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M J Holland

Publications and source records attributed to M J Holland.

At least 19 recordsLinked to original sources
PubMed2006

Bose-Einstein condensates in rotating lattices.

Strongly interacting bosons in a two-dimensional rotating square lattice are investigated via a modified Bose-Hubbard Hamiltonian. Such a system corresponds to a rotating lattice potential imprinted on a trapped Bose-Einstein condensate. Second-order quantum phase transitions between states of different symmetries are observed at discrete rotation rates. For the square lattice we study, there are four possible ground-state symmetries.

Journal Article↗
PubMed2005

An index of community ocular Chlamydia trachomatis load for control of trachoma.

Quantitative PCR (Q-PCR) technology has recently been applied to the measurement of ocular loads of Chlamydia trachomatis. We present an index called the community ocular C. trachomatis load (COCTL) which is similar to the community microfilarial load (CMFL) of onchocerciasis. Our index has the advantage of being scale-independent so that, for example, percentage changes are the same whether calculated per eye swab or per Q-PCR capillary. The COCTL for a population or subgroup is formed by adding the arbitrary concentration of 1 organism per ml to each individual Q-PCR quantification, calculating the geometric mean, and finally subtracting 1 per ml again. The use of the COCTL is illustrated in a study of trachoma in northern Tanzania. The COCTL is higher in people with clinical trachoma than those without (5.8 organisms per swab vs. 0.1), and in children aged six months to ten years than in the overall population (1.1 vs. 0.4). The COCTL index is potentially useful for sentinel sites, operational research and calibration of clinical measures of trachoma.

Administration, Oral↗
PubMed2005

Risk of trachomatous scarring and trichiasis in Gambians varies with SNP haplotypes at the interferon-gamma and interleukin-10 loci.

Experimental evidence implicates interferon gamma (IFNgamma) in protection from and resolution of chlamydial infection. Conversely, interleukin 10 (IL10) is associated with susceptibility and persistence of infection and pathology. We studied genetic variation within the IL10 and IFNgamma loci in relation to the risk of developing severe complications of human ocular Chlamydia trachomatis infection. A total of 651 Gambian subjects with scarring trachoma, of whom 307 also had potentially blinding trichiasis and pair-matched controls with normal eyelids, were screened for associations between single-nucleotide polymorphisms (SNPs), SNP haplotypes and the risk of disease. MassEXTEND (Sequenom) and MALDI-TOF mass spectrometry were used for detection and analysis of SNPs and the programs PHASE and SNPHAP used to infer haplotypes from population genetic data. Multivariate conditional logistic regression analysis identified IL10 and IFNgamma SNP haplotypes associated with increased risk of both trachomatous scarring and trichiasis. SNPs in putative IFNgamma and IL10 regulatory regions lay within the disease-associated haplotypes. The IFNgamma +874A allele, previously linked to lower IFNgamma production, lies in the IFNgamma risk haplotype and was more common among cases than controls, but not significantly so. The promoter IL10-1082G allele, previously associated with high IL10 expression, is in both susceptibility and resistance haplotypes.

Alleles↗
PubMed2005

Temporal cytokine gene expression patterns in subjects with trachoma identify distinct conjunctival responses associated with infection.

Ocular chlamydial disease is clinically diagnosed by the appearance of characteristic inflammatory changes and development of lymphoid follicles in the conjunctiva. Nucleic acid amplification tests and relatively non-invasive methods of sampling the conjunctival surface can be used to quantify the expression of chlamydial and host genes. Using quantitative real-time polymerase chain reaction to detect the presence of Chlamydia trachomatis (CT) 16S rRNA and human interleukin (IL)-1beta, IL-10, IL-12p40, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha transcripts we examined the immune response at the conjunctival surface in a cohort of children living in a trachoma-endemic village in The Gambia. Elevated cytokine transcript levels were associated with the presence of CT 16S rRNA. Subclinical infection (CT infection without clinical signs of disease) elicited an immune response that is proinflammatory in nature, with elevations in the transcription of IL-1beta, IFN-gamma and IL-12p40. Clinically apparent infections were associated with the elevation of mRNA for the multi-functional cytokine TNF-alpha (fibrotic, type 1 inflammatory and regulatory) and the counter regulatory cytokine, IL-10, in addition to the other proinflammatory cytokines. A positive correlation between IFN-gamma transcript levels and the amount of CT 16S rRNA expressed in conjunctiva was found.

Adolescent↗
PubMed2003

Plasmodium falciparum infection of the placenta affects newborn immune responses.

The effects of exposure to placental malaria infection on newborn immunological responses, in particular Th1/Th2 cytokines and antigen-presenting cell (APC) function, were compared between cord blood mononuclear cells (CBMC) from parasitized and non-parasitized placentas of Gambian women. Cells were analysed in vitro for their ability to respond to mitogens [phorbol myristate acetate (PMA)/ionomycin, phytohaemagglutinin (PHA)], a malaria-unrelated test antigen [purified protein derivative of Mycobacterium tuberculin[purified protein derivative (PPD)] and Plasmodium falciparum schizont extracts. Mitogens induced strong proliferation and secretion of high concentrations of both IL-13 and sCD30 in CBMC from both groups. Conversely, significantly lower amounts of IFN-gamma were induced in the parasitized group in response to low doses of PHA. Protein antigens induced very low amounts of all tested cytokines, in particular IFN-gamma. However, a significantly higher release of sCD30 was observed in response to schizont extracts in the parasitized group. Addition of LPS to activate APC to low doses of PHA or schizont extracts increased the IFN-gamma production in both groups but levels remained lower in CBMC from the parasitized group. This result correlates with the lower production of IL-12 found following lipopolysaccharide (LPS) stimulation in this group. Taken together, these data show that placental infection with P. falciparum affects Th1 differentiation and sCD30 priming of neonatal lymphocytes and that the probable mode of action is via APC.

Animals↗
PubMed2002

Ramsey fringes in a Bose-Einstein condensate between atoms and molecules.

In a recent experiment, a Feshbach scattering resonance was exploited to observe Ramsey fringes in a 85Rb Bose-Einstein condensate. The oscillation frequency corresponded to the binding energy of the molecular state. We show that the observations are remarkably consistent with predictions of a resonance field theory in which the fringes arise from oscillations between atoms and molecules.

Journal Article↗
PubMed2002

Signatures of resonance superfluidity in a quantum Fermi gas.

We predict a direct and observable signature of the superfluid phase in a quantum Fermi gas, in a temperature regime already accessible in current experiments. We apply the theory of resonance superfluidity to a gas confined in a harmonic potential and demonstrate that a significant increase in density will be observed in the vicinity of the trap center.

Journal Article↗
PubMed2001

Quantitation of Na+-K+-2Cl- cotransport splice variants in human tissues using kinetic polymerase chain reaction.

A kinetic reverse transcription-polymerase chain reaction (RT-PCR)-based assay is described that can discriminate and quantitate differentially spliced mRNAs. This assay should be generally applicable for high-throughput quantitation of differentially spliced transcripts. The utility of this method was assessed for spliced transcripts encoded by the human Na+-K+-2Cl- cotransporter gene hNKCC1. Evidence is presented that the NKCC1 isoform of the human Na+-K+-2Cl- cotransporter is differentially spliced analogous to that recently described for the mouse Na+-K+-2Cl- cotransporter gene BSC2. The nucleotide sequences of the two human splice variants predict Na+-K+-2Cl- cotransporter proteins differing only in length. Stable transfectants expressing these human splice variants, designated NKCC1a or NKCC1b, were constructed. Both splice variants produce functional Na+-K+-2Cl- cotransporters in vivo. The abundance of NKCC1 mRNA and patterns of differential splicing in 10 different tissue types and three cell lines were quantitated using the kRT-PCR assay. The results showed that the total amount of NKCC1 mRNA varied by more than 30-fold in the human tissues and cell lines examined. The ratio of NKCC1a/NKCC1b varied nearly 70-fold among these same tissues and cell lines suggesting that differential splicing of the NKCC1 transcript may play a regulatory role in human tissues.

Alternative Splicing↗
PubMed2000

The H159A mutant of yeast enolase 1 has significant activity.

The function of His159 in the enolase mechanism is disputed. Recently, Vinarov and Nowak (Biochemistry (1999) 38, 12138-12149) prepared the H159A mutant of yeast enolase 1 and expressed this in Escherichia coli. They reported minimal (ca. 0.01% of the native value) activity, though the protein appeared to be correctly folded, according to its CD spectrum, tryptophan fluorescence, and binding of metal ion and substrate. We prepared H159A enolase using a multicopy plasmid and expressed the enzyme in yeast. Our preparations of H159A enolase have 0.2-0.4% of the native activity under standard assay conditions and are further activated by Mg(2+) concentrations above 1 mM to 1-1.5% of the native activity. Native enolase 1 (and enolase 2) are inhibited by such Mg(2+) concentrations. It is possible that His159 is necessary for correct folding of the enzyme and that expression in E. coli leads to largely misfolded protein.

Amino Acid Substitution↗
PubMed2000

Transcript quantitation in total yeast cellular RNA using kinetic PCR.

Kinetically monitored, reverse transcriptase-initiated PCR (kinetic RT-PCR, kRT-PCR) is a novel application of kinetic PCR for high throughput transcript quantitation in total cellular RNA. The assay offers the simplicity and flexibility of an enzyme assay with distinct advantages over DNA microarray hybridization and SAGE technologies for certain applications. The reproducibility, sensitivity and accuracy of the kRT-PCR were assessed for yeast transcripts previously quantitated by a variety of methods including SAGE analysis. Changes in transcript levels between different genetic or physiological cell states were reproducibly quantitated with an accuracy of +/-20%. The assay was sufficiently sensitive to quantitate yeast transcripts over a range of more than five orders of magnitude, including low abundance transcripts encoding cell cycle and transcriptional regulators.

DNA Primers↗
PubMed2000

Proteins secreted by the parasitic nematode Nippostrongylus brasiliensis act as adjuvants for Th2 responses.

Infections with parasitic helminths such as Nippostronglyus brasiliensis induce dominant type 2 responses from antigen-specific T helper cells. The potency of the Th2 bias can also drive Th2 responses to bystander antigens introduced at the same time as infection. We now report that the Th2-promoting effect of infection can be reproduced with soluble N. brasiliensis excretory-secretory proteins (NES) released by adult parasites in vitro. Immunization of BALB/c mice with NES results in the production of IL-4 with elevated total serum IgE and specific IgG1 antibodies. NES is also able to stimulate IL-4 and polyclonal IgE production in other mouse strains (C57BL/6, B10.D2, CBA). These features are seen whether NES is administered without adjuvant as soluble protein in phosphate-buffered saline or with complete Freund's adjuvant which normally favors Th1 responses. Thus, NES possesses intrinsic adjuvanticity. Moreover, co-administration of hen egg lysozyme (HEL) with NES in the absence of other adjuvants results in generation of HEL-specific lymphocyte proliferation, IL-4 release and IgG1 antibody responses, documenting that NES can act as an adjuvant for third-party antigens. Proteinase K digestion or heat treatment of NES before immunization abolished the IL-4-stimulating activity, indicating that the factors acting to promote Th2 induction are proteins secreted by the adult parasite.

Adjuvants, Immunologic↗
PubMed2000

High-throughput SNP allele-frequency determination in pooled DNA samples by kinetic PCR.

We have developed an accurate, yet inexpensive and high-throughput, method for determining the allele frequency of biallelic polymorphisms in pools of DNA samples. The assay combines kinetic (real-time quantitative) PCR with allele-specific amplification and requires no post-PCR processing. The relative amounts of each allele in a sample are quantified. This is performed by dividing equal aliquots of the pooled DNA between two separate PCR reactions, each of which contains a primer pair specific to one or the other allelic SNP variant. For pools with equal amounts of the two alleles, the two amplifications should reach a detectable level of fluorescence at the same cycle number. For pools that contain unequal ratios of the two alleles, the difference in cycle number between the two amplification reactions can be used to calculate the relative allele amounts. We demonstrate the accuracy and reliability of the assay on samples with known predetermined SNP allele frequencies from 5% to 95%, including pools of both human and mouse DNAs using eight different SNPs altogether. The accuracy of measuring known allele frequencies is very high, with the strength of correlation between measured and known frequencies having an r(2) = 0.997. The loss of sensitivity as a result of measurement error is typically minimal, compared with that due to sampling error alone, for population samples up to 1000. We believe that by providing a means for SNP genotyping up to thousands of samples simultaneously, inexpensively, and reproducibly, this method is a powerful strategy for detecting meaningful polymorphic differences in candidate gene association studies and genome-wide linkage disequilibrium scans.

Animals↗
PubMed1999

Plinth padding confounds measures of posteroanterior spinal stiffness.

This study investigated whether the presence of plinth padding influences measured posteroanterior spinal stiffness. Two measures of posteroanterior stiffness, the slope of the loading curve (K) and the displacement at 30 N (D30) were made at three vertebral levels: L3, T12 and T6, on a rigid and a padded plinth in 24 asymptomatic subjects. Analysis of variance demonstrated a significant reduction in K and increase in D30 when measured on the padded compared to the rigid surface and an interaction effect for both the K and D30 measures, indicating that the effect of the padding depends upon the vertebral level tested. The correlations between the padded and unpadded stiffness measures ranged from 0.70 to 0.87. The data from this study suggest that the type of plinth surface needs to be standardised when evaluating PA stiffness.

Adult↗
PubMed1999

Vaccination against helminth parasites--the ultimate challenge for vaccinologists?

Helminths are multicellular pathogens which infect vast numbers of human and animal hosts, causing widespread chronic disease and morbidity. Vaccination against these parasites requires more than identification of effective target antigens, because without understanding the immunology of the host-parasite relationship, ineffective immune mechanisms may be invoked, and there is a danger of amplifying immunopathogenic responses. The fundamental features of the immune response to helminths are therefore summarised in the context of vaccines to helminth parasites. The contention between type-1 and type-2 responses is a central issue in helminth infections, which bias the immune system strongly to the type-2 pathway. Evidence from both human and experimental animal infections indicates that both lineages contribute to immunity in differing circumstances, and that a balanced response leads to the most favourable outcome. A diversity of immune mechanisms can be brought to bear on various helminth species, ranging from antibody-independent macrophages, antibody-dependent granulocyte killing, and nonlymphoid actions, particularly in the gut. This diversity is highlighted by analysis of rodent infections, particularly in comparisons of cytokine-depleted and gene-targeted animals. This knowledge of protective mechanisms needs to be combined with a careful choice of parasite antigens for vaccines. Many existing candidates have been selected with host antibodies, rather than T-cell responses, and include a preponderance of highly conserved proteins with similarities to mammalian or invertebrate antigens. Advantage has yet to be taken of parasite genome projects, or of directed searches for novel, parasite-specific antigens and targets expressed only by infective stages and not mature forms which may generate immunopathology. With advances under way in parasite genomics and new vaccine delivery systems offering more rapid assessment and development, there are now excellent opportunities for new antihelminth vaccines.

Animals↗
PubMed1999

Jaagsiekte retrovirus is widely distributed both in T and B lymphocytes and in mononuclear phagocytes of sheep with naturally and experimentally acquired pulmonary adenomatosis.

Jaagsiekte sheep retrovirus (JSRV) is a type D retrovirus specifically associated with a contagious lung tumor of sheep, sheep pulmonary adenomatosis (SPA). JSRV replicates actively in the transformed epithelial cells of the lung, and JSRV DNA and RNA have been detected in lymphoid tissues of naturally affected animals. To determine the lymphoid target cells of JSRV, CD4(+) T cells, CD8(+) T cells, B lymphocytes, and adherent cell (macrophage/monocyte) populations were isolated from the mediastinal lymph nodes of naturally affected sheep and lambs inoculated with JSRV. Cells were enriched to high purity and then analyzed for JSRV proviral DNA by heminested PCR, and the proviral burden was quantitated by limiting dilution analysis. JSRV proviral DNA was found in all subsets examined but not in appropriate negative controls. In sheep naturally affected with SPA, JSRV proviral burden was greatest in the adherent cell population. In the nonadherent lymphocyte population, surface immunoglobulin-positive B cells contained the greatest proviral burden, while CD4(+) and CD8(+) T cells contained the lowest levels of JSRV proviral DNA. In most of the cases (5 of 8), provirus also could be detected in the peripheral blood mononuclear cell (PBMC) population. A kinetic study of JSRV infection in the mediastinal lymphocyte population of newborn lambs inoculated with JSRV found that JSRV proviral DNA could be detected as early as 7 days postinoculation before the onset of pulmonary adenomatosis, although the proviral burden was greatly reduced compared to adult natural cases. This was reflected in the levels found in PBMC since proviral DNA was detected in 2 of 13 animals. At the early time points studied (7 to 28 days postinoculation) no one subset was preferentially infected. These data indicate that JSRV can infect lymphoid and phagocytic mononuclear cells of sheep and that dissemination precedes tumor formation. Infection of lymphoid tissue, therefore, may play an important role in the pathogenesis of SPA.

Animals↗
PubMed1999

Early interleukin-4: its role in the switch towards a Th2 response and IgE-mediated allergy.

The etiology of IgE-mediated allergies is complex and, thus far, not completely understood. A common feature, however, is the overproduction of IgE-inducing cytokines, e.g. interleukin-4(IL-4), compared to IgE-antagonistic cytokines, such as interferon-gamma or IL-12. IgE-inducing cytokines are produced by T helper type 2 (Th2) cells. The differentiation of naive T cells towards the Th2 phenotype seems to be crucially dependent upon the particular cytokines present in the early stages of an immune response. Concerning the factors driving Th2 differentiation, the so-called 'early IL-4' seems to play an important role, although there is some controversy over the degree of its requirement and its cellular source. We have recently demonstrated that basophils might be such a source, since they rapidly release IL-4 upon antigen-specific or nonantigen-specific stimuli, such as certain lectins. This makes lectins interesting candidates for inducing a Th2 response and IgE-mediated allergy in unsensitized individuals.

Humans↗
PubMed1998

Parasite immunology: pathways for expelling intestinal helminths.

Helminth parasites induce strong immune responses that are initiated by cytokines, in the first instance interleukin-4 and interleukin-13. Recent studies of knockout mice deficient in these mediators or their shared receptor have revealed discrete pathways required for expulsion of different gut parasites.

Animals↗