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Biomedical subjects

J Wilhelm

Publications and source records attributed to J Wilhelm.

At least 73 records · Page 4Linked to original sources
PubMed1990

Differentiation of human myeloid leukemia cell line ML-1 induced by retinoic acid and 1,25-dihydroxyvitamin D3.

Human myeloblastic leukemia cell line ML-1 was induced to differentiate by 1 mumol/l all-trans-retinoic acid (RA) or by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). After 4-6 days of the induction several differentiation-associated characteristics were observed: (1) Ability to stimulate respiration burst in the ML-1 induced cells as detected by nitroblue tetrazolium (NBT) test or by chemiluminescence (CL). (The percentage of the NBT-positive cells was up to 99% in the RA-induced cells and up to 85% in the 1,25(OH)2D3-induced cells.) (2) Substantially higher phagocytosis of colloid iron, latex or Staphylococcus particles was found in the induced cells. (3) The 1,25(OH)2D3-induced ML-1 cells expressed the monocytic enzyme NaF-inhibitable alpha-naphthyl butyrate esterase and the surface monocytic antigen CD-14. (4) A majority of the induced cells lost the morphological features of blast cells; while the 1,25(OH)2D3-treated cells acquired certain features of monocyte-macrophage differentiation, the RA-treated cells displayed several granulocytic characteristics. (5) Cytofluorometric DNA assay after treatment of the cells with colcemid showed that the decline observed in the growth rate of the induced cells was connected with their arrest in G1/G0 phase of the cell cycle. The obtained results indicate granulocytic differentiation of the RA-induced ML-1 cells and monocyto/macrophage differentiation of the 1,25-(OH)2-D3 induced cells.

Acid Phosphatase↗
PubMed1990

Metabolic aspects of membrane lipid peroxidation.

Lipid peroxidation is a free radical initiated chain oxidation of unsaturated lipids. With respect to the ubiquity of unsaturated fatty acids in the cellular membranes, the peroxidative damage has the potential to affect many cellular functions. Some of the products of lipid peroxidation are diffusible and can spread the damage far beyond the site of the original free radical attack. There is an interdependency between reactive oxygen species and lipid peroxidation - reactive oxygen species initiate the reactions of lipid peroxidation and are also produced in these reactions as intermediates. The generation of reactive oxygen species can be triggered either by nonenzymatic mechanisms, in which iron ions play the major role, or by a wide range of enzymatic systems. The primary damaging effect of lipid peroxidation is exerted by the interactions with proteins and DNA. These interactions are then revealed at the subcellular (cellular organelles), cellular, and organ levels. The production of lipid peroxides interferes with the regulation of several metabolic pathways. In this review, particular attention is focused on the interaction of non-specifically formed lipid peroxides with the regulatory factors produced by the controlled oxidation of arachidonic acid (prostaglandins and leukotrienes), the effects on ionic pumps and intracellular calcium metabolism, the participation of lipid peroxidation in the ageing process, and the modulation of hormonal regulations by lipid peroxidation. Lipid peroxidation is induced at the level of the whole organism by various extrinsic factors such as ionizing irradiation, physical activity, diet and fasting, and various drugs. There is increasing awareness of the association between pathologic states and lipid peroxidation. Among the most studied are inflammation, ischaemia-reperfusion injury, and atherogenesis. Lipid peroxidation also plays a dual and complex role in cancer. Organisms have developed an efficient multilevel protective system against lipid peroxidation, but this can be overwhelmed by certain pathologies.

Animals↗
PubMed1989

What do we measure by a luminol-dependent chemiluminescence of phagocytes?

The review presents a survey of published findings concerning the mechanism of luminol-dependent chemiluminescence in biological systems. The potential of various oxygen species (superoxide anion, hydrogen peroxide, hydroxyl radical) to react with luminol is discussed. The ability of commonly used enzymes (superoxide dismutase, catalase), inhibitors, and oxygen radical scavengers to discriminate between individual oxygen species is assessed together with the potential of a variety of substances encountered in biological systems to interfere in luminol-dependent chemiluminescence reactions. It is concluded that luminol-dependent chemiluminescence gives at present very little ability to discriminate between individual oxygen or radical species. Furthermore, luminol-dependent chemiluminescence used in biological systems is extremely prone to many interferences, which are very difficult to control.

Animals↗
PubMed1989

Lipid peroxidation and lipolysis during fasting.

The present work was aimed at investigation of lipid peroxidation during fasting and its effects upon metabolism of adipose tissue, especially lipolytic activity. An increase in the lipid peroxidation was demonstrated in an animal model (male rats) through accumulation of lipofuscin-like pigments (LFP), the end product of lipid peroxidation. The increased LFP levels correlated with a decrease in the activity of hormone-sensitive lipase. LFP content increased in the plasma, liver and adipose tissue. The time-course of the changes depended on the initial body mass of the animals. Correlations were found between lipolytic activity and LFP content in adipose tissue and in plasma. In the course of the repeated cycles of fasting--feeding, the changes of LFP and lipolysis were antiparallel to each other. During four cycles, there was a net increase in LFP and a net decrease in lipolysis. The lipolytic activity depended on many factors, among which we identified the initial body mass of animals, their age, and the way of feeding. The results obtained in this animal model enable application of the methods used in the investigation of fasting in obese patients.

Animals↗
PubMed1989

Time course of lipolytic activity and lipid peroxidation after whole-body gamma irradiation of rats.

The content of fluorescing products of lipid peroxidation (LFP) and hormone-stimulated lipolytic activity were determined in rat epididymal adipose tissue during a 29-day interval after whole-body gamma irradiation. An increase in LFP was accompanied by a decrease in lipolytic activity. It is suggested that these effects are interrelated and that the decrease in lipolysis in irradiated, semi fasting rats is an additional deteriorating factor leading to death in some animals.

Animals↗
PubMed1989

Changes of lipofuscin-like pigments in erythrocytes and spleen after whole-body gamma irradiation of rats.

Whole-body gamma irradiation of rats induced the formation of lipofuscin-like pigments in erythrocytes. Erythrocytes that were damaged by oxidation were scavenged in the spleen, and lipofuscin-like pigments were transferred from erythrocytes to the spleen during this process. The time course of lipofuscin-like pigments in erythrocytes and spleen indicates that the pigments were not induced by the action of free radicals produced by ionizing radiation but rather were a sequela of postirradiation metabolic changes.

Animals↗
PubMed1988

Structure-function analysis with tissue-type plasminogen activator. Effect of deletion of NH2-terminal domains on its biochemical and biological properties.

Tissue-type plasminogen activator (t-PA) is a mosaic protein containing several distinct structural domains attached to the serine protease catalytic unit present at its COOH terminus. To investigate structure-function relationships in t-PA, we deleted the NH2-terminal domains, finger and epidermal growth factor, by genetic engineering. The genes for the parent and mutant t-PA were expressed in a bovine papilloma virus-dependent mammalian cell system. The secreted proteins were purified to homogeneity. The mutant protein was processed to the expected size of about 60 kDa compared to approximately 68 kDa for the parent t-PA, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fibrin autography. While the mutant t-PA had amidolytic activity comparable to native t-PA, it did not bind appreciably to fibrin. Consequently, fibrin-dependent enzymic activity, i.e. plasminogen activation in the presence of soluble fibrin and fibrinolysis were lower than with native recombinant t-PA. The effect of deletion of NH2-terminal domains on the plasma half-life (t1/2) was investigated by injecting native and mutant t-PA into mice. While the majority of the t-PA disappeared initially with a t1/2 of about 2 min, mutant t-PA cleared at a much slower rate with t1/2 of about 50 min. These findings suggest that the NH2-terminal domains of t-PA not only determine its specificity for binding to fibrin but also mediate its clearance from plasma in vivo. Furthermore, the catalytic unit in t-PA seems to function autonomously.

Cell Line↗
PubMed1988

Construction and expression of hybrid plasminogen activators prepared from tissue-type plasminogen activator and urokinase-type plasminogen activator genes.

Recent data from several studies have suggested that the non-protease domains in tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) determine their biological specificities, including binding to fibrin clots and survival in the circulatory system (Van Zonneveld, A.-J., Veerman, H., and Pannekoek, H. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 4670-4674; Rijken, D. C., and Emeis, J. J. (1986) Biochem. J. 238, 643-646). Structural manipulations (e.g. deletions, additions, or substitutions) in these domains can thus be utilized to maximize the desired biological effects. Using recombinant DNA technology, we constructed a number of hybrid molecules from the t-PA and u-PA genes. In hybrid A, the epidermal growth factor and finger domains of t-PA (residues 1-91) were replaced by the epidermal growth factor and kringle of u-PA (residues 1-131). In hybrids B and C, the u-PA kringle (residues 50-131) was inserted either before (residue 92) or after (residue 261) the double-kringle region of t-PA. All these hybrid PAs containing three kringles were expressed in mouse fibroblast cells (C-127). The hybrid proteins were synthesized in predominantly a single-chain form with molecular weights of 70,000-80,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and were enzymatically active as assayed by the fibrin-agar plate method. In vitro studies on the binding of hybrid PAs to fibrin showed that hybrid B, like t-PA, possesses affinity toward fibrin, while hybrid A shows lower binding. This suggests that the finger domain, which is not present in hybrid A, plays a role in conferring fibrin affinity to the hybrid PAs. The enzymatic activities of the hybrids were compared with that of recombinant t-PA (rt-PA) expressed in the same vector/host system and found to be similar in activity toward a chromogenic peptide substrate. In addition, plasminogen activation with all the hybrid-PAs, as with rt-PA, was stimulated by fibrin, with the order of activity being rt-PA greater than or equal to hybrid B greater than hybrid C greater than hybrid A. This study shows the feasibility of shuffling functional domain(s) of known specificity in plasminogen activators which may lead to the design of a superior thrombolytic agent.

Cell Line↗
PubMed1988

Studies on lipid peroxidation in rat liver nuclei and isolated nuclear membranes.

Non-enzymatic and enzymatically-driven lipid peroxidation processes were studied in rat liver nuclei and isolated nuclear membranes, by evaluating the formation of thiobarbituric acid-chromophore, free malondialdehyde, lipofuscin-like pigments, and the degradation of polyunsaturated fatty acids of the nuclear membrane lipids. The results obtained show that: (1) both non-enzymatic and enzymatically driven lipid peroxidation processes are operative in cell nuclei and isolated nuclear membranes; (2) only for isolated nuclear membranes, a good qualitative and up to a great extent quantitative correlation between malondialdehyde and lipofuscin-like pigment formation was obtained; (3) there is a qualitative but not quantitative correlation between malondialdehyde formation and polyunsaturated fatty acid degradation; (4) lipid peroxidation processes in isolated nuclear membranes and intact nuclei have an essentially identical kinetic behaviour. No statistical differences in the relative increases in the concentrations of malondialdehyde and lipofuscin-like pigments or in the degradation of polyunsaturated fatty acids were obtained, when the two systems were compared, except in the presence of NADPH-ADP-Fe3+, which induced a significantly larger degradation of polyunsaturated fatty acids in isolated nuclear membranes than in intact nuclei, and (5) no malondialdehyde-DNA fluorescent adduct formation was observed in any of the experimental groups studied, as inferred from the characteristics of the fluorescent spectra of lipofuscin-like pigments extracted from incubated nuclear preparations.

Adenosine Diphosphate↗
PubMed1988

Lipid peroxidation inhibits norepinephrine-stimulated lipolysis in rat adipocytes. Reduction of beta-adreno-ceptor number.

The effect of lipid peroxidation on lipolysis depends on the intactness of the adipocyte plasma membrane. In the intact cells, the norepinephrine-stimulated lipolysis was inhibited, while the basal one was elevated. In the lysed cells, lipid peroxidation had no effect upon hormone-stimulated lipolysis, but the basal one was strongly inhibited. The effects of free radical damage (iron plus ascorbate ions) were compared to those of malondialdehyde, a non-radical product of lipid peroxidation. Although qualitatively similar, deterioration of plasma membrane induced by malondialdehyde was much lower than by free radicals. The changes in lipolytic response to norepinephrine were accompanied by a drastic reduction in the number of beta-adrenergic receptors.

Adipose Tissue↗
PubMed1988

Arterial oxygen saturation during Nd:YAG laser photoresection of endobronchial tumors under local anesthesia. Use of intermittent supplemental oxygen with pulse oximetry guidance.

Although Nd:YAG laser photoresection of endobronchial lung tumor can result in significant arterial oxygen desaturation, oxygen supplementation during procedures is often limited due to fear of intrabronchial combustion. We gave intermittent pulse supplemental oxygen to ten patients during 26 laser procedures performed under local anesthesia using SaO2 measured by a pulse oximeter as a guide. In four procedures (15.4 percent), severe oxygen desaturation contraindicated performing or completing laser phototherapy. In the remaining 22 procedures (84.6 percent), laser photoresection was safely and successfully performed without incident. Thus, pulse oximetry is a valuable tool and intermittent oxygen supplementation with pulse oximeter guidance an effective technique for maintaining adequate oxygenation during laser photoresection.

Adult↗
PubMed1987

Participation of superoxide in luminol-dependent chemiluminescence triggered by mineral dust in rabbit alveolar macrophages.

Luminol-dependent chemiluminescence (CL) triggered by mineral dust in rabbit alveolar macrophages depended on superoxide production as revealed by inhibition by superoxide dismutase and ferricytochrome c. The contribution of superoxide changed in the course of CL peak between 80-20%. The effects of ferricytochrome c were concentration-dependent: both stimulation and inhibition were observed. Ferricytochrome c and desferal also inhibited CL pathway which was not superoxide-dependent.

Animals↗
PubMed1987

Covalent cross-linking of AcVal-tRNA to Tetrahymena thermophila cytoplasmic ribosomes and two of its 17S rRNA mutants.

Tetrahymena thermophila 80S ribosomes have been cross-linked to non-enzymatically bound AcVal-tRNA, presumably at the ribosomal P-site. Like the ribosomes from Escherichia coli, yeast, and Artemia salina, cross-linking is exclusively to C-1609, the equivalent of the E. coli C-1400 residue. Mutation of the RNA from G-1707 to A or from U-1711 to C which results in resistance to paromomycin or hygromycin, respectively, failed to affect the rate, yield, or site of cross-linking. The presence of the antibiotics during cross-linking also was without effect. It is concluded that at these two positions the base changes made do not interfere with the tertiary structure of the decoding site.

Animals↗
PubMed1987

Stimulation of alveolar macrophages by mineral dusts in vitro: luminol-dependent chemiluminescence study.

Luminol-dependent chemiluminescence (CL) of normal (nonactivated) rabbit alveolar macrophages (AMs) was measured in suspension upon stimulation by various size fractions of one quartz dust sample or by various mineral dusts (quartz, corundum, anatas, and chrysotile asbestos as an example of fibrous dust). The CL-triggering capacity of the tested dusts was inhibited by their preincubation with autologous serum. The intensity of luminol-dependent CL induced by particulate dusts upon their action on AMs depended on the kind of dust, on the dust particle sizes, and on the ratio of the number of particles to the number of cells in a given suspension. The cytotoxicity and/or fibrogenicity of the dust and its capacity to trigger the luminol-dependent CL of nonadherent AMs were not directly correlated.

Animals↗
PubMed1986

Variables in xanthine oxidase-initiated luminol chemiluminescence: implications for chemiluminescence measurements in biological systems.

We tested the effects of generally used chemiluminescence inhibitors on an example of luminol chemiluminescence elicited by xanthine oxidase/hypoxanthine system, and attempted to assess their capabilities in discovering the reaction pathways leading to chemiluminescence. Luminol itself is a xanthine oxidase inhibitor and its concentration affects the reaction mechanism. Maximal chemiluminescence response was observed at luminol concentration inhibiting urate production. Chemiluminescence was totally inhibited by superoxide dismutase, the inhibition by catalase depended on luminol concentration. Ferricytochrome c, a detector of superoxide, either stimulated or inhibited chemiluminescence in a concentration-dependent manner. Chemiluminescence was highly stimulated by peroxidases. A pronounced inhibition of chemiluminescence was caused by chelators; 1 mM desferal and 0.01 mM diethyldithiocarbamate. It is suggested that measurement of luminol chemiluminescence is not a suitable method for discrimination among individual reactive oxygen species and their quantitative determination in biological systems.

Catalase↗