Harmaline interaction with sodium-binding sites in intestinal brush border sucrase.

The effect of harmaline on rabbit brush border sucrase has been studied at pH 6.8. An initial analysis in classical kinetic terms revealed harmaline to be a fully competitive inhibitor of the substrate, sucrose. In spite of this result however, the following hypothesis has been tested. Harmaline, which is positively charged in the physiological range of pH, might in fact compete, not directly with the substrate site, but rather with an allosterically-related sodium-binding site which has been postulated to be involved in the activation of sucrase by the alkali-metal ions (Mahmood and Alvarado, Arch. Biochem. Biophys. 168, 585, 1975). Because of its size, harmaline, when bound to the metal site, could at least partially overlap with the substrate site, thereby behaving as if it were an authentic fully competitive inhibitor of the substrate. This hypothesis appears to be confirmed by the fact that the alkali metals can completely reverse the inhibition caused by harmaline.     

The synthesis and X-ray structural characterization of mer and fac isomers of the technetium(I) nitrosyl complex [TcCl2(NO)(PNPpr)]

The nitrosyl complex H[TcNOCl₄] reacts with the tridentate ligand bis[(2-diphenylphosphino)propyl]amine (PNPpr) to yield a mixture of the mer or fac isomers of [TcCl₂(NO)(PNPpr)]. In acetonitrile, where the ligand is freely soluble, reaction occurs at room temperature to yield mostly the mer isomer with the linear nitrosyl ligand cis to the amine ligand; and the phosphine ligands arranged in a mutually trans orientation. The reaction in methanol requires reflux to dissolve the lipophilic ligand and generates the fac isomer of [TcCl₂(NO)(PNPpr)] as the major product, with the tridentate ligand in a facial arrangement, leaving the chlorides and nitrosyl ligand in the remaining facial sites. The steric bulk of the tridentate ligand’s diphenylphophino-moieties results in a significant distortion from octahedral geometry, with the P-Tc-P bond angle expanded to 99.48(4)°.The infrared spectra display absorptions from these nitrosyl ligands in the 1700 and 1800 cm⁻¹ regions for the fac and mer isomers, respectively. The ESI(+) mass spectra each display the parent ion at 647 m/z.     

Effect of Subliminal Lexical Priming on the Subjective Perception of Images: A Machine Learning Approach

The purpose of the study is to examine the effect of subliminal priming in terms of the perception of images influenced by words with positive, negative, and neutral emotional content, through electroencephalograms (EEGs). Participants were instructed to rate how much they like the stimuli images, on a 7-point Likert scale, after being subliminally exposed to masked lexical prime words that exhibit positive, negative, and neutral connotations with respect to the images. Simultaneously, the EEGs were recorded. Statistical tests such as repeated measures ANOVAs and two-tailed paired-samples t-tests were performed to measure significant differences in the likability ratings among the three prime affect types; the results showed a strong shift in the likeness judgment for the images in the positively primed condition compared to the other two. The acquired EEGs were examined to assess the difference in brain activity associated with the three different conditions. The consistent results obtained confirmed the overall priming effect on participants’ explicit ratings. In addition, machine learning algorithms such as support vector machines (SVMs), and AdaBoost classifiers were applied to infer the prime affect type from the ERPs. The highest classification rates of 95.0% and 70.0% obtained respectively for average-trial binary classifier and average-trial multi-class further emphasize that the ERPs encode information about the different kinds of primes.     

Mesenchymal stem cell mediated effects on microglial phenotype in cuprizone-induced demyelination model

Microglial cells have an essential role in neurodegenerative disorders, such as multiple sclerosis. They are divided into two subgroups: M1 and M2 phenotypes. Mesenchymal stem cells (MSC), with neuroprotective and immunomodulating properties, could improve these diseases. We evaluate the immunomodulating effects of MSC on microglial phenotypes and the improvement of demyelination in a cuprizone (CPZ) model of multiple sclerosis (MS). For inducing the chronic demyelination model, C57BL6 mice were given a diet with 0.2% CPZ (w/w) for 12 weeks. In the MSC group, cells were transplanted into the right lateral ventricle of mice. The expression of targeted genes was assessed by real-time polymerase chain reaction. M1 and M2 microglial phenotypes were assessed by immunohistochemistry of inducible nitric oxide synthase (iNOS) and Arg-1, respectively. Remyelination was studied by luxal fast blue (LFB) staining and electron microscopy (EM). We found that MSC transplantation reduced the expression level of M1-specific messenger RNA (mRNA; iNOS and CD86) but increased the expression level of M2 specific genes (CD206, Arg-1, and CX3CR1) in comparison to the CPZ group. Moreover, cell therapy significantly decreased the M1 marker (iNOS⁺ cells), but M2 marker (Arg-1⁺ cells) significantly increased in comparison with the CPZ group. In addition, MSC treatment significantly increased the CX3CL1 expression level in comparison with the CPZ group and led to improvement in remyelination, which was confirmed by LFB and EM images. The results showed that MSC transplantation increases the M2 and decreases the M1 phenotype in MS. This change was accompanied by decrease in demyelination and axonal injury and indicated that MSCs have a positive effect on MS by modification of microglia cells.     

Generation of hepatoma cell lines deficient in microsomal triglyceride transfer protein

The microsomal triglyceride transfer protein (MTP) is essential for the secretion of apolipoprotein B (apoB)48- and apoB100-containing lipoproteins in the intestine and liver, respectively. Loss of function mutations in MTP cause abetalipoproteinemia. Heterologous cells are used to evaluate the function of MTP in apoB secretion to avoid background MTP activity in liver and intestine-derived cells. However, these systems are not suitable to study the role of MTP in the secretion of apoB100-containing lipoproteins, as expression of a large apoB100 peptide using plasmids is difficult. Here, we report a new cell culture model amenable for studying the role of different MTP mutations on apoB100 secretion. The endogenous MTTP gene was ablated in human hepatoma Huh-7 cells using single guide RNA and RNA-guided clustered regularly interspaced short palindromic repeats-associated sequence 9 ribonucleoprotein complexes. We successfully established three different clones that did not express any detectable MTTP mRNA or MTP protein or activity. These cells were defective in secreting apoB-containing lipoproteins and accumulated lipids. Furthermore, we show that transfection of these cells with plasmids expressing human MTTP cDNA resulted in the expression of MTP protein, restoration of triglyceride transfer activity, and secretion of apoB100. Thus, these new cells can be valuable tools for studying structure-function of MTP, roles of different missense mutations in various lipid transfer activities of MTP, and their ability to support apoB100 secretion, compensatory changes associated with loss of MTP, and in the identification of novel proteins that may require MTP for their synthesis and secretion.     

Enhanced Plasmonic Light Absorption for Silicon Schottky-Barrier Photodetectors

Quantum efficiency of the silicon Schottky-barrier photodetector is limited by the weak interaction between the photons and electrons in the metal. By engineering the metal surfaces, metallic groove structures are proposed to achieve strong light absorption in the metal, where most of the energy is transferred into hot carriers near the Schottky barrier. The proposed broadband photodetector with a bi-grating metallic structure on the silicon substrate enables to absorb 76 % of the infrared light in the metal with a 200-nm bandwidth, while staying insensitive to the incident angle. These results pave a new promising way to attain high quantum efficiency silicon Schottky-barrier photodetectors.