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S Rapp

Publications and source records attributed to S Rapp.

32 records · Page 2Linked to original sources
PubMed1996

Microtubule-based peroxisome movement.

The association of peroxisomes with cytoskeletal structures was investigated both by electron microscopy and by kinetic analysis of peroxisome movement. The morphological studies indicated distinct interactions of peroxisomes with microtubules and frequently revealed multiple contact sites. The kinetic approach utilised microinjection and import of fluorescein-labeled luciferase in order to mark and track peroxisomes in vivo. Peroxisomal motility was analysed by time-lapse imaging and fluorescence microscopy. According to their movement peroxisomes were classified into two groups. Group 1 peroxisomes comprising the majority of organelles at 37 degrees C moved slowly with an average velocity of 0.024 +/- 0.012 micron/second whereas the movement of group 2 peroxisomes, 10-15% of the total population, was saltatory exhibiting an average velocity of 0.26 +/- 0.17 micron/second with maximal values of more than 2 microns/second. Saltations were completely abolished by the microtubule-depolymerising drug nocodazole and were slightly reduced by about 25% by cytochalasin D which disrupts the actin microfilament system. Double fluorescence labeling of both peroxisomes and microtubules revealed peroxisome saltations linked to distinct microtubule tracks. Cellular depletion of endogenous levels of NTPs as well as the use of 5'-adenylylimidodiphosphate, a nonhydrolysable ATP analog, applied to a permeabilised cell preparation both completely blocked peroxisomal movement. These data suggest an ATPase dependent, microtubule-based mechanism of peroxisome movement. Both the intact and the permeabilised cell system presented in this paper for the first time allow kinetic measurements on peroxisomal motility and thus will be extremely helpful in the biochemical characterisation of the motor proteins involved.

Actins↗
PubMed1993

Import of firefly luciferase into peroxisomes of permeabilized Chinese hamster ovary cells: a model system to study peroxisomal protein import in vitro.

A model system for the study of in vitro peroxisomal protein import is described. Chinese hamster ovary (CHO) cells were permeabilized by the bacterial toxin streptolysin O (SLO) and their peroxisomes thus became accessible for a model import protein. Firefly luciferase (FL), which was previously shown to be imported into mammalian peroxisomes in vivo, was used as the reporter protein. When SLO-permeabilized CHO cells were incubated with FL in the presence of an ATP-regenerating system, import of FL could be documented by immunofluorescence staining of the cells with monospecific anti-FL antiserum. FL import increased with time and was dependent on temperature and the presence of hydrolysable ATP, which could not be replaced by GTP. The model system functioned reproducibly and should be of use for investigating fundamental questions on the mechanism of peroxisomal protein import.

Adenosine Triphosphate↗
PubMed1990

Epidural and intravenous fentanyl infusions are clinically equivalent after knee surgery.

The management of postoperative pain with continuous epidural fentanyl infusion was compared with continuous intravenous fentanyl infusion. In a randomized, doubleblind protocol we prospectively studied 20 patients undergoing repair of the anterior cruciate ligament of the knee. The quality of analgesia and the incidence of side effects were documented. Compared with patients receiving continuous intravenous fentanyl infusion, at 18 h postoperatively patients given continuous epidural fentanyl infusion reported similar pain scores both at rest (22 +/- 25 vs 27 +/- 21, P = 0.52) and with ambulation (59 +/- 18 vs 56 +/- 22, P = 0.82). Plasma fentanyl levels were 1.8 +/- 0.4 and 1.7 +/- 0.4 ng/mL (P = 0.91) for the intravenous and epidural groups, respectively. There were no significant differences in the incidence of nausea, pruritus, or urinary retention. There was no respiratory depression in either group. We conclude that when compared with continuous intravenous fentanyl infusion, continuous epidural fentanyl infusion offers no clinical advantages for the management of postoperative pain after knee surgery.

Adolescent↗
PubMed1990

[Anesthesiologic implications in the Shy-Drager syndrome--a case report].

Based on a case report with vaginal hysterectomy, the anaesthetic implications are discussed in a patient with Shy-Drager syndrome, which is a degenerative disease in middle-aged to elderly patients, resulting in autonomic dysfunction. The syndrome is reviewed and the anaesthetic management is described. Adequate cardiovascular monitoring and maintenance of haemodynamic stability are important. The response to sympathomimetic drugs is unpredictable and may be extreme due to denervation hypersensitivity. In the postoperative period, signs of postural hypotension may be severe and require training by elevation of the upper part of the body, fluid therapy, sympathomimetics and fludrocortisone.

Anesthesia↗
PubMed1989

Ca2+-independent F-actin capping proteins. Cap 32/34, a capping protein from Dictyostelium discoideum, does not share sequence homologies with known actin-binding proteins.

Polyclonal and monoclonal antibodies against purified 32/34-kDa F-actin-capping protein from Dictyostelium discoideum were generated and used to isolate clones coding for both subunits from a lambda gt11 expression library. In addition genomic clones were isolated for the 34-kDa subunit. The sequences of the corresponding inserts were determined and the amino acid sequences of the proteins deduced. The amino acid sequences have been confirmed by sequencing tryptic peptides of both subunits. As judged from immunological data and sequence comparison, the subunits are completely different. Each of them is encoded by a single copy gene. The mRNAs are present throughout all stages of development. Severing proteins, which exert also capping activity, show no sequence similarity with the cap 32/34-kDa protein. However, a pronounced homology between the 32-kDa subunit and a hypothetical yeast protein was found indicating the presence of a protein homologous to the 32-kDa subunit of the D. discoideum capping protein in yeast.

Actin Depolymerizing Factors↗
PubMed1989

The Dictyostelium gelation factor shares a putative actin binding site with alpha-actinins and dystrophin and also has a rod domain containing six 100-residue motifs that appear to have a cross-beta conformation.

The 120-kD gelation factor and alpha-actinin are among the most abundant F-actin cross-linking proteins in Dictyostelium discoideum. Both molecules are homodimers and have extended rod-like configurations that are respectively approximately 35 and 40 nm long. Here we report the complete cDNA sequence of the 120-kD gelation factor which codes for a protein of 857 amino acids. Its calculated molecular mass is 92.2 kD which is considerably smaller than suggested by its mobility in SDS-PAGE. Analysis of the sequence shows a region that is highly homologous to D. discoideum alpha-actinin, chicken fibroblast alpha-actinin, and human dystrophin. This conserved domain probably represents an actin binding site that is connected to the rod-forming part of the molecule via a highly charged stretch of amino acids. Whereas the sequence of alpha-actinin (Noegel, A., W. Witke, and M. Schleicher. 1987. FEBS [Fed. Eur. Biochem. Soc.] Lett. 221:391-396) suggests that the extended rod domain of the molecule is based on four spectrin-like repeats with high alpha-helix potential, the rod domain of the 120-kD gelation factor is constructed from six 100-residue repeats that have a high content of glycine and proline residues and which, in contrast to alpha-actinin, do not appear to have a high alpha-helical content. These repeats show a distinctive pattern of regions that have high beta-sheet potential alternating with short zones rich in residues with a high potential for turns. This observation suggests that each 100-residue motif has a cross-beta conformation with approximately nine sheets arranged perpendicular to the long axis of the molecule. In the high beta-potential zones every second residue is often hydrophobic. In a cross-beta structure, this pattern would result in one side of the domain having a surface rich in hydrophobic side chains which could account for the dimerization of the 120-kD gelation factor subunits.

Actinin↗
PubMed1986

Identification of the major endogenous leukotriene metabolite in the bile of rats as N-acetyl leukotriene E4.

Mercapturic acid formation, an established pathway in the detoxication of xenobiotics, is demonstrated for cysteinyl leukotrienes generated in rats in vivo after endotoxin treatment. The mercapturate N-acetyl-leukotriene E4 (N-acetyl-LTE4) represented a major metabolite eliminated into bile after injection of [3H]LTC4 as shown by cochromatography with synthetic N-acetyl-LTE4 in four different HPLC solvent systems. The identity of endogenous N-acetyl-LTE4 elicited by endotoxin in vivo was additionally verified by enzymatic deacetylation followed by chemical N-acetylation. The deacetylation was catalyzed by penicillin amidase. Endogenous cysteinyl leukotrienes were quantified by radioimmunoassay after HPLC separation. A N-acetyl-LTE4 concentration of 80 nmol/l was determined in bile collected between 30 and 60 min after endotoxin injection. Under this condition, other cysteinyl leukotrienes detected in bile by radioimmunoassay amounted to less than 5% of N-acetyl-LTE4. The mercapturic acid pathway, leading from the glutathione conjugate LTC4 to N-acetyl-LTE4, thus plays an important role in the deactivation and elimination of these potent endogenous mediators.

Animals↗
PubMed1985

Leukotrienes as mediators in tissue trauma.

A significant increase in the production of cysteinyl leukotrienes was observed after mechanical or thermal trauma in the anesthesized rat. The amount of biliary N-acetyl-leukotriene E4, which represents a suitable indicator for blood plasma leukotrienes, was used as a measure of leukotriene generation. Cysteinyl leukotrienes were rapidly eliminated from blood plasma into bile where N-acetyl-leukotriene E4 was the major metabolite. Leukotrienes were at a much lower concentration in blood plasma than in bile and differed in the pattern of metabolites. The detected amounts of leukotrienes were sufficient to induce known phenomena associated with trauma, such as tissue edema and circulatory and respiratory dysfunction. Increased leukotriene generation appears to play an important role in the pathophysiology of tissue trauma.

Animals↗
PubMedDate not supplied

Role of leukotrienes in endotoxin action in vivo.

The cysteinyl leukotrienes LTC4, LTD4, and LTE4 play an important role within the network of mediators of endotoxin shock since they are capable of eliciting the generation of other lipid mediators of shock. Three lines of evidence support the conclusion that the cysteinyl leukotrienes are involved in the lethal shock-inducing action of endotoxin. (1) Endotoxin elicits the systemic production of cysteinyl leukotrienes in vivo. (2) Injection of these leukotrienes into sensitive species causes shock-like reactions, myocardial depression, and extravasation of plasma. (3) Cysteinyl leukotriene receptor antagonists and inhibitors of leukotriene synthesis prevent experimental endotoxin shock. Moreover, endotoxin induces a strong inhibition of the hepatobiliary elimination of cysteinyl leukotrienes, which normally represents the major pathway for deactivation of these mediators. This dual action of endotoxin, comprising enhanced synthesis and simultaneously impaired deactivation of potent mediators, points to a novel type of toxin action. The role of cysteinyl leukotrienes in endotoxin action does not exclude the involvement of additional shock-inducing factors released by endotoxin and their possible contribution to the formation of lipid mediators, including leukotrienes.

Animals↗