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Biomedical subjects

L A Norton

Publications and source records attributed to L A Norton.

At least 37 records · Page 2Linked to original sources
PubMed1988

Calcium incorporation in cultured chondroblasts perturbed by an electromagnetic field.

We tested the hypothesis that electric perturbation influences 45Ca incorporation in extracellular matrix (ECM) of cartilage in vitro. Hypertrophic chondroblasts of tibial epiphyses (HC), sternum (SC), and skin fibroblasts (F) were cultured from chick embryos. HC, SC, and F cells were micromass seeded three times per week and maintained at 37.5 degrees C with 5% CO2 for two weeks. Cultures were randomly designated control (C) or exposed (E) to a pulsed electromagnetic field (PEMF). A time course experiment of calcium incorporation for all cultured groups showed that 24 h of exposure produced the largest biological response in chondroblasts. Calcium incorporation required supplemental phosphate. Autoradiography data indicated that the calcium incorporation into macromolecules largely occurred in the ECM. 45Ca steady-state perturbation was enhanced by Streptomyces hyaluronidase (SH) but not by testicular hyaluronidase (TH). 45Ca incorporation experiments tested the effects of phosphate, SH, TH, and PEMF alone and in various combinations on these cultures. Only PEMF or SH plus PEMF with phosphate enhanced 45Ca incorporation. Other experiments examined the effect of rotenone or freeze-thawing on cells exposed to PEMF. PEMF plus freeze-thaw enhanced calcium incorporation in HC only. PEMF appeared to cause disruption of the ECM, enhancing the probability of matrix calcification.

Animals↗
PubMed1988

Pulsed electromagnetic fields alter phenotypic expression in chondroblasts in tissue culture.

We hypothesize that pulsed electromagnetic fields (PEMF) alter phenotypic expression of chondroblasts by promoting the production of alkaline phosphatase (AP) and altering the structure of proteoglycans. Chondroblasts from the hypertrophic zone of tibial epiphyses (HC), sternum (SC), and skin fibroblasts (F) were cultured from 16 day chick embryos. Cultures were randomly designated control (C) or experimental (E). E received PEMF for 24 h in a 6 h on, 6 h rest sequence. The controls were in the same incubator shielded by Mu metal. Assays for AP activity were performed and normalized to protein content. Proteoglycan synthesis assay involved labeling with 35S fractionating in a 5% to 20% surcrose gradient determining total protein and chondroitin sulfate content. PEMF showed no change of AP activity on F. A high AP basal activity was found in HC, but was not increased above the control. PEMF increased AP in the SC samples (E/C ratio). The sucrose gradient data showed a shift in peaks for SC only altering the ratio of carbohydrate to protein for the SC. Analysis of carbohydrate and protein indicated that the effect was decreased synthesis or degradation of protein. We conclude that PEMF alters the phenotypic expression of sternal chondroblasts in our in vitro system.

Alkaline Phosphatase↗
PubMed1988

The effect of aging cellular mechanisms on tooth movement.

In summary, there appears to be indirect evidence that the dentoalveolar system undergoes a number of changes with age. These changes have the potential of affecting the biologic response of these tissues to the forces of tooth movement. They should not, however, create a barrier toward the successful completion of orthodontic therapy in most cases.

Adult↗
PubMed1987

Normal radiographic anatomy and common anomalies seen in cephalometric films.

Lateral and posteroanterior cephalometric radiographs are used routinely in the diagnosis and quantification of dentofacial anomalies that require orthodontic treatment. The anatomic information that these films contain is occasionally overlooked as the clinician prepares tracings and makes measurements. With the increase of the average age of the orthodontic patient population, there is greater likelihood of the presence of disease. This article describes some important features of normal radiologic anatomy of the head and neck so that a clinician can better recognize pathologic changes. Common pathologic findings and anatomic anomalies are also illustrated.

Bone Diseases↗
PubMed1987

Self-induced trauma to the nails.

Both frequent and rare deformities of the nails have been reported that are due to self-inflicted damage. Some of these disorders may be confused with common diseases such as psoriasis, lichen planus, onychomycosis, or industrial injury. Awareness of the common patterns, inspection of the periungual tissues, observation of the patient's attitude toward his or her nail disorder, and inclusion of self-trauma in the differential diagnosis will lower the incidence of ineffective treatments and unnecessary laboratory tests.

Adult↗
PubMed1984

Bioelectric perturbations of bone. Research directions and clinical applications.

Bioelectric perturbation of living hard tissue produces clinically useful effects. It is being used effectively in the treatment of intractable orthopedic problems such as nonunion and avascular necrosis. Dental applications of this phenomenon are still in the early stages of research and development. Barring untoward circumstances, this form of local growth control may be used as an adjunct to localized bone induction therapy such as in the treatment of periodontal diseases, bone grafting or implantation of biocompatible products. It also appears to show promise in enhancing the rate of tooth movement or the stability of anchor teeth. The mechanism for these perturbation-induced changes in cells has not been explained. This is an active area of research with many implications for helping the clinician understand the molecular biology of hard-tissue cell proliferation, migration and differentiation.

Animals↗
PubMed1984

Orthodontic tooth movement response in Ehlers-Danlos syndrome: report of case.

The clinical manifestations of Ehlers-Danlos syndrome have been discussed. These include oral symptoms and problems with the integument, joints, and vasculature. An outline of the variations in the types of Ehlers-Danlos syndrome was given. The expected tissue response to tooth movement was discussed. Finally, a report of the orthodontic treatment of a patient with Ehlers-Danlos syndrome with its special clinical considerations was provided.

Child↗
PubMed1982

Effects of a pulsed electromagnetic field on a mixed chondroblastic tissue culture.

A mixed tissue culture predominantly composed of chondroblastic tissue was perturbed by a pulsed electromagnetic field (PEMF). Some cultures were nonconfluent, and purposely retarded in growth to resemble an atrophic nonunion, while others were grown to confluence in about one-half the time as a model for a hypertrophic nonunion. These two groups tested the effect of growth rate upon the products of cell proliferation and differentiation. The slowly growing cultures were stimulated to synthesize hydroxyproline. The rapidly growing cultures showed a large increase in lysozyme activity, and increase in hyaluronate and DNA, and a decrease in glycosaminoglycan. Exogenous lysozyme further decreased the glycosaminoglycan synthesis in the presence of PEMF. Chitotriose, a specific lysozyme inhibitor abolished this effect. Cycloheximide, a protein synthesis inhibitor, did not abolish the activation of lysozyme found in the matrix. Thus lysozyme appears to be activated by PEMF. These observations of the rapidly growing confluent cultures are consistent with events described in the normal healing of a bone fracture or endochrondral growth. Thus, PEMF appears to promote normal healing, probably by altering cartilaginous lysozyme activity in the matrix, and possibly the sequence of events leading to calcification.

Animals↗
PubMed1981

Periodontal considerations in orthodontic treatment.

Orthodontic treatment of a patient with periodontal problems is within the realm of a knowledgeable general practitioner. After a diagnosis is made, one must establish a problem list, a solution list, a logical sequential treatment plan, a mechanics plan, a retention plan, and a means of evaluating whether treatment objectives have been reached. Unfortunately, orthodontic treatment occasionally poses some hazards to the detention and its supporting structure. Recognition of these pitfalls and care during treatment will help avoid many problems. Dental scientists throughout the world are trying to understand the nature of these hazards. Their goal is to provide the practicing dentist with a means of preventing unwanted side effects and possible tissue destruction.

Adult↗
PubMed1980

Nail disorders. A review.

The nail is capable of only a limited number of pathologic responses. Some of these alterations, including idiopathic disorders, infections, tumors, and drug-induced reactions, are reviewed in the light of recent observations. Whenever possible, clinicopathologic correlation has been emphasized. Specific suggestions are made for diagnostic technics and treatment modalities.

Carcinoma, Squamous Cell↗
PubMed1980

Specific mechanics for abutment uprighting.

General practitioners can use adjunctive orthodontics in preparation for complex comprehensive dental restorative procedures. Two orthodontic educators from opposite sides of the world explain and illustrate the biomechanics of controlled abutment uprighting. Solutions to the common mechanical and clinical problems are discussed.

Biomechanical Phenomena↗
PubMed1978

DNA synthesis in cartilage cells is stimulated by oscillating electric fields.

External oscillating electric fields (1166 volts per centimeter, 5 hertz) enhanced the incorporation of [3H] thymidine into the DNA of chondrocytes isolated from the proliferative layer of embryonic (16 days) chick epiphysis. Verapamil or tetrodotoxin at 10(-6)M concentrations completely blocked the electric field effect. Tetracaine reduced the incorporation of [3H] thymidine in both control and electrically stimulated cells. The findings support the hypothesis that Na and Ca2 fluxes generated by the electrical perturbation trigger DNA synthesis in these cells.

Animals↗
PubMed1978

Cephalometrics for orthognathic surgery.

A cephalometric analysis especially designed for the patient who requires maxillofacial surgery was developed to use landmarks and measurements that can be altered by common surgical procedures. Because measurements are primarily linear, they may be readily applied to prediction overlays and study cast mountings and may serve as a basis for the evaluation of posttreatment stability.

Adult↗
PubMed1977

Epiphyseal cartilage cAMP changes produced by electrical and mechanical perturbations.

Epiphyseal cartilage from chick embryo was subjected in vitro for one to 15 minutes to static compressive forces or oscillating electric fields. The same stimuli were applied to suspensions of cells isolated from the epiphyses. At the end of the perturbation cAMP was measured in the tissue or cell extracts by radioimmunoassay. It was found that a physiological (60 g/cm2) static pressure reduced the cAMP content in the tissue and the separated cells. An oscillating electric field above 900 V/1.5 cm, 5Hz, enhanced the cAMP accumulation in the intact tissue. This effect was produced only when the long axis of the bones was oriented parallel to the electric field. In isolated cells an electric field above 750 V/1.5 cm, 5Hz, caused a decrease in cAMP content. Charged matrix macromolecules and orientation of the cells within the cell matrix may have a modulating effect on the initiation of this response. It is postulated that the change in cAMP is the early cellular signal in the response to an electrical or mechanical perturbation which leads to bone remodeling.

Animals↗
PubMed1977

Electrical stimulation of osteogenesis in periodontal defects.

Although the literature on bioelectrical phenomena is extensive, there is a paucity of research on its application in the field of dentistry. This study was designed to evaluate the effect of bioelectric phenomena on pathological osseous defects in the periodontium of Beagle dogs. Galvanic and thermocouple generators were designed to deliver a current in the nanoampere range. The galvanic unit implanted in the area of periodontal osseous defects in five dogs. These sites were randomly designated as experimental, active controls, and passive controls. The experimental and control units were implanted submucoperiosteally with the negative electrodes extending into the osseous defects. The bone was labeled with Procion Red H-8Bs at one week. Clinical and radiographic evaluation revealed no significant changes in the depth of the defects. The animals were sacrificed at 45 days and block sections were prepared. Histological measurement suggested that endosteal apposition was enhanced in all experimental sites as compared to controls. The results were discussed in relation to magnitude of current used, the influence of pathological bone, the potential of each type of experimental unit for clinical use, and the direction of further research in the area.

Animals↗