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J Hope

Publications and source records attributed to J Hope.

At least 19 recordsLinked to original sources
PubMed2000

Post-translational hydroxylation at the N-terminus of the prion protein reveals presence of PPII structure in vivo.

The transmissible spongiform encephalopathies are characterized by conversion of a host protein, PrP(C) (cellular prion protein), to a protease-resistant isoform, PrP(Sc) (prion protein scrapie isoform). The importance of the highly flexible, N-terminal region of PrP has recently become more widely appreciated, particularly the biological activities associated with its metal ion-binding domain and its potential to form a poly(L-proline) II (PPII) helix. Circular dichroism spectroscopy of an N-terminal peptide, PrP(37-53), showed that the PPII helix is formed in aqueous buffer; as it also contains an Xaa-Pro-Gly consensus sequence, it may act as a substrate for the collagen-modifying enzyme prolyl 4-hydroxylase. Direct evidence for this modification was obtained by mass spectrometry and Edman sequencing in recombinant mouse PrP secreted from stably transfected Chinese hamster ovary cells. Almost complete conversion of proline to 4-hydroxyproline occurs specifically at residue Pro44 of this murine protein; the same hydroxylated residue was detected, at lower levels, in PrP(Sc) from the brains of scrapie-infected mice. Cation binding and/or post-translational hydroxylation of this region of PrP may regulate its role in the physiology and pathobiology of the cell.

Amino Acid Sequence↗
PubMed2000

A single amino acid alteration in murine PrP dramatically alters TSE incubation time.

In order to investigate mutations linked to human TSEs, we have used the technique of gene targeting to introduce specific mutations into the endogenous murine PrP gene which resulted in a P101L substitution (Prnp(a101L)) in the murine PrP gene. This mutation is equivalent to the 102L mutation in the human PrP gene which is associated with Gerstmann-Sträussler syndrome. Since the mutated gene is in the correct chromosomal location and control of the mutant gene expression is identical to that of the wild type murine PrP gene, the precise effect of the 101L mutation in the uninfected and TSE infected mouse can be investigated in this transgenic model. Mice homozygous for this mutation (101LL) while showing no spontaneous TSE disease were more susceptible to TSE disease than wild type mice following inoculation with GSS infectivity. Disease was transmitted from these mice to mice both with and without the Prnp(a101L) allele. The 101L mutation does not therefore produce spontaneous genetic disease in mice but does dramatically alter incubation periods following TSE infection. Additionally, a rapid TSE transmission was demonstrated associated with extremely low amounts of PrP(Sc).

Amino Acid Substitution↗
PubMed2000

Prions and neurodegenerative diseases.

The long-term, progressive decay of the central nervous system typifies prion diseases, a group of rare, transmissible maladies affecting humans, sheep, cattle and some other types of mammal. Little is known about the early molecular events in its pathogenesis but the diverse roles of PrP, the prion protein, in its destructive action have recently been re-emphasised.

Animals↗
PubMed2000

Cytokine expression in periapical granulation tissue as assessed by immunohistochemistry.

The aims of this study were to investigate the expression of pro-inflammatory, anti-inflammatory and immune-related cytokines present in periapical lesions. We investigated the expression of cytokines: namely interleukins IL-2, IL-4, IL-6, IL-10 and interferon-gamma (IFN-gamma) in formalin-fixed, paraffin-embedded sections of periapical granulation tissue. The study samples were biopsies from 24 patients with periapical lesions: 12 with periapical granulomas and 12 patients with radicular cysts. Immunohistochemistry was also performed on tonsillar tissue which served as a control. We utilised a set of specific monoclonal antibodies and polyclonal monospecific antibodies to detect cells that expressed the different cytokines within the tissues. We also considered the nature of the periapical immune response by investigation of the T-helper 1 (Th-1) and T-helper 2 (Th-2) lymphocyte subsets using their cytokine profile, i.e., Th-1: IL-2 and IFN-gamma and Th-2: IL-4, IL-5 and IL-6. Only a few cells were weakly positive for the IL-2 protein in each of the tissue sections. Cells that expressed IL-4 or IL-6 were far more numerous than cells that expressed either IL-2 or IFN-gamma. Thus, we demonstrated a greater number of Th-2 cells in periapical lesions. This relative ratio of the T-cell subsets underlines the importance of the anti-inflammatory mechanisms taking place in the diseased tissue manifested by the wide array of IL-10-expressing cells: B cells, T suppressor cells (CD8 (+)) and tissue macrophages. The numbers of inflammatory cells expressing the anti-inflammatory molecules far outnumbered the cells that expressed pro-inflammatory cytokines. Thus, the downregulation of the inflammatory response and the predominant Th-2 or humoral immune response in periapical periodontitis may be important features that dictate the outcome of the disease process in the periapical lesion.

Adult↗
PubMed2000

Screening Congo Red and its analogues for their ability to prevent the formation of PrP-res in scrapie-infected cells.

Transmissible spongiform encephalopathies (TSEs) are incurable, fatal diseases. The dye Congo Red (CR) can cure cells infected with agents of the sheep TSE, scrapie, but is not used as a therapeutic or prophylactic agent in vivo, as its effects are small, possibly due to low blood-brain barrier permeability, and complicated by its intrinsic carcinogenicity. In this paper, the development is described of a structure-activity profile for CR by testing a series of analogues of this dye for their ability to inhibit the formation of the protease-resistant prion protein, PrP-res, a molecular marker for the infectious agent, in the scrapie-infected, SMB cell line. It was found that the central benzidine unit in CR, which gives the molecule potential carcinogenicity, can be replaced by other, less toxic moieties and that the sulphonate groups on the core molecule can be replaced by carboxylic acids, which should improve the brain permeability of these compounds. However, detailed dose-response curves were generated for several derivatives and they revealed that, while some compounds showed inhibition of PrP-res accumulation at high concentrations, at low concentrations they actually stimulated levels of PrP-res above control values.

Animals↗
PubMed1999

A single amino acid alteration (101L) introduced into murine PrP dramatically alters incubation time of transmissible spongiform encephalopathy.

A mutation equivalent to P102L in the human PrP gene, associated with Gerstmann-Straussler syndrome (GSS), has been introduced into the murine PrP gene by gene targeting. Mice homozygous for this mutation (101LL) showed no spontaneous transmissible spongiform encephalopathy (TSE) disease, but had incubation times dramatically different from wild-type mice following inoculation with different TSE sources. Inoculation with GSS produced disease in 101LL mice in 288 days. Disease was transmitted from these mice to both wild-type (226 days) and 101LL mice (148 days). In contrast, 101LL mice infected with ME7 had prolonged incubation times (338 days) compared with wild-type mice (161 days). The 101L mutation does not, therefore, produce any spontaneous genetic disease in mice but significantly alters the incubation time of TSE infection. Additionally, a rapid TSE transmission was demonstrated despite extremely low levels of disease-associated PrP.

Alleles↗
PubMed1999

Conflicting MRI signals from gliosis and neuronal vacuolation in prion diseases.

Magnetic resonance imaging (MRI) has given inconsistent results when used as a non-invasive diagnostic tool for Creutzfeldt-Jakob disease (CJD). In order to understand this finding, we studied a hamster model of scrapie by in vivo MRI and histopathology. Vacuolation of neurones/neuropil and gliosis were found to correlate with hypo-intense and hyper-intense changes in the conventional T2-weighted MR images, respectively. These opposing effects were shown to give rise to normal images of a scrapie-affected brain undergoing severe neurodegeneration, and may underlie the variability of previous CJD MRI data.

Animals↗
PubMed1999

Prions.

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Animals↗
PubMed1999

Brain bioenergetics in murine models of scrapie using in vivo 31P magnetic resonance spectroscopy.

The bioenergetic status of the brain in scrapie mouse models was investigated during the late, clinical phase of the disease, by in vivo phosphorus magnetic resonance spectroscopy (MRS). The only significant change observed in the scrapie-infected mice compared with controls was an increase in intracellular brain pH (7.20+/-0.06 vs 7.10+/-0.05). No other changes in energetic metabolism were observed in the infected mice beside a trend in the decrease of phosphomonoester (PME) level, possibly associated with an alteration in glycolytic intermediates. This study showed that even in the presence of severe cellular vacuolation and microglia infiltrate, cerebral bioenergetic is maintained.

Adenosine Triphosphate↗
PubMed1999

Site-specific characterization of the N-linked glycans of murine prion protein by high-performance liquid chromatography/electrospray mass spectrometry and exoglycosidase digestions.

The murine prion protein PrP gene encodes a protein of 254 amino acids with two consensus sites for Asn-linked glycosylation at codons 180 and 196. A partial site-specific study of the N-linked glycans from hamster PrP has previously been carried out by mass spectrometry [Stahl, N., Baldwin, M. A., Teplow, D. B., Hood, L., Gibson, B. W., Burlingame, A. L., and Prusiner, S. B. (1993) Biochemistry 32, 1991-2002] and revealed that the glycosylation at Asn-181 (equivalent to mouse 180) is heterogeneous, comprising over 30 glycoforms. The identification of the glycosylated peptide spanning Asn-197 was not reported. Recent technical advances in electrospray mass spectrometry now provide the sensitivity to detect low femtomole quantities of glycopeptides with >5000 mass resolution and 30 ppm mass measurement [Medzihradszky, K. F., Besman, M. J., and Burlingame, A. L. (1998) Rapid Commun. Mass Spectrom. 12, 472-478]. This performance coupled with stepwise exoglycosidase digestion has been employed to establish the differential nature of the structural complexity (glycoforms) of the glycans at Asn-180 and Asn-196 from a single strain infected with the ME7 strain. Some sixty structures have been found characterized by neutral and sialylated bi-, tri-, and tetraantennary complex-type bearing outer-arm alpha(1-3)-fucosylation (the Lewisx and sialyl-Lewisx epitopes), core alpha(1,6) fucosylation, and the presence of terminal HexNAc residues. The Lewisx trisaccharide is the major nonreducing structure at Asn-180, and significant amounts of both Lewisx and sialyl Lewisx epitopes are observed at Asn-196. The abundance of the Lewisx and sialyl Lewisx epitopes on murine PrPSc may indicate a role for these structures in the normal function of PrPC or the pathophysiology of PrPSc.

Amino Acid Sequence↗
PubMed1999

Preliminary assessment of whole-blood, red-cell and platelet- leucodepleting filters for possible induction of prion release by leucocyte fragmentation during room temperature processing.

Universal leucodepletion is being introduced in the U.K. to reduce a theoretical risk of Creutzfeldt-Jakob disease (CJD) transmission. If CJD infectivity is associated with leucocytes, any cell fragmentation associated with filtration could reduce the potential benefit. Four types each of whole blood, red cell and platelet leucodepletion filters were assessed after holding of blood units for at least 4 h at 22 degrees C. In all cases the mean residual leucocyte content was <1 000 000 per unit, with only two individual filtered whole blood units having a leucocyte content exceeding this. Evidence of leucocyte fragmentation during filtration was sought but not found by assay of soluble elastase, beta-thromboglobulin and normal prion protein, as well as by isotopic labelling of leucocyte external membrane. These preliminary studies indicate that it was possible to prepare leucodepleted blood components by filtration at room temperature, and that this appeared not to be associated with overt cell fragmentation. Definitive demonstration that fragmentation does not occur requires the development of improved general (non-specific) assays for cell membrane fragments.

Blood Component Removal↗
PubMed1999

Distribution of cell-associated prion protein in normal adult blood determined by flow cytometry.

Leucocyte subpopulations from normally healthy individuals were identified by recognized combinations of fluorochrome-conjugated antibodies to CD markers and stained by different monoclonal antibodies (MAb) to normal cellular prion protein (PrPC), including the 3F4 MAb. Cell preparations were examined by three-colour flow cytometry. All mononuclear leucocyte subpopulations and platelets expressed PrPC, but polymorphonuclear leucocytes and red blood cells expressed little or no PrPC. The amounts of PrPC expressed by the different cells were calculated by comparison to bead standards. Mononuclear leucocytes expressed 3000-4000 molecules of antibody-reactive PrPC per cell. Resting platelets expressed around 1400 molecules of PrPC per cell, whereas activated platelets expressed around 4800 molecules of PrPC per cell. Extrapolation of these values to the amounts of the various cells in whole blood showed that platelet PrPC accounted for at least 96% of cell-expressed PrPC in blood. The PrPC on mononuclear cells and platelets was sensitive to enzymatic treatment of cells by proteinase k and phosphatidylinositol-specific phospholipase C. Certain anti-PrPC MAbs which showed equivalent intensity of staining to MAb 3F4 on fresh cells showed relative reductions of staining compared to MAb 3F4 on stored cells, indicating possible structural alterations of PrPC under these conditions.

Adult↗
PubMed1999

Use of antipsychosis and adjunctive medications by an inner urban community psychiatric service.

OBJECTIVE: The aim of this paper is to survey patterns of use of new generation and conventional antipsychosis and adjunctive drugs by an inner urban community psychiatric service. METHOD: All prescriptions for antipsychosis medications and all patients receiving these drugs in May 1998 were identified. Case record review yielded demographic and diagnostic data. Information was also obtained directly from prescribers. RESULTS: Of 859 patients, 77% received antipsychosis medication; 53% of prescriptions for antipsychotics were for new generation drugs: risperidone (42%), olanzapine (37%) and clozapine (21%). Mean doses were 4.1+/-2.5 mg (risperidone), 14.7+/-8.2 mg (olanzapine) and 377.4+/-178.9 mg (clozapine). Doses for men tended to be higher than those for women, but the differences were not significant. DSM-IV diagnosis was schizophrenia for 74% of patients on atypicals, but patients with other diagnoses were also being treated with these drugs. Risperidone was more commonly used in combination with benzodiazepines and anticholinergics than olanzapine and clozapine, while clozapine was less likely to be combined with antidepressants and mood stabilisers. Of the conventionals, 66% were in depot form, mostly because of non-compliance. Combinations of antipsychotics were prescribed to 13% of patients. CONCLUSION: New generation antipsychosis medications were prescribed more commonly than conventional drugs in this service for a wide range of diagnoses. Adjunctive medications were commonly utilised. These findings underline the clinical complexity of antipsychotic treatment in a changing environment.

Adult↗
PubMed1999

Molecular analysis of ovine prion protein identifies similarities between BSE and an experimental isolate of natural scrapie, CH1641.

New variant Creutzfeldt-Jakob disease (vCJD) and bovine spongiform encephalopathy (BSE) are caused by the same strain of pathogen and, as sheep can develop experimental BSE, this has raised concern that humans may be at risk from eating mutton if BSE has naturally transmitted to sheep. Biochemical typing of abnormal prion proteins (PrPsc) has been suggested to detect BSE in sheep. Although this approach is ingenuous, we can now report biochemical evidence of strain variation in contemporary and archival brain tissue from cases of experimental BSE or experimental and natural scrapie in sheep. Interestingly, we found at least one isolate of natural scrapie (CH 1641) with a very similar, but not identical, PrPsc profile to BSE but which differs from BSE in its transmission characteristics to mice.

Animals↗
PubMed1999

Species-independent inhibition of abnormal prion protein (PrP) formation by a peptide containing a conserved PrP sequence.

Conversion of the normal protease-sensitive prion protein (PrP) to its abnormal protease-resistant isoform (PrP-res) is a major feature of the pathogenesis associated with transmissible spongiform encephalopathy (TSE) diseases. In previous experiments, PrP conversion was inhibited by a peptide composed of hamster PrP residues 109 to 141, suggesting that this region of the PrP molecule plays a crucial role in the conversion process. In this study, we used PrP-res derived from animals infected with two different mouse scrapie strains and one hamster scrapie strain to investigate the species specificity of these conversion reactions. Conversion of PrP was found to be completely species specific; however, despite having three amino acid differences, peptides corresponding to the hamster and mouse PrP sequences from residues 109 to 141 inhibited both the mouse and hamster PrP conversion systems equally. Furthermore, a peptide corresponding to hamster PrP residues 119 to 136, which was identical in both mouse and hamster PrP, was able to inhibit PrP-res formation in both the mouse and hamster cell-free systems as well as in scrapie-infected mouse neuroblastoma cell cultures. Because the PrP region from 119 to 136 is very conserved in most species, this peptide may have inhibitory effects on PrP conversion in a wide variety of TSE diseases.

Amino Acid Sequence↗