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Biomedical subjects

A Woda

Publications and source records attributed to A Woda.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effects of lesions in the trigeminal oralis and caudalis subnuclei on different orofacial nociceptive responses in the rat.

Behavioural responses to two different orofacial noxious stimulations were analysed following lesion of spinal trigeminal subnucleus oralis (Sp5O) in the rat. Lesions were obtained by intranuclear microinjections of quinolinic acid (0.4 microliter of 60 nmol/microliter solution). The control groups received microinjection of saline. Noxious stimulation was a subcutaneous injection of formalin into the upper lip or electrical stimulation of the tooth pulp. The measured behavioural responses were duration of rubbing induced by the formalin injection and thresholds of the jaw-opening reflex (JOR), head rotation (HR) and face rubbing (FR) evoked by the pulp stimulation. In addition, formalin injection was also performed in two groups of rats that had received intranuclear injection of quinolinic acid or saline into rostral subnucleus caudalis (Sp5C). Rubbing duration was not significantly modified by the lesion of Sp5O, whereas a significant decrease occurred after the lesion of rostral Sp5C. After the lesion of Sp5O, an increase in the threshold of JOR was observed whereas the thresholds of HR and FR were not significantly modified. These results suggest that Sp5O is not necessary for the processing and relay of nociceptive inputs triggered by intense stimulations of oral and perioral areas. However further experiments are needed to reconcile these results with the relevant data obtained from cell recording experiments which indicate the existence, in Sp5O, of neuronal activities related to the sensory discriminative aspect of intense nociception.

Animals↗
PubMed1998

Is there a correlation between scores of nociceptive behavioral responses to formalin injections given at different body sites in the rat?

Correlations between behavioural nociceptive responses to an injection of formalin solution in the hindpaw and upper lip were sought in 28 male rats divided into two groups. One group received a first injection in the hindpaw and 7 days later, a second one in the lip (paw-lip group). The injection order was reversed in the second group (lip-paw group). After each injection, the duration of lip rubbing for the orofacial formalin test, the duration of paw licking and the number of paw flinchings for the hindpaw test were measured. The Spearman test revealed no correlation between lip rubbing and paw flinching in either group but a significant correlation between lip rubbing and paw licking occurred in both groups.

Animals↗
PubMed1998

Evaluation of a dental benefit plan for children conducted in Auvergne, France, since 1992.

Usually, the French dental insurance system covers the cost of restorative treatment but does not reimburse the cost of preventive therapies. A French sick-fund covering self-employed persons tested a new dental benefit plan for children intended to provide an incentive to develop office-based preventive activities. The programme, which started in 1992, concerns all 4-year-old children of self-employed workers in a single French region (Auvergne). Participants undergo an annual examination by the dentist of their choice until their 15th birthday. If the child is seen every year, all services related to dental caries (preventive and restorative) are provided free of charge. An ongoing evaluation of the programme was necessary to determine its influence on the development of office-based preventive activities and the dental health of the participants. A cohort of children enrolled in the programme in 1992 was followed over 4 years to examine the patterns of service use. In addition, a cross-sectional study comparing the caries experience of all 8-year-old children participating continuously in the programme (test sample) with that of a sample of control children (n=90) was conducted in 1996. Data from the longitudinal follow-up indicate that 43.37% of the 551 children to whom the programme was offered in 1992 underwent an annual examination in the first year. Of the children enrolled in 1992, 55.2% were still participating in the programme in 1996. Results showed that independent practitioners continued to focus on restorative treatment rather than preventive therapy. Results from the cross-sectional study are in accordance with this trend. The number of caries-free children was identical in test and control samples and the mean dft, DMFT, DT and dt did not vary between the two groups (Student's t-test, P>0.05). However the mean number of filled teeth was significantly higher in the test children than in the controls (P<0.01). For children with caries, the mean dft was 23.5% greater in the test group than in the control group (P<0.05). In Auvergne, a large number of families were not ready to participate in a plan that required them to take their child to the dentist every year. There was not a perceived need for regular preventive dental care, an attitude probably reinforced by the interventionist approach undertaken by the dentists over the survey period. Moreover, the plan did not provide an incentive for dentists to develop office-based preventive activities.

Case-Control Studies↗
PubMed1998

A possible therapeutic solution for stomatodynia (burning mouth syndrome).

Stomatodynia is a difficult disease for both patients and clinicians. When facing true stomatodynia, i.e., idiopathic burning mouth, patients are offered poorly effective treatment. This open study reports the results of local application of clonazepam (0.5 or 1 mg) two or three times daily in 25 subjects who suffered from idiopathic stomatodynia. At the first evaluation, 4 weeks after the beginning of treatment, a visual analogue scale (VAS) that represented the intensity of pain decreased significantly from 6.2 +/- 0.3 to 3.0 +/- 0.5. At the second evaluation, 3 to 29 months after the first consultation, the VAS scores dropped significantly further to 2.6 +/- 0.5. Analysis of the individual results showed that 10 patients were totally cured and needed no further treatment, 6 patients had no benefit at all, and the remaining 9 patients had some improvement but were not considered to be cured since they did not wish to stop the treatment. Blood level tests that were performed 1 and 3 hours after the topical application revealed the presence of small amounts of the drug (3.3 ng/mL +/- 0.66 and 3.3 ng/mL +/- 0.52, respectively). The hypothesis that clonazepam acts locally to disrupt the neuropathologic mechanism that underlies stomatodynia is proposed. The risk factors that are recognized for this condition could decrease the density and/or ligand affinity of peripheral benzodiazepine receptors. This, in turn, could cause spontaneous pain from the tissues concerned.

Adult↗
PubMed1997

Effect of an NMDA receptor antagonist on the wind-up of neurons in the trigeminal oralis subnucleus.

Extracellular recordings of convergent neurons of the oralis subnucleus of the trigeminal sensory complex were performed in paralysed rats under halothane-N2O-O2 anesthesia using glass micropipettes. The effects of MK801, a noncompetitive NMDA receptor antagonist, were observed on the increased cell activity (wind-up), triggered by the repetition, at a low frequency (0.66 Hz) and high intensity (3 times the threshold of C-fiber response), of electrical stimulation of the receptive field. Successive cumulative doses (up to 1 mg/kg) of MK801 i.v. resulted in a dose-dependent decrease in the responses related to C-fiber input (11 cells). A single dose of 1 mg/kg applied in four cells had effects similar to the 1 mg/kg dose given cumulatively. Three units were either weakly or not modified by MK801. In a second experiment, recordings were performed in 12 cells for 80 min after an injection of a small dose of MK801 (0.15 mg/kg). C input was not significantly modified by the antagonist. The effects of MK801 on the first part of the wind-up response (wind-up proper) peaked between 15 and 50 min and returned to control values at about 80 min. The effects on the postdischarge followed approximately the same time course. It is concluded that despite being devoid of substantia gelatinosa, the oralis subnucleus contains neurons that display an NMDA receptor-linked wind-up similar to the phenomenon described in the dorsal horn of the spinal cord.

Action Potentials↗
PubMed1997

Effects of food texture and sample thickness on mandibular movement and hardness assessment during biting in man.

This study was designed to investigate the relationship among jaw movements, physical characteristics of food, and sensory perception of hardness in man. Vertical movements of the mandible were recorded with an infrared tracking device in humans during biting on two test foods, carrot and cheese. Samples of standard length (2 cm) and width (2 cm) were prepared in three different thicknesses (0.5, 1.0, and 1.5 cm). Nine subjects were asked to perform two types of bite with their incisor teeth. In the first, they cut through the food, then stopped and spat out the pieces (bite alone); in the second, biting was followed by mastication and swallowing (bite+chew). The 12 conditions (thickness x3, food x2, and bite x2) were presented in a random order within each block, and blocks were repeated five times (60 trials per subject). Subjects also estimated the hardness of the samples twice for each condition on visual analogue scales (VAS) 100 mm long. The duration, vertical amplitude, and maximum vertical velocity of the mandible during biting were calculated by computer for the three phases of the movements (opening, and fast and slow closing). Multilevel statistical models were used for data analysis. The estimated hardness scores associated with the first bite of thin carrot (59.0 VAS units) was significantly greater than for cheese (16.8 VAS units). The type of bite had no significant effect on these scores, but the estimate of hardness was significantly greater for the thickest sample (+13.3 VAS units). Food type had its strongest effect on the slow-closing phase. In particular, the peak velocity that followed the fracturing of the food sample was much greater for carrot than for cheese (thin, 34.1 mm.s-1 vs. 26.6 mm.s-1), and the difference between foods increased with thickness. The amplitude of opening was significantly greater for the thickest sample than for the other two. There were no significant relationships between VAS scores and the movement parameters. These results suggest that, when humans bite food: (1) changing the thickness of food has a greater effect on movement parameters than changing from soft to hard food, (2) the parameters of biting change little if biting is followed by mastication, (3) hardness perception is dependent on the thickness of food, (4) hardness perception is not different when food is removed from the mouth than when it is chewed and swallowed, and (5) there is no relationship between any of the parameters of movement that change with food type and the perceived hardness of food.

Adult↗
PubMed1996

Effects of systemic morphine on the activity of convergent neurons of spinal trigeminal nucleus oralis in the rat.

The spinal trigeminal nucleus oralis has been shown to relay nociceptive inputs mainly from the oral and perioral regions. In this study, we examined the effects of intravenous administration of morphine on C-fiber-evoked activities of spinal trigeminal nucleus oralis convergent neurons in halothane-anesthetized rats. Morphine depressed the C-fiber-evoked responses of spinal trigeminal nucleus oralis convergent neurons in a dose-related (3-12 mg/kg range) and naloxone-reversible fashion. The ED50 was 6.1 mg/kg, a dose similar to that found in the spinal horn. The observed strong depressive action of morphine on noxious-evoked activities of spinal trigeminal nucleus oralis neurons is consistent with our previous statement, based on electrophysiological studies, that this region plays an important role in the transmission of trigeminal nociceptive information. The effect of morphine on the spinal trigeminal nucleus oralis neurons is discussed in relation to its possible site and mechanism of action.

Animals↗
PubMed1996

Effects of morphine microinjections into the trigeminal sensory complex on the formalin test in the rat.

The aim of this study was to find out whether morphine locally applied into the different subnuclei of the spinal trigeminal nucleus could impair the behavioral response evoked by a tonic nociceptive stimulus. Microinjections of morphine were performed unilaterally in rats through a chronically implanted tube. The duration of the formalin-induced biphasic rubbing activity was used as a measure of nociception. Morphine, 0, 2, 7, or 14 microg, in 0.2 microl of saline were microinjected 10 min before a subcutaneous injection of formalin (1.5%) in the ipsilateral upper lip. Morphine microinjections into subnucleus oralis (Sp5O) and subnucleus caudalis (Sp5C) induced a significant decrease in rubbing duration of either the early or late phase of the response or both. The early response to formalin was depressed only after morphine injection into Sp5O. The late response was depressed by microinjections into both Sp5O and Sp5C. No significant effect was observed in subnucleus interpolaris (Sp5I). These results are further evidence for the role played by Sp5C in orofacial nociception. They also give support to the involvement of the Sp5O in perioral nociceptive mechanisms of short duration.

Analgesics, Opioid↗
PubMed1995

Enhanced nociceptive behaviour following conditioning injection of formalin in the perioral area of the rat.

The possible existence of long-term modifications in response to a transient nociceptive conditioning stimulation was investigated in the rat in three experiments. (1) A nociceptive conditioning stimulus was delivered in the form of a s.c. formalin injection (conditioning injection) in the left upper lip. Evaluation of the nociceptive behaviour triggered by another formalin injection (testing injection) made in the controlateral right upper lip was carried out in distinct groups of rats 7, 14 or 28 days after the conditioning. An enhanced nociceptive response at day 7 and 14 and a return to the baseline at day 28 were observed. (2) A similar protocol was developed with formalin used for both conditioning and testing but an anaesthetic blockade of the infraorbital nerve was performed just before the conditioning injection to suppress the initial barrage. The change observed at day 7 was suppressed by the nerve block. (3) A conditioning nociceptive stimulus was applied either ipsilaterally to the right lower lip or to the tail. An increased nociceptive response was observed when the conditioning stimulus was applied to the same side as the test stimulus but no increase in the formalin test response was detected when the conditioning stimulus was applied to the tail. These results indicated that, after a single formalin injection in the left upper lip, a hyperexcitability developed that depended on the initial barrage, lasted for at least 2 weeks, was no longer present at 4 weeks and might rely on a segmental mechanism. The hypothesis of a central sensitization triggered by an initial barrage and maintained by an ongoing input induced from the periphery is discussed.

Animals↗
PubMed1995

Antinociceptive effect of morphine microinjections into the spinal trigeminal subnucleus oralis.

We analysed the effects of morphine microinjections (0.2 microliter) into the subnucleus oralis (SNO), i.e. the rostral division of the spinal trigeminal nucleus, on the formalin test adapted for orofacial pain. Duration of rubbing following an injection (50 microliters) of formalin solution (1.5%) in the right upper lip of the rat was measured. Compared to microinjections of saline (NaCl, 0.9%) used as control, 90 and 180 nmol microliter-1 of morphine solution in the SNO significantly curtailed rubbing. This effect was dose-dependent, reversed by naloxone, and also site-specific to the SNO since no effect was observed after microinjection of morphine into areas adjacent to the SNO. These results are further evidence for the involvement of the SNO in perioral nociceptive mechanisms.

Animals↗
PubMed1995

Effects of subcutaneous formalin on the activity of trigeminal brain stem nociceptive neurones in the rat.

1. The subcutaneous injection of Formalin (5%, 50 microliters) into the receptive field of convergent (wide dynamic range) nociceptive neurons in the spinal dorsal horn has previously been reported to produce a prolonged biphasic response with a time course similar to the observed in behavioral experiments. However, conflicting data in other studies led us to examine the effects of Formalin on the activity of convergent nociceptive neurons at two levels of the trigeminal (V) brain stem complex, namely V subnuclei oralis (Sp5O) and caudalis (Sp5C). 2. Single neuron activity was extracellularly recorded in anesthetized rats. Each neuron was classified as convergent on the basis of its responses to both mechanical and transcutaneous electrical stimuli applied to its mechanoreceptive field (RF). All neurons responded to innocuous and noxious mechanical stimuli and had electrically evoked responses corresponding to both A and C fiber afferent inputs. Seventeen Sp5O and 32 Sp5C convergent neurons received an injection (50 microliters sc) of 5% Formalin into the center of their RF. 3. Three groups of neurons were distinguished: one group that was not activated by the Formalin injection (Sp5O, n = 1; Sp5C, n = 2), another group that responded only with an early and short-lasting response [monophasic neurons: Sp5O, n = 11 (65%); Sp5C, n = 10 (31%)], and a third group that responded with two phases separated by a short period of quiescence [biphasic neurons: Sp5O, n = 5 (29%); Sp5C, n = 20 (62.5%)]. The proportion of biphasic neurons was significantly higher in Sp5C than in Sp5O. 4. The first phases of the Sp5O neurons were not significantly different in terms of duration and frequency from those of the Sp5C neurons. However, duration and discharge frequency of the first phase of biphasic neurons were significantly greater than for monophasic neurons in Sp5C (nonsignificant in Sp5O). The second tonic period of excitation of all biphasic neurons was gradual in outset and offset, and long in duration (23-39 min). The duration of the second phase was significantly longer for the biphasic neurons in Sp5C than for those in Sp5O. 5. Our findings suggest that the mono- and biphasic neurons may have different roles in the transmission of nociceptive information induced by the peripheral injection of Formalin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Biometric analysis of tooth migration after approximal contact removal in the rat.

Nineteen 8-week-old female Sprague-Dawley rats were used to observe macroscopically the direction of tooth movements following removal of approximal contacts. In 10 rats, under anaesthesia, approximal contact between the second and third right maxillary molars (M2-M3) was removed by grinding. These animals and a control group of nine rats were housed with normal diet and water ad libitum for 7 weeks. After killing, the skulls of all animals were removed, dried, and fixed in a standardized position on a Horsley-Clarke type stereotaxic frame. Using a micromanipulator graduated to 1/100 mm and mobile in three orthogonal directions, distances between the teeth (M1 or M3) and some bone structures that served as landmarks were measured. These measurements showed the direction of tooth movements in the experimental approximal space. After statistical analysis of the data, the results showed that the approximal space between M2 and M3 was closed by both a distal drift of M1-M2 and a mesial migration of M3. It was concluded that, in the rat, a mesial drift exists that can be induced by the loss of approximal contact. This movement is distinct from the distal physiological dental migration classically described in histological studies.

Animals↗
PubMed1993

Sustained hyperalgesia can be induced in the rat by a single formalin injection and depends on the initial nociceptive inputs.

The present study was undertaken to find out if a hyperalgesia can be observed 1 week after a conditioning stimulation of the orofacial area of the rat. Sprague-Dawley rats received a left infraorbital infiltration with either bupivacaine or saline and then, 30 min thereafter, an injection of either saline or 10% formalin solution in the left upper lip. Four groups of animals were thus made up depending on their conditioning treatment. Seven days later, an algesimetric test initiated by a contralateral orofacial formalin injection was carried out. The duration of lip rubbing was significantly increased in formalin-conditioned groups. The hyperalgesia observed at 7 days was suppressed by an infraorbital nerve block carried out at the time of the conditioning stimulus. These results tend to indicate that a nociceptive message of short duration induces a trace in the central nervous system which can be retained for 1 week.

Analysis of Variance↗
PubMed1993

A biometric analysis in the rat of the horizontal component of physiological tooth migration and its response to altered occlusal function.

The direction and amplitude of physiological tooth migration, as well as the influence of occlusal force on this movement, were evaluated macroscopically in the rat by biometric means. The first experiment, which compared the position of the teeth in the anteroposterior plane of the maxilla between two groups of 20 and 28 rats killed at age 15 and 52 weeks, respectively, confirmed the distal direction of this drift. In a second experiment, after suppression of the antagonist occlusal contacts of the maxillary left dental hemiarch in nine rats, the migration of this hemiarch was compared to that of the hyperfunctional contralateral hemiarch and to that of the molars in a control group of 20 rats. A statistically significant (t-test) reduction of the physiological migration in the absence of occlusion, was revealed.

Animals↗
PubMed1993

Cholescintigraphy in the diagnosis of acute cholecystitis: morphine augmentation is superior to delayed imaging.

Morphine-augmented radionuclide hepatobiliary imaging has been used as an alternative to delayed imaging for the diagnosis of acute cholecystitis. Previous studies have indicated that the morphine-augmentation is as useful as, or more useful than, delayed imaging. A careful comparison of the efficacy of the two techniques appears warranted because: (1) most early studies did not compare the efficacy of the two techniques in a single report using comparable patient populations; (2) the reported efficacy of morphine-augmentation is based primarily on study designs which excluded cases of early gallbladder visualization without morphine, while most delayed imaging protocols included these cases; and (3) there were concerns about the potential consequences of a false-negative morphine examination. This study compared the efficacy of morphine-augmentation with delayed imaging in those cases in which the gallbladder was not visualized during the first hour of study. Of 306 consecutive patients who were scanned to rule out acute cholecystitis, the gallbladder was visualized within 1 hr in 215 cases. In the remaining 91 cases, 46 patients had delayed imaging (17 true-positive, 10 true-negative, 19 false-positive and 0 false-negative), and 45 had morphine-augmentation (24 true-positive, 15 true-negative, 4 false-positive and 2 false-negative). The data indicate that delayed imaging has a significantly lower specificity and positive-predictive value for acute cholecystitis than morphine-augmentation and a slightly higher (statistically insignificant) sensitivity and negative-predictive value. These results appear to be supported by a reanalysis of the data that has already been reported in the literature.

Acute Disease↗
PubMed1992

Intrathecal midazolam versus intrathecal morphine in orofacial nociception: an experimental study in rats.

The antinociceptive properties of intrathecal midazolam (15 and 30 micrograms) and intrathecal morphine (30 micrograms) were compared using an adaptation of the formalin test to the orofacial region in rats. Both midazolam and morphine were effective in reducing the nociceptive response of the second phase of this biphasic pain test. Only midazolam (30 micrograms) reduced also the first phase. These results confirm the existence of analgesic properties of midazolam in the case of long-lasting pain.

Animals↗
PubMed1992

Masseteric facilitation induced by electrical stimulation of rat orofacial tissues.

The effects of a conditioning electrical shock applied to the periodontium of the lower incisor or the glabrous area of the lower lip on the jaw-closing reflex in the anesthetized, non-paralysed rat were studied. The masseteric reflex was triggered by stimulation of the mesencephalic nucleus as a test shock and was recorded from the masseter muscle. There was facilitation of the jaw-jerk reflex, which culminated at an interval of 10-15 ms between the conditioning and the test shocks. This facilitation was not suppressed by digastric excision or by blocking a possible rebound closing reflex evoked by jaw opening. No inhibitory influence was observed. This facilitatory effects relies on an A alpha input and on cell bodies making up the mesencephalic nucleus. The direct excitatory electrical events observed in the masseter muscle after periodontal or labial stimulation proved to be due to the diffusion of the bioelectrical activity generated in the neighbouring jaw-opening muscles.

Animals↗