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Biomedical subjects

G Kraus

Publications and source records attributed to G Kraus.

At least 19 recordsLinked to original sources
PubMed1992

Determination of apovincaminic acid in serum by means of high-performance liquid chromatography.

A high-performance liquid chromatographic method for the determination of low concentrations in serum of apovincaminic acid, the main metabolite of vinpocetine, is reported. The assay includes a two-step ion-pair extraction with tetrabutylammonium as counter ion. Recovery is ca. 40%. Separation is performed on a narrow-range 5 microns particle size octadecylsilane modified silica packing. Heptanesulphonic acid is the pairing ion in the eluent, and the ultraviolet detection wavelength is 224 nm. Yohimbine serves as the internal standard. The assay is fast, accurate and sensitive quantifying at least 5 ng/ml apovincaminic acid in serum. The method was applied to the analysis of serum samples from aged subjects, treated with a 20-mg dose of vinpocetine.

Chromatography, High Pressure Liquid↗
PubMed1992

Intracranial abnormalities requiring emergency treatment: identification by a single midline tomographic slice versus complete CT of the head.

We retrospectively reviewed 89 noncontrast computerized tomographic scans of the head in trauma patients to determine whether a single midline image could reliably identify intracranial lesions significant enough to warrant emergency surgery. We found that a midline cut was able to detect 92% of all lesions for which emergency neurosurgical evacuation was considered necessary, though it detected only 71% of the more subtle abnormalities.

Brain↗
PubMed1992

Role of the fusogenic peptide sequence in syncytium induction and infectivity of human immunodeficiency virus type 2.

Syncytium induction is a characteristic feature of infection by human immunodeficiency virus (HIV) in vitro. The hydrophobic amino terminus of the transmembrane glycoprotein of HIV type 1 is an essential determinant of virus entry into the target cell population and the formation of syncytia in cell culture. To define the role of the HIV type 2 fusion peptide during infection and syncytium formation, we introduced 8 amino acid substitutions into the hydrophobic amino terminus of gp41, changing either the hydrophobicity, the charge, or the polarity of the amino acid. Viruses containing the envelope mutations were analyzed for their syncytium-inducing capacities, levels of infectivity, and envelope processing and expression. Mutations that increased the hydrophobic nature of the fusion peptide increased syncytium formation, whereas mutations which increased the charge and the polarity and/or decreased the hydrophobicity of the fusion domain severely reduced the capacity of the virus to induce syncytia. However, viruses severely compromised for syncytium formation exhibit only slightly lower levels of infectivity.

Amino Acid Sequence↗
PubMed1992

[Optimization of an enzyme immunoassay for the detection of antibodies against avian reoviruses--with special consideration of the calculation of results and test interpretation].

Selected steps in the establishment of an enzyme-immuno-assay (EIA) are shown with an EIA for detection of antibodies against avian reoviruses of chicken. The centre of this work is to show the various possibilities of calculation and interpretation of the test results. The definition of the cut-off-value is the basis for the interpretation of the assay and the consequences for the veterinarians in the field and the animal owners. Basic parameters (sensitivity, specificity, predication value, prevalence) of the test validation are discussed with the example of the examination of a new hen flock in the EIA, compared to serum neutralisation test.

Animals↗
PubMed1990

Simian immunodeficiency virus reverse transcriptase. Purification and partial characterization.

Native reverse transcriptase from simian immunodeficiency virus was purified from virus with good recovery to near homogeneity. The optimum reaction conditions of the enzyme were determined with respect to divalent cations, pH and ionic strength. The enzyme was shown to possess both RNA-dependent and DNA-dependent DNA synthesis activity. In addition, we could demonstrate an associated RNase H activity. Employing novel assay conditions, activated DNA as a heteropolymeric substrate was used more efficiently than the homopolymeric substrate poly(rA).oligo(dT) which in turn was used twofold more effectively as the template primer than poly(dC).oligo(dG). Other homopolymeric substrates, including poly(rC).oligo(dG), were also tested but were found to be poorly used by the reverse transcriptase. The Miachaelis-Menten constants were determined for each of the four nucleotides needed to elongate a natural template primer. Simultaneously, using dideoxyadenosine triphosphate as nucleotide analogue, we could show that this compound acts as a competitive inhibitor with respect to dATP, whereas it acts as a non-competitive inhibitor with respect to the other nucleotides. Gel electrophoretic analysis showed the enzyme to consist of two polypeptides with apparent molecular masses of 64 and 48 kDa. Using activity gel electrophoresis, we were able to demonstrate that both subunits exhibit DNA synthesis activity.

Animals↗
PubMed1990

Immunological studies of the basis for the apathogenicity of simian immunodeficiency virus from African green monkeys.

Potential reasons for the lack of pathogenicity of the simian immunodeficiency virus SIVagm in its natural host, the African green monkey (AGM, Cercopithecus aethiops), were investigated with respect to immunological mechanisms. The functional immune response of monkeys to infection was similar (though not identical) to that of humans to infection with human immunodeficiency virus type 1 (HIV-1). In the sera of infected animals, neutralizing antibodies were found to be low or absent, and in particular there was no neutralization of the various isolates by homologous sera. There was no detectable antibody/complement cytotoxicity, though AGM sera were able to initiate antibody-dependent cellular cytolysis of infected cells in the presence of healthy effector peripheral blood lymphocytes. As in the human/HIV system, macrophages from AGMs are readily infected by SIVagm. Two possibly important differences between the AGM/SIVagm system and the human/HIV system are (i) the low immune response of the AGMs to the core protein of SIVagm and (ii) the significantly lower inhibitory effect of SIVagm proteins on the proliferation of AGM lymphocytes.

Animals↗
PubMed1990

Famotidine. Pharmacokinetic properties and suppression of acid secretion in paediatric patients following cardiac surgery.

The pharmacokinetic and pharmacodynamic properties of the H2-receptor antagonist famotidine have been well described in adult subjects. However, similar data for children are not available. Therefore, this study looked at the disposition of the drug (given to prevent aspiration following cardiac surgery) in 10 paediatric patients with normal kidney function (age range 2 to 7 years, bodyweight 14 to 25 kg) after a single intravenous dose of famotidine 0.3 mg/kg. Plasma concentrations of the drug and gastric pH values were both monitored for 20 hours by high performance liquid chromatography and aspiration of gastric juice, respectively. Plasma famotidine concentrations declined with an elimination half-life of 3.3 +/- 1.8 h (mean +/- SD) and the drug was effective in elevating the gastric pH above 3.5 for about 9 hours in 6 patients. The variable volume of distribution and total plasma clearance of famotidine averaged 1.4 +/- 1.0 L/kg and 0.3 +/- 0.17 L/h/kg, respectively. In 4 patients unchanged famotidine could also be measured in a 12-hour urine fraction. The amount excreted (21 to 79%) correlated with clearance (r = 0.97). All these data are comparable to those obtained in healthy adults, indicating that paediatric patients receiving intensive medical treatment after cardiac surgery can handle famotidine in a way very similar to healthy adult subjects. A dosage of 0.3 mg/kg every 8 hours appears to be advisable.

Cardiac Surgical Procedures↗
PubMed1990

Use of monoclonal antibody against major internal protein p24 of bovine leukemia virus in capture ELISA.

A monoclonal antibody (4H4) against the major internal protein, p24, of bovine leukemia virus (BLV) is described. It recognizes a sequence determinant on the p24-molecule and displays high affinity to its antigen. The monoclonal antibody 4H4 was applied in capture ELISA for diagnosis of enzootic bovine leukosis, using crude BLV-preparation as antigen. This test is more sensitive than the immunodiffusion test and at least as sensitive as direct ELISA.

Animals↗
PubMed1989

The Bactec-system in the diagnosis of tuberculosis. Comparison of a conventional and the radiometric method (Bactec) for culturing, differentiation and susceptibility testing of mycobacteria.

A method developed in the USA (2, 6, 8) for the culturing, identification and differentiation of mycobacteria by means of a radiometric method (Bactec) was compared with a conventional method by examining 802 specimens received. Obviously better results were obtained with the new method: The number of positive cultures was 102 (12.7%) for Bactec against 87 (10.8%) for the conventional method. When using the radiometric method, the contamination rate (5.1%) was higher than for the conventional method (3.1%). It would, however, seem that this disadvantage can be offset by an increase in the alkali concentration during pretreatment of the specimens. After elimination of all paired samples one or both specimens were found to be contaminated, 743 specimens remained for direct comparison. Of these, 101 (13.6%) were positive when the Bactec method, and 84 (11.3%), when the conventional method was used. The superiority of the new method was most obvious with sputum specimens: 14.5% were positive when Bactec, and 12.2%, when the conventional method was used. For the Bactec method, the mean period until positive results could be recognized by daily readings was 15 days against 28 days for the conventional method with weekly readings. Sensitivity testing can be completed within 8 days. Owing to the costs of the radiometric method, it is recommended to limit its use of defined situations.

Bacteriological Techniques↗
PubMed1989

Isolation of human immunodeficiency virus-related simian immunodeficiency viruses from African green monkeys.

We have isolated lentivirus strains that are related to the human immunodeficiency virus (HIV) from African green monkeys (Cercopithecus aethiops; AGM). Although immunologically related, these SIVagm are clearly distinct from other simian immunodeficiency virus (SIV) isolates, including isolates from Macaca mulatta (SIVmac) or even from other AGM. The SIVagm strains described in this communication grow well in a limited number of human T-lymphoma lines. Virus density, morphology, and reverse transcriptase activity are characteristic of the lentivirus group. SIVagm exhibits the following pattern of major virus proteins: p18, p28, gp45, p64, gp140. They appear to bind to the target cell via the CD4 or its primate analogue. Four virus isolates have already been molecularly cloned for detailed genomic analysis and within this SIV agm group they exhibit the genomic variability that is typical of lentiviruses. AGMs infected with this virus apparently remain healthy and therefore SIVagm not only provides a virus model for vaccine studies but also allows investigation of the defense mechanisms (immunological and others) that keep the AGMs healthy. Furthermore, precise genomic analysis of these and other SIV strains will lead to a better understanding of the evolution and pathogenicity of human lentiviruses like HIV.

Animals↗
PubMed1989

Molecularly cloned simian immunodeficiency virus SIVagm3 is highly divergent from other SIVagm isolates and is biologically active in vitro and in vivo.

Simian immunodeficiency viruses have been isolated from African green monkeys originating from Ethiopia. A molecular clone, termed SIVagm3, was found to be highly divergent from SIVagmTYO-1 in terms of its restriction map and partial nucleotide sequence. A premature stop codon present in the transmembrane protein of SIVagm TYO-1 was absent in SIVagm3. SIVagm3 was biologically active in vitro and in vivo and displayed characteristics reminiscent of the wild-type virus. Biological activity was demonstrated by seroconversion of juvenile African green monkeys and Macaca nemestrina after inoculation. In contrast to antibody reactivity mainly directed against env proteins in naturally infected African green monkeys. African green monkeys and M. nemestrina infected with the cloned virus showed antibody reactivity directed against all major proteins as demonstrated by immunoblot analysis. The availability of a biologically fully competent molecular clone of SIVagm allows us now to address various pertinent questions in an animal model system which should help to understand features of human immunodeficiency virus infection in human beings.

Amino Acid Sequence↗
PubMed1988

[The modification of different element levels in human blood by occupational cadmium exposure].

The influence of occupational cadmium exposure on the electrolyte (Ca, Mg) and trace element (Fe, Cu, Zn, Mn) concentrations in blood, erythrocytes and serum was investigated. The study was performed at 62 cadmium exposed persons and 38 men not occupationally exposed. The cadmium blood levels of the workers from eight factories (cadmium electroplating, cadmium stearate processing and hard soldering) ranged from 1.0 to 23.7 micrograms Cd/l blood (median 4.2 micrograms/l), of the normal persons from 0.3 to 4.1 micrograms Cd/l blood (median 1.6 micrograms/l). Around 90% of the cadmium was found in the erythrocytes. The cadmium levels in serum were much lower and increased negligibly with elevated blood cadmium concentrations. An influence of cadmium on the concentrations of calcium, iron, copper and manganese in the blood compartments could not be found. In the compartments plasma and erythrocytes higher magnesium levels were detected in comparison to the normal group; a correlation to the cadmium levels did not exist. The medians for the zinc levels in blood, erythrocytes and serum in the exposed groups were significantly higher than the normal zinc levels and correlated with the blood cadmium levels. For blood samples with cadmium concentrations exceeding 10 micrograms/l the ratio of zinc to cadmium was reduced against zinc in spite of elevated zinc and increasing cadmium levels. A negative significant correlation was calculated for the relationships of cadmium and zinc in blood and erythrocytes. A significant change of the element concentrations in the sense of a transfer from one compartment to another was not detected.

Adult↗