Transport of endogenous nucleosides in guinea pig heart

The purpose of this study was to investigate the characteristics of transport of endogenous nucleosides into cardiac tissue from coronary circulation. The study was performed on the isolated perfused guinea pig heart, using the rapid paired tracers single-pass technique. The maximal cellular uptake (U(max)) and total cellular uptake (U(tot)) of adenosine, deoxyadenosine, thymidine, uridine, and cytidine were determined. The cellular uptake of adenosine was significantly higher than the cellular uptake of other studied nucleosides. To elucidate the mechanisms of nucleoside transport, competition studies were performed and the influence of S-(p-nitrobenzyl)-6-thioinosine (NBTI) and sodium ion absence on U(max) and U(tot) was investigated. Self- and cross-inhibition studies indicated the saturable mechanism of nucleosides transport into cardiac tissue and the involvement of different transport mechanisms for purine and pyrimidine nucleosides. The study also showed that both equilibrative-sensitive (es) and sodium-dependent transport were responsible for adenosine and thymidine cellular uptake.     

1,5-Hydride shift in Wolff-Kishner reduction of (20R)-3beta,20, 26-trihydroxy-27-norcholest-5-en-22-one: synthetic, quantum chemical, and NMR studies.

Heating (20R)-3beta,20,26-trihydroxy-27-norcholest-5-en-22-one (1) with hydrazine and KOH at 160 degrees C completely converted the steroid to a diastereoisomeric mixture of the new (20R,22RS)-27-norcholest-5-ene-3beta,20,22-triols (2). Exclusive formation of 2 suggests that the expected Wolff-Kishner reduction to a methylene group at the C-22 ketone in 1 was diverted to the C-26 position by a 1,5-hydride shift. All attempts under acid conditions failed to produce a C-22 phenyl hydrazone from 1. However, reaction of 1 was reacted with phenylhydrazine in hot KOH, gave the C-26 phenylhydrazone 4 as the sole product. Evidently, under alkaline conditions, first a hydride ion undergoes an intramolecular transfer from the C-26 CH(2)OH group to the C-22 ketone in 1, and then the phenylhydrazine traps the newly formed aldehyde. To examine this hypothesis, we constructed computer-simulated transition state models from quantum chemical calculations and then compared data from these models with NMR measurements of the reaction mixtures containing 2. The NMR data showed that the C-22 diastereoisomers of 2 are formed in a nearly 1:1 ratio exactly as predicted from the energy-optimized transition states, which were calculated for intramolecular 1,5-hydride shifts that produced each of the two C-22 diastereoisomers. Accordingly, these results support the hypothesis that an intramolecular 1,5-hydride shift mechanism promotes complete conversion of 1 to 2 under classical Wolff-Kishner reduction conditions.     

CPAP enhances and maintains chronic inflammation in hepatocytes to promote hepatocarcinogenesis

Chronic and persistent inflammation is a well-known carcinogenesis promoter. Hepatocellular carcinoma (HCC) is one of the most common inflammation-associated cancers; most HCCs arise in the setting of chronic inflammation and hepatic injury. Both NF-κB and STAT3 are important regulators of inflammation. Centrosomal P4.1-associated protein (CPAP), a centrosomal protein that participates primarily in centrosome functions, is overexpressed in HCC and can increase TNF-α-mediated NF-κB activation and IL-6-induced STAT3 activation. A transgenic (Tg) mouse model with hepatocyte-specific CPAP expression was established to investigate the physiological role of CPAP in hepatocarcinogenesis. Obvious inflammatory cell accumulation and fatty change were observed in the livers of CPAP Tg mice. The alanine aminotransferase (ALT) level and the expression levels of inflammatory genes, such as IL-6, IL-1β and TNF-α, were higher in CPAP Tg mice than in wild type (WT) mice. High-dose/short-term treatment with diethylnitrosamine (DEN) increased the ALT level, proinflammatory gene expression levels, and STAT3 and NF-κB activation in CPAP Tg mice; low-dose/long-term DEN treatment induced more severe liver tumor formation in CPAP Tg mice than in WT mice. CPAP can increase the expression of chemokine (C-C motif) ligand 16 (CCL-16), an important chemotactic cytokine, in human hepatocytes. CCL-16 expression is positively correlated with CPAP and TNF-α mRNA expression in the peritumoral part of HCC. In summary, these results suggest that CPAP may promote hepatocarcinogenesis through enhancing the inflammation pathway via increasing the expression of CCL-16.Subject terms: Liver cancer, Tumour immunology     

New analogues of AHMA as potential antitumor agents: synthesis and biological activity

A series of new analogues of 3-(9-acridinylamino)-5-hydroxymethylaniline (AHMA, 1) and AHMA-ethylcarbamate (2) were synthesized by introducing an O-alkylcarboxylic acid esters to the CH(2)OH function, displacing the CH(2)OH function with a dimethylaminocarboxamido group or with a methyl function introduced at the meta-, para- or ortho-position to the NH(2) group to form 5-(9-acridinylamino)-m-toluidines (AMTs), 5-(9-acridinylamino)-p-toluidines (APTs) or 5-(9-acridinylamino)-o-toluidines (AOTs), respectively. The inhibitions of a variety of human tumor cell growth, interactions with DNA as well as inhibitory effect against topoisomerase II (Topo II) of these new agents were studied. Among AMT, APT and AOT derivatives with dimethylaminoethylcarboxamido and Me at C4 and C5 of acridine moiety (i.e., 21c, 23c and 26c) were more cytotoxic than AHMA (1) and AHMA-ethylcarbamate (2), depending upon the tumor cell line tested. Detailed structure-activity relationships of the new analogues were studied.     

The tal gene undergoes chromosome translocation in T cell leukemia and potentially encodes a helix-loop-helix protein.

We have analyzed t(1;14)(p32;q11) chromosome translocations from two patients with T cell acute lymphocytic leukemia. The chromosome 1 breakpoints of these patients lie within a kilobasepair of each other, and thus define a genetic locus (designated tal) involved in T cell oncogenesis. Moreover, we have identified sequences within tal that potentially encode an amphipathic helix-loop-helix motif, a DNA-binding domain found in a variety of proteins that control cell growth and differentiation. The homology domain of tal is especially related to that of lyl-1, a gene on chromosome 19 that has also been implicated in T cell oncogenesis. Hence, tal and lyl-1 encode a distinct family of helix-loop-helix proteins involved in the malignant development of lymphocytes.     

Tetramethylpyrazine protects mice against thioacetamide-induced acute hepatotoxicity

In this study, the intraperitoneal administration of 1 mg/kg thioacetamide (TAA) produced hepatotoxicity in mice. The increase in serum SGOT and SGPT produced at 24 h by this regimen was decreased in a dose-dependent manner by coadministration of tetramethylpyrazine (TMP; 10, 25 and 50 mg/kg). A rise in serum interleukin-2 was similarly prevented. Increased concentrations of malondialdehyde (MDA) generated in vitro in liver homogenates prepared from TAA-treated mice were decreased by TMP treatments. The increase in MDA produced by TAA was also prevented by in vitro addition of TMP to liver homogenates. These results suggest that part of the hepatocellular injury induced by TAA is mediated by oxidative stress caused by the action of cytokines through lipid peroxidation. TMP appears to act by preventing lipid peroxidation.     

Signals of seminal vesicle autoantigen suppresses bovine serum albumin-induced capacitation in mouse sperm

Capacitation is the prerequisite process for sperm to gain the ability for successful fertilization. Unregulated capacitation will cause sperm to undergo a spontaneous acrosome reaction and then fail to fertilize an egg. Seminal plasma is thought to have the ability to suppress sperm capacitation. However, the mechanisms by which seminal proteins suppress capacitation have not been well understood. Recently, we demonstrated that a major seminal vesicle secretory protein, seminal vesicle autoantigen (SVA), is able to suppress bovine serum albumin (BSA)-induced mouse sperm capacitation. To further identify the mechanism of SVA action, we determine the molecular events associated with SVA suppression of BSA's activity. In this communication, we demonstrate that SVA suppresses the BSA-induced increase of intracellular calcium concentration ([Ca2+]i), intracellular pH (pH(i)), the cAMP level, PKA activity, protein tyrosine phosphorylation, and capacitation in mouse sperm. Besides, we also found that the suppression ability of SVA against BSA-induced protein tyrosine phosphorylation and capacitation could be reversed by dbcAMP (a cAMP agonist).     

Fractal analysis of STM images of lignin polymer obtained by in vitro synthesis

Lignin, the structural polymer of the plant cell walls, is produced by free radical polymerization of phenolic alcohols, catalyzed by different peroxidases. The mechanism and the structural organization of lignin in the cell have not been completely understood. In this study we applied fractal analysis to images of lignin polymer obtained using scanning tunneling microscope. The analysis showed the regularity of the polymer at different levels of organization. According to the results obtained, at the 95% confidence level, there is no significant difference in the fractal dimension between images representing different organizational levels of lignin. In other words, lignin produced in in vitro conditions has fractal structural organization and, consequently the polymer can be expected to be regular in in vivo conditions. The value of the fractal dimension 1.929 +/- 0.021 is in good agreement with the theoretically predicted value for polyaddition and polycondensation mechanism of polymerization. The mechanism of in vivo lignin synthesis is discussed in terms of various experimental and theoretical evidences. In this paper, we could show that fractal analysis of the lignin polymer is a useful complementary approach to the experimental data collection in structural and phenomenological studies.     

Fractal analysis of STM images of photochemical polymer of coniferyl alcohol

Fractal analysis was applied to images of photochemical lignin polymer obtained using scanning tunneling microscope. We studied the polymer obtained in vitro by ionic mechanism through UV radiation--induced polymerization. The analysis showed the regularity of the lignin-like polymer at different levels of organization. At the 95% confidence level, there was no significant difference in the fractal dimension between images representing different organizational levels of photochemical lignin. That means that lignin produced in in vitro conditions by photochemical mechanism of synthesis, has a fractal structural organization. The obtained values of the fractal dimension are in good agreement with the theoretically predicted value for the polyaddition and polycondensation mechanism of polymerization, known as the bulk model.     

Trace elements accumulation and temporal trends in leaves of urban deciduous trees (Aesculus hippocastanum and Tilia spp.)

Leaves of common deciduous trees: Aesculus hippocastanum and Tilia spp. from three parks within the urban area of Belgrade (Serbia) were studied as biomonitors of trace elements (Cr, Fe, Ni, Cu, Zn, and Pb) atmospheric pollution. The seasonal trace elements accumulation (September/May) in the leaves, and their temporal trends, were assayed in a multy-year period (2002–2006). Significant seasonal accumulation was evident in samples of A. hippocastanum for: Cr, Fe, Ni, Zn, and Pb, as well as in Tilia spp. leaves, except for Zn. For Cu, no regular seasonal accumulation was observed in leaves of the studied species. Decreasing temporal trend in leaf tissue concentrations were evident for Pb in A. hippocastanum (16.0 μg g^?1 in September of 2002 to 4.6 μg g^?1 in September of 2006) which is in accordance with the bulk atmospheric deposition measurements. The leaf Cu concentrations were the highest at one of the studied sites, also marked previously with extremely high atmospheric Cu loadings by some other monitoring (bulk deposition, particulate matter, moss) surveys. Decreasing Cu concentrations temporal trend at that site in the leaves of A. hippocastanum was evident through the studied years and also confirmed with the bulk deposition measurements. The Cr, Fe, Ni, and Zn leaf tissue concentrations remained at about the same level in the studied species throughout the experiment and no agreement was observed with the bulk deposition data. Comparing the studied biomonitors, the leaves of A. hippocastanum showed significantly higher elements accumulation and more consistency than Tilia spp., so it may be considered as more suitable species for assessment of Pb and Cu atmospheric pollution.