Understanding the mechanisms underlying cognitive control in psychosis.

BACKGROUND: Cognitive control (CC) involves a top-down mechanism to flexibly respond to complex stimuli and is impaired in schizophrenia. METHODS: This study investigated the impact of increasing complexity of CC processing in 140 subjects with psychosis and 39 healthy adults, with assessments of behavioral performance, neural regions of interest and symptom severity. RESULTS: The lowest level of CC (Stroop task) was impaired in all patients; the intermediate level of CC (Faces task) with explicit emotional information was most impaired in patients with first episode psychosis. Patients showed activation of distinct neural CC and reward networks, but iterative learning based on the higher-order of CC during the trust game, was most impaired in chronic schizophrenia. Subjects with first episode psychosis, and patients with lower symptom load, demonstrate flexibility of the CC network to facilitate learning, which appeared compromised in the more chronic stages of schizophrenia. CONCLUSION: These data suggest optimal windows for opportunities to introduce therapeutic interventions to improve CC.

Telomere length is a novel predictive biomarker of sensitivity to anti-EGFR therapy in metastatic colorectal cancer.

BACKGROUND: Telomeres are TTAGGG tandem repeats capping chromosomal ends and partially controlled by the telomerase enzyme. The EGFR pathway putatively regulates telomerase function, prompting an investigation of telomere length (TL) and its association with anti-epidermal growth factor receptor (EGFR) therapy in metastatic colorectal cancer (mCRC). METHODS: Colorectal cancer cell lines were treated with multiple drugs and sensitivity determined. Clinical information was gathered from 75 patients who had received anti-EGFR drugs. Telomere length was measured using a validated qRT-PCR technique. RESULTS: In CRC cell lines, TL independently predicted cetuximab sensitivity. Cells with shorter TL had growth inhibition of 18.6±3.41% as compared with 41.39±8.58% in longer TL (P=0.02). These in vitro findings were validated clinically, in a robust multivariate model. Among patients with KRas WT tumours, those with longer TL had a superior median progression-free survival (PFS) of 24.9 weeks than those with shorter TL; median 11.1 weeks, HR 0.31; P=0.048. CONCLUSION: Telomere length could be a potential unique biomarker predictive of clinical benefit (PFS) of mCRC patients treated with anti-EGFR therapy. This is the novel demonstration of a complex hitherto undescribed interaction, placing anti-EGFR therapy, EGFR pathway, and the telomerase complex within a clinical context.

ZNF804A genetic variation (rs1344706) affects brain grey but not white matter in schizophrenia and healthy subjects.

BACKGROUND: Genetic variation in the gene encoding ZNF804A, a risk gene for schizophrenia, has been shown to affect brain functional endophenotypes of the disorder, while studies of white matter structure have been inconclusive. METHOD: We analysed effects of ZNF804A single nucleotide polymorphism rs1344706 on grey and white matter using voxel-based morphometry (VBM) in high-resolution T1-weighted magnetic resonance imaging scans of 62 schizophrenia patients and 54 matched healthy controls. RESULTS: We found a significant (p < 0.05, family-wise error corrected for multiple comparisons) interaction effect of diagnostic group x genotype for local grey matter in the left orbitofrontal and right and left lateral temporal cortices, where patients and controls showed diverging effects of genotype. Analysing the groups separately (at p < 0.001, uncorrected), variation in rs1344706 showed effects on brain structure within the schizophrenia patients in several areas including the left and right inferior temporal, right supramarginal/superior temporal, right and left inferior frontal, left frontopolar, right and left dorsolateral/ventrolateral prefrontal cortices, and the right thalamus, as well as effects within the healthy controls in left lateral temporal, right anterior insula and left orbitofrontal cortical areas. We did not find effects of genotype of regional white matter in either of the two cohorts. CONCLUSIONS: Our findings demonstrate effects of ZNF804A genetic variation on brain structure, with diverging regional effects in schizophrenia patients and healthy controls in frontal and temporal brain areas. These effects, however, might be dependent on the impact of other (genetic or non-genetic) disease factors.

Should laparoscopic reversal of Hartmann's procedure be the first line approach in all patients?

BACKGROUND/AIMS: To assess if the laparoscopic reversal of Hartmann's can be attempted in all patients, without detriment to short or long-term outcomes if the patient is subsequently converted to open. METHODS: Retrospective review of a prospectively collected database of all reversals under 8 surgeons at a single unit over 105 months, two surgeons attempting laparoscopic reversal in all patients, two pre-selecting for the laparoscopic approach and four utilising the open approach. Long-term follow-up data for re-admissions, re-operations and incisional hernia rate obtained from a postal questionnaire. RESULTS: 45 laparoscopic and 50 primary open reversals were identified. There was no difference in the mean age or previous peritonitis rate in either group. Laparoscopic conversion rate was 29% (13 patients). On intention to treat analysis, a significant difference was identified in the overall 30-day post-operative surgical morbidity (8.9% Laparoscopic-attempted vs 26.0% Open, p = 0.030). There was no difference in operating times (mean 164 vs 172 min, p = 0.896) despite the 13 patients converted to an open procedure. Mean length of stay was significantly lower in the laparoscopic-attempted group at 6.8 days (5.2-8.4) vs 14.9 days (6.4-23.7) in the open group (p = 0.001). Anastomotic leak rates were not statistically different. The median follow up was 27 months (range 6-105); 60% of patients completed a postal follow-up questionnaire. There was no difference in short-term or long-term re-admission or reoperation rates. CONCLUSIONS: Laparoscopic reversal of Hartamann's is associated with shorter hospital stay and lower morbidity even in unselected patients. Long-term outcomes are similar.

Intramedullary ancient schwannoma of the cervical spinal cord: case report and review of literature.

We report a rare case of intramedullary ancient schwannoma of cervical spinal cord in a 68 year old patient. About 49 cases of intramedullary schwannomas and neurofibromas have been reported in the literature but to our knowledge there is no report of the 'ancient' variety of intramedullary schwannoma. The cell of origin of these tumours is the schwann cell, which normally does not exist in the parenchyma of the central nervous system. Many theories have been advanced to explain this paradox. According to one theory, these tumours arise from the perivascular nerve plexus of the pial vessels. This plexus was found mostly to exist along the branches of the anterior spinal artery. In our case, the tumour was supplied by two branches of the anterior spinal artery, which may add further support to the above theory.

The initial steps of biogenesis of cyanobacterial photosystems occur in plasma membranes.

During oxygenic photosynthesis in cyanobacteria and chloroplasts of plants and eukaryotic algae, conversion of light energy to biologically useful chemical energy occurs in the specialized thylakoid membranes. Light-induced charge separation at the reaction centers of photosystems I and II, two multisubunit pigment-protein complexes in the thylakoid membranes, energetically drive sequential photosynthetic electron transfer reactions in this membrane system. In general, in the prokaryotic cyanobacterial cells, the thylakoid membrane is distinctly different from the plasma membrane. We have recently developed a two-dimensional separation procedure to purify thylakoid and plasma membranes from the genetically widely studied cyanobacterium Synechocystis sp. PCC 6803. Immunoblotting analysis demonstrated that the purified plasma membrane contained a number of protein components closely associated with the reaction centers of both photosystems. Moreover, these proteins were assembled in the plasma membrane as chlorophyll-containing multiprotein complexes, as evidenced from nondenaturing green gel and low-temperature fluorescence spectroscopy data. Furthermore, electron paramagnetic resonance spectroscopic analysis showed that in the partially assembled photosystem I core complex in the plasma membrane, the P700 reaction center was capable of undergoing light-induced charge separation. Based on these data, we propose that the plasma membrane, and not the thylakoid membrane, is the site for a number of the early steps of biogenesis of the photosynthetic reaction center complexes in these cyanobacterial cells.

Amino acid residues that are critical for in vivo catalytic activity of CtpA, the carboxyl-terminal processing protease for the D1 protein of photosystem II.

CtpA, a carboxyl-terminal processing protease, is a member of a novel family of endoproteases that includes a tail-specific protease from Escherichia coli. In oxygenic photosynthetic organisms, CtpA catalyzes C-terminal processing of the D1 protein of photosystem II, an essential event for the assembly of a manganese cluster and consequent light-mediated water oxidation. We introduced site-specific mutations at 14 conserved residues of CtpA in the cyanobacterium Synechocystis sp. PCC 6803 to examine their functional roles. Analysis of the photoautotrophic growth capabilities of these mutants, their ability to process precursor D1 protein and hence evolve oxygen, along with an estimation of the protease content in the mutants revealed that five of these residues are critical for in vivo activity of CtpA. Recent x-ray crystal structure analysis of CtpA from the eukaryotic alga Scenedesmus obliquus (Liao, D.-I., Qian, J., Chisholm, D. A., Jordan, D. B. and Diner, B. A. (2000) Nat. Struct. Biol. 7, 749-753) has shown that the residues equivalent to Ser-313 and Lys-338, two of the five residues mentioned above, form the catalytic center of this enzyme. Our in vivo analysis demonstrates that the three other residues, Asp-253, Arg-255, and Glu-316, are also important determinants of the catalytic activity of CtpA.

Increased functional cell surface expression of CFTR and DeltaF508-CFTR by the anthracycline doxorubicin.

Cystic fibrosis (CF) is a disease that is caused by mutations within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The most common mutation, DeltaF508, accounts for 70% of all CF alleles and results in a protein that is defective in folding and trafficking to the cell surface. However, DeltaF508-CFTR is functional when properly localized. We report that a single, noncytotoxic dose of the anthracycline doxorubicin (Dox, 0.25 microM) significantly increased total cellular CFTR protein expression, cell surface CFTR protein expression, and CFTR-associated chloride secretion in cultured T84 epithelial cells. Dox treatment also increased DeltaF508-CFTR cell surface expression and DeltaF508-CFTR-associated chloride secretion in stably transfected Madin-Darby canine kidney cells. These results suggest that anthracycline analogs may be useful for the clinical treatment of CF.

Differential effects of mitomycin C and doxorubicin on P-glycoprotein expression.

Previous studies have demonstrated that mitomycin C (MMC) and other DNA cross-linking agents can suppress MDR1 (multidrug resistance 1) gene expression and subsequent functional P-glycoprotein (Pgp) expression, whereas doxorubicin and other anthracyclines increase MDR1 gene expression. In the present study, with stably transfected Madin-Darby canine kidney C7 epithelial cells expressing a human Pgp tagged with green fluorescent protein under the proximal human MDR1 gene promoter, we demonstrated that MMC and doxorubicin have differential effects on Pgp expression and function. Doxorubicin caused a progressive increase in the cell-surface expression of Pgp and function. In contrast, MMC initially increased plasma membrane expression and function at a time when total cellular Pgp was constant and Pgp mRNA expression had been shown to be suppressed. This was followed by a rapid and sustained decrease in cell-surface expression at later times, presumably as a consequence of the initial decrease in mRNA expression. These studies imply that there are at least two independent chemosensitive steps that can alter Pgp biogenesis: one at the level of mRNA transcription and the other at the level of Pgp trafficking. Understanding the combined consequences of these two mechanisms might lead to novel chemotherapeutic approaches to overcoming drug resistance in human cancers by altering either Pgp mRNA expression or trafficking to the membrane.

Functional enhancement of CFTR expression by mitomycin C.

Cystic fibrosis is caused by mutations in the CFTR gene. The most common of these mutations, DeltaF508, results in a protein that is not trafficked to the apical plasma membrane but instead is retained and degraded in the endoplasmic reticulum (ER) by the 26S proteosome. However, this protein is functional upon plasma membrane expression. It has been theoretically estimated that even a modest ( approximately 10%) increase in CFTR-associated chloride conductance can be beneficial in a clinical setting. Thus, understanding basic CFTR biogenesis is important, and identification of prototypical compounds that can increase CFTR expression and trafficking is potentially useful in the development of novel therapeutic strategies to treat cystic fibrosis. We report that mitomycin C (MMC) elicits such a response by increasing CFTR mRNA and protein expression in T-84 and HT-29 cells at very low, non-cytotoxic, pharmacologically relevant concentrations (0.1 microM) leading to enhanced chloride secretion. Thus, MMC may be a useful compound for understanding CFTR regulation and biogenesis.

Maf transcriptionally activates the mouse p53 promoter and causes a p53-dependent cell death.

An increase in the level of the tumor suppressor protein p53 can induce cell cycle arrest or cell death. Although mechanisms for regulating the life span of p53 have been described, there is growing evidence that transcriptional regulation of the p53 gene contributes significantly to controlling p53 protein levels and therefore the fate of a cell. However, the signal transduction pathways that lead to transcriptional activation of the p53 gene are poorly understood. The oncoprotein v-Maf and its cellular counterparts belong to the large combinatorially complex basic leucine zipper family of transcription factors, which include the AP1 family. To date few cellular targets of c-Maf have been identified. It is demonstrated here that v-Maf can bind as a homodimer to a variant Maf recognition element located between -66 and -54 upstream in the mouse p53 promoter. V-Maf and its cellular counterparts are shown to activate p53 expression through this site. The ability of v-Maf to activate p53 expression is modulated by AP1 family members. In addition, overexpression of v-Maf in primary cells leads to a p53-dependent cell death. Thus, Maf and members of the AP1 family are able to regulate p53 expression through this site in the p53 promoter.

Meniscal reconstruction. Part II: Outcome, potential complications, and future directions.

Currently, magnetic resonance imaging and second-look arthroscopy are the only methods available to objectively evaluate the outcome of meniscal reconstruction. While clinical studies indicate progressively improving outcomes of meniscal reconstruction, longer follow-up is needed to determine whether the natural history of joint degeneration can be altered. Part I of this comprehensive review, published in the April 1999 issue, discussed the anatomy and function of the meniscus, followed by the indications, techniques, and graft considerations for meniscal allograft reconstruction. Part II reviews the results, potential complications, and future directions of meniscal allograft reconstruction.

Meniscal reconstruction. Part I: indications, techniques, and graft considerations.

Menisci are specialized structures capable of bearing loads, absorbing shock, stabilizing, and lubricating the knee joint. Increased knowledge of meniscal anatomy and function, as well as studies of chronic anterior cruciate ligament-deficient and -reconstructed knees, have indicated that loss of meniscal function is associated with progression of degenerative changes within the knee. Meniscal reconstruction has been developed to preserve those functions prior to the development of significant degenerative changes in patients who have undergone meniscectomy. Indications are still being defined. Meniscal reconstruction has been achieved by either arthroscopically assisted or open techniques. Anatomic placement and secure fixation of the graft are requirements to allow the optimal revascularization needed for successful incorporation of the graft. Part I of this review will discuss the anatomy and function of the meniscus, followed by the indications, techniques, and graft considerations for meniscal allograft reconstruction. In Part II, which will be published in the May 1999 issue, we will review the results, potential complications, and future directions of meniscal allograft reconstruction.

Subunit dependent modulation of GABAA receptor function by neuroactive steroids.

Neurosteroids are potent, endogenous modulators of GABAA receptor function in the central nervous system. The endogenous progesterone metabolite allopregnanolone (ALP) and the synthetic steroid compound alphaxalone (AFX) have been shown to both directly activate and potentiate GABAA receptor-activated membrane current (IGABA). The role of different alpha and gamma subunit subtypes in modulation of IGABA by ALP and AFX was investigated using recombinant GABAA receptor isoforms expressed in Xenopus oocytes. Changing or removal of the alpha subunit subtype altered the efficacy of both ALP and AFX (alpha2beta1gamma2L>alpha1beta1gamma2L>>beta1gamma2L) to potentiate IGABA, but did not alter the potency of the neuroactive steroids at these receptor isoforms. The efficacy of ALP to enhance IGABA was also dependent on the gamma subunit subtype (alpha1beta1gamma3>alpha1beta1gamma2L = alpha1beta1gamma1). AFX also had higher efficacy in the alpha1beta1gamma3 receptor isoform compared to alpha1beta1gamma1. In contrast to ALP, the potency of AFX was greater in the alpha1beta1gamma3 and alpha1beta1gamma1 receptor isoforms compared to alpha1beta1gamma2L. This study provides evidence that the alpha subunit subtype determines the efficacy, but not the potency, of these neuroactive steroids to potentiate IGABA. The gamma3 subunit subtype increases the maximal efficacy of neuroactive steroids compared to other gamma subunit subtypes. These results suggest that the heteromeric assembly of different GABAA receptor isoforms containing different subunit subtypes results in multiple steroid recognition sites on GABAA receptors that in turn produce distinctly different modulatory interactions between neuroactive steroids acting at the GABAA receptor.

Selective modulation of collagenase 1 gene expression by the chemotherapeutic agent doxorubicin.

Matrix metalloproteinases (MMPs) play a crucial role in tumor cell invasion and metastasis due to their ability to digest basement membrane and extracellular matrix components, thereby facilitating cell movement through connective tissues. At noncytotoxic concentrations, i.e., concentrations lower than those normally used in cancer chemotherapy, the anthracycline doxorubicin specifically inhibited collagenase 1 (MMP-1) gene expression in the highly invasive and metastatic human melanoma cell line A2058. This inhibition was specific for collagenase 1 because it did not affect the expression of two other MMPs, gelatinase A (MMP-2) and gelatinase B (MMP-9). The reduction in collagenase 1 expression correlated with a decrease in the invasive ability of tumor cells through a collagen type I matrix and was independent of the cytotoxic and antiproliferative effects usually associated with this anticancer drug. The selective modulation of collagenase 1 expression by nontoxic doses of doxorubicin suggests a novel application for this chemotherapeutic agent, perhaps in combination therapy, because it decreases the invasive/metastatic potential of melanoma cells that are otherwise unaffected by this drug.

2',5'-Oligoadenylate-antisense chimeras cause RNase L to selectively degrade bcr/abl mRNA in chronic myelogenous leukemia cells.

We report an RNA targeting strategy, which selectively degrades bcr/abl mRNA in chronic myelogenous leukemia (CML) cells. A 2', 5'-tetraadenylate activator (2-5A) of RNase L was chemically linked to oligonucleotide antisense directed against either the fusion site or against the translation start sequence in bcr/abl mRNA. Selective degradation of the targeted RNA sequences was demonstrated in assays with purified RNase L and decreases of p210(bcr/abl) kinase activity levels were obtained in the CML cell line, K562. Furthermore, the 2-5A-antisense chimeras suppressed growth of K562, while having substantially reduced effects on the promyelocytic leukemia cell line, HL60. Findings were extended to primary CML cells isolated from bone marrow of patients. The 2-5A-antisense treatments both suppressed proliferation of the leukemia cells and selectively depleted levels of bcr/abl mRNA without affecting levels of beta-actin mRNA, determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The specificity of this approach was further shown with control oligonucleotides, such as chimeras containing an inactive dimeric form of 2-5A, antisense lacking 2-5A, or chimeras with altered sequences including several mismatched nucleotides. The control oligonucleotides had either reduced or no effect on CML cell growth and bcr/abl mRNA levels. These findings show that CML cell growth can be selectively suppressed by targeting bcr/abl mRNA with 2-5A-antisense for decay by RNase L and suggest that these compounds should be further explored for their potential as ex vivo purging agents of autologous hematopoietic stem cell transplants from CML patients.