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R Carr

Publications and source records attributed to R Carr.

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

Magnetisation reorientation in ultra-thin Fe films on Cu(100) upon deposition of Co.

Ultra thin films of Fe deposited on the (100) surface of a Cu single crystal exhibit a net perpendicular magnetic anisotropy. The addition of very low coverages of Co results in the easy magnetic direction reorienting into the film plane. This behavior is in contrast to the addition of similar amounts of Fe, whereupon the ferromagnetic response vanishes. This result is discussed in terms of the anisotropy energies derived from the spectroscopic data.

Journal Article↗
PubMed2001

Magnetic X-ray circular dichroism on in situ grown 3d magnetic thin films on surfaces.

Epitaxic thin and ultrathin films on surfaces allow crystallographic phases that do not occur naturally in the bulk to be stabilized. They also offer new possibilities for an improved understanding of soft X-ray photoabsorption in magnetic systems. Data collected using the Elliptically Polarizing Undulator at BL 5.2 of the Stanford Synchrotron Radiation Laboratory are presented herein. Fe, Co and Ni films were prepared on Cu(100) surfaces. L2,3-edge spectra were recorded with circular and linear light. Fresnel diffractometry was used to quantify the degree of transverse beam coherence. A quantitative analysis of the spectral features indicates a correlation of the spectral intensities and the transverse beam coherence. Resonant reflectivity spectra for Co ultrathin films that exhibit strong dichroism are presented. The reflectivity data indicate that interference effects of the reflected beams at the two interfaces are of importance, even for ultrathin films.

Journal Article↗
PubMed2001

Atypical lipoma of the tongue.

We report an atypical lipoma arising in the tongue of a 43-year-old man who presented with an indolent dorsal lingual swelling. Atypical lipomas contain multivacoulated lipoblasts, which distinguishes them from benign lipomas. The superficial location in this case distinguishes this tumour from well-differentiated liposarcoma, which is biologically similar in lacking the propensity for metastasis. The superficial location of atypical lipoma allows a complete resection, which is often not possible for the deep-seated counterpart. Atypical lipoma and well-differentiated liposarcoma, if left in situ, may undergo transition to de-differentiated liposarcoma. Atypical lipoma should be completely excised with a cuff of normal tissue in order to prevent repeated local recurrence and the possibility of de-differentiation.

Adult↗
PubMed2000

Strange magnetism and the anapole structure of the proton.

The violation of mirror symmetry in the weak force provides a powerful tool to study the internal structure of the proton. Experimental results have been obtained that address the role of strange quarks in generating nuclear magnetism. The measurement reported here provides an unambiguous constraint on strange quark contributions to the proton's magnetic moment through the electron-proton weak interaction. We also report evidence for the existence of a parity-violating electromagnetic effect known as the anapole moment of the proton. The proton's anapole moment is not yet well understood theoretically, but it could have important implications for precision weak interaction studies in atomic systems such as cesium.

Journal Article↗
PubMed2000

Camptothecin-stabilised topoisomerase I-DNA complexes in leukaemia cells visualised and quantified in situ by the TARDIS assay (trapped in agarose DNA immunostaining).

We have shown that the TARDIS assay (trapped in agarose DNA immunostaining) can be used to detect DNA-topoisomerase I (topo I) cleavable complexes in situ in individual cells following treatment with topo I-targeting drugs. This assay is a modification of the assay for DNA-topoisomerase II (topo II) cleavable complexes (Willmore et al., Mol Pharmacol 53: 78-85, 1998). Drug-stabilised topo I-DNA complexes were detected in situ by topo I-specific primary antibodies and then visualised using fluorescein isothiocyanate conjugated second antibodies. Immunofluorescence was then quantified using a cooled slow-scan coupled device camera and image analysis procedures. Camptothecin (CPT) was shown to stabilise topo I-DNA cleavable complexes in whole cells in a dose-dependent manner in both CCRF-CEM and K562 cells and in lymphoblasts from an adult with newly diagnosed acute myeloid leukaemia treated ex vivo with CPT. In K562 cells, cleavable complexes were found to be maximal between 30 and 90 minutes continuous exposure of CPT, and approximately 78% of cleavable complexes formed in these cells were found to be reversed within 5 minutes of drug removal. It has also been shown that the immunofluorescence detected by the TARDIS assay was specific for topo I-targeting agents. Hence, the TARDIS assay provides a powerful tool to determine the levels of drug-stabilised cleavable complexes in whole cells and thereby aid in the understanding of the mechanism of interaction between topo I-targeting drugs and their target.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Parity violation in elastic electron-proton scattering and the Proton's strange magnetic form factor

We report a new measurement of the parity-violating asymmetry in elastic electron scattering from the proton at backward scattering angles. This asymmetry is sensitive to the strange magnetic form factor of the proton as well as electroweak axial radiative corrections. The new measurement of A = -4.92+/-0.61+/-0.73 ppm provides a significant constraint on these quantities. The implications for the strange magnetic form factor are discussed in the context of theoretical estimates for the axial corrections.

Journal Article↗
PubMed2000

Influence of source coherence on x-ray absorption spectroscopy.

Core-level x-ray absorption spectroscopy measurements have been performed at the L3,2 edges of Fe and Co thin films. The degree of source coherence was varied using soft x rays from five different beam lines. We observe an increase of the L edge resonance intensities relative to the continuum states which we propose is due to the presence of transverse coherence in the exciting radiation.

Journal Article↗
PubMed2000

Living liver donor surgery: report of initial anesthesia experience.

The charts and anesthetic records of 12 patients who donated the left lateral segment of their liver to a related infant or child to treat liver failure were retrospectively reviewed. Blood loss, need for transfusion, fluids administered, surgical length, and perioperative complications were investigated. The records also were examined to determine the hemodynamic stability of patients undergoing donor hepatectomy to assess their need for invasive monitoring. There were no episodes of hypotension or hemodynamic instability. The average operating time was 9.6 +/- 1.1 hours. The blood loss was 562 +/- 244 mL (range 300 to 1100 mL). Four patients received their own cell saver blood (200 mL, 220 mL, 300 mL, 475 mL), and one patient received 1 U (350 mL) of predonated autologous blood. The average hemoglobin decreased significantly (p = 0.001) from a preoperative value of 14.1 +/- 1.2 to 12.3 +/- 1.8 g/dL in the recovery room. All patients were extubated in the operating room or recovery room. Patients were discharged home in 6.9 +/- 1.3 days (range 5 to 9 days). Living-related liver resection can be performed with noninvasive monitoring and without the need for heterologous blood products.

Adult↗
PubMed2000

Hypopyon uveitis and iris nodules in non-Hodgkin's lymphoma: ocular relapse during systemic remission.

We report the case history of a patient with peripheral non-Hodgkin's lymphoma in systemic remission, who presented with a pseudohypopyon and iris nodules. Iris biopsy confirmed the presence of intraocular tumour, which subsequently responded to orbital radiation. Ocular remission, however, was soon followed by a systemic relapse, suggesting that the eye may act as a sanctuary site for tumour cells during chemotherapy, and that cells may metastasize from the eye back to the periphery during systemic remission.

Adult↗
PubMed2000

A 5-year review of 71 consecutive anterior skull base tumours.

Techniques used in craniofacial surgery have found extensive application in the management of skull base tumours. The improved exposure gained via osteotomies for facial disassembly has facilitated the en-bloc resection of tumours with clear surgical margins, and the advent of vascularised seals has significantly reduced the risk of meningeal contamination. We present our experience with the extirpation and reconstruction of 71 benign and malignant tumours of the anterior skull base over a 5-year period. Survival and functional outcome data are presented, with an emphasis on the wide range of pathologies and primary treatment strategies seen at presentation. Criteria used in flap selection and the role of prosthetics are discussed. Observations are offered on salvage surgery, demonstrating that excellent palliation can be achieved, even in cases with massive recurrent disease.

Adolescent↗
PubMed1999

A randomized, controlled trial of prophylactic granulocyte-macrophage colony-stimulating factor in human newborns less than 32 weeks gestation.

OBJECTIVE: Preterm neonates undergoing intensive care have high morbidity from sepsis. These infants also frequently develop neutropenia, and when this is associated with sepsis, mortality is high. This study investigates the potential for granulocyte-macrophage colony-stimulating factor (GM-CSF) to effect a clinically relevant increase in neutrophil number when used prophylactically in high-risk preterm neonates, and assesses its safety in this population. DESIGN: In an open, randomized, controlled study, 75 neonates (25 small for gestational age) <32 weeks gestation were randomized to receive GM-CSF (10 microg/kg/d) by subcutaneous injection for 5 days from <72 hours after birth, or to a control group. The primary outcome measure was the neutrophil count during 14 days from study entry. The infants were monitored for potential toxicity. Clinical outcomes, sepsis, and mortality, were recorded, but this initial study was not designed to address clinical benefit. RESULTS: Prophylactic GM-CSF therapy completely abolished neutropenia in treated infants, when both well and septic, throughout the period of study. Neutropenia (</=1.7 x 10(9)/L) developed in 16 of 39 control infants. Five control infants experienced an acute decrease in neutrophil count coincident with the onset of sepsis. There was no evidence of hematologic, respiratory, or gastrointestinal toxicity in treated infants. Treated infants had a trend to fewer symptomatic, blood culture positive septic episodes than controls during 2 weeks from study entry (11/36 vs 18/39). CONCLUSION: Five-day prophylactic GM-CSF completely abolishes postnatal neutropenia and sepsis-induced neutropenia in preterm neonates at high risk of sepsis, and so removes an important risk factor for sepsis and sepsis-related mortality.GM-CSF, preterm neonates, neutropenia, sepsis.

Blood Cell Count↗
PubMed1998

Immunotoxicological assessment of methyl parathion in female B6C3F1 mice.

Methyl parathion is a widely used agricultural insecticide, and the recent unlicensed use of this compound in homes has led to the evacuation of approximately 1100 persons in Mississippi. Although the primary concern in such cases of acute exposure is neurotoxicity, a few organophosphorus compounds apparently have immunotoxic effects at dosages that do not produce neurotoxic symptoms. The purpose of the present study was to determine if this is the case for methyl parathion. Female B6C3F1 mice were exposed to methyl parathion by gavage, daily for 7, 14, 2 1, or 28 d (at 6 mg/kg/d). Exposure for 14-28 d produced significant, dose-responsive inhibition of acetylcholin-esterase (the target molecule for methyl parathion-induced neurotoxicity) in brain or plasma, indicating that the compound was active. The following immunological parameters were evaluated: white blood cell counts and differentials, spleen and thymus weight and cellularity, splenic natural killer cell activity, nitrite production by peritoneal macrophages following activation in vitro, antibody response to sheep erythrocytes in vitro and in vivo, the cytotoxic T lymphocyte response to allogeneic tumor cells, and resistance to Streptococcus agalactiae and B16F10 melanoma cells. Methylparathion at 1 or 3 mg/kg/d significantly increased splenic natural killer cell activity. Nitrite production by macrophages was increased in mice treated with 1, 3, or 6 mg/kg/d. The antibody response to sheep erythrocytes in vitro was significantly suppressed, but the humoral response to sheep erythrocytes in vivo was not affected. The cytotoxic T-lymphocyte response to allogeneic tumor cells was not significantly affected. Host resistance was not significantly decreased. Although it remains possible that immunological parameters not tested here may be affected by methyl parathion, the present results do not suggest substantial immunotoxic potential for this compound.

Acetylcholinesterase↗
PubMed1998

Detection of lymphoma in bone marrow by whole-body positron emission tomography.

Positron emission tomography (PET) is a whole-body imaging technique using 18 fluorine-fluorodeoxyglucose (FDG), whose uptake is increased in tumor cells. Published studies have shown PET to be an effective method of staging lymphoma and to be more sensitive than CT at detecting extranodal disease. The purpose of this study was to determine whether the increased marrow uptake of FDG observed in some lymphoma patients during routine staging PET scans represented marrow involvement by disease. PET scans of 50 patients with Hodgkin's (12) and non-Hodgkin's (38) lymphoma were analyzed by three independent observers and the marrow graded as normal or abnormal using a visual grading system. Unilateral iliac crest marrow aspirates and biopsies were performed on all patients. The PET scan and marrow histology agreed in 39 patients (78%), being concordant positive in 13 and concordant negative in 26 patients. In 8 patients the PET scan showed increased FDG uptake but staging biopsy was negative; in 4 of these 8 patients the PET scan showed a normal marrow background with focal FDG "hot spots" distant from the site biopsied. In 3 patients the marrow biopsy specimen was positive but the PET scan normal; 2 of these 3 patients had non-Hodgkin's lymphoma whose malignant cells did not take up FDG at lymph node or marrow disease sites. Therefore, there were only 5 patients (10%) in whom there was a difference between the PET scan and biopsy result which could not be fully explained. Visual interpretation of marrow FDG uptake during whole-body staging PET scans can correctly assess marrow disease status in a high proportion of lymphoma patients. PET has the potential to reduce the need for staging marrow biopsy.

Biopsy↗
PubMed1997

Combined liver-total bowel transplantation has no immunologic advantage over total bowel transplantation alone. A prospective study in a porcine model.

BACKGROUND: Rejection remains a major obstacle to successful bowel transplantation in humans. It has been suggested that a simultaneous liver transplant would shield the bowel graft from immunologic attack, but the liver shortage would be aggravated. In a preclinical model, we studied the influence of simultaneous liver grafting by comparing the incidence of early bowel rejection after combined liver-total (small- and large-) bowel transplants vs total bowel transplants alone. METHODS: We assessed the incidence of early post-transplant rejection, graft-vs-host disease, and infection after combined liver-total bowel transplants (group 1, n = 10) and total bowel transplants alone (group 2, n = 9) in outbred Yorkshire Landrace pigs. Liver and bowel grafts were transplanted orthotopically with portal vein drainage after recipient hepatectomy (group 1) and total enterectomy (groups 1 and 2). Posttransplant immunosuppression was performed with intravenous tacrolimus (whole blood levels, 15 to 30 ng/mL) and prednisolone. In groups 1 and 2, bowel biopsy specimens from the ileostomy were obtained daily. In group 1, liver biopsy specimens were obtained weekly. Rejection was graded according to a 4-point scoring system (none, mild, moderate, and severe). RESULTS: Overall graft survival at days 7, 14, and 21 was 89%, 44%, and 11%, respectively, in group 1 vs 100%, 100%, and 86%, respectively, in group 2 (P < .001). Death rates owing to (irreversible) rejection at days 7, 14, and 21 were 0% in groups 1 and 2 (P = .48). Grading of bowel rejection episodes, based on the results of daily biopsy specimens, was not significantly different between the groups whether on individual days or overall. In group 1, the incidence of liver rejection episodes was as high as 66% (day 14 and at autopsy). At autopsy, generalized graft-vs-host disease (skin, native intestine, and native liver) was noted in 55% of group 1 and 43% of group 2 pigs (P = .55). Graft-vs-host disease was noted concurrently with rejection episodes of the liver or bowel grafts. CONCLUSIONS: Simultaneous liver grafting did not further reduce the incidence of early bowel rejection or graft-vs-host disease when compared with total bowel transplants alone. Based on the results of this preclinical study, simultaneous liver grafting is not indicated for patients with short-bowel syndrome and normal liver function.

Animals↗
PubMed1997

Persistent polyclonal B-cell lymphocytosis in identical twins.

This is the first report of the unusual syndrome of persistent polyclonal B-cell lymphocytosis occurring in monozygotic twins. The syndrome is characterized by a lymphocytosis, with circulating atypical, binucleated lymphocytes, mild splenomegaly and raised serum IgM. It occurs predominantly in females, with serological evidence of previous EBV infection, and is associated with cigarette smoking and HLA-DR7 phenotype. The association with .DR7 suggests a genetic predisposition. Its occurrence in identical twins, documented here, provides stronger support for a hereditary/genetic basis for the syndrome.

Adult↗