Improved stereoselective synthesis of optically active methylene lactone, key intermediate for the synthesis of 1,2-oxidized furofuran lignan, by direct alpha-methylenation to butanolide.
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(3R)-3-[(1R)-1-(tert-Butyldimethylsilyl)oxy-1-(2-methoxy-4,5-methylenedioxyphenyl ) methyl]-2-methylene-4-butanolide, which is a key intermediate for the synthesis of 1,2-oxidized furofuran lignan, was stereoselectively synthesized from L-glutamic acid by applying direct methylenation to butanolide. (+info)
An aryl hydrocarbon receptor independent mechanism of JP-8 jet fuel immunotoxicity in Ah-responsive and Ah-nonresponsive mice.
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JP-8 jet fuel is handled extensively by personnel in the military and commercial airlines, despite the paucity of information regarding its potential human health effects. JP-8 is a complex mixture primarily consisting of kerosene plus aliphatic and aromatic hydrocarbons. Recent reports indicate that acute JP-8 exposure via inhalation or dermal routes can overtly and persistently impair immune function in mice. Data from preliminary studies in this laboratory assessing the immunotoxicity of JP-8 indicated that oral JP-8 exposure caused an increase in liver weight, a decrease in thymus weight, and a decrease in the PFC response. As these results were similar to classic effects elicited by TCDD, a strong AhR ligand, it was hypothesized that JP-8 may exert immunosuppression via a similar mechanism. To test this hypothesis, an Ah-responsive mouse strain (B6C3F1) and a classically non-responsive mouse strain (DBA/2) bearing a lower affinity AhR were gavaged with JP-8 for 7 days. The results suggest that both mouse strains were equally sensitive to JP-8's toxicity at several endpoints including thymus weight and cellularity, liver weight, and specific IgM antibody responses. Furthermore, JP-8 did not induce CYP1A1 or promote down regulation of the AhR when evaluated by Western blot in either B6C3F1 or DBA/2 mice. In vitro studies corroborated these findings as JP-8 did not induce CYP1A1, promote down regulation of the AhR, or activate an XRE-driven reporter gene in murine Hepa-1 cells. These results suggest that JP-8 may exert its toxicity via an AhR-independent mechanism. (+info)
Neoplastic transformation of guinea pig fetal cells in culture induced by chemical carcinogens.
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Twenty-four cell strains derived from freshly isolated diploid strain 2 guinea pig fetal cells exposed in utero or directly in culture to a carcinogenic or noncarcinogenic chemical were evaluated during 4 to 24 months of continuous cultivation. Morphological alterations in carcinogen, i.e., benzo(a)pyrene-, 7,12-dimethylbenz(a)anthracene-, 3-methylcholanthrene-, N-methyl-N'-nitro-N-nitrosoguanidine-, diethylnitrosamine-, aflatoxin B1-, or N-acetoxyacetylaminofluorene-treated cultures were seen shortly after treatment; transformation, a loss of cell orientation, did not occur for 4 or more months, was not seen in controls and did not uniformly appear simultaneously with the capacity of transformed cells to grow as tumors in irradiated syngeneic newborn guinea pigs. Changes in plating efficiency, saturation density, doubling time, and chromosome alterations of transformed cells also did not correlate with progressive tumor growth. Formation of colonies in 0.35% agar appeared subsequent to or concomitantly with morphological transformation, and in every case they developed concurrently with the potential for neoplastic growth. Controls originally treated with a noncarcinogen (acetone, polycyclic hydocarbon, or aromatic amide) did not form agar colonies or tumors after inoculation of 108 cells. Studies with guinea pig cells indicate that persistent alterations in some growth parameters occur prior to expression of tumor growth. The ability of cells to form colonies in agar and to produce tumors may require 4 to 18 months of culturing. Of the cell properties examined, colony formation in agar was the best indication of the neoplastic state. (+info)
Membranous nephropathy, hydrocarbon exposure and genetic variants of hydrocarbon detoxification.
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Modulation of biotransformation by genetic traits may be important in determining environmentally-induced nephrotoxicity. We conducted a case-control study to investigate the role of occupational hydrocarbon exposure, along with polymorphisms of the genes coding for N-acetyltransferase 2 (NAT2) and glutathione S-transferase mu (GSTmu), in the development of idiopathic membranous glomerulonephritis (IMGN). Patients (n=36) with biopsy-proven IMGN were matched with healthy controls for age, gender, and geographical area. Lifetime hydrocarbon exposure was assessed by a validated questionnaire. The polymorphisms of the NAT2 and GSTmu genes (GSTM1) were defined by use of a polymerase chain reaction on white-cell DNA from peripheral blood. Exposure to hydrocarbons was significantly greater in patients with IMGN than in controls (mean+/-SEM hydrocarbon exposure score 11 003+/-2955.7 vs. 4352+/-1418, p<0.02). NAT2 acetylator status was identical in patients and controls with 23 (63.9%) fast and 13 (36.1%) slow acetylators in each group. GSTmu was present in 15 (41.7%) patients and 16 (44.4%) controls. While occupational exposure to hydrocarbons remains a likely factor in its pathogenesis, further work is required to identify the genetic polymorphisms that modulate the risk of IMGN. (+info)
Methylene as a possible universal footprinting reagent that will include hydrophobic surface areas: overview and feasibility: properties of diazirine as a precursor.
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Methylene is one of, if not the, most reactive organic chemical known. It has a very low specificity, which makes it essentially useless for synthesis, but suggests a possible role in protein footprinting with special importance in labeling solvent accessible nonpolar areas, identifying ligand binding sites, and outlining interaction areas on protomers that form homo or hetero oligomers in cellular assemblies. The singlet species is easily and conveniently formed by photolysis of diazirine. The reactions of interest are insertion into C-H bonds and addition to multiple bonds, both forming strong covalent bonds and stable compounds. Reaction with proteins and peptides is reported even in aqueous solutions where the vast majority of the reagent is used up in forming methanol. Species containing up to 5 to 10 extra :CH2 groups are easily detected by electrospray mass spectroscopy. In a mixture of a 14 Kd protein and a noninteracting 1.7 Kd peptide, the distribution of mass peaks in the electrospray spectra was close to that expected from random modification of the estimated solvent accessible area for the two molecules. For analysis at the single residue level, quantitation at labeling levels of one 13CH2 group per 10 to 20 kDa of protein appears to be possible with isotope ratio mass spectroscopy. In the absence of reactive solvents, photolysis of diazirine produces oily polymeric species that contain one or two nitrogen atoms, but not more, and are water soluble. (+info)
Emulsifying activities of purified Alasan proteins from Acinetobacter radioresistens KA53.
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The bioemulsifier of Acinetobacter radioresistens KA53, referred to as alasan, is a high-molecular-weight complex of polysaccharide and protein. The emulsifying activity of the purified polysaccharide (apo-alasan) is very low. Three of the alasan proteins were purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had apparent molecular masses of 16, 31, and 45 kDa. Emulsification assays using the isolated alasan proteins demonstrated that the active components of the alasan complex are the proteins. The 45-kDa protein had the highest specific emulsifying activity, 11% higher than the intact alasan complex. The 16- and 31-kDa proteins gave relatively low emulsifying activities, but they were significantly higher than that of apo-alasan. The addition of the purified 16- and 31-kDa proteins to the 45-kDa protein resulted in a 1.8-fold increase in the specific emulsifying activity and increased stability of the oil-in-water emulsion. Fast-performance liquid chromatography analysis indicated that the 45-kDa protein forms a dimer in nondenaturing conditions and interacts with the 16- and 31-kDa proteins to form a high-molecular-mass complex. The 45-kDa protein and the three-protein complex had substrate specificities for emulsification and a range of pH activities similar to that of alasan. The fact that the purified proteins are active emulsifiers should simplify structure-function studies and advance our understanding of their biological roles. (+info)
New ordered metastable phases between the gel and subgel phases in hydrated phospholipids.
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Formation of low-temperature ordered gel phases in several fully hydrated phosphatidylethanolamines (PEs) and phosphatidylcholines (PCs) with saturated chains as well as in dipalmitoylphosphatidylglycerol (DPPG) was observed by synchrotron x-ray diffraction, microcalorimetry, and densitometry. The diffraction patterns recorded during slow cooling show that the gel-phase chain reflection cooperatively splits into two reflections, signaling a transformation of the usual gel phase into a more ordered phase, with an orthorhombic chain packing (the Y-transition). This transition is associated with a small decrease (2-4 microl/g) or inflection of the partial specific volume. It is fully reversible with the temperature and displays in heating direction as a small (0.1-0.7 kcal/mol) endothermic event. We recorded a Y-transition in distearoyl PE, dipalmitoyl PE (DPPE), mono and dimethylated DPPE, distearoyl PC, dipalmitoyl PC, diC(15)PC, and DPPG. No such transition exists in dimyristoyl PE and dilauroyl PE where the gel L(beta) phase transforms directly into subgel L(c) phase, as well as in the unsaturated dielaidoyl PE. The PE and PC low-temperature phases denoted L(R1) and SGII, respectively, have different hydrocarbon chain packing. The SGII phase is with tilted chains, arranged in an orthorhombic lattice of two-nearest-neighbor type. Except for the PCs, it was also registered in ionized DPPG. In the L(R1) phase, the chains are perpendicular to the bilayer plane and arranged in an orthorhombic lattice of four-nearest-neighbor type. It was observed in PEs and in protonated DPPG. The L(R1) and SGII phases are metastable phases, which may only be formed by cooling the respective gel L(beta) and L(beta') phases, and not by heating the subgel L(c) phase. Whenever present, they appear to represent an indispensable intermediate step in the formation of the latter phase. (+info)
The nucleotide changes governing cuticular hydrocarbon variation and their evolution in Drosophila melanogaster.
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The cuticular hydrocarbon (CH) pheromones in Drosophila melanogaster exhibit strong geographic variation. African and Caribbean populations have a high ratio of 5,9 heptacosadiene/7,11 heptacosadiene (the "High" CH type), whereas populations from all other areas have a low ratio ("Low" CH type). Based on previous genetic mapping, DNA markers were developed that localized the genetic basis of this CH polymorphism to within a 13-kb region. We then carried out a hierarchical search for diagnostic nucleotide sites starting with four lines, and increasing to 24 and 43 lines from a worldwide collection. Within the 13-kb region, only one variable site shows a complete concordance with the CH phenotype. This is a 16-bp deletion in the 5' region of a desaturase gene (desat2) that was recently suggested to be responsible for the CH polymorphism on the basis of its expression [Dallerac, R., Labeur, C., Jallon, J.-M., Knipple, D. C., Roelofs, W. L. & Wicker-Thomas, C. (2000) Proc. Natl. Acad. Sci. 97, 9449--9454]. The cosmopolitan Low type is derived from the ancestral High type, and DNA sequence variations suggest that the former spread worldwide with the aid of positive selection. Whether this CH variation could be a component of the sexual isolation between Zimbabwe and other cosmopolitan populations remains an interesting and unresolved question. (+info)