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Biomedical subjects

J Ellis

Publications and source records attributed to J Ellis.

At least 37 records · Page 2Linked to original sources
PubMed2001

Production, characterisation and applications of monoclonal antibodies to porcine circovirus 2.

The production, preliminary characterisation and applications of monoclonal antibodies (mabs) against six porcine circovirus 2 isolates are described. A total of 14 stable hybridomas were produced, of which 7 were characterised. All of the mabs characterised were of IgG isotype. All the mabs tested reacted by IIF with acetone-fixed cell cultures infected with PCV2 isolates from Canada, France, Spain, Denmark, USA and UK. No cross-reactivity with a porcine circovirus 1 field isolate was demonstrated using the panel of mabs tested. In addition, one of the seven mabs tested demonstrated neutralising activity against PCV2 isolates from Canada and France. The use of selected PCV2-specific mabs for the development of virus detection methodologies is described.

Animals↗
PubMed2001

The ovarian hormones and absence epilepsy: a long-term EEG study and pharmacological effects in a genetic absence epilepsy model.

In the first experiment, the relationship between the phase of the estrous cycle and the number of spontaneously occurring spike-wave discharges was investigated in WAG/Rij rats, a model for generalized absence epilepsy. The electroencephalogram (EEG) was continuously recorded for 96 h in eight rats chronically equipped with cortical EEG electrodes. A circadian pattern emerged for the number of spike-wave discharges: a nadir during the first hours of the light period, and an acrophase during the first hours of the dark period. This daily maximum was increased at proestrus day compared with the other days of the cycle, when the plasma level of progesterone is enhanced specifically at these hours of this day. This suggests that progesterone enhances spike-wave discharges. There was no difference in the first few hours of the light period in the number of spike-wave discharges between proestrus and the three other days, suggesting that estradiol has no effect on spike-wave discharges. In the second study, the effects of the systemic administration of progesterone and 17 beta-estradiol on spike-wave discharges and spontaneous behavior were investigated. It was shown that progesterone (20 and 30 mg/kg) but not estradiol (0.17-1.5 mg/kg) increased the number and total duration of spike-wave discharges. On the other hand, injection of RU 38486 (10 and 30 mg/kg), an antagonist of intracellular progesterone receptors, had no effect on spike-wave discharges and did not block the stimulatory effect of progesterone. The antagonist of 17 beta-estradiol tamoxifen (1 and 3 mg/kg) did not evoke alterations in the number or duration of spike-wave discharges. Our results indicate that progesterone aggravates spike-wave discharges, but is not mediated through intracellular receptors. Since progesterone is rapidly metabolized in the brain to the positive modulator of GABA(A) receptor allopregnanolone, which increases spike-wave discharges in WAG/Rij rats, it is possible that the epileptiformic effects of progesterone are mediated through this metabolite.

Animals↗
PubMed2001

The beta-globin locus control region versus gene therapy vectors: a struggle for expression.

Developmental control of gene expression has a major impact on the design of beta-globin retrovirus vectors for hematopoietic stem cell gene therapy of beta-thalassemia. It is obvious that the endogenous locus control region (LCR) elements that drive beta-globin gene expression in transgenic mice must be included in these vectors. However, the specific elements to use are not clear and require an understanding of LCR action. Moreover, retrovirus vectors contain silencer elements that function in stem cells and are dominant to LCR function. Recent studies on LCRbeta-globin transgenes and retrovirus silencing suggest ways to overcome this silencing effect after transfer into stem cells and carefully designed lentivirus vectors have exciting therapeutic benefit in animal models of beta-thalassemia. By building on 15 years of development, LCRbeta-globin vectors are now being tested in preclinical animal models and may ultimately lead to the long-sought cure for this genetic disease.

Animals↗
PubMed2001

Terrigenous clay deposition on estuarine sandflats: using stable isotopes to determine the role of the mud crab, Helice crassa Dana, in the recovery process.

Clay slurries, mixed in seawater, were deposited on intertidal mudflats in two contrasting estuaries in an experiment designed to evaluate the potential impact of soil erosion from adjacent urban developments on the biodiversity of the benthic communities, and the subsequent recovery mechanisms. Profiles of the natural abundance of stable isotopes from sediment cores where examined to determine immediate and longer-term impacts of the clay on the ambient sediments. The source clays with delta13C values of about -26 per thousand were easily distinguished from natural sediments with delta13C values of -19.7 +/- 1.1 per thousand at site OK and -14.2 +/- 0.9 per thousand at site WP, and bioturbation was seen to generate a gradient between these values. Physical processes of burial, or erosion and dispersal by estuarine flows initiated the recovery process. Repeated drying cycles left the clay surface cracked and able to trap natural sediments and food on the otherwise barren surface. Colonisation of the clay plots by the mud crab, Helice crassa, was important to the recovery process and depended on proximity to adjacent crab colonies. Burrowing activity by larger crabs enhanced the erosion of the clay surface while the resultant bioturbation blended the clay into the underlying sediments. Smaller crabs had less effect on erosion and bioturbation from their burrowing was mostly confined within the clay layer. Where the clay was more than 3 cm thick, they did not break through the bottom of the clay and the interface between clay and sediment was still sharp after 12 months. 13C variations also indicated that crab burrows and cracking of the clay surface moved natural sediment deep into the plots where it could be worked into the clay by subsequent crab burrowing activities thus enhancing recovery from the clay impact.

Aluminum Silicates↗
PubMed2001

The detrimental effects of physical restraint as a consequence for inappropriate classroom behavior.

Functional analyses produced inconclusive results regarding variables that maintained problem behavior for 2 students with developmental disabilities. Procedures were modified to include a contingent physical restraint condition based on in-class observations. Results indicated that tinder conditions in which physical restraint (i.e., basket-hold timeout) was applied contingent on problem behavior, rates of these behaviors increased across sessions for both subjects. Implications for the use of physical restraint in the classroom are discussed.

Adolescent↗
PubMed2001

Thoracic lymphatic pumping and the efficacy of influenza vaccination in healthy young and elderly populations.

The authors investigated whether thoracic lymphatic pumping (TLP) after FluShield vaccination enhanced the production of anti-influenza immunoglobulins in elderly individuals, who are at particular risk for influenza. Osteopathic students and non-TLP-treated elderly subjects served as controls. Serum antibody titers were quantified with enzyme-linked immunosorbent assay, and hemagglutination inhibition assay, both of which generated comparable results. While approximately 70% of the younger controls had increased anti-influenza immunoglobulin production on vaccination, only 30% to 35% of the aged population had increased antibody production. There was no significant enhancement in anti-influenza immunoglobulin production in the TLP-treated subjects. The authors' findings suggest that TLP in conjunction with influenza vaccination does not enhance immunization against influenza in otherwise healthy and active populations. However, such techniques may be of value when applied in conjunction with vaccination to nonambulatory patients or on actual influenza exposure of at-risk individuals.

Adult↗
PubMed2001

Levels of dimethylarginines and cytokines in mild and severe preeclampsia.

BACKGROUND: The objectives were 1. to evaluate if the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine was altered in mild and severe forms of preeclampsia, and 2. to assess the relationship between dimethylarginines and the cytokine response in preeclampsia. METHODS: Asymmetric and symmetric dimethylarginine were measured with high performance liquid chromatography in women with mild (n=13) and severe (n=32) preeclampsia and in normotensive pregnant controls (n=20). Interleukin-4, -6, -8, -10 and tumor necrosis factor-alpha were analyzed by immunoassays in women with mild (n=8) and severe (n=17) preeclampsia and in normotensive pregnant controls (n=14). The Mann Whitney U-test and Spearman Rank test were used for statistical analysis. RESULTS: The plasma levels of dimethylarginine were increased in preeclamptic subjects. The elevation of symmetric dimethylarginine was more pronounced than that of asymmetric dimethylarginine. The control levels of interleukin-6, -8 and -10 were significantly higher at term than at gestational week 32-36. Interleukin-6 and -8 were significantly elevated in subjects with severe, but not mild, preeclampsia, whereas TNF-alpha and IL-10 were not significantly altered. Symmetric dimethylarginine levels correlated significantly with arterial blood pressure and serum levels of creatinine and uric acid. Dimethylarginine levels in plasma were, however, not related to the cytokine response. CONCLUSIONS: Plasma concentrations of both asymmetric and symmetric dimethylarginine were significantly elevated both in mild and severe preeclampsia. Symmetric, but not asymmetric, dimethylarginine correlated to the severity of the condition. Plasma levels of interleukin-6 and -8 were also elevated in severe preeclampsia but no direct correlations were found between these cytokines and dimethylarginines.

Arginine↗
PubMed2001

Resistance gene analogs in barley and their relationship to rust resistance genes.

Regions of amino acid conservation in the NBS domain of NBS-LRR resistance proteins facilitated the PCR isolation of eight resistance gene analog (RGA) sequences from genomic DNA of rice, barley, and Aegilops tauschii. These clones and other RGAs previously isolated from maize, rice, and wheat were assigned to 13 classes by DNA-sequence comparison and by their patterns of hybridisation to restricted barley DNA. Using a doubled-haploid mapping population, probes from 12 RGA classes were used to map 17 loci in the barley genome. Many of these probes have been used for mapping in wheat, and the collective data indicate that the positions of orthologous RGAs are conserved between barley and wheat. RGA loci were identified in the vicinity of barley leaf rust resistance loci Rph4, Rph7, and Rph10. Recombinants were identified between RGA loci and Rph7 and Rph10, while a cluster of RGA sequences detected by probe 5.2 cosegregated with Rph4 in 55 F2 lines.

Blotting, Southern↗
PubMed2000

Retrovirus vector silencing is de novo methylase independent and marked by a repressive histone code.

Retrovirus vectors are de novo methylated and transcriptionally silent in mammalian stem cells. Here, we identify epigenetic modifications that mark retrovirus-silenced transgenes. We show that murine stem cell virus (MSCV) and human immunodeficiency virus type 1 (HIV-1) vectors dominantly silence a linked locus control region (LCR) beta-globin reporter gene in transgenic mice. MSCV silencing blocks LCR hypersensitive site formation, and silent transgene chromatin is marked differentially by a histone code composed of abundant linker histone H1, deacetylated H3 and acetylated H4. Retrovirus-transduced embryonic stem (ES) cells are silenced predominantly 3 days post-infection, with a small subset expressing enhanced green fluorescent protein to low levels, and silencing is not relieved in de novo methylase-null [dnmt3a-/-;dnmt3b-/-] ES cells. MSCV and HIV-1 sequences also repress reporter transgene expression in Drosophila, demonstrating establishment of silencing in the absence of de novo and maintenance methylases. These findings provide mechanistic insight into a conserved gene silencing mechanism that is de novo methylase independent and that epigenetically marks retrovirus chromatin with a repressive histone code.

Animals↗
PubMed2000

The crystal structures of chloramphenicol phosphotransferase reveal a novel inactivation mechanism.

Chloramphenicol (Cm), produced by the soil bacterium Streptomyces venezuelae, is an inhibitor of bacterial ribosomal peptidyltransferase activity. The Cm-producing streptomycete modifies the primary (C-3) hydroxyl of the antibiotic by a novel Cm-inactivating enzyme, chloramphenicol 3-O-phosphotransferase (CPT). Here we describe the crystal structures of CPT in the absence and presence of bound substrates. The enzyme is dimeric in a sulfate-free solution and tetramerization is induced by ammonium sulfate, the crystallization precipitant. The tetrameric quaternary structure exhibits crystallographic 222 symmetry and has ATP binding pockets located at a crystallographic 2-fold axis. Steric hindrance allows only one ATP to bind per dimer within the tetramer. In addition to active site binding by Cm, an electron-dense feature resembling the enzyme's product is found at the other subunit interface. The structures of CPT suggest that an aspartate acts as a general base to accept a proton from the 3-hydroxyl of Cm, concurrent with nucleophilic attack of the resulting oxyanion on the gamma-phosphate of ATP. Comparison between liganded and substrate-free CPT structures highlights side chain movements of the active site's Arg136 guanidinium group of >9 A upon substrate binding.

Adenosine Triphosphate↗
PubMed2000

Locus control region activity by 5'HS3 requires a functional interaction with beta-globin gene regulatory elements: expression of novel beta/gamma-globin hybrid transgenes.

The human beta-globin locus control region (LCR) contains chromatin opening and transcriptional enhancement activities that are important to include in beta-globin gene therapy vectors. We previously used single-copy transgenic mice to map chromatin opening activity to the 5'HS3 LCR element. Here, we test novel hybrid globin genes to identify beta-globin gene sequences that functionally interact with 5'HS3. First, we show that an 850-base pair (bp) 5'HS3 element activates high-level beta-globin gene expression in fetal livers of 17 of 17 transgenic mice, including 3 single-copy animals, but fails to reproducibly activate Agamma-globin transgenes. To identify the beta-globin gene sequences required for LCR activity by 5'HS3, we linked the 815-bp beta-globin promoter to Agamma-globin coding sequences (BGT34), together with either the beta-globin intron 2 (BGT35), the beta-globin 3' enhancer (BGT54), or both intron 2 and the 3' enhancer (BGT50). Of these transgenes, only BGT50 reproducibly expresses Agamma-globin RNA (including 7 of 7 single-copy animals, averaging 71% per copy). Modifications to BGT50 show that LCR activity is detected after replacing the beta-globin promoter with the 700-bp Agamma-globin promoter, but is abrogated when an AT-rich region is deleted from beta-globin intron 2. We conclude that LCR activity by 5'HS3 on globin promoters requires the simultaneous presence of beta-globin intron 2 sequences and the 260-bp 3' beta-globin enhancer. The BGT50 construct extends the utility of the 5'HS3 element to include erythroid expression of nonadult beta-globin coding sequences in transgenic animals and its ability to express antisickling gamma-globin coding sequences at single copy are ideal characteristics for a gene therapy cassette.

Animals↗
PubMed2000

Prenatal detection of trisomy 21: combined experience of two British hospitals.

A retrospective study was performed to determine the detection rate of trisomy 21 in two British hospitals using a combination of: (1) second trimester serum screening with maternal age, alphaFP and hCG; (2) karyotyping for raised maternal age and high background risk of aneuploidy; and (3) second trimester fetal anomaly ultrasonography at 18-22 week gestation. 36-410 women with a median age of 27 years were studied. Trisomy 21 detected by the combination of methods in both hospitals was compared with the actual number of pregnancies affected by trisomy 21, to determine the detection rate. Serum screening as the backbone of the service detected 31/48 (65%) trisomy 21 affected pregnancies. Karyotyping for maternal age and previous aneuploidy detected eight trisomy 21 affected pregnancies, and second trimester ultrasound a further six, giving a total detection rate of 45/56 (80%). Thus, the detection rate of trisomy 21 in our population is 65% by serum screening alone. This is similar to demonstration projects, but the addition of second trimester ultrasonography and karyotyping for maternal age and prior risk, contributes further to improve the overall sensitivity to 80%. The invasive procedure rate was 4.8% of all women.

Adult↗