Directional specificity and encoding of muscle forces and loads by stick insect tibial campaniform sensilla,including receptors with round cuticular caps

In many systems, loads are detected as the resistance to muscle contractions. We studied responses to loads and muscle forces in stick insect tibial campaniform sensilla, including a subgroup of receptors (Group 6B) with unusual round cuticular caps in oval-shaped collars. Loads were applied in different directions and muscle contractions were emulated by applying forces to the tibial flexor muscle tendon (apodeme). All sensilla 1) were maximally sensitive to loads applied in the plane of joint movement and 2) encoded muscle forces but did not discharge to unresisted movements. Identification of 6B sensilla by stimulation of cuticular caps demonstrated that receptor responses were correlated with their morphology. Sensilla with small cuticular collars produced small extracellular potentials, had low thresholds and strong tonic sensitivities that saturated at moderate levels. These receptors could effectively signal sustained loads. The largest spikes, derived from sensilla with large cuticular collars, had strong dynamic sensitivities and signaled a wide range of muscle forces and loads. Tibial sensilla are apparently tuned to produce no responses to inertial forces, as occur in the swing phase of walking. This conclusion is supported by tests in which animals 'stepped' on a compliant surface and sensory discharges only occurred in stance.     

Evaluation of nucleus pulposus fluid velocity and pressure alteration induced by cartilage endplate sclerosis using a poro-elastic finite element analysis

Biomechanics and Modeling in Mechanobiology - The nucleus pulposus (NP) in the intervertebral disk (IVD) depends on diffusive fluid transport for nutrients through the cartilage endplate (CEP)....     

Collective cell migration requires suppression of actomyosin at cell-cell contacts mediated by DDR1 and the cell polarity regulators Par3 and Par6

Collective cell migration occurs in a range of contexts: cancer cells frequently invade in cohorts while retaining cell-cell junctions. Here we show that collective invasion by cancer cells depends on decreasing actomyosin contractility at sites of cell-cell contact. When actomyosin is not downregulated at cell-cell contacts, migrating cells lose cohesion. We provide a molecular mechanism for this downregulation. Depletion of discoidin domain receptor 1 (DDR1) blocks collective cancer-cell invasion in a range of two-dimensional, three-dimensional and 'organotypic' models. DDR1 coordinates the Par3/Par6 cell-polarity complex through its carboxy terminus, binding PDZ domains in Par3 and Par6. The DDR1-Par3/Par6 complex controls the localization of RhoE to cell-cell contacts, where it antagonizes ROCK-driven actomyosin contractility. Depletion of DDR1, Par3, Par6 or RhoE leads to increased actomyosin contactility at cell-cell contacts, a loss of cell-cell cohesion and defective collective cell invasion.     

Loss of PTB or negative regulation of Notch mRNA reveals distinct zones of Notch and actin protein accumulation in Drosophila embryo

Polypyrimidine Tract Binding (PTB) protein is a regulator of mRNA processing and translation. Genetic screens and studies of wing and bristle development during the post-embryonic stages of Drosophila suggest that it is a negative regulator of the Notch pathway. How PTB regulates the Notch pathway is unknown. Our studies of Drosophila embryogenesis indicate that (1) the Notch mRNA is a potential target of PTB, (2) PTB and Notch functions in the dorso-lateral regions of the Drosophila embryo are linked to actin regulation but not their functions in the ventral region, and (3) the actin-related Notch activity in the dorso-lateral regions might require a Notch activity at or near the cell surface that is different from the nuclear Notch activity involved in cell fate specification in the ventral region. These data raise the possibility that the Drosophila embryo is divided into zones of different PTB and Notch activities based on whether or not they are linked to actin regulation. They also provide clues to the almost forgotten role of Notch in cell adhesion and reveal a role for the Notch pathway in cell fusions.     

Oxytocin increases invasive properties of endometrial cancer cells through phosphatidylinositol 3-kinase/AKT-dependent up-regulation of cyclooxygenase-1, -2, and X-linked inhibitor of apoptosis protein

Traditionally, oxytocin (OT) is well known to play a crucial role in the regulation of cyclic changes in the uterus, implantation of the embryo, and parturition. Recently, an additional role for OT has been identified in several types of cancer cells in which OT acts as a growth regulator. In endometrial cancer cells, OT is known to efficiently inhibit cellular proliferation. In the present study, we show that OT increases invasiveness of human endometrial carcinoma (HEC) cells, which are otherwise resistant to the growth-inhibiting effects of OT. Using pharmacological inhibitors, invasion assay, RNA interference, and immunofluorescence, we found that OT enhances the invasive properties of HEC cells through up-regulation of X-linked inhibitor of apoptosis protein (XIAP), matrix-metalloproteinase 2 (MMP2), and matrix-metalloproteinase 14 (MMP14). In addition, we show that OT-mediated invasion is both cyclooxygenase 1 (PTGS1) and cyclooxygenase-2 (PTGS2) dependent via the phosphatidylinositol 3-kinase/AKT (PIK3/AKT) pathway. PTGS2 knockdown by shRNA resulted in XIAP down-regulation. We also show that OT receptor is overexpressed in grade I to III endometrial cancer. Taken together, our results describe for the first time a novel role for OT in endometrial cancer cell invasion.     

Effect of a tail piece cysteine deletion on biochemical and functional properties of an epidermal growth factor receptor-directed IgA2 m(1) antibody

Antibodies of human IgA isotype are critical components of the mucosal immune system, but little is known about their immunotherapeutic potential. Compared with IgG antibodies, IgA molecules carry a C-terminal tail piece extension of 18 amino acids with a free cysteine at position 471. This cysteine is required for the formation of dimeric IgA antibodies, but may impair molecular characteristics of monomeric IgA antibodies as therapeutic reagents. Thus, we generated and characterized a d471-mutated antibody against the epidermal growth factor receptor (EGFR) and compared it to its respective IgA2 m(1) wild type antibody. Both wild type and mutated IgA antibodies demonstrated similar EGFR binding and were similarly efficient in inhibiting EGF binding and in blocking EGF-mediated cell proliferation. Recruitment of Fc-mediated effector functions like antibody-dependent cell-mediated cytotoxicity by monocytes, macrophages or PMN was similar, but the d471-mutated IgA exhibited different biochemical properties compared with wild type antibody. As expected, mutated IgA did not form stable dimers in the presence of human joining (J)-chain, but we also observed reduced levels of dimeric aggregates in the absence of J-chain. Furthermore, glycoprofiling revealed different glycosylation patterns for both antibodies, including considerably less mannosylation of d471-mutated antibodies. Overall, our results demonstrate that the deletion of the C-terminal cysteine of IgA2 did not affect the investigated effector functions compared with wild type antibody, but it improved biochemical properties of an IgA2 m(1) antibody against EGFR, and may thereby assist in exploring the immunotherapeutic potential of recombinant IgA antibodies.     

Recovery of <Emphasis Type="Italic">Bacillus</Emphasis> and <Emphasis Type="Italic">Pseudomonas</Emphasis> spp. from the ‘Fired Plots’ Under Shifting Cultivation in Northeast India

Soil samples, collected after the fire operations at agricultural sites under shifting cultivation in northeast India, were subjected to physico-chemical and microbial analysis. The fire affected various physico-chemical properties of the soil. Significant differences in pH and electrical conductivity were recorded in soil of fired and fallow plots. Significantly higher amounts of total organic carbon and nitrogen were estimated in fallow plots as compared to the fired. Difference in total phosphates was not significant. The fire operations resulted in stimulation of microbial communities. The bacteria were the most affected group followed by actinomycetes and fungi, respectively. The bacterial and actinomycetes counts were significantly higher in fired plots as compared to the fallow plots. The representative bacterial species recovered from the ‘fired plots’ belonged to the genus Bacillus and Pseudomonas. 16S rRNA analysis revealed their maximum similarity with B. clausii, B. licheniformis, B. megaterium, B. subtilis, B. thuringiensis, P. aeruginosa and P. stutzeri. Most of these species were found to be positive for phosphate solubilization and antagonism in plate based assays. In view of the importance of Bacillus and Pseudomonas species in plant growth promotion and biocontrol, recovery of these species after fire operations is indicative of the microbiological merit of shifting cultivation.     

NK dendritic cells are innate immune responders to Listeria monocytogenes infection

NK dendritic cells (NKDC) are recently described immunologic cells that possess both lytic and Ag-presenting function and produce prolific quantities of IFN-gamma. The role of NKDC in innate immunity to bacterial infection is unknown. Because IFN-gamma is important in the immune response to Listeria monocytogenes (LM), we hypothesized that NKDC play a critical role during LM infection in mice. We found that LM increased the frequency and activation state of NKDC in vivo. Using in vivo intracellular cytokine analysis, we demonstrated that NKDC are a major source of early IFN-gamma during infection with LM. Adoptive transfer of wild-type NKDC into IFN-gamma-deficient recipients that were subsequently infected with LM decreased bacterial burden in the liver and spleen and prolonged survival. In contrast, NK cells were depleted early during LM infection, produced less IFN-gamma, and conferred less protection upon adoptive transfer into IFN-gamma-deficient mice. In vitro, LM induction of IFN-gamma secretion by NKDC depended on TLR9, in addition to IL-18 and IL-12. Our study establishes NKDC as innate immune responders to bacterial infection by virtue of their ability to secrete IFN-gamma.     

Depth-dependent biomechanical and biochemical properties of fetal, newborn, and tissue-engineered articular cartilage

Adult articular cartilage has depth-dependent mechanical and biochemical properties which contribute to zone-specific functions. The compressive moduli of immature cartilage and tissue-engineered cartilage are known to be lower than those of adult cartilage. The objective of this study was to determine if such tissues exhibit depth-dependent compressive properties, and how these depth-varying properties were correlated with cell and matrix composition of the tissue. The compressive moduli of fetal and newborn bovine articular cartilage increased with depth (p<0.05) by a factor of 4-5 from the top 0.1 mm (28+/-13 kPa, 141+/-10 kPa, respectively) to 1 mm deep into the tissue. Likewise, the glycosaminoglycan and collagen content increased with depth (both p<0.001), and correlated with the modulus (both p<0.01). In contrast, tissue-engineered cartilage formed by either layering or mixing cells from the superficial and middle zone of articular cartilage exhibited similarly soft regions at both construct surfaces, as exemplified by large equilibrium strains. The properties of immature cartilage may provide a template for developing tissue-engineered cartilage which aims to repair cartilage defects by recapitulating the natural development and growth processes. These results suggest that while depth-dependent properties may be important to engineer into cartilage constructs, issues other than cell heterogeneity must be addressed to generate such tissues.     

MTHFR C677T Predisposes to POAG but Not to PACG in a North Indian Population: A Case Control Study

Hyperhomocysteinemia induced by the C677T genetic variant in MTHFR (methylenetetrahydrofolate reductase) has been implicated in neuronal cell death of retinal ganglion cells (RGC), which is a characteristic feature of glaucoma. However, association of MTHFR C677T with glaucoma has been controversial because of inconsistent results across association studies. Association between MTHFR C677T and glaucoma has not been reported in Indian population. Therefore, with a focus on neurodegenerative death of RGC in glaucoma, the current study aimed to investigate association of MTHFR C677T with Primary Open Angle Glaucoma (POAG) and Primary Angle Closure Glaucoma (PACG) in a North Indian population. A total of 404 participants (231 patients and 173 controls) were included in this study. Genotyping was performed by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism. A few random samples were also tested by direct sequencing. Genotypic and allelic distributions of the POAG and PACG cohorts were compared to that of controls by chi-square test and odds ratios were reported with 95% confidence intervals. Genotypic and allelic distributions between POAG cases and controls were significantly different (p = 0.03 and p = 0.01 respectively). Unlike POAG, we did not find significant difference in the genotypic and allelic distributions of C677T between PACG cases and controls (p>0.05). We also observed a higher proportion of TT associated POAG in females than that in males. However, this is a preliminary indication of gender specific risk of C677T that needs to be replicated in a larger cohort of males and females. The present investigation on MTHFR C677T and glaucoma reveals that the TT genotype and T allele of this polymorphism are significant risk factors for POAG but not for PACG in North Indian population. Ours is the first report demonstrating association of MTHFR C677T with POAG but not PACG in individuals from North India.