Search PubMed⌕ Search

Biomedical subjects

J Ellis

Publications and source records attributed to J Ellis.

At least 109 records · Page 6Linked to original sources
PubMed1999

Cubic crystals of chloramphenicol phosphotransferase from Streptomyces venezuelae in complex with chloramphenicol.

Chloramphenicol 3-O-phosphotransferase (CPT) from Streptomyces venezuelae ISP5230, a novel chloramphenicol-inactivating kinase, has been overexpressed and purified using Escherichia coli as the heterologous host. Crystals of CPT in complex with its substrate chloramphenicol (Cm) were obtained which were suitable for X-ray diffraction. The crystals belong to the cubic space group I4132 with unit-cell dimension a = 200.0 A. The initial CPT crystals diffracted to 3.5 A and the diffraction was improved significantly upon adding acetonitrile and Cm to the crystallization drop. The CPT-Cm crystals diffract to at least 2.8 A resolution.

Bacterial Proteins↗
PubMed1999

Site-directed mutagenesis reveals two epitopes involved in the subtype selectivity of the allosteric interactions of gallamine at muscarinic acetylcholine receptors.

Gallamine allosterically modulates the binding of classical muscarinic ligands with a potency order of M(2) > M(1),M(4) > M(3), M(5). We have suggested previously that the M(2)/M(5) and M(2)/M(3) selectivities are attributable to an epitope in the sixth transmembrane region or third outer loop (o3) region of the receptor. In this study, analysis of numerous point mutations in this region of the M(5) receptor found that a mutation of V --> N resulted in an increased affinity toward gallamine, suggesting that the asparagine residue at M(2)(419) is responsible for gallamine's M(2)/M(5) selectivity. Mutations in the other subtypes indicated that the acidic residues found at this position in M(1) and M(4) are associated with slightly higher affinity toward gallamine, whereas the valine and lysine residues of M(5) and M(3), respectively, are associated with significantly lower affinity. In the o2 region, replacement of an acidic sequence of M(2) (EDGE) by the corresponding neutral sequence of M(1) (LAGQ) reduced the affinity toward gallamine, as reported previously by others; the converse substitution of the acidic sequence into M(1) significantly increased affinity for gallamine. Substitution of the M(1) sequence into this region of M(5) markedly reduced affinity toward gallamine, whereas substitution into M(4) had no effect. All of the above mutations are consistent with gallamine binding with a similar orientation at each subtype, such that it interacts with acidic residues in the o2 region of M(3) and M(5) and with acidic residues in the o3 region of M(1) and M(4); gallamine appears to interact with both regions of the M(2) subtype.

Allosteric Regulation↗
PubMed1999

Amelioration of retroviral vector silencing in locus control region beta-globin-transgenic mice and transduced F9 embryonic cells.

Retroviral vectors are transcriptionally silenced in hematopoietic stem cells, and this phenomenon must be overcome for effective gene therapy of blood diseases. The murine stem cell virus (MSCV) vector completely silences beta-globin reporter genes regulated by locus control region (LCR) elements 5'HS2 to 5'HS4 in seven of eight transgenic mice. Here, we show that no single known MSCV silencer element is sufficient for complete LCR beta-globin transgene silencing. However, partial silencing of high-copy transgenes is conveyed by the MSCV direct repeat and promoter elements. The CpG methylation pattern of silenced and expressed MSCV promoter transgenes is virtually identical, demonstrating that silencing does not absolutely correlate with methylation status. Combined mutations in all four MSCV silencer elements leads to expression of beta-globin in 6 of 10 transgenic mice. The same mutations incorporated into the HSC1 retrovirus vector direct neo gene expression in 71% of transduced F9 embryonic carcinoma cells. These studies demonstrate that combined mutation of four retroviral silencer elements relieves complete silencing in most transgenic mice and transduced F9 cells and suggests that novel silencer elements remain. Enhanced expression of the HSC1 vector in primitive stem cells is well suited for blood gene therapy applications.

3T3 Cells↗
PubMed1999

Treatment of primary dysthymia with group cognitive therapy and pharmacotherapy: clinical symptoms and functional impairments.

OBJECTIVE: This study assessed the efficacy of antidepressant treatment (sertraline) and group cognitive behavior therapy, alone or in combination, in primary dysthymia. The clinical features of dysthymia, as well as the functional impairments associated with the illness (e.g., quality of life, stress perception, coping styles), were evaluated. METHOD: Patients (N = 97) diagnosed with primary dysthymia, but no other current comorbid disorder, received either sertraline or placebo in a double-blind design over 12 weeks. In addition, a subgroup of the patients (N = 49) received a structured, weekly group cognitive behavior therapy intervention. RESULTS: Treatment with sertraline, with or without group cognitive behavior therapy, reduced the functional impairment of depression. The reductions were similar in the drug-cognitive therapy group and in subjects who received the drug alone. Furthermore, while group cognitive behavior therapy alone reduced the depression scores, this effect was not significantly greater than the effect of the placebo. The drug treatment also induced pronounced improvement in the functional measures, and in some respects these effects were augmented by group cognitive behavior therapy. Among patients who responded favorably to cognitive behavior therapy, the improvements in the functional measures were similar to those who responded to drug treatment, whereas such functional changes were not seen among patients who responded to placebo. CONCLUSIONS: Sertraline treatment effectively reduces the clinical symptoms and functional impairments associated with dysthymia. Although the group cognitive behavior therapy intervention was less effective in alleviating clinical symptoms, it augmented the effects of sertraline with respect to some functional changes, and in a subgroup of patients it attenuated the functional impairments characteristic of dysthymia.

Adult↗
PubMed1999

Reproduction of lesions of postweaning multisystemic wasting syndrome in gnotobiotic piglets.

Neonatal gnotobiotic piglets were inoculated with tissue homogenates and low- and high-passage cell culture material to determine if the lesions of the newly described porcine postweaning multisystemic wasting syndrome (PMWS) could be reproduced. For this, 17 3-day-old gnotobiotic piglets were inoculated intranasally with pelleted chloroform-treated, filtered extracts from cell cultures, filter-sterilized homogenates of lymphoid tissue from PMWS-affected piglets, or control materials. Piglets were maintained in germ-free isolators for up to 5 weeks after infection prior to euthanasia and collection of samples for analysis. All piglets inoculated with the viral inocula developed lesions typical of PMWS, including generalized lymphadenopathy, hepatitis, nephritis, interstitial pneumonia, myocarditis, and gastritis. Porcine circovirus (PCV), as well as porcine parvovirus (PPV), was detected in tissues by virus reisolation, polymerase chain reaction analysis, or immunohistochemistry. All infected piglets developed moderate to high titers of antibody to PCV and moderate titers to PPV. No lesions, virus, or virus-specific antibodies were detected in sham-inoculated or uninoculated control piglets. These studies demonstrate that the lesions of PMWS can be experimentally reproduced in gnotobiotic piglets using filterable viral agents derived from pigs with PMWS and provide an experimental basis for further investigation into the pathogenesis and control of this emerging infectious disease in swine.

Animals↗
PubMed1999

Benchmarking: our stamp and its effects.

All children are entitled to high quality care Providing quality care is everyone's responsibility. Benchmarking promotes comparison and sharing of best practice. Effectiveness of benchmarking can not merely be considered in quantitative terms.

Benchmarking↗
PubMed1999

Experimental tests of prospective remembering: the influence of cue-event frequency on performance.

During recent years there has been an upsurge of interest in the processes underlying success or failure of intentions to perform an action in the future e.g. carry out an errand for a friend. Much of this research focuses on simulating these delayed-intention or prospective-memory tasks in the laboratory. A currently popular variant of these tasks is a repeated-instance event-based one in which the same action should be performed whenever a particular (repeated) event-cue occurs during an ongoing activity (e.g. a word in a running memory test of word recall). We report two experiments that investigated important dimensions of this task design, along which recent experimental tasks differ considerably, and explored their influence on prospective remembering. The results revealed that the variations in the event-cue frequencies explored here did not influence overall performance: relatively high event-cue frequency did not improve prospective remembering. However, performance was lower when event-cues were embedded in a general knowledge test than when a prose-reading task was used. Moreover, when remembering was compared for the first and final set of event-cues there was evidence for improvement over presentations during the general knowledge task and a contrasting decline using the prose task, under high event-cue frequency conditions only. The results have important repercussions for current experimental design and the development of tests of prospective remembering skills in particular population subgroups.

Adult↗
PubMed1999

Lack of evidence of conserved lentiviral sequences in pigs with post weaning multisystemic wasting syndrome.

In order to investigate the role of retroviruses in the recently described porcine postweaning multisystemic wasting syndrome (PMWS) serum and leukocytes were screened for reverse transcriptase (RT) activity, and tissues were examined for the presence of conserved lentiviral sequences using degenerate primers in a polymerase chain reaction (PCR). Serum and stimulated leukocytes from the blood and lymph nodes from pigs with PMWS, as well as from control pigs had RT activity that was detected by the sensitive Amp-RT assay. A 257-bp fragment was amplified from DNA from the blood and bone marrow of pigs with PMWS. This fragment was identical in size to conserved lentiviral sequences that were amplified from plasmids containing DNA from several lentiviruses. Cloning and sequencing of the fragment from affected pigs, however, did not reveal homology with the recognized lentiviruses. Together the results of these analyses suggest that the RT activity present in tissues from control and affected pigs is the result of endogenous retrovirus expression, and that a lentivirus is not a primary pathogen in PMWS.

Amino Acid Sequence↗
PubMed1999

Female circumcision: the prevalence and nature of the ritual in Eritrea.

This study evaluates the prevalence, complications, and attitudes concerning the practice of female circumcision among the women of Eritrea. Four hundred thirty-six Eritrean women from rural and urban environments were questioned about their perceptions and beliefs concerning female circumcision. Eighty-eight percent of those interviewed had undergone some form of female circumcision. Those who favored the continuation of the practice were more likely to be rural dwellers with little formal education, and they did so primarily out of tradition or cultural conformity. The direct and indirect consequences of this practice to the health of women and infants are considerable and as complex as the social, religious, and traditional factors that have led to its preservation.

Adult↗
PubMed1998

Overview and initial results of the very long baseline interferometry space observatory programme

High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli-arc-second-scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.

Journal Article↗
PubMed1998

Full activity from human beta-globin locus control region transgenes requires 5'HS1, distal beta-globin promoter, and 3' beta-globin sequences.

The locus control region (LCR) activates high-level human beta-globin transgene expression. LCR cassettes composed of 5'HS2-4 linked to the 815 bp beta-globin proximal promoter do not express fully. Here, we show that LCR (5'HS2-4) beta-globin transgenes that also contain either 5'HS1 or the distal promoter fail to express fully in single- and low-copy transgenic mice. In contrast, full expression is obtained in the presence of both 5'HS1 and the distal promoter. Nine factor binding sites were identified in 5'HS1, using in vitro DNaseI footprint and gel retardation assays, and these include a strong Sp1/Sp3 site, four GATA-1 sites, and two sites that encompass an ACTAAC motif. LCR (5'HS1-4) beta-globin transgene constructs with the distal promoter deleted or replaced by spacer DNA show that specific distal promoter sequences are required for full expression. An LCR (5'HS1-4) transgene construct with truncated downstream beta-globin gene sequences indicates that 3' sequences also play an important role. These results show that full expression of the beta-globin gene directed by the LCR requires 5'HS1, the distal beta-globin promoter, and 3' sequences, and has implications for gene therapy construct design and models of LCR activation.

Animals↗
PubMed1998

Permeabilization and fixation conditions for intracellular flow cytometric detection of the T-cell receptor zeta chain and other intracellular proteins in lymphocyte subpopulations.

Expression of the T-cell receptor (TCR) zeta chain in normal individuals was studied by two-color flow cytometric analysis using digitonin-permeabilized human peripheral blood lymphocytes. Optimal detection of the TCR zeta chain involved fixation of cells in 0.25% paraformaldehyde for 2 min and permeabilization with 500 microg/ml of digitonin at 4 degrees C. Permeabilized lymphocytes and monocytes displayed decreased forward light scatter properties. Neutrophils did not survive this permeabilization/fixation/washing procedure. Permeabilization did not affect the ability of antibodies to CD3, CD4, CD8, CD16, and CD19 to detect CD antigens on lymphocytes, and the percentage of lymphocytes reacting with these antibodies was comparable between untreated and permeabilized cells. Staining of the TCR zeta chain was accomplished by incubating permeabilized cells with unconjugated antibody to the zeta chain, followed by an FITC-conjugated F(ab')2 goat anti-IgG. Following TCR zeta chain staining, cells were blocked with 25 microg/ml of mouse IgG for 20 min to saturate the goat anti-mouse antibody and then incubated with a phycoerythrin-conjugated mouse antibody to a variety of lymphocyte surface antigens. The TCR zeta chain was observed in lymphocytes displaying CD3, CD4, CD8, CD16, or TCRgammadelta markers. This permeabilization/fixation/washing procedure was also validated for detection of another intracellular T-cell protein known as the cytolytic granule-associated protein, recognized by the TIA-1 antibody. Thus the technique can be applied to detection of at least two different intracellular T-cell markers.

Antibodies, Monoclonal↗
PubMed1998

Particle components of dark matter.

Particle candidates for astrophysical dark matter are reviewed, with particular emphasis on the lightest supersymmetric particle and the axion. The former is now constrained by accelerator experiments to have a mass above about 40 GeV, and ongoing searches at accelerators, in space, and in underground experiments have a good chance to detect it. A reevaluation of the constraint on the axion from supernova 1987a leaves open an interesting window where it may be detected if it constitutes the galactic halo.

Journal Article↗
PubMed1998

Structure and function of proteins controlling strain-specific pathogen resistance in plants.

Recently recognised structural and amino acid sequence similarities between plant disease resistance (R) proteins and animal proteins such as Apaf-1 and CED-4 are providing conceptual models for resistance protein function. Data from extensive DNA sequencing of resistance gene families are indicating that the leucine-rich repeat motif is an important determinant of gene-for-gene specificity and that intergenic DNA sequence exchange is a major contributor to R gene diversity.

Apoptosis↗