PSF is a novel corepressor that mediates its effect through Sin3A and the DNA binding domain of nuclear hormone receptors

Members of the type II nuclear hormone receptor subfamily (e.g., thyroid hormone receptors [TRs], retinoic acid receptors, retinoid X receptors [RXRs], vitamin D receptor, and the peroxisome proliferator-activated receptors) bind to their response sequences with or without ligand. In the absence of ligand, these DNA-bound receptors mediate different degrees of repression or silencing of gene expression which is thought to result from the association of their ligand binding domains (LBDs) with corepressors. Two related corepressors, N-CoR and SMRT, interact to various degrees with the LBDs of these type II receptors in the absence of their cognate ligands. N-CoR and SMRT have been proposed to act by recruiting class I histone deacetylases (HDAC I) through an association with Sin3, although they have also been shown to recruit class II HDACs through a Sin3-independent mechanism. In this study, we used a biochemical approach to identify novel nuclear factors that interact with unliganded full-length TR and RXR. We found that the DNA binding domains (DBDs) of TR and RXR associate with two proteins which we identified as PSF (polypyrimidine tract-binding protein-associated splicing factor) and NonO/p54(nrb). Our studies indicate that PSF is a novel repressor which interacts with Sin3A and mediates silencing through the recruitment of HDACs to the receptor DBD. In vivo studies with TR showed that although N-CoR fully dissociates in the presence of ligand, the levels of TR-bound PSF and Sin3A appear to remain unchanged, indicating that Sin3A can be recruited to the receptor independent of N-CoR or SMRT. RXR was not detected to bind N-CoR although it bound PSF and Sin3A as effectively as TR, and this association with RXR did not change with ligand. Our studies point to a novel PSF/Sin3-mediated pathway for nuclear hormone receptors, and possibly other transcription factors, which may fine-tune the transcriptional response as well as play an important role in mediating the repressive effects of those type II receptors which only weakly interact with N-CoR and SMRT.

CTLA4Ig inhibits airway eosinophilia and hyperresponsiveness by regulating the development of Th1/Th2 subsets in a murine model of asthma

Complete T-cell activation requires two distinct signals, one delivered via the T-cell receptor, and the second "co-stimulatory" signal through CD28/B7 ligation. Previous studies showed that the blockade of CD28/B7 ligation alters differentiation of Th1/Th2 lymphocyte subsets in vitro and in vivo. The present study was designed to determine the effect of a CD28/B7 antagonist (CTLA4Ig) on Th1/Th2 development in Schistosoma mansoni-sensitized and airway-challenged mice. Treatment of mice with CTLA4Ig beginning 1 wk after sensitization abolished airway responsiveness to intravenous methacholine determined 96 h following antigen challenge. We also found a significant reduction in bronchoalveolar lavage (BAL) eosinophilia, and reduced peribronchial eosinophilic infiltration and mucoid-cell hyperplasia. Furthermore, CTLA4Ig treatment significantly decreased interleukin (IL)-4 and IL-5 content in BAL fluid in vivo, and the production of IL-5 by lung lymphocytes stimulated with soluble egg antigen (SEA) in vitro. In contrast, the content of interferon-gamma in BAL fluid and supernatant from SEA-stimulated lung lymphocytes from CTLA4Ig-treated mice was increased significantly compared with untreated animals. Thus, CTLA4Ig inhibits eosinophilic airway inflammation and airway hyperresponsiveness in S. mansoni-sensitized and airway-challenged mice, most likely due to attenuated secretion of Th2-type cytokines and increased secretion of Th1-type cytokines.

Phosphorylation within the amino-terminal acidic domain I of the phosphoprotein of vesicular stomatitis virus is required for transcription but not for replication

Phosphorylation by casein kinase II at three specific residues (S-60, T-62, and S-64) within the acidic domain I of the P protein of Indiana serotype vesicular stomatitis virus has been shown to be critical for in vitro transcription activity of the viral RNA polymerase (P-L) complex. To examine the role of phosphorylation of P protein in transcription as well as replication in vivo, we used a panel of mutant P proteins in which the phosphate acceptor sites in domain I were substituted with alanines or other amino acids. Analyses of the alanine-substituted mutant P proteins for the ability to support defective interfering RNA replication in vivo suggest that phosphorylation of these residues does not play a significant role in the replicative function of the P protein since these mutant P proteins supported replication at levels > or = 70% of the wild-type P-protein level. However, the transcription function of most of the mutant proteins in vivo was severely impaired (2 to 10% of the wild-type P-protein level). The level of transcription supported by the mutant P protein (P(60/62/64)) in which all phosphate acceptor sites have been mutated to alanines was at best 2 to 3% of that of the wild-type P protein. Increasing the amount of P(60/62/64) expression in transfected cells did not rescue significant levels of transcription. Substitution with other amino acids at these sites had various effects on replication and transcription. While substitution with threonine residues (P(TTT)) had no apparent effect on transcription (113% of the wild-type level) or replication (81% of the wild-type level), substitution with phenylalanine (P(FFF)) rendered the protein much less active in transcription (< 5%). Substitution with arginine residues led to significantly reduced activity in replication (6%), whereas glutamic acid substituted P protein (P(EEE)) supported replication (42%) and transcription (86%) well. In addition, the mutant P proteins that were defective in replication (P(RRR)) or transcription (P(60/62/64)) did not behave as transdominant repressors of replication or transcription when coexpressed with wild-type P protein. From these results, we conclude that phosphorylation of domain I residues plays a major role in in vivo transcription activity of the P protein, whereas in vivo replicative function of the protein does not require phosphorylation. These findings support the contention that different phosphorylated states of the P protein regulate the transcriptase and replicase functions of the polymerase protein, L.

RNA polymerase of vesicular stomatitis virus specifically associates with translation elongation factor-1 alphabetagamma for its activity

An RNA-dependent RNA polymerase is packaged within the virions of purified vesicular stomatitis virus, a nonsegmented negative-strand RNA virus, which carries out transcription of the genome RNA into mRNAs both in vitro and in vivo. The RNA polymerase is composed of two virally encoded polypeptides: a large protein L (240 kDa) and a phosphoprotein P (29 kDa). Recently, we obtained biologically active L protein from insect cells following infection by a recombinant baculovirus expressing L gene. During purification of the L protein from Sf21 cells, we obtained in addition to an active L fraction an inactive fraction that required uninfected insect cell extract to restore its activity. The cellular factors have now been purified, characterized, and shown to be beta and gamma subunits of the protein synthesis elongation factor EF-1. We also demonstrate that the alpha subunit of EF-1 remains tightly bound to the L protein in the inactive fraction and betagamma subunits associate with the L(alpha) complex. Further purification of L(alpha) from the inactive fraction revealed that the complex is partially active and is significantly stimulated by the addition of betagamma subunits purified from Sf21 cells. A putative inhibitor(s) appears to co-elute in the inactive fraction that blocked the L(alpha) activity. The purified virions also package all three subunits of EF-1. These findings have a striking similarity with Qbeta RNA phage, which also associates with the bacterial homologue of EF-1 for its replicase function, implicating a possible evolutionary relationship between these host proteins and the RNA-dependent RNA polymerase of RNA viruses.

TLS (translocated-in-liposarcoma) is a high-affinity interactor for steroid, thyroid hormone, and retinoid receptors

Nuclear receptors for steroid hormones, thyroid hormone, retinoids, and vitamin D are thought to mediate their transcriptional effects in concert with coregulator proteins that modulate receptor interactions with components of the basal transcription complex. In an effort to identify potential coregulators, receptor fusions with glutathione-S-transferase were used to isolate proteins in nuclear extracts capable of binding nuclear hormone receptors. Glutathione-S-transferase fusions with mouse retinoid X receptor-alpha enabled the selective isolation of a 65-kDa protein (p65) from nuclear extracts of rat and human cells. Binding of p65 to mouse retinoid X receptor-alpha was centered around the DNA-binding domain. p65 also bound regions encompassing the DNA-binding domain in estrogen, thyroid hormone, and glucocorticoid receptors. p65 was identified as TLS (translocated-in-liposarcoma), a recently identified member of the RNP family of nuclear RNA-binding proteins whose members are thought to function in RNA processing. The N-terminal half of TLS bound to thyroid hormone receptor with high affinity while the receptor was bound to appropriate DNA target sites. Functional studies indicated that the N-terminal half of TLS can interact with thyroid hormone receptor in vivo. TLS was originally discovered as part of a fusion protein arising from a chromosomal translocation causing human myxoid liposarcomas. TLS contains a potent transactivation domain whose translocation-induced fusion with a DNA-binding protein (CHOP) yields a powerful transforming oncogene and transcription factor. The transactivation and RNA-binding properties of TLS and the nature of its interaction with nuclear receptors suggest a novel role in nuclear receptor function.

pRb and p16 protein alterations in human oral tumorigenesis

Cyclin dependent kinase inhibitor 2/multiple tumour suppressor gene 1 (CDKN2/MTS1) and retinoblastoma (Rb) tumour suppressor genes play important roles in the regulation of the cell cycle. The protein products of these genes p16INK4 (p16) and pRb, respectively, like p53 protein inhibit progression from G1 to S phase. p16 exerts its function through inhibition of CDK4-mediated phosphorylation of pRb. The pRb/p16 pathway is a critical target for molecular aberration at the G1-S checkpoint in a wide range of primary human tumours. The expression of p16 and pRb proteins was analyzed by immunohistochemistry in 35 cases of oral squamous cell carcinomas (SCCs), 22 cases of premalignant oral lesions and 30 normal oral tissues. Lack of pRb expression was observed in 23/35 (66%) oral SCCs and 14/22 (64%) premalignant lesions. Lack of p16 expression was observed in 22/35 (63%) oral SCCs and 13/22 (59%) premalignant lesions. Weak p16 and pRb immunoreactivities were observed in normal oral mucosal epithelium. The status of p16 and pRb was correlated with clinicopathological characteristics of the patients. Alteration in p16 expression showed significant correlation with tumour staging and progression (P = 0.024). Alteration in pRb/p16 expression correlated with heavy consumption of betel and tobacco. Our results suggest that alterations in the p16/pRb pathway are early events in oral tumorigenesis and may be involved in the development of betel- and tobacco-related oral malignancies.

TRFK-5 reverses established airway eosinophilia but not established hyperresponsiveness in a murine model of chronic asthma

We studied the effects of an anti-interleukin (IL)-5 monoclonal antibody (TRFK-5) or dexamethasone (DEX) to reverse already established airway hyperresponsiveness (AHR) and tissue eosinophilia in a Schistosoma mansoni antigen-sensitized and airway-challenged mouse model of chronic asthma. In this model at 4 d after antigen challenge there is dramatic bronchoalveolar lavage fluid (BAL) eosinophilia, AHR to intravenous methacholine (MCh), and histologic evidence of peribronchial eosinophilic infiltration and mucoid cell hyperplasia. These changes persist for up to 2 wk after antigen challenge. Treatment with DEX from Days 4 through 10 significantly reduced established airway eosinophilia compared with animals sham-treated with saline from Days 4 -10 (120 +/- 29 eosinophils/microl BAL for DEX-treated mice versus 382 +/- 60 eosinophils/microl BAL for sham-treated animals, p < 0.01). DEX-treated mice also had dramatically reduced mucoid cell hyperplasia, and airway responsiveness returned to normal. In contrast, TRFK-5 given during the same time period reduced airway eosinophilia (86 +/- 32 eosinophils/microl BAL versus 382 +/- 60 eosinophils/microl BAL, p < 0.01) but did not reduce goblet cell hyperplasia or reverse already established AHR. Treatment with DEX but not TRFK-5 also inhibited interferon gamma (IFN-gamma) content of BAL fluid (0.49 +/- 0.09 ng/ml BAL fluid for DEX versus 1.50 +/- 0.24 ng/ml BAL fluid and 1.36 +/- 0.13 ng/ml BAL fluid for TRFK-5 and sham-treated mice, respectively, both p < 0.001 versus DEX). Thus, treatment with DEX reduces established eosinophilic airway inflammation and AHR in S. mansoni-sensitized and airway-challenged mice but treatment with TRFK-5 reversed established eosinophilia without ameliorating established AHR. Together, these data suggest that once airway inflammation develops, neutralizing the effects of IL-5 or reducing eosinophilia alone may not result in inhibiting established AHR in atopic asthma.

CD28 interactions with either CD80 or CD86 are sufficient to induce allergic airway inflammation in mice

Previous studies have shown that the pan CD28/cytotoxic T lymphocyte antigen (CTL)A-4 antagonist CTLA4 immunoglobulin (Ig) inhibits eosinophilic airway inflammation in Schistosoma mansoni-sensitized and airway-challenged mice. In the present study, the importance of CD28 as well as the individual roles of CD80 and CD86 were examined in this system using wild-type and CD28 knockout (KO) mice. Unlike wild-type controls, CD28KO mice did not produce systemic IgE or eosinophilic airway inflammation after antigen challenge. However, a lymphocytic infiltrate and continued production of interferon-gamma was observed in these animals. Thus, CD28 is not essential for the initial recruitment of lymphocytes into antigen-challenged airways but critically regulates the allergic T-helper 2 phenotype. We next determined by polymerase chain reaction and flow cytometry that CD80 and CD86 molecules are constitutively expressed in the naive murine lung and on eosinophils in the allergic lung, suggesting a potential important role for both ligands in the development of asthma. Combined anti-CD80/anti-CD86 treatment throughout the antigen challenge period fully blocked the development of allergic airways, whereas a partial reduction was observed in mice treated with either anti-CD80 or anti-CD86 antibody alone. However, only anti-CD86 blocked systemic IgE production. Therefore, signaling through either CD80 or CD86 is sufficient to generate a partial local allergic response, whereas CD86 costimulation is essential to induce systemic allergic (IgE) reactions. Finally, combined anti-B7 monoclonal antibody treatment after sensitization reduced airway eosinophilia and interleukin (IL)-4/IL-5 cytokine secretion consistent with an ongoing role for CD28/B7 interactions in the effector phase of the disease. These results emphasize the importance of differential B7 expression on different cells and in different organs on subsequent CD28/B7-mediated immune events, including the potential for CD28/B7 blockade in the treatment of atopic airway disease in people.

Men who have sex with men and transgenders in Mumbai, India: an emerging risk group for STIs and HIV

BACKGROUND

Men who have sex with men and transgenders are an important risk group for sexually transmitted infections (STIs) and human immunodeficiency virus (HIV). They have risky sexual behaviors but low risk perception.

OBJECTIVES

To assess the sexual behavior, STIs, HIV and identify factors associated with HIV in men who have sex with men (MSM) and transgenders (TGs) in Mumbai.

METHODS

Participants were enrolled from two clinics in Mumbai. They completed an interviewer-administered questionnaire and were evaluated for STIs and HIV infection.

RESULTS

A total of 150 participants, 122 MSM and 28 TGs were evaluated; 17% of MSM and 68% of the TGs were HIV infected. HIV infection in MSM was associated with serological positivity for HSV2 IgG [adjusted odds ratio (aOR), 95% confidence interval (CI): 9.0 (2.2-36.9)], a positive Treponema pallidum hemagglutination assay (TPHA) [aOR (95% CI): 6.0 (1.5-24.0)], greater than five acts of receptive anal sex in the past six months [aOR (95% CI): 4.3 (1.2-15.0)] and per category increase in age (18-24 yrs, 25-29 yrs, > 30 yrs) [aOR (95% CI): 3.1 (1.3-7.1)] in multivariate analysis. Consistent condom use during receptive anal sex in the past six months was low (27%). Many MSM were married (22%) or had sex with females and may act as a 'bridge population'. HIV infection in TGs was associated with a positive TPHA [OR (95% CI): 9.8 (1.5-63.9)] and HSV 2 IgG [OR (95% CI): 6.7 (1.1-40.4)] in univariate analysis.

CONCLUSION

Prior STIs were strongly associated with HIV infection in MSM and TGs. These groups should be the focus of intensive intervention programs aimed at STI screening and treatment, reduction of risky sexual behavior and promotion of HIV counseling and testing.

Ets-1: a plausible marker of invasive potential and lymph node metastasis in human oral squamous cell carcinomas

The proto-oncogene Ets-1 is a transcription factor known to regulate the expression of a number of genes involved in extracellular matrix remodelling. It has been postulated to play a role in angiogenesis, cell migration, and regulation of tumour invasion. In betel and tobacco-related oral tumourigenesis, oral squamous cell carcinomas (SCCs) having a poor prognosis often exhibit extensive local disease with spread into regional lymph nodes. At present, no tumour marker is available to predict the metastatic potential of oral carcinomas. To elucidate the involvement of Ets-1 in human oral tumourigenesis, 60 cases of oral SCC, 30 potentially malignant lesions, and 30 samples of normal oral mucosa were examined by immunohistochemistry and the findings corroborated with immunoblotting. The relationship of Ets-1 expression with the degree of differentiation, lymph node metastasis, and tumour stage was determined in oral SCCs. Ets-1 was not detected in the normal oral epithelium. Among the 60 cases of oral SCC, 35 cases (58 per cent) showed positive staining for the Ets-1 protein in tumour cells. In potentially malignant lesions, 14 of 30 cases (47 per cent) showed Ets-1 immunopositivity. Ets-1 expression correlated significantly with tumour stage ( p=0.01) and lymph node metastasis ( p=0.005). The presence of Ets-1 mRNA in oral SCCs was confirmed by reverse transcription-polymerase chain reaction (RT-PCR). These findings suggest that overexpression of Ets-1 in potentially malignant lesions may be related to angiogenesis and its expression in oral SCCs may be one of the factors involved in tumour progression and lymph node metastasis.

MDM2/p53 co-expression in oral premalignant and malignant lesions: potential prognostic implications

The expression of MDM2 protein in betel and tobacco related oral malignancies in Indian population, its relationship to clinicopathological parameters and p53 protein expression was investigated. Sixty five oral squamous cell carcinomas (SCCs), 33 premalignant lesions (leukoplakia) and 30 normal oral tissues were assessed by immunohistochemical analysis. MDM2 protein was overexpressed in 51/65 (78%) oral SCCs and 17/33 (52%) premalignant lesions; 11/23 hyperplastic lesions and 6/10 dysplastic lesions. mdm2 gene amplification is an infrequent event in oral tumorigenesis. Elevation in the level of MDM2 protein not only in oral SCCs but also in premalignant lesions suggests that altered MDM2 expression is an early even in the pathogenesis of oral neoplasia. The hallmark of the study was the significant association of MDM2 expression with the p53 protein accumulation in 16/33 (49%) oral premalignant lesions (p = 0.001) and 39/65 (60%) malignant lesions (p = 0.021), suggesting an active role for MDM2 in binding and inactivating p53 in oral tumorigenesis. Further, significant association of MDM2/p53 co-expression was observed with advanced tumour stage (p = 0.0009), as well as lymph node metastasis (p = 0.0325) features associated with aggressive tumour behaviour and poor prognosis. Discordant MDM2+/p53-phenotype was observed in 12/65 (18%) oral SCCs suggesting a p53-independent role for MDM2 in the pathogenesis of a subset of oral carcinomas. In conclusion, alterations in MDM2 and p53 expression are early events likely to be involved in preinvasive stages in oral tumorigenesis and may be indicative of a 'gain of function' phenotype with more aggressive characteristics.

Circulating p53 antibodies, p53 gene mutational profile and product accumulation in esophageal squamous-cell carcinoma in India

Esophageal cancer (EC) in the Indian population presents in advanced stages with poor prognosis and warrants the identification of a non-invasive marker for early detection and better prognostic assessment. We have previously reported high prevalence of p53 protein accumulation in esophageal squamous-cell carcinomas (ESCCs). The present study was designed to determine (i) if esophageal cancer patients elicit a humoral immune response to intra-tumoral p53 protein accumulation and (ii) their relationship with p53 gene mutations. The goal was to compare the cellular events, p53 protein accumulation and gene mutations with the presence of serum anti-p53 antibodies (p53-Abs) and to assess the utility of serological p53-Ab analysis as a surrogate marker for p53 alterations in esophageal cancer. A high prevalence of circulating p53-Abs was observed in 36 of 60 (60%) ESCC patients. In a subset of 44 ESCCs, exons 5-9 of the p53 gene were examined for mutations by PCR and direct sequencing of PCR products. Mutational data have been correlated with p53-Abs and p53 protein accumulation in ESCCs. Circulating p53-Abs in ESCC patients were significantly associated with intra-tumoral p53 protein accumulation (p=0.0005). A strong correlation observed between humoral immune response against p53 protein, missense gene mutations and protein accumulation warrants the application of serological p53-Abs as a non-invasive surrogate marker in screening high-risk populations for early detection of malignancy.

Single donor-derived strongyloidiasis in three solid organ transplant recipients: case series and review of the literature

Donor-derived Strongyloides stercoralis infections in transplant recipients are a rare but recognized complication. In this case series, we report donor-derived allograft transmission of Strongyloides in three solid organ transplant recipients. Following detection of infection in heart and kidney-pancreas recipients at two different transplant centers, a third recipient from the same donor was identified and diagnosed. S. stercoralis larvae were detected in duodenal aspirates, bronchial washings, cerebrospinal fluid, urine and stool specimens. Treatment with ivermectin and albendazole was successful in two of the three patients identified. The Centers for Disease Control and Prevention was contacted and performed an epidemiologic investigation. Donor serology was strongly positive for S. stercoralis antibodies on retrospective testing while all pretransplant recipient serum was negative. There should be a high index of suspicion for parasitic infection in transplant recipients and donors from endemic regions of the world. This case series underscores the need for expanded transplant screening protocols for Strongyloides. Positive serologic or stool tests should prompt early treatment or prophylaxis in donors and recipients as well as timely notification of organ procurement organizations and transplant centers.

Alterations in p53 and pRb pathways and their prognostic significance in oesophageal cancer

The pRb (p16-pRb-cyclin D1) and p53 (p53-MDM2-p21) pathways play a critical role in tumorigenesis. To evaluate which of these cell cycle regulatory proteins are related to patients' prognosis, a comprehensive analysis of alterations in these components was carried out in 100 ESCCs (oesophageal squamous cell carcinoma) using immunohistochemistry and correlated with clinicopathological parameters by univariate analysis. Overexpression of p53, MDM2 and cyclin D1 proteins was observed in 73, 42 and 67% of the cases, respectively, while loss of expression of p21, p16 and pRb was observed in 36, 45 and 75% of the cases, respectively. Multiple logistic regression analysis revealed that loss of p16 immunoreactivity was a significant risk factor for tumour stage (pT) (Odds Ratio (OR)=3.3), whereas the loss of pRb was a significant risk factor for nodal metastasis (pN) (OR=8.8). MDM2 overexpression emerged as the most significant risk factor for distant organ metastasis (pM) (OR=4.6). Of the ESCC patients who underwent oesophagectomy, 50 cases were followed-up for a maximum period of 44 months and median of 16 months. Survival analysis revealed that Cyclin D1 overexpression is an adverse prognosticator for disease-free survival, as well as overall survival, and tumour stage (pT) is an adverse prognosticator for disease-free survival. In conclusion, these data support a model of oesophageal cancer pathogenesis in which both the pRb and p53 pathways are inactivated and suggests an in-depth evaluation of the clinical utility of these putative markers is warranted.

Novel polymorphism in p21(waf1/cip1) cyclin dependent kinase inhibitor gene: association with human esophageal cancer

p21(waf1/cip1), an important regulator of the cell cycle, binds to PCNA and acts as a mediator of the growth suppressing and apoptosis promoting functions of p53. We report a hitherto unobserved polymorphism in the carboxy terminal domain (codon 149) of p21(waf1/cip1) gene, the domain encoding the PCNA binding motif. The codon 149 polymorphism (GAT-->GGT) was observed in 42 of 50 (84%) esophageal squamous cell carcinomas (ESCCs) and eight of 50 (16%) normal individuals. The resultant amino acid substitution from aspartate to glycine may have vital implication in PCNA mediated cell cycle regulation by p21(waf1/cip1). The second polymorphism at codon 31, involving a C-->A transversion at nucleotide 168 (AGC-->AGA) changing the amino acid from serine to arginine, was observed in 2/50 (4%) ESCCs at a relatively lower frequency in the Indian population than that reported in the West. No significant association was observed between p21(wap1/cip1) polymorphism at codon 149 and p21(wap1/cip1) protein expression in ESCC in this cohort of patients. Interestingly, the frequency of p21(wap1/cip1) variants (codon 149) in ESCCs (18 of 19 cases) with wild-type p53 was significantly higher than in tumors with p53 mutations, suggesting that this polymorphism affects the p53 pathway and may play an important role in esophageal tumorigenesis. Analysis of p21(waf1/cip1) expression in relation to p53 gene and protein status revealed its induction by p53-dependent as well as independent pathways in esophageal tumorigenesis.

Outcomes of children with abdominal compartment syndrome

INTRODUCTION

Abdominal compartment syndrome (ACS) is a problem across all critical care scenarios and is associated with a high mortality. It has not been well described in pediatric populations.

OBJECTIVE

To describe the occurrence of ACS in a subset of critically ill pediatric patients and determine its effects on mortality and length of pediatric intensive care stay (PICU LOS). We also aimed to find predictors of mortality and development of ACS.

SETTING

25 bed tertiary pediatric intensive care unit.

PATIENTS

PATIENTS less than 50 kg on mechanical ventilation and a urethral catheter.

MEASUREMENTS

Intra-abdominal pressures (IAP) were monitored using the intra-vesical technique. ACS was defined as IAP of >12mmHg associated with new organ dysfunction or failure. Demographics, physiologic measures of organ dysfunction, PICU LOS and mortality were monitored.

MAIN RESULTS

14 (4.7%) of 294 eligible patients had ACS. Mortality was 50% among those with ACS versus 8.2% without (p<.001). PICU LOS stay did not differ between groups. No difference in mortality or PICU LOS was seen in primary versus secondary ACS or in patients who underwent abdominal decompression compared to those without decompression. IAP and ACS were independent predictors of mortality (odds ratio 1.53, 95% CI, 1.17 - 1.99 and 9.09, 95% CI, 1.07 - 76.84) respectively. IAP and a PRISM score of ≥17 were predictive of developing ACS.

CONCLUSIONS

ACS is a clinical problem that increases the risk of mortality in critically ill children. IAP and PRISM scores may help identify children likely to develop ACS.

Differential effects of beta-arrestins on the internalization, desensitization and ERK1/2 activation downstream of protease activated receptor-2

Beta-arrestins-1 and 2 are known to play important roles in desensitization of membrane receptors and facilitation of signal transduction pathways. It has been previously shown that beta-arrestins are required for signal termination, internalization, and ERK1/2 activation downstream of protease-activated-receptor-2 (PAR-2), but it is unclear whether they are functionally redundant or mediate specific events. Here, we demonstrate that in mouse embryonic fibroblasts (MEFs) from beta-arrestin-1/2 knockout mice, G alpha q signaling by PAR-2, as measured by mobilization of intracellular Ca(2+), is prolonged. Only expression of beta-arrestin-1 shortened the signal duration, whereas either beta-arrestin-1 or 2 was able to restore PKC-induced receptor desensitization. Beta-arrestin-1 also mediated early, while beta-arrestin-2 mediated delayed, receptor internalization and membrane-associated ERK1/2 activation. While beta-arrestin-1 colocalized with a lysosomal marker (LAMP-1), beta-arrestin-2 did not, suggesting a specific role for beta-arrestin-1 in lysosomal receptor degradation. Together, these data suggest distinct temporal and functional roles for beta-arrestins in PAR-2 signaling, desensitization, and internalization.

Loss of heterozygosity of a locus on 17p13.3, independent of p53, is associated with higher grades of astrocytic tumours

Amongst the human astrocytic tumours, the commonest of primary brain tumours, the clinical outcome of astrocytoma (AS) is significantly better than anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM). Often, low grade tumours can progress to or recur with a more malignant phenotype. Recent loss of heterozygosity (LOH) reports suspect the involvement of a tumour suppressor gene, different from p53, in the 17p13.3 region of the human chromosome. However, the effect of LOH of 17p13.3 region on tumour histology at presentation and prognosis is as yet undefined. As a first step to define the role of this putative oncogene in astrocytic tumour progression, we correlated the LOH of a locus, D17S379, in 17p13.3 region and the p53 locus in 17p13.1 region with the histopathology of astrocytic tumours by PCR based microsatellite and restriction fragment length polymorphism of DNA extracted from microdissected paraffin sections of 45 astrocytic tumours of different histopathological grades. LOH of D17S379 was significantly associated (P=0.02) with AA and GBM (high grade malignancy), while no such preferential association was found with LOH of p53. There were no mutations in the exons 5 to 9 of p53 gene in the five tumours with LOH of D17S379 but not of p53 region. In a case of AA with a heterogenous microscopic appearance, heterozygosity of D17S379 was lost only in the area with a more malignant histology while both areas had no LOH or mutation of p53. A locus at the 17p13.3 region, independent of the p53 locus, is involved in a large subset of astrocytic tumours during transformation into a more malignant phenotype, and thus may be a link in the chain of genetic events occurring in astrocytic tumour progression.

A detailed mechanical and microstructural analysis of ovine tricuspid valve leaflets

The tricuspid valve ensures unidirectional blood flow from the right atrium to the right ventricle. The three tricuspid leaflets operate within a dynamic stress environment of shear, bending, tensile, and compressive forces, which is cyclically repeated nearly three billion times in a lifetime. Ostensibly, the microstructural and mechanical properties of the tricuspid leaflets have mechanobiologically evolved to optimally support their function under those forces. Yet, how the tricuspid leaflet microstructure determines its mechanical properties and whether this relationship differs between the three leaflets is unknown. Here we perform a microstructural and mechanical analysis in matched ovine tricuspid leaflet samples. We found that the microstructure and mechanical properties vary among the three tricuspid leaflets in sheep. Specifically, we found that tricuspid leaflet composition, collagen orientation, and valve cell nuclear morphology are spatially heterogeneous and vary across leaflet type. Furthermore, under biaxial tension, the leaflets' mechanical behaviors exhibited unequal degrees of mechanical anisotropy. Most importantly, we found that the septal leaflet was stiffer in the radial direction and not the circumferential direction as with the other two leaflets. The differences we observed in leaflet microstructure coincide with the varying biaxial mechanics among leaflets. Our results demonstrate the structure-function relationship for each leaflet in the tricuspid valve. We anticipate our results to be vital toward developing more accurate, leaflet-specific tricuspid valve computational models. Furthermore, our results may be clinically important, informing differential surgical treatments of the tricuspid valve leaflets. Finally, the identified structure-function relationships may provide insight into the homeostatic and remodeling potential of valvular cells in altered mechanical environments, such as in diseased or repaired tricuspid valves. STATEMENT OF SIGNIFICANCE: Our work is significant as we investigated the structure-function relationship of ovine tricuspid valve leaflets. This is important as tricuspid valves fail frequently and our current approach to repairing them is suboptimal. Specifically, we related the distribution of structural and cellular elements, such as collagen, glycosaminoglycans, and cell nuclei, to each leaflet's mechanical properties. We found that leaflets have different structures and that their mechanics differ. This may, in the future, inform leaflet-specific treatment strategies and help optimize surgical outcomes.

The nature and significance of liver cell vacuolation following hepatocellular injury--an analysis based on observations on rats rendered tolerant to hepatotoxic damage

Swelling with nonlipid cytoplasmic vacuolation of diffusely distributed hepatocytes is seen consistently after mild acute and subacute liver injury. Several lines of evidence point to the possibility that this change may reflect a cellular adaptation beneficial to the host, rather than a degenerative change. The nature and significance of this morphological manifestation were tested in batches of albino rats given small doses of a variety of hepatotoxins, some of which were subsequently challenged with a large highly necrogenic dose of carbon tetrachloride (CCl4). Morphological and biochemical investigations showed that cytoplasmic vacuolation of liver cells following low doses of toxins was due to excess accumulation of glycogen, predominantly of the monoparticulate form. These cells lacked features of degeneration or regeneration and were much less susceptible to injury by the large dose CCl4, as assessed by structural and serum enzyme analyses. This tolerance to toxic damage seemed to be associated with excess accumulation of intracellular glycogen. We conclude from these and other observations on animal and human livers that many of the vacuolated hepatocytes seen in liver injury are cells adaptively altered to resist further insult rather than cells undergoing hydropic degeneration, as is commonly believed.

Prognostic factors in betel and tobacco related oral cancer

Paucity of well-defined prognostic molecular markers severely hampers prediction of the clinical course of squamous cell carcinoma (SCC) of oral cavity. The aim of the study was to evaluate the prognostic significance of impairments in the expression of proteins involved in cell cycle regulation and locoregional spread in oral SCC of habitual betel and tobacco chewers. A prospective study was performed in 105 betel and tobacco consumers with oral SCCs during the period 1988-1999, to evaluate the prognostic relevance of impairments in the expression of proteins involved in cell cycle regulation and locoregional spread. Alterations in the expression of p53, pRb, p16, MDM2, p21, and Ets-1 proteins were determined by immunohistochemical analysis in formalin fixed, paraffin embedded tissue sections from oral SCCs. Analysis of multiple molecular biological factors showed overexpression of p53 in 69/105 (66%) cases, MDM2 in 72/105 (69%) cases, p21 in 57/105 (54%) cases and Ets-1 in 64/105 (61%) cases. Loss of pRb was observed in 58/105 (55%) cases and p16 loss was observed in 72/105 (69%) cases. Interestingly, multivariate analysis revealed loss of pRb as the most significant predictor of advanced tumour stage [P=0.001; Odd's Ratio (OR)=3.5] and overexpression of Ets-1 protein was an independent risk factor for lymph node metastasis (OR: 10.1; P<10(-6)). Multiple logistic regression models showed that pRb loss [Hazard's Ratio (HR): 3.93] and p53 overexpression (HR: 2.97) may serve as adverse prognosticators for disease free survival of the patients. The data demonstrate multiple impairments in p53/MDM2/p21/Ets-1 and p16/pRb pathways in betel and tobacco related oral tumourigenesis.

Anti-tumor promoting activity of Asteracantha longifolia against experimental hepatocarcinogenesis in rats

Vegetables, natural products of plant origin and numerous non-nutritive dietary constituents have been shown to play a salutary role in cancer chemoprevention. The present study aims to evaluate the chemopreventive efficacy of the methanol fraction of Asteracantha longifolia seed extract against development of 2-acetylaminofluorene (2-AAF)-selected gamma-glutamyl transpeptidase (gamma-GT)-positive foci following diethylnitrosamine (DEN) initiation. Treatment of rats with doses 200 and 400 mg/kg body weight of methanol extract of A. longifolia seeds on alternate days, subsequent to carcinogen treatment, for 6 weeks significantly reduced the incidence and size distribution of gamma-GT-positive foci and tumor formation. Administration of A. longifolia seeds significantly (P<0.001) ameliorated the activities of antioxidant enzymes, glutathione peroxidase (GPx) and catalase (CAT), in a dose-dependent manner. Prophylactic administration of seed extract simultaneous to 2-AAF in the diet, at same doses, significantly suppressed 2-AAF and partial hepatectomy (PH)-induced ornithine decarboxylase (ODC) activity and [(3)H]thymidine incorporation into hepatic DNA, in a dose-dependent manner. Assimilation of the quantitative foci data together with the findings of the modulation of tumor promoting markers give ample evidence to the anti-tumor promoting potential of A. longifolia seeds against chemically-induced hepatocarcinogenesis in Wistar rats.