The observation that antagonists of the N-methyl-D-aspartate receptor (NMDAR), such as phencyclidine (PCP) and ketamine, transiently induce symptoms of acute schizophrenia had led to a paradigm shift ...from dopaminergic to glutamatergic dysfunction in pharmacological models of schizophrenia. The glutamate hypothesis can explain negative and cognitive symptoms of schizophrenia better than the dopamine hypothesis, and has the potential to explain dopamine dysfunction itself. The pharmacological and psychomimetic effects of ketamine, which is safer for human subjects than phencyclidine, are herein reviewed. Ketamine binds to a variety of receptors, but principally acts at the NMDAR, and convergent genetic and molecular evidence point to NMDAR hypofunction in schizophrenia. Furthermore, NMDAR hypofunction can explain connectional and oscillatory abnormalities in schizophrenia in terms of both weakened excitation of inhibitory γ-aminobutyric acidergic (GABAergic) interneurons that synchronize cortical networks and disinhibition of principal cells. Individuals with prenatal NMDAR aberrations might experience the onset of schizophrenia towards the completion of synaptic pruning in adolescence, when network connectivity drops below a critical value. We conclude that ketamine challenge is useful for studying the positive, negative, and cognitive symptoms, dopaminergic and GABAergic dysfunction, age of onset, functional dysconnectivity, and abnormal cortical oscillations observed in acute schizophrenia.
Background. With use of data from the Prospective Antifungal Therapy (PATH) Alliance registry, we performed this multicenter, prospective, observational study to assess the epidemiologic characters ...and outcomes of invasive fungal infection (IFI) in hematopoietic stem cell transplant (HSCT) recipients. Methods. Sixteen medical centers from North America reported data on adult HSCT recipients with proven or probable IFI during the period July 2004 through September 2007. The distribution of IFIs and rates of survival at 6 and 12 weeks after diagnosis were studied. We used logistic regression models to determine risk factors associated with 6-week mortality for allogeneic HSCT recipients with invasive aspergillosis (IA). Results. Two hundred thirty-four adult HSCT recipients with a total of 250 IFIs were included in this study. IA (59.2%) was the most frequent IFI, followed by invasive candidiasis (24.8%), zygomycosis (7.2%), and IFI due to other molds (6.8%). Voriconazole was the most frequently administered agent (68.4%); amphotericin B deoxycholate was administered to a few patients (2.1%). Ninety-three (46.7%) of 199 HSCT recipients with known outcome had died by week 12. The 6-week survival rate was significantly greater for patients with IA than for those with invasive candidiasis and for those with IFI due to the Zygomycetes or other molds (P<.001). The 6-week mortality rate for HSCT recipients with IA was 21.5%. At 6 weeks, there was a trend toward a worse outcome among allogeneic HSCT recipients with IA who received myeloablative conditioning (P=.07); absence of mechanical ventilation or/and hemodialysis (P=.01) were associated with improved survival. Conclusions. IA remains the most commonly identified IFI among HSCT recipients, but rates of survival in persons with IA appear to have improved, compared with previously reported data. Invasive candidiasis and IFI due to molds other than Aspergillus species remain a significant problem in HSCT recipients.
Synthetic genetics is a subdiscipline of synthetic biology that aims to develop artificial genetic polymers (also referred to as xeno-nucleic acids or XNAs) that can replicate in vitro and eventually ...in model cellular organisms. This field of science combines organic chemistry with polymerase engineering to create alternative forms of DNA that can store genetic information and evolve in response to external stimuli. Practitioners of synthetic genetics postulate that XNA could be used to safeguard synthetic biology organisms by storing genetic information in orthogonal chromosomes. XNA polymers are also under active investigation as a source of nuclease resistant affinity reagents (aptamers) and catalysts (xenozymes) with practical applications in disease diagnosis and treatment. In this review, we provide a structural perspective on known antiparallel duplex structures in which at least one strand of the Watson-Crick duplex is composed entirely of XNA. Currently, only a handful of XNA structures have been archived in the Protein Data Bank as compared to the more than 100 000 structures that are now available. Given the growing interest in xenobiology projects, we chose to compare the structural features of XNA polymers and discuss their potential to access new regions of nucleic acid fold space.
Local structural and metabolic as well as inter-regional connectivity abnormalities have been implicated in the neuropathology of major depressive disorder (MDD). How local tissue properties affect ...intrinsic functional connectivity is, however, unclear. Using a cross-sectional, multi-modal imaging approach, we investigated the relationship between local cortical tissue abnormalities and intrinsic resting-state functional connectivity (RSFC) in MDD.
A total of 20 MDD in-patients and 20 healthy controls underwent magnetic resonance imaging at 3 T for structural and functional imaging. Whole-brain cortical thickness was calculated and compared between groups. Regions with reduced cortical thickness defined seeds for subsequent whole-brain RSFC analyses. Contributions of structural tissue abnormalities on inter-regional RSFC were explicitly investigated.
Lower cortical thickness was observed in MDD in the right dorsomedial prefrontal cortex (PFC), superior temporal gyrus/temporal pole, middle-posterior cingulate cortex, and dorsolateral PFC. No differences in local fractional amplitude of low-frequency fluctuations were observed. Lower thickness in patients' dorsomedial PFC further directly and selectively affected its RSFC with the precuneus, which was unaffected by symptom severity. No effects of cortical thickness in other regions showing abnormal thickness were observed to influence functional connectivity.
Abnormal cortical thickness in the dorsomedial PFC in MDD patients was observed to selectively and directly affect its intrinsic connectivity with the precuneus in MDD patients independent of depression severity, thereby marking a potential vulnerability for maladaptive mood regulation. Future studies should include an unmedicated sample and replicate findings using independent component analysis to test for morphometric effects on network integrity.
TEM-1 β-lactamase degrades β-lactam antibiotics with a strong preference for penicillins. Sequence reconstruction studies indicate that it evolved from ancestral enzymes that degraded a variety of ...β-lactam antibiotics with moderate efficiency. This generalist to specialist conversion involved more than 100 mutational changes, but conserved fold and catalytic residues, suggesting a role for dynamics in enzyme evolution. Here, we develop a conformational dynamics computational approach to rationally mold a protein flexibility profile on the basis of a hinge-shift mechanism. By deliberately weighting and altering the conformational dynamics of a putative Precambrian β-lactamase, we engineer enzyme specificity that mimics the modern TEM-1 β-lactamase with only 21 amino acid replacements. Our conformational dynamics design thus re-enacts the evolutionary process and provides a rational allosteric approach for manipulating function while conserving the enzyme active site.
LY3009120 is a pan-RAF and RAF dimer inhibitor that inhibits all RAF isoforms and occupies both protomers in RAF dimers. Biochemical and cellular analyses revealed that LY3009120 inhibits ARAF, BRAF, ...and CRAF isoforms with similar affinity, while vemurafenib or dabrafenib have little or modest CRAF activity compared to their BRAF activities. LY3009120 induces BRAF-CRAF dimerization but inhibits the phosphorylation of downstream MEK and ERK, suggesting that it effectively inhibits the kinase activity of BRAF-CRAF heterodimers. Further analyses demonstrated that LY3009120 also inhibits various forms of RAF dimers including BRAF or CRAF homodimers. Due to these unique properties, LY3009120 demonstrates minimal paradoxical activation, inhibits MEK1/2 phosphorylation, and exhibits anti-tumor activities across multiple models carrying KRAS, NRAS, or BRAF mutation.
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•LY3009120 is a pan-RAF inhibitor of three RAF isoforms•LY3009120 occupies both protomers of RAF dimer and is a RAF dimer inhibitor•LY3009120 has minimal paradoxical pathway activation in Ras mutant cells•LY3009120 is active for RAS or BRAF mutant tumor cells in vitro and in vivo
Peng et al. show that LY3009120 inhibits all RAF isoforms and inhibits BRAF and CRAF homodimers and heterodimer. Moreover, LY3009120 induces minimal paradoxical activation in BRAF wild type cells. Importantly, LY3009120 exhibits anti-tumor activities in models carrying oncogenic KRAS, NRAS, or BRAF mutations.
Sensing and responding to temperature is crucial in biology. The TRPV1 ion channel is a well-studied heat-sensing receptor that is also activated by vanilloid compounds, including capsaicin. Despite ...significant interest, the molecular underpinnings of thermosensing have remained elusive. The TRPV1 S1-S4 membrane domain couples chemical ligand binding to the pore domain during channel gating. Here we show that the S1-S4 domain also significantly contributes to thermosensing and couples to heat-activated gating. Evaluation of the isolated human TRPV1 S1-S4 domain by solution NMR, far-UV CD, and intrinsic fluorescence shows that this domain undergoes a non-denaturing temperature-dependent transition with a high thermosensitivity. Further NMR characterization of the temperature-dependent conformational changes suggests the contribution of the S1-S4 domain to thermosensing shares features with known coupling mechanisms between this domain with ligand and pH activation. Taken together, this study shows that the TRPV1 S1-S4 domain contributes to TRPV1 temperature-dependent activation.
C99 is the transmembrane carboxyl-terminal domain of the amyloid precursor protein that is cleaved by γ-secretase to release the amyloid-β polypeptides, which are associated with Alzheimer's disease. ...Nuclear magnetic resonance and electron paramagnetic resonance spectroscopy show that the extracellular amino terminus of C99 includes a surface-embedded "N-helix" followed by a short "N-loop" connecting to the transmembrane domain (TMD). The TMD is a flexibly curved a helix, making it well suited for processive cleavage by γ-secretase. Titration of C99 reveals a binding site for cholesterol, providing mechanistic insight into how cholesterol promotes amyloidogenesis. Membrane-buried GXXXG motifs (G, Gly; X, any amino acid), which have an established role in oligomerization, were also shown to play a key role in cholesterol binding. The structure and cholesterol binding properties of C99 may aid in the design of Alzheimer's therapeutics.
Background. Invasive candidiasis is an important cause of morbidity and mortality among patients with health care–associated infection. The echinocandins have potent fungicidal activity against most ...Candida species, but there are few data comparing the safety and efficacy of echinocandins in the treatment of invasive candidiasis. Methods. This was an international, randomized, double-blind trial comparing micafungin (100 mg daily) and micafungin (150 mg daily) with a standard dosage of caspofungin (70 mg followed by 50 mg daily) in adults with candidemia and other forms of invasive candidiasis. The primary end point was treatment success, defined as clinical and mycological success at the end of blinded intravenous therapy. Results. A total of 595 patients were randomized to one the treatment groups and received at least 1 dose of study drug. In the modified intent-to-treat population, 191 patients were assigned to the micafungin 100 mg group, 199 to the micafungin 150 mg group, and 188 to the caspofungin group. Demographic characteristics and underlying disorders were comparable across the groups. Approximately 85% of patients had candidemia; the remainder had noncandidemic invasive candidiasis. At the end of blinded intravenous therapy, treatment was considered successful for 76.4% of patients in the micafungin 100 mg group, 71.4% in the micafungin 150 mg group, and 72.3% in the caspofungin group. The median time to culture negativity was 2 days in the micafungin 100 mg group and the caspofungin group, compared with 3 days in the micafungin 150 mg groups. There were no significant differences in mortality, relapsing and emergent infections, or adverse events between the study arms. Conclusions. Dosages of micafungin 100 mg daily and 150 mg daily were noninferior to a standard dosage of caspofungin for the treatment of candidemia and other forms of invasive candidiasis.
Many active organic compounds and organic effect materials are poorly soluble in water, or even insoluble. Aqueous forms of application thus require special formulation techniques to utilize or ...optimize the physiological (pharmaceuticals, cosmetics, plant protection, nutrition) or technical (varnishes, printing inks, toners) action. The most interesting properties of nanodispersions of active organic compounds and effect materials include the impressive increase in solubility, the improvement in biological resorption, and the modification of optical, electrooptical, and other physical properties which are achievable only with particle sizes in the middle or lower nanometer range (50–500 nm). Hence in addition to economic and ecological constraints there are also technical demands which appear to urgently require the development of new processes for the production of organic nanoparticles as alternatives to the established mechanical milling processes. In this context attention is drawn to the recent increase in research activities which have as their objective the continuous, automatic preparation of nanodispersed systems by precipitation from molecular solution. In this review the current state of knowledge of the fundamentals of particle formation from homogeneous solution and the effect of solvent and polymer additives on the morphology and supramolecular structure of the nanoparticle will be discussed. The practical implementation of this new formulation technology will be explored in detail for the carotenoids, a class of compounds of both physiological and technical interest.
Aqueous, nanodispersed formulations of organic active compounds and effect materials (see electron micrograph) allow a dramatic increase in solubility, an improvement in biological absorption, and the modification of physical properties. The current state of knowledge of the basics of particle formation from homogeneous solution, the influence of the solvent and polymer additives on the morphology, and the supramolecular structure of the nanoparticles, is illustrated with the carotenoids, an industrially interesting class of compounds.
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