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PubMed1997

Neutrophil-activating protein ENA-78 and IL-8 exhibit different patterns of expression in lipopolysaccharide- and cytokine-stimulated human monocytes.

The production of epithelial neutrophil-activating protein-78 (ENA-78) by normal human monocytes was studied in comparison with IL-8 upon stimulation with various stimuli. LPS at 100 ng/ml was a strong inducer of ENA-78, yielding a delayed up-regulation of steady state mRNA peaking at 24 h and causing a long-lasting ENA-78 protein secretion starting 20 h after induction. As shown by specific ELISA and immunoprecipitation, ENA-78 secretion by monocytes was not down-regulated for up to 72 h. Thus, ENA-78 production becomes effective when IL-8 synthesis is shut off, since IL-8 mRNA peaks at 4 to 12 h and approaches background levels at about 16 h. Induction of steady state ENA-78 mRNA by proinflammatory cytokines IL-1beta (10 ng/ml) and TNF-alpha (100 ng/ml) was weaker than that by LPS and yielded a biphasic kinetic with a first maximum at 8 to 12 h and a second at 20 to 28 h. Steady state IL-8 mRNA induced by LPS, IL-1beta, or TNF-alpha was superinduced or unchanged in the presence of cycloheximide (10 microg/ml). In contrast, ENA-78 mRNA was completely abrogated, suggesting the involvement of a newly synthesized protein intermediate necessary for ENA-78 up-regulation. Dexamethasone treatment reduced ENA-78 mRNA and protein levels by 60% of the LPS control level. This inhibition was identical when dexamethasone was added 8 h after LPS induction. These results demonstrate significant differences in the production of monocyte-derived IL-8 and ENA-78 and thus may suggest different roles for the two chemokines in acute or chronic inflammation.

Anti-Inflammatory Agents↗

PubMed1995

Effect of interferon gamma on T lymphocytes from patients with multiple sclerosis.

A central role in the complex immunology of MS is played by activated T lymphocytes. Proper antigenic stimulation, adequate major histocompatibility complex (MHC) coactivation and multiple cytokine signals regulate T-cell activation via the generation of intracellular calcium (Ca2+) transients necessary to up-regulate the genes controlling lymphocyte growth and differentiation. Interferon gamma (IFN-gamma) exerts an autocrine/paracrine control of T-lymphocyte activity and is able to co-mediate most demyelinating events occurring in MS patients. The mechanisms by which IFN-gamma exerts its effects include increased expression of MHC class II molecules on the surface of glial cells and stimulation of macrophage/microglial cell production of molecules toxic to myelin. Most intracellular events regulating these processes in lymphocytes are, however, still unknown. We have reported that in the majority of MS patients T lymphocytes (mainly CD4+) exposed to IFN-gamma show a Ca2+ influx whose ion permeability and pharmacological properties differ from those of all Ca2+ influxes so far described. This IFN-gamma-activated Ca2+ influx, which is probably sustained by a cationic channel, was observed in the majority of patients with MS, but only in a limited number of subjects affected by other neurological, active immune-mediated diseases or healthy control subjects. Moreover, the presence of the influx correlates with clinical and radiological evidence of disease activity and induces T-lymphocyte proliferation even when cells are suboptimally stimulated by activatory stimuli. We conclude that this new IFN-gamma-activated Ca2+ influx seems to be highly specific for MS (especially during its active phase), and could be important for the intracellular regulation of cells involved in demyelination. The presence of the influx in T lymphocytes from MS patients could account for the reported temporal association between infections and clinical relapses.

Antineoplastic Agents↗

PubMedDate not supplied

Vasopressin release, water channels, and vasopressin antagonism in cardiac failure, cirrhosis, and pregnancy.

Vasopressin (AVP) is released in response to both osmotic and nonosmotic stimuli. Nonosmotic-stimulated AVP release occurs in cardiac failure, cirrhosis, and pregnancy in response to alterations in arterial circulatory integrity. Cardiac failure in rats is associated with increased plasma AVP and hypothalamic AVP mRNA, and in humans, it is associated with cardiac failure. Plasma AVP concentrations are elevated when measured with a sensitive radioimmunoassay. Urinary concentrations of AVP-responsive aquaporin-2 water channels are also elevated in cardiac failure. V2 receptor antagonists correct the impaired solute-free water excretion seen in rats with low-output cardiac failure and reverse the upregulation of renal aquaporin-2 water channels. Orally active non-peptide-selective V2 receptor antagonists administered to patients with congestive cardiac failure decrease urinary concentrations of aquaporin-2, increase solute-free water clearance, and correct the hyponatremia. Cirrhosis of the liver results in splanchnic arterial vasodilation and increased vascular capacity, most likely secondary to increased nitric oxide production. This relative underfilling of the arterial circulation stimulates nonosmotic AVP release with resultant water retention. Aquaporin-2 gene expression is upregulated in the kidneys of rats with cirrhosis of the liver. AVP-2 receptor antagonists administered to animals with cirrhosis reverse the water retention. Human studies using orally active, non-peptide-selective V2 receptor antagonists in patients with cirrhosis are currently underway. Pregnancy is another state of nitric oxide-mediated arterial vasodilation that is associated with plasma AVP concentrations that are relatively high for the degree of hypoosmolality. Upregulation of the water channel aquaporin-2 in the renal papillae of pregnant rats has also been demonstrated, and this effect is reversed by administration of a V2 receptor antagonist.

Animals↗

PubMed1998

[Molecular mechanism of interleukin-8 gene expression].

Evidence is accumulating that interleukin-8 (IL-8), discovered as a potent neutrophil chemotactic factor, plays a crucial role in establishing acute neutrophil-mediated inflammation by exerting various activities against non-leukocytic as well as leukocytic cells. Various types of cells can rapidly produce a large amount of IL-8 upon stimulation with inflammatory stimuli, such as lipopolysaccharide, IL-1, and tumor necrosis factor (TNF). However, IL-8 production is tightly regulated at several levels, particularly at the transcriptional levels to prevent aberrant production. Our previous experiments demonstrated that IL-8 gene transcription requires the cooperative activation of a transcription factor, NF-kappa B, with an additional transcription factor, AP-1 or NF-IL6, depending on types of cells and stimuli. In addition, we recently observed that infection with Helicobacter pylori or cytomegalovirus activated NF-kappa B, therapy inducing IL-8 protein secretion as well as IL-8 gene transcription. Moreover, IL-8, in turn, enhanced cytomegalovirus replication and infectious virion production. Collectively, these results suggest the potential involvement of IL-8 in the pathology of bacterial or viral infection.

Cytomegalovirus↗

PubMed1976

Development of cerebellar somatosensory evoked potentials in the rat.

In lobule VIa of the vermis cerebelli of 69 male albino rats aged from 7 to 90 days we studied the somatosensory potential evoked by electrical stimulation of the sciatic nerve. A response consisting of a marked positive wave and a small negative wave was constantly present in the group of 9- to 10-day-old animals. At the end of the second week, an initial negative wave appeared. The response of 18-day-old animals consisted of 5 waves of alternating polarity and started with a small positive wave as in adult rats. During subsequent development only the relative size of the individual components changed, the later negative wave, N2, being the most marked component in adult animals. An attempted explanation of the possible origin of evoked potentials in young animals, based on the available data on the morphological development of the cerebellar cortex, is submitted. The latent periods, measured to the maxima of the individual waves, shorten abruptly between the 10th and 20th day and then undergo little change. Greater fatigability of the responses of young animals can be demonstrated by using rhythmical stimulation and paired stimuli. Somatosensory responses appear sooner than visual evoked potentials in the cerebellum, but they develop later than somatosensory evoked potentials in the cerebral cortex.

Aging↗

PubMed2002

Focal clonus elicited by electrical stimulation of the motor cortex in humans.

Focal clonic seizures are a frequent epileptic phenomenon. However, there are little data about their pathomechanism. In four patients with focal epilepsy and subdural electrodes, focal clonus was elicited by electrical stimulation of the motor cortex. Three additional patients underwent intraoperative stimulation of the spinal cord. Rhythmic clonic muscle responses were elicited by cortical stimulation with 20-50 Hz. The clonus consisted of simultaneous trains of compound muscle action potentials (CMAP) in agonistic and antagonistic muscles alternating with periods of muscular silence despite continuous stimulation. Clonus frequency decreased from 4.0-8.0 Hz at 50 Hz stimulation to 3.0-3.5 Hz at 20 Hz paralleled by a prolongation of the trains of CMAP. The stimulation frequency correlated with the number of stimuli blocked during relaxation. During the stable stimulation periods, the clonus frequency decreased over time. The number of stimuli which formed a train of CMAP and which were blocked during relaxation increased towards the end of the stimulation periods. Increasing intensity of stimulation at the same frequency converted a clonic to a tonic response. There was always an 1:1 relationship between stimulus and CMAP during spinal cord stimulation. We hypothesize that during cortical stimulation, clonus is elicited by synchronous activation of pyramidal tract (PT) neurons which results in excitation of intracortical GABA(B)ergic interneurons by recurrent axon-collaterals. This leads to stepwise hyperpolarization of PT neurons intermittently suppressing the output of PT neurons despite continuous stimulation. This mechanism can explain our finding that temporal and spatial summation of the stimuli were needed for clonus generation.

Action Potentials↗

PubMed2001

Studying semantics in the brain: the rapid stream stimulation paradigm.

Event-related potentials (ERPs) provide information about the temporal course of cognitive processes in the brain. They have proved to be a valuable tool in order to explore semantic aspects of word processing. However, to date, research in this field has been mostly concerned with the study of post-lexical features by means of the N400-paradigm. We introduce here the rapid stream stimulation paradigm, in which stimuli reflecting different levels of linguistic information are presented to subjects at a high rate of stimulation. The present protocol shows in detail how this paradigm can be applied. The application of the rapid stream stimulation paradigm evokes the recognition potential (RP), an ERP component that peaks at around 260 ms after stimuli onset and seems to be reflecting lexical selection processes. Results of studies that revealed the sensibility of the RP to visual-semantic aspects and the location of its neural generators within basal extrastriate areas are reported. Although some research has been conducted with the rapid stream stimulation paradigm much remains still to be done. Some of the possibilities that this paradigm offers are further discussed.

Brain↗

PubMedDate not supplied

Analysis of differentially regulated mRNAs in monocytic cells induced by in vitro stimulation with Kveim-Siltzbach test reagent.

Sarcoidosis is a granulomatous disorder of unknown origin. The sarcoid spleen-derived Kveim-Siltzbach test reagent (KSTR) elicits a sarcoid-specific, granulomatous response and was used to diagnose sarcoidosis. The active component and the pathomechanism by which KSTR induces granuloma are still unknown. This study investigated the KSTR-associated gene expression pattern in cells of patients with sarcoidosis or chronic beryllium disease (CBD). The monocytic-like cell line U937, alveolar macrophages of sarcoidosis patients, and peripheral blood monocytes of patients with CBD were stimulated with KSTR and other granuloma-associated stimuli. The KSTR-associated gene expression pattern was analyzed by means of differential display reverse transcription-polymerase chain reaction in combination with a multiple comparison of expressed sequence tags induced in response to KSTR and other granuloma-associated stimuli. Depending on the origin of cells tested, 3.7% to 14.6% of the analyzed sequence tags showed differential regulation induced by granuloma-associated stimuli. Alterations restricted to KSTR stimulation could be observed in 1.2% for the cell line U937, in 2.8% for blood monocytes of patients with CBD, and 1.3% for alveolar macrophages of sarcoidosis patients. These data are comparable to those achieved for the other granuloma-associated stimuli tested in this study. Therefore, it can be assumed that KSTR induces pathomechanisms for granuloma formation in sarcoidosis as beryllium in CBD.

Adult↗

PubMed1986

[Effects of tooth pulp stimulation on single unit activity of the amygdala in cats].

Responses induced by tooth pulp stimulation were studied in 27 gallamine immobilized adult cats. Single units were recorded from the amygdala using stainless steel microelectrodes. Of 57 amygdaloid neurons, 8 were responsive to only non-nociceptive (tap and/or hair bending) stimuli, 7 were responsive to both nociceptive (pinch) and non-nociceptive stimuli, 18 were responsive to nociceptive stimuli, non-nociceptive stimuli and tooth pulp stimulation, and the others did not respond to these stimuli. The neurons in the amygdala responsive to tooth pulp stimulation were localized in the nucleus amygdaloideus centralis (pars lateralis) [Acl], nucleus amygdaloideus centralis (pars medialis) [Acl] and nucleus amygdaloideus basalis (pars magnocellularis) [Abm]. The response induced by tooth pulp stimulation was depressed by morphine and reversed by naloxone. These results suggest that Acl, Acm and Abm in the amygdala may receive pain sensation evoked by tooth pulp stimulation. Moreover, there is a possibility that these nuclei may be related to the emotional component involved in nociceptive processing.

Afferent Pathways↗

PubMed1997

Evidence suggesting a transcortical pathway from cutaneous foot afferents to tibialis anterior motoneurones in man.

1. Stimulation of the superficial peroneal or the sural nerve (3 shocks, 3 ms interval, 1 ms duration, 2.5 x perception threshold) evoked a reflex activation of the tibialis anterior muscle at a latency of approximately 70-95 ms in all of nine healthy human subjects. Stimulation of the medial plantar nerve only rarely produced similar effects. The possibility that a transcortical pathway contributes to these late reflex responses was investigated by combining the cutaneous stimulations and a transcranial magnetic stimulation of the contralateral motor cortex. 2. A significant facilitation of short-latency peaks in the post-stimulus time histogram of single tibialis anterior motor units evoked by the transcortical magnetic stimulation was observed in eight out of nine subjects following stimulation of the superficial peroneal or sural nerves at the latency of the long-latency reflex. In contrast such a facilitation was only rarely seen when the medial plantar nerve was stimulated. 3. With the same timing for the stimuli, the superficial peroneal and sural nerve stimulations also produced a significant increase in the short-latency, presumed monosynaptic, facilitation of the tibialis anterior H reflex produced by the brain stimulation. 4. Similar facilitatory effects of the cutaneous stimuli could not be demonstrated when the magnetic stimulation of the cortex was replaced with electrical stimulation, implying that cortical excitability is affected by a conditioning cutaneous stimulation. 5. It is suggested that the long-latency reflexes in the tibialis anterior muscle evoked by activation of cutaneous afferents from the human foot are, at least partly, mediated by a transcortical pathway.

Adult↗

PubMed1997

Long-lasting depression of soleus motoneurons excitability following repetitive magnetic stimuli of the spinal cord in multiple sclerosis patients.

The effect of repetitive magnetic stimulation at the spinal level on the soleus H-reflex amplitude was evaluated in II MS patients with lower limb spasticity and in nine healthy subjects. In MS patients stimulation with a train of 16 stimuli at 25 Hz induced a decrease in amplitude to 61.2 +/- 25.7% of the unconditioned H-reflex amplitude at interstimulus interval (ISI) of 10-1000 ms (P < 0.01). The amount of decrease in H-reflex amplitude was highly dependent on the stimulation intensity and the placement of the coil, and to a lesser extent influenced by the stimulation frequency. No decrease in motor evoked potentials (MEPs) evoked by transcranial magnetic stimulation was seen following trains of 16 stimuli at mid-thoracic in contrast to the post-stimulation depression in H-reflex amplitude which could imply that mechanisms acting at presynaptic level were involved. In response to repetitive magnetic stimuli for 5 min, a long-lasting decrease in H-reflex amplitude to a level of about 70% of the pre-stimulation H-reflex amplitude occurred in MS patients (P < 0.01). A similar although not significant decrease was observed in healthy subjects. We propose that long-lasting depression of the soleus H-reflex amplitude after repetitive magnetic stimuli is due to long-term depression of the synaptic transmission.

Adult↗

PubMed1989

The effects of movements on caudate sensory responses.

The aim of this experiment was to assess the effects of movement on somatosensory processing in the caudate nucleus. Units were recorded extracellularly in the caudate of awake partially restrained cats. Unit responses were evoked by either natural stimuli (brushing and skin indentation) or transcutaneous electrical stimulation. Response patterns evoked by stimuli presented when the cat was at rest were compared to responses evoked by similar stimuli presented when the cat was either making buccolingual movements or turning its head. In the majority of cases, movement suppressed caudate somatosensory responses. However, impressive augmentation of responses was seen in some cells with either type of movement.

Action Potentials↗

PubMed1991

G protein activation and mediator release from human neutrophils and platelets after stimulation with sodium fluoride and receptor-mediated stimuli.

Human polymorphonuclear granulocytes (PMN) and platelets were pre-activated with a receptor-mediated stimulus [formyl-methionyl-leucyl-phenylalanine (FMLP) or thrombin, respectively] and subsequently incubated with sodium fluoride (NaF). We investigated various cell responses, such as chemiluminescence by PMN, platelet aggregation and the release of lipid mediators [i.e. leukotriene B4 (LTB4) and its omega-oxidation products from neutrophils and 12-hydroxy-eicosatetraenoic acid (12-HETE) from platelets]. As a marker of G protein involvement, the binding of [3H]guanylylimidodiphosphate (Gpp (NH) p) to the membrane fractions of stimulated cells was determined. PMN pre-stimulated with FMLP showed a synergistically enhanced generation of leukotrienes returning to control values with the time of preincubation. Platelets preliminary treated with thrombin followed by incubation with NaF resulted in a sub-additive and time-independent mediator generation. Neither chemiluminescence by PMN nor platelet aggregation showed a similar pattern compared to the mediator release: PMN preincubated with FMLP followed by NaF resulted in a second chemiluminescence response; the aggregation of platelets which were preincubated with thrombin was partially inhibited by the addition of NaF. Membrane fractions isolated from FMLP-pre-stimulated neutrophils showed a pattern in [3H]Gpp (NH) p-binding capacity that was comparable to the respective leukotriene release. With thrombin-prestimulated platelets, no similarities between Gpp (NH) p binding, aggregation or 12-HETE generation were observed. The sequential activation of different cell populations using the same kind of stimulation lead to different cell responses, indicating the diversity of G proteins and their control mechanisms.

Blood Platelets↗

PubMed2003

An animal model for surgical anesthesia and analgesia: characterization with isoflurane anesthesia and remifentanil analgesia.

UNLABELLED: With a traditional clamp test alone, quantitative evaluation of the level of surgical anesthesia/analgesia is not easy. We have developed a rabbit model that allows for repeated quantification of the varying level of surgical anesthesia/analgesia using both mechanical and electrical stimulation as simulated surgical stimuli. After tracheostomy and intravascular cannulations under isoflurane anesthesia, eight rabbits were placed on a sling that allowed for free movement of the head and extremities. The inspired isoflurane concentration was reduced from 3% to 1.5% and then to 0%. Remifentanil was then infused at 4 graded infusion rates (0.1-0.8 microg. kg(-1) x min(-1)). At each drug dose, analgesic variables were determined including the number of animals behaviorally unresponsive to clamping the forepaw (nonresponders) and threshold voltage of subcutaneous electrical stimulation (2 Hz, 5 Hz, and 50 Hz) required to evoke the head lift (HLT, pain detection/arousal threshold) and escape movement responses (EMT, pain tolerance threshold). With increasing drug doses, HLTs and EMTs at 5 Hz increased dose-dependently and most proportionately to increases in the number of nonresponders, a standard indicator of the anesthetic/analgesic level. Therefore, using the HLT and EMT at 5 Hz combined with a clamp test, this rabbit model allows for quantitative evaluation of the varying level of surgical anesthesia/analgesia. IMPLICATIONS: We have developed a rabbit model of surgical anesthesia and analgesia using both mechanical and electrical stimulation as simulated surgical stimuli, which allows for repeated, quantitative, and qualitative evaluation of the varying level of surgical anesthesia and analgesia, differentiation between sedative/hypnotic and analgesic components of drug actions, and simultaneous monitoring of all the clinically relevant physiological variables including cardiovascular and respiratory variables.

Analgesia↗

PubMed1995

Potentiation of the respiratory burst of human neutrophils by cycloheximide: regulation of reactive oxidant production by a protein(s) with rapid turnover?

Incubation of human neutrophils with the protein biosynthesis inhibitor cycloheximide for > or = 90 min results in a decreased ability to generate reactive oxidants during the respiratory burst. This implies that active protein biosynthesis is required to sustain the ability of these cells to generate reactive oxidants. However, short term incubation of neutrophils (40-60 min) with either cycloheximide or puromycin results in a significant increase in oxidase activity stimulated by either fMet-Leu-Phe (> 60%) or by leukotriene B4 (> 30%). However, after incubation for 40-60 min with these inhibitors of protein biosynthesis, the respiratory burst stimulated by PMA was unaffected whilst that stimulated by the particulate stimuli opsonised zymosan or latex beads was significantly inhibited. The enhanced oxidase activity stimulated by the soluble agonists was not explained by changes in receptor expression, alterations in intracellular Ca2+ levels or by enhanced degranulation. These results suggest that oxidase activity stimulated by soluble agonists in neutrophils is normally regulated by a short-lived, actively-synthesised protein(s).

Amino Acid Sequence↗

PubMed1995

Effects of a protein kinase C inhibitor, Ro 31-7549, on the activation of human leukocytes by particulate stimuli.

1. A new specific protein kinase C (PKC) inhibitor, Ro 31-7549, was used to explore the mechanisms by which particulate stimuli, quartz and chrysotile, stimulate human polymorphonuclear leukocytes (PMNL) to produce reactive oxygen metabolites (ROM). Also soluble stimuli, formyl-Methionyl-Leucyl-Phenylalanine (fMLP) and phorbol myristate acetate (PMA) were used. 2. Ro 31-7549 inhibited chrysotile-induced free intracellular calcium ([Ca2+]i) elevations but did not have an effect on quartz-induced elevations of [Ca2+]i. Both quartz and chrysotile induced production of ROM were partially inhibited by Ro 31-7549. fMLP-induced elevation of [Ca2+]i was inhibited by Ro 31-7549 whereas PMA did not affect [Ca2+]i. Ro 31-7549 strongly inhibited fMLP-induced ROM production, and completely abolished that induced by PMA. 3. These result suggest that PKC may have an important role in the activation of PMNL to produce ROM by particulate and soluble stimuli. However, the inhibition of chrysotile-, but not of quartz-induced [Ca2+]i elevations by Ro 31-7549 provides evidence that both PKC-dependent and -independent mechanisms may play a role in the activation of human leukocytes to produce ROM.

Adult↗

PubMed1992

Maximal electrical stimulation in neurogenic detrusor hyperactivity: experiences in multiple sclerosis.

OBJECTIVES: We report our experiences with maximal tolerable electrical stimulation in neurogenic bladder dysfunction due to multiple sclerosis. METHODS: 27 female patients were treated with an intravaginal electrode carrier and an external pulse generator. The devices were individually adjustable with respect to electrode positioning and stimulation parameters. The frequency was 20 Hz. The threshold for sensation of the electrical stimulus was determined by slowly increasing the current and care was taken to stimulate with maximal tolerable stimuli. Urodynamic evaluation was done before and after cessation of treatment. RESULTS: During stimulation, 85% of the patients were free of symptoms. Three months after cessation of treatment only 18% remained free of symptoms, but the symptoms were not as pronounced as before treatment. CONCLUSION: Electrical stimulation using intravaginal electrodes represents a practical technical choice to treat motor urge incontinence in multiple sclerosis patients, although chronic stimulation is needed to retain improvement.

Adult↗

PubMed1984

[Analysis of the paradoxical stage of neural cathodal parabiosis (the reciprocal inhibition of adjacent fibers)].

A preparation consisting of VIII-IX dorsal and ventral roots, the sciatic nerve and a single fiber of the tibial nerve was used to study changes in conduction reliability in a single nerve fiber by means of steady-state depolarization ("cathodal alteration") of the central part of the sciatic nerve: the depolarization led to a partial block of nerve fibers and to lowering of the safety factor in the single fiber tested. While a spinal root containing the fiber under study was stimulated with trains of stimuli (200/s) the number of APs traveling along the fiber depended on the stimulation strength, being maximal near the threshold. This suggests the influence of neighbouring fiber excitation on the conduction in the tested one. The effect was more obvious when all four roots were stimulated. The paradoxical decrease in the conducted APs caused by intensification of the stimulation, seems to reflect the electrical interaction between activated fibers. Possible mechanism of this interaction is discussed.

Action Potentials↗