Germ line p53 mutations in a familial syndrome of breast cancer, sarcomas, and other neoplasms

Familial cancer syndromes have helped to define the role of tumor suppressor genes in the development of cancer. The dominantly inherited Li-Fraumeni syndrome (LFS) is of particular interest because of the diversity of childhood and adult tumors that occur in affected individuals. The rarity and high mortality of LFS precluded formal linkage analysis. The alternative approach was to select the most plausible candidate gene. The tumor suppressor gene, p53, was studied because of previous indications that this gene is inactivated in the sporadic (nonfamilial) forms of most cancers that are associated with LFS. Germ line p53 mutations have been detected in all five LFS families analyzed. These mutations do not produce amounts of mutant p53 protein expected to exert a trans-dominant loss of function effect on wild-type p53 protein. The frequency of germ line p53 mutations can now be examined in additional families with LFS, and in other cancer patients and families with clinical features that might be attributed to the mutation.

Role of human cytochrome P-450 IIE1 in the oxidation of many low molecular weight cancer suspects

The role of human cytochrome P-450 IIE1 (P-450 IIE1) in the oxidation of a number of suspect carcinogens was examined by using a variety of approaches, including (1) selective inhibition of catalytic activity in human liver microsomes by diethyldithiocarbamate, which was found to be a selective mechanism-based inactivator of P-450 IIE1, (2) correlation of rates of different catalytic activities with each other and with chlorzoxazone 6-hydroxylation, an indicator of P-450 IIE1, in human liver microsomes, (3) demonstration of catalytic activity in reconstituted systems containing purified human P-450 IIE1, and (4) immunoinhibition of catalytic activity in human liver microsomes with rabbit anti-human P-450 IIE1. The results collectively indicate that P-450 IIE1 is a major catalyst of the oxidation of benzene, styrene, CCl4, CHCl3, CH2Cl2, CH3Cl, CH3CCl3, 1,2-dichloropropane, ethylene dichloride, ethylene dibromide, vinyl chloride, vinyl bromide, acrylonitrile, vinyl carbamate, ethyl carbamate, and trichloroethylene. Levels of P-450 IIE1 can vary considerably among individual humans--the availability of chlorzoxazone as a noninvasive probe of human P-450 IIE1 and of disulfiram (oxidized diethyldithiocarbamate) as an inhibitor may facilitate discernment of the in vivo significance of human P-450 IIE1 as a factor in the bioactivation and detoxication of these cancer suspects. Further, many investigations with diethyldithiocarbamate, disulfiram, and ethanol in humans and experimental animals may be interpreted in light of mechanisms involving P-450 IIE1.

Validation and reproducibility of food frequency questionnaire for Korean genome epidemiologic study

OBJECTIVE

To evaluate validity and reliability of the food-frequency questionnaire (FFQ) developed for the Korean Genome Epidemiologic Study (KoGES).

METHODS

FFQ was administered twice at 1-year interval (first FFQ (FFQ1) at the beginning and second FFQ (FFQ2) at the end of the study) and diet records (DRs) were collected for 3 days during each of the four seasons from December 2002 to May 2004 for those who attended the health examination center. At the end of the study period, we collected the 12-day DRs of 124 participants. The nutrient intakes from the DRs were compared with both FFQ1 and FFQ2.

RESULTS

The intakes of energy and some nutrients estimated from FFQ1 and FFQ2 were different from those assessed by the DRs. Especially, the consumption of carbohydrates was higher in FFQ1 and FFQ2 than in the DRs. The de-attenuated, age, sex and energy intake adjusted correlation coefficients between the FFQ2 and the 12-day DRs in Korean population ranged between 0.23 (Vitamin A) and 0.64 (carbohydrate). The median for all nutrients was 0.39. The correlations were similar when we compared nutrient densities of both methods. Joint classification of calorie-adjusted nutrient intakes assessed by FFQ2 and 12-day DRs by quartile ranged from 25.8% (vitamin A) to 39.5% (carbohydrate, iron) for exact concordance. Except vitamin A, the proportion of subjects classified into distant quartile was less than 7% in all nutrients. The median of correlations between the two FFQs 1 year apart were 0.45 for all nutrient intakes and 0.39 for nutrient densities.

CONCLUSIONS

We conclude that the FFQ we have developed appears to be an acceptable tool for assessing the nutrient intakes in this population. Further studies for calibration of the FFQ collected from multicenters participating in the KoGES are needed.

SPONSORSHIP

This study was supported by the budget of the National Genome Research Institute, Korea National Institute of Health (2002-347-6111-221).

Solution structure of the antiapoptotic protein bcl-2

The structures of two isoforms of Bcl-2 that differ by two amino acids have been determined by NMR spectroscopy. Because wild-type Bcl-2 behaved poorly in solution, the structures were determined by using Bcl-2/Bcl-x(L) chimeras in which part of the putative unstructured loop of Bcl-2 was replaced with a shortened loop from Bcl-x(L). These chimeric proteins have a low pI compared with the wild-type protein and are soluble. The structures of the two Bcl-2 isoforms consist of 6 alpha-helices with a hydrophobic groove on the surface similar to that observed for the homologous protein, Bcl-x(L). Comparison of the Bcl-2 structures to that of Bcl-x(L) shows that although the overall fold is the same, there are differences in the structural topology and electrostatic potential of the binding groove. Although the structures of the two isoforms of Bcl-2 are virtually identical, differences were observed in the ability of the proteins to bind to a 25-residue peptide from the proapoptotic Bad protein and a 16-residue peptide from the proapoptotic Bak protein. These results suggest that there are subtle differences in the hydrophobic binding groove in Bcl-2 that may translate into differences in antiapoptotic activity for the two isoforms.

Intestinal bacterial metabolism of flavonoids and its relation to some biological activities

Flavonoid glycosides were metabolized to phenolic acids via aglycones by human intestinal microflora producing alpha-rhamnosidase, exo-beta-glucosidase, endo-beta-glucosidase and/or beta-glucuronidase. Rutin, hesperidin, naringin and poncirin were transformed to their aglycones by the bacteria producing alpha-rhamnosidase and beta-glucosidase or endo-beta-glucosidase, and baicalin, puerarin and daidzin were transformed to their aglycones by the bacteria producing beta-glucuronidase, C-glycosidase and beta-glycosidase, respectively. Anti-platelet activity and cytotoxicity of the metabolites of flavonoid glycosides by human intestinal bacteria were more effective than those of the parental compounds. 3,4-Dihydroxyphenylacetic acid and 4-hydroxyl-phenylacetic acid were more effective than rutin and quercetin on anti-platelet aggregation activity. 2,4,6-Trihydroxybenzaldehyde, quercetin and ponciretin were more effective than rutin and ponciretin on the cytotoxicity for tumor cell lines. We insist that these flavonoid glycosides should be natural prodrugs.

Human apolipoprotein E receptor 2. A novel lipoprotein receptor of the low density lipoprotein receptor family predominantly expressed in brain

Isolation and characterization of a human cDNA demonstrated a novel lipoprotein receptor designated apolipoprotein E receptor 2 (apoER2). The new receptor consists of five functional domains resembling the low density lipoprotein (LDL) and very low density lipoprotein (VLDL) receptors. LDL receptor deficient Chinese hamster ovary cells expressing human apoER2 bound apoE rich beta-migrating VLDL with high affinity and internalized. LDL was bound with much lower affinity to these cells. The 4.5- and 8.5-kb mRNAs for the receptor were most highly expressed in human brain and placenta. In rabbit tissues, multiple species of the mRNA with 4, 4.5, 5.5, 8.5, and 11 kb were detected most intensely in brain and testis and, to a much lesser extent, in ovary, but were undetectable in other tissues. In rat adrenal pheochromocytoma PC12 cells, the receptor mRNA was induced by treatment of the cells with nerve growth factor. The receptor transcripts were detectable most intensely in the cerebellar cortex, choroid plexus, ependyma, hippocampus, olfactory bulb and, to a much lesser extent, in the cerebral cortex as revealed by in situ hybridization histochemistry. In the cerebellar cortex, the receptor transcripts were densely deposited in Purkinje cell somata.

Local structural elements in the mostly unstructured transcriptional activation domain of human p53

DNA transcription is initiated by a small regulatory region of transactivators known as the transactivation domain. In contrast to the rapid progress made on the functional aspect of this promiscuous domain, its structural feature is still poorly characterized. Here, our multidimensional NMR study reveals that an unbound full-length p53 transactivation domain, although similar to the recently discovered group of loosely folded proteins in that it does not have tertiary structure, is nevertheless populated by an amphipathic helix and two nascent turns. The helix is formed by residues Thr(18)-Leu(26) (Thr-Phe-Ser-Asp-Leu-Trp-Lys-Leu-Leu), whereas the two turns are formed by residues Met(40)-Met(44) and Asp(48)-Trp(53), respectively. It is remarkable that these local secondary structures are selectively formed by functionally critical and positionally conserved hydrophobic residues present in several acidic transactivation domains. This observation suggests that such local structures are general features of acidic transactivation domains and may represent "specificity determinants" (Ptashne, M., and Gann, A. A. F. (1997), Nature 386, 569-577) that are important for transcriptional activity.

Artificial intelligence in fracture detection: transfer learning from deep convolutional neural networks

AIM

To identify the extent to which transfer learning from deep convolutional neural networks (CNNs), pre-trained on non-medical images, can be used for automated fracture detection on plain radiographs.

MATERIALS AND METHODS

The top layer of the Inception v3 network was re-trained using lateral wrist radiographs to produce a model for the classification of new studies as either "fracture" or "no fracture". The model was trained on a total of 11,112 images, after an eightfold data augmentation technique, from an initial set of 1,389 radiographs (695 "fracture" and 694 "no fracture"). The training data set was split 80:10:10 into training, validation, and test groups, respectively. An additional 100 wrist radiographs, comprising 50 "fracture" and 50 "no fracture" images, were used for final testing and statistical analysis.

RESULTS

The area under the receiver operator characteristic curve (AUC) for this test was 0.954. Setting the diagnostic cut-off at a threshold designed to maximise both sensitivity and specificity resulted in values of 0.9 and 0.88, respectively.

CONCLUSION

The AUC scores for this test were comparable to state-of-the-art providing proof of concept for transfer learning from CNNs in fracture detection on plain radiographs. This was achieved using only a moderate sample size. This technique is largely transferable, and therefore, has many potential applications in medical imaging, which may lead to significant improvements in workflow productivity and in clinical risk reduction.

Trafficking of phosphatidylinositol 3-phosphate from the trans-Golgi network to the lumen of the central vacuole in plant cells

Very limited information is available on the role of phosphatidylinositol 3-phosphate (PI[3]P) in vesicle trafficking in plant cells. To investigate the role of PI(3)P during the vesicle trafficking in plant cells, we exploited the PI(3)P-specific binding property of the endosome binding domain (EBD) (amino acids 1257 to 1411) of human early endosome antigen 1, which is involved in endosome fusion. When expressed transiently in Arabidopsis protoplasts, a green fluorescent protein (GFP):EBD fusion protein exhibited PI(3)P-dependent localization to various compartments--such as the trans-Golgi network, the prevacuolar compartment, the tonoplasts, and the vesicles in the vacuolar lumen--that varied with time. The internalized GFP:EBD eventually disappeared from the lumen. Deletion experiments revealed that the PI(3)P-dependent localization required the Rab5 binding motif in addition to the zinc finger motif. Overexpression of GFP:EBD inhibited vacuolar trafficking of sporamin but not trafficking of H(+)-ATPase to the plasma membrane. On the basis of these results, we propose that the trafficking of GFP:EBD reflects that of PI(3)P and that PI(3)P synthesized at the trans-Golgi network is transported to the vacuole through the prevacuolar compartment for degradation in plant cells.

Rebleeding leads to poor outcome in ultra-early craniotomy for intracerebral hemorrhage

BACKGROUND

A modest benefit was previously demonstrated for hematoma evacuation within 12 hours of intracerebral hemorrhage onset. Perhaps surgery within 4 hours would further improve outcome.

METHODS

Adult patients with spontaneous supratentorial intracerebral hemorrhage were prospectively enrolled. Craniotomy and clot evacuation were commenced within 4 hours of symptom onset in all cases. Mortality and functional outcome were assessed at 6 months. This group of patients was compared with patients treated within 12 hours of symptom onset using the same surgical and medical protocols.

RESULTS

The study was stopped after a planned interim analysis of 11 patients in the 4-hour surgery arm. Median time to surgery was 180 minutes; median hematoma volume was 40 mL; median baseline NIH Stroke Scale score was 19 and Glasgow Coma Scale score was 12. Six-month mortality was 36% and median Barthel score was 75 in survivors. Postoperative rebleeding occurred in four patients, three of whom died. A relationship between postoperative rebleeding and mortality was apparent (p = 0.03). Rebleeding occurred in 40% of the patients treated within 4 hours, compared with 12% of the patients treated within 12 hours (p = 0.11). There was a clear correlation between improved outcome and smaller postsurgical hematoma volume (p = 0.04).

CONCLUSIONS

Surgical hematoma evacuation within 4 hours of symptom onset is complicated by rebleeding, indicating difficulty with hemostasis. Maximum removal of blood remains a predictor of good outcome.

Constitutive beta-glucosidases hydrolyzing ginsenoside Rb1 and Rb2 from human intestinal bacteria

When ginsenoside Rb1 and Rb2 were anaerobically incubated with human intestinal microflora, these ginsenosides were metabolized to 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol (compound K) and 20(S)-protopanaxadiol. Several kinds of intestinal bacteria hydrolyzed these ginsenosides. Eubacterium sp., Streptococcus sp. and Bifidobacterium sp., which more potently hydrolyzed gentiobiose than sophorose, metabolized ginsenoside Rb1 to compound K via ginsenoside Rd rather than gypenoside XVII. However, Fusobacterium K-60, which more potently hydrolyzed sophorose than gentiobiose, metabolized to compound K via gypenoside XVII. Ginsenoside Rb2 was also metabolized to compound K via ginsenoside Rd or compound O by human intestinal microflora. Eubacterium sp., Streptococcus sp. and Bifidobacterium sp. metabolized ginsenoside Rb2 to compound K via ginsenoside Rd rather than compound O. Fusobacterium K-60 metabolized ginsenoside Rb2 to compound K via compound O.

In vitro inhibition of dihydropyridine oxidation and aflatoxin B1 activation in human liver microsomes by naringenin and other flavonoids

Recent in vivo studies in humans have shown a dramatic effect of grapefruit juice in blocking the oxidation of dihydropyridine calcium channel blockers. The flavonoid naringin is the most abundant natural product specific for grapefruit and related citrus--the aglycone naringenin, known to be readily formed from naringin in humans, was found to inhibit the oxidation of the dihydropyridines nifedipine and felodipine in human liver microsomal preparations. These observations were of interest in light of the knowledge that the same human liver cytochrome P450 (IIIA4) appears to be a major catalyst in both nifedipine oxidation and aflatoxin B1 activation. Several flavones inhibited the in vitro activation of aflatoxin B1 in a system employing umuC gene activation due to DNA damage in Salmonella typhimurium TA1535/pSK1002, with naringenin being as effective as any. The high concentration of derivatives of naringenin in certain citrus fruits may be of relevance to cancer chemoprevention involving those carcinogens that are activated by cytochrome P-450IIIA4.

Molecular inflammation as an underlying mechanism of the aging process and age-related diseases

Aging is a biological process characterized by time-dependent functional declines that are influenced by changes in redox status and by oxidative stress-induced inflammatory reactions. An organism's pro-inflammatory status may underlie the aging process and age-related diseases. In this review, we explore the molecular basis of low-grade, unresolved, subclinical inflammation as a major risk factor for exacerbating the aging process and age-related diseases. We focus on the redox-sensitive transcription factors, NF-κB and FOXO, which play essential roles in the expression of pro-inflammatory mediators and anti-oxidant enzymes, respectively. Major players in molecular inflammation are discussed with respect to the age-related up-regulation of pro-inflammatory cytokines and adhesion molecules, cyclo-oxygenase-2, lipoxygenase, and inducible nitric oxide synthase. The molecular inflammation hypothesis proposed by our laboratory is briefly described to give further molecular insights into the intricate interplay among redox balance, pro-inflammatory gene activation, and chronic age-related inflammatory diseases. The final section discusses calorie restriction as an aging-retarding intervention that also exhibits extraordinarily effective anti-inflammatory activity by modulating GSH redox, NF-κB, SIRT1, PPARs, and FOXOs.

A metal complex that binds alpha-amino acids with high and predictable stereospecificity

Molecular recognition is the key step in a wide range of controlled separation and chemical transformation processes, with enzymes performing this task with an unsurpassed degree of selectivity. Enzymes contain only 20 simple amino acids, yet it remains difficult to rationalize or even predict these stereospecific recognition events. Nonetheless, the rational design of receptors able to recognize amino acids stereospecifically is attracting considerable interest because therapeutic drugs, that may be developed from chiral amino acid intermediates, are increasingly required in enantiomerically pure form. Early work has stimulated the development of efficient receptors based on small molecules, but binding of amino acids with high and predictable stereospecificity remains difficult to achieve. Directed molecular evolution, on the other hand, does select for RNA sequences or antibodies that bind amino acids with high specificity, but typically without providing insights into the molecular recognition mechanisms involved. Here we show that a rationally designed metal complex formed from a trivalent cobalt ion and a tetradentate ligand binds natural amino acids, including the simple yet challenging amino acid alanine, with high and predictable regio- and stereospecificity. We expect that our approach will allow the binding as well as separation and stereospecific catalytic formation of its target amino acids.

Soluble intracellular adhesion molecule-1 secreted by human umbilical cord blood-derived mesenchymal stem cell reduces amyloid-β plaques

Presently, co-culture of human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) with BV2 microglia under amyloid-β42 (Aβ42) exposure induced a reduction of Aβ42 in the medium as well as an overexpression of the Aβ-degrading enzyme neprilysin (NEP) in microglia. Cytokine array examinations of co-cultured media revealed elevated release of soluble intracellular adhesion molecule-1 (sICAM-1) from hUCB-MSCs. Administration of human recombinant ICAM-1 in BV2 cells and wild-type mice brains induced NEP expression in time- and dose-dependent manners. In co-culturing with BV2 cells under Aβ42 exposure, knockdown of ICAM-1 expression on hUCB-MSCs by small interfering RNA (siRNA) abolished the induction of NEP in BV2 cells as well as reduction of added Aβ42 in the co-cultured media. By contrast, siRNA-mediated inhibition of the sICAM-1 receptor, lymphocyte function-associated antigen-1 (LFA-1), on BV2 cells reduced NEP expression by ICAM-1 exposure. When hUCB-MSCs were transplanted into the hippocampus of a 10-month-old transgenic mouse model of Alzheimer's disease for 10, 20, or 40 days, NEP expression was increased in the mice brains. Moreover, Aβ42 plaques in the hippocampus and other regions were decreased by active migration of hUCB-MSCs toward Aβ deposits. These data suggest that hUCB-MSC-derived sICAM-1 decreases Aβ plaques by inducing NEP expression in microglia through the sICAM-1/LFA-1 signaling pathway.

Characterization of a Cys115 to Asp substitution in the Escherichia coli cell wall biosynthetic enzyme UDP-GlcNAc enolpyruvyl transferase (MurA) that confers resistance to inactivation by the antibiotic fosfomycin

The antibiotic fosfomycin inhibits bacterial cell wall biosynthesis by inactivation of UDP-GlcNAc enolpyruvyl tranferase (MurA). Prior work has established that Cys115 of Escherichia coli and Enterobacter cloacae MurA is the active site nucleophile alkylated by fosfomycin and implicated this residue in the formation of a covalent phospholactyl-enzyme adduct derived from substrate, phosphoenolpyruvate (PEP). On the basis of sequencing information from putative MurA homolog from Mycobacterium tuberculosis, we generated a C115D mutant of E. coli MurA that was highly active but fully resistant to time-dependent inhibition by fosfomycin. Fosfomycin still bound to the active site of C115D MurA, as established by the observed reversible competitive inhibition by fosfomycin. Fosfomycin still bound to the active site of C115D MurA, as established by the observed reversible competitive inhibition vs PEP. In contrast to the broad pH-independent behavior of wild-type (WT) MurA, C115D mutant activity titrated across the pH range examined (pH 5.5-9) with an apparent pKa approximately 6, with kcatC115D ranging from approximately 10kcatWT at pH 5.5 to <0.1kcatWT at pH9.0. Km(PEP)115D was relatively constant in the pH range examined and increased approximately 100-fold relative to Km(PEP)WT. A fosfomycin-resistant C115E mutant with -1% activity of the C115D mutant was found to follow a pH dependence similar to that observed for C115D MurA. The contrasting pH dependences of WT and C115D MurA was also observed in the reaction with the pseudosubstrate, (Z)-3-fluorophosphoenolpyruvate, strongly suggesting a role for Cys/Asp115 as the general acid in the protonation of C-3 of PEP during MurA-catalyzed enol ether transfer. The difference in nucleophilicity between the carboxylate side chains of Asp115 and Glu115 and the thiolate group of Cys115 suggests that covalent enzyme adduct formation is not required for catalytic turnover and, furthermore, provides a chemical rationale for the resistance of the C115D and C115E mutants to fosfomycin inactivation.

Light and brassinosteroid signals are integrated via a dark-induced small G protein in etiolated seedling growth

Plant growth and development are regulated through coordinated interactions between light and phytohormones. Here, we demonstrate that a dark-induced small G protein, pea Pra2, regulates a variant cytochrome P450 that catalyzes C-2 hydroxylation in brassinosteroid biosynthesis. The cytochrome P450 is dark-induced and predominantly expressed in the rapidly elongating zone of etiolated pea epicotyls, where Pra2 is also most abundant. Transgenic plants with reduced Pra2 exhibit a dark-specific dwarfism, which is completely rescued by exogenous brassinolide. Overexpression of the cytochrome P450 results in enhanced hypocotyl growth even in the light, which phenocopies the etiolated hypocotyls. We therefore propose that Pra2 and its orthologs are molecular mediators for the cross-talk between light and brassinosteroids in the etiolation process in plants.

Analysis of multigenerational families with thoracic aortic aneurysms and dissections due to TGFBR1 or TGFBR2 mutations

BACKGROUND

Mutations in the transforming growth factor beta receptor type I and II genes (TGFBR1 and TGFBR2) cause Loeys-Dietz syndrome (LDS), characterised by thoracic aortic aneurysms and dissections (TAAD), aneurysms and dissections of other arteries, craniosynostosis, cleft palate/bifid uvula, hypertelorism, congenital heart defects, arterial tortuosity, and mental retardation. TGFBR2 mutations can also cause TAAD in the absence of features of LDS in large multigenerational families, yet only sporadic LDS cases or parent-child pairs with TGFBR1 mutations have been reported to date.

METHODS

The authors identified TGFBR1 missense mutations in multigenerational families with TAAD by DNA sequencing. Clinical features of affected individuals were assessed and compared with clinical features of previously described TGFBR2 families.

RESULTS

Statistical analyses of the clinical features of the TGFBR1 cohort (n = 30) were compared with clinical features of TGFBR2 cohort (n = 77). Significant differences were identified in clinical presentation and survival based on gender in TGFBR1 families but not in TGFBR2 families. In families with TGFBR1 mutations, men died younger than women based on Kaplan-Meier survival curves. In addition, men presented with TAAD and women often presented with dissections and aneurysms of arteries other than the ascending thoracic aorta. The data also suggest that individuals with TGFBR2 mutations are more likely to dissect at aortic diameters <5.0 cm than individuals with TGFBR1 mutations.

CONCLUSION

This study is the first to demonstrate clinical differences between patients with TGFBR1 and TGFBR2 mutations. These differences are important for the clinical management and outcome of vascular diseases in these patients.

Intestinal bacterial beta-glucuronidase activity of patients with colon cancer

The fecal beta-glucuronidase activity of patients with colon cancer and healthy controls were measured to determine the relationship between the fluctuation of intestinal bacterial beta-glucuronidase and colon cancer. The fecal beta-glucuronidase activity of patients with colon cancer was 1.7 times higher than that of the healthy controls. However, when these fecal specimens were sonicated, the enzyme activity of patients with colon cancer was 12.1 times higher than that of the healthy controls. The fecal beta-glucuronidase activity of human intestinal bacteria was drastically induced by its substrate or the bile secreted after a subcutaneous injection of 1,2-dimethylhydrazine (DMH) and benzo[a]pyrene into rats. DMH- and benzo[a]pyrene-treated biles induced beta-glucuronidase activity in the human intestinal microflora by approximately 1.5- and 2.3-fold, respectively. They also induced beta-glucuronidase in E. coli HGU-3, which is a beta-glucuronidase-producing bacterium from the human intestine. D-saccharic acid 1,4-lactone similarly inhibited fecal beta-glucuronidase in several patients with colon cancer in addition to the healthy controls. This suggests that potent beta-glucuronidase activity is a prime factor in the etiology of colon cancer.

Identification of a signal that distinguishes between the chloroplast outer envelope membrane and the endomembrane system in vivo

Certain small outer envelope membrane proteins of chloroplasts are encoded by the nuclear genome without a cleavable N-terminal transit peptide. We investigated in vivo the targeting mechanism of AtOEP7, an Arabidopsis homolog of the small outer envelope membrane protein. AtOEP7 was expressed as a fusion protein with the green fluorescent protein (GFP) either transiently in protoplasts or stably in transgenic plants. In either case, fluorescence microscopy of transformed cells and protein gel blot analysis of fractionated proteins confirmed that the AtOEP7:GFP fusion protein was targeted to the chloroplast outer envelope membrane. In vivo targeting experiments revealed that two regions, the transmembrane domain (TMD) and its C-terminal neighboring seven-amino acid region, were necessary and sufficient for targeting to the chloroplast outer membrane. Substitution of aspartic acid or lysine residues with glycine residues or scrambling of the amino acid sequence of the seven-amino acid region caused mistargeting to the plasma membrane. Although the amino acid sequence of the TMD is not important for targeting, amino acid residues with large side chains inhibited targeting to the chloroplasts and resulted in the formation of large aggregates in the protoplasts. In addition, introduction of a proline residue within the TMD resulted in inhibition of targeting. Finally, a fusion protein, AtOEP7:NLS:GFP, was targeted efficiently to the chloroplast envelope membranes despite the presence of a nuclear localization signal. On the basis of these results, we conclude that the seven-amino acid region and the TMD are determinants for targeting to the chloroplast outer envelope membrane. The seven-amino acid region plays a critical role in AtOEP7 evading the endomembrane system and entering the chloroplast pathway, and the TMD plays critical roles in migration to the chloroplasts and/or subsequent insertion into the membrane.

Minimizing artifacts caused by metallic implants at MR imaging: experimental and clinical studies

OBJECTIVE

The purpose of this study was to investigate the effect of metallic implant positioning on MR imaging artifacts, to determine the optimal imaging conditions for minimizing artifacts, and to show the usefulness of artifact-minimizing methods in imaging of the knee.

MATERIALS AND METHODS

Using MR images of experimental phantoms (titanium alloy and stainless steel screws), we compared the magnitude of metal-induced artifacts for various pulse sequences, different imaging parameters for the fast spin-echo sequence, and different imaging parameters for several incremental angles between the long axis of the screw and the direction of the main magnetic field. In clinical MR imaging of knees with metallic implants (n = 19), we assessed geometric distortion of anatomic structures to compare the influence of different pulse sequences (n = 19), frequency-encoding directions (n = 7), and knee positions (n = 15).

RESULTS

Titanium alloy screws consistently produced smaller artifacts than did stainless steel screws. In experimental MR studies, artifacts were reduced with fast spin-echo sequences, with a screw orientation as closely parallel to the main magnetic field as possible, and, particularly, with smaller voxels that correlated positively with artifact size (R2 = .88, p < .01). In clinical MR studies, fast spin-echo MR imaging obscured articular structures less than did spin-echo imaging (8/19 patients). In particular, the anterior-posterior frequency-encoding direction (3/7 patients) and the flexion position of the knee (5/15 patients) were effective in reducing artifacts.

CONCLUSION

MR artifacts can be minimized by optimally positioning in the magnet subjects with metallic implants and by choosing fast spin-echo sequences with an anterior-posterior frequency-encoding direction and the smallest voxel size.

Enzymatic oxidation of ethyl carbamate to vinyl carbamate and its role as an intermediate in the formation of 1,N6-ethenoadenosine

The carcinogen ethyl carbamate has been postulated to be activated by oxidation to vinyl carbamate and then to an epoxide which can react with nucleic acids [Dahl, G.A., Miller, J. A., and Miller, E. C. (1978) Cancer Res. 38, 3793-3804]. To date, the enzymatic conversion of ethyl carbamate to vinyl carbamate had not been demonstrated. Recently, we obtained evidence that the same cytochrome P-450 enzyme (P-450 2E1) is involved in the oxidation of both ethyl carbamate and vinyl carbamate [Guengerich, F. P., Kim, D.-H., and Iwasaki, M. (1991) Chem. Res. Toxicol. 4, 168-179]. When human liver microsomes were incubated with NADPH and ethyl carbamate, the products vinyl carbamate, 2-hydroxyethyl carbamate, and ethyl N-hydroxycarbamate were detected by use of (a) combined capillary gas chromatography/chemical ionization mass spectrometry or (b) high-performance liquid chromatography of radioactive materials. A Km of approximately 54 microM was estimated for the conversion of vinyl carbamate to 1,N6-ethenoadenosine (in the presence of adenosine), but when the reaction was done with ethyl carbamate as the substrate, the rate of product formation was nearly first order in ethyl carbamate concentration (Km greater than 2 mM) and the rate was considerably slower than in the case of vinyl carbamate. The model derived with these parameters predicts a steady-state level of 0.22 microM vinyl carbamate, consonant with the value of approximately 0.2 microM estimated experimentally. A large kinetic deuterium isotope effect (greater than 7) was observed for the formation of 1,N6-ethenoadenosine from ethyl carbamate, and high isotope effects (6-8) were also noted for the formation of vinyl carbamate and 2-hydroxyethyl carbamate.(ABSTRACT TRUNCATED AT 250 WORDS)

A ginseng metabolite, compound K, induces autophagy and apoptosis via generation of reactive oxygen species and activation of JNK in human colon cancer cells

Compound K (20-O-(β-D-glucopyranosyl)-20(S)-protopanaxadiol) is an active metabolite of ginsenosides and induces apoptosis in various types of cancer cells. This study investigated the role of autophagy in compound K-induced cell death of human HCT-116 colon cancer cells. Compound K activated an autophagy pathway characterized by the accumulation of vesicles, the increased positive acridine orange-stained cells, the accumulation of LC3-II, and the elevation of autophagic flux. Whereas blockade of compound K-induced autophagy by 3-methyladenein and bafilomycin A1 significantly increased cell viability. In addition, compound K augmented the time-dependent expression of the autophagy-related proteins Atg5, Atg6, and Atg7. However, knockdown of Atg5, Atg6, and Atg7 markedly inhibited the detrimental impact of compound K on LC3-II accumulation and cell vitality. Compound K-provoked autophagy was also linked to the generation of intracellular reactive oxygen species (ROS); both of these processes were mitigated by the pre-treatment of cells with the antioxidant N-acetylcysteine. Moreover, compound K activated the c-Jun NH2-terminal kinase (JNK) signaling pathway, whereas downregulation of JNK by its specific inhibitor SP600125 or by small interfering RNA against JNK attenuated autophagy-mediated cell death in response to compound K. Compound K also provoked apoptosis, as evidenced by an increased number of apoptotic bodies and sub-G1 hypodiploid cells, enhanced activation of caspase-3 and caspase-9, and modulation of Bcl-2 and Bcl-2-associated X protein expression. Notably, compound K-stimulated autophagy as well as apoptosis was induced by disrupting the interaction between Atg6 and Bcl-2. Taken together, these results indicate that the induction of autophagy and apoptosis by compound K is mediated through ROS generation and JNK activation in human colon cancer cells.

Anti-Helicobacter pylori activity of herbal medicines

The extracts of Coptidis japonica (rhizoma), Eugenia caryophyllata (flower), Rheum palmatum (rhizoma), Magnolia officinalis (cortex) and Rhusjavanica (galla rhois) potently inhibited the growth of Helicobacter pylori (HP). However, these herbal extracts showed no inhibitory effect on HP urease except Galla rhois. Among the components separated from active herbal extracts by silica gel column chromatography, the inhibitory effects of decursinol angelate and decursin on the growth of HP were the most potent, followed by magnolol, berberine, cinnamic acid, decursinol and gallic acid. Minimum inhibitory concentrations (MICs) of decursin and decursinol angelate were 6-20 microg/ml.