Cell Elasticity Is Regulated by the Tropomyosin Isoform Composition of the Actin Cytoskeleton

The actin cytoskeleton is the primary polymer system within cells responsible for regulating cellular stiffness. While various actin binding proteins regulate the organization and dynamics of the actin cytoskeleton, the proteins responsible for regulating the mechanical properties of cells are still not fully understood. In the present study, we have addressed the significance of the actin associated protein, tropomyosin (Tpm), in influencing the mechanical properties of cells. Tpms belong to a multi-gene family that form a co-polymer with actin filaments and differentially regulate actin filament stability, function and organization. Tpm isoform expression is highly regulated and together with the ability to sort to specific intracellular sites, result in the generation of distinct Tpm isoform-containing actin filament populations. Nanomechanical measurements conducted with an Atomic Force Microscope using indentation in Peak Force Tapping in indentation/ramping mode, demonstrated that Tpm impacts on cell stiffness and the observed effect occurred in a Tpm isoform-specific manner. Quantitative analysis of the cellular filamentous actin (F-actin) pool conducted both biochemically and with the use of a linear detection algorithm to evaluate actin structures revealed that an altered F-actin pool does not absolutely predict changes in cell stiffness. Inhibition of non-muscle myosin II revealed that intracellular tension generated by myosin II is required for the observed increase in cell stiffness. Lastly, we show that the observed increase in cell stiffness is partially recapitulated in vivo as detected in epididymal fat pads isolated from a Tpm3.1 transgenic mouse line. Together these data are consistent with a role for Tpm in regulating cell stiffness via the generation of specific populations of Tpm isoform-containing actin filaments.     

PD-L1 Blockade Differentially Impacts Regulatory T Cells from HIV-Infected Individuals Depending on Plasma Viremia

Blocking the PD-1/PD-L1 pathway has emerged as a potential therapy to restore impaired immune responses in human immunodeficiency virus (HIV)-infected individuals. Most reports have studied the impact of the PD-L1 blockade on effector cells and neglected possible effects on regulatory T cells (Treg cells), which play an essential role in balancing immunopathology and antiviral effector responses. The aim of this study was to define the consequences of ex vivo PD-L1 blockade on Treg cells from HIV-infected individuals. We observed that HIV infection led to an increase in PD-1+ and PD-L1+ Treg cells. This upregulation correlated with disease progression and decreased under antiretroviral treatment. Treg cells from viremic individuals had a particularly high PD-1 expression and impaired proliferative capacity in comparison with Treg cells from individuals under antiretroviral treatment. PD-L1 blockade restored the proliferative capacity of Treg cells from viremic individuals but had no effect on its suppressive capacity. Moreover, it increased the viral production in cell cultures from viremic individuals. This increase in viral production correlated with an increase in Treg cell percentage and a reduction in the CD4/Treg and CD8/Treg cell ratios. In contrast to the effect of the PD-L1 blockade on Treg cells from viremic individuals, we did not observe a significant effect on the proliferative capacity of Treg cells from individuals in whom viremia was controlled (either spontaneously or by antiretroviral treatment). However, PD-L1 blockade resulted in an increased proliferative capacity of HIV-specific-CD8 T cells in all subjects. Taken together, our findings suggest that manipulating PD-L1 in vivo can be expected to influence the net gain of effector function depending on the subject’s plasma viremia.     

Integration of multi-objective structural optimization into cementless hip prosthesis design: Improved Austin-Moore model

A new strategy of multi-objective structural optimization is integrated into Austin-Moore prosthesis in order to improve its performance. The new resulting model is so-called Improved Austin-Moore. The topology optimization is considered as a conceptual design stage to sketch several kinds of hollow stems according to the daily loading cases. The shape optimization presents the detailed design stage considering several objectives. Here, A new multiplicative formulation is proposed as a performance scale in order to define the best compromise between several requirements. Numerical applications on 2D and 3D problems are carried out to show the advantages of the proposed model.     

DBA/2J Genetic Background Exacerbates Spontaneous Lethal Seizures but Lessens Amyloid Deposition in a Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a leading cause of dementia in the elderly and is characterized by amyloid plaques, neurofibrillary tangles (NFTs) and neuronal dysfunction. Early onset AD (EOAD) is commonly caused by mutations in amyloid precursor protein (APP) or genes involved in the processing of APP including the presenilins (e.g. PSEN1 or PSEN2). In general, mouse models relevant to EOAD recapitulate amyloidosis, show only limited amounts of NFTs and neuronal cell dysfunction and low but significant levels of seizure susceptibility. To investigate the effect of genetic background on these phenotypes, we generated APP^swe and PSEN1^de9 transgenic mice on the seizure prone inbred strain background, DBA/2J. Previous studies show that the DBA/2J genetic background modifies plaque deposition in the presence of mutant APP but the impact of PSEN1^de9 has not been tested. Our study shows that DBA/2J.APP^swePSEN1^de9 mice are significantly more prone to premature lethality, likely to due to lethal seizures, compared to B6.APP^swePSEN1^de9 mice—70% of DBA/2J.APP^swePSEN1^de9 mice die between 2-3 months of age. Of the DBA/2J.APP^swePSEN1^de9 mice that survived to 6 months of age, plaque deposition was greatly reduced compared to age-matched B6.APP^swePSEN1^de9 mice. The reduction in plaque deposition appears to be independent of microglia numbers, reactive astrocytosis and complement C5 activity.     

A new method of isolation and a new form of transketolase from baker's yeast]

A new procedure for the isolation of homogeneous transketolase from baker's yeast based on the use of enzyme-specific antibodies immobilized on a insoluble matrix has been developed. The enzyme yield is 90% of its total content in the original yeast extract. The eluate from the immunocolumn was found to contain a previously unknown form of transketolase which represents an enzyme-RNA complex.     

Interaction of rabbit skeletal muscle glycogen synthase I with substrate analogs--oxo-UDP hydrazones]

Inhibition of rabbit skeletal muscle glycogen synthase I was studied by using several synthetic substrate analogs: dansylhydrazone of oxo-UDP, 3-hydroxy-2-naphthoylhydrazone of oxo-UDP, salicyloylhydrazone of oxo-UDP, 1-oxyl-2,2,5,5-tetramethylpyrrolidine-3-carbonylhydrazone of oxo-UDP, N'-(dansyl)hydrazinocarbonylhydrazone of oxo-UDP and N'-(fluorenylidene-9)-hydrazinocarbonylhydrazone of oxo-UDP. All these compounds (with the exception of the nitroxyl-containing hydrazone) were characterized by a nonlinear dependence of the reverse reaction rate on the analog concentration in Dixon coordinates. The parabolic type of inhibition was due to the fact that the analogs tested except for the nitroxyl-containing hydrazone were able to interact both with the active center of the enzyme and with the FMN-binding site. The inhibition constants for oxo-UDP hydrazones were calculated for the both centers; their comparison revealed that the affinity of the analogs for the FMN-binding site increased with an increase in the radical hydrophobicity. These data suggest that the site with a high binding affinity for FMN is hydrophobic in nature. Apparently, isoalloxasine-like compounds display the highest affinity for this site.     

Characteristics of digital and palmar dermatoglyphics in people of different ages living in the territory of the Ukrainian Polesie]

Examination of dermatoglyphs in people aged 50-103 living in the territory of the Ukrainian Polesie has revealed age differences in some indices of dermatoglyphics: total crest count, palmar angle, character of the cutaneous pattern of fingers. It assumed that these differences have arisen as a consequence of selection of persons characterized by high reliability of the genotype functioning. The data obtained permit supposing that it is possible to use dermatoglyphics for determining hereditary predisposition of people to longevity.     

Mu-opioid-receptor-mediated inhibition of the N-type calcium-channel current.

The predominant consequences of mu-opioid-receptor activation are depression of both neuronal activity and transmitter release. Mu-Opioid agonists have previously been observed to increase a potassium conductance and to inhibit adenylate cyclase. We now report that activation of mu-opioid receptors directly decreases the N-type calcium-channel current in a differentiated, human neuroblastoma cell line (SH-SY5Y). The coupling between the mu-opioid receptor and the calcium channel involves a pertussis toxin-sensitive G protein and is independent of changes in adenylate cyclase activity. The inhibition of the calcium-channel current is voltage dependent because it is largely overcome by strong membrane depolarization. It is not associated with changes in the kinetics of current inactivation. Therefore, the mu-receptor belongs to the superfamily of G-protein-coupled, inhibitory neurotransmitter receptors which modulate the activity of calcium and potassium channels and adenylate cyclase.     

Genetic exchange between kingdoms.

Bacterial conjugation with two evolutionarily divergent yeasts has been observed in the laboratory. Whether such trans-kingdom conjugation events, other than the well known Agrobacterium-plant cell interaction, actually occur in nature is not known. However, a few putative events have recently been uncovered by gene (or protein) sequence analysis, suggesting that horizontal gene transfer between phylogenetic kingdoms may be a real phenomenon.