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Biomedical subjects

A Knoll

Publications and source records attributed to A Knoll.

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

Surface reconstruction of an ordered fluid: an analogy with crystal surfaces.

The surface structure of a lamellar polystyrene-block-polybutadiene-block-polymethylmethacrylate (SBM) triblock copolymer forms a complex reconstruction, which breaks the two-dimensional continuous translational symmetry of an ideal (homogeneous) SBM surface. Despite the very different types of matter and order, our findings reveal a remarkable analogy with the well-known phenomenon of surface reconstruction of single crystals, in particular, with the (2x1) "buckling row" reconstruction of the Si(100) surface. Similarities and differences between both classes of materials are discussed on the basis of symmetry considerations.

Journal Article↗
PubMed2001

Intensive care after minimally invasive and conventional coronary surgery: a prospective comparison.

OBJECTIVE: The purpose of this study was to compare the intensive care course of patients after minimally invasive coronary surgery to conventional coronary artery bypass grafting. DESIGN: Prospective observational study. SETTING: Intensive care unit of a university hospital. PATIENTS AND PARTICIPANTS: One hundred and five patients with two-vessel disease consecutively scheduled for elective coronary bypass surgery were enrolled. INTERVENTIONS: Two techniques of revascularization were performed: the Octopus procedure via median sternotomy without cardiopulmonary bypass (n = 52) and conventional coronary artery bypass grafting CABG (n = 53). MEASUREMENTS AND RESULTS: Three major categories describing the patients' postoperative course were defined: (1) clinical and laboratory findings, i.e., transfusion rate, catecholamine support, duration of ventilation, Simplified Acute Physiology Score II (SAPS II), serum levels of cardiac enzymes and lactic acid; (2) postoperative complications, i.e., incidence of myocardial infarction (MI), atrial fibrillation (AF), and neurological deficits; (3) this category was defined as "the extent of care" as represented by the Therapeutic Intervention Scoring System (TISS), and the length of stay in the ICU and in the hospital. In the Octopus group significantly lower figures were noted for duration of ventilation [6.1(5.5/9.5) vs 10.2(8.2/11.8) h], cardiac enzymes (CK-MB-Mass [5.1(2.0/8.3) vs 31.3(21.4/39.3) ng/ml], and lactic acid [2.0(1.5/3.3) vs 3.2(2.2/6.5) mmol/l]), incidence of AF (2/52 vs 9/53), and neurological deficits (0/52 vs 4/53), TISS score [72(44/83) vs 84(73/93)], LOS in the ICU [2(1/2) vs 2(2/2) days], and in the hospital [6(5/9) vs 9(8/12) days]. Catecholamine support, SAPS II scores, and incidence of MI of each group did not differ significantly. CONCLUSIONS: Off-pump coronary surgery via the Octopus technique was superior to conventional CABG regarding the course of patients in the early postoperative period. This implies benefits for the patients and the entire healthcare system.

APACHE↗
PubMed2000

Peroxisomal beta-oxidation enzyme gene expression in the developing mouse brain.

Using the northern blot technique, the steady-state levels for the mRNAs encoding acyl-CoA oxidase, pristanoyl-CoA oxidase, trans2, 3enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase multifunctional enzyme type 2, 3-ketoacyl-CoA thiolase and sterol-carrier-protein x during postnatal brain development were measured. The developmental patterns obtained for each mRNA species studied were similar, with an increase in the mRNA level between birth and postnatal day 5, followed by a gradual decrease to 34-55% of the maximal value at postnatal day 30. These results are in agreement with a coordinately controlled expression of the genes involved in VLCFA beta-oxidation during brain development. Moreover, comparison of these developmental profiles with that obtained for ceramide galactosyltransferase showed that the set-up of the very-long-chain fatty acids beta-oxidation system is independent of the myelinating signal in the central nervous system.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2000

Perception of traffic accident risk and decision to drive under light alcohol consumption--a double-blind experimental study.

PURPOSE: Public traffic safety campaigns in Germany have focussed on the changing risk perception of young drivers. While there is some consensus that perceptions of risk affect driving, less is understood about the relationship and interaction of alcohol consumption and risk perception on the decision to drive. We examined the influence of light alcohol consumption on risk perception and decision to drive, and the interaction of alcohol consumption and cognitive feedback on the handicapping effect of alcohol on risk perception and decision to drive. METHOD: In a double-blind block-randomized experimental study of 104 young drivers between 19 and 24 years of age, with two experimentally manipulated independent factors of alcohol consumption (three levels: 0% BAC, 0.015% BAC, 0.03% BAC) and feedback (positive or negative), we assessed three dependent variables: perception of traffic accident risk, subjective judgement about driving-relevant cognitive performance, decision to drive a car. Analyses of variance and covariance were used to analyze differences between levels of experimental factors. RESULTS: We found that persons with 0.015 BAC performed better than persons in both other alcohol conditions on the standardized risk perception task. Perceived handicap of driving was significantly more pronounced for negative feedback compared to positive feedback with no influence of the level of alcohol consumption. No significant influence on decision to drive was found of either level of alcohol consumption, feedback or sex. IMPLICATIONS: Decision to drive in young drivers could not be influenced by feedback or light consumption. Public health approaches have to find better determining factors.

Accidents, Traffic↗
PubMed1999

Involvement of lipoxygenase-dependent production of fatty acid hydroperoxides in the development of the hypersensitive cell death induced by cryptogein on tobacco leaves.

Lipid peroxidation was investigated in relation with the hypersensitive reaction in cryptogein-elicited tobacco leaves. A massive production of free polyunsaturated fatty acid (PUFA) hydroperoxides dependent on a 9-lipoxygenase (LOX) activity was characterized during the development of leaf necrosis. The process occurred after a lag phase of 12 h, was accompanied by the concomitant increase of 9-LOX activity, and preceded by a transient accumulation of LOX transcripts. Free radical-mediated lipid peroxidation represented 10% of the process. Inhibition and activation of the LOX pathway was shown to inhibit or to activate cell death, and evidence was provided that fatty acid hydroperoxides are able to mimic leaf necrotic symptoms. Within 24 h, about 50% of leaf PUFAs were consumed, chloroplast lipids being the major source of PUFAs. The results minimize the direct participation of active oxygen species from the oxidative burst in membrane lipid peroxidation. They suggest, furthermore, the involvement of lipase activity to provide the free PUFA substrates for LOX. The LOX-dependent peroxidative pathway, responsible for tissue necrosis, appears as being one of the features of hypersensitive programmed cell death.

Algal Proteins↗
PubMed1999

Gene expression of peroxisomal beta-oxidation enzymes in rat brain.

Despite increasing insight into peroxisomal beta-oxidation, it is still not clear which enzymes catalyze very-long-chain fatty acid degradation. Using the northern blot and RT-PCR techniques, a brain-specific expression is demonstrated for acyl-CoA oxidase 3II mRNA, thiolase-A and trans2,3enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase multifunctional enzyme type 2.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

High metabolism and subsequent elongation of 3-hydroxyeicosanoyl-CoA in very-long-chain fatty acid deficient PNS of Trembler mice.

The developmental patterns of the overall fatty acid elongation and of the last two partial activities of microsomal elongase (dehydration and reduction of 3-hydroxyacyl-CoA) were investigated in the PNS of normal and Trembler mice. Unexpectedly, Trembler microsomes synthesized normal C22-CoA amounts from 3-hydroxyeicosanoyl-CoA (3-OHC20-CoA), a C18-CoA elongation intermediate. Hydroxy- acyl-CoA dehydrase and enoyl-CoA reductase activities were found to be higher in the mutant than in the control, whatever the stage of development. Moreover, C20-CoA elongation led to normal C22-CoA and C24-CoA formation in the mutant whereas C20-CoA formation from C18-CoA was always far lower in Trembler than in control. C18-CoA condensing enzyme emerges as the only elongation step involved in the VLCFA deficit evidenced in Trembler PNS.

Acyl Coenzyme A↗
PubMed1999

Trembler as a mouse model of CMT1A?

The Trembler mouse suffers from a dominantly inherited autosomal mutation that results in an abnormal myelination of the peripheral nervous system. Biochemical studies have shown that dysmyelination is the primary event, demyelination being a late-occurring process. The expression of myelin protein genes has been studied. The steady-state levels for PMP22 mRNA represent 10 and 5% of normal values in the nerves of heterozygous and homozygous Trembler, respectively. This is due to a reduced expression of the specific transcript driven by the promoter 1 of the PMP22 gene. Collective results indicate that Trembler dysmyelination is not necessarily the consequence of a large accumulation of the mutated PMP22 protein. Moreover, it appears that the situation in the Trembler is different from that encountered in most CMT1A patients, where an increased PMP22 gene dosage is responsible for the disease. Therefore, the Trembler mutant is perhaps not an ideal model for this human neuropathy.

Animals↗
PubMed1999

Hydroxyacyl-CoA dehydrase and trans-2,3-enoyl-CoA reductase activities are consistent with long-chain fatty acid accumulation during rat brain development.

The developmental changes of microsomal 3-hydroxyacyl-CoA dehydrase and trans-2,3-enoyl-CoA reductase activities were analyzed and compared to very-long-chain fatty acid content and biosynthesis in rat brain. Contrary to the elongation rate of eicosanoyl-CoA and 3-hydroxyeicosanoyl-CoA, which paralleled myelination during brain maturation, the two partial activities of fatty acid elongation were already present at the earliest stages of development. One day after birth, 3-hydroxyacyl-CoA dehydrase and trans-2,3-enoyl-CoA reductase specific activities already represented 54.8% and 49.6% of the adult values, respectively. As a contribution to the quantitative estimation of the brain's ability to form its own VLCFA, it is shown that dehydrase and reductase activities are sufficient to allow the biosynthesis of all rat brain VLCFA at any age.

Acyl-CoA Dehydrogenases↗