PubMed Health⌕ Search

Biomedical subjects

M S Lewis

Publications and source records attributed to M S Lewis.

At least 19 recordsLinked to original sources
PubMed2006

Caregiver cognitive status and potentially harmful caregiver behavior.

The association between caregiver cognitive status and potentially harmful caregiver behavior was assessed in a sample of 180 caregiver-care recipient dyads. Compromised cognitive status was identified in 39% of these informal caregivers. Beyond variance explained by demographic factors, amount of care provided, care recipient cognitive status, and caregiver depressed affect, care recipients reported more frequently being subjected to potentially harmful caregiver behavior when their caregivers evidenced compromised cognitive status. While preliminary, critical areas of caregiver cognition appeared to be deficits in language comprehension and memory. Results indicate that compromised cognitive status is common among informal caregivers of impaired elders and that this may adversely influence the quality of care they provide.

Adult↗
PubMed2006

The sensitivity and specificity of three common statistical rules for the classification of post-operative cognitive dysfunction following coronary artery bypass graft surgery.

BACKGROUND: The application of statistical rules to determine post-operative cognitive dysfunction (POCD) has varied, and partially explains the wide range of reported incidences of POCD in the literature. The current study assessed the sensitivity and specificity of three commonly used statistical rules in a sample of coronary artery bypass graft (CABG) patients and healthy non-surgical controls. METHODS: Two hundred and four CABG patients [mean age, 68.8 years; standard deviation (SD), 7.0 years] completed neuropsychological assessment pre-operatively (baseline) and 1 week and 3 months post-operatively. Ninety age- and gender-matched non-surgical controls (mean age, 67.8 years; SD, 7.9 years) completed the same tasks at the same time points. POCD was determined in each group using three rules: the 1SD decline on two or more tasks; the 20% decline on 20% of tasks rule; and a modified reliable change index. RESULTS: The modified reliable change index demonstrated the greatest combination of sensitivity and specificity. The 20% decline on 20% of tasks rule detected the largest incidence of impairment in the CABG group, but showed large incidences of false positive classifications in the control group. The 1SD rule detected the lowest incidence of POCD in the CABG group, but detected a larger incidence of impairment in the control group. CONCLUSIONS: The use of the modified reliable change index is recommended, given the sensitivity to change it displayed and the low rates of false positive classification in the control sample. The use of control groups in future research is also recommended.

Aged↗
PubMed2004

Detection of cognitive decline after coronary surgery: a comparison of computerized and conventional tests.

BACKGROUND: Postoperative cognitive decline is a common complication after coronary artery bypass graft (CABG) surgery. Postoperative cognitive decline is defined on the basis of change in cognitive function detected with repeated assessments using neuropsychological tests. Therefore improvement in neuropsychological testing instruments may increase our understanding of postoperative cognitive decline. METHODS: Fifty patients undergoing CABG surgery completed both a conventional and a computerized battery of tests before and 6 days after CABG surgery. Fifty age- and education-matched controls completed the same test batteries 6 days apart. The reliability and the sensitivity to postoperative cognitive decline were computed for each battery. RESULTS: Both test batteries detected postoperative cognitive decline 6 days after CABG surgery. For the computerized battery, the reliability of the reaction times (intraclass correlation 0.89-0.92) was greater than for any test from the conventional battery (intraclass correlation 0.56-0.71), although accuracy measures were less reliable (intraclass correlation 0.61-0.89). The computerized battery detected all the cases of POCD identified by the conventional test battery and also five cases that were classified as normal by the conventional tests. CONCLUSION: Computerized tests are suitable for measuring cognitive change after CABG surgery and may detect change in a greater proportion of patients 6 days after CABG surgery than conventional neuropsychological tests.

Aged↗
PubMed2002

An international evaluation of CODOX-M and CODOX-M alternating with IVAC in adult Burkitt's lymphoma: results of United Kingdom Lymphoma Group LY06 study.

BACKGROUND: Burkitt's lymphoma (BL) is a rare and rapidly progressive form of B-cell non-Hodgkin's lymphoma. Cyclophosphamide, vincristine, doxorubicin, high-dose methotrexate (CODOX-M)/ifosfamide, etoposide and high-dose cytarabine (IVAC) is a highly effective alternating non-cross-resistant regimen developed by Magrath et al. (Magrath I., Adde M., Shad A. et al. J Clin Oncol 1996; 14: 925-934) at the US National Cancer Institute. The aim was to confirm these results in a larger, international, multi-centre study using International Prognostic Index-based criteria to assign prognostic groups, whilst slightly simplifying the protocol. PATIENTS AND METHODS: A phase II study where: (i) low risk (LR) patients were treated with three cycles of modified CODOX-M; and (ii) high risk (HR) patients received treatment with four cycles of alternating modified CODOX-M and IVAC chemotherapy. Target of 60 patients, fit for protocol treatment, from 16 to 60 years of age with locally diagnosed, non-HIV-related, non-organ-transplant-related BL. RESULTS: Results are given for 52 of 72 registered patients whose pathological eligibility was confirmed by central pathology review: 12 LR plus 40 HR. The majority of patients (n = 41) completed protocol treatment, but toxicity was severe, especially myelosuppression and mucositis. Overall, 2-year event-free survival (EFS) was 64.6% (95% CI 50.4% to 78.9%) and 2-year overall survival (OS) was 72.8% (95% CI 59.4% to 86.3%). For LR, 2-year EFS was 83.3% and OS was 81.5%. For HR, 2-year EFS was 59.5% and OS was 69.9%. CONCLUSIONS: This study confirms high cure rates with this CODOX-M/IVAC approach.

Adult↗
PubMed2001

Restricted chromosomal silencing in nucleolar dominance.

Failure of one parent's chromosomes to organize nucleoli in an interspecific hybrid is an epigenetic phenomenon known as nucleolar dominance. Selective gene silencing on a scale of millions of bp is known to be involved, but the full extent to which nucleolus organizer region (NOR)-bearing chromosomes are inactivated beyond the NORs is unknown. Aided by genome sequence data for Arabidopsis thaliana, we have mapped the extent of nucleolar dominance-induced silencing in Arabidopsis suecica, the allotetraploid hybrid of A. thaliana and Arabidopsis arenosa. Using a sensitive reverse transcription PCR assay, we show that the four A. thaliana NORs, each approximately 4 Mbp in size, are approximately 99.5% silenced in A. suecica vegetative leaves, whereas the NORs inherited from A. arenosa remain fully active. The two A. thaliana NORs, NOR2 and NOR4, abut the telomeres on chromosomes 2 and 4, thus there are no genes distal to the NORs. The three protein-coding genes nearest NOR4 on its centromere-proximal side, the closest of which is only 3.1 kb from rRNA gene sequences, are shown to be transcribed in the hybrid despite the silencing of the adjacent approximately 4-Mbp NOR. These data argue against hypotheses in which NOR inactivation is attributed to the spread of silencing from adjacent chromosomal regions, but favor models in which NORs or rRNA genes are the targets of regulation.

Arabidopsis↗
PubMed2001

Analytical ultracentrifugation studies of translin: analysis of protein-DNA interactions using a single-stranded fluorogenic oligonucleotide.

Translin is a recently identified nucleic acid binding protein that appears to be involved in the recognition of conserved sequences found at many chromosomal breakpoints. Previous reports indicate that, based on gel filtration analysis and electron microscopy of protein-DNA complexes, translin forms an octameric structure that binds the DNA. In this study, we further examine the possibility of self-association of translin and its interactions with DNA by analytical ultracentrifugation. Sedimentation velocity analysis of translin indicates that the predominant species sediments with a sedimentation coefficient of 8.5 S and has a frictional ratio, f/f(omicron), of 1.35; these data are consistent with the presence of an octamer with an ellipsoidal configuration; a small amount of a component with significantly higher mass is also present. Equilibrium sedimentation studies of translin at three different protein concentrations also indicate that the predominant species present is an octamer with a minor fraction of aggregated species. Neither monomer nor dimer was detected. Sedimentation equilibrium studies of translin with an FITC-labeled single-stranded oligonucleotide were performed to examine the interaction. A novel analysis method has been developed to analyze protein-nucleic acid interactions based on global fitting of scans of 280 and 490 nm to appropriate mathematical models. Utilizing this method, it was determined that the DNA binding species of translin is an octamer binding a single-stranded oligonucleotide with a DeltaG degrees value of -9.49 +/- 0.12 kcal/mol, corresponding to a dissociation constant, K(d), of 84 +/- 17 nM. On the basis of this evidence and electron microscopy, it is envisioned that translin forms an annular structure of eight subunits, hydrodynamically an oblate ellipsoid, which binds DNA at chromosomal breakpoints.

DNA, Single-Stranded↗
PubMed2001

Kinetics and thermodynamics of beta 2-microglobulin binding to the alpha 3 domain of major histocompatibility complex class I heavy chain.

The major histocompatibility complex (MHC) class I molecule plays a crucial role in cytotoxic lymphocyte function. Functional class I MHC exists as a heterotrimer consisting of the MHC class I heavy chain, an antigenic peptide fragment, and beta2-microglobulin (beta2m). beta2m has been previously shown to play an important role in the folding of the MHC heavy chain without continued beta2m association with the MHC complex. Therefore, beta2m is both a structural component of the MHC complex and a chaperone-like molecule for MHC folding. In this study we provide data supporting a model in which the chaperone-like role of beta2m is dependent on initial binding to only one of the two beta2m interfaces with class 1 heavy chain. beta2-Microglobulin binding to an isolated alpha3 domain of the class I MHC heavy chain accurately models the biochemistry and thermodynamics of beta2m-driven refolding. Our results explain a 1000-fold discrepancy between beta2m binding and refolding of MHC1. The biochemical study of the individual domains of complex molecules is an important strategy for understanding their dynamic structure and multiple functions.

Animals↗
PubMed2001

Prothrombin time inhibition detected with recombinant but not with conventional thromboplastins in two patients with high-titre IgM and moderate-titre IgA anticardiolipin antibodies.

We report two cases of high-titre IgM and moderate-titre IgA anticardiolipin antibodies (ACA) in whom prothrombin times (PT) derived using recombinant thromboplastins (rTP) were prolonged but were normal when measured with conventional thromboplastins. The anticoagulant nature of these antibodies cannot be categorized as the classical lupus type. We suggest that routine screening for the presence of antiphospholipid antibodies (APA) should be performed in patients who fall into this category.

Aged↗
PubMed2001

Inactivation of DNA mismatch repair by increased expression of yeast MLH1.

Inactivation of DNA mismatch repair by mutation or by transcriptional silencing of the MLH1 gene results in genome instability and cancer predisposition. We recently found (P. V. Shcherbakova and T. A. Kunkel, Mol. Cell. Biol. 19:3177-3183, 1999) that an elevated spontaneous mutation rate can also result from increased expression of yeast MLH1. Here we investigate the mechanism of this mutator effect. Hybridization of poly(A)(+) mRNA to DNA microarrays containing 96.4% of yeast open reading frames revealed that MLH1 overexpression did not induce changes in expression of other genes involved in DNA replication or repair. MLH1 overexpression strongly enhanced spontaneous mutagenesis in yeast strains with defects in the 3'-->5' exonuclease activity of replicative DNA polymerases delta and epsilon but did not enhance the mutation rate in strains with deletions of MSH2, MLH1, or PMS1. This suggests that overexpression of MLH1 inactivates mismatch repair of replication errors. Overexpression of the PMS1 gene alone caused a moderate increase in the mutation rate and strongly suppressed the mutator effect caused by MLH1 overexpression. The mutator effect was also reduced by a missense mutation in the MLH1 gene that disrupted Mlh1p-Pms1p interaction. Analytical ultracentrifugation experiments showed that purified Mlh1p forms a homodimer in solution, albeit with a K(d) of 3.14 microM, 36-fold higher than that for Mlh1p-Pms1p heterodimerization. These observations suggest that the mismatch repair defect in cells overexpressing MLH1 results from an imbalance in the levels of Mlh1p and Pms1p and that this imbalance might lead to formation of nonfunctional mismatch repair complexes containing Mlh1p homodimers.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Analysis of transport experiments using pseudo-absorbance data.

The measurement of the concentration distribution of a macromolecule across a solution column by absorption optics usually requires optical transmission profiles of both the sample solution and the buffer, measured under identical conditions, to calculate the absorbance as the logarithm of the ratio of reference to sample intensity. For transport experiments, however, where the changes in the local macromolecule concentration with time are measured, a reference buffer intensity is not necessarily required. We demonstrate that the logarithm of the light transmitted through the sample solution, referred to as pseudo-absorbance, can suffice to determine macromolecular transport parameters of interest, with little loss of precision. Local changes in illumination of the sample column or in the detection efficiency of the transmitted light, as well as temporal fluctuations of the light source intensity can be well-described by consideration of time-invariant and radial-invariant signal components in the pseudo-absorbance data, using the systematic noise decomposition techniques developed recently (Schuck, P., and Demeler, B. (1999) Biophys. J. 76, 2288-2296). The practical use of the method is demonstrated with double-sector and single-sector sedimentation velocity experiments, and with analytical electrophoresis experiments. It is shown that pseudo-absorbance analysis can increase the capacity of a sedimentation velocity experiment in ultracentrifugation, and, in general, can considerably simplify the requirements of optical design.

Animals↗
PubMed2000

Interaction of chromogranin B and the near N-terminal region of chromogranin B with an intraluminal loop peptide of the inositol 1,4, 5-trisphosphate receptor.

Given the interaction of the inositol 1,4,5-trisphosphate receptor (IP(3)R) with chromogranins A (CGA) and B (CGB), two major Ca(2+) storage proteins of secretory granules that have been shown to be IP(3)-sensitive intracellular Ca(2+) store of neuroendocrine cells, we have investigated the potential interaction of the intraluminal loop regions of the IP(3)R with both intact CGB and the conserved near N-terminal region of CGB. The interaction studies carried out with CGB and glutathione S-transferase fusion proteins of intraluminal loop regions of bovine type 1 IP(3)R showed that CGB interacts with intraluminal loop 3-2 (the second loop formed between transmembrane regions 5 and 6) of the IP(3)R at both pH 5.5 and 7.5. Analytical ultracentrifugation studies also indicated that CGB interacts with the same intraluminal loop region of the IP(3)R and the interaction was much stronger than that between CGA and the loop. Moreover, the conserved near N-terminal region of CGB also interacted with the intraluminal loop region of the IP(3)R. The CGB interaction with the IP(3)R intraluminal loop peptide at pH 7.5 showed a DeltaG(0) value of -8.1 kcal/mol at 37 degrees C for a 1:1 stoichiometry, indicating a K(d) of approximately 1.9 micrometer. These results give insight into the molecular organization of the IP(3)-sensitive Ca(2+) store.

Amino Acid Sequence↗
PubMed2000

A capillary whole blood method for measuring the INR.

This study describes a method of measuring the INR on native whole blood capillary samples using Innovin recombinant thromboplastin. Modification of the reagent was necessary to compensate for the nonoptimal level of calcium in the sample/reagent mixture. Ninety-five percent of results obtained by the capillary blood method were no more than 0.42 INR higher or 0.38 INR lower than the venous blood method. The effect of changes in haematocrit was minimal. Significant differences in results were found between the Innovin and Thrombotest capillary blood methods. Provided the reagent was properly stored, there was no reagent drift and satisfactory results were obtained on samples supplied by UKNEQAS (coagulation) from previous trials. The method described is a convenient, simple and accurate method of measuring the INR using native capillary whole blood and Innovin recombinant thromboplastin.

Blood Coagulation Tests↗
PubMed1999

Factors in cardiac risk stratification of candidates for renal transplant.

BACKGROUND: Renal transplant candidates are at high risk of fatal and nonfatal cardiac events. METHODS: This study evaluated five clinical risk factors--age at least 50 years, insulin-requiring diabetes mellitus, angina, congestive heart failure and an abnormal electrocardiogram (ECG) (excluding left ventricular hypertrophy)--that had been used in the first tier of a two-tiered prospectively applied risk stratification algorithm. RESULTS: Using multiple logistic regression analysis, age at least 50 years, abnormal ECG, and diabetes mellitus were independently predictive of cardiac death. Of the two remaining clinical risk factors, the presence of angina had independent predictive value for nonfatal cardiac events (myocardial infarction, coronary angioplasty, bypass surgery, and unstable angina). The independent predictive value of congestive heart failure approached statistical significance. CONCLUSION: Clinical risk-factor analysis is helpful in identifying renal transplant candidates at high risk for fatal or nonfatal cardiac events.

Algorithms↗
PubMed1998

The oxyR gene from Erwinia carotovora: cloning, sequence analysis and expression in Escherichia coli.

Homologs of the Escherichia coli oxyR gene were identified in several Erwinia species, using a combination of PCR and Southern hybridization analysis. The oxyR gene from Erwinia carotovora was isolated on a cosmid clone and characterized. The gene and deduced gene product shared high level sequence identity with their E. coli counterparts (78 and 89% identity, respectively). In E. coli, the oxyR gene is a transcriptional activator that, under oxidizing conditions, induces expression of a set of oxidative defence genes. OxyR null mutants are, therefore, sensitive to hydrogen peroxide. Introduction of the E. carotovora oxyR gene into an E. coli oxyR mutant resulted in transformants that were hydrogen peroxide resistant, indicating that the Erwinia protein was functional in E. coli.

Amino Acid Sequence↗
PubMed1998

Thermodynamics of human DNA ligase I trimerization and association with DNA polymerase beta.

The interaction between human DNA polymerase beta (pol beta) and DNA ligase I, which appear to be responsible for the gap filling and nick ligation steps in short patch or simple base excision repair, has been examined by affinity chromatography and analytical ultracentrifugation. Domain mapping studies revealed that complex formation is mediated through the non-catalytic N-terminal domain of DNA ligase I and the N-terminal 8-kDa domain of pol beta that interacts with the DNA template and excises 5'-deoxyribose phosphate residue. Intact pol beta, a 39-kDa bi-domain enzyme, undergoes indefinite self-association, forming oligomers of many sizes. The binding sites for self-association reside within the C-terminal 31-kDa domain. DNA ligase I undergoes self-association to form a homotrimer. At temperatures over 18 degreesC, three pol beta monomers attached to the DNA ligase I trimer, forming a stable heterohexamer. In contrast, at lower temperatures (<18 degreesC), pol beta and DNA ligase I formed a stable 1:1 binary complex only. In agreement with the domain mapping studies, the 8-kDa domain of pol beta interacted with DNA ligase I, forming a stable 3:3 complex with DNA ligase I at all temperatures, whereas the 31-kDa domain of pol beta did not. Our results indicate that the association between pol beta and DNA ligase I involves both electrostatic binding and an entropy-driven process. Electrostatic binding dominates the interaction mediated by the 8-kDa domain of pol beta, whereas the entropy-driven aspect of interprotein binding appears to be contributed by the 31-kDa domain.

Chromatography, Affinity↗
PubMed1998

Interaction between an intraluminal loop peptide of the inositol 1,4,5-trisphosphate receptor and the near N-terminal peptide of chromogranin A.

The near N-terminal region of chromogranin A (CGA) has been shown to be the secretory vesicle membrane binding region, and tetrameric chromogranin A has been demonstrated to bind four molecules of an intraluminal loop peptide of the inositol 1,4,5-trisphosphate (IP3) receptor. It was therefore necessary to determine whether the conserved near N-terminal region of CGA interacts with the intraluminal loop region of the IP3 receptor. In the present study, we found that the proposed anchor region of CGA, the conserved near N-terminal region, does indeed interact with the intraluminal loop region of the IP3 receptor at the intravesicular pH of 5.5, further strengthening the case for the potential interaction between tetrameric chromogranins and tetrameric IP3 receptors in the cell.

Calcium Channels↗