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Biomedical subjects

D Hicks

Publications and source records attributed to D Hicks.

At least 19 recordsLinked to original sources
PubMed2006

A comparative analysis of collagen VI production in muscle, skin and fibroblasts from 14 Ullrich congenital muscular dystrophy patients with dominant and recessive COL6A mutations.

Ullrich congenital muscular dystrophy (UCMD) is caused by recessive and dominant mutations in COL6A genes. We have analysed collagen VI expression in 14 UCMD patients. Sequencing of COL6A genes had identified homozygous and heterozygous mutations in 12 cases. Analysis of collagen VI in fibroblast cultures derived from eight of these patients showed reduced extracellular deposition in all cases and intracellular collagen VI staining in seven cases. This was observed even in cases that showed normal collagen VI labelling in skin biopsies. Collagen VI immunolabelling was reduced in all the available muscle biopsies. When comparisons were possible no correlation was seen between the extent of the reduction in the muscle and fibroblast cultures, the mode of inheritance or the severity of the clinical phenotype. Mutations affecting glycine substitutions in the conserved triple helical domain were common and all resulted in reduced collagen VI. This study expands the spectrum of collagen VI defects and shows that analysis of skin fibroblasts may be a useful technique for the detection of collagen VI abnormalities. In contrast, immunohistochemical analysis of skin biopsies may not always reveal an underlying collagen VI defect.

Adolescent↗
PubMed2005

Advanced granulomatous lesions in Mycobacterium bovis-infected cattle are associated with increased expression of type I procollagen, gammadelta (WC1+) T cells and CD 68+ cells.

The pathognomonic characteristic of tuberculosis (TB) is the formation of a tuberculous granuloma. The objective of this study was to classify lymph node granulomas from experimentally infected calves into different histopathological stages and characterize them further by studying cell types and markers of fibrosis associated with each of the stages. Four stages of granuloma were identified and mRNA and protein expression for cell markers, cytokines and pro-fibrotic markers were studied by immunohistochemistry (IHC) and in-situ hybridization (ISH). In advanced stage granulomas, there was an increase in the expression of TGF-beta, and of type I procollagen as demonstrated by IHC and ISH. As the granulomas advanced, there were fewer CD3+T cells and they tended to be more prominent towards the periphery of the lesions, with a steady increase in the number of CD68+ cells and gammadelta (WC1+) T cells. Granuloma classification and application of cell cytokine markers will assist in improving understanding of the pathogenesis of bovine TB and may help to identify the immunopathology of active disease versus contained or inactive disease. Such disease correlates may help to inform the development of improved diagnostic methods and support vaccine development programmes.

Animals↗
PubMed2004

Detection and genetic typing of type 2 porcine circoviruses in archived pig tissues from the UK.

Porcine circovirus 2 (PCV-2) is implicated as the causative agent of post-weaning multisystemic wasting syndrome (PMWS) and is also associated with porcine dermatitis and nephropathy syndrome (PDNS). The recent emergence of epidemic PMWS in the United Kingdom was predated by sporadic cases of PDNS dating back to the early 1980's. The aim of this study was to investigate whether PCV-2 DNA was present in archival tissues, and if so, to investigate the relatedness of these viruses with contemporary strains of PCV-2. DNA extracted from paraffin wax-embedded tissue blocks ( n = 68), was subjected to a TaqMan polymerase chain reaction (PCR) targeting a fragment of ORF1 of PCV-2. Positive results were obtained from 41% (9/22), 31% (4/13) and 32% (8/25) of submissions from the 1990's, 1980's and 1970's respectively. The presence of PCV-2 antigen in some of these tissues was confirmed by immunohistochemistry (IHC). A PCR targeting ORF2 was used to obtain sequence data for phylogenetic analysis. Sequences from 5 archival tissues were unique but showed high genetic identity to PCV-2 sequence obtained from a 2000 PDNS case. These data demonstrate that similar isolates of PCV-2 have been present in the UK pig population for more than 30 years.

Animals↗
PubMed2004

The relative proportions of sirolimus metabolites in blood using HPLC with mass-spectrometric detection.

Measurement of sirolimus in blood as a guide to dose adjustment is an accepted practice. To date, most data have resulted from the use of a chromatographic technique. With the imminent introduction of an immunoassay into this field, there is a need to know whether metabolites that could interfere with the performance of this assay, causing a bias compared with measurements made by a chromatographic assay, vary over a period of time or with changes in concomitant immunosuppressive therapy. This preliminary study measured several sirolimus metabolites in blood samples from a variety of clinical settings, using high-performance liquid chromatography with tandem mass-spectrometric detection. Two metabolites known to cross-react in one immunoassay system, single hydroxylation products and 41-O-demethyl rapamycin, were found to constitute the bulk of the metabolic products. They were also found to form a remarkably stable proportion of all metabolites measured, both with respect to the time since transplantation and the concomitant use of cyclosporine or tacrolimus. It is concluded that the analytical bias due to cross-reactivity with metabolites, inherent in this immunoassay, should be consistent across a wide spectrum of patients receiving the drug.

Biotransformation↗
PubMed2001

Energy dependence of particle multiplicities in central Au+Au collisions.

We present the first measurement of the pseudorapidity density of primary charged particles in Au+Au collisions at root square[s(NN)] = 200 GeV. For the 6% most central collisions, we obtain dN(ch)/d(eta)/(/eta/<1) = 650+/-35(syst). Compared to collisions at root square[s(NN)] = 130 GeV, the highest energy studied previously, an increase by a factor of 1.14+/-0.05 at 90% confidence level, is found. The energy dependence of the pseudorapidity density is discussed in comparison with data from proton-induced collisions and theoretical predictions.

Journal Article↗
PubMed2001

Alternate FGF2-ERK1/2 signaling pathways in retinal photoreceptor and glial cells in vitro.

Basic fibroblast growth factor (FGF2) stimulates photoreceptor survival in vivo and in vitro, but the molecular signaling mechanism(s) involved are unknown. Immunohistochemical and immunoblotting analyses of pure photoreceptors, inner retinal neurons, and Müller glial cells (MGC) in vitro revealed differential expression of the high affinity FGF receptors (FGFR1-4), as well as many cytoplasmic signaling intermediates known to mediate the extracellular signal-regulated kinase (ERK1/2) pathway. FGF2-induced tyrosine phosphorylation in vitro exhibited distinct profiles for each culture type, and FGF2-induced ERK1/2 activation was observed for all three preparations. Whereas U0126, a specific inhibitor of ERK kinase (MEK), completely abolished FGF2-induced ERK1/2 tyrosine phosphorylation and survival in cultured photoreceptors, persistent ERK1/2 phosphorylation was observed in cultured inner retinal cells and MGC. Furthermore U0126 treatment entirely blocked nerve growth factor-induced ERK1/2 activation in MGC, as well as FGF2-induced ERK1/2 activation in cerebral glial cells. Taken together, these data indicate that FGF2-induced ERK1/2 activation is entirely mediated by MEK within photoreceptors, which is responsible for FGF2-stimulated photoreceptor survival. In contrast, inner retina/glia possess alternative, cell type, and growth factor-specific MEK-independent ERK1/2 activation pathways. Hence signaling and biological effects elicited by FGF2 within retina are mediated by cell type-specific pathways.

Animals↗
PubMed2001

Multiple phosphorylated isoforms of NRL are expressed in rod photoreceptors.

NRL, a bZIP transcription factor of the Maf subfamily, interacts with the homeodomain protein CRX and synergistically regulates rhodopsin expression. Here we report that six isoforms of NRL (29-35 kDa) are generated by phosphorylation and expressed specifically in the mammalian retina. The anti-NRL antibody also cross-reacts with a cytosolic 45-kDa protein, which is detected in neuronal tissues but is not encoded by the NRL gene. In both human retinal cell cultures and sections of fetal and adult human retina, NRL is present in the nuclei of developing and mature rods but not cones. We propose that NRL regulates rod photoreceptor-specific gene expression and is involved in rod differentiation.

Alkaline Phosphatase↗
PubMed2001

Imiquimod for the treatment of genital warts: a quantitative systematic review.

OBJECTIVE: To review published randomised controlled trials to assess the benefit and harm of imiquimod in the treatment of external genital warts. DATA SOURCES: MEDLINE (1966 - December 2000), Cochrane Library (Issue 3, 2000) and PubMed (December 15, 2000), review articles and reference lists. REVIEW METHODS: Included studies had to be randomised trials of imiquimod, to be full published papers, and to have a comparison group. Quality of trial reporting was assessed. Relative benefit and number needed to treat were calculated for the main outcomes of wart clearance at the end of therapy, of at least 50% reduction in wart area, and of complete clearance at the end of treatment and no recurrence of warts during a follow-up period, as well as for adverse effect withdrawal or lack of efficacy withdrawal. RESULTS: There were six trials, all with quality scores of 3 (out of 5) or greater. In five trials with HIV-negative patients complete clearance of warts at the end of treatment occurred in 51% of patients treated with imiquimod 2% or 5% cream and 6% of placebo treated patients. The number needed to treat was 2.2 (95% confidence interval 2.0 to 2.6). In four trials at least 50% wart area reduction occurred with 72% of patients treated with imiquimod 5% cream and 20% of placebo treated patients. The number needed to treat was 1.9 (1.7 to 2.2). In three trials complete clearance of warts at the end of treatment plus no recurrence occurred in 37% of patients treated with imiquimod 5% cream and 4% of those treated with placebo. The number needed to treat was 3.0 (2.5 to 3.8). Adverse event withdrawal was rare and no more likely with imiquimod than with placebo. Imiquimod was not effective in one trial in HIV-positive patients. CONCLUSION: The evidence base for imiquimod in treating genital warts is of high quality and the necessary size from which to draw useful conclusions. Imiquimod is effective in home application, though not in patients with HIV infection with the evidence presently available.

AIDS-Related Opportunistic Infections↗
PubMed2001

Rod-cone interactions: developmental and clinical significance.

During the last decade, numerous research reports have considerably improved our knowledge about the physiopathology of retinal degenerations. Three non-mutually exclusive general areas dealing with therapeutic approaches have been proposed; gene therapy, pharmacology and retinal transplantations. The first approach involving correction of the initial mutation, will need a great deal of time and further development before becoming a therapeutic tool in human clinical practice. The observation that cone photoreceptors, even those seemingly unaffected by any described anomaly, die secondarily to rod disappearance related to mutations expressed specifically in the latter, led us to study the interactions between these two photoreceptor populations to search for possible causal links between rod degeneration and cone death. These in vivo and in vitro studies suggest that paracrine interactions between both cell types exist and that rods are necessary for continued cone survival. Since the role of cones in visual perception is essential, pending the identification of the factors mediating these interactions underway, rod replacement by transplantation and/or neuroprotection by trophic factors or alternative pharmacological means appear as promising approaches for limiting secondary cone loss in currently untreatable blinding conditions.

Animals↗
PubMed2001

Recent developments in the management of type 2 diabetes.

Type 2 diabetes is a common, chronic disease, with a high risk of macrovascular and microvascular complications that lead to premature death and disability. The disease is managed largely in primary care and its rising prevalence will increase the workload of community nurses. The forthcoming Diabetes National Service Framework will aim to improve the standards of diabetic care, while scientific and technological developments offer new treatments that may also improve the outlook for patients. There is as yet no case for population screening for type 2 diabetes, but community nurses are ideally placed to carry out local screening initiatives based on consensus guidelines.

Community Health Nursing↗
PubMed2001

Expression of X-linked retinoschisis protein RS1 in photoreceptor and bipolar cells.

PURPOSE: To examine the biochemical properties, cell expression, and localization of RS1, the product of the gene responsible for X-linked juvenile retinoschisis. METHODS: Rs1h mRNA expression was measured from the eyes of wild-type and rd/rd mice by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). Specific antibodies raised against the N terminus of RS1 were used as probes to examine the properties and distribution of RS1 in retina, retinal cell cultures, and transfected COS-1 cells by Western blot analysis and immunofluorescence microscopy. RESULTS: Rs1h mRNA expression was detected in the retina of postnatal day (P)11 and adult CD1 mice, but not homozygous rd/rd mice by Northern blot analysis. However, Rs1h expression was detected in rd/rd mice by RT-PCR. RS1 migrated as a single 24-kDa polypeptide under disulfide-reducing conditions and a larger complex (>95 kDa) under nonreducing conditions in the membrane fraction of retinal tissue homogenates and transfected COS-1 cells. RS1 antibodies specifically stained rod and cone photoreceptors and most bipolar cells, but not Müller cells, ganglion cells, or the inner limiting membrane of adult and developing retina as revealed in double-labeling studies. RS1 antibodies also labeled retinal bipolar cells of photoreceptorless mice and retinal bipolar cells grown in cell culture. CONCLUSIONS: RS1 is expressed and assembled in photoreceptors of the outer retina and bipolar cells of the inner retina as a disulfide-linked oligomeric protein complex. The secreted complex associates with the surface of these cells, where it may function as a cell adhesion protein to maintain the integrity of the central and peripheral retina.

Animals↗
PubMed2001

Selective excitotoxic degeneration of adult pig retinal ganglion cells in vitro.

PURPOSE: Excitotoxicity is proposed to play a prominent role in retinal ganglion cell (RGC) death ensuing from diseases such as glaucoma and ischemia, but cell culture studies have used tissue from newborn rodents, yielding conflicting data that implicate either N-methyl D-aspartate (NMDA) or non-NMDA glutamate (Glu) receptor-mediated pathways. Excitotoxic RGC death was examined in vitro in this study, using adult pigs, a large-animal model for human retina. METHODS: Adult pig retina (and for comparative purposes young and adult rat retina) were dissociated and maintained in monolayer culture. Medium was supplemented with Glu or pharmacologic agonists or antagonists, and surviving RGCs and other retinal neurons were quantified using specific immunolabeling methods. Electrophysiological responses to externally applied Glu of RGCs in culture were recorded using whole-cell patch-clamp techniques. RESULTS: Application of Glu led to selective, dose-dependent losses in large RGCs (maximal 37% decrease at 1 mM; median effective dose [ED50], approximately 80 microM) and neurite damage in surviving RGCs. Application of Glu agonists and Glu receptor subclass antagonists showed that large RGC death was mediated through both NMDA and non-NMDA receptor pathways. Small RGCs, amacrine cells, and all other retinal neurons were resistant to Glu-induced death. By comparison, rat retinal cultures displayed heightened RGC vulnerability to Glu, mediated exclusively by non-NMDA receptor-mediated pathways. Amacrine cells were unaffected by NMDA but were very sensitive to kainate application (>90% loss). Other retinal neurons were unaffected by any treatment. CONCLUSIONS: The molecular pathways underlying excitotoxic RGC death in vitro (non-NMDA or NMDA-preferring Glu receptors) vary among species and developmental stages. The selective elimination of adult pig large RGCs by NMDA receptor-mediated pathways more closely resembles human and animal glaucoma in vivo than other published culture models, providing a simplified experimental system for investigating the pharmacologic and toxicologic bases of glaucoma-like neuronal death.

Animals↗
PubMed2001

Hypoglycemia induces general neuronal death, whereas hypoxia and glutamate transport blockade lead to selective retinal ganglion cell death in vitro.

PURPOSE: To examine the impact of experimental ischemia and interruption of glutamate transport on retinal neuronal cell, especially retinal ganglion cell (RGC), survival in vitro. METHODS: Cell cultures were prepared from adult pig retinas and maintained under different experimental conditions of increasing hypoglycemia, environmental hypoxia (delayed postmortem period or atmospheric PO2 <2%), or chemical hypoxia (potassium cyanide), or in the presence of glutamate transporter blockers L-trans-pyrrolidine-2,4-dicarboxylic acid (tPDC) and L(-)-threo-3-hydroxyaspartic acid (THA), or the glutamine synthetase inhibitor methionine sulfoximine (MS). After 48 hours, cells were returned to standard culture conditions and allowed to develop for 5 days, when they were fixed and immunostained with different retinal neuronal phenotypic markers. RESULTS: Control normoxic cultures contained large numbers of immunocytochemically identified photoreceptors (PRs), bipolar cells (BCs), amacrine cells (ACs), and RGCs after 7 days in vitro. A 24-hour postmortem delay before culture led to significant reductions in all types (40%-70%), proportionately greater in ACs and RGCs. Lowering of sugar levels also led to increased losses in all cell types, whereas potassium cyanide treatment deleteriously affected only ACs and RGCs. Ambient hypoxia led to consistent reductions only in the number of RGCs, which were exacerbated by addition of high concentrations of glutamate. Inclusion of glutamate receptor antagonists had a partial protective effect against RGC loss. Treatment with tPDC and THA also led to selective RGC death, but MS had no effect on any cells. CONCLUSIONS: Different components of the ischemic pathologic process (hypoxia, hypoglycemia, glutamate transport failure) lead to distinctly different patterns of neuronal loss in adult retina in vitro. RGCs are especially vulnerable, corresponding to their in vivo susceptibility. These data may suggest neuroprotective strategies for limiting retinal damage during ischemia.

ATP-Binding Cassette Transporters↗
PubMed2001

Selective serotonin reuptake inhibitors and isoniazid: evidence of a potential adverse interaction.

BACKGROUND: Recognizing a potential interaction between isoniazid (INH), a weak monoamine oxidase inhibitor, and serotonin reuptake inhibitors (SSRIs), we assessed medication discontinuation rates in human immunodeficiency virus-infected individuals taking an SSRI, INH, or both. METHOD: We retrospectively reviewed treatment records to determine if patients on an SSRI, INH, or both completed drug therapy in accordance with a treatment plan (e.g., 12 months of INH therapy). Patients on both medications constituted the study group; patients taking either an SSRI or INH alone constituted comparison groups. RESULTS: There were no significant differences between the groups based on age, gender, CD4%, or CD4 count. Seven of the 10 patients (70%) in the study group discontinued therapy, which was significantly greater than the 2 of 14 (14%) in the SSRI group (P = 0.01) and the 4 of 18 (22%) in the INH group (p = 0.02) who discontinued therapy. CONCLUSION: Medication discontinuation rates for patients prescribed an SSRI coincident with INH were significantly higher than for individuals prescribed these medications separately. These differences cannot be accounted for on the basis of age, gender, or CD4%, but they may be attributable to increased side effects caused by interactions between these medications.

Adult↗