Direct Regulation of Osteocytic Connexin 43 Hemichannels through AKT Kinase Activated by Mechanical Stimulation

Connexin (Cx) 43 hemichannels in osteocytes are thought to play a critical role in releasing bone modulators in response to mechanical loading, a process important for bone formation and remodeling. However, the underlying mechanism that regulates the opening of mechanosensitive hemichannels is largely unknown. We have recently shown that Cx43 and integrin α5 interact directly with each other, and activation of PI3K appears to be required for Cx43 hemichannel opening by mechanical stimulation. Here, we show that mechanical loading through fluid flow shear stress (FFSS) increased the level of active AKT, a downstream effector of PI3K, which is correlated with the opening of hemichannels. Both Cx43 and integrin α5 are directly phosphorylated by AKT. Inhibition of AKT activation significantly reduced FFSS-induced opening of hemichannels and disrupted the interaction between Cx43 and integrin α5. Moreover, AKT phosphorylation on Cx43 and integrin α5 enhanced their interaction. In contrast to the C terminus of wild-type Cx43, overexpression of the C-terminal mutant containing S373A, a consensus site previously shown to be phosphorylated by AKT, failed to bind with α5 and hence could not inhibit hemichannel opening. Together, our results suggest that AKT activated by FFSS directly phosphorylates Cx43 and integrin α5, and Ser-373 of Cx43 plays a predominant role in mediating the interaction between these two proteins and Cx43 hemichannel opening, a crucial step to mediate the anabolic function of mechanical loading in the bone.     

IgG subclass specificity to C1q determined by surface plasmon resonance using Protein L capture technique

Recombinant monoclonal antibodies (mAbs) have become an important category of biological therapeutics. mAbs share the same structures and biological functions as endogenous IgG molecules. One function is complement-dependent cytotoxicity (CDC) initiation by binding of C1q. Traditionally, ELISA methods have been utilized to measure C1q binding. A new robust capture method was established in this study to measure the binding affinity of C1q to antibodies by surface plasmon resonance (SPR). The utility of this method was demonstrated by determination of the difference in IgG subclass specificity of C1q binding.     

Influence of silver nanoparticles on the enhancement and transcriptional changes of glucosinolates and phenolic compounds in genetically transformed root cultures of Brassica rapa ssp. rapa

Bioprocess and Biosystems Engineering - Glucosinolates (GSLs) and phenolic compounds (PCs) are biologically active and involved in the defense reaction of plants; these compounds have a beneficial...     

Effect of salt-stress on translocation of photosynthates in pigeon-pea

Summary An investigation was carried out in order to study the effect of salts namely NaC1 and Na₂SO₄ on the rate of translocation of photosynthates in pigeonpea, at the pod filling stage. At the concentration of 10 EC NaC1 only 17% of the¹⁴C assimilates are translocated from the source leaf to the other parts of the plant. Out of this pods receive about 8%. On the other hand even at a concentration of 15 EC Na₂SO₄ about 30% of the total¹⁴C assimilates get translocated and out of this pods receive about 12%. From this it may be concluded that under salt-stress conditions the rate of translocation of photosynthates is adversely affected and between the two salts, NaC1 was discovered to have a marked inhibitory effect.     

Optimization of parameters in the batch kinetic studies of glucose isomerisation by arthrobacter sp.

Vital parameters like temperature, pH and agitation are optimized in the kinetic studies of glucose isomerisation carried out in a batch fashion. A 4-litre fermentor with temperature, pH, agitation and other controls is used. It is found that the two parameters — temperature and pH, do not have an interacting effect on each other. A temperature of 60°C, a pH of 8.0 and a speed of 200 rpm are found to be better suited for the production of fructose syrups starting from glucose by arthrobacter sp. An upper limit of 20 minutes on the residence time is suggested for use in the design of flow reactors.     

Radiobiology of alpha particles. III. Cell inactivation by alpha-particle traversals of the cell nucleus

Cell inactivation after exposure to collimated 3.5-MeV alpha particles in three hamster cell lines, V79, CHO-10B, and HS-23, one mouse cell line, C3H 10T1/2, and a human skin fibroblast cell line were studied. Several parameters were investigated for each cell line. Theoretical calculations were performed to find the distribution of energy deposited in the nuclear volume for each cell line. The mean number of alpha-particle traversals required to induce a lethal lesion varied between two for HS-23 cells and six for C3H 10T1/2 cells. The number of traversals per unit area and the total track length of alpha particles that inactivated a cell were found to be nearly constant for the hamster and mouse cell lines. These quantities were found to be lower for the human skin fibroblast cell line. The RBE values for all cell lines were found to be about 3.8 at 10% survival. Thus cell lines that are more sensitive to alpha radiation are also more sensitive to gamma radiation. The average number of alpha-particle traversals producing a single lethal lesion is greater than one. The passages of alpha particles through the cell nucleus that do not kill the cell may lead to carcinogenic effects.