Role of GABA Deficit in Sensitivity to the Psychotomimetic Effects of Amphetamine

Some schizophrenia patients are more sensitive to amphetamine (AMPH)-induced exacerbations in psychosis–an effect that correlates with higher striatal dopamine release. This enhanced vulnerability may be related to gamma-aminobutyric acid (GABA) deficits observed in schizophrenia. We hypothesized that a pharmacologically induced GABA deficit would create vulnerability to the psychotomimetic effects to the ‘subthreshold'' dose of AMPH in healthy subjects, which by itself would not induce clinically significant increase in positive symptoms. To test this hypothesis, a GABA deficit was induced by intravenous infusion of iomazenil (IOM; 3.7 μg/kg), an antagonist and partial inverse agonist of benzodiazepine receptor. A subthreshold dose of AMPH (0.1 mg/kg) was administered by intravenous infusion. Healthy subjects received placebo IOM followed by placebo AMPH, active IOM followed by placebo AMPH, placebo IOM followed by active AMPH, and active IOM followed by active AMPH in a randomized, double-blind crossover design over 4 test days. Twelve healthy subjects who had a subclinical response to active AMPH alone were included in the analysis. Psychotomimetic effects (Positive and Negative Syndrome Scale (PANSS)), perceptual alterations (Clinician Administered Dissociative Symptoms Scale (CADSS)), and subjective effects (visual analog scale) were captured before and after the administration of drugs. IOM significantly augmented AMPH-induced peak changes in PANSS positive symptom subscale and both subjective and objective CADSS scores. There were no pharmacokinetic interactions. In conclusion, GABA deficits increased vulnerability to amphetamine-induced psychosis-relevant effects in healthy subjects, suggesting that pre-existing GABA deficits may explain why a subgroup of schizophrenia patients are vulnerable to AMPH.     

Transcranial magnetic stimulation and auditory hallucinations in schizophrenia

12 patients with schizophrenia and auditory hallucinations received 1 Hz transcranial magnetic stimulation of left temporoparietial cortex. In a double-blind crossover trial, active stimulation significantly reduced hallucinations relative to sham stimulation.     

SHIP, SHIP2, and PTEN activities are regulated in vivo by modulation of their protein levels: SHIP is up-regulated in macrophages and mast cells by lipopolysaccharide

The phosphatidylinositol-3 kinase (PI3K) pathway plays a central role in regulating numerous biologic processes, including survival, adhesion, migration, metabolic activity, proliferation, differentiation, and end cell activation through the generation of the potent second messenger PI-3,4,5-trisphosphate (PI-3,4,5-P(3)). To ensure that activation of this pathway is appropriately suppressed/terminated, the ubiquitously expressed 54-kDa tumor suppressor PTEN hydrolyzes PI-3,4,5-P(3) to PI-4,5-P(2), whereas the 145-kDa hematopoietic-restricted SH2-containing inositol 5'-phosphatase SHIP (also known as SHIP1), the 104-kDa stem cell-restricted SHIP sSHIP, and the more widely expressed 150-kDa SHIP2 break it down to PI-3,4-P(2). In this review, we focus on the properties of these phospholipid phosphatases and summarize recent data showing that the activities of these negative regulators often are modulated by simply altering their protein levels. We also highlight the critical role that SHIP plays in lipopolysaccharide-induced macrophage activation and in endotoxin tolerance.     

A review of staging chest CT in trunk and extremity soft tissue sarcoma

Objectives:To determine the incidence of pulmonary metastases on chest CT in trunk and extremity soft tissue sarcoma based on two size criteria, and to identify factors associated with metastases.Methods:Retrospective review of chest CT studies in patients with trunk and extremity soft tissue sarcoma over an 18-month period. Data collected included patient age/sex, tumour location, size and relationship to fascia. All chest CTs were reviewed for the presence of metastases which were diagnosed according to two size criteria: multiple nodules > 5 mm in size or multiple nodules > 10 mm in size. Follow-up CT studies were reviewed in cases initially considered indeterminate.Results:127 males and 73 females were included (mean age 57.1 years; range 10–90 years). 147 (73.5%) tumours were deep to the fascia and 53 (26.5%) superficial. Tumour size classified according to the 12 AJCC 2019 criteria was: T1 = 52, T2 = 76, T3 = 39, T4 = 33. Based on nodule size >5 mm, 73 (36.5%) patients had no metastases, 42 (21%) had metastases, while 85 (42.5%) studies were indeterminate. Based on nodule size >10 mm, 73 (36.5%) patients had no metastases, 28 (14%) had metastases, while 99 (49.5%) studies were indeterminate. Larger maximum dimension of the primary tumour was a risk factor for pulmonary metastases using both size criteria.Conclusion:The incidence of pulmonary metastases at presentation in trunk and extremity soft tissue sarcoma is 14–21%. 42.5–49.5% of chest CTs were indeterminate.Advances in knowledge:The incidence of pulmonary metastases at presentation in trunk and extremity soft tissue sarcoma is 14–21%. Indeterminate pulmonary nodules are also very common.     

Lipid-Lowering Efficacy of Ezetimibe in Patients with Atherosclerotic Cardiovascular Disease: A Systematic Review and Meta-Analyses

Patients with atherosclerotic cardiovascular disease (ASCVD), especially those with recent (< 1 year) acute coronary syndrome (ACS), are at high risk for recurrent cardiovascular events. This risk can be reduced by lowering low-density lipoprotein cholesterol (LDL-C) levels. A comprehensive meta-analysis on the LDL-C-lowering efficacy of ezetimibe is lacking. This study attempts to address this gap. A systematic literature review of randomized controlled trials evaluating the LDL-C-lowering efficacy of ezetimibe in the ASCVD population was conducted. MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were searched for publications from database inception to August 2018 and for conference abstracts from 2015 to August 2018. Meta-analyses were conducted to evaluate the LDL-C-lowering efficacy of ezetimibe in the ASCVD population and the recent ACS subgroup. In total, 12 studies were eligible for the meta-analyses. Treatment with combination ezetimibe plus statin therapy showed greater absolute LDL-C reduction than statin monotherapy (mean difference − 21.86 mg/dL; 95% confidence interval [CI] − 26.56 to − 17.17; p < 0.0001) after 6 months of treatment (or at a timepoint closest to 6 months). Similarly, in patients with recent ACS, combination ezetimibe plus statin therapy was favorable compared with statin monotherapy (mean treatment difference − 19.19 mg/dL; 95% CI − 25.22 to − 13.16; p < 0.0001). Ezetimibe, when added to statin therapy, provided a modest additional reduction in LDL-C compared with statin monotherapy. However, this may not be sufficient for some patients with ASCVD who have especially high LDL-C levels despite optimal statin therapy.     

Glycolipid GD3 and GD3 synthase are key drivers for glioblastoma stem cells and tumorigenicity

The cancer stem cells (CSCs) of glioblastoma multiforme (GBM), a grade IV astrocytoma, have been enriched by the expressed marker CD133. However, recent studies have shown that CD133⁻ cells also possess tumor-initiating potential. By analysis of gangliosides on various cells, we show that ganglioside D3 (GD3) is overexpressed on eight neurospheres and tumor cells; in combination with CD133, the sorted cells exhibit a higher expression of stemness genes and self-renewal potential; and as few as six cells will form neurospheres and 20–30 cells will grow tumor in mice. Furthermore, GD3 synthase (GD3S) is increased in neurospheres and human GBM tissues, but not in normal brain tissues, and suppression of GD3S results in decreased GBM stem cell (GSC)-associated properties. In addition, a GD3 antibody is shown to induce complement-dependent cytotoxicity against cells expressing GD3 and inhibition of GBM tumor growth in vivo. Our results demonstrate that GD3 and GD3S are highly expressed in GSCs, play a key role in glioblastoma tumorigenicity, and are potential therapeutic targets against GBM.Glioblastoma multiforme (GBM) is extremely infiltrative and difficult to treat, and most patients develop recurrence after therapy. Over the past decade, many studies have suggested that bulk GBM tumors harbor cancer stem cells (CSCs) (1, 2), a distinct subpopulation of cancer cells that are able to initiate new tumors efficiently, have long-term self-renewal capacity, and survive better against chemo- or radiotherapy (2–4). CD133 has become a widely used marker for the enrichment of GBM CSCs (GSCs) and other tumor types (5–10). However, recent studies have shown that CD133 is not specific for GSCs because CD133⁻ cells also possess tumor-initiating potential (11–13), indicating the need to identify more specific and exclusive markers for GSCs to facilitate our understanding of GSCs and therapeutic development against GBM. Several reports have proposed L1CAM, A2B5, integrin α6, MET, and CD15 as markers for GSCs (14–18). However, none of these protein markers could be used specifically to identify GSCs, and no study was reported with respect to glycans as potential markers, although glycan biosynthesis involves multiple genes and it is possible to create different structures in cancer progression. It is noted that ganglioside D2 (GD2) and ganglioside D3 (GD3) were found on the surface of neural stem cells (NSCs) and that stage-specific embryonic antigen 3 (SSEA3) and SSEA4 were found on embryonic stem cells and cancer cells (19–21), but there is no glycan marker found on the surface of GSCs.Gangliosides are sialic acid-containing glycosphingolipids (GSLs) that are most abundant in the nervous system (22). The expression levels and patterns of gangliosides during brain development shift from simple gangliosides, such as GM3 and GD3, to complex gangliosides, such as GM1, GD1a, GD1b, and GT1b (23, 24). Moreover, several unique ganglioside markers, including SSEA3, SSEA4, GD2, and GD3, have been identified in stem cells (19). GD3, a b-series ganglioside containing two sialic acids, is highly expressed in mouse and human embryonic NSCs (20, 25). In cancers, GD3 is highly accumulated in human primary melanoma tissues as well as in established melanoma cell lines (26), whereas human normal melanocytes express no or minimal levels of GD3 (27). Moreover, malignant gliomas contain higher levels of GD3, and its expression correlates with the degree of malignancy (28). GD3 is produced from the precursor GM3 by the activity of GD3 synthase (GD3S), which mediates the properties of CSCs through the c-MET signaling pathway and correlates with poor prognosis in triple-negative human breast tumors (29). These findings suggest that GD3 may play an important role in the transformation of normal cells into tumors, and imply that GD3 could be a cell surface marker for GSCs.This study was designed to identify glycan markers for the enrichment of GBM stem cells and then uses these enriched GBM stem cells to characterize tumorigenicity, their association with clinical GBM specimens, and their regulation in tumor progression. The results showed that GD2 and GD3 were positively stained on GBM neurospheres. We found that cells with high GD3 expression display functional characteristics of GSCs. Suppression of GD3S, a critical enzyme for GD3 synthesis, impeded neurosphere formation and tumor initiation. The expression of GD3S correlated with the grades of astrocytomas and mediated self-renewal through c-Met activation. Furthermore, a GD3 antibody was found to eliminate the GD3⁺ cells through complement-dependent cytotoxicity (CDC) in vitro and to suppress tumor growth in mice. These results suggest that GD3 could be a significant biomarker for GSCs, that CD3 could be combined with CD133 for the enrichment of GSCs, and that both GD3 and GD3S could be targets for the development of new therapies against GBM.     

Synergistic antileukemic interactions between 17-AAG and UCN-01 involve interruption of RAF/MEK- and AKT-related pathways

Interactions between the protein kinase C (PKC) and Chk1 inhibitor UCN-01 and the heat shock protein 90 (Hsp90) antagonist 17-AAG have been examined in human leukemia cells in relation to effects on signal transduction pathways and apoptosis. Simultaneous exposure (30 hours) of U937 monocytic leukemia cells to minimally toxic concentrations of 17-AAG (eg, 400 nM) and UCN-01 (eg, 75 nM) triggered a pronounced increase in mitochondrial injury (ie, loss of mitochondrial membrane potential [Deltapsim]; cytosolic release of cytochrome c), caspase activation, and apoptosis. Synergistic induction of apoptosis was also observed in other human leukemia cell types (eg, Jurkat, NB4). Coexposure of human leukemia cells to 17-AAG and the PKC inhibitor bisindolylmaleimide (GFX) did not result in enhanced lethality, arguing against the possibility that the PKC inhibitory actions of UCN-01 are responsible for synergistic interactions. The enhanced cytotoxicity of this combination was associated with diminished Akt activation and marked down-regulation of Raf-1, MEK1/2, and mitogen-activated protein kinase (MAPK). Coadministration of 17-AAG and UCN-01 did not modify expression of Hsp90, Hsp27, phospho-JNK, or phospho-p38 MAPK, but was associated with further p34cdc2 dephosphorylation and diminished expression of Bcl-2, Mcl-1, and XIAP. In addition, inducible expression of both a constitutively active MEK1/2 or myristolated Akt construct, which overcame inhibition of ERK and Akt activation, respectively, significantly attenuated 17-AAG/UCN-01-mediated lethality. Together, these findings indicate that the Hsp90 antagonist 17-AAG potentiates UCN-01 cytotoxicity in a variety of human leukemia cell types and suggest that interference with both the Akt and Raf-1/MEK/MAP kinase cytoprotective signaling pathways contribute to this phenomenon.     

Effectiveness of near-peer simulation for managing the acutely deteriorating patient among residents of an internal medicine junior residency programme

INTRODUCTIONNear-peer teaching is gaining popularity as a teaching modality, as it improves the learner’s understanding, is targeted at an appropriate level and promotes familiarisation. This study was initiated to evaluate the effectiveness of incorporating near-peer instruction into simulation-based training within a junior residency programme.METHODS42 first-year residents from an internal medicine junior residency programme were recruited. Participants underwent a simulation-based training programme conducted over five weeks. Each week involved either an emergency or acute clinical scenario. A structured questionnaire was administered prior to and after the course to compare participants’ perceived knowledge, experience and confidence in managing the clinical scenarios.RESULTSIn our study, 83% of participants agreed/strongly agreed that the scenarios were realistic. There were improvements in perceived knowledge, experience and confidence after the course. The greatest improvement was seen for experience (post-simulation: median 7.00 [interquartile range (IQR) 6.00‒8.00] vs. pre-simulation: median 5.00 [IQR 3.00–6.25]). 65% of participants were keen to help with future training.CONCLUSIONNear-peer simulation training was found to be a viable and valuable method of instruction for first-year residents for increasing experience, instilling confidence and improving perceived knowledge. Integration of such programmes within medical education curricula shows good promise of continuity, with many first-year residents inspired to organise subsequent sessions.