Highly radiation sensitive type IA FBGs for dosimetry applications

We have studied Co60 ionizing radiation effect on the characteristics of Type IA fiber Bragg gratings. A record Bragg peak shift of 190 pm was observed for a grating written in Fibercore PS-1250/1500 photosensitive fiber at a radiation dose of 116 kGy. Type IA and Type I gratings show different kinetics under radiation and during post-radiation annealing, which can be used for the design of a grating based dosimetry system.

Bone marrow stromal cells stimulate neurite outgrowth over neural proteoglycans (CSPG), myelin associated glycoprotein and Nogo-A

In animal models, transplantation of bone marrow stromal cells (MSC) into the spinal cord following injury enhances axonal regeneration and promotes functional recovery. How these improvements come about is currently unclear. We have examined the interaction of MSC with neurons, using an established in vitro model of nerve growth, in the presence of substrate-bound extracellular molecules that are thought to inhibit axonal regeneration, i.e., neural proteoglycans (CSPG), myelin associated glycoprotein (MAG) and Nogo-A. Each of these molecules repelled neurite outgrowth from dorsal root ganglia (DRG) in a concentration-dependent manner. However, these nerve-inhibitory effects were much reduced in MSC/DRG co-cultures. Video microscopy demonstrated that MSC acted as "cellular bridges" and also "towed" neurites over the nerve-inhibitory substrates. Whereas conditioned medium from MSC cultures stimulated DRG neurite outgrowth over type I collagen, it did not promote outgrowth over CSPG, MAG or Nogo-A. These findings suggest that MSC transplantation may promote axonal regeneration both by stimulating nerve growth via secreted factors and also by reducing the nerve-inhibitory effects of the extracellular molecules present.

Human intervertebral disc cells promote nerve growth over substrata of human intervertebral disc aggrecan

Study Design. Coculture assays of the migration and interaction of human intervertebral disc cells and chick sensory nerves on alternate substrata of collagen and aggrecan. Objective. To examine the effects of aggrecan on disc cell migration, how disc cells and sensory nerves interact, and whether disc cells affect previously reported inhibitory effects of aggrecan on sensory nerve growth. Summary of Background Data. Human intervertebral disc aggrecan is inhibitory to sensory nerve growth in vitro, suggesting that a loss of aggrecan from the disc may have a role in the increased innervation seen in disc degeneration. Endothelial cells that appear to co-migrate with nerves into degenerated intervertebral disc express neurotrophic factors, but the effects of disc cells on nerve growth are not known. Methods. Human disc cells were seeded onto tissue culture plates that had been coated with type I collagen and human intervertebral disc aggrecan. Explants of chick dorsal root ganglions (DRGs) were subsequently added to the plates and sensory neurite outgrowth stimulated by the addition of nerve growth factor. Time-lapse video and fluorescence microscopy were used to examine the migration and interaction of the disc cells and sensory neurites, in the context of the different matrix substrata. The effects of disc cell conditioned medium on nerve growth were also examined. Results. Disc cells spread and migrated on collagen until they encountered the aggrecan substrata, where some cells, but not all, were repelled. In coculture, DRG neurites extended onto the collagen/disc cells until they encountered the aggrecan, where, like the disc cells, many were repelled. However, in the presence of disc cells, some neurites were able to cross onto this normally inhibitory substratum. The number of neurite crossings onto aggrecan correlated significantly with the number of disc cells present on the aggrecan. In control experiments using DRG alone, all extending neurites were repelled at the collagen/aggrecan border. Conditioned medium from disc cell cultures stimulated DRG neurite outgrowth on collagen but did not increase neurite crossing onto aggrecan substrata. Conclusions. Human disc cells migrate across aggrecan substrata that are repellent to sensory DRG neurites. Disc cells synthesize neurotrophic factors in vitro that promote neurite outgrowth. Furthermore, the presence of disc cells in coculture with DRG partially abrogates the inhibitory effects of aggrecan on nerve growth. These findings have important implications for the regulation of nerve growth into the intervertebral disc, but whether disc cells promote nerve growth in vivo remains to be determined.

Human intervertebral disc aggrecan inhibits endothelial cell adhesion and cell migration in vitro

STUDY DESIGN: The effect of human intervertebral disc aggrecan on endothelial cell growth was examined using cell culture assays. OBJECTIVE: To determine the response of endothelial cells to human intervertebral disc aggrecan, and whether the amount and type of aggrecan present in the intervertebral disc may be implicated in disc vascularization. SUMMARY OF BACKGROUND DATA: Intervertebral disc degeneration has been associated with a loss of proteoglycan, and the ingrowth of blood vessels and nerves. Neovascularization is a common feature also of disc herniation. Intervertebral disc aggrecan is inhibitory to sensory nerve growth, but the effects of disc aggrecan on endothelial cell growth are not known. METHODS: Aggrecan monomers were isolated separately from the anulus fibrosus and nucleus pulposus of human lumbar intervertebral discs, and characterized to determine the amount and type of sulfated glycosaminoglycan side chains present. The effects of these aggrecan isolates on the cellular adhesion and migration of the human endothelial cell lines, HMEC-1 and EAhy-926, were examined in vitro. RESULTS: Homogenous substrata of disc aggrecan inhibited endothelial cell adhesion and cell spreading in a concentration dependent manner. In substrata choice assays, endothelial cells seeded onto collagen type I migrated over the collagen until they encountered substrata of disc aggrecan, where they either stopped migrating, retreated onto the collagen, or, more commonly, changed direction to align along the collagen-aggrecan border. The inhibitory effect of aggrecan on endothelial cell migration was concentration dependent, and reduced by enzymatic treatment of the aggrecan monomers with a combination of chondroitinase ABC and keratinase/keratinase II. Anulus fibrosus aggrecan was more inhibitory to endothelial cell adhesion than nucleus pulposus aggrecan. However, this difference did not relate to the extent to which the different aggrecan isolates were charged, as determined by colorimetric assay with 1,9-dimethylmethylene blue, or to marked differences in the distribution of chondroitin sulfated and keratan sulfated side chains. CONCLUSIONS: Human intervertebral disc aggrecan is inhibitory to endothelial cell migration, and this inhibitory effect appears to depend, in part, on the presence of glycosaminoglycan side chains on the aggrecan monomer.

Cardiac dysfunction and cell damage across clinical stages of severity in growth-restricted fetuses

Objective - The purpose of this study was to assess cardiac function and cell damage in intrauterine growth-restricted (IUGR) fetuses across clinical Doppler stages of deterioration. Study Design - One hundred twenty appropriate-for-gestational-age and 81 IUGR fetuses were classified in stages 1/2/3 according umbilical artery present/absent/reversed end-diastolic blood flow, respectively. Cardiac function was assessed by modified-myocardial performance index, early-to-late diastolic filling ratios, cardiac output, and cord blood B-type natriuretic peptide; myocardial cell damage was assessed by heart fatty acid–binding protein, troponin-I, and high-sensitivity C-reactive protein. Results - Modified-myocardial performance index, blood B-type natriuretic peptide, and early-to-late diastolic filling ratios were increased in a stage-dependent manner in IUGR fetuses, compared with appropriate-for-gestational-age fetuses. Heart fatty acid–binding protein levels were higher in IUGR fetuses at stage 3, compared with control fetuses. Cardiac output, troponin-I, and high-sensitivity C-reactive protein did not increase in IUGR fetuses at any stage. Conclusion - IUGR fetuses showed signs of cardiac dysfunction from early stages. Cardiac dysfunction deteriorates further with the progression of fetal compromise, together with the appearance of biochemical signs of cell damage.

Annealing and temperature coefficient study of type IA fibre Bragg gratings inscribed under strain and no strain - Implications to optical fibre component reliability

The annealing properties of Type IA Bragg gratings are investigated and compared with Type I and Type IIA Bragg gratings. The transmission properties (mean and modulated wavelength components) of gratings held at predetermined temperatures are recorded from which decay characteristics are inferred. Our data show critical results concerning the high temperature stability of Type IA gratings, as they undergo a drastic initial decay at 100°C, with a consequent mean index change that is severely reduced at this temperature However, the modulated index change of IA gratings remains stable at lower annealing temperatures of 80°C, and the mean index change decays at a comparable rate to Type I gratings at 80°C. Extending this work to include the thermal decay of Type IA gratings inscribed under strain shows that the application of strain quite dramatically transforms the temperature characteristics of the Type IA grating, modifying the temperature coefficient and annealing curves, with the grating showing a remarkable improvement in high temperature stability, leading to a robust grating that can survive temperatures exceeding 180°C. Under conditions of inscription under strain it is found that the temperature coefficient increases, but is maintained at a value considerably different to the Type I grating. Therefore, the combination of Type I and IA (strained) gratings make it possible to decouple temperature and strain over larger temperature excursions.

Use of dual-grating sensors formed by different types of fiber Bragg gratings for simultaneous temperature and strain measurements

We report on a systematic investigation of the dependence of both temperature and strain sensitivities on the fiber Bragg grating type, including the well-known Type I, Type IIA, and a new type that we have designated Type IA, using both hydrogen-free and hydrogenated B/Ge codoped fibres. We have identified distinct sensitivity characteristics for each grating type, and we have used them to implement a novel dual-grating, dual-parameter sensor device. Three dual-grating sensing schemes with different combinations of grating type have been constructed and compared, and that of a Type IA-Type IIA combination exhibits the best performance, which is also superior to that of previously reported grating-based structures. The characteristics of the measurement errors in such dual-grating sensor systems is also presented in detail. © 2004 Optical Society of America.

Human mesenchymal stem cells stimulate EaHy926 endothelial cell migration:combined proteomic and in vitro analysis of the influence of donor-donor variability

Mesenchymal stem cells (MSCs) stimulate angiogenesis within a wound environment and this effect is mediated through paracrine interactions with the endothelial cells present. Here we report that human MSC-conditioned medium (n=3 donors) significantly increased EaHy-926 endothelial cell adhesion and cell migration, but that this stimulatory effect was markedly donor-dependent. MALDI-TOF/TOF mass spectrometry demonstrated that whilst collagen type I and fibronectin were secreted by all of the MSC cultures, the small leucine rich proteoglycan, decorin was secreted only by the MSC culture that was least effective upon EaHy-926 cells. These individual extracellular matrix components were then tested as culture substrata. EaHy-926 cell adherence was greatest on fibronectin-coated surfaces with least adherence on decorin-coated surfaces. Scratch wound assays were used to examine cell migration. EaHy-926 cell scratch wound closure was quickest on substrates of fibronectin and slowest on decorin. However, EaHy-926 cell migration was stimulated by the addition of MSC-conditioned medium irrespective of the types of culture substrates. These data suggest that whilst the MSC secretome may generally be considered angiogenic, the composition of the secretome is variable and this variation probably contributes to donor-donor differences in activity. Hence, screening and optimizing MSC secretomes will improve the clinical effectiveness of pro-angiogenic MSC-based therapies.

Highly sensitive type IA fiber Bragg gratings as sensors in radiation environments

Type IA fiber gratings have unusual physical properties compared with other grating types. We compare with performance characteristics of Type IA and Type I Bragg gratings exposed to the effects of Co60 gamma-irradiation. A Bragg peak shift of 190 pm was observed for Type IA gratings written in Fibercore PS-1250/1500 photosensitive fiber at a radiation dose of 116 kGy. This is the largest wavelength shift recorded to date under radiation exposure. The Type IA and Type I gratings show different kinetics under radiation and during post-radiation annealing; this can be exploited for the design of a grating based dosimetry system. © 2012 SPIE.