Large-diameter Fibers Research Articles

Electrospinning of poly(methyl methacrylate) nanofibers in a pump-free process

Abstract The effects of processing parameters, including solution concentration, viscosity, nozzle diameter, voltage bias and the nozzle to collector distance, on the morphology and diameters of poly(methyl methacrylate) (PMMA) fibers have been systematically investigated, using a unique pump-free electrospinning method. For PMMA solution concentrations less than the critical entanglement concentration, ce, prolate spheroid-shaped droplets or beads with fibers were formed, whereas at concentrations above ce, good quality bead-free fibers were formed. Quantitative analysis revealed a linear dependence between the solution viscosity and fiber diameter. Larger fiber diameters were achieved by increasing the nozzle diameter and voltage bias. Increasing the bias voltage has the additional effect of broadening the diameter distribution, as a result of splaying and splitting. By contrast, when the strength of the electrical field was reduced by increasing the distance between the nozzle and collector, the overall fiber diameter was reduced.

Electrospun Rapamycin-Eluting Polyurethane Fibers for Vascular Grafts

To develop rapamycin-eluting electrospun polyurethane (PU) vascular grafts that could effectively suppress local smooth muscle cell (SMC) proliferation. Rapamycin (RM) was incorporated in PU fibers by blend electrospinning using three distinct blending methods. The drug release profiles and the bioavailability of RM-containing PU fibers in the form of fibrous mats and vascular grafts were evaluated up to 77days in vitro. RM-contained PU fibers generated by the three distinct blending methods exhibited significantly different fiber diameters (200-500nm) and distinct RM release kinetics. Young's moduli of the electrospun fibrous mats increased with higher RM contents and decreased with larger fiber diameters. For all blending methods, RM release kinetics was characteristic of a Fickian diffusion for at least 77days in vitro. RM-PU fibers generated via powder blending showed the highest encapsulation efficiency. The RM in grafts made of these fibers remained bioactive and was still able to inhibit smooth muscle cell proliferation after 77days of continual in vitro release. Electrospun RM-containing PU fibers can serve as effective drug carriers for the local suppression of SMC proliferation and could be used as RM-eluting scaffolds for vascular grafts.

Macrophage functional polarization (M1/M2) in response to varying fiber and pore dimensions of electrospun scaffolds

In this study, we investigated the effect of fiber and pore size of an electrospun scaffold on the polarization of mouse bone marrow-derived macrophages (BMMΦs) towards regenerative (M2) or inflammatory (M1) phenotypes. BMMΦs were seeded on Polydioxanone (PDO) scaffolds electrospun from varying polymer concentrations (60, 100, and 140 mg/ml). Higher polymer concentrations yielded larger diameter fibers with larger pore sizes and porosity. BMMΦ cultured on these scaffolds showed a correlation between increasing fiber/pore size and increased expression of the M2 marker Arginase 1 (Arg1), along with decreased expression of the M1 marker inducible nitric oxide synthase (iNOS). Secretion of the angiogenic cytokines VEGF, TGF-β1 and bFGF was higher among cultures employing larger fiber/pore size scaffolds (140 mg/ml). Using a 3D in vitro angiogenesis bead assay, we have demonstrated that the M2-like profile of BMMΦ induced by the 140 mg/ml is functional. Furthermore, our results show that the pore size of a scaffold is a more critical regulator of the BMMΦ polarization compared to the fiber diameter. The study also shows a potential role for MyD88 in regulating M1 BMMΦ signaling on the large vs. small fiber/pore size PDO scaffold. These data are instructive for the rationale design of implantable prosthetics designed to promote in situ regeneration.

Study and Implementation of Large-Diameter Fiber Termination Used in High Power Dental Treatment

Large diameter (0.4~0.8mm) fiber termination is widely used in the gum related cares. However, cost-effective shaped fiber is not yet developed for high power (~5W) laser application. In this study, we have demonstrated the feasibility of using two stepping motors with a patented axial movement (0.005mm increments) method. The key parameters are investigated using finite element modeling. The results show that larger fiber diameter with less number of feeding increments can damage the fiber during polishing process.

Hypoxia Affects the Structure of Breast Cancer Cell-Derived Matrix to Support Angiogenic Responses of Endothelial Cells

Hypoxia, a common feature of the tumor environment and participant in tumor progression, is known to alter gene and protein expression of several Extracellular Matrix (ECM) proteins, many of which have roles in angiogenesis. Previously, we reported that ECM deposited from co-cultures of Neonatal Fibroblasts (NuFF) with breast cancer cells, supported 3-dimensional vascular morphogenesis. Here, we sought to characterize the hypoxic ECM and to identify whether the deposited ECM induce angiogenic responses in Endothelial Cells (ECs). NuFF and MDA-MB-231 breast cancer cells were co-cultured, subjected to alternating cycles of 24 hours of 1% (hypoxia) and 21% (atmospheric) oxygen and de-cellularized for analyses of deposited ECM. We report differences in mRNA expression profiles of matrix proteins and crosslinking enzymes relevant to angiogenesis in hypoxia-exposed co-cultures. Interestingly, overt differences in the expression of ECM proteins were not detected in the de-cellularized ECM; however, up-regulation of the cell-binding fragment of fibronecin was observed in the conditioned media of hypoxic co-cultures. Ultrastructure analyses of the de-cellularized ECM revealed differences in fiber morphology with hypoxic fibers more compact and aligned, occupying a greater percent area and having larger diameter fibers than atmospheric ECM. Examining the effect of hypoxic ECM on angiogenic responses of ECs, morphological differences in Capillary-Like Structures (CLS) formed atop de-cellularized hypoxic and atmospheric ECM were not evident. Interestingly, we found that hypoxic ECM regulated the expression of angiogenic factors and matrix metalloproteinases in CLS. Overall, we report that in vitro, hypoxia does not alter the composition of the ECM deposited by co-cultures of NuFF/MDA-MB-231, but rather alters fiber morphology, and induces vascular expression of angiogenic growth factors and metalloproteinases. Taken together, these results have important implications for understanding how the hypoxic matrix may regulate angiogenesis in tumors.

The influence of fiber diameter of electrospun poly(lactic acid) on drug delivery

Electrospinning is a simple process for the production of fibers with diameters in the range from submicron to micron. Herein we aim to explore the influence of fibrous diameter on the drug delivery. The feasible methods by making choice of solvents and changing flow rate were used to prepare 5-fluorouracil-loaded polylactide (PLA) fibers with a large diameter gap. The drug release behavior in vitro was investigated and analyzed in phosphate buffer solution. The drug distribution and fiber diameter both affected the initial burst release. The results showed that all the asspun fibers could not avoid of burst release. The coarse fibers exhibited slight burst release as compared to fine fibers. During the second stage, the fine fibers released faster than that of the coarse fibers. For the whole release stage, the large-diameter fibers seemed to be beneficial for drug release in the long term and smoothly. The MTT results showed that the cytotoxicity of drugs was maintained.

Actividad espontánea de nociceptores cutáneos en pacientes con neuropatía de fibras delgadas

Painful polyneuropathy may result from selective impairment of small diameter nerve fibers, while tactile and motor functions are preserved. In these patients clinical and electrophysiological assessment is usually unrevealing. We report three patients with a pure painful polyneuropathy. One of them had neurogenic pruritus additionally. Quantitative sensory analysis disclosed a slight warm hypoesthesia (3/3) and paradoxical hot sensation (2/3) in the feet. Intraneural recordings from the peroneal nerve demonstrated abnormal spontaneous activity in 8 of 17 nociceptive afferents. One of them displayed double firing reflecting impulse multiplication. These results support the notion that patients with pain or pruritus with a distal distribution similar to a polyneuropathy, could have small diameter afferent fiber damage, despite normal function of large diameter fibers.

Electrospun fibre diameter, not alignment, affects mesenchymal stem cell differentiation into the tendon/ligament lineage

Efforts to develop engineered tendons and ligaments have focused on the use of a biomaterial scaffold and a stem cell source. However, the ideal scaffold microenvironment to promote stem cell differentiation and development of organized extracellular matrix is unknown. Through electrospinning, fibre scaffolds can be designed with tailorable architectures to mimic the intended tissue. In this study, the effects of fibre diameter and orientation were examined by electrospinning thin mats, consisting of small (< 1 µm), medium (1-2 µm) or large (> 2 µm) diameter fibres with either random or aligned fibre orientation. C3H10T1/2 model stem cells were cultured on the six different electrospun mats, as well as smooth spin-coated films, and the morphology, growth and expression of tendon/ligament genes were evaluated. The results demonstrated that fibre diameter affects cellular behaviour more significantly than fibre alignment. Initially, cell density was greater on the small fibre diameter mats, but similar cell densities were found on all mats after an additional week in culture. After 2 weeks, gene expression of collagen 1α1 and decorin was increased on all mats compared to films. Expression of the tendon/ligament transcription factor scleraxis was suppressed on all electrospun mats relative to spin-coated films, but expression on the large-diameter fibre mats was consistently greater than on the medium-diameter fibre mats. These results suggest that larger-diameter fibres (e.g. > 2 µm) may be more suitable for in vitro development of a tendon/ligament tissue.

Diabetes increases mechanical sensitivity and causes morphological abnormalities in the sural nerve that are prevented by treadmill training

In this investigation we evaluated the effects of treadmill training on mechanical sensitivity and sural nerve morphology in diabetic rats. Rats were divided into 3 groups: control (C); diabetic (D); and trained diabetic (TD). Training was performed for 8 weeks. Mechanical sensitivity was evaluated using von Frey filaments. Sural nerve analysis included fiber area, diameter, density of myelinated fibers, area occupied by connective tissue, myelin sheath thickness, and g-ratio. Animals in the D group had a reduced mechanical sensitivity threshold. Morphometric study showed that the D group had a smaller myelinated fiber area and diameter, higher density of fibers and area occupied by connective tissue, thinner myelin sheath, and higher g-ratio. The D group had a higher percentage of small myelinated fibers and a lower percentage of large-diameter myelinated fibers than the C and TD groups. Training prevents functional and morphological abnormalities in the sural nerve caused by diabetes.

Preparation and characterization of lotus ceramics with different pore sizes and their implication for the generation of microbubbles for CO2 sequestration applications

Four kinds of porous mullite ceramics, named lotus ceramics because of the similarity of their microstructure with lotus roots, were prepared by an extrusion method using rayon fibers of four different diameters (8.1, 9.6, 16.8 and 37.6μm) as the pore formers. The physicochemical properties of these samples were characterized to test their applicability for the generation of microbubbles. The lotus ceramic samples contained pores of 9.4, 10, 15.6 and 30μm size and porosities of 45–48%. SEM micrographs confirmed that the cylindrical pores were oriented unidirectionally along the extrusion direction and the degree of alignment was greater with larger fiber diameter. The permeability for gaseous CO2 increased with increasing pore size from 3×10−13 to 8×10−13m2. The four lotus ceramic samples, a commercial air stone (72μm) and two simple tubes (1000 and 3500μm) were used to generate microbubbles in water under ambient conditions from a gas mixture of CO2 and air. It was found that the bubble size could be decreased with bubblers of smaller pore size. In the bubble size measurements for pure CO2 and air, the air bubbles were larger than the CO2 bubbles due to partial dissolution of CO2 into the water during bubbling. In order to generate smaller size bubbles using porous ceramic bubblers, the liquid must penetrate through the pores of the lotus ceramics before the gas is introduced into the system.

Morphometry of dermal nerve fibers in human skin

# {#article-title-2} “Morphometry of dermal nerve fibers in human skin”1 is the first comprehensive analysis of nerve fibers in both the dermal and the intraepidermal portions of 3-mm punch biopsies using widely available laboratory techniques. Expanding the analysis of skin biopsies to include dermal as well as intraepidermal regions might allow 1) examination of longer segments of axons in addition to measures of fiber density, 2) expansion of the range of axon types measured, including larger diameter fibers and axons that innervate mechanoreceptors and sweat glands, and 3) comparison of changes in the distal limb extreme axon terminals with those in more proximal regions. The report provides clear evidence that the assessment of dermal nerve fibers is feasible; it uses …

An evaluation of muscle maintenance costs during fiber hypertrophy in the lobster Homarus americanus: are larger muscle fibers cheaper to maintain?

Large muscle fiber size imposes constraints on muscle function while imparting no obvious advantages, making it difficult to explain why muscle fibers are among the largest cell type. Johnston and colleagues proposed the 'optimal fiber size' hypothesis, which states that some fish have large fibers that balance the need for short diffusion distances against metabolic cost savings associated with large fibers. We tested this hypothesis in hypertrophically growing fibers in the lobster Homarus americanus. Mean fiber diameter was 316±11 μm in juveniles and 670±26 μm in adults, leading to a surface area to volume ratio (SA:V) that was 2-fold higher in juveniles. Na(+)/K(+)-ATPase activity was also 2-fold higher in smaller fibers. (31)P-NMR was used with metabolic inhibitors to determine the cost of metabolic processes in muscle preparations. The cost of Na(+)/K(+)-ATPase function was also 2-fold higher in smaller than in larger diameter fibers. Extrapolation of the SA:V dependence of the Na(+)/K(+)-ATPase over a broad fiber size range showed that if fibers were much smaller than those observed, maintenance of the membrane potential would constitute a large fraction of whole-animal metabolic rate, suggesting that the fibers grow large to reduce maintenance costs. However, a reaction-diffusion model of aerobic metabolism indicated that fibers in adults could attain still larger sizes without diffusion limitation, although further growth would have a negligible effect on cost. Therefore, it appears that decreased fiber SA:V makes larger fibers in H. americanus less expensive to maintain, which is consistent with the optimal fiber size hypothesis.

Localization of Nerve Fibers in Colonic Polyps, Adenomas, and Adenocarcinomas by Immunocytochemical Staining for PGP 9.5

PGP 9.5 is a cytoplasmic protein and is a specific marker for neurites and neurons. Using anti-PGP 9.5, this study aimed to localize nerve fibers in normal colons, polyps, adenomas and adenocarcinomas. Colonic polyps, adenomas and T(1) to T(3) adenocarcinomas with adjacent normal colon were immunostained for PGP 9.5 using rabbit anti-PGP 9.5. In normal colon, numerous nerve fibers were localized in inner and outer muscles, from which submucosa and lamina propria were innervated. In hyperplastic polyps and tubular adenomas, the stalk revealed Meissner's plexus and large-diameter nerve fibers, and fine nerve fibers innervated abundantly in lamina propria of hyperplastic polyps and small tubular adenomas. In villous adenomas, large-diameter nerve fibers and Meissner's plexus were localized in the stalk whereas a few or no fine nerve fibers were localized in fine stroma. In adenocarcinomas, more fine fibers were localized in submucosal stroma adjacent to the invading carcinoma in T(1) carcinomas but there were no nerve fibers in the midst of tumors in T(2) and T(3) carcinomas. There were focally and sporadically increased nerve fibers adjacent to invading cancer nests in 5 of 8 T(2) cases. In T(3) carcinomas, fragmented Auerbach's plexus were noted in cancer-invaded colonic muscles and there were no increased fine nerve fibers in the cancer-invaded subserosa in the majority of cases. PGP 9.5 immunostaining revealed tumor-associated neurogenesis in submucosa but no obviously increased nerve fibers within cancer-invaded muscles. This lack of tumor-associated neurogenesis supports insidious and often silent clinical presentation of colonic carcinomas until invading through the colonic wall to adjacent organs.

A computational model for estimating recruitment of primary afferent fibers by intraneural stimulation in the dorsal root ganglia

Primary afferent microstimulation has been proposed as a method for activating cutaneous and muscle afferent fibers to restore tactile and proprioceptive feedback after limb loss or peripheral neuropathy. Large populations of primary afferent fibers can be accessed directly by implanting microelectrode arrays in the dorsal root ganglia (DRG), which provide a compact and stable target for stimulating a diverse group of sensory fibers. To gain insight into factors affecting the number and types of primary afferents activated, we developed a computational model that simulates the recruitment of fibers in the feline L7 DRG. The model comprises two parts. The first part is a single-fiber model used to describe the current–distance relation and was based on the McIntyre–Richardson–Grill model for excitability. The second part uses the results of the singe-fiber model and published data on fiber size distributions to predict the probability of recruiting a given number of fibers as a function of stimulus intensity. The range of intensities over which exactly one fiber was recruited was approximately 0.5–5 µA (0.1–1 nC per phase); the stimulus intensity at which the probability of recruiting exactly one fiber was maximized was 2.3 µA. However, at 2.3 µA, it was also possible to recruit up to three fibers, albeit with a lower probability. Stimulation amplitudes up to 6 µA were tested with the population model, which showed that as the amplitude increased, the number of fibers recruited increased exponentially. The distribution of threshold amplitudes predicted by the model was similar to that previously reported by in vivo experimentation. Finally, the model suggested that medium diameter fibers (7.3–11.5 µm) may be recruited with much greater probability than large diameter fibers (12.8–16 µm). This model may be used to efficiently test a range of stimulation parameters and nerve morphologies to complement results from electrophysiology experiments and to aid in the design of microelectrode arrays for neural interfaces.

Thermal manipulations during broiler embryogenesis improves post-hatch performance under hot conditions

Previous studies on broilers conducted in our laboratory showed that intermittent thermal manipulation (TM) of 39.5 °C every 12 h during embryonic days E7–E16 improved thermoregulative parameters in the embryo and post-hatch, as well as the broilers' ability to cope with heat challenge at marketing age. The aim of this study was to investigate the effect of intermittent TM of 39.5 °C (65% RH) for 12 h/d (12 H), during E7–E16, on post-hatch performance and thermoregulation under both optimal and hot conditions. Chicks from the control and TM treatments were raised under “regular” conditions until 21 d of age. Then, each treatment was divided into 2 sub-treatments (growth conditions) – optimal conditions (25 °C) and hot conditions of 32 °C for 12 h/d – until 35 d of age. Under optimal conditions, no difference in growth rates was found between TM and control throughout the growth period, but TM had significantly larger relative breast muscle weight, and on days 13, 25, and 35 breast muscle in the TM treatment contained a higher percentage of large-diameter fibers than controls. Consequently, average fiber diameter was significantly larger in TM than in control. Relative weight of the abdominal fat pad was significantly lower in the TM treatment than in control, under both environmental conditions. Hot conditions negatively affected growth rates of broilers in both treatments. The TM chickens showed no body-weight advantage over controls, nevertheless, feed conversion between days 21 and 35 was lower in the TM chickens of both sexes than in controls. This could be attributed to lower body temperature and lower plasma thyroid hormone levels found in the TM chickens, indicating lower heat production rates. Greater muscle growth and lower relative weight of abdominal fat pad were found in the TM chickens than in controls, under hot conditions. It can be concluded that TM during embryonic development improves performance as well as thermoregulation.

Ultrastructural organization of muscle fiber types and their distribution in the rat superior rectus extraocular muscle

Extraocular muscles (EOMs) are unique as they show greater variation in anatomical and physiological properties than any other skeletal muscles. To investigate the muscle fiber types and to understand better the structure-function correlation of the extraocular muscles, the present study examined the ultrastructural characteristics of the superior rectus muscle of rat. The superior rectus muscle is organized into two layers: a central global layer of mainly large-diameter fibers and an outer C-shaped orbital layer of principally small-diameter fibers. Six morphologically distinct fiber types were identified within the superior rectus muscle. Four muscle fiber types, three single innervated fibers (SIFs) and one multiple innervated fiber (MIF), were recognized in the global layer. The single innervated fibers included red, white and intermediate fibers. They differed from one another with respect to diameter, mitochondrial size and distribution, sarcoplasmic reticulum and myofibrillar size. The orbital layer contained two distinct MIFs in addition to the red and intermediate SIFs. The orbital MIFs were categorized into low oxidative and high oxidative types according to their mitochondrial content and distribution. The highly specialized function of the superior rectus extraocular muscle is reflected in the multiplicity of its fiber types, which exhibit unique structural features. The unique ultrastructural features of the extraocular muscles and their possible relation to muscle function are discussed.

Contribution of afferent pathways to nerve injury-induced spontaneous pain and evoked hypersensitivity

A predominant complaint in patients with neuropathic pain is spontaneous pain, often described as burning. Recent studies have demonstrated that negative reinforcement can be used to unmask spontaneous neuropathic pain, allowing for mechanistic investigations. Here, ascending pathways that might contribute to evoked and spontaneous components of an experimental neuropathic pain model were explored. Desensitization of TRPV1-positive fibers with systemic resiniferatoxin (RTX) abolished spinal nerve ligation (SNL) injury-induced thermal hypersensitivity and spontaneous pain, but had no effect on tactile hypersensitivity. Ablation of spinal NK-1 receptor-expressing neurons blocked SNL-induced thermal and tactile hypersensitivity as well as spontaneous pain. After nerve injury, upregulation of neuropeptide Y (NPY) is observed almost exclusively in large-diameter fibers, and inactivation of the brainstem target of these fibers in the nucleus gracilis prevents tactile but not thermal hypersensitivity. Blockade of NPY signaling within the nucleus gracilis failed to block SNL-induced spontaneous pain or thermal hyperalgesia while fully reversing tactile hypersensitivity. Moreover, microinjection of NPY into nucleus gracilis produced robust tactile hypersensitivity, but failed to induce conditioned place aversion. These data suggest that spontaneous neuropathic pain and thermal hyperalgesia are mediated by TRPV1-positive fibers and spinal NK-1-positive ascending projections. In contrast, the large-diameter dorsal column projection can mediate nerve injury-induced tactile hypersensitivity, but does not contribute to spontaneous pain. Because inhibition of tactile hypersensitivity can be achieved either by spinal manipulations or by inactivation of signaling within the nucleus gracilis, the enhanced paw withdrawal response evoked by tactile stimulation does not necessarily reflect allodynia.

Nonablative 4-MHz Dual Radiofrequency Wand Rejuvenation Treatment for Periorbital Rhytides and Midface Laxity

To evaluate the wrinkle-reducing effects of 4-MHz radiofrequency (RF) energy applied to human periorbital, frontal, and midface facial skin using clinical wrinkle grading, patient self-satisfaction survey, and limited histologic studies. Thirty-two patients, ranging from 29 to 71 years of age with skin types varying from class I to class III using the Fitzpatrick Wrinkle Classification system, underwent 8 weekly treatment sessions of nonablative RF therapy on the periorbital, frontal, and midface regions and were subjected to follow up for 6 months after treatment. Pretreatment and post-treatment evaluations were compared. Two female subjects gave informed consent for RF treatment for the right upper eyelid and no treatment for left upper eyelid. Specimens from both upper eyelids then underwent histologic examination using light and transmission electron microscopy. Pre- and post-RF treatment evaluation by 3 independent observers using the Fitzpatrick wrinkle classification system showed progressive improvements in wrinkle score at 1-, 3-, and 6-month intervals (p < 0.01). Self-evaluation of 32 patients using a 9-point rating scale after application of RF treatment also showed improving satisfaction (p < 0.01). The most commonly noted adverse reaction was transient erythema (62.5%) lasting from a few hours to a day. Transmission electron microscopy (25,000×) showed scattered diffuse changes in collagen fibril architecture with a shift from smaller-diameter collagen fibers in the untreated samples to larger-diameter fibers in the treated samples and a loss of distinct fibril borders. Four-megahertz dual RF wand delivery rejuvenation treatment produces a reduction in periorbital and midface rhytides.

Blockade of Persistent Sodium Currents Contributes to the Riluzole-Induced Inhibition of Spontaneous Activity and Oscillations in Injured DRG Neurons

In addition to a fast activating and immediately inactivating inward sodium current, many types of excitable cells possess a noninactivating or slowly inactivating component: the persistent sodium current (INaP). The INaP is found in normal primary sensory neurons where it is mediated by tetrodotoxin-sensitive sodium channels. The dorsal root ganglion (DRG) is the gateway for ectopic impulses that originate in pathological pain signals from the periphery. However, the role of INaP in DRG neurons remains unclear, particularly in neuropathic pain states. Using in vivo recordings from single medium- and large-diameter fibers isolated from the compressed DRG in Sprague-Dawley rats, we show that local application of riluzole, which blocks the INaP, also inhibits the spontaneous activity of A-type DRG neurons in a dose-dependent manner. Significantly, riluzole also abolished subthreshold membrane potential oscillations (SMPOs), although DRG neurons still responded to intracellular current injection with a single full-sized spike. In addition, the INaP was enhanced in medium- and large-sized neurons of the compressed DRG, while bath-applied riluzole significantly inhibited the INaP without affecting the transient sodium current (INaT). Taken together, these results demonstrate for the first time that the INaP blocker riluzole selectively inhibits INaP and thereby blocks SMPOs and the ectopic spontaneous activity of injured A-type DRG neurons. This suggests that the INaP of DRG neurons is a potential target for treating neuropathic pain at the peripheral level.

Structural properties of the corticospinal tract in the human brain: a magnetic resonance imaging study at 7 Tesla

Several fibre tracts can be accurately located using conventional Magnetic Resonance Images (MRI) of the human brain, including the corticospinal tract (CST), which appears as a T (1)-weighted hypointense/T (2)-weighted hyperintense patch in the posterior part of the posterior-limb of the internal capsule (PLIC). Here we use high-field MRI (7T) to assess the quantitative MRI properties of the CST at the PLIC level in 22 healthy young male participants. We used three different imaging modalities: the T (1) and T (2) relaxation times (T (1) and T (2)) and the Magnetization Transfer Ratio (MTR). These measurements obtained in the CST were compared with those in the anterior two-thirds of the PLIC. We observed longer T (1) and T (2) and lower MTR in the CST region compared with the adjacent (control) PLIC region. This effect is consistent with the presence of sparsely distributed, large-diameter fibres described in previous histological studies and, as such, might reflect lower myelin density and/or different morphology of fibres in the CST.