Evaluation of reference sites for scalp potentials evoked by painful and non-painful sural nerve stimulation

The objective of this study was to evaluate reference sites for recording the middle- and long-latency scalp potentials elicited by painful and non-painful sural nerve stimulation. Somatosensory evoked potentials (SEPs) were recorded from the scalp, the mastoid, the earlobe, the neck, and the wrist. Each site was referenced to the sterno-vertebral (SV) electrode, which is a balanced non-cephalic reference with essentially no ECG contamination.There was little or no activity recorded between the wrist and SV, and the SV was located within a region extending from the rostral neck to the wrist where the potentials were stable over space. Hence, the SV reference is indifferent for the middle- and long-latency potentials evoked by painful and non-painful sural nerve stimulation. There was, however, significant activity recorded from the earlobe and mastoid, sites which are frequently used as references for the SEP. It is important that investigators using these cephalic references to study the middle- and long-latency peaks of the SEP be aware of this activity as it will distort SEPs recorded from single sites and the SEP scalp topography, distortions which could unnecessarily complicate their interpretation.     

Differential effects of nitric oxide on the responsiveness of tactile hairs

The responses of tactile hairs located on legs of the desert locust Schistocerca gregaria (Forskål) are modulated by nitric oxide (NO). There are two types of tactile hair on the tibia of the hind leg of the locust which differ in their thresholds for mechanical stimulation, their location on the leg and in the effect of NO on their responses to deflection. The spike response rates of mechanosensory neurons of low-threshold hairs decreased when exposed to elevated NO levels caused by perfusion of the leg with saline containing the NO donor PAPANONOate. In contrast, in high-threshold hairs, which show low responsiveness under control conditions, an increase in spike rates was observed during PAPANONOate application. These opposing effects of NO reduce the differences in the spike responses of the two types of tactile hairs to mechanical stimulation and are likely to have an impact on behaviours elicited by mechanical stimulation of the legs.     

Biology and therapy of fibromyalgia: pain in fibromyalgia syndrome

Fibromyalgia (FM) pain is frequent in the general population but its pathogenesis is only poorly understood. Many recent studies have emphasized the role of central nervous system pain processing abnormalities in FM, including central sensitization and inadequate pain inhibition. However, increasing evidence points towards peripheral tissues as relevant contributors of painful impulse input that might either initiate or maintain central sensitization, or both. It is well known that persistent or intense nociception can lead to neuroplastic changes in the spinal cord and brain, resulting in central sensitization and pain. This mechanism represents a hallmark of FM and many other chronic pain syndromes, including irritable bowel syndrome, temporomandibular disorder, migraine, and low back pain. Importantly, after central sensitization has been established only minimal nociceptive input is required for the maintenance of the chronic pain state. Additional factors, including pain related negative affect and poor sleep have been shown to significantly contribute to clinical FM pain. Better understanding of these mechanisms and their relationship to central sensitization and clinical pain will provide new approaches for the prevention and treatment of FM and other chronic pain syndromes.     

Differential effects of central serotonin manipulation on hyperactive and stereotyped behaviour

The locomotor response following injection of dopamine into the nucleus accumbens was attenuated by the injection of 5HT and potentiated by the injection of methysergide into the same site. D-amphetamine-induced locomotor activity was also reduced by the intra-accumbens injection of 5HT. In contrast, apomorphine- induced stereotyped behaviour (sniffing, licking, biting, gnawing) was reduced by systematic administration of the putative 5HT receptor antagonists, cyproheptadine and metergoline. In addition the low intensity sniffing responses produced by a low dose of apomorphine were converted to high intensity biting, gnawing or licking by the putative 5HT receptor agonist, quipazine or the putative 5HT uptake blocker, ORG 6582. The selective induction of either hyperactive or stereotyped behaviour may therefore be influenced by the functional state of central serotonergic systems.     

Stress and psychophysiological dysregulation in patients with fibromyalgia syndrome

Fibromyalgia syndrome (FMS) is a prevalent musculoskeletal pain disorder characterized by diffuse pain and associated psychophysiological symptoms. Despite extensive research in the past 3 decades, the etiology and pathophysiology of FMS and effective treatment approaches are yet to be delineated. Recently, it has been suggested that FMS may be related to hypofunctional stress systems, particularly in the autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis. Studies have demonstrated that patients with FMS exhibit lowered sympathoadrenal reactivity to stress. These findings seem to be consistent with the large volume of research indicating the inverse relationship between pain sensitivity and sympathetic reactivity. In this paper, we discuss the role of stress in the pain experience in general, stress in patients with FMS, and review the studies evaluating the ANS and HPA functions in response to various stressors.     

Parasite infection rather than tactile stimulation is the proximate cause of cleaning behaviour in reef fish.

Cleaning behaviour is a popular example of non-kin cooperation. However, quantitative support for this is generally sparse and the alternative, that cleaners are parasitic, has also been proposed. Although the behaviour involves some of the most complex and highly developed interspecific communication signals known, the proximate causal factors for why clients seek cleaners are controversial. However, this information is essential to understanding the evolution of cleaning. I tested whether clients seek cleaners in response to parasite infection or whether clients seek cleaners for tactile stimulation regardless of parasite load. Parasite loads on client fish were manipulated and clients exposed to cleaner fish and control fish behind glass. I found that parasitized client fish spent more time than unparasitized fish next to a cleaner fish. In addition, parasitized clients spent more time next to cleaners than next to control fish, whereas unparasitized fish were not attracted to cleaners. This study shows, I believe for the first time, which is somewhat surprising, that parasite infection alone causes clients to seek cleaning by cleaners and provides insight into how this behaviour evolved.     

Positive effects of tactile versus kinesthetic or vestibular stimulation on neuroendocrine and ODC activity in maternally-deprived rat pups

Previous studies in our laboratory have shown that even short-term separation of preweanling rat pups from the mother produces adverse effects in the pup. These include alterations in ornithine decarboxylase activity and in the secretion of growth hormone and corticosterone. The present study demonstrates that while intermittent heavy stroking effectively reverses or prevents all the changes associated with maternal deprivation neither kinesthetic nor vestibular stimulation affects these responses. The results verify earlier findings from this laboratory indicating that tactile interactions between rat pups and their mother modulate pup physiology and provide experimental support for the hypothesized role of tactile stimuli on early infant development.     

Behavioral and neuronal investigations of hypervigilance in patients with fibromyalgia syndrome

Painful stimuli are of utmost behavioral relevance and thereby affect attentional resources. In health, variable effects of pain on attention have been observed, indicating alerting as well as distracting effects of pain. In the human brain, these effects are closely related to modulations of neuronal gamma oscillations. As hypervigilance as an abnormal increase of attention to external stimuli has been implicated in chronic pain states, we assumed both attentional performance and pain-induced gamma oscillations to be altered in patients with fibromyalgia syndrome (FMS). We recorded electroencephalography from healthy subjects (n = 22) and patients with FMS (n = 19) during an attention demanding visual reaction time task. In 50% of the trials we applied painful laser stimuli. The results of self-assessment questionnaires confirm that patients with FMS consider themselves hypervigilant towards pain as compared to healthy controls. However, the experimental findings indicate that the effects of painful stimuli on attentional performance and neuronal gamma oscillations do not differ between patients and healthy subjects. We further found a significant correlation between the pain-induced modulation of visual gamma oscillations and the pain-induced modulation of reaction times. This relationship did not differ between groups either. These findings confirm a close relationship between gamma oscillations and the variable attentional effects of pain, which appear to be comparable in health and disease. Thus, our results do not provide evidence for a behavioral or neuronal manifestation of hypervigilance in patients with FMS.     

Stretch reflex inhibition using electrical stimulation in normal subjects and subjects with spasticity

The effect of electricallys timulating the tibialis anterior muscle on the stretch reflex of the soleus muscle in normal subjects and subjects with spasticity is investigated. Stimulation of the tibialis anterior just prior to the onset of a mechanical disturbance, which causes a stretch in the soleus, inhibits the stretch reflex of the soleus in normal subjects and may inhibit clonus in subjects with spasticity.     

Influence of concurrent tactile stimulation on somatosensory evoked potentials following posterior tibial nerve stimulation in man

A topographical study was made of SEPs following stimulation of the right posterior tibial nerve at the ankle, with and without concurrent tactile stimulation of the soles of either foot or the palm of the right hand. Effects of the interfering stimulus were best demonstrated by subtracting the wave forms to derive ‘difference’ potentials.The majority of SEP components were significantly attenuated by tactile stimulation of the ipsilateral foot, and the difference wave form was of similar morphology to the control response. Components of opposite polarity peaking at 39 msec were consistent with the field of a cortical generator with dipolar properties, situated in the contralateral hemisphere just posterior to the vertex with the positive poles oriented towards the ipsilateral side. By analogy with median SEP findings, these potentials were believed to originate in the foot region of area 3b where neurones are mainly concerned with cutaneous sensory processing.When the tactile stimulus was applied to the contralateral foot, difference potentials maximally recorded just posterior to the vertex were of smaller amplitude but similar morphology to ipsilateral foot difference components. This suggested the possibility that input from the two lower extremities may converge at cortical or subcortical level, the effect being manifested in the response of certain neurones in area 3b. With both contralateral foot and ipsilateral hand stimulation, other difference potentials were present which suggested that there may be cortical regions responding to combinations of sensory stimuli applied to various parts of the body surface.     

Differential effects of lysosomotropic amines and polyamines on processing and biological activity of EGF

The effects of lysosomotropic amines and polyamines on rat fibroblasts were studied after the administration of epidermal growth factor (EGF) in order to determine whether the intracellular processing of EGF was important for transmission of its biological signal. Following the addition of EGF, cell cultures exhibited a dose-dependent increase in ornithine decarboxylase (ODC) activity. This increase in ODC activity was drastically reduced by both methylamine, a representative lysosomotropic amine, and putrescine, a polyamine precursor. However, inasmuch as methylamine inhibited EGF-induced DNA synthesis by greater than 50%, putrescine had no inhibitory effect. Lysosomotropic amines, but not polyamines, prevented EGF processing as evidenced by their ability to block the release of intracellular 125EGF and by their ability to inhibit the formation of the final intracellular processed product of EGF, as determined by isoelectric focusing. These data suggest that the processing of EGF is consistent with the induction of DNA synthesis and ODC activity. The cellular mechanisms involved in inhibition of ODC induction by polyamines appear to be distinct from those involved in lysosomotropic amines.     

Effect of sensory stimulation applied under the great toe on postural ability in patients with fibromyalgia

Abstract

Fibromyalgia (FM) is a chronic pain syndrome, characterised by several symptoms. One of the most prevalent symptoms in FM is balance impairment that compromise the autonomy, function and performance status of patients.

Purpose: The main objective of the present study was to evaluate the effect of sensory stimulation provided by the use of a low additional thickness of 0.8?mm placed under the great toes bilaterally on the centre of pressure (CoP) measures in patients with FM. It was hypothesised that postural ability would change with a low focal additional thickness used to compute these measures.

Materials and Method: Twenty-four patients with FM voluntarily participated in this study. Postural performance during quiet standing was investigated through the CoP displacements recorded using a force-plate. Sensory stimulation was provided by a small additional thickness of 0.8?mm placed under the great toe bilaterally and two conditions were compared: additional thickness 0 (control) and 0.8?mm.

Results: An improvement of body balance through spatial parameters with sensory cutaneous stimulation applied under the great toe bilaterally were observed in patients with FM. Our results showed a significant decrease of surface area and mean speed of CoP, associated to a significant decrease of variance of speed. An additional observation is that sagittal (Y) mean position of the CoP gets more anterior (+ 5?mm) relative to control condition.

Conclusion: These findings brings new clinical perspectives in the development of intervention strategies in the management of patients with FM and balance disorders, completing validated therapeutic strategies.     

Development of a tactile stimulator with simultaneous visual and auditory stimulation using E-Prime software

In this study, a tactile stimulator was developed, which can stimulate visual and auditory senses simultaneously by using the E-Prime software. This study tried to compensate for systematic stimulation control and other problems that occurred with previously developed tactile stimulators. The newly developed system consists of three units: a control unit, a drive unit and a vibrator. Since the developed system is a small, lightweight, simple structure with low electrical consumption, a maximum of 35 stimulation channels and various visual and auditory stimulation combinations without delay time, the previous systematic problem is corrected in this study. The system was designed to stimulate any part of the body including the fingers. Since the developed tactile stimulator used E-Prime software, which is widely used in the study of visual and auditory senses, the stimulator is expected to be highly practical due to a diverse combination of stimuli, such as tactile–visual, tactile–auditory, visual–auditory and tactile–visual–auditory stimulation.     

Treatment of the painful shoulder syndrome with amitriptyline and lithium carbonate

Thirty-four patients with painful shoulder syndrome (PSS) were psychologically assessed and the results compared with those from a control group presenting other musculoskeletal disorders. A significantly greater prevalence of depression was found in the former group. Fifty-six patients with PSS were treated with only lithium and amitriptyline for four months; 44 patients showed marked clinical improvement and radiologic clearing of dystrophic calcification. Lithiumamitriptyline therapy, when compared with physiotherapy in another series of 11 patients, was found to be far superior. Some possible biochemical links between depression and PSS are outlined, and the theory that PSS may be a clinical entity of psychogenic origin is discussed.     

Indirect effects of fish on foraging behaviour and leaf processing by the isopod Lirceus fontinalis

1. We examined whether the isopod, Lirceus fontinalis, an important facultative shredder in low-order streams in the eastern United States, responded to chemical cues of the skin mucus of five fish species varying in relatedness and feeding habits, and if fish-induced alterations in the foraging activity of isopods indirectly affected leaf processing. 2. In the laboratory, isopods generally responded to the presence of fish mucus by reducing their activity. Isopods were most responsive in water containing the skin mucus of predatory sunfish (Lepomis) and least responsive in water treated with mucus from algivorous stonerollers (Campostoma anomalum). 3. Rates of leaf disc breakdown by isopods in the laboratory were significantly reduced when isopods were exposed to chemical cues of confined green sunfish (L. cyanellus). 4. The rate of leaf processing in a fishless reach of a headwater stream was four to five times greater by isopods 7—10mmTL (total length) than those ≤ 5mm TL. Rates of leaf processing by isopods in low-order streams may be affected directly by the size structure of the isopod population and indirectly by the presence of fish.     

Differential effects of amylin on memory processing using peripheral and central routes of administration.

Amylin is a peptide hormone secreted from the beta cells of the pancreatic islets. Amylin was administered peripherally or centrally following weak or strong training on footshock avoidance conditioning in a T-maze. Under conditions of weak training, amylin improved memory retention in a dose-dependent manner. Under conditions of strong training, it impaired retention over the same dose range. Central administration of amylin in mice given strong training impaired retention but had no effect on the retention of mice given weak training. These findings suggest that the mechanisms of action by which amylin altered memory processing are different for peripheral and central administration. Peripherally secreted amylin may play a role in the amnesia seen in diabetes and the memory enhancement following glucose administration.     

Characterization of glycosaminoglycans in urine from patients with nephrotic syndrome and control subjects, and their effects on lipoprotein in lipase

Previously we found that the α₁-acid glycoprotein fraction from urine of patients with the nephrotic syndrome stimulated the lipoprotein lipase reaction in vivo and in vitro. The activator was separated from the α₁-acid glycoprotein and identified as a glycosaminoglycan. The studies reported here were undertaken to characterize and quantify the glycosaminoglycans contained in urine of patients with the nephrotic syndrome and to compare these to the glycosaminoglycans in urine of control subjects. We found that free low molecular weight glycosaminoglycans, heparan sulfate and chondroitin 4-sulfate, are excreted in both patients with the nephrotic syndrome and controls, however, patients with the nephrotic syndrome excreted much less of both glycosaminoglycans. The free form of heparan sulfate was found to be the activator which stimulated the lipoprotein lipase reaction in vitro in the presence of apolipoprotein C_II. In addition, the urine from patients with the nephrotic syndrome contained a protein-glycosaminoglycan complex which was absent in control urine. Glycosaminoglycans in the complex could be released by papain digestion or by trichloroacetic acid. Our evidence indicates that this glycosaminoglycan fraction is a low charge form of chondroitin sulfate.