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PubMed1992

Regioselectivity of the insertion reactions of some aromatic diazo compound complexes with cyclomaltoheptaose.

Pyrolysis of solid complexes of aromatic diazo compounds with cyclomaltoheptaose (beta-cyclodextrin) yields either derivatives via insertion of carbene into hydroxyl groups. The distribution of the 2-, 3-, and 6-O-isomers indicates that the regioselectivity is moderate. The guest geometry is not as important as its size in determining the ratios of regioisomers. The origins of the regioselectivity are discussed.

Carbohydrate Conformation↗

PubMed1988

Carbon isotope geochemistry of hydrocarbons in the Cerro Prieto geothermal field, Baja California Norte, Mexico.

Hydrocarbon abundances and stable-isotopic compositions were measured in wells M5, M26, M35 and M102, which represent a range of depths (1270-2000 m) and temperatures (275-330 degrees C) in the field. In order to simulate the production of the geothermal hydrocarbons, gases were collected from the pyrolysis of lignite in the laboratory. This lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field, but which have experienced much lower subsurface temperatures. In both the well and the laboratory observations, high-temperature environments favored higher relative concentrations of methane, ethane and benzene and generally higher delta 13C-values in the individual hydrocarbons. The best correlation between the laboratory and well data is obtained when laboratory-produced gases from experiments conducted at lower (400 degrees C) and higher (600 degrees C) temperatures are mixed. This improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments.

Carbon Dioxide↗

PubMed1980

Isolation and characterization of active metabolites of tryptophan-pyrolysate mutagen, TRP-P-2, formed by rat liver microsomes.

The mutagenic compound derived from the pyrolysis of tryptophan, 3-amino-1-methyl-5H-pyrido-[4,3b]indole (Trp-P-2) was metabolized by rat liver microsomes to more than four metabolites, separable by high performance liquid chromatography. Among these metabolites, two metabolites, M-3 and M-4 were directly active in increasing the frequency of mutation in Salmonella typhimurium TA98. Treatments of rats with polychlorinated biphenyl (PCB) or 3-methylcholanthrene dramatically induced the activity of liver microsomes to form these active metabolites, while treatment with phenobarbital was without effect. A major active metabolite (M-3) formed the pentacyano-ammine ferroate, which is known to be formed by reaction of sodium pentacyano-ammine ferroate with some hydroxylamines. Further this metabolite was oxidized to the minor active metabolite (M-4) with potassium ferricyanide or gamma-manganese dioxide, and was reduced back to Trp-P-2 with titanium trichloride. These results indicated that the major active metabolite of Trp-P-2, which is formed by cytochrome P-450, is the 3-hydroxyamino derivative.

Animals↗

PubMed1995

Chemical properties of the ultimate metabolites of 2-amino-5-phenylpyridine (PHE-P-1) and its ortho-methyl derivative.

The reactivity of the N-acetoxy metabolite of 2-amino-5-phenylpyridine (Phe-P-1), a pyrolysis product of phenylalanine, towards 2'-deoxyguanosine (dG), 2'-deoxyguanosine-3'-monophosphate (dGMP) and DNA was studied and compared with that of the ortho-methyl derivative. Reaction of 2-acetoxyamino-5-phenylpyridine (N-OAc-APP) with dG resulted in substitution at the 8-position of this nucleoside by the ortho carbon of the amine. The major reaction, however, was acetylation of dG. In contrast, 2-acetoxyamino-3-methyl-5-phenyl-pyridine (N-OAc-MeAPP) mainly attacked the 8-position of dG by the exocyclic nitrogen and hardly any acetylation of the nucleoside occurred. The adducts were chromatographically isolated and characterized by their mass and NMR spectra. Upon reaction of N-acetoxy compounds with DNA and dGMP, formation of the same adducts was observed, besides the formation of minor amounts of unidentified compounds, as was established by 32P-postlabelling analysis. The amount of DNA-bound amine, formed by the interaction of N-OAc-APP with DNA, was approximately 15 times smaller than that observed after the reaction with the corresponding ortho-methyl derivative under the same conditions.

Aminopyridines↗

PubMed1995

32P-postlabelling analysis of dibenz[a,j]acridine-DNA adducts in mice: identification of proximate metabolites.

N-Heterocyclic polynuclear aromatics are widely-occurring environmental pollutants formed during the pyrolysis of nitrogen-containing organic chemicals. Dibenz[a,j]acridine (DBA), a member of this class, has been shown to be a skin carcinogen in mice. We undertook studies to determine the organ distribution of DBA-DNA adducts and to identify the DBA metabolites which lead to the formation of carcinogen-DNA adducts in vivo. DBA and its metabolites, trans-DBA-1,2-dihydrodiol (DBA-1,2-DHD) trans-DBA-3,4-dihydrodiol (DBA-3,4-DHD) and trans-DBA-5,6-dihydrodiol (DBA-5,6-DHD), were topically applied on mice. DNA was isolated using enzyme-solvent extraction methods, and analyzed for carcinogen-DNA adducts using 32P-postlabelling. In skin, DBA produced two distinct adducts (Adducts 1 and 2). The same two adducts were seen when DBA-3,4-DHD was applied. In addition, the total adduct level elicited by DBA-3,4-DHD was twice that of the parent compound. Two adducts (Adducts 3 and 4) were also seen in mouse skin when DBA-5,6-DHD was applied, but these differed chromatographically from adducts seen with DBA. However, when DBA-3,4-DHD was applied and analyzed using sensitive nuclease P1 32P-postlabelling, all four adducts could be detected. These results suggest that the major route of DBA activation to DNA-binding species in skin is through formation of DBA-3,4-DHD and subsequent metabolism of this compound to a bay-region diol-epoxide. However, we postulate that another activation pathway may proceed through a bis-dihydrodiol-epoxide.

Acridines↗

PubMed1990

Mass spectrometric analysis of O-peracetylated derivatives of 1-monomycoloylglycerol isolated from Corynebacterium pseudotuberculosis, Rhodococcus rhodochrous and R. lentifragmentus.

1-Monomycoloylglycerols from Corynebacterium pseudotuberculosis, Rhodococcus rhodochrous and R. lentifragmentus were reacted with acetic acid ahydride in the presence of pyridine. On infrared spectra the reaction products showed a sharp characteristic absorption of the acetyl ester group at 1235 cm-1; the hydroxyl group absorption (3400 cm-1) was absent. O-Peracetylated monomycoloylglycerols were analyzed by mass spectrometry under electron impact mode. The most common and representative peaks were associated to the following remarkable fragments: (a) peak at m/z 159 represented the backbone of the glycerol unit of peracetylated monomycoloylglycerols; it constituted the diagnostic and base peak of that group of compounds; (b) peak representing the glycerol moiety together with the alpha-subunit of the mycolic acid moiety; it gave the size of the chain length of the hydrocarbon side chain of that mycolic acid; and (c) a series of peaks of acylium ions minus 60 mass units (acetic acid) indicated the size of the chain length of the esterified mycolic acid. Therefore, acetylation of monomycoloylglycerol becomes the derivatized compound suitable for mass spectrometry. Moreover, the derivatives are more thermostable and resistant to pyrolysis. By associating these properties, separation and identification of homologs of monomycoloylglycerols are further expected.

Corynebacterium↗

PubMed1991

Time course dependent changes in contents and physical properties of glycolipid species in Rhodococcus rhodochrous.

The yield of trehalose dimycolate (TDM), the major glycolipid species elaborated by Rhodococcus rhodochrous, a producer of approx. C40-mycolic acid, was not constant in cells cultured for different periods of time. From cells collected at 24, 36, 72, 144 and 172 h of cultivation the following percentages of TDM in diethyl ether soluble lipids (DESL) were found: 10.8%, 23.4%, 10.0%, 9.0% and 5.0%, respectively. In turn, the cellular content accounted for approx. 0.6%, 1.2%, 0.9%, 0.6% and 0.2%, respectively. On the other hand, the yield of galactose monomycolate (GalMM), a minor glycolipid species maintained at approx. 3.4% in DESL during the different periods of time examined; this value represented about 0.3% of the cellular content. The melting temperatures of TDMs fell between 37 degrees C to approximately 97 degrees C with the lowest value from cells grown for 36 h, whereas the melting temperatures of the GalMMs were in a narrow range between 56 degrees C and 64 degrees C. The methyl ester derivatives of the constituent fatty acid moieties of DTMs and GalMMs migrated on thin layer chromatography like methyl esters of C40-C46 mycolic acids, therefore faster than methyl esters of C28-C34 mycolic acids but slower than methyl esters of C50-C56 mycolic acids. Further analysis of the products of pyrolysis of the methyl ester derivatives of the fatty acid moiety released from TDM after alkaline hydrolysis was carried out using gas chromatography combined mass spectrometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Cord Factors↗

PubMed1987

Isotopic characterisation of kerogen-like material in the Murchison carbonaceous chondrite.

Isotopic data for C, H and N in acid-resistant residues from carbonaceous chondrites show substantial variability during stepwise pyrolysis and/or combustion. After subtraction of contributions due apparently to inorganic C grains, of probably circumstellar origin, considerable isotopic variability remains, attributable to the kerogen-like organic fraction. That variability may be interpreted in terms of three or four distinct components, based on C, H and N isotopes. The relative proportions of those components vary significantly from sample to sample. The different isotopic components are tentatively identified in terms of specific chemical/structural moieties within the kerogen-like material. This combination of chemical, structural and isotopic information suggests a complex for meteoritic organic matter. At least three components within the organic populations as a whole still carry a signature of apparently interstellar D-enrichment. Part, at least, of the interstellar carrier consisted of reactive entities, not solely polymers.

Carbon↗

PubMed1995

Evidence for gammacerane as an indicator of water column stratification.

A new route for the formation of gammacerane from tetrahymanol is proposed; in addition to dehydration and hydrogenation, sulphurisation and early C-S cleavage are shown to be important in the pathway of formation, especially in marine sediments. Evidence is twofold. First, relatively large amounts of the gammacerane skeleton are sequestered in S-rich macromolecular aggregates formed by natural sulphurisation of functionalised lipids. Selective cleavage of polysulphide linkages with MeLi/MeI led to formation of 3-methylthiogammacerane, indicating that the gammacerane skeleton is primarily bound via sulphur at position 3, consistent with the idea that tetrahymanol (or the corresponding ketone) is the precursor for gammacerane. Second, upon mild artificial maturation of two sediments using hydrous pyrolysis, gammacerane is released from S-rich macromolecular aggregates by cleavage of the relatively weak C-S bonds. The stable carbon isotopic compositions of gammacerane and lipids derived from primary producers and green sulphur bacteria in both the Miocene Gessoso-solfifera and Upper Jurassic Allgau Formations indicate that gammacerane is derived from bacterivorous ciliates which were partially feeding on green sulphur bacteria. This demonstrates that anaerobic ciliates living at or below the chemocline are important sources for gammacerane, consistent with the fact that ciliates only biosynthesize tetrahymanol if their diet is deprived of sterols. This leads to the conclusion that gammacerane is an indicator for water column stratification, which solves two current enigmas in gammacerane geochemistry. Firstly, it explains why gammacerane is often found in sediments deposited under hypersaline conditions but is not necessarily restricted to this type of deposits. Secondly, it explains why lacustrine deposits may contain abundant gammacerane since most lakes in the temperate climatic zones are stratified during summer.

Animals↗

PubMed1988

An assessment of urease-based enzyme-linked immunosorbent assay.

The use of urease in enzyme-linked immunosorbent assays (ELISAs) offers the advantages of convenience and safety. However, urease-based ELISA, performed in standard microtitre format, could result in false positive reactions upon prolonged incubation. False positive reactions appeared when wells containing substrate solution absorbed ammonia liberated from a reactive well nearby. Thus, the intensity of the false reaction was proportional to that of the urease reaction. The transfer of ammonia was demonstrated by pyrolysis-mass spectrometry. When urease conjugates were compared with peroxidase conjugates in the detection of IgG and IgM, there was no evidence that one enzyme was superior to the other in terms of increasing the sensitivity or the speed of ELISA.

Ammonia↗

PubMed1983

In vivo acetylcholine turnover in rat heart.

The in vivo uptake of choline (Ch) and synthesis of acetylcholine (ACh) in rat heart were studied using a pyrolysis mass fragmentography (PMF) method. Deuterium labeled Ch was pulse injected (i.v.) into anesthetized rats. Labeled and unlabeled Ch and ACh were measured by PMF in hearts at various times following injection. From these data we calculated the specific activities of Ch and ACh, rate constants for ACh and turnover rates of ACh. After an initial equilibration period of approximately 2 min, the specific activities of Ch and ACh decayed in a parallel manner with half-times of 28.2 and 28.8 min respectively. Between 2 and 60 min the calculated ACh turnover rate was 0.144 nmol/g/min. Unlike brain Ch, heart Ch levels are very stable with time following sacrifice. No advantage was found in using microwave irradiation to stabilize heart ACh and Ch content.

Acetylcholine↗

PubMed1985

The distribution of acetylcholine and choline in guinea pig heart.

The regional distributions of acetylcholine (ACh) and choline (Ch) in the guinea pig heart were investigated with a pyrolysis-mass fragmentography technique. Using ACh as a marker for cholinergic neurons, we have described a pattern of parasympathetic innervation in the guinea pig heart. This distribution is very similar to that suggested by studies using several different cholinergic indicators in various species. Atrial areas receive richer parasympathetic innervation than ventricular areas, with the right portions receiving more than the left. The nodal areas were the most abundantly innervated regions examined. Ch content is not a good indicator for cholinergic innervation as the regional distribution of ACh and Ch throughout the guinea pig heart are not strongly associated.

Acetylcholine↗

PubMed1995

Effects of methylecgonidine on acetylcholine-induced bronchoconstriction and indicators of lung injury in guinea pigs.

The fumarate salt of methylecgonidine (MEG; anhydroecgonine methylester), a pyrolysis product of cocaine, has previously been shown to antagonize contractions of guinea pig isolated trachea induced by acetylcholine (ACh) and other spasmogenics. We determined the effects of MEG fumarate on ACh-induced bronchoconstriction in vivo. Specific airway conductance (SGaw) was measured in guinea pigs receiving 30-300 mg/kg s.c. MEG fumarate and exposed one hour later to nebulized ACh (0.2-3.2%; by inhalation). MEG fumarate did not induce any changes in SGaw; neither did it antagonize dose-dependent decreases in SGaw induced by ACh. However, tremors, salivation, startle and increased numbers of fecal boli were observed after MEG administration. Thus, unlike antagonism of ACh-induced contractions of guinea pig isolated trachea observed in vitro, MEG fumarate does not antagonize ACh-induced bronchoconstriction in vivo, even at doses which induced changes in grossly-observable behavior. Inhalation of a condensation aerosol of MEG base induced lung damage as evidenced by the presence of blood and higher levels of protein and lactate dehydrogenase in the lung lavage fluid of MEG-treated animals than of control animals. Aerosols of MEG fumarate, on the other hand, did not induce lung damage when inhaled. These results extend previous observations that MEG base may contribute to detrimental pulmonary effects of crack smoking.

Acetylcholine↗

PubMed1977

Mutagenic activity of amino acid pyrolyzates in Salmonella typhimurium TA 98.

Pyrolyzates of 25 amino acids and 5 indole derivatives were tested for mutagenicity in the histidine-requiring mutant Salmonella typhimurium TA 98. Significant mutagenic activity was detected with pyrolyzates of most of the amino acids. These pyrolyzates required a liver microsomal fraction, as representative of mammalian metabolism, to be detected as mutagens. Among the pyrolyzates tested, the highest mutagenic activity was observed with that of L-tryptophan. As little as 10 microgram of the pyrolyzate of L-tryptophan had detectable mutagenic activity toward TA 98. The optimal pyrolysis temperatures for the formation of mutagenic products were shown to be 500 degrees C for L-tryptophan and 600 degrees C for the other amino acids. The results from pyrolyses of some indole derivatives suggest that an amino group at the alpha-position to the carboxyl group of L-tryptophan plays an important role in the formation of mutagens.

Amino Acids↗

PubMed1984

Toxicity of 1-phenylcyclohexene and its interaction with phencyclidine.

The toxicity of 1-phenylcyclohexene (PC), a pyrolysis product of phencyclidine (PCP), and its interaction with PCP were evaluated. The ip LD50 of PC in Swiss male mice was 22 mmol/kg. Treatment of mice with PC at 2.2 mmol/kg/day, ip, for up to 7 days increased the liver/body weight ratio, which returned to normal within 7 days after PC withdrawal. Increases of 32% in serum glutamic-oxalacetic transaminase (SGOT) and 94% in serum glutamic-pyruvic transaminase (SGPT) were observed within 4 hr following the initial (Day 1) dose of PC. Smaller increases in the SGOT activity continued following Day 2 and 3 PC administrations. The SGPT activity remained elevated after these treatments. Activities of both enzymes, however, returned to normal within 24 hr following daily PC injections. No pathologic changes were observed in liver, brain, spleen, kidneys, and lungs with light microscopy. PC treatment for 4 days at 2.2 or 4.4 mmol/kg produced proliferation along with dilatation and fragmentation of the endoplasmic reticulum in liver. Scattering of ribosomes in the cytoplasm and dilatation of rough-surfaced cisternae were prominent at the higher dosage. Pretreatment of animals for 4 days with PC (1.1, 2.2, and 4.4 mmol/kg, ip) decreased pentobarbital- (60 mg/kg) induced sleeping time by 27, 64, and 80% and lowered PCP- (16.4 mumol/kg) stimulated locomotor activity by 18, 28, and 41%, respectively. Pretreatment of animals with PC for 1 hr inhibited (ED50: 2.3 mmol/kg) the PCP-induced locomotion. These results indicate that the PC treatment during a 7-day period produces some undesirable effects on liver function, which are reversible on its discontinuation. However, PC also weakens toxic effects of PCP.

Animals↗

PubMed1990

gamma-Aminobutyric acid antagonism produced by an organophosphate-containing combustion product.

Results from [35S]t-butylbicyclophosphorothionate (TBPS) binding and gamma-aminobutyric acid (GABA)-dependent 36Cl- uptake indicated that the pyrolysis product of liquid trimethylol propane (TMP) containing organic phosphates interacts with the GABA/benzodiazepine receptor chloride ionophore complex (GBRC) producing a receptor-mediated reduction in 36Cl- flux. The pyrolysate-ligand interaction was competitive and directly proportional to the trimethylol propane phosphate (TMPP) content of the combustion product. TBPS displacement demonstrated that TMPP had less affinity than did TBPS and picrotoxin, but greater affinity than GABA, racemic dimethylbutyl barbituric acid (DMBB), clonazepam, and phenobarbital for their respective recognition sites. Addition of exogenous GABA was a necessary condition for demonstrating clonazepam-induced ligand displacement, thus being indicative of an allosteric interaction. The same rank order held for altering GABA-dependent 36Cl- uptake with the caveat of inhibitors vs enhancers, and noting that pentobarbital was less potent than DMBB. Concentration-dependent ligand displacement by GBRC agonists and antagonists quantitatively correlated with alterations in GABA-dependent 36Cl- uptake. The median convulsant dose (CD50) of pyrolysate TMPP was higher than that of synthetic TMPP. The presence of combustion by-products altering the dispositional kinetics of the former is felt to be the reason for this difference. Under our experimental conditions, phenobarbital was the most effective antidote for pyrolysate (TMPP) toxicity. The inhalant convulsant, flurothyl, was found not to displace [35S]TBPS binding, not to affect GABA-dependent 36Cl- uptake, and not to respond to the anticonvulsants in a manner consistent with a strict GABAA receptor phenomenon.

Animals↗

PubMed1991

3-Methylindole-induced splenotoxicity: biochemical mechanisms of cytotoxicity.

3-Methylindole (3-MI) is a pneumotoxic metabolite of L-tryptophan that can form in the digestive tracts of humans and ruminants as a result of microbial protein metabolism. Alternatively, human lungs can be directly exposed to 3-MI formed during protein pyrolysis and inhalation of tobacco smoke. 3-MI has been shown to cause acute lung injury in both ruminants and rodents. The present studies demonstrate that the spleen is also a target for 3-MI-induced toxicity. A dose-dependent decrease in splenic weight (24-75%) and nucleated splenic cell number (22-68%) was observed 24 hr after intraperitoneal injection of 3-MI (50-300 mg/kg) to intact and adrenalectomized rats. These findings were associated with significant alterations in splenic histopathology. Mice appeared less affected by 3-MI than rats as no splenotoxicity was observed at doses less than 200 mg/kg. Other mono- and dimethyl-substituted indoles did not decrease mouse spleen cell numbers when administered in vivo. Phenobarbital pretreatment in vivo protected against 3-MI-induced splenotoxicity, suggesting a role for cytochrome P450-mediated metabolism of 3-MI in the splenotoxicity of this compound. Exposure of rat or mouse splenic cells to 3-MI (1 mM) in vitro resulted in toxic changes over 24 hr. However, equimolar concentrations of the structurally related mono- and dimethylindoles were also toxic in vitro, and preincubation with a variety of inhibitors of cytochrome P450 or prostaglandin synthase in vitro failed to protect against 3-MI-mediated toxicity to splenic cells in culture. These results suggest mechanisms of 3-MI splenotoxicity also exist that do not require bioactivation, and indicate a possible role for alkylindoles in suppression of immune function.

Adrenalectomy↗

PubMed1990

Sonochemistry of volatile and non-volatile solutes in aqueous solutions: e.p.r. and spin trapping studies.

Recent spin trapping studies of the free radical intermediates generated by the sonolysis of aqueous solutions are reviewed. Studies of rare gas saturated solutions of volatile solutes (e.g., methanol and ethanol) and of non-volatile solutes (acetate, amino acids, sugars, pyrimidines, nucleotides and surfactants) are consistent with the theory of three reaction zones in aqueous sonochemistry. The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions lead to the thermal dissociation of water vapour into hydrogen atoms and hydroxyl radicals. Reactions take place in the gas phase (pyrolysis reactions), in the region of the gas-liquid interface, and in the bulk of the solution at ambient temperature (similar to radiation chemistry reactions). By use of the rare gases with different thermal conductivities, the contributions of individual reaction steps with widely different energies of activation can be evaluated.

Alcohols↗