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Biomedical subjects

A Rot

Publications and source records attributed to A Rot.

49 records · Page 3Linked to original sources
PubMed1991

Inhibitory and promoting effects of carbon tetrachloride-induced liver cirrhosis on the diethylnitrosamine hepatocarcinogenesis in rats.

The modifying effect of the experimentally induced liver cirrhosis on the diethylnitrosamine (DENA)-hepatocarcino-genesis was investigated in male Fischer 344 rats. Cirrhosis was produced by either repeated intragastric doses of CCl4 for 3 months or by simultaneous administration of CCl4 and phenobarbital (PB) in drinking water for 6 weeks. The hepatocarcinogenic regimen consisted of multiple ip. administrations of DENA (10 mg/kg b.w. per dose, up to a total dose of 200 mg/kg b.w.). All the animals were killed 8 months after starting the experiment. The chronic CCl4-post-treatment exerted a strong promoting effect, while the established cirrhosis completely prevented the formation of hepatocellular carcinomas.

Animals↗
PubMed1991

Chemotactic potency of recombinant human neutrophil attractant/activation protein-1 (interleukin-8) for polymorphonuclear leukocytes of different species.

In order to establish the species cross-reactivity of the human neutrophil attractant/activation protein-1 (interleukin-8, NAP-1/IL-8) and find which experimental species are responsive to the human cytokine, blood polymorphonuclear leukocytes (PNMLs) were isolated from chicken, dog, goat, guinea-pig, monkey, mouse, pig, rabbit, and rat and their in vitro migration in response to this cytokine was investigated. PMNLs from all of the tested species migrated in response to recombinant human NAP-1/IL-8 (rhNAP-1/IL-8). The potency of rhNAP-1/IL-8 for the PMNLs of different species varied and was considerably lower than its potency for human cells. The morphological study combined with the leukocyte enumeration in the intradermal rhNAP-1/IL-8 injection sites established an in vivo proinflammatory potency of rhNAP-1/IL-8 for rabbit and rat that was comparable to the observed in vitro chemotactic potency of rhNAP-1/IL-8 for neutrophils of these species.

Animals↗
PubMed1989

Staphylococcus aureus tetrapeptide with high chemotactic potency and efficacy for human leukocytes.

A chemotactic tetrapeptide from culture fluids of Staphylococcus aureus was purified to homogeneity by reverse-phase high-pressure liquid chromatography. The peptide comprises equimolar methionine, leucine, isoleucine, and phenylalanine. It inhibited binding of fluoresceinated fMet-Leu-Phe-Lys to human monocytes, which showed that it interacted with the formyl-methionyl peptide receptor and suggested that it was a formyl-methionyl peptide. Based on a comparison of dose-response curves for inhibition of fluoresceinated fMet-Leu-Phe-Lys binding, the relative affinity of the peptide for the receptor was comparable to that of fMet-Leu-Phe-Lys. At optimal concentrations, chemotactic efficacy (percentage of monocytes migrating to the attractant) was 53 +/- 4%, in contrast to 36 +/- 3% for the reference attractant fMet-Leu-Phe. Since approximately 60% of human monocytes have formyl-peptide receptors, the bacterial peptide is capable of attracting all receptor-bearing monocytes.

Amino Acids↗
PubMed1987

A series of six ligands for the human formyl peptide receptor: tetrapeptides with high chemotactic potency and efficacy.

We recently isolated, from culture fluids of Staphylococcus aureus, a chemotactic peptide that comprised equimolar quantities of methionine, leucine, phenylalanine, and isoleucine. It interacted with the formylmethionyl peptide receptor of human leukocytes and had considerably higher potency and efficacy than the widely studied tripeptide agonist fMet-Leu-Phe. On the assumption that the attractant was a formylmethionyl tetrapeptide, we synthesized the six possible sequences and tested the products for chemotactic potency and efficacy, as well as their capacity to inhibit binding of fluorescein isothiocyanate-labeled fMet-Leu-Phe-Lys to human monocytes. The concentrations required for inhibition of fluorescein-labeled fMet-Leu-Phe-Lys binding by the six peptides covered three orders of magnitude. Chemotactic potency (concentration that caused 50% of the maximum chemotactic response) ranged from 3.1 X 10(-11) M to 6.4 X 10(-10) M; efficacy (percentage of monocytes migrating at optimal attractant concentration) ranged from 41% to 66%. When the six synthetic tetrapeptides were ranked for chemotactic efficacy, they paired according to the position of phenylalanine. The average percentage migration was 66% for the two peptides with phenylalanine in position 3, 51% for phenylalanine in position 4, and 41% for phenylalanine in position 2. Since the published value for the percentage of human monocytes with detectable formyl peptide receptors is 60%, it is apparent that the two tetrapeptides with phenylalanine in position 3 (fMet-Ile-Phe-Leu and fMet-Leu-Phe-Ile) are full chemotactic agonists, which are capable of inducing migration of all the receptor-bearing cells. This is in contrast to the tripeptide fMet-Leu-Phe, which induces migration of only 50% of monocytes with receptors (efficacy of 33%). Since the chemotactic efficacy of the six tetrapeptides covers a wide range, the series may be useful to investigate signals that lead to directed movement after occupancy of receptors by chemoattractants.

Binding, Competitive↗
PubMed1986

Chemoattractant efficacy: oxidation of stimulus by responding cells.

Although all human neutrophils have receptors for formyl-methionyl-leucyl-phenylalanine, only 20-30% migrate in vitro at optimal attractant concentrations. Since this attractant can be oxidized by myeloperoxidase from stimulated neutrophils, we determined if its efficacy was increased by protection from oxidation. Efficacy was increased by reducing agents and by molecules with oxidizable sulfur, 10(-5) M methionine or 1.5 X 10(-6) M albumin. The antioxidant effect was on the attractant, not the cells: albumin in the cell compartment did not increase responses. Furthermore, antioxidants had no effect on efficacy of fNle-Leu-Phe-Nle-Tyr-Lys, an attractant that also stimulated superoxide release but had no oxidizable sulfur.

Ascorbic Acid↗
PubMed1986

Staphylococcus aureus-derived chemoattractant activity for human monocytes.

Products of bacteria are potent chemoattractants for mammalian leukocytes. Several reports suggest that these attractants are small peptides. We compared the properties of culture fluids of Staphylococcus aureus with fMet-Leu-Phe, considered a prototype of bacterial attractant. Chemotactic activity for human monocytes of Staph. aureus culture filtrates was determined in multiwell chemotaxis chambers. At optimal concentrations, the filtrate attracted almost twice as many monocytes as fMet-Leu-Phe (53 +/- 5% of input number compared with 30 +/- 3%, in a series of ten experiments). Gel-filtration characteristics and susceptibility to proteolytic digestion suggested that chemotactic activity was due to peptides with a molecular size range of 500-2,000 daltons. Reverse-phase high-pressure liquid chromatography (HPLC) of unfractionated filtrate revealed nine peaks of chemotactic activity, most of which was in five of the peaks. One peak accounted for 40% of total activity. Individual peaks, like the unfractionated material, were capable of attracting about twice as many monocytes as the optimal concentration of fMet-Leu-Phe. Quantitative bioassay of the HPLC peaks showed that only 5% of the total Staph. aureus chemotactic activity eluted in the position of fMet-Leu-Phe. This is in contrast to the report that fMet-Leu-Phe accounted for 70% of neutrophil lysosomal enzyme-releasing activity of Escherichia coli culture fluid. In summary, chemotactic activity for monocytes of Staph. aureus culture fluid is due to peptides other than fMet-Leu-Phe; these peptides recruit a higher percentage of monocytes than fMet-Leu-Phe.

Chemotactic Factors↗
PubMed1985

Expression of MHC class II antigens on bile duct epithelium in experimental graft versus host disease.

Recently we observed the expression of MHC class II antigens on bile duct epithelium in human liver transplantation rejection. In this report we present evidence for the expression of MHC class II antigens on bile duct epithelium in experimental GVHD. These findings support the idea, that the target tissue elements in liver transplantation rejection and GVHD are the bile ducts, on the other hand this is a new experimental model for the analysis of MHC class II antigen expression on epithelial tissue.

Animals↗
PubMedDate not supplied

Demonstration of the organ preference of liver selected 'high metastatic' Lewis lung tumor cell line.

The experimental metastasis patterns of 'low metastatic' Lewis lung tumor (LLT) and liver selected 'high metastatic' LLT-HH were studied following their arterial dissemination. In previous reports it was shown that both tumor lines develop metastases only in the first encountered organ. Here the liver preference of the liver selected cell line is demonstrated. The model of two LLT cell lines can provide experimental evidence for both the 'mechanical' and 'seed and soil' theories of metastasis formation, depending on the site of tumor cell injection.

Animals↗