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Biomedical subjects

I Brock

Publications and source records attributed to I Brock.

At least 19 recordsLinked to original sources
PubMed2006

Charmonium Decays of Y(4260), psi(4160), and psi(4040).

Using data collected with the CLEO detector operating at the CESR e+e- collider at sqrt[s]=3.97-4.26 GeV, we investigate 15 charmonium decay modes of the psi(4040), psi(4160), and Y(4260) resonances. We confirm, at 11 sigma significance, the BABAR Y(4260)-->pi+pi- J/psi discovery, make the first observation of Y(4260)--> pi(0)pi(0) J/psi (5.1 sigma), and find the first evidence for Y(4260)-->K+K- J/psi(3.7 sigma). We measure e+e- cross sections at sqrt[s]=4.26 GeV as sigma(pi+pi- J/psi)=58(+12)(-10)+/-4 pb, sigma(pi(0)pi(0) J/psi)=23(+12)(-8)+/-1 pb, and sigma(K+K- J/psi)=9(+9)(-5)+/-1 pb, in which the uncertainties are statistical and systematic, respectively. Upper limits are placed on other decay rates from all three resonances.

Journal Article↗
PubMed2006

Measurements of the exclusive decays of the upsilon(5S) to meson final states and improved B(s)* mass measurement.

Using 420 pb(-1) of data collected on the upsilon(5S) resonance with the CLEO III detector, we reconstruct B mesons in 25 exclusive decay channels to measure or set upper limits on the decay rate of upsilon(5S) into B meson final states. We measure the inclusive B cross section to be sigma(upsilon(5S) --> BB(X)) = (0.177 +/- 0.030 +/- 0.016) nb and make the first measurements of the production rates of sigma(upsilon(5S) --> B*B*) = (0.131 +/- 0.025 +/- 0.014) nb and sigma(upsilon(5S) --> BB*) = (0.043 +/- 0.016 +/- 0.006) nb, respectively. We set 90% confidence level limits of sigma(upsilon(5S) -->BB) < 0.038 nb, sigma(upsilon(5S) --> B(*)B(*)pi) < 0.055 nb and sigma(upsilon(5S) --> BBpipi) < 0.024 nb. We also extract the most precise value of the B(s)* mass to date, M(B(s)*) = (5411.7 +/- 1.6 +/- 0.6) MeV/c2.

Journal Article↗
PubMed2006

New measurements of Cabibbo-suppressed decays of mesons with the CLEO-c detector.

Using of data collected with the CLEO-c detector, we report on first observations and measurements of Cabibbo-suppressed decays of D mesons in the following six decay modes: pi+ pi- pi0 pi0, pi+ pi+ pi- pi- pi0, pi+ pi0 pi0, pi+ pi+ pi- pi0, eta pi0, and omega pi+ pi-. Improved branching fraction measurements in eight other multipion decay modes are also presented. The measured D --> pi pi rates allow us to extract the ratio of isospin amplitudes A(DeltaI = (3/2) / A(DeltaI = (1/2)) = 0.420 +/- 0.014(stat) +/- 0.016(syst) and the strong phase shift of delta1 = (86.4 +/- 2.8 +/- 3.3) degrees, which is quite large and now more precisely determined.

Journal Article↗
PubMed2001

Performance of whole blood IFN-gamma test for tuberculosis diagnosis based on PPD or the specific antigens ESAT-6 and CFP-10.

OBJECTIVE: To evaluate the QuantiFERON-TB test in BCG-vaccinated, non-BCG-vaccinated and tuberculosis (TB) patient donor groups, and to compare its diagnostic performance with that of a blood test based on the Mycobacterium tuberculosis specific antigens ESAT-6 and CFP-10. DESIGN: Analysis of the IFN-gamma responses of whole blood cells from BCG-vaccinated or non-BCG-vaccinated donors or patients with tuberculosis, stimulated with PPD, ESAT-6 or CFP-10 antigens, and evaluation of the specificity and sensitivity of the test. RESULTS: None of the non-vaccinated donors showed positive responses to M. tuberculosis-PPD, ESAT-6 or CFP-10. In BCG-vaccinated donors, 9/19 (47%) donors responded to the QuantiFERON-TB test based on M. tuberculosis-PPD, whereas 2/19 (10.5%) responded to either ESAT-6 or CFP-10. Comparable levels of sensitivity were obtained with the QuantiFERON-TB test based on M. tuberculosis-PPD (79%) and ESAT-6 or CFP-10 antigens (72%). CONCLUSION: Our results demonstrate that the whole blood test based on M. tuberculosis-PPD did not efficiently distinguish BCG-vaccinated donors from individuals with disease due to M. tuberculosis. The introduction of new recombinant antigens specific for M. tuberculosis, such as ESAT-6 or CFP-10, should increase the specificity of the whole blood test and enable discrimination between TB infection, atypical mycobacterial reactivity and reactivity due to BCG vaccination. Such a test would provide a quantum improvement over the current practice of using the tuberculin skin test for TB control and elimination.

Adult↗
PubMed2000

Comparative evaluation of low-molecular-mass proteins from Mycobacterium tuberculosis identifies members of the ESAT-6 family as immunodominant T-cell antigens.

Culture filtrate from Mycobacterium tuberculosis contains protective antigens of relevance for the generation of a new antituberculosis vaccine. We have identified two previously uncharacterized M. tuberculosis proteins (TB7.3 and TB10.4) from the highly active low-mass fraction of culture filtrate. The molecules were characterized, mapped in a two-dimensional electrophoresis reference map of short-term culture filtrate, and compared with another recently identified low-mass protein, CFP10 (F. X. Berthet, P. B. Rasmussen, I. Rosenkrands, P. Andersen, and B. Gicquel. Microbiology 144:3195-3203, 1998), and the well-described ESAT-6 antigen. Genetic analyses demonstrated that TB10.4 as well as CFP10 belongs to the ESAT-6 family of low-mass proteins, whereas TB7.3 is a low-molecular-mass protein outside this family. The proteins were expressed in Escherichia coli, and their immunogenicity was tested in cultures of peripheral blood mononuclear cells from human tuberculosis (TB) patients, Mycobacterium bovis BCG-vaccinated donors, and nonvaccinated donors. The two ESAT-6 family members, TB10.4 and CFP10, were very strongly recognized and induced gamma interferon release at the same level (CFP10) as or at an even higher level (TB10.4) than ESAT-6. The non-ESAT-6 family member, TB7.3, for comparison, was recognized at a much lower level. CFP10 was found to distinguish TB patients from BCG-vaccinated donors and is, together with ESAT-6, an interesting candidate for the diagnosis of TB. The striking immunodominance of antigens within the ESAT-6 family is discussed, and hypotheses are presented to explain this targeting of the immune response during TB infection.

Amino Acid Sequence↗
PubMed1999

Meningiomas, dicentric chromosomes, gliomas, and telomerase activity.

Lack of telomere maintenance during cell replication leads to telomere erosion and loss of function. This can result in telomere associations which probably cause the dicentric chromosomes seen in some tumour cells. One mechanism of telomere maintenance in dividing cells is the action of telomerase, a ribonucleoprotein enzyme that adds TTAGGG repeats onto telomeres and compensates for their shortening during cell division. Over 90 per cent of extracranial malignant neoplasms have been found to have telomerase activity. This study sought to determine if there was a relationship between absence of telomerase activity and presence of dicentric chromosomes in meningiomas and to what extent the other main group of central nervous system tumours, the gliomas, expressed telomerase activity. Telomerase activity was measured on 25 meningiomas and 29 gliomas. Four of the meningiomas were atypical variants and 11 were positive for dicentric chromosomes. Twenty-five of 29 gliomas were glioblastoma multiforme tumours. Measures were taken to ensure absence of false positives due to primer-dimer interaction and false negatives due to protein degradation or the presence of Taq polymerase inhibitors. All 25 meningiomas and the four low-grade gliomas (WHO grade II) were telomerase activity-negative. Seven (28 per cent) of the 25 glioblastoma multiforme tumours showed telomerase activity. The absence of telomerase activity in meningiomas and the high frequency of telomere associations support the hypothesis that these tumours are benign, transformed but pre-crisis. The relatively low frequency of telomerase activity in the malignant glioblastoma multiforme suggests that most of these tumours may have other mechanisms of telomere maintenance and that the potentially therapeutic telomerase inhibitors will not be of great value in the future management of the majority of patients suffering from these tumours.

Brain Neoplasms↗
PubMed1995

Sequential coexpression of the multidrug resistance genes MRP and mdr1 and their products in VP-16 (etoposide)-selected H69 small cell lung cancer cells.

Resistance to drugs included in the multidrug-resistance phenotype has been attributed to overexpression of either mdr1 or MRP genes and their products in numerous cell lines, while coexpression, to our knowledge, has not previously been reported in the same cells. Human small cell lung cancer H69/VP cells were developed by continuous incubation in increasing doses of VP-16. In reverse transcription-PCR assays we found over-expression of both mdr1 and multidrug-resistance protein (MRP) genes, and immunoblots showed both elevated P-glycoprotein and MRP in H69/VP cells. Double immunocytochemical staining demonstrated the expression of both MRP and P-glycoprotein in the same cells, indicating that the observations do not result from the selection of two independent clones. Examination of early passages of H69/VP cells showed that overexpression of MRP mRNA occurred prior to mdr1. Thus, cell lines and clinical samples in the future should be tested for both mdr1/P-glycoprotein and MRP since a positive result for one of the phenotypes does not preclude the existence of the other.

ATP Binding Cassette Transporter, Subfamily B, Mem↗