Characterization of the main transition of dinervonoylphosphocholine liposomes by fluorescence spectroscopy

The structural dynamics of the main phase transition of large unilamellar dinervonoylphosphocholine (DNPC) vesicles was investigated by steady state and time-resolved fluorescence spectroscopy of the membrane incorporated fluorescent lipid analog, 1-palmitoyl-2[10-(pyren-1-yl)]decanoyl-sn-glycero-3-phosphocholine (PPDPC). These data were supplemented by differential scanning calorimetry (DSC) and fluorescence anisotropy measured for 1-palmitoyl-2-(3-(diphenylhexatrienyl) propanoyl)-sn-glycero-3-phosphocholine (DPHPC). The collected data displayed several discontinuities in the course of the main transition and the pretransition. The discontinuities seen in the fluorescence properties may require modification of the existing models for phospholipid main transition as a first order process. From our previous study on dipalmitoylphosphocholine (DPPC), we concluded the transition to involve a first-order process resulting in the formation of an intermediate phase, which then converts into the liquid crystalline state by a second order process. Changes in the physical properties of the DNPC matrix influencing probe behavior were similar to those reported previously for PPDPC in DPPC. In gel state DNPC [(T-T(m))<-10] the high values for excimer/monomer emission ratio (I(e)/I(m)) suggest enrichment of the probe in clusters. In this temperature range, excimer fluorescence for PPDPC (mole fraction X(PPDPC)=0.02) is described by two formation times up to (T-T(m)) approximately -10, with a gradual disappearance of the fractional intensity (I(R1)) of the shorter formation time (tau(R1)) with increasing temperature up to (T-T(m)) approximately -10. This would be consistent with the initiation of the bilayer melting at the PPDPC clusters and the subsequent dispersion of the one population of PPDPC domains. A pronounced decrement in I(e) starts at (T-T(m))=-10, continuing until T(m) is reached. No decrease was observed in fluorescence quantum yield in contrast to our previous study on DPPC/PPDPC large unilamellar vesicles (LUVs) [J. Phys. Chem., B 107 (2003) 1251], suggesting that a lack of proper hydrophobic mismatch may prevent the formation of the previously reported PPDPC superlattice. With further increase in temperature and starting at (T-T(m)) approximately -1, I(e), tau(R2), and excimer decay times (tau(D)) reach plateaus while increment in trans-->gauche isomerization continues. This behavior is in keeping with an intermediate phase existing in the temperature range -1<(T-T(m))<4 and transforming into the liquid disordered phase as a second order process, the latter being completed when (T-T(m))-->4 and corresponding to approximately 50% of the total transition enthalpy.     

Dynamics of decapentaplegic expression during regeneration of the Drosophila melanogaster wing imaginal disc

Regeneration of an imaginal disc involves highly ordered proliferation and pattern regulation of the newly formed tissue. Although the general principles of imaginal disc regeneration have been extensively studied, knowledge of the underlying molecular mechanisms is far from complete. Results from other model organisms suggest that regeneration is the result of local recapitulation of the normal patterning genes. To analyze the dynamics of one major Drosophila patterning gene, decapentaplegic (dpp), in wing imaginal disc regeneration, a vital GFP reporter together with iontophoretic cell labeling were used. Our observations reveal that the restoration of compartment-border-specific dpp expression is a common event in imaginal disc regeneration. However, we did not find evidence of an upregulation of dpp expression during the regeneration process.     

Screening for restriction endonucleases in aerobic,thermophilic eubacteria

Summary A total of 216 Icelandic aerobic, heterotrophic, thermophiles belonging to three different genera were screened for type II restriction endonucleases. The frequency of positive strains was 44% for both Thermus and Bacillus but 63% for Rhodothermus. Approximately half of the enzymes from each group were characterised and a total of 14 different restriction enzymes were found. In all cases they were isoschizomers of known enzymes. Thermus contained 9 different types, Bacillus 6 and Rhodothermus had 3. This is the first time that isoschizomers of BspEI, BglI, EagI and EcoRV are found in Thermus and BstBI and EcoRV are found in Rhodothermus.     

Human epidermal growth factor concentrations in urine, but not in saliva and serum, depend on thyroid state

To evaluate the effects of thyroid hormones on the concentration of epidermal growth factor (EGF), we determined values for the immunoreactive EGF concentration in the urine (U-irEGF) of newborn infants with congenital hypothyroidism (N = 19), and in urine, saliva and serum of adult patients with hypothyroidism (N = 11) and hyperthyroidism (N = 8). The values were expressed as SD score (SDS), i.e. deviation in SD units from their mean value of healthy subjects of the same age and sex. The SDS of relative U-irEGF (ng/mg creatinine) was lower (P less than 0.01) in newborn infants with congenital hypothyroidism (-0.8 +/- 0.2; mean +/- SEM) than in healthy infants. Their relative U-irEGF correlated with their serum T4 concentrations (r = 0.59, P less than 0.01). The SDS of relative U-irEGF was lower (P less than 0.01) in adult hypothyroid patients (-1.2 +/- 0.5) and higher (P greater than 0.05) in adult hypothyroid patients (0.9 +/- 0.6) than in healthy adult subjects. When subsequently euthyroid, their SDS of relative U-irEGF increased to -0.5 +/- 0.3 (P less than 0.01), and decreased to -0.7 +/- 1.1 (P less than 0.05), respectively. The irEGF concentrations in saliva and serum were not significantly different between the hypothyroid and hyperthyroid patients. Our results indicate that urinary excretion of irEGF in man is dependent on thyroid hormone.     

Association between dental health and acute myocardial infarction.

Known risk factors for coronary heart disease do not explain all of the clinical and epidemiological features of the disease. To examine the role of chronic bacterial infections as risk factors for the disease the association between poor dental health and acute myocardial infarction was investigated in two separate case-control studies of a total of 100 patients with acute myocardial infarction and 102 controls selected from the community at random. Dental health was graded by using two indexes, one of which was assessed blind. Based on these indexes dental health was significantly worse in patients with acute myocardial infarction than in controls. The association remained valid after adjustment for age, social class, smoking, serum lipid concentrations, and the presence of diabetes. Further prospective studies are required in different populations to confirm the association and to elucidate its nature.     

Protein kinase C subtypes in endothelial cells

Activation of protein kinase C (PKC) has been linked to the regulation of class II expression on endothelial cells by interferon-gamma (IFN-gamma). PKC subtypes in endothelial cells were analyzed using three different approaches, the immunoperoxidase staining of native and IFN-gamma stimulated cells cultured on chamber slides as well as immuno- and Northern blotting. All approaches revealed that of the conventional subtypes, alpha is the predominant form of PKC in endothelial cells. Even though IFN-gamma is able to induce PKC translocation to particulate fractions, no translocation was detected in histological stainings. Western blot studies as well as mRNA studies revealed that IFN-gamma is unable to increase the total amount of PKC in endothelial cells.     

Metabolism of carbosulfan. I. Species differences in the in vitro biotransformation by mammalian hepatic microsomes including human

The in vitro metabolism of carbosulfan, a widely used carbamate insecticide, by hepatic microsomes from human, rat, mouse, dog, rabbit, minipig, and monkey was studied. Altogether eight (8) phase I metabolites were detected by LC–MS; phase II metabolites were not found in human homogenates fortified with appropriate cofactors. The primary metabolic pathways were the initial oxidation of sulfur to carbosulfan sulfinamide (‘sulfur oxidation pathway’) and the cleavage of the nitrogen sulfur bond (N–S) to give carbofuran and dibutylamine (‘carbofuran pathway’). Carbofuran was further hydroxylated to 3-hydroxycarbofuran and/or 7-phenolcarbofuran, which were further oxidized to 3-ketocarbofuran or 3-hydroxy-7-phenolcarbofuran, respectively, and finally to 3-keto-7-phenolcarbofuran. 3-Hydroxycarbofuran was the main metabolite in all species, but otherwise there were some qualitative interspecies differences in carbofuran pathway metabolites. Only rabbit liver microsomes were able to metabolize carbofuran via hydroxylation to 7-phenolcarbofuran. Carbofuran was not detected in dog liver microsomes due to rapid further metabolism. In general, liver microsomes from all seven species produced more toxic products (carbofuran, 3-hydroxy-carbofuran, 3-ketocarbofuran) more rapidly than a detoxification product (carbosulfan sulfinamide). Differences in intrinsic hepatic clearances (CL_int) between the lowest and highest species were moderate; 2-fold for the carbofuran pathway, 2.7-fold for carbosulfan sulfinamide and 6.2-fold for dibutylamine. Our studies, although restricted to in vitro metabolic data from human and animal hepatic preparations, provide valuable quantitative carbosulfan-specific data for risk assessment, which suggest that interspecies differences, for carbosulfan active chemical moiety, in toxicokinetics are within the standard applied factor for species extrapolation in toxicokinetics. These results will be valuable in further defining the risks associated with exposure to carbosulfan.     

The siderophore ferricrocin produced by specific foliar endophytic fungi in vitro

Production of extracellular siderophores is typical for many plant-associated microbes, both mutualistic and antagonistic. Various strains of mycorrhizal fungi produce siderophores, and siderophore production by pathogenic fungi is typically associated with virulence. We analyzed extracellular siderophore production along with production of antibacterial and antioxidant compounds in foliar endophytic fungi of Scots pine (Pinus sylvestris L.) and Labrador tea (Rhododendron tomentosum Harmaja). The siderophore produced in vitro was ferricrocin, quantities ranging between 7.9 and 17.6 μg/l. Only the fungi with antibacterial activity produced ferricrocin and any well-known siderophores were not detected in the broths of antioxidant-producing fungi. Therefore, production of ferricrocin is typical for some, but not all foliar endophytic fungi. Ferricrocin was detected in the leaves of Labrador tea, which suggests that ferricrocin may play a role in vivo in the interaction between the endophyte and plant host.