Terminal Products Research Articles

Aerobic metabolism of diclosulam on U.S. and South American soils.

Degradation of the sulfonanilide herbicide diclosulam was studied on nine soils from three countries to determine the rates and products of aerobic metabolism. Diclosulam was applied to four agricultural soils from the United States, three from Argentina, and two from Brazil at a rate of 0.1 ppm, equivalent to approximately twice the maximum field application rate of 52 g of active ingredient/ha. U.S. and Brazilian soils were incubated in the dark at 25 degrees C at 75% 0.3 bar moisture; Argentinean soils were incubated in the dark at 20 degrees C and 45% moisture holding capacity. Samples were analyzed up to one year after treatment. Two-compartment DT(50) and DT(90) values averaged 28 +/- 12 and 190 +/- 91 days, respectively. Three soil metabolites reached levels of >10% of applied in at least one soil and were identified as the 5-hydroxy analogue of diclosulam (5-OH-diclosulam), aminosulfonyl triazolopyrimidine (ASTP), and the 8-chloro-5-hydroxy analogue of diclosulam (8-Cl-diclosulam). The terminal products of diclosulam soil metabolism were mineralization to CO(2) and bound soil residues. Apparent sorption coefficients (K(d)) were determined on a subset of samples by extraction with a 0. 01 M CaCl(2) solution followed by an acidified acetone extraction. Initial sorption coefficients were similar to those obtained in a batch equilibrium study and averaged 1.1 L/kg for the six soils tested. K(d) coefficients for the metabolites, when available, tended to be slightly lower than that for diclosulam. Sorptivity of diclosulam and degradates increased with time.

Basin scale natural gas source, migration and trapping traced by noble gases and major elements: the Pakistan Indus basin

He, Ne and Ar concentrations, He and Ar isotopic ratios, carbon isotopic ratios and chemical compositions of hydrocarbon gases were measured in natural gas samples from gas-producing wells in the Indus basin, Pakistan, where no oil has ever been found. 3He/ 4He ratios are in the range 0.01–0.06 Ra (Ra is the atmospheric value of 1.38×10 −6) indicating the absence of mantle-derived helium despite the Trias extension. 40Ar/ 36Ar ratios range from 296 to 800, consistent with variable additions of radiogenic argon to atmospheric, groundwater-derived argon. Rare gas concentrations show large variations, from 6×10 −5 to 1×10 −3 mol/mol for 4He and from 3×10 −7 to 3×10 −5 mol/mol for 36Ar. In general, 36Ar concentrations are high compared to literature data for natural gas. CO 2 and N 2 concentrations are variable, ranging up to 70 and 20%, respectively. Mantle-derived He is not observed, therefore CO 2 and N 2 are not mantle-derived either. Hydrocarbon gas maturity is high, but accumulation efficiency is small, suggesting that early-produced hydrocarbons, including oil, were lost as well as mantle helium. This is consistent with the generally late, Pliocene, trap formation, and explains the high N 2 concentrations, since N 2 is the final species generated at the end of organic matter maturation. Based on δ 13C data, CO 2 originates from carbonate decomposition. Very elevated 20Ne/ 36Ar ratios are found, reaching a maximum of 1.3 (compared to 0.1–0.2 for air-saturated water and 0.5 for air), and these high values are related to the lowest rare gas concentrations. We suggest that this highly fractionated signature is the trace of the past presence of oil in the basin and appeared in groundwater. We propose a model where oil–water contact is followed by gas–water contact, both with Rayleigh distillation for rare gas abundance ratios, thereby generating the fractionated 20Ne/ 36Ar signature in groundwater first and transferring it to gas later. Assuming the gas–water contact occurred shallower than present reservoir depths, this model explains the generally high 36Ar concentrations and low CH 4/ 36Ar ratios compared to other studies on younger basins. It thus provides a historical perspective on fluid transfer in a sedimentary basin, where a gas accumulation may have been buried to greater depth since formation. Rare gas and major element data point to mixing between two gas pulses produced successively. The very CO 2–N 2-rich gases are terminal products of organic matter maturation which have been trapped after important migration. This gas was followed by a more typical thermogenic gas which mixed with it.

Photolytic Cleavage and Condensation Reactions of Cyclohexa-2,4-dienones with Diamines

Cyclohexa-2,4-diene-1-one sulfone derivate undergoes ring cleavage to afford bis-amides containing a diene moiety on irradiation with visible light in the presence of various diamines.

Enrichment of an endosulfan-degrading mixed bacterial culture.

An endosulfan-degrading mixed bacterial culture was enriched from soil with a history of endosulfan exposure. Enrichment was obtained by using the insecticide as the sole source of sulfur. Chemical hydrolysis was minimized by using strongly buffered culture medium (pH 6.6), and the detergent Tween 80 was included to emulsify the insecticide, thereby increasing the amount of endosulfan in contact with the bacteria. No growth occurred in control cultures in the absence of endosulfan. Degradation of the insecticide occurred concomitant with bacterial growth. The compound was both oxidized and hydrolyzed. The oxidation reaction favored the alpha isomer and produced endosulfate, a terminal pathway product. Hydrolysis involved a novel intermediate, tentatively identified as endosulfan monoaldehyde on the basis of gas chromatography-mass spectrometry and chemical derivatization results. The accumulation and decline of metabolites suggest that the parent compound was hydrolyzed to the putative monoaldehyde, thereby releasing the sulfite moiety required for growth. The monoaldehyde was then oxidized to endosulfan hydroxyether and further metabolized to (a) polar product(s). The cytochrome P450 inhibitor, piperonyl butoxide, did not prevent endosulfan oxidation or the formation of other metabolites. These results suggest that this mixed culture is worth investigating as a source of endosulfan-hydrolyzing enzymes for use in enzymatic bioremediation of endosulfan residues.

Vapor phase treatment of PCE in a soil column by lab-scale anaerobic bioventing

Microbial destruction of highly chlorinated organic compounds must be initiated by anaerobic followed by aerobic dechlorination. In-situ dechlorination of vadose zone soil contaminated with these compounds requires, among other factors, the establishment of highly reductive anaerobic conditions in the unsaturated subsurface. Such conditions may be established by delivering appropriate gas mixtures to the subsurface, i.e., “anaerobic bioventing”. The gas must include an electron donor. This study was conducted as a feasibility study for anaerobic bioventing, using tetrachloroethene (PCE) as a test contaminant and H 2 as the electron donor. Using a soil column inoculated with anaerobic dechlorinating bacteria, to simulate the vadose zone, experimental results showed that by passing a gas composed of 1% H 2 and >0.1% CO 2 in N 2, methanogenic conditions were established and that PCE (fed as a vapor in the gas stream) was rapidly converted with terminal products vinyl chloride (VC) and trans-dichloroethene ( trans-DCE). PCE half life in the column was 7 min, while parameter estimation yielded a first order PCE degradation rate k PCE, of 0.098 min −1. Intermediate products detected but not accumulated in the column were trichloroethylene (TCE) and cis-dichloroethene ( cis-DCE). The high dechlorination rates observed for PCE make anaerobic bioventing an attractive method that can potentially be integrated in an in-situ remediation process to treat contaminated soils in the unsaturated zone.

Successive reactions of iron carbonyl cations with methanol

The reactivity of Fe(CO) n + cations with methanol has been investigated using a triple-cell Fourier transform ion cyclotron resonance apparatus. Successive substitutions of the CO ligands by methanol occur rapidly with similar rates. For n = 3–5 the last CO ligand is not replaced, and the terminal substitution products are FeCO(CH 3OH) n−1 +. A second reaction pathway is observed for n = 3–5, in which two CO ligands are replaced by one methanol molecule. This pathway occurs even if the Fe(CO) n + ions have been radiatively relaxed before reaction, providing information on the bond energies in the product ions. Strong internal energy effects are observed on the reaction rates and branching ratios for further substitution of the intermediate products. The substitution product Fe(CH 3OH) + from FeCO + reacts further, with C–O bond cleavage followed by substitution. The resulting Fe[C 2, H 7, O 2] + ion undergoes either isomerization or collisional deactivation, then slow association with methanol. The reaction of Fe +, due to excited states only, begins with formation of FeOH + and involves the same final steps as in the preceding case.

Activation of Different Lipoxygenase Isozymes Induces Apoptosis in Human Erythroleukemia and Neuroblastoma Cells

We investigated the ability of different hydroperoxides generated by lipoxygenase isozymes to induce programmed cell death (PCD) in human cells. Erythroleukemia K562 and neuroblastoma CHP100 cells were used, because they showed high basal activity of lipoxygenase. The hydroperoxides generated by 5-, 12-, or 15-lipoxygenases from linoleate, linolenate, or arachidonate, and the corresponding hydroxides, were able to induce PCD in both cell types, in a concentration- and time-dependent manner. After 24 h, K562 and CHP100 cells showed 2.5- to 3.5-fold more apoptotic bodies than the untreated controls. PCD elicited by lipoxygenase products was independent of intracellular glutathione concentration, and did not require mRNA transcription or protein synthesis. On the other hand, lipoxygenase products evoked an immediate and sustained rise in cytoplasmic calcium (within seconds), followed by mitochondrial uncoupling (within hours). Unlike the hydro(pero)xides, the terminal products of the arachidonate cascade (i.e., leukotrienes, prostaglandins and thromboxane) were not cytotoxic.

Metabolic detoxification: implications for thresholds.

The fact that chemical carcinogenesis involves single, isolated, essentially irreversible molecular events as discrete steps, several of which must occur in a row to finally culminate in the development of a malignancy, rather suggests that an absolute threshold for chemical carcinogens may not exist. However, practical thresholds may exist due to saturable pathways involved in the metabolic processing, especially in the metabolic inactivation, of such compounds. An important example for such a pathway is the enzymatic hydrolysis of epoxides via epoxide hydrolases, a group of enzymes for which the catalytic mechanism has recently been established. These enzymes convert their substrates via the intermediate formation of a covalent enzyme-substrate complex. Interestingly, the formation of the intermediate proceeds faster by orders of magnitude than the subsequent hydrolysis, ie, the formation of the terminal product. Under normal circumstances, this does not pose a problem, since the microsomal epoxide hydrolase (mEH), the epoxide hydrolases with the best documented importance in the metabolism of carcinogens, is highly abundant in the liver, the organ with the highest capacity to metabolically generate epoxides. Computer simulation provides evidence that the high amount of mEH enzyme is favorable for the control of the steady-state level of a substrate epoxide and can keep it extremely low. However, once the mEH is titrated out under conditions of extraordinarily high epoxide concentration, the epoxide steady-state level steeply rises, leading to a sudden burst of the genotoxic effect of the noxious agent. This prediction of the computer simulation is nicely supported by experimental work. V79 Chinese hamster cells that we have genetically engineered to express human mEH at about the same level as that observed in human liver are completely protected from any measurable genotoxic effect of the model compound styrene oxide (STO) up to a dose of 100 microM in the cell culture medium (toxicokinetic threshold). In V79 cells that do not express mEH, STO leads to the formation of DNA strand breaks in a dose-dependent manner with no toxicokinetic threshold observable. Above 100 microM, the genotoxic effect of STO in the mEH-expressing cell line parallels the one in the parental cell line. Thus, the saturable protection from STO-induced strand breaks by mEH represents a typical example of a practical threshold. However, it must be pointed out that even in the presence of protective amounts of mEH, a minute but definite level of STO is present that does not contribute sufficiently to the strand break formation to overcome the background noise of the detection procedure. As pointed out above, absolute thresholds probably do not exist in chemical carcinogenesis.

Synthesis and reactivity of hydrazido(2-) and imido derivatives of titanium(IV) tetratolylporphyrin.

Titanium porphyrin hydrazido complexes (TTP)Ti = NNR2 (TTP = meso-tetra-p-tolylporphyrinato dianion; R = Me (1), Ph (2)) were synthesized by treatment of (TTP)TiCl2 with 1,1-disubstituted hydrazines H2NNR2 (R = Me, Ph) in the presence of piperdine. The nucleophilic character of the hydrazido moiety was demonstrated in the reactions of complexes 1 and 2 with p-chlorobenzaldehyde, which yielded the titanium oxo complex (TTP)-Ti = O and the respective hydrazones. Protonation of complexes 1 and 2 with phenol or water produced the 1,1-disubstituted hydrazine along with (TTP)Ti(OPh)2 or (TTP)Ti = O, respectively. Similar reactivity of p-chlorobenzaldehyde and phenol with (TTP)Ti = NiPr, 3, was observed. The reaction of complex 3 with nitrosobenzene cleanly formed the azo compound iPrN = NPh and the terminal oxo product (TTP)Ti = O.

Rock magnetic properties related to thermal treatment of siderite: Behavior and interpretation

Detailed analyses of rock magnetic experiments were conducted on the oxidation products of high‐purity natural crystalline siderite that were thermally treated in air atmosphere. Susceptibilities increase sharply between 400° and 530°C indicative of some new ferrimagnetic mineral phase generation. Both a drop (between 540° and 590°C) on the heating cycle and a dramatic increase (from 590°C to 520°C) on the cooling cycle occurred and are well consistent with the characteristic of magnetite. A distinct Hopkinson‐type susceptibility peak indicates that hematite is the terminal product if siderite is heated to 700°C over and over. It has been revealed in detail that the original inverse magnetic susceptibility fabric contributed by the crystalline anisotropy of siderite in siderite‐bearing specimens is changed to a normal magnetic fabric during incremental heating over 410°–490°C. This is a result of dominant contributions from the distribution anisotropy of newly transformed ferromagnetic minerals. A strong chemical‐viscous remanent magnetization could be produced during siderite oxidation in an external field. Rock magnetic experimental results show that magnetite, maghemite, and hematite are the transformation products of high‐temperature oxidation of siderite in air. Maghemite was not completely inverted to hematite even at temperature as high as 690°C during incremental thermal treatments. The mineral transformation processes were confirmed by conventional optical microscopic observation, X‐ray diffractometry and Mössbauer spectroscopic analyses. These results indicate that the rock magnetic methods used here are reliable and highly sensitive in detecting very small magnetic phase changes in rocks. We conclude that these temperaturedependent variations of magnetic properties can be used as criteria for identification of siderite in rocks and sediments. Furthermore, it is clear that great care should be exercised in thermal demagnetization of siderite‐bearing rocks in paleomagnetic, magnetic anisotropy, and rock magnetic studies.

Use of D-dimer assays in the diagnosis of venous thrombosis.

In the course of fibrin formation, the D-domains of adjacent fibrin molecules within the fibrin polymer are covalently linked by factor XIIIa, leading to the formation of a D-domain dimer. Proteolysis of this cross-linked fibrin generates fibrin fragments D-dimer and E as terminal products. Fragment D-dimer therefore is an indicator for the proteolysis of cross-linked fibrin, whereas the monomeric fragment D can stem from fibrinogen and non-cross-linked fibrin. Various monoclonal antibodies have been prepared that distinguish between fragments D-dimer and D and allow the detection of fibrin derivatives in the presence of fibrinogen. These anti-D-dimer-antibodies have been shown to react with fragment D-dimer, but also detect dimeric D-domains within larger fibrin compounds, including cross-linked fibrin complexes generated in an early phase of coagulation activation. Assay systems for D-dimer antigen therefore may uncover intravascular clot formation early, by detection of fibrin complexes, and after completion of clot formation, by the detection of proteolytic fragments released from the particulate clot. Various trials have shown that low concentrations of D-dimer antigen in the blood exclude recent venous thrombosis or pulmonary embolism. Elevated levels may be caused by venous thrombotic disease, but also by a variety of other conditions, leading to intra- or extravascular fibrin formation. Assay systems include manual immunoagglutination assays, immunofiltration assays, microtiter plate enzyme-linked immunosorbent assay (ELISA) systems, automated ELISA systems, and latex-enhanced photometric immunoassays. According to clinical studies, D-dimer assays may be the "first line" of technical screening in symptomatic outpatients with suspected venous thrombosis or pulmonary embolism, but further prospective management trials, and improved standardization of assay systems, are needed for the validation of this approach.

Strategies to manage inbreeding accumulation in swine breeding company nucleus herds: Some case studies

Modern swine breeding is undergoing a series of changes that affect the underlying strategies for genetic improvement. Increased competition among fewer breeding companies requires rapid genetic improvement to maintain competitive advantage. The result is intense selection pressure within swine industry nucleus populations. Selection pressure is enhanced through the use of artificial insemination, embryo transfer, and, potentially, marker-assisted selection. This increased selection pressure raises concerns due to the more rapid accumulation of inbreeding within these populations. The current strategies used to control the accumulation of inbreeding are somewhat simplistic. The methods often include arbitrary restrictions on the percentage of sows mated to a single sire, the number of sires retained from a full and half-sib family, the avoidance of matings between closely related individuals, and elimination of families presumed to be segregating for alleles with deleterious effects on fitness. As demonstrated by classic genetic theory, when the previously listed methods to minimize inbreeding are used, inbreeding is delayed, but it is inevitably accumulated within nucleus herds. The rate of accumulation typically is between 0.3 and 0.6% per annum. Composite lines addressing specific market needs, particularly for terminal sires, may offer short-term solutions for nucleus level inbreeding. Most parent and terminal products are produced from line crosses wherein inbreeding is eliminated in the resulting progeny. Understanding the causes of inbreeding depression continues to be important in order to improve the performance of purelines in multiplication, leading to more efficient transfer of genetic improvement.

Study on fragmentation behavior of 5/7/6-type taxoids by tandem mass spectrometry.

The mass spectrometric behaviors of seven compounds, namely four 4beta(20),5-oxetane 5/7/6-type taxoids (i.e. taxayuntin A, taxayuntin B, taxayuntin and taxayuntin C) and three 4(20)-methylene 5/7/6-type taxoids (i.e. brevifoliol, taxchinin A and 7-acetyl-10-deacetyl-7-debenzoylbrevifoliol) have been investigated by the positive ion FAB-MS/MS technique. The fragmentation has been correlated with the types and positions of substituents of these compounds. It has been found that with the OH group at the C-10 position, taxayuntin A, taxayuntin B and 7-acetyl-10-deacetyl-7-debenzoylbrevifoliol are dominated by the loss of H2O, while with the BzO group at the C-10 position, taxayuntin, taxayuntin C, brevifoliol and taxchinin A preferentially eliminate the BzO group. In addition, C-2 is an active site, and neutral loss from the C-2 position readily occurs. The four 4beta(20),5-oxetane 5/7/6-type taxoids produce the terminal product ion with a stable conjugated system at m/z 311, while the 4(20)-methylene 5/7/6-type taxoids brevifoliol and 7-acetyl-10-deacetyl-7-debenzoylbrevifoliol produce this ion at m/z 237, and taxchinin A at m/z 253. Interestingly, characteristic fragment ions involving the loss of a 118 u group were observed for taxayuntin, and a possible fragmentation mechanism is given. The major fragmentation pathways and mechanisms of ion formation for the compounds are proposed on the basis of CID spectra and accurate mass measurements. The results of this paper will be helpful for structural analysis of analogs.

Consecutive Halogen Transfer between Various Functional Groups Induced by Reaction of Hypohalous Acids: NADH Oxidation by Halogenated Amide Groups

Cyclic dipeptides (c-Gly2, c-Ser2, c-Gly-Phe, etc.) were used as simple protein models to investigate the HOCl-induced generation and reactivity of chlorinated amide groups. The pH dependence of the kinetics of amide chlorination reveals that ClO− (not HOCl) is the reactive agent. N-Chlorinated cyclopeptides are stable up to 30 min, they exhibit narrow absorption bands around 215 nm, and they are capable of oxidizing certain biological substrates, the reactivity decreasing in the order GSH > ascorbate > methionine > NADH ⪢ GSSG. The chloroamide is less reactive, but much more selective in its reactions, than HOCl or ClO−; thus, with formation of the chloroamide prolonged oxidative effects, directed toward specific target molecules, can be expected. Chlorination of NADH, yielding a catalytically inactive species (NAD/Cl), was investigated in most detail because it is likely to be an important and highly lethal process. The chloroamide group is far more reactive toward NADH than chloroamines derived from primary amines. Chloronucleotides formed by reaction of ClO− with inosine, GMP, TMP, or UMP are capable of quantitative chlorine transfer to cyclopeptides; however, no chlorine transfer between the amide nitrogen and primary amines is detectable, in either direction. The results presented enable prediction of chlorine transfer cascades induced by HOCl/ClO−, involving nucleotides, peptide amide groups, and final target molecules. Chlorinated NAD(P)H, as a stable terminal product of consecutive chlorine transfer reactions, might be a useful biological marker for assessing the role of HOCl in inflammatory events. Bromination by BrO− of cyclopeptides is more than two orders of magnitude faster than chlorination by ClO−, and the reactivity of bromoamide with NADH exceeds that of chloroamide by more than four orders of magnitude.

PfSUB-2: a second subtilisin-like protein in Plasmodium falciparum merozoites

Erythrocyte invasion by the malaria merozoite requires the activity of merozoite proteases. We have previously identified a Plasmodium falciparum protein belonging to the superfamily of subtilisin-like serine proteases, which is expressed in a subset of secretory organelles in free merozoites. Here we describe the identification of a second P. falciparum subtilisin-like merozoite protein. Called PfSUB-2, it is encoded by a single copy gene and is expressed as a large putative type I integral membrane protein which undergoes extensive post-translational processing. The terminal processing product is expressed in an apical location in merozoites. PfSUB-2 may mediate one or more of the serine protease activities known to be associated with erythrocyte invasion.

The Fatty Acid and Monosaccharide Compositions of Three Neutral and Three Phosphorylated Glycolipids Isolated from Leishmania donovani Promastigotes Grown in a Chemically Defined Medium

Several lipids and macromolecular lipoconjugates of Leishmania spp. have now been well characterized; however, the glycolipids of L. donovani have not been thoroughly examined. In the present study, 3 neutral and 3 phosphorylated glycolipids were detected in promastigote forms of the organism grown in a chemically defined medium. The fatty acid and sugar compositions of these glycolipids, isolated and purified by adsorption column chromatography and thin-layer chromatographic procedures, were identified and quantified by gas-liquid chromatography and mass spectrometry. Myristate (14:0), palmitate (16:0), palmitoleate (16:1), stearate (18:0), oleate (18:1), and linoleate (18:2) were the major fatty acids in all 6 glycolipids. Arabinose, mannose, glucose, and galactose were detected in the glycolipids. The biochemical nature of these lipids suggested that the major components in the isolated preparations of the 6 glycolipids are diacylglycerophospholipids, distinct from the major precursors of macromolecular lipoconjugates such as the lipid anchors of cell surface antigens that have been reported. These appear to be terminal products of lipid biosynthesis in this parasite.

Signal transduction pathway for anterior-posterior development in Drosophila.

In Drosophila, the establishment of embryonic polarity along the anterior-posterior axis of the egg is determined by the activity of maternal gene products that accumulate during oogenesis. Amongst these are the Bicoid, the Nanos, and the terminal class gene products, some of which are oncoproteins involved in signal transduction for the formation of terminal structures in the embryo. Several signal transduction pathways have been described in Drosophila, and this review explores the potential of oncogene studies using one of those pathways - the terminal class signal transduction pathway - to better understand the cellular mechanisms of proto-oncogenes that mediate cellular responses in vertebrates including humans.

Excision of IS492 requires flanking target sequences and results in circle formation in Pseudoalteromonas atlantica.

The gram-negative marine bacterium Pseudoalteromonas atlantica produces extracellular polysaccharide (EPS) that is important in biofilm formation by this bacterium. Insertion and precise excision of IS492 at a locus essential for extracellular polysaccharide production (eps) controls phase variation of EPS production in P. atlantica. Examination of IS492 transposition in P. atlantica by using a PCR-based assay revealed a circular form of IS492 that may be an intermediate in transposition or a terminal product of excision. The DNA sequence of the IS492 circle junction indicates that the ends of the element are juxtaposed with a 5-bp spacer sequence. This spacer sequence corresponds to the 5-bp duplication of the chromosomal target sequence found at all IS492 insertion sites on the P. atlantica chromosome that we identified by using inverse PCR. IS492 circle formation correlated with precise excision of IS492 from the P. atlantica eps target sequence when introduced into Escherichia coli on a plasmid. Deletion analyses of the flanking host sequences at the eps insertion site for IS492 demonstrated that the 5-bp duplicated target sequence is essential for precise excision of IS492 and circle formation in E. coli. Excision of IS492 in E. coli also depends on the level of expression of the putative transposase, MooV. A regulatory role for the circular form of IS492 is suggested by the creation of a new strong promoter for expression of mooV by the joining of the ends of the insertion sequence element at the circle junction.

Carbon monoxide-mediated alterations in paracellular permeability and vesicular transport in acetaminophen-treated perfused rat liver.

This study aimed to examine whether acetaminophen (AAP), an anti-inflammatory agent producing hepatocellular damages with its overdose, evokes hepatocellular dysfunction through mechanisms involving carbon monoxide (CO) generated by heme oxygenase (HO). In perfused rat livers, CO and bilirubin were determined in venous perfusate and bile samples as indices of heme degradation. Biliary excretion of transportally injected horseradish peroxidase was also determined to assess paracellular junctional permeability and vesicular transport across hepatocytes. AAP at 20 mmol/L induced a transient choleresis, followed by a reduction of bile output. Under these circumstances, the release of CO and bilirubin IXalpha, terminal products of the HO-mediated heme degradation, became 2. 5-fold greater than the control. The rate of CO production appeared stoichiometric to the degradation rate of microsomal cytochrome P-450. Mechanisms for the AAP-induced cholestasis involved an increase in the junctional permeability that coincided with a reduction of vesicular transport across hepatocytes. Clotrimazole, a cytochrome P-450 inhibitor, or zinc protoporphyrin IX, an HO inhibitor, but not copper protoporphyrin IX, which did not inhibit HO, attenuated these AAP-induced changes. Furthermore, administration of CO at concentrations comparable with those induced by AAP elicited a marked elevation of the paracellular junctional permeability concurrent with a reduction of transcellular vesicular transport, mimicking effects of the AAP administration. Thus, CO serves as a putative regulator of hepatocellular function that is overproduced through acute heme degradation during xenobiotic transformation.

Effect of total flavonoids of Astragalus on nitroxide in ischemia reperfusion injury

To study the protective effect of total flavonoids of Astragalus (TFA) on ischemia/reperfusion injury. Change of nitrite (NO2-), the terminal product of nitric oxide (NO) metabolism, and the effect of TFA and chloroquine (a phospholipase A2 inhibitor) on it were observed with hemorrhagic shock/reperfusion injury (S/R) rabbit model. Plasma NO2- content was positively correlated with blood pH and total carbon dioxide content lowering. TFA and chloroquine could block the decrease of NO in certain degree and might have some effect on maintaining acid-base balance of body. TFA has protective effect on ischemia/reperfusion injury.