PubMed Health⌕ Search

Biomedical subjects

J Allan

Publications and source records attributed to J Allan.

At least 19 recordsLinked to original sources
PubMed2006

Development of non-agglutination microarray blood grouping.

Microarray technology provides an opportunity to monitor multiple parameters simultaneously. High-throughput applications such as blood donation screening could greatly benefit from performing various tests on a single testing platform. Blood grouping represents one part of the donation testing complementing the screening for blood-borne pathogens. Blood group serology traditionally exploited agglutination as the detection method. In this investigation, we have adapted blood grouping reactions to a solid-phase microarray substrate in a non-agglutination reaction format as an initial step in the development of a combined microarray testing platform. We have investigated immobilization of proprietary antibodies on multiple surfaces and monitored their performance under various reaction conditions. For the first time, highly specific blood grouping has been achieved on a planar microarray using directly labelled erythrocytes or a secondary labelled reagent using fluorescent signal end point readout. We have also complemented microarray data with a label-free, surface plasmon resonance-based Biacore platform data and used the real time quantitative measurement to rank anti-A antibodies according to the strength of reaction with the immobilized synthetic blood group antigen A.

Blood Grouping and Crossmatching↗
PubMed2005

Association of pronuclear Z score with rates of aneuploidy in in vitro-fertilised embryos.

The present study aimed to correlate the Z-scoring system to outcomes in in vitro fertilisation (IVF) cycles performed in conjunction with preimplantation genetic diagnosis. In 178 cycles, a total of 468 pronuclear embryos was scored prospectively using the Z score before culture and biopsy on Day 3 to detect chromosomes 13, 16, 18, 21, 22, X and Y. The results showed significant differences between Z1 and Z4 scoring embryos, with Z1 giving an increased biopsy rate (83.3% v. 51.1%), embryo quality (> or = fair: 83.3% v. 57.8%) and embryo growth rate (> or = six cells: 87.0% v. 44.4%). The incidence of chromosomally normal embryos decreased from Z1 to Z4 (Z1: 40%; Z2: 29.7%; Z3: 22.7%; Z4: 13.6%; P < 0.04). Thus, the Z scoring, mainly Z1 and Z4, correlated significantly with the expected embryo outcomes and preimplantation genetic diagnosis findings. Further improvement of pronuclear scoring with the use of a two-stage assessment is proposed.

Abortion, Habitual↗
PubMed2005

Localized versus regional hyperthermia: comparison of xenotransplants treated with a small animal ultrasound system and waterbath limb immersion.

The response of xenotransplants were compared with waterbath immersion vs focal ultrasound (US) hyperthermia using tumour growth delay, immunhistochemistry and histopathology assays. Waterbath hyperthermia was performed by limb immersion. Precautions were taken to minimize total body heating by surrounding the mouse with plastic insulators. Thermometry was performed with clinical-grade, 20-gauge needle thermocouples and monitored with a Labthermics unit. Significant differences in cytotoxicity between ultrasound and waterbath treatment of tumors at 43 degrees C were observed as determined by TUNNEL assay. Conversely, contralateral (non-treated) tumours in animals treated with similar temperature demonstrated no significant differences between modalities. Western blot analysis revealed increased hsp70 induction at 43 degrees C in waterbath vs focal ultrasound hyperthermia. Comparison of tumour growth delay between tumours heated with waterbath vs ultrasound at 43 degrees C but not at 41 degrees C revealed significant differences. This is the first study comparing localized vs regional hyperthermia using the small animal ultrasound system (SAHUS) delivery system. Consistent ultrasound hyperthermia can be achieved throughout a xenotransplant. At equivalent temperature of 43 degrees C for 60?min, waterbath hyperthermia demonstrated greater local response vs ultrasound hyperthermia.

Animals↗
PubMed2005

Influence of RANTES, SDF-1 and TGF-beta levels on the value of interleukin-7 as a predictor of virological response in HIV-1-infected patients receiving double boosted protease inhibitor-based therapy.

OBJECTIVES: Interleukin-7 (IL-7), RANTES (regulated on activation, normal T cell expressed and secreted), stromal cell-derived factor-1 (SDF-1) and transforming growth factor-beta (TGF-beta) appear to share certain biological properties in vitro and all are involved in HIV-1 disease progression. Our earlier observations indicated that IL-7 levels decrease upon CD4 T-cell recovery and represent a new, independent predictor of virological response. Here, we examine associations among circulating levels of IL-7, RANTES, SDF-1 and TGF-beta in hopes of gaining insight into their contribution to the predictive value of IL-7. METHODS: Levels of IL-7, RANTES, SDF-1 and TGF-beta, and immune and viral parameters were assessed in HIV-1-infected patients. RESULTS: Cross-sectional (n=148) and longitudinal (n=36) analyses showed that levels of IL-7, but not RANTES, SDF-1 or TGF-beta, were increased in HIV-1-infected adults compared with those of healthy controls. In the cross-sectional study, levels of IL-7 were correlated with RANTES (r=0.31, P=0.002) and TGF-beta (r=0.53, P<0.001) but not with SDF-1 (r=0.12, P=0.22), and these associations were more pronounced in patients with CD4 T-cell counts >200 cells/microL. In contrast to IL-7, levels of RANTES, SDF-1 and TGF-beta were not correlated with CD4 T-cell counts. Longitudinal analysis revealed a marked decline in IL-7 levels accompanied by an increase in CD4 T-cell count following antiretroviral therapy (ART), but no changes in RANTES, SDF-1 or TGF-beta levels. Multivariate regression analysis showed no influence of baseline RANTES, SDF-1 or TGF-beta levels on the value of IL-7 as a predictor of virological response at 48 weeks. CONCLUSIONS: Collectively, these results indicate that changes in IL-7 levels did not induce changes in RANTES, SDF-1 or TGF-beta. Furthermore, they indicate that RANTES, SDF-1 or TGF-beta levels do not explain the predictor value of IL-7 in patients receiving ART.

Adult↗
PubMed2003

Nucleosome positioning signals and potential H-DNA within the DNA sequence of the imprinting control region of the mouse Igf2r gene.

The imprinting control region within the second intron of the mouse Igf2r gene contains a CpG island comprising direct repeats, an imprinting box and the Air antisense promoter which is blocked by the methylation imprint on the active maternal allele. We have investigated the structural features of this DNA, including a mapping of all nucleosome positioning signals within the nucleotide sequence. A discrete series of strong positioning signals distinguished the direct repeat region from the much more diverse positioning capacity of the sequence encompassing the known regulatory elements. At only a few locations did CpG methylation modulate the use of this positioning information. Direct effects upon histone-DNA interactions are therefore unlikely to contribute significantly to the means by which the imprint may establish allele-specific chromatin architecture and determine Air expression. A strand-specific obstruction to DNA polymerase was observed between the repeat and regulatory regions. The same region adopts triple-stranded H-DNA structures in supercoiled DNA, according to pH and divalent cation exposure. Methylation did not modulate the occurrence or form of this structure under the conditions tested. This finding nevertheless adds to the repertoire of potential H-DNA structures found in the vicinity of regulatory sequences-here, in an imprinting context.

Animals↗
PubMed2003

Nucleosome positioning signals in the DNA sequence of the human and mouse H19 imprinting control regions.

We have investigated the sequences of the mouse and human H19 imprinting control regions (ICRs) to see whether they contain nucleosome positioning information pertinent to their function as a methylation-regulated chromatin boundary. Positioning signals were identified by an in vitro approach that employs reconstituted chromatin to comprehensively describe the contribution of the DNA to the most basic, underlying level of chromatin structure. Signals in the DNA sequence of both ICRs directed nucleosomes to flank and encompass the short conserved sequences that constitute the binding sites for the zinc finger protein CTCF, an essential mediator of insulator activity. The repeat structure of the human ICR presented a conserved array of strong positioning signals that would preferentially flank these CTCF binding sites with positioned nucleosomes, a chromatin structure that would tend to maintain their accessibility. Conversely, all four CTCF binding sites in the mouse sequence were located close to the centre of positioning signals that were stronger than those in their flanks; these binding sites might therefore be expected to be more readily incorporated into positioned nucleosomes. We found that CpG methylation did not effect widespread repositioning of nucleosomes on either ICR, indicating that allelic methylation patterns were unlikely to establish allele-specific chromatin structures for H19 by operating directly upon the underlying DNA-histone interactions; instead, epigenetic modulation of ICR chromatin structure is likely to be mediated principally at higher levels of control. DNA methylation did, however, both promote and inhibit nucleosome positioning at several sites in both ICRs and substantially negated one of the strongest nucleosome positioning signals in the human sequence, observations that underline the fact that this epigenetic modification can, nevertheless, directly and decisively modulate core histone-DNA interactions within the nucleosome.

Animals↗
PubMed2003

Interleukin-7 levels may predict virological response in advanced HIV-1-infected patients receiving lopinavir/ritonavir-based therapy.

OBJECTIVES: To examine the relationship between levels of the T-cell regulatory cytokine interleukin-7 (IL-7) and CD4 cell counts during immune reconstitution and to assess its prognostic value in advanced HIV-1-infected patients receiving lopinavir/ritonavir-based therapy. METHODS: Thirty-six HIV-1-infected adults who completed 48 weeks of follow-up visits were included in this prospective study. Patients having failed two or more antiretroviral therapy regimens were treated with lopinavir/ritonavir-based therapy. An enzyme-linked immunosorbent assay was used to determine IL-7 plasma levels, flow cytometry was used to analyse cell surface antigens, and polymerase chain reaction was used to quantify plasma HIV-1. RESULTS: Pretreatment IL-7 levels were elevated in all patients (mean 11.0 pg/mL) and were negatively correlated with CD4 cell counts and age (r=-0.59, P<0.001 and r=-0.57, P<0.001, respectively). During the course of treatment, IL-7 levels decreased by 34% while CD4 cell numbers progressively increased by 88%. Multivariate regression analysis showed that only pretreatment IL-7 levels predicted viral load at 48 weeks when controlling for baseline CD4 cell counts, viral load and patient demographics. CONCLUSIONS: These findings are consistent with regulation of T-cell recovery by IL-7, and suggest that IL-7 measurements might be used to predict virological response.

Adult↗
PubMed2002

Reduced levels of gamma-interferon secretion in response to chlamydial 60 kDa heat shock protein amongst women with pelvic inflammatory disease and a history of repeated Chlamydia trachomatis infections.

Peripheral lymphocytes in uninfected fertile controls, women with various histories of Chlamydia trachomatis infection, pelvic inflammatory disease (PID) and infertility not due to C. trachomatis infection (endometriosis) were cultured overnight with PHA mitogen and the 60 kDa chlamydial heat shock protein. Plasma samples were then assayed for levels of gamma-interferon and IL-10 using a commercial ELISA system. Women with PID and those with a history of multiple C. trachomatis infections showed reduced gamma-interferon production in response to cHSP60, not seen in women infected only once and those with infertility due to other causes (endometriosis). Secretion of IL-10 in response to cHSP60 did not vary significantly across the various patient groups, though all patients showed elevated levels of total IL-10 compared with uninfected controls.

Bacterial Outer Membrane Proteins↗
PubMed2001

Distinctive higher-order chromatin structure at mammalian centromeres.

The structure of the higher-order chromatin fiber has not been defined in detail. We have used a novel approach based on sucrose gradient centrifugation to compare the conformation of centromeric satellite DNA-containing higher-order chromatin fibers with bulk chromatin fibers obtained from the same mouse fibroblast cells. Our data show that chromatin fibers derived from the centromeric domain of a chromosome exist in a more condensed structure than bulk chromatin whereas pericentromeric chromatin fibers have an intermediate conformation. From the standpoint of current models, our data are interpreted to suggest that satellite chromatin adopts a regular helical conformation compatible with the canonical 30-nm chromatin fiber whereas bulk chromatin fibers appear less regularly folded and are perhaps intermittently interrupted by deformations. This distinctive conformation of the higher-order chromatin fiber in the centromeric domain of the mammalian chromosome could play a role in the formation of heterochromatin and in the determination of centromere identity.

3T3 Cells↗
PubMed2000

The effect of sodium citrate in arterial catheters on acid-base and electrolyte measurements.

OBJECTIVE: To compare the effects of heparin or sodium citrate used to anticoagulate indwelling arterial catheters on acid-base and electrolyte measurements. DESIGN: Randomized controlled trial. SETTING: Medical-surgical university-affiliated intensive care unit. SUBJECTS: Twenty patients with indwelling arterial catheters. INTERVENTIONS: Patients were randomly allocated to have ten 1-mL aliquots of blood sampled serially from an arterial catheter maintained with either heparin or sodium citrate. A sample then obtained by arterial puncture provided true measurement values. Acid-base and electrolyte measurements of whole blood were obtained from each sample by means of a Coming 860 analyzer. MEASUREMENTS AND MAIN RESULTS: Contamination with sodium citrate lowered ionized calcium and pH but increased glucose and Pco2. Heparin produced negligible effects on those measurements. When sodium citrate was used, reliable measurements were not obtained for ionized calcium, pH, and glucose, even after 9 mL of blood had been discarded. However, reliable P(CO2) measurements were obtained after 2 mL of blood was discarded. CONCLUSIONS: Sodium citrate used to maintain arterial catheters can contaminate blood samples. The result of that contamination can mimic severe hypocalcemia, metabolic acidosis, and mild hyperglycemia. Failure to recognize the effects of sodium citrate on acid-base and electrolyte measurements may lead to changes in treatment that could affect patient outcome adversely.

Acid-Base Equilibrium↗
PubMed2000

Patient-centered documentation: an effective and efficient use of clinical information systems.

After 2 years of experience with a basic computerized system for documenting care, the nursing leaders in an inner city hospital undertook a redesign process to create an effective and efficient system for documentation that also provided data for monitoring care processes, patient outcomes, and staff performance. The basic system was a source of frustration and dissatisfaction for nurses, physicians, and managers. The redesigned system has exceeded the expectations of staff and physicians and delighted managers. Managers can now access the clinical data collected by the staff to create meaningful reports describing the patient population, identifying patients needs, monitoring staff compliance with care standards, and tracking improvements in care processes.

Documentation↗