Enhanced microfibrillated cellulose-based film by controlling the hemicellulose content and MFC rheology.

Understanding of how hemicellulose acts on the rheology of microfibrillated cellulose in suspension or after drying is insufficient. In this study, different concentrations of hemicellulose in the cellulose pulp of Eucalyptus sp. were obtained by alkaline treatment with potassium hydroxide. The treated pulps and the suspension of microfibrils obtained were characterized by thermogravimetric analysis, zeta potential, scanning electron microscopy, rheological analysis, X-ray diffraction and dynamic mechanical analysis. The lowest hemicellulose content obtained was approximately 2% wt. Treatments with KOH above 10% did not cause a significant reduction in hemicellulose content and caused a change in the type of cellulose crystallinity. The rheological analysis showed that the apparent viscosity of the suspensions was strongly influenced by the presence of hemicellulose. The morphology of the MFC films of the treated pulps presented the appearance of voids with the reduction of hemicellulose content, generating a decrease in its mechanical properties.

Phrenic nerve diabetic neuropathy in rats: unmyelinated fibers morphometry.

We have demonstrated that phrenic nerves' large myelinated fibers in streptozotocin (STZ)-induced diabetic rats show axonal atrophy, which is reversed by insulin treatment. However, studies on structural abnormalities of the small myelinated and the unmyelinated fibers in the STZ-model of neuropathy are limited. Also, structural changes in the endoneural vasculature are not clearly described in this model and require detailed study. We have undertaken morphometric studies of the phrenic nerve in insulin-treated and untreated STZ-diabetic rats and non-diabetic control animals over a 12-week period. The presence of neuropathy was assessed by means of transmission electron microscopy, and morphometry of the unmyelinated fibers was performed. The most striking finding was the morphological evidence of small myelinated fiber neuropathy due to the STZ injection, which was not protected or reversed by conventional insulin treatment. This neuropathy was clearly associated with severe damage of the endoneural vessels present on both STZ groups, besides the insulin treatment. The STZ-diabetes model is widely used to investigate experimental diabetic neuropathies, but few studies have performed a detailed assessment of either unmyelinated fibers or capillary morphology in this animal model. The present study adds useful information for further investigations on the ultrastructural basis of nerve function in diabetes.

Ultrastructural morphology and morphometry of phrenic nerve in rats.

Despite numerous literature reports on the morphometry of the myelinated fibers of phrenic nerves in rats, a systematic study of the longitudinal and lateral symmetry of the unmyelinated fibers morphometry is not available. In this study, we have undertaken ultrastructural and morphometric studies of the phrenic nerve in adult rats, assessing two different levels (proximal and distal) from both right and left sides. Phrenic nerves of adult male Wistar rats were prepared for epoxy resin embedding and transmission electron microscopy. Morphometric analysis was performed with the aid of computer software, which took into consideration the unmyelinated fiber number, density, area, and diameter, as well as ratio between myelinated and unmyelinated fibers, and the percentage of the fascicular area occupied by the myelinated and unmyelinated fibers. Comparison of data from proximal and distal segments on the same side and from the same levels between sides was performed. Differences were considered significant when P < 0.05. The most important finding is that morphometric parameters of the phrenic nerve unmyelinated fibers in adult rats are both longitudinally and laterally symmetric. This study adds important morphometric information about the unmyelinated fibers of the phrenic nerves in adult rats for proximal and distal levels on both sides of the animal.

Peripheral nerve morphometry: Comparison between manual and semi-automated methods in the analysis of a small nerve.

Manual nerve morphometry has been usually described as tedious, time consuming, difficult to perform correctly and subject to many sources of errors. The above considerations might suggest that fully automated image analysis systems could be ideally programmed to analyze myelinated fibers. However, operator intervention is necessary to manually eliminate dark tissue elements such as pericytes and Schwann cell nuclei. The aims of the present study were to compare the manual and semi-automated techniques in the evaluation of a small nerve, comparing the most commonly used morphometric parameters for nerve descriptions. The aortic depressor nerves (ADN) of male Wistar rats (N = 12) were prepared with conventional techniques for epoxy resin embedding. Manual morphometry was performed on photomicrographs using a digitizing tablet. Semi-automated morphometry was performed with the aid of computer software, on the same negative images used on the photographic procedure, which were scanned and digitized to a microcomputer. Our results show no differences between data obtained with both methods, for any of the evaluated parameters (area, perimeter, diameters, myelin sheath thickness, g ratio, distribution histograms). In conclusion, manual morphometry reproduced data obtained with semi-automated technique in a small nerve, with the advantages of being less-expensive and an affordable method.