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Biomedical subjects

C Korn

Publications and source records attributed to C Korn.

At least 19 recordsLinked to original sources
PubMed2006

Efficiency of initiating cell adhesion in hydrodynamic flow.

We theoretically investigate the efficiency of initial binding between a receptor-coated sphere and a ligand-coated wall in linear shear flow. The mean first passage time for binding decreases monotonically with increasing shear rate. Above a saturation threshold of the order of a few 100 receptor patches, the binding efficiency is enhanced only weakly by increasing their number and size, but strongly by increasing their height. This explains why white blood cells in the blood flow adhere through receptor patches localized to the tips of microvilli, and why malaria-infected red blood cells form elevated receptor patches (knobs).

Biomechanical Phenomena↗
PubMed2001

Identification of functionally relevant histidine residues in the apoptotic nuclease CAD.

The caspase-activated DNase CAD (DFF40/CPAN) degrades chromosomal DNA during apoptosis. Chemical modification with DEPC inactivates the enzyme, suggesting that histidine residues play a decisive role in the catalytic mechanism of this nuclease. Sequence alignment of murine CAD with four homologous apoptotic nucleases reveals four completely (His242, His263, His304 and His308) and two partially (His127 and His313) conserved histidine residues in the catalytic domain of the enzyme. We have changed these residues to asparagine and characterised the variant enzymes with respect to their DNA cleavage activity, structural integrity and oligomeric state. All variants show a decrease in activity compared to the wild-type nuclease as measured by a plasmid DNA cleavage assay. H242N, H263N and H313N exhibit DNA cleavage activities below 5% and H308N displays a drastically altered DNA cleavage pattern compared to wild-type CAD. Whereas all variants but one have the same secondary structure composition and oligomeric state, H242N does not, suggesting that His242 has an important structural role. On the basis of these results, possible roles for His127, His263, His304, His308 and His313 in DNA binding and cleavage are discussed for murine CAD.

Amino Acid Sequence↗
PubMed2001

IDEA: a large-scale project on electronic identification of livestock.

The aim of the IDEA (Identification électronique des animaux) project is to collect information on the feasibility of the introduction into the European Union (EU) of an animal electronic identification system, as referred to in Directive 92/102 and Regulation 1760/2000. The project will run for a period of four years (1998-2001) and will include one million animals in six countries (France, Germany, Italy, The Netherlands, Portugal and Spain). The Joint Research Centre, as technical co-ordinator of the project, provides technical support in terms of testing and certification of electronic identification devices, establishment of the central database, transmission and recording of data and evaluation of results. Identification has been undertaken in cattle, sheep, goats and buffalo using three types of electronic tags (ruminal bolus, ear tag and injectable transponder). The performance of these tags is checked at defined intervals until recovery in the slaughterhouse. The evaluation of the results in terms of the performance of the device and the necessary organisational support structures will lead to recommendations for a system to trace animals from birth to slaughterhouse, including the appropriate technology to be applied in any generalised system for the livestock sector in the EU.

Animal Identification Systems↗
PubMed2000

Genetic engineering of Escherichia coli to produce a 1:1 complex of the anabaena sp. PCC 7120 nuclease NucA and its inhibitor NuiA.

A series of T7-promoter based bicistronic expression vectors was constructed in order to produce the complex of the Anabaena sp. PCC 7120 DNA/RNA non-specific nuclease NucA and its inhibitor NuiA. With all constructs, tandem expression of nucA and nuiA results in aggregation and inclusion body formation of NucA, independent of the order of the genes, the relative expression of the two proteins and the temperature applied during expression. Two constructs in which nuiA is the first and nucA the second cistron lead to an approximately one order of magnitude higher expression of nuiA compared with nucA. In these cells inclusion bodies are formed which contain NucA and NuiA in a 1:1 molar ratio. The complex can be solubilized with 6M urea after disruption of the cells by sonication, renatured by dialysis and purified to homogeneity. 2mg of the complex are obtained from 1l Escherichia coli culture. As shown by gel filtration and analytical ultracentrifugation, our system leads to a highly pure and homogeneous complex preparation, as required for biophysical and structural studies. Thus, our new method is a superior alternative for the production of the NucA/NuiA complex in which separately produced nuclease and inhibitor are mixed, and an excess of one or the other component, as well as aggregates of NucA, have to be removed from the preparation.

Algal Proteins↗
PubMed1998

Comparison of the effects of ularitide acetate and other bronchorelaxing substances on the thrombin-induced permeability raise of human endothelial cell monolayers.

Endothelial cell contraction plays a pivotal role in vascular leakage. It increases the extravasation of fluid and macromolecules from the lumen into the interstitium. This is also true for bronchial edema. Previous studies have indicated that an elevation of intracellular adenosine-3',5'-cyclic monophosphate (cAMP) or guanosine-3',5'-cyclic monophosphate (cGMP), respectively, can counteract this vascular leakage by improving the endothelial barrier function in analogy to the relaxation of smooth muscle cells. To investigate the potential antiedemateous effects of ularitide acetate (CAS 115966-23-9), isoproterenol hemisulfate (CAS 6078-56-4), sodium nitroprusside (CAS 13755-38-9, SNP), aminophylline (CAS 317-34-0), and combinations of these compounds, their effects on thrombin-induced macromolecular permeability raise in relation to cGMP- or cAMP-levels, respectively, in a model of human umbilical vein endothelial cells (HUVECs) were examined. Ularitide acetate, isoproterenol hemisulfate, and SNP all increased the amount of cyclic nucleotides and decreased the raise in permeability in the following order of potency: isoproterenol hemisulfate > ularitide acetate > SNP. Aminophylline raised both cGMP- and cAMP-levels in a weaker amount and was not able to decrease the thrombin-induced permeability raise on its own. By way of contrast, preincubation of HUVECs with aminophylline resulted in a more than additive potentiation of the cGMP-levels and the permeability lowering induced by ularitide-acetate. These in vitro-data indicate that ularitide-acetate, especially in combination with phosphodiesterase (PDE) inhibitors, could probably have beneficial effects in bronchial permeability edema.

Albumins↗
PubMed1998

Synergistic effects of ularitide acetate with classical bronchorelaxants on guinea-pig tracheal smooth muscle.

Ularitide (CAS 118812-69-4, urodilatin) is a member of the family of the atrial natriuretic peptides. In the present study, the relaxant effects of ularitide acetate, isoproterenol (isoprenaline) hemisulfate, aminophylline, zaprinast, and different combinations between these drugs were investigated on methacholine chloride-precontracted guinea-pig tracheal smooth muscle. Ularitide acetate was a weaker bronchorelaxant than isoproterenol hemisulfate and aminophylline. Moreover the relaxation induced by ularitide acetate was reversible, while the relaxation induced by isoproterenol hemisulfate, aminophylline, and zaprinast was irreversible. Combinations between in each case two of these substances were overadditive, if the phosphodiesterase-inhibiting component was applicated before the combination partner. Their effects were only additive, if the combination partners were applicated simultaneously. All combinations between ularitide acetate and isoproterenol hemisulfate, aminophylline, or zaprinast respectively relaxed the tracheas irreversibly. These results suggest that ularitide acetate might be a novel partner for classical bronchorelaxants in potent bronchorelaxing combinations in the therapy of asthma bronchiale.

Aminophylline↗
PubMed1996

Vocational outcome of aphasic patients following severe traumatic brain injury.

The incidence and course of aphasia, and its impact on vocational outcome, were determined in a group of 351 patients with severe traumatic brain injury (TBI). Aphasia was found in 11.1%, the common forms being amnestic (56%, 22/39), expressive (10.3%, 4/39) and receptive (10.5%, 8/39), as found on the first language assessment. No age difference was found between the aphasic and non-aphasic patients. Coma was more common in the aphasics than the non-aphasics (95% and 82%, respectively), although its mean duration was shorter. Aphasics had more severe locomotor deficits (p < 0.01, Fisher test) and tended towards more severe cognitive disorders (p = 0.07, Fisher test). There was no difference between the groups in incidence of behavioural disturbances or occupational outcome. Most of the aphasic patients improved after therapy, and two recovered completely. The presence of aphasia did not have negative prognostic implications for occupational outcome.

Activities of Daily Living↗
PubMed1995

Recall of informed consent after endoscopic procedures.

PURPOSE: The aim of this study was to determine if recall of informed consent is affected by the timing of obtaining informed consent before endoscopic procedures. METHODS: Sixty patients scheduled for colonoscopy or esophagogastroduodenoscopy were enrolled in this prospective, randomized study. Each patient received informed consent 24 to 72 hours or immediately before the procedure, and follow-up occurred one to three days postprocedure. RESULTS: There was no statistically significant difference in recall of informed consent or the individual elements of informed consent (indication, risks, benefits, alternatives) between the two groups. CONCLUSION: Recall of informed consent is similar whether consent is obtained immediately or several days before endoscopic procedures.

Amnesia, Retrograde↗
PubMed1994

Non-exponential behavior of the nuclear magnetization in H-doped copper oxides.

Measurement of the spin lattice relaxation time in H-doped Y2BaCuO5 and YBa2Cu3O6 has revealed a power law growth of the nuclear magnetization M for short times following a saturation pulse sequence. Preliminary experimental results yield exponents of 1/2 and 1/3, depending on the amount of hydrogen present in the sample. We extend Blumberg's theory for relaxation due to paramagnetic centers via dipole-dipole interaction in the absence of spin diffusion to obtain M approximately tD/6 where D is the dimensionality of the system. This yields exponents of 1/2 and 1/3 for three- and two-dimensional systems, respectively. At long times the magnetization growth becomes exponential.

Copper↗
PubMed1992

Frequency selectivity as a potential measure of noise damage susceptibility.

The notched-noise procedure of Patterson (1974, Journal of the Accoustical Society of America, 55, 802-809; 1976, Journal of the Acoustical Society of America, 59, 640-654) was employed in revealing changes in auditory frequency selectivity (FS) in noise-exposed industrial workers in manufacturing plants in which noise levels in the working environment exceeded 90 dB(A). With 4 kHz as the test frequency, both threshold and FS measures were applied to three groups of non-exposed young adults (total N = 61) for reference values and to workers in three different factories, some ('noise-exposed') working in noise levels over 90 dB(A) (total N = 222). In another study involving 185 workers only the FS test was repeated after a work session, and the results are reported on 31 who worked in high noise levels. Pre-work-shift data showed that when thresholds were better than 30-dB HL most FS values were 10 dB or more, while subjects with hearing threshold levels beyond that showed reduced FS. Two post-work-shift studies of 144 ears of the noise-exposed workers showed significant deleterious changes in both thresholds and FS but the relationships were different in the two studies. The findings indicate that the notched-noise test is sensitive to noise-induced auditory damage, even after a single work-shift. Attractive features of the procedure are that it reduces the need for a quiet test environment and that it can be more resistant to testee manipulation or threshold 'learning' effects, often seen in industrial audiometric testing.

Acoustics↗