Contribution of CD95 ligand-induced neutrophil infiltration to the bystander effect in p53 gene therapy for human cancer

Clinical trials of adenoviral p53 gene therapy provide the evidence that the bystander effect induced by the wild-type p53 gene transfer on adjacent tumor cells contributes to tumor progression; its mechanism, however, remains uncharacterized. We report in this work that injection of adenovirus expressing the human wild-type p53 gene (Ad5CMVp53) into established human colorectal tumors in nu/nu mice resulted in CD95 ligand (CD95L) overexpression, followed by a massive neutrophil infiltration. Culture supernatants of human colorectal cancer cells infected with Ad5CMVp53 exhibited a potent chemotactic activity against murine polymorphonuclear neutrophils, which could be abolished by the anti-CD95L mAb (NOK-1). In vivo cell depletion experiments indicated that neutrophils were in part responsible for the antitumor effect of the Ad5CMVp53 infection. Our data directly suggest that overexpression of CD95L by the wild-type p53 gene transfer induces neutrophil infiltration into human colorectal tumors, which may play a critical role in the bystander effect of p53 gene therapy.

Celecoxib prevents tumor growth in vivo without toxicity to normal gut: lack of correlation between in vitro and in vivo models

Nonsteroidal anti-inflammatory drugs have potential for use in the prevention and/or treatment of colorectal cancer. We have studied the cytotoxic effect of a specific COX-2 inhibitor, celecoxib, against LLC, HCA-7, and HCT-15 cells grown in cell culture and have compared these results with its effect on HCA-7 cells grown as xenografts in nude mice. "High-dose" celecoxib (>20 microM) reduced the viability of all three cell lines in vitro as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometric analysis demonstrated that this loss of viability was attributable to the induction of apoptosis. Significantly, concentrations of the drug <10 microM had no effect on cell viability in vitro. The cytotoxic effects of high-dose celecoxib were independent of COX-2 inhibition because similar effects were observed in cox-2 (+/+), cox-2 (+/-) and cox-2 (-/-) fibroblasts. A plasma concentration of 2.3+/-0.7 microM was achieved when celecoxib (1250 mg/kg of chow) was fed to animals ad libitum. Despite a lack of toxicity at 2-3 microM celecoxib in vitro, there was attenuation of HCA-7 xenograft growth in vivo. Celecoxib had no effect on apoptosis, cell division, or the epithelial architecture of the normal gut in treated mice. These results support the need for additional clinical evaluation of celecoxib for treatment and/or prevention of colorectal cancer in humans.

Posttranscriptional regulation of cyclooxygenase-2 in rat intestinal epithelial cells

Modulation of cyclooxygenase-2 (COX-2) mRNA stability plays an important role in the regulation of its expression by oncogenic Ras. Here, we evaluate COX-2 mRNA stability in response to treatment with two known endogenous promoters of gastrointestinal cancer, the bile acid (chenodeoxycholate; CD) and ceramide. Treatment with CD and ceramide resulted in a 10-fold increase in the level of COX-2 protein and a four-fold lengthening of the half-life of COX-2 mRNA. COX-2 mRNA stability was assessed by Northern blot analysis and by evaluating the AU-rich element located in the COX-2 3'-UTR. A known inhibitor of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK), PD98059, reversed the effects of CD or ceramide to stabilize COX-2 mRNA. Overexpression of a dominant-negative ERK-1 or ERK-2 protein also led to destabilization of COX-2 mRNA. Treatment with a p38 MAPK inhibitor, PD169316, or transfection with a dominant-negative p38 MAPK construct reversed the effect of CD or ceramide to stabilize COX-2 mRNA. Expression of a dominant-negative c-Jun N-terminal kinase (JNK) had no effect on COX-2 mRNA stability in cells treated with CD or ceramide. We conclude that posttranscriptional mechanisms play an important role in the regulation of COX-2 expression during carcinogenesis.

Vanadate enhances but does not normalize glucose transport and insulin receptor phosphorylation in skeletal muscle from obese women with gestational diabetes mellitus

OBJECTIVE

We compared the insulin-mimetic effects of vanadate, a protein-tyrosine phosphatase inhibitor, with the effects of insulin on skeletal muscle glucose transport and insulin receptor and insulin receptor substrate 1 phosphorylation to test the hypothesis that protein-tyrosine phosphatases participate in pregnancy-induced insulin resistance.

STUDY DESIGN

Skeletal muscle fiber strips were obtained from the rectus abdominis during cesarean delivery in 7 patients with gestational diabetes mellitus, 11 pregnant women with normal glucose tolerance (pregnant control group), and 11 nonpregnant women undergoing elective surgery (nonpregnant control group). Muscle tissues were incubated in vitro for 15 to 60 minutes with or without maximal insulin (100 nmol/L) or sodium vanadate (6 micromol/L). Insulin receptor and insulin receptor substrate 1 tyrosine phosphorylation were measured, as was 2-deoxyglucose transport. The levels of protein-tyrosine phosphatase 1B were measured by Western blot analysis.

RESULTS

Vanadate stimulated maximal 2-deoxyglucose transport more than did insulin alone in all samples (P<.05), but the value was still less in muscle tissues from pregnant control subjects and patients with gestational diabetes mellitus (P<.05). In muscle tissues from pregnant control subjects vanadate increased tyrosine phosphorylation of the insulin receptor and insulin receptor substrate 1 to levels similar to those in muscle tissues from nonpregnant control subjects. In patients with gestational diabetes mellitus vanadate increased insulin receptor and insulin receptor substrate 1 tyrosine phosphorylation, but these values remained less than in muscle tissues from nonpregnant control subjects (P<.05). Protein-tyrosine phosphatase 1B levels were not significantly different in skeletal muscles from each group.

CONCLUSION

Vanadate did not restore normal glucose transport activity during pregnancy complicated by gestational diabetes mellitus, which indicates that decreased glucose uptake is probably not caused by impaired tyrosine phosphorylation events alone. Increased serine kinase activity and impaired glucose transporter 4 translocation probably contribute to insulin signaling abnormalities associated with pregnancy, especially in patients with gestational diabetes mellitus.

The bootstrap procedure in individual bioequivalence

A bootstrap-type hypothesis test procedure for assessing individual (or population) bioequivalence between two drug formulations is suggested in a draft guidance from the United States Food and Drug Administration (FDA). The purpose of this article is to study the unknown properties of this test procedure and propose some improved test procedures. We find that: the FDA's bootstrap computation is not correct; the power of the FDA's test can be very low; the use of the REML method suggested in the draft guidance does not have any advantage over the use of simpler methods such as the moment method; and the method of sample size determination in the draft guidance is inappropriate. We study the size and power of different bootstrap test procedures and suggest a method for sample size determination. It is our hope that this article will draw some attention to further research in this area, and eventually a satisfactory statistical method can be implemented for assessing individual (or population) bioequivalence.

Regulation of constitutive cyclooxygenase-2 expression in colon carcinoma cells

Cyclooxygenase-2 (COX-2) is not normally expressed in the human large intestine, but its levels are increased in the majority of human colorectal carcinomas. Here we investigate the regulation of constitutive COX-2 expression and prostaglandin production in human colorectal carcinoma cells. Both COX-2 mRNA and protein were expressed in well differentiated HCA-7, Moser, LS-174, and HT-29 cells, albeit at different levels. COX-2 expression was not detected in several poorly differentiated colon cancer cell lines including DLD-1. Transcriptional regulation played a key role for the expression of COX-2 in human colon carcinoma cells, and both the nuclear factor for interleukin-6 regulatory element and the cAMP-response element were responsible for regulation of COX-2 transcription. COX-2 mRNA was more stable in HCA-7 cells than in the other cell lines tested. Both transcriptional and post-transcriptional regulation of COX-2 involved the MAP kinase pathway. Modulation of the Akt/protein kinase B or Rho B signaling pathways altered the levels of COX-2 expression. Furthermore, COX-2 protein is degraded through ubiquitin proteolysis, and its half-life was approximately 3.5-8 h. HCA-7 cells produced significant quantities of prostaglandin E(2) and other prostaglandins. Moser and LS-174 cells also generated prostaglandins, but levels were significantly lower than that observed in HCA-7 cells.

Full-length GB virus C (Hepatitis G virus) RNA transcripts are infectious in primary CD4-positive T cells

GB virus C (GBV-C or hepatitis G virus) is a recently described flavivirus which frequently leads to chronic viremia in humans. Although GBV-C is associated with acute posttransfusion hepatitis, it is not clear if the virus is pathogenic for humans. We constructed a full-length cDNA from the plasma of a person with chronic GBV-C viremia. Peripheral blood mononuclear cells (PBMCs) transfected with full-length RNA transcripts from this GBV-C clone resulted in viral replication. This was demonstrated by serial passage of virus from cell culture supernatants, detection of increasing concentrations of positive- and negative-sense GBV-C RNA over time, and the detection of the GBV-C E2 antigen by confocal microscopy. In addition, two types of GBV-C particles were identified in cell lysates; these particles had buoyant densities of 1.06 and 1.12 to 1.17 g/ml in sucrose gradients. PBMCs sorted for expression of CD4 contained 100-fold-more GBV-C RNA than CD4-negative cells. Taken together, these data demonstrate that RNA transcripts from GBV-C full-length cDNA are infectious in primary CD4-positive T cells. In contrast, RNA transcripts from an infectious hepatitis C virus clone did not replicate in the same cell culture system. Infectious RNA transcripts from GBV-C cDNA should prove useful for studying viral replication and may allow identification of differences between GBV-C and hepatitis C virus cultivation in vitro.

Expression of intrinsic factor in rat and murine gastric mucosal cell lineages is modified by inflammation

Intrinsic factor is produced primarily by chief cells in rat and mouse, but 4 to 11% of isolated rat parietal cells also contain intrinsic factor. To test whether local conditions could alter the distribution of intrinsic factor expression, two rodent models of chronic lymphocytic gastric inflammation were examined. Immunocytochemistry was performed using antiserum against human intrinsic factor and H/K ATPase (a parietal cell marker), counting the percent of intrinsic factor-positive parietal cells. HLA-B27 transgenic rats develop chronic gastritis at age 3 months. Congenic controls expressed intrinsic factor in 8.9 +/- 3.8% (mean +/- SD) of parietal cells; in inflamed areas of transgenic rats 21 +/- 5.2% (P < 0.0001) of parietal cells were positive. In adjacent areas without inflammatory infiltrate 16 +/- 3.6% of parietal cells contained intrinsic factor. C57BL/6 mice inoculated with Helicobacter felis develop gastritis by 4 weeks. After 4 and 8 weeks of infection, intrinsic factor-positive parietal cells increased from 7.8 +/- 2.8% in the congenic controls to 17.6 +/- 4.1% in the inflamed gastric body (P < 0.0001). Isolated rat parietal cells incubated with interleukin-1beta demonstrated a twofold increase in intrinsic factor-positive parietal cells. These studies are consistent with the concept that intrinsic factor expression is both predetermined in chief cells and can be expressed in parietal cells in response to local inflammatory factors. The differences between inflamed and adjacent noninflamed areas in the rat model suggest a tissue gradient of soluble inducer(s), possibly cytokines.

Decreased Akt kinase activity and insulin resistance in C57BL/KsJ-Leprdb/db mice

Recent studies suggest that the serine/threonine kinase protein kinase B (PKB or Akt) is involved in the pathway for insulin-stimulated glucose transporter 4 (GLUT4) translocation and glucose uptake. In this study we examined the components of the Akt signaling pathway in skeletal muscle and adipose tissue in vivo from C57BL/KsJ-Lepr(db/db) mice (db/db), a model of obesity, insulin resistance, and type II diabetes. There were no changes in the protein levels of GLUT4, p85alpha, or Akt in tissues from db/db mice compared with non-diabetic littermate controls (+/+). In response to acute insulin administration, GLUT4 recruitment to the plasma membrane increased twofold in muscle and adipose tissue from +/+ mice, but was significantly reduced by 42-43% (P<0.05) in both tissues from db/db mice. Insulin increased Akt-Ser(473) phosphorylation by two- to fivefold in muscle and adipose tissue from all mice. However, in db/db mice, maximal Akt-Ser(473) phosphorylation was decreased by 32% (P<0.05) and 69% (P<0.05) in muscle and adipose tissue respectively. This decreased phosphorylation in db/db mice corresponded with a significant decrease in maximal Akt kinase activity using a glycogen synthase kinase-3 fusion protein as a substrate (P<0.05). The level of insulin-stimulated tyrosine phosphorylation of p85alpha from phosphatidylinositol 3 (PI 3)-kinase, which is upstream of Akt, was also reduced in muscle and adipose tissue from db/db mice (P<0.05); however, there was no change in extracellular signal-regulated kinase-1 or -2 phosphorylation. These data implicate decreased insulin-stimulated Akt kinase activity as an important component underlying impaired GLUT4 translocation and insulin resistance in tissues from db/db mice. However, impaired insulin signal transduction appears to be specific for the PI 3-kinase pathway of insulin signaling, while the MAP kinase pathway remained intact.

Human coronavirus 229E infects polarized airway epithelia from the apical surface

Gene transfer to differentiated airway epithelia with existing viral vectors is very inefficient when they are applied to the apical surface. This largely reflects the polarized distribution of receptors on the basolateral surface. To identify new receptor-ligand interactions that might be used to redirect vectors to the apical surface, we investigated the process of infection of airway epithelial cells by human coronavirus 229E (HCoV-229E), a common cause of respiratory tract infections. Using immunohistochemistry, we found the receptor for HCoV-229E (CD13 or aminopeptidase N) localized mainly to the apical surface of airway epithelia. When HCoV-229E was applied to the apical or basolateral surface of well-differentiated primary cultures of human airway epithelia, infection primarily occurred from the apical side. Similar results were noted when the virus was applied to cultured human tracheal explants. Newly synthesized virions were released mainly to the apical side. Thus, HCoV-229E preferentially infects human airway epithelia from the apical surface. The spike glycoprotein that mediates HCoV-229E binding and fusion to CD13 is a candidate for pseudotyping retroviral envelopes or modifying other viral vectors.

Deletion of chromosomes 9p and 17 associated with abnormal expression of p53, p16/MTS1 and p15/MTS2 gene protein in hepatocellular carcinomas

OBJECTIVE

Fifteen loci on chromosome 9p and 17 were analyzed to clarify the involvement of loss of heterozygosity (LOH) in hepatocellular carcinoma (HCC) in Chinese patients positive for hepatitis B (HBV) and/or hepatitis C (HCV) infection. Expression of tumor suppressor genes (TSG) of p53, p16, and p15 gene was found to correlate with a deletion of these genes.

METHODS

Immunohistochemistry and PCR-based microsatellite polymorphism analysis techniques were used.

RESULTS

A high frequency of LOH was detected on chromosome 9p24 at locus D9S54 (61.8%) and 9p21, concentrated at loci D9S1747 (52.4%) and D9S1752 (51.8%). On chromosome 17, high frequent LOH was concentrated on 17p at the p53 gene locus (53.8%) and locus D17S520 (52.8%). p53 protein expression was increased in HCC, which correlated with p53 gene loss. Expression of p16 and p15 protein decreased in HCC when LOH occurred at locus D9S1752 (p15 gene locus) or at locus D9S1747 and D9S1748 (p16 gene is located between these 2 loci). LOH at the p53 gene and p15 gene loci was closely associated with HBV and HCV co-infection in HCC. No significant relationship between LOH and HCC clinico-pathological outcomes was observed.

CONCLUSION

High frequency LOH occurs on chromosomes 9p and 17 in HCC in Chinese patients. Such sites may contain several putative tumor suppressor genes critically involved in the development and/or progression of HCC. Deletion of p53, p16, or p15 tumor suppressor genes may cause abnormal expression of the protein product of these genes. HBV and/or HCV infection may be closely associated with LOH p53 and/or p15 gene expression.

p50(Cdc37) can buffer the temperature-sensitive properties of a mutant of Hck

Genetic studies have previously revealed that Cdc37p is required for the catalytic competence of v-Src in yeast. We have reasoned that temperature-sensitive mutants of Src family kinases might be more sensitive to the cellular level of p50(Cdc37), the mammalian homolog of Cdc37p, than their wild-type counterpart, thus potentially providing a unique opportunity to elucidate the involvement of p50(Cdc37) in the folding and stabilization of Src family kinases. A temperature-sensitive mutant of a constitutively active form of Hck (i.e., tsHck499F) was created by mutating two amino acids within the kinase domain of Hck499F. Significantly, overexpression of p50(Cdc37) rescues the catalytic activity of tsHck499F at 33 degrees C, while partially buffering it against inactivation at higher temperatures (e.g., 37 and 39 degrees C). Hsp90 function is required for tsHck499F activity and its stabilization by p50(Cdc37), but overexpression of Hsp90 is not sufficient to stabilize tsHck499F. Overexpression of p50(Cdc37) promotes the association of tsHck499F with Hsp90, suggesting that the cellular level of p50(Cdc37) might be the rate-limiting step in the association of tsHck499F with Hsp90. A truncation mutant of p50(Cdc37) that cannot bind Hsp90 still has a limited capacity to rescue the catalytic activity of tsHck499F and promote its association with Hsp90. This is a particularly important observation, since it argues that rather than solely acting as a passive adapter protein to tether tsHck499F to Hsp90, p50(Cdc37) may also act allosterically to enhance the association of tsHck499F with Hsp90. The findings presented here might also have implications for our understanding of the evolution of protein kinases and tumor development.

V3 sequence analysis and biological characterization of HIV-1 isolates from asymptomatic and early symptomatic Tanzanian individuals

The aim of this study was to determine HIV-1 V3 sequences, in vitro biological characteristics and co-receptor usage of virus isolates from Tanzania. Virus was isolated from 14 of 17 samples investigated. Four of the isolates induced syncytia in MT-2 cells and used the CXCR4 co-receptor, while the remaining 10 isolates used the CCR5 co-receptor characteristic of non-MT-2 tropic viruses. One of the four MT-2 tropic isolates also used the CCR5 and CCR3 co-receptors. Proviral DNA was detected in all 14 isolates and PCR products were subjected to DNA sequencing. Unambiguous V3 amino acid sequences were obtained from 11 amplificates. Phylogenetic analysis indicated that these sequences were divergent and clustered in HIV-1 subtypes A, C or D. Sequences from the viruses that induced syncytia in MT-2 cells presented characteristic V3 phenotype-associated amino acids. Results of co-receptor analysis are in concordance with the isolate phenotype as determined by replication and induction of syncytia in MT-2 cells. The considerable diversity illustrated by a limited number of isolates from Tanzania is in accordance with reports from other regions of Africa.

Evidence of subtype B-like sequences in the V3 loop region of human immunodeficiency virus type 1 in Kilimanjaro, Tanzania

The aim of this study was to determine the nucleotide sequence of the third variable (V3) domain of HIV-1 gp120 from strains circulating in the Kilimanjaro region of Tanzania. DNA from this region was amplified from patient peripheral blood lymphocytes using polymerase chain reaction and then subjected to automated DNA sequencing. Subtype A, B, C, and D-like sequences were identified. Subtype B has not previously been described in Tanzania.

Oncogenic Ras-mediated cell growth arrest and apoptosis are associated with increased ubiquitin-dependent cyclin D1 degradation

The cellular responses to activated Ras vary depending on cell type. Normal cells are often induced into pathways that lead to cell growth arrest, senescence, and/or apoptosis in response to activated Ras expression. These are important protective anti-tumorigenic responses that restrict the propagation of cells bearing activated oncogenes. Here we show that induction of Ha-Ras(Val-12) in Rat-1 fibroblasts resulted in G(1) growth arrest and apoptosis with loss of viable cells that is accompanied by a marked decrease in cyclin D1 levels via increased ubiquitin-proteasome-dependent cyclin D1 turnover. This is in contrast with a rat intestinal epithelial cell line in which induction of Ha-Ras(Val-12) results in transformation associated with sustained proliferation and increased levels of cyclin D1, that is not accompanied by anoikis or apoptosis. Expression of the cyclin D1 mutant (T286A) that contains an alanine for threonine 286 substitution and is resistant to ubiquitin-proteasome degradation in the Ha-Ras(Val-12) expressing Rat-1 cells resulted in a sustained transformed phenotype with no accumulation of cells in G(1). Inhibition of mitogen-activated protein kinase (MEK1/2) pathway partially reversed the Ras-mediated decrease in cyclin D1. Induction of Ha-Ras(Val-12) resulted in activation of Akt kinase and inactivation of glycogen-synthase-3beta kinase that are associated with reduction of cyclin D1 protein. These results suggest that Ras-mediated cyclin D1 degradation in Rat-1 cells appears to be partially dependent on activation of mitogen-activated protein kinase pathway and independent of glycogen-synthase-3beta kinase pathway.

Induction of apoptosis in human esophageal cancer cells by sequential transfer of the wild-type p53 and E2F-1 genes: involvement of p53 accumulation via ARF-mediated MDM2 down-regulation

Transcriptional factor E2F-1 as well as tumor suppressor p53 have been shown to cause apoptosis independently in some types of human cancer cells when overexpressed. Here we report that sequential transfer of the wild-type p53 and E2F-1 genes efficiently induces apoptosis in human esophageal cancer cells and that E2F-1 overexpression directly, activates expression of p14 (ARF), which inhibits MDM2-mediated p53 degradation, resulting in the stabilization of p53. Infection of human esophageal cancer cell lines T.Tn and TE8 with adenovirus vector-expressing E2F-1 (Ad-E2F-1) enhanced mRNA and protein expression of ARF and decreased MDM2 protein expression. Transfection of ARF plasmid decreased MDM2 protein expression, which in turn increased p53 protein expression. Infection of T.Tn and TE8 cells first with adenovirus-expressing wild-type p53 (Ad-p53) and then with Ad-E2F-1 resulted in rapid induction of apoptosis; in contrast, simultaneous infection with Ad-E2F-1 and Ad-p53 had no significant antitumor effect. As shown by Western blot analysis, infection with suboptimal concentrations of Ad-E2F-1 induced the accumulation of exogenous p53 transduced by suboptimal concentrations of Ad-p53. Moreover, Ad-E2F-1-mediated ARF expression inhibited the up-regulation of MDM2 by overexpressed p53 in TE8 cells. Thus, overexpression of ectopic E2F-1 protein may stabilize endogenous as well as ectopic p53 protein via the E2F-1/ARF/MDM2/p53 regulatory pathway and, in this way, render cells more sensitive to apoptosis, an outcome that has important implications for the treatment of human esophageal cancers.

p50(cdc37) is a nonexclusive Hsp90 cohort which participates intimately in Hsp90-mediated folding of immature kinase molecules

Hsp90 and p50(cdc37) provide a poorly understood biochemical function essential to certain protein kinases, and recent models describe p50(cdc37) as an exclusive hsp90 cohort which links hsp90 machinery to client kinases. We describe here the recovery of p50(cdc37) in immunoadsorptions directed against the hsp90 cohorts FKBP52, cyp40, p60HOP, hsp70, and p23. Additionally, monoclonal antibodies against FKBP52 coadsorb maturation intermediates of the hsp90-dependent kinases p56(lck) and HRI, and the presence of these maturation intermediates significantly increases the representation of p50(cdc37) and hsp90 on FKPB52 machinery. Although the native heterocomplex between hsp90 and p50(cdc37) is salt-labile, their dynamic interactions with kinase substrates produce kinase-chaperone heterocomplexes which are highly salt-resistant. The hsp90 inhibitor geldanamycin does not directly disrupt the native association of hsp90 with p50(cdc37) per se, but does result in the formation of salt-labile hsp90-kinase heterocomplexes which lack the p50(cdc37) cohort. We conclude that p50(cdc37) does not simply serve as a passive structural bridge between hsp90 and its kinase substrates; instead, p50(cdc37) is a nonexclusive hsp90 cohort which responds to hsp90's nucleotide-regulated conformational switching during the generation of high-affinity interactions within the hsp90-kinase-p50(cdc37) heterocomplex.

Enhanced H(2)O(2)-induced cytotoxicity in "epithelioid" smooth muscle cells: implications for neointimal regression

Vascular smooth muscle cells (SMCs) are phenotypically diverse. Although most medial SMCs can be classified as "fusiform," others are of the "epithelioid" phenotype. Proliferation and apoptosis of epithelioid SMCs may contribute importantly to neointimal formation and regression, respectively. Because reactive oxygen species (ROS) are increased in vascular injury and can induce apoptosis of SMCs, we compared the effects of ROS on epithelioid and fusiform SMCs. Epithelioid and fusiform SMC lines were clonally isolated from rat aortic media and studied under similar conditions and passage numbers. H(2)O(2) produced dose- and time-dependent cytotoxicity that was enhanced in epithelioid compared with fusiform cells. After 24-hour exposure to 50 micromol/L H(2)O(2), epithelioid cell numbers were reduced by 34+/-5% versus a 3+/-5% (P<0.05) reduction in fusiform cell numbers. Similar results were obtained whether H(2)O(2) was administered to growth-arrested or growing cells or when epithelioid and fusiform cells were exposed to extracellular O(2)(.-). To investigate whether apoptosis contributed to enhanced ROS-induced cytotoxicity in epithelioid SMCs, terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick-end labeling (TUNEL) staining was performed. The incidence of TUNEL positivity was 5-fold increased in epithelioid versus fusiform SMCs after treatment with 50 micromol/L H(2)O(2) (19+/-1% epithelioid versus 5+/-1% fusiform, P<0.05). Enhanced H(2)O(2)-induced apoptosis in epithelioid SMCs was confirmed by DNA laddering. Furthermore, when balloon-injured aortas were exposed to H(2)O(2) ex vivo, enhanced apoptosis was observed in neointimal compared with medial SMCs. These results suggest that epithelioid SMCs exhibit enhanced sensitivity to ROS-induced apoptosis, which may play an important role in neointimal regression.

Virulence of the phytopathogen Pseudomonas syringae pv. maculicola is rpoN dependent

We cloned the rpoN (ntrA and glnF) gene encoding sigma(54) from the phytopathogen Pseudomonas syringae pv. maculicola strain ES4326. The P. syringae ES4326 rpoN gene complemented Pseudomonas aeruginosa, Escherichia coli, and Klebsiella aerogenes rpoN mutants for a variety of rpoN mutant phenotypes, including the inability to utilize nitrate as sole nitrogen source. DNA sequence analysis of the P. syringae ES4326 rpoN gene revealed that the deduced amino acid sequence was most similar (86% identity; 95% similarity) to the sigma(54) protein encoded by the Pseudomonas putida rpoN gene. A marker exchange protocol was used to construct an ES4326 rpoN insertional mutation, rpoN::Km(r). In contrast to wild-type ES4326, ES4326 rpoN::Km(r) was nonmotile and could not utilize nitrate, urea, C(4)-dicarboxylic acids, several amino acids, or concentrations of ammonia below 2 mM as nitrogen sources. rpoN was essential for production of the phytotoxin coronatine and for expression of the structural genes encoding coronamic acid. In addition, ES4326 rpoN::Km(r) did not multiply or elicit disease symptoms when infiltrated into Arabidopsis thaliana leaves, did not elicit the accumulation of several Arabidopsis defense-related mRNAs, and did not elicit a hypersensitive response (HR) when infiltrated into tobacco (Nicotiana tabacum) leaves. Furthermore, whereas P. syringae ES4326 carrying the avirulence gene avrRpt2 elicited an HR when infiltrated into Arabidopsis ecotype Columbia leaves, ES4326 rpoN::Km(r) carrying avrRpt2 elicited no response. Constitutive expression of ES4326 hrpL in ES4326 rpoN::Km(r) partially restored defense-related mRNA accumulation, showing a direct role for the hrp cluster in host defense gene induction in a compatible host-pathogen interaction. However, constitutive expression of hrpL in ES4326 rpoN::Km(r) did not restore coronatine production, showing that coronatine biosynthesis requires factors other than hrpL.

Vanadyl(IV) binding to mammalian ferritins. An EPR study aided by site-directed mutagenesis

During its metabolism, vanadium is known to become associated with the iron storage protein, ferritin. To elucidate probable vanadium binding sites on the protein, VO2+ binding to mammalian ferritins was studied using site-directed mutagenesis and EPR spectroscopy. VO2+-apoferritin EPR spectra of human H-chain (100% H), L-chain (100% L), horse spleen (84% L, 16% H) and sheep spleen (45% L, 55% H) ferritins revealed the presence of alpha and beta VO2+ species in all the proteins, implying that the ligands for these species are conserved between the H- and L-chains. The alpha species is less stable than the beta species and decreases with increasing pH, demonstrating that the two species are not pH-related, a result contrary to earlier proposals. EPR spectra of site-directed HuHF variants of several residues conserved in H- and L-chain ferritins (Asp-131, Glu-134, His-118 and His-128) suggest that His-118 near the outer opening of the three-fold channel is probably a ligand for VO2+ and is responsible for the beta signals in the EPR spectrum. The data indicate that VO2+ does not bind to the Asp-131 and Glu-134 residues within the three-fold channels nor does it bind at the ferroxidase site residues Glu-62 or His-65 or at the putative nucleation site residues Glu-61,64,67. While the ferroxidase site is not a site for VO2+ binding, mutation of residues Glu-62 and His-65 of this site to Ala affects VO2+ binding at His-118, located some 17 A away. Thus, VO2+ spin probe studies provide a window on structural changes in ferritin not seen in most previous work and indicate that long-range effects caused by point mutations must be carefully considered when drawing conclusions from mutagenesis studies of the protein.

Increased insulin receptor substrate-1 and enhanced skeletal muscle insulin sensitivity in mice lacking CCAAT/enhancer-binding protein beta

CCAAT/enhancer-binding protein beta (C/EBPbeta) controls gene transcription and metabolic processes in a variety of insulin-sensitive tissues; however, its role in regulating insulin responsiveness in vivo has not been investigated. We performed hyperinsulinemic-euglycemic clamps in awake, non-stressed, chronically catheterized adult mice homozygous for a deletion in the gene for C/EBPbeta (C/EBPbeta(-/-)). Fasting plasma insulin, glucose, and free fatty acid (FFA) levels were significantly lower in C/EBPbeta(-/-) mice compared with wild-type (WT) controls. Acute hyperinsulinemia (4 h) suppressed hepatic glucose production, phosphoenolpyruvate carboxykinase mRNA, and plasma FFA to a similar extent in WT and C/EBPbeta(-/-) mice, suggesting that C/EBPbeta deletion does not alter the metabolic and gene regulatory response to insulin in liver and adipose tissue. In contrast, using submaximal (5 milliunits/kg/min) and maximal (20 milliunits/kg/min) insulin infusions, whole-body glucose disposal was 77% (p < 0.01) and 33% (p < 0.05) higher in C/EBPbeta(-/-) mice, respectively, compared with WT mice. Maximal insulin-stimulated 3-O-methylglucose uptake in isolated soleus muscle was 54% greater in C/EBPbeta(-/-) mice (p < 0.05). Furthermore, insulin-stimulated insulin receptor and Akt Ser(473) phosphorylation and phosphatidylinositol 3-kinase activity were 1.6-2.5-fold greater in skeletal muscle from C/EBPbeta(-/-) mice compared with WT mice. The level of insulin receptor substrate-1 protein was increased 2-fold in skeletal muscle from C/EBPbeta(-/-) mice. These results demonstrate that C/EBPbeta deletion decreases plasma FFA levels and increases insulin signal transduction specifically in skeletal muscle, and both contribute to increased whole-body insulin sensitivity.

Improvements in dating tooth enamel by ESR

ESR dating requires that growth curves be determined by interpreting complex spectra. Spectra, however, can vary significantly in shape and field position between different samples, or occasionally between subsamples, even though the mineralogy remains the same. In some cases, this spectral variability does not affect the resulting accumulated dose calculation. In other cases, signal subtraction may be needed. However, some samples that until recently might have been considered unsuitable for dating are now shown to yield accurate and precise results because a broad interference peak is integral to the hydroxyapatite signal. By studying the spectrum at the Q-band frequency, it can be shown that the interfering signal in most cases is not a problem for dating. A second concern has been that artificially irradiating sample aliquots can introduce a short-lived component that is simply an unstable enhancement of the dating signal. The apparent accumulated dose from growth curves created immediately after irradiation is considerably greater than that after annealing, although the curve's shape remains unchanged. Annealing both the natural and artificially irradiated signal shows the dating signal's lifetime to be greater than 10(10) years.

On statistical analysis for placebo-challenging designs in clinical trials

In clinical trials, appropriate designs are often chosen to address scientific/medical questions of particular interest to the investigator. For a chosen statistical design, however, standard statistical procedures may not be applicable owing to the nature of the design. In this paper we examine statistical methods for analysis of data collected from a placebo-challenging design which is often considered for assessment of the efficacy of drug products for indication of erectile dysfunction. An example concerning a clinical trial conducted with 120 male patients with erectile dysfunction is used to illustrate the derived statistical methods. Some recommendations to the randomization procedure for the study design of this kind are also made.