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Biomedical subjects

F Levy

Publications and source records attributed to F Levy.

At least 37 records · Page 2Linked to original sources
PubMed2000

Long-term trends in susceptibility of Moraxella catarrhalis: a population analysis.

A retrospective, population analysis of antimicrobial susceptibility patterns was performed on Moraxella catarrhalis isolates recovered from a single medical centre to detect temporal trends and infer potential mechanisms of reduced susceptibility. The duration of this study, June 1984 to July 1994, encompassed the period during which the frequency of beta-lactamase production expanded from 30 to 96% in the population. MICs of penicillin G, cefamandole, ceftriaxone, amoxycillin/clavulanate, imipenem, clarithromycin, tetracycline, ciprofloxacin and trimethoprim/sulphamethoxazole for a representative sample of 375 isolates were determined. Analyses were conducted to test for variation in susceptibility among isolates, correlations of susceptibility levels among different antimicrobial agents, and temporal patterns in susceptibility. All antimicrobials except clarithromycin displayed significant differences among isolates within years, and mean MICs of all antimicrobial agents except tetracycline and clarithromycin varied significantly between years. Temporal trends to a reduction in susceptibility were detected to four of five beta-lactam antimicrobials (all except cefamandole). Significant correlations in MICs were uncovered among all pairs of four beta-lactam antimicrobials in both producers and non-producers of beta-lactamase. In contrast, cefamandole MICs were correlated only with ceftriaxone and penicillin, and these were limited to beta-lactam producing isolates; cefamandole and amoxycillin/clavulanate showed a correlation limited to non-producing isolates. For some antimicrobials, trends toward decreasing susceptibility may have been caused by an increased proportion of beta-lactamase producing isolates in the population, but the observation of significant decreases in susceptibility limited to beta-lactamase-producing isolates suggests that the underlying factors were different forms of beta-lactamase, beta-lactamase-dependent modifiers and/or additional factors.

Anti-Bacterial Agents↗
PubMed2000

DNA breakage in asbestos-treated normal and transformed (TSV40) rat pleural mesothelial cells.

Asbestos has been shown to induce cell cycle arrest, DNA repair and some abnormalities consistent with DNA damage but not DNA breakage. The purpose of the study was to investigate DNA breakage in asbestos-exposed rat pleural mesothelial cells (RPMC). RPMC were compared with their transformed counterparts, RPMC-TSV40 (i.e. p53-inactivated by infection with a retroviral recombinant encoding the SV40 large T antigen), as in the latter cells the cell cycle does not arrest and DNA repair is deficient due to ineffective p53-dependent cell cycle control. RPMC and RPMC-TSV40 were exposed to chrysotile and crocidolite asbestos and also to camptothecin for comparison. The presence of DNA breakage was determined using the single cell gel (Comet) assay with alkaline electrophoresis and quantified by measuring comet tail length (TL) and the percentage of total DNA in the tail and calculating tail moment (TM). We found that comets were generated by both types of asbestos in RPMC and in RPMC-TSV40 as well as by camptothecin in RPMC. On a per weight basis, chrysotile induced more abnormalities in comet parameters than did crocidolite. The comet TL and TM increased with fibre concentration, although less so with crocidolite than with chrysotile. When exposed to chrysotile at similar concentrations, RPMC consistently showed more abnormal comet parameters than did RPMC-TSV40. We concluded that asbestos causes DNA breakage and suggest that some of the DNA breakage measured was due to repair mechanisms in the normal RPMC.

Animals↗
PubMed1999

Spatial and temporal genetic structure in chloroplast and allozyme markers in phacelia dubia implicate genetic drift

For neutral genes, uniparental inheritance is expected to reduce effective population size relative to biparentally inherited genes. In finite populations, the ensuing genetic drift can cause stronger spatial and temporal differentiation. An intrapopulation polymorphism in chloroplast DNA was used to examine relative spatial and temporal population structure of chloroplast and allozyme markers in the annual plant Phacelia dubia. There was significant differentiation among populations at chloroplast markers but not for allozyme loci. A fine-scale analysis showed significant structure among sites within populations for chloroplast markers and local heterozygote deficiencies at allozyme loci. These spatial analyses suggest that gene flow via pollen exceeds that via seed. Temporal variation in chloroplast markers, assessed over a 10-year period, was evident in two of four populations, and allozyme loci were characterized by temporal variation in rare-allele frequencies. Population structure appeared to be related to the intensity and type of human disturbance influencing each population. Habitat destruction promoted isolation and enhanced differentiation, whereas mowing increased seed dispersal and reduced differentiation for chloroplast markers. At this time, genetic drift appears to be the primary force shaping chloroplast gene frequencies.

Journal Article↗
PubMed1999

Covert orienting of visual spatial attention in attention deficit hyperactivity disorder: does comorbidity make a difference?

Attentional performance in children with attention deficit hyperactivity disorder (ADHD) with and without comorbid disorders was examined using the Covert Orienting of Visuospatial Attention Task (COVAT) and the Continuous Performance Task (CPT). The relationship between these two tasks was also examined. The results showed no overall differences on the attention tasks between children with ADHD alone and those with ADHD plus other disorders. Compared to non-ADHD control children, children with ADHD showed a deficit in the disengage operation of covert visuospatial attention, suggesting a difficulty in the endogenous mode of orienting. The ADHD children also showed a general performance deficit on the CPT. Although there was a general slowing on both attention tasks in the ADHD group, there was no relationship between invalid cue effect sizes on the COVAT and the CPT measures. These results indicate that these two attention tasks may be tapping both similar and independent underlying cognitive processes in ADHD.

Journal Article↗
PubMed1998

[Air quality and microbiologic contamination in operating theatres].

The present study concerns the air quality and microbiological contamination in two newly built operating theatres; one with laminar air flow (LAF) equipment for cardio-thoracic operations, and one with conventional ventilation for urological operations. Both theatres had an identical number of air exchanges (17/h), identical microclimatic conditions and they employed the same cleaning procedures. In the LAF-ventilated operating theatre bacterial contamination of the air was effectively reduced to less than 10 colony-forming units (CFU)/m3 in all 125 samples (1 m3 per sample) tested. In most samples, 118/125, the bacterial count was less than 5 CFU/m3, despite the presence of ten persons. The conventionally ventilated theatre reached values up to 120 CFU/m3 during the most active period of the day when approximately seven persons were present. The LAF ventilation reduced both the content of particles in the air and contamination by bacteria on the floor. In both theatres cleaning procedures had only a low impact on CFU in the air and on the floor. The use of diathermia markedly increased the level of small particles in the air, and this may influence the air quality in the operating theatres.

Air Conditioning↗
PubMed1998

Functional brain electrical activity mapping in boys with attention-deficit/hyperactivity disorder.

BACKGROUND: Symptoms of attention-deficit/hyperactivity disorder (ADHD) have been associated with frontal lobe deficits. We used a novel brain electrical imaging method to investigate rapid and continuous changes in brain activity during the continuous performance task (CPT) in normal boys and in boys with ADHD. The amplitude and latency topography of the steady-state visually evoked potential (SSVEP) were examined while subjects performed the "X" version of the CPT (CPT-X; the reference task) and the "A-X" version of the CPT (CPT-AX). METHODS: Seventeen boys meeting DSM-III-R criteria for ADHD and 17 age-matched controls participated in the study. Brain electrical activity was recorded from 64 scalp sites. During the reference task, subjects pressed a microswitch on the unpredictable appearance of the letter X. During the CPT-AX, subjects were required to press the microswitch on the appearance of the letter X only if an A had preceded it. RESULTS: In the interval between the appearances of the A and the X of the correct trials of the CPT-AX, control boys showed transient reductions in SSVEP latency at right prefrontal sites. By contrast, boys with ADHD showed no change or an increase in prefrontal SSVEP latency at right prefrontal sites. CONCLUSION: Our results suggest increased speed of prefrontal neural processing in children without ADHD following a priming stimulus, and a deficit in such processes in children with ADHD.

Adolescent↗
PubMed1998

Directions of aetiologic research on attention deficit hyperactivity disorder.

OBJECTIVE: The aim of this paper is to review and integrate recent literature on aetiological factors that have been postulated for attention deficit hyperactivity disorder (ADHD). METHOD: Recent studies relating to perinatal brain damage, intra-uterine toxic effects, neurochemical, brain imaging and genetic studies are reviewed, and those considered most significant are discussed. Where possible, recent findings are integrated and directions of future research are suggested. Clinical implications are briefly discussed. RESULTS: Perinatal studies indicate that children with a birth weight under 750 g may be disadvantaged for attentional skills. Magnetic resonance imaging (MRI) and steady state visually evoked potential studies show differences in prefrontal, caudate and parietal areas in ADHD children, suggesting right hemispheric dysfunction. Functional MRI studies hold promise in further elucidating attentional systems in the central nervous system that are involved in ADHD. Genetic studies suggest genes related to dopaminergic systems may be important. CONCLUSIONS: Recent research on ADHD has made considerable advances, particularly in the areas of brain imaging and genetic studies. Genetic studies should provide further aetiological understandings of ADHD, leading to more targeted treatments.

Attention Deficit Disorder with Hyperactivity↗
PubMed1998

Endothelin participates in increased circulating atrial natriuretic peptide early after human heart transplantation.

BACKGROUND: Hemodynamic improvement after heart transplantation is expected to normalize the neuroendocrine balance, but circulating atrial natriuretic peptide (ANP) remains elevated. Endothelin stimulates ANP secretion and its concentration increases after heart transplantation, suggesting a role for this peptide in the cardiovascular adaptative response to heart transplantation. METHODS: To investigate whether endothelin may induce ANP increase in heart transplant recipients, we monitored daily ANP, endothelin, and related hormonal, biologic, and hemodynamic parameters before and during the first week after either heart transplantation (n = 15) or coronary artery bypass grafting (n = 10). RESULTS: Surgery induced a transient secretory peak of arginine vasopressin and endothelin in both groups at day 1. Bypass grafting did not modify normal ANP (11.8 +/- 2.1 pmol/L), endothelin (2.4 +/- 0.3 pmol/L), renin activity (0.11 +/- 0.04 pmol/L/sec), or aldosterone (492 +/- 122 pmol/L) values. Heart transplantation normalized the renin-aldosterone axis, but the early decrease observed for ANP (from 27.2 +/- 4.8 to 21.14 +/- 1.4 pmol/L) was only partial and transient. Endothelin further increased (from 4.4 +/- 0.8 to 9.14 +/- 1.8 pmol/L; p < 0.01) after transplantation. Positive correlations were observed between endothelin, isoproterenol dose, creatinine, right atrial pressure, and ANP, but multiple correlation analysis showed the important role of endothelin (r = 0.69, p < 0.001). Cyclic guanosine monophosphate correlated with ANP (r = 0.65, p < 0.001). CONCLUSIONS: Elevated endothelin, suggesting vascular dysfunction, likely contributes to the ANP increase observed early after heart transplantation. Furthermore, ANP, through a cardiac endothelium feedback, may act in the maintenance of circulatory homeostasis in heart transplant recipients.

Adult↗
PubMed1997

[Floor cleaning methods of patients' room. Effect on bacteria, dirt and particles].

The effect of floor cleaning on bacteria, organic materials and particles in the patients' rooms was studied at Ullevål University Hospital, Oslo, Norway. Four cleaning methods were compared; dust-adhesive (dry), humified, wet mopping, and regular wet washing (RWW) without a mop. The following tests were taken from the floor before and after cleaning: bacterial counts (colony forming units = CFU) and ATP (presence of organic materials), and from the air: CFU/m3 air, and particle counts/m3 air. Humified mopping and dry mopping reduced the bacterial counts from the floor by 75% and 55% respectively (p = 0.005 and p = 0.014, using contact medium). The wet mopping had no statistically significant effect, while the wet washing even increased the CFU on the floor by 35-50% (p = 0.017 with contact medium, and p = 0.028 with petrifilm). The two wet methods were the most effective, however, in removing organic materials from the floor; 65% to 70% reduction (p = 0.051 and p =0.008). The CFU/m3 air was low both before (50-130 CFU/m3) and after (70-110 CFU/m3) cleaning. A slight increase in airborne particles was measured after dry mopping. Combined use of humified mopping and wet mopping is recommended, but is dependent on a well prepared and finished floor surface.

Air Microbiology↗
PubMed1997

Albumin-impregnated prosthetic graft for infrarenal aortic replacement: effects on the incidence and volume of perioperative blood transfusion.

We retrospectively reviewed 290 cases in which an albumin-impregnated polyester prosthetic graft was used for surgical management of aortic bifurcation disease between November 1987 and December 1990. The purpose of this review was to determine the incidence and volume of blood transfusion and to evaluate the rate of patency and the incidence of infection achieved using this type of prosthesis. The indication for surgery was abdominal aortic aneurysm (AAA) in 218 cases (190 elective procedures and 28 emergency procedures) and occlusive disease of the aortic bifurcation (ODAB) in 72 cases. Mean follow-up was 25.5 +/- 13.4 months (range: 1 and 50 months). The incidence of blood transfusion for elective AAA and ODAB surgery was 30.2% and 32.3% intraoperatively, 21.3% and 12.9% postoperatively, and 40.4% and 42.6% overall. The mean number of red cell packs transfused for elective AAA and ODAB surgery was respectively 1 and 0.8 intraoperatively, 0.4 and 0.6 postoperatively, and 1.4 and 1 overall. No immediate or late graft infection prosthesis was observed in any patient in this series. Primary and secondary patency was 95.5% and 97.5% at 6 months with no graft thrombosis during further follow-up. The fact that use of an impregnated graft in management of aortic bifurcation disease was accompanied by a high incidence and volume of blood transfusion suggests that these grafts do not reduce perioperative blood loss. Use of an impregnated prosthesis had no effect on the rate of patency and the incidence infection.

Aged↗
PubMed1997

Attention-deficit hyperactivity disorder: a category or a continuum? Genetic analysis of a large-scale twin study.

OBJECTIVE: To investigate heritability and continuum versus categorical approaches to attention-deficit hyperactivity disorder (ADHD), using a large-scale twin sample. METHOD: A cohort of 1,938 families with twins and siblings aged 4 to 12 years, recruited from the Australian National Health and Medical Research Council Twin Registry, was assessed for ADHD using a DSM-III-R-based maternal rating scale. Probandwise concordance rates and correlations in monozygotic and dizygotic twins and siblings were calculated, and heritability was examined using the De Fries and Fulker regression technique. RESULTS: There was a narrow (additive) heritability of 0.75 to 0.91 which was robust across familial relationships (twin, sibling, and twin-sibling) and across definitions of ADHD as part of a continuum or as a disorder with various symptom cutoffs. There was no evidence for nonadditive genetic variation or for shared family environmental effects. CONCLUSIONS: These findings suggest that ADHD is best viewed as the extreme of a behavior that varies genetically throughout the entire population rather than as a disorder with discrete determinants. This has implications for the classification of ADHD and for the identification of genes for this behavior, as well as implications for diagnosis and treatment.

Attention Deficit Disorder with Hyperactivity↗
PubMed1997

Discrimination of attention deficit hyperactivity disorder by the continuous performance test.

OBJECTIVE: To investigate the Continuous Performance Test in discriminating a group of 56 attention deficit hyperactivity disorder (ADHD) children from 56 school children individually matched for age, sex and social class. METHODOLOGY: The children all completed the Continuous Performance Task (CPT). The mothers and teachers completed a Conners Parent-Teacher Rating Scale for the clinic children. RESULTS: The ADHD sample was selected so that the average IQ was 99.8 to match the school sample. A non-parametric discriminant function showed that the subtests of the CPT that best discriminated ADHD were age-normalized errors of commission (NCPTC) and age-normalized mean reaction time (NMNRT). CONCLUSION: Optimal use of the CPT for discrimination of ADHD should include age normalization and mean reaction time to targets. Further evoked potential studies may show brief cortical events involved in reaction time over the course of the CPT, and the processes involved in behavioural control.

Attention Deficit Disorder with Hyperactivity↗
PubMed1997

Role of IL-13 in CD4 T cell-dependent IgE production in atopy.

IgE isotype switching of human B cells requires physical interaction of T and B cells via surface molecules, and either IL-4 or IL-13 secreted by T cells. In this study we analyzed the role of IL-4 versus IL-13 in IgE production in atopy. We found that peripheral blood mononuclear cells (PBMC) from atopic individuals but not from nonatopic subjects secreted IgE without addition of IL-4 or IL-13, if T and B cells were simultaneously activated by anti-CD3 mAb and soluble CD40L, respectively. IgE production by atopic PBMC was dependent on endogenously secreted IL-4 and IL-13, since it could be blocked by a combination of anti-IL-4 plus anti-IL-13 antibodies. No differences in the B cell compartment of nonatopics and atopics were detectable, since PBMC from both donor populations secreted comparable amounts of IgE, if only the B cells were activated by soluble CD40L plus either exogenous IL-4 or IL-13. Further phenotypic analysis of T cells from atopics revealed that activated CD4+45RO- secreted IL-4 but no IL-13, whereas CD4+45RO+ memory T cells secreted low amounts of IL-4, but large amounts of IL-13. Accordingly, prolonged activation of native CD4+45RO- T cells in vitro induced expression of CD45RO, and strongly favored secretion of IL-13 rather than IL-4. Addition of exogenous IL-4 during activation further increased both IL-4 and IL-13 production to a similar degree. However, the potential of CD4 T cells from atopics to deliver contact-dependent activation signals to B cells and to induce IgE production (in the absence of soluble CD40L) increased with prolonged activation, and coincided with IL-13 rather than IL-4 production. Under similar conditions, CD8 effector cells secreted IL-13 but no IL-4, did not express CD40L, and could not help Ig(E) production by B cells. These results suggest that, in atopy, persistently stimulated CD4+45RO+memory/effector T cells provide contact-dependent activation signals to B cells, and that these cells may induce IgE switching largely via secretion of IL-13.

Adult↗
PubMed1997

Analysis of cell cycle disruptions in cultures of rat pleural mesothelial cells exposed to asbestos fibers.

The control of DNA integrity in mammalian cells is important to maintain the cell homeostasis and prevent neoplastic transformation. Control of cell division and cell death permits repair or elimination of damaged cells. Since asbestos fibers can produce DNA damage, chromosome alterations and apoptosis in several sorts of cells, including mesothelial cells, it was interesting to investigate cell cycle disturbances in rat pleural mesothelial cells (RPMC) treated with asbestos fibers. Cell cycle analyses were performed in RPMC exposed to crocidolite (10 and 20 microg/cm2) and chrysotile (5 and 10 microg/cm2) for different times (4 to 48 h). Both fiber types entailed a G2/M accumulation in agreement with a delay in the mitosis course. Chrysotile fibers produced a G0/G1 accumulation associated with a time-dependent p53 and p21 expression. Crocidolite exposure resulted in a delay in the G1/S transition paralleling a low rate of p53 expression. These results are in agreement with a DNA damaging potential of asbestos fibers since similar results were found following RPMC exposure to gamma rays. In asbestos-treated RPMC, a low rate of apoptosis was found suggesting that RPMC may follow a DNA repair pathway that could contribute to the formation of DNA lesions. In addition, the cell cycle disturbances at the G2/M checkpoint suggest that genetically altered cells have progressed through the cycle and support the already published findings on the ability of asbestos fibers to impair cell division.

Animals↗