Computational insights into pH-dependence of structure and dynamics of pyrazinamidase: A comparison of wild type and mutants

The mycobacterial enzyme pyrazinamidase (PZase) is the target of key tuberculosis drug, pyrazinamide. Mutations in PZase cause drug resistance. Herein, three point mutations, W68G, L85P, and V155G, were investigated through over 8 µs of molecular dynamics simulations coupled with essential dynamics and binding pocket analysis at neutral (pH = 7) and acidic (pH = 4) ambient conditions. The 51-71 flap region exhibited drastic displacement leading to enlargement of binding cavity, especially at the lower pH. Accessibility of solvent to the active site of the mutant enzymes was also reduced. The protonation of key surface residues at low pH results in more contribution of these residues to structural stability and integrity of the enzyme and reduced interactions with solvent molecules, which acts as a cage, keeping the enzyme together. The observed results suggest a pattern of structural alterations due to point mutations in PZase, which is consistent with other experimental and theoretical investigations and, can be harnessed for drug design purposes.     

Pollen morphological studies in subfamily Suaedoideae (Chenopodiaceae)

The pollen morphology of two Bienertia species and 28 Suaeda species from the Old World has been studied with light and scanning electron microscopy. Pollen morphological characters used in this study include pollen diameter, pore number, pore diameter, operculum diameter, chord distance, exine thickness, plus number and characteristics of exine spinules and operculum spinules. Using these characters, the pollen of Bienertia is clearly distinguished from that of Suaeda. In addition, pollen data support recent molecular studies which merge the genus Borszczowia into Suaeda. The pollen grains of Suaeda show notable variation; in some cases this allows morphological distinctions to be made between species. Taxonomically, pore number is observed to be a more useful character than pollen diameter. Principal components analysis (PCA) shows only a weak correlation between pollen characters and habit (life form), habitat, mode of photosynthesis or phylogenetic relationships. Interestingly, however, the annual C₃ and C₄ species of section Schoberia are usually characterised by a higher pore number than the perennial C₄ species.     

Cannabinoids attenuate norepinephrine-induced melatonin biosynthesis in the rat pineal gland by reducing arylalkylamine N-acetyltransferase activity without involvement of cannabinoid receptors

Cannabinoids modulate neuronal and neuroendocrine circuits by binding to cannabinoid receptors acting upon cAMP/Ca(2+)-mediated intracellular signaling cascades. The rat pineal represents an established model to investigate intracellular signaling processes because a well defined input, the neurotransmitter norepinephrine, is transformed via cAMP/Ca(2+)-dependent mechanisms into an easily detectable output signal, the biosynthesis of melatonin. Here we investigated the impact of cannabinoids on norepinephrine-regulated melatonin biosynthesis in the rat pineal. We demonstrated that treatment of cultured rat pineals with 9-carboxy-11-nor-delta-9-tetrahydrocannabinol (THC), cannabidiol or cannabinol significantly reduced norepinephrine-induced arylalkylamine N-acetyltransferase (AANAT) activity and melatonin biosynthesis. These effects were not mimicked by the cannabinoid receptor agonist WIN55,212-2 and were not blocked by cannabinoid 1 and 2 receptor antagonists. The cannabinoids used did not affect norepinephrine-induced increases in cAMP/Ca(2+) levels. Notably, cannabinoids were found to directly inhibit AANAT activity in lysates of the pineal gland. This effect was specific in so far as cannabinoids did not influence the activity of hydroxyindole-O-methyltransferase (HIOMT), the last enzyme in melatonin biosynthesis. Taken together, our data strongly suggest that cannabinoids inhibit AANAT activity and attenuate melatonin biosynthesis through intracellular actions without involvement of classical cannabinoid receptor-dependent signaling cascades.     

Engineering porous scaffolds using gas-based techniques

Scaffolds are used in tissue engineering as a matrix for the seeding and attachment of human cells. The creation of porosity in three-dimensional (3D) structures of scaffolds plays a critical role in cell proliferation, migration, and differentiation into the specific tissue while secreting extracellular matrix components. These pores are used to transfer nutrients and oxygen and remove wastes produced from the cells. The lack of oxygen and nutrient supply impedes the cell migration more than 500μm from the surface. The physical properties of scaffolds such as porosity and pore interconnectivity can improve mass transfer and have a great impact on the cell adhesion and penetration into the scaffolds to form a new tissue. Various techniques such as electrospinning, freeze-drying, and solvent casting/salt leaching have been used to create porosity in scaffolds. The major issues in these methods include lack of 3D structure, control on pore size, and pore interconnectivity. In this review, we provide a brief overview of gas-based techniques that have been developed for creating porosity in scaffolds.     

Application of a dissimilarity index of EEG and its sub-bands on prediction of induced epileptic seizures from rat's EEG signals

ObjectiveEpileptic seizures are defined as manifest of excessive and hyper-synchronous activity of neurons in the cerebral cortex that cause frequent malfunction of the human central nervous system. Therefore, finding precursors and predictors of epileptic seizure is of utmost clinical relevance to reduce the epileptic seizure induced nervous system malfunction consequences. Researchers for this purpose may even guide us to a deep understanding of the seizure generating mechanisms. The goal of this paper is to predict epileptic seizures in epileptic rats.MethodsSeizures were induced in rats using pentylenetetrazole (PTZ) model. EEG signals in interictal, preictal, ictal and postictal periods were then recorded and analyzed to predict epileptic seizures. Epileptic seizures were predicted by calculating an index in consecutive windows of EEG signal and comparing the index with a threshold. In this work, a newly proposed dissimilarity index called Bhattacharyya Based Dissimilarity Index (BBDI), dynamical similarity index and fuzzy similarity index were investigated.ResultsBBDI, dynamical similarity index and fuzzy similarity index were examined on case and control groups and compared to each other. The results show that BBDI outperforms dynamical and fuzzy similarity indices. In order to improve the results, EEG sub-bands were also analyzed. The best result achieved when the proposed dissimilarity index was applied on Delta sub-band that predicts epileptic seizures in all rats with a mean of 299.5 s.ConclusionThe dissimilarity of neural network activity between reference window and present window of EEG signal has a significant increase prior to an epileptic seizure and the proposed dissimilarity index (BBDI) can reveal this variation to predict epileptic seizures. In addition, analyzing EEG sub-bands results in more accurate information about constituent neuronal activities underlying the EEG since certain changes in EEG signal may be amplified when each sub-band is analyzed separately.SignificanceThis paper presents application of a dissimilarity index (BBDI) on EEG signals and its sub-bands to predict PTZ-induced epileptic seizures in rats. Based on the results of this work, BBDI will predict epileptic seizures more accurately and more reliably compared to current indices that increases epileptic patient comfort and improves patient outcomes.     

Susceptibility of mouse minute virus to inactivation by heat in two cell culture media types

Viral contaminations of biopharmaceutical manufacturing cell culture facilities are a significant threat and one for which having a risk mitigation strategy is highly desirable. High temperature, short time (HTST) mammalian cell media treatment may potentially safeguard manufacturing facilities from such contaminations. HTST is thought to inactivate virions by denaturing proteins of the viral capsid, and there is evidence that HTST provides ample virucidal efficacy against nonenveloped or naked viruses such as mouse minute virus (MMV), a parvovirus. The aim of the studies presented herein was to further delineate the susceptibility of MMV, known to have contaminated mammalian cell manufacturing facilities, to heat by exposing virus‐spiked cell culture media to a broad range of temperatures and for various times of exposure. The results of these studies show that HTST is capable of inactivating MMV by three orders of magnitude or more. Thus, we believe that HTST is a useful technology for the purposes of providing a barrier to adventitious contamination of mammalian cell culture processes in the biopharmaceutical industry. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Wolbachia infection in West Nile Virus vectors of northwest Iran

Mosquito-borne viral diseases are serious health problems in many countries. Various methods have been used for controlling the vectors of these diseases. Among symbiotic bacteria, the members of the genus Wolbachia are the most ubiquitous symbionts of arthropods and play key roles in their host biological characteristics with various effects on their hosts. The identification of these bacteria in Iranian mosquitoes is limited to a few studies. The current study was carried out to determine (1) the Wolbachia infection of probable arbovirus vectors (Aedes caspius, Culex pipiens, Culex theileri and Culiseta longiareolata), (2) the Wolbachia strain(s) infecting the mosquitoes, and (3) the geographical distribution of the Wolbachia strain(s) in the northwest of Iran. Eight species including Ae. caspius, Anopheles hyrcanus, An. maculipennis, Cx. hortensis, Cx. modestus, Cx. pipiens, Cx. theileri, and Cs. longiareolata were identified, amongst which Ae. caspius with 63.1% and An. hyrcanus with 0.3% were the most and the least abundant species, respectively. The results of semi-nested PCR using Wolbachia surface protein (wsp) fragment assays showed that Wolbachia infection was present in three out of the four above mentioned arboviral vector species (Aedes caspius, Culex pipiens, Culex theileri and Culiseta longiareolata), where the highest infection rate was seen in Cx. pipiens. The infection rates of mosquitoes with Wolbachia in the species of Cx. pipiens, Cs. longiareolata, Cx. theileri, and Ae. caspius were 96.9%, 11.5%, 5.2% and 0%, respectively.