PubMed Health⌕ Search

Biomedical subjects

P Ludwig

Publications and source records attributed to P Ludwig.

At least 19 recordsLinked to original sources
PubMed1992

Loss of cytosolic 15-lipoxygenase activity in A23187-stimulated human leukocytes: involvement of a translocation process?

We focused our study on the subcellular redistribution of 15-lipoxygenase in human leukocytes challenged with A23187 and arachidonic acid (AA). We found that in cytosolic fractions of stimulated cells the 15-lipoxygenase (15-LO) activity, measured as 15-HETE, was 65% less than in controls. However, no activity was found in cell membranes. This effect was complete within 2 min of incubation and was correlated in a dose dependent manner to exogenously added AA. No significant difference in cytosolic distribution of 15-LO activity was observed when cells were stimulated in presence of various concentrations of Ca++. Immunoblot analysis showed that the loss of cytosolic 15-LO activity registered after challenging with A23187 was associated with a concomitant loss of the enzyme content in the cytosol, suggesting the possibility of a translocation process. Neither the 15-LO activity nor the enzyme was, however, found in the cell membrane under our present experimental conditions. But, addition of protease inhibitors showed a slight increase of 15-LO activity in the membrane fraction. Despite the small effect, this may indicate a translocation of 15-LO following challenge of human leukocytes with A23187.

Adult↗
PubMed1992

The HIV-1 surface protein gp120 has no effect on transmembrane signal transduction in T cells.

The ability of HIV-1 envelope glycoprotein gp120 to induce transmembrane signaling processes in human T cells and tumor T-cell lines was investigated. Differently glycosylated gp120 preparations were characterized with respect to their purity, the fraction of native gp120, and the affinity of the gp120-CD4 interaction. These data were used to establish experimental conditions that allow a substantial fraction of the CD4 receptor to be complexed with gp120 in the course of the experiments. The results are in contrast to several previous studies since no effect of gp120 on the intracellular Ca2+ concentration, the metabolism of inositol phosphates and arachidonic acid, protein kinase C translocation, and tyrosine phosphorylation was found. Cross-linking of the gp120:CD4 complex by anti-gp120 antibodies did not elicit additional effects.

Arachidonic Acids↗
PubMed1979

The lipoxygenase of reticulocytes. Purification, characterization and biological dynamics of the lipoxygenase; its identity with the respiratory inhibitors of the reticulocyte.

A lipoxygenase has been purified from rabbit reticulocyte-rich anaemic blood cells. It possesses a molecular weight of 78 000 and an isoelectric point of 5.5 and contains 5% neutral sugars and two iron atoms per enzyme molecule. The lipoxygenase has proved to be identical with the inhibitors of respiratory proteins described formerly. The actions of the lipoxygenase on linoleic acid, phospholipids, mitochondrial and erythrocyte membranes and electron transfer particles were studied. A special feature of the reticulocyte lipoxygenase is the suicidal character of its action on lipids. With electron transfer particles the reticulocyte lipoxygenase causes a loss of acid-labile sulfur which accompanies respiratory inhibition; the strong respiratory inhibition is not exerted by soybean lipoxygenase. The reticulocyte lipoxygenase acts preferably on mitochondrial membranes as compared with cell membranes of the erythrocyte; erythrocyte cytosol moderates the action on mitochondrial membranes. Furthermore, the lipoxygenase reaction can concomitantly and irreversibly inactivate sulfhydryl enzymes as demonstrated with muscle glyceraldehyde-3-phosphate dehydrogenase. The occurrence of the lipoxygenase here described is restricted to reticulocytes; very low amounts were observed in bone marrow and no lipoxygenase was detectable in normal blood. During the course of an experimental anaemia the lipoxygenase is produced owing to superinduction in large amounts, which may persist for a long time since they escape inactivation. Preliminary evidence was obtained for the occurrence of other lipoxygenases in tissues of lung, spleen, kidney and also epithelial tumours.

Amino Acids↗
PubMed1979

[Kinetics and load distribution of supported free-end prostheses. IV. Effect of the saddle curvature on the saddle resp. abutment kinetics and the load distribution in prosthesis beds without abutments].

The influence of the saddle curvature on abutment tooth kinetics and abutment tooth stress was studied with unilateral rigid and movable free-end saddle dentures. The results showed that, independent of the length of the saddle and/or of the saddle curvature, considerable horizontal and vertical extrusive abutment tooth stress is present in addition to vertical intrusive abutment tooth stress. The saddle kinetics are basically influenced by the form of the saddle. The kinetics cannot be altered appreciably because of the mechanical characteristics of the connecting elements; it can only be surpressed at the cost of increased pier stress.

Biomechanical Phenomena↗
PubMed1979

[Free fatty acids as inhibitors of the respiratory chain in testicular homogenates].

The supernatants of the 440 000 . g . min centrifugation of homogenates of rat, bull and boar testicles and sperm inhibit the NADH-oxidase activity of non-phosphorylating submitochondrial particles (ETP). Whereas no inhibitory activity was observed with young rats (150 g), a marked inhibition was detected with heavier animals. The inhibitory activity of testicles was located in the microsomal fraction. The reaction of the testicular inhibitor with the ETP is initiated by an instant reversible binding followed by a slow irreversible inhibition of the electron transport. The reason of the time-dependence is neither an interaction between the enzymes of the ETP and those of the microsomal electron transport nor a slow degradation of the ETP by microsomal phospholipases. Some observations indicate an indirect involvement of phospholipase via the formation of free fatty acids (FFA). The inhibitory fraction could be solubilized from the microsomes both by sodium cholate treatment and by ethanol extraction. After separation of the lipid classes by chromatography on silica gel and gas-chromatographic analysis the inhibitory fraction was identified as a mixture of free fatty acids (FFA) of different chain lengths and degree of saturation. Thus a new effect of FFA on the mitochondrial electron transport has been detected which is different from other actions known up till now. The degradation of the phospholipids of the endoplasmic reticulum in the spermatozoa may be the source of the enhanced formation of FFA. An inhibition of the cell respiration presumably does not occur in vivo. The high FFA level in the testicular homogenates of sexually mature animals is a consequence of an intensive FFA metabolism, especially of high phospholipase activity.

Animals↗
PubMed1978

Interrelated lipid alterations and their influence on the proliferation and fusion of cultured myogenic cells.

We have cultured myogenic cells derived from primary explants and a cell line (L6) in a lipid-depleted medium (LDM) and produced large alterations of the fatty acyl and polar headgroup composition and of the cellular sterol levels. These alterations were produced by altering the composition of the media as follows: removing biotin and providing exogenous fatty acid; removing choline and providing exogenous ethanolamine or choline analogues; and by adding 25-OH cholesterol, an inhibitor of 3-hydroxy-3-methylglutarate (HMG)-CoA reductase. Relatively small, secondary alterations of other lipid classes accompany the large primary alteration. In general, they are not obviously compensatory for the primary alteration by retaining some physical property. We have explored the influence of these lipid alterations on myoblast proliferation and fusion into myotubes. In general, considerable variability appears tolerated, but there also appear to be limits. Long-term cultures grown in media containing a single fatty acid do not proliferate indefinitely, and the fatty acid does not become the sole fatty acyl component of the phospholipids. This phenomenon is also observed for cultures enriched in phosphatidylethanolamine (PE) or phosphatidyldimethylethanolamine (PDME). The influence of the lipid alterations on fusion is particularly interesting. The inclusion of 25-OH cholesterol inhibits fusion. Enrichment of the fatty acyl chains with elaidate or the polar headgroups with PE also inhibits fusion, but in contrast to that by 25-OH cholesterol, a significant fraction of the myoblasts are aligned and interacting with each other. Oleate enrichment enhances the rate of fusion.

Animals↗
PubMed1976

[Kinetics and stress distribution of supported free-end prostheses. I. Effect of the frame stability on the kinematics of the saddle and the stress on the edentulous prosthesis bed].

By means of inductive pressure and motion recorders, the influence of the stability of the framework, the extension of the saddle and type and location of anchorage on the kinetic properties of the denture and the distribution of load between edentulous base and abutment teeth was studied in three different free-end dentures. The findings are discussed with respect to the planning and technical design of dentures.

Biomechanical Phenomena↗
PubMed1976

[Kinematics and load distribution in braced free-end dentures. III. Influence of saddle surfaces on saddle kinematics and on the load-distribution abutiments-edentulous prosthesis saddle. Discussion and results].

In two upper-jaw free-end dentures with proximal rigid anchorage and equal average saddle width, the relationship between resilience of the mucous membrane of the alveolar ridge, the saddle area and the distribution of the load between abutment teeth and edentulous denture-bearing base was studied.

Alveolar Process↗
PubMed1976

[Quantitative studies on the retention mechanism of complete dentures. I. Studies on a phantom model].

In four full maxillary dentures, the physical mechanisms of retention were examined and quantitatively determined by inductive pressure and motion recorders, in tests performed on a model and on the patients. In addition to capillary or viscous forces, the pressure difference existing in the space between denture and palate on the one hand and the oral environment on the other and resulting during pull-off, provides the greatest retaining effect.

Denture Retention↗