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Biomedical subjects

W Beck

Publications and source records attributed to W Beck.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Differential diagnosis of medically relevant flea species and their significance in dermatology].

Different flea species may infest humans temporarily. Such arthropods should be considered as a possible cause of erythematous and pruritic papules and nodules of unclear origin. Bites from animal fleas can be seen in people with close contact to domestic or wild animals. This dermatosis may often be misdiagnosed. Several flea species including Pulex irritans, Ctenocephalides canis, Ctenocephalides felis, Ceratophyllus gallinae, Ceratophyllus columbae and Archaeopsylla erinacei may infest human skin, causing symptoms. Flea bite-allergy and the role of various flea species as disease vectors are also discussed.

Animals↗
PubMed1997

Two types of modified cardiac Na+ channels after cytosolic interventions at the alpha-subunit capable of removing Na+ inactivation.

Failure of inactivation is the typical response of voltage-gated Na+ channels to the cytosolic presence of proteolytic enzymes, protein reagents such as N-bromoacetamide (NBA) or iodate, and antibodies directed against the linker between domains III and IV of the alpha-subunit. The present patch clamp experiments with cardiac Na+ channels aimed to test the hypothesis that these interventions may provoke the occurrence of non-inactivating Na+ channels with distinct kinetic properties. A site-directed polyclonal antibody (anti-SLP2, target sequence 1481-1496 of the cardiac Na+ channel alpha-subunit) eliminated fast Na+ inactivation to induce burst activity which was accompanied by the occurrence of two open states. A deactivation process terminated channel activity during membrane depolarization proceeding with time constants of close to 40 ms (at -40 mV). NBA-modified and iodatemodified Na+ channels were kinetically indistinguishable from the anti-SLP2-modified type since they likewise deactivate and, thus, attain an only moderate Po of close to 20%. This is fundamentally different from the behaviour of enzymatically-modified Na+ channels: after cytosolic proteolysis with alpha-chymotrypsin, trypsin or pronase, mean Po during membrane depolarization amounted to approximately 40% because deactivation operated extremely slowly and less efficiently (time constants 100-200 ms at -40 mV, as a minimum) or was virtually non-operating. Invitro cleavage of the synthetic linker sequence 1481-1496 confirmed that this part of the alpha-subunit provides a substrate for these peptidases or reactants for NBA but cannot be chemically modified by iodate. This iodate resistance indicates that iodate-modified Na+ channels are based on a structural alteration of still another region which is also involved in Na+ inactivation, besides the linker between domains III and IV of the alpha-subunit. Endogenous peptidases such as calpain did not affect Na+ inactivation. This stresses the stochastic nature of a kinetic peculiarity of cardiac Na+ channels, mode-switching to a non-inactivating mode.

Acetamides↗
PubMed1997

The use of a long-lifetime component of tryptophan to detect slow orientational fluctuations of proteins.

The membrane protein porin and a synthetic polypeptide of 21 hydrophobic residues were inserted into detergent micelles or lipid membranes, and the fluorescence of their single tryptophan residue was measured in the time-resolved and polarized mode. In all cases, the tryptophan fluorescence exhibits a long-lifetime component of about 20 ns. This long-lifetime component was exploited to detect slow orientational motions in the range of tens of nanoseconds via the anisotropy decay. For this purpose, the analysis of the anisotropy has to be extended to account for different orientations of the dipoles of the short- and long-lifetime components. This is demonstrated for porin and the polypeptide solubilized in micelles, in which the longest relaxation time reflects the rotational diffusion of the micelle. When the polypeptide is inserted into lipid membranes, it forms a membrane-spanning alpha-helix, and the slowest relaxation process is interpreted as reflecting orientational fluctuations of the helix.

Diffusion↗
PubMed1997

Impact of membrane choice and blood flow pattern on coagulation and heparin requirement--potential consequences on lipid concentrations.

BACKGROUND: We reasoned that procoagulant activity, and by implication heparin requirement, during haemodialysis are influenced, amongst other factors, by the type of membranes and the geometry of the blood line system. In addition, there are indications that heparin has dose-dependent effects on the lipid status of chronic haemodialysis patients. METHODS: In a parallel group design we compared patients treated with cuprophane (CU) and polycarbonate-polyether (PC-PE) plate dialysers. In both groups, blood line geometry was varied by including in a first phase and omitting in a second phase drip chambers in the arterial blood line. End-points were changes in coagulation parameters, i.e. thrombin-antithrombin III complex (TAT), plasmin-anti-plasmin complex (PAP), and prothrombin fragment (F1 + 2) concentrations measured by sandwich ELISA. Subsequently all patients were switched to PC-PE dialysers for 6 months and the heparin dose was reduced in a stepwise fashion. Lipid levels and coagulation parameters were monitored. Finally, in an ancillary study, the correlation between heparin dose and LDL/HDL ratio was assessed in patients chronically exposed to PC-PE membranes and low doses of heparin. RESULTS: Post-dialytic concentrations of coagulation and fibrinolysis parameters were significantly lower in the PC-PE group (TAT 31.0 +/- 4.4 micrograms/l; PAP 1180 +/- 148 micrograms/l; F1 + 2 4.2 +/- 0.4 nmol/l) compared to the CU group (TAT 57.3 +/- 10.8 micrograms/l; PAP 1789 +/- 185 micrograms/l; F1 + 2 8.8 +/- 1.0 nmol/l), independently of the use of an arterial drip chamber. Omission of the arterial drip chamber led to lower TAT in the CU group (42.2 +/- 5.8 micrograms/l, P < 0.05), but not in the PC-PE group. In contrast, PAP and F1 + 2 concentrations did not change significantly in either group. Down-titration of heparin dose (from 20.4 +/- 1.1 to 9.4 +/- 0.9 IU/kg/h) was associated with a significant decrease in serum triglycerides (from 2.9 +/- 0.9 to 2.0 +/- 0.6 mmol/l, P < 0.05), LDL-cholesterol (from 3.4 +/- 0.2 to 2.7 +/- 0.4 mmol/l, P < 0.05) and LDL/HDL-ratio (from 3.2 +/- 0.3 to 2.0 +/- 0.3, P < 0.05) with no significant change of total or HDL-cholesterol after 6 months. In an ancilliary analysis, a correlation between lipid parameters (LDL/HDL ratio) and heparin dose was confirmed in 24 patients chronically exposed to PC-PE membranes (r = 0.473, P < 0.05). CONCLUSIONS: In a prospective exploratory study (i) heparin requirement is lower with the use of a polycarbonate-polyether membrane compared to a cuprophane membrane, (ii) heparin requirement is influenced by blood line geometry (decreased with omission of an arterial drip chamber), and (iii) in patients on polycarbonate-polyether membranes down-titration of heparin is associated with a reduction of serum triglycerides, LDL cholesterol, and LDL/HDL ratio. Our data suggest that reduction of heparin dose improves lipid profile. These preliminary observations require confirmation by parallel group controlled studies with controlled dietary intake.

Aged↗
PubMed1997

Induction of an epitope-specific humoral immune response by lipopeptide-hapten conjugates: enhancement of the anti-melittin response by a synthetic T helper (Th)-cell epitope.

Lipopeptides of bacterial origin constitute potent immunoadjuvants when combined with antigens. After the immunization with lipopeptides covalently coupled to non-immunogenic low-molecular-mass antigens or haptens, a hapten-specific humoral immune response can often be obtained. The response against synthetically prepared melittin fragments was further enhanced by the additional introduction of a T helper (Th)-cell epitope into the lipopeptide-hapten conjugate. The Th-cell epitope applied, which is presented by the MHC class II molecule of the BALB/c (H-2d) haplotype, consisted of a synthetic 16-amino-acid oligopeptide derived from sperm whale myoglobin. The immune-enhancing effect was most pronounced for the melittin-derived peptide fragments [Mel(1-16)] and [Mel(17-26)-CONH2]. Antibodies obtained after 3 immunizations with the conjugates recognized the synthetic as well as the native melittin molecule. Our results show that it is possible to markedly enhance a weak hapten-specific immune response by coupling the haptens to a lipopeptide conjugated to a haplotype-specific T helper-cell epitope. The novel conjugates are well suited for the optimization of immunization procedures, and for the development of novel synthetic vaccines.

Adjuvants, Immunologic↗
PubMed1997

[Allergenicity and specific protein profiles of mange mites Chorioptes bovis, Psoroptes ovis (Acari: Psoroptidae), Saroptes suis and Notoedres cati (Acari: Sarcoptidae) using SDS-PAGE and immunoblotting].

A main point of immunoparasitological research in regard to pest arthropod-infestation is biochemical and immunological characterization of antigens. Precondition of own examinations to the specific protein pattern of mange mites were in quality and amount sufficient antigen preparations in mite extract solutions. For mite separation and antigen refinement field strains of Chorioptes bovis, Psoroptes ovis, Sarcoptes suis and Notoedres cati from definitive host animals cattle, sheep, pig and cat have been used. Parasites were isolated in a migration procedure. After having applicated subepidermally a low dose of mite extract solutions in sensitized animals allergic skin changes (Immediate reaction type 1) became apparent. SDS-PAGE exhibited specific protein patterns of 4 pathogen mite species. For Chorioptes bovis 16, Psoroptes ovis 15, Sarcoptes suis 27, and Notoedres cati 36 fractions have been detected. Proteins are antigens or allergen structures to be found in saliva, faecal output or moulting products of developmental stages and other metabolites of the parasites. Protein components were transferred onto nitrocellulosis. Immunoblotting made fractions with antigen activity visible.

Allergens↗
PubMed1997

[Development of a computer-assisted thermoelectric Peltier cold test procedure with integrated photoplethysmography unit for noninvasive evaluation of acral skin circulation].

Local cold provocation tests are an important, non-invasive diagnostic tool for collecting information about skin perfusion during exposure to cold. In patients suffering from vasospastic circulatory disorders such as Raynaud's phenomenon, it is of particular importance to be able to collect data about acral circulation during the cooling test in the asymptomatic intervals between naturally occurring attacks. By carrying out a series of cold provocation tests, for example, patient response to a newly initiated therapy can be assessed. Here we present a recently developed, computer-aided thermoelectric Peltier device with an integrated finger holder for carrying out local cold provocation tests. The electronic control unit of the Peltier element make it possible to cool or heat to predefined temperatures. At the same time, the temperature of both the finger holder and the skin can be measured. A photoplethysmographic sensor is also integrated within the device, enabling the response of the pulse waves to the controlled temperature changes to be monitored accurately. It is also possible to measure simultaneously laser Doppler flux and capillary pressure in the nailfold and to perform nailfold capillaroscopy to determine red blood cell velocity. The new device provides us with the technical means to study the interrelationship between acral skin perfusion and the thermal regulation of the skin.

Blood Flow Velocity↗
PubMed1996

[Knee joint arthroses and work-related factors].

Occupational risk factors for arthrosis of the knee confirmed by x-ray were evaluated in a case-control study comprising 115 male and 86 females cases. Controls (95 men and 87 women) were free of symptoms of the musculoskeletal system. For both sexes age-adjusted odds ratios were calculated. Elevated odds rations were found in men working on their knees (OR 2.2), being exposed to vibrations of the upper limbs (OR 2.8), or adverse climatic conditions--humidity, coldness, or current air (OR 2.0). Men working in the metal industry or in other not further classified blue collar jobs also showed increased odds ratios (OR 3.2 and 3.1). In women odds rations were elevated for working in a standing position (OR 2.1) and for working with heavy tools (OR 6.1).

Adult↗
PubMed1996

[Animal mite-induced epizoonoses and their significance in dermatology].

Different mite species may infest humans temporarily; such arthropods should be considered a possible cause of pruritic skin reactions of unclear origin. Pseudo-scabies is a common problem. This self-limiting dermatosis may often be misdiagnosed. Several mite species including Sarcoptes scabiei var. canis, Sarcoptes scabiei var. bovis, Notoedres cati, Cheyletiella yasguri, Cheyletiella blakei, Dermanyssus gallinae and Ophionyssus natricis may infest human skin, causing symptoms. Other less common animal mites, Neotrombicula autumnalis and foodstuff mites are also discussed.

Animals↗
PubMed1996

A 'mixed' self-assembled monolayer for an impedimetric immunosensor.

A synthetic peptide with the amino acid sequence 135-154 of the capsid protein VP1 of the foot-and-mouth-disease virus was modified with omega-hydroxyundecanethiol and applied together with non-derivatised omega-hydroxyundecanethiol for consecutive adsorption onto gold electrodes according to self-assembling procedures. The binding of a specific antibody to prepared recognition layers could be monitored by measurement of impedance or capacitance. In order to avoid non-specific effects, all measurements were performed in the presence of BSA. The complex between the antigenic peptide and the antibody was split by applying 6 M urea solution. The gold electrodes were mounted into an optimised flow-through system in order to perform capacitance-time measurements. The immobilised peptide can be recognised repeatedly by specific antibodies.

Amino Acid Sequence↗
PubMed1995

[Arthroses of the finger joints and thumb saddle joint and occupationally related factors].

In a one-to-one matched case control study, 37 cases with rhizarthrosis (31 female, 6 male) and 44 cases with osteoarthritis in the finger joints (35 female, 9 male) were compared to their matches equal in sex and age regarding occupational strains. For calculating the odds ratios matching was maintained. In females the risk of rhizarthrosis was elevated for typists (OR 5.0, CI 1.27-19.59) and for work involving dexterity (OR 2.0, CI 0.77-5.23). In both sexes an elevated odds ratio for osteoarthritis in the finger joints was found for repetitive work (OR 3.8, CI 1.52-9.49).

Adult↗
PubMed1994

Conformational mapping of the cytosolic linker between domains III and IV of the cardiac Na+ channel protein and binding studies with a site-directed channel modifying antibody.

By combining antibody binding studies with conformational mapping using synthetic peptides, the structure of the cytosolic linker between domains III and IV of the cardiac Na+ channel alpha-subunit was analyzed. Inside-out patch clamp experiments with isolated cardiac Na+ channels from neonatal rat cardiocytes confirmed that a polyclonal antibody against amino acids 1490-1507 of the cardiac Na+ channel recognizes the linker in situ since Na+ inactivation became significantly retarded. Epitope fine mapping with a series of overlapping peptides identified the sequence YYNAMKKLG (corresponding to amino acids 1496-1504 of the cardiac sodium channel alpha-subunit) as the binding locus of the site directed antibody, an interesting result with respect to structure-function relationships because the functionally important hydrophobic amino-acid cluster in position 1487-1489 is not included. Circular dichroism measurements of synthetic 20-mer peptides in hydrophilic and lipophilic environments provided indications for a notable alpha-helical content only for segment GGQDIFMTEEQKKYYNAMKK. This sequence corresponds to amino acids 1483-1502 in the linker and adopts a highly ordered pattern of charge distribution due to this helical conformation. Ordered structure and helix dipole moment represent physical properties which may be important in a refined model for explaining the function of the linker in terminating the open channel configuration.

Amino Acid Sequence↗
PubMed1994

HPLC separation of enterobactin and linear 2,3-dihydroxybenzoylserine derivatives: a study on mutants of Escherichia coli defective in regulation (fur), esterase (fes) and transport (fepA).

Reversed-phase HPLC separation of enterobactin and its 2,3-dihydroxybenzoylserine derivatives was used for a comparative analysis of mutants of Escherichia coli, defective in the regulation of enterobactin biosynthesis (fur), enterobactin transport (fepA) and enterobactin esterase (fes). A complete separation of all 2,3-dihydroxybenzoylserine compounds was achieved: the monomer (DHBS), the linear dimer (DHBS)2 and trimer (DHBS)3, the cyclic trimer, enterobactin, as well as 2,3-dihydroxybenzoic acid. The production of all these compounds was followed after ethylacetate extraction from acidified culture fluids. Enterobactin was found to be the predominant product in all mutant strains. The mutant strains behaved differently with regard to the breakdown products. All degradation products, such as DHBS, (DHBS)2 and (DHBS)3, were detected in the overproducing fur mutant where both transport and esterase are still functioning, while only the monomer, DHBS, was detected in the fepA mutant and no degradation was found in the esterase-deficient fes mutant. From the pattern of breakdown products it may be inferred that the esterase acts in two different ways, depending on whether transport is functioning or not. Thus, esterolytic cleavage of ferric enterobactin after entering the cells results in a mixture of all three hydrolysis products, i.e. DHBS, (DHBS)2 and (DHBS)3, while cleavage of iron-free enterobactin subsequent to its biosynthesis yields only the monomer. Thus, the results of quantitative HPLC analysis of enterobactin and its breakdown products show that different enterobactin esterase products arise, depending on whether iron is bound to enterobactin or not.

Bacterial Outer Membrane Proteins↗
PubMed1994

Lipopeptide-polyoxyethylene conjugates as mitogens and adjuvants.

Two lipopeptide analogues of the Escherichia coli lipoprotein rendered water-soluble by polyoxyethylene were tested for mitogenicity in vitro in murine and human B lymphocytes and for adjuvant activity in vivo in mice. These highly amphiphilic lipopeptides retained the biological activity other lipopeptides usually exerted which supports the hypothesis of specific interactions of lipopeptides with membranes of reactive cells. The activation of human B lymphocytes by these lipopeptides was much less pronounced compared to that of murine cells. However, given in combination with anti-CD40 antibodies plus interleukin-4, human B lymphocytes could synergistically be stimulated to proliferate. As an adjuvant, the polyoxyethylene linked lipopeptides were almost as potent as Freund's adjuvants and other basic lipopeptides. Being water-soluble, these novel analogues are easy to apply and they are suitable for field studies as adjuvants when sonication can not usually be provided.

Adjuvants, Immunologic↗
PubMed1994

[Tyndallometry with the laser flare cell meter and biochemical protein determination in the aqueous humor of eyes with pseudoexfoliation syndrome].

UNLABELLED: Slit-lamp examination and flare measurement in eyes with pseudoexfoliation (PSX) syndrome frequently reveal signs of impairment of the blood-aqueous barrier. We studied both aqueous flare and aqueous protein concentration in PSX eyes to verify and quantify these alterations. PATIENTS: Aqueous flare was measured using the Laser Flare-Cell Meter Kowa FC-1000 in 158 normal control eyes (age 56.0 +/- 12.0 years), in 60 PSX eyes (age 72.5 +/- 9.4 years), and in 84 eyes with primary chronic open-angle glaucoma (PCOAG) (age 56.3 +/- 12.4 years). Total aqueous protein concentration was determined biochemically in 12 "normal" control eyes with senile cataracts (age 57.6 +/- 20.4 years), in 27 PSX eyes (age 72.6 +/- 9.1 years), and in 25 PCOAG eyes (age 63.3 +/- 13.5 years). After the primary aqueous humor was aspirated during cataract extraction or trabeculectomy, a modified BCA-Peirce method was employed. RESULTS: In PSX eyes, both aqueous flare (12.3 +/- 8.2 photon counts/ms) and aqueous protein concentration (0.42 +/- 0.16 mg/ml total protein) were significantly increased in comparison with normal control eyes (4.3 +/- 1.1 photon counts/ms and 0.22 +/- 0.08 mg/ml) and with PCOAG eyes (4.7 +/- 1.6 photon counts/ms and 0.26 +/- 0.09 mg/ml) (P < 0.0001). Differences between normal control eyes and PCOAG eyes were not significant (P > 0.05). There was a high correlation between aqueous flare measurements and aqueous protein concentration in eyes with PSX (y = 0.27x + 0.29, r = 0.65, P = 0.0006, n = 24). CONCLUSIONS: Our results indicate that impairment of the blood-aqueous barrier with an increase in aqueous protein concentration is a feature of PSX and may be quantified both by flare measurement and biochemical protein determination. These alterations should be considered in the pharmacological and surgical treatment of PSX eyes.

Adult↗
PubMed1993

MHC/peptide binding studies indicate hierarchy of anchor residues.

MHC class I molecules present octa- or nonapeptides derived from cellular proteins. Such peptides adhere to strict rules, which are individual to each MHC allele. Synthetic peptides conforming to these rules or peptides being at variance at critical residues were assayed for binding to MHC class I molecules. The binding assay employed the peptide-induced stabilization of MHC molecules of RMA-S cells. The data indicate that most proline-free peptides conforming to the allele-specific motifs of Kb or Db bind to the respective molecules, whereas peptides missing only one of the two allele-specific anchor residues lost their capacity to stabilize class I molecules on RMA-S cells. The residues allowed at anchor positions of the Kb motif are not equal in their binding efficiency and can be ordered in a hierarchic row. Residues at nonanchor positions may also influence efficiency of peptide binding or may require deviations from the standard peptide length.

Amino Acid Sequence↗