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J Lehmann

Publications and source records attributed to J Lehmann.

At least 109 records · Page 6Linked to original sources
PubMed1998

Long-term effects of repeated maternal separation on three different latent inhibition paradigms.

In the present study we investigated the effect of repeated maternal separation on postnatal days 12, 14, 16, and 18 for 6 h/day on Wistar rats on three latent inhibition (LI) paradigms: two-way active avoidance, conditioned emotional response (CER), and conditioned taste aversion (CTA). In addition, hyperactivity induced by d-amphetamine and stereotypies induced by apomorphine were evaluated. In all three LI experiments, the control animals showed only marginal LI, whereas the maternally separated animals showed enhanced LI (only males in CTA). In two-way active avoidance within the nonpreexposed condition maternally separated animals showed improved acquisition of avoidance learning compared with the control animals. Sensitivity in response to amphetamine and apomorphine was not altered by the maternal separation procedure. Thus, maternal separation in this study, contrary to previous reports, but in line with results obtained following early handling before weaning, led to enhancement of the LI phenomenon as assessed in each of the three procedures. As our maternal separation procedure (6 h on days 12, 14, 16, and 18) led to behavioral outcomes that differed from those reported by Ellenbroek and Cools (24 h on day 10), it is suggested that maternal separation regimens that are dissimilar may lead to different and sometimes opposite behavioral effects.

Amphetamine↗
PubMed1998

Kinetics of DNA strand breaks and protection by antioxidants in UVA- or UVB-irradiated HaCaT keratinocytes using the single cell gel electrophoresis assay.

The aim of this study was to characterize the genotoxic action of UVA and UVB in human keratinocytes by application of the single cell gel electrophoresis assay (SCGE assay). Dose dependence of DNA damage, the time course of its repair, and the influence of cellular antioxidant status were assessed. Irradiation with UVA or UVB both resulted in a dose-dependent increase in the level of DNA damage. A time course study to evaluate the repair kinetics in keratinocytes irradiated with 5 J/cm2 UVA revealed an immediate occurrence of DNA effects which subsequently disappeared within about 1 h, indicating removal of DNA lesions. This rapid repair of DNA damage is consistent with the observation that 5 J/cm2 UVA did not impair cellular viability. In contrast, exposure to 15 mJ/cm2 UVB resulted in a prolonged repair of DNA damage which lasted about 25 h. Thus, the repair kinetics of UVA- and UVB-induced DNA damage clearly differed from each other, implicating the induction of different types of DNA lesions by UVA and UVB. Neither a pretreatment with Mg-ascorbyl phosphate or D,L-alpha-tocopherol, nor depletion of endogenous glutathione altered cellular sensitivity to UVB. In contrast, the DNA damaging effects of UVA could be counteracted by a pretreatment with these antioxidants. These observations confirm that the UVA-induced effects on DNA are related to radical mediated strand breaks and DNA lesions forming alkali-labile sites. The UVB-induced effects mainly occur as a consequence of excision repair-related strand breaks. The observed repair kinetics of DNA lesions and the influence of cellular antioxidant status may help to elucidate protective mechanisms against the carcinogenic effects of UV radiation present in sunlight.

Antioxidants↗
PubMed1998

Murine leishmaniosis: a paradigm for the importance of T helper 1 and T helper 2 cells.

The murine model of leishmaniosis is a prototypic example for the critical role played by T helper cells in immunity to pathogens. Cytokines, such as interleukin-12 and interleukin-4, are the major regulatory factors for differentiation of naive T helper cells into T helper 1 and T helper 2 cells, respectively. T helper 1 cells, which are cellular immune mechanisms involving gamma interferon production, are associated with protection against murine leishmaniosis. Loss of T helper 1 activity (i.e., reduced gamma interferon production and lack of macrophage activation) leads to a fatal progressive course of murine leishmaniosis. Knowledge of the murine model of leishmaniosis is now contributing to studies of infectious diseases in humans, livestock and companion animals. Greater insight into the pathogenesis, diagnosis and therapy of infectious diseases will be gained from the analysis of cytokine-dependent regulation of T helper responses during infection. In particular, the development of prophylactic and therapeutic vaccines will benefit significantly from these studies.

Animals↗
PubMed1997

The biochip. A new membrane bioreactor system for the cultivation of animal cells in defined tissue-like cell densities.

Based on the laminar structure of the human liver tissue, a high cell density membrane bioreactor was developed that emulates a cell layer thickness of 40 microns. The "biochip" consists of a platinum-coated metal cell grid covered with two microfiltration membranes to form separate cell chambers of defined volume. Starting with a continuous chemostat process, the viability of a model suspension cell culture could be stabilized at 98%. In a second step these cells were transferred into the biochip system and were cultivated successfully for several days under tissue-like cell densities in a modified membrane holder under cross-flow conditions.

Animals↗
PubMed1997

About a symmetry of the genetic code.

Considering the three codonic positions as independent, it is possible to explain the grouping of the 64 trinucleotides (without AAA, TTT, CCC and GGG) into three equal sets T0, T1 and T2 according to their preferable reading frame (0, 1 or 2) in coding sequences. Supposing that the two complementarity strands of DNA are coding, it is demonstrated that the complementary of a codon is classified in to the same set, which has been observed statistically (with a few exceptions) in the coding sequences by Arquès & Michel [(1996) J. theor. Biol. 182, 45-58] and Arquès et al. [(1997) J. theor. Biol. 185, 241-253]. Finally, the circular property of the code pointed out by these authors is demonstrated, and a direct consequence to biological considerations of these properties is discussed.

Animals↗
PubMed1997

Organic nitrates. II. Synthesis and biological activities of 4-nitrooxymethylphenyl-1,4-dihydropyridines.

Both 2-nitrooxymethyl-4-phenyl- (2) and 4-nitrooxymethylphenyl-1,4-dihydropyridines (3) represent new combinations of two different vasodilating structures. 2 could not be isolated due to its spontaneous lactonization. Derivatives of 3 were obtained via Hantzsch synthesis using nitrooxymethylated benzaldehydes. The inotropic potency in isolated porcine trabecular muscles and the vasodilator activity in isolated porcine coronary arteries of four nitrooxyphenyl-dihydropyridines were determined. Nitrendipine (NTD) and glyceryl trinitrate (GTN) were used for reference. 3 were negative inotropic, however, less than NTD and--except for the dicyano derivative 3d--more than GTN. Vasodilator properties were less pronounced than that of both nitrendipine and GTN. Vascular selectivity was low.

Animals↗
PubMed1997

Young Investigator Award presentation at the 13th annual meeting of the ESMRMB, September 1996, Prague. Quantification of pulmonary water compartments by magnetic resonance.

The purpose of this study was to quantify pulmonary water compartments of total, intravascular, and extravascular lung water in excised and perfused sheep lungs with the use of magnetic resonance imaging techniques. Total lung water was measured by proton density maps calculated from multi-spin-echo images. Intravascular lung water was evaluated by magnetic resonance angiography before and after injection of gadolinium diethylenetriamine penta-acetic acid polylysine, a macromolecular paramagnetic contrast agent. Intravascular lung water was calculated from signal intensity histogram changes comparing pre- and postcontrast angiograms. Extravascular water was calculated as the difference between total and intravascular lung water. Quantities of total and intravascular lung water measured by magnetic resonance techniques were compared to reference results obtained from wet/dry weight gravimetry and Evans blue dilution performed after imaging. Magnetic resonance and reference results correlated significantly (total lung water: r = 0.93, p < 0.001; intravascular lung water: r = 0.80, p < 0.001; extravascular lung water: r = 0.89, p < 0.001). Therefore, we conclude that quantitative magnetic resonance techniques are potentially useful for the clinical evaluation of pulmonary water compartments.

Animals↗
PubMed1997

Capillary blood glucose monitoring. Are you putting yourself and your patients/clients at risk?

The performance of portable capillary blood glucose monitoring is now a widely accepted skill performed by nurses in a variety of settings. A person may have their blood glucose level taken by a nurse in the acute care setting, home environment, community health setting, doctor's surgery, work place or in community blood glucose screening program. This article aims to highlight the precautions necessary for the safe delivery of this component of care.

Blood Glucose Self-Monitoring↗
PubMed1997

[Magnetic resonance imaging of the degree of pulmonary edema using a macromolecular contrast medium].

PURPOSE: Development and experimental validation of a method tor the quantification of pulmonary oedema by measurement of total lung water and intravascular lung water and by calculation of extravascular lung water. MATERIAL AND METHODS: Isolated sheep lung preparations with unilateral pulmonary oedema were perfused (pulsatile pump) and examined under ventilatory arrest and during ventilation. Total lung water was calculated from proton density obtained from a multi-spin echo sequence and gravimetrically (reference method). Pulmonary intravascular volume was calculated from signal intensity histograms obtained from 3D-TOF MR-angiograms before and after application of the macromolecular contrast medium gadolinium-DTPA-polylysine. The reference method was a dye-dilution technique. Extravascular lung water was calculated as the difference between total lung water and pulmonary intravascular volume. RESULTS: Under ventilatory arrest, the magnetic resonance technique for the measurement of extravascular lung water correlated well with the reference technique (r = 0.89, n = 42 lungs). In 10 lungs the correlation coefficients were r = 0.95 (ventilatory arrest) and r = 0.92 (ventilated lungs). CONCLUSION: The results demonstrate that magnetic resonance imaging enhanced by a macromolecular contrast medium may be applicable for quantification of pulmonary oedema.

Animals↗
PubMed1997

[MR imaging of experimental pulmonary embolism using a macromolecular contrast medium].

PURPOSE: To evaluate macromolecular contrast-enhanced MR-angiography for the detection of experimentally induced pulmonary artery embolism and to determine the size of the smallest detectable embolised vessel. METHODS: Pulmonary artery embolism was artificially induced in eight isolated perfused sheep lungs by injecting room air into the main pulmonary artery. The pulmonary vascular system enhanced by macromolecular gadolinium-DTPA-polylysine was imaged with a flow-sensitive gradient-echo technique. RESULTS: Pulmonary artery embolism was demonstrated in all eight lungs by an obvious cut-off phenomenon in the contrast-enhanced arteries proximal to the pulmonary air emboli. The smallest detectable embolised artery measured 1.6 mm in diameter and was located in the 6th generation of the pulmonary vascular system. CONCLUSIONS: In this experimental study MR angiography enhanced by a macromolecular contrast agent allowed noninvasive diagnosis of pulmonary artery embolism.

Animals↗
PubMed1996

Synthesis and application of alpha-D-mannosyl clusters as photoaffinity ligands for mannose-binding proteins: concanavalin A as a model receptor.

Mono-, di-, and tri-antennary alpha-D-mannopyranosyl derivatives were synthesized as oligosaccharide mimics. The compounds vary in the length of the acyclic aglyconic spacers linking, in the case of the di- and tri-antennary derivatives, the glycosyl endgroups. By haemagglutination assay (Coombs test) the affinity of the alpha-D-mannopyranosyl ligands against Con A was determined in comparison with methyl alpha-D-mannopyranoside. Affinity enhancement and strong cross-linking capacity were found with the di- and tri-antennary compounds where alpha-D-mannopyranosyl endgroups are separated by spacers of 5-37 atoms in length. The optimal ligand had Ki of 5.1 microM in comparison with 3.12 microM for methyl alpha-D-mannopyranoside. The monoantennary compound and, to certain extents, one di- and short tri-antennary ligands with short spacer lengths did not differ significantly in affinity from methyl alpha-D-mannopyranoside. A triantennary, radiolabelled ligand equipped with a photolabile diazirino group was used to covalently modify Con A by photoaffinity labelling. A significant degree of covalent cross-linking of Con A monomers was observed.

Affinity Labels↗
PubMed1996

[A case-based and multi-media computer learning program on the topic of myocardial infarct, angina pectoris and mitral valve stenosis].

BACKGROUND: Principles in the field of cognitive psychology and problem-based learning together with recent progress in multimedia technologies are providing the basis for the development of case-based and computer-assisted learning systems. With reference to the information-overload of theoretical and factual knowledge in medical education these programs can be an efficient tool to satisfy the current need for new, practical, skill-related forms of knowledge transfer. METHODS: Apple-Macintosh Computers were selected to develop interactive, multimedia patient-simulations on mitral stenosis, angina pectoris and myocardial infarction. INSTRUCTIONAL AIM AND CONTENTS: The user acquires knowledge and skills about the leading symptoms, differential diagnoses, the use and analysis of laboratory examinations and the process of diagnostic reasoning while working through the computer-simulated cases. PEDAGOGICAL DESIGN AND CONCLUSION: Important pedagogical principles associated with computer-assisted learning were employed in the program. Clinical situations can be simulated repeatedly and for every student in an authentic manner. Therefore the program can serve as a preparation for and a supplement to practical clinical education. Compared to conventional teaching media the development of instructional multimedia software requires a tremendous amount of time and resources. Thus, controlled studies are important to objectify the overall advantages such programs can have.

Angina Pectoris↗
PubMed1996

Measuring diabetes-related attitudes: the use of a USA-developed instrument with Australian nurses.

The revised Diabetes Attitudes Scale (DAS) was completed by nearly 1000 nurses and nursing students in South Australia. Confirmatory factor analysis was used to compare the factor structure with that previously obtained in the USA with patients with diabetes. The instrument was found to be robust. It was concluded that only one item of the 50-item scale is unsuitable for inclusion in studies which aim to compare patient and health professional attitudes.

Attitude of Health Personnel↗
PubMed1996

Isolation and structural characterization of fucosylated gangliosides with linear poly-N-acetyllactosaminyl chains from human granulocytes.

The isolation and structural characterization of fucosylated neolacto-series gangliosides with linear poly-N-acetyllactosaminyl chains from normal human granulocytes is described. Gangliosides were purified by consecutive use of anion exchange HPLC on Fractogel TMAE-650(S), adsorption and reversed phase HPLC on Nucleosil 50-7 and Nucleosil 7C18 columns, respectively. TLC immunostaining with carbohydrate specific monoclonal antibodies, fast atom bombardment-mass spectrometry (FAB-MS) of the permethylated derivatives and gas chromatography-electron impact mass spectrometry (GC-EIMS) of partially methylated alditol acetates were used for structure elucidations. One ganglioside was identified as sialyl Lewis(x) antigen with nLcOse6Cer core, Neu5-Ac alpha 2-3Gal beta 1-4 (Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4Glc NAc beta 1-3 Gal beta 1-4Glc beta 1-1Cer. Furthermore, monosialylated ceramide deca-, undeca-, dodeca- and tridecasaccharides with three (nLcOse8Cer) and four (nLcOse10Cer) linear lactosaminyl repeats were identified, carring one to three fucoses. The ceramide portions were found to contain C18 sphingosine and predominantly C16:0 fatty acids. All monosialogangliosides were homogenous concerning their terminal alpha 2-3 Neu5Ac-sialylation, but different in their fucosylation status. Beside VI3Neu5Ac, V3Fuc-nLcOse6Cer, in two of the fucosylated polylactosaminyl ganglioside fractions the sialyl Lewis(x) epitope was found, whereas five species expressed the terminal VIM-2 motif. The role of protein linked sialy Lewis(x) epitope of human granulocytes as a ligand for endothelial leukocyte adhesion molecule-1 (ELAM-1; E-selectin) and platelet activation-dependent granule external membrane protein (PADGEM; P-selectin) is well documented. However, the involvement of endothelial cells E-and/or P-selectin mediated cell-cell adhesion via lipid bound sialyl Lewis(x) and/or VIM-2 epitopes on human granulocytes has to be proved in further investigations.

Carbohydrate Sequence↗