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P Middleton

Publications and source records attributed to P Middleton.

At least 37 records · Page 2Linked to original sources
PubMed2001

Cell surface expression and turnover of the alpha-subunit of the epithelial sodium channel.

The renal epithelial cell line A6, derived from Xenopus laevis, expresses epithelial Na(+) channels (ENaCs) and serves as a model system to study hormonal regulation and turnover of ENaCs. Our previous studies suggest that the alpha-subunit of Xenopus ENaC (alpha-xENaC) is detectable as 150- and 180-kDa polypeptides, putative immature and mature alpha-subunit heterodimers. The 150- and 180-kDa alpha-xENaC were present in distinct fractions after sedimentation of A6 cell lysate through a sucrose density gradient. Two anti-alpha-xENaC antibodies directed against distinct domains demonstrated that only 180-kDa alpha-xENaC was expressed at the apical cell surface. The half-life of cell surface-expressed alpha-xENaC was 24-30 h, suggesting that once ENaC matures and is expressed at the plasma membrane, its turnover is similar to that reported for mature cystic fibrosis transmembrane conductance regulator. No significant changes in apical surface expression of alpha-xENaC were observed after treatment of A6 cells with aldosterone for 24 h, despite a 5.3-fold increase in short-circuit current. This lack of change in surface expression is consistent with previous observations in A6 cells and suggests that aldosterone regulates ENaC gating and increases channel open probability.

Aldosterone↗
PubMed2000

Differential effects of protein kinase C on the levels of epithelial Na+ channel subunit proteins.

Regulation of epithelial Na(+) channel (ENaC) subunit levels by protein kinase C (PKC) was investigated in A6 cells. PKC activation altered ENaC subunit levels, differentially decreasing the levels of both beta and gamma, but not alphaENaC. Temporal regulation of beta and gammaENaC by PKC differed; gammaENaC decreased with a time constant of 3.7 +/- 1.0 h, whereas betaENaC decreased in 13.9 +/- 3. 0 h. Activation of PKC also resulted in a decrease in trans-epithelial Na(+) reabsorption for up to 48 h. PMA activation of PKC resulted in negative feedback inhibition of PKC protein levels beginning within 4 h. Both beta and gammaENaC levels, as well as transport tended toward pretreatment values after 48 h of PMA treatment. PKC inhibitors attenuated the effects of PMA on ENaC subunit levels and Na(+) transport. These results directly show for the first time that PKC differentially regulates ENaC subunit levels by decreasing the levels of beta and gamma but not alphaENaC protein. These results imply a PKC-dependent, long term decrease in Na(+) reabsorption.

Aldosterone↗
PubMed2000

Anti-D administration after childbirth for preventing Rhesus alloimmunisation.

BACKGROUND: The development of Rh immunisation and its prophylactic use since the 1970s has meant that severe Rhesus D (RhD) alloimmunisation is now rarely seen. OBJECTIVES: The objective of this systematic review was to assess the effects of giving anti-D to Rhesus negative women, with no anti-D antibodies, who had given birth to a Rhesus positive infant. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Controlled Trials Register, MEDLINE (from 1966 to January 1999) and reference lists of relevant articles. Date of last search of Cochrane Controlled Trials Register: January 1999. SELECTION CRITERIA: Randomised trials in Rhesus negative women without antibodies who were given anti-D immunoglobulin postpartum compared with no treatment or placebo. DATA COLLECTION AND ANALYSIS: Assessments of inclusion criteria, trial quality and data extraction were done by each author independently. Initial analyses included all trials. Other analyses assessed the effect of trial quality, ABO compatibility and dose. MAIN RESULTS: Six eligible trials compared postpartum anti-D prophylaxis with no treatment or placebo. The trials involved over 10,000 women, but trial quality varied. Anti-D lowered the incidence of RhD alloimmunisation six months after birth (relative risk 0.04, 95% confidence interval 0.02 to 0.06), and in a subsequent pregnancy (relative risk 0.12, 95% confidence interval 0. 07 to 0.23). These benefits were seen regardless of the ABO status of the mother and baby and when anti-D was given within 72 hours of birth. Higher doses (up to 200 micro grams) were more effective than lower doses (up to 50 micro grams) in preventing RhD alloimmunisation in a subsequent pregnancy. REVIEWER'S CONCLUSIONS: Anti-D, given within 72 hours after childbirth, reduces the risk of RhD alloimmunisation in Rhesus negative women who have given birth to a Rhesus positive infant. However the evidence on the optimal dose is limited.

Female↗
PubMed2000

Examining impacts of visibility and PM strategies before implementation.

One of the major challenges facing the world today is defining paths to sustainable futures. Part of the challenge is developing a national energy strategy that promotes an adequate energy supply for the United States, while enhancing environmental quality and maintaining U.S. competitiveness in the world economy. To assist in this challenge, we have developed a screening technique to analyze the effectiveness of different proposed emissions reduction strategies. The technique, referred to as the visibility assessment screening technique (VAST), is designed to examine possible impacts on visibility of emission changes of sulfur oxides, nitrogen oxides, volatile organic compounds (i.e., SO2, NOx, and VOC) and fine and coarse particulate matter (PM). The influence of relative humidity, natural aerosols, and the chemical interconnections among sulfur and nitrogen components of aerosols in determining the effectiveness of Clean Air Act Amendment and other projected energy-related emissions changes on eastern and western visibility are explored. The effectiveness of these strategies on particulate matter impacts and potentially on ozone is also noted.

Air Pollution↗
PubMed2000

Rubella virus vaccine associated arthropathy in postpartum immunized women: influence of preimmunization serologic status on development of joint manifestations.

OBJECTIVE: To measure preimmunization rubella virus (RV)-specific IgG levels and to relate these to the development of acute and chronic (persistent or recurrent) joint manifestations following rubella vaccination. METHODS: Specific IgG was determined by whole RV enzyme immunoassays (EIA) (Abbott Rubazyme and M33, an in-house method), immunoblot, neutralization domain peptide (BCH-178c) EIA, and neutralization bioassay in prevaccine samples of 268 RV seronegative women (Abbott absorbance < 0.999 units) who had received monovalent live attenuated RA27/3 strain RV vaccine in a clinical trial that recorded joint manifestations. RESULTS: Of rubella vaccinated women tested for prevaccine antibodies, 21.7% were actually positive (> or = 10 IU/ml) by M33 EIA, 33.2% had Abbott values > or = 0.250 units, and 47.6% had RV protein-specific antibody (immunoblot), while only 17.6% were positive (> or = 10 IU/ml) by neutralization domain peptide EIA and 12.7% had neutralization titers > or = 1:8. Seropositivity by the various methods was compared to recorded occurrence of acute and chronic arthropathy (arthralgia and/or arthritis) after RV vaccination. Relative to women who had no joint manifestations, prevaccine seropositivity rates for subjects with acute arthropathy were significantly (p < 0.05) lower in the Abbott test (< 0.250 units), BCH-178c peptide EIA, and neutralization bioassay, while those who also developed chronic arthropathy had significantly lower prevaccine seropositivity rates for the Abbott (< 0.250 units) and M33 EIA and neutralization bioassay. CONCLUSION: Results suggest that risk for arthropathy following RA27/3 rubella vaccination may be higher in women who have very low prevaccine levels of antibody, particularly in assays measuring functional (neutralizing) antibodies.

Adult↗
PubMed1999

Ca2+ sensitivity of BK channels in GH3 cells involves cytosolic phospholipase A2.

To test the hypothesis that intracellular Ca2+ activation of large-conductance Ca2+-activated K+ (BK) channels involves the cytosolic form of phospholipase A2 (cPLA2), we first inhibited the expression of cPLA2 by treating GH3 cells with antisense oligonucleotides directed at the two possible translation start sites on cPLA2. Western blot analysis and a biochemical assay of cPLA2 activity showed marked inhibition of the expression of cPLA2 in antisense-treated cells. We then examined the effects of intracellular Ca2+ concentration ([Ca2+]i) on single BK channels from these cells. Open channel probability (Po) for the cells exposed to cPLA2 antisense oligonucleotides in 0.1 microM intracellular Ca2+ was significantly lower than in untreated or sense oligonucleotide-treated cells, but the voltage sensitivity did not change (measured as the slope of the Po-voltage relationship). In fact, a 1,000-fold increase in [Ca2+]i from 0.1 to 100 microM did not significantly increase Po in these cells, whereas BK channels from cells in the other treatment groups showed a normal Po-[Ca2+]i response. Finally, we examined the effect of exogenous arachidonic acid on the Po of BK channels from antisense-treated cells. Although arachidonic acid did significantly increase Po, it did so without restoring the [Ca2+]i sensitivity observed in untreated cells. We conclude that although [Ca2+]i does impart some basal activity to BK channels in GH3 cells, the steep Po-[Ca2+]i relationship that is characteristic of these channels involves cPLA2.

Arachidonic Acid↗
PubMed1998

Carboxylmethylation of the beta subunit of xENaC regulates channel activity.

The action of aldosterone to increase apical membrane permeability in responsive epithelia is thought to be due to activation of sodium channels. Aldosterone stimulates methylation of a 95-kDa protein in apical membrane of A6 cells, and we have previously shown that methylation of a 95-kDa protein in the immunopurified Na+ channel complex increases open probability of these channels in planar lipid bilayers. We report here that aldosterone stimulates carboxylmethylation of the beta subunit of xENaC in A6 cells. In vitro translated beta subunit, but not alpha or gamma, serves as a substrate for carboxylmethylation. Carboxylmethylation of ENaC reconstituted in planar lipid bilayers leads to an increase in open probability only when beta subunit is present. When the channel complex is immunoprecipitated from A6 cells and analyzed by Western blot with antibodies to the three subunits of xENaC, all three subunits are recognized as constituents of the complex. The results suggest that Na+ channel activity in A6 cells is regulated, in part, by carboxylmethylation of the beta subunit of xENaC.

Aldosterone↗
PubMed1997

Randomised double-blind placebo-controlled study on adverse effects of rubella immunisation in seronegative women.

BACKGROUND: The objective of our study was to investigate the association of adverse clinical musculoskeletal and neurological events in healthy postpartum women with live attenuated (RA27/3 strain) rubella-virus vaccine, and to assess the frequency of acute and recurrent arthralgia and arthritis and associations with acute and recurrent muscle pain (myalgia) and neurological manifestations (paraesthesias). METHODS: We used a randomised placebo-controlled, double-blind design in a community setting. 636 women were enrolled and, after 90 women dropped out, 546 healthy women aged 18-41 years, who were rubella seronegative on routine screening were immunised parenterally with either monovalent live attenuated (RA27/3 strain) rubella vaccine (n = 270) or saline placebo (n = 276) in the postpartum period. Outcome measures were the occurrence of acute and persistent or recurrent joint manifestations (arthralgia or arthritis) at 1, 3, 6, 9, and 12 months after immunisation. Occurrence of muscle pain (myalgia), and neurological symptoms (paraesthesia) was also assessed at the same times. FINDINGS: 543 women completed 1-month follow-up. 456 women completed the 12-month assessment. There were no differences at the time of immunisation between rubella vaccine and placebo groups in distribution of age, ethnic origin, parity, time between delivery and immunisation, breastfeeding history, or histories of earlier rubella vaccination or joint complaints. Results indicated a significantly higher incidence (p = 0.006; odds ratio = 1.73 [95% CI = 1.17-2.57]) of acute joint manifestations in rubella-vaccine recipients (30%) than in placebo recipients (20%). Frequency of chronic (recurrent) arthralgia or arthritis was only marginally significant (p = 0.042; 1.58 [1.01-2.45]). INTERPRETATION: RA27/3 rubella vaccine given to seronegative women during the postpartum period was significantly associated with development of acute arthralgia or arthritis. Although the numbers of women assessed and length of follow-up revealed only marginally significant differences in persistent or recurrent joint manifestations between rubella vaccine and placebo recipients, it is possible that susceptible women who are given rubella vaccination may experience this outcome.

Adolescent↗
PubMed1997

Alpha interferon gene deletions in post-transplant lymphoma.

Post-transplant lymphoproliferative disorder (PTLD) is a well-recognized complication of organ transplant and has been associated with high mortality using conventional chemotherapy. We have investigated 11 cases of PTLD for alterations to the interferon alpha (IFNA) and p16 genes on chromosome 9p using archival material. 4/9 (44%) cases had deletions of the IFNA genes, in contrast to 1/59 (1.7%) cases of intermediate/high-grade de novo NHL drawn from the same geographical region. PTLD may therefore represent a distinct NHL subgroup exhibiting distinct gene pathology.

Chromosomes, Human, Pair 9↗
PubMed1994

VAT for dental practices--a short guide.

There have been many stories concerning VAT and dental practices over the past year, sometimes true but often distorting the facts. This article attempts to document the current state of play so that practitioners can make their own decision on registration.

Dental Equipment↗
PubMed1994

Molecular heterogeneity of variant Philadelphia translocations in childhood acute lymphoblastic leukaemia.

In acute lymphoblastic leukemia (ALL), it is unclear whether variant Philadelphia (Ph) translocations have the same molecular and clinical implications as the classical translocation. Two children with Ph+ ALL with variant translocations are described. One, in whom cytogenetic remission was not achieved, had evidence of translocation of c-abl to chromosome 22, rearrangement of minor breakpoint cluster region (mBCR) and expression of hybrid bcr/abl transcripts. In the other case, no gene rearrangement was found and complete remission was achieved. Variant Ph translocations in childhood ALL are heterogeneous at the molecular level. Molecular studies coupled with observations of clinical outcome are needed in larger numbers of such children to determine whether poor clinical response correlates with bcr/abl involvement and to allow planning of appropriate therapeutic strategies.

Child↗
PubMed1993

Lipid modifications of G proteins: alpha subunits are palmitoylated.

A small number of membrane-associated proteins are reversibly and covalently modified with palmitic acid. Palmitoylation of G-protein alpha and beta subunits was assessed by metabolic labeling of subunits expressed in simian COS cells or insect Sf9 cells. The fatty acid was incorporated into all of the alpha subunits examined (alpha s, alpha o, alpha i1, alpha i2, alpha i3, alpha z, and alpha q), including those that are also myristoylated (alpha o, alpha i, and alpha z). Palmitate was released by treatment with base, suggesting attachment to the protein through a thioester or ester bond. Limited tryptic digestion of activated alpha o and alpha s resulted in release of the amino-terminal portions of the proteins and radioactive palmitate. These data are consistent with palmitoylation of the proteins near their amino termini, most likely on Cys-3. Reversible acylation of G-protein alpha subunits may provide an additional mechanism for regulation of signal transduction.

Animals↗
PubMed1993

Dentistry--the challenge of the nineties.

Members of the dental profession over the past decade have been forced to recognise their identity as small businesses as well as healthcare professionals. This recognition has been painful for many.

Dentistry↗
PubMed1992

Philadelphia positive acute leukaemia with minor breakpoint cluster rearrangement may be a stem cell disease.

The biology of Philadelphia chromosome positive (Ph+) acute lymphoblastic leukaemia (ALL) is the subject of much interest. We present a case of Ph+ ALL with a minor breakpoint cluster (mBCR) rearrangement who subsequently relapsed with Ph+ mBCR+ acute myeloid leukaemia and later with Ph+ mBCR+ acute stem cell leukaemia. This case provides further evidence that Ph+ ALL with a mBCR rearrangement may arise from a pluripotent stem cell with similar potential to that of chronic granulocytic leukaemia to undergo blastic crises with differing lineage characteristics.

Acute Disease↗
PubMed1991

Secondary acute lymphoblastic leukaemia with 4:11 translocation following treatment for Hodgkin's disease: case report and review of the literature.

It is apparent that treatment of Hodgkin's disease can be complicated by the development of secondary leukaemia. Most such leukaemias are of the non-lymphocytic type. We describe here a patient treated for Hodgkin's disease with chemo- and radiotherapy who developed secondary acute lymphoblastic leukaemia with a non-random chromosomal abnormality t(4;11). The frequency of such cases is assessed by a literature review and evidence for their pluripotent cell origin is discussed.

Adult↗