Ultrastructural Morphology and Morphometry of Phrenic Nerve in Rats

Abstract

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.

Morphometric analysis of the phrenic nerve in male and female Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR)

“…The phrenic nerve consisted of a single fascicle in most segments studied for both SHR genders (Figure 2), in agreement with previous descriptions for other animal strains (17,20). No clear morphological differences were observed between segments, sides or genders.…”

“…The importance of examining the right and left phrenic nerves resides in the fact that there are reports of lateral asymmetry in these nerves for male normotensive rats (20,26). This lateral asymmetry was confirmed in the present study for both genders in SHR, with the left phrenic nerve usually being smaller than the right nerve, particularly in the distal segment.…”

Phrenic nerve diabetic neuropathy in rats: unmyelinated fibers morphometry

“…All nerves showed good preservation and all segments studied (proximal and distal from right and left sides) consisted of a single fascicle. Morphological and morphometric observations on the control nerves did not differ from previous observations ( Langford and Schmidt, 1983 ; Song et al, 1999 ; Fazan et al, 2009 ). STZ animals showed large myelinated fibers with clear signs of axonal atrophy and small myelinated fibers with axonal atrophy and demyelination signs (Fig.…”

“…The investigator was blinded to group identity during the morphometry process. The endoneural space of the nerves was fully scanned and 11–20 digital images (depending on the fascicle size) were obtained for each nerve, without overlap of the microscopic fields, as described previously ( Sato et al, 2006 ; Fazan et al, 2009 ). Using the image analysis software, the total number of the unmyelinated fibers was counted, and their area and diameter were measured.…”

Endurance training induces structural and morphoquantitative changes in rat vagus nerve

“…[11][12][13][14] It contains afferent and efferent myelinated and unmyelinated axons, involved in vital reflexes such as cardiovascular, pulmonary and gastrointestinal input to and from the central nervous system. [15][16][17] It contains also a number of collagen fibers in the interstitial space among nerve fibers. 18 In this study we have used electron microscopy to check the influence of aerobic training on quantitative aspects from myelinated and unmyelinated fibers of the vagus nerve using the Wistar rat as an animal model.…”