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Biomedical subjects

G Hahn

Publications and source records attributed to G Hahn.

At least 19 recordsLinked to original sources
PubMed1992

Enantiospecific high-performance liquid chromatographic assay with fluorescence detection for the monoamine oxidase inhibitor tranylcypromine and its applicability in pharmacokinetic studies.

In order to be able to measure low concentrations of tranylcypromine enantiomers in biological material, chiral fluorescent derivatization and high-performance liquid chromatography (HPLC) were employed. The internal standard S-(+)-amphetamine and borate-sodium hydroxide buffer pH 11 were added to plasma or urine sample aliquots. o-Phthaldialdehyde was used for precolumn derivatization in combination with the chiral mercaptan N-acetylcysteine. HPLC resolution of the diastereoisomeric derivatives was possible on an octadecylsilane column. The mobile phase consisted of sodium phosphate buffer solution pH 6.5, methanol and tetrahydrofuran. The fluorescence of the eluate was monitored at 344/442 nm. The intra-day coefficients of variation were below 10%, the limit of determination was 0.5 ng/ml. The assay was found to be applicable for routine analyses in a preliminary pharmacokinetic study, in which an oral dose of 20 mg racemic tranylcypromine sulfate was administered to three healthy volunteers. The plasma concentrations were generally low, and those of S-(-)-tranylcypromine significantly exceeded those of the R-(+)-enantiomer. Average maximum concentrations were 57.5 and 6.3 ng/ml for S- and R-tranylcypromine, respectively. While S-tranylcypromine was well detectable within the whole study period (8 h), R-tranylcypromine concentrations fell below the detection limit after 4 h in two out of the three studied volunteers.

Chromatography, High Pressure Liquid↗
PubMed1991

Rapid assay for the quantification of piretanide in biological fluids.

Piretanide was determined from plasma and urine using reversed-phase high-performance liquid chromatography. Plasma was extracted with diethylether at pH 4 using bumetanide as internal standard. The chromatographic separation was performed on an octadecylsilane column (ODS) with acetonitrile/pH 7 phosphate buffer (3:7, v/v). In order to determine piretanide in urine, bumetanide was added to a urine aliquot. Then the sample was centrifuged and the supernatant directly injected without extraction followed by chromatography on an ODS column with a mixture of methanol and pH 7 phosphate buffer (12:13, v/v). The compounds were detected by their intrinsic fluorescence, monitoring the eluate at 287/450 nm. Total chromatography times were 8 min for plasma and 13 min for urine samples. The method was applied for the assay of piretanide in plasma of healthy volunteers after i.v. or p.o. dosage of 6 mg piretanide.

Administration, Oral↗
PubMed1991

Antigenic and genetic homogeneity of Streptococcus uberis strains from the bovine udder.

DNA- fingerprints (Hind III) of Streptococcus uberis field isolates from New York State and Europe showed substantial homogeneity, but were different to those of the type strain of the newly proposed psychrophilic species S. parauberis. S. uberis strains had major SDS-heat extracted antigens of molecular masses (Mr) less than 14, 40-41, 42-43, 59-61, 80-86 and 118-122 kDa following immunoblotting with rabbit hyperimmune sera. Bovine sera and milk reacted with the 40-41 and 118-122 kDa antigens. Variations in the Mr of particular bands were too unevenly distributed to permit formation of subgroups. Although cross reactive, the sizes of the antigens of S. parauberis strain NCDO 2020 were substantially different to those of S. uberis, the most prominent antigen having a Mr of 50 kDa. The antigenic and genetic data therefore strongly support the introduction of S. parauberis as a distinct species. S. uberis strains reacted with antiserum to Lancefield groups B, E, G and P, their grouping reactions showing no correlation with DNA and immunoblot fingerprints. Lancefield grouping of S. uberis therefore appears to have little value in identification.

Animals↗
PubMed1991

Comparison of chromogenic and fluorogenic substances for differentiation of coliforms and Escherichia coli in soft cheese.

In food hygiene the differentiation of Escherichia coli and coliforms as index resp. indicator organisms is very important as a basis for the assessment of good manufacturing practice (gmp). Using a fluorogenic (MUG) and chromogenic (X-gal) substrate the laborious methods have become more simple and reliable. A new German DIN standard method (10.183, part 3) was used as a base to examine 200 soft cheese samples for coliforms and Escherichia coli comparing different media, parameters and incubation times. It could be shown that an incubation of 48 h is absolutely necessary for E. coli and coliforms in both media, that X-gal is a quicker and more sensitive parameter for total coliforms than gas production and that the combination of fluorescence and indole is slightly superior to fluorescence and gas for the identification of E. coli. To sum up, the new fluorescence principle, integrated in new standard methods will be an excellent tool to simplify the differentiation of E. coli and coliforms in food hygiene. Additionally, X-gal as a chromogenic substrate for all coliforms, including E. coli, may be integrated in further standard methods.

Bacteriological Techniques↗
PubMed1991

[Quantitative and qualitative MRI changes in temporal lobe epilepsy. A comparison with normal parameters of nuclear magnetic resonance tomography].

Magnetic resonance imaging (MRI) often reveals no pathology in patients with temporal lobe epilepsy (TLE) who are candidates for surgery, even though post-surgery histology reveals atrophy or sclerosis. To differentiate these pathologies in MRI, we performed a standardized acquisition and a quantitative analysis of MRI data (qMRI). The standard values of 43 healthy subjects (both sex, left and right handed) were compared with those of 10 patients with TLE and unilateral EEG focus. A reduced estimated total brain extension, a significant atrophy of both temporal lobes with accentuation on the focus side and a significant hippocampal atrophy on focus-side were seen even in patients with no visually detectable pathology. The analysis of the signal intensities did not give additional information. Thus, qMRI is a helpful additional tool in the course of presurgical evaluation for focus lateralization.

Adolescent↗
PubMed1991

Acute and chronic hypothermia in a man with spinal cord injury: environmental and pharmacologic causes.

It is well known that people with spinal cord injuries can develop hypothermia when exposed to an unusually cold environment. Hypothermia can also develop during inpatient rehabilitation, particularly as a side effect of certain medications. We present a patient with C4 incomplete spinal cord injury whose core body temperature was chronically subnormal, and who developed acute hypothermia on several occasions during inpatient rehabilitation. The results of tests of his autonomic function were abnormal. Acute hypothermia (core temperature approximately 34C) was induced when he was challenged with nifedipine. The serum level of phenytoin became elevated to toxic levels during two episodes of acute hypothermia, but the serum level of carbamazepine did not change appreciably. This case demonstrates that people with spinal cord injuries are at risk for hypothermia, that hypothermia can be induced by nifedipine, and that significant thermal challenges can occur during routine inpatient rehabilitation. In addition, hypothermia appears to affect the metabolism of phenytoin.

Adult↗
PubMed1990

Multiple breath washout of He and SF6 in panting dogs.

Pulmonary gas transport mechanisms in panting were studied by multiple breath washout of two poorly soluble inert gases of similar solubility but different diffusivity (He and SF6). The experiments were performed in 6 chronically tracheotomized conscious dogs (mean body weight 31.0 kg) which, upon exposure to elevated room temperature, were enforced to thermal panting (mean breathing frequency 288/min). After equilibration of lung gas with 1% He and 1% SF6 followed by changeover to test gas-free air, end-tidal gas concentrations during multiple breath washout were recorded by mass spectrometry. The washout time course was analyzed into 3 exponential components. The initial fast component was considered to be in part determined by the transient response of the measuring system, whereas the intermediate and the slow component could be attributed to lung washout. The mean He/SF6 ratio of medium and slow rate constants was 1.06 and 1.13, respectively (both values differing from 1.0 at P less than 0.001). It is concluded that gas transport in dog lungs during panting was mainly determined by convection, diffusion-dependent processes being discernible but playing a minor role.

Animals↗
PubMed1990

Resonant frequency of the chest-lung system by analysis of the respiratory flow curve.

1. Resonant frequency of the chest-lung system in six tracheotomized, spontaneously breathing dogs was determined by analyzing the shape of the respiratory flow curve. 2. The resonant frequency was calculated from the periodic deviations from a sinusoidal flow pattern observed in the inspiratory phase of the breathing cycle. 3. Mean (+/- S.D.) resonant frequency was 6.1 +/- 0.9 Hz which was very close to the panting frequency (5.7 Hz) of the same dogs. 4. Resonant frequencies of the respiratory system in various species are compared.

Animals↗
PubMed1979

Erythromelalgia.

Erythromelalgia is an extraordinary disorder of unknown etiology and pathophysiology that resembles the post-traumatic reflex dystrophy syndromes but has not been described previously in the orthopedic literature. Its distinctive triad of intense burning extremity pain associated with erythema and increased skin temperature are diagnostic. Primary or idiopathic and a secondary or associated form have been identified. The latter occurs in association with an underlying disease process, especially myeloproliferative disorders. Treatment with pharmacologic agents and surgery are ineffective except in the secondary group where treatment of the associated disorder generally results in a remission. Symptoms in the primary group can be minimized by appropriate environmental control with cooling and avoiding heat-producing situations that would raise skin temperature above a critical thermal threshold.

Adolescent↗
PubMed1979

[Results from the Central Laboratory for Streptococci Research in Kiel from 1965 to 1977 - a survey (author's transl)].

At the Central Laboratory for Streptococci Research at the Institute for Hygiene of the Federal Dairy Research Centre in Kiel a data bank has been established which comprises as well bibliographical data (until now more than 8000 titles out of the international literature concerning streptococci) as laboratory data of all strains which have been identified since 1965. For this present publication as a survey the total material covering 34,935 strains was analyzed and interpreted. Besides a short introduction describing the general examination procedure for streptococci and the encoding of results for the data bank the material is condensed in different tables considering the incidence of pathogenic species occuring mainly in man and animals. In addition findings of enterococci and lactic streptococci are presented. 41.8% of the strains examined were isolated from human specimens, 46.7% from cattle and the remaining ones from pigs, horses, dogs, laboratory animals and others. Only 2.0% of all cultures could not be identified as one of the known species. Remarkable observations are - the high incidence of group B-Streptococci in man - the unexpected frequency of typical "human" streptococci as those of group F and G and also Sc. milleri and Sc. MG in different animals - the possible interrelation of group L- and P-streptococci in pigs and cattle - the overlap of Sc. faecalis and Sc. faecium in man and animals showing no typical distribution as it is postulated in the literature - the high percentage of unidentifiable streptococci from pigs and laboratory animals as an eventual indication for some new species. In consecuting papers some problems emerging from the presented material and own experiments will be discussed as - interrelation of group B-Streptococci in man and cattle - incidence and importance of enterococci in humans, animals and foodstuffs and - classification of species not to identify by serological grouping.

Animals↗
PubMed1977

Mandibular reconstruction.

The stainless steel 316 mesh tray with cancellous bone offers a method of mandibular reconstruction which theoretically is appealing from the viewpoint of basic osseous healing. The results in fity-two patients at twenty different institutions indicates encouraging results. Further evaluation of this method is recommended.

Adolescent↗
PubMed1977

Lymphocyte activation by streptococcal antigens in psoriasis.

Cell-mediated immune responses in 28 hospitalized patients with psoriasis and in 36 healthy controls were studied using the two-step leukocyte migration agarose test. Specific cell-mediated immunity to A-streptococcal cell wall and cell membrane antigens occurred significantly more often in patients with psoriasis than in the control group. A statistically significant correlation between psoriasis-associated antigens of the HLA-B locus and cellular immune reactivity to A-streptococcal antigens or clinical course was not found. When patients with guttate psoriasis were compared separately with the control group, leukocyte migration inhibition induced by cell-free supernatants of A-streptococcal antigen-exposed mononuclear cell cultures was found to be more frequent than in other forms of psoriasis.

Adolescent↗