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Biomedical subjects

A Woda

Publications and source records attributed to A Woda.

At least 73 records · Page 4Linked to original sources
PubMed1987

[Participation of the rostral portion of the spinal nucleus of the trigeminal sensory complex in nociception].

Single unit responses elicited through noxious mechanical stimulation of orofacial receptive fields were recorded, with glass micro-electrodes, within the rat ventrobasal complex of the thalamus. The evoked activities were compared before and after de-afferentation of the caudal sub-nucleus by trigeminal tractotomy at the level of the obex. Only units responding to noxious stimulation of oral receptive fields were unaffected by tractotomy. These results provide evidence that the rostral part of the spinal nucleus is involved in trigeminal painful sensation.

Animals↗
PubMed1987

[Analysis of mandibular movements in present-day humans by examination of the striae found on the facets of wear].

The analysis of the microscopic appearance of the dental wear facets in contemporary european subjects has been conducted using the replica method. It showed the presence of numerous striae running in various directions. The angle of each stria with the sagittal plane was measured: 1540 angle values were recorded on 6 facet types belonging to 3 groups of teeth. Statistical analysis showed that the striae distribution on the various facets studied was not random. The facets of the palatal edges and facets of the upper central incisors showed mainly parasagittal striae indicating propelling movements. The striae of the wear facets of the canine tips showed no definite direction. The palatal facets of canines as well as the working and non-working facets of the molars showed 2 groups of striae oriented obliquely, forward and inside and also forward and outside. The molar working facets also had parasagittal striae. The significance of the 2 groups of oblique striae is discussed in relation to the occlusal kinematic during mastication.

Adult↗
PubMed1986

Effects, in the rat, of various stressing procedures on the jaw-opening reflex induced by tooth-pulp stimulation.

Jaw-opening reflex (JOR) induced by a repetitive tooth-pulp stimulation delivered at 1 Hz was observed in awake, freely-moving rats. Modifications of the reflex responses of the digastric muscle were produced by foot-shock stimulation, by an oesophageal administration of placebo and a subcutaneous injection of saline. Subcutaneous injection of saline evoked a total disappearance of the reflex which returned within 30 s. Foot shock delivered for 10 s and repeated twice a minute for 30 min of intensity, just below the vocalization threshold, evoked a marked decrease of the reflex to 60 +/- 6 per cent of the control value (n = 10). Administration of arabic gum by oesophageal tube gave either: the same transient disappearance as for the subcutaneous injection in 6 rats; a progressive 28 min +/- 11 (n = 6) return to the initial value; a progressive return to a subcontrol value of 52 +/- 4 per cent (n = 7). The application of two successive stimuli resulted in a more pronounced JOR decrease. The response to electrical foot shock can be explained by a central analgesia induced by stress.

Animals↗
PubMed1986

Is electrical stimulation of the rat incisor an appropriate experimental nociceptive stimulus?

The purpose of this study was to determine whether or not tooth pulp stimulation in the rat can selectively activate the pulp nerve fibers without excitation of the periodontium and to decide if the nerve fibers situated in the pulp of the rat's incisor are involved in the nociceptive reactions caused by an intrapulpal stimulation. The experiments were carried out on 20 awake and freely moving Sprague-Dawley rats. Bipolar stimulating electrodes were inserted into the pulp of the left lower incisor and in the right incisor after removal of the pulp. Special cares were taken to avoid, on the right side, direct stimulation of the stump of the apical nerve. The jaw opening reflexes were recorded from the digastric muscles ipsilaterally to the stimulated teeth and the thresholds were compared. Using the same animals, four typical and reproducible nociceptive behavioral reactions caused by a long tooth pulp stimulation were also observed (shock of 0.5 ms at 50 Hz during 1 s). The stimulus intensity was progressively increased, and the threshold of each reaction was recorded. For each of the 20 rats tested, the jaw opening reflex and the nociceptive reactions did not disappear after removal of the pulp, but the threshold of the responses to the stimulation of the nonvital tooth were significantly above the threshold of the responses to the stimulation of the vital incisor. The conclusion was tooth pulp stimulation activates the periodontal nerve fibers in the rat, and stimulation of the incisor pulp is significant in pain study in the rat because the thresholds of the jaw opening reflex and the nociceptive reactions were increased after the tooth pulp tissue was removed.

Animals↗
PubMed1984

Variations of the jaw opening reflex observed in awake, freely moving rats.

Long term variations of the jaw opening reflex (J.O.R.) induced by tooth pulp stimulation (T.P.S.) have been investigated in the awake, freely moving rat. This study was specially centered on variations which could occur during the utilization of the J.O.R. as a test for analgesic drugs. Bipolar electrodes were implanted in the inferior incisor tooth pulp for stimulation and in digastric muscle for recording. J.O.R. recordings were subsequently integrated. Long term variations of J.O.R. were then observed during uninterrupted T.P.S. (1 Hz) alone or during subcutaneous (s.c.) injection, gavage or foot shock in addition to T.P.S.: --8 out of a total of 24 rats, observed during long uninterrupted T.P.S., showed a decrease of the J.O.R. The mean of reflex values, 15 min later, was 74 +/- 6% (n = 8) of the prestimulation level; --s.c. injection of saline, light handling, experimentator's brisk irruption, or sudden noise evoked a total disappearance of the reflex which completely returned within 30 sec; --gavage of arabic gum syrup gave either: . the same transient disappearance as for the s.c. injection in 6 rats; . a progressive, 28 min +/- 11 (n = 6), return to the initial value; . a progressive return to a subcontrol value of 52 +/- 4% (n = 7); --a 30 min foot shock delivered for 10 sec twice a minute at the infra-vocalization threshold evoked a marked decrease of the reflex reaching to 68 +/- 6% (n = 10) of the control (prestimulation level).

Analgesia↗
PubMed1983

The properties of cells in the cat trigeminal main sensory and spinal subnuclei activated by mechanical stimulation of the periodontium.

Neurophysiological exploration of the trigeminal sensory complex was done on 42 cats under ketamine anaesthesia, paying special attention to units receiving a periodontal input. Among 492 cells recorded in the trigeminal sensory complex, 73 responded to mechanical stimulation of the periodontium and were precisely localized histologically. Thalamic stimulation was also delivered to the ipsi and contralateral ventro-posterior nucleus to test for antidromic responses. Results of this systematic study were plotted on reference drawings of the full extent of the trigeminal sensory complex.

Animals↗
PubMed1982

Physiological Properties of neurons in different parts of the cat trigeminal sensory complex.

The following points emerge from a systematic investigation of the 4 divisions of the cat trigeminal sensory complex. (1) The subnucleus oralis receives a large representation from the oral cavity, a region also represented in the 3 other divisions of the trigeminal sensory complex. (2) Nucleus principalis cells project heavily to the contralateral and to the ipsilateral ventroposterior thalamus. Ipsilateral projections are only from the oral cavity representation. (3) Units responding to noxious mechanical stimulation have been found at two different loci: the subnucleus caudalis for the entire trigeminal area, and subnucleus oralis for the oral cavity alone. (4) The dental pulp projects to the 4 divisions of the trigeminal sensory complex, but the heaviest projection was found in the rostral part (nucleus principalis and subnucleus oralis). (5) Three distinct types of post-synaptic responses were found to be evoked by dental pulp stimulation: (a) short latency, consistent and synaptically secure, (b) strongly variable latency, inconstant and easily fatigued and (c) a class showing progressive enhancement by progressive increase in stimulus intensity and repetition.

Animals↗
PubMed1979

Nonfunctional and functional occlusal contacts: a review of the literature.

A review of the literature on occlusal contacts emphasizes the following points. 1. Contacts in centric occlusion do not correspond to any ideal occlusal diagram. 2. Canine protection and group function appear to correspond to two successive states of the evolving dentition under the effect of abrasion. In most lateral occlusions, two maxillary teeth, of which one is the canine, are involved. 3. During mastication, tooth contacts exist. They occur most often during a sliding movement in which the direction and the origin are variable. This justifies the concept of an occlusal field of mastication. 4. During unilateral mastication, the chewing of the food is performed by working as well as nonworking contact. This imposes the distinction between the chewing and nonchewing sides (functional) and the working and nonworking sides (kinematic). 5. Centric occlusion is the occlusion most often used during mastication. It is also the occlusion for which the masticatory forces are the greatest. 6. The bibliographic data concerning occlusal contracts during swallowing are largely contradictory. It nevertheless seems that the occlusal contacts obey laws nearly the same as those governing the occlusal contact during mastication (sliding on an occlusal field of deglutition, and the importance of centric occlusion).

Deglutition↗
PubMed1977

[Identification using glass microelectrodes of the activities recorded in the neighborhood of axons and cell bodies of the trigeminal sensory complex].

Using glass micropipettes unitary activities were recorded at the level of the trigeminal sensory complex. Iontophoresis of pontamine blue allowed us to localise the recording loci. Two types of spikes were observed, they were distinguished on the basis of their shape: one corresponds to an axon spike, the other to a cell body spike.

Action Potentials↗
PubMed1977

Sensation evoked by bipolar intrapulpal stimulation in man.

Bipolar intrapulpal stimulation was applied to human teeth using the same procedure as in animal experiments. The effects of variation of stimulus parameters on the quality of sensation were studied. A prepain sensation exists which cannot be explained by diffusion of the stimulus to periodontal tissues. When the intensity of stimulation is increased, the prepain sensation is gradually replaced by a pinprick sensation. With long, high intensity stimulation, an acute long lasting very painful sensation appears. To evoke a pinprick sensation the best stimulation seems to be a 50 msec train (0.5 msec, 300 Hz, 0.5 mA). Longer train duration and a higher intensity of current are necessary to evoke a long lasting, acute very painful sensation. Since the exclusively Adelta and C nerve fiber content of the dental pulp is well documented and since it is possible to avoid current diffusion outside the dental pulp cavity, the tooth pulp implantation seems to be a good technic for studying pain, as long as the investigator uses adequate stimulation.

Dental Pulp↗
PubMed1977

Mapping of the trigeminal sensory complex of the cat. Characterization of its neurons by stimulations of peripheral field, dental pulp afferents and thalamic projections.

From a new systematic investigation of the 4 divisions of the trigeminal sensory complex, the following points are emphasized: 1. The subnucleus oralis receives a large representation from the oral cavity, a region also represented in the three other divisions of the trigeminal sensory complex. 2. Units responding to noxious mechanical stimulation have been found in two different loci: the subnucleus caudalis for the whole trigeminal area, and the subnucleus oralis for the oral cavity. 3. The dental pulp projects to the four divisions of the trigeminal sensory complex, but the heaviest projection is found in its rostral part (the main nucleus and subnucleus oralis). 4. Three distinct types of responses were found following dental pulp stimulation: primary, non primary and responses strongly enhanced by an increase in stimulus parameters.

Animals↗
PubMed1977

Thalamic and mid-brain responses to dental pulp afferent messages in awake cats.

1. Central projections of messages evoked by dental pulp stimulation have been searched for in awake cats and recorded at unitary level. A head-top frame screwed to the skull served to fix the animal in the stereotaxic instrument precisely and in the usual orientation. 2. Three types of responses could be distinguished, each with characteristic thalamic localization: --one was of the specific type: it occurred at short latency, followed rapid rates of stimulation, and was localized in VPM and SG; --a second type had longer latency, did not follow rapid rates of stimulation, was frequently bilateral, and was localized in VPM, CM-Pf and Posterior Group; --the third type was a complex response, exhibiting inhibitory and excitatory phases; extremely labile, it disappeared during wakefulness; it was found in LP and CM-Pf. 3. The responses elicited by dental pulp stimulation and recorded in the periaqueductal grey matter mostly originated from face muscle messages provoked by the jaw opening reflex. 4. The possible contributions to pain perception made by each of the different thalamic responses is discussed, as well as the adequacy of dental pulp stimulation for producing a purely nociceptive signal.

Action Potentials↗
PubMed1976

Tooth pulp projection to the trigeminal complex and jaw opening reflex in the cat.

The J.O.R. elecitied by pulpal, palatal or periodontal stimulations was recorded on the cat digastric nerve. As shown by the frontal sections of the brain stem the caudal subnucleus is not directly involved in this reflex. However after exclusion of the more rostral part of the interpolar subnucleus the pulpal induced J.O.R. is abolished although the palatal or periodontal induced J.O.R. is only partially suppressed.

Animals↗