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A Eckhardt

Publications and source records attributed to A Eckhardt.

At least 19 recordsLinked to original sources
PubMed2004

Capillary electrophoretic separation of proteins and peptides by ion-pairing with heptanesulfonic acid.

Heptanesulfonic acid as ion-pairing agent was used for the separation of mixtures of low and high molecular mass peptides/proteins by capillary electrophoresis. The separation conditions used were: capillary 37 cm (30 cm to the detector) x 75 microm i.d., voltage 10 kV, phosphate buffer 50 mmol/l, ion-pairing agent heptanesulfonic acid at three different concentrations, namely, 0, 20 or 100 mmol/l, pH 2.5. The separation reflected the ion-pairing equilibria between the ion-pairing agent and the peptide/protein analytes. The influence of ion-pairing on sample mobility (running time) was more pronounced in case of the higher-molecular peptides as compared to the low molecular ones. This difference offers the possibility to separate low and high molecular peptides/proteins that under the absence of the ion-pairing agent would co-migrate. The principle of this approach was demonstrated on a randomly selected set of peptides/proteins; the practical applicability was demonstrated on a set of CNBr peptides arising from a naturally occurring mixture of collagen types I and III.

Animals↗
PubMed2003

Preparative procedures and purity assessment of collagen proteins.

Collagens represent a large family (25 members identified so far) of closely related proteins. While the preparative procedures for the members that are ubiquitous and present in tissues in large quantities (typically fibre and network forming collagens types I, II, III, IV and V) are well established, the procedures for more recently discovered minor collagen types, namely those possessing large non-collagenous domain(s) in their molecule, are mostly micropreparative and for some collagenous proteins even do not exist. The reason is that the proof of their existence is based on immunochemical staining of tissue slices and nucleic database searching. Methods of preparation and identification of constituting alpha-polypeptide chains as well as collagenous and non-collagenous domains are also reviewed. Methods for revealing non-enzymatic posttranslational modifications (particularly of the fibre forming collagen types) are briefly described as well.

Chromatography, Liquid↗
PubMed2001

Evaluation of peptide electropherograms by multivariate mathematical-statistical methods. I. Principal component analysis.

Depository effects in slowly metabolised proteins, typically glycation or the estimation of products arising from the reaction of unsaturated long-chain-fatty acid metabolites (possessing aldehydic groups) are very difficult to assess owing to their extremely low concentration in the protein matrix. In order to reveal such alterations we applied deep enzymatic fragmentation resulting in a set of small peptides, which, if modified, are likely to change their electrophoretic properties and can be visualised on the resulting profile. Peptide maps of collagen (a mixture of collagen types I and III digested by bacterial collagenase) were applied as the model protein structure for detecting the nonenzymatic posttranslational changes originating during various physiological conditions like high fructose diet and hypertriglyceridemic state. Capillary electrophoresis in acidic media (sodium phosphate buffer, pH 2.5) was used as the separation method capable of (partial) separation of over 60 peptide peaks. Two to 13 changes were revealed in the profiles obtained reflecting the physiological conditions of the animals tested. Combination of peptide profiling with subsequent t-test evaluation of individual peak areas and principal component analysis based on cumulative peak areas of individual sections of the electropherograms allowed to determine in which section (part) of the electropherogram the physiological state indicating changes occurred. Simultaneously it was possible to reveal the qualitative differences between the four physiological regimes investigated (i.e., which regime affects the collagen molecules most and which affects them least). The approach can be used as guidance for targeted preseparation of the very complex peptide mixture.

Animals↗
PubMed2001

Mixtures of nonionic and anionic surfactants: interactions with low-molecular-mass homopeptides.

The interaction between low molecular-mass homopeptides and mixtures of nonionic and anionic surfactants has been assessed by using reversed-phase thin-layer chromatography. The relative strength of interaction for mixtures of sodium dodecylsulfate and tridecylalcohol diglycolate (GNX) at the molar ratios of 8:2, 6:4, 4:6 and 2:8 has been calculated and its relationship with the physicochemical parameters (number of amino acid units, hydrophobicity, side chain bulkiness, electronic characteristics) of peptides has been computed by stepwise regression analysis. Each peptide interacted with each surfactant mixture the strength of interaction markedly depending on both the character of the peptide and the composition of the surfactant mixture. The hydrophobicity and electronic properties of the amino acid units exerted the highest influence on the strength of interaction at the highest concentration of the nonionic surfactant (GNX) whereas the number of amino acid units in the peptide molecule and the bulkiness of the amino acid side chain governed the strength of interaction at the lowest concentration of GNX.

Anions↗
PubMed2001

Interaction of surfactants with homologous series of peptides studied by reversed-phase thin-layer chromatography.

The relative strength of interaction between anionic (SDS) and nonionic surfactant (octaethoxylated oleyl alcohol, GEN) and homologous series of peptides was determined by reversed-phase thin-layer chromatography (RP-TLC) carried out on alumina layers impregnated with paraffin oil. The relative strength of interaction was calculated and was correlated with the physicochemical parameters of peptides. It was established that each peptide interacted with both surfactants and with their mixture (1:1, m/m). The relative strength of interaction depended on the number of amino acid units in the peptide, side chain bulk and electronic properties and hydrophobicity of the amino acids. The impact of individual parameters highly depended on the character of surfactant. The data prove that the retention order of peptides can be modified by adding different surfactants and surfactant mixtures to the mobile phase resulting in improved separation.

Chromatography, Thin Layer↗
PubMed2000

A possible role of the oxidant tissue injury in the development of hypoxic pulmonary hypertension.

Chronic sojourn in hypoxic environment results in the structural remodeling of peripheral pulmonary arteries and pulmonary hypertension. We hypothesize that the pathogenesis of changes in pulmonary vascular structure is related to the increase of radical production induced by lung tissue hypoxia. Hypoxia primes alveolar macrophages to produce more hydrogen peroxide. Furthermore, the increased release of oxygen radicals by other hypoxic lung cells cannot be excluded. Several recent reports demonstrate the oxidant damage of lungs exposed to chronic hypoxia. The production of nitric oxide is high in animals with hypoxic pulmonary hypertension and the serum concentration of nitrotyrosine (radical product of nitric oxide and superoxide interaction) is also increased in chronically hypoxic rats. Antioxidants were shown to be effective in the prevention of hypoxia induced pulmonary hypertension. We suppose that the mechanism by which the radicals stimulate of the vascular remodeling is due to their effect on the metabolism of vascular wall matrix proteins. Non-enzymatic protein alterations and/or activation of collagenolytic matrix metalloproteinases may also participate. The presence of low-molecular weight cleavage products of matrix proteins stimulates the mesenchymal proliferation in the wall of distal pulmonary arteries. Thickened and less compliant peripheral pulmonary vasculature is then more resistant to the blood flow and the hypoxic pulmonary hypertension is developed.

Animals↗
PubMed1998

Arthroplasty of the forefoot in rheumatoid arthritis: long-term results after Clayton procedure.

The present study aims to evaluate long-term results after Clayton resection arthroplasty in patients with symptomatic arthritis of the forefeet. From 1970 to 1995, 109 patients with a total of 184 rheumatoid forefeet underwent Clayton's procedure at an average age of 60 years. Forty-seven of them returned with 82 operated feet for follow-up by means of patient history, physical examination and radiograph an average of 12.8 years later. Overall outcome was judged as successful in 60 of the 82 cases with complete pain relief, remarkably improved gait capacity and use of normal shoes. Sixteen of the feet were definitely improved, but slight to moderate pain, inadequate balance and contact with the ground, limited walking distance and use of large shoes were signs of decreased operation success. The remaining 5 feet showed recurrent splay-foot deformity with intolerable pain, functional disability and restricted gait capacity even though specially made surgical shoes were used. The Clayton procedure appears to be a suitable method for surgical correction of symptomatic rheumatoid forefeet.

Adult↗
PubMed1997

Dosage adjustment of antiinfective therapy in patients with renal impairment.

Schematic dosage adjustments for aminoglycosides, vancomycin, and ciprofloxacin were derived from published data on the prolongation of elimination half-lives in patients with renal impairment. Therapeutic drug monitoring was retrospectively evaluated with 84 severely ill patients, 29 of whom needed renal replacement therapy (35%). Mortality (n = 27) and antiinfective failures were high (n = 23). Toxicity was suspected in 5 patients, though it was demonstrated only in 1 case. As compared to the patients with normal renal function, patients with renal impairment exhibited peak levels that tended to be lower, although their trough levels tended to be higher; the aminoglycoside troughs even were significantly elevated in renal replacement patients (1.0 mg/l (0.6-1.4) versus 0.6 mg/l (0.3-0.8)). Seen in relation to toxicity, antiinfective failure was by far the greater problem even with dosage adjustments at high trough levels. Multivariate analysis showed antiinfective failure to be significantly correlated to 10 canonical variables (age, weight, leucocyte count, peak level, trough level, initial creatinine, increase in creatinine, fever, change of dosage, and renal replacement therapy). Among these variables, it were neither drug levels nor renal replacement, but only persistent fever and deteriorating renal function that independently contributed to antiinfective failure. For adjustment of antiinfective therapy, paradoxically we conclude that trough concentrations higher than normal must be allowed for to avoid underdosage in renal replacement patients.

Aminoglycosides↗
PubMed1996

Transient expression of the mitogen-activated protein kinase phosphatase MKP-1 (3CH134/ERP1) in the rat brain after limbic epilepsy.

The immediate early gene-encoded enzyme, MAP kinase phosphatase 1 (MKP-1), is thought to be a key element in controlling cellular signalling pathways activated by MAP kinases. Since MAP kinase have been demonstrated to participate in neuronal stimulus-transcription coupling following seizure activity, the present study investigated the induction of MKP-1 in the rat brain after limbic epilepsy. MKP-1 expression was studied with a polyclonal antiserum by Western blots, immunocytochemistry and immuno-electron microscopy at different time periods between 1 and 24 h after kainic acid-induced limbic seizures. MKP-1 induction was identified in dentate granule cells of the hippocampus but not in pyramidal neurons, furthermore in neurons of the outer layers of the neocortex, as well as in neurons of the lateral nucleus of the bed of the stria terminalis. Immuno-electron microscopy demonstrated that MKP-1 was localized in the neuronal nucleus, where the substrate of MKP-1, activated MAP kinases, are also found. In view of the restricted areas of MKP-1 expression and the widespread areas of altered MAP kinases activity it can be concluded that in the majority of CNS populations other mechanisms than MKP-1 induction are responsible for the shut-off of MAP kinases following seizure activity. MKP-1 may contribute in the specific subpopulations where it is induced to the post-translational control of inducible transcription factors of the fos, jun and myc family.

Animals↗
PubMed1996

[Vertigo and anxiety disorders--results of interdisciplinary evaluation].

BACKGROUND: Vertigo is a common symptom that often remains unexplained despite extensive medical evaluation. Psychiatric and psychosomatic disorders are usually considered after all somatic causes of vertigo have been ruled out. METHODS: Eighty-three patients referred to neurological or psychosomatic outpatient treatment received an extensive neurootologic and psychosomatic evaluation: one (or two) diagnostic psychiatric psychodynamic exploration(s), a structured interview, psychometric tests (SCL-90-R, STAI-G X2 and GBB). The patients were divided into four diagnostic groups: psychic causes only (psychogenic group), neurootologic causes only (somatic group), both diagnoses (psychosomatic group), neither diagnosis (group IV). RESULTS: Twenty-three patients had organic vertigo, thirty-nine patients had psychogenic vertigo and in seventeen cases a vestibular lesion initiated the development of a neurotic disorder, particular anxiety disorder. Most of the patients of the psychogenic and psychosomatic group had anxiety or phobic disorders. The patients with psychogenic or psychosomatic symptoms of vertigo generally report a higher level of subjective distress; the periods of disability are significant longer. CONCLUSIONS: The study suggests that assessment of psychiatric and psychosomatic symptoms should always accompany, not follow, neurootologic evaluation of vertigo. An early interdisciplinary therapy should be started to prevent the chronicity of the symptomatology.

Adult↗
PubMed1993

[Depersonalization and self-injury].

Patients with deliberate self harm syndrome and with factitious disorders often describe depersonalisation phenomena, during which they have a diminished pain sensitivity or analgesia. The self-mutilating act can stop the depersonalisation temporarily. Concerning the psychodynamic processes there are common traits between depersonalisation and self-mutilation. The connections between depersonalisation and self-mutilating behaviour are described. Depersonalisation is understood as a defense mechanism, ranging between mature and immature defense mechanisms. An illustrative case is demonstrated.

Adult↗
PubMed1992

[Artificial diseases (self-induced diseases)--a review].

Factitious disorders have gained greater significance in all medical specialties during recent years, and continue to pose difficult problems. At present factitious disorders can be divided into four sub-types, the pretence and/or production of somatic and/or psychic medical symptoms being central to all. Apart from disturbance of ego structure the self and the body image (self) a specific disturbance of the doctor-patient relationship is of pathognomonic value. An integrated therapeutic approach (combination of palliative measures, somatic therapy and psychotherapy) seems to be most successful. In the differential diagnosis, factitious diseases have to be delineated from many other diseases in which self-destructive behaviour may occur.

Adult↗
PubMed1991

Evaluation of protective mAbs against Pseudomonas aeruginosa outer membrane protein I by C1q binding assay.

Seven monoclonal antibodies (mAbs) against the outer membrane proteins (OPRs) F, H and I of Pseudomonas aeruginosa were prepared. Western blot analysis has shown the mAbs to cross-react with all 17 serotypes of P. aeruginosa according to the International Antigenic Typing Scheme. Two of the mAbs (2A1, 6A4) protected mice against fatal P. aeruginosa pneumonia. The protective potential of the mAbs did not correlate with the immunoglobulin isotype nor with the fine antigen specificity and the in vitro bactericidal activity of the mAbs. Only the binding of the first complement component C1q of the mAbs as estimated in vitro by an ELISA was significantly correlated with their protective potential.

Animals↗
PubMed1990

Selective solubilization of chlorosome proteins in Chloroflexus aurantiacus.

Proteins were solubilized selectively from chlorosomes of Chloroflexus aurantiacus by electrophoretic gel filtration according to Griebenow et al. Whereas the 11 kDa and 18 kDa proteins were extracted almost completely, the remaining modified chlorosomes contained high amounts of pigment and c-protein. It was concluded that the c-protein in contradiction to the publication by Griebenow et al. is indeed localized in the interior of Chloroflexus chlorosomes.

Bacteria↗
PubMed1990

Protection against experimental Pseudomonas aeruginosa infection by recombinant P. aeruginosa lipoprotein I expressed in Escherichia coli.

Lipoprotein I (OprI) is one of the major proteins of the outer membrane of Pseudomonas aeruginosa. OprI is a candidate for a vaccine against P. aeruginosa, because it cross-reacts antigenically in all serotype strains of the International Antigenic Typing Scheme. We recently cloned and expressed the gene coding for OprI in Escherichia coli. This heterologously expressed OprI was used successfully to immunize mice against P. aeruginosa. In addition, OprI from serogroup 12 of P. aeruginosa was highly purified by preparative isoelectric focusing and used for immunization of mice. Both vaccines protected the mice against a challenge with a four- to fivefold 50% lethal dose of P. aeruginosa.

Animals↗