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Biomedical subjects

J A Wallace

Publications and source records attributed to J A Wallace.

At least 19 recordsLinked to original sources
PubMed1991

Castable glass ceramic crowns and their reaction to endodontic therapy.

The purpose of this investigation was to determine how castable glass (Dicor) crowns would react to both cold testing and endodontic access intervention. Full crown preparations were made on six extracted maxillary teeth. The teeth were then forwarded to Dentsply International, York, Pa. Six castable glass crowns were fabricated to fit these teeth and returned to us. Subsequently the teeth were dried and the crowns were cemented. Scanning electron micrographs of the cemented crowns were made, and endodontic access openings were drilled. The teeth were also cold tested with standard methods. The teeth were then again subjected to scanning electron microscopy to determine any changes the crowns might have undergone. One crown cracked around the gingival collar as scanning electron microscopy was performed. The other crowns did not exhibit any problems such as cracking or crazing from either the access openings or the cold testing.

Ceramics↗
PubMed1991

Pulse oximetry as a diagnostic tool of pulpal vitality.

The technology of pulse oximetry has allowed significant advances in the medical field yet its use in dentistry has been virtually unexplored. This study investigates the potential of the pulse oximeter to detect vascular integrity within the human tooth. Forty-nine young adults were evaluated for the vitality of their maxillary central incisors utilizing thermal, electrical, and oximetric techniques. The pulse oximeter was found to indicate a pulse rate and oxygen saturation reading for the vital teeth and no readings for the teeth previously endodontically treated. The accuracy of this diagnostic method supports the need for additional study in the use of the pulse oximeter to interpret the pathological processes of the pulp.

Adult↗
PubMed1991

Effects of hydrogen sulfide exposure on surface properties of lung surfactant.

Hydrogen sulfide is an irritant and chemical asphyxiant gas that exerts its primary toxic effects on the respiratory and neurological systems. Exposure to hydrogen sulfide above a threshold value of 200-300 ppm is characterized by the sudden onset of hemorrhagic pulmonary edema. The purpose of this study was to determine whether this response is associated with changes in the surface properties of pulmonary surfactant. Bronchoalveolar lavage fluid was retrieved from the lungs of Fischer 344 rats exposed to two concentrations of hydrogen sulfide or fresh air for 4 h. Surface tension-lowering properties were assayed using a captive bubble surface tensiometer. Lung injury was assessed by histopathology and measurements of total protein and lactate dehydrogenase activity in the lavagate. Marked abnormalities in surfactant activity were demonstrated in the lavagates from rats exposed to the highest concentration (300 ppm) of hydrogen sulfide. These involved the properties of adsorption to the air-water interface and surface tension lowering under quasi-static interfacial compression. Exposure to 200 ppm hydrogen sulfide had no effect on minimum surface tension despite a significant increase in protein and lactate dehydrogenase in the lavagate. This would suggest a threshold-type response for the inhibition of surfactant activity by hydrogen sulfide. In vitro studies using normal rat surfactant showed that the abnormalities in surfactant activity were due to inhibitors in the edema fluid and not to a direct effect of sulfide on surfactant. The pathophysiological consequences of increased alveolar surface tension after hydrogen sulfide exposure may need to be considered in the clinical setting.

Adsorption↗
PubMed1990

Pulpal and root sensitivity rated to periodontal therapy.

The purpose of this clinical investigation was to determine if periodontal treatment consisting of scaling, root planing, and periodontal surgery produced any change in pulpal or root sensitivity. Ten patients were tested, with a total of 84 observations. There were 42 periodontally treated teeth, with 42 contralateral teeth serving as control specimens. The teeth were evaluated with stimuli from an electric pulp tester, cold, and air. The electric pulp tester was found to be reliable in assessing the pulpal sensitivity. Neither the amount of periodontal destruction nor the extent of periodontal treatment had any effect on the pulp. Scaling and root planing had no significant effect on root sensitivity. Periodontal surgery was directly related to root sensitivity in terms of the extent of root surface exposure. An association was observed clinically between plaque accumulation after periodontal surgery and root sensitivity.

Adult↗
PubMed1990

Epithelial rests' function in replantation: is splinting necessary in replantation?

The problem of resorption during replantation in relationship to the epithelial rests and a lack of splinting was studied. Ten mongrel dogs were used. Two dogs served as control subjects, while eight had their mandibular incisors intentionally replanted and studied histologically. It was observed that where rests of Malassez were present we did not see resorption, and the lack of splinting did not result in resorption or loss of teeth. It appears we can stain epithelial rests of Malassez with immunofluorescent antibodies and use this technique for further study of this tissue.

Animals↗
PubMed1988

Co-localization of tyrosine hydroxylase (TH)- and serotonin (5-HT)-immunoreactive innervation in the rat pituitary gland.

Adult male Sprague-Dawley rats were examined for possible co-localization of tyrosine hydroxylase (TH) and serotonin (5-HT) within innervation of the pituitary neurointermediate lobe. Use of sheep antiserum to TH and a secondary antibody coupled to fluorescein isothiocyanate (FITC), followed by rabbit anti-5-HT, then rhodamine-coupled second antibody, produced co-existent staining in some, but not all fibers of both the neural and intermediate lobes, using paraffin embedded tissues. Application of a combination of the two primary antibodies followed by sequential application of secondary antibody also resulted in co-localized antigens in selected fibers. Multiple 'classic' neurotransmitters within the same nerve terminals may modulate selected areas of endocrine tissue to control hormone release.

Animals↗
PubMed1987

Two populations of tyrosine hydroxylase-positive cells occur in the spinal cord of the chick embryo and hatchling.

The existence of tyrosine hydroxylase (TH)-containing neurons in the spinal cord of the chick embryo was investigated by anti-TH immunocytochemistry. Two populations of intensely immunostained cells were observed along the entire extent of the cord, beginning late in chick embryogenesis. One group of TH-positive cells was particularly numerous and found ventral to the central canal. The other group, which was smaller in number, was located along the superficial and lateral border of the dorsal horn of the spinal cord. When examined by the glyoxylic acid histofluorescence technique, cells could be visualized only very infrequently ventral to the central canal, and not at all within the dorsal horn. However, after pretreatment of hatchlings with the catecholamine synthesis precursor L-DOPA, cells ventral to the canal were readily observed by histofluorescence, while the dorsally located cells seldom visualized. Since these populations of TH-positive cells appear to only partially express the catecholaminergic phenotype, these cells may provide a model in which factors regulating the expression of neurotransmitter phenotypes can be examined in neurons of the developing CNS.

Animals↗
PubMed1987

Effects of the serotonin-uptake inhibitor, fluoxetine, on immunoreactive serotonin innervation in the rat pituitary gland.

Serotonin (5-HT)-immunoreactive innervation can be demonstrated in both the pars intermedia and pars nervosa of the rat pituitary gland. Fluoxetine hydrochloride, a 5-HT uptake inhibitor, was administered in single or multiple doses to adult male Sprague-Dawley rats to examine the possibility that 5-HT present in pituitary fibers may be due to uptake of the indoleamine. Paraffin-embedded sections of pituitaries from fluoxetine-treated rats revealed diminution or loss of 5-HT fiber staining in the intermediate, but not in the neural lobe, in all animals examined. Multiple doses of fluoxetine produced the most consistent effects on immunostaining. These observations along with results of our previous studies suggest that the intermediate lobe innervation immunoreactive for 5-HT may be due to uptake of indoleamine from extrinsic sources, while the pars nervosa terminals containing 5-HT most likely originate from 5-HT neuronal perikarya in the lower brainstem or hypothalamus.

Animals↗
PubMed1986

Serotonin-immunoreactive nerve fibers of the rat pituitary: effects of anticatecholamine and antiserotonin drugs on staining patterns.

Serotonin-immunoreactive (5-HT-IR) nerve fibers observed in the pars intermedia and pars nervosa of the rat pituitary gland were examined after treatment of animals with antiserotonergic or anti-catecholaminergic drugs. p-Chlorophenylalanine, (PCPA), an inhibitor of 5-HT synthesis, eliminated staining in both areas of pituitary gland. p-Chloroamphetamine (PCA), a serotonin neurotoxin, did not produce a significant change in 5-HT-IR from control tissue. Unexpectedly, 6-hydroxydopamine (6-OHDA), a catecholamine neurotoxin, eliminated 5-HT staining in the pars intermedia, but not in the pars nervosa. These observations suggest that 5-HT present in fibers innervating the intermediate and neural lobes is synthesized in axons locally, or is taken up into fibers from extrinsic sources. In addition, catecholamines and 5-HT may co-exist in nerve terminals of both lobes of the pituitary gland.

Animals↗
PubMed1986

Analysis of the change in number of serotonergic neurons in the chick spinal cord during embryonic development.

The existence of serotonin (5-HT)-containing neurons in the spinal cord of the chick embryo was examined by anti-5-HT immunocytochemistry. The first immunoreactive cells were observed in embryos at 7 days of incubation (E7) and were initially located within the floor plate of the early spinal cord. By E9, immunostained cells occurred throughout the length of the spinal cord and were frequently encountered in most transverse sections of the cord. When examined at later embryonic ages of E12, 17 and at hatching (E21 or 22), the 5-HT cells became progressively more difficult to find with the advancing age of the embryos. To determine if this population of spinal cord 5-HT neurons actually diminished during development, a detailed quantitative analysis was undertaken to estimate the number of 5-HT cells in the cord of chick embryos at different ages. The results of this investigation demonstrated that the size of the 5-HT neuronal population rose rapidly from E7 and plateaued (at approximately 3500 neurons) between E9 and E12. As anticipated, the number of 5-HT cells at E17 decreased at all cord levels. Surprisingly, however, the number of spinal cord 5-HT neurons at hatching increased (depending on the cord level) either back to, or above, the counts estimated for the earlier ages of E9 and E12. Therefore, cells expressing the 5-HT phenotype in the spinal cord of the chick embryo persist throughout the period of embryonic development, rather than appear transiently.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

An immunocytochemical study of the development of central serotoninergic neurons in the chick embryo.

The development of central serotoninergic neurons in the chick embryo has been investigated immunocytochemically by utilizing an antiserum to serotonin (5-HT). Immunoreactive neurons are first detected in the brainstem on embryonic day 4 (E4, stage 23), days earlier than 5-HT systems have been detected previously by biochemical techniques. The earliest 5-HT-containing cells at E4 appear rostral to the pontine flexure, yet by E5, 5-HT neuronal groups are observed throughout the brainstem from just caudal to the mesencephalic flexure to the cervical flexure. During this and subsequent phases of development, two distinct patterns of cellular migration seem to be involved in the formation of the various 5-HT neuronal groups. One pattern involves a ventral migration of 5-HT cells, which appears dependent upon the directional guidance of midline radial processes (formed by floor plate cells) that extend across the neuroepithelium. The other pattern involves a lateral migration of cells, followed by an aggregation and rearrangement of 5-HT neurons into distinct subgroups or clusters. Through these patterns of migration most components of the 5-HT neuronal system can be recognized as early as E12, with the mature organization of the 5-HT cell groups occurring by E17. One unexpected finding was the comparatively late appearance (between E9 and E12) of 5-HT neurons in the paraventricular organ of the hypothalamus. Thus, in comparison to the initial observation of the majority of brainstem 5-HT neurons at E4 to E5, the hypothalamic 5-HT cells appear after a delay of between 5 and 7 days. Such differences illustrate the fact that neurons sharing a common neurotransmitter phenotype do not necessarily share the same developmental timetable for the expression of that particular phenotype, or they may undergo neurogenesis during considerably different periods of embryogenesis.

Animals↗
PubMed1985

A pilot study of the clinical problem of regionally anesthetizing the pulp of an acutely inflamed mandibular molar.

The diplomates of the American Association of Endodontists were surveyed regarding difficulties in regionally anesthetizing acutely painful mandibular molar teeth. Frequently patients developed evidence of adequate regional block anesthesia but experienced pain when the dentist attempted access. A pilot projection was undertaken to determine if a scientific basis existed for this problem. With the animal under general anesthesia, the mandibular nerve of a cat was isolated and then regionally blocked. A stimulating electrode was implanted in a cuspid tooth and a receiving electrode in the cortex of the brain. When a state of inflammation was created in the tooth in the presence of a regional block, there was an increasing cortical response to this stimulation. It was concluded that the pilot project offered a realistic technique for the study of this clinical entity.

Acute Disease↗
PubMed1985

Inadequate treatment: a pathway to surgery.

A patient developed postendodontic pain 3 years after undergoing root canal therapy in a maxillary first premolar tooth. Radiographic examination revealed that a recently extracted impacted second premolar had originally obscured the x-ray view of a third root on the first premolar. Endodontic therapy in the unfilled root was rejected because the tooth had been restored with full coverage. Apicoectomies and retroseals were performed on all roots, and the tooth became asymptomatic.

Adult↗