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Biomedical subjects

J Lechner

Publications and source records attributed to J Lechner.

51 records · Page 3Linked to original sources
PubMed1991

[Indocyanine green test in the dog].

The ICG test is recommended as a replacement for the nowadays rarely performed BSP test. ICG has less side effects, and it has a greater range of use. Extrahepatic influences are of little importance. Disadvantages are the greater cost and extra equipment required, the labile nature of the dye solution and the calculation procedure. Reference ("normal") values of the clearance coefficient are 0.044 to 0.131 min-1 and those for the half life 5.2 to 11.2 min. The test is suitable for information about the secretion of the whole liver and the state of its circulation.

Animals↗
PubMed1990

Demonstration of extensive brainstem projections to medial and lateral thalamus and hypothalamus in the rat.

We use the method of retrograde transport of colloidal gold with silver intensification to map locations of brainstem neurons projecting to various nuclei of the medial and lateral thalamus (Menetrey, Histochemistry 83, 391-395, 1985; Seeley and Field, Brain Res. 449, 177-191, 1988). In rats injections of less than 1.0 microliters of a gold-wheatgerm agglutinin-horseradish peroxidase complex were restricted to the centrum medianum, centralis lateralis, medialis dorsalis, zona incerta, ventrobasal thalamic complex, or medial or lateral hypothalamus. Injections in the centralis lateralis, with some involvement of centrum medianum and medial medialis dorsalis, labeled numerous neurons throughout the rostrocaudal extent of the midbrain periaqueductal gray, and adjacent reticular formation, dorsal raphe nucleus and substantia nigra. These labeled neurons were distributed bilaterally, but with a preponderance ipsilaterally. Numerous neurons in the deep layers of the ipsilateral superior colliculus and in the anterior pretectal nucleus were also labeled. Many neurons in the pontomedullary raphe nuclei (including nucleus raphe magnus), locus coeruleus and dorsolateral parabrachial nuclei, and in the pontomedullary reticular formation, were labeled bilaterally. Fewer were seen bilaterally in the lateral reticular nucleus and nucleus of the solitary tract, with relatively few in the dorsal aspect of the trigeminal nucleus caudalis. Injections restricted largely to the centrum medianum labeled fewer cells in the brainstem, but with similar distributions. An injection restricted to the centralis lateralis also resulted in a similar distribution of labeled neurons in midbrain and nucleus raphe magnus but did not label neurons at more caudal medullary levels. An injection restricted to zona incerta labeled numerous neurons in a distribution similar to that following medial thalamic injections, except that many more were observed in the contralateral sensory trigeminal nucleus and in the dorsal column nuclei. Injections of the ventrobasal thalamic nucleus labeled many neurons in the trigeminal and dorsal column nuclei, but many fewer neurons in the midbrain, periaqueductal gray and reticular formation compared with medial thalamic injections. Labeled neurons were also seen in the superior and inferior colliculi, due presumably to involvement by the injection of the lateral posterior and magnocellular medial geniculate nuclei, respectively. Injections in the lateral hypothalamus labeled numerous neurons in a distribution similar to that seen following medial thalamic injections.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1990

Periodontium and vitamin E and A in pregnancy.

The evaluation of the clinical condition of periodontium by means of the epidemiological indexes and the level of oral hygiene in two weeks intervals in the course of physiological pregnancy in 39 women in good general health revealed the maximum of inflammatory changes of periodontium in the 8th month of pregnancy with the amelioration shortly before delivery. Simultaneous follow-up of the physiological levels of vitamin E and A in four weeks intervals showed the decline of the mean levels of both vitamins in the course of the 8th month and their marked elevation shortly before delivery; therefore remains questionable, if this elevation reaching over their physiological range, contributes to the amelioration of the condition of periodontium observed at the same time.

Female↗
PubMed1989

[Poxvirus infection in a cat].

For the first time, a poxvirus infection was diagnosed as an etiologic agent of dermal disease in a living domestic cat in Germany. A literature survey, the clinical symptoms of the infection and the diagnostic procedures are described. Poxvirus infections should be considered as a differential diagnosis in feline dermatologic problems.

Animals↗
PubMed1989

[The test of a centrifugal hematology system for use in clinical practice].

The QBC is a centrifugal haematology system. Modified haematocrit capillaries are measured optically. The parameters haematocrit, total leukocyte count, relative and absolute values of granulocyte and lympho-/monocyte fractions, and total thrombocyte count are stated. The microhaematocrit method, the counting chamber, and the differential blood count are reference methods. Blood samples of the dog, cat and horse were used for the study. As a screening method the QBC analysis meets all requirements for the veterinary practice.

Animals↗
PubMed1988

Interaction of two barbiturates and an antihistamine on body temperature and motor performance of mice.

As an example for a drug combination used as a sedative (Vesparax) the actions of secobarbital (S), brallobarbital (B) and the antihistamine etodroxizine (E) were studied in mice after single and concomitant oral application. S and B caused a dose-dependent increase of exploratory locomotor performance enclosing a short period of locomotor depression. Such excitatory effect was suppressed by concomitant application. E produced a decrease in locomotion and--when added to S and B--enhanced their sedative effects. Explorative rearing was suppressed by low doses of S and B, by B, by E, and by all the combinations, whereas high single doses of S and B (20 mg/kg and 25 mg/kg, resp.) caused a triphasic temporal pattern. Motor coordination was investigated by means of fixed-bar and rotarod procedures. Increasing doses of S and B impaired motor performance within a small dose range. In concomitant applications rotarod performance revealed a dose-additive synergism whereas the effect was moderately superadditive in the fixed-bar test. Neither in single applications nor in combinations E showed any effects. Rectal temperature was poorly affected by the single drugs, but hypothermia was strongly enhanced by concomitant application of S and B and further potentiated by addition of E. The results suggest that responses to combinations of drugs even belonging to the same category cannot sufficiently be deduced from the single components alone.

Animals↗
PubMed1987

The primary structure of a procaryotic glycoprotein. Cloning and sequencing of the cell surface glycoprotein gene of halobacteria.

The hexagonally patterned surface layer of halobacteria consists of a true glycoprotein. This procaryotic glycoprotein has recently been shown to exhibit novel features with respect to saccharide structure and saccharide biosynthesis. The primary structure and the location of glycosylation sites were determined by cloning and sequencing of the glycoprotein gene of Halobacterium halobium. According to the predicted amino acid sequence, the glycoprotein is synthesized with a N-terminal leader sequence of 34 amino acid residues reminiscent of eucaryotic and procaryotic signal peptides. A hydrophobic stretch of 21 amino acid residues at the C terminus probably serves as a transmembrane domain. 14 threonine residues are clustered adjacent to this membrane anchor and linked to these threonines are all the disaccharides of the cell surface glycoprotein. 12 N-glycosylation sites are distributed over the polypeptide chain.

Amino Acid Sequence↗
PubMed1985

Transient methylation of dolichyl oligosaccharides is an obligatory step in halobacterial sulfated glycoprotein biosynthesis.

Biosynthesis of sulfated saccharides that are linked to asparagine residues in the cell surface glycoprotein of Halobacterium halobium via a glucose residue involves sulfated dolichyl-monophosphoryl oligosaccharide intermediates (Lechner, J., Wieland, F., and Sumper, M. (1985) J. Biol. Chem. 260, 860-866). During isolation and characterization of these lipid oligosaccharides we detected a group of related compounds containing additional unidentified sugar residues. Here we report that: 1) the unknown sugar residues were 3-O-methylglucose, linked peripherally to the lipid-saccharide intermediates; 2) the 3-O-methylglucose residues in the oligosaccharides occur only at the lipid-linked level but are absent at the protein-linked level; 3) cell surface glycoprotein biosynthesis in Halobacteria in vivo is drastically depressed when S-adenosylmethionine-dependent methylation is inhibited, indicating that methylation is an obligatory step during glycoprotein synthesis. We propose a mechanism for the transport of lipid oligosaccharides through the cell membrane, involving an intermediate stage in which the saccharide moieties are transiently modified with 3-O-methylglucose.

3-O-Methylglucose↗
PubMed1985

Biosynthesis of sulfated saccharides N-glycosidically linked to the protein via glucose. Purification and identification of sulfated dolichyl monophosphoryl tetrasaccharides from halobacteria.

A novel type of N-glycosidic linkage, asparaginyl glucose, occurs in the cell surface glycoprotein of halobacteria (Wieland, F., Heitzer, R., and Schaefer, W. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 5470-5474). Sulfated oligosaccharides containing glucuronic acids are attached to the polypeptide chain via this linkage. Here we describe the isolation and chemical characterization of lipid-linked precursors of these saccharides, and these have the following new features. Rather than the bacterial undecaprenol, a C60-dolichol is the carrier lipid. The oligosaccharide is bound to this lipid via a monophosphate, rather than a pyrophosphate bridge. Sulfation of the saccharides is completed while they are linked to lipid and does not occur after transfer of the saccharides to protein.

Asparagine↗
PubMed1985

Normal human bronchial epithelial cells do not show an adaptive response after treatment with N-methyl-N'-nitro-N-nitrosoguanidine.

Normal human bronchial epithelial cells cultured in serum-free medium were exposed to low doses o N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) to examine whether increased cellular resistance and increased activity of the DNA-repair enzyme O6-methylguanine-DNA methyltransferase could be induced. After treatment with single doses of MNNG a dose-dependent decrease in O6-methylguanine-DNA methyltransferase activity was observed, as expected for this unique repair system. The activity recovered to the starting level in about 24 h when a dose that consumed approximately 65% of the enzyme activity (0.2 micrograms/ml) was given, but did not exceed the activity in the untreated control. Furthermore, treatment every 6 h for 4-5 days with non-toxic concentrations of MNNG (0.04-0.12 micrograms/ml) did not increase O6-methylguanine-DNA methyltransferase activity. Neither was cell survival following a range of challenge doses significantly increased. Our data suggest that human bronchial epithelial cells do not adapt to MNNG.

Bronchi↗
PubMed1982

Studies of host factors in carcinogenesis using cultured human tissues and cells.

Recent progress in the development of conditions for culturing epithelial tissues and cells from adult humans has provided cancer researchers with an opportunity to investigate directly the various facets of carcinogenesis in human cells. Studies of activation and deactivation of several classes of chemical carcinogens have revealed that the metabolic pathways and the predominant adducts formed with DNA are generally similar in humans and experimental animals. Wide quantitative interindividual differences are found in humans and other outbred animal species. When the metabolic capabilities of specimens from different levels of biological organization are compared, the profile of benzo[a]pyrene metabolites is similar in cultured tissues and cells, but subcellular fractions, e.g., microsomes, produce a qualitatively and quantitatively aberrant pattern. To test the interactive effects of cell types in the metabolic activation of carcinogens and to assess further interindividual differences among people, human tissue- and cell-mediated mutagenesis assays have been developed. The fact that terminally differentiated cells such as pulmonary alveolar macrophages can activate benzo[a]pyrene and mediate an increase in frequencies of mutations and sister chromatid exchanges in cocultivated 'detector' cell populations, i.e., Chinese hamster V79 cells, suggests that non-target cells of chemical carcinogens may play an important role in the activation of environmental carcinogens. Malignant transformation of human epithelial and fibroblastic cells in vitro has been accomplished by several research groups. Asbestos, a cocarcinogenic agent in bronchogenic carcinogenesis, has been found to induce polyploid epithelial lesions with atypical cells in human bronchial explants. Carcinogenesis studies using cultured human tissues and cells are providing new insights into the mechanisms of carcinogenesis and are useful in identifying host factors that influence individual risk to environmental carcinogens.

Biotransformation↗
PubMedDate not supplied

Interferon alpha2b increases paracellular permeability of renal proximal tubular LLC-PK1 cells via a mitogen activated protein kinase signaling pathway.

The therapeutic administration of Interferon alpha2b (IFNalpha) is often accompanied by impaired renal function, i.e. reduced glomerular filtration rate and sometimes a so-called "capillary leak syndrome". To clarify the mechanism behind the renal dysfunction, confluent monolayers of LLC-PK1 cells were used as a model system to analyze the effects of IFNalpha on renal tubular epithelium. Examination of epithelial barrier function via measurement of transepithelial resistance (TER) revealed a dose dependent increase in paracellular permeability by IFNalpha treatment. The effect was reversible upon removal of IFNalpha at doses up to 5 x 10(3) U/mL. Apical or basolateral application of IFNalpha yielded the same decrease in TER. Tyrphostin A25, an inhibitor of phosphotyrosine kinases, ameliorated the IFNalpha induced decrease of TER. In order to unravel intracellular signal transduction pathways that may mediate IFNalpha induced changes of epithelial barrier function, we inhibited IFNalpha signaling through a mitogen activated protein kinase pathway by the Mek1 inhibitor PD98059. The inhibitor could be shown to prevent IFNalpha induced decrease of transepithelial resistance. Inhibitors of the p38 mitogen activated protein kinase pathway did not affect IFNalpha mediated changes of epithelial barrier function, indicating a highly specific role for the Mek/Erk pathway. Activation of mitogen activated protein kinase pathways by epidermal growth factor or anisomycin could not, per se, imitate the effect of IFNalpha on the paracellular permeability of LLC-PK1 monolayers. These findings provide evidence that IFNalpha can affect barrier function in renal epithelial cells via activation of the Mek/Erk pathway.

Animals↗