Patient-Derived Tumor Explants As a "Live" Preclinical Platform for Predicting Drug Resistance in Patients

An understanding of drug resistance and the development of novel strategies to sensitize highly resistant cancers rely on the availability of suitable preclinical models that can accurately predict patient responses. One of the disadvantages of existing preclinical models is the inability to contextually preserve the human tumor microenvironment (TME) and accurately represent intratumoral heterogeneity, thus limiting the clinical translation of data. By contrast, by representing the culture of live fragments of human tumors, the patient-derived explant (PDE) platform allows drug responses to be examined in a three-dimensional (3D) context that mirrors the pathological and architectural features of the original tumors as closely as possible. Previous reports with PDEs have documented the ability of the platform to distinguish chemosensitive from chemoresistant tumors, and it has been shown that this segregation is predictive of patient responses to the same chemotherapies. Simultaneously, PDEs allow the opportunity to interrogate molecular, genetic, and histological features of tumors that predict drug responses, thereby identifying biomarkers for patient stratification as well as novel interventional approaches to sensitize resistant tumors. This paper reports PDE methodology in detail, from collection of patient samples through to endpoint analysis. It provides a detailed description of explant derivation and culture methods, highlighting bespoke conditions for particular tumors, where appropriate. For endpoint analysis, there is a focus on multiplexed immunofluorescence and multispectral imaging for the spatial profiling of key biomarkers within both tumoral and stromal regions. By combining these methods, it is possible to generate quantitative and qualitative drug response data that can be related to various clinicopathological parameters and thus potentially be used for biomarker identification.

Exploring the potential of BH3 mimetic therapy in squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) is the sixth most common cancer worldwide, with overall survival of less than 50%. Current therapeutic strategies involving a combination of surgery, radiation, and/or chemotherapy are associated with debilitating side effects, highlighting the need for more specific and efficacious therapies. Inhibitors of BCL-2 family proteins (BH3 mimetics) are under investigation or in clinical practice for several hematological malignancies and show promise in solid tumors. In order to explore the therapeutic potential of BH3 mimetics in the treatment of SCCHN, we assessed the expression levels of BCL-2, BCL-X_L, and MCL-1 via Western blots and immunohistochemistry, in cell lines, primary cells derived from SCCHN patients and in tissue microarrays containing tumor tissue from a cohort of 191 SCCHN patients. All preclinical models exhibited moderate to high levels of BCL-X_L and MCL-1, with little or no BCL-2. Although expression levels of BCL-X_L and MCL-1 did not correlate with patient outcome, a combination of BH3 mimetics to target these proteins resulted in decreased clonogenic potential and enhanced apoptosis in all preclinical models, including tumor tissue resected from patients, as well as a reduction of tumor volume in a zebrafish xenograft model of SCCHN. Our results show that SCCHN is dependent on both BCL-X_L and MCL-1 for apoptosis evasion and combination therapy targeting both proteins may offer significant therapeutic benefits in this disease.

BH3-only proteins are dispensable for apoptosis induced by pharmacological inhibition of both MCL-1 and BCL-XL

The impressive selectivity and efficacy of BH3 mimetics for treating cancer has largely been limited to BCL-2 dependent hematological malignancies. Most solid tumors depend on other anti-apoptotic proteins, including MCL-1, for survival. The recent description of S63845 as the first specific and potent MCL-1 inhibitor represents an important therapeutic advance, since MCL-1 is not targeted by the currently available BH3 mimetics, Navitoclax or Venetoclax, and is commonly associated with chemoresistance. In this study, we confirm a high binding affinity and selectivity of S63845 to induce apoptosis in MCL-1-dependent cancer cell lines. Furthermore, S63845 synergizes with other BH3 mimetics to induce apoptosis in cell lines derived from both hematological and solid tumors. Although the anti-apoptotic BCL-2 family members in these cell lines interact with a spectrum of pro-apoptotic BH3-only proteins to regulate apoptosis, these interactions alone do not explain the relative sensitivities of these cell lines to BH3 mimetic-induced apoptosis. These findings necessitated further investigation into the requirement of BH3-only proteins in BH3 mimetic-mediated apoptosis. Concurrent inhibition of BCL-X_L and MCL-1 by BH3 mimetics in colorectal HCT116 cells induced apoptosis in a BAX- but not BAK-dependent manner. Remarkably this apoptosis was independent of all known BH3-only proteins. Although BH3-only proteins were required for apoptosis induced as a result of BCL-X_L inhibition, this requirement was overcome when both BCL-X_L and MCL-1 were inhibited, implicating distinct mechanisms by which different anti-apoptotic BCL-2 family members may regulate apoptosis in cancer.

DRP-1 is required for BH3 mimetic-mediated mitochondrial fragmentation and apoptosis

The concept of using BH3 mimetics as anticancer agents has been substantiated by the efficacy of selective drugs, such as Navitoclax and Venetoclax, in treating BCL-2-dependent haematological malignancies. However, most solid tumours depend on MCL-1 for survival, which is highly amplified in multiple cancers and a major factor determining chemoresistance. Most MCL-1 inhibitors that have been generated so far, while demonstrating early promise in vitro, fail to exhibit specificity and potency in a cellular context. To address the lack of standardised assays for benchmarking the in vitro binding of putative inhibitors before analysis of their cellular effects, we developed a rapid differential scanning fluorimetry (DSF)-based assay, and used it to screen a panel of BH3 mimetics. We next contrasted their binding signatures with their ability to induce apoptosis in a MCL-1 dependent cell line. Of all the MCL-1 inhibitors tested, only A-1210477 induced rapid, concentration-dependent apoptosis, which strongly correlated with a thermal protective effect on MCL-1 in the DSF assay. In cells that depend on both MCL-1 and BCL-XL, A-1210477 exhibited marked synergy with A-1331852, a BCL-XL specific inhibitor, to induce cell death. Despite this selectivity and potency, A-1210477 induced profound structural changes in the mitochondrial network in several cell lines that were not phenocopied following MCL-1 RNA interference or transcriptional repression, suggesting that A-1210477 induces mitochondrial fragmentation in an MCL-1-independent manner. However, A-1210477-induced mitochondrial fragmentation was dependent upon DRP-1, and silencing expression levels of DRP-1 diminished not just mitochondrial fragmentation but also BH3 mimetic-mediated apoptosis. These findings provide new insights into MCL-1 ligands, and the interplay between DRP-1 and the anti-apoptotic BCL-2 family members in the regulation of apoptosis.

High CIP2A levels correlate with an antiapoptotic phenotype that can be overcome by targeting BCL-XL in chronic myeloid leukemia

Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a predictive biomarker of disease progression in many malignancies, including imatinib-treated chronic myeloid leukemia (CML). Although high CIP2A levels correlate with disease progression in CML, the underlying molecular mechanisms remain elusive. In a screen of diagnostic chronic phase samples from patients with high and low CIP2A protein levels, high CIP2A levels correlate with an antiapoptotic phenotype, characterized by downregulation of proapoptotic BCL-2 family members, including BIM, PUMA and HRK, and upregulation of the antiapoptotic protein BCL-XL. These results suggest that the poor prognosis of patients with high CIP2A levels is due to an antiapoptotic phenotype. Disrupting this antiapoptotic phenotype by inhibition of BCL-XL via RNA interference or A-1331852, a novel, potent and BCL-XL-selective inhibitor, resulted in extensive apoptosis either alone or in combination with imatinib, dasatinib or nilotinib, both in cell lines and in primary CD34(+) cells from patients with high levels of CIP2A. These results demonstrate that BCL-XL is the major antiapoptotic survival protein and may be a novel therapeutic target in CML.

The transrepression arm of glucocorticoid receptor signaling is protective in mutant huntingtin-mediated neurodegeneration

The unfolded protein response (UPR) occurs following the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and orchestrates an intricate balance between its prosurvival and apoptotic arms to restore cellular homeostasis and integrity. However, in certain neurodegenerative diseases, the apoptotic arm of the UPR is enhanced, resulting in excessive neuronal cell death and disease progression, both of which can be overcome by modulating the UPR. Here, we describe a novel crosstalk between glucocorticoid receptor signaling and the apoptotic arm of the UPR, thus highlighting the potential of glucocorticoid therapy in treating neurodegenerative diseases. Several glucocorticoids, but not mineralocorticoids, selectively antagonize ER stress-induced apoptosis in a manner that is downstream of and/or independent of the conventional UPR pathways. Using GRT10, a novel selective pharmacological modulator of glucocorticoid signaling, we describe the importance of the transrepression arm of the glucocorticoid signaling pathway in protection against ER stress-induced apoptosis. Furthermore, we also observe the protective effects of glucocorticoids in vivo in a Drosophila model of Huntington's disease (HD), wherein treatment with different glucocorticoids diminished rhabdomere loss and conferred neuroprotection. Finally, we find that growth differentiation factor 15 has an important role downstream of glucocorticoid signaling in antagonizing ER stress-induced apoptosis in cells, as well as in preventing HD-mediated neurodegeneration in flies. Thus, our studies demonstrate that this novel crosstalk has the potential to be effectively exploited in alleviating several neurodegenerative disorders.

Which patients are seen by an occupational psychiatry service?

BACKGROUND

Common mental disorders are the leading cause of sickness absence but are frequently misdiagnosed and undertreated. It is against this background that a specialist occupational psychiatry clinic was established at a London teaching hospital.

AIMS

To explore the nature of patients and complaints seen in the clinic and investigate whether this form of service provision reached patients who may have otherwise been missed in the gap between primary and secondary care.

METHODS

We reviewed the case notes of 51 consecutive new clinic assessments using a data extraction form, gathering information on socio-demographic and occupational details; the nature, duration and severity of symptoms [as assessed by Health of the Nation Outcome Scale (HoNOS)]; diagnosis; prior treatment and the outcome of the clinic appointment.

RESULTS

Only half of those seen in the new clinic were currently on sick leave. The most common diagnosis was depression with most having symptoms lasting longer than 9 months. Sixty-five per cent had a medium or high HoNOS rating. Although 75% had received treatment from their general practitioner, the majority remained functionally impaired, and only 31% had been seen in secondary care.

CONCLUSIONS

Specialist occupational psychiatry clinics do not replicate the work already being done by standard mental health services. Patients referred to a new specialist clinic within an occupational health department had chronic, debilitating psychiatric illnesses, which in many cases had failed to respond adequately to primary care treatment and were at risk of falling into the gap between primary and secondary services.

Novel modeling of combinatorial miRNA targeting identifies SNP with potential role in bone density

MicroRNAs (miRNAs) are post-transcriptional regulators that bind to their target mRNAs through base complementarity. Predicting miRNA targets is a challenging task and various studies showed that existing algorithms suffer from high number of false predictions and low to moderate overlap in their predictions. Until recently, very few algorithms considered the dynamic nature of the interactions, including the effect of less specific interactions, the miRNA expression level, and the effect of combinatorial miRNA binding. Addressing these issues can result in a more accurate miRNA:mRNA modeling with many applications, including efficient miRNA-related SNP evaluation. We present a novel thermodynamic model based on the Fermi-Dirac equation that incorporates miRNA expression in the prediction of target occupancy and we show that it improves the performance of two popular single miRNA target finders. Modeling combinatorial miRNA targeting is a natural extension of this model. Two other algorithms show improved prediction efficiency when combinatorial binding models were considered. ComiR (Combinatorial miRNA targeting), a novel algorithm we developed, incorporates the improved predictions of the four target finders into a single probabilistic score using ensemble learning. Combining target scores of multiple miRNAs using ComiR improves predictions over the naïve method for target combination. ComiR scoring scheme can be used for identification of SNPs affecting miRNA binding. As proof of principle, ComiR identified rs17737058 as disruptive to the miR-488-5p:NCOA1 interaction, which we confirmed in vitro. We also found rs17737058 to be significantly associated with decreased bone mineral density (BMD) in two independent cohorts indicating that the miR-488-5p/NCOA1 regulatory axis is likely critical in maintaining BMD in women. With increasing availability of comprehensive high-throughput datasets from patients ComiR is expected to become an essential tool for miRNA-related studies.

Role of NOXA and its ubiquitination in proteasome inhibitor-induced apoptosis in chronic lymphocytic leukemia cells

BACKGROUND

Bortezomib has been successfully used in the treatment of multiple myeloma and has been proposed as a potential treatment for chronic lymphocytic leukemia. In this study we investigated the mechanism by which bortezomib induces apoptosis in chronic lymphocytic leukemia cells.

DESIGN AND METHODS

Using western blot analysis, we monitored the regulation of BCL2 family members, proteins of the unfolded protein response (endoplasmic reticulum stress response) and activation of caspases in relation to induction of apoptosis (measured by annexin-propidium iodide staining and loss of mitochondrial membrane potential) by bortezomib in chronic lymphocytic leukemia cells.

RESULTS

Bortezomib induced apoptosis through activation of the mitochondrial pathway independently of changes associated with endoplasmic reticulum stress. Perturbation of mitochondria was regulated by a rapid and transcription-independent increase of NOXA protein, which preceded release of cytochrome c, HtrA2, Smac and activation of caspase-9 and -3. NOXA had a short half life (approximately 1-2 h) and was ubiquitinated on at least three primary lysine residues, resulting in proteasomal-dependent degradation. Down-regulation of NOXA, using short interfering RNA in chronic lymphocytic leukemia cells, decreased bortezomib-induced apoptosis. Finally bortezomib when combined with seliciclib resulted in a stronger and earlier increase in NOXA protein, caspase-3 cleavage and induction of apoptosis in chronic lymphocytic leukemia cells.

CONCLUSIONS

These results highlight a critical role for NOXA in bortezomib-induced apoptosis in chronic lymphocytic leukemia cells and suggest that this drug may become more efficient for the treatment of chronic lymphocytic leukemia if combined with other agents able to interfere with the basal levels of MCL1.

The fate of benzene-oxide

Metabolism is a prerequisite for the development of benzene-mediated myelotoxicity. Benzene is initially metabolized via cytochromes P450 (primarily CYP2E1 in liver) to benzene-oxide, which subsequently gives rise to a number of secondary products. Benzene-oxide equilibrates spontaneously with the corresponding oxepine valence tautomer, which can ring open to yield a reactive alpha,beta-unsaturated aldehyde, trans-trans-muconaldehyde (MCA). Further reduction or oxidation of MCA gives rise to either 6-hydroxy-trans-trans-2,4-hexadienal or 6-hydroxy-trans-trans-2,4-hexadienoic acid. Both MCA and the hexadienal metabolite are myelotoxic in animal models. Alternatively, benzene-oxide can undergo conjugation with glutathione (GSH), resulting in the eventual formation and urinary excretion of S-phenylmercapturic acid. Benzene-oxide is also a substrate for epoxide hydrolase, which catalyzes the formation of benzene dihydrodiol, itself a substrate for dihydrodiol dehydrogenase, producing catechol. Finally, benzene-oxide spontaneously rearranges to phenol, which subsequently undergoes either conjugation (glucuronic acid or sulfate) or oxidation. The latter reaction, catalyzed by cytochromes P450, gives rise to hydroquinone (HQ) and 1,2,4-benzene triol. Co-administration of phenol and HQ reproduces the myelotoxic effects of benzene in animal models. The two diphenolic metabolites of benzene, catechol and HQ undergo further oxidation to the corresponding ortho-(1,2-), or para-(1,4-)benzoquinones (BQ), respectively. Trapping of 1,4-BQ with GSH gives rise to a variety of HQ-GSH conjugates, several of which are hematotoxic when administered to rats. Thus, benzene-oxide gives rise to a cascade of metabolites that exhibit biological reactivity, and that provide a plausible metabolic basis for benzene-mediated myelotoxicity. Benzene-oxide itself is remarkably stable, and certainly capable of translocating from its primary site of formation in the liver to the bone marrow. However, therein lies the challenge, for although there exists a plethora of information on the metabolism of benzene, and the fate of benzene-oxide, there is a paucity of data on the presence, concentration, and persistence of benzene metabolites in bone marrow. The major metabolites in bone marrow of mice exposed to 50 ppm [(3)H]benzene are muconic acid, and glucuronide and/or sulfate conjugates of phenol, HQ, and catechol. Studies with [(14)C/(13)C]benzene revealed the presence in bone marrow of protein adducts of benzene-oxide, 1,4-BQ, and 1,4-BQ, the relative abundance of which was both dose and species dependent. In particular, histones are bone marrow targets of [(14)C]benzene, although the identity of the reactive metabolite(s) giving rise to these adducts remain unknown. Finally, hematotoxic HQ-GSH conjugates are present in the bone marrow of rats receiving the HQ/phenol combination. In summary, although the fate of benzene-oxide is known in remarkable detail, coupling this information to the site, and mechanism of action, remains to be established.

The E3 ubiquitin ligase cIAP1 binds and ubiquitinates caspase-3 and -7 via unique mechanisms at distinct steps in their processing

Inhibitor of apoptosis (IAP) proteins are widely expressed throughout nature and suppress cell death under a variety of circumstances. X-linked IAP, the prototypical IAP in mammals, inhibits apoptosis largely through direct inhibition of the initiator caspase-9 and the effector caspase-3 and -7. Two additional IAP family members, cellular IAP1 (cIAP1) and cIAP2, were once thought to also inhibit caspases, but more recent studies have suggested otherwise. Here we demonstrate that cIAP1 does not significantly inhibit the proteolytic activities of effector caspases on fluorogenic or endogenous substrates. However, cIAP1 does bind to caspase-3 and -7 and does so, remarkably, at distinct steps prior to or following the removal of their prodomains, respectively. Indeed, cIAP1 bound to an exposed IAP-binding motif, AKPD, on the N terminus of the large subunit of fully mature caspase-7, whereas cIAP1 bound to partially processed caspase-3 in a manner that required its prodomain and cleavage between its large and small subunits but did not involve a classical IAP-binding motif. As a ubiquitin-protein isopeptide ligase, cIAP1 ubiquitinated caspase-3 and -7, concomitant with binding, in a reaction catalyzed by members of the UbcH5 subfamily (ubiquitin carrier protein/ubiquitin-conjugating enzymes), and in the case of caspase-3, differentially by UbcH8. Moreover, wild-type caspase-7 and a chimeric caspase-3 (bearing the AKPD motif) were degraded in vivo in a proteasome-dependent manner. Thus, cIAPs likely suppress apoptosis, at least in part, by facilitating the ubiquitination and turnover of active effector caspases in cells.

Death receptor-induced apoptosis reveals a novel interplay between the chromosomal passenger complex and CENP-C during interphase

Despite the fact that the chromosomal passenger complex is well known to regulate kinetochore behavior in mitosis, no functional link has yet been established between the complex and kinetochore structure. In addition, remarkably little is known about how the complex targets to centromeres. Here, in a study of caspase-8 activation during death receptor-induced apoptosis in MCF-7 cells, we have found that cleaved caspase-8 rapidly translocates to the nucleus and that this translocation is correlated with loss of the centromere protein (CENP)-C, resulting in extensive disruption of centromeres. Caspase-8 activates cytoplasmic caspase-7, which is likely to be the primary caspase responsible for cleavage of CENP-C and INCENP, a key chromosomal passenger protein. Caspase-mediated cleavage of CENP-C and INCENP results in their mislocalization and the subsequent mislocalization of Aurora B kinase. Our results demonstrate that the chromosomal passenger complex is displaced from centromeres as a result of caspase activation. Furthermore, mutation of the primary caspase cleavage sites of INCENP and CENP-C and expression of noncleavable CENP-C or INCENP prevent the mislocalization of the passenger complex after caspase activation. Our studies provide the first evidence for a functional interplay between the passenger complex and CENP-C.

Detection of DNA strand breaks and oxidized DNA bases at the single-cell level resulting from exposure to estradiol and hydroxylated metabolites

Long-term exposure to steroidal estrogens is a key factor contributing to increases in the risk of developing breast cancer. Proposed mechanisms include receptor-activated increases in the rate of cell proliferation leading to the accumulation of genetic damage resulting from reading errors, and the production of DNA damage by species arising from metabolism of 17beta-estradiol (E2) resulting in mutations. In support of the second mechanism, catechol metabolites of E2 induce DNA damage in vitro. In the present study, utilizing the single-cell gel electrophoresis (Comet) assay, we observed increases in the number of single-strand breaks in estrogen receptor alpha-positive (MCF-7) and -negative (MDA-MB-231) breast cancer cells exposed to E2 (for 24 hr) or 4-hydroxy-17beta-estradiol (4-OH-E2; for 2 hr). The concentrations of 4-OH-E2 sufficient to induce these effects were approximately 100 nM, substantially lower than reported previously. The catechol 2-hydroxy-17beta-estradiol (2-OH-E2) also induced strand breaks. 2-OH-E2, often referred to as an improbable carcinogen in humans, is not a major metabolite of E2 in the breast; however, our findings show that it is as DNA-damaging as 4-OH-E2. Formamidopyrimidine glycosylase posttreatment of E2-, 4-OH-E2-, and 2-OH-E2-exposed MCF-7 cells led to an up to sixfold increase in mean tail moment, suggesting that oxidative DNA damage was formed. Comet formation could be partially attenuated by coincubation with dimethylsulfoxide, attributing a small DNA-damaging role to oxyradicals emanating from catechol redox cycling. Similar findings were obtained with MDA-MB-231 cells, indicating that estrogen receptor status is not relevant to these effects. Our observations show that exposure to E2 adds to the oxidative load of cells, and this may contribute to genomic instability.

Characterisation of metabolites of the putative cancer chemopreventive agent quercetin and their effect on cyclo-oxygenase activity

Quercetin (3,5,7,3′,4′-pentahydroxyflavone) is a flavone with putative ability to prevent cancer and cardiovascular diseases. Its metabolism was evaluated in rats and human. Rats received quercetin via the intravenous (i.v.) route and metabolites were isolated from the plasma, urine and bile. Analysis was by high-performance liquid chromatography and confirmation of species identity was achieved by mass spectrometry. Quercetin and isorhamnetin, the 3′-O-methyl analogue, were found in both the plasma and urine. In addition, several polar peaks were characterised as sulphated and glucuronidated conjugates of quercetin and isorhamnetin. Extension of the metabolism studies to a cancer patient who had received quercetin as an i.v. bolus showed that (Quercetin removed) isorhamnetin and quercetin 3′-O-sulphate were major plasma metabolites. As a catechol, quercetin can potentially be converted to a quinone and subsequently conjugated with glutathione (GSH). Oxidation of quercetin with mushroom tyrosinase in the presence of GSH furnished GSH conjugates of quercetin, two mono- and one bis-substituted conjugates. However, these species were not found in biomatrices in rats treated with quercetin. As cyclo-oxygenase-2 (COX-2) expression is mechanistically linked to carcinogenesis, we examined whether quercetin and its metabolites can inhibit COX-2 in a human colorectal cancer cell line (HCA-7). Isorhamnetin and its 4′-isomer tamarixetin were potent inhibitors, reflected in a 90% decrease in prostaglandin E-2 (PGE-2) levels, a marker of COX-2 activity. Quercetin was less effective, with a 50% decline. Quercetin 3- and 7-O-sulphate had no effect on PGE-2. The results indicate that quercetin may exert its pharmacological effects, at least in part, via its metabolites.

Caspase activation inhibits proteasome function during apoptosis

The ubiquitin/proteasome system regulates protein turnover by degrading polyubiquitinated proteins. To date, all studies on the relationship of apoptosis and the proteasome have emphasized the key role of the proteasome in the regulation of apoptosis, by virtue of its ability to degrade regulatory molecules involved in apoptosis. We now demonstrate how induction of apoptosis may regulate the activity of the proteasome. During apoptosis, caspase activation results in the cleavage of three specific subunits of the 19S regulatory complex of the proteasome: S6' (Rpt5) and S5a (Rpn10), whose role is to recognize polyubiquitinated substrates of the proteasome, and S1 (Rpn2), which with S5a and S2 (Rpn1) holds together the lid and base of the 19S regulatory complex. This caspase-mediated cleavage inhibits the proteasomal degradation of ubiquitin-dependent and -independent cellular substrates, including proapoptotic molecules such as Smac, so facilitating the execution of the apoptotic program by providing a feed-forward amplification loop.

XIAP inhibition of caspase-3 preserves its association with the Apaf-1 apoptosome and prevents CD95- and Bax-induced apoptosis

Ligation of death receptors or formation of the Apaf-1 apoptosome results in the activation of caspases and execution of apoptosis. We recently demonstrated that X-linked inhibitor-of-apoptosis protein (XIAP) associates with the apoptosome in vitro. By utilizing XIAP mutants, we now report that XIAP binds to the 'native' apoptosome complex via a specific interaction with the small p12 subunit of processed caspase-9. Indeed, we provide the first direct evidence that XIAP can simultaneously bind active caspases-9 and -3 within the same complex and that inhibition of caspase-3 by the Linker-BIR2 domain prevents disruption of BIR3-caspase-9 interactions. Recent studies suggest that inhibition of caspase-3 is dispensable for its anti-apoptotic effects. However, we clearly demonstrate that inhibition of caspase-3 is required to inhibit CD95 (Fas/Apo-1)-mediated apoptosis, whereas inhibition of either caspase-9 or caspase-3 prevents Bax-induced cell death. Finally, we illustrate for the first time that XIAP mutants, which are incapable of binding to caspases-9 and -3 are completely devoid of anti-apoptotic activity. Thus, XIAP's capacity to maintain inhibition of caspase-9 within the Apaf-1 apoptosome is influenced by its ability to simultaneously inhibit active caspase-3, and depending upon the apoptotic stimulus, inhibition of caspase-9 or 3 is essential for XIAP's anti-apoptotic activity.

Bcl-2 and Bcl-xL inhibit CD95-mediated apoptosis by preventing mitochondrial release of Smac/DIABLO and subsequent inactivation of X-linked inhibitor-of-apoptosis protein

Bcl-2 and Bcl-x(L) are reported to inhibit CD95-mediated apoptosis in "type II" but not in "type I" cells. In the present studies, we found that stimulation of CD95 receptors, with either agonistic antibody or CD95 ligand, resulted in the activation of caspase-8, which in turn processed caspase-3 between its large and small subunits. However, in contrast to control cells, those overexpressing either Bcl-2 or Bcl-x(L) displayed a distinctive pattern of caspase-3 processing. Indeed, the resulting p20/p12 caspase-3 was not active and did not undergo normal autocatalytic processing to form p17/p12 caspase-3, because it was bound to and inhibited by endogenous X-linked inhibitor-of-apoptosis protein (XIAP). Importantly, Bcl-2 and Bcl-x(L) inhibited the release of both cytochrome c and Smac from mitochondria. However, since Smac alone was sufficient to promote caspase-3 activity in vitro by inactivating XIAP, we proposed the existence of a death receptor-induced, Smac-dependent and apoptosome-independent pathway. This type II pathway was subsequently reconstituted in vitro using purified recombinant proteins at endogenous concentrations. Thus, mitochondria and associated Bcl-2 and Bcl-x(L) proteins may play a functional role in death receptor-induced apoptosis by modulating the release of Smac. Our data strongly suggest that the relative ratios of XIAP (and other inhibitor-of-apoptosis proteins) to active caspase-3 and Smac may dictate, in part, whether a cell exhibits a type I or type II phenotype.

Comparisons of the effects of tamoxifen, toremifene and raloxifene on enzyme induction and gene expression in the ovariectomised rat uterus

This study compares the actions of oestradiol, tamoxifen, toremifene and raloxifene on enzyme and gene expression in uterine tissues of ovariectomised rats over 72 h. The time-course for the induction of ornithine decarboxylase by the compounds showed a rapid biphasic response, while for creatine kinase brain type (BB) there was a continued increase over 72 h. The efficacy of induction showed that, with both markers, oestradiol gave the highest induction level, followed by tamoxifen or toremifene and then raloxifene. RT-PCR demonstrated that all compounds decreased oestrogen receptor (ER) alpha, ERbeta and ERbeta2 gene expression, 8-24 h after the first dose, suggesting that down-regulation of ER is not the primary cause of the difference in efficacy between these compounds. Using cDNA arrays, expression of 512 genes was examined in the uteri of oestradiol- or tamoxifen-treated rats. Both compounds resulted in the up-regulation of heat-shock protein 27, telomerase-associated protein 1 and secretin. However, most surprising was the marked down-regulation of Wilms' tumour and retinoblastoma genes. We speculate that this may result in a loss of regulation of the transition from the G1 to the S phase in the cell cycle and may make cells more vulnerable to the carcinogenic effects of tamoxifen in this tissue.

Adenomyosis--a result of disordered stromal differentiation

Adenomyosis is a fairly frequent disorder in adult women characterized by the haphazard location of endometrial glands and stroma deep within the myometrium of the uterus. This study compared the effects on uterine development of the selective estrogen receptor modulators, tamoxifen, toremifene, and raloxifene with estradiol when given orally to female mice on days 2 to 5 after birth. Uterine adenomyosis was found in all (14 of 14) mice dosed with tamoxifen and most mice (12 of 14) treated with toremifene, but in none of the vehicle-dosed controls, in only one animal treated with raloxifene at 42 and 90 days after dosing and in none of the mice treated with estradiol at 42 days. At 6 days, the uterus in the groups that developed a high incidence of adenomyosis showed histological evidence of disturbed differentiation of the myometrium. Gene-expression XY-scatterplots using Clontech mouse 1.2 Atlas mouse cDNA expression arrays analyzing total uterine RNA showed nerve growth factor-alpha, preadipocyte factor-1, and insulin-like growth factor-2 were key genes differentially modified by tamoxifen or toremifene treatment, relative to the controls. As these genes may play an important role in regulating differentiation and development of the myometrium, these data suggest that adenomyosis may be caused primarily by defects in the formation of the myometrium.

Characterization and imaging of A6 epithelial cell clones expressing fluorescently labeled ENaC subunits

A6 model renal epithelial cells were stably transfected with enhanced green fluorescent protein (EGFP)-tagged alpha- or beta-subunits of the epithelial Na(+) channel (ENaC). Transfected RNA and proteins were both expressed in low abundance, similar to the endogenous levels of ENaC in native cells. In living cells, laser scanning confocal microscopy revealed a predominantly subapical distribution of EGFP-labeled subunits, suggesting a readily accessible pool of subunits available to participate in Na(+) transport. The basal level of Na(+) transport in the clonal lines was enhanced two- to fourfold relative to the parent line. Natriferic responses to insulin or aldosterone were similar in magnitude to the parent line, while forskolin-stimulated Na(+) transport was 64% greater than control in both the alpha- and beta-transfected lines. In response to forskolin, EGFP-labeled channel subunits traffic to the apical membrane. These data suggest that channel regulators, not the channel per se, form the rate-limiting step in response to insulin or aldosterone stimulation, while the number of channel subunits is important for basal as well as cAMP-stimulated Na(+) transport.

Delayed penile replantation after prolonged warm ischemia

We report a case of microsurgical replantation of traumatic self-amputation of penis after prolonged warm ischemia as a result of delayed presentation. At 12 weeks postoperative follow-up evaluation, the patient exhibited good urinary flow, spontaneous erection, and a normal response to pharmacological stimulation.

Recruitment, activation and retention of caspases-9 and -3 by Apaf-1 apoptosome and associated XIAP complexes

During apoptosis, release of cytochrome c initiates dATP-dependent oligomerization of Apaf-1 and formation of the apoptosome. In a cell-free system, we have addressed the order in which apical and effector caspases, caspases-9 and -3, respectively, are recruited to, activated and retained within the apoptosome. We propose a multi-step process, whereby catalytically active processed or unprocessed caspase-9 initially binds the Apaf-1 apoptosome in cytochrome c/dATP-activated lysates and consequently recruits caspase-3 via an interaction between the active site cysteine (C287) in caspase-9 and a critical aspartate (D175) in caspase-3. We demonstrate that XIAP, an inhibitor-of-apoptosis protein, is normally present in high molecular weight complexes in unactivated cell lysates, but directly interacts with the apoptosome in cytochrome c/dATP-activated lysates. XIAP associates with oligomerized Apaf-1 and/or processed caspase-9 and influences the activation of caspase-3, but also binds activated caspase-3 produced within the apoptosome and sequesters it within the complex. Thus, XIAP may regulate cell death by inhibiting the activation of caspase-3 within the apoptosome and by preventing release of active caspase-3 from the complex.

A study of the measurement errors associated with the analysis of velar movements assessed from lateral videofluoroscopic investigations

OBJECTIVE

The analysis of lateral videofluoroscopic images of velar movements during speech is a commonly used tool in the management of the cleft palate patient. This study tests the general hypothesis that measurements of velar movements taken from lateral videofluoroscopic images are accurate and reliable.

METHOD

A measurement system was used that allowed for the rapid assessment of velopharyngeal distance, soft palate velocity during the closure cycle, extension of the soft palate at maximum closure, and the angular lift of the soft palate above the plane of the hard palate. Ten recordings of soft palate movement during speech were randomly chosen from lateral X-rays of 27 normal adults. The video recordings were captured by digital frame grabber for subsequent analysis by three operators using a standard PC that was running image-analysis software. The uncertainties associated with the above measurements were analyzed in terms of the errors introduced by the inherent calibration and nonlinearity of the imaging system, the inaccuracy of the patient setup, and the operator-dependent measurement error.

RESULTS

For both absolute dimensions and ratiometric measurements, the measurement uncertainties related to the inherent nonlinearity in the imaging system were shown to be less than 2%. Typical patient misalignments as a result of a 10 degree head rotation and a 10-mm translation out of the measurement plane introduced errors of between 2% and 3%. Results showed that the average standard deviation for measurement of gap size was 1.2 mm, extension ratio was 0.11, angular lift was 3.1 degrees, and soft palate velocity was 15.5 mm/second. The intra-class correlation coefficient generally showed a good agreement between operators, typically in the range 0.8 to 0.9.

CONCLUSION

Measurements of velopharyngeal distance, extension of the soft palate at maximum closure, and the angular lift of the soft palate above the plane of the hard palate assessed from lateral videofluoroscopic images are reliable and accurate. The soft palate velocity during the closure cycle can also be determined, but clinical interpretations based on this parameter should be constrained by the measurement uncertainties.

A test of the structural model of initiation of dieting among adolescent girls

This article reports alternative findings from a pilot study to those presented recently (Strong GF, Huon KG. J. Psychosom. Res., 1998; 44:315-326) in regard to the proposed model of sociopsychological processes involved in the initiation of dieting among young adolescent girls. One hundred thirteen female high school pupils completed a battery of questionnaires that assessed dieting status, dietary restraint, autonomous functioning, skill-related functioning, social influence, and family functioning. The results indicate that family functioning predicts dietary restraint but that this effect is mediated by peer influence to diet. Furthermore, family functioning was associated with autonomous functioning, suggesting that this relationship should be pursued in a future test of the model. This pattern of results is different from an earlier test of the model, which indicated only a parental influence on dieting status. The results confirm that peer influences should be retained as a causal factor in a reformulated structural model.

An audit of anthropometric measurements by medical and physiotherapy staff in patients with ankylosing spondylitis

BACKGROUND

The main treatments for ankylosing spondylitis (AS) are physical (exercise and stretching), and one way of measuring the effectiveness of these therapies is to record spinal movements in a standardized way. Patients are often seen in both medical (rheumatology) and physiotherapy clinics where duplicate information on their progress may be obtained. The purpose of this study was to assess the completeness of data collection for patients attending both medical and physiotherapy clinics.

DESIGN

An audit of data recorded in medical and physiotherapy notes.

SUBJECTS

Patient records identified either from computerized databases (Huddersfield and Bradford) or from a clinic at which only AS patients attended (Leeds). Data from attendances over a defined period were retrieved and recorded on a standard form. All patients thus identified were then cross-matched against those patients attending for physiotherapy during the same period and, where a match occurred, the same data were retrieved from the physiotherapy notes. MINIMUM DATA SET FOR AUDIT: Before data collection started all participants agreed on the minimum data set required for adequate monitoring of patients with AS. The anthropometric measurements included height, chest expansion, cervical rotation, tragus to wall, modified Schober's flexion, extension, lumbar side flexion, intermalleolar abduction, and interfingertip abduction.

RESULTS

Of 182 medical notes screened, 46 patients had not been seen in the defined period, leaving 136 notes to be reviewed. Of these, 52 patients had been seen in physiotherapy in the same period. In general, measurements were infrequently found in medical notes (only chest expansion in 58%, Schober's flexion in 48% and tragus to wall in 47% were measured with any regularity by medical staff). In contrast, corresponding data from physiotherapy notes were more complete (Schober's flexion and lumbar side flexion in 96%, height in 87%, intermalleolar distance in 87% and cervical rotation in 83%).

CONCLUSIONS

Follow-up and monitoring of AS patients in these medical clinics is clearly inadequate. Physiotherapy-led clinics have already been started in one of the study hospitals and the other centres are reviewing their arrangements for AS follow-up, including the possibility of a combined approach to patient management.

An audit of anthropometric measurements by medical and physiotherapy staff in patients with ankylosing spondylitis

BACKGROUND

The main treatments for ankylosing spondylitis (AS) are physical (exercise and stretching), and one way of measuring the effectiveness of these therapies is to record spinal movements in a standardized way. Patients are often seen in both medical (rheumatology) and physiotherapy clinics where duplicate information on their progress may be obtained. The purpose of this study was to assess the completeness of data collection for patients attending both medical and physiotherapy clinics.

DESIGN

An audit of data recorded in medical and physiotherapy notes.

SUBJECTS

Patient records identified either from computerized databases (Huddersfield and Bradford) or from a clinic at which only AS patients attended (Leeds). Data from attendances over a defined period were retrieved and recorded on a standard form. All patients thus identified were then cross-matched against those patients attending for physiotherapy during the same period and, where a match occurred, the same data were retrieved from the physiotherapy notes. MINIMUM DATA SET FOR AUDIT: Before data collection started all participants agreed on the minimum data set required for adequate monitoring of patients with AS. The anthropometric measurements included height, chest expansion, cervical rotation, tragus to wall, modified Schober's flexion, extension, lumbar side flexion, intermalleolar abduction, and interfingertip abduction.

RESULTS

Of 182 medical notes screened, 46 patients had not been seen in the defined period, leaving 136 notes to be reviewed. Of these, 52 patients had been seen in physiotherapy in the same period. In general, measurements were infrequently found in medical notes (only chest expansion in 58%, Schober's flexion in 48% and tragus to wall in 47% were measured with any regularity by medical staff). In contrast, corresponding data from physiotherapy notes were more complete (Schober's flexion and lumbar side flexion in 96%, height in 87%, intermalleolar distance in 87% and cervical rotation in 83%).

CONCLUSIONS

Follow-up and monitoring of AS patients in these medical clinics is clearly inadequate. Physiotherapy-led clinics have already been started in one of the study hospitals and the other centres are reviewing their arrangements for AS follow-up, including the possibility of a combined approach to patient management.

Development of an economic model for the management of upper gastrointestinal disease in primary care. Preliminary findings

Health economic models for identifying therapeutic options that maximise health benefits from limited healthcare resources are being developed in a number of therapeutic areas. The development of such a model for upper gastrointestinal (UGI) symptoms to support decision-making by primary care clinicians is of particular importance, given the prevalence of this symptomatology. This economic model was based upon the clinical guidelines aimed at improving the management of UGI disorders at the primary care level that were developed by the International Gastro Primary Care Group. This paper discusses the derivation, methodology and results of the economic model developed to assess the resource implications arising from these clinical guidelines. In order to construct the economic model, it was necessary to identify the following: every therapeutic pathway followed by patients resource use along each pathway the probabilities of following alternative pathways. One crucial factor underlying the interpretation of results obtained from any economic model is the time period covered by the model. The model presented here analysed the initial 12-month treatment period of 'new' patients presenting with UGI symptoms. In order to test the implications of a longer term perspective, the model is currently being developed to analyse resource use over a 24-month period. The model demonstrates that utilising the predominant symptom approach to the diagnosis and treatment of patients with UGI disorders appears to provide significant benefits in terms of patient management and effective resource use. This factor, together with the more intensive use of Helicobacter pylori eradication therapy, provides the potential to reduce the cost of drugs for the treatment of UGI disorders by approximately 15% in the UK. A major strength of the model is its adaptability to a wide range of clinical and cost scenarios. Such adaptability enables the model to effectively reflect the potential resource implications in countries exhibiting significantly different levels of cost and patient management. In this manner, the model provides one valuable method by which clinicians can be supported in optimising the management of UGI disorders within current resource constraints.

Customising an international disease management model to the needs of individual countries. Application to upper gastrointestinal disease

The baseline economic model for upper gastrointestinal (UGI) disease was developed in the context of patterns of care and resource use within the UK. It provided the opportunity to evaluate the extent to which an economic model developed in one country could be applied to meet the pharmacoeconomic information needs of decision makers in another. The choice of countries for analysis was restricted to countries within the International Gastro Primary Care Group (IGPCG) who had previously agreed on the appropriateness of the basic clinical algorithm to their domestic healthcare environment. This provided a potential sample of 9 countries (Australia, Austria, Germany, Italy, The Netherlands, Sweden, Switzerland, the UK and the USA) of which the UK, Germany, Sweden and Switzerland were chosen as providing a broad spectrum of strategic and operating environments in which to test the international transferability of the economic model. The process and results obtained provide valuable evidence of the extent to which economic analyses can be transferred across national borders.

2-Hydroxy-4-glutathion-S-yl-17beta-estradiol and 2-hydroxy-1-glutathion-S-yl-17beta-estradiol produce oxidative stress and renal toxicity in an animal model of 17beta-estradiol-mediated nephrocarcinogenicity

Chronic exposure of male Syrian hamsters to a variety of estrogens has been linked with a high incidence of renal carcinoma. The basis of this species and tissue specificity remains to be resolved. We have recently shown that (i) 17beta-estradiol is nephrotoxic in the hamster in a manner dependent upon the activity of gamma-glutamyl transpeptidase and (ii) 17beta-estradiol is metabolized to a variety of catechol estrogen glutathione conjugates (Butterworth et al., Carcinogenesis, 18, 561-567, 1997). We report that the catechol estrogen glutathione conjugates exhibit redox properties similar to those of the catechol estrogens, and maintain the ability to generate superoxide radicals. Administration of 2-hydroxy-4-glutathion-S-yl-17beta-estradiol or 2-hydroxy-1-glutathion-S-yl-17beta-estradiol (0.27-5.0 micromol/kg) to Syrian hamsters, produces mild nephrotoxicity. Repeated daily administration of 2-hydroxy-4-glutathion-S-yl-17beta-estradiol causes a sustained elevation in urinary markers of renal damage and in the concentration of renal protein carbonyls and lipid hydroperoxides. Catechol estrogen oxidation and conjugation of glutathione in the liver, followed by the selective uptake of the redox active conjugates in tissues rich in gamma-glutamyl transpeptidase may contribute to 17beta-estradiol-induced renal tumors in the hamster.

Formation of catechol estrogen glutathione conjugates and gamma-glutamyl transpeptidase-dependent nephrotoxicity of 17beta-estradiol in the golden Syrian hamster

In an animal model of hormone-mediated carcinogenesis, male golden Syrian hamsters develop renal carcinoma following prolonged exposure to 17beta-estradiol. The basis for the species and tissue specificity is unclear. Detailed information on the disposition of 17beta-estradiol in this model is lacking. Because catechol estrogens have been implicated in this model of carcinogenesis, we investigated the metabolism and nephrotoxicity of 17beta-estradiol in golden Syrian hamsters, with emphasis on the formation of catechol estrogen thioethers. 17beta-Estradiol (50 micromol/kg, i.p.) is a mild nephrotoxicant, causing significant elevations in the urinary excretion of gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase, glutathione S-transferase (GST) and glucose. Increases in renal protein carbonyls and lipid hydroperoxides, which are markers of oxidative damage, also occur after administration of 17beta-estradiol (50 micromol/kg, i.p.). 17beta-Estradiol-mediated nephrotoxicity is reduced by treating animals with acivicin, an inhibitor of gamma-GT, implying that toxicity is mediated by metabolites requiring metabolism by this enzyme. Following administration of 17beta-[14C]estradiol (100 micromol/kg) to hamsters, 9.7% of the dose is recovered in bile after 5 h, the majority (7.9%) representing aqueous metabolites. Seven catechol estrogen GSH conjugates were identified, 2-hydroxy-1,4-bis-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-estrone, 2-hydroxy-1-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-17beta-estradiol, and 2-hydroxy-1-(glutathion-S-yl)-17beta-estradiol. At 5.4 micromol/kg of 17beta-estradiol, a dose-reflective of daily exposure levels in the hamster model of nephrocarcinogenicity, 12% of the dose is recovered within 5 h as a combination of GSH conjugates of 2- and 4-hydroxy-17beta-estradiol and 2- and 4-hydroxyestrone. In summary, oxidation of catechol estrogens, followed by GSH conjugation, occurs in vivo and 17beta-estradiol is a mild nephrotoxicant in a manner dependent on the activity of gamma-GT.

17 beta-estradiol metabolism by hamster hepatic microsomes: comparison of catechol estrogen O-methylation with catechol estrogen oxidation and glutathione conjugation

Catechol estrogens, the cytochromes P450 mediated metabolites of 17 beta-estradiol, undergo further metabolism either via catechol O-methyltransferase (COMT) catalyzed methylation, or by oxidation and subsequent thioether formation with glutathione (GSH). Secondary metabolites of 17 beta-estradiol arising from both these metabolic pathways have been identified in vivo. However, the relative contribution of catechol O-methylation, and catechol oxidation followed by GSH conjugation, to the disposition of the catechol estrogens is unclear. We have therefore quantified both pathways of catechol estrogen disposition, generated in situ from 17 beta-estradiol, in hamster hepatic microsomes. 17 beta-Estradiol was readily converted to 2- and 4-hydroxy-17 beta-estradiol, both of which were effectively methylated in the presence of COMT (300 units/mL). Addition of GSH (50 microM-1 mM) to microsomal incubations resulted in the formation of four catechol estrogen-derived GSH conjugates. Three conjugates of 2-hydroxy-17 beta-estradiol were identified: 2-hydroxy-1,4-bis(glutathione-S-yl)-17 beta-estradiol, 2-hydroxy-1-glutathione-S-yl-17 beta-estradiol, and 2-hydroxy-4-glutathione-S-yl-27 beta-estradiol. In contrast, just one GSH conjugate of 4-hydroxy-17 beta-estradiol was identified: 4-hydroxy-1-glutathione-S-yl-17 beta-estradiol. When a combination of COMT and GSH were simultaneously added to microsomal incubations, both metabolic pathways competed for the same pool of catechol estrogens, and ascorbate dramatically influenced which of these two pathways predominate. In the presence of ascorbate, catechol estrogen methylation predominated over catechol estrogen oxidation and GSH conjugation. In the absence of ascorbic acid, catechol estrogen methylation, and catechol estrogen oxidation inked to GSH conjugation, contributed equally to the disposition of the catechol estrogens. 17 beta-Estradiol 2- and 4-hydroxylase activity was always higher in the absence of ascorbate, irrespective of whether GSH or COMT was used as the trapping agent. Thus, the usual method (COMT plus ascorbate) of determining 17 beta-estradiol 2- and 4-hydroxylase activity underestimates enzyme activity by approximately 50% when compared to the value obtained when GSH is used to trap the o-quinones in the absence of ascorbate. A reassessment of 17 beta-estradiol 2- and 4-hydroxylase activity in different species and tissues is required to permit a more informed evaluation of the role of catechol estrogens in estrogen-induced carcinogenesis.

17 beta-Estradiol metabolism by hamster hepatic microsomes. Implications for the catechol-O-methyl transferase-mediated detoxication of catechol estrogens

We have shown that the metabolism of 17 beta-estradiol in hamster liver microsomes is concentration-dependent. At low (< 25 microM) concentrations of 17 beta-estriol, 16 alpha-hydroxylase activity predominated, and estriol was the major metabolite. At higher concentrations (25-75 microM), 16 alpha-hydroxylation and aromatic hydroxylation at C2 contributed equally to 17 beta-estradiol metabolism. Aromatic C4-hydroxylation was maximal at 75 microM of 17 beta-estradiol and was always less than C2-hydroxylation. Dehydrogenation of the 17 beta-hydroxyl group to the ketone (estrone) was also observed, but both estrone and 2-hydroxyestrone were minor (approximately 3%) metabolites of 17 beta-estradiol, only detectable at concentrations of 50 microM and above. Catechol-O-methyl transferase (COMT) effectively converted both 2- and 4-hydroxyl-17 beta-estradiol to their corresponding monomethoxy metabolites. Effective reducing conditions are required for COMT activity, because catechol estrogens are readily oxidized to their corresponding ortho-quinones, and ascorbic acid is routinely added to assays of COMT activity. Interestingly, although ascorbic acid (1 mM) increased the recovery of 2- and 4-hydroxy-17 beta-estradiol from microsomal incubations, it decreased the recovery of the methoxy metabolites (approximately 40%). Since the enediol function of ascorbate resembles that of a catechol group, ascorbate is a substrate for COMT and probably competes with the catechol estrogens for methylation. Because previous studies describing the ability of COMT to inhibit the covalent binding of electrophilic reactive metabolites of [4-(14)C]17 beta-estradiol to microsomal protein were performed in the presence of high (100 mM) Mg2+ concentrations, we also investigated the effects of Mg2+ on 17 beta-estradiol metabolism. Concentrations of Mg2+ > 10 mM inhibited the metabolism of 17 beta-estradiol, as evidenced by i) the increased recovery of substrate; ii) a decrease in the formation of estriol, estrone, and 2-, and 4-hydroxy-17 beta-estradiol; iii) a decrease in the recovery of water-soluble metabolites when incubations were performed in the presence of glutathione (GSH) to trap the reactive electrophilic metabolites; and iv) a decrease in the amount of reactive electrophilic metabolites bound to microsomal protein. GSH also decreased the covalent binding of electrophilic metabolites of [4-(14)C]17 beta-estradiol to microsomal protein, with the concomitant formation of water-soluble metabolites. Thus, both COMT and GSH combine to limit the formation of electrophilic metabolites from 17 beta-estradiol. The relative importance of each of these pathways to the disposition of the catechol estrogens remains to be determined.

Metachromatic leukodystrophy: a case report of a child with an equinus deformity

The authors discuss an unusual disorder of myelin metabolism. Initial presentation was due to an unstable gait pattern. Characteristics of the disease and a representative case are evaluated.

The detection of subchronic testicular damage using urinary creatine: studies with 2-methoxyethanol

We have previously shown that a number of testicular toxicants administered acutely to rats raise urinary creatine. The aim of this study was to determine if this creatinuria was maintained during subchronic testicular damage. Repeated exposure of rats to 2-methoxyethanol for 10 days administered in the drinking water caused significant testicular damage at the highest dose. The urinary creatine:creatine ratio was significantly increased in the animals receiving the highest dose (220 mg/kg per day) and also those receiving doses of 87 mg/kg per day. Increases in the ratio seen after the lowest dose (43 mg/kg per day) were significant in some cases, but showed more variability. Relative testicular weight was only significantly reduced after the highest dose. Increases in body weight over the time of exposure were only significantly lower after the highest dose of 2-methoxyethanol. The results indicate that urinary creatine may be a useful biomarker for chronic testicular damage.

The frontal sinus in frontoethmoidal meningoencephaloceles

We performed a review of all patients with frontoethmoidal meningoencephaloceles (FEME) in whom frontal sinus development would be expected to be complete. Frontal sinus absence is the predominant finding. The potential role of the FEME in producing a structural blockage to normal frontal sinus development is suggested. Surgical correction of the encephalocele should include augmentation of the glabella to compensate for the combined effects of the FEME and the surgical osteotomies in this region.

A novel role for carboxylesterase in the elevation of cellular cysteine by esters of cysteine

Esters of cysteine, such as cysteine isopropylester (CIPE) or cysteine cyclohexylester (CCHE), are efficient delivery systems for cysteine to cells. After enzymic cleavage, the esters of cysteine provide a source of cellular cysteine, which may support reduced glutathione (GSH) synthesis and/or act as a direct chemoprotectant. Reducing esterase activity of rat lung slices or isolated hepatocytes with paraoxon or bis(4-nitrophenyl) phosphate or by reducing the temperature to 4 degrees dramatically altered the metabolism of esters of cysteine; the initial increase in cellular cysteine was slowed, the residency time of cysteine esters in the extracellular pool was prolonged without substantially enhancing the levels of intracellular ester. Incubation of lung slices with CIPE at 4 degrees led to a marked increase in cellular cysteine, which prior inhibition of esterase activity abolished. Inhibiting the neutral amino acid uptake systems, ASC and L, while effecting the uptake of cysteine, did not reduce the elevation of cellular cysteine by CIPE. We propose that the elevation of cellular cysteine by esters of cysteine may be mediated by membrane associated esterase activity.

Elevation of cysteine and replenishment of glutathione in rat lung slices by cysteine isopropylester and other cysteine precursors

In this study, we have used a rat lung slice model to compare the ability to several potential cysteine delivery systems (L-cysteine isopropylester, L-cysteine cyclohexylester, N-acetylcysteine, L,2-oxo-4-thiazolidine carboxylic acid and cysteine) to elevate cysteine and glutathione (GSH) levels in control lung slices and slices depleted of their GSH by diethyl maleate. The esters of cysteine produced the greatest rise in lung slice cysteine. All the cysteine delivery systems were capable of replenishing GSH in lung slices previously depleted of GSH by diethyl maleate.