Ginkgo biloba extract modifies hypoglycemic action of tolbutamide via hepatic cytochrome P450 mediated mechanism in aged rats

We examined hepatic cytochrome P450 (CYP)-mediated interactions between Ginkgo biloba extract (GBE) and tolbutamide, an oral anti-diabetic agent, in aged and young rats. Tolbutamide was orally given to rats with or without GBE treatment, and time-dependent changes in blood glucose were monitored. The basal activity of six CYP subtypes in liver was lower in the aged rats than in the young rats, while the inductions of these enzymes by 5 day pretreatment of 0.1% GBE diet were more in the aged rats. Further, the pretreatment of GBE significantly attenuated the hypoglycemic action of tolbutamide in the aged rats, corresponding well to the enhanced activity of (S)-warfarin 7-hydroxylase, which is responsible for CYP2C9 subtype, a major isoform metabolizing tolbutamide. In contrast, the simultaneous administration of GBE with tolbutamide potentiated the hypoglycemic action of this drug. The in vitro experiments revealed that GBE competitively inhibited the metabolism of tolbutamide by (S)-warfarin 7-hydroxylase in the rat liver microsomes. In the young rats, the 5 day pretreatment with GBE significantly attenuated the hypoglycemic action of tolbutamide, but a simultaneous treatment had little influence on the tolbutamide effect. In conclusion, the present study has shown that the simultaneous and continuous intake of GBE significantly affects the hypoglycemic action of tolbutamide, possibly via a hepatic CYP enzyme-mediated mechanism, particularly in the aged rats. Therefore, it is anticipated that the intake of GBE as a dietary supplement with therapeutic drugs should be cautious, particularly in elderly people.     

Inhibitors of superoxide dismutases: A cautionary tale

An extensive search resulted in the identification of pamoic acid as an inhibitor of superoxide dismutases. Pamoic acid appeared to rapidly and reversibly inhibit all types of superoxide dismutases and did so in both the cytochrome c reduction and in the dianisidine photooxidation assays, used to measure this activity. It could nevertheless be shown that pamoic acid did not at all inhibit superoxide dismutase but rather diminished the sensitivity of the assays. The mechanism proposed to account for this effect involved oxidation of pamoate, by O₂^?, to yield a pamoate radical which can then reduce cytochrome c or oxidize pyrogallol. Pamoate thus competes with superoxide dismutase for the available O₂^?, without affecting the observable effects of that O₂^? upon cytochrome c or upon pyrogallol. It consequently makes these assays less responsive to superoxide dismutase, while appearing to be without effect in the absence of superoxide dismutase. Several of the predicted consequences of this proposal were affirmed. Other workers, interested in finding inhibitors for superoxide dismutases, are hereby forwarned of this subtle snare.     

Osteopontin gene polymorphisms as predictors for the efficacy of interferon therapy in chronic hepatitis C Egyptian patients with genotype 4

This study aimed to determine the relationship between osteopontin gene polymorphisms and its protein level and the efficacy of interferon‐based therapies in Hepatitis C virus (HCV) patients. Hundreds HCV patients genotype 4, treated with pegylated interferon alfa‐2b plus ribavirin and 60 healthy subjects were enrolled. All individuals were subjected to clinical and laboratory parameters, including hepatitis markers and HCV quantitation by real‐time polymerase chain reaction. Single nucleotide polymorphisms (SNPs) of osteopontin (OPN) gene (nucleotide ?155, ?443 and ?1748) were analysed by direct sequencing in addition to estimation of serum level of OPN. SNP at ?443 (C/C versus C/T, T/T) was found to represent predictors for treatment response by univariate logistic regression analysis. OPN serum level was independent predictors for treatment response by both univariate and multivariate logistic regression analysis. SNP at nucleotide ?443 and serum OPN protein levels could be used as useful markers to predict the efficacy of treatment. Copyright © 2013 John Wiley & Sons, Ltd.     

Plasmodium berghei: a mouse model for the "sudden death" and "malarial lung" syndromes

A mouse model for the "sudden death" and "malarial lung" syndromes is described. Mice of the C3H/z strain succumb suddenly approximately 7 days after an infection with Plasmodium berghei becomes patent, at a time when parasitemia is still moderate (6 to 8%). Death could be shown to be due to anaphylactoid shock, probably induced by soluble immune complexes. Increased vascular permeability caused transudation and leakage of serum proteins into the interstitium and the alveoli. The lungs were found to be edematous, with a fine granular precipitate in the alveoli and adherent to the vascular walls. The precipitates reacted with antiglobulins G and M, and could be shown to also contain malaria antigens and C3/4. A dramatic drop in hematocrit was recorded several hours before death, indicating the sudden release of malaria antigens. The myocardium of animals that had died very suddenly showed a patchy loss of phosphorylase activity. This loss of activity was much more extensive, and sometimes almost total, when there had been an agonal period of several (1 to 3) hours before death. In these cases the irreversibility of the myocardial damage was also indicated by the loss of activity of the dehydrogenases, as well as by typical inflammatory reactions of granulocytic and histiocytic infiltrations. The hearts thus presented a typical picture of the acute and peracute shock syndromes. In acute shock cardiac insufficiency develops so suddenly that death ensues before irreversible damage has occurred, and cardiac insufficiency can only be demonstrated by the most sensitive of enzyme histochemical means. In the present case shock was induced by the anaphylactoid activity of immune complexes with the lung as target organ. The described syndrome appears analogous to human "malarial lung."     

Photosynthesis of Cockspur [Echinochloa crus-galli (L.) Beauv.] at Sites of Naturally Elevated CO2 Concentration

High abundance of cockspur (Echinochloa crus-galli) at the geothermal carbon dioxide spring area in Staveinci indicates that this species is able to grow under widely varying CO₂ concentrations. Living cockspur plants can even be found very close to gas-releasing vents where growth is significantly reduced. Plant height correlated well with CO₂ exposure. The ¹³C value of the CO₂ spring air was –3.9 and ¹³C values of high-, medium-, and low-CO₂ plants were –10.14, –10.44, and –11.95 , respectively. Stomatal response directly followed the prevailing CO₂ concentrations, with the highest reduction of stomatal conductance in high CO₂ concentration grown plants. Analysis of the curves relating net photosynthetic rate to intercellular CO₂ concentration (P _N-C_i curves) revealed higher CO₂ compensation concentration in plants growing at higher CO₂ concentration. This indicates adjustment of respiration and photosynthetic carbon assimilation according to the prevailing CO₂ concentrations during germination and growth. There was no difference in other photosynthetic parameters measured.     

POR C of Arabidopsis thaliana: a third light- and NADPH-dependent protochlorophyllide oxidoreductase that is differentially regulated by light

During the sequencing of the genome of Arabidopsis thaliana a gene has been identified that encodes a novel NADPH-protochlorophyllide oxidoreductase (POR)-like protein (accession number AC 002560). This protein has been named POR C. We have expressed the POR C protein in Escherichia coli and have determined its in vitro activity. POR C shows the characteristics of a light-dependent and NADPH-requiring POR similar to POR A and POR B. The expression of the POR C gene differs markedly from that of the POR A and POR B genes. In contrast to the POR A and POR B mRNAs, the POR C mRNA has been shown previously to accumulate only after the beginning of illumination. In light-adapted mature plants only POR B and POR C mRNAs were detectable. The amounts of both mRNAs show pronounced diurnal rhythmic fluctuations. While the oscillations of POR B mRNA are under the control of the circadian clock, those of POR C mRNA are not. Another difference between POR B and POR C was found in seedlings that were grown under continuous white light. The concentration of POR C mRNA rapidly declined and soon dropped beyond the limit of detection, after these seedlings were transferred to the dark. On the other hand, POR B mRNA was unaffected by this light/dark shift. When seedlings were exposed to different light intensities, the amounts of POR B mRNA remained the same, while POR A and POR C mRNAs were modulated in an inverse way by these light intensity changes. POR A mRNA was still detectable in seedlings grown under low light intensities but disappeared at higher light intensities, while the mRNA concentration of POR C rose with increasing light intensities. These different responses to light suggest that the functions of the three PORs of Arabidopsis are not completely redundant, but may allow the plant to adapt its needs for chlorophyll biosynthesis more selectively by using preferentially one of the three enzymes under a given light regime.     

Src Homology 2 Domain Containing Protein 5 (SH2D5) Binds the Breakpoint Cluster Region Protein,BCR, and Regulates Levels of Rac1-GTP

SH2D5 is a mammalian-specific, uncharacterized adaptor-like protein that contains an N-terminal phosphotyrosine-binding domain and a C-terminal Src homology 2 (SH2) domain. We show that SH2D5 is highly enriched in adult mouse brain, particularly in Purkinjie cells in the cerebellum and the cornu ammonis of the hippocampus. Despite harboring two potential phosphotyrosine (Tyr(P)) recognition domains, SH2D5 binds minimally to Tyr(P) ligands, consistent with the absence of a conserved Tyr(P)-binding arginine residue in the SH2 domain. Immunoprecipitation coupled to mass spectrometry (IP-MS) from cultured cells revealed a prominent association of SH2D5 with breakpoint cluster region protein, a RacGAP that is also highly expressed in brain. This interaction occurred between the phosphotyrosine-binding domain of SH2D5 and an NxxF motif located within the N-terminal region of the breakpoint cluster region. siRNA-mediated depletion of SH2D5 in a neuroblastoma cell line, B35, induced a cell rounding phenotype correlated with low levels of activated Rac1-GTP, suggesting that SH2D5 affects Rac1-GTP levels. Taken together, our data provide the first characterization of the SH2D5 signaling protein.     

Membrane-associated phosphoinositides-specific phospholipase C forms from <Emphasis Type="Italic">Catharanthus roseus</Emphasis> transformed roots

We have previously reported that Catharanthus roseus transformed roots contain at least two phosphatidylinositol 4,5-bisphosphate-phospholipase C (PLC) activities, one soluble and the other membrane associated. Detergent, divalent cations, and neomycin differentially regulate these activities and pure protein is required for a greater understanding of the function and regulation of this enzyme. In this article we report a partia purification of membrane-associated PLC. We found that there are at least two forms of membrane-associated PLC in transformed roots of C. roseus. These forms were separated on the basis of their affinity for heparin. One form shows an affinity for heparin and elutes at approx 600 mM KCl. This form has a molecular mass of 67 kDa by size exclusion chromatography and Western blot analysis, whereas the other form does not bind to heparin and has a molecular mass of 57 kDa. Possible differential regulation of these forms during transformed root growth is discussed.     

Molecular action of vitamin E in lipoprotein oxidation: implications for atherosclerosis

The oxidation theory of atherosclerosis proposes that the oxidative modification of low-density lipoproteins (LDL) plays a central role in the disease. Although a direct causative role of LDL oxidation for atherogenesis has not been established, oxidized lipoproteins are detected in atherosclerotic lesions, and in vitro oxidized LDL exhibits putative pro-atherogenic activities. alpha-Tocopherol (alpha-TOH; vitamin E), the major lipid-soluble antioxidant present in lipoproteins, is thought to be antiatherogenic. However, results of vitamin E interventions on atherosclerosis in experimental animals and cardiovascular disease in humans have been inconclusive. Also, recent mechanistic studies demonstrate that the role of alpha-TOH during the early stages of lipoprotein lipid peroxidation is complex and that the vitamin does not act as a chain-breaking antioxidant. In the absence of co-antioxidants, compounds capable of reducing the alpha-TOH radical and exporting the radical from the lipoprotein particle, alpha-TOH exhibits anti- or pro-oxidant activity for lipoprotein lipids depending on the degree of radical flux and reactivity of the oxidant. The model of tocopherol-mediated peroxidation (TMP) explains the complex molecular action of alpha-TOH during lipoprotein lipid peroxidation and antioxidation. This article outlines the salient features of TMP, comments on whether TMP is relevant for in vivo lipoprotein lipid oxidation, and discusses how co-antioxidants may be required to attenuate lipoprotein lipid oxidation in vivo and perhaps atherosclerosis.     

Differential requirement for the N-terminal catalytic domain of the DNA polymerase ε p255 subunit in the mitotic cell cycle and the endocycle

In Drosophila, the 255kDa catalytic subunit (dpolεp255) and the 58kDa subunit of DNA polymerase ε (dpolεp58) have been identified. The N-terminus of dpolεp255 carries well-conserved six DNA polymerase subdomains and five 3'→5' exonuclease motifs as observed with Polε in other species. We here examined roles of dpolεp255 during Drosophila development using transgenic fly lines expressing double stranded RNA (dsRNA). Expression of dpolεp255 dsRNA in eye discs induced a small eye phenotype and inhibited DNA synthesis, indicating a role in the G1-S transition and/or S-phase progression of the mitotic cycle. Similarly, expression of dpolεp255 dsRNA in the salivary glands resulted in small size and endoreplication defects, demonstrating a critical role in endocycle progression. In the eye disc, defects induced by knockdown of dpolεp255 were rescued by overexpression of the C-terminal region of dpolεp255, indicating that the function of this non-catalytic domain is conserved between yeast and Drosophila. However, this was not the case for the salivary gland, suggesting that the catalytic N-terminal region is crucial for endoreplication and its defect cannot be complemented by other DNA polymerases. In addition, several genetic interactants with dpolεp255 including genes related to DNA replication such as RFC, DNA primase, DNA polη, Mcm10 and Psf2 and chromatin remodeling such as Iswi were also identified.