Simultaneous time-space resolved reflectivity and interferometric measurements of dielectrics excited with femtosecond laser pulses

13 pags., 7 figs., 1 tab.Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results have been simulated in the frame of a multiple-rate equation model including light propagation. The comparison of the temporal evolution of the reflectivity and the interferometric measurements at 400 nm clearly shows that the two techniques interrogate different material volumes during the course of the process. While the former is sensitive to the evolution of the plasma density in a very thin ablating layer at the surface, the second yields an averaged plasma density over a larger volume. It is shown that self-trapped excitons do not appreciably contribute to carrier relaxation in fused silica at fluences above the ablation threshold, most likely due to Coulomb screening effects at large excited carrier densities. For both materials, at fluences well above the ablation threshold, the maximum measured plasma reflectivity shows a saturation behavior consistent with a scattering rate proportional to the plasma density in this fluence regime. Moreover, for both materials and for pulse energies above the ablation threshold and delays in the few tens of picoseconds range, a simultaneous >low reflectivity> and >low transmission> behavior is observed. Although this behavior has been identified in the past as a signature of femtosecond laser-induced ablation, its origin is alternatively discussed in terms of the optical properties of a material undergoing strong isochoric heating, before having time to substantially expand or exchange energy with the surrounding media.This work has been partly funded by Laserlab-Europe (Grant Agreement No. 284464, EU’s Seventh Framework Programme, Project No. SLIC002014), by the Spanish Ministry of Economy and Competiveness (Project No. TEC2014-52642- C2-1-R) as well as by the Danish Council for Independent Research | Natural Sciences. M.G.-L. acknowledges the FPU (Formación de Profesorado Universitario) Grant No. AP2012- 0217 awarded by the Spanish Ministry of Education.Peer Reviewe

Proteolysis in Danish blue cheese during ripening

Proteolysis in Danish blue cheese was studied during 9 weeks' ripening. Levels of pH 4.6-soluble N as a percentage of total N increased from 7.2% to 25%, indicating extensive proteolysis. Urea-polyacrylamide gel electrophoretograms confirmed the extent of proteolysis through chymosin and plasmin action early in ripening, but later the action of Penicillium roqueforti proteinases became apparent. The proteolytic specificity of Penicillium roqueforti PR-R proteinases on αS1- and β-casein was determined in a model system. Regions most susceptible to proteinase action in αS1-casein were 6–40, 69–99, 124–147 and 155–199, with a total of 91 cleavage sites identified; regions in β-casein susceptible to proteolysis were 43–87, 101–119, 161–185 and 192–209 with a total of 118 cleavage sites identified. A large number of peptides was identified cheese extracts during 9 weeks ripening, principally from αS1-casein regions 1–40, 105–136 and 150–176 and β-casein regions 6–14, 46–68, 101–140 and 193–209

Cerebrospinal fluid biomarkers for predicting development of multiple sclerosis in acute optic neuritis: a population-based prospective cohort study

Background: Long-term outcome in multiple sclerosis (MS) depends on early treatment. In patients with acute optic neuritis (ON), an early inflammatory event, we investigated markers in cerebrospinal fluid (CSF), which may predict a diagnosis of MS. Methods: Forty patients with acute ON were recruited in a prospective population-based cohort with median 29 months (range 19–41) of follow-up. Paired CSF and serum samples were taken within 14 days (range 2–38), prior to treatment. Prospectively, 16/40 patients were by a uniform algorithm diagnosed with MS (MS-ON) and 24 patients continued to manifest isolated ON (ION) during follow-up. Levels of cytokines and neurofilament light chain (NF-L) were measured at the onset of acute ON and compared to healthy controls (HC). Significance levels were corrected for multiple comparisons (“q”). The predictive value of biomarkers was determined with multivariable prediction models using nomograms. Results: CSF TNF-α, IL-10, and CXCL13 levels were increased in MS-ON compared to those in ION patients (q = 0.021, 0.004, and 0.0006, respectively). MS-ON patients had increased CSF pleocytosis, IgG indices, and oligoclonal bands (OCBs) compared to ION (q = 0.0007, q = 0.0058, and q = 0.0021, respectively). CSF levels of IL-10, TNF-a, IL-17A, and CXCL13 in MS-ON patients correlated with leukocyte counts (r > 0.69 and p < 0.002) and IgG index (r > 0.55, p < 0.037). CSF NF-L levels were increased in ON patients compared to those in HC (q = 0.0077). In MS-ON, a progressive increase in NF-L levels was observed at 7 to 14 days after disease onset (r = 0.73, p < 0.0065). Receiver-operating characteristic (ROC) curves for two multivariable prediction models were generated, with IL-10, CXCL13, and NF-L in one (“candidate”) and IgG index, OCB, and leukocytes in another (“routine”). Area under the curve was 0.89 [95% CI 0.77–1] and 0.86 [0.74–0.98], respectively. Predictions of the risk of MS diagnosis were illustrated by two nomograms. Conclusions: CSF TNF-α, IL-10, CXCL13, and NF-L levels were associated with the development of MS, suggesting that the inflammatory and neurodegenerative processes occurred early. Based on subsequent diagnosis, we observed a high predictive value of routine and candidate biomarkers in CSF for the development of MS in acute ON. The nomogram predictions may be useful in the diagnostic work-up of MS

MOG-IgG in NMO and related disorders: a multicenter study of 50 patients. Part 1: Frequency, syndrome specificity, influence of disease activity, long-term course, association with AQP4-IgG, and origin

BACKGROUND: Antibodies to myelin oligodendrocyte glycoprotein (MOG-IgG) have been suggested to play a role in a subset of patients with neuromyelitis optica and related disorders. OBJECTIVE: To assess (i) the frequency of MOG-IgG in a large and predominantly Caucasian cohort of patients with optic neuritis (ON) and/or myelitis; (ii) the frequency of MOG-IgG among AQP4-IgG-positive patients and vice versa; (iii) the origin and frequency of MOG-IgG in the cerebrospinal fluid (CSF); (iv) the presence of MOG-IgG at disease onset; and (v) the influence of disease activity and treatment status on MOG-IgG titers. METHODS: 614 serum samples from patients with ON and/or myelitis and from controls, including 92 follow-up samples from 55 subjects, and 18 CSF samples were tested for MOG-IgG using a live cell-based assay (CBA) employing full-length human MOG-transfected HEK293A cells. RESULTS: MOG-IgG was detected in 95 sera from 50 patients with ON and/or myelitis, including 22/54 (40.7 %) patients with a history of both ON and myelitis, 22/103 (21.4 %) with a history of ON but no myelitis and 6/45 (13.3 %) with a history of longitudinally extensive transverse myelitis but no ON, and in 1 control patient with encephalitis and a connective tissue disorder, all of whom were negative for AQP4-IgG. MOG-IgG was absent in 221 further controls, including 83 patients with AQP4-IgG-seropositive neuromyelitis optica spectrum disorders and 85 with multiple sclerosis (MS). MOG-IgG was found in 12/18 (67 %) CSF samples from MOG-IgG-seropositive patients; the MOG-IgG-specific antibody index was negative in all cases, indicating a predominantly peripheral origin of CSF MOG-IgG. Serum and CSF MOG-IgG belonged to the complement-activating IgG1 subclass. MOG-IgG was present already at disease onset. The antibodies remained detectable in 40/45 (89 %) follow-up samples obtained over a median period of 16.5 months (range 0-123). Serum titers were higher during attacks than during remission (p < 0.0001), highest during attacks of simultaneous myelitis and ON, lowest during acute isolated ON, and declined following treatment. CONCLUSIONS: To date, this is the largest cohort studied for IgG to human full-length MOG by means of an up-to-date CBA. MOG-IgG is present in a substantial subset of patients with ON and/or myelitis, but not in classical MS. Co-existence of MOG-IgG and AQP4-IgG is highly uncommon. CSF MOG-IgG is of extrathecal origin. Serum MOG-IgG is present already at disease onset and remains detectable in the long-term course. Serum titers depend on disease activity and treatment status

Multicentre comparison of a diagnostic assay: Aquaporin-4 antibodies in neuromyelitis optica

Objective Antibodies to cell surface central nervous system proteins help to diagnose conditions which often respond to immunotherapies. The assessment of antibody assays needs to reflect their clinical utility. We report the results of a multicentre study of aquaporin (AQP) 4 antibody (AQP4-Ab) assays in neuromyelitis optica spectrum disorders (NMOSD). Methods Coded samples from patients with neuromyelitis optica (NMO) or NMOSD (101) and controls (92) were tested at 15 European diagnostic centres using 21 assays including live (n=3) or fixed cell-based assays (n=10), flow cytometry (n=4), immunohistochemistry (n=3) and ELISA (n=1). Results Results of tests on 92 controls identified 12assays as highly specific (0-1 false-positive results). 32 samples from 50 (64%) NMO sera and 34 from 51 (67%) NMOSD sera were positive on at least two of the 12 highly specific assays, leaving 35 patients with seronegative NMO/spectrum disorder (SD). On the basis of a combination of clinical phenotype and the highly specific assays, 66 AQP4-Ab seropositive samples were used to establish the sensitivities (51.5-100%) of all 21 assays. The specificities (85.8-100%) were based on 92 control samples and 35 seronegative NMO/SD patient samples. Conclusions The cell-based assays were most sensitive and specific overall, but immunohistochemistry or flow cytometry could be equally accurate in specialist centres. Since patients with AQP4-Ab negative NMO/SD require different management, the use of both appropriate control samples and defined seronegative NMOSD samples is essential to evaluate these assays in a clinically meaningful way. The process described here can be applied to the evaluation of other antibody assays in the newly evolving field of autoimmune neurology

Simultaneous time-space resolved reflectivity and interferometric measurements of dielectrics excited with femtosecond laser pulses

13 pags., 7 figs., 1 tab.Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results have been simulated in the frame of a multiple-rate equation model including light propagation. The comparison of the temporal evolution of the reflectivity and the interferometric measurements at 400 nm clearly shows that the two techniques interrogate different material volumes during the course of the process. While the former is sensitive to the evolution of the plasma density in a very thin ablating layer at the surface, the second yields an averaged plasma density over a larger volume. It is shown that self-trapped excitons do not appreciably contribute to carrier relaxation in fused silica at fluences above the ablation threshold, most likely due to Coulomb screening effects at large excited carrier densities. For both materials, at fluences well above the ablation threshold, the maximum measured plasma reflectivity shows a saturation behavior consistent with a scattering rate proportional to the plasma density in this fluence regime. Moreover, for both materials and for pulse energies above the ablation threshold and delays in the few tens of picoseconds range, a simultaneous >low reflectivity> and >low transmission> behavior is observed. Although this behavior has been identified in the past as a signature of femtosecond laser-induced ablation, its origin is alternatively discussed in terms of the optical properties of a material undergoing strong isochoric heating, before having time to substantially expand or exchange energy with the surrounding media.This work has been partly funded by Laserlab-Europe (Grant Agreement No. 284464, EU’s Seventh Framework Programme, Project No. SLIC002014), by the Spanish Ministry of Economy and Competiveness (Project No. TEC2014-52642- C2-1-R) as well as by the Danish Council for Independent Research | Natural Sciences. M.G.-L. acknowledges the FPU (Formación de Profesorado Universitario) Grant No. AP2012- 0217 awarded by the Spanish Ministry of Education.Peer Reviewe