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Biomedical subjects

L R Christensen

Publications and source records attributed to L R Christensen.

11 recordsLinked to original sources
PubMed1995

Etiologic aspects and orthodontic treatment of unilateral localized arrested tooth-development combined with hearing loss.

In this study a case has been presented involving localized, arrested maxillary tooth development, asymmetric maxillary development, and unilateral loss of hearing. No similar case seems to have been described before. The orthodontic treatment comprised extraction of four permanent tooth germs in the maxilla and autotransplantation of mandibular teeth, followed by the use of fixed orthodontic appliances and a one-unit bridge restoration. Etiologic aspects are discussed. It is suggested that a severe attack of mumps that involved massive swelling of the parotid glands immediately after chicken pox and measles at the age of 4 to 5 years, may have resulted in a neurologic reduction of hearing and arrested tooth development. The teeth in which root development in relation to mumps does not appear to have been reported previously, whereas hearing loss after mumps has been reported. In the search for verification of this possible connection, children with arrested tooth development should be examined for reduction of hearing, and children with hearing loss after mumps ought to have their dental development checked.

Bicuspid↗
PubMed1994

Aetiological aspects of mandibular tooth agenesis--focusing on the role of nerve, oral mucosa, and supporting tissues.

The purpose of the present investigation was to consider possible aetiological aspects of mandibular tooth agenesis by comparing the pattern of mandibular molar and premolar agenesis with radiological evidence of the mandibular canal. Orthopantomograms from 33 children affected by agenesis of at least four premolar and/or molar teeth in the mandible were investigated. Three children were affected by ectodermal dysplasia. Two anthropological mandibles with absence of mandibular canals were included in the study for comparison. According to the investigation, agenesis should be divided into three groups, based on an analysis of agenesis location, the presence of nerve canals in the jaws, and finally, data on possible bone, skin and oral mucosa abnormalities. The three aetiological groups suggested are: agenesis related to nerve tissue, agenesis related to the oral epithelium, and agenesis related to the supporting tissue.

Adolescent↗
PubMed1993

GAP43 identifies developing muscle cells in human embryos.

GAP43 has long been regarded as a neurone specific molecule present intraneuronally in both the central and peripheral nervous system, especially during development and regeneration. GAP43 has, however, recently been demonstrated in developing muscle cells of the chicken. In the prsent investigation, we have used immunohistochemistry to investigate whether GAP43 is also expressed in developing human muscle cell. Using specific monoclonal antibodies as markers for developing muscle cells (desmin) and axon terminals (synaptophysin), our results show that GAP43 is expressed in aneural, human embryonic muscle cells.

Antibodies, Monoclonal↗
PubMed1993

Immunocytochemical demonstration of nerve growth factor receptor (NGF-R) in developing human fetal teeth.

Evidence is accumulating that nerve growth factor receptor (NGF-R or p75NGFR) can mediate cell growth and differentiation of non-neuronal cells. NGF-R expression was studied in developing teeth of human embryos and fetuses between the 6th and 18th weeks of gestation, using a monoclonal mouse-anti-human NGF-R antibody. In contrast to earlier findings in rodents, the NGF-R expression of the human dental papilla was found to be transient. NGF-R was present in the condensing ecto-mesenchymal cells of the dental papilla in the early cap stage tooth germ. In later developmental stages, a shift of the NGF-R expression from the papilla to the cytoplasmic membrane of the inner enamel epithelium (IEE) was demonstrated. As in rodent odontogenesis, the NGF-R immunoreactivity of the IEE remained until the odontoblasts started secretion of predentinal matrix in the late bell state. The mitotic activity in the IEE was detected by an antibody against proliferating cell nuclear antigen (PCNA) and showed that the NGF-R expression of the IEE decreased as the cell proliferation ceased. We propose that NGF-R may, be involved in differential and/or proliferative events of human odontogenesis.

Embryo, Mammalian↗
PubMed1993

An immunocytochemical study of the innervation of developing human fetal teeth using protein gene product 9.5 (PGP 9.5).

Developing teeth of 32 human fetuses (crown-rump length 11-205 mm) were examined immunohistochemically by antisera to protein gene product 9.5 (PGP 9.5) in an attempt to shed light upon the possible role of innervation in odontogenesis. As a control for the specificity of PGP 9.5 as a neuronal marker, the results were verified by immunocytochemical co-localization in peripheral nerves of neurone-specific enolase, neurofilaments and S-100 protein. The dental follicle received the first nerve fibres in the early cap stage. At this stage, fibroblasts differentiated in the presence of nerve fibres and formed the dental follicle surrounding the developing tooth. In the dental papilla, however, no fibres were demonstrated until the dentine and enamel matrices had formed, about half of the present height of the tooth germ. Most nerve fibres were localized in the basal part of the papilla until the last stage examined and usually followed the blood vessels of the papilla. Thus the effect of innervation on tooth development may be associated with the development of the dental follicle. A novel finding was that functional odontoblasts were not only positive for S-100 but also for PGP 9.5, indicating their neural crest origin.

Antibodies, Monoclonal↗
PubMed1993

Comparison of human dental and craniofacial maturation on prenatal profile radiographs.

The present study reveals new data concerning the prenatal interrelationship between maturation of teeth and basicranial bones. By using radiographs of the mid-sagittal tissue segment of 43 human craniums, the developmental relationship between a well-defined stage of the central maxillary incisor development and the development of the basicranium was determined. Histological controls were performed to verify the radiographic findings. The study shows a close connection between the incisor development and the cranial development. Furthermore, comparisons are performed to the generally used parameters for prenatal growth, i.e. the crown-rump length (CRL) and the gestational age (GA). A thorough understanding of developmental interactions between the teeth and cranium is important for the understanding of normal, as well as pathological craniofacial development, including tooth development.

Embryonic and Fetal Development↗
PubMed1986

Radiology of colonic interposition and its associated complications.

A retrospective review of the medical records, pathology reports, and radiographic studies of 81 patients who had undergone colonic interposition was undertaken, with special attention to postoperative complications. Both early (within 30 days postoperatively, 81 patients) and late (later than 30 days postoperatively, 57 patients) complications were reviewed. Early findings included anastomotic narrowing (18 patients), anastomotic leak (13), aspiration (11), and ischemic necrosis of the colon (3). Late findings included aspiration (9 patients), anastomotic strictures (8), gastric stasis (6), redundancy and tortuosity of the colon (5), anastomotic ulcers (4), gastrocolic reflux (3), and gastroesophageal reflux into the residual esophagus (2).

Colon↗
PubMedDate not supplied

A radiographic and histologic evaluation of the patellar tendon after harvesting its central third.

Nineteen consecutive patients undergoing anterior cruciate ligament reconstruction using the central third of the ipsilateral patellar tendon were included in the study. Serial magnetic resonance images revealed that the donor-site gap in the tendon decreased with time (mean follow-up, 26 months). The thickness was significantly increased compared with the intact contralateral patellar tendon, regardless of when the magnetic resonance imaging was performed. Ultrasonography showed the same findings at a mean follow-up of 26 months. Histologic evaluation of the repair tissue in the central part of the tendon, as well as the tissue in the peripheral part of the patellar tendon at the donor site, revealed a significant increase in cellularity and vascularity as compared with normal control tendons. Thus, 2 years after the harvesting procedure, the patellar tendon displayed significant radiographic and histologic abnormalities. On the basis of these findings, reharvest of the patellar tendon, at least up to 2 years after primary harvest, cannot be recommended.

Adolescent↗