Changes In Fiber Morphology Research Articles

Changes in white matter fiber density and morphology across the adult lifespan: A cross-sectional fixel-based analysis.

White matter (WM) fiber bundles change dynamically with age. These changes could be driven by alterations in axonal diameter, axonal density, and myelin content. In this study, we applied a novel fixel‐based analysis (FBA) framework to examine these changes throughout the adult lifespan. Using diffusion‐weighted images from a cohort of 293 healthy volunteers (89 males/204 females) from ages 21 to 86 years old, we performed FBA to analyze age‐related changes in microscopic fiber density (FD) and macroscopic fiber morphology (fiber cross section [FC]). Our results showed significant and widespread age‐related alterations in FD and FC across the whole brain. Interestingly, some fiber bundles such as the anterior thalamic radiation, corpus callosum, and superior longitudinal fasciculus only showed significant negative relationship with age in FD values, but not in FC. On the other hand, some segments of the cerebello‐thalamo‐cortical pathway only showed significant negative relationship with age in FC, but not in FD. Analysis at the tract‐level also showed that major fiber tract groups predominantly distributed in the frontal lobe (cingulum, forceps minor) exhibited greater vulnerability to the aging process than the others. Differences in FC and the combined measure of FD and cross section values observed between sexes were mostly driven by differences in brain sizes although male participants tended to exhibit steeper negative linear relationship with age in FD as compared to female participants. Overall, these findings provide further insights into the structural changes the brain's WM undergoes due to the aging process.

Role of α-Synuclein Regions in Nucleation and Elongation of Amyloid Fiber Assembly.

α-Synuclein is an intrinsically disordered protein whose aggregation in the form of amyloid fibers is directly implicated in Parkinson's disease and other neurological disorders. α-Synuclein is composed of three different regions. The central region (61-95), called NAC, is responsible for protein fibrillation. The N-terminal region (1-61) has some helical propensity and can be divided into H1 (1-31) and H2 (32-61), while the highly acidic C-terminal region (96-140) is completely disordered. It has been postulated that the acidic character of the C-terminus, as well as the interaction between the soluble N- and C- terminal parts, protects the NAC region from fibrillation. In consequence, N- and C-terminal deletions increase α-synuclein fibrillation. Both N- and C-terminal truncations are common in synucleinopathies, but despite their clinical relevance, to date, there are no systematic and exhaustive studies that quantify the effect of these truncations in fiber nucleation and elongation. In this work, we measured both nucleation and fibrillation elongation kinetics in order to study the influence of N- and C-terminal deletions, including the simultaneous deletion of several regions, in α-synuclein fibrillation. We also tested whether the fibrillation prone mutation A53T had an additional effect when combined with truncations. Furthermore, our cross-seeding experiments showed that the deletions studied induce changes in fiber morphology. Our results unravel then the role of the different α-synuclein regions and the A53T mutation in the nucleation and elongation of amyloid fibers.

Сравнительный структурно-динамический анализ ультратонких волокон поли-(3-гидроксибутирата), модифицированного комплексами тетрафенилпорфирина с металлами

Проведены комплексные исследования, сочетающие рентгеноструктурный анализ, термофизические, динамические измерения зондовым методом и сканирующую электронную микроскопию. Рассмотрена особенность кристаллической и аморфной структуры ультратонких волокон на основе поли(3-гидроксибутирата) (ПГБ), содержащего минорные концентрации (0–5%) комплексов тетрафенилпорфирина (ТФП) с марганцем (в форме MnCl2 ), цинком и железом (в форме FeCl3 ). Показано, что при добавлении в волокна ПГБ указанных комплексов меняется морфология волокон, наблюдается изменение кристалличности и замедление молекулярной подвижности в плотных и рыхлых аморфных областях ПГБ в следующей последовательности: ПГБ/ТФП, ПГБ/Zn–ТФП, ПГБ/MnCl2 –ТФП, FeCl3 –ТФП. Температурное воздействие на волокна (их отжиг при 140°С) приводит к резкому росту кристалличности и молекулярной подвижности в аморфных областях волокон. Их экспозиция в водной среде при 70°С приводит к росту энтальпии плавления и замедлению молекулярной динамики только в исходном ПГБ, но к значительному снижению энтальпии в модифицированных волокнах. Молекулярная подвижность цепей в аморфных областях при этом возрастает. Полученные волокнистые материалы обладают бактерицидными свойствами и должны найти применение при создании новых терапевтических систем антибактериального и противоопухолевого действия.

Characterization of Pretreated Fractions and Cellulosic Ethanol Production from Steam-Exploded Eucalyptus urograndis

Biomass conversion processes have become increasingly important to mitigate fossil fuel consumption and to increase the contribution of renewable fuels into the world energy matrix. In this study, Eucalyptus urograndis wood chips were pretreated by autocatalytic steam explosion to produce cellulosic ethanol after enzymatic hydrolysis and fermentation. These experiments were organized in a central composite rotatable design using temperatures and reaction times ranging from 174 to 216 °C and from 4 to 11 min, respectively. Mass yields, cellulose degree of polymerization, and glucose yields after enzymatic hydrolysis showed a linear correlation with pretreatment severity. The best condition was set at 210 °C for 5 min due to its higher glucose yield after pretreatment and enzymatic hydrolysis. Pectins were almost completely solubilized after pretreatment while galactoglucomannans were more resistant to acid hydrolysis than arabinoglucuronoxylans. Alkaline delignification led to 90.3% lignin removal from steam-exploded materials, but its effect on enzymatic hydrolysis was almost negligible. For the best pretreatment condition, analyses by confocal laser scanning microscopy and solid-state nuclear magnetic resonance revealed important changes in fiber morphology and chemical composition, respectively. Enzymatic hydrolysis at 4 wt % total solids with Cellic CTec2 and Cellic CTec3 (Novozymes) led to 22.4 and 27.8 g L–¹ glucose equivalents in 96 h, respectively, whose fermentation with a commercial strain of Saccharomyces cerevisiae led to ethanol productivities greater than 3.5 g L–¹ h–¹ in 6 h.

Dissolution of Stone Wool Fibers with Phenol-urea-formaldehyde Binder in a Synthetic Lung Fluid.

Mineral wool products, composed of stone wool fibers and organic binder, are used in many construction applications. Among all their beneficial properties, the most important requirement is safety for human health, such as when fibers are inhaled. For determining long-term toxicity, biosolubility and biopersistence studies in vitro and in vivo are essential. In vitro fiber dissolution rate, which depends on the medium, fiber composition, and the surface available for dissolution, is a key parameter in determining biopersistence of the material in vivo. We investigated how organic binder (phenol-urea-formaldehyde), which can partially shield fiber surfaces from the solution, influences fiber dissolution kinetics in synthetic lung fluid (modified Gamble's solution) at pH 4.5 and temperature 37 °C, in vitro. Dissolution experiments were made in batch and continuous flow using stone wool fibers with typical insulation product binder amounts (0-6 wt %), applied by the standard industrial process. Dissolution rates were determined from element concentrations in the reacted solution, and changes in fiber surface composition and morphology were monitored. Stone wool fiber dissolution was close to stoichiometric and was similar, whether or not the material contained binder. The high dissolution rate (508 ng of fiber/cm2/h) is explained by Al and Fe complexing agents, that is, citrate and tartrate, in the synthetic lung fluid. The organic binder mainly forms micrometer-sized discrete droplets on the fiber surfaces rather than a homogeneous thick coating. During in vitro tests, fibers with organic binder preferentially dissolved in the areas free of binder, forming cavities, whereas the untreated fibers dissolved homogeneously. Propagation of cavities undermined the binder droplets, leading to complete fiber dissolution. Thus, presence of organic binder on stone wool fibers, produced by the standard industrial process, had no measurable effect on dissolution rate in synthetic lung fluid containing Al and Fe complexing agents.

Low-load Resistance Exercise During Inactivity is Associated With Greater Fibre Area and Satellite Cell Expression in Older Skeletal Muscle

Age-related sarcopenia is accelerated by physical inactivity. Low-load resistance exercise (LLRE) counters inactivity-induced muscle atrophy in older adults, but changes in muscle fibre morphology are unstudied. The PURPOSE of this study was to determine the impact of LLRE during short-term inactivity (step-reduction) on muscle fibre size, satellite cell (SC) and capillarity content in older skeletal muscle. METHODS: Fourteen older (~71 years) male adults underwent 14 days of step reduction (<1500 steps/day) while performing six sessions of LLRE (~30% maximal strength) with one leg (SR + EX) while the contralateral leg served as an untrained control (SR). Seven healthy ambulatory age-matched male adults (~69 years) served as a comparator group (COM). Muscle biopsies were taken from the vastus lateralis after 14 days, and immunohistochemical analysis was performed to determine muscle fibre cross-sectional area (CSA), myonuclear content, SC content (PAX7+ cells), and total (C:F) and fibre type-specific (C:Fi) capillary-to-fibre ratios. RESULTS: Type I and II fibre CSA was greater in SR + EX compared with SR. Whereas there were no differences across fibre types between SR + EX and CON, type II fibre CSA was significantly lower in SR compared with COM. Type II myonuclear domain was greater in SR + EX compared with COM and SR. Pax7+ cells associated with type I and II fibres were lower in SR compared with SR + EX. Type II PAX7+ cells were also lower in SR compared with COM with a similar trend for type I fibres. There were trends for a lower C:Fi in SR compared with SR + EX for both fibre types with no differences for each compared with COM. Minimal LLRE during a period of decreased physical activity is associated with greater muscle fibre CSA, SC content, and capillarization. CONCLUSION: These results support the use of LLRE as an effective countermeasure to inactivity-induced alterations in muscle morphology with age.

C-ring testing of nuclear grade silicon carbide composites at temperatures up to 1900 °C

Silicon carbide matrix reinforced with silicon carbide fiber (SiC-SiC) composite is an advantageous material for many high temperature applications due to retention of room temperature strength above 1100 °C, which is the current operational limit for many high temperature metals. For the nuclear industry, this property, along with excellent radiation tolerance, has made SiC-SiC an attractive cladding material for the accident tolerant fuel program. The mechanical strength at high temperatures of these composites needs to be evaluated to address improvements in the third generation of Nicalon fibers, fabrication processes, as well as tested in a form-factor relevant to fuel cladding. In this work, mechanical strength of SiGA™ composite tubes, a SiC-SiC composite fabricated at General Atomics using the current generation of Hi-Nicalon Type S SiC fiber and chemical vapor infiltration processing (CVI) of the matrix, was evaluated at temperatures up to 1100 °C in ambient air and ∼1900 °C in an inert gas environment with nominal 30–60 min dwell time. The results of this study show full retention of room temperature strength at both test regimes. Some degradation of material toughness was observed at temperatures above ∼1760 °C. During this study, effects of interphase, fiber, and matrix morphological changes as a function of temperature were investigated.

Neuromuscular Plasticity in a Mouse Neurotoxic Model of Spinal Motoneuronal Loss.

Despite the relevant research efforts, the causes of amyotrophic lateral sclerosis (ALS) are still unknown and no effective cure is available. Many authors suggest that ALS is a multi-system disease caused by a network failure instead of a cell-autonomous pathology restricted to motoneurons. Although motoneuronal loss is the critical hallmark of ALS given their specific vulnerability, other cell populations, including muscle and glial cells, are involved in disease onset and progression, but unraveling their specific role and crosstalk requires further investigation. In particular, little is known about the plastic changes of the degenerating motor system. These spontaneous compensatory processes are unable to halt the disease progression, but their elucidation and possible use as a therapeutic target represents an important aim of ALS research. Genetic animal models of disease represent useful tools to validate proven hypotheses or to test potential therapies, and the conception of novel hypotheses about ALS causes or the study of pathogenic mechanisms may be advantaged by the use of relatively simple in vivo models recapitulating specific aspects of the disease, thus avoiding the inclusion of too many confounding factors in an experimental setting. Here, we used a neurotoxic model of spinal motoneuron depletion induced by injection of cholera toxin-B saporin in the gastrocnemius muscle to investigate the possible occurrence of compensatory changes in both the muscle and spinal cord. The results showed that, following the lesion, the skeletal muscle became atrophic and displayed electromyographic activity similar to that observed in ALS patients. Moreover, the changes in muscle fiber morphology were different from that observed in ALS models, thus suggesting that some muscular effects of disease may be primary effects instead of being simply caused by denervation. Notably, we found plastic changes in the surviving motoneurons that can produce a functional restoration probably similar to the compensatory changes occurring in disease. These changes could be at least partially driven by glutamatergic signaling, and astrocytes contacting the surviving motoneurons may support this process.

Kinetic Analysis of Cellulose Acetate/Cellulose II Hybrid Fiber Formation by Alkaline Hydrolysis

Cellulose acetate (CA) can be converted to cellulose II through a deacetylation process using ethanolic NaOH solution. Infrared spectroscopy was used to observe the degree of acetylation by comparing the absorption intensities of C═O and C–O stretches. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) analysis, which only measures a few microns into the fiber diameter, was compared with FTIR, which measures the whole fiber cross-section. Steady deacetylation of the whole fiber over 180 min was observed with FTIR to eventual complete deacetylation. In comparison, ATR-FTIR shows deacetylation occurring more rapidly to complete deacetylation after 90 min, indicating rapid deacetylation of the CA fiber periphery. Data were fitted to a pseudo-second order kinetic model, with high correlation (R² > 0.99), and it was observed that the deacetylation rate (k₂) observed with ATR-FTIR (−0.634 min⁻¹) was twice as rapid as the deacetylation rate observed with FTIR (−0.315 min⁻¹). IR observations were in agreement with the analysis of fiber cross-sections by confocal microscopy, where it was observed that changes in fiber morphology occurred with treatment time and progressive hydrolysis of cellulose acetate to cellulose II. A differential fiber chemical composition was created within the CA fiber cross-section; after 5 min, the outer regions of the fiber cross-section are hydrolyzed to cellulose II and this hydrolysis increases heterogeneously with time to complete hydrolysis after 180 min and conversion to cellulose II. These results indicate the potential to produce fibers with a differential periphery/core structure, which can be accurately designed according to the relative degrees of cellulose II/CA required for specific applications by varying the treatment time in application of this model.

Longitudinal Changes in Corneal Cell and Nerve Fiber Morphology in Young Patients with Type 1 Diabetes with and without Diabetic Retinopathy: A 2-Year Follow-up Study.

We have previously used in vivo corneal confocal microscopy (IVCCM) to demonstrate significant alterations in the corneal epithelial cells, stromal keratocytes, and subbasal nerves in young patients with type 1 diabetes mellitis (T1DM), especially those with diabetic retinopathy (DR). We have evaluated the change in corneal cellular and subbasal nerve morphology over 2 years in young patients with T1DM with or without DR. A total of 19 patients with T1DM, without (n = 12) and with (n = 7) DR and 19 age- and sex-matched healthy control subjects underwent quantification of corneal cellular and subbasal nerve plexus morphology by using IVCCM at baseline and after 2 years. There was no significant change in corneal basal epithelial, posterior stromal keratocyte, or endothelial cell densities over 2 years. However, there was a significant reduction in corneal nerve branch (P = 0.03) and total nerve branch density (P = 0.04) in patients without DR and a significant reduction in corneal nerve fibre density (P = 0.004) in those with DR. IVCCM can detect a progressive loss of corneal nerve fibers in young patients with T1DM and may allow the identification of individuals at risk of neuropathy progression for more active risk factor reduction.

Fibrin Density and Tension Regulates Fibrinolytic Susceptibility

Fibrin fibers provide structural and mechanical integrity to blood clots until their dissolution during fibrinolysis. This work seeks to deconvolve the respective fibrinolytic influences of enzyme kinetics and enzyme perfusion rates into clots from clot structure and fiber properties. Here we consider the lysis of fibers within small, 2-D networks, which have polymerized between ridges. We tracked changes in fiber morphology within a 24-hour period during lysis. We find that fibers follow several possible degradation pathways during the lytic process including transverse cleavage, fiber bundling, structural elongation due to network rearrangements, tension loss, and network collapse. Transverse cleavage of individual fibers results in network rearrangements due to the redistribution of the tension in the yet-to-be-cleaved fibers. Network rearrangements and remnants of cleaved fibers often lead to fibers bundling into thicker fibers which are more resistant to fibrinolysis. When the final strand holding the network in place is transversely cleaved, the remaining fibers recoil and collapse onto the ridge. These effects highlight the inherent tension in fibrin networks and its role in governing fibrinolytic degradation. This is further emphasized by the observation that lysis kinetics depend strongly on fiber density. Fibers in high-density areas, and presumably under more tension, lyse at earlier time points and more rapidly than fibers in low-density areas. Fibrinolysis initiated with low (0.1 U/mL) concentrations of plasmin occurs more slowly than with high (1.0 U/mL) concentrations of plasmin, and structural rearrangement due to tension redistribution is more prominent. These results identify the different pathways whereby a fibrin network is cleared out of an area by the lytic enzyme plasmin. Inherent fiber tension plays an important role in regulating this process.

Immobilization of α-amylase in ultrafine polyvinyl alcohol (PVA) fibers via electrospinning and their stability on different substrates

The objective of this study was to immobilize α-amylase in ultrafine polyvinyl alcohol (PVA) fibers by electrolysis and to evaluate its stability at different temperatures and pHs using various starch substrates such as corn starch and germinated and ungerminated wheat starches. The α-amylase-loaded ultrafine fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and loadability and enzymatic activity evaluations. Incorporation of the enzyme resulted in a slight change in fiber morphology; the fibers became flatter and thicker with increasing enzyme concentration. The mean diameters ranged from 187 to 282 nm. FT-IR spectra indicated that the enzyme was incorporated into the fibers. PVA showed a high loading capacity for α-amylase at all concentrations tested (1.0, 1.5, and 2.0% w/v), indicating that PVA is an excellent support. The enzymatic activity of α-amylase was tested on the different starch substrates; the activity was higher in the immobilized form than in the free form. Enzymatic immobilization improved the stability of α-amylase over a wide range of temperatures and pHs. Enzymatic activity was highest when germinated wheat starch was used as the substrate at different temperatures and pHs, indicating great potential for its application in hydrolysis with α-amylase.

Morphological study of stabilization and carbonization of polyacrylonitrile/TiO2 nanofiber mats

Polyacrylonitrile belongs to the most often used precursors for carbon fibers. Using electrospinning, polyacrylonitrile nanofiber mats can be prepared and afterwards stabilized and carbonized to prepare carbon nanofiber mats which, by adding other materials, will be useful for several applications. One of these materials is TiO2, which has photocatalytic properties and can thus be used as a photocatalyst for photodegradation of dyes. Here, we report on a detailed study of electrospinning, stabilization, and carbonization of electrospun polyacrylonitrile/TiO2 mats with varying TiO2 content. Depending on the amount of TiO2 in the nanofibers, the fiber morphology changes strongly, indicating an upper limit for the preparation of carbon/TiO2 nanofibers with smooth surface, but offering an even increased inner surface of the rougher carbon/TiO2 nanofibers with increased TiO2 content due to better maintenance of the fibrous structure during stabilization.

Enzymatically treated curaua fibers in poly(butylene succinate)-based biocomposites

The aim of this work is to elucidate the reinforcing potential of enzymatically treated curaua fibers in biodegradable poly(butylene succinate) (PBS)-based composites. The effect of two different enzymes, i.e. cellulase and pectinase, was evaluated. Untreated and enzymatically treated curaua fibers were characterized in terms of thermal stability (TGA), crystallinity (XRD) and surface morphology (SEM). The composite characteristics were investigated by mechanical test (tensile and flexural resistance), thermal stability and SEM micrographs of the fractured surfaces. Enzymatic treatments resulted in a significant change in morphology of curaua fibers, while their thermal stability and crystallinity were not affected much. SEM investigation of tensile fractured surfaces of composites showed strong adhesion between fibers and matrix.

Deinkability of different secondary fibers by enzymes

AbstractThe efficiency and effects of enzymatic deinking using xylanase and lipase mixed with amylase (XLA) for deinking secondary fibers were investigated for mixed office waste (MOW), photocopy prints (PHOT) and old newspapers (ONP). The optical and physical properties of deinked pulps were evaluated. Changes in fiber morphology, crystallinity index and functional groups were also monitored. The results show that for non-impact prints (MOW and PHOT), a maximum deinking efficiency of 19.9 % and 13.9 % were obtained with enzymatic deinking (XLA), respectively. For ONP, conventional alkaline demonstrated the highest efficiency of 12.20 %. XLA treatment significantly improved the tensile index and tear index of MOW and PHOT but caused a slightly reduction for ONP, relative to respective blank. It was found that kink index and curl index were significantly decreased, caused a 55.6 % reduction in the kink index for PHOT and a 35.8 % reduction in the curl index for ONP. FT-IR observation show that the relative intensity of the alkaline/enzymatic-deinked pulp has changed differently according to the type of wastepaper. These results indicate the synergistic effects of xylanase, lipase and amylase making enzymatic treatment a promising method that can substitute alkaline deinking for non-impact prints.

Low-load resistance exercise during inactivity is associated with greater fibre area and satellite cell expression in older skeletal muscle.

BackgroundAge‐related sarcopenia is accelerated by physical inactivity. Low‐load resistance exercise (LLRE) counters inactivity‐induced muscle atrophy in older adults, but changes in muscle fibre morphology are unstudied. We aimed to determine the impact of LLRE during short‐term inactivity (step‐reduction) on muscle fibre size and capillarity as well as satellite cell (SC) content in older skeletal muscle.MethodsFourteen older (~71 years) male adults underwent 14 days of step reduction (<1500 steps/day) while performing six sessions of LLRE (~30% maximal strength) with one leg (SR + EX) while the contralateral leg served as an untrained control (SR). Seven healthy ambulatory age‐matched male adults (~69 years) served as a comparator group (COM). Muscle biopsies were taken from the vastus lateralis after 14 days, and immunohistochemical analysis was performed to determine muscle fibre cross‐sectional area (CSA), myonuclear content, SC content (PAX7+ cells), and total (C:F) and fibre type‐specific (C:Fi) capillary‐to‐fibre ratios.ResultsType I and II fibre CSA was greater in SR + EX compared with SR. Whereas there were no differences across fibre types between SR + EX and CON, type II fibre CSA was significantly lower in SR compared with COM. Type II myonuclear domain was greater in SR + EX compared with COM and SR. Pax7+ cells associated with type I and II fibres were lower in SR compared with SR + EX. Type II PAX7+ cells were also lower in SR compared with COM with a similar trend for type I fibres. There were trends for a lower C:Fi in SR compared with SR + EX for both fibre types with no differences for each compared with COM.ConclusionsMinimal LLRE during a period of decreased physical activity is associated with greater muscle fibre CSA, SC content, and capillarization. These results support the use of LLRE as an effective countermeasure to inactivity‐induced alterations in muscle morphology with age.

The role of optical coherence tomography in neuro-ophthalmology

Optical coherence tomography (OCT) is an ocular imaging technique that can complement the neuro-ophthalmic assessment, and inform our understanding regarding functional consequences of neuroaxonal injury in the afferent visual pathway. Indeed, OCT has emerged as a surrogate end-point in the diagnosis and follow up of several demyelinating syndromes of the central nervous system (CNS), including optic neuritis (ON) associated with: multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and anti-myelin oligodendrocyte glycoprotein (MOG) antibodies. Recent advancements in enhanced depth imaging (EDI) OCT have distinguished this technique as a new gold standard in the diagnosis of optic disc drusen (ODD). Moreover, OCT may enhance our ability to distinguish cases of papilledema from pseudopapilledema caused by ODD. In the setting of idiopathic intracranial hypertension (IIH), OCT has shown benefit in tracking responses to treatment, with respect to reduced retinal nerve fiber layer (RNFL) measures and morphological changes in the angling of Bruch’s membrane. Longitudinal follow up of OCT measured ganglion cell-inner plexiform layer thickness may be of particular value in managing IIH patients who have secondary optic atrophy. Causes of compressive optic neuropathies may be readily diagnosed with OCT, even in the absence of overt visual field defects. Furthermore, OCT values may offer some prognostic value in predicting post-operative outcomes in these patients. Finally, OCT can be indispensable in differentiating optic neuropathies from retinal diseases in patients presenting with vision loss, and an unrevealing fundus examination. In this review, our over-arching goal is to highlight the potential role of OCT, as an ancillary investigation, in the diagnosis and management of various optic nerve disorders.

Cellulase pretreatment for enhancing cold caustic extraction-based separation of hemicelluloses and cellulose from cellulosic fibers

The effective separations of cellulose and hemicelluloses from cellulosic fibers are the prerequisite for creating high-value to the abundant and green cellulose materials. In this study, the process concept of cellulase pretreatment, followed by a cold caustic extraction (CCE) was investigated for a softwood sulfite pulp. The results showed that the cellulase pretreatment led to favorable fiber morphological changes, including the increases of the specific surface area (SSA), pore volume and diameter, and the water retention value (WVR). These changes can induce more pronounced fiber swelling in the subsequent CCE process so that the hemicelluloses removal is enhanced. After the cellulase pretreatment (cellulase dosage of 1 mg/g) and CCE process, the cellulose purity was as high as 97.49%, while the hemicelluloses removal selectivity reached 76.42%.

Understanding the interactions of cellulose fibres and deep eutectic solvent of choline chloride and urea

A deep eutectic solvent composed of choline chloride (ChCl) and urea has been recently introduced as a promising cellulose compatible medium that enables e.g. fibre spinning. This paper clarifies the influence of such a solvent system on the structure and chemical composition of the cellulosic pulp fibres. Special emphasis was placed on the probable alterations of the chemical composition due to the dissolution of the fibre components and/or due to the chemical derivatisation taking place during the DES treatment. Possible changes in fibre morphology were studied with atomic force microscopy and scanning electron microscopy. Chemical compositions of pulp fibres were determined from the carbohydrate content, and by analysing the elemental content. Detailed structural characterisation of the fibres was carried out using spectroscopic methods; namely X-Ray Photoelectron Spectroscopy, solid state Nuclear Magnetic Resonance and Raman Spectroscopy. No changes with respect to fibre morphology were revealed and negligible changes in the carbohydrate composition were noted. The most significant change was related to the nitrogen content of the pulp after the DES treatment. Comprehensive examination using spectroscopic methods revealed that the nitrogen originated from strongly bound ChCl residuals that could not be removed with a mild ethanol washing procedure. According to Raman spectroscopic data and methylene blue adsorption tests, the cationic groups of ChCl seems to be attached to the anionic groups of pulp by electrostatic forces. These findings will facilitate the efficient utilisation of DES as a cellulose compatible medium without significantly affecting the native fibre structure.

Distinct reorganization of collagen architecture in lipopolysaccharide-mediated premature cervical remodeling.

Previous work has identified divergent mechanisms by which cervical remodeling is achieved in preterm birth (PTB) induced by hormone withdrawal (mifepristone) or lipopolysaccharide (LPS). Our current study aims to document how collagen architecture is modified to achieve premature cervical remodeling in mice treated with LPS as a model of infection-induced inflammation. Cervices were collected on gestation day (d) 15 from mice with premature cervical ripening induced by LPS and compared to d15 and d18 controls as well as a hormone withdrawal PTB model. Second harmonic generation (SHG) and electron microscopy were utilized for visualization of collagen morphology and ultrastructure. LPS-mediated premature cervical ripening is characterized by unique structural changes in collagen fiber morphology. LPS treatment increased the interfibrillar spacing of collagen fibrils. A preferential disruption of collagen fiber architecture in the subepithelial region compared to midstroma region was evidenced by increased pores lacking collagen signal in SHG images in the LPS-treated mice. Coinciding with this alteration, the infiltration of neutrophils was concentrated in the subepithelial stromal region as compared to midstromal region implicating the potential role of immune cells to extracellular matrix reorganization in inflammation-induced preterm cervical ripening. The current study demonstrates a preferential disorganization of collagen interfibrillar spacing and collagen fiber structure in LPS-mediated ripening.