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David J Hughes

Publications and source records attributed to David J Hughes.

6 recordsLinked to original sources
PubMed2007

Membrane fouling by cell-protein mixtures: in situ characterisation using multi-photon microscopy.

Fouling of the membrane by cell and protein mixtures can result in severe flux declines, leading to the eventual need to clean or replace the membrane. In this study multi-photon microscopy, a fluorescence-based technique is used to 3-D image in situ the fouling of microfiltration membranes by suspensions containing combinations of washed yeast, bovine serum albumin (BSA) and ovalbumin. Appropriate fluorescent labelling allows the three foulant species to be clearly identified. Images correlate well with filtration data and clearly show the cake of yeast cells capturing protein aggregates. The proteins exhibited very different filtration behaviour. When filtering washed yeast together with ovalbumin and/or a 50:50 mixture by mass of BSA and ovalbumin, the ovalbumin fouling dominates the system. Capture of aggregates by the cake did not reduce fouling of the membrane by the protein and increased the resistance of the cake. For mixtures of BSA and washed yeast, the presence of a cake of yeast cells did reduce fouling of the membrane by the protein, however, the extra resistance due to the cake resulted in a flux lower than that when filtering BSA alone.

Biofilms↗
PubMed2006

In situ three-dimensional characterization of membrane fouling by protein suspensions using multiphoton microscopy.

Fouling of microfiltration membranes leads to severe flux declines and the need to clean or replace the membrane. In situ 3D characterization of protein fouling both on the surface and within the pores of the membrane was achieved using multiphoton microscopy. Time-lapse images of the fouled membrane were obtained for single suspensions and mixtures of fluorescently labeled bovine serum albumin and ovalbumin. Deposited protein aggregates were visible on the membrane and evidently play an important role in fouling. A combination of 3D images and resistance versus time data was used to identify the dominant fouling mechanism. Fouling is initially internally dominated, but after 1 and 15 min for ovalbumin and bovine serum albumin, respectively, the fouling becomes externally dominated. This is in good agreement with two-stage protein fouling models.

Animals↗
PubMed2005

Breast cancer risk in BRCA1 and BRCA2 mutation carriers and polyglutamine repeat length in the AIB1 gene.

Marked variation in phenotypic expression among BRCA1 and BRCA2 mutation carriers may be partly explained by modifier genes that influence mutation penetrance. Variation in CAG/CAA repeat lengths coding for stretches of glutamines in the C-terminus of the AIB1 protein (amplified in breast cancer 1, a steroid receptor coactivator) has been proposed to modify the breast cancer risk in women carrying germline BRCA1 mutations. We genotyped the AIB1 repeat length polymorphism from the genomic DNA of a group of 851 BRCA1 and 324 BRCA2 female germline mutation carriers to estimate an association with breast cancer risk modification. Hazard ratios (HR) were calculated using a Cox proportional hazards model. For BRCA1 and BRCA2 mutation carriers, analyzed separately and together, we found that women who carried alleles with 28 or more polyglutamine repeats had no increased risk of breast cancer compared to those who carried alleles with fewer repeats (HR for BRCA1/2 carriers = 0.88, 95% CI [confidence interval] = 0.75-1.04). Analyzing average repeat lengths as a continuous variable showed no excess risk of breast cancer (BC) in BRCA1 or BRCA2 mutation carriers (HR for average repeat length in BRCA1/2 carriers = 1.01, 95% CI = 0.92-1.11). These results strongly suggest that contrary to previous studies, there is no significant effect of AIB1 genetic variation on BC risk in BRCA1 mutation carriers and provide an indication that there is also no strong risk modification in BRCA2 carriers.

Acetyltransferases↗
PubMed2005

Common BRCA2 variants and modification of breast and ovarian cancer risk in BRCA1 mutation carriers.

The HH genotype of the nonconservative amino acid substitution polymorphism N372H in the BRCA2 gene was reported to be associated with a 1.3- to 1.5-fold increase in risk of both breast and ovarian cancer. As these studies concerned sporadic cancer cases, we investigated whether N372H and another common variant located in the 5'-untranslated region (203G > A) of the BRCA2 gene modify breast or ovarian cancer risk in BRCA1 mutation carriers. The study includes 778 women carrying a BRCA1 germ-line mutation belonging to 403 families. The two BRCA2 variants were analyzed by the TaqMan allelic discrimination technique. Genotypes were analyzed by disease-free survival analysis using a Cox proportional hazards model. We found no evidence of a significant modification of breast cancer penetrance in BRCA1 mutation carriers by either polymorphism. In respect of ovarian cancer risk, we also saw no effect with the N372H variant but we did observe a borderline association with the 5'-untranslated region 203A allele (hazard ratio, 1.43; CI, 1.01-2.00). In contrast to the result of Healey et al. on newborn females and adult female controls, we found no departure from Hardy-Weinberg equilibrium in the distribution of N372H alleles for our female BRCA1 carriers. We conclude that if these single-nucleotide polymorphisms do modify the risk of cancer in BRCA1 mutation carriers, their effects are not significantly larger than that of N372H previously observed in the general population.

Adult↗
PubMed2004

In vivo function of a gammaherpesvirus virion glycoprotein: influence on B-cell infection and mononucleosis.

The human gammaherpesviruses Epstein-Barr virus and Kaposi Sarcoma-associated herpesvirus both contain a glycoprotein (gp350/220 and K8.1, respectively) that mediates binding to target cells and has been studied in great detail in vitro. However, there is no direct information on the role that these glycoproteins play in pathogenesis in vivo. Infection of mice by murid herpesvirus 4 strain 68 (MHV-68) is an established animal model for gammaherpesvirus pathogenesis and expresses an analogous glycoprotein, gp150. To elucidate the in vivo function of gp150, a recombinant MHV-68 deficient in gp150 production was generated (vgp150Delta). The productive viral replication in vitro and in vivo was largely unaffected by mutation of gp150, aside from a partial defect in the release of extracellular virus. Likewise, B-cell latency was established. However, the transient mononucleosis and spike in latently infected cells associated with the spread of MHV-68 to the spleen was significantly reduced in vgp150Delta-infected mice. A soluble, recombinant gp150 was found to bind specifically to B cells but not to epithelial cells in culture. In addition, gp150-deficient MHV-68 derived from mouse lungs bound less well to spleen cells than wild-type virus. Thus, gp150 is highly similar in function in vitro to the Epstein-Barr virus gp350/220. These results suggest a role for these analogous proteins in mononucleosis and have implications for their use as vaccine antigens.

Animals↗