Modelling the transition from simple to complex Ca2+oscillations in pancreatic acinar cells

A mathematical model is proposed which systematically investigates complex calcium oscillations in pancreatic acinar cells. This model is based on calcium-induced calcium release via inositol trisphosphate receptors (IPR) and ryanodine receptors (RyR) and includes calcium modulation of inositol (1,4,5) trisphosphate (IP₃) levels through feedback regulation of degradation and production. In our model, the apical and the basal regions are separated by a region containing mitochondria, which is capable of restricting Ca²⁺ responses to the apical region. We were able to reproduce the observed oscillatory patterns, from baseline spikes to sinusoidal oscillations. The model predicts that calcium-dependent production and degradation of IP₃ is a key mechanism for complex calcium oscillations in pancreatic acinar cells. A partial bifurcation analysis is performed which explores the dynamic behaviour of the model in both apical and basal regions.     

Depletion of chondrocyte primary cilia reduces the compressive modulus of articular cartilage

Primary cilia are slender, microtubule based structures found in the majority of cell types with one cilium per cell. In articular cartilage, primary cilia are required for chondrocyte mechanotransduction and the development of healthy tissue. Loss of primary cilia in Col2aCre;ift88^fl/fl transgenic mice results in up-regulation of osteoarthritic (OA) markers and development of OA like cartilage with greater thickness and reduced mechanical stiffness. However no previous studies have examined whether loss of primary cilia influences the intrinsic mechanical properties of articular cartilage matrix in the form of the modulus or just the structural properties of the tissue. The present study describes a modified analytical model to derive the viscoelastic moduli based on previous experimental indentation data. Results show that the increased thickness of the articular cartilage in the Col2aCre;ift88^fl/fl transgenic mice is associated with a reduction in both the instantaneous and equilibrium moduli at indentation strains of greater than 20%. This reveals that the loss of primary cilia causes a significant reduction in the mechanical properties of cartilage particularly in the deeper zones and possibly the underlying bone. This is consistent with histological analysis and confirms the importance of primary cilia in the development of a mechanically functional articular cartilage.     

The metabolism of human mesenchymal stem cells during proliferation and differentiation

Human mesenchymal stem cells (MSCs) reside under hypoxic conditions in vivo, between 4% and 7% oxygen. Differentiation of MSCs under hypoxic conditions results in inhibited osteogenesis, while chondrogenesis is unaffected. The reasons for these results may be associated with the inherent metabolism of the cells. The present investigation measured the oxygen consumption, glucose consumption and lactate production of MSCs during proliferation and subsequent differentiation towards the osteogenic and chondrogenic lineages. MSCs expanded under normoxia had an oxygen consumption rate of ～98 fmol/cell/h, 75% of which was azide-sensitive, suggesting that these cells derive a significant proportion of ATP from oxidative phosphorylation in addition to glycolysis. By contrast, MSCs differentiated towards the chondrogenic lineage using pellet culture had significantly reduced oxygen consumption after 24 h in culture, falling to ～12 fmol/cell/h after 21 days, indicating a shift towards a predominantly glycolytic metabolism. By comparison, MSCs retained an oxygen consumption rate of ～98 fmol/cell/h over 21 days of osteogenic culture conditions, indicating that these cells had a more oxidative energy metabolism than the chondrogenic cultures. In conclusion, osteogenic and chondrogenic MSC cultures appear to adopt the balance of oxidative phosphorylation and glycolysis reported for the respective mature cell phenotypes. The addition of TGF-β to chondrogenic pellet cultures significantly enhanced glycosaminoglycan accumulation, but caused no significant effect on cellular oxygen consumption. Thus, the differences between the energy metabolism of chondrogenic and osteogenic cultures may be associated with the culture conditions and not necessarily their respective differentiation.     

Metabolic engineering of seeds can achieve levels of omega-7 fatty acids comparable with the highest levels found in natural plant sources

Plant oils containing ω-7 fatty acids (FAs; palmitoleic 16:1Δ(9) and cis-vaccenic 18:1Δ(11)) have potential as sustainable feedstocks for producing industrially important octene via metathesis chemistry. Engineering plants to produce seeds that accumulate high levels of any unusual FA has been an elusive goal. We achieved high levels of ω-7 FA accumulation by systematic metabolic engineering of Arabidopsis (Arabidopsis thaliana). A plastidial 16:0-ACP desaturase has been engineered to convert 16:0 to 16:1Δ(9) with specificity >100-fold than that of naturally occurring paralogs, such as that from cat's claw vine (Doxantha unguis-cati). Expressing this engineered enzyme (Com25) in seeds increased ω-7 FA accumulation from <2% to 14%. Reducing competition for 16:0-ACP by down-regulating the β-ketoacyl-ACP synthase II 16:0 elongase further increased accumulation of ω-7 FA to 56%. The level of 16:0 exiting the plastid without desaturation also increased to 21%. Coexpression of a pair of fungal 16:0 desaturases in the cytosol reduced the 16:0 level to 11% and increased ω-7 FA to as much as 71%, equivalent to levels found in Doxantha seeds.     

Forskolin ameliorates mancozeb‐induced testicular and epididymal toxicity in Wistar rats by reducing oxidative toxicity and by stimulating steroidogenesis

In the present study, we have tested the beneficial effects of forskolin in protecting the mancozeb‐induced reproductive toxicity in rats. Adult male Wistar rats were exposed to either mancozeb (500 mg/kg body weight/day) or forskolin (5 mg/kg body weight/day) or both for 65 days and analyzed for spermatogenesis and steroidogenesis and testicular and epididymal oxidative toxicity. A significant decrease in daily sperm production, epididymal sperm count, motile, viable, and hypo‐osmotic swelling‐tail swelled sperm was observed in mancozeb‐treated rats. The activity levels of testicular 3β‐hydroxysteroid dehydrogenase and 17β‐hydroxysteroid dehydrogenase and circulatory testosterone levels were significantly decreased in mancozeb‐treated rats. Exposure to mancozeb resulted in a significant decrease in glutathione levels and superoxide dismutase and catalase activity levels with an increase in lipid peroxidation levels in the testes and epididymis. Coadministration of forskolin mitigated the mancozeb‐induced oxidative toxicity and suppressed steroidogenesis and spermatogenesis.     

Hemin-induced platelet activation and ferroptosis is mediated through ROS-driven proteasomal activity and inflammasome activation: Protection by Melatonin

Reactive oxygen species (ROS) are capable of inducing cell death or apoptosis. Recently, we demonstrated that lipid-ROS can mediate ferroptosis and activation of human platelets. Ferroptosis is an intracellular iron-mediated cell death, distinct from classical apoptosis and necrosis, which is mediated through the accumulation of ROS, lipid peroxides and depletion of cellular GSH. Lately, we demonstrated that hemoglobin degradation product hemin induces ferroptosis in platelets via ROS and lipid peroxidation. In this study, we demonstrate that hemin-induced ferroptosis in platelets is mediated through ROS-driven proteasome activity and inflammasome activation, which were mitigated by Melatonin (MLT). Although inflammasome activation is linked with pyroptosis, it is still not clear whether ferroptosis is associated with inflammasome activation. Our study for the first time demonstrates an association of platelet activation/ferroptosis with proteasome activity and inflammasome activation. Although, high-throughput screening has recognized ferrostatin-1 (Fer-1) and liproxstatin-1 (Lip-1) as potent ferroptosis inhibitors, having an endogenous antioxidant such as MLT as ferroptosis inhibitor is of high interest. MLT is a well-known chronobiotic hormone that regulates the circadian rhythms in vertebrates. It also exhibits potent antioxidant and ROS quenching capabilities. MLT can regulate fundamental cellular functions by exhibiting cytoprotective, oncostatic, antiaging, anti-venom, and immunomodulatory activities. The ROS scavenging capacity of MLT is key for its cytoprotective and anti-apoptotic properties. Considering the anti-ferroptotic and anti-apoptotic potentials of MLT, it could be a promising clinical application to treat hemolytic, thrombotic and thrombocytopenic conditions. Therefore, we propose MLT as a pharmacological and therapeutic agent to inhibit ferroptosis and platelet activation.     

Regeneration in the auditory system of nymphal and adult bush crickets Tettigonia viridissima

Regeneration and reestablishment of synaptic connections is an important topic in neurobiological research. In the present study, the regeneration of auditory afferents and the accompanying effects in the central nervous system are investigated in nymphs and adults of the bush cricket Tettigonia viridissima L. (Orthoptera: Tettigoniidae). In all animals in which the tympanal nerve is crushed, neuronal tracing shows a regrowth of the afferents into the prothoracic ganglion. This regeneration is seen in both adult and nymphal stages and starts 10–15 days after nerve crushing. Physiological recordings from the leg nerve indicate a recovery of tympanal fibres and a formation of functional connections to interneurones in the same time range. Electrophysiological recordings from the neck connective suggest additional contralateral sprouting of interneurones and the formation of aberrant connections. The regeneration processes of the tympanal nerve in nymphal stages and adults appear to be similar.     

Synthesis of pochoxime prodrugs as potent HSP90 inhibitors

Pochoximes are potent inhibitors of heat shock protein 90 (HSP90) based on the radicicol pharmacophores. Herein we present a pharmacokinetics and pharmacodynamics evaluation of this compound series as well as a phosphate prodrug strategy to facilitate formulation and improve oral bioavailability.     

Effects of growth factors on cell proliferation and monoclonal antibody production of batch hybridoma cultures

Summary Effects of growth factors such as EGF, FGF and IL-2 on cell proliferation and monoclonal antibody production in a hybridoma cell line adapted to a completely defined serum-free medium were determined in batch cultures. The results indicate that the presence of growth factors in the medium enhances the antibody secretion without significantly affecting the growth rate. The specific antibody secretion rate of cells grown in serum-free medium supplemented with growth factors was 35% higher than those grown in serum-free medium alone.