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Abstract
Objective To investigate sympathetic function in the peripheries of patients on chronic ambulatory peritoneal dialysis (CAPD) using noninvasive techniques. Design Comparison of peripheral blood flowresponses in sympathetic vasoconstrictor reflexes in CAPD patients and matched control subjects. Setting Tertiary care hospital and research institution. Patients Twenty-three clinically stable CAPD patients and 23 control subjects matched for age, sex, and drug therapy. Main Outcome Measures Sympathetic activity assessed from the reductions in hand and foot blood flow induced by a deep breath and by body surface cooling. Cardiac autonomic activity measured by the changes in heart rate produced by deep breathing, a Valsalva maneuver, and standing from lying. Results A deep breath induced mean decreases in hand blood flow of 65.1% in the patients and 82.8% in their matched controls. Corresponding reductions in the foot were 46.0% and 70.0%. Body surface cooling reduced mean hand blood flow by 50.3% in the patients an d 71.8% in the control subjects. Corresponding values in the foot were 26.7% and 43.6%. The differences in response between the patients and their matched control subjects were all significant (p < 0.01). Cardiac autonomic function assessed by standard tests of heart rate variability was significantly impaired in the patients compared with the control subjects in two of the three tests used (p < 0.001). Conclusions Cardiovascular autonomic impairment can affect the peripheral circulation as well as the heart in patients on dialysis, and this may have implications for cardiovascular homeostasis.
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Affiliation(s)
- Sarbjit V. Jassal
- Departments of Geriatric Medicine, Belfast City Hospital, Belfast, Northern Ireland
| | - Judith A. Allen
- Physiology, Belfast City Hospital, Belfast, Northern Ireland
| | - James F. Douglas
- The Queen's University of Belfast; Department of Nephrology, Belfast City Hospital, Belfast, Northern Ireland
| | - Robert w. Stout
- Departments of Geriatric Medicine, Belfast City Hospital, Belfast, Northern Ireland
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2
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Kirby LC, Banerjee A, Augustine T, Douglas JF. An ethical dilemma: malignant melanoma in a 51-year-old patient awaiting simultaneous kidney and pancreas transplantation for type 1 diabetes. Br J Dermatol 2017; 175:172-4. [PMID: 27484276 DOI: 10.1111/bjd.14554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2016] [Indexed: 11/26/2022]
Abstract
Malignant melanoma is a high-risk skin cancer that, in potential transplant recipients, is considered a substantial contraindication to solid organ transplantation due to significant risk of recurrence with immunosuppression. Current guidelines stipulate waiting between 3 and 10 years after melanoma diagnosis. However, in young patients with end-stage organ failure and malignant melanoma, complex ethical and moral issues arise. Assessment of the true risk associated with transplantation in these patients is difficult due to lack of prospective data, but an autonomous patient can make a decision that clinicians may perceive to be high risk. The national and worldwide shortage of available organs also has to be incorporated into the decision to maximize the net benefit and minimize the risk of graft failure and mortality. The incidence of malignant melanoma worldwide is increasing faster than that of any other cancer and continues to pose ethically challenging decisions for transplant specialists evaluating recipients for solid organ transplantation.
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Affiliation(s)
- L C Kirby
- Southport and Ormskirk District General Hospital, Ormskirk, U.K
| | - A Banerjee
- Wirral University Teaching Hospital, Wirral, U.K
| | - T Augustine
- Manchester Royal Infirmary, Manchester, U.K.,University of Manchester, Manchester, U.K
| | - J F Douglas
- Belfast City and Royal Victoria Hospitals, Belfast, U.K.,Queen's University Belfast, Belfast, U.K
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3
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Douglas JF. Dimitrios Oreopoulos, the plane tree of Kos and the Belfast City Hospital. Ulster Med J 2014; 83:31-6. [PMID: 24757266 PMCID: PMC3992091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Accepted: 08/29/2013] [Indexed: 11/15/2022]
Affiliation(s)
- James F Douglas
- Ballyrobert House, 5 Coyle's Lane, Belfast Road, Bangor BT15 1UF
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4
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Abstract
Advances in kidney transplantation over the past six decades have been impressive, but have not eliminated the significant variability in outcome related to donor organ quality. Organ shortage means that, in addition to 'standard' deceased donor kidneys (SD), 'non-standard donor' (NSD), 'expanded criteria donor', or 'marginal' kidneys, which fail to meet standard criteria and are often associated with less good outcomes, are now being transplanted into selected recipients as a means of increasing the donor pool. A similar, but less-documented, practice has developed in living donation. This article outlines the clinical rationale and ethical argument underpinning the use of such donor kidneys and examines their legal status in the UK, which we claim remains largely undefined and untested. While it is probable that the general principles governing medico-legal consent and liability also apply to organ donation, the special circumstances of donation, notably the inadequate supply of donors and the emphasis on a 'gift relationship', make it difficult to know how far existing medico-legal precedents can or should apply. The non-standard status of deceased donor organs creates potential problems for the validity of 'appropriate consent' to donation required by statute. It may also be relevant to the use of interventions intended to optimise deceased donor organ quality. Furthermore, the SD/NSD distinction in clinical practice may produce unexpected legal effects. For example, the recent UK Regulations 2012, which bring into force the EU Directive on standards of quality and safety of human organs intended for transplantation, could produce a negative legal restraint on the use of NSD kidneys. There is an urgent need for clarification of the effect of using NSDs in areas such as recipient and donor consent, liability for negligence, and the law of product liability. Some argue that the need for non-standard organs results from society's failure to compel the retrieval of all suitable standard organs from the deceased as a community resource. However, the Human Tissue Acts of 2004 and 2006 (Scotland), which govern organ donation and transplantation in the UK, expressly require individual consent or authorisation in the decision to donate. This emphasis on individual autonomy appears to chime with prevailing public opinion. However, the sense of medico-legal security gained by uncritical observance of the existing law and of directives published under its authority may be an obstacle to the development of a system which adequately meets the needs of recipients while safeguarding donor autonomy.
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Affiliation(s)
- Antonia J Cronin
- NIHR Biomedical Research Centre, Guy's and St. Thomas' NHS Foundation Trust and MRC Centre for Transplantation, King's College, London SE1 9RT, UK.
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5
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Affiliation(s)
- Antonia J Cronin
- NIHR Biomedical Research Centre, Guy's and St. Thomas' NHS Foundation Trust, MRC Centre for Transplantation, King's College London, London SE1 9RT, UK.
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6
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Plumb NC, Reber TJ, Koralek JD, Sun Z, Douglas JF, Aiura Y, Oka K, Eisaki H, Dessau DS. Low-energy (<10 meV) feature in the nodal electron self-energy and strong temperature dependence of the Fermi velocity in Bi{2}Sr{2}CaCu{2}O{8+δ}. Phys Rev Lett 2010; 105:046402. [PMID: 20867869 DOI: 10.1103/physrevlett.105.046402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Indexed: 05/29/2023]
Abstract
Using low photon energy angle-resolved photoemission, we study the low-energy dispersion along the nodal (π,π) direction in Bi{2}Sr{2}CaCu{2}O{8+δ} as a function of temperature. Less than 10 meV below the Fermi energy, the high-resolution data reveal a novel "kinklike" feature in the electron self-energy that is distinct from the larger well-known kink roughly 70 meV below E{F}. This new kink is strongest below the superconducting critical temperature and weakens substantially at higher temperatures. A corollary of this finding is that the Fermi velocity v{F}, as measured in this low-energy range, varies rapidly with temperature-increasing by almost 30% from 70 to 110 K. The behavior of v{F}(T) appears to shift as a function of doping, suggesting a departure from simple "universality" in the nodal Fermi velocity of cuprates.
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Affiliation(s)
- N C Plumb
- Department of Physics, University of Colorado, Boulder, Colorado 80309-0390, USA.
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7
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Douglas JF, Cronin AJ. Requested allocation of a deceased donor organ: laws and misconceptions. J Med Ethics 2010; 36:321. [PMID: 20511353 DOI: 10.1136/jme.2010.037135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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8
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Hobbie EK, Simien DO, Fagan JA, Huh JY, Chung JY, Hudson SD, Obrzut J, Douglas JF, Stafford CM. Wrinkling and strain softening in single-wall carbon nanotube membranes. Phys Rev Lett 2010; 104:125505. [PMID: 20366547 DOI: 10.1103/physrevlett.104.125505] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Indexed: 05/29/2023]
Abstract
The nonlinear elasticity of thin supported membranes assembled from length purified single-wall carbon nanotubes is analyzed through the wrinkling instability that develops under uniaxial compression. In contrast with thin polymer films, pristine nanotube membranes exhibit strong softening under finite strain associated with bond slip and network fracture. We model the response as a shift in percolation threshold generated by strain-induced nanotube alignment in accordance with theoretical predictions.
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Affiliation(s)
- E K Hobbie
- Department of Physics, Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, USA.
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9
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Douglas JF, Craig WJC. Long-term survival after renal transplantation: the influence of pretransplant bilateral nephrectomy. Clin Transpl 2010:133-140. [PMID: 21696036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The long-term survival of first successful renal transplants, along with overall patient survival, was studied retrospectively in 309 recipients at Belfast City Hospital between 1968 and 1986, of whom 155 had undergone prior bilateral nephrectomy (BN) and 154 had not (non-BN). The groups were comparable as regards mean age, gender, primary diagnoses, clinical status, pre-existing hypertension and pre-transplant dialysis and transfusion. There were 34 organs (BN 14, non-BN 20) from living related donors. Donor ages were comparable, as were histocompatibility findings. Recipients more than 60, with diabetic nephropathy, or with other co-morbidity were excluded. All recipients took azathioprine and low-dose steroid as maintenance antirejection, fewer than 3% switching to cyclosporine or other drugs during first graft survival. Mean BN graft survival was 15.9 years (95% CI 14.1-17.7) compared to 12.9 for non-BN (95% CI 11.3-14.5; p < 0.01). Mean BN patient survival was 19.4 years (95% CI 17.6-21.2) and non-BN was 14.9 years (95% CI 13.2-16.6; p < 0.01). Cumulative BN graft survival was 76.8% at 5 years, 61.6% at 10 years, and 37.4% at 20 years, compared to 67.1%, 53.5% and 27.0% for non-BN (p < 0.01). Overall BN patient survival was 84.5% at 5 years, 74.2% at 10 years and 51.6% at 20 years, with non-BN equivalents of 72.3%, 49.0% and 24.5%, respectively (p < 0.01). Long-term BN survivors also had less hypertension than non-BN (22.8% v 54.8% at 20 years; p < 0.05) which may be relevant to their better survival. Overall (BN plus non-BN) median graft (14.4 years) and patient (17.6 years) survival are testimony to the continuing long-term success of the low-dose steroid regime followed in Belfast from 1968 to 1986.
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Affiliation(s)
- James F Douglas
- Department of Nephrology and Clinical Pharmacology, Queen's University, UK
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10
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Affiliation(s)
- Antonia J Cronin
- MRC Centre for Transplantation, King's College London, London, UK.
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11
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Iwasawa H, Douglas JF, Sato K, Masui T, Yoshida Y, Sun Z, Eisaki H, Bando H, Ino A, Arita M, Shimada K, Namatame H, Taniguchi M, Tajima S, Uchida S, Saitoh T, Dessau DS, Aiura Y. Isotopic fingerprint of electron-phonon coupling in high-Tc cuprates. Phys Rev Lett 2008; 101:157005. [PMID: 18999630 DOI: 10.1103/physrevlett.101.157005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Indexed: 05/27/2023]
Abstract
Angle-resolved photoemission spectroscopy with low-energy tunable photons along the nodal direction of oxygen isotope substituted Bi(2)Sr(2)CaCu(2)O(8+delta) reveals a distinct oxygen isotope shift near the electron-boson coupling "kink" in the electronic dispersion. The magnitude (a few meV) and direction of the kink shift are as expected due to the measured isotopic shift of phonon frequency, and are also in agreement with theoretical expectations. This demonstrates the participation of the phonons as dominant players, as well as pinpointing the most relevant of the phonon branches.
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Affiliation(s)
- H Iwasawa
- Department of Applied Physics, Tokyo University of Science, Shinjuku-ku, Tokyo 162-8601, Japan
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12
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Koralek JD, Douglas JF, Plumb NC, Griffith JD, Cundiff ST, Kapteyn HC, Murnane MM, Dessau DS. Experimental setup for low-energy laser-based angle resolved photoemission spectroscopy. Rev Sci Instrum 2007; 78:053905. [PMID: 17552839 DOI: 10.1063/1.2722413] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
A laser-based angle resolved photoemission (ARPES) system utilizing 6 eV photons from the fourth harmonic of a mode-locked Ti:sapphire oscillator is described. This light source greatly increases the momentum resolution and photoelectron count rate, while reducing extrinsic background and surface sensitivity relative to higher energy light sources. In this review, the optical system is described, and special experimental considerations for low-energy ARPES are discussed. The calibration of the hemispherical electron analyzer for good low-energy angle-mode performance is also described. Finally, data from the heavily studied high T(c) superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) is compared to the results from higher photon energies.
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Affiliation(s)
- J D Koralek
- Department of Physics, University of Colorado, Boulder, CO 80309-0390, USA
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13
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Anopchenko A, Psurek T, VanderHart D, Douglas JF, Obrzut J. Dielectric study of the antiplasticization of trehalose by glycerol. Phys Rev E Stat Nonlin Soft Matter Phys 2006; 74:031501. [PMID: 17025634 DOI: 10.1103/physreve.74.031501] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 04/08/2006] [Indexed: 05/12/2023]
Abstract
Recent measurements have suggested that the antiplasticizing effect of glycerol on trehalose can significantly increase the preservation times of proteins stored in this type of preservative formulation. In order to better understand the physical origin of this phenomenon, we examine the nature of antiplasticization in trehalose-glycerol mixtures by dielectric spectroscopy. These measurements cover a broad frequency range between 40 Hz to 18 GHz (covering the secondary relaxation range of the fragile glass-former trehalose and the primary relaxation range of the strong glass-former glycerol) and a temperature (T) range bracketing room temperature (220 K to 350 K). The Havriliak-Negami function precisely fits our relaxation data and allows us to determine the temperature and composition dependence of the relaxation time tau describing a relative fast dielectric relaxation process appropriate to the characterization of antiplasticization. We observe that increasing the glycerol concentration at fixed T increases tau (i.e., the extent of antiplasticization) until a temperature dependent critical "plasticization concentration" xwp is reached. At a fixed concentration, we find a temperature at which antiplasticization first occurs upon cooling and we designate this as the "antiplasticization temperature," Tant. The ratio of the tau values for the mixture and pure trehalose is found to provide a useful measure of the extent of antiplasticization, and we explore other potential measures of antiplasticization relating to the dielectric strength.
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Affiliation(s)
- A Anopchenko
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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14
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Sun Z, Chuang YD, Fedorov AV, Douglas JF, Reznik D, Weber F, Aliouane N, Argyriou DN, Zheng H, Mitchell JF, Kimura T, Tokura Y, Revcolevschi A, Dessau DS. Quasiparticlelike peaks, kinks, and electron-phonon coupling at the (pi,0) regions in the CMR oxide La2-2x Sr1+2x Mn2 O7. Phys Rev Lett 2006; 97:056401. [PMID: 17026121 DOI: 10.1103/physrevlett.97.056401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Indexed: 05/12/2023]
Abstract
Using angle-resolved photoemission, we have observed sharp quasiparticlelike peaks in the prototypical layered manganite La(2-2x)Sr(1+2x)Mn(2)O(7) (x=0.36,0.38). We focus on the (pi,0) regions of k space and study their electronic scattering rates and dispersion kinks, uncovering bilayer-split bands, the critical energy scales, momentum scales, and strengths of the interactions that renormalize the electrons. To identify these bosons, we measured phonon dispersions in the energy range of the kink by inelastic neutron scattering, finding a good match in both energy and momentum to the oxygen bond-stretching phonons.
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Affiliation(s)
- Z Sun
- Department of Physics, University of Colorado, Boulder, CO 80309, USA
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15
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Koralek JD, Douglas JF, Plumb NC, Sun Z, Fedorov AV, Murnane MM, Kapteyn HC, Cundiff ST, Aiura Y, Oka K, Eisaki H, Dessau DS. Laser based angle-resolved photoemission, the sudden approximation, and quasiparticle-like spectral peaks in Bi2Sr2CaCu2O(8+delta). Phys Rev Lett 2006; 96:017005. [PMID: 16486502 DOI: 10.1103/physrevlett.96.017005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Indexed: 05/06/2023]
Abstract
A new low photon energy regime of angle-resolved photoemission spectroscopy is accessed with lasers and used to study the high T(C) superconductor Bi2Sr2CaCu2O(8+delta). The low energy increases bulk sensitivity, reduces background, and improves resolution. With this we observe spectral peaks which are sharp on the scale of their binding energy--the clearest evidence yet for quasiparticles in the normal state. Crucial aspects of the data such as the dispersion, superconducting gaps, and the bosonic coupling kink are found to be robust to a possible breakdown of the sudden approximation.
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Affiliation(s)
- J D Koralek
- Department of Physics, University of Colorado, Boulder, Colorado 80309-0390, USA.
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16
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Wang H, Douglas JF, Satija SK, Composto RJ, Han CC. Early-stage compositional segregation in polymer-blend films. ACTA ACUST UNITED AC 2005; 67:061801. [PMID: 16241248 DOI: 10.1103/physreve.67.061801] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2003] [Indexed: 11/07/2022]
Abstract
The existence of a transient period during the surface enrichment of a binary polymer blend by one of its components has been suggested by previous theoretical and experimental studies as well as computer simulations. Taking advantage of the high depth resolution of neutron reflectivity and the slow dynamics of polymers near their glass transition, we investigate this early-stage surface compositional enrichment in a phase separating polymer blend for the first time. Two stages of surface enrichment layer growth are observed. A rapid local surface enrichment at the chain segmental level occurs first, followed by a slower growth of a diffuse layer having a scale on the order of the bulk correlation length and the radius of gyration of the surface enriching polymer chains.
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Affiliation(s)
- H Wang
- Department of Materials Science and Engineering, Michigan Technological University, Michigan 49931, USA.
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17
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Abstract
Thin polymeric films are increasingly being utilized in diverse technological applications, and it is crucial to have a reliable method to characterize the stability of these films against dewetting. The parameter space that influences the dewetting of thin polymer films is wide (molecular mass, temperature, film thickness, substrate interaction) and a combinatorial method of investigation is suitable. We thus construct a combinatorial library of observations for polystyrene (PS) films cast on substrates having orthogonal temperature and surface energy gradients and perform a series of measurements for a range of molecular masses (1800 g/mol < M < 35 000 g/mol) and film thicknesses h (30 nm < h < 40 nm) to explore these primary parameter axes. We were able to obtain a near-universal scaling curve describing a wetting-dewetting transition line for polystyrene films of fixed thickness by introducing reduced temperature and surface energy variables dependent on M. Our observations also indicate that the apparent polymer surface tension gamma(p) becomes appreciably modified in thin polymer films from its bulk counterpart for films thinner than about 100-200 nm, so that bulk gamma(p) measurements cannot be used to estimate the stability of ultrathin films. Both of these observations are potentially fundamental for the control of thin film stability in applications where film dewetting can compromise film function.
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Affiliation(s)
- K M Ashley
- Polymer Program, Department of Chemistry, Howard University, Washington, DC 20059, USA
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Affiliation(s)
- A M Woodman
- Regional Nephrology Unit, Belfast City Hospital, Belfast BT9 7AB, Northern Ireland.
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19
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Middleton D, Douglas JF, Opelz G, Doehler B, McGeown MG. One thousand renal transplants in Belfast (1968-1998). Clin Transpl 2004:151-64. [PMID: 16704148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The first kidney transplant was performed in Belfast in 1968. During the next 30 years 1,000 transplants were undertaken at this unit. Data were analysed on 937 cadaveric transplants, 815 first and 122 regrafts. There were 63 living transplants. Long-term follow-up was achieved for all grafts except one live transplant. All recipients had follow-up of at least 5 years. One- and 5-year graft survival rates were 78.9% and 65.0% for first cadaveric grafts, 83.6% and 66.4% for regrafts and 85.7% and 68.3% for living transplants. Nine of 41 transplants performed more than 30 years ago are still functioning. Multivariate analysis determined risk factors for graft survival as recipient age, donor age, HLA-A mismatching, HLA cytotoxic antibody level and year of transplant. A conservative regime regarding the use of immunosuppression, HLA matching and crossmatching has proved successful in accomplishing good graft survival at this unit.
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Affiliation(s)
- Derek Middleton
- Northern Ireland Histocompatibility and Immunogenetics Laboratory, Belfast City Hospital, Belfast, Northern Ireland
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20
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Soles CL, Douglas JF, Wu WL, Dimeo RM. Incoherent neutron scattering and the dynamics of confined polycarbonate films. Phys Rev Lett 2002; 88:037401. [PMID: 11801085 DOI: 10.1103/physrevlett.88.037401] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2001] [Indexed: 05/23/2023]
Abstract
Incoherent elastic neutron scattering measurements are performed on thin (75 to 1015 A) polycarbonate films supported on Si wafers. We find that the mean-square atomic displacement <u(2)> is diminished by thin film confinement. For film thicknesses comparable to the unperturbed dimensions of the macromolecule, we observe two characteristic crossover temperatures in <u(2)> as a function of temperature T, one above and the other below the bulk T(g). Furthermore, the harmonic force constant kappa, defined by the low temperature dependence of <u(2)> (i.e., kappa approximately k(B)T/<u(2)>), increases as the film thickness decreases. These observations suggest that the atoms are more strongly localized in the thin supported films.
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Affiliation(s)
- C L Soles
- NIST Polymers Division, Gaithersburg, Maryland 20899-8541, USA
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21
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Mansfield ML, Douglas JF, Garboczi EJ. Intrinsic viscosity and the electrical polarizability of arbitrarily shaped objects. Phys Rev E Stat Nonlin Soft Matter Phys 2001; 64:061401. [PMID: 11736179 DOI: 10.1103/physreve.64.061401] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2001] [Indexed: 11/07/2022]
Abstract
The problem of calculating the electric polarizability tensor alpha(e) of objects of arbitrary shape has been reformulated in terms of path integration and implemented computationally. The method simultaneously yields the electrostatic capacity C and the equilibrium charge density. These functionals of particle shape are important in many materials science applications, including the conductivity and viscosity of filled materials and suspensions. The method has been validated through comparison with exact results (for the sphere, the circular disk, touching spheres, and tori), it has been found that 10(6) trajectories yield an accuracy of about four and three significant figures for C and alpha(e), respectively. The method is fast: For simple objects, 10(6) trajectories require about 1 min on a PC. It is also versatile: Switching from one object to another is easy. Predictions have also been made for regular polygons, polyhedra, and right circular cylinders, since these shapes are important in applications and since numerical calculations of high stated accuracy are available. Finally, the path-integration method has been applied to estimate transport properties of both linear flexible polymers (random walk chains of spheres) and lattice model dendrimer molecules. This requires probing of an ensemble of objects. For linear chains, the distribution function of C and of the trace (alpha(e)), are found to be universal in a size coordinate reduced by the chain radius of gyration. For dendrimers, these distribution functions become increasingly sharp with generation number. It has been found that C and alpha(e) provide important information about the distribution of molecular size and shape and that they are important for estimating the Stokes friction and intrinsic viscosity of macromolecules.
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Affiliation(s)
- M L Mansfield
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA
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McGeown MG, Douglas JF, Middleton D. One thousand renal transplants at Belfast City Hospital: post-graft neoplasia 1968-1999, comparing azathioprine only with cyclosporin-based regimes in a single centre. Clin Transpl 2001:193-202. [PMID: 11512313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
From 1968-1999, 868 recipients of 1,000 renal transplants were followed up for neoplasia. Altogether, 102 tumours were diagnosed in 94 patients (11.8% incidence). Eighty-seven occurred among 750 single and 15 occurred among 118 multiple graft recipients. Three of 11 patients with pre-existing tumour developed posttransplant neoplasia, either new or recurrent. The most frequently seen posttransplant neoplasms were squamous carcinoma of skin, basal cell carcinoma (BCC), posttransplant lymphoproliferative disease (PTLD) and gastro-intestinal (GI) cancer. Forty-one tumour-related deaths occurred (44% mortality). Patients on CSA (C) regimes had a greater cumulative incidence of tumour after transplantation than those on azathioprine and low-dose prednisolone alone (A regime) had--12.7% (34 of 268) vs. 4.5% (15 of 335) of those at risk up to 5 years (relative increased rate of incidence 2.4) with more early cases of PTLD. C-regime patients who developed neoplasia had been prescribed significantly higher CSA doses than tumour-free controls (4.5 vs. 3.4 mg/kg/day; p = 0.014). Patients who made a late conversion from the A to the C regime subsequently developed more neoplasms than nonconverted controls (25.7% vs. 12%), mainly due to early and often aggressive squamous carcinoma. Transplant survival figures were similar for both A- and C-regime groups. These findings suggest that current CSA doses are higher than are necessary for optimal graft survival and thus increase the risk of early neoplasia without any compensatory advantage. A dose reduction of CSA to less than 3.5 mg/kg/day in long-surviving, stable graft recipients should reduce tumour risk without imperilling function. Late conversion from the A to the C regime should be avoided where possible and CSA doses in this situation kept to a minimum.
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Affiliation(s)
- M G McGeown
- Department of Medicine, Queen's University of Belfast, Belfast, Northern Ireland
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23
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Smith AP, Douglas JF, Meredith JC, Amis EJ, Karim A. Combinatorial study of surface pattern formation in thin block copolymer films. Phys Rev Lett 2001; 87:015503. [PMID: 11461474 DOI: 10.1103/physrevlett.87.015503] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2000] [Indexed: 05/23/2023]
Abstract
Surface pattern formation in diblock copolymer films is investigated as a function of film thickness h and molecular mass M. Smooth films are observed for certain h ranges centered about multiples of the lamellar thickness L0, and we attribute this effect to an increase in the surface chain density with h in the outer brushlike copolymer layer. We also observe apparently stable labyrinthine surface patterns for other h ranges, and the average size of these patterns is found to scale as lambda approximately L0(-2.5). Hole and island patterns occur for h ranges between those of the labyrinthine patterns and the smooth regions, and their size similarly decreases with L0 and M.
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Affiliation(s)
- A P Smith
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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24
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Martys NS, Douglas JF. Critical properties and phase separation in lattice Boltzmann fluid mixtures. Phys Rev E Stat Nonlin Soft Matter Phys 2001; 63:031205. [PMID: 11308640 DOI: 10.1103/physreve.63.031205] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2000] [Indexed: 11/07/2022]
Abstract
Basic equilibrium properties of lattice Boltzmann (LB) fluid mixtures (coexistence curve, surface tension, interfacial profile, correlation length) are calculated to characterize the critical phenomena occurring in these model liquids and to establish a reduced variable description allowing a comparison with real fluid mixtures. We observe mean-field critical exponents and amplitudes so that the LB model may be useful for modeling high molecular weight polymer blends and other fluid mixtures approximated over a wide temperature range by mean-field theory. We also briefly consider phase separation under quiescent and shearing conditions and point out the strong influence of interacting boundaries on the qualitative form of the late-stage phase-separation morphology.
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Affiliation(s)
- N S Martys
- Building Materials Division, Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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25
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Allegrini P, Douglas JF, Glotzer SC. Dynamic entropy as a measure of caging and persistent particle motion in supercooled liquids. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:5714-24. [PMID: 11970467 DOI: 10.1103/physreve.60.5714] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/1998] [Indexed: 04/18/2023]
Abstract
The length-scale dependence of the dynamic entropy is studied in a molecular dynamics simulation of a binary Lennard-Jones liquid above the mode-coupling critical temperature T(c). A number of methods exist for estimating the entropy of dynamical systems, and we utilize an approximation based on calculating the mean first-passage time (MFPT) for particle displacement because of its tractability and its accessibility in real and simulation measurements. The MFPT dynamic entropy S(epsilon) is defined as equal to the inverse of the average first-passage time for a particle to exit a sphere of radius epsilon. This measure of the degree of chaotic motion allows us to identify characteristic time and space scales and to quantify the increasingly correlated particle motion and intermittency occurring in supercooled liquids. In particular, we identify a "cage" size defining the scale at which the particles are transiently localized, and we observe persistent particle motion at intermediate length scales beyond the scale where caging occurs. Furthermore, we find that the dynamic entropy at the scale of one interparticle spacing extrapolates to zero as the mode-coupling temperature T(c) is approached.
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Affiliation(s)
- P Allegrini
- Polymers Division and Center for Theoretical and Computational Materials Science, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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26
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Lee BP, Douglas JF, Glotzer SC. Filler-induced composition waves in phase-separating polymer blends. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:5812-22. [PMID: 11970479 DOI: 10.1103/physreve.60.5812] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/1999] [Indexed: 04/18/2023]
Abstract
The influence of immobile filler particles (spheres, fibers, platelets) on polymer-blend phase separation is investigated computationally using a generalization of the Cahn-Hilliard-Cook (CHC) model. Simulation shows that the selective affinity of one of the polymers for the filler surface leads to the development of concentration waves about the filler particles at an early stage of phase separation in near critical composition blends. These "target" patterns are overtaken in late-stage phase separation by a growing "background" spinodal pattern characteristic of blends without filler particles. The linearized CHC model is used to estimate the number of composition oscillations emanating from isolated filler particles. In far-off-critical composition blends, an "encapsulation layer" grows at the surface of the filler rather than a target pattern. The results of these simulations compare favorably with experiments on filled phase-separating ultrathin blend films in which the filler particles are immobilized on a solid substrate.
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Affiliation(s)
- B P Lee
- Polymers Division and Center for Theoretical and Computational Materials Science, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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27
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Ishinabe T, Douglas JF, Nemirovsky AM, Freed KF. Examination of the 1/d expansion method from exact enumeration for a self-interacting self-avoiding walk. ACTA ACUST UNITED AC 1999. [DOI: 10.1088/0305-4470/27/4/006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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28
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Abstract
BACKGROUND Autonomic neuropathy is frequently present in dialysis patients. In addition, deterioration of autonomic function occurs with ageing. This study examines the true prevalence of autonomic neuropathy in elderly dialysis patients and questions whether the combination of age and uraemia further increases the chance of dysautonomia being present. METHODS We compared the results of five different tests (30:15 ratio; Valsalva ratio; heart rate response to deep breathing and the blood pressure responses to sustained hand grip and standing) of parasympathetic and combined parasympathetic and sympathetic dysfunction in older haemodialysis patients (mean age 70.2 years), younger haemodialysis patients (mean age 48.1 years) and two groups of subjects with normal renal function (mean age 73.0 years and 42.5 years respectively). RESULTS Parasympathetic dysfunction was most prevalent in older patients on dialysis (65.9% (95% confidence intervals 51.4-80.4%), compared with 33.3% (95% confidence intervals 19.0-47.5% in younger dialysis patients), and 11.8 and 0% in the old and young control groups respectively). Combined parasympathetic and sympathetic dysfunction was seen in 41.5% (95% confidence intervals 26.5-56.5%) and 11.9% (95% confidence intervals 2.1-56.5%) of the old and young dialysis patients respectively but not in any of the control subjects. No interaction was seen between age and subject type. CONCLUSIONS We conclude that although older dialysis patients have severe impairment of cardiovascular autonomic innervation, the prevalence of dysfunction is not higher than would be expected in an ageing population with uraemia.
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Douglas JF. Laudatio for Professor Mary G. McGeown. Nephrol Dial Transplant 1998; 13:1380-3. [PMID: 9641164 DOI: 10.1093/ndt/13.6.1380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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30
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Jassal SV, Allen JA, Douglas JF, Stout RW. Autonomic function in patients on continuous ambulatory peritoneal dialysis. ARCH ESP UROL 1998; 18:46-51. [PMID: 9527029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE To investigate sympathetic function in the peripheries of patients on chronic ambulatory peritoneal dialysis (CAPD) using noninvasive techniques. DESIGN Comparison of peripheral blood flow responses in sympathetic vasoconstrictor reflexes in CAPD patients and matched control subjects. SETTING Tertiary care hospital and research institution. PATIENTS Twenty-three clinically stable CAPD patients and 23 control subjects matched for age, sex, and drug therapy. MAIN OUTCOME MEASURES Sympathetic activity assessed from the reductions in hand and foot blood flow induced by a deep breath and by body surface cooling. Cardiac autonomic activity measured by the changes in heart rate produced by deep breathing, a Valsalva maneuver, and standing from lying. RESULTS A deep breath induced mean decreases in hand blood flow of 65.1% in the patients and 82.8% in their matched controls. Corresponding reductions in the foot were 46.0% and 70.0%. Body surface cooling reduced mean hand blood flow by 50.3% in the patients and 71.8% in the control subjects. Corresponding values in the foot were 26.7% and 43.6%. The differences in response between the patients and their matched control subjects were all significant (p < 0.01). Cardiac autonomic function assessed by standard tests of heart rate variability was significantly impaired in the patients compared with the control subjects in two of the three tests used (p < 0.001). CONCLUSIONS Cardiovascular autonomic impairment can affect the peripheral circulation as well as the heart in patients on dialysis, and this may have implications for cardiovascular homeostasis.
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Affiliation(s)
- S V Jassal
- Department of Geriatric Medicine, The Queen's University of Belfast, Northern Ireland
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Abstract
Arrhythmias are frequent among the dialysis population and can cause symptoms of palpitations or dizziness. Since autonomic disturbances are known to cause an increased arrhythmogenic stimulus, we questioned whether the presence of central autonomic neuropathy increased the frequency of arrhythmias as identified by 24-hour electrocardiographic monitoring in dialysis patients. Seventy-one patients were randomly chosen from patients established on dialysis in two centers. The mean age of the patients was 71.3 years (median age, 67 years) and median duration on dialysis was 17.0 months (range, 1 to 175 months). Four patients had diabetes. Each patient was tested for autonomic control of blood pressure and heart rate, and underwent Holter electrocardiographic monitoring, commencing 30 minutes before dialysis, for a 24-hour period. The tapes were then analyzed for ventricular and atrial rhythm changes. There was a significantly increased incidence of arrhythmias in individuals with abnormal blood pressure responses (P = 0.005), heart rate responses (P = 0.01), and combined blood pressure and heart rate responses (P = 0.004). We conclude that patients with autonomic dysfunction had an increased frequency of arrhythmias during dialysis.
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Affiliation(s)
- S V Jassal
- Department of Geriatric Medicine, Queen's University, Belfast, United Kingdom.
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32
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Abstract
Oncogenicity studies of methyl tertiary-butyl ether (MTBE) vapor were conducted in CD-1 mice and Fischer 344 rats. Fifty animals of each sex per species per group were exposed for 6 h a day, 5 days per week to 0 (control), 400, 3000 and 8000 ppm MTBE vapor in air for 18 months (mice) and 24 months (rats). Both species showed reversible central nervous system depression at 8000 ppm for the first week of exposure, which continued for mice for the study duration. For the 8000 ppm mice, reduced body weight gain and early mortality prior to terminal euthanasia were exposure related. In the males, these deaths appear to be due to exacerbation of uropathy or dysuria, which occurs spontaneously in this strain. Increases in absolute and relative liver (both sexes) and kidney weight (males only) were seen at 3000 and 8000 ppm and decreases in brain and spleen weights were also noted (the latter decreases were without microscopic lesions and occurred at 8000 ppm only). An increase in hepatocellular hypertrophy occurred in both sexes at the two highest concentrations. The only neoplastic lesion found in this study in mice was an increased incidence of hepatocellular adenomas in females at the 8000 ppm exposure. In a follow-up study, a statistically significant elevation of cell proliferation in female mouse liver has been shown to occur following 5 days, but not 28 days, of exposure to 8000 ppm MTBE, suggesting that MTBE induces mitogenesis. For male rats, early euthanasia was required at week 82 and week 97 for the 8000 and 3000 ppm groups, respectively, due to excessive mortality from a severe progressive nephrosis. The end stage of this process appeared earlier in the male rats of all MTBE exposure groups; the incidence of this lesion and mortality for exposed females was comparable to control females. No exposure-related changes in hematological parameters were observed for any group at any time point, but a decrease in corticosterone levels was seen for male rats from the 8000 ppm group. Absolute and relative kidney and liver weight increases occurred in 3000 and 8000 ppm exposure groups, but the liver weight change was not accompanied by histopathological change. At study termination, increases in the incidence and severity of a chronic nephropathy in males from all exposure groups and in females exposed to 3000 and 8000 ppm was associated with secondary lesions of hyperplasia of the parathyroid and mineralization of tissues. Renal tubular cell tumors were increased in male rats exposed to 3000 and 8000 ppm. This may be associated with an accumulation of protein (stainable by Mallory's Heidenhain) in kidney tubular epithelial cells after 4 weeks of exposure. An increased incidence of interstitial cell adenomas of the testes was seen in males exposed to 3000 and 8000 ppm but was believed to be an artefact of an unusually low control incidence and not considered to be exposure related. Based on the above effects, the no-observed-effect level (NOEL) for chronic toxicity is 400 ppm, and the NOEL for carcinogenic effects is 3000 ppm (mice) and 400 ppm (rats).
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Affiliation(s)
- M G Bird
- Exxon Biomedical Sciences, Inc., East Millstone, NJ 08875, USA
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33
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Sigfússon G, Fricker FJ, Bernstein D, Addonizio LJ, Baum D, Hsu DT, Chin C, Miller SA, Boyle GJ, Miller J, Lawrence KS, Douglas JF, Griffith BP, Reitz BA, Michler RE, Rose EA, Webber SA. Long-term survivors of pediatric heart transplantation: a multicenter report of sixty-eight children who have survived longer than five years. J Pediatr 1997; 130:862-71. [PMID: 9202606 DOI: 10.1016/s0022-3476(97)70270-1] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Short-term survival after pediatric heart transplantation is now excellent, but ultimately the efficacy of this procedure will depend on duration and quality of survival. We sought to evaluate the clinical course of long-term survivors of heart transplantation in childhood. METHODS Patients who had undergone heart transplantation at the university hospitals of Stanford, Columbia, and Pittsburgh between 1975 and 1989 and survived longer than 5 years from transplantation were identified and their clinical courses retrospectively reviewed. RESULTS Sixty eight children have survived more than 5 years from transplantation, and 60 (88%) are currently alive with a median follow-up of 6.8 years (5 to 17.9 years). Thirteen have survived more than 10 years from transplantation. Renal dysfunction caused by immunosuppressive agents was common, and two patients required late renal transplantation. Lymphoproliferative disease or other neoplasm occurred in 12 patients, but none resulted in death. Coronary artery disease was diagnosed in 13 patients (19%), leading to retransplantation in eight. Death after 5 years was related to acute or chronic rejection in 5 of 8 cases. Two of the deaths were directly related to noncompliance with immunosuppressive medication. All survivors are in New York Heart Association class 1. CONCLUSIONS Long-term survival with good quality of life can be achieved after heart transplantation in childhood, though complications of immunosuppression remain common. Posttransplantation coronary artery disease is emerging as the main factor limiting long term graft and patient survival.
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Affiliation(s)
- G Sigfússon
- Department of Pediatrics, University of Pittsburgh, Pennsylvania, USA
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Abstract
Methyl tertiary-butyl ether (MTBE) is one of the highest production volume chemicals in the USA. Previous results from in vitro genetic toxicity studies suggested that it was not mutagenic. However, chronic exposure at high levels resulted in liver tumors in female mice and kidney tumors in male rats. The current program assessed in vivo genotoxicity and also explored the possibility that a mutagenic mechanism was involved in the carcinogenic process. The specific tests used included the Drosophila sex-linked-recessive-lethal test, the rat bone marrow cytogenetics test, the mouse bone marrow micronucleus test and the in vivo-in vitro hepatocyte unscheduled DNA synthesis test in the mouse. All tests produced negative results, indicating that the potential for in vivo mutagenic activity was low. These data also suggest that the tumorigenic activity was probably the result of a non-genotoxic process.
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Affiliation(s)
- R H McKee
- Exxon Biomedical Sciences, Inc., East Millstone, NJ 08875, USA
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35
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Bevan C, Tyl RW, Neeper-Bradley TL, Fisher LC, Panson RD, Douglas JF, Andrews LS. Developmental toxicity evaluation of methyl tertiary-butyl ether (MTBE) by inhalation in mice and rabbits. J Appl Toxicol 1997; 17 Suppl 1:S21-9. [PMID: 9179724 DOI: 10.1002/(sici)1099-1263(199705)17:1+3.3.co;2-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pregnant CD-1 mice (30 per group) and female New Zealand White rabbits (15 per group) were exposed by inhalation to 0, 1000, 4000 and 8000 ppm methyl tertiary-butyl ether (MTBE) vapor for 6 h a day during gestational days (GD) 6-15 and 6-18, respectively. Maternal body weights, clinical observations and food consumption were recorded throughout gestation for both species. At scheduled euthanization (GD 18 for mice and GD 29 for rabbits), fetuses were weighed, sexed and examined for external, visceral (including craniofacial) and skeletal alterations. For both species, the pregnancy rate was high and equivalent across all groups; no pregnant animals died or aborted. There were no does that delivered early, but there were three mouse dams in the control group and two dams in the 4000 ppm group that delivered early and were removed from the study. In mice, maternal body weights, body weight gain, corrected maternal gestational weight change and food consumption were significantly reduced in mice at 8000 ppm. Hypoactivity and ataxia were observed in dams exposed to 4000 and 8000 ppm. Gestational parameters affected at 8000 ppm included post-implantation loss (due to increased late resorptions and dead fetuses) and altered sex ratio (decreased males); fetal body weights per litter were reduced at 4000 and 8000 ppm. There was a significantly increased incidence of cleft palate at 8000 ppm; this resulted in increased incidences of pooled external and visceral malformations and of total malformations at this exposure concentration. There were also treatment-related increases in the incidence of individual skeletal variations at 4000 and 8000 ppm. In rabbits, maternal weight gain and food consumption were significantly reduced at 4000 and 8000 ppm. Relative liver weights were also reduced at 8000 ppm. All gestational parameters were equivalent across all groups, including pre- and post-implantation loss, fetal sex ratios, litter size and fetal weights/litter. There was no evidence of treatment-related teratogenicity observed at any dose tested in rabbits. The no-observed-effect levels (NOELs) for maternal and developmental toxicity were both 1000 ppm in mice and 1000 ppm and at least 8000 ppm, respectively, in rabbits.
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Affiliation(s)
- C Bevan
- Exxon Biomedical Sciences, Inc., East Millstone, NJ 08875, USA
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36
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Bird MG, Burleigh-Flayer HD, Chun JS, Douglas JF, Kneiss JJ, Andrews LS. Oncogenicity studies of inhaled methyl tertiary-butyl ether (MTBE) in CD-1 mice and F-344 rats. J Appl Toxicol 1997; 17 Suppl 1:S45-55. [PMID: 9179727 DOI: 10.1002/(sici)1099-1263(199705)17:1+3.3.co;2-b] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oncogenicity studies of methyl tertiary-butyl ether (MTBE) vapor were conducted in CD-1 mice and Fischer 344 rats. Fifty animals of each sex per species per group were exposed for 6 h a day, 5 days per week to 0 (control), 400, 3000 and 8000 ppm MTBE vapor in air for 18 months (mice) and 24 months (rats). Both species showed reversible central nervous system depression at 8000 ppm for the first week of exposure, which continued for mice for the study duration. For the 8000 ppm mice, reduced body weight gain and early mortality prior to terminal euthanasia were exposure related. In the males, these deaths appear to be due to exacerbation of uropathy or dysuria, which occurs spontaneously in this strain. Increases in absolute and relative liver (both sexes) and kidney weight (males only) were seen at 3000 and 8000 ppm and decreases in brain and spleen weights were also noted (the latter decreases were without microscopic lesions and occurred at 8000 ppm only). An increase in hepatocellular hypertrophy occurred in both sexes at the two highest concentrations. The only neoplastic lesion found in this study in mice was an increased incidence of hepatocellular adenomas in females at the 8000 ppm exposure. In a follow-up study, a statistically significant elevation of cell proliferation in female mouse liver has been shown to occur following 5 days, but not 28 days, of exposure to 8000 ppm MTBE, suggesting that MTBE induces mitogenesis. For male rats, early euthanasia was required at week 82 and week 97 for the 8000 and 3000 ppm groups, respectively, due to excessive mortality from a severe progressive nephrosis. The end stage of this process appeared earlier in the male rats of all MTBE exposure groups; the incidence of this lesion and mortality for exposed females was comparable to control females. No exposure-related changes in hematological parameters were observed for any group at any time point, but a decrease in corticosterone levels was seen for male rats from the 8000 ppm group. Absolute and relative kidney and liver weight increases occurred in 3000 and 8000 ppm exposure groups, but the liver weight change was not accompanied by histopathological change. At study termination, increases in the incidence and severity of a chronic nephropathy in males from all exposure groups and in females exposed to 3000 and 8000 ppm was associated with secondary lesions of hyperplasia of the parathyroid and mineralization of tissues. Renal tubular cell tumors were increased in male rats exposed to 3000 and 8000 ppm. This may be associated with an accumulation of protein (stainable by Mallory's Heidenhain) in kidney tubular epithelial cells after 4 weeks of exposure. An increased incidence of interstitial cell adenomas of the testes was seen in males exposed to 3000 and 8000 ppm but was believed to be an artefact of an unusually low control incidence and not considered to be exposure related. Based on the above effects, the no-observed-effect level (NOEL) for chronic toxicity is 400 ppm, and the NOEL for carcinogenic effects is 3000 ppm (mice) and 400 ppm (rats).
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Affiliation(s)
- M G Bird
- Exxon Biomedical Sciences, Inc., East Millstone, NJ 08875, USA
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37
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Abstract
Methyl t-butyl ether (MTBE) is a commonly used octane booster in gasoline. This study examines the pharmacokinetics and disposition of MTBE in Fischer-344 rats after i.v., oral, dermal and inhalation routes of administration. Groups of male and female rats were given single i.v. (40 mg kg-1), oral (40 and 400 mg kg-1) and dermal (40 and 400 mg kg-1 in occluded chambers) doses of [14C]MTBE. For inhalation studies, rats were exposed nose-only for 6 h to low (400 ppm), high (8000 ppm) and repeated daily 6-h low (400 ppm x 15 days) chamber concentrations of [14C]MTBE. Blood, expired air, and excreta (urine and feces) were collected at selected times up to 7 days post-dose and quantified for 14C content. Plasma concentrations of MTBE and t-butyl alcohol (TBA) were quantified and mean values used for pharmacokinetic analysis. The mean total recoveries of 14C ranged from 91 to 105%. Methyl t-butyl ether was rapidly and completely absorbed after oral and inhalation exposures; dermal absorption was low. After all routes, MTBE was rapidly eliminated from blood (ti = 0.5 h) by exhalation and metabolism to TBA. At the high doses, metabolism was saturated and the proportion of renal 14C excretion decreased relative to the pulmonary route. At 48 h post-exposure, virtually all of the 14C was eliminated. The major metabolites recovered in urine were 2-methyl-1,2-propanediol and alpha-hydroxyisobutyric acid. There were no significant gender or route-dependent differences in the pharmacokinetics and disposition of MTBE.
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Affiliation(s)
- M J Miller
- Exxon Biomedical Science, Inc., East Millstone, NJ 08875, USA
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Lington AW, Dodd DE, Ridlon SA, Douglas JF, Kneiss JJ, Andrews LS. Evaluation of 13-week inhalation toxicity study on methyl t-butyl ether (MTBE) in Fischer 344 rats. J Appl Toxicol 1997; 17 Suppl 1:S37-44. [PMID: 9179726 DOI: 10.1002/(sici)1099-1263(199705)17:1+3.3.co;2-h] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Methyl-t-butyl ether (MTBE) is widely used as an octane enhancing agent in gasoline. A 13-week inhalation study was conducted in Fischer 344 rats to provide information on potential target organs and toxicity of MTBE, and to ascertain a no-observed-adverse-effect level (NOAEL) for MTBE. Male and female Fischer 344 rats were exposed to target doses of MTBE vapor of 0, 800, 4000 and 8000 ppm for 6 h a day, 5 days per week for 13 weeks: MTBE produced no mortalities. At 8000 ppm, males and females showed a decrease in body weights compared to controls. The only notable effect on clinical observation was ataxia at 8000 ppm, which was apparent during the first 4 weeks of treatment. Mild hematological and clinical chemistry changes were observed in the 8000 ppm group. At 8000 ppm, animals showed increased serum levels of corticosteroids, which suggest some stress-like effect. At necropsy, there were no treatment-related gross lesions. Absolute and relative organ weights (liver, adrenals and kidneys) were increased in both sexes at 4000 and 8000 ppm, but there were no microscopic lesions in these tissues with the exception of the kidney. Microscopic examination of other tissues revealed no effects with the exception that at 8000 ppm, male rats showed: mild increased size of hyaline droplets within the kidney, mild increase in hemosiderosis in the spleen and higher incidence of hyperplasia in the lymph nodes. The highest NOAEL was judged at 800 ppm.
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Affiliation(s)
- A W Lington
- Exxon Biomedical Sciences, Inc., East Millstone, NJ 08875, USA
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Abstract
Methyl tertiary-butyl ether (MTBE) is an oxygenate that is added to gasoline to boost octane and enhance combustion, thereby reducing carbon monoxide and hydrocarbon tailpipe emissions. The acute and subchronic neurotoxicity of MTBE were evaluated in rats using a functional observation battery (FOB), measures of motor activity (MA) and a neuropathological evaluation. In the acute study, rats were exposed once to 0, 800, 4000 or 8000 ppm MTBE by inhalation for 6 h and then evaluated three times over a 24-h period. In the FOB evaluations, treatment-related effects were seen at the 1-h session immediately following exposure and were indicative of transient central nervous system (CNS) depression. Effects were most apparent in the high-dose group (8000 ppm) but were also evident to a lesser extent in the mid-dose (4000 ppm) group. Labored respiration, ataxia, duck-walk gait and decreases in muscle tone, hind-limb grip strength and treadmill performance were the most frequently noted findings. No significant effects were observed in the FOB when testing was conducted at 6 h and 24 h post-exposure. The pattern of motor activity measured in the different dose groups following exposure was also in keeping with a reversible CNS-depressant effect of MTBE. In the subchronic study, rats were exposed to 0, 800, 4000 or 8000 ppm MTBE for 6 h a day, 5 days per week, for 13 weeks. No persistent or cumulative effects on neurobehavioral function were found. Body weights and absolute brain weights were reduced in the 8000 ppm group, however there were no differences among groups when brain weight was expressed relative to body weight. No histopathological changes were noted in the brains or peripheral nervous tissues of MTBE-exposed animals. In summary, MTBE produced signs of acute reversible CNS depression following exposure to 8000 ppm and, to a lesser extent, to 4000 ppm vapor. The no-observed-adverse-effect level for these effects was 800 ppm in the present study. No persistent or cumulative neurotoxic effects were observed following exposure to MTBE at concentrations up to 8000 ppm for 13 weeks.
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Affiliation(s)
- W C Daughtrey
- Exxon Biomedical Sciences, Inc. East Millstone, NJ 08875, USA
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Douglas JF. Swelling and growth of polymers, membranes, and sponges. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 54:2677-2689. [PMID: 9965381 DOI: 10.1103/physreve.54.2677] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Sung L, Karim A, Douglas JF, Han CC. Dimensional crossover in the phase separation kinetics of thin polymer blend films. Phys Rev Lett 1996; 76:4368-4371. [PMID: 10061272 DOI: 10.1103/physrevlett.76.4368] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Garboczi EJ, Douglas JF. Intrinsic conductivity of objects having arbitrary shape and conductivity. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 53:6169-6180. [PMID: 9964979 DOI: 10.1103/physreve.53.6169] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Jassal SV, Douglas JF, Stout RW. Prognostic markers in older patients starting renal replacement therapy. Nephrol Dial Transplant 1996; 11:1052-7. [PMID: 8671968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
AIMS We assessed all patients starting renal replacement therapy during a 1-year period to identify factors influencing 1-year survival in older and younger dialysis patients. METHODS Data was collected from 113 patients. Twenty-four possible prognostic factors were introduced into a multivariate, time-based analysis. RESULTS Hazard ratios, and hence risk of mortality, were increased with increasing alcohol consumption, cardiac dyskinesis, age at onset of dialysis, serum phosphate, number of comorbid illnesses, and Karnofsky score (listed in decreasing order of risk). Risk of death within 1 year was reduced in patients with normal serum albumin and higher Barthel scores at the time of commencing dialysis. No age interactions were found. In the elderly age group the risk of death was also increased if left ventricular dilatation was present. Comorbidity and the age of onset were not independent risk factors in patients aged over 65 years at the time of starting dialysis. CONCLUSIONS All factors listed above increase the 1-year mortality of elderly patients. Factors known to increase medium-term morbidity in dialysis patients including diabetes mellitus, ischaemic heart disease, and hypertension do not appear to be important in the short-term survival of older patient on dialysis.
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Affiliation(s)
- S V Jassal
- Department of Geriatric Medicine, Queen's University of Belfast, Whitla Medical Building, 97 Lisburn Road, Belfast, BT9 7BL, UK
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Hobbie EK, Nakatani AI, Yajima H, Douglas JF, Han CC. Shear suppression of critical fluctuations in a diluted polymer blend. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 53:R4322-R4325. [PMID: 9964914 DOI: 10.1103/physreve.53.r4322] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Hsu DT, Quaegebeur JM, Michler RE, Smith CR, Rose EA, Kichuk MR, Gersony WM, Douglas JF, Addonizio LJ. Heart transplantation in children with congenital heart disease. J Am Coll Cardiol 1995; 26:743-9. [PMID: 7642869 DOI: 10.1016/0735-1097(95)00253-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVES The aim of this study was to describe heart transplantation in children with congenital heart disease and to compare the results with those in children undergoing transplantation for other cardiac diseases. BACKGROUND Reports describe decreased survival after heart transplantation in children with congenital heart disease compared with those with cardiomyopathy. However, transplantation is increasingly being considered in the surgical management of children with complex congenital heart disease. Present-day results from this group require reassessment. METHODS The diagnoses, previous operations and indications for transplantation were characterized in children with congenital heart disease. Pretransplant course, graft ischemia time, post-transplant survival and outcome (rejection frequency, infection rate, length of hospital stay) were compared with those in children undergoing transplantation for other reasons (n = 47). RESULTS Thirty-seven children (mean [+/- SD] age 9 +/- 6 years) with congenital heart disease underwent transplantation; 86% had undergone one or more previous operations. Repair of extracardiac defects at transplantation was necessary in 23 patients. Causes of death after transplantation were donor failure in two patients, surgical bleeding in two, pulmonary hemorrhage in one, infection in four, rejection in three and graft atherosclerosis in one. No difference in 1- and 5-year survival rates (70% vs. 77% and 64% vs. 65%, respectively), rejection frequency or length of hospital stay was seen between children with and without congenital heart disease. Cardiopulmonary bypass and donor ischemia time were significantly longer in patients with congenital heart disease. Serious infections were more common in children with than without congenital heart disease (13 of 37 vs. 6 of 47, respectively, p = 0.01). CONCLUSIONS Despite the more complex cardiac surgery required at implantation and longer donor ischemic time, heart transplantation can be performed in children with complex congenital heart disease with success similar to that in patients with other cardiac diseases.
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Affiliation(s)
- D T Hsu
- Department of Pediatrics, College of Physicians and Surgeons, Columbia University, Babies Hospital, New York, New York 10032, USA
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Garboczi EJ, Snyder KA, Douglas JF, Thorpe MF. Geometrical percolation threshold of overlapping ellipsoids. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 52:819-828. [PMID: 9963485 DOI: 10.1103/physreve.52.819] [Citation(s) in RCA: 201] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
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Douglas JF, Ishinabe T. Self-avoiding-walk contacts and random-walk self-intersections in variable dimensionality. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 51:1791-1817. [PMID: 9962837 DOI: 10.1103/physreve.51.1791] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kholodenko AL, Douglas JF. Generalized Stokes-Einstein equation for spherical particle suspensions. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 51:1081-1090. [PMID: 9962752 DOI: 10.1103/physreve.51.1081] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
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Karim A, Satija SK, Douglas JF, Ankner JF, Fetters LJ. Neutron reflectivity study of the density profile of a model end-grafted polymer brush: Influence of solvent quality. Phys Rev Lett 1994; 73:3407-3410. [PMID: 10057373 DOI: 10.1103/physrevlett.73.3407] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Douglas JF, Zhou HX, Hubbard JB. Hydrodynamic friction and the capacitance of arbitrarily shaped objects. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1994; 49:5319-5331. [PMID: 9961860 DOI: 10.1103/physreve.49.5319] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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