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Biomedical subjects

J Ellis

Publications and source records attributed to J Ellis.

At least 73 records · Page 4Linked to original sources
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↗
PubMed2000

Experimental infection of colostrum deprived piglets with porcine circovirus 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) potentiates PCV2 replication.

Experimental infection of colostrum-deprived (CD) pigs with a combined inoculum of porcine circovirus 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) potentiated the replication and distribution of PCV2 virus, when compared with pigs inoculated with PCV2 alone. The replication and distribution of PRRSV in dually infected pigs was not enhanced, when compared to pigs inoculated with PRRSV alone. The mechanisms involved in the potentiation of PCV2 replication in PCV2/PRRSV and PCV2/porcine parvovirus (PPV) dually infected pigs may relate to the fact that monocyte/macrophage cell types are common targets of these 3 viruses.

Animals↗
PubMed2000

The generation of plant disease resistance gene specificities.

We are gaining an understanding of the molecular basis of resistance specificity and of the natural processes that generate different specificities. This is a prerequisite for the genetic engineering of new plant disease-resistance genes to control diseases for which naturally occurring resistance is inadequate. DNA sequence analysis indicates that point mutation, recombination and selection can generate and maintain the high levels of polymorphism observed in resistance genes. Comparisons of closely related resistance proteins indicate that specificity can be determined by variation in at least two regions. One of these contains leucine-rich repeats, which are a common feature of most resistance proteins.

Amino Acid Sequence↗
PubMed2000

Structure, function and evolution of plant disease resistance genes.

Gene-for-gene plant disease resistance involves two basic processes: perception of pathogen attack, followed by responses to limit disease. Perception involves receptors with high degrees of specificity for pathogen strains, which are encoded by disease resistance genes. Large repertoires of distantly related resistance (R) genes with diverse recognitional specificities are found within a single plant species. The generation of R-gene polymorphism involves gene duplication, followed by DNA-sequence divergence by point mutation, and by deletion and duplication of intragenic DNA repeats encoding blocks of leucine-rich elements. Recombination between related genes reassorts this variation to further diversify gene sequences. Pathogen pressure selects functional resistance specificities and results in the maintenance of R-gene diversity. Recent genome-sequence data reveal that the NBS-LRR (i.e. nucleotide-binding site-leucine-rich repeat) class of R genes represents as much as 1% of the Arabidopsis genome. Experimental data have shown that the LRR has a role in determination of specificity. Mutation experiments, in which R-gene signaling has been dissociated from specificity in constitutive signal mutants, have provided the potential for non-specific resistance to be expressed from pathogen-infection-induced promoters in transgenic plants.

Evolution, Molecular↗
PubMed2000

Seventeen more novel HLA-A locus alleles.

This paper describes seventeen novel HLA-A locus alleles: A*0106, *0235, *0236, *0237, *1105, *2302, *2303, *24032, *2422, *2424, *2503, *2613, *3007, *3203, *3204, *6809 and *6810. All alleles were identified due to unexpected probe reaction patterns during routine SSOP typing. Exons 2 and 3 of these alleles were subsequently characterized by DNA sequencing. The alleles represent a shuffling of sequence motifs, likely by interallelic conversion, expanding the diversity of the HLA system.

Alleles↗