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PubMed2005

Multistate reactivity in styrene epoxidation by compound I of cytochrome p450: mechanisms of products and side products formation.

Density functional theoretical calculations are used to elucidate the epoxidation mechanism of styrene with a cytochrome P450 model Compound I, and the formation of side products. The reaction features multistate reactivity (MSR) with different spin states (doublet and quartet) and different electromeric situations having carbon radicals and cations, as well as iron(III) and iron(IV) oxidation states. The mechanisms involve state-specific product formation, as follows: a) The low-spin pathways lead to epoxide formation in effectively concerted mechanisms. b) The high-spin pathways have finite barriers for ring-closure and may have a sufficiently long lifetime to undergo rearrangement and lead to side products. c) The high-spin radical intermediate, (4)2(rad)-IV, has a ring closure barrier as small as the C--C rotation barrier. This intermediate will therefore lose stereochemistry and lead to a mixture of cis and trans epoxides. The barriers for the production of aldehyde and suicidal complexes are too high for this intermediate. d) The high-spin radical intermediate, (4)2(rad)-III, has a substantial ring closure barrier and may survive long enough time to lead to suicidal, phenacetaldehyde and 2-hydroxostyrene side products. e) The phenacetaldehyde and 2-hydroxostyrene products both originate from crossover from the (4)2(rad)-III radical intermediate to the cationic state, (4)2(cat,z(2) ). The process involves an N-protonated porphyrin intermediate that re-shuttles the proton back to the substrate to form either phenacetaldehyde or 2-hydroxostyrene products. This resembles the internally mediated NIH-shift observed during benzene hydroxylation.

Cytochrome P-450 Enzyme System↗
PubMed2004

The productivity of health care and health production functions.

This paper derives a necessary and sufficient condition under which increased health care productivity must lead to decreased (increased) demand for health care as long as the demand for health care is inelastic (elastic). It is shown that this condition identifies a class of health production functions, which may provide useful guidance to empirical studies that depend wholly or partly on the correct specification of a health production function. As an illustration, it is demonstrated that this class of production functions may be useful for empirical studies that test the hypothesis that schooling, increasing the efficiency of health production, leads to a larger health output from a given set of health inputs. The paper also offers broader classes of production functions that would enable one to test this relationship between the demand elasticity and the effect of health care productivity on health care demand.

Efficiency↗
PubMed1991

Regulation of interferon production by human monocytes: requirements for priming for lipopolysaccharide-induced production.

Macrophages are uniquely responsive to bacterial lipopolysaccharide (LPS) for activation of a number of host defense functions and production of bioactive mediators. One potentially important mediator produced by LPS-stimulated macrophages is interferon (IFN-alpha/beta). In contrast to murine observations, we have observed that freshly isolated human monocytes, purified by counter-current centrifugal elutriation, do not produce interferon in response to LPS. This is not due to a lack of response to LPS, as assessed by the induction of other monokines, or to an incapacity for IFN production, since IFN was inducible by poly-I,C treatment of monocytes in the absence of any other exogenous stimulus. However, human monocytes can be primed for the production of IFN in response to LPS if they are cultured in the presence of either granulocyte-macrophage colony stimulating factor (GM-CSF) or interferon-gamma (IFN-gamma). The IFN secreted is of the alpha subtype. Monocytes primed with GM-CSF or IFN-gamma also maintained LPS responses for production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1). M-CSF did not prime monocytes for LPS-induced IFN production, although it did enhance production of TNF-alpha and promoted monocyte survival. Northern analysis indicated that the induction of IFN-alpha by LPS was regulated primarily at the mRNA level. The highly regulated production of IFN-alpha by monocytes/macrophages has important implications for autocrine action of interferons in the activation and differentiation of these cells.

Animals↗
PubMed1996

A novel expression system for Salmonella typhimurium allowing high production levels, product secretion and efficient recovery.

A novel expression system for heterologous production in Salmonella typhimurium, taking advantage of the promoter, signal sequence and two IgG-binding domains (ZZ) from staphylococcal protein A, has been investigated. The production of two different fusion proteins, ZZ-M3 and ZZ-M5, was characterized in terms of production levels, product localization (periplasma or culture medium) and product quality after affinity purification. High expression levels and efficient product secretion were obtained, making the system attractive for vaccine development. The potential use of S. typhimurium as host for heterologous production in biotechnology is discussed.

Amino Acid Sequence↗
PubMed1986

Natural killer-cell activity, interferon-alpha 2 production, and interleukin-2 production in cyclosporine-treated and conventionally immunosuppressed human allograft recipients.

Natural killer (NK) activity, interferon (IFN)-alpha production, and interleukin-2 (IL-2) production were measured in renal transplant recipients undergoing immunosuppression with either azathioprine and steroids (Az + P) or cyclosporine (CyA). Overall, both IFN-alpha production and IL-2 production were impaired in these two groups compared with identical studies in healthy individuals. However, on the basis of control data these two patient groups were divided into those with "normal" NK activity and those with "low" NK activity. In the CyA group those with a low NK reaction produced less IL-2 and IFN-alpha than those with normal NK activity. No such relationship between cytokine production and NK activity was discerned in the Az + P group. These data conflict with in vitro studies, which have failed to demonstrate any effect of CyA on IFN-alpha production. In addition, they suggest that whereas cyclosporine influences NK activity in vivo by inhibiting cytokine production, other factors may play a role in impairing NK activity in conventionally immunosuppressed patients.

Adolescent↗
PubMed1994

Production of prostaglandins D2 and E2 by mouse fibroblasts and astrocytes in culture caused by Trypanosoma brucei brucei products and endotoxin.

A study was made to characterize the effects of living Trypanosoma brucei brucei and its products on prostaglandin D2 (PGD2) and PGE2 production by fibroblasts and astrocytes. Cultured fibroblasts were prepared from Microtus agrestis embryos and astrocyte cultures were prepared from neonatal rats. The cultures were maintained in low-endotoxin or defined media (i.e. endotoxin-free). The PG production was compared with and studied in combination with a defined lipopolysaccharide (LPS) from Escherichia coli. Living T. b. brucei were without effect on PG production. Preparations of T. b. brucei prepared by freeze-thawing and sonication produced dose- and time-dependent increases in PGD2 and PGE2 synthesis by both cell types. LPS caused a similar pattern of increases. The combination of parasite products with LPS caused synergistic production to levels higher than the maximal production by each mitogen alone. The findings have important implications for several pathological features that accompany trypanosomiasis.

Animals↗
PubMed1998

Early-appearing tumor-infiltrating natural killer cells play an important role in the nitric oxide production of tumor-associated macrophages through their interferon production.

Both natural killer (NK) cells and macrophages are thought to be the main effectors responsible for early antitumor defense. In this study, we investigated the role of tumor-infiltrating NK cells in initiating nitric oxide (NO) production by tumor-associated macrophages (TAM). The in vivo depletion of NK cells prior to the i.p. inoculation of melanoma cells resulted in a significant decrease in the NO production of the TAM prepared from the peritoneal exudate cells (PEC). Such prior NK cell depletion also decreased the ability of TAM to show any antitumor activity in vitro. The addition of NG-monomethyl-L-arginine (Me-L-Arg) to the culture partially inhibited the ability of TAM to suppress the proliferation of melanoma cells and also decreased their cytolytic activity against melanoma cells. These results suggest that the TAM exhibited both cytostatic and cytolytic activities through their NO production. In an in vivo assay, the administration of Me-L-Arg permitted the more rapid growth of i.p. inoculated melanoma cells compared with the control. On the other hand, the decreased NO production of TAM, resulting from the prior NK cell depletion, was restored by the i.p. administration of interferon gamma (IFN gamma). In addition, the in vivo administration of anti-IFN gamma mAb into mice inoculated i.p. with melanoma cells also significantly decreased the NO production of TAM in peritoneal exudate cells. Furthermore, the tumor-infiltrating NK cells produced a considerable level of IFN gamma. Overall, these results indicate that early-appearing tumor-infiltrating NK cells play an important role in the NO production of TAM through their IFN gamma production.

Animals↗
PubMed1990

The developmental effect of overexpressing a Ubx product in Drosophila embryos is dependent on its interactions with other homeotic products.

We report the developmental effects of expressing an Ultrabithorax (Ubx) product under the hsp70 promoter. Heat induction gives rise to a high, ubiquitous expression of Ubx product that lasts for several hours. We find that whether or not the overexpression of Ubx has a developmental effect on a particular body region of the larva depends on the interactions with the resident homeotic genes. In head and thorax the Ubx product overrides Sex combs reduced, Antennapedia, and probably other homeotic genes and dictates its own developmental program. In abdominal segments A1-A8 the overexpressed Ubx product establishes a normal pattern, alone (A1) or in combination with abdominal-A (A2-A4) and Abdominal-B (A5-A8), indicating that the excess of product is irrelevant. In segment A9 the highly expressed Ubx product is phenotypically suppressed by the r product of Abdominal-B. The presence of high levels of Ubx protein is also irrelevant in the telson.

Animals↗
PubMed1985

Mutagenicity tests of lipid oxidation products in Salmonella typhimurium: monohydroperoxides and secondary oxidation products of methyl linoleate and methyl linolenate.

Nine hydroperoxy and hydroperoxy-epidioxy oxidation products derived from either autoxidation (AO) or photosensitized oxidation (PO) of methyl linoleate (MLo) or methyl linolenate (MLn) were tested for mutagenic activity by the Salmonella typhimurium his+ reversion assay using strains TA100, TA98, TA102, TA97 and TA1537. All nine oxidation products, monohydroperoxides from AO-MLn (I) or from PO-MLn (II), dihydroperoxides from PO-MLo (III), AO-MLn (IV) or PO-MLn (V), hydroperoxy epidioxides from PO-MLo (VI), AO-MLn (VII) or PO-MLn (VIII) and hydroperoxy bis-epidioxides from PO-MLn (IX), were weakly mutagenic in strains TA97 and/or TA100. The hydroperoxy epidioxides (VI-IX) exhibited significantly greater activity in strain TA97 than did the monohydroperoxides (I, II) or the dihydroperoxides (III-V). In strain TA100, all of the oxidation products tested exhibited similar activity. No major differences between products derived from autoxidized and photooxidized MLn (I v. II, IV v. V, VII v. VIII) were obtained. Rat-liver S-9 reduced the toxicity of all oxidation products to the tester strains. The greatest mutant yields were usually obtained in the presence of S-9, but mutagenic potency was sometimes greater without S-9. The structural feature common to all of the mutagenic oxidation products was the presence of a hydroperoxy group, suggesting that this characteristic is responsible for the observed mutagenicity, either directly or through a common degradative pathway to reactive products of lower molecular weight.

Animals↗
PubMed2005

Benthic primary production during emersion: In situ measurements and potential primary production in the Seine Estuary (English Channel, France).

A two year survey of benthic primary production during periods of emersion was performed on two stations of an intertidal mudflat (a muddy-sand station and a muddy station) in the Seine Estuary (English Channel, France). The goals of this study were to investigate the seasonal variations of metabolism, to estimate daily potential primary production variation at the annual scale and to estimate the annual potential primary production of the mudflat. Primary production and respiration were estimated by in situ measurements of carbon dioxide fluxes. Chlorophyll a concentration exhibited a great variability on both locations. Gross community production ranged from ca. 0 to 77 mg C m(-2) h(-1) at the muddy-sand location and from ca. 0 to 122 mg C m(-2) h(-1) at the muddy location. Community respiration showed a seasonal trend following temperature variations (up to 28.51 mg C m(-2) h(-1) in the muddy-sand and up to 23.40 mg C m(-2) h(-1) in the mud). Daily potential primary production was calculated, according to seasonal variations of photosynthetic parameters calculated using three photosynthesis versus irradiance curves obtained for the muddy location. The annual gross community primary production was 135 g C m(-2) yr(-1), leading to a low autotrophic annual budget, considering an annual community respiration of 110 g C m(-2) yr(-1).

Animals↗
PubMed2005

Peroxynitrite-induced oxidation and nitration products of guanine and 8-oxoguanine: structures and mechanisms of product formation.

Peroxynitrite induces DNA base damage predominantly at guanine (G) and 8-oxoguanine (8-oxoG) nucleobases via oxidation reactions. Nitration products are also observed, consistent with the generation of radical intermediates that can recombine with the (.)NO(2) formed during peroxynitrite degradation. The neutral G radical, G(.), reacts with (.)NO(2) to yield 8-nitroguanine (8-nitroG) and 5-nitro-4-guanidinohydantoin (NI), while for 8-oxoG we have proposed a reactive guanidinylidene radical intermediate. The products generated during peroxynitrite-mediated 8-oxoG oxidation depend on oxidant flux, with dehydroguanidinohydantoin (DGh), 2,4,6-trioxo-[1,3,5]triazinane-1-carboxamidine (CAC) and NO(2)-DGh predominating at high fluxes and spiroiminodihydantoin (Sp), guanidinohydantoin (Gh) and 4-hydroxy-2,5-dioxo-imidazolidine-4-carboxylic acid (HICA) predominating at low fluxes. Both product sets are observed at intermediate fluxes. It is therefore important in model systems to ensure that the relative concentrations are well controlled to minimize competing reactions that may not be relevant in vivo. Increasingly sophisticated systems for modeling peroxynitrite production in vivo are being developed and these should help with predicting the products most likely to be formed in vivo. Together with the emerging information on the genotoxic and mutational characteristics of the individual oxidation products, it may be found that the extent of tissue damage, mutational spectra and, hence, cancer risk may change as a function of peroxynitrite fluxes as different product combinations predominate.

DNA↗
PubMed2002

A comparison of the properties of the major commercial PBDPO/PBDE product to those of major PBB and PCB products.

Decabromodiphenyl oxide (DBDPO), a highly effective polybrominated diphenyl oxide (PBDPO) flame retardant (FR) used primarily in electrical and electronic equipment, is the second highest volume brominated flame retardant (BFR) and accounts for 82% of the PBDPO usage globally. The apparent similarities in chemical structure between the DBDPO, polychlorinated and polybrominated biphenyl (PCB, PBB) molecules have led to the presumption that these substances also share similar toxicological and environmental properties. However, DBDPO's physical/chemical properties, applications, environmental release, and toxicology differ substantially from the former PCB/PBB products. DBDPO is a heavier and larger molecule than components of the predominant PCB/PBB products used in the past, and the commercial DBDPO product has a lower water solubility and vapor pressure than the former PCB and PBB products. DBDPO's detection in the environment is generally in sediments near known point sources, and its primary use in thermoplastics limits its environmental release from end products. PBB environmental release has been primarily associated with one accident occurring in the US in 1973. The PCBs, used in applications with a high potential for environmental release, were detected in diverse locations around the world as early as in the 1970s. Current releases of PCB are considered related to an environmental cycling process of congeners previously released into the environment; however, DBDPO's physical/chemical properties do not indicate a similar potential. Extensive testing of the DBDPO commercial product has demonstrated that it is toxicologically and pharmacokinetically different from the predominant PCB and PBB products used in the past. Thus, although the chemical structures of DBDPO, PBB, and PCB appear similar, the properties of DBDPO are distinctly different.

Bromobenzenes↗
PubMed1994

Endogenous production of tumor necrosis factor by primary cultures of murine calvarial cells: influence on IL-6 production and osteoclast development.

We have previously shown that tumor necrosis factor (TNF) and interleukin-1 (IL-1) acted synergistically to stimulate the production of IL-6 by bone marrow stromal and osteoblastic cells; and that an antibody to IL-6 inhibited TNF-induced osteoclast development in murine calvarial cell cultures. Prompted by this evidence, we have now examined whether TNF and/or IL-1 are produced by murine calvarial cells, and whether these cytokines are involved in IL-6 production and osteoclast formation. When cultured under basal conditions, calvarial cells produced TNF and IL-6, and were able to form bone resorbing osteoclasts. A neutralizing antibody against TNF suppressed both basal IL-6 production and the formation of bone resorbing osteoclasts. The anti-TNF antibody also inhibited IL-6 production in response to exogenous IL-1 or parathyroid hormone (PTH). In contrast, a neutralizing anti-IL-1 receptor antibody had no effect on basal, TNF- or PTH-stimulated IL-6 production. These findings suggest that TNF, but not IL-1, is produced by murine bone cells and that endogenous TNF induces the IL-6 production, osteoclast formation, and bone resorption exhibited by these cultures under basal conditions. Furthermore, bone cell-derived TNF amplifies the stimulatory effect of exogenous IL-1 or PTH on IL-6 production by calvarial cells.

Animals↗
PubMed1983

Platelet products and vascular PGI2 production.

The effects of products synthesized and/or secreted by activated platelets on production of PGI2 by human, rat and rabbit vascular rings were investigated. Of the platelet dense body constituents, 5HT stimulated PGI2 production by vascular tissue of all three species whereas ADP was active only on rat tissue. Of the lipids produced during platelet activation, PAF stimulated PGI2 production by vascular tissue of all three species, Lysophosphatidate was less active than PAF on rabbit and human tissue and inactive in rat tissue, and the TxA2-mimetic, U46619, was inactive on vascular tissue of all three species. It is concluded that there are species variations in the effects of agonists on vascular PGI2 production and that platelet-derived products other than platelet-derived growth factor and beta-thromboglobulin could modulate PGI2 production to regulate platelet activation in vivo.

Adenosine Diphosphate↗
PubMed1997

Incineration of biomass and utilization of product gas as a CO2 source for crop production in closed systems: gas quality and phytotoxicity.

This study addressed the recycle of carbon from inedible biomass to CO2 for utilization in crop production. Earlier work identified incineration as an attractive approach to resource recovery from solid wastes because the products are well segregated. Given the effective separation of carbon into the gaseous product stream from the incinerator in the form of CO2 we captured the gaseous stream produced during incineration of wheat inedible biomass and utilized it as the CO2 source for crop production. Injection rate was based on maintenance of CO2 concentration in the growing environment. The crop grown in the closed system was lettuce. Carbon was primarily in the form of CO2 in the incinerator product gas with less than 8% of carbon compounds appearing as CO. Nitrogen oxides and organic compounds such as toluene, xylene, and benzene were present in the product gas at lower concentrations (< 4 micromol mol-1); sulfur containing compounds were below the detection limits. Direct utilization of the gaseous product of the incinerator as the CO2 source was toxic to lettuce grown in a closed chamber. Net photosynthetic rates of the crop was suppressed more than 50% and visual injury symptoms were visible within 3 days of the introduction of the incinerator gas. Even the removal of the incinerator gas alter two days of crop exposure and replacement with pure CO2 did not eliminate the toxic effects. Both organic and inorganic components of the incinerator gas are candidates for the toxin.

Air Pollutants↗
PubMed2001

Carbofuran suppresses T-cell-mediated immune responses by the suppression of T-cell responsiveness, the differential inhibition of cytokine production, and NO production in macrophages.

The effects of carbofuran (2,3-dihydro-2,2-dimethyl-7-benzo-furanol N-methylcarbamate) on the functions of T cells in splenocytes and peritoneal macrophages were examined in view of T-cell-mediated immune response (CMIR) in male C57BL/6 mice. Intraperitoneal administration of carbofuran (0.075, 0.15 and 0.3 mg/kg body weight) resulted in significant suppression of delayed type hypersensitivity (DTH), indicating that it caused the suppression of CMIR. Carbofuran decreased Concanavalin A (Con A)- and alloantigen-induced proliferation, and interleukin (IL)-2 production of splenocytes. In vitro addition of rIL-2 could not completely restore the suppressed T-cell proliferation, and IL-2-induced proliferation of Con A-activated splenocytes was also suppressed, which implied that carbofuran caused defects in IL-2 production and responsiveness of splenocytes to IL-2, leading to the suppression of T-cell proliferation. Con A-induced production of interferon-gamma (IFN-gamma) was significantly suppressed by carbofuran, while that of IL-4 was not affected. The production of transforming growth factor-beta from splenocytes was also significantly inhibited by carbofuran. Judging from these results, carbofuran might directly suppress the cytokine production in T helper 1 (Th1) cells. In addition, IFN-gamma-induced production of nitric oxide (NO) in macrophages was also inhibited by carbofuran, which might be one of the important mechanisms of carbofuran-induced CMIR suppression in mice. Collectively, the present study suggests that carbofuran might suppress CMIR through the suppression of T-cell responsiveness, IFN-gamma production in Th1 cells, and NO generation in macrophages.

Animals↗
PubMed2002

Is past academic productivity predictive of radiology resident academic productivity?

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether academic productivity in college and medical school is predictive of the number of publications produced during radiology residency. MATERIALS AND METHODS: The authors reviewed the records of 73 radiology residents who completed their residency from 1990 to 2000. Academic productivity during college, medical school, and radiology residency, other postgraduate degrees, and past careers other than radiology were tabulated. The personal essay attached to the residency application was reviewed for any stated academic interest. Residents were classified as being either previously productive or previously unproductive. Publication rates during residency and immediately after residency were compared for the two groups. For the productive residents, a correlation analysis was used to examine the relationship between past frequency of publication and type of previous activity. Least-squares regression analysis was used to investigate the relationship between preresidency academic productivity, advanced degrees, stated interest in academics, and other careers and radiology residency publications. RESULTS: There was no statistically significant difference in the number of articles published by those residents who were active and those who were not active before residency (P = .21). Only authorship of papers as an undergraduate was weakly predictive of residency publication. CONCLUSION: These selected measures of academic productivity as an undergraduate and during medical school are not helpful for predicting publication during residency. There was no difference in publication potential between those residents who were academically productive in the past and those who were not.

Achievement↗
PubMed2005

Characterization of the product radical structure in the Co(II)-product radical pair state of coenzyme B12-dependent ethanolamine deaminase by using three-pulse 2H ESEEM spectroscopy.

Molecular structural features of the product radical in the Co(II)-product radical pair catalytic intermediate state in coenzyme B(12)- (adenosylcobalamin-) dependent ethanolamine deaminase from Salmonella typhimurium have been characterized by using X-band three-pulse electron spin-echo envelope modulation (ESEEM) spectroscopy in the disordered solid state. The Co(II)-product radical pair state was prepared by cryotrapping holoenzyme during steady-state turnover on excess 1,1,2,2-(2)H(4)-aminoethanol or natural abundance, (1)H(4)-aminoethanol. Simulation of the (2)H/(1)H quotient ESEEM (obtained at two microwave frequencies, 8.9 and 10.9 GHz) from the interaction of the unpaired electron localized at C2 of the product radical with nearby (2)H nuclei requires four types of coupled (2)H, which are assigned as follows: (a) a single strongly coupled (effective dipole distance, r(eff) = 2.3 A) (2)H in the C5' methyl group of 5'-deoxyadenosine, (b) two weakly coupled (r(eff) = 4.2 A) (2)H in the C5' methyl group, (c) one (2)H coupling from a beta-(2)H bonded to C1 of the product radical (isotropic hyperfine coupling, A(iso) = 4.7 MHz), and (d) a second type of C1 beta-(2)H coupling (A(iso) = 7.7 MHz). The two beta-(2)H couplings are proposed to arise from two C1-C2 rotamer states of the product radical that are present in approximately equal proportion. A model is presented, in which C5' is positioned at a distance of 3.3 A from C2, which is comparable with the C1-C5' distance in the Co(II)-substrate radical pair intermediate. Therefore, the C5'methyl group remains in close (van der Waals) contact with the substrate and product radical species during the radical rearrangement step of the catalytic cycle, and the C5' center is the sole mediator of radical pair recombination in ethanolamine deaminase.

Binding Sites↗