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M Krol

Publications and source records attributed to M Krol.

32 records · Page 2Linked to original sources
PubMed1996

Effect of substance P and its precursor alpha-protachykinin on intracellular free calcium concentration in human polymorphonuclear leukocytes.

The increase in intracellular free calcium concentration is an important step in signal transduction leading to phagocyte activation. The undecapeptide substance P can influence various functions of human polymorphonuclear leukocytes, including chemotaxis, phagocytosis, and respiratory burst. In this study we investigated the ability of low-concentration (that can occur in vivo) substance P (10(-7) M) and its precursor alpha-protachykinin (3 x 10(-7) M) to increase the intracellular free calcium concentration in human polymorphonuclear leukocytes. Cells isolated from ten healthy donors were incubated with substance P or alpha-protachykinin in 1 mM calcium medium for 5 min and the intracellular free calcium concentration was monitored using the fluorescent calcium indicator Fura-2am. Polymorphonuclear leukocytes from 40% of donors responded to both agonists. The substance P- and alpha-protachykinin-induced increase in intracellular free calcium concentration was 59 +/- 13 nM and 58 +/- 12 nM and the extracellular calcium influx contributed to 87 +/- 8% and 54 +/- 8% of the calcium response, respectively. alpha-Protachykinin released almost all the calcium from intracellular stores, while substance P mobilized only 24 +/- 5% of this calcium pool. Finally, cells that responded to a single challenge with substance P and alpha-protachykinin were able to increase their intracellular free calcium concentration in response to each of three consecutive stimulations with these agonists. This may be an additional mechanism by which substance P and its precursor modify the function of human polymorphonuclear leukocytes.

Calcium↗
PubMed1996

Comparison of PAF- and fMLP-induced [Ca2+]i transients in human polymorphonuclear leukocytes.

Changes of [Ca2+]i in human polymorphonuclear leukocytes (PMNL) were studied. PMNL suspension was activated three times every 5 min with 10(-7) M PAF and fMLP. Both PAF and fMLP, induced three consecutive [Ca2+]i transients in PMNL suspended in medium with 1 mM Ca2+. The first Ca2+ response was a result of Ca2+ release from internal stores and the extracellular Ca2+ influx, while the second and third responses were completely dependent on Ca2+ influx from extracellular space. The contribution of Ca2+ from intracellular stores to the first PAF-induced Ca2+ response was about 1.4-fold lower in comparison with the first fMLP induced Ca2+ response (27 +/- 1 vs 37 +/- 6% (p < 0.05). Previous addition of PAF enhanced 3-fold (p < 0.001) the PMNL response to fMLP while cells pretreated with fMLP failed to increase their [Ca2+]i after challenge with PAF. PMNL from 40% of donors did not respond to PAF in the presence of 100 nM Ca2+. However, the cells responding to PAF as the cells treated with fMLP or cyclopiazonic acid released almost the entire Ca2+ from intracellular stores after challenge. Subtraction of mean [Ca2+]i transients in the presence of 100 nM Ca2+ from that obtained in medium with 1 mM Ca2+ showed that, in PMNL stimulated with PAF in contrast to the cells treated with fMLP, the onset of Ca2+ influx from extracellular space precedes Ca2+ release from intracellular stores. These results suggest that PAF-induced Ca2+ influx from extracellular space is at least partly independent of Ca2+ release from intracellular stores.

Blood Coagulation Factors↗
PubMed1996

Increased content of hydrogen peroxide in the expired breath of cigarette smokers.

Cigarette smoking causes an influx of mononuclear phagocytes and polymorphonuclear leucocytes into the lower airways. These cells have altered oxygen metabolism and release more H2O2 than phagocytes from nonsmokers. In this study, we intended to determine whether asymptomatic cigarette smokers exhale more H2O2 than healthy nonsmokers. The content of H2O2 in the expired condensate of 27 nonsmokers and 33 cigarette smokers was measured spectrofluorimetrically (homovanillic acid method). The mean H2O2 level in the expired breath condensate of all cigarette smokers was about fivefold higher than that found in the whole nonsmoker group (0.24 +/- 0.32 versus 0.05 +/- 0.11 nM). However, only 16 smokers (49%) and 6 nonsmokers (22%) had detectable levels of H2O2 in expired breath that reached values 0.49 +/- 0.28 and 0.23 +/- 0.10 nM, respectively. Although the cigarette smoking status was similar for both male and female smokers, females expired 2.5 fold less H2O2 than males (0.15 +/- 0.24 (n = 21) versus 0.38 +/- 0.39 (n = 12) nM. No correlation was found between expired H2O2 levels and cigarette smoking status expressed as the daily cigarette consumption, cumulative cigarette consumption and urinary cotinine concentration. It is suggested that in some smokers, expressed H2O2 can be a noninvasive marker of oxidant overload in the lower airways related to cigarette smoking.

Adult↗
PubMed1995

Abscisic acid induced protection against photoinhibition of PSII correlates with enhanced activity of the xanthophyll cycle.

The exogenous application of abscisic acid (ABA) to barely seedlings resulted in partial protection of the PSII photochemistry against photoinhibition at low temperature, the effect being most pronounced at 10(-5) M ABA. This was accompanied by higher photochemical quenching (qP) in ABA-treated leaves. A considerable increase (122%) in the amount of total carotenoids and xanthophylls (antheraxanthin, violaxanthin and zeaxanthin) was also found in the seedlings subjected to ABA. The activity of the xanthophyll cycle measured by the epoxidation state of xanthophylls under high-light treatment was higher in ABA-treated plants compared with the control. This corresponds to a higher value (0.411) of non-photochemical quenching (qNP) observed in ABA-treated than in control (0.306) leaves.

Abscisic Acid↗
PubMed1995

Effect of cytochalasin B on intracellular free calcium concentration in human polymorphonuclear leukocytes after repeated stimulation with n-formyl-methionyl-leucyl-phenylalanine.

Cytochalasin B can influence various functions of human polymorphonuclear leukocytes, including chemotaxis, lysosomal enzyme release, and reactive oxygen species generation. In this study we investigated the effect of cytochalasin B on the increase in intracellular free calcium concentration after three consecutive additions of 10(-7) M N-formyl-methionyl-leucyl-phenylalanine. The interval between stimulations was 5 min. Intracellular free calcium concentration was monitored using the fluorescent calcium indicator FURA-2AM. Cytochalasin B (3.3 micrograms/ml) added 60 s before the cell stimulation enhanced all three polymorphonuclear leukocyte calcium responses by increasing the N-formyl-methionyl-leucyl-phenylalanine-induced calcium influx from the extracellular space. Cytochalasin B increased the peak intracellular free calcium concentration and elevated the plateau phase level, but had no influence on its shape. In addition, pretreatment with cytochalasin B of polymorphonuclear leukocytes suspended in low calcium medium restored their capacity to respond to a third stimulation with N-formyl-methionyl-leucyl-phenylalanine. Finally, in resting cells cytochalasin B caused a moderate increase in intracellular free calcium concentration which was independent of extracellular calcium.

Adult↗
PubMed1995

Changes of intracellular free calcium concentration in human polymorphonuclear leukocytes after repeated stimulations with N-formyl-methionyl-leucyl-phenylalanine.

A rapid transient rise in the intracellular free calcium concentration ( Ca2+]i) is an important step in human polymorphonuclear leukocytes (PMNL) activation. This can be caused by many inflammatory mediators and has been implicated in the regulation of various cellular reactions. In this study we investigated the changes of [Ca2+]i in human PMNL activated three times with 10(-7)M n-formyl-methionyl-leucyl-phenylalanine (FMLP). PMNL in the presence of 1 mM Ca2+ were able to respond to three consecutive stimulations with FMLP. The first Ca2+ response was the highest one and was a result of Ca2+ release from internal stores (which was responsible for about 30% of maximal increment in [Ca2+]i) and the extracellular Ca2+ influx. Experiments with PMNL suspended in a medium containing 100 nM Ca2+ and pretreated with 1 nM Ni2+ (an inorganic calcium channel blocker) revealed that the second and third response is completely dependent on the extracellular Ca2+ influx. Changes of the time interval between stimulations had no influence on the occurrence of extracellular Ca2+ influx related to second addition of FMLP. Elongation of the time interval up to 30 min did not restore the release of Ca2+ from internal stores. It indicates the occurrence of dissociation of Ca2+ release from intracellular stores and extracellular Ca2+ influx during the second and third PMNL response to FMLP.

Calcium↗
PubMed1994

Protective effect of ambroxol against heat- and hydrogen peroxide-induced damage to lung lipids in mice.

We wanted to determine whether ambroxol, a drug which stimulates the release of surfactant by type II pneumocytes, can protect lung lipids from peroxidative damage in mice. Animals were injected intraperitoneally with ambroxol, 0.169 mmol.kg-1, or 1 ml buffer once a day for three consecutive days. Lipid peroxidation was then induced in lung homogenates either by means of heat, 50 degrees C, or H2O2, 10 mmol.l-1. The lung homogenates from ambroxol-treated animals revealed decreased lipid peroxidation in response to both stimuli. The heat- and H2O2-induced generation of conjugated dienes (a first lipid peroxidation product) in ambroxol-treated lung homogenates was 3.7 and 3.1 fold lower than in the lungs from buffer-injected mice. Ambroxol, as an inhibitor of heat- and H2O2-induced lipid peroxidation, was equipotent to and stronger than the two antioxidants, N-acetylcysteine and methionine, respectively. Ambroxol was not able to protect heart and liver lipids. These results suggest that ambroxol can sufficiently enhance the antioxidant defence in lung tissue and can act as a lung lipid antioxidant.

Acetylcysteine↗
PubMed1992

Differential Detergent Stability of the Major Light-Harvesting Complex II in Thylakoids Isolated from Monocotyledonous and Dicotyledonous Plants.

A survey of isolated thylakoids from 11 different higher plant species (Spinacia oleracea L., Pisum sativum L., Vicia faba L., Brassica napus L., Vigna sinensis L., Vinca minor L., Secale cereale L., Triticum aestivum L., Triticosecale Wittn., Hordeum vulgare L., Zea mays L.) indicated that the ratio of the oligomeric:monomeric form of the light-harvesting complex II was twofold higher for the dicots (3.16 +/- 0.35) than the monocots (1.64 +/- 0.25) examined under identical separation procedures. Under conditions specifically designed to stabilize the oligomeric form in vitro, we show that the oligomeric form of dicot light-harvesting complex II is twice as stable to solubilization in the presence of sodium dodecyl sulfate (SDS) than that observed for monocots. This decreased stability of monocot light-harvesting complex II is associated with a twofold increase in the trienoic fatty acid level of thylakoid phosphatidylglycerol but with no significant changes in the trienoic fatty acid levels in the major galactolipids. In addition, SDS polyacrylamide gel electrophoresis and western blot analyses with monoclonal antibodies indicated that monocots exhibited greater heterogeneity in the polypeptide complements associated with subfractions of light-harvesting complex II than the dicots examined. The data indicate that the oligomeric form of the light-harvesting complex II is not the result of a simple oligomerization of a common monomeric unit. We suggest that the difference in stability of the oligomeric form of light-harvesting complex II in isolated thylakoids of monocots and dicots is probably due to a differential accessibility to SDS. The differential SDS accessibility may be due to differences in thylakoid protein-protein and/or protein-lipid interactions.

Journal Article↗
PubMed1989

Low Temperature-Induced Decrease in trans-Delta-Hexadecenoic Acid Content Is Correlated with Freezing Tolerance in Cereals.

The effect of growth at 5 degrees C on the trans-Delta(3)-hexadecenoic acid content of phosphatidyl(d)glycerol was examined in a total of eight cultivars of rye (Secale cereale L.) and what (Triticum aestivum L.) of varying freezing tolerance. In these monocots, low temperature growth caused decreases in the trans-Delta(3)-hexadecenoic acid content of between 0 and 74% with concomitant increases in the palmitic acid content of phosphatidyl(d)glycerol. These trends were observed for whole leaf extracts as well as isolated thylakoids. The low growth temperature-induced decrease in the trans-Delta(3)-hexadecenoic acid content was shown to be a linear function (r(2) = 0.954) of freezing tolerance in these cultivars. Of the six cold tolerant dicotyledonous species examined, only Brassica and Arabidopsis thaliana L. cv Columbia exhibited a 42% and 65% decrease, respectively, in trans-Delta(3)-hexadecenoic acid content. Thus, the relationship between the change in trans-Delta(3)-hexadecenoic acid content of phosphatidyl(d)glycerol and freezing tolerance cannot be considered a general one for all cold tolerant plant species. However, species which exhibited a low growth temperature-induced decrease in trans-Delta(3)-hexadecenoic acid also exhibited a concomitant shift in the in vitro organization of the light harvesting complex II from a predominantly oligomeric form to the monomeric form. We conclude that the proposed role of phosphatidyl(d)glycerol in modulating the organization of light harvesting complex II as a function of growth temperature manifests itself to varying degrees in different plant species. A possible physiological role for this phenomenon with respect to low temperature acclimation and freezing tolerance in cereals is discussed.

Journal Article↗
PubMed1989

Identification and Partial Characterization of the Denaturation Transition of the Light Harvesting Complex II of Spinach Chloroplast Membranes.

Differential scanning calorimetry was employed to investigate the structure of spinach (Spinacia oleracea) chloroplast membranes. In a low ionic strength Hepes-buffered medium, major calorimetric transitions were resolved at 42.5 degrees C. (A), 60.6 degrees C (B), 64.9 degrees C (C(1)), 69.6 degrees C (C(2)), 75.8 degrees C (D), 84.3 degrees C (E), and 88.9 degrees C (F). A lipid melting transition was also commonly seen at 17 degrees C in scans starting at lower temperatures. The D transition was demonstrated by four independent methods to derive from denaturation of the light harvesting complex associated with photosystem II (LHC-II). Evidence for this conclusion was as follows: (a) the endotherm of the isolated LHC-II (74.0 degrees C) was very similar to that of D (75.8 degrees C); (b) the denaturation temperature of the 27 kilodalton LHC-II polypeptide determined in intact chloroplast membranes by thermal gel analysis was identical to the temperature of the D transition at pH 7.6 and after destabilization by shifting the pH to 6.6 or by addition of Mg(2+); (c) analysis of the stability of the LHC-II complex by electrophoresis in native gels demonstrated that the complex dissociates during the D transition, both at pH 7.6 and 6.6; and (d) the 77 Kelvin fluorescence maximum of LHC-II in chloroplasts was seen to shift to lower wavelengths (indicating gross denaturation of LHC-II), at the temperature of the D transition when examined at either of the above pHs. With this identification, five of the eight major endotherms of the chloroplast membrane have now been assigned.

Journal Article↗
PubMed1988

Overwintering Periwinkle (Vinca minor L.) Exhibits Increased Photosystem I Activity.

The effects of natural, overwintering conditions on photosystem I and photosystem II activity were examined in isolated thylakoids of periwinkle (Vinca minor L.), an endemic, cold-tolerant, herbaceous evergreen. DCMU-Insensitive photosystem I activity (ascorbate/dichlorophenolindophenol --> methylviologen) exhibited a twofold increase in light-saturated rates upon exposure to low temperature and freezing stress with no effect on the apparent quantum yield of this reaction. DCMU-Sensitive photosystem II activity (H(2)O --> dichlorlophenolindophenol) exhibited only minor fluctuations in light-saturated rates but a 50% decrease in the apparent quantum yield of this reaction upon exposure to overwintering conditions. This was correlated with a decrease in the 77 degrees K fluorescence emission at 694 nanometers. These functional changes occurred with no detectable changes in the relative chlorophyll contents of the chlorophyll-protein complexes or the chlorophyll-thylakoid protein. The chlorophyll a/b varied less than 10% during any single growth year. Analyses of total leaf extracts indicated that all lipid classes exhibited increased levels of linoleic and linolenic acid. Neither the trans-Delta(3)-hexadecenoic acid level nor the ratio of oligomeric:monomeric light harvesting of photosystem II was affected by exposure to winter stress. The content of the major chloroplast lipids monogalactosyldiacylglycerol, digalactosyldiacylglycerol, phosphatidyl-diacyl-glycerol, and sulfoquinovosyldiacylglycerol exhibited minor fluctuations, whereas phosphatidylcholine and phosphatidylethanolamine content doubled on a mole percent or chlorophyll basis. We conclude that the previously reported increase in photosystem I activity during controlled, low temperature growth is observed during exposure to natural overwintering conditions. This appears to occur with minimal changes in the structure and composition of the photosynthetic apparatus of periwinkle.

Journal Article↗
PubMed1987

Low Temperature Development Induces a Specific Decrease in trans-Delta-Hexadecenoic Acid Content which Influences LHCII Organization.

Lipid and fatty acid analyses were performed on whole leaf extracts and isolated thylakoids from winter rye (Secale cereale L. cv Puma) grown at 5 degrees C cold-hardened rye (RH) and 20 degrees C nonhardened rye (RNH). Although no significant change in total lipid content was observed, growth at low, cold-hardening temperature resulted in a specific 67% (thylakoids) to 74% (whole leaves) decrease in the trans-Delta(3)-hexadecenoic acid (trans-16:1) level associated with phosphatidyldiacylglycerol (PG). Electron spin resonance and differential scanning calorimetry (DSC) indicated no significant difference in the fluidity of RH and RNH thylakoids. Separation of chlorophyll-protein complexes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the ratio of oligomeric light harvesting complex:monomeric light harvesting complex (LHCII(1):LHCII(3)) was 2-fold higher in RNH than RH thylakoids. The ratio of CP1a:CP1 was also 1.5-fold higher in RNH than RH thylakoids. Analyses of winter rye grown at 20, 15, 10, and 5 degrees C indicated that both, the trans-16:1 acid levels in PG and the LHCII(1):LHCII(3) decreased concomitantly with a decrease in growth temperature. Above 40 degrees C, differential scanning calorimetry of RNH thylakoids indicated the presence of five major endotherms (47, 60, 67, 73, and 86 degrees C). Although the general features of the temperature transitions observed above 40 degrees C in RH thylakoids were similar to those observed for RNH thylakoids, the transitions at 60 and 73 degrees C were resolved as inflections only and RH thylakoids exhibited transitions at 45 and 84 degrees C which were 2 degrees C lower than those observed in RNH thylakoids. Since polypeptide and lipid compositions of RH and RNH thylakoids were very similar, we suggest that these differences reflect alterations in thylakoid membrane organization. Specifically, it is suggested that low developmental temperature modulates LHCII organization such that oligomeric LHCII predominates in RNH thylakoids whereas a monomeric or an intermediate form of LHCII predominates in RH thylakoids. Furthermore, we conclude that low developmental temperature modulates LHCII organization by specifically altering the fatty composition of thylakoid PG.

Journal Article↗