Characterization of transient noise in Advanced LIGO relevant to gravitational wave signal GW150914

On September 14, 2015, a gravitational wave signal from a coalescing black hole binary system was observed by the Advanced LIGO detectors. This paper describes the transient noise backgrounds used to determine the significance of the event (designated GW150914) and presents the results of investigations into potential correlated or uncorrelated sources of transient noise in the detectors around the time of the event. The detectors were operating nominally at the time of GW150914. We have ruled out environmental influences and non-Gaussian instrument noise at either LIGO detector as the cause of the observed gravitational wave signal.

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4_{-0.9}^{+0.7}×10^{-22}. The inferred source-frame initial black hole masses are 14.2_{-3.7}^{+8.3}M_{⊙} and 7.5_{-2.3}^{+2.3}M_{⊙}, and the final black hole mass is 20.8_{-1.7}^{+6.1}M_{⊙}. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440_{-190}^{+180}  Mpc corresponding to a redshift of 0.09_{-0.04}^{+0.03}. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

Properties of the Binary Black Hole Merger GW150914

On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a gravitational-wave transient (GW150914); we characterize the properties of the source and its parameters. The data around the time of the event were analyzed coherently across the LIGO network using a suite of accurate waveform models that describe gravitational waves from a compact binary system in general relativity. GW150914 was produced by a nearly equal mass binary black hole of masses 36_{-4}^{+5}M_{⊙} and 29_{-4}^{+4}M_{⊙}; for each parameter we report the median value and the range of the 90% credible interval. The dimensionless spin magnitude of the more massive black hole is bound to be <0.7 (at 90% probability). The luminosity distance to the source is 410_{-180}^{+160}  Mpc, corresponding to a redshift 0.09_{-0.04}^{+0.03} assuming standard cosmology. The source location is constrained to an annulus section of 610  deg^{2}, primarily in the southern hemisphere. The binary merges into a black hole of mass 62_{-4}^{+4}M_{⊙} and spin 0.67_{-0.07}^{+0.05}. This black hole is significantly more massive than any other inferred from electromagnetic observations in the stellar-mass regime.

GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015. GW150914 was observed with a matched filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203000 years, equivalent to a significance greater than 5.1 σ.

GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015. GW150914 was observed with a matched filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203000 years, equivalent to a significance greater than 5.1 σ.

Tests of General Relativity with GW150914

The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 10^{13}  km. In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.

GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes

The LIGO detection of the gravitational wave transient GW150914, from the inspiral and merger of two black holes with masses ≳30M_{⊙}, suggests a population of binary black holes with relatively high mass. This observation implies that the stochastic gravitational-wave background from binary black holes, created from the incoherent superposition of all the merging binaries in the Universe, could be higher than previously expected. Using the properties of GW150914, we estimate the energy density of such a background from binary black holes. In the most sensitive part of the Advanced LIGO and Advanced Virgo band for stochastic backgrounds (near 25 Hz), we predict Ω_{GW}(f=25  Hz)=1.1_{-0.9}^{+2.7}×10^{-9} with 90% confidence. This prediction is robustly demonstrated for a variety of formation scenarios with different parameters. The differences between models are small compared to the statistical uncertainty arising from the currently poorly constrained local coalescence rate. We conclude that this background is potentially measurable by the Advanced LIGO and Advanced Virgo detectors operating at their projected final sensitivity.

GW150914: The Advanced LIGO Detectors in the Era of First Discoveries

Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of 10^{-23}/sqrt[Hz] at 100 Hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. On September 14, 2015, the Advanced LIGO detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [B. P. Abbott et al., Phys. Rev. Lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. The event, GW150914, was observed with a combined signal-to-noise ratio of 24 in coincidence by the two detectors. Here, we present the main features of the detectors that enabled this observation. At full sensitivity, the Advanced LIGO detectors are designed to deliver another factor of 3 improvement in the signal-to-noise ratio for binary black hole systems similar in mass to GW150914.

Observation of Gravitational Waves from a Binary Black Hole Merger

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo

We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg2 to 20 deg2 will require at least three detectors of sensitivity within a factor of ∼ 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Variation in cephalic volatile substances in relation to worker age and behavior in the stingless bee, scaptotrigona postica

Head extracts of adult workers of the Brazilian stingless bee Scaptotrigona postica (Trigonini, Meliponinae: Apidae) were analysed for volatile substances by gas chrom atography/ mass spectroscopy. Individual worker bees performing clearly defined tasks and representing five age groups were collected. A total of 36 compounds was identified, 22 of which had not been previously described for a Trigona species.

The major components are 2-heptanol, 2-tridecanone, 2-pentadecanone, Z-5-tetradecenylbutanoate and Z-7-hexadecenylbutanoate. 11 of the 36 compounds increase in concentration with age, but only 2 decrease. The other substances are present in more or less constant concentrations. These data are discussed assuming more complicated pheromone-m ediated interactions within an age-dependent polyethism between old workers acting inside and outside the nest than between young house bees

Identification of Cyclic Enolethers from Insects: Alkyldihydropyranes from Bees and AIkyldihydro-4H-pyran-4-ones from a Male Moth*

Mass spectrometric fragmentation patterns of alkyl-3,4-dihydro-2H-pyranes and alkyl-2,3-dihydro-4H-pyran-4-ones are described. Through GC/MS analyses, respective compounds showing unbranched carbon skeletons are identified for the first time as volatile signals of social and solitary bees and of the male moth Hepialus hecta L.

Purification and Characterization of Cystathionine (beta)-Lyase from Lactococcus lactis subsp. cremoris B78 and Its Possible Role in Flavor Development in Cheese

An enzyme that degrades sulfur-containing amino acids was purified from Lactococcus lactis subsp. cremoris B78; this strain was isolated from a mixed-strain, mesophilic starter culture used for the production of Gouda cheese. The enzyme has features of a cystathionine (beta)-lyase (EC 4.4.1.8), a pyridoxal-5(prm1)-phosphate-dependent enzyme involved in the biosynthesis of methionine and catalyzing an (alpha),(beta)-elimination reaction. It is able to catalyze an (alpha),(gamma)-elimination reaction as well, which in the case of methionine, results in the production of methanethiol, a putative precursor of important flavor compounds in cheese. The native enzyme has a molecular mass of approximately 130 to 165 kDa and consists of four identical subunits of 35 to 40 kDa. The enzyme is relatively thermostable and has a pH optimum for activity around 8.0; it is still active under cheese-ripening conditions, viz., pH 5.2 to 5.4 and 4% (wt/vol) NaCl. A possible essential role of the enzyme in flavor development in cheese is suggested.

The first record on Brazilian stingless bees published 450 years ago by Hans Staden

Only a few decades after 1492, when Christopher Columbus arrived on a Caribbean island and Pedro Alvares Cabral claimed Brazil for Portugal in 1500, a German mercenary gave the first description of stingless bees in 1557. He got to know them when he was imprisoned for months by an anthropophagous tribe in the coastal region of Santos, today in the State of São Paulo. This rather short but nevertheless extremely exact record on stingless bees is hidden in the first book on Brazil. Three species and important aspects of their life history were treated. This early description has been completely overlooked by bee scientists until now. My note intends to close this evident gap.

Comparative study of nest architecture and colony structure of the fungus-growing ants, Mycocepurus goeldii and M. smithii

Nest architecture and demography of the non leaf-cutting fungus-growing ant species Mycocepurus goeldii and M. smithii (Attini: Formicidae) were studied in an agroforest habitat near Manaus, Brazil during the excavation of 13 nests. Both species built their nests in two different ways. The first type possessed a "tree-like" architecture, in which a vertical tunnel led downwards and lateral tunnels branched off at 90 degrees angles from the main tunnel, with a chamber at the end of each side branch. Alternatively, other nests displayed a "necklace-like" architecture, where the main tunnel also led down vertically, but entered each chamber from the top and exited it at the bottom, resulting in an architecture where chambers appeared like pearls on a necklace. The nest systems of M. goeldii and M. smithii consisted of 1-21 or 1-15 chambers, respectively. Of 199 excavated chambers, 57 % contained fungus-gardens. Chambers not containing fungus gardens were filled with organic matter from decaying fungus gardens or earthworm feces. Only M. smithii workers deposited loose soil in abandoned chambers during the construction of new nest chambers. Workers of M. smithii constructed significantly smaller chambers than those of M. goeldii. In both species, fungus garden-containing chambers were larger than non-garden chambers and were homogenously distributed in the soil between 17 cm and 105 cm depth. Neither fungus gardens nor abandoned chambers were encountered more frequently in deeper or shallower soil strata indicating that ants of both species did not abandon shallower versus deeper chambers, or move the colony to deeper soil layers with increasing colony age. Fungus gardens were suspended from the ceiling of the subterranean chambers and originated as small mycelial tufts. Through continual addition of organic debris, the tufts first grew vertically to strands before they expanded laterally until most of the chamber volume was filled with fungus garden curtains. New garden chambers were found at depths ranging from 17 to 83 cm, suggesting that new garden chambers were not constructed in deeper soil strata with increasing colony age. The size of M. goeldii and M. smithii colonies was dependent on their age. Worker counts varied between a few individuals in recently founded colonies and 1352 workers in an adult M. goeldii colony. The ratio of worker number per fungus garden chamber was higher in M. goeldii colonies than M. smithii colonies; the M. goeldii colonies were more populous. Both species were oligogynous with a maximum of four and three queens observed in a single chamber of M. goeldii and M. smithii, respectively. The reproductive status of each queen was unknown. In both species the ratio of brood to workers was approximately 2:3. Larvae and pupae were unequally distributed throughout the nest, but were only located in chambers containing a garden. Their location in the chamber was dependent upon the developmental state of the fungus garden.

Is nitric oxide involved in the tolerance of Calomys callosus as a reservoir host towards Trypanosoma cruzi infection?

Trypanosoma cruzi, the agent of Chagas disease, is known to cause enhanced nitric oxide (NO) production, which might be involved in host resistance. The inducible nitric-oxide-synthase (iNOS) is assumed to be responsible for the NO increase after several infections. We studied the potential role of NO in Calomys callosus, a natural reservoir of this protozoan parasite. The concentration of NO was determined in spleen and liver of animals infected with two different T. cruzi strains, BOL and BOL-SB. Furthermore, the iNOS mRNA expression was quantified in the same cell types. NO production was detectable in both tissues exhibiting only slight differences compared to non-infected controls. All measured NO values were significantly lower than those reported for a number of different mouse strains, which displayed extremely enhanced NO levels after T. cruzi infection. Surprisingly, iNOS mRNA expression was induced in infected C. callosus but without subsequent increase of NO levels, indicating a post-transcriptional regulation mechanism. In summary, our results, indicate that the tolerance of C. callosus to T. cruzi is only accompanied by non-toxic NO intracellular concentrations.

Six Trypanosoma cruzi strains characterized by specific gene expression patterns

The intracellular parasite Trypanosoma cruzi, the causative agent of Chagas disease, is known to comprise heterogeneous populations. One possibility to explain the obviously distinct phenotypes of different T. cruzi strains is differential expression of particular genes. This could result in environmental adaptations of the parasite within host organs, leading to distinct clinical symptoms. With the aim of identifying differentially expressed genes, we examined different T. cruzi strains by suppression subtractive hybridization analysis. The isolated clones were sequenced and Blasted for sequence-homology with known T. cruzi genes. A stage-specific glycoprotein (82gp), an 85-kDa protein with homology to heat-shock proteins, a beta-tubulin gene, a hexosetransporter, a dehydrogenase/ prostaglandin F2alpha-synthase and a cathepsin B-like protease were identified. The expression of these genes was analyzed by RT-PCR. Diverse expression patterns were detected for different T. cruzi strains, but no specific correlation between the gene expression and the classification of groups could be found. We discuss the presumed importance of these T. cruzi gene expression patterns for future strategies of molecular therapy of Chagas disease. For pathological studies, other parameters such as distinct gene/antigen expression could also be of interest, because they probably likewise correlate with distinct phenotypes.

Tyramine functions as a toxin in honey bee larvae during Varroa-transmitted infection by Melissococcus pluton

From wounds of honey bee pupae, caused by the mite Varroa destructor, coccoid bacteria were isolated and identified as Melissococcus pluton. The bacterial isolate was grown anaerobically in sorbitol medium to produce a toxic compound that was purified on XAD columns, gelfiltration and preparative HPLC. The toxic agent was identified by GC-MS and FTICR-MS as tyramine. The toxicity of the isolated tyramine was tested by a novel mobility test using the protozoon Stylonychia lemnae. A concentration of 0.2 mg/ml led to immediate inhibition of mobility. In addition the toxicity was studied on honey bee larvae by feeding tyramine/water mixtures added to the larval jelly. The lethal dosis of tyramine on 4-5 days old bee larvae was determined as 0.3 mg/larvae when added as a volume of 20 microl to the larval food in brood cells. Several other biogenic amines, such as phenylethylamine, histamine, spermine, cadaverine, putrescine and trimethylamine, were tested as their hydrochloric salts for comparison and were found to be inhibitory in the Stylonychia mobility test at similar concentrations. A quantitative hemolysis test with human red blood cells revealed that tyramine and histamine showed the highest membranolytic activity, followed by the phenylethylamine, trimethylamine and spermine, while the linear diamines, cadaverine and putrescine, showed a significantly lower hemolysis when calculated on a molar amine basis. The results indicate that tyramine which is a characteristic amine produced by M. pluton in culture, is the causative agent of the observed toxic symptoms in bee larvae. Thus this disease, known as European foulbrood, is possibly an infection transmitted by the Varroa destructor mite.

Ultrastructure and bacterial infection of wounds in honey bee ( Apis mellifera) pupae punctured by Varroa mites

The damage to western honey bee, Apis mellifera, colonies caused by the originally Asian ectoparasitic mite Varroa destructor is mainly a consequence of the infestation of host bee pupae. In the capped brood cell, female mites puncture the host's integument at preferred sites in order to suck haemolymph. Due to repeated feeding by the mother mite and her progeny, these perforations are kept open until shortly before the imaginal moult of the bee. Thereafter scarring takes place, thus preventing microbial infection after the adult bee has emerged from the protected environment of the sealed brood cell. However, colonies of various bacteria were found in the open wounds of about 15-30% of all inspected host pupae with an abundance depended on the level of host brood cell infestation by the mite. The small punctures of the pupal integument are difficult to detect but, by vital staining with trypan blue, the wounds can be visualised. The ultrastructure of the pupal wounds, the bacterial colonies and the scarring process are documented by a series of scanning electron micrographs.

Molecular genetic characterization of different Trypanosoma cruzi strains and comparison of their development in Mus musculus and Calomys callosus

Trypanosoma cruzi populations are characterized by diverse morphology, heterogeneous biological behavior, high genetic variability, and distinctly different clinical courses. The first objective of this work was to characterize different strains of T. cruzi with various molecular markers [simple-sequence-repeat PCR, randomly amplified polymorphic DNA (RAPD)-PCR, mini-exon genes]. All examined strains could be divided into two major lineages. Only one strain showed a different banding pattern in RAPD-PCR, which could be a further indication of the existence of a third lineage. The second aim was to examine the biological behavior of the different strains. Two animal models, Calomys callosus and Mus musculus, were infected. The results provide strong evidence that the biological behavior of the strains is not only lineage-specific. It appears that all factors, such as the infecting strain belonging to a certain lineage, the predominant morphological form of the isolate, and the immune response of the respective infected host, play an important role in the course of this infection.

Microsatellite instability in Drosophila spellchecker1 (MutS homolog) mutants

We have cloned a mutS homolog from Drosophila melanogaster called spellchecker1 (spel1) and have constructed spel1 mutant flies. MutS proteins promote the correction of DNA mismatches and serve important roles in DNA replication, recombination, and repair. The spel1 gene belongs to a subfamily of mutS first characterized by the MSH2 gene of yeast and which also includes hMSH2, one of the two major hereditary nonpolyposis colon cancer loci of humans. Like msh2 mutants in other species, we find that flies lacking the spel1 gene suffer a highly increased rate of instability in long runs of dinucleotide repeats when analyzed after 10-12 fly generations. Using a new assay, we have also discovered that mutations in spel1 decrease the stability of a dinucleotide repeat when it is copied into the site of a double-strand break during gene conversion. Contrary to the case in mammalian cells, spel1 deficiency does not affect tolerance of flies to a methylating agent nor does it affect resistance to gamma-irradiation.

Cytochrome P450, peroxisome proliferation, and cytoplasmic fatty acid-binding protein content in liver, heart and kidney of the diabetic rat

Diabetes mellitus generally results in an increased systemic fatty acid mobilization which can be associated with an increase in mitochondrial and peroxisomal beta-oxidation of fatty acids in selected tissues. The latter is usually accompanied by a concomitant increase in the tissue content of cytoplasmic fatty acid-binding protein (FABP) which functions in the intracellular translocation of fatty acids. It was previously found that in liver clofibrate-induced proliferation of peroxisomes and increase in FABP expression each are dependent on the induction by cytochrome P4504A1 -mediated (CYP4A1) formation of dicarboxylic acids. We studied whether peroxisome proliferation and an increase of FABP contents in liver, heart and kidney of streptozotocin-induced diabetic rats are also accompanied by an increase of CYP4A1 activity, as this would indicate a possible regulatory role for dicarboxylic acids in peroxisome proliferation and FABP induction in diabetic organs other than liver. In livers of the diabetic rat, a concomitant increase was observed of the activities of CYP4A1 and the peroxisomal key enzyme fatty acyl-CoA oxidase (FACO) and of the FABP content. In the diabetic heart FACO activity and FABP content also increased, but there was no induction of CYP4A1 activity. Conversely, in diabetic kidney there was no increase in FACO activity nor FABP content in spite of a marked induction of CYP4A1 activity. It is concluded that streptozotocin-induced diabetes leads to increased peroxisome proliferation and increased levels of FABP in both liver and heart, which only in liver is accompanied by an induction of the cytochrome P450 system. Consequently, it is not likely that dicarboxylic acids are involved in the induction of peroxisome proliferation in the heart.

The role of mast cells and histamine in leukocyte-endothelium interactions in four rat strains

The objective of the present study was to determine the role of mast cells and histamine in leukocyte-endothelium interactions in mesenteric venules of four rat strains: Brown Norway, Lewis, Sprague-Dawley and Wistar. Intravital microscopy showed that the mast cell stabilizer cromoglycate (5 mg/kg i.v. just before exteriorization of the mesentery) did not affect the baseline level and velocity of leukocyte rolling in any of the four strains. This finding is in agreement with the observation that cromoglycate pretreatment only slightly influenced mast cell degranulation in all strains except the Brown Norway. After mast cell stabilization, only in Sprague-Dawley did topical administration of histamine (10(-4) M) result in a significant increase in the level of leukocyte rolling and a decrease in the rolling velocity compared with the time control. Histamine induced leukocyte adhesion only in the Brown Norway strain. In conclusion, the hypothesis presented in other studies, that degranulation of mast cells, and more specifically the release of histamine, is of major importance for the induction of leukocyte-endothelium interactions in rat mesenteric venules is not generally applicable; the present study shows a clear strain dependency.

Mast cell-mediated induction of ICAM-1, VCAM-1 and E-selectin in endothelial cells in vitro: constitutive release of inducing mediators but no effect of degranulation

Mast cell (MC)-mediated induction of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and of E-selectin was studied in cultures of rat heart endothelial cells (EC) and human umbilical vein EC (HUVEC) respectively. MC induced VCAM-1 and E-selectin, but hardly any ICAM-1 in EC. Induction was not dependent on MC degranulation, but seemed to be provoked by constitutively released substances, other than histamine, from MC. Co-incubation of MC and EC, allowing for direct contact between the two cell types, was more potent in induction than MC co-incubated separately from EC using a permeable membrane. MC were less potent in induction than exogenous added cytokines or LPS. Induction of cell adhesion molecules in rat heart EC was MC-specific, since EC incubations with either rat cardiomyocytes or heart fibroblasts had no effect. The data show that rat MC, independent of degranulation, secrete mediators relevant for the induction of a specific set of EC adhesion molecules in vitro. This suggests a (supportive) role for MC in cell-adhesion molecule induction in the endothelium in settings of early or mild inflammation. The results are discussed in the context of inflammatory processes in the heart in vivo.

Dietary modulation of fatty acid composition of mast cell phospholipids does not affect histamine release induced by compound 48/80

OBJECTIVE AND DESIGN

In the present study we determined the extent to which the degranulation process in mast cells was related to the fatty acid composition of membrane phospholipids.

MATERIAL

Peritoneal mast cells were isolated from Wistar rats (3 groups of 18 animals each), fed for 6 weeks diets which differed in their fatty acid compositions: (i) genuine salmon oil, abundant in (n-3) fatty acids, (ii) sunflower seed oil, rich in (n-6) fatty acids, particularly linoleic acid, and (iii) hydrogenated coconut oil, rich in saturated fatty acids.

METHODS

Mast cells (10(6)/ml) were stimulated with various concentrations of the mast cell-degranulating agent, compound 48/80 (0.1-10 micrograms/ml). The extent of mast cell degranulation was quantified by determination of histamine in the supernatants using HPLC techniques.

RESULTS

No differences in compound 48/80-induced histamine release between the three dietary groups for any of the concentrations of compound 48/80 tested were found. Analysis of variance followed by Tukey's method for multiple comparisons was used to evaluate the effect of changes in the dietary fat type.

CONCLUSION

These findings strongly suggest that in contrast to the formation of eicosanoids, the process of mast cell degranulation by a receptor-independent pathway is not controlled by the fatty acid composition of membrane phospholipids.

Antigen-evoked mast cell degranulation in the isolated rat heart: no effect on subsequent ischemia-reperfusion induced damage

In the present study, the possible role of mast cells in ischemia/reperfusion-induced myocardial injury was evaluated in the isolated 'mast cell depleted' rat heart. Hearts isolated from sensitized and non-sensitized rats were perfused according to Langendorff. After 30 min of normoxic perfusion, hearts were challenged with antigen, a procedure which is known to result in a massive mast cell degranulation in sensitized hearts. After another 20 min, both 'mast cell depleted' and control hearts were subjected to 30 min of ischemia followed by 30 min of reperfusion. The release of lactate dehydrogenase (LDH) was determined, to quantitate the extent of irreversible injury of cardiomyocytes. Histamine release was measured to establish mast cell degranulation. Coronary flow (CF) and left ventricular developed pressure (LVDP) were monitored to study the consequences of the procedures on hemodynamic recovery. It was found that both CF and LVDP significantly increased during the first min after antigen challenge. These changes were accompanied by an almost complete degranulation of cardiac mast cells. The increase in CF and LVDP values were rapidly followed by a decrease, reaching minimal values of 159 +/- 4% and 85 +/- 4% of those before administration of antigen, respectively, at 2-3 min after antigen challenge. No effect of antigen challenge on LDH release were found indicating that mast cell degranulation did not compromise myocyte integrity. During reperfusion following 30 min of ischemia both the increase in CF and LVDP in 'mast cell-depleted' hearts were not significantly different from those in control (non-sensitized) hearts. Similarly, at the end of the reperfusion-phase, CF and LVDP values in sensitized hearts were comparable to those in control hearts. Reperfusion results in increased LDH release, which at no point in time was significantly different between sensitized and non-sensitized hearts. In non-sensitized hearts histamine release during the reperfusion phase was not detectable. Therefore, the results indicate that in the isolated rat heart, mast cells are most likely not involved in acute ischemia/reperfusion-induced myocardial injury.

Production and characterization of spontaneous rat heart endothelial cell lines

Endothelial cells (EC) are important regulatory cells in physiology and pathology. in vitro studies with rat EC from heart tissue are hampered by laborious isolation and purification procedures, low yield, and limited lifespan of the cells. Therefore, it is essential to obtain long-term heart EC lines that offer a more adequate in vitro system for studying rat heart EC. An ex vivo perfusion model was used to isolate EC from rat heart. Isolation and culture conditions were modified to allow spontaneous development of immortalized rat heart EC (RHEC) lines. Produced cell lines were tested for endothelial nature using a panel of markers. The selected RHEC lines were subsequently tested for a series of phenotypic and functional properties representative of EC in the context of physiologic and inflammatory functions in vivo. A series of three spontaneous RHEC lines was produced from 13 isolations from Lewis rat hearts: RHEC-3, RHEC-10, and RHEC-11. These lines were stable for more than 30 passages (RHEC-3 for more than 100). The cell lines were tumorigenic and developed hemangiomas on in vivo injection. All three lines expressed major histocompatibility complex (MHC) class I but no MHC class II. Intercellular adhesion molecule 1 was only expressed by RHEC-3. Cytokine stimulation induced vascular cell adhesion molecule 1 in RHEC-3 and RHEC-11 as well as MHC class II in all three lines in different quantities. The phenotypic characteristics of the different RHEC lines resembled the myocardial microvascular endothelium in situ. The three lines expressed angiotensin-converting enzyme, and they responded to histamine and ATP but not to thrombin and bradykinin. They constitutively produced small amounts of endothelin and high levels of tissue plasminogen activator; they produced little (after stimulation with phorbol-ester PMA) or no von Willebrand factor. The RHEC lines produced thromboxane A2 but no prostacyclin; on stimulation with arachidonic acid and A23187, they produced prostaglandin E2. Therefore, we conclude the following. 1) The described isolation and culture technique is successful for production of spontaneous stable EC lines from rat heart. 2) RHEC-3, -10, and -11 can be considered a series of different lines representative of the heterogeneity of heart microvascular endothelium in vivo. 3) The RHEC lines offer a series of valuable tools to study various heart EC functions and mechanisms in physiology and pathology.

Lack of evidence for a role of mast cell degranulation in acute hypoxia/reoxygenation-induced injury in the isolated rat heart

In the present study, we evaluated the potential role of mast cell degranulation in acute hypoxia/reoxygenation-induced injury to cardiomyocytes in the isolated rat heart. Histamine release was determined to delineate the extent of mast cell degranulation, whereas the release of creatine kinase (CK) and lactate dehydrogenase (LDH) was assessed to quantitate the extent of irreversible injury to cardiomyocytes. The suitability of peroxidase (PO) as a marker for mast cell degranulation was also evaluated. Reoxygenation resulted in a release of histamine corresponding with 6.5% +/- 0.6% of total tissue content, whereas LDH, CK and PO release amounted to 30% +/- 2%, 28% +/- 2% and 32% +/- 3% of their respective tissue contents. Identical perfusion in the presence of the mast cell stabilizer lodoxamide tromethamine resulted in a reduced histamine release (2.8% +/- 0.1%) of total tissue content upon reoxygenation, but the release of LDH, CK or PO was not influenced. Cumulative histamine release did not correlate with the amount of LDH, CK or PO released. Treatment with consecutive bolus injections of the mast cell degranulating compound 48/80 during normoxic perfusion resulted in an almost complete histamine release, whereas PO release remained below detection limit. When the compound 48/80-treated hearts were subjected to hypoxia/reoxygenation, the release of LDH, CK or PO during reoxygenation again remained unchanged, whereas histamine release was negligible. Determination of PO activity of freshly isolated cardiomyocytes demonstrated that the bulk of PO in rat hearts was located in this particular cell type. Therefore we conclude that in the isolated rat heart, PO release is not a specific marker of mast cell degranulation. In addition, our data provide no firm evidence that in this experimental model, mast cell degranulation contributes to a significant extent to acute hypoxia/reoxygenation-induced injury to cardiomyocytes.

Transmural changes in mast cell density in rat heart after infarct induction in vivo

The cardiac distribution of mast cells was investigated after the induction of acute myocardial infarction in the rat. The left anterior descending coronary artery (LAD) was occluded by ligation in the infarct group, whereas in sham rats only a superficial ligature was placed beside the LAD. Rats of both groups were killed at 4, 7, 14, 21, 35, and 85 days following surgery. Hearts were excised and formalin-fixed. Mast cell densities were monitored in subepicardial and subendocardial layers of the left ventricle (LV) in 6 microns thick toluidine blue-stained cross-sections. In control (non-operated) animals, mast cell densities were comparable in the LV subepicardial and subendocardial layers (1.5-2.0 cells per mm2). Following infarction, the mast cell density at the subepicardial site of the infarction gradually increased, reaching a maximum of 25 cells per mm2 on day 21, while a non-significant increase was observed at the subendocardial site. In the non-infarcted regions, the mast cell density increased transiently to reach a maximum of 7 cells per mm2 on day 35 in the subepicardial layer. Again, changes in mast cell density in the subendocardial layer were non-significant. In the sham group, a gradual increase to 9 cells per mm2 on day 21 and a subsequent decrease to 5 cells per mm2 on day 85 were observed in the subepicardial layers. These findings indicate a massive accumulation of mast cells in the subepicardial layers of the infarcted region and a small but significant effect of the surgical procedure on cardiac mast cell deposition, especially in the outer layers of the left ventricle.

Differential release of histamine and prostaglandin D2 in rat peritoneal mast cells: roles of cytosolic calcium and protein tyrosine kinases

We studied how the release of histamine and prostaglandin D2 (PGD2) were connected in stimulated rat peritoneal mast cells, and to what extent these processes were controlled by the cytosolic Ca2+ concentration, [Ca2+]i, and protein tyrosine kinases. In the presence of 1 mM CaCl2, the G-protein activating compound 48/80 (10 micrograms/ml) evoked a transient rise in [Ca2+]i and a relatively high secretion of histamine, but only a low release of PGD2. In contrast, 5 microM thapsigargin (an inhibitor of endomembrane Ca(2+)-ATPases) and 5 microM ionomycin evoked high and prolonged rises in [Ca2+]i, and stimulated the cells to release relatively small amounts of histamine and high amounts of PGD2. Stimulation of the cells with CaCl2 and 10 microM ATP4- gave only minor quantities of histamine and PGD2, despite of the micromolar level of [Ca2+]i reached. When CaCl2 was replaced by EGTA, rises in [Ca2+]i as well as release of histamine and PGD2 were reduced with each agonist, but the preference of agonists to release more histamine or PGD2 remained unchanged. In mast cells with depleted Ca2+ stores, the addition of CaCl2 stimulated the store-regulated Ca2+ entry resulting in a prolonged rise in [Ca2+]i. However, simultaneous addition of compound 48/80 and CaCl2 was required for release of histamine and PGD2. In cells with full stores, PGD2 release evoked by compound 48/80 was greatly reduced by genistein and methyl-2,5-dihydroxycinnamate, two structurally unrelated inhibitors of protein tyrosine kinases, whereas histamine secretion was not influenced by these inhibitors. Similarly, with thapsigargin or ionomycin as agonist, PGD2 release was more sensitive to the tyrosine kinase inhibitors than histamine secretion. We conclude that in activated rat peritoneal mast cells: (i) the influx of extracellular Ca2+ potentiates agonist-evoked rises in [Ca2+]i as well as histamine secretion and PGD2 release; (ii) the amplitude of the [Ca2+]i rise does not determine the preferential effect of agonists to release more histamine or more PGD2; (iii) the relatively high PGD2 release evoked by thapsigargin and ionomycin is probably due to their potency to evoke a prolonged rise in [Ca2+]i and to activate protein tyrosine kinases.

Rapid and highly sensitive high-performance liquid chromatographic method for the determination of histamine and 3-methylhistamine in biological samples using fluorescamine as the derivatizing agent

A highly sensitive and rapid high-performance liquid chromatographic assay for the determination of histamine and 3-methylhistamine in biological samples using 1-methylhistamine as the internal standard is described. Samples were purified and concentrated on cation-exchange columns and derivatized with fluorescamine. The lower detection limit was 20 pg on-column. Linearity was demonstrated up to 20 ng on-column. The samples could be derivatized simultaneously before injection and were stable for 7 days. The method was used for the determination of histamine and related compounds in coronary perfusates, extracts of homogenized rat hearts, and supernatants of stimulated peritoneal mast cells.

Formation of prostanoids and hydroxy fatty acids by stimulated peritoneal mast cells: role of the dietary fat type in rat

To study the influence of membrane fatty acid composition on the formation of prostanoids and hydroxy fatty acids by rat peritoneal mast cells (MC), animals were fed three different types of fatty acids: mackerel oil (MO), abundant in n-3 fatty acids; sunflower seed oil (SO), rich in linoleic acid; and hydrogenated coconut oil (HCO), mainly containing saturated fatty acids. The presence of n-3 fatty acids in the diet resulted in the incorporation of 20:5(n-3), 22:5(n-3) and 22:6(n-3) in MC phospholipids. A decrease of arachidonic acid, 20:4(n-6), was observed in MC-phospholipids of the MO-fed animals. Furthermore, increasing the relative amounts of 18:2(n-6) in the diet (SO group) led to an increased incorporation of linoleic acid, 18:2(n-6) in MC phospholipids when compared to both other dietary groups. The changes in MC phospholipid fatty acid composition were (partly) reflected in the formation of prostanoids and hydroxy fatty acids upon stimulation with the calcium ionophore A23187. The decrease in arachidonic acid content in MC phospholipids of MO-fed rats resulted in a decreased formation of PGD2 when compared to both other groups. Also, the increased amounts of 18:2(n-6) in MC phospholipids of SO-fed rats resulted in an increased formation of 9- and 13-HODE upon stimulation. The results show that modifications in the fatty acid composition of the diet influences MC membrane fatty acid composition which ultimately results in changes in prostanoid and hydroxy fatty acid synthesis by MC upon stimulation with the calcium ionophore A23187.

Production of arachidonic acid metabolites in adult rat cardiac myocytes, endothelial cells, and fibroblast-like cells

Cells were incubated in the presence of the Ca2+ ionophore A23187 (10 microM) and arachidonic acid (AA, 80 microM). The release of eicosanoids from subcultivated cardiac endothelial and fibroblast-like cells amounted to 23.3 +/- 4.5 and 2.0 +/- 0.4 nmol/mg cellular protein per 30 min, respectively. The release from isolated cardiomyocytes remained below the detection limit of the high-performance liquid chromatography assay (< 0.00015 nmol/assay). When a very sensitive radioimmunoassay was applied, cardiomyocytes released 0.002 +/- 0.0001 nmol prostacyclin per milligram cellular protein per 30 min. Prostaglandin (PG) E2 and PGF2 alpha, 12-hydroxyheptadecatrienoic acid, 11- and 15-hydroxyeicosatetraenoic acid, and thromboxane B2 were the main eicosanoids released by endothelial cells. The stable product of prostacyclin, 6-keto-PGF1 alpha, contributed relatively little to the total amount of eicosanoids formed by endothelial cells. Fibroblast-like cells released predominantly PGE2 and 6-keto-PGF1 alpha and, to a lesser extent, 12-hydroxyheptadecatrienoic and 15-hydroxyeicosatetraenoic acids. Neither endothelial cells nor fibroblast-like cells released leukotrienes. A23187 stimulated eicosanoid release from endothelial cells when exogenous AA was below 40 microM. Addition of albumin reduced the amount of eicosanoids produced. Histamine and bradykinin did not influence 6-keto-PGF1 alpha and PGE2 production in cardiomyocytes. Histamine only gave rise to a slight but significantly higher release of 6-keto-PGF1 alpha in endothelial cells.

DNA homology requirements for mitotic gap repair in Drosophila

We used P transposable-element mobilization to study the repair of double-strand DNA breaks in Drosophila melanogaster premeiotic germ cells. Distribution of conversion tracts was found to be largely unaffected by changes in the length of sequence homology between the broken ends and the template, suggesting that only a short match is required. However, the frequency of repair was highly sensitive to single-base mismatches within the homologous region, ranging from 19% reversion when there were no mismatches to 5% when 15 mismatches were present over a 3455-bp span.

Effects of butylated hydroxyanisole on arachidonic acid and linoleic acid metabolism in relation to gastrointestinal cell proliferation in the rat

In order to determine the effect of oral administration of 2(3)-tert-butyl-4-hydroxyanisole (BHA; dose-level: 1.5% BHA of the diet) on arachidonic acid (AA) and linoleic acid (LA) metabolism in correlation with changes in gastrointestinal cell kinetics, we coadministered two inhibitors of prostaglandin H synthase, acetylsalicylic acid (ASA) and indomethacin (IM), to rats. Coadministration of ASA (0.2%) and IM (0.002%) in the drinking water, resulted in a significant reduction of the BHA-induced enhancement of cell proliferation in forestomach and glandular stomach. ASA completely counteracted the effect of BHA on labeling indices in colon/rectum whereas IM exhibited no effect in this organ. Both inhibitors had no direct effect on cell kinetics in the control groups. ASA, and to a lesser degree IM, inhibited prostaglandin E2 release in all tissues examined. Whereas ASA did inhibit lipoxygenase-mediated metabolism of AA in forestomach tissue, ASA did not affect the release of AA- and LA-derived hydroxy fatty acids in glandular stomach and colon/rectum. IM did not affect lipoxygenase production. BHA, however, appeared to be a strong inhibitor of both routes of AA metabolism. While ASA nor IM affected LA metabolism, BHA inhibited both prostaglandin H synthase-mediated and lipoxygenase-mediated metabolism of AA and LA. A causal role of AA or LA metabolites in the process of cell proliferation enhancement induced by BHA, can therefore be excluded. Prostaglandin H synthase may, however, be involved in BHA activation by converting the hydroquinone metabolite of BHA to the corresponding quinone by redox cycling, which is probably accompanied by reactive intermediate production.

Ischemia and reperfusion induced formation of eicosanoids in isolated rat hearts

Isolated, ejecting rat hearts, perfused with Krebs-Henseleit buffer, were exposed to various periods of global ischemia. Arachidonic acid (AA) accumulated significantly in the ischemic heart when the duration of ischemia exceeded 45 min. During 30 min of reperfusion, tissue levels of AA raised steadily to values of 10.5, 17.7, and 63.1 nmol/g, after 30, 45, and 60 min of ischemia, respectively. During reperfusion, significant amounts of AA metabolite prostacyclin (determined as stable metabolite 6-ketoprostaglandin F1 alpha, by radioimmunoassay and high-performance liquid chromatography) were released after 30, 45, and 60 min of ischemia. Beside prostacyclin, only small amounts of thromboxane B2 could be found during reperfusion. In contrast to increasing amounts of AA in reperfused tissue, prostacyclin release was maximal during the first 5 min of reperfusion and declined rapidly thereafter. Relatively small proportions of the accumulated AA are converted into prostacyclin, i.e., less than 1%. When hearts were treated with mepacrine, AA accumulation was almost completely abolished during 60 min of ischemia. The cumulative release of prostacyclin was found to be reduced to 134 pmol/g during 30 min of subsequent reperfusion. A close, rectilinear correlation could be established between AA accumulation and cumulative prostacyclin release during reperfusion. It is likely, however, that the site of bulk AA accumulation and that of conversion of AA into eicosanoids does not coincide in the ischemic and reperfused heart because of the low conversion rates of AA into prostacyclin and the different time courses of AA accumulation and prostacyclin production after reinstallation of flow.

Significance of myocardial eicosanoid production

The precise role of eicosanoids in the development of myocardial injury during ischemia and reperfusion is still a matter of debate. Enhanced local production of these bioactive compounds appears to be a common response to tissue injury. Most likely, the cardiac tissue has the capacity to generate prostaglandins, thromboxanes as well as leukotrienes. Prostacyclin (PGI2) is the major eicosanoid produced by the jeopardized myocardium. In addition, at sites of tissue injury activation of platelets and infiltrating leukocytes results in the formation of considerable amounts of thromboxanes and leukotrienes. The production of eicosanoids requires prior release of arachidonic acid (AA) from phospholipids. Both ischemia and reperfusion are associated with a rise in the tissue level of AA. The absence of a proportional relationship between the tissue level of AA and the amounts of PGI2 produced suggests that the sites of AA accumulation and PGI2 formation are different. It is conceivable that AA accumulation is mainly confined to myocytes, whereas the capacity to synthesize PGI2 mainly resides in vascular cells. Both beneficial and detrimental effects of eicosanoids on cardiac tissue have been described. Prostaglandins act as vasodilators. Besides, some of the prostaglandins, especially PGI2, are thought to possess cyto-protective properties. Thromboxanes and leukotrienes may impede blood supply by increasing smooth muscle tone. Besides, leukotrienes augment vascular permeability. Experimental studies, designed to evaluate the effect of pharmacological agents, like PGI2-analogues and lipoxygenase and cyclo-oxygenase inhibitors, indicate that eicosanoids influence the outcome of myocardial injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of a cytomegalovirus infection on functions and arachidonic acid metabolism of rat peritoneal macrophages

An intraperitoneal (rat) cytomegalovirus (RCMV) infection in the rat caused an influx of mononuclear cells, which have been altered in functions and arachidonic acid (AA) metabolism. Phagocytosis has been increased considerably 3 days postinfection (p.i.), whereas the release of prostacyclin, thromboxane A2, 12-hydroxyheptadecatrienoic acid (HHT), 5-hydroxyeicosatetraenoic acid (5-HETE), and leukotriene B4 (LTB4) was inhibited for more than 80%. The release of superoxide anions and the chemiluminescence response (CL) upon opsonized zymosan stimulation did not differ from those observed in resident peritoneal macrophages. Additionally, the levels of cyclic nucleotides (cAMP and cGMP) were low in both resident and influx macrophages (day 3 p.i.). In contrast, peritoneal macrophages harvested on day 10 p.i. still showed a high level of phagocytosis. However, the intracellular level of cyclic AMP had decreased fivefold, whereas CL response and superoxide anion release were inhibited significantly. Moreover, the production of prostacyclin, LTB4, and 5-HETE was still suppressed in contrast to thromboxane synthesis, which has selectively been restored in these macrophages. A direct regulatory role of AA metabolites in changes in macrophage functions that were due to a RCMV infection could not be demonstrated.

Determination of prostaglandins and thromboxane in whole blood by high-performance liquid chromatography with fluorimetric detection

A highly sensitive and specific assay for the quantitation of prostaglandins (PGs) such as PGE1, PGE2, PGF1 alpha, PGF2 alpha, 6-keto-PGF1 alpha, and including thromboxane B2, is described. The method involves the addition of PGF1 alpha and PGE1 as the internal standards, extraction from whole blood and purification by silica gel column chromatography. Following conversion into the methoximes, purification by reversed-phase chromatography and esterification with panacyl bromide, samples are analysed by high-performance liquid chromatography with fluorimetric detection. The lower limit of detection of the eicosanoids 6-keto-PGF1 alpha, thromboxane B2 and PGF2 alpha in blood is ca. 50 pg/ml and that of PGE2 is 100 pg/ml. Assay linearity is demonstrated over a range from 60 pg to 60 ng of eicosanoid injected. The method allows simultaneous assessment of prostaglandins and thromboxane extracted from complex biological fluids at picogram levels.

Treatment of experimental cytomegalovirus infections with acyclovir

Subcutaneous (s.c.) administration of Acyclovir (ACV) (100 mg/1 kg bodyweight) resulted in an ACV blood level of 80 microM at 2 h post infection. Thereafter the level declined rapidly reaching undetectable levels at 12 h post infection. Administration of pro-ACV (100 mg/kg body weight) by s.c. or intravenous (i.v.) route resulted in ACV levels of 75 microM and 160 microM respectively after 30 min. But here again the blood level of ACV declined rapidly and was completely disappeared after 12 h. Continuous administration of pro-ACV in daily doses of 100, 250 and 350 mg/kg body weight resulted in ACV blood levels of 15 microM, 19 microM and 39 microM, respectively. The effect of ACV and pro-ACV on the replication of CMV was measured in immunesuppressed rats. In rats inoculated with RCMV the daily administration of 25 to 50 mg ACV per kg body weight by s.c. injections twice daily, did not result in a reduction of virus titers in spleen and liver, but when the RCMV-infected rats were treated by 100 mg pro-ACV per kg body weight virus titers in the spleen and liver were significantly reduced as compared with those in sham-treated animals.

Influence of intracellular Ca2+-overload in eicosanoid synthesis of the myocardium

Intracellular Ca2+-overload in the myocardium can be induced not only after readmission of Ca2+-containing fluid to rat hearts previously perfused with a Ca2+-free buffer, a phenomenon called "the calcium paradox", but also during administration of a Ca2+-ionophore to cardiac tissue. In rat hearts, the myocardial damage induced by the Ca2+ paradox was more pronounced than that after administration of the Ca2+-ionophore A23187, as indicated by the amount of lactate dehydrogenase released. The accumulation of NEFA, and especially arachidonic acid, was greater during the Ca2+ paradox than after the administration of the Ca2+-ionophore. Administration of the Ca2+-ionophore resulted in a considerable release of 6-keto-F1 alpha (the stable breakdown product of prostacylclin), and LTD4 and LTE4 (breakdown products of LTC4). In contrast, the formation of eicosanoids was absent during the Ca2+ paradox. It is concluded that the relation between Ca2+-overload and accumulation of arachidonic acid is ambiguous and that there is no close relation between the amount of arachidonic acid accumulated and the formation of eicosanoids in Ca2+-overloaded tissue. The absence of eicosanoid formation during the Ca2+ paradox might be explained by compartmentation of the arachidonic acid accumulation and its converting enzymes or impairment of the enzymatic machinery required for eicosanoid synthesis.

Accumulation of lipids and lipid-intermediates in the heart during ischaemia

The content of non-esterified fatty acids (NEFA) and their CoA and carnitine esters is low in normoxic cardiac tissue. The majority of fatty acids is esterified in the triacylglycerol and phosphoglyceride pool. During myocardial ischaemia beta-oxidation of fatty acids is inhibited. In addition, turnover of the esterified fatty acid pools is most likely disturbed. Accumulation of hydroxy fatty acids, acylCoA and acylcarnitine rapidly occurs after the onset of ischaemia. The accumulation of NEFA is a slower process. In addition to extracellular sources, NEFA originate also from intracellular lipid pools, most likely from phosphoglycerides. Although it has been suggested that activation of phospholipase A2 occurs in ischaemic tissue, the mechanism underlying the enhanced degradation of phosphoglycerides ist still incompletely understood.

A quantitative method for assessing the third complement factor (C3) attached to the surface of opsonized Pseudomonas aeruginosa: interrelationship between C3 fixation, phagocytosis and complement consumption

A direct enzyme-linked immunoassay is described for the determination of C3 that becomes attached to the surface of bacteria upon incubation in serum. The assay uses horseradish peroxidase-conjugated rabbit antiserum specific for human C3. In this study various Pseudomonas aeruginosa strains, Escherichia coli and Staphylococcus aureus were opsonized under different conditions and the amount of C3 fixed to the bacterial surface was measured directly. The extent of C3 fixation was compared with the percentage of phagocytosis by human polymorphonuclear leukocytes and with the complement consumption in the fluid phase. It was demonstrated that C3 fixation closely correlated with the percentage of phagocytosis but not with complement consumption. The method can be performed with relatively simple equipment and could be used in routine laboratories in order to determine the extent of opsonization of Pseudomonas aeruginosa and other bacteria and to detect opsonic defects in the sera of patients.

Role of lipopolysaccharide in opsonization and phagocytosis of Pseudomonas aeruginosa

When the opsonization of various Pseudomonas aeruginosa strains--PAC 1, its O-chain-deficient mutant PAC 605, and an intermediate strain, P14--was measured either directly by determination of the amount of C3b attached to the bacterial surface or indirectly by assessing phagocytosis by human polymorphonuclear leukocytes and the responses of chemiluminescence, it was demonstrated that PAC 1 was opsonized and phagocytized to a lower extent than P14 and PAC 605. In contrast to PAC 605, PAC 1 showed an increased consumption of complement in the fluid phase and a rapid release of lipopolysaccharide antibodies bound to the bacterial surface due to the alternative pathway of the complement system. Furthermore, it was shown that with respect to PAC 1 and PAC 605, the lack of an O-chain resulted in increased sensitivity to serum and decreased virulence. From both in vivo and in vitro experiments, we concluded that the structure of the O-antigen polysaccharide chain of lipopolysaccharide is an important virulence factor of P. aeruginosa against the defense mechanisms of the host.