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R Berger

Publications and source records attributed to R Berger.

At least 55 records · Page 3Linked to original sources
PubMed2002

Element specific surface reconstructions of islands during surfactant-mediated growth on Si (111).

The early stages of surfactant- (As, Sb) mediated homoepitaxial growth on Si (111) are examined by scanning tunneling microscopy and extensive ab initio calculations of Si(n) clusters (n</=12). The results reveal the different microscopic behavior of the two surfactants: On As-covered Si (111), one exclusively finds two-dimensional islands with double-layer height which show the (1 x 1) terrace structure. On Sb-covered Si (111), the islands show two different reconstructions: at the rim of the islands a (1 x 1) structure appears, while in the center the (square root 3 x square root 3) terrace structure is observed.

Journal Article↗
PubMed2002

Observation of saturation of energy transfer between copropagating beams in a flowing plasma.

Experiments demonstrate energy and power transfer between copropagating, same frequency, beams crossing at a small angle in a plasma with a Mach 1 flow. The process is interpreted as amplification of the low intensity probe beam by the stimulated scatter of the high intensity pump beam. The observed probe amplification increases slowly with pump intensity and decreases with probe intensity, indicative of saturation limiting the energy and power transfer due to ion-wave nonlinearities and localized pump depletion. The results are consistent with numerical modeling including ion-wave nonlinearities.

Journal Article↗
PubMed2002

Resting oxygen consumption and in vivo ADP are increased in myopathy due to complex I deficiency.

BACKGROUND: Patients with isolated complex I deficiency (CID) in skeletal muscle mitochondria often present with exercise intolerance as their major clinical symptom. OBJECTIVE: To study the in vivo bioenergetics in patients with complex I deficiency in skeletal muscle mitochondria. METHODS: In vivo bioenergetics were studied in three of these patients by measuring oxygen uptake at rest and during maximal exercise, together with forearm ADP concentrations ([ADP]) at rest. Whole-body oxygen consumption at rest (VO(2)) was measured with respiratory calorimetry. Maximal oxygen uptake (VO(2)max) was measured during maximal exercise on a cycle ergometer. Resting [ADP] was estimated from in vivo (31)P MRS measurements of inorganic phosphate, phosphocreatine, and ATP content of forearm muscle. RESULTS: Resting VO(2) was significantly increased in all three patients: 128 +/- 14% (SD) of values in healthy control subjects. VO(2)max in patients was on average 2.8 times their VO(2) at rest and was only 28% of VO(2)max in control subjects. Resting [ADP] in forearm muscle was significantly increased compared with healthy control subjects (patients 26 +/- 2 microM, healthy controls 9 +/- 2 microM). CONCLUSION: In patients with CID, the increased whole-body oxygen consumption rate at rest reflects increased electron transport through the respiratory chain, driven by a decreased phosphorylation potential. The increased electron transport rate may compensate for the decreased efficiency of oxidative phosphorylation (phosphorylation potential).

Adenosine Diphosphate↗
PubMed2002

Improved direct measurement of A(b) and A(c) at the Z(0) pole using a lepton tag.

The parity violation parameters A(b) and A(c) of the Zb(b) and Zc(c) couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the Z(0) pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-1998 SLD sample of 550,000 Z(0) decays produced with highly polarized electron beams, we measure A(b) = 0.919+/-0.030(stat)+/-0.024(syst), and A(c) = 0.583+/-0.055(stat)+/-0.055(syst).

Journal Article↗
PubMed2002

Surfactant mediated heteroepitaxy versus homoepitaxy: kinetics for group-IV adatoms on As-passivated Si(111) and Ge(111).

Using ab initio calculations we have determined the paths and activation energies for diffusion of group-IV atoms (Si, Ge, and Sn) on top of the As layer on As-passivated Si(111), and for exchange with an As atom. The kinetics of Si, Ge, and Sn adatoms is substantially different: Si adatoms are readily incorporated under the As layer. Ge adatoms diffuse far on top of the As layer and can reach existing steps. We show for the first time that the ratio between diffusion and exchange barriers depends strongly on the strain of the growing Ge film. Sn atoms remain on top of the As layer.

Journal Article↗
PubMed2002

Tc and Re chelates of 8alpha-amino-6-methyl-ergoline: synthesis and affinity to the dopamine D2 receptor.

The influence of structural changes at the 8alpha-amino position of 8alpha-amino-6-methyl-ergoline on the lipophilicity and affinity to the D2 receptor was studied. 8alpha-amino-6-methyl-ergoline (1) was converted into the derivatives (2a-f) by mercaptoacetylation of the amino group to make it possible to prepare the rhenium and technetium complexes (3, 4a,b). Binding tests on cloned human dopamine D2 receptors show that the affinities of the coordination compounds (IC50 values between 50 and 240 nM) are less than those of the derivatives 2a-f (IC50=3-50 nM) but more than those of the parent compound 1. Biodistribution studies of the Tc complexes 4a,b performed on Wistar rats show a slow blood clearance with substantial accumulation and retention in the liver and kidneys and low brain uptake.

Animals↗
PubMed2002

A pilot study to assess physician knowledge in transfusion medicine.

INTRODUCTION: An assessment of transfusion medicine knowledge and practice in Canada was carried out over a 3-week period. METHODS: Fifty-five questions were posed to evaluate both basic information on blood and blood products and on clinical use. The form was distributed through the Canadian Society for Transfusion Medicine with designated individuals asked to handle regional distribution. Some used provincial mailing lists, others distributed within each hospital. Approximately, 2000 forms were sent, including 500 in French. RESULTS: A total of 294 forms were returned; answers were recorded as 'correct', 'incorrect', 'no answer' or with 'added comments'. Overall, 52% of the questions were answered correctly or were answered with qualifying comments. In clinical practice questions, 63% were answered correctly or with qualifying comments. Basic knowledge questions drew correct answers in 37% of the cases. Several issues were answered poorly. The volume of an apheresis plasma unit was correctly estimated by less than 10% of respondents with many understanding the volume (500-600 mL) by as much as 300-400 mL. Anaesthesiologists responded most often (21%); few haematologists participated (4%). Provincial response varied: most were received from Ontario (30%) and British Columbia (22%). CONCLUSIONS: The answers show that clinical application of transfusion is generally accompanied by a questioning process - it is not entirely by rote. Basic knowledge about products needs improvement.

Blood Transfusion↗
PubMed2002

Prediction of outcome by neurohumoral activation, the six-minute walk test and the Minnesota Living with Heart Failure Questionnaire in an outpatient cohort with congestive heart failure.

AIMS: To compare the precursor of atrial and brain natriuretic peptide (N-ANP, N-BNP), brain natriuretic peptide (BNP), big endothelin-1, the 6-min walk test and the Minnesota Living with Heart Failure Questionnaire (LHFQ) with regard to short-term outcome in an ambulatory heart failure population. METHODS AND RESULTS: Ninety-six individuals (left ventricular ejection fraction of 26+/-10%) were included in the study. Within 1 day blood samples of N-ANP, N-BNP, BNP and big endothelin-1 were obtained, and the 6-min walk test and LHFQ were measured. The predictive power of these variables - including renin-angiotensin system antagonist therapy - in respect of 1-year event-free survival were calculated with a Cox regression analysis. All investigated variables had the power to predict outcome in a univariate analysis. Multivariate analysis revealed that N-ANP (chi-square=58 P<0.0001), BNP (chi-square=8 P<0.01), the LHFQ (chi-square=6 P<0.02) and the renin-angiotensin system antagonist (chi-square=4 P<0.05), are independent predictors. CONCLUSION: We conclude that, in an open clinical cohort of patients with large differences in the progression of the disease, N-ANP, BNP and LHFQ are the most reliable predictors of worsening heart failure in the short term. However, the dosage of the ACE inhibitor influenced short-term survival in this population.

Activities of Daily Living↗
PubMed2002

Selection of autologous CD4+ T-cells for adoptive T-cell substitution in patients with CD23+ B-cell CLL.

BACKGROUND: B-cell CLL (B-CLL) is accompanied by a progressive decrease in cellular immune functions, and treatment-related immunosuppression can further aggravate T-cell immunodeficiency. To reduce the risks of T-cell depletion, it seems feasible to collect autologous CD4+ cells at an early disease stage and subsequently reinfuse them during periods of profound T-cell depletion. METHOD: We describe a two-step cell-selection method to obtain highly enriched CD4+ T-cells from leukapheresis compounds of patients with CD23+ B-CLL. The double selection procedure was performed using the CellPro Ceperate device, and consisted of CD4+ selection followed by CD23 purging to further remove contaminating CD23+ B-cells from the CD4+ cell fraction. The results of eight runs performed with leukapheresis material obtained from eight patients with CD23+ B-CLL at different disease stages are presented. RESULTS: The CD4/CD23 double cell-selection procedure resulted in the purification of > 90% CD4+ cells. Median recovery of CD4+ T lymphocytes after selection was 46%, and was negatively affected by the initial tumor cell load. The final T-cell fraction still contained lymphocytes of the B-CLL clone, as determined by FACS and PCR. The cell-processing procedure had no impact on T-cell function, as assessed by the in vitro production of the cytokine interferon-gamma. Moreover, the selected CD4+ cells retained their capacity to co-stimulate mitogen-induced B-cell IgG production in vitro. CONCLUSION: The described CD4 selection/CD23 depletion strategy is a suitable approach to obtaining high numbers of functional active autologous CD4+ T cells for adoptive T-cell transfer in patients with CD23+ BCLL.

Aged↗
PubMed2001

Synthesis of nodulisporic acid 2' '-oxazoles and 2' '-thiazoles.

[reaction--see text] The semisynthetic conversion of nodulisporic acid A (1) into a set of three heterocyclic side chain derivatives provided compounds, highlighted by 6, with an improved spectrum of ectoparasiticidal activity and pharmacokinetic profile relative to the natural product.

Animals↗
PubMed2001

B-cell acute lymphoblastic leukemia with tandem t(14;14)(q11;q32).

Translocation (14;14)(q11;q32) was associated with acute lymphoblastic leukemia in a child. The B-cell lineage of the leukemic cells led us to perform FISH studies, which showed that the chromosomal breakpoints were telomeric to TCRA/D and IGH loci. These findings show that FISH analyses are necessary when unusual features are associated with a recurrent translocation.

Burkitt Lymphoma↗
PubMed2001

Involvement of a human gene related to the Drosophila spen gene in the recurrent t(1;22) translocation of acute megakaryocytic leukemia.

The recurrent t(1;22)(p13;q13) translocation is exclusively associated with infant acute megakaryoblastic leukemia. We have identified the two genes involved in this translocation. Both genes possess related sequences in the Drosophila genome. The chromosome 22 gene (megakaryocytic acute leukemia, MAL) product is predicted to be involved in chromatin organization, and the chromosome 1 gene (one twenty-two, OTT) product is related to the Drosophila split-end (spen) family of proteins. Drosophila genetic experiments identified spen as involved in connecting the Raf and Hox pathways. Because almost all of the sequences and all of the identified domains of both OTT and MAL proteins are included in the predicted fusion protein, the OTT-MAL fusion could aberrantly modulate chromatin organization, Hox differentiation pathways, or extracellular signaling.

Amino Acid Sequence↗
PubMed2001

Effects of endothelin a receptor blockade on endothelial function in patients with chronic heart failure.

BACKGROUND: Chronic heart failure (CHF) is associated with impaired endothelium-dependent vasodilation and increased basal vascular tone due, in part, to elevated endothelin-1 plasma levels. In the present study, we investigated whether a reduction of vascular tone using an endothelin A receptor blocker attenuates the impairment of endothelium-dependent, flow-mediated vasodilation (FMD). METHODS AND RESULTS: Twenty-one patients with CHF randomly received either the endothelin A receptor blocker LU 135252 (30 mg/d, n=7; 300 mg/d, n=7) or a placebo (n=7). Using high-resolution ultrasound, FMD and endothelium-independent, nitroglycerin-induced dilation of the brachial artery were assessed at baseline in the 21 patients with CHF and in 11 controls and after 3 weeks treatment in the 21 patients with CHF. FMD at baseline was impaired in all 21 patients with CHF (3.2+/-2%) when compared with the 11 controls (9.7+/-4.9%; P=0.0005). In comparison with baseline, FMD significantly improved after 3 weeks of treatment with LU 135252 in all 14 patients receiving it (from 3.0+/-2.0% to 4.9+/-2.9%; P=0.04), but FMD remained unchanged with placebo. Subgroup analysis, according to different dosages, revealed a significant increase of FMD compared with baseline (from 2.4+/-1.5% to 5.5+/-2.4%; P=0.03) in the patients treated with the low-dose (30 mg/d), whereas a high dose of 300 mg/d failed to increase FMD significantly. Improvement in the high-dose group, however, may have been masked by reduced vasodilator capacity due to a significant increase in vessel size (from 4.8+/-0.4 to 5.1+/-0.7 mm; P=0.03). CONCLUSIONS: These results suggest that endothelin A receptor blockade improves FMD in CHF patients.

Blood Flow Velocity↗
PubMed2001

The TEL-Jak2 oncoprotein induces Socs1 expression and altered cytokine response in Ba/F3 cells.

The leukemia-associated TEL-Jak2 fusion protein possesses a constitutive tyrosine kinase activity and transforming properties in hematopoietic cell lines and animal models. In the murine pro-B Ba/F3 cell line, this fusion constitutively activates the Signal Transducer and Activator of Transcription 5 (Stat5) factors and, as a consequence, induces the sustained expression of various Stat5-target genes including the Cytokine Inducible SH2-containing protein (Cis) gene, which codes for a member of the Suppressor of Cytokine Signaling (Socs) protein family. In TEL-Jak2-transformed Ba/F3 cells, we also observed the upregulation of the Socs1 gene, whose product has been reported to negatively regulate the Jak kinase activity. In transient transfection experiments, Socs1 physically interacts with TEL-Jak2 and interferes with the TEL-Jak2-induced phosphorylation and activation of Stat5 factors, probably through the Socs1-induced proteasome-mediated degradation of the fusion protein. Interestingly, TEL-Jak2-expressing Ba/F3 cells were found to be resistant to the anti-proliferative activities of gamma interferon (IFN-gamma) seemingly as a consequence of Socs1 constitutive expression. These results indicate that the Socs1-dependent cytokine feedback loop, although active, is bypassed by the TEL-Jak2 fusion, but may play a role in the leukemogenic process by altering the cytokine responses of the leukemic cells. Our results also suggest that Socs1 plays a role in shutting down the signaling from the normally activated Jak2 kinase by inducing its proteasome-dependent degradation.

Animals↗
PubMed2001

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons.

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.

Journal Article↗
PubMed2001

First symmetry tests in polarized Z0 decays to bbg.

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.

Journal Article↗