temporally regulated gene expression, we examined the mb-1 promoter region for interactions with cell type-specific DNA binding proteins. Here, we report the characterization of a novel nuclear factor that recognizes the mb-1 promoter. This DNA binding activity, termed Early B cell Factor, or EBF, is expressed in early stage B cells, but not in late stage B cells, T cells or non-lymphoid cells. EBF recognizes the nucleotide sequence 5'-CAAGGGAAT-3' in the mb-1 and major histocompatibility complex (MHC) class II A alpha d promoters. The binding of EBF to DNA was characterized by DNase I footprinting and by methylation interference analysis which indicated both major and minor groove contacts. The specificity of EBF binding is distinct from that of other nuclear factors expressed in hematopoietic cells. EBF appears to consist of at least two polypeptides of approximately 70-75 kDa and 80-85 kDa. The EBF binding site was important for maximal mb-1 promoter activity in early stage B cells. Moreover, the EBF binding site conferred correct lineage- and stage-specific transcriptional activity upon a heterologous promoter in a context-dependent manner. Thus, EBF appears to represent an important transcriptional regulator of B cell specific gene expression.

B-Lymphocytes↗
PubMed1991

Gene for lymphoid enhancer-binding factor 1 (LEF1) mapped to human chromosome 4 (q23-q25) and mouse chromosome 3 near Egf.

LEF-1 is a 54-kDa nuclear protein that is expressed specifically in pre-B and T-cells. It binds to a functionally important site in the T-cell receptor alpha enhancer and contributes to maximal enhancer activity. LEF-1 is a member of a family of regulatory proteins that share homology with the high mobility group protein 1 (HMG1). The location of the LEF1 gene on human and mouse chromosomes was determined by Southern blot analysis of DNA from panels of interspecies somatic cell hybrids using a murine cDNA probe. Human-specific DNA fragments were detected in all somatic cell hybrids that retained the human chromosomal region 4cen-q31.2. Fluorescent in situ hybridization with two biotin-labeled overlapping human genomic cosmids revealed a specific hybridization signal at 4q23-q25. The homologous locus in the mouse was mapped to chromosome 3 by Southern analysis of rodent x mouse hybrid cell DNA. This chromosomal location was confirmed by the use of a restriction fragment length polymorphism (RFLP) in recombinant inbred mouse strains. The results of this RFLP analysis indicated that the mouse Lef-1 gene was closely linked to Pmv-39 and Egf and was likely placed between these loci, both of which were previously mapped to distal mouse chromosome 3. Our mapping results did not suggest involvement of this gene in previously mapped genetic disorders or in known neoplasia-associated translocation breakpoints.

Animals↗
PubMed1991

LEF-1, a gene encoding a lymphoid-specific protein with an HMG domain, regulates T-cell receptor alpha enhancer function [corrected].

Lymphoid-specific cDNA clones were isolated that encode a nuclear protein with homology to the chromosomal nonhistone protein HMG-1 and to putative regulators of cell specialization, including the mammalian testis-determining factor SRY and fungal mating-type proteins. The gene represented by the isolated cDNA clones, termed LEF-1 (lymphoid enhancer-binding factor 1), is developmentally regulated and expressed in pre-B and T lymphocytes but not in later-stage B cells or nonlymphoid tissues. Both endogenous and recombinant LEF-1 were shown to bind to a functionally important site in the T-cell antigen receptor (TCR) alpha enhancer. Maximal TCR alpha enhancer activity was found to parallel the cell type-specific expression pattern of LEF-1. Moreover, forced expression of recombinant LEF-1 in late stage B cells increases TCR alpha enhancer function. Taken together, these data suggest that LEF-1 is a regulatory participant in lymphocyte gene expression and differentiation.

Amino Acid Sequence↗
PubMed1991

Heterogeneously initiated transcription from the pre-B- and B-cell-specific mb-1 promoter: analysis of the requirement for upstream factor-binding sites and initiation site sequences.

The mb-1 gene, encoding a membrane immunoglobulin-associated protein, is developmentally regulated and expressed specifically in pre-B and mature B lymphocytes. Analysis of the TATA-less mb-1 promoter indicated that it directs initiation of transcription from multiple sites. Promoter sequences between -68 and +70 conferred the correct pattern of cell type-specific transcription upon a heterologous gene. Two nuclear factor-binding sites that are important for promoter function were identified between -59 and -38. Both sites interacted with ubiquitous nuclear factors in vitro. One of these factors was identified as Sp1. Multimerized copies of both factor-binding sites augmented expression from a heterologous minimal promoter in both lymphoid and nonlymphoid cells, suggesting that additional mb-1 promoter sequences are involved in determining the correct cell type specificity. Analysis of the heterogeneity of transcription initiation indicated that a mutation which increased the distance between upstream sequences and the region of initiation resulted in the utilization of a novel set of initiation sites. Moreover, an insertion of a TATA element into the mb-1 promoter at -30 biased initiation of transcription to +1 but did not abolish the use of the other sites. Mutation of an initiator sequence homology encompassing one of the major initiation sites had only a minor effect on its utilization. From these data, we conclude that upstream factor-binding sites in the TATA-less mb-1 promoter define a region in which initiation of transcription occurs at multiple sites.

Animals↗