Nerve Bundles (nerve + bundle)

Distribution by Scientific Domains

Selected Abstracts

Simulation of nerve bundle activation by simultaneous multipoint extracellular stimulation with surface electrodes

Hirokazu Takahashi
Abstract Neural prostheses for restoring lost functions can benefit from selective activation of nerves. We previously proposed a multipoint gating stimulation, which can selectively activate a desired portion of a nerve bundle, regardless of the density of the electrode. In this paper, we discuss the design of an electrode array and effective strategies to determine the stimulus parameters. Large electrodes were less affected by the relative location of the electrodes and the nodes of Ranvier, suggesting that a rectangular electrode, whose long side along a nerve bundle is longer than the internodal distance (i.e., on the order of 1 mm), would be more effective than a disk electrode. We were able to estimate an appropriate current at each electrode on the basis of a blocking threshold, above which no spike propagation was permitted. For lateral gating stimulation, the gate current should be set above the threshold, while for depthwise gating stimulation, the gate current should be set below the threshold. The spatial resolutions of lateral and depthwise gating stimulation were theoretically estimated to be at least 50 ,m when the grid spacing of the array was 1.2 mm. 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(6): 31,40, 2009; Published online in Wiley InterScience ( DOI 10.1002/ecj.10064 [source]

Role of Increased Penile Expression of Transforming Growth Factor-,1 and Activation of the Smad Signaling Pathway in Erectile Dysfunction in Streptozotocin-Induced Diabetic Rats

Lu Wei Zhang MD
ABSTRACT Introduction., It has been suggested that transforming growth factor-,1 (TGF-,1) plays an important role in the pathogenesis of diabetes-induced erectile dysfunction. Aim., To investigate the expression and activity of Smad transcriptional factors, the key molecules for the initiation of TGF-,-mediated fibrosis, in the penis of streptozotocin (STZ)-induced diabetic rats. Methods., Fifty-two 8-week-old Sprague,Dawley rats were used and divided into control and diabetic groups. Diabetes was induced by an intravenous injection of STZ. Main Outcome Measures., Eight weeks later, erectile function was measured by electrical stimulation of the cavernous nerve (N = 12 per group). The penis was harvested and stained with Masson trichrome or antibody to TGF-,1, phospho-Smad2 (P-Smad2), smooth muscle ,-actin, and factor VIII (N = 12 per group). Penis specimens from a separate group of animals were used for TGF-,1 enzyme-linked immunosorbent assay (ELISA), P-Smad2/Smad2, phospho-Smad3 (P-Smad3)/Smad3, fibronectin, collagen I, and collagen IV western blot, or hydroxyproline determination. Results., Erectile function was significantly reduced in diabetic rats compared with that in controls. The expression of TGF-,1, P-Smad2, and P-Smad3 protein evaluated by ELISA or western blot was higher in diabetic rats than in controls. Compared with that in control rats, P-Smad2 expression was higher mainly in smooth muscle cells and fibroblasts of diabetic rats, whereas no significant differences were noted in endothelial cells or in the dorsal nerve bundle. Cavernous smooth muscle and endothelial cell contents were lower in diabetic rats than in controls. Cavernous fibronectin, collagen IV, and hydroxyproline content was significantly higher in diabetic rats than in controls. Conclusion., Upregulation of TGF-,1 and activation of the Smad signaling pathway in the penis of diabetic rats might play important roles in diabetes-induced structural changes and deterioration of erectile function. Zhang LW, Piao S, Choi MJ, Shin H-Y, Jin H-R, Kim WJ, Song SU, Han J-Y, Park SH, Mamura M, Kim S-J, Ryu J-K, and Suh J-K. Role of increased penile expression of transforming growth factor-,1 and activation of the Smad signaling pathway in erectile dysfunction in streptozotocin-induced diabetic rats. J Sex Med 2008;5:2318,2329. [source]

Multiple sites of L-histidine decarboxylase expression in mouse suggest novel developmental functions for histamine

Kaj Karlstedt
Abstract Histamine mediates many types of physiologic signals in multicellular organisms. To clarify the developmental role of histamine, we have examined the developmental expression of L-histidine decarboxylase (HDC) mRNA and the production of histamine during mouse development. The predominant expression of HDC in mouse development was seen in mast cells. The HDC expression was evident from embryonal day 13 (Ed13) until birth, and the mast cells were seen in most peripheral tissues. Several novel sites with a prominent HDC mRNA expression were revealed. In the brain, the choroid plexus showed HDC expression at Ed14 and the raphe neurons at Ed15. Close to the parturition, at Ed19, the neurons in the tuberomammillary (TM) area and the ventricular neuroepithelia also displayed a clear HDC mRNA expression and histamine immunoreactivity (HA-ir). From Ed14 until birth, the olfactory and nasopharyngeal epithelia showed an intense HDC mRNA expression and HA-ir. In the olfactory epithelia, the olfactory receptor neurons (ORN) were shown to have very prominent histamine immunoreactivity. The bipolar nerve cells in the epithelium extended both to the epithelial surface and into the subepithelial layers to be collected into thick nerve bundles extending caudally toward the olfactory bulbs. Also, in the nasopharynx, an extensive subepithelial network of histamine-immunoreactive nerve fibers were seen. Furthermore, in the peripheral tissues, the degenerating mesonephros (Ed14) and the convoluted tubules in the developing kidneys (Ed15) showed HDC expression, as did the prostate gland (Ed15). In adult mouse brain, the HDC expression resembled the neuronal pattern observed in rat brain. The expression was restricted to the TM area in the ventral hypothalamus, with the main expression in the five TM subgroups called E1,E5. A distinct mouse HDC mRNA expression was also seen in the ependymal wall of the third ventricle, which has not been reported in the rat. The tissue- and cell-specific expression patterns of HDC and histamine presented in this work indicate that histamine could have cell guidance or regulatory roles in development. 2001 Wiley-Liss, Inc. [source]

Ultrastructure of the tentacle nerve plexus and putative neural pathways in sea anemones

Jane A. Westfall
Abstract. Neurons of sea anemone tentacles receive stimuli via sensory cells and process and transmit information via a plexus of nerve fibers. The nerve plexus is best revealed by scanning electron microscopy of epidermal peels of the tentacles. The nerve plexus lies above the epidermal muscular layer where it appears as numerous parallel longitudinal and short interconnected nerve fibers in Calliactis parasitica. Bipolar and multipolar neurons are present and neurites form interneuronal and neuromuscular synaptic contacts. Transmission electron microscopy of cross sections of tentacles of small animals, both C. parasitica and Aiptasia pallida, reveals bundles of 50,100 nerve fibers lying above groups of longitudinal muscle fibers separated by intrusions of mesoglea. Smaller groups of 10,50 slender nerve fibers are oriented at right angles to the circular muscle formed by the bases of the digestive cells. The unmyelinated nerve fibers lack any glial wrapping, although some bundles of epidermal fibers are partially enveloped by cytoplasmic extensions of the muscle cells; small gastrodermal nerve bundles lie between digestive epithelial cells above their basal myonemes. A hypothetical model for sensory input and motor output in the epidermal and gastrodermal nerve plexuses of sea anemones is proposed. [source]

Interstitial Cajal-like cells in rat mesentery: an ultrastructural and immunohistochemical approach

M. E. Hinescu
Abstract Interstitial Cajal-like Cells (ICLC) were recently recognized in a plethora of non-digestive organs. Here, we describe a cell type of rat mesentery sharing ultrastructural and immunohistochemical features with ICLC. Mesenteric ICLC were demonstrated by transmission electron microscopy (TEM) and further tested by light microscope immunohistochemistry. The cell described here fulfils the TEM diagnostic criteria accepted for ICLC: location in the connective interstitium; close vicinity to nerves, capillaries and other interstitial cells; characteristic long, moniliform cell processes; specialized cell-to-cell junctions; caveolae; mitochondria at 5,10% of cytoplasmic volume; rough endoplasmic reticulum at about 1,2%; intermediate and thin filaments, microtubules; undetectable thick filaments. The processes of this mesenteric ICLC were particularly long, with a mean length of 24.91 ,m (10.27,50.83 ,m), and a convolution index of 2.32 (1.37,3.63) was calculated in order to measure their potential length. Mean distances versus main target cells of ICLC,nerve bundles, vessels, adipocytes and macrophages,were 110.69, 115.80, 205.07 and 34.65 nm, respectively. We also tested the expression of CD117/c-kit, CD34, vimentin, ,-smooth muscle actin, nestin, NK-1, tryptase and chymase and the antigenic profile of the mesenteric ICLC was comparable if not identical with that recently observed in ICLC from other extra-digestive tissues. Due to the peculiar aspect of the mesenteric ICLC processes it can be hypothesized that these cells form a three-dimensional network within the mesentery that is at the same time resistant and deformable following stretches consequent to intestine movements, mainly avoiding blood vessels closure or controlling blood vessels rheology. It remains, however, to be established if and how such cells are connected with the archetypal enteric ICC. [source]

Neurokinin 1-receptors and sensory neuropeptides in tendon insertions at the medial and lateral epicondyles of the humerus Studies on tennis elbow and medial epicondylalgia

Bjrn-Ove Ljung
Abstract There is no information on the sensory innervation at the flexor muscle origin at the medial epicondyle of the humerus and it is not known if substance P receptors (Neurokinin 1-receptors, NK1-R) are present in tendon insertions in general. In the present investigation, we have studied the muscle origin in patients suffering from medial epicondylalgia and tennis elbow. Immunohistochemistry and antibodies to substance P (SP) and CGRP as well as the general nerve marker PGP 9.5 were used. Specific immunoreactions were observed in nerve bundles and as free nerve fibers. The immunoreactive structures were partly seen in association with some of the blood vessels. The observations constitute a morphological correlate for the occurrence of nerve mediated effects in this region. By using immunohistochemistry and antibodies to NK1-R, the distribution of this receptor was studied at the insertion of the proximal tendon of the extensor carpi radialis brevis muscle at the lateral epicondyle. Specific immunoreactions were seen as varicose fibers occurring as single fibers or grouped into bundles, indicating that SP has effects in the nerves in this region. The results give further evidence for a possible neurogenic involvement in the pathophysiology of tennis elbow and in medial epicondylalgia. 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

Evaluation of Jitter by Stimulated Single-Fiber Electromyography in Normal Dogs

Sonia Aor
Single-fiber electromyography (SFEMG), a technique used to investigate neuromuscular transmission, has been described previously in the pelvic limb of dogs. Because preferential involvement of isolated muscle groups can occur in disorders of neuromuscular transmission, SFEMG waabone in the peroneus longus (PL), extensor carpi radialis (ECR), and orbicularis oculi (OO) muscles of 10 adult, clinically normal dogs. Jitter was calculated as the mean absolute value of the consecutive differences in latency of 50 single muscle fiber action potentials after stimulation of intramuscular nerve bundles at the level of the motor point in at least 20 muscle fibers per muscle. Bilateral recordings were performed in 3 dogs. Mean jitter values were determined for each muscle, and differences among muscle groups and among dogs were compared. The upper limits of mean consecutive difference (mean plus 3 standard deviations) for the PL, ECR, and OO muscles were 21.94, 22.53, and 23.39 ,s, respectively, and the upper limit of mean consecutive difference for individual muscle fibers in the respective fiber pools was 28.62, 36.39, and 35.68 (JLs. Jitter values for the ECR and OO were significantly higher than the jitter value for the PL muscle (P < .05). Significant differences among muscles or dogs or between sides were not observed for the ECR. Significant differences among dogs were observed for OO jitter values and were attributed to extremely low jitter values in 1 dog. Significant differences were demonstrated between sides for the PL and were attributed to small sample size. Results of this study provide normative data that can be used in the application of the stimulated SFEMG technique to dogs with suspected disorders of neuromuscular transmission. [source]

Visualisation of needle position using ultrasonography

ANAESTHESIA, Issue 2 2006
G. A. Chapman
Summary Anaesthetists and intensivists spend a considerable proportion of their working time inserting needles and catheters into patients. In order to access deeper structures like central veins and nerves, they have traditionally relied on surface markings to guide the needle into the correct position. However, patients may present challenges due to anatomical abnormalities and size. Irrespective of the skill of the operator, there is the ever-present risk of needle misplacement with the potential of damage to structures like arteries, nerve bundles and pleura. Repeated attempts, even if ultimately successful, cause patient suffering and probably increase the risk of infection and other long term complications. Portable and affordable, high-resolution ultrasound scanners, has accelerated the interest in the use of ultrasound guidance for interventional procedures. Ultrasound guidance offers several advantages including a greater likelihood of success, fewer complications and less time spent on the procedure. Even if the target structure is identified correctly there is still the challenge to place the needle or other devices in the optimum site. The smaller and deeper the target, the greater the challenge and potential usefulness of ultrasound guidance. As a result of limited training in the use of ultrasound we believe that many clinicians fail to use it to its full potential. A lack of understanding, with regard to imaging the location of the needle tip remains a major obstacle. Needle visualisation and related topics form the basis for this review. [source]