Somatic Fibers Research Articles

Somatic afferent modulation of thoracic (T9-T10) spinal neurons receiving gastric mechanical input in rats

The aim was to determine whether somatic afferent fiber stimulation influences thoracic spinal neuronal activity responding to gastric distensions. Extracellular potentials of single T9-T10 spinal neurons were recorded in anesthetized male rats. Ipsilateral median and peroneal nerve afferent stimulation (MNAS, PNAS) was delivered by electrodes. Inflation of a latex balloon was used to produce gastric distension. MNAS and PNAS (1.5 mA, 50 Hz, 10 sec) altered activity of 63% and 66% of the spinal neurons excited or inhibited by gastric distension, respectively. MNAS more frequently reduced spinal neuronal activity with excitatory responses to gastric distension than did PNAS (p < 0.05). PNAS more likely increased neuronal activity with low-threshold excitatory responses to gastric distension than MNAS (p < 0.05). Peripheral somatic afferent information utilizes central pathways to modulate gastric afferent processing in T9-T10 spinal neurons. Thus, somatic afferent stimulation might be used to treat gastric pain and/or hypersensitivity.

Cutaneous silent period changes in Type 2 diabetes mellitus patients with small fiber neuropathy

Small myelinated (A-delta) and unmyelinated (C) somatic sensory fibers are initially affected and may be the earliest exhibited sign of neuropathy in glucose dysmetabolism. Cutaneous silent period (CSP) is an inhibitory spinal reflex and its afferents consist of A-delta nerve fibers. The aim of this study was to evaluate CSP changes in Type 2 diabetic patients with small fiber neuropathy. Forty-three patients and 41 healthy volunteers were included. CSP latency and duration, as well as CSP latency difference of the upper and lower extremities, were examined. Nerve conduction studies were within normal limits in both groups. Lower extremity CSP latency was longer (122.1+/-15.5 vs. 96.4+/-6.4 ms; p<0.001), CSP duration was shorter (29.5+/-8.9 vs. 43.1+/-5.0 ms; p<0.001), and latency difference was longer (48.1+/-12.6 vs. 22.7+/-3.7; p<0.001) in patients than controls. The difference was more significant in patients with neuropathic pain. No significant difference existed in upper extremity on CSP evaluation. The CSP evaluation together with nerve conduction study, has been demonstrated to be beneficial and performance of latency difference in addition to CSP latency and duration may be a valuable parameter in electrophysiological assessment of diabetic patients with small fiber neuropathy. An additional CSP evaluation may be considered in cases which nerve conduction studies do not provide sufficient information.

Small fiber neuropathy in female patients with fabry disease

Recent studies suggest that heterozygous female Fabry disease (FD) patients develop peripheral neuropathy. We used skin biopsy to define somatic and autonomic peripheral nerve characteristics in 21 females with FD who were mainly asymptomatic and had normal renal function. Somatic epidermal and dermal autonomic nerve fiber reductions were found, prevalently in the leg, and no differences were found between symptomatic and asymptomatic individuals. Our findings suggest that females with FD, although asymptomatic, may have somatic and autonomic small fiber neuropathy.

Determination of nerve conduction abnormalities in patients with impaired glucose tolerance

Recent studies have shown that impaired glucose tolerance (IGT) is associated with dysfunction in the peripheral and autonomic nerves. The aim of this study was to determine the electrophysiological abnormalities of IGT. To determine electrophysiological abnormality in the large sensorimotor and sudomotor autonomic nerves with IGT patients, 43 patients and 34 healthy subjects have been studied. Subjective neuropathy symptoms, neurological examination and the electrophysiological findings were evaluated. When conduction of large somatic fibers only was evaluated, the ratio of electrophysiological abnormality was found to be 21%. In addition, where sympathetic skin response was evaluated the sudomotor autonomic abnormality ratio was 28% in upper extremities, 53% in lower extremities, and 16% in upper and lower extremities together. The percentages of abnormal electrophysiological parameters in different motor and sensory nerves were 39.5% in the peroneal motor nerve, 20.9% in the median motor and sural sensory nerves, 18.6% in the median sensory nerve, 16.3% in the tibial motor nerve, 14% in the ulnar sensory nerve, and 2.3% in the ulnar motor nerve. While distal motor latency was the most frequent abnormal parameter in the median and tibial motor nerves, the amplitude changes in the peroneal and ulnar motor nerves were also prominent. In sensory evaluation, the onset latency in the median-ulnar sensory nerves and the amplitude in the sural sensory nerve were found to be evident abnormalities.

PO5.57 Quantitative Analysis of Somatic and Autonomic Small Fibers in Diabetic Neuropathy

PO5.57 Quantitative Analysis of Somatic and Autonomic Small Fibers in Diabetic Neuropathy

Localization of 5S and 25S rRNA genes on somatic and meiotic chromosomes in Capsicum species of chili pepper.

The loci of the 5S and 45S rRNA genes were localized on chromosomes in five species of Capsicum, namely, annuum, chacoense, frutescens, baccatum, and chinense by FISH. The 5S rDNA was localized to the distal region of one chromosome in all species observed. The number of 45S rDNA loci varied among species; one in annuum, two in chacoense, frutescens, and chinense, and four in baccatum, with the exceptions that 'CM334' of annuum had three loci and 'tabasco' of frutescens had one locus. 'CM334'-derived BAC clones, 384B09 and 365P05, were screened with 5S rDNA as a probe, and BACs 278M03 and 262A23 were screened with 25S rDNA as a probe. Both ends of these BAC clones were sequenced. FISH with these BAC probes on pachytenes from 'CM334' plant showed one 5S rDNA locus and three 45S rDNA loci, consistent with the patterns on the somatic chromosomes. The 5S rDNA probe was also applied on extended DNA fibers to reveal that its coverage measured as long as 0.439 Mb in the pepper genome. FISH techniques applied on somatic and meiotic chromosomes and fibers have been established for chili to provide valuable information about the copy number variation of 45S rDNA and the actual physical size of the 5S rDNA in chili.

Neurophysiological evaluation of sexual dysfunction in familial amyloidotic polyneuropathy--Portuguese type.

Familial amyloidotic polyneuropathy (FAP)--Portuguese type, is an autosomal dominant polyneuropathy related with an abnormal transthyrretin (TTR Met 30). In males, the first complaint can be sexual dysfunction. Fifteen FAP patients, mean age 37 +/- 7.7 years, mean disease duration 5.2 +/- 2.2 years, all males, complaining of sexual dysfunction were studied with pudendal evoked potentials (PEP), bulbocavernous reflex (BCR) and sympathetic skin response (SSR). PEP and BCR reflect the central somatosensory pathways and sacral arch functioning; SSR relates with autonomic pathways. The aims of this study were: to correlate clinical and EMG scores with somatic and autonomic fibres involvement; to evaluate the timing of somatic and autonomic nerves lesion in disease evolution. Results showed: that PEP and BCR abnormalities have a statistically significant correlation with clinical and EMG scores; abnormal SSR in the plant precede other clinical or EMG abnormalities in the present study.

Skeletal Muscle &amp; Muscular Dystrophy: A Visual Approach

Abstract Histologically, muscle is conveniently divided into two groups, striated and nonstriated, based on whether the cells exhibit cross-striations in the light microscope (Figure 3). Smooth muscle is involuntary: its contraction is controlled by the autonomic nervous system. Striated muscle includes both cardiac (involuntary) and skeletal (voluntary). The former is innervated by visceral efferent fibers of the autonomic nervous system, whereas the latter is innervated by somatic efferent fibers, most of which have their cell bodies in the ventral, motor horn of the spinal cord. Smooth muscle is designed to have slow, relatively sustained contractions, while striated muscle contracts rapidly and usually phasically. Both cardiac and smooth muscle cells are mononucleated, whereas skeletal muscle cells (fibers) are multinucleated. [In aging hearts or hypertrophied hearts, cardiac muscle cells are often binucleated.] Multinucleation of skeletal muscle arises during development by the cytoplasmic fusion of ...

The Beneficial Effects of C-Peptide on Diabetic Polyneuropathy

Diabetic polyneuropathy (DPN) is a common complication in diabetes. At present, there is no adequate treatment, and DPN is often debilitating for patients. It is a heterogeneous disorder and differs in type 1 and type 2 diabetes. An important underlying factor in type 1 DPN is insulin deficiency. Proinsulin C-peptide is a critical element in the cascade of events. In this review, we describe the physiological role of C-peptide and how it provides an insulin-like signaling function. Such effects translate into beneficial outcomes in early metabolic perturbations of neural Na+/K+-ATPase and nitric oxide (NO) with subsequent preventive effects on early nerve dysfunction. Further corrective consequences resulting from this signaling cascade have beneficial effects on gene regulation of early gene responses, neurotrophic factors, their receptors, and the insulin receptor itself. This may lead to preventive and corrective results to nerve fiber degeneration and loss, as well as, promotion of nerve fiber regeneration with respect to sensory somatic fibers and small nociceptive nerve fibers. A characteristic abnormality of type 1 DPN is nodal and paranodal degeneration with severe consequences for myelinated fiber function. This review deals in detail with the underlying insulin-deficiency-related molecular changes and their correction by C-peptide. Based on these observations, it is evident that continuous maintenance of insulin-like actions by C-peptide is needed in peripheral nerve to minimize the sequences of metabolic and molecular abnormalities, thereby ameliorating neuropathic complications. There is now ample evidence demonstrating that C-peptide replacement in type 1 diabetes promotes insulin action and signaling activities in a more enhanced, prolonged, and continuous fashion than does insulin alone. It is therefore necessary to replace C-peptide to physiological levels in diabetic patients. This will have substantial beneficial effects on type 1 DPN.

Evaluation of Conduction Properties of Somatic and Sympathetic Sudomotor Fibers in Patients With Epilepsy

To assess the function of fast somatic nerve fibers and sympathetic sudomotor system in patients with partial or generalized seizures, receiving various therapeutic regimes. The authors studied 60 patients (mean age 36.7 +/- 12.5 years) and 60 matched healthy controls by clinical, conventional nerve conduction study, and sympathetic skin responses (SSR) from hand and foot. Compared with controls, patients showed a tendency, occasional reaching significant level, to conduction slowing and amplitude reduction in the sensory and less often in the motor nerve study. Clinical signs of neuropathy were disclosed in 8.3% of patients, whereas at least one abnormal sensory parameter was evident in 18.3%. Mean SSR latencies in the patients were significantly prolonged. At least one SSR abnormality was shown in 20 (33.3%) patients; six of these had absent SSR from the hand or/and the foot. Polytherapy (vs. monotherapy) and topiramate, but not any other particular drug, seemed to have a negative effect on SSR measurements. The results suggested that despite the insignificant clinical manifestations of neuropathy, an electrophysiological examination was able to demonstrate some subclinical abnormalities of the fast somatic fibers in the peripheral nerves and of the sympathetic sudomotor function in a considerable number of epileptic patients.

Somatic innervation of the feline lower urinary tract

Electrical stimulation of pudendal nerve sensory pathways can evoke excitatory bladder reflexes. However, the precise peripheral innervation pattern of these somatic fibers remains unclear. In adult male cats, we investigated pudendal nerve innervation of the lower urinary tract (LUT) by employing anatomical (Sihler's stain) and electrophysiological (selective electrical nerve stimulation) techniques. The stained specimens revealed differential innervation of the proximal and distal urethrae by fibers derived from the sensory branch of the pudendal nerve. Cranial sensory branch fibers penetrated the prostate to terminate along the intraluminal surface of the urethra, whereas the dorsal nerve of the penis primarily innervated the glans penis. Further examination of the proximal urethra showed a separate pathway (deep perineal nerve) that inserted directly into the external urethral sphincter. These observations were confirmed electrophysiologically by the measured urethral sphincter activity evoked in response to selective nerve stimulation. Electrical activation of the sensory pathway evoked only reflex (latency = 8.9 ± 1.1 ms) contractions of the urethral muscle, whereas stimulation of the perineal pathway elicited direct (latency = 1.3 ± 0.1 ms) responses. Our findings identify specific pudendal nerve sensory pathways that can be used potentially to restore bladder function in persons with spinal cord injury and also treat LUT symptoms such as urinary retention.

Facial expression analysis

Facial expressions refer to movements of the mimetic musculature of the face. The vast majority of these muscles are innervated by the VIIth cranial nerve, emanating from the brainstem between the pons and medulla (Figure 1). The nerve includes a motor root that supplies somatic muscle fibers to the muscles of the face, scalp, and outer ear, enabling the muscle movements that comprise facial expressions. The sensory part of the nerve enables and augments some aspects of taste and sound (Standring, 2005).

Morphological changes of cholinergic nerve fibers in the urinary bladder after establishment of artificial somatic-autonomic reflex arc in rats

To establish an artificial somatic-autonomic reflex arc in rats and observe the following distributive changes of neural fibers in the bladder. Adult Sprague-Dawley rats were randomly divided into three groups: control group, spinal cord injury (SCI) group, and reinnervation group. DiI retrograde tracing was used to verify establishment of the model and to investigate the transport function of the regenerated efferent axons in the new reflex arc. Choline acetyltransferase (ChAT) in the DiI-labeled neurons was detected by immunohistochemistry. Distribution of neural fibers in the bladder was observed by acetylcholine esterase staining. DiI-labeled neurons distributed mainly in the left ventral horn from L3 to L5, and some of them were also ChAT-positive. The neural fibers in the bladder detrusor reduced remarkably in the SCI group compared with the control (P < 0.05). After establishment of the somatic-autonomic reflex arc in the reinnervation group, the number of ipsilateral fibers in the bladder increased markedly compared with the SCI group (P < 0.05), though still much less than that in the control (P < 0.05). The efferent branches of the somatic nerves may grow and replace the parasympathetic preganglionic axons through axonal regeneration. Acetylcholine is still the major neurotransmitter of the new reflex arc. The controllability of detrusor may be promoted when it is reinnervated by the pelvic ganglia efferent somatic motor fibers from the postganglionic axons.

Small‐fiber involvement in spinobulbar muscular atrophy (Kennedy's disease)

We assessed the involvement of cutaneous innervation in two subjects with a molecularly confirmed diagnosis of spinobulbar muscular atrophy (SBMA) using antidromic nerve conduction studies, quantitative sensory testing, and sweat tests, as well as immunohistochemical techniques and confocal microscopy of glabrous and hairy skin biopsy. Both patients showed a marked reduction in amplitude of sensory action potentials and moderate or severe abnormalities of tactile thresholds and mechanical pain perception. A severe reduction of sweat drops on the Silastic imprint test and a widespread loss of small myelinated and unmyelinated fibers in hairy skin were also observed. Fiber loss involved either somatic or autonomic fibers and did not show any distal-proximal gradient. These results, together with loss of Meissner corpuscles and their large myelinated afferent fibers in glabrous skin, confirmed the extensive involvement of sensory neurons of large and small size and revealed an autonomic skin denervation in SBMA.

Voiding reflex in chronic spinal cord injured cats induced by stimulating and blocking pudendal nerves

To induce efficient voiding in chronic spinal cord injured (SCI) cats. Voiding reflexes induced by bladder distension or by electrical stimulation and block of pudendal nerves were investigated in chronic SCI cats under alpha-chloralose anesthesia. The voiding efficiency in chronic SCI cats induced by bladder distension was very poor compared to that in spinal intact cats (7.3 +/- 0.9% vs. 93.6 +/- 2.0%, P < 0.05). In chronic SCI cats continuous stimulation of the pudendal nerve on one side at 20 Hz induced large amplitude bladder contractions, but failed to induce voiding. However, continuous pudendal nerve stimulation (20 Hz) combined with high-frequency (10 kHz) distal blockade of the ipsilateral pudendal nerve elicited efficient (73.2 +/- 10.7%) voiding. Blocking the pudendal nerves bilaterally produced voiding efficiency (82.5 +/- 4.8%) comparable to the efficiency during voidings induced by bladder distension in spinal intact cats, indicating that the external urethral sphincter (EUS) contraction was caused not only by direct activation of the pudendal efferent fibers, but also by spinal reflex activation of the EUS through the contralateral pudendal nerve. The maximal bladder pressure and average flow rate induced by stimulation and bilateral pudendal nerve block in chronic SCI cats were also comparable to those in spinal intact cats. This study shows that after the spinal cord is chronically isolated from the pontine micturition center, bladder distension evokes a transient, inefficient voiding reflex, whereas stimulation of somatic afferent fibers evokes a strong, long duration, spinal bladder reflex that elicits efficient voiding when combined with blockade of somatic efferent fibers in the pudendal nerves.

Differential sensitivity of thick and thin fibers to HIV and therapy-induced neuropathy

The study assessed HIV-related and anti-retroviral therapy-induced neuropathy in myelinated and unmyelinated nerve fibers. One hundred consecutive HIV patients were examined clinically and standard nerve conduction velocities were measured. In addition, electrically induced sympathetic skin response (SSR) was assessed in the palms and soles. The difference in delay of SSR in palms and soles (ΔSSR) was calculated as an indirect measure of C-fiber conduction velocity. Thick fiber conduction velocities significantly decreased with age and increasing stage of the disease, whereas no effect of stage was found for ΔSSR ( p = 0.6). In contrast, medication of at least one of the most known neurotoxic drugs zalcitabine, stavudine, or didanosine did not result in significantly lower conduction velocities in thick fibers (51.29 ± 3.4 m/s vs. 50.86 ± 3.5 m/s), but was related to an increased ΔSSR. ΔSSR allows an indirect measurement of C-fiber conduction velocity. In HIV this measure of unmyelinated sympathetic fibers was most sensitive to anti-viral treatment whereas conduction velocity of myelinated somatic fibers was more sensitive to disease-related neuropathy. The results suggest that HIV neuropathy preferably affects myelinated and anti-retroviral therapy unmyelinated fibers.

Urinary retention due to an isolated sacral root injury caused by sacral fracture

A case report. Urodynamic laboratory in a university hospital, Chiba, Japan. A young woman who suffered from urinary retention following a skiing accident. A sacral X-ray (lateral view) revealed an S2-3 sacral fracture. The patient gradually regained the ability to urinate. At 3 months after the accident, she still suffered difficult urination, although her neurological findings were normal. A urodynamic study showed an acontractile detrusor and a neurogenic sphincter electromyogram (EMG), together indicative of isolated sacral nerve injury. It was postulated that the S2-3 sacral fracture had led to bilateral traction of the S2-3 nerve roots, producing transient bladder paralysis (parasympathetic fibers) and incomplete sphincter paresis (somatic fibers). Sacral fracture is also of high clinical suspicion for urinary retention in frail elderly people, because it can result from simple falls.

Exploring the neurophysiological basis of chest wall allodynia induced by experimental oesophageal acidification – evidence of central sensitization1

In somatic models of central sensitisation (CS) allodynia develops following changes to somatic A-beta fibres, allowing these afferents which normally only process innocuous sensations to encode pain. The aim of this study was to determine whether somatic allodynia induced by visceral sensitisation occurs via N-Methyl-D-Aspartate (NMDA) receptor mediated changes to the neurophysiological characteristics of somatic A-beta fibres. Twelve healthy subjects had oesophageal, chest wall and foot pain thresholds (PT) to electrical stimulation measured, and chest wall evoked potentials (CEP) recorded before and 30 minutes after distal oesophageal acidification on 2 separate visits. Intravenous ketamine (an NMDA receptor antagonist) or saline was given 30 minutes post acid with repeated oesophageal and chest wall PT measurements and CEP recordings. Distal oesophageal acidification reduced PT to electrical stimulation on the anterior chest wall (37 +/- 10 mA v 29 +/- 7 mA p = 0.01) and proximal oesophagus (46 +/- 10 mA v 33 +/- 11 mA p = 0.001) but not the foot (37 +/- 25 mA v 39 +/- 23 mA p = 0.12). The induction of chest wall somatic allodynia was accompanied by a reduction in the latency of the P1 (36 +/- 3 ms to 30 +/- 4 ms p = 0.016) and P2 (87 +/- 7 ms to v 76 +/- 7 ms p = 0.049) components of the CEP. NMDA receptor antagonism reversed both visceral and somatic pain hypersensitivity but did not affect CEP latencies. These data provide objective neurophysiological evidence that CS contributes to the development of somatic allodynia following visceral sensitisation.

Electromyography of pelvic floor muscles

Pelvic floor muscles (PFM) are intimately involved in function of lower urinary tract, the anorectum and sexual functions, therefore their neural control transcends the primarily important somatic innervation of striated muscle, as they are directly involved in “visceral activity”. Neural control of pelvic organs is affected by a unique co-ordination of somatic and autonomic motor nervous systems. Visceral and somatic sensory fibres supply sensory information from pelvic organs; their input influences through central integrative mechanisms also pelvic floor muscle activity. Anatomically, somatic afferent and efferent nerves of the sacral cord segments, reflexly integrated at the spinal cord and brainstem level, conduct neural control of PFM. The inputs from several higher centres influence the complex reflex control and are decisive for voluntary control, and for socially adapted behaviour related to excretory functions.

Prevalence of somatic small fiber neuropathy in obesity

Somatic cutaneous small sensory fiber neuropathy (SSFN) can be an early manifestation of impaired glucose tolerance and diabetes mellitus and/or insulin resistance among obese subjects and is often associated with pain, wound occurrence and impaired wound healing. It is yet unclear as to whether SSFN is prevalent among obese individuals without glucose and/or insulin dysregulation despite abundant evidence of delayed wound healing. To observe whether there is hypofunctioning of stimulated capsaicin-sensitive cutaneous nerves (small sensory fibers) in obese subjects with/without hyperglycemia and hyperinsulinemia. Fifty-eight morbidly obese and 15 lean subjects were recruited for small fiber testing of the forearm in a cross-sectional study. Hyperglycemia was observed in 35 obese subjects. Of 25 obese subjects, hyperinsulinemia was noted in 15, 14 of which were hyperglycemic. No subjects demonstrated symptoms/signs of neuropathy over the hairy skin of the forearm. In fact, a neurological examination revealed that 37 subjects were asymptomatic in the legs and only four complained of a neuropathic pain in the foot. Virtually all subjects were exposed to a set of capsaicin-sensitive tests and measures which were identified by capsaicin desensitization procedures. These tests, conducted while in a supine position in bed at the Banner Good Samaritan Medical Center, Phoenix, examined the two principle roles of cutaneous SSFs, namely conveying pain signals to the CNS and controlling local neurogenic vasodilatation (flare; axon-reflex). Heat-induced pain was assessed by verbal reports of sensation after accommodation and heat-, capsaicin-, and transcutneous stimulation- induced blood flow was measured by laser Doppler flowmetry with probes placed at the site of stimulation and 1 cm remote from the site, the latter to evaluate flare latency and intensity of flare. Significant depression of pain and flare responses were observed in the obese subjects in all but one test. Decreased pain and flare responses were noted in all subjects without hyperglycemia and hyperinsulinemia. Age negatively correlated with capsaicin-induced flare in both the obese and normal groups. SSFN was prevalent in the cohort of morbidly obese subjects in a skin area without neurological symptoms or signs and in subjects with/without hyperglycemia and hyperinsulinemia. SSFN may be a serious factor in observations of impaired wound healing among obese subjects, a particularly worrisome problem in an obese aging population given the propensity for small fiber impairment in aging subjects. Small fiber impairment in the younger obese population may signal an early aging phenomenon.