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Biomedical subjects

A Woda

Publications and source records attributed to A Woda.

At least 55 records · Page 3Linked to original sources
PubMed1992

Stimulation of craniofacial muscle afferents induces prolonged facilitatory effects in trigeminal nociceptive brain-stem neurones.

Stimulation of small-diameter afferents supplying deep tissues has been shown to increase the excitability of spinal cord neurones responding to cutaneous afferent inputs. This facilitation has been implicated as integral central mechanisms of deep pain that may contribute to the tenderness and spread and/or referral of pain following injury of deep tissues. In view of the recent documentation of deep craniofacial afferent inputs, as well as cutaneous afferent inputs to the trigeminal (V) spinal tract nucleus, we wished to determine the effects of deep inputs excited by the small-fibre irritant mustard oil on trigeminal nociceptive neurones. The extracellular activity of single brain-stem neurones was recorded in subnuclei caudalis and oralis of the V spinal tract nucleus of anaesthetized rats. The neurones were classified as low-threshold mechanosensitive (LTM), wide dynamic range (WDR) and nociceptive specific (NS) on the basis of their cutaneous mechanoreceptive field properties and their responses evoked by electrical stimulation of their cutaneous afferent inputs. Injection of 5% mustard oil (2-5 microliters) into the deep masseter muscle produced a facilitatory effect in 12 of 27 nociceptive neurones tested in caudalis and in 5 of 12 nociceptive neurones in oralis. This effect was reflected in an expansion of the cutaneous mechanoreceptive field, an increase in spontaneous activity or an increase in responsivity to electrical stimulation of cutaneous afferent inputs to the neurones. The facilitation was reversible and typically became apparent within 3-5 min of the injection, reached its peak at 5-10 min, and lasted for 20-30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1991

Oral nociceptive activity in the rat superior colliculus.

Single units were recorded using extracellular glass microelectrodes in all laminae of the superior colliculus of the rat under halothane nitrous oxide anaesthesia. Fifty-one units were encountered which responded to a low intensity mechanical stimulus applied to a contralateral or bilateral field located in the oral sphere (intraoral 11, perioral 16), on the face (29) or on the rest of the body (21). Sixteen units responded to a jaw movement. Sixty-one cells were recorded which were preferentially (10) or only (51) activated (30) or inhibited (21) by noxious stimuli. Contralateral or bilateral mechanoreceptive fields located in intraoral (34) and perioral (35) areas were frequent. There is therefore a high incidence of the nociceptive representation of the mouth in the superior colliculus. The other functional properties of the nociceptive units were similar to those reported in other studies. From the subsequent histological localization of the recorded units, it appeared that the nociceptive projections from the intraoral and perioral regions to the superior colliculus reach the lateral part of the intermediate and deep layers of the superior colliculus.

Anesthesia↗
PubMed1991

Responses of trigeminal subnucleus oralis nociceptive neurones to subcutaneous formalin in the rat.

Extracellular recordings of 33 single nociceptive neurones of the trigeminal subnucleus oralis (SNO) were made in rats under halothane nitrous oxide anaesthesia. These neurones were tested for their responses to a s.c. injection of formalin in their receptive field. Such a chemical noxious stimulation is known to induce a biphasic response of nociceptive dorsal horn neurones, the second period of which would be due to inflammation. Twenty-three neurones were characterized as nociceptive non-specific (NnS) and 10 as nociceptive specific neurones (NS). Formalin activated both SNO NS and NnS neurones, but, when they responded, NS neurones (n = 5) showed only the first phase of activity while NnS neurones showed either one (n = 13) or two phases (n = 6). Biphasic responses were most often observed for NnS neurones with A delta- and C-fibre inputs. These results indicate that the time-course similarity between the behavioural and the neuronal responses to formalin exists only for some SNO convergent neurones and that therefore the SNO does not seem to be very involved in the inflammatory component of the pain caused by formalin.

Animals↗
PubMed1991

A study of human jaw movements deduced from scratches on occlusal wear facets.

In a previous investigation, scratches on tooth wear facets provided information about functional movements of the mandible in the occlusal range. Depending on the type of facet observed, two or three main directions were found. The aim now was to answer two questions: (1) how long does it take for a newly formed scratch to disappear? and (2) do the observed orientations of the scratches change over a long period of time? Eleven wear facets from lower first molars were analysed in four subjects with good natural dentition. Scratches recorded on cellulose replicas were observed under an interference microscope. The same wear facets were recorded one, two, three and six months later. From the photographs of the replicas, a sample of scratches was selected at random and their direction was measured. In the first part of the study, scratches absent at the time of the first observation appeared one month later; 87% of the new scratches had disappeared after one month. Ninety-six percent of the same group of scratches had disappeared after two months. In the second part of the study the angle made by each scratch with the sagittal plane was recorded. It was found that: (1) jaw movements in their occlusal phase can take any possible direction and (2) the distribution of the observed scratches was not random; preferential orientations exist and those present on the working facets are different from those on the non-working facets. Similar orientations were identified 6 months later.

Adult↗
PubMed1991

Supraeruption of the unopposed maxillary first molar.

Supraeruption of the maxillary first molar in the absence of the mandibular first molar was observed in subjects with both normal and pathologic periodontics. Both the migration of the gingival margin and the increase in the crown height were evaluated in terms of the length of time the antagonist tooth had been missing. Values obtained were compared with those of a reference group with complete normal dentitions. The results show that in the first years following the loss of the opposing tooth, supraeruption is mainly due to growth of the periodontium. Later or in the case of periodontal pathosis, tooth movement beyond the occlusal plane is due principally to active eruption.

Adolescent↗
PubMed1991

An evaluation of four methods of root canal preparation using 14C urea.

One-hundred twenty single-rooted teeth were used in vitro in order to compare the four following methods of endodontic preparation: manual, Giromatic, MM 3000 Sonic Air with, and sonic air without the contact shaping technique. Each endodontic preparation was filled according to the McSpadden technique. Teeth were immersed in 14C urea. Radioactivity was evaluated qualitatively by autoradiography and quantitatively by scintigraphy. Data were statistically analyzed with a nonparametric test. The results show that the highest degree of leakage occurs with the manual method and that for the three other methods, maximum leakage takes place near the apices.

Dental Leakage↗
PubMed1991

Clinical evaluation of the accuracy of the Evident RCM Mark II Apex Locator.

The accuracy of the Evident RCM Mark II in locating the apical foramen was evaluated in 37 human teeth scheduled for extraction. After extraction, the difference between the position of the apical foramen determined electronically and its real anatomical location was measured under a binocular microscope, using a micrometer mobile in x, y, and z coordinates. The results show that in 86% (n = 37) of the cases, an accurate location +/- 0.5 mm of the apical foramen was obtained.

Adolescent↗
PubMed1990

Demonstration with [14C]2-deoxyglucose of brain structures involved in the masticatory activity of the hedgehog (Erinaceus europaeus).

The different brain structures activated during mastication in the hedgehog were revealed using Sokoloff's 2-deoxy-D-[1-14C]glucose technique. Brain sections of animals having received an injection of 2-deoxy-D-[1-14C]glucose during mastication were compared with those of animals treated during calm waking. Only brain structures that presented a 20% increase in glucose consumption were considered. The greatest increases were observed in the bulbar parvocellular reticulum and the trigeminal spinal nucleus (+80%), followed by structures also involved in mastication such as the trigeminal motor nucleus (+73%) and the hypoglossal nucleus (+64%). Other activated areas, not directly involved in mastication, were for example, the area postrema (55%), the olfactory (44%) and visual cortex (41%). This study emphasizes the importance of the bulbar parvocellular reticulum during mastication.

Animals↗
PubMed1990

Properties of nociceptive and non-nociceptive neurons in trigeminal subnucleus oralis of the rat.

Recent studies have provided evidence suggesting the involvement of rostral components of the V brainstem complex such as trigeminal (V) subnucleus oralis in orofacial pain mechanisms. Since there has been no detailed investigation of the possible existence of nociceptive oralis neurons in the rat to substantiate this recent evidence, the present study was initiated to determine if neurons responsive to noxious orofacial stimuli were present in subnucleus oralis and to characterize their functional properties. In anesthetized rats, recordings were made of the extracellular activity of single neurons functionally characterized as low-threshold mechanoreceptive (LTM), wide dynamic range (WDR) or nociceptive-specific (NS) neurons. The 342 LTM neurons responded only to light mechanical stimulation of orofacial tissues. The mechanoreceptive field of the LTM neurons included the intraoral region in 28% and was localized to the adjacent perioral area in 65%. For 95% the field was localized within one V division. Responses evoked in LTM neurons by electrical stimulation of the orofacial mechanoreceptive field revealed A fiber afferent inputs but no activity that could be attributed to C fiber afferent inputs. The 72 nociceptive neurons included 52 WDR neurons which responded to light (e.g. tactile) as well as noxious (e.g. heavy pressure; pinch) mechanical stimulation of perioral cutaneous and intraoral structures, and 20 NS neurons which responded exclusively to noxious mechanical stimuli. They also differed from the LTM neurons in that 36% of the WDR and 20% of the NS neurons had a mechanoreceptive field involving more than one V division. However, in accordance with our findings for the LTM neurons, the majority of WDR and NS neurons had a mechanoreceptive field involving the intraoral and perioral representations of the mandibular and/or maxillary divisions; those neurons having a mandibular field which especially included intraoral structures predominated in the dorsomedial zone of subnucleus oralis whereas those with a perioral mechanoreceptive field which particularly involved the maxillary division were concentrated in the ventrolateral zone of oralis. In contrast to the LTM neurons, 57% of the WDR and 67% of the NS neurons showed evidence of electrically evoked C fiber as well as A fiber afferent inputs from their mechanoreceptive field. We also noted suppression of the electrically evoked responses by heating of the tail or pinching of the paw. This effect was considered to be a reflection of diffuse noxious inhibitory controls, and was seen in NS as well as WDR neurons; most, but not all, of these neurons received A fiber as well as C fiber orofacial afferent inputs.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1990

Analysis of tooth movement into an extraction space in the rat.

The purpose of this study was to evaluate the amplitude, direction and nature (translation or rotation) of the movements of teeth bordering an extraction site. Two experimental approaches were used. In one series of experiments, second maxillary molars were removed in 10 anaesthetized rats. To allow precise measurements of tooth movement into the extraction space, small cavities were drilled in the proximal surfaces of the first and third molars facing the gap. An elastomer impression was taken and the distance between the two cavities was recorded. This measurement was repeated 1, 2 and 3 months later. After killing the rats, the skulls were dried. The direction of movement was observed on occlusal photographs, and lateral X-rays were used to evaluate the nature of the drift (translation or rotation) observed. To evaluate the impact of occlusal forces on the tooth movements, a second experimental system was used in which the antagonistic occlusal contacts on the test side were removed (12 rats). In the first experiments, the average reduction of the extraction gap was 40.7 +/- 1.8% of the initial value, and in the second experiment, 44.7 +/- 3.3%. In both experimental systems the movement was derived largely from a mesial drift of the third molar, and its rate decreased with time. Furthermore, the drift of the third molar comprised one-third rotation and two-thirds translation. Student's t-test showed no influence of occlusal forces on the tooth movements.

Analysis of Variance↗
PubMed1989

Responses of neurones in the ventrobasal complex of the thalamus to orofacial noxious stimulation after large trigeminal tractotomy.

Single units were recorded, using extra-cellular glass microelectrodes, in the ventrobasal complex of the thalamus of rats under halothanenitrous oxide anaesthesia. The animals had previously undergone a large bilateral section of the trigeminal sensory complex just above the obex to deprive the caudal part of the trigeminal sensory complex (subnucleus caudalis) of its trigeminal afferents. As observed on frontal slices our lesions impaired the whole descending tract and, in most cases, the intratrigeminal pathways between the rostral and the caudal part of the complex. Forty-seven units responding to a somatic mechanical noxious stimulation applied to the trigeminal area were recorded in these conditions. Forty-two of these had a receptive field (or at least a part of it) in or around the oral and nasal cavities, and 5 in the peripheral part of the face. These data confirm the hypothesis that the rostral part of the trigeminal sensory complex participates in pain sensory pathways, as a first relay site between nociceptive primary afferents coming from oral, perioral and perinasal areas, and the ventrobasal complex of the thalamus. In addition, they suggest that the intratrigeminal pathways are not essential for the transmission of these nociceptive inputs, to the lateral thalamus.

Action Potentials↗
PubMed1989

Effects of tractotomy on nociceptive reactions induced by tooth pulp stimulation in the rat.

The effects of a trigeminal tractotomy on nociceptive reactions induced by electrical stimulation of an inferior incisor were studied in freely moving rats. Behavioral tests were based on the observation of three reactions: jaw opening reflex, face scratching with forepaws, and head rotation toward the stimulated side. These reactions appear successively when the stimulation intensity increases. The results were evaluated by comparing a test group with a sham-operated group. Both groups were prepared surgically in the same way but only the former had undergone tractotomy. The results were as follows: The threshold of the jaw opening reflex triggered by stimulation of the tooth pulp ipsilateral to the tractotomy was not modified; however, the threshold of the face-scratching and the head rotation reactions rose (P less than or equal to 0.05) after tractotomy. These data suggest that the rostral part of the trigeminal sensory complex is involved in oral nociception. However, the modification of the face-scratching and head rotation thresholds reveals that the subnucleus caudalis also participates in this function when a certain level of pain is reached. The thresholds of the three nociceptive reactions evoked by stimulation of the contralateral tooth pulp were significantly lower in the test group than those in the sham-operated group (P less than or equal to 0.001), which is interpreted as being indicative of an modulating effect of the subnucleus caudalis on the contralateral trigeminal sensory complex. This effect was probably revealed by the use of a sham-operated group as a control.

Animals↗
PubMed1988

Localisation of the first-order neurone of the jaw opening reflex elicited by periodontal stimulation.

The localisation of the first-order neurone of the jaw-opening reflex (JOR), provoked by periodontal stimulation, was investigated in the rat. A section of the mandibular part of the trigeminal ganglion was carried out without impairing the motor root. It suppressed the reflex triggered by the stimulation of the lower incisor. Bilateral destruction of the mesencephalic nucleus and tract does not modify the JOR. These results suggest that the first-order neurone of the reflex is located in the trigeminal ganglion.

Animals↗
PubMed1988

The rostral part of the trigeminal sensory complex is involved in orofacial nociception.

Single units responsive to noxious mechanical stimulation of orofacial receptive fields were recorded within the ventrobasal complex of the rat thalamus. The induced activities were compared before and after deafferentation of the subnucleus caudalis by a trigeminal tractotomy performed at the obex level. The receptive fields activated by noxious stimulation were classified as 'oral' when included in the oral, perioral or paranasal areas, and as 'facial' when included in facial regions distant from the oral cavity. After tractotomy, the unit responses to noxious stimulation of an oral field remained unchanged in 8 cases, decreased in 3 cases, and were suppressed in 4 cases. For units responding to noxious stimulation of a facial field, the responses were suppressed in 8 cases, decreased in two cases and remained unchanged in two other cases. So it appears that the rostral part of the trigeminal sensory complex (1) receives nociceptive afferents mainly from the oral and perioral areas and (2) is a relay in ascending pathways which convey painful sensations.

Action Potentials↗
PubMed1987

[Proposal of a new analgesia test based on the observation of nociceptive behavior induced by electric stimulation of dental pulp in the rat].

Dental pulp was electrically stimulated in the awake rat. When the stimulus intensity was progressively increased the following four nociceptive reactions successively appeared: jaw opening reflex, scratching, head rotation, vocalization. The threshold of these four reactions was observed before and after administration of three antalgic drugs. No action of the three drugs was observed for the jaw opening reflex. However each drug showed different actions on the other three reactions.

Analgesia↗