Natural process--natural selection

Life is supported by a myriad of chemical reactions. To describe the overall process we have formulated entropy for an open system undergoing chemical reactions. The entropy formula allows us to recognize various ways for the system to move towards more probable states. These correspond to the basic processes of life i.e. proliferation, differentiation, expansion, energy intake, adaptation and maturation. We propose that the rate of entropy production by various mechanisms is the fitness criterion of natural selection. The quest for more probable states results in organization of matter in functional hierarchies.     

Modifications of Diflunisal and Meclofenamate Carboxyl Groups Affect Their Allosteric Effects on GABAA Receptor Ligand Binding

Gamma-aminobutyric acid type A receptors (GABA_AR) are allosterically modulated by the nonsteroidal anti-inflammatory drugs diflunisal and fenamates. The carboxyl group of these compounds is charged at physiological pH and therefore penetration of the compounds into the brain is low. In the present study we have transformed the carboxyl group of diflunisal and meclofenamate into non-ionizable functional groups and analyzed the effects of the modifications on stimulation of [³H]muscimol binding and on potentiation of γ-aminobutyric acid-induced displacement of 4′-ethenyl-4-n-[2,3-³H]propylbicycloorthobenzoate. N-Butylamide derivative of diflunisal modulated radioligand binding with equal or higher potency than the parent compound, while diflunisalamide showed reduced allosteric effect as compared to diflunisal. Amide derivative of meclofenamate equally affected radioligand binding parameters, while both diflunisal and meclofenamate methyl esters were less active than the parent compounds. Our study clearly demonstrates that an intact carboxyl group in diflunisal and meclofenamate is not indispensable for their positive GABA_AR modulation. Further derivatization of the compound might yield compounds with higher selectivity for GABA_ARs that could be utilized in drug development.     

Large variation among photoreceptors as the basis of visual flexibility in the common backswimmer

The common backswimmer, Notonecta glauca, uses vision by day and night for functions such as underwater prey animal capture and flight in search of new habitats. Although previous studies have identified some of the physiological mechanisms facilitating such flexibility in the animal''s vision, neither the biophysics of Notonecta photoreceptors nor possible cellular adaptations are known. Here, we studied Notonecta photoreceptors using patch-clamp and intracellular recording methods. Photoreceptor size (approximated by capacitance) was positively correlated with absolute sensitivity and acceptance angles. Information rate measurements indicated that large and more sensitive photoreceptors performed better than small ones. Our results suggest that backswimmers are adapted for vision in both dim and well-illuminated environments by having open-rhabdom eyes with large intrinsic variation in absolute sensitivity among photoreceptors, exceeding those found in purely diurnal or nocturnal species. Both electrophysiology and microscopic analysis of retinal structure suggest two retinal subsystems: the largest peripheral photoreceptors provide vision in dim light and the smaller peripheral and central photoreceptors function primarily in sunlight, with light-dependent pigment screening further contributing to adaptation in this system by dynamically recruiting photoreceptors with varying sensitivity into the operational pool.     

The influence of mitonuclear genetic variation on personality in seed beetles

There is a growing awareness of the influence of mitochondrial genetic variation on life-history phenotypes, particularly via epistatic interactions with nuclear genes. Owing to their direct effect on traits such as metabolic and growth rates, mitonuclear interactions may also affect variation in behavioural types or personalities (i.e. behavioural variation that is consistent within individuals, but differs among individuals). However, this possibility is largely unexplored. We used mitonuclear introgression lines, where three mitochondrial genomes were introgressed into three nuclear genetic backgrounds, to disentangle genetic effects on behavioural variation in a seed beetle. We found within-individual consistency in a suite of activity-related behaviours, providing evidence for variation in personality. Composite measures of overall activity of individuals in behavioural assays were influenced by both nuclear genetic variation and by the interaction between nuclear and mitochondrial genomes. More importantly, the degree of expression of behavioural and life-history phenotypes was correlated and mitonuclear genetic variation affected expression of these concerted phenotypes. These results show that mitonuclear genetic variation affects both behavioural and life-history traits, and they provide novel insights into the maintenance of genetic variation in behaviour and personality.     

Polyplex-mediated gene transfer and cell cycle: effect of carrier on cellular uptake and intracellular kinetics, and significance of glycosaminoglycans

BACKGROUND: Here we report on studies that probe whether the intracellular kinetics of plasmid DNA (pDNA) and cell surface glycosaminoglycans (GAGs) are modified during the cell cycle in a way that can be correlated with changes in gene transfer efficiency with poly(ethyleneimine) (PEI) and poly-L-lysine (PLL) polyplexes. METHODS: Synchronized D407 retinal cells were transfected with PEI and PLL polyplexes using a luciferase reporter. The free and/or loosely complexed nuclear pDNA was determined by real-time PCR, and compared with transgene expression, the rate of pinocytosis by FITC-dextran uptake and the content of cell surface GAGs. RESULTS: The amount of free and/or loosely complexed nuclear pDNA between cell cycle phases varied approximately 4-20 times (G1 < S < G2/M). Both carriers delivered pDNA in a similar way into the nucleus (PLL vs. PEI < or = 3.5-fold), but PEI was approximately 10-100 times more efficient in gene expression than PLL (G1 < G2/M < S). The rate of pinocytosis increased up to 70-fold from G1 to middle S phase. Cell surface heparan and chondroitin sulfate increased 50-80%, and hyaluronan decreased 50% when the cells went from G1 through S to G2/M. CONCLUSIONS: The data obtained indicates that no single parameter (pinocytosis, cell surface GAGs, nuclear uptake) solely accounts for the differential pDNA uptake or expression during cell cycle, and that the main difference in PLL- and PEI-mediated transfections seems to be at the nuclear level.     

Low molecular weight hyaluronan shielding of DNA/PEI polyplexes facilitates CD44 receptor mediated uptake in human corneal epithelial cells

AIM: It was the aim of this study to prepare purified DNA/PEI polyplexes, which are coated with hyaluronan to facilitate CD44 receptor mediated uptake of the DNA/PEI polyplex and to reduce unspecific interactions of the complex with negatively charged extracellular matrix components on the ocular surface. METHODS: Hyaluronans of different molecular weights (<10 kDa, 10-30 kDa and 30-50 kDa) were isolated after enzymatic degradation of high molecular weight hyaluronan via ultrafiltration by centrifugation. The influence of the different hyaluronans used for coating on the stability and transfection efficiency of the complexes was evaluated in vitro. Transfection and uptake studies were performed in human corneal epithelial (HCE) cells. CD44 receptor expression of this cell model was evaluated by immunohistochemistry. RESULTS: Coating of purified DNA/PEI polyplexes with low molecular weight hyaluronan (<10 kDa) facilitated receptor-mediated uptake via the CD44 receptor in HCE cells, increased complex stability in vitro, and effectively shielded the positive surface charges of the polyplex without decreasing its transfection efficiency. Higher molecular weights and larger amounts of hyaluronan in the complexes resulted in lesser improvements in the stability and transfection efficacy of the complexes. CONCLUSIONS: Coating of polyplexes with low molecular weight hyaluronan is a promising strategy for gene delivery to the ocular surface, where CD44 receptor mediated uptake decreased cytotoxicity and reduced non-specific interactions with the negatively charged extracellular matrix components are considered beneficial for increased transfection efficiency of non-viral vectors.     

Human isometric force production and electromyogram activity of knee extensor muscles in water and on dry land

This study was designed to determine trial-to-trial and day-to-day reproducibility of isometric force and electromyogram activity (EMG) of the knee extensor muscles in water and on dry land as well as to make comparisons between the two training conditions in muscle activity and force production. A group of 20 healthy subjects (12 women and 8 men) were tested three times over 2 weeks. A measurement session consisted of recordings of maximal and submaximal isometric knee extension force with simultaneous recording of surface EMG from the vastus medialis, vastus lateralis and biceps femoris muscles. To ensure identical measurement conditions the same patient elevator chair was used in both the dry and the wet environment. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) showed high trial-to-trial (ICC = 0.95-0.99, CV = 3.5%-11%) and day-to-day reproducibility (ICC=0.85-0.98, CV=11%-19%) for underwater and dry land measurements of force and EMG in each muscle during maximal contractions. The day-to-day reproducibility for submaximal contractions was similar. The interesting finding was that underwater EMG amplitude decreased significantly in each muscle during maximal (P < 0.01-P < 0.001) and submaximal contractions (P < 0.05-P < 0.001). However, the isometric force measurements showed similar values in both wet and dry conditions. The water had no disturbing effect on the electrodes as shown by slightly lowered interelectrode resistance values, the absence of artefacts and low noise levels of the EMG signals. It was concluded that underwater force and EMG measurements are highly reproducible. The significant decrease of underwater EMG could have electromechanical and/or neurophysiological explanations.     

Host poly(ADP-ribose) polymerases (PARPs) in acute and chronic bacterial infections

Protein ADP-ribosylation is a reversible post-translational modification, which alters protein activity, localization, interactome or stability, leading to perturbation of cell signaling. This review summarizes the emerging data indicating that host cell ADP-ribosylating enzymes, poly(ADP-ribose) polymerases (PARPs), influence the course of a bacterial infection, in parallel to ADP-ribosylating bacterial toxins. Host cell PARP targeting could be an efficient therapeutic approach to treat certain bacterial infections, possibly by repurposing the approved or clinical trial PARP inhibitors developed for cancer therapy.