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Biomedical subjects

A Seubert

Publications and source records attributed to A Seubert.

At least 19 recordsLinked to original sources
PubMed2005

Identification of a mutation in the ovine uroporphyrinogen decarboxylase (UROD) gene associated with a type of porphyria.

Porphyria is a group of at least eight diseases caused by abnormalities in the chemical steps that lead to haeme production. The different types of porphyria show different signs and symptoms and can be strongly influenced by environmental factors. Mutations of the uroporphyrinogen decarboxylase (UROD) gene have been shown to be causative for porphyria cutanea tarda (PCT) in humans. Porphyria is a rare disorder in livestock. Although disorders of haeme biosynthesis have been described in cattle, pigs, sheep and cats, PCT has only been reported in pigs. We observed typical signs of porphyria (photosensitivity and porphyrinuria) in a flock of German Blackface sheep and postulated that the porphyria could be caused by a mutation in the UROD gene. To investigate this, we cloned and sequenced the ovine UROD gene. We identified a single point mutation (C --> T) in UROD which leads to an amino acid substitution at Leu 131 Pro, which is located within the active cleft site of the UROD protein.

Animals↗
PubMed2002

Solution of a multiple-scattering inverse problem: electron diffraction from surfaces.

We present a solution to the multiple-scattering inverse problem for low-energy electron diffraction that enables the determination of the three-dimensional atomic structure of an entire surface unit cell directly from measured data. The solution requires a knowledge of the structure of the underlying bulk crystal and is implemented by a maximum entropy algorithm.

Journal Article↗
PubMed2002

Sulfoacylated poly(styrene-divinylbenzene) copolymers as resins for cation chromatography. Comparison with sulfonated, dynamically coated and silica gel cation exchangers.

Most important properties of an ion chromatographic resin are influenced by the resin matrix, the type of functional group and the ion-exchange capacity. Highly crosslinked PS-DVB resins of 5 microm diameter have been functionalized by sulfoacylation, by sulfonation and by dynamic coating over a wide range of exchange capacities. These materials allow a study of the influence of different ion-exchange sites and capacities. The influence of the degree of functionalization on resin performance is completely reverse for sulfoacylated and sulfonated resins. The HETP values for all observed analytes (Cu, Pb, Zn, Ni, Co, Cd, Mn, Ca, Mg) in a tartaric acid elution system decrease for sulfoacylated resins with increasing capacity, for sulfonated resins with decreasing capacity. The performance of sulfoacylated exchangers is better than for dynamically coated ones and far better than for sulfonated resins. The performance of silica gel based cation-exchangers such as BioSil CAT is in most cases better than observed for sulfoacylated resins.

Cation Exchange Resins↗
PubMed2002

Comparison of different activity parameters in atopic dermatitis: correlation with clinical scores.

BACKGROUND: Several laboratory markers have been described to correlate positively with disease activity of atopic dermatitis (AD). These include soluble adhesion molecules and eosinophil granular proteins. Although the correlation of these parameters with the severity and extent of skin involvement has been repeatedly studied in the past, no systematic investigation has been performed over a lengthy period of time. In addition, no subjective disease parameters recorded by the patient have been included in studies dealing with disease activity. OBJECTIVES: To assess the validity of different objective and subjective parameters [soluble E-selectin (sE-selectin), soluble vascular cell adhesion molecule-1 (sVCAM-1), eosinophil cationic protein (ECP), urinary nitrate excretion (reflecting endogenous nitric oxide formation) and the patients' impressions of pruritus, sleeplessness and skin status] as markers of AD disease activity. METHODS: Twenty patients were examined for 1 year and their skin status was evaluated by an established score (SCORAD). sE-selectin, sVCAM-1 and ECP were analysed by commercial test kits. Urinary nitrate concentration was measured by gas chromatography-mass spectrometry. The subjective parameters, pruritus, sleeplessness and impression of skin status, were recorded by the patients on a visual analogue scale. RESULTS: In this long-term trial, only sE-selectin and the subjective parameters showed a statistically significant correlation with the SCORAD score. CONCLUSIONS: Our data indicate that basic clinical scoring remains a most effective and relevant method of recording skin disease activity in AD.

Adolescent↗
PubMed2001

Invasion and persistent intracellular colonization of erythrocytes. A unique parasitic strategy of the emerging pathogen Bartonella.

The expanding genus Bartonella includes zoonotic and human-specific pathogens that can cause a wide range of clinical manifestations. A productive infection allowing bacterial transmission by blood-sucking arthropods is marked by an intraerythrocytic bacteremia that occurs exclusively in specific human or animal reservoir hosts. Incidental human infection by animal-adapted bartonellae can cause disease without evidence for erythrocyte parasitism. A better understanding of the intraerythrocytic lifestyle of bartonellae may permit the design of strategies to control the reservoir and transmittable stages of these emerging pathogens. We have dissected the process of Bartonella erythrocyte parasitism in experimentally infected animals using a novel approach for tracking blood infections based on flow cytometric quantification of green fluorescent protein-expressing bacteria during their interaction with in vivo-biotinylated erythrocytes. Bacteremia onset occurs several days after inoculation by a synchronous wave of bacterial invasion into mature erythrocytes. Intracellular bacteria replicate until reaching a stagnant number, which is sustained for the remaining life span of the infected erythrocyte. The initial wave of erythrocyte infection is followed by reinfection waves occurring at intervals of several days. Our findings unravel a unique bacterial persistence strategy adapted to a nonhemolytic intracellular colonization of erythrocytes that preserves the pathogen for efficient transmission by blood-sucking arthropods.

Animals↗
PubMed2001

Double-blind placebo-controlled house dust mite control measures in adult patients with atopic dermatitis.

BACKGROUND: Avoidance of allergens has been shown to be of benefit in patients with atopic asthma sensitized to indoor allergens. In atopic dermatitis, there is so far little information about the effect of house dust mite elimination strategies. OBJECTIVES: We therefore performed a randomized controlled study of house dust mite control in patients with this disease. METHODS: Twenty adult patients with moderate to severe atopic dermatitis were included. Inclusion criteria were a positive RAST to house dust mite antigen (CAP class > 3) and a concentration of > 2 microg g(-1) of the house dust mite antigen Der p1 in the patient's mattress dust. Patients were randomized to either the active treatment group (allergen-impermeable mattress encasing, acaricide spray containing tannic acid and benzylbenzoate) or a control group (allergen-permeable encasing, spray containing water and traces of ethanol). Severity of disease was estimated every 2 months by an established score (SCORAD), and eosinophil cationic protein (ECP) in the serum was determined by enzyme-linked immunosorbent assay. Furthermore, the use of topical steroids was quantified. Patients assessed daytime pruritus and pruritus-induced sleeplessness weekly on a visual analogue scale. The study lasted 1 year. RESULTS: At the end of the study, the active treatment group showed a statistically significant reduction in Der p1 exposure as compared with the control group. However, when comparing the change from the start to the end of the study, there was no statistically significant difference between active treatment and control groups as measured by the SCORAD score and by ECP levels in the serum. Some patients in the active treatment group reported less pruritus-induced sleeplessness, but there was no statistically significant difference between the two treatment groups. CONCLUSIONS: For adult patients with atopic dermatitis it was shown that 1 year of house dust mite avoidance reduced the allergen exposure, but an improvement of overall disease activity was not demonstrated.

Adolescent↗
PubMed2000

Simultaneous determination of inorganic disinfection by-products and the seven standard anions by ion chromatography.

For the first time, an ion chromatographic method for the simultaneous determination of the disinfection by-products bromate, chlorite, chlorate, and the so-called seven standard anions, fluoride, chloride, nitrite, sulfate, bromide, nitrate and orthophosphate is presented. The separation of the ten anions was carried out using a laboratory-made high-capacity anion-exchanger. The high capacity anion-exchanger allowed the direct injection of large sample volumes without any sample pretreatment, even in the case of hard water samples. For quantification of fluoride, chloride, nitrite, sulfate, bromide, nitrate, orthophosphate and chlorate, a conductivity detection method was applied after chemical suppression. The post-column reaction, based on chlorpromazine, was optimized for the determination of chlorite and bromate. The method detection limit for bromate measured in deionized water is 100 ng/l and for chlorite, it is 700 ng/l. In hard drinking water, the method's detection limits are 700 ng/l (bromate) and 3.5 microg/l (chlorite). The method's detection limits for the other eight anions, determined by conductivity detection, are between 100 microg/l (nitrite) and 1.6 mg/l (chlorate).

Anions↗
PubMed2000

Spacer-modified stationary phases for anion chromatography: alkyl- and carbonylalkylspacers--a comparison.

A comparison of two separation columns for high-capacity anion chromatography is presented. The distinctive feature of both packing materials is the structure of the alkyl-chain (spacer-group) between the polymer-backbone and the functional group. All other parameters, e.g. exchange capacity, functionality and length of the spacer-arm, are identical. The retention behavior of the so-called standard-anions is investigated on both columns under identical chromatographic conditions using an experimental design technique in the course of which the composition of the elution system applied is varied. The statistical treatment of the retention data offers the possibility to explain the different chromatographic behavior of both stationary phases, at least qualitatively.

Journal Article↗
PubMed2000

Influence of column geometry on the ion chromatographic separation of aluminium species.

The dependence of the degree of disintegration and therefore the applicability of ion chromatography for the speciation of aluminium fluoride species was examined for two different column geometries, a standard bore and a microbore column. Besides mathematical calculations, the temperature of the separation column was varied between -5 and 50 degrees C for the observation of a temperature-dependent decomposition of the species. All species were detected by UV photometry after post-column reaction with Tiron. The results showed that the disintegration of the higher coordinated Al fluoride species (AlFn with n >2) could be dramatically reduced utilizing the microbore technique. In contrast to the standard bore technique the column temperature is of minor importance. The agreement between speciation data experimentally determined by microbore chromatography and those calculated using stability constants is quite good. The standard bore technique showed bigger differences between calculated and experimentally determined species distributions.

Journal Article↗
PubMed2000

Comparison of ion chromatographic methods based on conductivity detection, post-column-reaction and on-line-coupling IC-ICP-MS for the determination of bromate.

An established method for the determination of the disinfection by-product bromate is ion chromatography (IC). This paper presents a comparison of three IC methods based on either conductivity detection (IC-CD), a post-column-reaction (IC-PCR-VIS) or the on-line-coupling with inductively coupled plasma mass spectrometry (IC-ICP-MS). Main characteristics of the methods such as method detection limits (MDL), time of analysis and sample pretreatment are compared and applicability for routine analysis is critically discussed. The most sensitive and rugged method is IC-ICP-MS, followed by IC-PCR-VIS. The photometric detection is subject to a minor interference in real world samples, presumably caused by carbonate. The lowest sensitivity is shown by the IC-CD method as slowest method compared, which, in addition, requires a sample pretreatment. The highest amount of information is delivered by IC-PCR-VIS, which allows the simultaneous determination of the seven standard anions and bromate.

Anions↗
PubMed1999

Application of experimental design for the characterisation of a novel elution system for high-capacity anion chromatography with suppressed conductivity detection.

A novel elution system for the application of high-capacity anion exchangers with suppressed conductivity detection in ion chromatography is presented. The ternary elution system is based on perchloric acid, sodium hydroxide and sodium carbonate. The novel elution system was applied to a self-made high-capacity anion-exchange column (Q = 453 mu equiv. Cl-). A central composite design with 20 experiments was used to investigate the influence of the eluent compounds, which varied from 0.2 to 1.0 mM HClO4, 20 to 100 mM NaOH and 0 to 20 mM Na2CO3, on the retention factor k' of seven common anions. A quadratic model including interactions was postulated. The model equations were used to estimate retention factors at known eluent compositions. No significant differences of calculated and experimental retention factors were found. Further statistical analysis was done by analysis of variance. The results showed that the three eluent compounds have completely different effects on the retention behaviour of the anions investigated. The elution of soft and weakly hydrated anions like bromide and nitrate is strongly influenced by the content of perchloric acid, whereas strongly hydrated anions like fluoride and sulphate are mainly affected by the hydroxide or carbonate content of the eluent. The results can qualitatively be explained comparing the relation of ionic radii to charge for eluent and analyte anions. As a consequence, the retention of the anions investigated can easily be manipulated by varying the contents of the eluent compounds. The usefulness of the novel elution system and high-capacity anion chromatography is demonstrated by the determination of trace anions in phosphate and fluoride matrices.

Anion Exchange Resins↗
PubMed1999

Inverse correlation of domestic exposure to Dermatophagoides pteronyssinus antigen patch test reactivity in patients with atopic dermatitis.

BACKGROUND: In recent years considerable interest in the pathogenetic role of aeroallergens exacerbating atopic dermatitis (AD) has emerged. The 'atopy patch test' with aeroallergens was introduced by Platts-Mills et al. as an experimental model and as a diagnostic tool. However, its relevance for the clinical manifestation of AD is still not clear. OBJECTIVE: We asked whether there is a relationship between the individual antigen exposure to the major allergen of Dermatophagoides pteronyssinus (Der p 1) and the immunological markers of sensitization to Der p 1 or the clinical severity of AD. METHODS: We investigated 92 patients with moderate to severe AD. For clinical evaluation the SCORAD severity score was used. Patch tests were performed with purified Der p 1. Specific IgE was measured by a commercial assay. Der p 1 exposure was quantified in a sample of the patient's mattress dust by using a commercial ELISA. RESULTS: No correlation between SCORAD, Der p 1 exposure and RAST could be established. However, there was an unexpected significant inverse correlation between the quantity of mite antigen in the mattress dust and patch test reactivity. Patients with a high antigen load (> 25 microg/g) mostly had a negative patch test. Also, when Der p 1 was correlated to the mattress area (m2) in this group all patch tests were negative. A possible explanation could be that continuous exposure of the skin to house dust mite allergen Der p 1 may induce a down-regulation of the skin immune system of patients with AD. CONCLUSION: Although the mechanism of this phenomenon is presently unknown, our study shows that a positive allergen patch test alone should not be an indication to undertake allergen exclusion measures in AD patients.

Adolescent↗
PubMed1996

On-line coupling of ion chromatography and atomic spectrometry for ultra trace analysis in high purity molybdenum- and tungsten-silicide.

The well-established technique of on-line coupling ion chromatography and atomic spectrometry for ultra trace analysis in high purity molybdenum and tungsten is extended to include the silicides MoSi(x) and WSi(x). An additionally included matrix elimination step allows an almost interference-free trace analysis in the silicide matrices. Reproducibility and accuracy of the on-line method were checked by comparison with several other methods, such as isotope dilution, radiochemical neutron activation analysis, direct determination by atomic absorption analysis and not at least with glow discharge mass spectrometry. The results show the high potential of the on-line method for reaching detection limits in the pg g(-1) range, but they show also remaining problems with contamination and system calibration.

Journal Article↗
PubMed1994

2,2',4,4',5,5'-hexabromobiphenyl: its toxicokinetics, biotransformation and porphyrinogenic action in rats.

The porphyrinogenic action of 2,2',4,4',5,5'-hexabromobiphenyl and its toxicokinetics were studied in female Wistar rats that were treated every other day for 6 wk with oral doses of 112 mg/kg body weight. Subsequently, the animals were kept for a further period of 22.5 months but without supply of the brominated biphenyl. 10.5 months after cessation of treatment the compound reached a maximum concentration in the adipose tissue followed by a gradual decline of its content. In the liver the concentration of the substance started to decrease 3 months after cessation of treatment. In the excreta, hexabromobiphenylol and two pentabromobiphenyls were detected as metabolites. The rate of biotransformation amounted to about 5%. At the end of the dosing period no alterations in the content and profile of the hepatic porphyrins were observed. Urinary porphyrins and their precursors delta-aminolaevulinic acid and porphobilinogen were slightly elevated. The urinary porphyrin pattern and faecal porphyrin content and pattern did not differ from those of the controls. 15 and 18 months after cessation of treatment (16.5 and 19.5 months after the start of treatment) two animals were found to have marked alterations in the content and profile of hepatic porphyrins with uro- and heptacarboxyporphyrin predominating. It was concluded that there is an extreme delayed individual porphyric response to 2,2',4,4',5,5'-hexabromobiphenyl in female rats.

Animals↗
PubMed1993

2,2',3',4,4'5,5'-Hepatachlorobiphenyl (PCB 180)--on its toxicokinetics, biotransformation and porphyrinogenic action in female rats.

The toxicokinetics and biotransformation of 2,2',3',4,4',5,5'-heptachlorobiphenyl, as well as its influence on the activity of microsomal and cytosolic enzymes and on the porphyrin pathway in the liver were studied in female rats following oral treatment with 7 mg/kg every other day for 3 months. One day after cessation of treatment the concentration of the compound in liver, spleen, CNS and blood was 100-500 times and in the trachea it was only 5 times less than in the adipose tissue. The daily excretion with the feces and urine amounted to 35 and 1.5 micrograms, respectively. In both excreta, heptachlorobiphenylol was identified as a metabolite. The biotransformation rate was estimated to be about 5%. Investigations of the liver revealed increases in the relative liver weight, total cytochrome P-450 content, O-deethylation of 7-ethoxycoumarin and in the activity of glutathione S-transferases. Disturbances of the hepatic porphyrin pathway were not detected. Only at the end of a post-dosing period of 12 months did the hepatic uroporphyrinogen decarboxylase show diminished activity. Only one of these animals with diminished enzyme activity showed drastically elevated porphyrins. In these animals, the fecal and urinary porphyrins did not differ from controls. At no time did heptachlorobiphenyl influence the urinary excretion of delta-aminolevulinic acid and porphobilinogen. The results indicate 1) that this congener shows expected toxicokinetics with the exception of being accumulated in the trachea and 2) that this congener induces disturbances of the hepatic porphyrin pathway several months after cessation of treatment.

Animals↗
PubMed1990

[Results of treatment of porphyria cutanea tarda with bloodletting and chloroquine].

In 59 patients showing clear clinical and biochemical signs of porphyria cutanea tarda (PCT), we tested 3 different modes of therapy: 20 patients received combined treatment with repeated bleeding and chloroquine, 24 patients were exclusively treated with oral chloroquine in low doses, and 15 patients underwent repeated phlebotomy only. On an average, the time necessary for remission amounted to 3.5, 10.2, and 12.5 months, respectively. So the combined therapy proved the quickest. In patients with the acquired form of PCT, the pattern of urinary porphyrin normalized; those suffering from hereditary PCT retained the typically high uro/copro ratio. The values of the plasma porphyrin count and the plasma porphyrin index (PPI), which had been greatly enhanced before, went down to normal after therapy.

Administration, Oral↗
PubMed1990

[Data processing the the RAST laboratory].

We describe a clinical laboratory information system for the RAST laboratory based on personal computers. In developing this system, we paid special attention to easy handling which does not require any computer experience on the user's side. Data storage and retrieval are managed by a relational database system with fast data access. Aside from the usual functions of a laboratory information system, the laboratory work is facilitated by a clear distribution of samples, the possible on-line connection to various analyzers, as well as the provision of cumulative results and a fast access to archive data.

Allergens↗