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Biomedical subjects

D A Harris

Publications and source records attributed to D A Harris.

At least 19 recordsLinked to original sources

Review of surgical management of aldosterone secreting tumours of the adrenal cortex.

AIMS: To evaluate the investigation and surgical management of primary hyperaldosteronism. Retrospective case note analysis of thirty-three patients who underwent adrenalectomy for primary hyperaldosteronism between 1982 and 2001 and a current relevant literature review. METHODS: The records of twelve male and twenty-one female patients, age range 18 to 81 (mean 48 years) were reviewed. Eleven operations were performed by an open approach and twenty-two laparoscopically. Preoperative investigations included computed tomography (CT), magnetic resonance imaging (MRI), selective venous sampling and seleno-cholesterol isotope scanning, along with biochemical and hormonal assays. Twenty-six benign adenomas, three nodular hyperplastic lesions, one primary adrenal hyperplasia and three functional carcinomas were excised. Mean follow up was 12 months. RESULTS: Patients had a mean blood pressure of 185/107 mmHg for 6.2 years mean duration. The mean severity of hypokalaemia was 2.7 mmol/l. Sensitivity of CT scanning was 85%, and of MRI 86%. Fifty percent of seleno-cholesterol scans were accurate. Mean operating time was 158 min for laparoscopic adrenalectomy whilst open surgery took 129 min (p=0.2, NS). Two cases commenced laparoscopically required open access for control of primary haemorrhage whilst one other bleed was managed via the operating ports. Mean postoperative stay was significantly shorter for the laparoscopic group (3 days compared with 7.9 days, p<0.0001). Thirty day mortality was zero. There were three infective complications in the open group (two chest, one wound) with no postoperative complications in the laparoscopic group. All patients were cured of hypokalaemia, whilst 62% cure of hypertension was achieved. Of those patients whose blood pressure was improved preoperatively by spironolactone 78% were cured by adrenalectomy. Adrenalectomy led to an overall reduction in the mean number of anti-hypertensive medications (2.3 drugs preoperative to 0.6 postoperative, p<0.0001). Of those not cured, 58% had improved blood pressure control requiring less medication on average (1.6 drugs compared with 2.6 drugs, p=0.08). Mean age of patients not cured by surgery was 55 years, whilst those cured was 44 years (p=0.03). CONCLUSIONS: Primary hyperaldosteronism is a rare but important cause of hypertension. Selective venous sampling is a useful tool where investigations are inconclusive and fail to lateralise secretion. Patients with primary hyperaldosteronism enjoy lower complication rates and earlier discharge with the advent of laparoscopic surgery. Most patients will be cured of their hypertension and all of hypokalaemia. Laparoscopic adrenalectomy is now the accepted method of surgery for benign hyperaldosteronism. Those with bilateral disease due to idiopathic hyperaldosteronism (IHA) are not candidates for surgery and should be treated medically.

Adenoma↗

Search for nu(mu)-->nu(e) and nu(mu)-->nu(e) oscillations at NuTeV.

Limits on nu(mu)-->nu(e) and nu(mu)-->nu(e) oscillations are extracted using the NuTeV detector with sign-selected nu(mu) and nu(mu) beams. In nu(mu) mode, for the case of sin(2)2alpha = 1, Delta(m)(2)>2.6 eV(2) is excluded, and for Delta(m)(2)>>1000 eV(2), sin(2)2alpha>1.1 x 10(-3). The NuTeV data exclude the high Delta(m)(2) end of nu(mu)-->nu(e) oscillation parameters favored by the LSND experiment without the need to assume that the oscillation parameters for nu and nu are the same. We present the most stringent experimental limits for nu(mu)(nu(mu))-->nu(e)(nu(e)) oscillations in the large Delta(m)(2) region.

Journal Article↗

Precise determination of electroweak parameters in neutrino-nucleon scattering.

The NuTeV Collaboration has extracted the electroweak parameter sin(2)theta(W) from the measurement of the ratios of neutral current to charged current nu and (-)nu cross sections. Our value, sin(2)theta((on-shell))(W) = 0.2277 +/- 0.0013(stat) +/- 0.0009(syst), is 3 standard deviations above the standard model prediction. We also present a model independent analysis of the same data in terms of neutral-current quark couplings.

Journal Article↗

Extraction of R = sigma(L)/sigma(T) from CCFR nu(mu)-Fe and nu(mu)-Fe differential cross sections.

We report on the extraction of R = sigma(L)/sigma(T) from CCFR nu(mu)-Fe and nu(mu)-Fe differential cross sections. The CCFR differential cross sections do not show the deviations from the QCD expectations that are seen in the CDHSW data at very low and very high x. R as measured in nu(mu) scattering is in agreement with R as measured in muon and electron scattering. All data on R for Q(2)>1 GeV(2) are in agreement with a NNLO QCD calculation which uses NNLO parton distribution functions and includes target mass effects. We report on the first measurements of R in the low x and Q(2)<1 GeV(2) region (where an anomalous large rise in R for nuclear targets has been observed by the HERMES Collaboration).

Journal Article↗

Mutant prion proteins are partially retained in the endoplasmic reticulum.

Familial prion diseases are linked to point and insertional mutations in the prion protein (PrP) gene that are presumed to favor conversion of the cellular isoform of PrP to the infectious isoform. In this report, we have investigated the subcellular localization of PrP molecules carrying pathogenic mutations using immunofluorescence staining, immunogold labeling, and PrP-green fluorescent protein chimeras. To facilitate visualization of the mutant proteins, we have utilized a novel Sindbis viral replicon engineered to produce high protein levels without cytopathology. We demonstrate that several different pathogenic mutations have a common effect on the trafficking of PrP, impairing delivery of the molecules to the cell surface and causing a portion of them to accumulate in the endoplasmic reticulum. These observations suggest that protein quality control in the endoplasmic reticulum may play an important role in prion diseases, as it does in some other inherited human disorders. Our experiments also show that chimeric PrP molecules with the sequence of green fluorescent protein inserted adjacent to the glycolipidation site are post-translationally modified and localized normally, thus documenting the utility of these constructs in cell biological studies of PrP.

Animals↗

Search for the lepton family number violating process nu(mu)e(-) --> mu(-)nu(e).

The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process nu(mu)e(-)-->mu(-)nu(e), and to measure the cross section of the standard model inverse muon decay process nu(mu)e(-)-->mu(-)nu(e). NuTeV measures the inverse muon decay asymptotic cross-section slope sigma/E to be (13.8 +/- 1.2 +/- 1.4) x 10(-42) cm(2)/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the cross-section ratio sigma(nu(mu)e(-)-->mu(-)nu(e))/sigma(nu(mu)e(-)-->mu(-)nu(e)) < or = 1.7% at 90% C.L. for V-A couplings and < or = 0.6% for scalar couplings.

Journal Article↗

Observation of an anomalous number of dimuon events in a high energy neutrino beam.

A search for long-lived neutral particles ( N0's) with masses above 2.2 GeV/c(2) that decay into at least one muon has been performed using an instrumented decay channel at the NuTeV experiment at Fermilab. Data were examined for particles decaying into the final states mumu, mu(e), and mu(pi). Three mumu events were observed over an expected standard model background of 0.069+/-0.010 events; no events were observed in the other modes.

Journal Article↗

First measurement of the low- x, low- Q(2) structure function F(2) in neutrino scattering.

A new structure function analysis of CCFR deep inelastic nu-N and nu-N scattering data is presented for previously unexplored kinematic regions down to Bjorken x = 0.0045 and Q(2) = 0.3 GeV(2). Comparisons to charged lepton scattering data from NMC and E665 experiments are made and the behavior of the structure function F(2)(nu)2 is studied in the limit Q(2)-->0.

Journal Article↗

Measurements of F2 and xF(nu)(3) - xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe Data in a Physics Model-Independent Way.

We report on the extraction of the structure functions F2 and DeltaxF(3) = xF(nu)(3)-xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe differential cross sections. The extraction is performed in a physics model-independent (PMI) way. This first measurement of DeltaxF(3), which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The ratio of the F2 (PMI) values measured in nu(mu) and mu scattering is in agreement (within 5%) with the predictions of next-to-leading-order parton distribution functions using massive charm production schemes, thus resolving the long-standing discrepancy between the two sets of data.

Journal Article↗

Copper converts the cellular prion protein into a protease-resistant species that is distinct from the scrapie isoform.

Several lines of evidence have suggested that copper ions play a role in the biology of both PrP(C) and PrP(Sc), the normal and pathologic forms of the prion protein. To further investigate this intriguing connection, we have analyzed how copper ions affect the biochemical properties of PrP(C) extracted from the brains of transgenic mice and from transfected cells. We report that the metal rapidly and reversibly induces PrP(C) to become protease-resistant and detergent-insoluble. Although these two properties are commonly associated with PrP(Sc), we demonstrate using a conformation-dependent immunoassay that copper-treated PrP is structurally distinct from PrP(Sc). The effect of copper requires the presence of at least one of the five octapeptide repeats normally present in the N-terminal half of the protein, consistent with the idea that the metal alters the biochemical properties of PrP by directly binding to this region. These results suggest potential roles for copper in prion diseases, as well as in the physiological function of PrP(C).

Animals↗

Primary myopathy and accumulation of PrPSc-like molecules in peripheral tissues of transgenic mice expressing a prion protein insertional mutation.

A nine-octapeptide insertional mutation in the prion protein (PrP) gene is associated with an inherited variant of Creutzfeldt-Jakob disease in humans. Transgenic mice that express the mouse PrP homologue of this mutation (designated PG14) under control of a PrP promoter display a progressive neurological disorder characterized by ataxia, apoptosis of cerebellar granule cells, and accumulation in the brain of mutant PrP molecules that display the biochemical hallmarks of PrP(Sc), the pathogenic isoform of PrP. In this report, we have investigated the expression of PG14 PrP in the peripheral tissues of these mice. We found highest levels of mutant PrP in the brain and spinal cord, intermediate levels in skeletal muscle, heart, and testis and low levels in kidney, lung, spleen, intestine, and stomach. Up to 70% of the PG14 PrP expressed in peripheral tissues was detergent-insoluble, and digestion with low concentrations of proteinase K yielded a PrP 27-30 fragment. These results suggest that the mutant protein was converted to a physical state reminiscent of PrP(Sc), although its infectivity remains to be determined. Histological analysis of skeletal muscle, one of the peripheral tissues with the highest level of PG14 PrP, revealed features indicative of a progressive, primary myopathy, including central nuclei, necrotic and regenerating fibers, and variable fiber size. These results indicate that the PG14 mutation structurally alters the protein in a way that promotes conversion to a PrP(Sc)-like state, regardless of the tissue context, and suggest that accumulation of PrP(Sc) can have deleterious effects on skeletal muscle cells as well as on neurons.

Aging↗

Prion diseases: what is the neurotoxic molecule?

A great deal of effort has been devoted during the past 20 years to defining the chemical nature of prions, the infectious agents responsible for transmissible spongiform encephalopathies. In contrast, much less attention has been paid to elucidating how prions actually damage the central nervous system. Although it is commonly assumed that PrP(Sc), the protein constituent of infectious prions, is the primary culprit, increasing evidence indicates that this may not be the case. Several alternative molecular forms of PrP are reasonable candidates for the neurotoxic species in prion diseases, although it is still too early to tell whether these or other ones will turn out to be the true instigating factors. The cellular pathways activated by neurotoxic forms of PrP that ultimately result in neuronal death are also being investigated, and several possible mechanisms have been uncovered, including the operation of quality control processes in the endoplasmic reticulum. Elucidating the distinction between the infectious and neurotoxic forms of PrP has important implications for designing therapy of prion diseases, as well as for understanding pathogenic mechanisms operative in other neurodegenerative disorders and the role of prion-like states in biology.

Adult↗

Boundary lubrication by lubricin is mediated by O-linked beta(1-3)Gal-GalNAc oligosaccharides.

Lubrication of mammalian joints is mediated by lubricin, a product of megakaryocyte stimulating factor gene (MSF; GenBank accession #U70136) expression. Lubricin (M(r) approximately 240 kDa) is a mucinous glycoprotein which is 50% (w/w) post-translationally modified with beta(1-3)Gal-GalNAc incompletely capped with NeuAc, and lubricates apposed cartilaginous surfaces in the boundary mode through an unknown mechanism. Both bovine and human lubricin were purified from synovial fluid and digested with recombinant glycosidases. Released oligosaccharides were identified and quantified by fluorophore assisted carbohydrate electrophoresis (FACE). Corresponding digests of human lubricin were also assayed in a friction apparatus oscillating latex rubber against polished glass at a pressure of 0.35 x 10(6) N/m(2) and the coefficient of friction (mu) was measured. Digestion with alpha2,3-neuraminidase decreased lubricating ability by 19.3%. Partial removal of beta(1-3)Gal-GalNAc moieties by endo-alpha-N-acetyl-D-galactosaminidase reduced lubricating ability by 77.2%. Human lubricin digested with combined alpha2,3-neuraminidase and beta1-3,6-galactosidase continued to lubricate at 52.2% of its nominal value. Both bovine and human lubricin released 48.6% and 54.4% of total beta(1-3)Gal-GalNAc sidechains following digestion with endo-alpha-N-acetyl-D-galactosaminidase. Biological boundary lubrication by synovial fluid in vitro is provided primarily by extensive O-linked beta(1-3)Gal-GalNAc.

Acetylgalactosamine↗

A transmembrane form of the prion protein contains an uncleaved signal peptide and is retained in the endoplasmic Reticulum.

Although there is considerable evidence that PrP(Sc) is the infectious form of the prion protein, it has recently been proposed that a transmembrane variant called (Ctm)PrP is the direct cause of prion-associated neurodegeneration. We report here, using a mutant form of PrP that is synthesized exclusively with the (Ctm)PrP topology, that (Ctm)PrP is retained in the endoplasmic reticulum and is degraded by the proteasome. We also demonstrate that (Ctm)PrP contains an uncleaved, N-terminal signal peptide as well as a C-terminal glycolipid anchor. These results provide insight into general mechanisms that control the topology of membrane proteins during their synthesis in the endoplasmic reticulum, and they also suggest possible cellular pathways by which (Ctm)PrP may cause disease.

Animals↗

Pott's puffy tumour: an unusual presentation and management.

Pott's puffy tumour is a rare clinical entity in this era of antibiotics. It is usually seen as a complication of frontal sinusitis. This is the first report of Pott's puffy tumour presenting as a complication of maxillary sinusitis. This is also the first reported case of Pott's puffy tumour treated with debridement and gentamicin beads. We discuss the clinical presentation and successful treatment of this rare disease.

Abscess↗

Most pathogenic mutations do not alter the membrane topology of the prion protein.

The prion protein (PrP), a glycolipid-anchored membrane glycoprotein, contains a conserved hydrophobic sequence that can span the lipid bilayer in either direction, resulting in two transmembrane forms designated (Ntm)PrP and (Ctm)PrP. Previous studies have shown that the proportion of (Ctm)PrP is increased by mutations in the membrane-spanning segment, and it has been hypothesized that (Ctm)PrP represents a key intermediate in the pathway of prion-induced neurodegeneration. To further test this idea, we have surveyed a number of mutations associated with familial prion diseases to determine whether they alter the proportions of (Ntm)PrP and (Ctm)PrP produced in vitro, in transfected cells, and in transgenic mice. For the in vitro experiments, PrP mRNA was translated in the presence of murine thymoma microsomes which, in contrast to the canine pancreatic microsomes used in previous studies, are capable of efficient glycolipidation. We confirmed that mutations within or near the transmembrane domain enhance the formation of (Ctm)PrP, and we demonstrate for the first time that this species contains a C-terminal glycolipid anchor, thus exhibiting an unusual, dual mode of membrane attachment. However, we find that pathogenic mutations in other regions of the molecule have no effect on the amounts of (Ctm)PrP and (Ntm)PrP, arguing against the proposition that transmembrane PrP plays an obligate role in the pathogenesis of prion diseases.

Amino Acid Substitution↗

Accumulation of protease-resistant prion protein (PrP) and apoptosis of cerebellar granule cells in transgenic mice expressing a PrP insertional mutation.

We have generated lines of transgenic mice that express a mutant prion protein (PrP) containing 14 octapeptide repeats whose human homologue is associated with an inherited prion dementia. These mice develop a neurological illness with prominent ataxia at 65 or 240 days of age, depending on whether the transgene array is, respectively, homozygous or hemizygous. Starting from birth, mutant PrP is converted into a protease-resistant and detergent-insoluble form that resembles the scrapie isoform of PrP, and this form accumulates dramatically in many brain regions throughout the lifetime of the mice. As PrP accumulates, there is massive apoptosis of granule cells in the cerebellum. Our analysis provides important insights into the molecular pathogenesis of inherited prion disorders in humans.

Animals↗